Imagine That IP Law Blog

On January 12, the United States Court of Appeals for the Federal Circuit (Appeals Court) issued its decision in Grace Instrument Industries, LLC v. Chandler Instruments Company, LLC. The case was an appeal from the United States District Court for the Southern District of Texas (District Court). Grace v. Chandler teaches us that care should be taken to avoid indefinite claim terms when possible. However, when a claim term is questioned, its meaning is ultimately determined in how it is explained in the specification and how it is discussed during prosecution.

In May 2020, Grace sued Chandler for infringement of its U.S. Patent No. 7,412,877 (the ‘877 patent). Grace contended that Chandler’s Model 7600 viscometer infringed its patent on multiple claims. This patent covers a device to eliminate errors when measuring fluid viscosity in oil wells. In particular, the device may eliminate errors caused by a sample mixing with pressurization fluid.

The District Court noted that prior to the ‘877 patent, there were at least two approaches for how sample fluid could be separated from pressurization fluid, and both approaches could ultimately lead to errors during testing. The ‘877 patent proposes a solution, including a viscometer that has an “enlarged chamber.” That chamber is situated in between a chamber that holds the sample fluid and a part of the pressure vessel that is a pressurization fluid inlet. The large size of this chamber means that the sample fluid level does fall below the transition point between the “enlarged chamber” and the lower chamber when pressurization fluid is applied.

In July 2021, the District Court issued its claim construction order for this case. In its order, the District Court said that in claims 1 and 4 of the ‘877 patent, the term “enlarged chamber” was indefinite. According to the District Court, the word “enlarged” is a “term of degree” and that it “necessarily calls for some comparison against some baseline.” Additionally, the District Court agreed with Chandler on the construction of the term “means for driving said rotor to rotate located in at least one bottom section” as it was used in the ‘877 patent. The District Court also agreed with Chandler that the patent’s wording of “located in at least one bottom section” modified the phrase “means for driving” not “rotor.”

Grace appealed the claim construction order, as well as the District Court’s constructions of the means language that was used. The Appeals Court found that the District Court erred in finding that the “enlarged chamber” was indefinite and remanded for further fact finding, and affirmed the District Court’s construction of the “means” language.

Regarding the “enlarged chamber” term, the Appeals Court found that District Court erred in its finding of indefiniteness, and erred in relying on extrinsic evidence (the dictionary) when the intrinsic evidence (specification, prosecution history, etc.) was sufficient. The Appeals Court noted that a claim term may be clearly redefined without an explicit statement of redefinition, and that when an applicant acts as their own lexicographer, this will govern over extrinsic definitions.

Regarding the “means” language, the Appeals Court affirmed that the patent’s wording of “located in at least one bottom section” modified the phrase “means for driving” not “rotor.” The Appeals Court found that this interpretation was supported by the specification, the plain meaning of the claims, as well as other related claims.

Grace v. Chandler teaches us that care should be taken during prosecution when arguing the meaning of claim terms outside of what is explicitly provided in the specification, as any clarifications or explanations made by the applicant or applicant’s representative will ultimately affect how a court construes a given claim term, regardless of what a dictionary may say. If there is concern over the sufficiency of a specification in regards to a claim term, prosecution can also provide the opportunity to clarify the record, even if the claim term is not raised as an issue during prosecution. Additionally, when reciting modifying language in a claim, “wherein” clauses should be considered to make clear what it is that is being modified. Often times claims will contain a series of terms followed by some modifying language, and without clarification (e.g., using a wherein clause to specifically call out what is being modified) it is left to the reader to determine which term in the series of terms is actually being modified, which may ultimately lead to an unintended claim meaning.