IP Law Daily, PATENT—S.D.N.Y.: Plumbing fixtures maker defeats bid to overturn jury verdict invalidating bathtub design patent, (Jul 28, 2026)

By Saurabh Kashyap, B.A., M.A., LL.B., LL.M.

The court upheld a jury's finding that the asserted design patent was invalid based on an on-sale bar.

A federal district court in New York has denied post-trial motions by plumbing fixtures manufacturer Kohler Co. seeking judgment as a matter of law or a new trial after a jury found its asserted bathtub design patent invalid under the on-sale bar. The court also granted in part a motion by plumbing products distributor Signature Plumbing Specialties LLC for attorney fees, concluding that several of Kohler's patent claims were exceptionally weak, while declining to award fees for the claim that proceeded to trial or for dismissed state-law claims (Kohler Co. v. Signature Plumbing Specialties LLC, No. 1:23-cv-09686-AS-SDA (S.D.N.Y. Jul. 24, 2026)).

Dispute. The plaintiff, Kohler Co., manufactures bathtubs, faucets, and other plumbing fixtures. The defendant, Signature Plumbing Specialties LLC, distributes plumbing products. Kohler sued Signature for infringing several design patents covering plumbing fixtures and also asserted state-law claims for tortious interference and unfair competition. The court dismissed the state law claims and two patent claims, and Kohler later voluntarily dismissed all but one remaining patent claim.

The case ultimately centered on U.S. Design Patent No. D678,487 (the ’487 patent), which claims the ornamental design of a bathtub. Kohler alleged that Signature's BT2092 bathtub infringed the patent.

Signature argued that the '487 patent was invalid under the on-sale bar because it had sold an earlier bathtub model, the BT2006, more than one year before Kohler applied for the patent. According to Signature, the BT2092 differed from the BT2006 only by a one-inch increase in height required for Americans with Disabilities Act compliance and otherwise embodied the same design. After a bifurcated two-day trial limited to the invalidity issue, the jury found the '487 patent invalid, prompting both parties to file post-trial motions.

Invalidity challenge. Kohler first argued that the evidence presented at trial was legally insufficient to support the jury's finding of an invalidating prior sale. It criticized testimony from Signature founder Keith Kugler and contended that his account lacked adequate corroboration.

The court rejected those arguments, emphasizing that the jury had heard testimony, invoices, diagrams, photographs, and other documentary evidence supporting Signature's contention that the BT2006 had been sold to a Manhattan residential development in 2008, years before the patent's critical date. While Kohler highlighted perceived weaknesses in Kugler's testimony, those points raised only factual disputes that the jury was entitled to resolve. The court explained that it could not reassess witness credibility or substitute its judgment for that of the jury when reviewing a Rule 50 motion.

The court also rejected Kohler's contention that the testimony was insufficient because it came from an interested witness. Unlike cases relying solely on uncorroborated oral testimony, Signature had introduced numerous invoices, diagrams, specification sheets, and photographs corroborating Kugler's account. Viewed collectively, that evidence satisfied the Federal Circuit's corroboration requirements for proving an invalidating prior sale.

Vanmoor doctrine. Kohler next challenged the court's application of Vanmoor v. Wal-Mart Stores, Inc., 201 F.3d 1363, 1366 (Fed. Cir. 2000), arguing that Signature could not rely on Kohler's infringement allegations to establish invalidity because the earlier BT2006 and the accused BT2092 were different products.

The court disagreed. It found that the record established only a single physical difference between the two bathtubs—a 1-inch increase in height to comply with ADA requirements. Kohler repeatedly asserted that the products differed but never presented any evidence of a meaningful design distinction. Because the designs were otherwise identical, the court held that Vanmoor applied. Under that decision, a defendant may accept the plaintiff's infringement allegations solely for purposes of proving an on-sale bar defense, even while separately contesting infringement.

The court concluded that the one-inch height difference did not create a different design as a matter of law. Comparing the situation to shoes of different sizes sharing the same design, the court held that differences in dimensions alone did not alter the claimed ornamental design. Accordingly, once the jury found that the BT2006 had been sold before the critical date, the prior sale anticipated the asserted design patent.

Other post-trial issues. The court also rejected Kohler's remaining requests for a new trial. It found no abuse of discretion in bifurcating the invalidity trial from infringement issues and rejected Kohler's Seventh Amendment arguments as both procedurally forfeited and substantively meritless. The court likewise upheld its jury instructions, evidentiary rulings, and decision not to conduct claim construction, concluding that none of the alleged errors individually or cumulatively justified disturbing the jury's verdict.

Attorney fees. Applying the Supreme Court's Octane Fitness standard, the court concluded that three patent claims involving faucet designs constituted exceptional cases because Kohler failed to meaningfully investigate dispositive prior-art issues, neglected readily available evidence undermining its claims, or advanced infringement theories that were objectively weak. Those claims involved U.S. Design Patent Nos. D767,732, D823,988, and D613,824.

By contrast, the court declined to award fees relating to the bathtub patent that proceeded to trial. Although Kohler ultimately lost before the jury, its invalidity challenge had survived summary judgment and raised genuine factual disputes regarding the alleged prior sale. The court also refused to award fees for another patent claim that Kohler voluntarily dismissed during litigation or for the dismissed state-law tort claims, concluding that those aspects of the case did not stand out sufficiently to justify fee shifting. The amount of recoverable fees was referred to a magistrate judge for a report and recommendation.

The Case is No. 1:23-cv-09686-AS-SDA.

Judge: Subramanian, A.

Attorneys: Kadie M. Jelenchick (Foley & Lardner, LLP) for Kohler Co. Michael P. Kahn (Akin Gump Strauss Hauer & Feld LLP) for Signature Plumbing Specialties LLC.

Companies: Kohler Co.; Signature Plumbing Specialties LLC

Cases: Patent NewYorkNews