Patent Infringement Under the Doctrine of Equivalents: Still an Inquiry of Insubstantial Differences

By

Stanislaus Aksman
Michael E. Fogarty
Linda Y. Sung

© August 1995
WILLIAN BRINKS HOFER GILSON & LIONE
Washington, D.C. 20006

I. Introduction

The Court of Appeals for the Federal Circuit ("Federal Circuit") recently dispelled uncertainties regarding the test for proving patent infringement under the doctrine of equivalents. Hilton Davis Chemical Co. v. Warner-Jenkinson Co., Inc., No. 93-1088, slip op. at 15 (Fed. Cir. August 8, 1995)(decided en banc). Reaffirming the insubstantial differences inquiry promulgated in Graver Tank v. Linde Air Products Co., 339 U.S. 605 (1950), the court outlined the relevant considerations and clarified when and how the doctrine of equivalents should be invoked.

II. Your Client's Patent Infringement Problem

To exemplify the importance of the Federal Circuit holding, consider the following fact situation.

Your client, Fluxco Products Co., asked you to determine if their U.S. Patent No. 2,043,960 to Jones is infringed by an electric welding flux composition marketed by Groover Manufacturing Co., Inc. under the name of "SuperWeld 500." The Jones patent is directed to an electric welding flux composition "containing a major proportion of alkaline earth metal silicate." Suitable alkaline earth metal silicates disclosed in the specification were silicates of magnesium and calcium. Also, Jones stated that manganese silicate (not an alkaline earth metal silicate) may suitably replace the alkaline earth metal silicate, but it was not one of the preferred silicates.

SuperWeld 500 is composed principally of manganese silicate. Fluxco also provided you with scientific evidence, including sworn declarations by scientists skilled in this area of technology, that manganese silicate is very similar in many of its reactions to magnesium silicate. The evidence also establishes that SuperWeld 500 is substantially similar and produces the same kind and quality of weld operation as a flux composition principally containing magnesium silicate.

Until recently, the patent infringement analysis would have been fraught with uncertainties. Presently, thanks to the Hilton Davis decision, it is substantially more straightforward. Prior to analyzing the foregoing problem, a brief review of some of relevant patent law concepts is in order.

III. What Is A Patent?

A patent grants an inventor a limited exclusionary right, which allows the inventor to exclude others from making, using or selling the invention for a limited time (usually twenty years from the filing date)1. In return for the grant of the exclusionary right, the inventor discloses the complete invention to the public so as to promote the progress of science.

Every patent contains: 1) a specification, which typically includes a detailed description of the invention, and 2) at least one claim. The claims recite the patentable aspect(s) of the invention, and serve to define the scope of the exclusionary right afforded the inventor. If necessary, the specification can be used to interpret specific terms set forth in the claims.

IV. Patent Infringement

An infringement analysis entails two steps. The first step is claim construction or interpretation, i.e., determining the meaning and scope of the patent claims. The second step is comparing the properly construed claims to the device accused of infringing.

In the second step of analyzing infringement, one must determine whether properly construed claims of the patent are infringed. More specifically, the accused product or method can only infringe if it includes every limitation recited by the patent claim. Historically, two theories were available to the patentee for establishing that the accused product or method infringed the claims of the patent: 1) literal infringement, and 2) infringement under the doctrine of equivalents.

Under literal infringement, the accused product or method infringed if it "exactly" satisfied the definition of the invention as recited by at least one claim of the patent. If the accused product or method was not "exactly" covered by a claim, a patent could still be infringed under the doctrine of equivalents if the changes made in the accused product or method represented insubstantial deviations from the patent claim. However, a certain amount of doubt was cast on the universal availability of the doctrine of equivalents in every infringement determination by some pronouncements from the Federal Circuit, as detailed below.

V. Doctrine of Equivalents - An Old Concept

The doctrine of equivalents is a well-established concept by which the courts have allowed an expanded scope of protection afforded patents to protect the patentee from the unscrupulous copier, who would copy an invention with only an insubstantial or slight change from the wording of the patent. See, Union Paper Bag Machine Co. v. Murphy, 97 U.S. 120, 125 (1878).

