The U.S. Court of Appeals for the Federal Circuit has held that the ordinary and customary meaning of claim terms may trump even prosecution history distinguishing a prior art reference. W.E. Hall Company, Inc. v. Atlanta Corrugating, LLC, Case No. 03-1417 (Fed. Cir. June 7, 2004) (Gajarsa, J.).
The claim at issue recited an underground pipe with a "plurality of open channels" that, according to the applicant, provided strength and increased hydraulic efficiency. During prosecution, to overcome a prior art reference describing a pipe having channels—but also having a reinforcement element in each channel to close and strengthen the channel—the applicant amended the claim to add the limitation "single piece construction" and to change the open format "comprising" transition term to the partially-closed forms "consisting essentially of."
Atlanta’s accused pipe included channels containing an "insert element" that closed, but did not strengthen, the channel. To read the partially closed claim on the Atlanta pipe, Hall argued (based on the prosecution history) that "open channel" means a channel without a reinforcement element, but with a non-structural metal insert. Hall further alleged that "single piece construction" means a construction with a single structural element, but also with non-structural elements.
The district court interpreted the term "single piece construction" to mean a pipe having only one piece and found that the prosecution history did not require a departure from the ordinary and customary meaning of the term "open channel," so as to include "channels that were closed with metal inserts." The court further held that the partially closed term "consisting essentially of" did not allow the claim to read on a pipe having metal inserts because such inserts would materially affect the properties of the invention.
The Federal Circuit affirmed, finding that, in this case, "the inventor was not his own lexicographer" and that "[w]e therefore rely on the plain and ordinary meaning of the terms." The Court also noted that prosecution history cannot limit claim scope without clear evidence that the "applicants had disavowed coverage of the relevant subject matter."
The Federal Circuit found no intrinsic evidence to suggest that "Hall intended to use the terms in a manner other than according to their ordinary meanings" and held the term "open channel" cannot be interpreted to include a non-structural insert which closes, but does not reinforce, the channel. Similarly, the Court found no evidence to interpret the term "single piece construction" to mean a pipe that also includes non-structural pieces.
Practice Note: This case demonstrates the danger of using the partially closed transition term "consisting essentially of," especially in an apparatus claim. Patent applicants should consider maintaining the open term "comprising" and then adding a minimal claim limitation if necessary to avoid prior art.
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