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 meaningless. The Court also cautioned that even though the specification only directly referenced a multi-piece apparatus, a single-piece construction is not excluded because the claimed invention should not be limited to preferred embodiments or specific examples in the specification.