U.S. Supreme Court
Festo Corporation v. Shoketsu Kinzoku Kogyo Kabushiki Co.
535 U.S. 722
2002
Justice Kennedy delivered the opinion of
the Court.
This case requires us to address once
again the relation between two patent law concepts, the doctrine of equivalents
and the rule of prosecution history estoppel. The Court considered the same
concepts in Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U. S. 17
(1997), and reaffirmed that a patent protects its holder against efforts of copyists
to evade liability for infringement by making only insubstantial changes to a
patented invention. At the same time, we appreciated that by extending
protection beyond the literal terms in a patent the doctrine of equivalents can
create substantial uncertainty about where the patent monopoly ends. Id., at
29. If the range of equivalents is unclear, competitors may be unable to
determine what is a permitted alternative to a patented invention and what is
an infringing equivalent.
To reduce the uncertainty,
Warner-Jenkinson acknowledged that competitors may rely on the prosecution
history, the public record of the patent proceedings. In some cases the Patent
and Trademark Office (PTO) may have rejected an earlier version of the patent
application on the ground that a claim does not meet a statutory requirement
for patentability. 35 U. S. C. § 132 (1994 ed., Supp. V). When the patentee
responds to the rejection by narrowing his claims, this prosecution history
estops him from later arguing that the subject matter covered by the original,
broader claim was nothing more than an equivalent. Competitors may rely on the
estoppel to ensure that their own devices will not be found to infringe by
equivalence.
In the decision now under review the
Court of Appeals for the Federal Circuit held that by narrowing a claim to
obtain a patent, the patentee surrenders all equivalents to the amended claim
element. Petitioner asserts this holding departs from past precedent in two
respects. First, it applies estoppel to every amendment made to satisfy the
requirements of the Patent Act and not just to amendments made to avoid
pre-emption by an earlier invention, i. e., the prior art. Second, it holds
that when estoppel arises, it bars suit against every equivalent to the amended
claim element. The Court of Appeals acknowledged that this holding departed
from its own cases, which applied a flexible bar when considering what claims
of equivalence were estopped by the prosecution history. Petitioner argues that
by replacing the flexible bar with a complete bar the Court of Appeals cast
doubt on many existing patents that were amended during the application process
when the law, as it then stood, did not apply so rigorous a standard.
We granted certiorari to consider these
questions.
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 (U. S. Patent No. 4,354,125), 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. (They were multiply dependent.) 35 U. S. C. § 112 (1994
ed.). The inventor, Dr. Stoll, submitted a new application designed to meet the
examiner's objections and also added certain references to prior art. 37 CFR §
1.56 (2000). The second patent, the Carroll Patent (U. S. Patent No.
3,779,401), 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 United States District Court for the
District of Massachusetts 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 Co. 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 judges since our decision in
Warner-Jenkinson. 187 F. 3d 1381 (1999).
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. Id., at 566. 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.
Id., at 574-575. 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. Id., at 562. 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. 234 F. 3d, at 601-616.
We granted certiorari. 533 U. S. 915
(2001).
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." Autogiro Co. of America v. United States, 384 F. 2d 391, 397 (Ct.
Cl. 1967). 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.
See Winans v. Denmead, 15 How. 330, 347 (1854).
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,
supra, 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." Id., at 343. 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." Id.,
at 347 (opinion of Campbell, J.).
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." Id., at 607. 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 . . . ."
Id., at 617.
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." 520 U. S., at 28.
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." Schriber-Schroth Co. v.
Cleveland Trust Co., 311 U. S. 211, 220-221 (1940). 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 Goodyear Dental Vulcanite Co. v. Davis,
102 U. S. 222, 228 (1880) ("In view of [the amendment] there can be no
doubt of what [the patentee] understood he had patented, and that both he and
the commissioner regarded the patent to be for a manufacture made exclusively
of vulcanites by the detailed process"); 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 WarnerJenkinson 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." 520 U. S., at 30-32. While we made
clear that estoppel applies to amendments made for a "substantial reason
related to patent ability," id., at 33, 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 patent ability, the
court might consider whether it was the kind of reason that nonetheless might
require resort to the estoppel doctrine. Id., at 40-41.
Petitioner is correct that estoppel has
been discussed most often in the context of amendments made to avoid the prior
art. See Exhibit Supply Co., supra, at 137; Keystone Driller Co. v. Northwest
Engineering Corp., 294 U. S. 42, 48 (1935). Amendment to accommodate prior art
was the emphasis, too, of our decision in Warner-Jenkinson, supra, at 30. 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. 35 U. S. C. §§ 101-103 (1994 ed.
and Supp. V). In addition, the patent application must describe, enable, and
set forth the best mode of carrying out the invention. § 112 (1994 ed.). 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, 489 U. S., at 150-151. 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 a patentee from challenging a wide range of alleged equivalents made or
distributed by competitors, 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. E. g., Goodyear Dental Vulcanite Co., 102 U. S., at
230; Hurlbut v. Schillinger, 130 U. S. 456, 465 (1889).
The Court of Appeals ignored the
guidance of WarnerJenkinson, which instructed that courts must be cautious before
adopting changes that disrupt the settled expectations of the inventing
community. See 520 U. S., at 28. 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. 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." Id., at 32, n. 6; see also id., at 41 (Ginsburg, J.,
concurring) ("The new presumption, if applied woodenly, might in some
instances unfairly discount the expectations of a patentee who had no notice at
the time of patent prosecution that such a presumption would apply"). 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 patent ability:
"Where no explanation is
established, however, the court should presume that the patent application had
a substantial reason related to patent ability 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." Id., at 33.
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." Ibid.
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,
see Brief for United States as Amicus Curiae 22-28, 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. Exhibit
Supply, 315 U. S., at 136-137 ("By the amendment [the patentee] recognized
and emphasized the difference between the two phrases and proclaimed his
abandonment of all that is embraced in that difference"). 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 patent
ability, 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, SMC 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.
It is so ordered.