Abstract: A manual displacement control is provided for varying the displacement of a hydraulic pump. The pump has a tiltable swashplate and is used in a hydraulic system which includes a control valve having an axially movable spool for metering control fluid to modulate the swashplate position. A displacement control linkage has a non-linear coupling element and a resilient override spring serially connected between the input lever and the valve spool. A torsional centering spring is connected between the input lever and the override spring to generate a feedback force which opposes a control force applied thereto and urges the input lever to a position representative of the no flow position of the pump swashplate. An adjustable connection is provided for centering the valve spool while maintaining a corresponding neutral position of the input lever and swashplate during assembly of the displacement control.

Abstract: An engine override control for an engine (10) which drives a vehicle transmission (18) and an auxiliary variable displacement pump (20) and which is operable to increase engine speed beyond a set engine speed command to increase flow from the auxiliary pump which has reached maximum displacement at said set engine speed under the control of flow-compensator control (60). A valve (31) controls the delivery of fluid from the pump to a load (34) and associated orifices (42a) and (43a) establish a pressure differential between the pressure of fluid supplied by the auxiliary pump (20) and the operating pressure applied to the load. A cylinder (80) responsive to the pressure differential acts on a control member (12) for the engine governor to increase the speed of the engine when the pressure differential falls below a predetermined value.

Abstract: A displacement control for a variable displacement hydraulic motor wherein the control is a summing pressure compensator control which is responsive to the pressures of a plurality of loads so that the average, weighted average, or total pressures of the loads can be sensed to generate a control signal for increasing the displacement of at least one motor when the plurality of pressures have a sum or average above a predetermined level. The summing pressure compensator control can also include an overpressure sensing device which is responsive to the pressure of one load, or the highest pressure of more than one load, to also provide a control signal to increase motor displacement. The increase in motor displacement limits the pressure of the motor system.

Abstract: The present invention relates to a travel speed control for a hydrostatically propelled harvesting machine or the like, and more particularly to a control system which automatically slows the travel speed of the harvesting machine at a fast rate in response to lugging of the engine and subsequently allows recovery of the travel speed to be at a fast rate initially, followed by a slow recovery rate to insure stability of the control system while minimizing the time required for travel speed recovery.

Abstract: The output speed droop compensating control is associated with a variable displacement pump connected to a motor in a fluid system. The pump has a swash plate urged in one direction by a hydraulic fluid pressure moment acting through the pistons of the pump and a servo control cylinder having a control piston connected to the swash plate. The control includes a control valve connected to the control cylinder and having a set position for maintaining a fluid pressure in the control cylinder to set the position of the swash plate for a particular pump displacement. The control valve is movable from the set position to adjust the position of the swash plate by connection of the control cylinder to either control pressure or drain.

Abstract: In the preferred form, the invention disclosed herein provides a single servo control valve to modulate the flow of control fluid to a servo mechanism of a variable displacement pump wherein the single valve is provided with both a manual primary input and an electro-hydraulic secondary input which modulates the primary input. The servo valve is spring biased toward a neutral position with the manual input displacement command being applied to such servo valve through a resilient linkage. Also applied to the servo valve is a hydraulic signal which is electrically controlled to modify the displacement of the servo valve relative to the yieldably applied manual input.

Abstract: A displacement control for a pump or motor having a swash plate for setting displacement includes a control device operatively connected to the swash plate and a control valve having connections to a source of pressure and drain for operating said control cylinder. The control valve has a neutral position wherein the swash plate is at or near a minimum displacement position. The control valve is operable to other positions for setting the displacement of the pump or motor and, additionally, is movable to a control position other than the neutral position or normal displacement-setting positions in response to an operative failure of the control valve positioning system which enables the swash plate to move to a position which minimizes any adverse effects from the occurrence of said operative failure. In a pump, the swash plate moves to a zero displacement position upon the occurrence of a failure while, in a motor, the swash plate moves to a maximum displacement position.