Telcordia Technologies, Inc. v. Cisco Systems (Fed. Cir. 2010)
Chief Judge Rader and Judge Prost sparred over the level of explanation necessary to ensure that a means plus function (MPF) claim is found definite. The Patent Act (35 U.S.C. 112 p6) permits claim limitations written as a "means or step for performing a specified function." The statute provides that an MPF "claim [limitation] shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof." However, the claim will be found indefinite and therefore invalid if the specification fails to include at least some structure that is clearly linked or associated with the claimed function. “The question is not whether one of skill in the art would be capable of implementing a structure to perform the function, but whether that person would understand the written description itself to disclose such a structure.” (Quoting Tech. Licensing Corp. v. Videotek, Inc., 545 F.3d 1316, 1338 (Fed. Cir. 2008)).
Telcordia's patent in this case is directed to a double-ring network that is designed to withstand either a line-cut or a failed node. One element of the claim requires a "monitoring means, associated with the first ring and the second ring, for evaluating the integrity of the multiplexed subrate communications on the first ring and the second ring."
Writing for the majority, Chief Judge Rader (joined by Judge Lourie) held that the claimed "monitoring means" had been properly described in the specification. The dissent cited the same precedent but could not find anything in the specification that links disclosed structures to the claimed function. In discussing the opinion, Foley's Hal Wegner described the opinion as "pitting the leader of the older generation [of Federal Circuit Judges] against a contender from the next generation."
Stats: About 15% of newly issued patent included at least one claim having an MPF limitation. And, of those patents that include an MPF limitation, about half recite fewer than five such limitations. It appears that attorneys are using MPF claim language primarily as a back-up. Longer claim-sets are more likely to include means-plus function language. Thus 21% of patents with above-average-sized claimsets (by character count) include a means-plus-function limitation while only 11% of patents with below-average-sized claimsets include an MPF limitation. Looking claim-by-claim, I found that only 3% of the recently issued patents include means-plus-function limitations in every independent claim. Patents with MPF terms are more frequently associated with non-assigned patents (usually individual inventors). Patents arising from certain countries are much more likely to include MPF limitations. The chart below looks at the most common foreign filing jurisdiction for priority claims and reports the percentage of US patents arising from those foreign filings that include MPF limitations. [More Data]