The U.S. Court of Appeals for the Federal Circuit has shed some additional light on the application of prosecution history estoppel under Festo to certain narrowing claim amendments. Specifically, the Court held that where a narrowing amendment is made to one feature in a claim and a distinguishing argument is presented with regard to another feature in the same claim, absent a clear and unmistakable surrender of subject matter within the substance of the distinguishing argument, prosecution history estoppel does not prevent the patentee from relying on the doctrine of equivalents for the second feature. AquaTex Industries, Inc. v. Techniche Solutions, Case No. 05-1088 (Fed. Cir. Aug. 19, 2005) (Mayer, J.).
The AquaTex patent disclosed a method of cooling a person involving the use of a "fiberfill batting material." During prosecution, the U.S. Patent and Trademark Office (UPSTO) examiner rejected the claim in view of prior art that showed cooling using natural fibers. AquaTex distinguished its invention by arguing the applied reference failed "to disclose or suggest the fiberfill batting and polymeric fibers and/or particles of the composite material in the claimed method." AquaTex also amended an independent claim to further recite that cooling occurs "by evaporation." In light of the claim amendment and distinguishing argument, the examiner withdrew the rejection and issued the patent.
Techniche Solutions, who manufactured a product that used both natural and synthetic fibers, argued AquaTex’s statements disavowed the claim scope of natural fibers. The trial court agreed, holding AquaTex was barred from asserting that the claimed "fiberfill batting material" could be partially composed of natural fibers. Techniche appealed.
The Federal Circuit, citing Festo, emphasized that application of the doctrine of equivalents may be barred both in circumstances where narrowing amendments are made for the purposes of patentability, and where arguments are made to an examiner which clearly and unmistakably surrender subject matter. Noting the matter surrendered by the limiting claim amendment bore no relation to the composition of the fiberfill batting, the Court conducted a separate argument-based estoppel analysis. Concluding AquaTex’s argument merely stated how the prior art material retained moisture and reminded the examiner how the overall composition of the materials was used, the Court reasoned these representations "are not a clear disavowal of claim scope" and reversed the district court’s grant of summary judgment as to availability of equivalents as it related to the claimed fiberfill batting material.
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