Claim construction should not be limited by the goal of the patent unless the goal could not be achieved with alternative construction; terms should be construed with an eye toward use of the same term in related patents.

A party found to infringe a patent initiated ex parte reexamination proceedings to challenge the validity of the infringed, but now expired, claims. The Board of Patent Appeals and Interferences (the “Board”) held that one infringed claim was invalid as anticipated by prior art based on its claim construction. The patentee appealed, stating that the Board improperly construed a claim term by not including two functional limitations.

The Federal Circuit affirmed the Board’s decision, rendering the claim invalid. Because the Board was construing an expired patent, it properly used the more thorough analysis of a district court, and did not follow the practice of using the broadest reasonable construction. 

Regarding the first functional limitation, the panel found that, absent “words of manifest exclusion or clear disavowals,” a claim term should not be restricted to only the preferred embodiments. Further, because the claim term was not shown to be a term of art, the ordinary meaning of the term based on the context of the claims, specification, and prosecution history was applied. Finally, in other patents within the same family, the claim term at issue was differentiated from other claims that specifically claimed the functional limitation sought by the patentee. Because claim terms in related patents have the same meaning, unless otherwise compelled, the doctrine of claim differentiation warranted affirming the Board’s construction.

Regarding the second functional limitation, the panel rejected the notion that the goal of the invention required its inclusion. Because the goal could still be achieved, albeit less efficiently, that doctrine did not preclude an alternative construction. The Federal Circuit affirmed the Board’s construction because the limitation must be present for the claim to function as written. Under the Board’s affirmed construction, the identified prior art anticipated the claim at issue.

A copy of the opinion can be found here.