In determining the scope of patent protection under a patent, the claims are construed literally to determine whether the accused product infringes the patent’s claims. If infringement is not literally found, then a determination is made whether those elements or limitations not literally found in the accused product can nevertheless be found to encompass the accused product under the doctrine of equivalents.
The doctrine of equivalents is a court-made doctrine to prevent infringers from altering one minor element of a claim to avoid infringement. The doctrine of equivalents can effectively broaden the scope of the claims of the patent to include insubstantial changes. However, the doctrine of equivalents is also limited by other considerations. For example, if the patent applicant clearly disavowed subject matter during prosecution or in the patent specification, then the doctrine of equivalents cannot be relied upon to encompass that disavowed subject matter.
In Ring & Pinion Service, Inc. v. ARB Corp. Ltd. (Fed. Cir. 2014), the appeal was directed to whether the foreseeability of an equivalent structure would prevent the application of the doctrine of equivalents to broaden the scope of a claim limitation. R & P relied on two different cases to argue that foreseeability of an equivalent structure prevents broadening of the claim limitations, namely, Sage Products, Inc. v. Devon Ind., 126 F.3d 1420 (Fed. Cir. 1997) and Chiuminatta Concerte Concepts, Inc. v. Cardinal Industries, Inc., 145 F.3d 1303 (Fed. Cir. 1998).
The Federal Circuit disagreed. The Federal Circuit stated that:
“There is not, nor has there ever been, a foreseeability limitation on the application of the doctrine of equivalents.”
The Federal Circuit reasoned that if foreseeability was a limitation to the application of the doctrine of equivalents, then it would directly conflict with other rules. In particular, it has long been clear that known interchangeability weighs in favor of finding infringement under the doctrine of equivalents. If the doctrine of equivalents can be used to broaden claim limitations to include known interchangeable components, then a rule that foreseeability limits the application of the doctrine of equivalents would be in conflict with such holdings.
Moreover, the Federal Circuit clarified that Sage Products is not on point. That court held that claim vitiation, not foreseeability, prevented the application of the doctrine of equivalents. The Chiuminatta case dealt with the issues of timing and function with respect to the doctrine of equivalents and equivalence under section 112(f) (means-plus-function limitations), not foreseeability.
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