Background

Pennwalt sued Durand-Wayland for infringing claims 1, 2, 10 and 18 (claims at issue) of its U.S. Patent No. 4,106,628 (the ’628 patent) on an invention entitled “Sorter for Fruit and the Like.” Following a nonjury trial on the issues of patent infringement and validity, the district court issued an opinion concluding that the accused devices did not infringe any of the claims at issue, either literally or under the doctrine of equivalents.

Pennwalt appeals from the district court’s holding of noninfringement, both literally and under the doctrine of equivalents, and its award of costs against Pennwalt. Our disposition of this appeal requires resolution of the single question of whether the district court’s finding of no infringement was clearly erroneous.

Opinion

The ’628 patent claims a sorter. The principal object of the invention is to provide a rapid means for sorting items, such as fruit, by color, weight, or a combination of these two characteristics. The sorter recited in claims 1 and 2 conveys items along a track having an electronic-weighing device that produces an electrical signal proportional to the weight of the item, along with signal comparison means, clock means, position-indicating means, and discharge means, each of which performs specified functions. The specification describes the details of a “hard-wired” network consisting of discrete electrical components which perform each step of the claims, e.g., by comparing the signals from the weighing device to reference signals and sending an appropriate signal at the proper time to discharge the item into the container corresponding to its weight. The combined sorter of claims 10 and 18 is a multifunctional apparatus whereby the item is conveyed across the weighing device and also carried past an optical scanner that produces an electrical signal proportional to the color of the item. The signals from the weighing device and color sensor are combined and an appropriate signal is sent at the proper time to discharge the item into the container corresponding to its color and weight.

Durand-Wayland manufactures and sells two different types of sorting machines. The first accused device, the “Microsizer,” sorts by weight only and employs software labeled either Version 2 or Version 5. The second accused device employs software labeled Version 6 and sorts by both color and weight through the use of the “Microsizer” in conjunction with a color detection apparatus called a “Microsorter.”

Infringement Under the Doctrine of Equivalents

Under the doctrine of equivalents, infringement may be found (but not necessarily if an accused device performs substantially the same overall function or work, in substantially the same way, to obtain substantially the same overall result as the claimed invention. That formulation, however, does not mean one can ignore claim limitations.

Pennwalt argues that the “accused machines simply do in a computer what the patent illustrates doing with hard-wired circuitry,” and asserts that “this alone is insufficient to escape infringement.” If Pennwalt was correct that the accused devices differ only in substituting a computer for hard-wired circuitry, it might have a stronger position for arguing that the accused devices infringe the claims. The claim limitations, however, require the performance of certain specified functions. Theoretically, a microprocessor could be programmed to perform those functions. However, the district court found that the microprocessor in the accused devices was not so programmed.

After a full trial, the district court made findings that certain functions of the claimed inventions were “missing” from the accused devices and those which were performed were “substantially different.” The district court observed that “because the `Microsizer’ uses different elements and different operations (on the elements it does use) than the elements and operations disclosed in the patent in suit to achieve the desired results, infringement can only be found if the different elements and operations are the legal equivalents of those disclosed in the patent in suit.” It is clear from this that the district court correctly relied on an element-by-element comparison to conclude that there was no infringement under the doctrine of equivalents, because the accused devices did not perform substantially the same functions as the Pennwalt invention. For example, the district court found in part:

The machine described in the patent in suit uses shift registers that respond to “clock pulses” in order to indicate the various positions of the items to be sorted before each item is discharged. The “Microsizer” does not have any “indicating means” to determine positions of the items to be sorted since the microprocessor stores weight and color data, not the positions of the items to be sorted. After a piece of fruit has been analyzed by the “Microsorter” and while it is in transit from the optical detection means to the weight scale, the color value determined by the “Microsorter” is sorted in a color value queue. A color value queue pointer (which changes in value) points to the location of the data corresponding to the next piece of fruit to reach the weight scale. A weight value queue pointer (which also changes in value) is used to correspond to the number of cups between the weight scale and the drop location. The microprocessor software utilizes a random access memory that stores the digital numbers which resulted from the conversion of the analog signals generated by the “Microsorter” and the weight scale, and the queue pointers (under clock control) point to the memory location that has the data about a piece of fruit. The data is never “shifted” around, but rather is just stored in memory until the software routines call for data to be utilized in subsequent portions of the program(s). Thus, the “Microsizer” has neither a “first position indicating means” nor a “second position indicating means.” The machine described in the patent in suit produces signals that indicate where the fruit is, i.e., track the progression of each cup. The “Microsizer” does not.

Pennwalt asks us to reweigh the testimony, urging that the testimony of the court-appointed expert, Dr. Vacroux, is so strongly supportive of the contrary finding of infringement under the doctrine of equivalents that the district court’s finding of no infringement cannot stand. Pennwalt, however, misconstrues the effect of Dr. Vacroux’s testimony. Dr. Vacroux was a technical, not a legal, expert. He was not expected to, and did not, analyze infringement under a legal standard. He was not concerned, for example, with the scope of equivalents to which the claims were entitled in view of the prosecution history. In this light, the reports and testimony of Dr. Vacroux fully support the district court’s finding of no infringement, rather than Pennwalt’s position.

Pennwalt relies on the conclusory statement in Dr. Vacroux’s initial written report in which he characterized the accused devices as “functionally equivalent” to the “invention.” However, Dr. Vacroux also stated therein that “the new designs could be totally equivalent to those they replaced, although the components and methods used differed significantly.” Further, when Dr. Vacroux was called to testify, and, in response to detailed questioning by the court, Dr. Vacroux testified that the accused devices performed “some of the same type of operations” but “in a different way” from the claimed invention.

Dr. Vacroux’s statement that the accused devices performed only “some of the same type of operations” supports the court’s finding that some were not. It does not conflict with any of his other testimony or with his written report. Thus, on the issue of whether the accused devices performed each of the functional limitations of the claim or its equivalent and, thus, operated in substantially the same way, the district court followed its expert precisely. The court cannot be faulted for finding no infringement where the expert’s testimony as to facts negates a finding of equivalency under the correct legal standard.

With respect to the scope of equivalent functions, the court correctly limited the claims, based upon review of the prosecution history, stating that “the claims of the patent should be read in light of the careful phraseology [of functions] chosen by the inventors” because “the machine disclosed in the patent-in-suit was carefully described so that it did not read on the prior art.” As the court correctly noted, the invention was not a pioneer, but an improvement in a crowded art. The claims are “broad” with respect to what type of product can be sorted, i.e., “items” and, thus, sorters of all types of “items” fall within the relevant prior art. The claims are narrow, however, with respect to how the claimed sorter operates. Originally, the claims contained no position indicating means element with its associated functional limitations. The addition of that element was crucial to patentability. A device that does not satisfy this limitation at least equivalently does not function in substantially the same way as the claimed invention.

The trial court found that the accused devices do not have any position indicating means to determine positions of the items to be sorted. Specifically with respect to claims 10 and 18, the court correctly held that “the microprocessor stores weight and color data, not the positions of the items to be sorted.” Since each of the claims at issue requires a position indicating means and the same analysis applies to each, we set forth only the relevant language of claim 10:

first position indicating means responsive to a signal from said clock means and said signal from said second comparison means for continuously indicating the position of an item to be sorted while the item is in transit between said optical detection means and said electronic weighing means,

second position indicating means responsive to the signal from said clock means, the signal from said first comparison means and said first position indicating means for generating a signal continuously indicative of the position of an item to be sorted after said item has been weighed.

The testimony of Dr. Alford, Durand-Wayland’s expert, was that the accused machine had no component which satisfied either of the above limitations defining position indicating means, and Pennwalt has admitted that the accused machines do not sort by keeping track of the physical location of an item in transit, continuously or otherwise, as required by each of these limitations.

Pennwalt argues that there is a way to find out where an item is physically located on the track in the accused machine. Its witness, Dr. Moore, testified “you could find the location of a particular fruit as it moves from the scale to the drop by counting the distance from the stored value for that fruit back to the place the pointer is indicating at the start of the queue.” (Emphasis added.) Dr. Alford, Durand-Wayland’s expert, admitted this was possible. Thus, Pennwalt asserts that the accused devices have “position indicating means.”

One need not explain the technology to understand the inadequacy of Dr. Moore’s testimony. As Dr. Moore himself indicates, the accused machine simply does not do what he explains “could” be done. It is admitted that the physical tracking of fruit is not part of the way in which the Durand-Wayland sorter works, in contrast to the claimed sorter which requires some means for “continuously indicating the position of an item to be sorted.” While a microprocessor theoretically could be programmed to perform that function, the evidence led the court to a finding that the Durand-Wayland machines performed a substantially different function from that which each of the claims requires.

With respect to the other limitations of claim 10, Pennwalt admits that the asserted “position indicating means” of Durand-Wayland does not meet the limitation that the means must be “responsive to...said signal from said second comparison means” because no comparison is made on the Durand-Wayland machine before the discharge point. However, Pennwalt contends that Durand-Wayland “has merely changed the position of an operable element, but the operation and results achieved are the same as those claimed.” Pennwalt’s analysis is flawed in significant respects.

First, the claim requires that the “position indicating means” must be responsive to certain specified signals. Thus, finding some combination of components in the accused device that might also be labeled a “position indicating means” is a meaningless exercise when such combination is not responsive to the specified signal.

Second, the district court correctly rejected Pennwalt’s assertion that the memory component of the Durand-Wayland sorter which stores information as to weight and color of an item performed substantially the same functions as claimed for the position indicating means. The district court found that a memory function is not the same or substantially the same as the function of “continuously indicating” where an item is physically located in a sorter. On this point the record is indisputable that before the words “continuously indicating” were added as an additional limitation, the claim was unpatentable in view of prior art which, like the accused machines, stores the information with respect to sorting criteria in memories, but did not “continuously” track the location.

Thus, the facts here do not involve later-developed computer technology which should be deemed within the scope of the claims to avoid the pirating of an invention. On the contrary, the inventors could not obtain a patent with claims in which the functions were described more broadly. Having secured claims only by including very specific functional limitations, Pennwalt now seeks to avoid those very limitations under the doctrine of equivalents. This it cannot do. Simply put, the memory components of the Durand-Wayland sorter were not programmed to perform the same or an equivalent function of physically tracking the items to be sorted from the scanner to the scale or from the scale to its appropriate discharge point as required by the claims.

Contrary to Pennwalt’s arguments, the district court did not disregard the need to consider a range of equivalent functions under the doctrine of equivalents. Rather, upon evaluation of the evidence, the court concluded, as a fact, that no component in the Durand-Wayland devices performed a function within the permissible range of equivalents for the function of the first position indicating means. That function is required by all of the claims at issue. No means in the accused devices performs that function and thus there could be no literal infringement. No means with an equivalent function was substituted in the accused devices and thus there can be no infringement under the doctrine of equivalents. The district court’s finding of no infringement is not clearly erroneous.

