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Patentee brought infringement action against competitor, alleging that competitor's ultrafiltration method for purifying dye infringed patented method under doctrine of equivalents.
Petitioner and respondent both manufacture dyes from which impurities must be removed.
(b) This Court rejects petitioner's primary argument, that the doctrine of equivalents, as set out in Graver Tank in 1950, is inconsistent with, and thus did not survive, particular aspects of Congress' 1952 revision of the Patent Act, 35 U.S.C. § 100 et seq. Petitioner's first three arguments in this regard-that the doctrine (1) is inconsistent with § 112's requirement that a patentee specifically “claim” the covered invention, (2) circumvents the patent reissue process under §§ 251-252, and (3) is inconsistent with the primacy of the Patent and Trademark Office (PTO) in setting a patent's scope-were made in Graver Tank, supra, at 613-615, and n. 3, 70 S.Ct., at 858-860, and n. 3, in the context of the 1870 Patent Act, and failed to command a majority. The 1952 Act is not materially different from the 1870 Act with regard to these matters.
We do, however, share the concern of the dissenters below that the doctrine of equivalents, as it has come to be applied since Graver Tank, has taken on a life of its own, unbounded by the patent claims. There can be no denying that the doctrine of equivalents, when applied broadly, conflicts with the definitional and public-notice functions of the statutory claiming requirement.
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 from 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.
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.”
In our view, the particular linguistic framework used is less important than whether the test is probative of the essential inquiry: Does the accused product or process contain elements identical or equivalent to each claimed element of the patented invention? Different linguistic frameworks may be more suitable to different cases, depending on their particular facts. A focus on individual elements and a special vigilance against allowing the concept of equivalence to eliminate completely any such elements should reduce considerably the imprecision of whatever language is used. An analysis of the role played by each element in the context of the specific patent claim will thus inform the inquiry as to whether a substitute element matches the function, way, and result of the claimed element, or whether the substitute element plays a role substantially different from the claimed element. With these limiting principles as a backdrop, we see no purpose in going further and micromanaging the Federal Circuit's particular word choice for analyzing equivalence. We expect that the Federal Circuit will refine the formulation of the test for equivalence in the orderly course of case-by-case determinations, and we leave such refinement to that court's sound judgment in this area of its special expertise.