The US Court of Appeals for the Federal Circuit reversed a preliminary injunction in a patent infringement action, finding that the district court’s claim construction raised, at a minimum, substantial questions regarding infringement and that the patentee failed to establish irreparable harm. Ridge Corp. et al. v. Kirk NationaLease Co. et al., Case No. 25-1254 (Fed. Cir. July 13, 2026) (Dyk, Mayer, Taranto, JJ.)

Ridge Corporation, the exclusive licensee of manufacturer Cold Chain’s patent directed to an insulated overhead door, sued truck leasing and maintenance company Kirk NationaLease Co. (KNL) for patent infringement, tortious interference with business relationships, and false patent marking. After the Federal Circuit vacated an initial preliminary injunction because Ridge lacked standing to sue without the patent owner, Cold Chain joined the present action as a plaintiff. The district court again granted a preliminary injunction, concluding that the plaintiffs had demonstrated a likelihood of success on the merits. KNL appealed.

KNL argued that the district court improperly construed several disputed claim limitations and, therefore, erred in concluding that the plaintiffs were likely to succeed on the merits. The Federal Circuit agreed, explaining that a preliminary injunction should not issue where an accused infringer raises one or more substantial questions concerning infringement – questions that the patentee cannot show lack substantial merit.

The Federal Circuit identified three claim limitations that raised substantial questions of noninfringement:

• The district court improperly construed the limitation requiring a panel that is “flexible along the entire length of the panel,” explaining that both the claim language and prosecution history supported a narrower construction.
• The accused product raised a substantial question regarding the limitation requiring that “foam insulating material” form the second outermost surface of the door because the prosecution history distinguished prior art sandwich constructions on that basis.
• The district court construed the term “insulated overhead door” too broadly, explaining that the specification and industry evidence supported construing the term as referring to a door suitable for cold-storage applications.

The Federal Circuit also determined that the district court erred in finding irreparable harm. Ridge asserted that it had reduced prices because of the defendants’ allegedly infringing products, but the Court found no evidence establishing the required causal nexus between the accused sales and Ridge’s pricing decisions. The Court likewise rejected Ridge’s reliance on its false-marking and tortious-interference claims because there was no credible evidence that the challenged conduct was likely to recur, making prospective injunctive relief inappropriate.

Practice note: This decision illustrates that a patentee seeking preliminary injunctive relief must establish more than a plausible infringement theory. Where the accused infringer raises substantial questions regarding claim construction or infringement, a preliminary injunction is inappropriate.