Ring & Pinion Serv. Inc. v. ARB Corp. Ltd

The patent claims an improved automobile locking differential: the differential is a mechanism that allows wheels to rotate at different speeds relative to each other. When locked, a differential distributes torque so that wheels spin at the same rate. R&P sought declaratory judgment that its Ziplocker product did not infringe the patent. Following claim construction, the parties stipulated that the Ziplocker product literally met every limitation of claim 1 except the “cylinder means formed in” limitation, but that the Ziplocker included an “equivalent” cylinder and that the Ziplocker cylinder would have been foreseeable to a person of ordinary skill in the art when the application was filed. The parties agreed that “should the Court hold ... that foreseeability of an equivalent at the time of application prevents use of the doctrine of equivalents,... the accused differential would not infringe under the doctrine of equivalents” or that should the court hold that foreseeability does not prevent use of the doctrine of equivalents, the accused differential would infringe under that doctrine. The district court held that, while foreseeability did not preclude application of the doctrine of equivalents, a finding of infringement under the doctrine would vitiate the “cylinder means formed in” limitation and granted summary judgment of non-infringement. The Federal Circuit reversed, holding that the district court improperly applied the doctrine of claim vitiationView "Ring & Pinion Serv. Inc. v. ARB Corp. Ltd" on Justia Law