The statutory authority for "step-plus-function" claims can be found in 35 U.S.C. 112, paragraph 6.
"An element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof."
While the distinction between function and structure in a means-plus-function claim may be straightforward enough, the distinction between a "step" (an act) and a function is a lot more difficult to make. Several courts have tried over the years. The Federal Circuit, for example, once stated that a function refers to "what a claim element ultimately accomplishes" while an act corresponds to "how the function is accomplished" (Macco Corp. v. U.S. 303 F.3d 1316, 1327 (Fed. Cir. 2002)). Over the years, however, that distinction has been very difficult to see in a number of real-world cases. The result has been that courts have been loathe to interpret a claim as a "step-plus-function" claim. In fact, many legal scholars recommend that Congress simply remove the "step for" language from the statute.
"An element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof."
While the distinction between function and structure in a means-plus-function claim may be straightforward enough, the distinction between a "step" (an act) and a function is a lot more difficult to make. Several courts have tried over the years. The Federal Circuit, for example, once stated that a function refers to "what a claim element ultimately accomplishes" while an act corresponds to "how the function is accomplished" (Macco Corp. v. U.S. 303 F.3d 1316, 1327 (Fed. Cir. 2002)). Over the years, however, that distinction has been very difficult to see in a number of real-world cases. The result has been that courts have been loathe to interpret a claim as a "step-plus-function" claim. In fact, many legal scholars recommend that Congress simply remove the "step for" language from the statute.