The doctrine of equivalents cases culminated in Graver Tank. Upon review of the Graver Tank decision, it is clear that Graver Tank merely restated the existing law regarding infringement under the doctrine of equivalents. Infringement by equivalency existed if the accused device "perform[ed] substantially the same function in substantially the same way to obtain substantially the same result." Graver Tank 339 U.S. at 608. This test has been referred to as the "function-way-result" test or a "tripartite test." The scope of claimed equivalents under the doctrine was limited by applying "prosecution history estoppel," to estop the patentee from reading his claims on the portion(s) of the invention surrendered during prosecution of the patent application to obtain grant of the patent.

VI. The Doctrine Under The Federal Circuit

The doctrine of equivalents has gone through various transformations since the formation of the Federal Circuit in 1982.

A. Initially Interpreted Broadly

Initially the Federal Circuit took a broad view of the doctrine of equivalents. The court in Hughes Aircraft Co. v. U.S., 717 F.2d 1351 (Fed. Cir. 1983), seemingly refused to apply prosecution history estoppel to limit the scope of equivalents afforded the claims of the patent in suit. The fact that a claim was amended during prosecution to overcome a prior art rejection under 35 U.S.C. §§ 102 or 103 did not prevent the patentee from recapturing under the doctrine of equivalents some of the subject matter that was surrendered during prosecution.

B. Application of the Doctrine Narrows - All Elements Rule

A few years after Hughes, the Federal Circuit began to apply the doctrine more narrowly. In Perkin-Elmer Corp. v. Westinghouse Elec. Corp., 822 F.2d 1528 (Fed. Cir. 1987), the court adopted what has been referred to as the "All Elements Rule." This rule required the presence of every element of the claims in the alleged infringing device, either literally or equivalently, in order to find infringement. Further, the court reemphasized the All Elements Rule in Pennwalt Corp. v. Durand-Wayland, Inc., 833 F.2d 931 (Fed. Cir. 1987) (en banc), cert. denied, 485 U.S. 961 (1988).

In Wilson Sporting Goods Co. v. David Geoffrey & Assoc., 904 F.2d 677 (Fed. Cir. 1990) cert. denied, 498 U.S. 992 (1990), the Federal Circuit elaborated on the prior art estoppel limitation. The doctrine could not afford a patent claim a scope of equivalents so broad that a claim corresponding to the equivalent structure would have been unpatentable in view of the prior art.

The court created the "hypothetical claim" test in which one had to create a hypothetical claim sufficient in scope to cover the alleged infringing structure literally, as well as the patent claim in issue. If the U.S. Patent and Trademark Office would have rejected the hypothetical claim over the prior art, the patent claim could not be afforded a scope of equivalents sufficient to cover the accused structure. Accordingly, there would be no infringement under the doctrine of equivalents.

C. Expansion Of The All Elements Rule

In Corning Glass Works v. Sumitomo Electric U.S.A., Inc., 868 F.2d 1251 (Fed. Cir. 1987), the Federal Circuit arguably expanded the Perkin-Elmer All Elements Rule. In Corning Glass, the claims for a two-layer optical waveguide achieved a greater refraction index in an inner core than in an outer cladding layer by adding a positive dopant material to the core. The accused article obtained the same effect by adding a negative dopant to the cladding layer. The limitation of a positively doped core was equivalent to the negatively doped cladding of an accused device. Moreover, the court did not believe that the doctrine of equivalents could be governed by a precise, definitive equation.

This expansion of the "All Elements Rule" was supported by Pennwalt, which did not require one-to-one correspondence. Elements can be combined to achieve the equivalent element.

In Sun Studs, Inc. v. ATA Equipment Leasing, Inc., 872 F.2d 978 (Fed. Cir. 1989) the Federal Circuit, citing Graver Tank, held that it was legal error to require a separate element in the accused device for each element in the claim.

