Criticism of Prior Art Limits Scope of Equivalents

L.B. Plastics, Inc. v. Amerimax Home Products, Inc., [2006-1465](September 12, 2007)[DYK, Newman, Rader] The Federal Circuit affirmed summary judgment that the asserted claims of U.S. Patent No. 6,463,700 were not infringed literally or under the doctrine of equivalents.
SIGNIFICANCE: Patent's criticism of prior art limits applicability of doctrine of equivalents to criticized structures.
BRIEF: The '700 patent claimed a composite gutter guard with a mesh layer over a guard patent. During prosecution the patentee amended the claims to add the limitation a continuous heat weld defining an uninterrupted longitudinal weld to distinguish a patent disclosing spot welds. The accused product had a mesh attached to the guard panel by means of an adhesive, hot glue. The Federal Circuit said that "[i]n construing claims we search for the ordinary and customary meaning of a claim term to a person of ordinary skill in the art. We determine this meaning by looking first at intrinsic evidence such as surrounding claim language, the specification, the prosecution history, and also at extrinsic evidence, which may include expert testimony and dictionaries. The intrinsic recorded provided little disclosure about the uninterrupted longitudinal weld, so the Federal Circuit found it proper to turn to extrinsic evidence. The Federal Circuit agreed with the district court's construction of weld, and concluded that the district court was correct in ruling that adhesive did not literally infringe the "weld" requirement. The Federal Circuit then turned to the doctrine of equivalents, which "allows the patentee to claim those insubstantial alterations that were not captured in drafting the original patent claim but which could be created through trivial changes." The Federal Circuit noted that "when a specification excludes certain prior art alternatives from the literal scope of the claims and criticizes those prior art alternatives, the patentee cannot then use the doctrine of equivalents to capture those alternatives. The Federal Circuit noted the criticism of adhesives in the specification, and observed that since the patentee elected to distinguish prior art attachment means and to limit its claim to continuous welded attachments, a person of ordinary skill in the art reading the specification would clearly conclude that the inventor thought that adhesive attachments generally were undesirable. The Federal Circuit held that the patentee cannot use the doctrine of equivalents to expand welding to include adhesives.