Federal Circuit Places Limits on Numerical Amount in Patent Claim

Interpreting a numerical claim limitation requires examining the specification and prosecution history, rather than acontextually performing a significant digits analysis

In reversing a district court’s claim construction of an amount expressed as 0.001%, the Federal Circuit recognized that the ordinary meaning of the amount would allow, as the district court found, rounding of amounts of 0.0005% to 0.0014% to satisfy the term, as the amount was expressed as a single significant digit. Nevertheless, the Federal Circuit, in a “close call,” construed the term in view of the context of the specification, which disparaged formulations having slightly different amounts, including 0.0005%, and prosecution history where the patentee took out broad qualifiers such as “about” and the other different amounts from the claims.

Accordingly, it construed 0.001% as that precise number, with only minor variations, i.e., 0.00095% to 0.00104% and remanded for the district court to find in the first instance whether the accused product infringes the asserted claims under the proper claim construction.

Also, in affirming a determination of nonobviousness, the Federal Circuit found substantial evidence that the prior art relied upon taught away from the proposed combination.