Bennett, Senior Circuit Judge, dissenting in part, with whom Cowen, Senior Circuit Judge, and Smith and Newman, Circuit Judges, join.

I agree with the majority that the district court’s finding of no literal infringement of the ‘628 patent claims has not been shown to be clearly erroneous. However, I believe that the district court failed to consider the doctrine of equivalents issue in accord with the precedents of both this court and the Supreme Court. The in banc majority in this case, in affirming the district court, does not follow the precedents of this court. While the court sitting or hearing a case in banc can overrule its prior decisions, it must do so openly and affirmatively, not sub silentio. The majority apparently, curiously, prefers not to acknowledge expressly the significant number of our prior decisions being overruled by its opinion. Therefore, I respectfully dissent from the majority’s discussion of and conclusion on the issue of infringement under the doctrine of equivalents.

The majority has made shortsighted policy choices. The majority has contrived an analytical framework for the doctrine of equivalents that is little more than a redundant literal infringement inquiry, which renders the doctrine of equivalents so unduly restrictive and inflexible as to end its usefulness as judicial doctrine. As this court is confronted in the future with different factual settings in the varied and increasingly complex technologies that comprise this court’s patent cases, the court will be forced to admit (or ignore) the full extent of the ties with which it has bound itself today.

The majority facially retains the historical test set forth in Graver Tank for infringement under the doctrine of equivalents, by stating that infringement in such instances may be found if an accused device performs substantially the same overall function or work, in substantially the same way, to obtain substantially the same overall result as the claimed invention. But in practical effect, the majority has eviscerated the underlying rationale of the Graver Tank test by requiring, under the doctrine of equivalents, an exact equivalent for each element of the claimed invention. The majority in fact commends the district court for undertaking the proper doctrine of equivalents determination, which the majority describes as an element by element comparison of the accused device and the patent in suit. However, the purported “element by element comparison” was never the extent of the doctrine of equivalents analysis under our here-ignored precedents which also required that the analysis be undertaken in light of the entirety of the accused device and entirety of the patent in suit. See, e.g., Hughes Aircraft Co. v. United States, 717 F.2d 1351 (Fed. Cir. 1983).

Our precedents undeniably require application of the doctrine of equivalents to the invention as a whole. This required the fact finder to decide by viewing the accused device as a whole whether it and the claimed invention operate in substantially the same way and have substantially the same function and result as the claimed invention.

The majority’s departure from our recent precedents is illustrated by an examination of Hughes Aircraft Co. v. United States, which is clearly being overruled by the majority, despite not even being mentioned in its opinion. In Hughes, this court squarely addressed the issue of infringement under the doctrine of equivalents of claims containing means-plus-function limitations. The invention in Hughes was an “apparatus” (a space satellite) and the representative claim contained multiple limitations, some of which were written in means-plus-function form, including (1) means for providing an indication of the spin angle to a location external to the satellite; (2) means for receiving control signals from the external source; and (3) means for applying fluid to a fluid expulsion means within a fixed time period after the receipt of a control signal from the external location. The allegedly infringing spacecraft replaced the three above-enumerated steps with an on-board computer which did not transmit the data to an external source, receive a control signal from that external source, or respond to the received signal as expressly required by the claim limitations.

The Hughes decision held that the accused spacecraft with the position computed and retained on-board was the equivalent of the claimed satellite with its position calculated on the ground, since the devices performed substantially the same function in substantially the same way to reach the same result, and that this conclusion was not estopped by the prior art or prosecution history. This conclusion was reached in full recognition of the failure of the accused spacecraft to meet separately three limitations of the claims in issue.

Despite any protestations to the contrary, it should be beyond dispute that infringement could not have been found in Hughes under the analysis announced by the majority today. In fact, the majority’s current analysis under the doctrine of equivalents amounts to nothing more than the search for “obvious and exact equivalents” that this court denounced in Hughes. This is aptly illustrated by the majority’s reliance on the Durand microprocessor not being programmed to perform each of the functions required by the claim limitations, even though it was theoretically possible to so program the microprocessor, as grounds for affirmance of the finding of no infringement under the doctrine of equivalents.

Although the majority asserts Pennwalt’s case might be stronger if the accused devices only substituted a computer for hard-wired circuitry, the district court found that “the machine described in the patent in suit and the ‘Microsizer’ are virtually identical except for the control system that conducts the sorting operation.” The majority does not criticize that finding. Furthermore, the district court’s finding that the Microsizer performed different functions than the patent in suit was solely part of the district court’s analysis leading to its finding that there was no literal infringement, and can be characterized as nothing more than a recognition of the inherent differences in hard-wired circuitry and microprocessors. If, as under the district court’s and the majority’s analyses, the use of software and a computer or microprocessor to perform the function of hard-wired circuitry is enough to find that a device employing a microprocessor performs different functions and operations, then no device that employs computers or microprocessors could ever under the doctrine of equivalents infringe a prior patent on a device that employs hard-wired circuitry. The extent of the doctrine of equivalents inquiry cannot be confined, as it was by the district court and the majority, to the mere change to the use of a computer or microprocessor.

The claimed invention of the ’628 patent employs shift registers to shift sequentially weight and color data corresponding to a specific item from one memory register to an adjoining register as that item moves along the conveyor belt. The data is placed and shifted across shift registers containing the same number of registers as there are conveyor locations between one detection means (for weight or color) and either the next detection means or the discharge point. Thus, the shifted data in the claimed invention represents weight and color data, not position, and could only be used to indicate position in the literal sense by physically counting where in the shift register is the data for a given item. Just as in the accused device, although it could be done, it is not.

Both devices do, however, continually store the data corresponding to a particular item until it has reached the proper drop location corresponding to its color and weight characteristics. The claimed invention does this through the use of shift registers as described above while the accused device stores the data in a queue and uses pointers which move synchronously with the movement of the conveyor cups. The real question to be answered here, one which the district court and the majority never reached, is whether the queues and pointers perform in substantially the same way the functions of the claimed position indicating means when the latter are interpreted in light of the specification. The majority also holds that since Pennwalt added the limitation “continuously indicating” to the claims containing the position indicating means element, it cannot use the doctrine of equivalents to avoid that limitation. But whether the patent claims were amended by adding “continuously indicating” in order to distinguish from the noncontinuous methods employed in prior art, is not relevant here since the Durand device also performs continuously the “position indicating” function.

Finally, the majority’s treatment of the limitation that the first position indicating means be “responsive to...said signal from said second comparison means” is the clearest illustration of the shortcomings of the majority’s approach to the doctrine of equivalents. Pennwalt concedes that the Durand devices do not literally infringe claims 10 and 18 because that limitation is not literally met. In the claimed invention, the color grade from the color head is compared to the reference values and converted into data form, which then is stored directly in the first position indicating means while the item is in transit to the weight scale. In the Durand device, the color grade is stored directly and is not compared to the reference values until the item has reached the weight scale.

The majority rejected as significantly flawed Pennwalt’s assertion that Durand’s mere change of the position of an operable element was not enough to avoid infringement under the doctrine of equivalents. However, the only apparent flaw noted by the majority is that the claim requires that the position indicating means be responsive to certain signals and that without being responsive to the specified signal, any other combination of elements cannot be deemed to contain an equivalent of the functional limitations describing the position indicating means. In my view, a comparison to the color reference values occurring in the Durand device after the item reaches the weight scale is an equivalent function whether or not its first position indicating means is responsive to a signal from a comparison means, when the accused device is viewed in its entirety and compared to the claimed invention as a whole. To preclude the possibility of finding equivalent functions and therefore preclude finding infringement under the doctrine of equivalents simply because the accused device does not perform its functions in the same order as the claimed invention reduces the doctrine of equivalents, in practical effect, to nothing more than the test for literal infringement.

As discussed above, the majority is overruling this court’s recent teachings that require consideration of the claimed invention as a whole when making the doctrine of equivalents analysis. The overruling of our precedents is, of course, permissible since the court sua sponte sits in banc. However, even when sitting in banc, this court can only overrule its own prior decisions, not those of the Supreme Court. I believe that the majority’s opinion departs significantly from the clear teachings of the Supreme Court, specifically those in Graver Tank, and, in fact, adopts the position and the spirit of the dissenting opinions rejected in Graver Tank.

In Graver Tank, the patent claims at issue involved an electrical welding process containing a combination of an alkaline earth metal silicate and any other silicate. The patented composition actually used silicates of calcium and magnesium, which were both alkaline earth metal silicates. The accused composition used silicates of calcium and manganese, the latter not being an alkaline earth metal. That difference prevented the finding of literal infringement. Nevertheless, the Supreme Court noted that the two compositions used the same mechanical methods, were identical in operation, and produced the same kind and quality of weld.

The key issue became whether the substitution of a nonalkaline earth metal (manganese) for the alkaline earth metal (magnesium) claimed in the patent was, under the circumstances of the case and in view of the prior art and the technology involved, a sufficiently insubstantial change which justified application of the doctrine of equivalents. The Supreme Court concluded, despite the claim language, that the use of manganese was an insubstantial change. In fact, the Court found infringement under the doctrine of equivalents despite several prior art patents which disclosed the use of manganese in welding fluxes, and despite the patent specification itself indicating that the patentee had experimented with using manganese in its fluxes.

The current case presents, as did Graver Tank and as does any case involving the doctrine of equivalents, a choice between conflicting policies. On the one hand, there is the historic right of affording the public fair notice of what the patentee regards as his claimed invention in order to allow competitors to avoid actions which infringe the patent and to permit “designing around” the patent. On the other hand, equally important to the statutory purpose of encouraging progress in the useful arts, is the policy of affording the patent owner complete and fair protection of what was invented. The resulting tension between the competing policies has been long recognized and the inability to reconcile fully the two views has long been accepted by the courts.

To require a one-to-one correspondence creates a bright line rule easier to apply, but costly in terms of unfair results in exceptional cases. Such inequity has been rejected by the Supreme Court and, up until today, by our own precedents. The slight gain in predictability resulting from the majority’s opinion will be greatly outweighed by the loss resulting from the inability to remedy inequities resulting from insubstantial changes to and substitutions in patent claims, as the Court recognized in Graver Tank.

Had the majority in this case been confronted with the facts of Graver Tank, it is doubtful that it would have ever looked beyond the claim limitation specifically requiring an alkaline earth metal. Yet the Court’s discussion and analysis in Graver Tank illustrates both the shortsightedness of the policy choices and the shortcomings in the analysis adopted by this majority in the current opinion.

