The U.S. Court of Appeals for the Federal Circuit recently reiterated the rule of Warner-Jenkinson, that the doctrine of equivalents will not be applied so broadly as to wholly eliminate a limitation recited in a claim. Cooper Cameron Corp. v. Kvaerner Oilfield Products Corp., Nos. D1-1383, -1408 (Fed. Cir. May 14, 2002).

Cooper owns patents related to subsea wellheads that protect the well during maintenance and repair. The claim at issue recites, "[a] wellhead comprising … a workover port extending laterally through the wall of the spool tree from between the two plugs" (emphasis added). The accused device had a workover port placed above the two plugs. Cooper claimed infringement of its patent under the doctrine of equivalents.

The Federal Circuit affirmed the district court’s grant of summary judgment, holding that the defendant’s workover port enters the wellhead assembly "above" the two plugs, which "cannot be equivalent to a connection ‘between the two plugs.’" The Court rejected Cooper’s argument that the location of the workover port was irrelevant to its operation and thus was not an essential element to the claim, reasoning that to ignore Cooper’s decision to include "between" as a limitation in the claim would vitiate the limitation, in violation of the all-limitations rule.

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