IP Law Daily, PATENT—Fed. Cir.: Infringement rulings vacated and reversed in school-bus sign dispute between commercial lighting makers, (Nov 13, 2025)

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

District court misconstrued the design-patent term “transparency,” and the evidence could not support a jury finding of utility-patent infringement under the doctrine of equivalents.

The U.S. Court of Appeals for the Federal Circuit vacated a jury verdict that had found Opti-Luxx Inc. liable for infringing Smartrend Manufacturing Group (SMG) Inc.’s design patent and reversed the judgment of infringement on SMG's utility patent. The panel held that the district court misconstrued the key design-patent term "transparency," requiring a new trial, and further determined that no reasonable jury could have found infringement of the asserted utility patent under the doctrine of equivalents. The court also ruled that Opti-Luxx had forfeited any objection to SMG's expert testimony but prevailed because the erroneous claim construction tainted the verdict (Smartrend Manufacturing Group (SMG), Inc. v. Opti-Luxx Inc., Nos. 24-1616, 24-1650 (Fed. Cir. Nov. 13, 2025)).

SMG, a manufacturer of illuminated signage products, sued Opti-Luxx, a competing producer of lighting and sign systems for commercial vehicles. Both companies operate in the highly regulated school-bus safety-equipment market, which requires illuminated, legible, and durable warning signage. Their competitive relationship centered on Opti-Luxx’s release of a one-piece LED-illuminated “SCHOOL BUS” sign, which SMG viewed as an imitation of its own modular signage systems.

The dispute involved two patents. First, SMG asserted U.S. Design Patent No. D932,930 (the D930 patent), titled “LED Light Panel,” which claims an ornamental design “as shown and described.” The drawings include oblique-shading lines intended to depict transparency. Second, SMG asserted U.S. Patent No. 11,348,491 (the ’491 patent), which covers an illuminated school-bus sign assembly comprising a translucent panel, opaque lettering, a separate mounting frame, an LED light board, and a spacer that creates a sealed gap between the LEDs and panel.

SMG filed suit in the Western District of Michigan alleging that Opti-Luxx’s single-piece illuminated sign infringed both patents. At trial, the jury agreed with SMG and found infringement. The district court denied Opti-Luxx’s motions for judgment as a matter of law (JMOL), construed “transparency” to include both transparent and translucent surfaces, allowed SMG’s expert to testify as to the ordinary observer’s perspective, and entered a permanent injunction. Opti-Luxx appealed.

Expert testimony and the ordinary observer. On appeal, Opti-Luxx argued that SMG’s expert, Mr. York, lacked the qualifications necessary to testify regarding the ordinary observer for the D930 design. The Federal Circuit declined to reach the question in depth because Opti-Luxx had forfeited its objection. The court emphasized that York’s expert report clearly disclosed his opinions on the ordinary observer, yet Opti-Luxx did not object when SMG moved to admit him as an expert. Citing Sundance, Inc. v. DeMonte Fabricating Ltd., 550 F.3d 1356 (Fed. Cir. 2008), the court held that the district court acted within its discretion in admitting the testimony.

Although it provided extensive discussion of how expert testimony may be used to address the ordinary-observer standard—drawing on Egyptian Goddess, Inc. v. Swisa, Inc., 543 F.3d 665 (Fed. Cir. 2008) (en banc), and Gorham Co. v. White, 81 U.S. 511 (1871)—the court ultimately concluded that any error in admitting York’s testimony was not preserved and did not independently warrant reversal.

Claim construction- “transparency.” The Federal Circuit held that the district court committed reversible error by construing “transparency” to mean both transparent and translucent. Focusing on the design patent’s “as shown and described” clause and the description defining oblique shading lines as denoting transparency, the court concluded that the patentee limited the claim to transparent surfaces. Because the Manual of Patent Examining Procedure permits—but does not require—oblique shading to depict both translucency and transparency, the patentee's express description controlled. The district court's broader construction contradicted the intrinsic record and improperly expanded the scope of the design, contrary to the principles reaffirmed in Curver Luxembourg, SARL v. Home Expressions Inc., 938 F.3d 1334 (Fed. Cir. 2019). The court vacated the design-patent judgment and remanded for a new trial under the correct construction.

Construction of “frame” in the ’491 patent. SMG argued that the district court misconstrued “frame” by limiting it to a “separate, distinct component.” The Federal Circuit rejected that argument, reviewing the intrinsic record de novo under Phillips v. AWH Corp., 415 F.3d 1303 (Fed. Cir. 2005) (en banc). The specification repeatedly distinguished the frame from the sign panel, describing it as a removable mounting structure used for easy replacement, customization, and serviceability. Applying Poly-America, L.P. v. API Industries, Inc., 839 F.3d 1131 (Fed. Cir. 2016), and similar cases, the panel affirmed the district court’s narrow construction and rejected SMG’s attempt to broaden the term to encompass integrated frames.

Doctrine of equivalents. Turning to the doctrine of equivalents, the Federal Circuit held that the district court should have granted JMOL in Opti-Luxx’s favor. The key question concerned the claimed “frame” element. Under the function-way-result test articulated in Graver Tank & Manufacturing Co. v. Linde Air Products Co., 339 U.S. 605 (1950), SMG was required to show that Opti-Luxx’s integrated frame performed substantially the same function in substantially the same way to achieve substantially the same result.

The court held that the ’491 patent’s intrinsic evidence defined the frame’s function with clarity: the frame must be a separate structure that allows the sign panel to be removably received, replaced, and customized without uninstalling the entire device. Drawing on Hill-Rom Co. v. Kinetic Concepts, Inc., 209 F.3d 1337 (Fed. Cir. 2000), the Federal Circuit concluded that no reasonable jury could find equivalence when the accused product undisputedly lacked the ability to remove or exchange the sign panel. SMG’s expert conceded the accused sign was “not capable” of performing those functions. Because SMG failed to prove equivalence for a required claim element, the verdict could not stand.

Thus, the Federal Circuit reversed the utility-patent judgment, vacated the design-patent judgment and the related injunction, and remanded.

The Case is Nos. 24-1616, 24-1650.

Judge: Dyk, T.

Attorneys: Thomas W. Cunningham (Brooks Kushman PC) for Smartrend Manufacturing Group [SMG], Inc. Gaetan Gerville-Reache (Warner Norcross and Judd LLP) for Opti-Luxx Inc.

Companies: Smartrend Manufacturing Group [SMG], Inc.; Opti-Luxx Inc.

Cases: Patent FedCirNews MichiganNews