Literal differences between the claimed and accused devices should always exist before the issue of infringement under the doctrine is reached. The majority’s holding in this case that the making of the color grade comparisons after the item reaches the weight scale in the Durand device is enough to avoid infringement under the doctrine is nothing more than a conclusion that any unimportant and insubstantial changes and substitutions which take the accused device “outside the claim” are also sufficient to show that the accused device does not function in substantially the same way as the claimed invention. Thus, the same features which defeat the possibility of literal infringement are now being used to preclude possible application of the doctrine of equivalents. Up until now, this court has rejected such a limited view of the doctrine. Furthermore, in Graver Tank the Supreme Court made clear that the doctrine of equivalents was not to be so limited:

Equivalence, in the patent law, is not the prisoner of a formula and is not an absolute to be considered in a vacuum. It does not require complete identity for every purpose and in every respect. In determining equivalents, things equal to the same thing may not be equal to each other and, by the same token, things for most purposes different may sometimes be equivalents. Consideration must be given to the purpose for which an ingredient is used in a patent, the qualities it has when combined with the other ingredients, and the function which it is intended to perform.

The application of the doctrine of equivalents to “the claimed invention as a whole” as expressed by this court in Hughes, is inherent in the policy expressed in Graver Tank. In order to determine equivalency in light of “the purpose for which an ingredient is used in a patent” and “the qualities it has when combined with the other ingredients” as mandated by the Supreme Court, it is indeed necessary to view the entire claim as a whole, and not merely to conduct an element by element comparison. It is only after such an analysis that the fact finder can determine, in light of the entire claim and all of its limitations, whether the changes or substitutions made alter substantially the way that the accused device works when compared to the claimed invention as a whole.

Thus, the proper inquiry was and should remain whether the devices considered as a whole satisfy the tripartite test of Graver Tank. That question has yet to be properly and completely considered by the trial court in this case. I would vacate the district court’s decision of noninfringement under the doctrine of equivalents, and remand for a proper consideration of that question in light of the law set out in our prior precedents and this opinion.

Nies, Circuit Judge, additional views.

No precedent is overruled or even modified by the majority opinion. I join the majority opinion in all respects and write only to add a review of that precedent.

It is axiomatic under our precedent that one cannot obtain patent protection for an inventive concept or for the heart or “essence” of an invention or for an achieved result. That basic principle cannot be avoided under the rubric of “protection of the invention as a whole.” The statute requires that the inventor particularly point out and distinctly claim the subject matter of his invention. 35 U.S.C. § 112 ¶ 2.

A patent claim is not intended to be and cannot be only a general suggestion of an invention. The invention is defined by the limitations set out in the claim which thereby fix the scope of protection to which the patentee is entitled. The limitations defining the invention tell the public what it cannot make, use, or sell. Equally important, the limitations defining the invention tell the public what it can make, use, or sell without violating the patentee’s rights.

It is also axiomatic that infringement requires that the claim “read on” the accused device. That means that the patent owner must show structure in the accused device that satisfies the limitations chosen by the inventor to define his invention. An infringement analysis, thus, requires that the courts look at each element of the claim, that is, proceed through the claim element-by-element, and look for correspondence in the allegedly infringing device. If an accused device does not contain at least an equivalent for each limitation of the claim, there is no infringement because a required part of the claimed invention is missing. Indeed, this hoary principle has long been known as the “All Elements” rule.

Thus, when an element is entirely missing, that is, when the accused device does not contain either the exact element of the claim or its equivalent, there is no infringement. Conversely, an element is not “missing” if an equivalent has been substituted.

Every Supreme Court decision which has addressed the issue of infringement of a patent claim, beginning with Prouty v. Draper, 41 U.S. (16 Pet.) 335 (1842) — and the precedent is voluminous — has held that where a part of the claimed invention, that is, a limitation of the claim, is lacking in the accused device exactly or equivalently, there is no infringement.

The precedent on the legal standard for infringement is not simply a policy choice by the courts. Other precedent permits no lesser standard. Violation of rights arising from a patent grant carries serious penalties. As a matter of due process under the Fifth Amendment, reasonable notice must be given to the public of what conduct must be avoided. Whether in civil or criminal proceedings, it is unequivocally established that that basic right to notice applies. Thus, Congress placed in the statute the requirement that the patent application “conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention.” 35 U.S.C. § 112 ¶ 2. That requirement reflects the need for notice of what constitutes violation of a patentee’s rights. The public cannot be held to “obedience to a rule or standard which was so vague and indefinite as really to be no rule or standard at all.” Further, the courts cannot, by interpretation, place a gloss on the statutory requirement which has that effect.

An infringement standard as vague as application of the “invention as a whole,” which permits claim limitations to be read out of the claim, would nullify the statutory requirement and violate due process. It would also run counter to the specific limitations and protections of 35 U.S.C. §§ 251 and 252 with respect to broadening claims after issuance.

The doctrine of equivalents was created as a matter of equity, but its application does not depend simply on “equities.” Infringement on the basis of judicial fiat or jury sympathies resolving the vague question of whether a “fraud” has been committed on the “invention as a whole” cannot be the law.

Newman, Circuit Judge.

This court, sitting in banc, has dealt a conspicuous change to a major jurisprudence in patent cases: the judicially created “doctrine of equivalents”.

The court has adopted a view of the “doctrine” that facially contradicts the leading decisions of this court and of the Supreme Court. The court has also ordered a dramatic retrenchment in its equitable authority. Yet the majority declines to distinguish or discuss its departure from binding precedent, indeed declines even to cite this court’s closest decisions. The majority can not be oblivious to the in banc weight of its opinion, or to the muddle of uncertainty that it will cause.

The dissent, recognizing stare decisis, challenged the majority to explain. The majority does not respond. I must express dismay at this judicial style. The technology-based community can not be reassured by our avoidance of the responsibility, so recently assigned to this court, for coherent guidance in the patent law. Critical changes should not be made within a stonewall of silence.

1. The district court found, and the Federal Circuit quoted, the following comparison of how the accused “Microsizer”/”Microsorter” devices and the device that the specification described worked:

The machine described in the patent in suit uses shift registers that respond to “clock pulses” in order to indicate the various positions of the items to be sorted before each item is discharged. The “Microsizer” does not have any “indicating means” to determine positions of the items to be sorted since the microprocessor stores weight and color data, not the positions of the items to be sorted. After a piece of fruit has been analyzed by the “Microsorter” and while it is in transit from the optical detection means to the weight scale, the color value determined by the “Microsorter” is sorted in a color value queue. A color value queue pointer (which changes in value) points to the location of the data corresponding to the next piece of fruit to reach the weight scale. A weight value queue pointer (which also changes in value) is used to correspond to the number of cups between the weight scale and the drop location. The microprocessor software utilizes a random access memory that stores the digital numbers which resulted from the conversion of the analog signals generated by the “Microsorter” and the weight scale, and the queue pointers (under clock control) point to the memory location that has the data about a piece of fruit. The data is never “shifted” around, but rather is just stored in memory until the software routines call for data to be utilized in subsequent portions of the program(s). Thus, the “Microsizer” has neither a “first position indicating means” nor a “second position indicating means.” The machine described in the patent in suit produces signals that indicate where the fruit is, i.e., track the progression of each cup. The “Microsizer” does not.

The differences included use of a microprocessor and DRAM memory instead of a shift register and other hard-wired components. The Federal Circuit emphasized the absence of a first and second position indicating means and the failure of the accused devices to store position data in memory.

Would an engineer viewing the hardware implementation consider the accused devices to be obvious alternative implementations? Is that the applicable legal test? Was the accused software implementation a part of the prior art at the time of the invention? Was it an obvious variation of the prior art? Is any of that material?

2. The majority denied that the “accused devices differ only in substituting a computer for hard-wired circuitry.” Such a case, if it had been present, would have given the patentee “a stronger position for arguing” equivalency. Judge Bennett’s dissent challenges this analysis as “unfair” and “contrived.” He suggests that under that kind of analysis, “no device that employs computers or microprocessors could ever under the doctrine of equivalents infringe a prior patent on a device that employs hard-wired circuitry.” Do you agree? The dissent then asserts:

The real question to be answered here, one which the district court and the majority never reached, is whether the queues and pointers perform in substantially the same way the functions of the claimed position indicating means when the latter are interpreted in light of the specification.

What would be your answer to the “never reached” question? Is it the “real question”?

3. Part of this controversy is over the nuts and bolts of applying the function aspect of the function-way-result test. What does the majority say is the function to be considered? What does Judge Bennett say? Is his concept of “equivalent function” different in substance from simply defining the function to be considered in carrying out the function-way-result test at a higher level of abstraction than the majority does? Does that remind you of anything from copyright law?

Do you suppose that there might be a similar issue in addressing the way aspect of the function-way-result test?

4. In order to provide greater certainty (presumably, that means assuring the business community of more reliable and rational advice from patent lawyers on whether to engage in particular conduct) the Federal Circuit decrees element-by-element comparison. Judge Nies’ concurrence adds:

An infringement standard as vague as application of the “invention as a whole,” which permits claim limitations to be read out of the claim, would nullify the statutory requirement and violate due process. ...[It] does not depend simply on “equities.” Infringement on the basis of judicial fiat or jury sympathies resolving the vague question of whether a “fraud” has been committed on the “invention as a whole” cannot be the law.

Yet, the Pennwalt court pervasively views the application of the doctrine of equivalents to the claims (a species of claim interpretation, in that it determines claim scope) as a fact issue, tested by the “clearly erroneous” rule (where the trial was by a judge) and, presumably, tested by a “no reasonable jury” rule (where trial was by jury). This led two commentators to observe:

To compound the uncertainty, the Federal Circuit in Pennwalt indicated that it is prepared to allow the jury to decide in virtually every case whether the doctrine of equivalents applied. [Adelman and Francione, The Doctrine of Equivalents in Patent Law: Questions that Pennwalt Did Not Answer, 137 U. Pa. L. Rev. 673, 679 (1989).]

The proper role of the jury in deciding infringement under the doctrine of equivalents was raised in Hilton Davis Chemical Co. v. Warner-Jenkinson Co., 62 F.3d 1512 (Fed. Cir. 1995), reversed, 520 U.S. 17 (1997). Judge Plager’s dissent argued that the doctrine of equivalents has become “a virtually uncontrolled and unreviewable license to juries to find infringement if they so choose.” 62 F.3d at 1538.

5. Judge Nies stated that it is a basic principle that looking to the “gist” or “essence” of an invention is not a legitimate substitute for looking to the claims:

It is axiomatic under our precedent that one cannot obtain patent protection for an inventive concept or for the heart or “essence” of an invention or for an achieved result. That basic principle cannot be avoided under the rubric of “protection of the invention as a whole.” The statute requires that the inventor particularly point out and distinctly claim the subject matter of his invention. 35 U.S.C. § 112 ¶ 2.

That principle continues to govern. But would it be possible that the scope accorded a claim element under the doctrine of equivalents might vary depending on the importance or unimportance to the invention of the element? For example, in the notional invention of “the picture frame,” the essence or gist of the invention is having four suitably mitred pieces of wood fastened together to surround the picture. It does not matter very much whether the pieces are glued, screwed, nailed, or otherwise fastened to one another. In another invention, it might be necessary that the elements be removably fastened, such as with an electromagnetic latch. Might courts allow “nail” or “fastening means”a wide range of equivalents in the first case, but allow “latch” a narrow range of equivalents in the second case? See IMS Tech., Inc. v. Haas Automation, Inc., 206 F.3d 1422 (Fed. Cir.), cert. dism’d, 530 U.S. 1299 (2000) ("[W]hen in a claimed 'means' limitation the disclosed physical structure is of little or no importance to the claimed invention, there may be a broader range of equivalent structures than if the physical characteristics of the structure are critical in performing the claimed function in the context of the claimed invention.").

