Under Kennametal, a prior art reference with a missing limitation is not sufficient to establish anticipation simply because a skilled artisan would “at once envisage” the limitation 

The alleged infringer petitioned for an inter partes review of an independent claim of a patent, directed to a method for controlling torque in an electric motor. The Patent Trial and Appeal Board (PTAB) relied on Kennametal Inc. v. Ingersoll Cutting Tool Co., 780 F.3d 1376, 1381 (Fed. Cir. 2015) to hold the challenged claim as unpatentable based on anticipation.

On appeal, the Federal Circuit reversed the PTAB’s finding. The court held that the PTAB had improperly applied Kennametal, explaining that the anticipation standard in Kennametal does not stand for the proposition that a prior art reference missing a claimed limitation could nonetheless anticipate the claim if a skilled artisan “would at once envisage” the missing limitation. Rather, Kennametal is limited to whether the disclosure of a limited number of combination possibilities discloses one of the possible combinations. 

Unlike in Kennametal, where the prior art reference disclosed both the elements of the challenged claim and further taught a limited number of combination possibilities of the disclosed elements, the prior art reference here did not in fact disclose an element of the claimed invention and could not support the PTAB’s finding of anticipation. The Federal Circuit concluded that “Kennametal does not permit the PTAB to fill in missing limitations simply because a skilled artisan would immediately envision them.”