Appeal No. 1997-0961
Application No. 08/254,654
sealed hydraulic valve system which operates with a solenoid driven magnetic
actuator. The magnetic actuator effects controlled movements of a core rod
linked to a pilot. The pilot, in turn, causes actuation of the main valve. Actual
valve position is remotely ascertained by the position of the core within the
magnetic field by means of a linear variable differential transformer (LVDT).
The LVDT generates a signal predeterminately related to the position of the
driver rod within the magnetic field. The LVDT signal is compared by an
electronic comparator to an input command signal calibrated to a specific valve
position. Deviation between the LDVT [sic: LVDT] feedback signal and input
command signal generates an error signal which is amplified and applied to the
solenoid to vary the magnetic field to correct the valve position. The fast
continuous feedback control permits constant accurate positioning of the main
valve to an accuracy within 0.5% of the valve=s command position.
A copy of the appealed claims is appended to appellants= brief.
The following references are relied upon by the examiner as evidence of obviousness in
support of his rejection under 35 U.S.C. ' 103:
Fales 3,850,196 Nov. 26, 1974
Schwelm 5,178,358 Jan. 12, 1993
Claims 2 through 11 stand rejected under 35 U.S.C. ' 103 as being unpatentable over
Schwelm in view of Fales.
According to the examiner=s findings (see page 2 of the final office action (Paper No.
20 mailed April 14, 1995) and pages 3 and 4 of the examiner=s answer (Paper No. 27 mailed
September 10, 1998)), Schwelm=s valve control system comprises an inductive displacement
transducer 14 having an output signal that indicates the actual position of the main valve 8, a
control valve 6 for operating the main valve 8, a proportional magnet 4 for controlling the
control valve 6 and a closed loop circuit between transducer 14 and magnet 4. In his answer
(see page 4), the examiner has taken the position that Schwelm=s closed loop circuit
Ainherently includes a comparator means and deviation control means.@
The Schwelm patent lacks an express disclosure that the inductive displacement
2
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