Source: https://cyber.harvard.edu/IPCoop/97warn1.html
Timestamp: 2019-04-19 19:20:03+00:00

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The essential facts of this case are few. Petitioner Warner-Jenkinson Co. and respondent Hilton Davis Chemical Co. manufacture dyes. Impurities in those dyes must be removed. Hilton Davis holds United States Patent No. 4,560,746 ('746 patent), which discloses an improved purification process involving "ultrafiltration." [*10] The '746 process filters impure dye through a porous membrane at certain pressures and pH levels,* resulting in a high purity dye product.
"In a [*11] process for the purification of a dye . . . the improvement which comprises: subjecting an aqueous solution . . . to ultrafiltration through a membrane having a nominal pore diameter of 5-15 Angstroms under a hydrostatic pressure of approximately 200 to 400 p.s.i.g., at a pH from approximately 6.0 to 9.0, to thereby cause separation of said impurities from said dye . . . ." App. 36-37 (emphasis added).
The inventors added the phrase "at a pH from approximately 6.0 to 9.0" during patent prosecution. At a minimum, this phrase was added to distinguish a previous patent (the "Booth" patent) that disclosed an ultrafiltration process operating at a pH above 9.0. The parties disagree as to why the low-end pH limit of 6.0 was included as part of the claim.
[*12] In 1986, Warner-Jenkinson developed an ultrafiltration process that operated with membrane pore diameters assumed to be 5-15 Angstroms, at pressures of 200 to nearly 500 p.s.i.g., and at a pH of 5.0. Warner-Jenkinson did not learn of the '746 patent until after it had begun commercial use of its ultrafiltration process. Hilton Davis eventually learned of Warner-Jenkinson's use of ultrafiltration and, in 1991, sued Warner-Jenkinson for patent infringement.
As trial approached, Hilton Davis conceded that there was no literal infringement, and relied solely on the doctrine of equivalents. Over Warner-Jenkinson's objection that the doctrine of equivalents was an equitable doctrine to be applied by the court, the issue of equivalence was included among those sent to the jury. The jury found that the '746 patent was not invalid and that Warner-Jenkinson infringed upon the patent under the doctrine of equivalents. The jury also found, however, that Warner-Jenkinson had not intentionally infringed, and therefore awarded only 20% of the damages sought by Hilton Davis. The District Court denied Warner-Jenkinson's post-trial motions, and entered a permanent injunction prohibiting Warner-Jenkinson [*13] from practicing ultrafiltration below 500 p.s.i.g. and below 9.01 pH. A fractured en banc Court of Appeals for the Federal Circuit affirmed. 62 F.3d 1512 (CA Fed. 1995).
There were three separate dissents, commanding a total of 5 of 12 judges. Four of the five dissenting judges viewed the doctrine of equivalents as allowing an improper expansion of claim scope, contrary to this Court's numerous holdings that it is the claim that defines the invention and gives notice to the public of the limits of the patent monopoly. Id., at 1537-1538 (Plager, J., dissenting). The fifth dissenter, the late Judge Nies, was able to reconcile the prohibition against enlarging [*14] the scope of claims and the doctrine of equivalents by applying the doctrine to each element of a claim, rather than to the accused product or process "overall." Id., at 1574 (Nies, J., dissenting). As she explained it, "the 'scope' is not enlarged if courts do not go beyond the substitution of equivalent elements." Ibid. All of the dissenters, however, would have found that a much narrowed doctrine of equivalents may be applied in whole or in part by the court. Id., at 1540-1542 (Plager, J., dissenting); id., at 1579 (Nies, J., dissenting).
"What constitutes equivalency must be determined against the context of the patent, the prior art, and the particular circumstances of the case. 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. An important factor is whether persons reasonably skilled in the art would have known of the interchangeability of an ingredient not contained in the patent with one that was." Id., at 609.
Petitioner's primary argument in this Court is that the doctrine of equivalents, as set out in Graver Tank in 1950, did not survive the 1952 revision of the Patent Act, 35 U.S.C. @ 100 et seq., because it is inconsistent with several aspects of that Act. In particular, petitioner argues: (1) the doctrine of equivalents is inconsistent with the statutory requirement that a patentee specifically "claim" the invention covered by a patent, 35 U.S.C. @ 112; (2) the doctrine circumvents the patent reissue process--designed to correct mistakes in drafting or the like--and avoids the express limitations on that process, 35 U.S.C. @@ 251-252; (3) the doctrine is inconsistent with the primacy of the Patent and Trademark Office (PTO) in setting the scope of a patent through the patent prosecution process; and (4) the doctrine was implicitly rejected as a general matter by Congress' specific and limited inclusion [*17] of the doctrine in one section regarding "means" claiming, 35 U.S.C. @ 112, P6. All but one of these arguments were made in Graver Tank in the context of the 1870 Patent Act, and failed to command a majority.