Background

This is a patent infringement action brought by plaintiff Lockwood against American Airlines, Inc. Lockwood is the inventor and owner of the two patents involved in this suit. Lockwood alleges that American infringes U.S. Patent No. 32,115 (’115 patent) and U.S. Patent No. 4,567,359 (’359 patent) by providing its SABREVISION system to travel agents.

The Lockwood patents relate to interactive, audiovisual systems and apparatus useful in computerized reservation systems. American’s recent enhancement of its computerized “Sabre” reservation system, SABREVISION, provides interactive visual presentation of information, e.g. descriptions of resorts, hotels and cruises beyond the traditional scheduling and prices.

A. The ’115 Patent

The ’115 patent is entitled “Self–Service Terminal.” It claims a self-contained, transportable machine for promoting and dispensing goods and services. The ’115 patent discloses a fully automated, self-service terminal for dispensing voice and video information, goods and printed documents, and for accepting orders and payments directly from customers by coins or credit cards, without the need for a live salesperson. The terminal is installed for direct access by prospective customers. It has a video display and a loudspeaker for presenting information to customers, a printer, a goods dispenser, a coin box and credit card reader for accepting payments, and a telephone for communicating with the staff of a remote central station. With the aid of the video display, the customer is able to interact with the system to select the offered goods and services. It was described by Lockwood’s patent attorney as “an automated teller machine...with the addition of an audiovisual display to give information about the product or service sold through the terminal.”

Lockwood alleges that American has infringed claim 11 of the ’115 patent.

B. The ’359 Patent

The ’359 patent claims a collection of similar machines interconnected through a computer network. The machines automatically dispense information, services and products to customers in a self-service fashion. The self-service information and sales terminals contain automation which creates, for example, a “fictitious insurance agent” to interactively communicate with prospective customers, to collect customer information and to provide information to customers on various alternative insurance policies. If the customer decides to make a purchase, the terminal accepts the customer’s credit card, institutes a credit check and, on approval, dispenses a policy.

Lockwood claims that American has infringed independent claim 1 and dependent claims 2, 4 and 7.

C. The American SABREVISION System

The SABREVISION system is a manually operated system in which a travel agent gathers sales information from a customer either in person or by telephone. The travel agent then uses a computer terminal access schedule, cost and availability information stored in the central Sabre computer. The travel agent may also access a stored library of still photographs of places of interest to travelers such as hotels, restaurants, and cruise ships, as well as maps of countries, cities and airports, and display these still images on the computer terminal screen. The travel agent then gives the information to the customer as if it had been looked up in the agent’s library of travel reference books.

If the customer decides to purchase a ticket, the travel agent solicits credit information or accepts cash payment from the customer. If a credit card is used, the travel agent must manually type in the credit information on the keyboard of the agent’s computer terminal. Once credit is approved, the Sabre host computer commands a ticket printer at the travel agency to print a ticket which the travel agent delivers to the customer. The SABREVISION system accepts no information directly from the customer.

American moves for summary judgment on non-infringement grounds. In short, American’s argument is that the Lockwood patents do not cover the SABREVISION system because the claims in each patent recite a type of self-contained, self-service computerized vending machine designed to replace travel agents or other sales personnel through advanced automation. In contrast, American argues that the SABREVISION system is not self-contained and is not sufficiently automated to replace travel agents. To the contrary, American argues it is an in-office computer system used exclusively by travel agents.

Additionally, American argues that Lockwood is estopped from arguing that the SABREVISION system is “equivalent” to that which the patents may cover. It argues that the arguments Lockwood made when prosecuting the patents are inconsistent with the equivalency arguments Lockwood now makes.

Lockwood argues that summary judgment must be denied because there are material issues of fact relating to the definition of several of the terms in the claims.

Discussion

I. Standard

Claim construction is a question of law which may be resolved on summary judgment. The words in a claim should be given their ordinary meaning unless it appears that the inventor used them differently. It is Lockwood’s burden on this motion to come forward with sufficient evidence in support of his proposed claim construction to warrant a trial.

II. Alleged Infringement of ’115 Patent

A. Literal Infringement

Infringement is found only when each and every limitation of a patent claim is met by the accused product exactly or by a substantial equivalent. This court agrees with American that claim 11 contains several elements which are lacking in the accused SABREVISION system.

(1) Self-Contained Apparatus

The preamble of claim 11 of the ’115 patent recites the claimed invention as a “substantially contained apparatus dimensioned to be easily transported.” American submits evidence of the prosecution history which indicates that Lockwood specifically added this preamble language to distinguish his invention from a prior art patent, which served as the examiner’s principal reference for rejecting Lockwood’s broader claims.

The accused SABREVISION system does not have any feature to correspond to this limitation. SABREVISION is a computer system made up of a multitude of separate apparatuses which are distributed throughout the office space occupied by a travel agency for the convenience of the travel agents. This system is not transportable and is not contained in any kind of housing.

Lockwood argues that, on the contrary, the SABREVISION system is self-contained. It argues and submits expert testimony to the effect that “self-contained” means an apparatus or collection of components which includes the material necessary for the apparatus to function on its own. Additionally, it argues that the SABREVISION system is easily transportable because the parts are easily transportable and the system can be easily delivered and set up.

Lockwood argues that American can not avoid infringement by simply adding additional computers to the claimed invention, which is the basic apparatus. However, this court agrees with American that the essence of the SABREVISION is the fact that it is an office network, not a self-contained “customer-oriented” computer such as Lockwood’s patent describes.

(2) Audiovisual Means

The first limitation following the preamble of claim 11 requires “an audiovisual means for selectively dispensing information from a plurality of data sources.” In its ordinary sense, the word “audiovisual” connotes the use of both the sense of sound and the sense of sight. See Webster’s Ninth New Collegiate Dictionary.

Lockwood argues that the term audio-visual includes in its ordinary meaning the use of either sight or sound, or both. It points to the definition of “audiovisual works” in the copyrights statute, 17 U.S.C. § 101, which describes them as “works that consist of a series of related images which are intrinsically intended to be shown by the use of machines or devices such as projectors, viewers, or electronic equipment, together with accompanying sounds, if any. Thus, Lockwood argues that the SABREVISION system would still be considered an audiovisual means, even if it doesn’t produce sound.

However, this court finds that the use of the term audiovisual in the specification of the ’115 patent is wholly consistent with the definition of audiovisual which incorporates both sound and sight. For example, the specification states “a high quality audiovisual travel log can utilize practically all the human senses to motivate and influence a customer to select a particular vacation or destination.” Additionally, during prosecution of the ’115 patent, Lockwood argued the significance of audio capability to distinguish claim 11 over the Yuris patent, which had only video capability. He stated, “Yuris does not feature any means to promote the goods or services by audio or audiovisual means.” Thus, it is clear that he also drew a distinction between the two terms. The only logical conclusion is that audiovisual was meant to include both audio and visual capability.

In contrast the Lockwood’s patent, the SABREVISION system relies exclusively on sight, not sound. The SABREVISION system has no audio capability, apart from an industry standard “beep” from the personal computer. The beep does not dispense any information. Additionally, SABREVISION does not have the means to retrieve and cause to output audio information which is stored on a removable media, as required by the specification. Thus, the system lacks the audio portion of the claim limitation “an audiovisual means for selectively dispensing information.”

(3) Customer Operated Means

Three limitations of claim 11 require “customer operated means” within the self-contained, transportable machine. These limitations are:

a) customer operated means for selecting information to be dispensed on said audio-visual means

b) means operated by the customer for selecting at least one item to be dispensed by said electromechanical means

c) means for directing the operation of said audio-visual means, said means operated by the customer.

Lockwood argues that a travel agent is a “customer” for purposes of American’s business. He argues that American has adapted the software and physical placement of the hardware for a delivery of a higher grade of service by their travel agent customers. In any event, Lockwood argues that the fact that use by a customer is specified in its claim does not limit the patent claim. Rather, it argues that the patent claim relates to an apparatus, and it is irrelevant who uses that apparatus for purposes of determining whether the patent has been infringed.

However, this court finds that SABREVISION satisfies none of the three limitations relating to customer operation because it is operated by a travel agent, not a customer. The specification makes clear that the inventors intended the word “customer” to exclude travel agents. In the “Background of the Invention” section, the inventors describe the expensive and cumbersome prior art system of relying upon travel agents to fulfill the needs of customers. Consequently, the inventors saw a need for “a new device capable of performing the promotion and sales of services such as those commonly dispensed by travel agencies, in a fully automated fashion.” Their solution to the problem of the high cost of travel agents, was to invent the ’115 patent.

Thus, it is clear from the inventor’s own description of their invention that the intent was to eliminate the expense of hiring travel agents by replacing them with automated machines. The invention is not a new and improved tool for use by travel agents. Rather, this court agrees with American’s assertion that customer operation is a key component of the invention. If this were not the case, the stated purpose of the invention would be defeated.

(4) Means for Accepting Payment

Claim 11 requires that the device include “at least one electromechanical means for accepting payment.” The specification of the ’115 patent discloses two electromechanical means for accepting payment: a coin box, and a credit card reader.

Lockwood argues that using the computer keyboard for validation of a person’s credit is equivalent to using the credit card reader disclosed in the ’115 patent for the same purpose, because keyboards are commonly used as a backup in the event the card reader is unable to read the card. Therefore, Lockwood concludes the SABREVISION system has at least one electromechanical means for accepting payment.

However, this court finds that the SABREVISION system does not have any automated payment means or their equivalents. In the SABREVISION system payment is accepted by a travel agent who types the customer’s credit card number into a personal computer keyboard. Thus, each means of accepting payment is dependent upon the manual labor of a travel agent.

B. Doctrine of Equivalents

This court agrees with defendant that the doctrine of equivalents should not be applied in this case because Lockwood has asserted no equitable facts or circumstances that would justify its application in this case. It notes that application of the doctrine of equivalents is the exception and not the rule.

Even if the doctrine of equivalents had applicability to this case, to prove infringement, Lockwood must establish that the accused device performs substantially the same function, in substantially the same way, to obtain substantially the same result as the claimed invention. If the accused device does not have corresponding features equivalent to each claim limitation, there can be no infringement as a matter of law. Lockwood cannot meet its burden in this case because of the missing elements in the claims previously discussed.

Furthermore, the doctrine of prosecution history estoppel (file wrapper estoppel) limits the application of the doctrine of equivalents in this case. Prosecution history estoppel forbids the patentee’s reliance on the doctrine of equivalents in litigation if that reliance would be inconsistent with amendments or arguments the patentee made before the patent examiner.

