Over a vigorous dissent, a panel of the U.S. Court of Appeals for the Federal Circuit vacated a grant of summary judgment, finding that the district court had improperly imported unclaimed functions into a means-plus-function claim limitation. Applied Medical Resources Corporation v. United States Surgical Corporation, Case No. 05-1314 (Fed. Cir. May 15, 2006) (Prost, J.; Dyk, J. dissenting).
The claim in issue related to a trocar device with a "floating septum seal" that allows a surgical instrument to be inserted into an abdomen inflated with insufflation gas. The device simultaneously prevents the gas from leaking out, thus maintaining the inflation of the abdomen. The disputed claim limitation recited "means disposed circumferentially outwardly of the valve portions for supporting the valve portions within the seal housing, the supporting means being movable relative to the housing to permit the valve portions to float relative to the axis of the cannula."
Consistent with a ruling in a prior litigation, the district court found the claim term in issue to be a §112, ¶6 claim element, and the specification contained two corresponding disclosed structures. As to one of these structures Applied conceded the accused device was not the same as or the structural equivalent of it. Although the parties disputed the definition of several terms in the functional recitation, the district court left those unresolved but adopted Applied’s proposed construction of which the functions required. It then concluded the accused devices performed the recited functions, albeit in a substantially different way as compared to the remaining disclosed corresponding structure. Finding that the patentee had provided no "particularized testimony or linking argument" to establish equivalence, the court went on to hold that no reasonable jury could find the structures were equivalent. Applied appealed.
The Federal Circuit, considering the claim construction issue de novo, repeated its well-established syllogism that construction of a means-plus-function limitation requires (a) interpretation of "the claimed function" and (b) the identity of the corresponding structure in the written description of the patent that performs that function. Literal infringement of a means-plus-function limitation requires "that the relevant structure in the accused device perform the identical function required in the claim and be identical or equivalent to the corresponding structure in the specification."
Once identified, the patentee must show the relevant structure is equivalent to the disclosed structure; the two must "perform the identical function in substantially the same way, with substantially the same result." Any differences between the way the functions are performed must be insubstantial. Here, the parties agreed (a) that the claim required the performances of two functions, i.e., "supporting" and "permit to float," and (b) the identification of corresponding disclosed structures. However, they disagreed as to what the two functions required.
As a general rule, the Court observed that a district court errs (1) when it improperly imports unclaimed functions into a means-plus-function limitation during claimed construction to require more than is actually claimed or (2) when it improperly determines the way in which the disclosed structure performs the previously defined function. The majority opinion held that the lower court committed the second type of error when it improperly imported unclaimed functions into the two recited functions and then examined, for purposes of infringement, how the disclosed corresponding structures performed these other "extraneous" functions.
In dissent, Judge Dyk argued the district court’s construction of the requirements of the claimed function did not improperly import unclaimed functions. He opined the majority interpreted the recited function "more broadly than the claim language or written descriptions would support." According to the dissent, limiting the claim element by the way in which the corresponding disclosed structure performs the recited function is consistent with Federal Circuit precedent.
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