[*18] The 1952 Patent Act is not materially different from the 1870 Act with regard to claiming, reissue, and the role of the PTO. Compare, e.g., 35 U.S.C. @ 112 ("The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention") with The Consolidated Patent Act of 1870, ch. 230, @ 26, 16 Stat. 198, 201 (the applicant "shall particularly point out and distinctly claim the part, improvement, or combination which he claims as his invention or discovery"). Such minor differences as exist between those provisions in the 1870 and the 1952 Acts have no bearing on the result reached in Graver Tank, and thus provide no basis for our overruling it. In the context of infringement, we have already held that pre-1952 precedent survived the passage of the 1952 Act. See Aro Mfg. Co. v. Convertible Top Replacement Co., 365 U.S. 336, 342, 5 L. Ed. 2d 592, 81 S. Ct. 599 (1961) (new section defining infringement "left intact the entire body of case law on direct infringement"). We see no reason to reach a different result here.
Thus, under this new provision, an applicant can describe an element of his invention by the result accomplished or the function served, rather than describing the item or element to be used (e.g., "a means of connecting Part A to Part B," rather than "a two-penny nail"). Congress enacted @ 112, P6 in response to Halliburton Oil Well Cementing Co. v. Walker, which rejected claims that "do not describe the invention but use 'conveniently functional language at the exact point of novelty,'" 329 U.S. 1, 8, 67 S. Ct. 6, 91 L. Ed. 3 (1946) (citation omitted). See In re Donaldson Co., [*20] 16 F.3d 1189, 1194 (CA Fed. 1994) (Congress enacted predecessor of @ 112, P6 in response to Halliburton); In re Fuetterer, 50 C.C.P.A. 1453, 319 F.2d 259, 264, n. 11 (CCPA 1963) (same); see also, 2 D. Chisum, Patents @ 8.04, at 63-64 (1996) (discussing 1954 commentary of then-Chief Patent Examiner P. J. Federico). Section 112, P6 now expressly allows so-called "means" claims, with the proviso that application of the broad literal language of such claims must be limited to only those means that are "equivalent" to the actual means shown in the patent specification. This is an application of the doctrine of equivalents in a restrictive role, narrowing the application of broad literal claim elements. We recognized this type of role for the doctrine of equivalents in Graver Tank itself. 339 U.S. at 608-609. The added provision, however, is silent on the doctrine of equivalents as applied where there is no literal infringement.
"[A] distinction can be drawn that is not too esoteric between substitution of an equivalent for a component in an invention [*22] and enlarging the metes and bounds of the invention beyond what is claimed. . . . . .
"Where a claim to an invention is expressed as a combination of elements, as here, 'equivalents' in the sobriquet 'Doctrine of Equivalents' refers to the equivalency of an element or part of the invention with one that is substituted in the accused product or process. . . . . .
"This view that the accused device or process must be more than 'equivalent' overall reconciles the Supreme Court's position on infringement by equivalents with its concurrent statements that 'the courts have no right to enlarge a patent beyond the scope of its claims as allowed by the Patent Office.' [Citations omitted.] The 'scope' is not enlarged if courts do not go beyond the substitution of equivalent elements." 62 F.3d at 1573-1574 (Nies, J., dissenting) (emphasis in original).
Petitioner first argues that Graver Tank never purported to supersede a well-established limit on non-literal infringement, known variously as "prosecution history estoppel" and "file wrapper estoppel." See Bayer Aktiengesellschaft v. Duphar Int'l Research B.V., 738 F.2d 1237, 1238 (CA Fed. 1984). According to petitioner, any surrender of subject matter during patent prosecution, regardless of the reason for such surrender, precludes recapturing any part of that subject matter, [*24] even if it is equivalent to the matter expressly claimed. Because, during patent prosecution, respondent limited the pH element of its claim to pH levels between 6.0 and 9.0, petitioner would have those limits form bright lines beyond which no equivalents may be claimed. Any inquiry into the reasons for a surrender, petitioner claims, would undermine the public's right to clear notice of the scope of the patent as embodied in the patent file.
We can readily agree with petitioner that Graver Tank did not dispose of prosecution history estoppel as a legal limitation on the doctrine of equivalents. But petitioner reaches too far in arguing that the reason for an amendment during patent prosecution is irrelevant to any subsequent estoppel. In each of our cases cited by petitioner and by the dissent below, prosecution history estoppel was tied to amendments made 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. Thus, in Exhibit Supply Co. v. Ace Patents Corp., Chief Justice Stone distinguished inclusion of a limiting phrase in an original patent claim from the "very [*25] different" situation in which "the applicant, in order to meet objections in the Patent Office, based on references to the prior art, adopted the phrase as a substitute for the broader one" previously used. 315 U.S. 126, 136, 62 S. Ct. 513, 86 L. Ed. 736 (1942) (emphasis added). Similarly, in Keystone Driller Co. v. Northwest Engineering Corp., 294 U.S. 42, 79 L. Ed. 747, 55 S. Ct. 262 (1935), estoppel was applied where the initial claims were "rejected on the prior art," id., at 48, n. 6, and where the allegedly infringing equivalent element was outside of the revised claims and within the prior art that formed the basis for the rejection of the earlier claims, id., at 48.
