You stick the patented "game call apparatus" in your mouth and blow.

The accused Tone Trough [sold by Hunter's Specialties] 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’s patents.

The district court denied summary judgment motions, considering the dispute to be fact based. A major issue was '567 claim 21 term "roof-of-mouth engaging portion." The issue went to whether Hunter's Tone Trough "operates when touching the roof of a user’s mouth."

Hunter’s Specialties then requested a Markman hearing to interpret the term “engaging” in claim 21 of the ’567 patent. On March 15, 2004, the court construed that term to mean to “come into contact with.” Primos v. Hunter’s Specialties, No. C01-004 (N.D. Iowa Mar. 15, 2004) (“Claim Construction Order”). The court rejected Hunter’s Specialties’ construction of the term “engaging” as “interlocking,” noting that while the word “interlocking,” as defined in a standard dictionary, may be appropriate in the context of a transmission or a latch, it is not appropriate in the context of the roof of one’s mouth.

Then there was the issue of applying the doctrine of equivalents.

Hunter’s Specialties again moved for summary judgment, asserting that prosecution history estoppel barred the application of the doctrine of equivalents as to the ’578 patent in light of our intervening decision in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd., 344 F.3d 1359 (Fed. Cir. 2003). The court determined that the term “plate” was amended during prosecution by describing it as “having a length,” but that that amendment did not narrow the scope of the claim because “all physical objects have a length.” Primos v. Hunter’s Specialties, No. C01-004 MJM (N.D. Iowa Mar. 12, 2004) (“Prosecution History Estoppel Order”). The court also observed that the term “plate” was amended to require that it be “differentially spaced” above the membrane, which narrowed the scope of the claim. Id. According to the court, the subject matter surrendered by that amendment involved “objects that are not differentially spaced above the membrane.” Because the Tone Trough contained a dome that was spaced above the membrane and therefore arguably did not fall within that surrendered area, the court denied summary judgment of no infringement under the doctrine of equivalents as to the ’578 patent.

Finally, there was a flap over a piece of prior art.

Finally, before trial, Primos filed a motion requesting that a device known as the Aluminum Flap Call not be introduced as evidence during trial. The court granted that motion, and noted in its order that, throughout discovery, Hunter’s Specialties never identified the Aluminum Flap Call as invalidating prior art.

The court refused Hunter's request for a new trial, so Hunter appealed.

Claim Construction

The CAFC was obliging in agreeing with Primos about "engaging."

We agree with Primos that the district court correctly construed the term “engaging” to mean “to come into contact with.” As this court explained in Phillips v. AWH Corp., we ordinarily construe claim terms to have their customary meaning as understood by a person of ordinary skill in the art. 415 F.3d 1303, 1312-17 (Fed. Cir. 2005) (en banc). In ascertaining the ordinary and customary meaning of a claim term, a court’s primary focus should be on the intrinsic evidence of record, viz., the claims, the specification, and, if in evidence, the prosecution history. Id. Starting with the language of claim 21, the terms “engaging” and “sealing” are both expressly recited in the claim and therefore “engaging” cannot mean the same thing as “sealing”; if it did, one of the terms would be superfluous.

Doctrine of Equivalents

An asserted claim used the term "plate," the construction of which Hunter naturally wanted narrowed to exclude its Tone Trough device, which had a dome. The court had found that Hunter's dome was equivalent to Primos' claimed plate. The CAFC agreed, with “[t]here is no set formula for determining whether a finding of equivalence would vitiate a claim limitation, and thereby violate the all limitations rule. Rather, courts must consider the totality of the circumstances of each case and determine whether the alleged equivalent can be fairly characterized as an insubstantial change from the claimed subject matter without rendering the pertinent limitation meaningless.”

Hunter’s Specialties challenges the application of the doctrine of equivalents on the ground that prosecution history estoppel applies to the term “plate.” Hunter’s Specialties specifically asserts that amendments to the term “plate” narrowed the scope of the claim and were made for reasons relating to patentability. According to Hunter’s Specialties, prosecution history estoppel therefore barred the doctrine of equivalents for that claim term. Primos responds that the district court properly applied the doctrine of equivalents. It reasons that the first amendment made to the term “plate”—that it include a “length”—did not narrow the scope of the claim. As to the second amendment made to the term “plate”—that it be “differentially spaced” above the membrane—that amendment bears no more than a tangential relationship to the accused Tone Trough. In particular, Primos contends that the territory surrendered by that amendment consists of objects that are not differentially spaced above the membrane. Because the accused device’s “dome” is differentially spaced above the membrane, Primos asserts that the “differentially spaced” amendment does not pertain to the disputed element in the accused device and it is therefore merely tangential to the accused device. According to Primos, prosecution history estoppel thus does not apply to prevent the application of the doctrine of equivalents here.

