Federal Circuit Finds Term Not Limited by Arguments Made During Prosecution

Nystrom obtained U.S. Patent No. 5,474,831 for a board having a convex top surface for use in constructing a flooring surface of a deck, and filed suit against TREX in the U.S. District Court for the Eastern District of Virginia, alleging TREX had infringed the ‘831 patent.  TREX counterclaimed, seeking a declaratory judgment of non-infringement, invalidity, and unenforceability, and alleging antitrust violations by Nystrom, his company, and his attorneys.  The district court held a Markman hearing and issued a claim construction ruling construing the disputed claim term “convex top surface” to mean “an upper surface with an outward curve that has a ratio of its radius of curvature to width of the board between 4:1 to 6:1”.

In its ruling, the district court noted that “the specification does not contain any indication that the term convex top surface is to be assigned a specific range of curvature”, but relied on statements Nystrom made in the prosecution history in arguing the patentability of a dependent claim, wherein Nystrom stated that “[i]t should be noted, however, that the ratio of the radius of curvature of a board to its width can vary within certain relatively narrow limits, e.g. from about 4:1 to about 6:1, and still meet the basic objectives of the invention, although the preferred ratio is about 5:1”, and that “[a]nything much outside this range does not provide satisfactory performance and/or is not acceptable to the consumer”.  The district court concluded that Nystrom’s statement that “[a]nything much outside this range . . . is not acceptable” implied that his statement regarding a range of 4:1 to 6:1 for the radius of curvature ratio applied to the entire patent, and was not intended to apply solely to the dependent claim being argued.

On appeal, Nystrom argued that the district court erred by ignoring the ordinary and customary meaning of the claim term “convex top surface”, which is “an upper surface with an outward curve”, and by finding instead that Nystrom limited this claim term to mean a convex top surface having a radius of curvature ratio in the range of 4:1 to 6:1 to distinguish the invention over a prior art reference.  The court of appeals agreed with Nystrom, pointing out that the district court had ignored the fact that at the time Nystrom made the statements the district court had relied on, the dependent claim being argued contained the following language expressly providing for a radius of curvature ratio of about 5:1:  “said top surface having a radius of curvature that is approximately five times as great as the width of the board, thereby defining a smoothly shaped and shallow convex top surface that sheds water . . . .”


The court of appeals said that Nystrom’s statements were expressly directed to the dependent claim being argued, and there was no indication that Nystrom intended the claim “convex top surface” in all of the pending claims to be limited to a specific radius of curvature ratio.  Accordingly, the court of appeals found that the prosecution history did not redefine or disclaim the term “convex top surface” in the claims, and held that the correct construction of this term is the ordinary and customary meaning of an upper surface that curves or bulges outward, as the exterior of a sphere.

A copy of the case can be found at Nystrom v. TREX Company, Inc., 424 F.3d 1136 (Fed. Cir.  2005) reh’g en banc denied 2005 U.S. App. LEXIS 26669 (Fed. Cir. 2005).


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