Motors: expansible chamber type – With motive fluid valve – Relatively movable serial valves
Reexamination Certificate
2007-01-16
2007-01-16
Leslie, Michael (Department: 3745)
Motors: expansible chamber type
With motive fluid valve
Relatively movable serial valves
C091S447000
Reexamination Certificate
active
11103922
ABSTRACT:
Disclosed is a hydraulic control valve having a holding valve with improved response characteristics. The hydraulic control valve includes a valve housing including a pump path communicating with a hydraulic pump, a tank path communicating with an oil tank, and first and second cylinder ports communicating with a hydraulic cylinder, a control spool movably provided in the valve housing, cutting the pump path off the first and second cylinder ports in a neutral state and selectively connecting the pump path and the tank path with the first and second cylinder ports while moving in left and right directions if pilot signal pressures are applied thereto, a holding valve provided between the second cylinder port and the control spool, cutting off the second cylinder port when the control spool is in a neutral state and holding load of the hydraulic cylinder so as not to cause natural drop of the hydraulic cylinder, and an actuating path for the holding valve connecting hydraulic oil of the second cylinder port to the tank path when the control spool is in a neutral state.
REFERENCES:
patent: 3943825 (1976-03-01), Bianchetta et al.
patent: 4192346 (1980-03-01), Iizumi
patent: 4204459 (1980-05-01), Johnson
patent: 4732076 (1988-03-01), Ewald
patent: 5259293 (1993-11-01), Brunner
patent: 6186044 (2001-02-01), Hajek, Jr. et al.
patent: 6691510 (2004-02-01), Kariya et al.
patent: 6907815 (2005-06-01), Kim
patent: 2-72201 (1990-03-01), None
Patent Abstracts of Japan of JP 2-72201 dated Mar. 12, 1990.
Ladas & Parry LLP
Leslie Michael
Volvo Construction Equipment + Holding Sweden AB
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