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Prosecution History Estoppel Does Not Preclude Application of the Doctrine of Equivalents

05-1001
June 14, 2006

Decision icon Decision

Last Month at the Federal Circuit - July 2006

Judges: Newman, Lourie (author), Prost

 In Primos, Inc. v. Hunter’s Specialties, Inc., Nos. 05-1001, -1376 (Fed. Cir. June 14, 2006), the Federal Circuit affirmed a district court’s judgment of literal infringement of U.S. Patent No. 5,520,567 (“the ’567 patent”) and infringement of U.S. Patent No. 5,415,578 (“the ’578 patent”) under the DOE.

The two patents-in-suit disclose an apparatus that hunters use to simulate animal sounds. The patented “mouth call” device consists of a frame, a membrane that vibrates to produce sound, and a plate extending above the membrane. The mouth call is placed within the user’s mouth and held in place by the user’s tongue. The user then forces air through a gap between his or her tongue and the membrane, causing the membrane to vibrate and emit a sound that replicates the call of an animal.

Primos, Inc. (“Primos”) alleged that Hunter’s Specialties, Inc.’s (“Hunter’s Specialties”) “Tone Trough” product infringes the patents-in-suit. The accused Tone Trough device is a mouth call device that has a dome instead of a plate extending above the membrane. At trial, a jury found that the Tone Trough device literally infringed the ’567 patent, and infringed the ’578 patent under the DOE.

On appeal, the question of literal infringement of the ’567 patent hinged on the district court’s construction of the claim term “engaging.” The Federal Circuit agreed with the district court’s construction of “engaging” to mean “to come into contact with,” and rejected Hunter’s Specialties’s argument that the term meant “sealing” or “interlocking.” The Court pointed out that the terms “engaging” and “sealing” are both expressly recited in the asserted claim and therefore “engaging” cannot mean the same as “sealing,” or else one of the terms would be superfluous. Furthermore, a figure in the patent showed a plate of the device touching the roof of the mouth but not having an interlocking relationship, thus supporting the district court’s construction of “engaging” to mean “to come into contact with.” The Court explained that it does not normally interpret a claim term to exclude a preferred embodiment.

Hunter’s Specialties further argued that prosecution history estoppel bars application of the DOE to the claim term “plate” because amendments to the term narrowed the scope of the claim and were made for reasons relating to patentability. The Federal Circuit noted that during prosecution, the claim term “plate” was amended in two ways: (1) by requiring that it have a “length,” and (2) by adding the limitation that the plate be “differentially spaced” above the membrane. Citing the Supreme Court’s decision in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 740 (2003), the Federal Circuit observed that “when a patent claim is amended during prosecution for reasons relating to patentability, there is a presumption that the patentee surrendered all the territory between the original claim limitation and the amended claim limitation.” Slip op. at 12. The Court noted, however, that this presumption may be overcome when the “rationale underlying the amendment may bear no more than a tangential relation to the equivalent in question.” Id.

With regard to the claim amendments, the Federal Circuit concluded that the addition of the term “length” did not narrow the scope of the claim because every physical object has a length. Further, the Court concluded that the “differentially spaced” limitation did narrow the claim and, thus, Primos surrendered plates that are not differentially spaced above the membrane. The Court found, however, that the dome in the accused Tone Trough device is differentially spaced above the membrane. Because it found that the Tone Trough device included the spacing, the Court concluded that the amendment was merely tangential to the contested element in the accused device and, accordingly, prosecution history estoppel did not prevent the application of the DOE.

Hunter’s Specialties also argued that substituting the accused dome for the “plate” in claim 2 would vitiate the “plate” limitation, in violation of the “all limitations rule.” The Federal Circuit noted that the “all limitations rule” bars a finding of infringement under the DOE if such a finding would vitiate a particular claim element. After assessing the totality of the circumstances, the Court concluded that the equivalence would not entirely eliminate the “plate”limitation and, thus, was not barred by the “all limitations rule.”

The Federal Circuit next found that the district court did not abuse its discretion in excluding from evidence a prior art device that was identified shortly before trial began and after discovery had closed. Lastly, the Court rejected Hunter’s Specialties’s assertion that itwas unfairly prejudiced by an instruction to the jury that it could draw an adverse inference from an opinion withheld due to the assertion of the attorney-client privilege by another defendant in the case. Although agreeing that the instruction was erroneous, the Court found that the adverse-inference jury instruction did not prejudice Hunter’s Specialties because the instruction did not apply to Hunter’s Specialties but only to the defendant who asserted the attorney-client privilege.