Federal Circuit Affirms Noninfringement Finding in Ladder Patent Dispute

The U.S. Court of Appeals for the Federal Circuit (CAFC) on Thursday affirmed a district court’s grant of summary judgment of noninfringement in favor of Tricam Industries, Inc. in a patent infringement suit brought by Little Giant Ladder Systems, LLC. The decision held that Tricam’s ladders did not infringe Little Giant’s patent, either literally or under the doctrine of equivalents, and that the district court correctly construed the key claim term “cavity.”

On appeal, Little Giant challenged the district court’s claim construction, its exclusion of Mr. Smith’s infringement opinion, and its summary judgment of noninfringement. Judges Reyna and Freeman joined Judge Chen in the opinion, affirming the district court’s judgment in its entirety.

Little Giant alleged that Tricam’s ladders, which feature a locking mechanism called Speed Lock, infringed its U.S. Patent No. 10,767,416. The ‘416 patent is directed to a multi-position ladder with an improved locking mechanism designed for “enhanced ease of use, stability[,] and safety.” The inventors sought to address the problem of prior art ladders that “can result in the pinching of one[‘s] fingers or hands” and “can be awkward and difficult for some people to perform.”

The district court construed “cavity” as “a hollowed-out space (not passing all the way through),” and the Federal Circuit noted that the parties had “essentially agreed” on this construction. The court also determined that a “substantial amount” of a bracket must be “disposed within” this cavity, meaning “more than a majority” of the bracket is “placed inside of” the hollowed-out space.

Following claim construction, the district court granted Tricam’s motion for summary judgment of noninfringement. The court found no literal infringement because Little Giant’s sole basis for literal infringement of the “cavity” limitation rested on the excluded testimony of its expert, Mr. Smith. The district court explained that the space in Tricam’s Speed Lock handle was “akin to a tunnel that passes all the way through” and therefore could not be a “cavity” as construed. Furthermore, the court found that amendment-based estoppel barred Little Giant from asserting infringement under the doctrine of equivalents.

Little Giant argued that the district court’s construction “contradicts the plain meaning of ‘cavity’ and stands in direct conflict with the intrinsic record.” The Federal Circuit rejected Little Giant’s invitation to rewrite the construction, noting that Little Giant had never argued below or in its opening brief against the inclusion of the phrase “not passing all the way through.” The opinion emphasized that a party may not introduce new claim construction arguments on appeal. The Federal Circuit also pointed to the prosecution history, where the patent examiner had described the cavity as “a hollowed out space in a mass, such as a cavity in a tooth, where the hollowed space doesn’t pass all the way through.”

Furthermore, the Federal Circuit found that Mr. Smith contradicted the court’s construction by “essentially reconstru[ing] the cavity limitation to mean any hollowed-out space that does not pass through in every direction.” Although the claim construction explicitly stated that “the claimed cavity does not include hollowed-out spaces that are unbounded on both ends,” such as a “tunnel” or a “taco shell,” Mr. Smith opined that such spaces would satisfy the cavity limitation. The CAFC held that the district court did not abuse its discretion by excluding Mr. Smith’s infringement opinion “based on a claim construction that is materially different from the construction adopted by the parties and the court.”

On literal infringement, the CAFC noted that Little Giant’s sole argument required prevailing on the “cavity” claim construction. It was undisputed that only 20% of the bracket’s volume was placed within the accused spaces, falling short of the “more than a majority” requirement. The opinion further noted that “‘Little Giant identifies no other evidence’ to support literal infringement.”

Regarding the doctrine of equivalents, the Federal Circuit agreed that prosecution history estoppel applied. During prosecution, the applicant had amended claim 1 to recite “the first bracket is disposed within a cavity defined by the first component” to overcome a prior art reference. The CAFC agreed that the surrendered territory is between “designs where the bracket is concealed between the handle and the rails” and “where it is disposed within a cavity of the handle.” Tricam’s Speed Lock falls within this surrendered territory because “the majority of the bracket is concealed between the handle and the rail simply because that concealment occurs by placing substantial portions of the bracket inside a space that is not a cavity,” the opinion quoted.

The CAFC also rejected Little Giant’s argument that the tangential relation exception to estoppel applied. The district court found “the difference between concealment (or something being hidden between the handle and the rail) and being disposed within a cavity, was at the heart of the amendments.” The Federal Circuit agreed, holding that Little Giant had not met its burden of proving that the objectively apparent reason for the narrowing amendment was only tangentially related to the equivalent in question.