Federal Circuit Vacates District Court's Claim Construction Based On Claim Differentiation

In Littelfuse, Inc. v. Mersen USA EP Corp., No. 2021-2013 (Fed. Cir. Apr. 4, 2022), the Federal Circuit vacated and remanded the district court's ruling of non-infringement based on an erroneous claim construction that would leave the dependent claims with no scope.

The patent-in-suit, U.S. Patent No. 9,564,281, is directed to a fuse end cap electrically connecting a fuse and an electrical conductor. The district court accepted Mersen's claim construction that the fuse end cap recited in the independent claims is a multi-piece apparatus. The Federal Circuit disagreed, finding that it may also be a single-piece construction because the dependent claims recite a single-piece apparatus. The Court emphasized that by definition, an independent claim is broader in scope than a dependent claim, and hence an embodiment recited in a dependent claim should also be covered by the corresponding independent claim. Otherwise, the dependent claim would have no scope and thus be