Means-Plus-Function Construction Can Lead to Indefiniteness

In Unicorn Global Inc. v. Golab, Inc. No. 3:19-CV-0754-N (N.D. Tex. May 26, 2020), the Northern District of Texas construed several disputed terms of U.S. Patent No. 9,376,155 and U.S. Patent No. 9,452,802, and found claims to be indefinite means-plus-function claims without having structure described in the specifications. The patents are directed to personal transportation devices known as hoverboards which include a divided platform with wheels on opposite ends. A rider stands on the platform and tilts halves of the platform to control movement of the hoverboard.

Most notable of the construed claim terms was “limiting shaft.” Plaintiff and patent owner Unicorn conclusorily asserted that the term should be given its plain and ordinary meaning. Defendant and alleged infringer Golab argued that “limiting shaft” was means a plus-function term and could not be defined. The court started by stating that the term “sounds like a structural element” and was presumed not to be means-plus-function because there was no specific recitation of “means.” However, the court determined that the presumption was rebutted because “limiting shaft” clearly described a function, i.e., limiting relative rotation between two objects connected by the shaft, and further because Unicorn failed to provide evidence that described a structure of  the “limiting shaft” or what a person skilled in the art would understand as a plain and ordinary meaning of the term. After construing “limiting shaft” as means-plus-function recitation, the court found the term was indefinite under section 112 because Unicorn failed to identify structure.

Golab also argued that “rotating mechanism” was means-plus-function. Both Golab and Unicorn provided their own expert testimony regarding whether the term would connotate particular structure to a person skilled in the art. Ultimately the court found Unicorn’s expert more persuasive, highlighting portions of Unicorn’s expert testimony that included portions of the patents and prior art describing structure that a person of ordinary skill would recognize as a “rotating mechanism. The court also pointed to claim differentiation and other court cases construing “mechanism” as not a nonce word that invokes means-plus-function construction and concluded that “rotating mechanism” is not a means-plus-function recitation.

As an interesting aside, the court also found in Unicorn’s favor for a reminder of the other terms in dispute. Many of Golabs’ arguments appeared overreaching, with the court describing Golab as “load[ing] up a relatively simple term with a variety of baggage from the specification.”

Lessons for Practice

This case highlights the importance of being mindful when modifying nouns with verbs in the claims, as such terms may be construed as means-plus-function terms. Developing a diverse claim set may be beneficial to against means-plus-function construction. Describing sufficient structure in the specification may help avoid definitions. In the case at hand, Unicorn’s claim may have fared better had the patents described sufficient structure or had narrowing dependent claims directed toward the limiting shaft. Perhaps simply claiming the “limiting shaft” as a “shaft” may have been enough.