Addressing the question of structural equivalents under the means-plus function limitation (§112, ¶ 6), the U.S. Court of Appeals for the Federal Circuit affirmed the district court’s grant of summary judgment, finding that the district court correctly construed the critical claim element of the asserted patent as a means-plus-function limitation. Welker Bearing Co. v. PHD, Inc., Case No. 06-13345 (Fed. Cir., Dec. 15, 2008) (Rader, J.).

Welker Bearing asserted two patents directed to welding pin clamps against two of PHD’s clamping products “Clamp 1” and “Clamp 2.” The Federal Circuit upheld the lower courts rulings of non-infringement for both accused products.

With respect to Clamp 1, Welker Bearing argued that PHD infringed by failing its affirmative duty to take the accused product off the market once the asserted patent issued. Affirming the district court’s ruling of non-infringement, the Federal Circuit noted that the record does lacks any evidence that PHD continued to offer its product for sale once the patent issued. “Mere possession of a product which becomes covered by a subsequently issued patent does not constitute an infringement of that patent until the product is used, sold, or offered for sale in the United States during the term of the patent.”

Next, the Federal Circuit addressed the question of whether the district court correctly construed the claim element “mechanism for moving said finger” to imply a means-plus-function limitation. Court precedent applies means-plus-function treatment “only to purely functional limitations that do not provide the structure that performs the recited function.” The Court noted that applicant could have added additional modifiers to supply more structural context to the ambiguous term “mechanism,” e.g., a “finger displacement mechanism,” a “lateral projection/retraction mechanism” or even a “clamping finger actuator.” Without any additional qualifier, the Court determined that “mechanism” lacks structure and the district court was correct in applying the means-plus-function limitation. 

As a means-plus-function claim element, the limitation “mechanism” requires a corresponding structure in the specification for its broad functional language. The Court pointed out that literal infringement of a claim limitation under means-plus-function treatment “requires that the relevant structure in the accused device perform the identical function recited in the claim and be identical or equivalent to the corresponding structure in the specification.” The Court noted that, although the asserted claim does not on its face require any rotating mechanism, construing “mechanism” as a means-plus-function limitation compels defining “mechanism for moving said finger” to include a rotating central post¾the only structure provided for “mechanism” in the specification. The Court concluded that, because PHD’s Clamp 2 is a linear moving mechanism for finger movement and does not use any rotational movement, the accused product is substantially different from the construed claim and does not infringe.

Practice Note: Patent drafters should be mindful when using means-plus-function language in their claims. Even if the claim does not include the word “means,” the means-plus-function doctrine may apply to similar generic words that lack structure. Under the means-plus-function doctrine, a claim that appears broadly written on its face will be limited to the particular structures disclosed in the specification that perform the claim function and structural equivalent.