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Process Control Corp. v. HydReclaim Corp., No. 98-1082, -1277, 1999 U.S. App. LEXIS 21409, 52 U.S.P.Q.2d (BNA) 1029 (Fed. Cir. Sept 7. 1999).




  1. Whether a term, defined in the first part of a claim and subsequently used in a second part, that uses identical language can be construed to have two different meanings within the same invention.
  2. Whether a claim that is construed to have a nonsensical method of operation is invalid for failure to comply with the utility requirement of 35 U.S.C. § 101 and the enablement requirement of 35 U.S.C. § 112, paragraph 1.


  1. No. The fact that a term is accompanied by identical language in both uses precludes its construction from having two different meanings within the same invention.
  2. Yes. If a patent claim is subject to only one interpretation, and that interpretation renders the claim nonsensical, it is therefore inoperative and fails to meet the utility and enablement requirements necessary for patent validity.


HydReclaim Corporation ("HydReclaim") owns U.S. Patent No. 5,148,943(the ‘943 patent), which is directed to continuous gravimetric blenders used by the plastics industry. The patent describes a method for regulating the quality of blended material in a plastics production process by monitoring the change in weight of materials in the mixing chamber rather than the volume as the previous system did. HydReclaim initially sued Process Control Corporation ("Process Control"), a competitor in the field of material blending, alleging infringement of the ‘943 patent; the action, however, was dismissed on the grounds of lack of jurisdiction. Process Control, alleging that the ‘943 patent was invalid and thus, unenforceable, subsequently filed an action for a declaratory judgment in district court. The district court adopted HydReclaim’s argument that the claim language was susceptible to two reasonable constructions and ruled that the ‘943 patent was valid, enforceable, and willfully infringed. Process Control appealed the decision.

Process Control challenged the district court’s claim construction for various reasons, including that the term "discharge rate" as used in clauses [b] and [d] must have the same meaning throughout the claim. Process Control stressed that since identical language surrounded both occurrences of the term, the original definition in clause [b] should control. The Federal Circuit adopted Process Control’s construction of the term "discharge rate" finding that the term had not been otherwise redefined and that redefinition would make the term contrary to that explicitly defined in the claim. The Federal Circuit stated that a term will not be given a secondary or separate meaning unless the patent clearly redefines the term such that one reasonably skilled in the art would understand that the patentee intended to redefine the claim.

The Federal Circuit’s conclusion that the definition of "discharge rate" in clause [b] controlled throughout the patent led it to find that clause [d] was nonsensical. The Court found that where the only reasonable claim interpretation leads to a nonsensical construction, the claim must be judged invalid. Thus, the Federal Circuit ruled that the claim was invalid because its proper construction rendered the claim "inoperative", and therefore unable to fulfill the utility and enablement requirements of 35 U.S.C. §§ 101 and 112, paragraph 1. The Federal Circuit, therefore, reversed the district court’s finding of patent validity and vacated its finding of infringement.


Prepared by the liibulletin-patent Editorial Board.

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