Patent Law

Construing the "Function" of a Means-Plus-Function Claim Element

By Dennis Crouch

Gregory Baran v. Medical Device Technologies (Fed. Cir. 2010)

Dr. Baran sued MDTech for infringing his patents covering automated biopsy instruments. Soon-to-be Federal Circuit Judge Kathleen O'Malley over-saw the district court case. After construing several disputed claims, Judge O'Malley ordered summary judgment of non-infringement. On appeal, the Federal Circuit affirmed.

Means-Plus-Function: I'll focus on an interesting question raised regarding Baran's means-plus-function (MPF) limitation. The limitation reads as follows: a 'release means for retaining the guide in the charged position.' 

35 USC 112 p6 provides for MPF claim elements expressed 'as a means or step for performing a specified function.'  The statute calls for the limitation to be 'construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.'  Federal Circuit precedent has logically added that the statutory 'corresponding structure' are structures that perform the claimed function.

What is the Claimed Function?: Here, the Federal Circuit was asked to construe Baran's MPF element to identify the claimed function.  MDTech argued that the claimed 'release means for retaining' required a structure that exhibited both a releasing function and a retaining function.  Dr. Baran argued that the claimed function was only that of retaining.  On appeal, the Federal Circuit agreed with the lower court that the means-preamble 'release' added a functional limitation to the claim element.

[T]he claim language recites both a release function and a retention function. Dr. Baran's argument regarding the placement of the term 'release' is unavailing. The relevant inquiry is whether the term at issue is purely functional. See Signtech USA, Ltd. v. Vutek, Inc., 174 F.3d 1352, 1356 (Fed. Cir. 1999) (construing 'ink delivery means' to be equivalent to 'means for ink delivery' because 'ink delivery' was purely functional language); Al-Site Corp. v. VSI Int'l, Inc., 174 F.3d 1308, 1318 (Fed. Cir. 1999) ('[W]hen it is apparent that the element invokes purely functional terms . . . the claim element may be a means-plus-function element despite the lack of express means-plus-function language.'). In the context of the '797 patent, the term 'release' is not an idle description but a vital function to be performed by the means-plus-function element. The patent does not recite a biopsy instrument that retains indefinitely without release; rather, the contemplated function is to retain for the express purpose of producing a spring-loaded release on demand. The claim language ties both functions to the same means-plus-function element, so it is appropriate that the element be construed accordingly.

Although it is difficult to take-away lessons from claim construction decisions, a potential best-practices approach to drafting MPF claims may be to eliminate any adjectives tied directly to the 'means.'  Of course, my best practice suggestion is intended for those times when you want to draft MPF claims with clarity.

Full post as published by Patently Obvious on August 17, 2010 (boomark / email).