U.S. Patent No. 8,011,458 is directed to a steering system in a zero turn radius (ZTR) vehicle (pages 2-3). The claim recites a “mechanical control assembly . . . configured to,” which was held to not be a means-plus-function term by the district court (pages 2-3 and 5-7). “Mechanical control assembly” is similar to other black-box words held to be nonce terms like means (page 11). The coupling to specific devices in the claim connotes structure, but this is offset by the functional language (pages 11-12). “Mechanical control assembly” does not have an established meaning in the art for structure but instead operates as a generic label (page 12). The specification teaching of a ZTR control assembly with structural details is mere disclosure of a structure that corresponds to the “mechanical control assembly,” not an indication of a specific structure for the limitation (page 13). There is no indication in the specification that the nonce term is being defined as the ZTR control assembly and such interpretation would render the functional language superfluous (page 14). The prosecution history indicating the limitation as structural deals with the limitation outside the means-plus-function context and is not inconsistent with a means-plus-function interpretation (pages 14-15). The limitation “mechanical control assembly” is a mean-plus function limitation (page 15).
Hindsight: To use means-plus-function for narrowing a claim, recite “means.” For other terms, recite known structure or define the term with the definition being structural. Use the specification to make it clear that the term is structural. Rather than reciting a defined, generic term, a list of alternative structures (i.e., the species) may be recited with the risk of avoiding infringement by using an non-recited species.