Addressing the doctrine of equivalents infringement of a means-plus-function limitation, the U.S. Court of Appeals for the Federal Circuit reversed and remanded a grant of summary judgment of non-infringement based on an improper application of the doctrine of claim vitiation and a disregard of the parties’ joint stipulation, finding that there is no foreseeability bar to the application of the doctrine of equivalents. Ring & Pinion Service, Inc. v. ARB Corp. LTD., Case No. 13-1238 (Fed. Cir., Feb. 19, 2014) (Moore, J.).
Ring & Pinion sued ARB seeking a declaratory judgment of non-infringement by its automobile locking differential. The parties agreed that Ring & Pinion’s product literally satisfied every limitation of the asserted claim except a “cylinder means” limitation. The parties further agreed that the accused product included an “equivalent” cylinder and that the equivalent cylinder in Ring & Pinion’s product would have been foreseeable to a person having ordinary skill in the art at the time the application for the asserted patent was filed.
The parties stipulated that infringement would be determined by resolution of a single legal issue: whether an equivalent is barred under the doctrine of equivalents because it was foreseeable at the time of the patent application. The district court found that, while foreseeability did not preclude the application of the doctrine of equivalents, a finding of equivalence in this case would vitiate the “cylinder means” limitation. After the district court granted summary judgment of non-infringement to Ring & Pinion, ARB appealed.
The Federal Circuit explained that there is not, nor has there ever been, a foreseeability limitation on the application of the doctrine of equivalents. Excluding equivalents that were foreseeable at the time of patenting would directly conflict with precedent that “known interchangeability” supports infringement under the doctrine of equivalents.
Similarly, the Federal Circuit found that there is no foreseeability bar to the application of the doctrine of equivalents in the context of means-plus-function limitations. The Court explained that there are two differences between the equivalence determination made in the context of literal infringement under § 112(f) and a doctrine of equivalents determination for the same limitation: timing and function. Regarding timing, equivalence under section 112(f) is evaluated at the time of issuance, whereas equivalence under the doctrine of equivalents is evaluated at the time of infringement. Hence, an after-arising technology can be found to be an equivalent under the doctrine of equivalents even though it cannot be an equivalent under the literal infringement analysis of.
Regarding function, a finding of non-infringement under § 112(f) based solely on the lack of identical function does not preclude a finding of equivalence under the doctrine of equivalents. However, when the accused technology was known at the time of patenting and the functions are identical, the structural equivalence inquiry under § 112 and the structural equivalence portion of the doctrine of equivalents are coextensive.
The Federal Circuit then turned to the district court’s application of the doctrine of claim vitiation, that it is improper under the doctrine of equivalents to read a claim element to encompass an accused product where such a reading would essentially “vitiate” that claim element. The Federal Circuit found that the district court erred by finding, on summary judgment, that capturing the accused cylinder design as an equivalent to the recited “cylinder means” limitation would vitiate the claim limitation as a matter of law simply because of the parties’ joint stipulation on equivalence.