[*26] It is telling that in each case this Court probed the reasoning behind the Patent Office's insistence upon a change in the claims. In each instance, a change was demanded because the claim as otherwise written was viewed as not describing a patentable invention at all--typically because what it described was encompassed within the prior art. But, as the United States informs us, there are a variety of other reasons why the PTO may request a change in claim language. Brief for United States as Amicus Curiae 22-23 (counsel for the PTO also appearing on the brief). And if the PTO has been requesting changes in claim language without the intent to limit equivalents or, indeed, with the expectation that language it required would in many cases allow for a range of equivalents, we should be extremely reluctant to upset the basic assumptions of the PTO without substantial reason for doing so. Our prior cases have consistently applied prosecution history estoppel only where claims have been amended for a limited set of reasons, and we see no substantial cause for requiring a more rigid rule invoking an estoppel regardless of the reasons for a change.
[*27] In this case, the patent examiner objected to the patent claim due to a perceived overlap with the Booth patent, which revealed an ultrafiltration process operating at a pH above 9.0. In response to this objection, the phrase "at a pH from approximately 6.0 to 9.0" was added to the claim. While it is undisputed that the upper limit of 9.0 was added in order to distinguish the Booth patent, the reason for adding the lower limit of 6.0 is unclear. The lower limit certainly did not serve to distinguish the Booth patent, which said nothing about pH levels below 6.0. Thus, while a lower limit of 6.0, by its mere inclusion, became a material element of the claim, that did not necessarily preclude the application of the doctrine of equivalents as to that element. See Hubbell v. United States, 179 U.S. 77, 82, 45 L. Ed. 95, 21 S. Ct. 24 (1900) ("'All [specified elements] must be regarded as mater-ial,'" though it remains an open "'question whether an omitted part is supplied by an equivalent device or instrumentality'" (citation omitted)). Where the reason for the change was not related to avoiding the prior art, the change may introduce a new element, but it does not necessarily preclude infringement [*28] by equivalents of that element.
We are left with the problem, however, of what to do in a case like the one at bar, where the record seems not to reveal the reason for including the lower pH limit of 6.0. In our view, holding that certain reasons for a claim amendment may avoid the application of prosecution history estoppel is not tantamount to holding that the absence of a reason for an [*29] amendment may similarly avoid such an estoppel. Mindful that claims do indeed serve both a definitional and a notice function, we think the better rule is to place the burden on the patent-holder to establish the reason for an amendment required during patent prosecution. The court then would decide whether that reason is sufficient to overcome prosecution history estoppel as a bar to application of the doctrine of equivalents to the element added by that amendment. Where no explanation is established, however, the court should presume that the PTO 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 equivalents as to that element. The presumption we have described, one subject to rebuttal if an appropriate reason for a required amendment is established, gives proper deference to the role of claims in defining an invention and providing public notice, and to the primacy of the PTO in ensuring that the claims allowed cover only subject matter that is properly patentable in a proffered patent application. Applied in this fashion, prosecution [*30] history estoppel places reasonable limits on the doctrine of equivalents, and further insulates the doctrine from any feared conflict with the Patent Act.
Petitioner next argues that even if Graver Tank remains good law, the case held only that the absence of substantial differences was a necessary element for infringement under the doctrine of equivalents, not that it was sufficient for such a result. Brief for Petitioner 32. Relying on Graver Tank's references to the problem of an "unscrupulous copyist" and "piracy," 339 U.S. at 607, petitioner would require judicial exploration of the equities of a case before allowing application of the doctrine of equivalents. To be sure, Graver Tank refers [*31] to the prevention of copying and piracy when describing the benefits of the doctrine of equivalents. That the doctrine produces such benefits, however, does not mean that its application is limited only to cases where those particular benefits are obtained.
Elsewhere in Graver Tank the doctrine is described in more neutral terms. And the history of the doctrine as relied upon by Graver Tank reflects a basis for the doctrine not so limited as petitioner would have it. In Winans v. Denmead, 56 U.S. 330, 15 HOW 330, 343, 14 L. Ed. 717 (1854), we described the doctrine of equivalents as growing out of a legally implied term in each patent claim that "the claim extends to the thing patented, however its form or proportions may be varied." Under that view, application of the doctrine of equivalents involves determining whether a particular accused product or process infringes upon the patent claim, where the claim takes the form--half express, half implied--of "X and its equivalents."
