In a rare decision involving application of the doctrine of equivalents for an amended claim term, the U.S. Court of Appeals for the Federal Circuit agreed with a district court that prosecution history estoppel did not preclude the application of the doctrine of equivalents where only a tangential relationship existed between the claim amendments and the equivalent in question. Primos, Inc. v. Hunter's Specialties, Inc., Case Nos. 05-1001, -1376 (Fed. Cir. June 14, 2006) (Lourie, J.).
This appeal involved a patent for a "Game Call Apparatus," which hunters use to simulate animal sounds. The invention contained a diaphragm mouth consisting of a frame, a membrane to produce sound, a flexible peripheral edge and a shelf or plate extending above the membrane. Patentee Primos filed a patent infringement suit against its competitor, Hunter’s. Hunter's accused device is a diaphragm mouth call device that, among other features, contains a dome extending above the membrane, instead of a shelf or plate, as claimed in Primos’ patents.
The Federal Circuit first reviewed the district court’s finding of literal infringement, holding that the district court correctly construed "engaging" to mean "to come into contact with" rather than "sealing." The Federal Circuit referred to Phillips in its review of the district court's claim construction, determining that the court properly focused on the intrinsic record to construe the terms to have their customary meaning as understood by a person of ordinary skill in the art. Since "engaging" and "sealing" were both expressly recited in the same claim, they could not be construed as having the same meaning. Moreover, the figures in the specification illustrated a device positioned with several points of contact between the roof of the user’s mouth and the device.
The Federal Circuit also agreed with the district court that the prosecution history did not preclude application of the doctrine of equivalents. In this case, interestingly, the Festo presumption that the patentee surrendered the territory between the original claim limitation and the amended claim limitation was successfully rebutted. The presumption was overcome because the rationale underlying the amendment had only a tangential relationship to the equivalent in question. At issue was the term "plate, " which had been amended to require that the plate (1) have a "length," and (2) be "differentially spaced" above the membrane. The Court agreed with the district court that the addition of the term "length" did not narrow the claim because every physical object has a length. The Court further agreed with the district court that the territory surrendered by the "differentially spaced" amendment comprises plates that are not differentially spaced above the membrane. Pointing out that the accused device, however, included a dome, rather than a plate, and that the dome includes the spacing, the Court concluded the amendment was merely tangential to the contested element in the accused device, and thus prosecution history estoppel did not prevent application of the doctrine of equivalents. Finally, the Court rejected the argument that application of the doctrine of equivalents should have been precluded because substitution of the accused dome for the claimed "plate" would vitiate the "plate" limitation and thereby violate the all limitations rule.
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