In MTD Products Inc. v. Iancu, [2017-2292] (August 12, 2019), the Federal Circuit vacated the Board’s obviousness determination, ruling that the Board erred in finding the term “mechanical control assembly” was not a means-plus-function term governed by § 112, ¶ 6.

U.S. Patent No. 8,011,458 discloses a steering and driving system for zero turn radius (“ZTR”) vehicles. Both of the independent claims contain the phrase “mechanical control assembly.”

The essential inquiry of whether a claim element invokes § 112, ¶ 6 is not merely the presence or absence of the word “means” but whether the words of the claim are understood by persons of ordinary skill in the art to have a sufficiently definite meaning as the name for structure. One way to demonstrate that a claim limitation fails to recite sufficiently definite structure is to show that, although not employing the word “means,” the claim limitation uses a similar nonce word that can operate as a substitute for “means” in the context of § 112, ¶ 6. Generic terms like “module,” “mechanism,” “element,” and “device” are commonly used as verbal con-structs that operate, like “means,” to claim a particular function rather than describe a sufficiently definite structure. Even if the claims recite a nonce term followed by functional language, other language in the claim might inform the structural character of the limitation-in-question or otherwise impart structure to the claim term.

In assessing whether the claim limitation is in means-plus-function format, one does not merely consider an introductory phrase (e.g., “mechanical control assembly”) in isolation, but look to the entire passage, including functions performed by the introductory phrase. The ultimate question is whether the claim language, read in light of the specification, recites sufficiently definite structure to avoid § 112, ¶ 6.

The Federal Circuit agreed with the Board that the term “mechanical control assembly” is similar to other generic, black-box words that it has held to be nonce terms similar to “means” and subject to § 112, ¶ 6 because the term does not connote sufficiently definite structure to one of ordinary skill in the art. The Federal Circuit further agreed that the rest of the claim language of the disputed phrase is primarily, but not entirely, functional.

The Federal Circuit said, however, that the Board erred when it relied on the specification’s description of a “ZTR control assembly” to conclude that the claim term “mechanical control assembly” had an established structural meaning. The fact that the specification discloses a structure corresponding to an asserted means-plus-function claim term does not necessarily mean that the claim term is understood by persons of ordinary skill in the art to connote a specific structure or a class of structures.

The Federal Circuit found that the Board’s analysis implied that so long as a claim term has corresponding structure in the specification, it is not a means-plus-function limitation. This view would leave § 112, ¶ 6 without any application, because any means-plus-function limitation that met the statutory requirements, i.e., which includes having corresponding structure in the specification, would end up not being a means-plus-function limitation at all.

The Federal Circuit also disagreed with the Board’s interpretation of the prosecution history, finding that arguing that a limitation connotes structure and has weight is not inconsistent with claiming in means-plus-function format since means-plus-function limitations connote structure.

Given the lack of any clear and undisputed statement foreclosing application of § 112, ¶ 6, the Federal Circuit concluded that the Board erred in giving dispositive weight to the equivocal statements it cited in the prosecution history.