Background
Westport Fuel Systems Canada Inc. owns U.S. Patent Nos. 6,298,829 and 6,575,138, which concern directly actuated fuel-injection valves containing a passive hydraulic link. The disputed claims require hydraulic fluid to act substantially as a solid, with its thickness remaining substantially constant while the actuator is activated, while allowing adjustment when the actuator is inactive.
Robert Bosch LLC and Mercedes-Benz USA, LLC petitioned for inter partes review, arguing that the challenged claims would have been obvious over prior-art references Wirbeleit and Klügl. The Patent Trial and Appeal Board found that Bosch had not proved any challenged claim obvious because Klügl did not disclose the disputed hydraulic-link limitation. Bosch appealed the Board’s two final written decisions.
The Court’s Holding
The Federal Circuit affirmed. Substantial evidence supported the Board’s finding that Klügl’s hydraulic fluid did not act substantially as a solid with substantially constant thickness during actuation. Klügl repeatedly described the membrane surrounding its pressure chamber as flexible, and the Board reasonably found that the membrane would flex during actuation, causing the fluid to change shape in a manner inconsistent with the claimed solid-like behavior.
The court also upheld the Board’s decision to discount Bosch’s expert testimony as incomplete, contradictory, and inconsistent with Klügl’s express disclosure. Bosch’s arguments that the membrane might not flex enough to meaningfully change fluid thickness, or that a skilled artisan could design the injector to minimize flexing, lacked adequate record support and conflicted with Klügl’s repeated description of a flexible membrane. The court likewise rejected Bosch’s procedural-error arguments.
Key Takeaways
- An IPR petitioner must prove each disputed claim limitation by a preponderance of the evidence; a reference’s express description can defeat an asserted reading of the prior art.
- The Board may discount expert testimony that is incomplete, internally contradictory, or contradicted by the cited reference.
- Conclusory attorney argument and assertions about how a skilled artisan could redesign a prior-art device do not establish what the reference actually discloses.
Why It Matters
The nonprecedential decision illustrates the evidentiary burden facing IPR petitioners when an obviousness theory depends on a specific physical property or operating behavior in the prior art. Petitioners need record evidence connecting the reference’s disclosed structure to every claimed functional limitation.
It also underscores the deference the Federal Circuit gives to the Board’s factfinding and credibility assessments. Where the Board’s reading of a reference is supported by its text and credible expert evidence, competing interpretations and unsupported design possibilities generally will not justify reversal.