Appeal 2006-3268
Application 10/479,696
The pressure P2 approximates the pressure in mixing chamber 4 and
is influenced by the pressure Pg (Hofmann: col. 4, ll. 25-28; col. 5, ll. 12-
15). Accordingly, pressure P2 and Pg are interdependent such that a change
in one of them affects the other. Therefore, the pressure Pg controls pressure
P2, and thus provides a measurement of the pressure P2.
From the foregoing, we find the “pressure recording element” in
Hofmann’s device constitutes the gas line 18 which provides pneumatic
feedback of the pressure condition in the mixing chamber 4 (and hence
pressure P2) to maintain the pressure drop (P2-P1) across the metering valve
16 constant. Thus, pressure P2 is pneumatically sensed, measured and
recorded via interdependent pressure Pg, which is used to control the
pressure control valve 50 such that the pressure drop (P2-P1) across the
metering valve 16 is maintained constant.
Accordingly, Hofmann discloses Appellant’s claim 13 feature “a
pressure recording element recording pressure changes at an output side of a
metering device” and with which a “means for regulating a pressure of the
reducing agent” interacts “so that the pressure changes have an influence on
the pressure regulation.” Moreover, Hofmann discloses Appellant’s claim
26 feature “recording pressure changes at a side of the metering device
facing the catalytic converter system, the pressure changes having an
influence on the pressure regulation.”
Furthermore, because Hofmann’s gas line 18 acts to sense, measure
and record pressure changes, we find that Hofmann discloses a “pressure
sensor” (i.e., gas line 18) as claimed by Appellant in claim 21.
10
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