The U.S. Court of Appeals for the Federal Circuit has articulated a framework in which to construe method claims to determine if a step-plus-function limitation is present. Masco Corp. v. Mas-Hamilton Group, Inc., Case No. 01-5107 (Fed. Cir. Aug. 28, 2002).
This case is related to an earlier lawsuit between Mas-Hamilton and LaGard concerning the parent of patents in suit. In that case, the district court determined (and the Federal Circuit affirmed) that the accused device, an electronic lock that is the same as the one in issue here, did not infringe certain apparatus claims, either literally or under the doctrine of equivalents.
In the present case, the Court of Claims was asked to construe certain method claims directed to use of that electronic lock. In doing so, the court construed various method steps and held that the claimed step of "holding the lever in a position" is not a step-plus-function limitation because "holding" comprises an act that precludes §112, ¶ 6 treatment. Similarly, the court held that the step of "operably connecting the lever and the dial" is not a step-plus function limitation, because "connecting" is an act. However, the court held that the step of "transmitting a force" is a step-plus function limitation, because "transmitting" is a function, not an act.
The Federal Circuit affirmed the Court of Claims ruling regarding "holding the lever" and "operably connecting" steps. However, the Federal Circuit reversed with regard to the "transmitting" step, explaining that in the context of method claims, the use of the term "steps for" signals the drafter’s intent to invoke §112, ¶6. "However, even where the drafter employs the ‘step for’ language, §112, ¶6 is implicated … only when steps plus function without acts are present." (Emphasis in original.)
The Federal Circuit, referencing the admonition from the U.S. Supreme Court in Festo that its decision of law should not "disrupt patentees’ settled expectations regarding the scope of their claims," emphasized that "[w]here the claim drafter has not signaled his intent to invoke §112, ¶6 by using the ‘step[s] for’ language, we are unwilling to resort to that provision to constrain the scope of coverage of a claim limitation without a showing that the limitation contains nothing that can be construed as an act." The Court then went on to hold that "where a method claim does not contain the term ‘step[s] for,’ a limitation of that claim cannot be construed as a step-plus-function limitation without a showing that the limitation contains no act."
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