IP Law Daily, PATENT—Fed. Cir.: Claim construction errors warrant reversal of summary judgment in paint atomizer dispute, (Mar 23, 2026)

By Kevin M. Finson, J.D.

Assertions of infringement of a patent for a rotary atomizer must go to the jury because the description of a shape as “generally” or “substantially” conical did not necessarily exclude or include the accused product, which contained some undulation or curvature.

Although a district court properly excluded expert testimony of a person qualified in paint and color matching, the court incorrectly construed key claim terms, warranting reversal of a grant of summary judgment in favor of an accused infringer, the U.S. Court of Appeals for the Federal Circuit has held. The relevant art for the patent claims in question was fluid dynamics involved in rotary atomizer design. In the Federal Circuit’s view, the district court erred in construing “generally conical/substantially conical” to exclude any curves or undulations and erred in construing “rear cover attached to the bell cup” to require that the rear cover and bell cup be formed from separate pieces. A jury trial was required under the correct constructions to determine if the accused product infringed the asserted claims (Durr Systems, Inc. v. EFC Systems, Inc., No. 24-2158 (Fed. Cir. Mar. 20, 2026)).

Patents-in-suit. Durr Systems, Inc., owned the five patents-in-suit, which shared a specification and were directed to rotary atomizers for particulate paints. The patented rotary atomizer included a bell cup with features that encouraged laminar (nonturbulent) flow and thus produced uniform paint droplets that lie flat on the surface. A key feature of the patented atomizer was the bell cup’s “generally conical overflow surface.”

Infringement allegations. Durr sued EFC Systems, Inc. for infringement. EFC manufactured and sold a bell cup that was useable in Durr’s rotary atomizers. EFC’s bell cup’s overflow surface was slightly curved, and its rear cover was not made from a separate piece from the bell cup itself. The district court granted EFC’s motion to exclude Durr’s expert and then granted summary judgment in favor of EFC. Durr appealed.

Claim construction. Durr argued that the district court erred in construing the limitation “generally/substantially conical” surface as a “surface that consists of one or more conical portions but without undulations or curved portions (e.g., a surface consisting of portions of two cones, etc.)” The appellate court concluded that the terms “generally” and “substantially” gave enough leeway that the described surface could include some undulations or curved portions and still remain conical enough to fall within the claimed shape. A jury trial would be required to determine if the accused product fell within the scope of the claim.

Expert testimony. Durr’s proposed expert’s area of expertise was paint and color matching, not the fluid dynamics of rotary atomizers. The court found no error in the trial court’s determination that a person of ordinary skill in the art would be someone with knowledge of fluid dynamics, and therefore it did not err in excluding the paint and color matching expert.

Conclusion. The court affirmed the decision to exclude Durr’s expert witness’s testimony and reversed the claim construction underlying the summary judgment decision, remanding the case for further proceedings on that issue.

The Case is No. 24-2158.

Judge: Dyk, T.

Attorneys: Jeffrey A. Lamken (MoloLamken LLP) for Durr Systems, Inc. Travis William Bliss (Panitch Schwarze Belisario & Nadel LLP) for EFC Systems, Inc.

Companies: Durr Systems, Inc.; EFC Systems, Inc.

Cases: Patent FedCirNews