Lockwood’s amendments and arguments to the patent examiner prevent Lockwood from now contending that any of the claims of the ’115 patent cover the accused SABREVISION system. Defendant submits evidence that Lockwood’s claims were significantly narrowed during prosecution of the original and reissued ’115 patent in order to overcome the examiner’s rejections based on earlier automated ticketing devices and computer reservation systems. For example, the examiner rejected claim 9 of the original ’115 application for obviousness over the Wahlberg patent. Wahlberg disclosed an automated, multiple-transaction business machine for applications, among others, of displaying flight schedules and dispensing airline tickets. Lockwood responded to this rejection by amending the preamble of claim 9 (the same preamble that is now contained in claim 11 of the ’115 patent). He changed the language “An apparatus for automatically dispensing goods and services to a customer which comprises” to read: “A substantially self-contained apparatus dimensioned to be easily transported and installed at a commercial location comprising.”

In an argument to overcome the rejection of claim 9 and convince the examiner to allow the amended claim, Lockwood stated that the Wahlberg patent describes:

a complete system, being more in the nature of a computer system than a product. Applicant's device, on the other hand, is a free standing self-contained unit which can be moved from location to location.

Thus, the SABREVISION system is precisely what Lockwood said his invention is not — “a complete system, being more in the nature of a computer system than a product.” Lockwood’s statements to the examiner prevent him from now arguing that the SABREVISION system is equivalent to his claimed invention.

In opposition, Lockwood asserts the same arguments that he did on the direct infringement issue. He disputes American’s definitions of the terms in the claim and argues that according to his definitions, American has infringed the patents both directly and under the doctrine of equivalents.

III. Alleged Infringement of '359 Patent

Like the ’115 patent, the claims of the ’359 patent each contain several limitations which limit the claimed invention to customer operated devices. For example, claim 1 requires:

1. “audio-visual” means for interacting with a customer

2. means for storing a sequence of audio and video information to be selectively transmitted to a customer

3. customer operated input means for gathering information from a customer

4. means for storing information and orders input by a customer.

This court makes similar findings regarding non–infringement to the ones it made with regard to the ’115 patent. The SABREVISION system does not infringe the ’359 patent because it is not equipped for customer use and lacks the required audio-visual means.

Furthermore, Lockwood’s contrary arguments during prosecution of the patent estop him from now contending that the accused SABREVISION system infringes the ’359 patent.

For example, American submits evidence that during the prosecution of the ’359 patent, Lockwood argued for allowance of his patent on the basis that it provided a level of automation which was sufficient to eliminate the need for live salespersons. American argues that since systems with the level of automation of the SABREVISION system existed prior to the ’359 patent, Lockwood had to differentiate the ’359 patent on this basis. Thus, it argues that he cannot now claim that systems like the SABREVISION system which do not completely replace the salesperson’s role are infringing.

Lockwood is also prevented from arguing that the travel agents who use the system are customers within the meaning of his patent claims. Defendant submits evidence that when explaining his patent during prosecution, Lockwood drew distinctions between travel agents and customers. He envisioned the system as one which allows insurance companies or travel agents to interact with customers utilizing the various components of the system to create fictitious salespersons.

Additionally, this court notes that the specification states:

an additional object of this invention is to provide such service by means of simulated personal interview with a fictitious agent created by audio-visual devices from pre-recorded sound, images and synthesized data...

Thus, the self–service terminal of the ’359 patent must provide for movielike quality audiovisual presentations, including both motion pictures and audio capabilities, in order to create a simulated personal interview. However, the SABREVISION does not provide this type of presentation because its video images are only still photographs without sound.

In opposition, Lockwood repeats his arguments concerning the definitions of “customers” and “audiovisual.” He asserts that travel agents are American’s “customer” for purposes of the infringement issue. Additionally, he argues that the SABREVISION system has the capability to store a sequence of audiovideo information to be selectively transmitted to a customer. He argues that to be capable of infringing an accused device need only be capable of operating in an infringing mode.

Thus, the self–service terminal of the ’359 patent must provide for movielike quality audiovisual presentations, including both motion pictures and audio capabilities, in order to create a simulated personal interview. However, the SABREVISION does not provide this type of presentation because its video images are only still photographs without sound.

In opposition, Lockwood repeats his arguments concerning the definitions of “customers” and “audiovisual.” He asserts that travel agents are American’s “customer” for purposes of the infringement issue. Additionally, he argues that the SABREVISION system has the capability to store a sequence of audiovideo information to be selectively transmitted to a customer. He argues that to be capable of infringing an accused device need only be capable of operating in an infringing mode.

However, in order for the SABREVISION system to infringe the Lockwood patents based on its mere capability to store audio information, it would have to perform the identical function claimed. See Pennwalt Corp. v. Durand-Wayland, Inc. (no infringement where defendant’s machine was capable of performing the claimed function, but was not actually programmed to do so). Since it is undisputed that the SABREVISION does not perform the identical function of storing audio information, there is no infringement.

Conclusion

The essence of Lockwood’s opposition is that there are disputed issues of material fact regarding the terms in the claimed patents. However, this court agrees with defendant that there is no indication that Lockwood intended the terms to mean anything different than their ordinary meaning.

The claims of a patent must be interpreted in light of the specification and prosecution history. This court finds that the opinion testimony relied on by Lockwood is inconsistent with the specification and prosecution history of the patents. Lockwood’s witnesses do not explain how anything in the patents or their file histories led them to draw any conclusions regarding the meaning of the relevant claim language. In contrast, defendant has convincingly argued that based on the common meaning of terms like the word “customer,” and the prosecution history of the Lockwood patents, that the SABREVISION system does not infringe the Lockwood patents.

Upon due consideration of the parties’ memoranda and exhibits, the arguments advanced at hearing, and for the reasons set forth above, the court hereby grants defendant’s motion for summary judgment on non-infringement grounds.



Enright, District Judge.

Background

Plaintiff Lockwood is moving for reconsideration of this court’s order granting defendant’s motion for summary judgment on non–infringement grounds. This court held that as to both patents in issue, the ’115 and ’359 patents, no literal infringement had occurred. As to the applicability of the doctrine of equivalents to the two patents, this court held that the doctrine of equivalents should not apply because no facts presented supported an application of the doctrine and plaintiff was estopped to use the doctrine of equivalents under the doctrine of prosecution history estoppel (file wrapper estoppel). Under this doctrine a patentee may not rely on the doctrine of equivalents where the reliance would be inconsistent with amendments or arguments that the patentee made before the patent examiner.

This court refused to enter a final judgment in the case as to the infringement issue, but rather kept the two remaining counterclaims of defendant American Airlines to be heard in the normal course. This court granted the defendant’s motion to strike plaintiff’s jury demand and granted defendant’s request to file a second amended answer. Plaintiff is currently seeking a writ of mandamus from the Federal Circuit to reinstate his jury demand in this case.

Plaintiff argues that the doctrine of equivalents is applicable in this case and under the doctrine the devices are the equivalent because only “insubstantial” differences exist between defendant’s SABREVISION and the patented devices. Plaintiff supplies a report showing the number of times the patents have been cited in other patents and how this supports the theory that the patents are “pioneering inventions” and, as such, the balance to consider the doctrine of equivalents weighs more heavily in their favor. Plaintiff states that because the patents have been cited so many times they are “pioneering devices” and this weighs in favor of applying the doctrine of equivalents. Plaintiff states a new patent (the “CIP” patent) was allowed by the patent office and is being issued to Lockwood; this CIP is a continuation-in-part of the ’359 patent and has five claims. Plaintiff asserts this new patent does not mention the terms “customer” and “audiovisual” as addressed in this court’s prior decision; therefore, these terms are insignificant and unnecessary to the patentability of the invention. Plaintiff also states this new CIP patent was found by the PTO to be patentable over pertinent prior art cited by defendants. Plaintiff then goes on to discuss the application of the doctrine of equivalents as it pertains to a “hypothetical patent claim.” This court notes that the above argument fails to address the issue of whether the doctrine of equivalents should be applied in this case, because of file wrapper estoppel.

Plaintiff next outlines equitable reasons why the doctrine of equivalents should be applied. In our prior decision this court stated that no equitable reasons were sufficient to apply the doctrine of equivalents, and the plaintiff was estopped from using the doctrine by prosecution history estoppel. Because prosecution history estoppel will prevent the application of the doctrine of equivalents, and this court finds no convincing new reason that the court’s prior finding of prosecution history estoppel was in error, plaintiff should not now be able to enjoy the benefits of an application of the doctrine of equivalents. Similarly, plaintiff’s arguments for the application of the doctrine of equivalents is not sufficient to evoke its application when balanced against the policy concerns of making the stated claims of patents something the public can rely upon as the bounds of the patented invention.

Upon due consideration of the parties’ memoranda and exhibits, the arguments advanced at hearing, and for the reasons set forth above, the court hereby denies plaintiff’s motion for reconsideration.



Enright, District Judge.

Background

This case began as a patent infringement claim by plaintiff Lockwood against defendant American Airlines. Plaintiff claimed infringement of two United States patents (numbers ’115 and ’359) and defendant filed counterclaims seeking declarations that the two patents are invalid, unenforceable, not infringed, and seeking attorney fees. This court entered summary judgment for non–infringement by defendant on the two patents. Subsequently this court denied plaintiff’s request to enter final judgment and instructed the parties to proceed on the remaining counterclaims. Additionally, the court denied plaintiff’s motion for reconsideration of the prior order. Then, the court granted plaintiff leave to file a second amended complaint to include infringement on a newly–issued patent, No. 5,309,355 (‘355 patent), which is at issue in these motions.

The parties now present the court with two substantive motions: (1) defendant’s motion for summary judgment of non–infringement of patent ’355 and plaintiff’s cross–motion for summary judgment of infringement of patent ’355 and (2) defendant’s motion for summary judgment of invalidity of patent ’355.

. . .

II. American’s Motion for Summary Judgment of Non-Infringement of Patent ’355 and Lockwood’s Motion for Summary Judgment of Infringement of Patent ’355

A. Background

Lockwood originally alleged that American’s SABREVISION computer reservation system infringed Lockwood’s 1982 patent (’115) and his 1986 patent (’359). The court ruled on summary judgment that American infringed neither patent. Since that time, Lockwood has amended his complaint to allege that American’s SABREVISION system infringes another patent, the 1994 patent (’355).

The SABREVISION system is a manually operated system in which a travel agent gathers sales information from a customer either in person or by telephone. The travel agent then uses a computer terminal access schedule, cost and availability information stored in the central sabre computer. The travel agent may also access a stored library of still photographs of places of interest to travelers such as hotels, restaurants, and cruise ships, as well as maps of countries, cities and airports, and display these still images on the computer terminal screen. The travel agent then gives the information to the customer as if it had been accessed in the agent’s library of travel reference books.

