United States: A New Means-Plus-Function Presumption?

Determining how to draft and avoid drafting patent claim elements in means-plus-function format for coverage under 35 U.S.C. §112, sixth paragraph (hereinafter 112(6)), as well as determining whether an existing claim element invokes 112(6), are absolute requirements for skilled patent attorneys. While the Court of Appeals for the Federal Circuit (hereinafter the "Federal Circuit") has had several recent opportunities to clarify this issue, a quagmire of uncertainties have been created in the areas of claim drafting and claim interpretation. In view of these uncertainties, patent practitioners should take steps to ensure that claim elements intended to invoke 112(6) and claim elements intended not to invoke 112(6) are treated as intended.

According to 112 (6): "[a]n element in a claim for a combination may be expressed as a means or a step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof." Once a determination has been made that an element in a claim has been expressed in terms of means-plus-function language, thus invoking 112(6), the element is construed as covering only "the corresponding structure, material, or acts described in the specification and equivalents thereof." Therefore, a determination that 112(6) has been invoked often results in a narrower interpretation of the claim element than would otherwise have resulted if a broad generic term had been used in the claim to describe the particular claim element. The following recent decisions by the Federal Circuit illustrate the manner in which the Federal Circuit has recently dealt with this issue.

In Greenberg v. Ethicon Endo-Surgery, Inc., 91 F.3d 1580, 39 U.S.P.Q.2d 1783 (Fed. Cir. 1996), decided August 8, 1996, the Federal Circuit addressed, inter alia, the issue of whether claim language reciting a "detent mechanism" invoked 112(6). Greenberg, brought suit against Ethicon for infringement of Greenberg's patent, U.S. Patent No. 4,674,501 (hereinafter the '501 patent). At trial, the district court found that the claim language reciting a "detent mechanism" constituted a means for performing a specified function and thus invoked the provisions of 112(6). This determination was based in part on the district court's finding that "detent mechanism" is defined in terms of function. The district court then granted Ethicon's motion for summary judgement, concluding that although the detent-type mechanisms in each of the accused devices performed the function of the claimed detent mechanism element, the evidence proffered by Greenberg was inadequate to show that the detents found on the accused devices were structurally equivalent to the detent mechanism disclosed in the specification of the '501 patent. Only one embodiment of the detent mechanism was disclosed in the ‘501 patent.

On appeal, the Federal Circuit reversed the district court and held that the claim language did not fall within the purview of 112(6). With respect to the functionality of the element, "detent mechanism", the court held that the fact that the element is defined in terms of function is insufficient to convert the term into a means-plus-function element. The court stated that what is important is not whether the element is defined in terms of what it does, but whether the term used to describe the element has a well understood meaning in the art. The court also noted the permissive language of 112(6), which states that an element in a claim for a combination "may be expressed" as a means for performing a specific function, and held that "[t]he question then is whether, in the selection of claim language, the patentee must be taken to have exercised [the option of using means-plus-function language]".

Finally, the court held that "it is fair to say that the use of the term 'means' has come to be so closely associated with 'means-plus-function' claiming that it is fair to say that the use of the term 'means' (particularly as used in the phrase "means for") generally invokes section 112(6) and that the use of a different formulation generally does not."

On November 1, 1996, the Federal Circuit again addressed the triggering of 112(6) in York Products, Inc. v. Central Tractor Farm & Family Center and Custom Form Mfg., 99 F.3d 1568, 40 U.S.P.Q.2d 1619 (Fed. Cir. 1996). York involved U.S. Patent No. 4,958,876 (hereinafter the '876 patent) issued to York. An independent claim of the ‘876 patent recited "means formed on the upwardly extending liner sidewall portions including a plurality of spaced apart, vertically extending ridge members protruding from the liner sidewall portions and forming load locks".

One of the issues addressed on appeal was whether this language triggered 112(6). In addressing this issue, the court cited Greenberg, supra, for the proposition that "the use of the word 'means' triggers a presumption that the inventor used this term advisedly to invoke the statutory mandates for means-plus-function clauses" (emphasis added). The court went on to state, however, that "mere incantation of the word 'means' in a clause reciting predominantly structure cannot evoke [112(6)]." In analyzing the means clause, the court stated that the word "means" was followed by a "detailed recitation of structure" and that the language did not link the "means" to a function. The court held: "[w]ithout an identified function, the term 'means' in this claim cannot invoke [112(6)] ... Without a 'means' sufficiently connected to a recited function, the presumption in use of the word 'means' does not operate."

Therefore, York follows the holding in Greenberg for support of the holding that the use of the word "means" triggers a presumption that the inventor used this term advisedly to invoke 112(6). York, however, recognizes an exception to the rule set forth in Greenberg which results in a rebuttal of the presumption when (1) "means" is followed by a detailed recitation of structure which describes the "means" and (2) the claim language does not link the "means" to function.

