IP Law Daily, PATENT—Fed. Cir.: Court erred by construing dependent claims broader than independent claims, (Apr 4, 2022)

By Kevin M. Finson, J.D.

A claim construction involving fuse end caps was in error because it resulted independent claims that were narrower than their dependent claims.

The holder of a patent directed to fuse end caps showed that the district court erred in claim construction, the U.S. Court of Appeals for the Federal Circuit has held. The trial court improperly adopted a construction under which independent claims were more limited that their dependent claims (Littelfuse, Inc. v. Mersen USA Ep Corp., April 4, 2022, Bryson, W.).

Littelfuse, Inc. (Littelfuse) was the owner of U.S. Patent No. 9,564,281 (the ’281 patent), which was directed to a “fuse end cap for providing an electrical connection between a fuse and an electrical conductor.” Littelfuse filed suit alleging that Mersen USA EP Corp. (Mersen) infringed the ’281 patent. After claim construction, the parties stipulated to a judgment of non-infringement and Littelfuse appealed the trial court’s claim construction.

Claim construction. The trial court had held, in accordance with Mersen’s argument, that the fuse end cap and fastening stem described in claims 1 and 10 did not cover a single-piece apparatus, meaning one where the end cap was formed from a single piece of material.

The Federal Circuit held that this was not a correct claim construction because it caused inconsistency with the other claims in the patent; claims one and ten were independent claims, which would necessarily be broader than their dependent claims. However, under the trial court’s construction, the independent claims were more limited than their dependent claims, which recited both multi-piece and single-piece designs. “By definition, an independent claim is broader than a claim that depends from it, so if a dependent claim reads on a particular embodiment of the claimed invention, the corresponding independent claim must cover that embodiment as well,” the Federal Circuit explained. The court also noted that a construction that excluded single-piece apparatus was consistent with the specification, and that the trial court erred by using the specification to improperly limit the claims to a preferred embodiment.

The district court recognized the inconsistency between its conclusion that claims 1 and 10 cover only a multi-piece apparatus and the recitation of a single-piece apparatus in claims 8, 9, 19 and 20. The court resolved that inconsistency by inferring that the examiner’s rejoinder of those dependent claims was based “on a misunderstanding of those claims.” The record in this case, however, did not support the conclusion that the examiner made a mistake in rejoining claims 8, 9, 19, and 20, the appellate court said. The court concluded that the claim construction of the “fastening stem” limitation that is most consistent with the claims, specification, and prosecution history did not confine claims 1 and 10 to embodiments in which the fuse end cap was formed from multiple pieces of material.

Finding that the trial court erred in claim construction, the judgment of non-infringement was vacated and the case was remanded for the district court to adopt a new construction of the “fastening stem” limitations that allows for the independent claims to cover both single-piece and multi-piece embodiments.

The case is No. 2021-2013

Attorneys: Thomas J. Meloro (Willkie Farr & Gallagher LLP) for LittelFuse, Inc. Thomas E. Bejin (Bejin Bieneman PLC) for Mersen USA EP Corp.

Companies: LittelFuse, Inc.; Mersen USA EP Corp.

Cases: Patent FedCirNews GCNNews