If the customer decides to purchase a ticket, the travel agent solicits credit information or accepts cash payment from the customer. If a credit card is used, the travel agent must manually type in the credit information on the keyboard of the agent’s computer terminal. Once credit is approved, the sabre host computer commands a ticket printer at the travel agency to print a ticket which the travel agent delivers to the customer. The SABREVISION system accepts no information directly from the customer. On a technical level, the system consists of two major subsystems, the first located at the office of a travel agent and the second comprises the host computer, and the communications network and links.

B. Discussion

The 1994 patent contains only one independent claim, claim 1, and if American does not infringe this claim, then it cannot infringe any of the dependent claims as a matter of law. Lockwood’s 1994 patent claims an automated machine which generates sales presentations tailored to individual customer’s needs: the computer accepts information about a customer, analyzes it and then composes and displays a motion-picture sales presentation tailor-made to that customer.

American asserts that the SABREVISION system is an enhancement of American’s sabre computer reservation system, which is a worldwide network of travel agent computer terminals that American has used since the early 1960s. The SABREVISION enhancement consists primarily of a videodisc, known as a CD-ROM, added to the sabre system. Essentially, this videodisc is an electronic library which is intended to supplement or replace the library of tour books which most travel agents maintain.

1. Literal Infringement

This court finds that American’s system does not literally infringe the 1994 patent. Literal infringement may be found only where the accused product includes components or functions which exactly correspond to each and every claim limitation. To determine whether the claims of a patent are literally infringed, the claims must be construed in light of the prosecution history. The court previously ruled that American does not infringe two of Lockwood’s patents and it stated that Lockwood could not establish infringement merely by submitting declarations of expert witnesses who ignore the specification and file history of the patents. The court does not entirely disagree with American’s assertion that Lockwood makes the same “mistake” again because, as before, Lockwood relies almost exclusively on the opinion of his expert witness, Dr. Tuthill, whose declaration is irreconcilable with the specification and file history of the 1994 patent.

Here, Lockwood does not refer to the specification or prosecution history of the 1994 patent. See Senmed, Inc. v. Richard-Allan Medical Industries, Inc., 888 F.2d 815, 819 (Fed. Cir. 1989) (where specification and prosecution history are clear, they are “as a matter of law, compelling and conclusive of the proper claim interpretation”). Rather than look to the specification and prosecution history, Lockwood and his expert invoke the SABREVISION device as their principal claim construction tool, repeatedly looking to the structure and functions of the sabre system device to construe the language of the claims.

In addition, the court finds that Lockwood possibly narrowed the meaning of his claims in order to gain their allowance: American introduces evidence that Lockwood expressly represented to the PTO that his claims regarding the 1994 patent are narrower in scope than the claims of his 1986 patent. Lockwood argued that the 1994 claims should therefore be patentable as well, and the PTO thereafter withdrew its rejection and allowed the 1994 patent to issue. The court finds American’s argument persuasive that Lockwood cannot now claim that American infringes his “narrow” 1994 patent when the court has already ruled on summary judgment that American does not infringe any claim of the broader 1986 order.

Additionally, the court finds that literal infringement has not occurred because Lockwood’s patent possesses claim elements which are not part of American’s system. American’s SABREVISION does not include the automated “merchandising apparatus” required by Lockwood’s claims. According to claim 1 in Lockwood’s patent, the apparatus is a “merchandising apparatus” which is more sophisticated than American’s machine for retrieving a single still photograph from a videodisc. In addition, the court finds that SABREVISION system does not display the “individualized sales presentation” evident in Lockwood’s patent. American persuasively argues that this specification is an audio-visual presentation which is more elaborate and sophisticated than SABREVISION’s display of a single still photograph. Unlike American’s system, Lockwood’s machine analyzes the customer’s characteristics and composes a sales presentation accordingly; it can select a particular region or city which would appeal to the customer; it can incorporate up-to-date information not found on the videodisc; and it can selectively combine customer information to retrieve still photographs.

The court finds that American’s system does not “compose” a sales presentation and it cannot combine its still photographs to create a single presentation (it can only create a list of hotels from which the agent can select photographs one at a time). Its system does not “selectively combine” customer information to retrieve its still photographs. It merely retrieves a list of hotels which satisfies every customer criteria entered by agents. The system does not have the required “programmable means for directing the operation” of the Lockwood patent, and the American does not have a “means for collecting and storing service or price rate information from each institution.” Finally, its videodisc does not store the three types of information required by the patent’s claims 2-5.

2. Doctrine of Equivalents

In addition, the court finds that American’s SABREVISION system does not infringe the 1994 patent under the doctrine of equivalents, which states that infringement may be found if an accused device performs substantially the same function in substantially the same way to achieve substantially the same result. On this motion, American need only establish that its SABREVISION system lacks one of the features of Lockwood’s claimed invention. Pennwalt Corp. v. Durand-Wayland, Inc. The court already ruled that there are no equitable facts or circumstances in this case which would justify applying the doctrine of equivalents, which is an exception rather than a rule.

As an initial matter, American presents evidence that Lockwood’s conduct during this litigation may not entitle him to the benefits of equity. The court previously ruled that American’s SABREVISION system did not infringe Lockwood’s patents because American’s system has no “audiovisual” capability and it is not “customer” operated. Prior to filing this action, Lockwood amended the claims of his then-pending 1994 patent to delete the term “audiovisual.” His patent attorney stated that he made this change in “anticipation of litigation.” The attorney also testified that he omitted the word “customer” from the claims in “anticipation of litigation.” Hence, American claims that Lockwood knew all along that these terms were critical limitations in his patents. Rather than wait for the issuance of his 1994 patent, however, he went forward with the litigation on the 1982 and 1986 patents and purposely omitted the terms from the 1994 patent application.

Even if the doctrine of equivalents applies to this case, Lockwood must show some structure or function in the SABREVISION system which is at least equivalent to every limitation of the claimed invention. Hoganas AB v. Dresser Industries, Inc., 9 F.3d 948, 954 (Fed. Cir. 1993). The court finds that this requirement is not met in the present case. For example, American’s system has no structure or computer program which corresponds to the “means for composing” an individualized sales presentation, which is required in Lockwood’s patent. In the SABREVISION system, all selection and arrangement of photographs is done manually by the travel agent. In addition, American persuades the court that, unlike Lockwood’s patent, the SABREVISION does not “selectively combine” customer information or create a “sales presentation” at all.

Finally, the court finds that the doctrine of prosecution history estoppel circumscribes the application of the doctrine of equivalents in the present case. Under the doctrine of prosecution history estoppel, a patentee’s reliance on the doctrine of equivalents in litigation is forbidden, if that reliance would be inconsistent with amendments or arguments the patentee made before the patent examiner. This doctrine applies when a reasonable competitor, after reviewing the patent’s prosecution history, would conclude that the patentee relinquished any claim to the subject matter at issue. American persuasively demonstrates that Lockwood overcame the prior art by expressly relinquishing any claim to subject matter broad enough to cover the SABREVISION. Lockwood’s representations to the PTO that his 1994 patent was narrower in scope than his 1986 patent, discussed above, now prevent him from contending that the SABREVISION system infringes his 1994 patent under the doctrine of equivalents.

Therefore, the court finds that infringement has not incurred in this case. Based on the foregoing discussion, as well as the parties’ memoranda, exhibits, and oral arguments, the court hereby grants American’s motion for summary judgment of non–infringement of the ‘355 patent.

1. The Federal Circuit granted Lockwood’s petition for mandamus, holding that the Seventh Amendment guaranteed Lockwood a right to jury trial on validity. In re Lockwood, 50 F.3d 966 (Fed. Cir. 1995). The Supreme Court then granted certiorari, on American Airlines’ petition to overturn the mandamus. Before argument, Lockwood withdrew his demand for jury trial, mooting the Seventh Amendment controversy. Lockwood stated that he could not afford the cost and delay of Supreme Court review. The Supreme Court then vacated its certiorari order. 116 S. Ct. 29 (1995).

2. In Lockwood I the district court found that no equitable facts or circumstances justified invocation of the doctrine of equivalents. For some years a debate raged over whether proof that the patentee wore a white hat or that the accused infringer wore a black hat was a threshold condition that must be met before the doctrine of equivalents could play any role in a patent infringement case. In Hilton Davis Chemical Co. v. Warner–Jenkinson Co., 62 F.3d 1512 (Fed. Cir. 1995)(en banc), reversed, 117 S. Ct. 1040 (1997), the Federal Circuit held that no equitable threshold need be satisfied before application of the doctrine of equivalents. Judge Lourie’s dissenting opinion presents arguments why copying, designing around, and independent development — a spectrum of equity and its converse, piracy — should be considerations in an equivalency analysis. See 62 F.3d at 1547-49. The Supreme Court reversed on a narrow basis, holding estoppel rebuttably presumed because the patentee had not explained the amendment to have been made for a reason creating no disclaimer of the subject matter that the amendment apparently excluded.

3. Lockwood I injects the doctrine of file wrapper estoppel or prosecution history estoppel into its equivalency analysis. This is now an important — possibly dominating — aspect of any doctrine of equivalents analysis, preventing a patentee’s “recapture” of “surrendered” subject matter. The latter is ordinarily matter surrendered by an amendment to avoid a prior art rejection. But, more broadly, it includes anything definitely disclaimed, such as by distinction of the prior art in an Information Disclosure Statement.

The Federal Circuit repeatedly held (for example, in Hilton Davis) that file wrapper estoppel does not apply automatically to any subject matter excluded from a claim by amendment; instead, it applies only where the surrender was motivated by a desire to avoid possibly invalidating prior art. Thus in Hilton Davis, the Federal Circuit held file wrapper estoppel inapplicable against coverage under the doctrine of equivalents of a process operating at pH 5.0 where the claim had been amended to cover operation “at a pH from approximately 6.0 to 9.0.” The Federal Circuit considered that the 6.0 figure was not etched in marble because the addition of pH limits had been made to avoid a prior art process operating at pH above 9.0.

As you may anticipate, the issue of whether one who wants to utilize technology seemingly excluded from a claim must psychoanalyze the file wrapper to determine whether the doctrine of equivalents permits recapture of excluded subject matter remained a controversial issue despite the Hilton Davis decision. Throughout the late 1990s, different Federal Circuit panels differently answered the following questions about the doctrine of equivalents and prosecution history estoppel.

• Does prosecution history estoppel apply only to to those amendments made to overcome prior art under § 102 and § 103, or does it apply to any amendment made for a reason affecting the issuance of a patent (such as overcoming an enablement rejection or an indefiniteness issue)?

• Should a "voluntary" claim amendment — one not required by the examiner or one not made in response to a rejection by an examiner for a stated reason — create prosecution history estoppel?

• If a claim amendment creates a prosecution history estoppel, what range of equivalents, if any, is available under the doctrine of equivalents for the claim element so amended?

• When no explanation for a claim amendment is established, thus invoking the presumption of prosecution history estoppel under the Supreme Court's Warner-Jenkinson decision, what range of equivalents, if any, is available under the doctrine of equivalents for the claim element so amended?

