Our Patent Case Summaries provide a weekly summary of the precedential patent-related opinions issued by the Court of Appeals for the Federal Circuit and the opinions designated precedential or informative by the Patent Trial and Appeal Board.
Ethanol Boosting Systems, LLC, et al. v. Ford Motor Co.
Nos. 24-1381, -1382, -1383 (Fed. Cir. (PTAB) Dec. 23, 2025). Opinion by Chen, joined by Clevenger and Hughes.
EBS sued Ford for infringement of three patents directed to optimized fuel management systems that contain two injection mechanisms (direct injection and port injection) for internal combustion engines. EBS argued that certain “directly injected fuel” terms (the “DI Fuel terms”) should be given their plain and ordinary meaning, while Ford sought a construction requiring that the directly injected fuel be (1) different from the fuel used in the port injection system and (2) contain an anti-knock agent other than gasoline.
While waiting for the district court’s ruling on claim construction, Ford filed three IPR petitions challenging the three asserted patents. In its petitions, Ford proposed giving the DI Fuel terms their plain and ordinary meaning, just as EBS advocated in the district court litigation.
Before the Patent Trial and Appeal Board ruled on whether to institute the IPRs, the district court adopted Ford’s claim construction positions and then granted the parties’ stipulated judgment of noninfringement. EBS appealed, challenging the claim construction ruling.
After the district court’s claim construction ruling, the Board construed the DI Fuel terms to require a fuel different from the fuel used in the port injector, consistent with the district court’s ruling. And the Board held that under this construction, Ford’s prior-art challenges fell short. Ford then petitioned for rehearing, explaining that EBS had appealed the district court’s claim construction and urging the Board to reconsider institution after the Federal Circuit resolves EBS’s then-pending appeal.
As to EBS’s appeal, the Federal Circuit reversed the claim construction. The Board then granted Ford’s rehearing request and instituted the IPRs. At the end of the IPR proceedings, the Board issued Final Written Decisions applying the Federal Circuit’s claim construction and finding all challenged claims unpatentable as obvious. EBS then filed this appeal, raising three main arguments.
First, EBS argued that the Board lacked authority to “stay” its rehearing decision on institution to await the Federal Circuit’s opinion addressing EBS’s challenge to the district court’s claim construction. The Federal Circuit disagreed, explaining that EBS’s argument “effectively asks us to de-institute the IPRs,” which “conflicts with 35 U.S.C. § 314(d)’s reviewability bar for IPR institution determinations and precedent interpreting that provision.”
The Federal Circuit also rejected EBS’s characterization of its challenge as an attack on the Board’s purportedly ultra vires “stay” because EBS failed to “establish[] that the Board truly issued a ‘stay’ at all.” Instead, the Board “simply waited to rule on the rehearing decision until [the Federal Circuit] settled the claim construction,” which was a “sound reason[]” given that the Federal Circuit’s decision “would address the very claim term that the Board hinged its initial denial of institution upon.”
Second, EBS alleged error in the Board’s claim construction of “fuel.” The Board had adopted the Federal Circuit’s claim construction based on EBS’s prior appeal. But in that prior appeal, EBS challenged only one part of the district court’s construction. EBS then relied on the mandate rule to argue that the non-appealed portion of the claim construction was “controlling law,” not only on the district court proceeding but also on the IPR proceedings. The Federal Circuit disagreed because, for example, “our law-of-the-case doctrine—which relates very closely to the mandate rule—does not apply across different cases.”
The Federal Circuit also analyzed and upheld the Board’s applied claim construction, observing that EBS never even asked the Board to construe the DI Fuel terms. The court ruled that “the Board did not abuse its discretion by not evaluating a claim construction argument that neither party raised.” But in any event, the Federal Circuit analyzed the claim construction and “disagree[d] with EBS on the merits.”
Third and finally, the Federal Circuit addressed and rejected EBS’s challenges to the Board’s substantive findings of unpatentability. The Federal Circuit again disagreed with EBS, holding that substantial evidence supported the Board’s findings. Thus, the Federal Circuit affirmed all three Board decisions.