Power plants – Pressure fluid source and motor – Servo-motor having externally operated control valve sets...
Patent
1980-10-07
1982-12-21
Walton, George L.
Power plants
Pressure fluid source and motor
Servo-motor having externally operated control valve sets...
60445, 60452, 60447, 417217, 417218, F16H 3946, F04B 4902
Patent
active
043642306
ABSTRACT:
A hydraulic circuit is provided to prevent overspeeding the prime mover powering a hydrostatic transmission. The hydrostatic transmission includes a hydraulic motor fluidly coupled to a hydraulic pump. The hydraulic pump is driven by the prime mover and the hydraulic motor drives a rotational load. The hydraulic pump includes a swash plate tilted by a servomechanism. The servomechanism receives hydraulic fluid from a pump powered by the prime mover. A valve is operated to shut-off the hydraulic fluid to the servomechanism in the event that the pressure in either of the two conduits joining together the hydraulic pump and the hydraulic motor exceeds a pre-set maximum value or if the pressure in an auxiliary line exceeds the same pre-set maximum value or if the sum of the two pressures exceeds the pre-set maximum value. The pre-set maximum value is a variable quantity having its maximum value when the angle of tilt on a swash plate within the hydraulic pump is zero or when the plate is approximately perpendicular to the axis of rotation of the plate. It is proportional to the horsepower demanded from the prime mover. By shutting off the supply of hydraulic fluid to the servomechanism when the auxiliary pressure or any of the two pressures in the two lines coupling hydraulic motor with the hydraulic pump becomes excessive, the hydraulic pump is precluded from being operated to load the prime mover in such a matter that the prime mover and pump would accelerate to an overspeed condition. This circuit is superior to those devices which sense an engine overspeed condition and then react because this circuit prevents the overspeed condition from occurring in the first place.
REFERENCES:
patent: 3217493 (1965-11-01), Kempson et al.
patent: 3898807 (1975-08-01), Habiger
patent: 4189921 (1980-02-01), Knapp
patent: 4212164 (1980-07-01), Young
patent: 4216656 (1980-08-01), Hamma
J. I. Case Company
Walton George L.
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