In Malta v. Schulmerich Carillons, Inc., 952 F.2d 1320 (Fed. Cir. 1991), reh'g denied, 959 F.2d 923 (Fed. Cir. 1992), the Federal Circuit accepted the tripartite test set forth in Graver Tank for determining infringement under the doctrine, but stated that it was not the only way to do so. Judge Rich mentioned the equitable principles set forth in Graver Tank, indicating that the equivalency of a required limitation varied from case to case due to many variables.

D. Is The Doctrine The Exception, Not The Rule?

London v. Carson Pirie Scott & Co., 946 F.2d 1534 (Fed. Cir. 1991) appears to be the first instance in which the Federal Circuit questioned the universal application of the doctrine of equivalents in the absence of literal infringement. Judge Lourie stated:

[a]pplication of the doctrine of equivalents is the exception, however, not the rule.

Id. at 1538. Arguably, this dicta indicated that the doctrine may not be available for proving infringement in every instance.

In International Visual Corp. v. Crown Metal Mfg. Co., Inc., 991 F.2d 768 (Fed. Cir. 1993), Judge Lourie, in a concurring opinion, made the following four points: 1) the doctrine of equivalents is an equitable doctrine, 2) the doctrine of equivalents should not be automatically applied in every case, 3) the alternative to the universal application of the doctrine of equivalents may be adding additional requirements to the tripartite test, and 4) the finding of the additional requirements should be an independent equitable test.

Other non-precedential opinions had also mentioned the need for examination of the equities between the parties before the doctrine of equivalents could be applied.2

IV. Hilton Davis Clarifies The Doctrine

Against this background, the Federal Circuit in Hilton Davis, supra, began the discussion of the doctrine of equivalents by stating:

This case presents an opportunity to restate -- not to revise -- the test for infringement under the doctrine of equivalents.

(Hilton Davis, No. 93-1088, slip op. at 5.)

The decision provided answers to the following three questions posed by the court:

1. Does a finding of infringement under the doctrine of equivalents require anything in addition to proof of the facts that there are the same or substantially the same (a) function, (b) way, and (c) result, the so-called triple identity test of Graver Tank, and cases relied on therein? If yes, what?

2. Is the issue of infringement under the doctrine of equivalents an equitable remedy to be decided by the court, or is it, like literal infringement, an issue of fact to be submitted to the jury in a jury case?

3. Is application of the doctrine of equivalents by the trial court to find infringement of the patentee's right to exclude, when there is not literal infringement of the claim, discretionary in accordance with the circumstances of the case?

The court held that: (1) the Graver Tank tripartite test to determine "insubstantial differences," with a few embellishments, is still a proper test for determining infringement under the doctrine, (2) infringement under the doctrine is a question of fact to be decided by a fact-finder, and (3) the doctrine must be applied absent literal infringement.

A. What Is The Test?

Infringement under the doctrine of equivalents requires proof of insubstantial differences between the claimed and accused products or processes. Hilton Davis, No. 93-1088, slip op. at 6.3 The substantiality of the differences is assessed from the perspective of a person of ordinary skill in the art of the invention, and it is assessed according to an objective standard. Id. While the tripartite test often suffices to show the extent of such differences, it arose in an era characterized by relatively simple technology. Graver Tank, 339 U.S. at 609. As technology becomes more sophisticated, and innovative processes more complex, the function-way-result test may not invariably suffice to show insubstantial differences. Hilton Davis, No. 93-1088, slip op. at 8.

1. Function-Way-Result May Suffice

As discussed above, the Graver Tank test consists of three prongs to assess whether the claimed and accused products or processes: (1) perform substantially the same function, (2) in substantially the same way, (3) to obtain substantially the same result. Graver Tank 339 U.S. at 608. In many cases, including Hilton Davis, this analysis was sufficient.4 It goes too far, however, to describe this test as "the" test for equivalency under the doctrine of equivalents. Hilton Davis, No. 93-1088, slip op. at 8.