I

Petitioner Festo Corporation owns two patents for an improved magnetic rodless cylinder, a piston-driven device that relies on magnets to move objects in a conveying system. The device has many industrial uses and has been employed in machinery as diverse as sewing equipment and the Thunder Mountain ride at Disney World. Although the precise details of the cylinder's operation are not essential here, the prosecution history must be considered.

Petitioner's patent applications, as often occurs, were amended during the prosecution proceedings. The application for the first patent, the Stoll Patent, was amended after the patent examiner rejected the initial application because the exact method of operation was unclear and some claims were made in an impermissible way. The inventor, Dr. Stoll, submitted a new application designed to meet the examiner's objections and also added certain references to prior art. The second patent, the Carroll Patent, was also amended during a reexamination proceeding. The prior art references were added to this amended application as well. Both amended patents added a new limitation — that the inventions contain a pair of sealing rings, each having a lip on one side, which would prevent impurities from getting on the piston assembly. The amended Stoll Patent added the further limitation that the outer shell of the device, the sleeve, be made of a magnetizable material.

After Festo began selling its rodless cylinder, respondents (whom we refer to as SMC) entered the market with a device similar, but not identical, to the ones disclosed by Festo's patents. SMC's cylinder, rather than using two one-way sealing rings, employs a single sealing ring with a two-way lip. Furthermore, SMC's sleeve is made of a nonmagnetizable alloy. SMC's device does not fall within the literal claims of either patent, but petitioner contends that it is so similar that it infringes under the doctrine of equivalents.

SMC contends that Festo is estopped from making this argument because of the prosecution history of its patents. The sealing rings and the magnetized alloy in the Festo product were both disclosed for the first time in the amended applications. In SMC's view, these amendments narrowed the earlier applications, surrendering alternatives that are the very points of difference in the competing devices — the sealing rings and the type of alloy used to make the sleeve. As Festo narrowed its claims in these ways in order to obtain the patents, says SMC, Festo is now estopped from saying that these features are immaterial and that SMC's device is an equivalent of its own.

The District Court disagreed. It held that Festo's amendments were not made to avoid prior art, and therefore the amendments were not the kind that give rise to estoppel. A panel of the Court of Appeals for the Federal Circuit affirmed. 72 F.3d 857 (1995). We granted certiorari, vacated, and remanded in light of our intervening decision in Warner-Jenkinson v. Hilton Davis Chemical Co., 520 U.S. 17 (1997). After a decision by the original panel on remand, 172 F.3d 1361 (1999), the Court of Appeals ordered rehearing en banc to address questions that had divided its udges since our decision in Warner-Jenkinson.

The en banc court reversed, holding that prosecution history estoppel barred Festo from asserting that the accused device infringed its patents under the doctrine of equivalents. 234 F.3d 558 (2000). The court held, with only one judge dissenting, that estoppel arises from any amendment that narrows a claim to comply with the Patent Act, not only from amendments made to avoid prior art. More controversial in the Court of Appeals was its further holding: when estoppel applies, it stands as a complete bar against any claim of equivalence for the element that was amended. The court acknowledged that its own prior case law did not go so far. Previous decisions had held that prosecution history estoppel constituted a flexible bar, foreclosing some, but not all, claims of equivalence, depending on the purpose of the amendment and the alterations in the text. The court concluded, however, that its precedents applying the flexible bar rule should be overruled because this case-by-case approach has proved unworkable. In the court's view, a complete bar rule, under which estoppel bars all claims of equivalence to the narrowed element, would promote certainty in the determination of infringement cases.

Four judges dissented from the decision to adopt a complete bar. In four separate opinions, the dissenters argued that the majority's decision to overrule precedent was contrary to Warner-Jenkinson and would unsettle the expectations of many existing patentees. Judge Michel, in his dissent, described in detail how the complete bar required the Court of Appeals to disregard 8 older decisions of this Court, as well as more than 50 of its own cases.

We granted certiorari.

II

The patent laws "promote the Progress of Science and useful Arts" by rewarding innovation with a temporary monopoly. U.S.Const., Art. I, § 8, cl. 8. The monopoly is a property right; and like any property right, its boundaries should be clear. This clarity is essential to promote progress, because it enables efficient investment in innovation. A patent holder should know what he owns, and the public should know what he does not. For this reason, the patent laws require inventors to describe their work in "full, clear, concise, and exact terms," 35 U.S.C. § 112 as part of the delicate balance the law attempts to maintain between inventors, who rely on the promise of the law to bring the invention forth, and the public, which should be encouraged to pursue innovations, creations, and new ideas beyond the inventor's exclusive rights. Bonito Boats, Inc. v. Thunder Craft Boats, Inc., 489 U.S. 141, 150 (1989).

Unfortunately, the nature of language makes it impossible to capture the essence of a thing in a patent application. The inventor who chooses to patent an invention and disclose it to the public, rather than exploit it in secret, bears the risk that others will devote their efforts toward exploiting the limits of the patent's language:

An invention exists most importantly as a tangible structure or a series of drawings. A verbal portrayal is usually an afterthought written to satisfy the requirements of patent law. This conversion of machine to words allows for unintended idea gaps which cannot be satisfactorily filled. Often the invention is novel and words do not exist to describe it. The dictionary does not always keep abreast of the inventor. It cannot. Things are not made for the sake of words, but words for things.

The language in the patent claims may not capture every nuance of the invention or describe with complete precision the range of its novelty. If patents were always interpreted by their literal terms, their value would be greatly diminished. Unimportant and insubstantial substitutes for certain elements could defeat the patent, and its value to inventors could be destroyed by simple acts of copying. For this reason, the clearest rule of patent interpretation, literalism, may conserve judicial resources but is not necessarily the most efficient rule. The scope of a patent is not limited to its literal terms, but instead embraces all equivalents to the claims described.

It is true that the doctrine of equivalents renders the scope of patents less certain. It may be difficult to determine what is or is not an equivalent to a particular element of an invention. If competitors cannot be certain about a patent's extent, they may be deterred from engaging in legitimate manufactures outside its limits, or they may invest by mistake in competing products that the patent secures. In addition, the uncertainty may lead to wasteful litigation between competitors, suits that a rule of literalism might avoid. These concerns with the doctrine of equivalents, however, are not new. Each time the Court has considered the doctrine, it has acknowledged this uncertainty as the price of ensuring the appropriate incentives for innovation, and it has affirmed the doctrine over dissents that urged a more certain rule. When the Court in Winans v. Denmead first adopted what has become the doctrine of equivalents, it stated that "[t]he exclusive right to the thing patented is not secured if the public are at liberty to make substantial copies of it varying its form or proportions." The dissent argued that the Court had sacrificed the objective of "[f]ul[l]ness, clearness, exactness, preciseness, and particularity, in the description of the invention."

The debate continued in Graver Tank & Mfg. Co. v. Linde Air Products Co., 339 U.S. 605 (1950), where the Court reaffirmed the doctrine. Graver Tank held that patent claims must protect the inventor not only from those who produce devices falling within the literal claims of the patent but also from copyists who make unimportant and insubstantial changes and substitutions in the patent which, though adding nothing, would be enough to take the copied matter outside the claim, and hence outside the reach of law. Justice Black, in dissent, objected that under the doctrine of equivalents, a competitor

cannot rely on what the language of a patent claims. He must be able at the peril of heavy infringement damages, to forecast how far a court relatively unversed in a particular technological field will expand the claim's language. . . .

Most recently, in Warner-Jenkinson, the Court reaffirmed that equivalents remain a firmly entrenched part of the settled rights protected by the patent. A unanimous opinion concluded that if the doctrine is to be discarded, it is Congress and not the Court that should do so:

[T]he lengthy history of the doctrine of equivalents strongly supports adherence to our refusal in Graver Tank to find that the Patent Act conflicts with that doctrine. Congress can legislate the doctrine of equivalents out of existence any time it chooses. The various policy arguments now made by both sides are thus best addressed to Congress, not this Court.

III

Prosecution history estoppel requires that the claims of a patent be interpreted in light of the proceedings in the PTO during the application process. Estoppel is a "rule of patent construction" that ensures that claims are interpreted by reference to those "that have been cancelled or rejected." The doctrine of equivalents allows the patentee to claim those insubstantial alterations that were not captured in drafting the original patent claim but which could be created through trivial changes. When, however, the patentee originally claimed the subject matter alleged to infringe but then narrowed the claim in response to a rejection, he may not argue that the surrendered territory comprised unforeseen subject matter that should be deemed equivalent to the literal claims of the issued patent. On the contrary,

[b]y the amendment [the patentee] recognized and emphasized the difference between the two phrases[,] ... and [t]he difference which [the patentee] thus disclaimed must be regarded as material.

Exhibit Supply Co. v. Ace Patents Corp., 315 U.S. 126, 136-137 (1942).

A rejection indicates that the patent examiner does not believe the original claim could be patented. While the patentee has the right to appeal, his decision to forgo an appeal and submit an amended claim is taken as a concession that the invention as patented does not reach as far as the original claim. See Wang Laboratories, Inc. v. Mitsubishi Electronics America, Inc., 103 F.3d 1571, 1577-1578 (CA Fed. 1997) ("Prosecution history estoppel . . . preclud[es] a patentee from regaining, through litigation, coverage of subject matter relinquished during prosecution of the application for the patent"). Were it otherwise, the inventor might avoid the PTO's gatekeeping role and seek to recapture in an infringement action the very subject matter surrendered as a condition of receiving the patent.

Prosecution history estoppel ensures that the doctrine of equivalents remains tied to its underlying purpose. Where the original application once embraced the purported equivalent but the patentee narrowed his claims to obtain the patent or to protect its validity, the patentee cannot assert that he lacked the words to describe the subject matter in question. The doctrine of equivalents is premised on language's inability to capture the essence of innovation, but a prior application describing the precise element at issue undercuts that premise. In that instance, the prosecution history has established that the inventor turned his attention to the subject matter in question, knew the words for both the broader and narrower claim, and affirmatively chose the latter.

A

The first question in this case concerns the kinds of amendments that may give rise to estoppel. Petitioner argues that estoppel should arise when amendments are intended to narrow the subject matter of the patented invention — for instance, amendments to avoid prior art — but not when the amendments are made to comply with requirements concerning the form of the patent application. In Warner-Jenkinson, we recognized that prosecution history estoppel does not arise in every instance when a patent application is amended. Our "prior cases have consistently applied prosecution history estoppel only where claims have been amended for a limited set of reasons," such as

to avoid the prior art or otherwise to address a specific concern — such as obviousness — that arguably would have rendered the claimed subject matter unpatentable.

While we made clear that estoppel applies to amendments made for a "substantial reason related to patentability," we did not purport to define that term or to catalog every reason that might raise an estoppel. Indeed, we stated that even if the amendment's purpose were unrelated to patentability, the court might consider whether it was the kind of reason that nonetheless might require resort to the estoppel doctrine.