We agree with Primos that the district court correctly determined that prosecution history estoppel does not apply here to preclude the application of the doctrine of equivalents. As the Supreme Court explained in Festo, 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. 535 U.S. at 740. There are situations, however, in which a patentee may overcome that presumption. Id. One such situation is when the “rationale underlying the amendment may bear no more than a tangential relation to the equivalent in question.” Id. at 740-41.

The term “plate” in claim 2 of the ’578 patent 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. The district court correctly recognized that the addition of the term “length” did not narrow the scope of the claim because every physical object has a length. The district court also determined that adding the limitation that the plate be “differentially spaced” above the membrane did narrow the scope of the claim, and the court assumed that the reason for the amendment was a substantial one relating to patentability. We agree with the district court, however, that the territory surrendered by the “differentially spaced” amendment comprises plates that are not differentially spaced above the membrane. That conclusion is consistent with the prosecution history. The patentee added the “differentially spaced” limitation to distinguish the diaphragm mouth call from a prior art device that consisted of a shelf-like structure positioned on top of the membrane without any spacing. The accused device, however, includes a dome that is spaced above the membrane. Because the accused device’s dome includes the spacing, the amendment was merely tangential to the contested element in the accused device, and thus prosecution history estoppel does not apply to prevent the application of the doctrine of equivalents.

Hunter’s Specialties also argues that the court should not have allowed the application of the doctrine of equivalents because, by doing so, the claim limitation “plate” in claim 2 of the ’578 patent was vitiated. According to Hunter’s Specialties, the court’s construction of the term “plate” requires a specific structure “of relatively uniform thickness and flatness which may also have some moderate curvature to it. Hunter’s Specialties asserts that allowing a “dome” to be considered an equivalent to a “plate” would eliminate that limitation from the claim. Primos responds that the “all limitations rule” is not applicable to the circumstances in this case. According to Primos, the term “plate” does not convey a definitive, geometric shape or structure, and thus that claim limitation was not vitiated. Primos asserts that the district court properly allowed the jury to consider whether a “dome” was equivalent to a “plate” and that in doing so, no claim limitation was eliminated.

We agree with Primos that the application of the doctrine of equivalents was not improper in this case. Under the doctrine of equivalents, “a product or process that does not literally infringe upon [sic] the express terms of a patent claim may nonetheless be found to infringe if there is ‘equivalence’ between the elements of the accused product or process and the claimed elements [sic] of the patented invention.” Warner-Jenkinson Co., Inc. v. Hilton Davis Chem. Co., 520 U.S. 17, 21 (1997) (citation omitted). The “all limitations rule” restricts the doctrine of equivalents by preventing its application when doing so would vitiate a claim limitation. Warner-Jenkinson, 520 U.S. at 29 (stating that the doctrine of equivalents cannot be applied broadly so as to “effectively eliminate that [claim] element in its entirety”); Lockheed Martin Corp., 324 F.3d at 1321 (“[I]f a court determines that a finding of infringement under the doctrine of equivalents ‘would entirely vitiate a particular claim element,’ then the court should rule that there is no infringement under the doctrine of equivalents.” (citation omitted)).

On appeal, Hunter's Specialties argues that we should reverse the jury’s finding of equivalence because the substitution of the accused dome for the claimed “plate” would vitiate the “plate” limitation and thereby violate the all limitations rule. As the district court recognized, Hunter’s Specialties is essentially contending that there can be no equivalent to the claimed “plate.” Our precedent has recognized that “[t]here is no set formula for determining whether a finding of equivalence would vitiate a claim limitation, and thereby violate the all limitations rule. Rather, courts must consider the totality of the circumstances of each case and determine whether the alleged equivalent can be fairly characterized as an insubstantial change from the claimed subject matter without rendering the pertinent limitation meaningless.” Freedman Seating Co. v. Am. Seating Co., 420 F.3d 1350, 1359 (Fed. Cir. 2005) (citations omitted). Thus, because Primos’s theory of equivalence (i.e., that a dome is equivalent to the claimed “plate”) does not “effectively eliminate . . . [the ‘plate’ limitation] in its entirety,” it does not violate the all limitations rule. Noting that Hunter’s Specialties has not challenged whether the jury’s finding is supported by substantial evidence, we affirm the jury’s finding that the accused dome is equivalent to the claimed “plate.”

Prior Art Exclusion

We agree with Primos that the district court did not abuse its discretion in excluding the Aluminum Flap Call from evidence. The record reflects that the Aluminum Flap Call was not located until after discovery had closed. Moreover, although the Aluminum Flap Call may have been mentioned during discovery, it was never identified to the court as an invalidating prior art device. The district court prevented Hunter’s Specialties from introducing the Aluminum Flap Call into evidence because it “did not demonstrate diligence in attempting to locate the call during discovery” and because during discovery Hunter’s Specialties did not assert that it was claiming the Aluminum Flap Call as invalidating prior art. That determination was not an abuse of discretion. It was well within the district court’s province to determine that because the Aluminum Flap Call was not identified as potential prior art until after discovery had closed and shortly before trial commenced, it would then be unfair to permit its introduction into evidence.