Welker Bearing v. PhD, Inc. (Fed. Cir. 2008)
Mechanism For: Welker's patent claims a clamping mechanism for holding parts in place when welding. The appeal focuses on construction of a "mechanism for moving said finger." Affirming a prior similar ruling, the Federal Circuit found that the claim structure "mechanism for [performing a function]" is presumptively interpreted as a means-plus-function claim element.
"The term 'mechanism' standing alone connotes no more structure than the term 'means.'" Quoting MIT v. Abacus Software, 462 F.3d 1344 (Fed. Cir. 2006).
Instead of claiming a "mechanism for moving said finger," the patentee could have claimed a "finger displacement mechanism." Opining on that counterfactual, the Federal Circuit noted that it would not have presumed a means-plus-function construction.
"If claim 1 … had recited, e.g., a "finger displacement mechanism," a "lateral projection/retraction mechanism," or even a "clamping finger actuator," this court could have inquired beyond the vague term "mechanism" to discern the understanding of one of skill in the art. If that artisan would have understood such language to include a structural component, this court's analysis may well have turned out differently. Instead the applicant chose to express this claim element as "a means or step for performing a specified function without the recital of structure, material, or acts in support thereof.""
A reminder here: means-plus-function language is akin to fools gold. Welker's "mechanism" claim appears broadly written until means claim interpretation doctrine limited to the particular structures disclosed in the specification that perform the claim function and structures that are only insubstantially different. Here, Welker described a linear finger movement which was considered substantially different from a rotational movement.
Means-Plus-Function Equivalents versus Doctrine of Equivalents: Means-plus-function claims are interpreted to cover only structures disclosed in the specification that perform the claimed function and, in addition, any equivalents of those disclosed structures. On its face, this appears duplicative of the traditional doctrine of equivalents (DOE). In this case, the Federal Circuit spells out some differences between the two. Most notably, "an equivalent structure [for means-plus-function analysis] under § 112 ¶ 6 must have been available at the time of the issuance of the claim, whereas the doctrine of equivalents can capture after-arising technology developed after the issuance of the patent." This statement by the court does not, however, precisely explain the distinction. For means-plus-function claims, court precedent allows the doctrine of equivalents to only capture after-arising technology. [Link] "Indeed this case does not present a case for equivalents under the doctrine of equivalents at all. This case presents only the question of structural equivalents under §112 ¶ 6."