|Do you foresee a bright future |
for the doctrine of equivalents?
The case originated from a declaratory judgment action for non-infringement filed by Ring & Pinion Services against ARB Corporation, before the District Court for the Western District of Washington. The plaintiff sought declaratory judgment that one of its products did not infringe US Patent No. 5,591,098, which claimed an improved automobile locking differential. The parties agreed that the plaintiff's product met every limitation of Claim 1 of the '098 patent, except the limitation concerning 'cylinder means formed in said differential carrier and housing an actuator position[ed] to cause movement of said locking means relative to said carrier'. They also acknowledged that the product included an 'equivalent' cylinder, which would have been foreseeable to a person of ordinary skill in the art at the time of patent filing. In light of these considerations, the parties stipulated that the outcome of the case depended upon the resolution of a single legal issue, namely whether foreseeability precluded the application of the doctrine of equivalents. The district court provided a negative answer to this question, holding that foreseeability of an equivalent at the time of application did not prevent use of the related doctrine. The court, however, ruled that a finding of infringement under the doctrine of equivalents would have vitiated the claim limitation. Thus, it granted summary judgment of non-infringement to the plaintiff.
The Federal Circuit clarified that '[t]here is not, nor has there ever been, a foreseeability limitation on the application of the doctrine of equivalents'. In this perspective, the panel recited previous case law according to which 'known interchangeability' is a key factor to be taken into account when establishing infringement under the doctrine of equivalents analysis (see, inter alia, Abraxis Bioscience Inc. v Mayne Pharma Inc. and Interactive Pictures Corp. v Infinite Pictures Inc.). It also rejected Ring & Pinion's reliance on Sage Products Inc. v Devon Industries Inc. and on Chiuminatta Concrete Concepts Inc. v Cardinal Industries Inc.. With regard to the first case, the court observed that it merely recognized the possibility that a finding of infringement under the doctrine of equivalents may vitiate a claim limitation. On the second case, the judges clarified that:
In Chiuminatta, we explained that there are two differences between the equivalence determination made for literal infringement purposes under § 112(f) and a doctrine of equivalents determination for the same limitation: timing and function. Equivalence under section 112(f) is evaluated at the time of issuance [Al-Site Corp. v VSI International Inc.]. Equivalence under the doctrine of equivalents, in contrast, is evaluated at the time of infringement. Hence, an after-arising technology, a technology that did not exist at the time of patenting, 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 § 112(f).The appellate court, however, did not uphold the judgment of non-infringement rendered at first instance, noting that claim vitiation 'is not an exception to the doctrine of equivalents, but instead a legal determination that the evidence is such that no reasonable jury could determine two elements to be equivalent' (Deere & Co. v Bush Hog LLC). The panel noted that, in the case in hand, the parties had jointly stipulated to equivalence, agreeing that there were no remaining issues of fact. Thus, it concluded that the district court should have granted summary judgment of infringement to the patentee, in light of its findings on the applicability of the doctrine of equivalents, and of the parties' joint stipulation.
The second difference between literal infringement and doctrine of equivalents infringement under § 112(f) relates to the function of the element. For literal infringement, the accused structures must perform the function recited in the claim (identical function). The doctrine of equivalents covers accused structures that perform substantially the same function in substantially the same way with substantially the same results. The doctrine of equivalents thus covers structures with equivalent, but not identical, functions. This is true whether the accused equivalent was known at the time of patenting or later arising.