Caterpillar Tractor Co.

William D McMillan

Cyril W Habiger

Walter Z Ruseff

Allyn J Hein

Glenn E Ferre, Deceased

David L Persson

Control system for pilot operated valve

A hydraulic system for controlling the displacement of a plurality of variable displacement pumps driven by a single prime mover including a source of pilot fluid under pressure including a fixed displacement pump adapted to be driven by the prime mover proportional to the speed thereof, a double-piloted, underspeed valve having an inlet and an outlet, the outlet being adapted to be connected to the variable displacement pumps for controlling displacement thereof, a conduit connecting one of the pilots to the source, an additional conduit, including a flow restricting device, connecting the other of the pilots to the source, and a summing valve having ports adapted to be connected to respective ones of the pumps, a port connected to the second conduit and a port connected to the inlet of the underspeed valve.

Hydraulic control for variable displacement pumps

A pump control assembly for a variable displacement pump has adjustable biasing means for providing improved control of the pump.

Pump control assembly having adjustable biasing means

A hydraulic power system having a plurality of variable displacement pumps for supplying pressurized fluid for manipulation of an implement includes control means operative to automatically adjust pump displacement to the output horsepower of a prime mover driving the pumps of a system. The control system includes underspeed valve means responsive to a deviation in the speed of the prime mover from a predetermined normal speed to transmit a fluid pressure signal to a servo control means for adjusting the displacement of the pumps. The underspeed valve means includes adjusting means for adjusting the underspeed valve to respond to a deviation from other engine speeds different from the normal operating speed.

Part throttle control -- pump override

A hydrostatic unit of the type contemplated by the present invention includes one or more pump and motor combinations interconnected by means of a conventional closed loop. Controls for the hydrostatic unit include a speed control and vent valve assembly as well as a venturi manifold which functions to normally establish a selected pressure differential in a pair of supply conduits. In order to automatically regulate displacement of each pump unit in response to both engine or prime mover speed and instant load conditions, an underspeed actuator valve unit is hydraulically responsive to the differential pressure in the two conduits and also to changes in output pressure developed by the pump unit.

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Joliet, IL, United States of America

William D McMillan