Claim Construction: “Consisting of”
Conoco Inc Vs Energy & Environmental International – Federal Circuit No 05-1363,
August 17, 2006
The alleged patent infringement
This case discusses whether the term “consisting of” in the patent as a transition word fully excludes the addition of any other elements in the claimed invention. For background, a claim that uses the word “comprises” describes anything that includes the listed elements and is not exclusive of any additional elements. A claim that uses the words “consisting of” in general is limited to cover things that only consist of the listed elements. In practice that means that “an invention comprising A, B and C” would be infringed if A, B, C, and D are present in an infringing embodiment, while it would not be infringed if the words “consisting of” is used in the place of “comprises”. “An invention consisting of A, B, and C” is infringed only if no other elements are present in the infringing embodiment.
The patent in question refers to drag-reducing agents(DRA) used in gas and oil pipelines to reduce friction. It allows for a more efficient pumping of the liquid into the lines. The process of producing the DRA was stated in the claim using “consisting of” as the transitional word. DRA involves a water and alcohol mixture to produce a stable, non-agglomerating composition of the solid friction-reducing agent. The alleged infringer also proclaimed that an additional element, MIBK, a standard industrial alcohol impurity, was strategically added to avoid infringement.
The Court stated that the additional element must be connected to the invention in question to avoid infringement(Norian). But the court reserved the matter of whether the accused would be excluded from the judgement based on the impurities not generally related to the component.
- If the additional element is not connected to the invention, the infringement is not avoided. For example, in the Norian case, there was a chemical kit that consisted of a discrete list of chemicals. A spatula was added to the kit, and it was claimed to not infringe because the terms “consisting of” would preclude the inclusion of any further elements.
- If the additional element is connected to the invention and is related to the list of elements given, infringement is not avoided.
In summary, this gives more latitude to patent owners when interpreting claims that use the word “consisting of” as a transitional phrase. Patent infringement is continuing to become more technical to interpret.
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