Chapter §16.06 Infringement of Means-Plus-Function Claim Elements

• Jurisdiction: United States

§16.06 Infringement of Means-Plus-Function Claim Elements

As discussed in Chapter 2 of this treatise, means-plus-function claiming is a technique for drafting patent claims that uses functional language to generically recite what an element of the invention does rather than its structure.⁴⁸¹ Such claim limitations are governed by 35 U.S.C. §112(f).⁴⁸² The statute not only permits the use of means-plus-function claim elements but also includes an important provision concerning the scope of such elements. Scope issues are directly pertinent to infringement, as described below.

[A] Literal Infringement

The literal scope of a means-plus-function claim includes the statutory "equivalents thereof." In that sense, at least, the statutory equivalents of 35 U.S.C. §112(f) are not the same analytically as the "equivalents" referred to in application of the judicially created doctrine of equivalents, addressed infra.⁴⁸³ As Professor Chisum has explained, "[u]nlike the doctrine of equivalents, which compares a patent claim with an accused product or process, Section 112/6 [post-AIA, §112(f)] entails a comparison of one structure, material or act (that in the specification) to another structure, material or act (that in a product or process alleged to be covered by the patent claim)."⁴⁸⁴

Despite these differences, the Federal Circuit has sanctioned the use of the same "insubstantial differences" test for equivalency under 35 U.S.C. §112(f) as under the doctrine of equivalents.⁴⁸⁵ Because one way of establishing insubstantial differences is to apply the classic tripartite "function, way, and result" test,⁴⁸⁶ the Federal Circuit also has held that this test collapses to "way" and "result" when applied to §112(f) claim elements.⁴⁸⁷ This is because in order to have literal infringement of a means-plus-function claim, the function performed by the accused component must be identical, not merely insubstantially different, to the function recited in the claim. Thus, the "substantially identical function" part of the function-way-result test is not applicable when determining literal infringement of a means-plus-function claim.⁴⁸⁸

[B] Infringement Under the Judicially-Created Doctrine of Equivalents

§16.06 Infringement of MPF Elements

The previous discussion focused exclusively on the literal scope of a means-plus-function element in a claim. Can there be infringement of a claim drafted in means-plus-function format under the judicially created doctrine of equivalents? This...