Even though an accused process contained unrecited components in addition to those the claimed invention "consisted of," the U.S. Court of Appeals for the Federal Circuit affirmed a district court’s claim constructions and its legal conclusions of infringement. Conoco, Inc. v. Energy & Envtl. Int'l, L.C ., Case Nos. 05-1363, -1461 (Fed. Cir., Aug. 17, 2006) (Gajarsa, J.).
Conoco is the holder of U.S. Patent No. 5,244,937 (the `937 patent) and U.S Patent No. 6,172,151 (the `151 patent), which it asserted EEI had infringed. The technology relates to processes for making drag-reducing agents (DRAs) for use in oil and gas pipelines. The addition of DRAs increases pumping efficiency by reducing the friction experienced by liquid as it flows through a pipeline. The active ingredient of DRAs are high-molecular-weight polymers. The district court held that EEI processes for making DRAs literally infringed the `937 patent and infringed Conoco’s `151 patent under the doctrine of equivalents.
On appeal, various claim constructions were at issue. In particular, an asserted claim of Conoco's `937 patent contains a limitation that the claimed process "consists of" water or a water-alcohol mixture. In challenging the district court’s construction, EEI contended that Conoco’s use of the transition phrase "consisting of" limits the scope of the patent to cover processes performing only the recited steps of the patent and nothing further. Accordingly, EEI contended its accused processes should escape infringement because it used methyl isobutyl ketone (MIBK), a non-alcohol component not recited on the `937 patent claims.
The Federal Circuit stated that, although the transitional phase "consisting of" is a term of art in patent law and signifies restriction and exclusion of unrecited steps or components, this exclusion is not absolute. For example, "consisting of" does not exclude impurities that a person of ordinary skill in the art would ordinarily associate with the recited materials. Also, "consisting of" does not exclude additional components or steps that are unrelated to the invention.
Since EEI did not challenge the "consisting of" construction prior to appeal, the Federal Circuit declined to review the construction de novo and instead applied a clear error analysis. The Federal Circuit found substantial evidence that MIBK is a common impurity in industrial alcohols. MIBK is added to alcohols to prevent a liquor tax from being applied because it makes the alcohol undrinkable by humans. As such, MIBK is normally associated with the alcohol component of the `937 invention and is implicitly adopted by the ordinary meaning of the components themselves. With regard to the asserted equivalents infringement of the `151 claim, the Court agreed that an examiner’s amendment to add the fatty acid wax limitation to one of the claims was not related to patentability and did not preclude.
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