Abstract: A pressure override control which utilizes pump output flow for destroking of a variable displacement pump to minimize loss of power and generation of heat and which includes modifications to the displacement control valve for the pump and, particularly, the cross connection of displacement-controlling servo motors when the displacement control valve is in a neutral position with blocking of communication of said servo motors to a displacement control pressure and drain whereby the pump cannot be positioned in a maximum displacement position in response to certain system malfunctions in the power override control circuitry.

Abstract: A vehicle engine accessory drive system is disclosed including a hydraulic fan motor (M) and a power steering gear mechanism (SG) in series flow relationship. The system includes a variable displacement power steering pump assembly (P) which is the sole source of fluid for the system, and includes a variable displacement pumping element (PE) and a displacement control valve (CV). The displacement control valve includes a pilot valve (35) which is responsive to the demand for cooling to vary the fluid pressure in a signal chamber (63). The displacement control valve is operable to communicate a control fluid pressure to a stroking cylinder (SC) to control the fluid delivery rate of the pumping element. At a first relatively lower temperature, the displacement control valve maintains the fluid delivery rate of the pumping element at Z, and at a second relatively higher temperature, to maintain the fluid delivery rate at X.

Abstract: The invention relates to a control unit for an adjustable volume pump of the type having external controls for varying the volume output thereof. A pump for driving a hydraulic motor has the output pressure thereof increase as the motor load increases. The control unit hereof is responsive to the output pressure of the pump and regulates the pump controls to maintain a substantially constant volume through output for the pump despite varying load conditions on the hydraulic motor driven by the pump.

Abstract: A hydrostatic drive system having a closed loop front wheel drive circuit and a closed loop rear wheel drive circuit. A variable displacement pump in each of the circuits is cammed to vary the displacement delivered to dual displacement wheel motors to provide two speed ranges for the drive system. A servosystem uses hydraulic fluid to cam the displacement of the variable displacement pump and a hydraulic control to selectively engage each of the drive ranges.

Abstract: An engine speed control for a variable speed engine wherein the engine can have a set speed to operate at a relatively low working speed or at an idle speed and which is adjustable to increase engine speed. The engine drives plural pumps and a control circuit is responsive to a certain flow rate from either of said pumps to increase the speed of the engine to provide for additional flow from the pumps. In a hydrostatic transmission as usable in the drive of a vehicle, there are a pair of fluid translating devices, in the form of a pump and a motor, with at least one of the devices being of variable displacement and having a displacement control responsive to a speed control signal. In such a system, the engine which powers the hydrostatic transmission is set at a desired speed of operation below maximum speed and is adjusted in response to the speed control signal for increase in said engine speed when the speed control signal exceeds a predetermined level.

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.

Abstract: A control system is disclosed for use with pressure-driven loads, such as reversible motors. The system allows the loads to be driven at varying speeds and also allows the loads to be reversed. However, the system is so designed that an operator cannot subject the loads to pressure shock caused by abrupt changes in pressure by adjusting the system too rapidly. The system disclosed is suitable for use with either hydraulic or pneumatic loads.

Abstract: Pump-motor hydraulic power system incorporation means to limit the power transmitted and the pressure in the transmission lines. High pressure line is connected to one end of a servo motor comprising a cylinder with a spring loaded piston therein. When the pump pressure increases above a certain amount it overcomes the spring and moves the piston and the piston rod to a blocking position, acting to limit movement of the three way control valve or to move the three way control valve back if it already exceeds the limit imposed by the power limiter's piston rod.

Abstract: A control system is disclosed for a hydrostatic transmission of the type including a prime mover driven variable displacement pump, the displacement of which is controlled by a pair of strokers (28, 30). Flow of pressurized control fluid from the charge pump to one of the strokers, and from the other stroker to tank, is controlled by a main control valve (34). The control system includes an auxiliary control valve (44) defining passages (98, 100, 102) communicating between the lines connecting the main control valve and the strokers. The auxiliary control valve includes an on-off, electro-hydraulic valve (46) which prevents flow through the auxiliary valve in response to an electrical signal in one condition, and permits flow in response to an electrical signal in another condition.

Abstract: An electro-hydraulic auxiliary drive system providing power to the non-driven steerable wheels of an agricultural tractor utilizing hydraulic power in a parallel circuit from a pressure compensated pump which varies torque supplied to the auxiliary system by sensing the relative speed between the front and rear wheels and increases the torque to the auxiliary system when a set percentage of slip is determined between the front and rear wheels. The steerable wheels are driven by hydraulic motors connected in parallel through a flow divider valve and supplied by a variable displacement pressure compensated pump. When the electronic control receives an indication of slip from the main drive wheels it energizes a solenoid causing the pressure compensation level of the variable displacement pump to increase the torque output of the auxiliary drive system, with the percentage of slip being proportional to the increased torque.

Abstract: A hydraulic follow-up for use with a hydraulic system placed between a rotating input member and a rotating output member. The hydraulic system is a hydrostatic transmission for driving a tractor, and comprises a hydrostatic pump and a hydrostatic motor driven by the pump. When the hydrostatic pump is angularly shifted with respect to the input member, the shifting is controlled by the hydraulic follow-up, which also shifts the motor in relation to the output member.

Abstract: A hydrostatic converter has at least one hydromotor and at least one pump. The characteristic curve of the pump, which represents the relationship between pressure and stroke volume, has a hyperbolic part. The performance graph of the hydromotor, which represents the relationship between motor driving torque and motor speed, also has a hyperbolic part. A torque controller, including a regulating unit, is associated with the pump for producing a variable auxiliary force for displacing the hyperbolic part of the performance graph of the hydromotor. Automatic, stepless adjustment of the rate of revolution and torque takes place at the hydromotor as a function of the load, in both the full and partial load ranges.

Abstract: An integrated transmission-engine control for a transmission, such as a hydrostatic transmission having a variable displacement unit connectable to an engine and a second displacement unit connected to an output shaft, including fluid pressure-operated ratio governor means for the transmission, fluid pressure-operated means for controlling the supply of fuel to an engine, a power demand valve for converting a particular power demand to a particular fluid pressure primary control signal. The primary control signal is applied to the ratio governor means in opposition to a signal representing engine speed to set the transmission ratio for a desired engine speed and also applied to the fuel supply controlling means to establish a fuel setting to match engine horsepower to engine speed for minimum fuel consumption.

Abstract: A piston pump having a housing and an angularly adjustable swash plate for controlling piston displacement and the flow of fluid discharged from the pump has control means for controllably positioning the swash plate in response to a load pressure.

Abstract: A control system comprising an actuator having a fluid responsive member movable in at least first and second directions and two sources for controlling the fluid responsive member. A first of these sources includes a servo pump which pumps fluid from one side of the fluid responsive member to the other to thereby control the position of the fluid responsive member. A second of these sources includes a valve which controls the supply of fluid under pressure to the fluid responsive member and the return of fluid from the fluid responsive member. The servo pump and valve are arranged in parallel with their flows being summed at the actuator.