Argument-Based Estoppel Avoided by Simultaneous Unrelated Amendment

In Aquatex Industries, Inc. v. Techniche Solutions (Fed. Cir.; August 19, 2005) the court did not find the "clear and unmistakable surrender of subject matter required to invoke argument-based prosecution history estoppel." In this case, the dispute centered on whether the term "fiberfill batting material" in U.S. Patent No. 6,371,977 (left) should be construed to encompass only synthetic fibers in the following claim:

A method of cooling a person by evaporation, comprising:
providing a multi-layered, liquid-retaining composite material comprising a fiberfill batting material, and hydrophilic polymeric fibers that absorb at least about 2.5 times the fiber’s weight in water;
soaking said multi-layered composite in a liquid;
employing said multi-layered, liquid-retaining composite material as a garment or a flat sheet and evaporatively cooling said person.

The specification stated "[t]he particular fiberfill is not known to be critical. That is, any commercial fiberfill may be used as long as it does not adversely affect the performance of the end composite." However, all of the cited examples were comprised entirely of synthetic materials. The extrinsic evidence of record, in the form of technical dictionaries, also supported construing "fiberfill" as a purely synthetic fiber because it is consistently defined as such.

The claim was also rejected for lack of novelty over U.S. Patent No. 4,897,297 ("the ’297 patent") where the examiner noted that the disclosed fiberfill batting material was a "mixture of synthetic polymer pulp or wood pulp, which is a fiber." However, in response to the rejection, AquaTex amende the claim to include the "evaporatively cooling" limitation and stated that "the ’297 Patent fails to disclose or suggest the fiberfill batting and polymeric fibers and/or particles of the composite material in the claimed method."

Nonetheless, the Federal Circuit did not find a clear disavowel of claim scope:

Techniche and the trial court believe this argument limited claim coverage of fiberfill to only synthetic fibers. The argument, however, does not address or even relate to the composition of the fiberfill batting. Rather, it was based on the ’297 patent not teaching or suggesting the overall composition of materials, or the use of the disclosed compress to cool a person through evaporation. The compress of the ’297 patent was designed to retain much of its liquid over long periods of time, thus giving the material a high heat capacity and a high insulative value. ’297 patent, col. 6, ll. 24-55. The claimed invention of the ’977 patent achieves
cooling through evaporation.

The arguments made during prosecution, and the corresponding addition of the claim limitation "by evaporation," indicate that AquaTex was distinguishing the overall method of cooling of its claimed invention from that of the ’297 patent. The subject matter surrendered by the narrowing amendment bears no relation to the composition of the fiberfill batting material. There is no indication in the prosecution history whether or not AquaTex agreed or disagreed with the examiner’s statement that the fiberfill found in the prior art comprised natural fibers. Thus, the trial court erred in holding that prosecution history estoppel barred AquaTex from asserting infringement under the doctrine of equivalents. Upon remand the trial court must consider whether or not each limitation of the claims in dispute, or its equivalent, is present in the accused Techniche products. See Graver Tank, 339 U.S. at 608.