2. Additional Evidence

Because equivalence, in the patent law, is not the prisoner of formula, the available relevant evidence may vary from case to case. Hilton Davis, No. 93-1088, slip op. at 9. Thus, when a record presents other evidence relevant to the substantiality of the differences, the fact-finder must consider it. Id. Accordingly, the presence of such additional factors will depend on the way the parties frame their arguments and then the trial judge must decide whether the proffered evidence is relevant.

a. Known Interchangeability

An "important factor" to be considered, quite apart from function, way and result "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." Graver Tank, 339 U.S. at 609.5 Known interchangeability of the accused and claimed elements is potent evidence that one of ordinary skill in the relevant art would have considered the change insubstantial. Hilton Davis, No. 93-1088, slip op. at 10.

b. Copying

Evidence of copying is relevant to infringement under the doctrine of equivalents because it supports an objective evaluation of insubstantial differences -- not a subjective evaluation of bad faith intent. The fact-finder may infer that a copyist has made a fair copy with only insubstantial changes. Hilton Davis, No. 93-1088, slip op. at 10. The per curiam opinion clearly points out that intent is not an element of infringement. Id.

Since intent is not considered, evidence of independent development is not itself relevant to infringement under the doctrine of equivalents, however, such evidence may refute an accusation of copying. Hilton Davis, No. 93-1088, slip op. at 11. Further, evidence of independent development itself provides no information about the substantiality of the differences. Id.

c. Designing Around

Evidence of "designing around" patent claims weighs against a finding of infringement under the doctrine. Hilton Davis, No. 93-1088, slip op. at 11-12. The fact-finder may infer that a competitor who has attempted to design around has designed substantial changes into the new product to avoid infringement. Id.

B. Infringement Under The Doctrine Is Question Of Fact, Not Equity

Looking to Supreme Court precedent and its own decisions, the Federal Circuit reemphasized that infringement, whether literal or under the doctrine of equivalents, is a question of fact. Hilton Davis, No. 93-1088, slip op. at 13.6

While several recent opinions have referred to the doctrine of equivalents as "equitable," that term should be interpreted in its broadest sense -- equity as general fairness -- not an "equitable relief" as an alternative to legal remedies. Hilton Davis, No. 93-1088, slip op. at 14. The proposition that every patent owner is entitled to invoke the doctrine of equivalents is "inimical to the hypothesis that the doctrine is equitable." Id.

Therefore, application of the doctrine is a question for the fact-finder, either a judge in a bench trial or the jury in a jury case. Id. at 15. No showing of "equity," in any sense other than general fairness, is required. Id. at 17.

Even though the second step of evaluating infringement, either literal or under the doctrine of equivalents, is a question of fact, the first step, claim construction, is a question of law. See Markman v. Westview Instruments, 52 F.3d 967, 34 U.S.P.Q.2d 1321 (Fed. Cir. 1995) (en banc), mot. granted, cert. granted, 132 L.Ed.2d 921 (1995). The Supreme Court has granted certiorari to determine whether claim construction should be a question of law for a judge rather than a jury in a jury trial.

Thus, under the present state of the law, in ruling on the issue of infringement, a judge will first determine the meaning and scope of the patent claims as a question of law, and then a fact-finder, i.e., the jury in a jury trial or the judge in a bench trial, will determine whether the accused device infringes the properly construed claims as a matter of fact either literally or under the doctrine of equivalents.

C. Always Apply Doctrine Absent Literal Infringement

When the record shows no literal infringement, application of the doctrine of equivalents is not a matter of discretion for the trial judge. Hilton Davis, No. 93-1088, slip op. at 16. This necessarily flows from the rationale for determining that infringement under the doctrine is a question of fact. Id. at 15-16.

D. Dissenting Opinions

Three dissenting opinions offered differing perspectives. Judge Plager's dissent propounded the equitable nature of the doctrine and thus the lack of its universal availability, pointing to historical accuracy and public interest. In a second dissent, Judge Lourie also advocated the equitable nature of the doctrine and agreed that additional evidence must be considered, but substantiality of differences did not encompass all the relevant factors. Judge Lourie's dissent outlined a more complex test to be applied by a judge as a discretionary matter. In a third dissent, Judge Nies avoided answering whether the doctrine was a matter of law or equity, yet disagreed that the majority restated the test, rather it had revised it.

