Another reminder to use means-plus-function claiming sparingly and with caution. The possibility that an ordinarily skilled artisan (e.g., expert witness) could find a structure that would work does not satisfy the disclosure requirements of means-plus-function claiming under § 112. “That ordinary skilled artisans could carry out the recited function in a variety of ways is precisely why claims written in ‘mean-plus-function’ form must disclose the particular structure that is used to perform the recited function.”
Background / Facts: The patented technology here relates to control and protection circuits for electronic lighting ballasts commonly used in fluorescent lighting. The claims recite novel circuitry that works in conjunction with “voltage source means” for providing the device with useable DC voltage.
Issue(s): Whether the “voltage source means” is a means-plus-function limitation but without any corresponding structure in the specification capable of providing the recited DC voltage to the device.
Holding(s): Yes. Starting with the construction issue, because claim 1 recites a “voltage source means,” there is a presumption that means-plus-function claiming under § 112, ¶ 6, applies. The claim goes on to merely recite the corresponding function: “providing a constant or variable magnitude DC voltage between the DC input terminals.” The term “voltage source” implies that voltage is provided, but the claim only sets out an indication of what the element “does, not what it is structurally.” Means-plus-function claiming under § 112, ¶ 6, therefore applies. The specification, however, fails to disclose any structure capable of “providing a constant or variable magnitude DC voltage between the DC input terminals” as claimed. Despite the various structure for performing this function offered by expert witnesses, the specification does not refer to a rectifier or any other structure capable of converting AC supply voltage into useable DC voltage. Nor does the specification disclose structure capable of supplying useable DC voltage directly from a DC supply voltage. Rather, it simply mentions drawing power from a power line source and DC supply voltages without specifying a capable structure or class of structures. Accordingly, because the term “voltage source means” in claim 1 invokes means-plus-function claiming under § 112, ¶ 6, and because the specification contains no corresponding structure, the asserted claims are invalid for indefiniteness under § 112, ¶ 2.