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No Special Rule of Claim Construction for Nonnumerically Limited Descriptive Claim Terms

September 06, 2001
McDonell, Leslie A.

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Last Month at the Federal Circuit - October 2001

Judges: Newman, Friedman, and Linn (author)

In Ecolab, Inc. v. Envirochem, Inc., No. 00-1402 (Fed. Cir. Sept. 6, 2001), the Federal Circuit vacated a district court’s grant of SJ of literal infringement as being based on an erroneous construction of the claim term “substantially uniform” and remanded to the district court for further proceedings. The Federal Circuit affirmed the district court’s determination that neither equitable estoppel nor laches applies against Ecolab, Inc. (“Ecolab”) because Envirochem, Inc.

(“Envirochem”) had not alleged, and the record did not show, that Envirochem had suffered prejudice. Ecolab sued Envirochem for infringement of U.S. Patent No. Re. 32,818 (“the ‘818 patent”) relating to a solid detergent cast for use in commercial dishwashing machines. In denying a motion for preliminary injunction, the district court initially interpreted the claim term “substantially uniform” as describing a cast in which the concentration of alkalinity and phosphates may vary between 0.0 percent and 6.6 percent based on data presented to the PTO during prosecution. As a result of this claim construction, Envirochem moved for SJ of noninfringement.

The case was then reassigned to a different judge who reconstrued the claims and denied Envirochem’s motion. Under the new claim construction, the term “substantially uniform” was found to mean “a level of continuity of the elements from top-to-bottom throughout the cast such that a homogeneous cleaning solution is formed over the life of the cast.” The district court then granted Ecolab’s motion for SJ of literal infringement.

While the Federal Circuit agreed that no basis exists for inferring a numerical limitation into the term “substantially uniform,” it held that the district court, upon reconstruing the claims, improperly had read a functional limitation into the term. Specifically, the Federal Circuit found that the district court’s construction of “substantially uniform” erroneously defined the term according to the purpose of the invention, did not give the term its ordinary and accustomed meaning, and did not recognize the proper relevance and effect of an affidavit submitted during prosecution.

The Federal Circuit noted that when the intrinsic evidence does not provide a special meaning for a claim term, the term is to be given its ordinary and accustomed meaning. It also noted that the term “substantially uniform” expressly modifies the term “alkaline detergent” and, thus, is not tied to any overall function of the detergent. Next, the Federal Circuit reviewed an affidavit submitted during prosecution of the ‘818 patent to distinguish the claims from the prior art. The distinction was based on measuring the concentrations of ingredients in the top and bottom quarters of the casts, not by measuring the homogeneity of the cleaning solution formed after spraying the exposed surface of the cast with water. The Federal Circuit emphasized that all express representations made by or on behalf of the applicant to the Examiner to induce a patent grant limit the interpretation of the claims so as to exclude any interpretation that may have been disclaimed or disavowed during prosecution in order to obtain claim allowance.

As a result of its analysis, the Federal Circuit determined that the term “substantially uniform” as related to the “alkaline detergent cast” means “largely, but not wholly the same in form” or “very near consistency of elements from top-to-bottom throughout the cast” and remanded the case to the district court to determine whether Envirochem’s products literally infringe the claims under this construction. The Federal Circuit pointed out that the limitation “substantially uniform” narrowed the scope of the claim and was added to the claim by amendment for a reason relating to patentability. Thus, the Federal Circuit concluded that prosecution history estoppel bars a finding of infringement under the DOE as to the “substantially uniform” limitation.

As to laches and estoppel, the Federal Circuit ruled that the hiring of new employees, modification of equipment, and engagement in sales and marketing activities are damages normally associated with a finding of infringement and do not constitute the type of damages necessary for a finding of economic prejudice.