V. Conclusion

The Federal Circuit's decision in Hilton Davis hopefully stabilizes the application of the doctrine of equivalents to determine patent infringement. Questions of whether the doctrine of equivalents should be applied by a jury in a jury case and whether the doctrine should always be applied absent literal infringement have been answered with a resounding affirmative. Further, the restated test requires proof of insubstantial differences which can include the Graver Tank tripartite test as well as additional evidence. Nevertheless, it remains to be seen how such additional evidence will influence the determination of infringement under the doctrine of equivalents, as technology and the proffered evidence become more sophisticated.

VI. Postscriptum-Fluxco's Patent Is Infringed

Your client, Fluxco, should be pleased with the holding of Hilton Davis. Although Fluxco's patent is not literally infringed by SuperWeld 500, it is clearly infringed under the doctrine of equivalents because the differences between the claimed flux and the accused flux are insubstantial. See Graver Tank, in which the factual situation was eerily reminiscent to that of your client's problem.

1.See, U.S. Const. Art. I, § 8, cl. 8. 2.See, e.g. Shat-R-Shield, Inc. v. Trojan Inc., 968 F.2d 1226 (Fed. Cir. 1992), Illinois Tool Works Inc. v. Rawlplug Co. Inc., 975 F.2d 868 (Fed. Cir. 1992), and American Home Products Corp. v. Johnson & Johnson, 979 F.2d 216 (Fed. Cir. 1992). 3.See also Valmont Indus., Inc. v. Reinke Mfg. Co., 983 F.2d 1039, 1043, 25 U.S.P.Q.2d 1451, 1454 (Fed. Cir. 1993); Charles Greiner & Co. v. Mari-Med Mfg., Inc., 962 F.2d 1031, 1036, 22 U.S.P.Q.2d 1526, 1529 (Fed. Cir. 1992); London v. Carson Pirie Scott & Co., 946 F.2d 1534, 1538, 20 U.S.P.Q.2d 1456, 1458 (Fed. Cir. 1991); Slimfold Mfg. Co. v. Kinkead Indus., Inc., 932 F.2d 1453, 1457, 18 U.S.P.Q.2d 1842, 1846 (Fed. Cir. 1991); Moleculon Research Corp. v. CBS, Inc., 872 F.2d 407, 409, 10 U.S.P.Q.2d 1390, 1392 (Fed. Cir. 1989); Pennwalt Corp. v. Durand-Wayland, Inc., 833 F.2d 931, 935, 4 U.S.P.Q.2d 1737, 1739 (Fed. Cir. 1987) (en banc), cert. denied, 485 U.S. 961, and cert. denied, 485 U.S. 1009 (1988); Perkin-Elmer Corp. v. Westinghouse Elec. Corp., 822 F.2d 1528, 1532, 3 U.S.P.Q.2d 1321, 1324 (Fed. Cir. 1987). 4.See Hilton Davis, No. 93-1088 at 21; Valmont, 983 F.2d at 1043; London, 946 F.2d at 1538; Slimfold, 932 F.2d at 1457; Moleculon, 872 F.2d at 410; Pennwalt, 833 F.2d at 934-35. 5.See also Corning Glass Works v. Sumitomo Elec. U.S.A., Inc., 868 F.2d 1251, 1261, 9 U.S.P.Q.2d 1962, 1969 (Fed. Cir. 1989), Thomas & Betts Corp. v. Litton Sys., Inc., 720 F.2d 1572, 1579, 220 U.S.P.Q. 1, 6 (Fed. Cir. 1983). 6.Citing Winans v. Denmead, 56 U.S. (15 How.) 330, 338 (1854); SRI Int'l v. Matsushita Elec. Corp., 775 F.2d 1107, 1125, 227 U.S.P.Q. 577, 589 (Fed. Cir. 1985) (en banc). See also Graver Tank, 339 U.S. at 609-610.

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