In re Donaldson Co., Inc.

Holding that 35 U.S.C. § 112 ¶ 6, which limits means-plus-function claims to the structures described in the specification and their equivalents, "applies regardless of the context in which the interpretation of means-plus-function language arises, i.e., whether as part of a patentability determination in the PTO or as part of a validity or infringement determination in a court"