"The substantial equivalent of a thing, in the [*32] sense of the patent law, is the same as the thing itself; so that if two devices do the same work in substantially the same way, and accomplish substantially the same result, they are the same, even though they differ in name, form, or shape."
If the essential predicate of the doctrine of equivalents is the notion of identity between a patented invention and its equivalent, there is no basis for treating an infringing equivalent any differently than a device that infringes the express terms of the patent. Application of the doctrine of equivalents, therefore, is akin to determining literal infringement, and neither requires proof of intent.
Petitioner also points to Graver Tank's seeming reliance on the absence of independent experimentation by the alleged infringer as supporting an equitable defense to the doctrine of equivalents. The Federal Circuit explained this factor by suggesting that an alleged infringer's behavior, be it copying, designing around a patent, or independent experimentation, indirectly reflects the substantiality of the differences between the patented invention and the accused device or process. According to the Federal Circuit, a person aiming to copy [*33] or aiming to avoid a patent is imagined to be at least marginally skilled at copying or avoidance, and thus intentional copying raises an inference--rebuttable by proof of independent development--of having only insubstantial differences, and intentionally designing around a patent claim raises an inference of substantial differences. This explanation leaves much to be desired. At a minimum, one wonders how ever to distinguish between the intentional copyist making minor changes to lower the risk of legal action, and the incremental innovator designing around the claims, yet seeking to capture as much as is permissible of the patented advance.
But another explanation is available that does not require a divergence from generally objective principles of patent infringement. In both instances in Graver Tank where we referred to independent research or experiments, we were discussing the known interchangeability between the chemical compound claimed in the patent and the compound substituted by the alleged infringer. The need for independent experimentation thus could reflect knowledge--or lack thereof--of interchangeability possessed by one presumably skilled in the art. The known [*34] interchangeability of substitutes for an element of a patent is one of the express objective factors noted by Graver Tank as bearing upon whether the accused device is substantially the same as the patented invention. Independent experimentation by the alleged infringer would not always reflect upon the objective question whether a person skilled in the art would have known of the interchangeability between two elements, but in many cases it would likely be probative of such knowledge.
Finally, petitioner proposes that in order to minimize conflict with the notice function of patent claims, the doctrine of equivalents should be limited to equivalents that are disclosed within the patent itself. A milder version of this argument, which found favor with the dissenters below, is that the doctrine should be [*35] limited to equivalents that were known at the time the patent was issued, and should not extend to after-arising equivalents.
The various opinions below, respondents, and amici devote considerable attention to whether application of the doctrine of equivalents is a task for the judge or for the jury. However, despite petitioner's argument below that the doctrine should be applied by the judge, in this Court petitioner makes only passing reference to this issue. See Brief for Petitioner 22, n. 15 ("If this Court were to hold in Markman v. Westview Instruments, Inc., 116 S. Ct. 1384, 134 L. Ed. 2d 577 (1996), that judges rather than juries are to construe patent claims, so as to provide a uniform definition of the scope of the legally protected monopoly, it would seem at cross-purposes to say that juries may nonetheless expand the claims by resort to a broad notion of 'equivalents'"); Reply Brief for Petitioner 20 (whether judge or jury should apply the doctrine of equivalents depends on how the Court views the nature of the inquiry under the doctrine of equivalents).
All that remains is to address the debate regarding the linguistic framework under which "equivalence" is determined. Both the parties and the Federal Circuit spend considerable time arguing whether the so-called "triple identity" test--focusing on the function served by a particular claim element, the way that element serves that function, and the result thus obtained by that element--is a suitable method for determining equivalence, or whether an "insubstantial differences" approach is better. There seems to be substantial agreement that, while the triple identity test may be suitable for analyzing mechanical devices, it often provides a poor framework for analyzing other products or processes. On the other hand, the insubstantial differences test offers little additional guidance as to what might render any given difference "insubstantial."
Today we adhere to the doctrine of equivalents. The determination of equivalence should be applied as an objective inquiry on an element-by-element basis. Prosecution history estoppel continues to be available [*41] as a defense to infringement, but if the patent-holder demonstrates that an amendment required during prosecution had a purpose unrelated to patentability, a court must consider that purpose in order to decide whether an estoppel is precluded. Where the patent-holder is unable to establish such a purpose, a court should presume that the purpose behind the required amendment is such that prosecution history estoppel would apply. Because the Court of Appeals for the Federal Circuit did not consider all of the requirements as described by us today, particularly as related to prosecution history estoppel and the preservation of some meaning for each element in a claim, we reverse and remand for further proceedings consistent with this opinion.

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