Appeal No. 1998-0091
Application No. 08/404,054
pressures the two discs bottom out against each other thereby
preventing damage to the pressure sensor"). However, Bell
does not describe this as constituting a short-circuit
problem, presumably because the bottoming out
occurs at pressures outside of the desired measurement range,
as explained in the following limitation in Bell's claim 1:
means including said members and said fused
glass frit for permitting said electrically
conductive plates to deflect toward one another
without touching throughout said predetermined
measurement range while allowing said plates to
engage one another and bottom out under high
overload pressure conditions, so that said pressure
sensor is protected against impairment.
Hegner's "Background of the Invention" describes prior
art
capacitive pressure sensors of the type which include a
diaphragm and substrate made, for example, of ceramic or
glass, and having respective conductive layers formed of
silicon carbide, niobium, or tantalum (col. 1, lines 10-25).
These components are joined together using a ring-shaped part
of active brazing material, which has the disadvantage that
the uncovered (by conductive material) portions of the
substrate and diaphragm become contaminated, making the
-8-
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