Appeal No. 1998-0294
Application No. 08/318,726
53 et seq.). This reference teaches that the porous body can
be heated by the direct passage of current through it, or by
“an insulated electrical heating coil arranged on the inner
peripheral surface, i.e., around the central longitudinal duct
4, or on the outer peripheral surface 17 or even inside the
porous body 1," in which cases “heating takes place by heat
convection” (column 3, lines 21-26).
It is axiomatic that the mere fact that the prior art
structure could be modified does not make such a modification
obvious unless the prior art suggests the desirability of
doing so. See In re Gordon, 733 F.2d 900, 902, 221 USPQ 1125,
1127 (Fed. Cir. 1984). In the Japanese device, a layer of ice
that is being maintained on the surface of a filter material
is heated by means located internally in a support tube to
cause sublimation of the ice into a vapor. This is profoundly
different in theory, structure and operation from the
Schladitz system, in which a liquid is vaporized while passing
through a porous member owing to heat being applied to the
porous member from the outside (in the example chosen by the
examiner). In our view, the examiner’s conclusion that one of
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