In Cole v. Kimberly-Clark Corp., 102 F.3d 524, 41 U.S.P.Q.2d 1001 (Fed. Cir. 1996), decided December 6, 1996, the Federal Circuit addressed the question of whether the claim language "perforation means extending from the leg band means to the waist band means through the outer impermeable layer means for tearing the outer impermeable layer means for removing the training brief in case of an accident by the user", recited in U.S. Patent No. 4,743,239 (hereinafter the '239 patent), triggered 112(6).

Cole filed suit against Kimberly-Clark (hereinafter K-C) for infringement of the '239 patent, and K-C filed a motion for summary judgement of noninfringement. With respect to Cole's claim of literal infringement, the district court held that "[t]he only reasonable reading of [perforation means in claim 1] is that the sides of her invention tear by means of a perforation, but K-C's accused products do not have perforations". The district court found that K-C's briefs "have seems which have been bonded together and are capable of tearing. When the side seems are torn, it becomes obvious that the sides are not held together by perforations as they leave a jagged tear line." Based on these findings, the district court granted K-C's motion for summary judgement of no literal infringement, holding that "as used in Cole's patent, a 'perforation means' is a perforation" and none of K-C's accused products include perforations.

On appeal, Cole argued that the district court erred with respect to its finding of no literal infringement because the "perforation means ... for tearing" element of claim 1 was a means-plus-function element under 112(6), and thus must by construed to cover all elements disclosed in the specification of the '239 patent and their equivalents. The specification of the '239 patent referred to scoring, scored sides, and perforations. The district court had found that "perforation means" did not qualify as a means-plus-function element under 112(6) because it includes the word "perforation" and, therefore, refers to a definite structure to perform the tearing function.

On appeal, the Federal Circuit held that "[t]o invoke [112(6)], the alleged means-plus-function claim element must not recite a definite structure which performs the described function." The court held that the claim language "perforation means ... for tearing" did not invoke 112(6) because "it describes the structure supporting the tearing function (i.e., perforations)". The court found that the "claim describes not only the structure that supports the tearing function, but also its location (extending from the leg band to the waist band) and extent (extending through the outer impermeable layer)." The court held that "[a]n element with such a detailed recitation of its structure, as opposed to its function, cannot meet the requirements of the statute."

The majority opinion in Cole does not even mention York or Greenberg. With respect to the first factor set forth in York, it is the opinion of the authors that the claim language in Cole does not provide a "detailed recitation" of structure because although "perforation means" does specify some structure, the word "perforation" is fairly broad in that it merely describes a condition relating to some degree of pre-piercing or pre-punching of the material without completely severing the material. With respect to the second factor in York, the means is definitely linked to the function of tearing because the claim recites the words "for tearing". Therefore, it appears that the holding in Cole is not consistent with the holdings in York and Greenberg.

Finally, in O.I. Corp. v. Tekmar Co. Inc., 42 U.S.P.Q.2d 1777 (Fed. Cir. 1997), decided on May 22, 1997, the court examined the issue of whether the district court erred in applying 112(6) to the word "passage" contained in the phrase "means for passing the analyte slug through a passage...". Although the Federal Circuit found that "means for passing the analyte slug" clearly invoked 112(6), the court found that the district court erred in applying 112(6) to the word "passage". Thus, even if a claim element appears to be covered by 112(6), a closer reading of the element may reveal that one or more parts of the element may be outside 112(6).

In holding that the "means for passing" clause invoked 112(6), the court cited Greenberg for the proposition that the use of the "phrase ‘means for’ generally invokes [112(6)]". The court also cited Cole for the proposition that, in order to invoke 112(6), the "means-plus-function limitation must not recite definite structure for performing the described function". Therefore, since the claim referred to "means for passing", which clearly indicated the function provided by the means, and since no structure was given for the means, this language invoked 112(6). Thus, while the court did not cite York or examine this issue in terms of a presumption, the basic rules for triggering 112(6) do not appear to have been changed.

In view of the Federal Circuit's disparate treatment of the issues relating to the invocation of 112(6), it is probably wise to draft a set of claims which use means-plus-function format and a set of claims which clearly do not. This will demonstrate an intent to invoke 112(6) on one hand and an intent not invoke 112(6) on the other. In the claims which do not use means-plus-function format, it is preferable to recite broad terms for the claim elements without reciting any function. The terms used to define the claim elements should not themselves be stated in terms of function. If a term must be used which by its name conjures up how the element functions, the term should have a well-understood meaning in the art. With respect to the set of claims that use means-plus-function claiming, structural adjectives should never be placed in front of the word "means"; the function should immediately follow the word "means"; and care should be taken in describing locational structure.