18
Syllabus
skilled in the art would have known of the interchangeability of an ingredient not contained in the patent with one that was. Pp. 24-25. (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, 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. Also unpersuasive is petitioner's fourth argument, that the doctrine of equivalents was implicitly rejected as a general matter by Congress' specific and limited inclusion of it in § 112, ¶ 6. This new provision was enacted as a targeted cure in response to Halliburton Oil Well Cementing Co. v. Walker, 329 U. S. 1, 8, and thereby to allow so-called "means" claims describing an element of an invention by the result accomplished or the function served. Moreover, the statutory reference to "equivalents" appears to be no more than a prophylactic against potential side effects of that cure, i. e., an attempt to limit the application of the broad literal language of "means" claims to those means that are "equivalent" to the actual means shown in the patent specification. Pp. 25-28. (c) The determination of equivalence should be applied as an objective inquiry on an element-by-element basis. The Court is concerned that the doctrine, as it has come to be broadly applied since Graver Tank, conflicts with the Court's numerous holdings that a patent may not be enlarged beyond the scope of its claims. The way to reconcile the two lines of authority is to apply the doctrine to each of the individual elements of a claim, rather than to the accused product or process as a whole. Doing so will preserve some meaning for each of a claim's elements, all of which are deemed material to defining the invention's scope. So long as the doctrine does not encroach beyond these limits, or beyond related limits discussed in the Court's opinion, infra, at 30-34, 39, n. 8, and 39-40, it will not vitiate the central functions of patent claims to define the invention and to notify the public of the patent's scope. Pp. 28-30. (d) Petitioner is correct that Graver Tank did not supersede the well-established limitation on the doctrine of equivalents known as "prosecution history estoppel," whereby a surrender of subject matter during patent prosecution may preclude recapturing any part of that
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