Appeal No. 1998-0649 Page 7
Application No. 08/309,323
remains open. Ruchser’s invention is directed to dealing with
this situation and it involves the use of the pistons 76 and 78
responding to unequal pressures. More specifically, as
depicted in Ruchser’s Figure 3, because of the location of
pressures introduced by the malfunction, the full supply
pressure is built up in the working chamber 72 via the supply
inlet 20, annular passage 51, connecting passage 54, annular
passage 60 and conduit 64. Meanwhile, working chamber 74 is
vented via the conduit 66, open valve seat 45 and the open
valve seat of working piston 16, to the return outlet, i.e.,
pressure relief device, 24. See column 5, lines 1-16 of
Ruchser. Thus, the operation of the Ruchser device in the
event of a malfunction makes it clear that the pistons 76 and
78 and the sliding member 80 are in a slidable relationship
with each other and all move within the same cavity.
Accordingly, we agree with the examiner’s assessment that the
cavity in Ruchser, which holds pistons 76 and 78, sliding
member 80 and the electrical equipment, may reasonably be
considered to be a single “housing chamber,” as claimed. This
being the case, and that housing chamber being vented to
pressure relief device 24, via the conduit 66, open valve seat
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