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Claim Loses Ordinary Meaning During Prosecution History

January 08, 2002
Hartmann, Anthony A.

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Last Month at the Federal Circuit - February 2002

Judges: Gajarsa (author), Schall, and Linn

In Rheox, Inc. v. Entact, Inc., No. 01-1001 (Fed. Cir. Jan. 8, 2002), the Federal Circuit affirmed a district court’s grant of SJ of noninfringement by Entact, Inc. (“Entact”) of U.S. Patent No. 5,162,600 (“the ‘600 patent”), assigned to Rheox, Inc. (“Rheox”).

The claims of the ‘600 patent are directed to methods of remediating lead from lead-contaminated soil by the application of a composition primarily comprising “calcium orthophosphate.” Rheox filed suit against Entact, alleging infringement of at least claim 1 of the ‘600 patent by Entact’s use of triple superphosphate (“TSP”) to remediate lead-contaminated soil. It was undisputed that TSP is primarily monocalcium orthophosphate.

The district court recognized that the ordinary meaning of the term “calcium orthophosphate” encompasses compounds comprising Ca2+ cations and PO4 3- anions, such as monocalcium orthophosphate, dicalcium orthophosphate, and tricalcium diorthophosphate. However, upon considering the prosecution history, the district court determined that Rheox had excluded monocalcium orthophosphate and, thus, TSP from the claims.

Specifically, when Rheox filed its application, claim 1 recited “an agent selected from the group consisting of calcium, zinc, magnesium or ammonium phosphate. . . .” Dependent claim 3 recited “wherein said calcium, zinc, magnesium or ammonium phosphate compounds are selected from the group consisting of calcium orthophosphate, . . . dicalcium orthophosphate, . . . monocalcium orthophosphate, . . . tricalcium diorthophosphate. . . .” In response to an obviousness rejection, wherein the reference taught water-soluble phosphate treatment agents, Rheox amended claim 1 to recite “consisting essentially of calcium orthophosphate” and cancelled claim 3.

In addition, Rheox asserted that the amendments were made to distinguish between the water-soluble compounds of the reference and the substantially water-insoluble compounds of the invention. Rheox asserted that the claimed compounds had a solubility of 0.002g/100mL, which the district court had noted was the solubility of tricalcium orthophosphate, and referred to the claimed compound when using the formula for tricalcium orthophosphate. In view of both Rheox’s amendment and argument before the PTO, the district court had held that “calcium orthophosphate” of claim 1 was intended to mean “tricalcium orthophosphate” and to exclude monocalcium orthophosphate and TSP. Accordingly, SJ of noninfringement was granted.

On appeal, the Federal Circuit assessed whether the patentee had relinquished a particular claim construction based on the totality of the prosecution history rather than any individual segments. Rheox argued on appeal that only those compounds that are less soluble than the compounds of the reference were disclaimed. However, the Court noted that if that were true, Rheox would never have deleted all references to TSP from the claims, particularly since TSP was the preferred embodiment. The Court also noted that Rheox had argued to the PTO that the claimed compounds were thousands of times less soluble than the reference when, in fact, TSP was not even three times less soluble.

Accordingly, the Federal Circuit concurred with the district court’s conclusion that Rheox had disclaimed both monocalcium orthophosphate and TSP from the claims in order to obtain patentability and, thus, affirmed SJ of noninfringement by Entact. The Federal Circuit went further to note that while claim constructions that exclude preferred embodiments are rare, where the prosecution history requires a claim construction that excludes some but not all of the preferred embodiments, such a construction is permissible and meets he standard of highly persuasive evidentiary support.