Appeal No. 95-3876
Application 08/222,009
element in mean-plus-function language be construed to cover
only the minimum "corresponding structure, material, or acts
described in the specification and equivalents thereof"
necessary to perform the function. Construing a mean-plus-
function limitation to cover more structure than is necessary
to perform the function adopts a narrower than necessary
interpretation and amounts to reading limitations into the
claim, especially where such limitations are used to
distinguish over the prior art. I find that the structure to
perform the function of "removing the enabling voltage at the
gate" can be appellants' transistors Q4 and Q5, which
structure finds direct correspondence in transistors 22 and 23
in the control voltage generation circuit 18 of Iwata.
Therefore, the "control means . . . for removing the enabling
voltage at the gate" does not define over the structure in
Iwata even if structure is considered under § 112, sixth
paragraph.
Appellants' specification describes that the IGBT is
switched off when transistor Q3 is turned on (specification,
page 20, lines 3-6): "When the transistor Q3 is so switched
on, the gate of the insulated gate bipolar transistor IGBT is
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Last modified: November 3, 2007