Processing All Things Federal Circuit
January 30, 2023 - Last Week in the Federal Circuit

Last Week In The Federal Circuit (January 17 – January 20): “Larger Than” Or “Large Enough”?

Last Week In The Federal Circuit (March 21-25):  Oil is a Hot Commodity These Days—Even on the Federal Circuit

If you think claim construction is more fun than watching paint peel, then you’re probably a patent lawyer. And what’s more fun than claim construction? Claim construction with an indefiniteness challenge, as happened in this week’s case of the week.

Case of the (recent) week: Grace Instrument Industries, LLC v. Chandler Instruments Co., No. 21-2370

Panel: Judges Chen, Cunningham, and Stark, with Judge Chen writing the opinion

You should read this case if: you have a matter involving claim indefiniteness

Is the claim term “enlarged chamber” indefinite when it’s not a term of art in the relevant field and the patent never specifies what the chamber must be larger than? The Federal Circuit said no in Grace Instrument.

The patent claimed a pressurized device and a viscometer, which oil-well drillers use to measure drilling fluid viscosity (roughly, its thickness). Fluid viscosity can change with pressure, and pressure can be high deep down in an oil well. Because drillers often carefully control drilling fluid viscosity, they need to measure that viscosity accurately at the real-world pressures existing in a well. Viscometers often use a special pressurization fluid to replicate that high pressure when measuring the viscosity of a sample of drilling fluid. But any mixing of the pressurization fluid with the sample throws off the measurement. Enter the patent’s “enlarged chamber.” According to the patent, mixing could be avoided by separating the sample drilling fluid in an enlarged chamber—for example, one that “is still at least half filled with sample fluid” at maximum pressure to avoid spilling over in the chamber with pressurization fluid.

During claim construction, the district court held that “enlarged chamber” is indefinite. Relying on dictionary definitions, the district court explained that “enlarged” was a term of degree that “necessarily calls for some comparison against some baseline.” But the patent gave no “objective” baseline for that comparison. The district court rejected the patent owner’s argument that ordinarily skilled artisans would understand “enlarged chamber” by its purpose to be “large enough” for its task of measuring fluid viscosity without mixing. 

The Federal Circuit vacated that judgment. It emphasized that context is key, even when interpreting words that are “not a term of art.” That context comes from intrinsic evidence, including the patent’s description and the prosecution history. Here, that evidence showed that an “enlarged chamber” is merely one that is “large enough” for its identified purpose rather than “larger than something else.” “The district court erred in its reliance on extrinsic evidence” to “contradict the scope and meaning of ‘enlarged chamber’ that a skilled artisan would ascertain by reading the intrinsic record.” The Court nevertheless remanded the indefiniteness issue because the district court never reached additional arguments, including some based on extrinsic evidence—those arguments were best addressed by the district court in the first instance.

Precedential opinions: 1

Non-precedential opinions: 13

Rule 36: 7

Longest pending case from argumentPersonalized Media Communications, LLC v. Apple Inc., No. 21-2275 (197 days)

Shortest (non-Rule 36) pending case from argument: SynQor, Inc. v. Vicor Corporation, No. 21-2211 (44 days)