Power plants – Pressure fluid source and motor – Servo-motor having externally operated control valve sets...
Patent
1975-09-25
1976-12-28
Geoghegan, Edgar W.
Power plants
Pressure fluid source and motor
Servo-motor having externally operated control valve sets...
60451, 60465, 60488, F16H 3946
Patent
active
039993876
ABSTRACT:
A hydrostatic transmission for accelerating, driving and braking a high inertia load, such as the swing mechanism of a power shovel or crane, includes an engine-driven swashplate-type variable displacement constant speed reversible main hydraulic pump coupled in a closed loop circuit to a swashplate-type fixed displacement variable speed reversible hydraulic motor. A pair of control lever operated pilot pressure modulated pump displacement control valves selectively direct control fluid from an engine-driven fixed displacement constant speed charge pump to the stroking pistons of the servo control cylinders on the main pump to thereby control motor direction and speed. The charge pump also supplies replenishing fluid to the main pump/motor circuit through replenishing check valves. A network of three flow control valves is connected across the main pump/motor circuit and to the charge pump outlet to measure the fluid pressure drop across the motor and thus provide a torque feedback signal to modulate the control valves and thereby maintain maximum motor torque for the control lever position selected. A balancing signal is also transmitted from the charge pump to further modulate the control valves and thereby render them insensitive to variations in charge pump pressure appearing in the torque feedback signal.
REFERENCES:
patent: 2932948 (1960-04-01), Neff et al.
patent: 3788773 (1974-01-01), Van der Kolk
patent: 3788774 (1974-01-01), Roesslein
patent: 3823558 (1974-07-01), Tittman et al.
patent: 3901031 (1975-08-01), Knapp et al.
Geoghegan Edgar W.
Nilles James E.
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