The US Court of Appeals for the Federal Circuit addressed the
tension between the intrinsic and extrinsic record in claim
construction, holding that the intrinsic record should be relied on
first. The Court therefore reversed a district court finding of
indefiniteness based on dictionary definitions and expert
testimony. Grace Instrument Industries, LLC v. Chandler
Instruments Company, LLC, Case Nos. 21-2370; -2370 (Fed. Cir.
Jan. 12, 2023) (Chen, Cunningham, Stark, JJ.)
Grace owns a patent for a liquid pressurized viscometer used
commonly to test the viscosity of drilling fluid that is used to
drill oil wells. Grace's viscometer uses an “enlarged
chamber” between a lower chamber and a pressurization fluid
inlet. According to the patent specification, this enlarged chamber
was designed to reduce the measurement error in prior viscometer
models that was caused by the mixing of sample fluid and
pressurization fluid or by friction emanating from a seal in
