It’s Not the Size of the Chamber That Matters, It’s How You Describe It in the Intrinsic Record

| Brandon G. Smith


Before Chen, Cunningham, and Stark. Appeal from the United States District Court for the Southern District of Texas.

Summary: Terms of degree are not indefinite when the specification provides guidance as to their meaning.

Grace Instrument Industries (“Grace”) brought an infringement claim against Chandler Instruments for infringement of its patent for a viscometer, a device used by oil and gas drillers to test the viscosity of a drilling fluid sample in a lab setting before it is used downhole. The District Court held that the term “enlarged chamber” was indefinite based, in part, on dictionary definitions because it necessarily required a comparison against some baseline that was not provided in the specification.

The Federal Circuit overturned the indefiniteness finding for “enlarged chamber,” instead adopting a construction that required the chamber to be “large enough” to perform a function. The court reasoned that the intrinsic record explained that the size of the enlarged chamber was determined based on whether it was “large enough to accomplish a particular function,” not whether it was “larger than some [undefined] baseline object.” Thus, the intrinsic record provided sufficient guidance to the skilled artisan as to the meaning of “enlarged chamber,” and the term was not indefinite.

The parties also disputed the construction of certain means-plus-function terms, and specifically the structure required to perform the claimed function. Here, the Federal Circuit affirmed the district court’s construction, agreeing that the district court’s construction was consistent with the language of the claim and the intrinsic record as a whole. The Federal Circuit also found Grace’s arguments for alternative construction to rely on circular logic that was unpersuasive.

Editor: Paul Stewart

Sara Witty (California Admission Pending)