“The Patent Act allows an inventor to claim an element of his invention by the function it performs rather than by its precise structure. Such a claim covers ‘the corresponding structure’ the specification discloses for performing the function ‘and equivalents thereof.’ 35 U.S.C. § 112(f). One structure is equivalent to another if it performs ‘substantially the same function in substantially the same way to obtain the same result.’ Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605, 608 (1950) (quotation marks omitted). Equivalence ‘is a determination of fact,’ and a key consideration is whether skilled artisans ‘would have known of the interchangeability’ of the substituted feature. Id. at 609; see Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17, 36 (1997) (interchangeability bears on ‘whether the accused device is substantially the same as the patented invention’). The Federal Circuit affirmed summary judgment of noninfringement under a different rule. Whatever the patentee proves about the two structures as wholes, the court held, it loses as a matter of law unless it also goes through the disclosed structure component by component and, for each one not found in the accused device, explains why that component may be disregarded, as though the individual components of the disclosed structure were themselves elements of the claim. See Pet. App. 12a-14a.”
“The Question Presented is: Whether a patentee’s statutory entitlement to ‘equivalents thereof’ under 35 U.S.C. § 112(f) may be extinguished as a matter of law, regardless of the evidence comparing the structures as wholes, whenever the patentee does not separately account for each component of the disclosed structure or explain why any should be omitted.”