Petitioner is correct that estoppel has been discussed most often in the context of amendments made to avoid the prior art. Amendment to accommodate prior art was the emphasis, too, of our decision in Warner-Jenkinson. It does not follow, however, that amendments for other purposes will not give rise to estoppel. Prosecution history may rebut the inference that a thing not described was indescribable. That rationale does not cease simply because the narrowing amendment, submitted to secure a patent, was for some purpose other than avoiding prior art.

We agree with the Court of Appeals that a narrowing amendment made to satisfy any requirement of the Patent Act may give rise to an estoppel. As that court explained, a number of statutory requirements must be satisfied before a patent can issue. The claimed subject matter must be useful, novel, and not obvious. In addition, the patent application must describe, enable, and set forth the best mode of carrying out the invention. These latter requirements must be satisfied before issuance of the patent, for exclusive patent rights are given in exchange for disclosing the invention to the public. See Bonito Boats. What is claimed by the patent application must be the same as what is disclosed in the specification; otherwise the patent should not issue. The patent also should not issue if the other requirements of § 112 are not satisfied, and an applicant's failure to meet these requirements could lead to the issued patent being held invalid in later litigation.

Petitioner contends that amendments made to comply with § 112 concern the form of the application and not the subject matter of the invention. The PTO might require the applicant to clarify an ambiguous term, to improve the translation of a foreign word, or to rewrite a dependent claim as an independent one. In these cases, petitioner argues, the applicant has no intention of surrendering subject matter and should not be estopped from challenging equivalent devices. While this may be true in some cases, petitioner's argument conflates the patentee's reason for making the amendment with the impact the amendment has on the subject matter.

Estoppel arises when an amendment is made to secure the patent and the amendment narrows the patent's scope. If a § 112 amendment is truly cosmetic, then it would not narrow the patent's scope or raise an estoppel. On the other hand, if a § 112 amendment is necessary and narrows the patent's scope — even if only for the purpose of better description — estoppel may apply. A patentee who narrows a claim as a condition for obtaining a patent disavows his claim to the broader subject matter, whether the amendment was made to avoid the prior art or to comply with § 112. We must regard the patentee as having conceded an inability to claim the broader subject matter or at least as having abandoned his right to appeal a rejection. In either case estoppel may apply.

B

Petitioner concedes that the limitations at issue — the sealing rings and the composition of the sleeve — were made for reasons related to § 112, if not also to avoid the prior art. Our conclusion that prosecution history estoppel arises when a claim is narrowed to comply with § 112 gives rise to the second question presented: does the estoppel bar the inventor from asserting infringement against any equivalent to the narrowed element or might some equivalents still infringe? The Court of Appeals held that prosecution history estoppel is a complete bar, and so the narrowed element must be limited to its strict literal terms. Based upon its experience, the Court of Appeals decided that the flexible bar rule is unworkable because it leads to excessive uncertainty and burdens legitimate innovation. For the reasons that follow, we disagree with the decision to adopt the complete bar.

Though prosecution history, estoppel can bar challenges to a wide range of equivalents, its reach requires an examination of the subject matter surrendered by the narrowing amendment. The complete bar avoids this inquiry by establishing a per se rule, but that approach is inconsistent with the purpose of applying the estoppel in the first place — to hold the inventor to the representations made during the application process and to the inferences that may reasonably be drawn from the amendment. By amending the application, the inventor is deemed to concede that the patent does not extend as far as the original claim. It does not follow, however, that the amended claim becomes so perfect in its description that no one could devise an equivalent. After amendment, as before, language remains an imperfect fit for invention. The narrowing amendment may demonstrate what the claim is not, but it may still fail to capture precisely what the claim is. There is no reason why a narrowing amendment should be deemed to relinquish equivalents unforeseeable at the time of the amendment and beyond a fair interpretation of what was surrendered. Nor is there any call to foreclose claims of equivalence for aspects of the invention that have only a peripheral relation to the reason the amendment was submitted. The amendment does not show that the inventor suddenly had more foresight in the drafting of claims than an inventor whose application was granted without amendments having been submitted. It shows only that he was familiar with the broader text and with the difference between the two. As a result, there is no more reason for holding the patentee to the literal terms of an amended claim than there is for abolishing the doctrine of equivalents altogether and holding every patentee to the literal terms of the patent.

This view of prosecution history estoppel is consistent with our precedents and respectful of the real practice before the PTO. While this Court has not weighed the merits of the complete bar against the flexible bar in its prior cases, we have consistently applied the doctrine in a flexible way, not a rigid one. We have considered what equivalents were surrendered during the prosecution of the patent, rather than imposing a complete bar that resorts to the very literalism the equivalents rule is designed to overcome.

The Court of Appeals ignored the guidance of Warner-Jenkinson, which instructed that courts must be cautious before adopting changes that disrupt the settled expectations of the inventing community. In that case, we made it clear that the doctrine of equivalents and the rule of prosecution history estoppel are settled law. The responsibility for changing them rests with Congress. Ibid. Fundamental alterations in these rules risk destroying the legitimate expectations of inventors in their property. The petitioner in Warner-Jenkinson requested another bright-line rule that would have provided more certainty in determining when estoppel applies but at the cost of disrupting the expectations of countless existing patent holders, but we rejected that approach:

To change so substantially the rules of the game now could very well subvert the various balances the PTO sought to strike when issuing the numerous patents which have not yet expired and which would be affected by our decision.

As Warner-Jenkinson recognized, patent prosecution occurs in the light of our case law. Inventors who amended their claims under the previous regime had no reason to believe they were conceding all equivalents. If they had known, they might have appealed the rejection instead. There is no justification for applying a new and more robust estoppel to those who relied on prior doctrine.

In Warner-Jenkinson, we struck the appropriate balance by placing the burden on the patentee to show that an amendment was not for purposes of patentability:

Where no explanation is established, however, the court should presume that the patent application had a substantial reason related to patentability for including the limiting element added by amendment. In those circumstances, prosecution history estoppel would bar the application of the doctrine of equivalents as to that element.

When the patentee is unable to explain the reason for amendment, estoppel not only applies, but also "bar[s] the application of the doctrine of equivalents as to that element." These words do not mandate a complete bar; they are limited to the circumstance where "no explanation is established." They do provide, however, that when the court is unable to determine the purpose underlying a narrowing amendment — and hence a rationale for limiting the estoppel to the surrender of particular equivalents — the court should presume that the patentee surrendered all subject matter between the broader and the narrower language.

Just as Warner-Jenkinson held that the patentee bears the burden of proving that an amendment was not made for a reason that would give rise to estoppel, we hold here that the patentee should bear the burden of showing that the amendment does not surrender the particular equivalent in question. This is the approach advocated by the United States as Amicus Curiae, and we regard it to be sound. The patentee, as the author of the claim language, may be expected to draft claims encompassing readily known equivalents. A patentee's decision to narrow his claims through amendment may be presumed to be a general disclaimer of the territory between the original claim and the amended claim. There are some cases, however, where the amendment cannot reasonably be viewed as surrendering a particular equivalent. The equivalent may have been unforeseeable at the time of the application; the rationale underlying the amendment may bear no more than a tangential relation to the equivalent in question; or there may be some other reason suggesting that the patentee could not reasonably be expected to have described the insubstantial substitute in question. In those cases the patentee can overcome the presumption that prosecution history estoppel bars a finding of equivalence.

This presumption is not, then, just the complete bar by another name. Rather, it reflects the fact that the interpretation of the patent must begin with its literal claims, and the prosecution history is relevant to construing those claims. When the patentee has chosen to narrow a claim, courts may presume the amended text was composed with awareness of this rule and that the territory surrendered is not an equivalent of the territory claimed. In those instances, however, the patentee still might rebut the presumption that estoppel bars a claim of equivalence. The patentee must show that, at the time of the amendment, one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the alleged equivalent.

IV

On the record before us, we cannot say petitioner has rebutted the presumptions that estoppel applies and that the equivalents at issue have been surrendered. Petitioner concedes that the limitations at issue — the sealing rings and the composition of the sleeve — were made in response to a rejection for reasons under § 112, if not also because of the prior art references. As the amendments were made for a reason relating to patentability, the question is not whether estoppel applies, but what territory the amendments surrendered. While estoppel does not effect a complete bar, the question remains whether petitioner can demonstrate that the narrowing amendments did not surrender the particular equivalents at issue. On these questions, respondents may well prevail, for the sealing rings and the composition of the sleeve both were noted expressly in the prosecution history. These matters, however, should be determined in the first instance by further proceedings in the Court of Appeals or the District Court.

The judgment of the Federal Circuit is vacated, and the case is remanded for further proceedings consistent with this opinion.

1. Until the 1980s, invocation of the doctrine of equivalents in patent infringement litigation was not common. It was applied mainly to overcome claims drafting oversights and perceived unfairness. Beginning around the late 1980s, however, it became routine to assert the doctrine of equivalents in every patent infringement case. By the same token, it became malpractice to fail to address it in infringement opinion letters. The growth of the doctrine began to have the effect of substantially increasing legal expenses in patent matters. As a result, courts and legal counsel increasingly turned to prosecution history estoppel to counter assertions of equivalency. The battle escalated.

By the late 1990s, most judges on the Federal Circuit began to regret the excessive encouragement that their court had initially extended to the use of the doctrine of equivalents. They progressively increased the force of prosecution history estoppel to limit the perceived excess of the doctrine of equivalents.

Before the Festo decision, the Federal Circuit had applied a flexible rule to prosecution history estoppel. The scope of the estoppel depended on the total background facts surrounding the amendment. But the Federal Circuit, sitting en banc in Festo, concluded that the flexible-bar rule is unworkable because it leads to excessive uncertainty and burdens legitimate competitive enterprise. Presumably, this judgment reflected the Federal Circuit's experience in many cases involving the interplay of the doctrine of equivalents and prosecution history estoppel.

Accordingly, the Federal Circuit, by a substantial majority, decided that narrowing the scope of a claim to overcome its rejection in the patent office had the effect of barring any assertion that anything that the amendment surrendered is covered by the doctrine of equivalents. The Supreme Court, however, reinstated the "flexible bar."

2. One formulation of the Supreme Court's rule in Festo is this:

The patentee must show that at the time of the amendment one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the alleged equivalent.

What does this new rule mean in practice? In describing the new rule, the Court stated, "This presumption is not, then, just the complete bar by another name." That is apparently true as to later discovered technology. But how does the rule apply to the ordinary and most common case, that of already known technology? Then the rule may really be just the complete bar against the doctrine of equivalents, by another name. It would seem always to be possible, particularly when given utterly accurate hindsight, for the infringer's counsel to draft a patent claim that would have literally encompassed the alleged equivalent. He simply rewrites the actual claim, substituting in the accused equivalent, which by hypothesis was a known element of the art. For example, cross out the word that the patentee used to describe the claimed subject matter ans write in a description of the known technology that the infringer used. How is the patentee supposed to show that at the time of the amendment she, or one skilled in the art, could not reasonably be expected to have drafted the same claim?

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