“Literal infringement of a means-plus-function limitation requires that the relevant structure in the accused device perform the identical function recited in the claim and be identical or equivalent to the corresponding structure in the specification. A structure in the accused device constitutes an equivalent to the corresponding structure in the patent only if the accused structure performs the identical function ‘in substantially the same way, with substantially the same result.’” Is that clear? To some folks, at least, no!
(International Trade Commission v. General Protecht Group, Inc.)
The I.T.C. found that certain ground fault interrupters – electrical devices designed to prevent people from electrocuting themselves in their own bathrooms – infringed a patent owned by Pass & Seymour, Inc. The patent claims at issue included an element recited in means-plus-function form, “latching means for releasably retaining the conducting member in the first position.” The patent disclosed a mechanical device wherein a spring “biased” (patent attorney lingo meaning “pushed or held”) the conducting member in the first position. The corresponding structure in the accused device was a magnet. The administrative law judge (ALJ) at the I.T.C. held that this magnetic latch was “equivalent” to the mechanical one disclosed in the patent. The I.T.C. adopted this position and General Protecht appealed to the C.A.F.C.
Reversed. General Protecht’s structure used only a magnet in place of the disclosed mechanical device which required, “a spring latching member, a pin with a shoulder extending through a hole in the spring latching member, and a spring biasing the pin to pull against the force of the spring latching member. [O]ne system that accomplishes the same function mechanically and another system that accomplishes the same function using magnetic force ‘function in fundamentally different ways.’”
Not giving up, Pass & Seymour pointed to expert testimony that “magnets were well known as latches.” Not good enough ruled the C.A.F.C. “This testimony ‘goes to the function or result of these systems, and begs the issue of the way in which [the mechanical] systems and the [magnetic] systems actually work.’”
THE LESSON TO BE LEARNED: Claims with means-plus-function limitations are nowhere near as broad as some folks seem to think they are.
This is one of a number of examples in which the ITC appears to be more flexible (i.e., lenient) than the CAFC and district courts (the other example I'm thinking of is the ITC's quite-broad "domestic industry" standard). It will be interesting to see what develops from this tension, and which side wins.