Abstract: An improved fluid flow control apparatus is utilized in association with a vehicle having a single variable displacement pump for supplying fluid to both a steering apparatus and an auxiliary apparatus. The fluid flow control apparatus includes a pair of variable size orifices one of which is associated with the steering apparatus and the other of which is associated with the auxiliary apparatus. Upon actuation of either the steering or auxiliary apparatus, the size of the associated orifice is varied to provide a variation in a load signal and effect a change in the displacement of the pump. During simultaneous operation of both the steering and auxiliary apparatus, a priority valve assembly is utilized to block fluid flow to the auxiliary apparatus if the fluid output from the pump is insufficient to satisfy the demand for steering fluid. The priority valve assembly includes a main valve member with an internal chamber in which a secondary valve member or piston is disposed.

Abstract: An automatic control for reducing a flow pressure compensated variable displacement pump to a standby condition while the pump operated motor is lowering a heavy static load. The pressure in the motor exhaust line caused by the static load actuates the control to cut-off pressure to the downstream sensing line of the pump flow control. A bleed orifice in that downstream sensing line depressurizes the line causing the pump displacement servo to stroke back the displacement of the pump to a standby condition.

Abstract: A cable winch control having means for sensing the magnitude of the load in elation to the torque being delivered by the power means to the winding drum. The sensed signal is fed back to a manual controller for the drum winding means, to alert the operator to dangerous load situations that could damage the equipment or break the cable. The feedback signal exerts a restraining force on the controller opposing movement thereof, from a neutral "low-load" position to either the "wind-in" or "wind-out" condition. Therefore, the feedback signal has a fail-safe characteristic that prevents runaway movement of the controller in either direction.

Abstract: A hydraulic system having pilot line fluid feedback from a fluid motor to valving which operates to change pump output to compensate for motor demand includes a pressure regulator valve for maintaining a predetermined minimum pressure in the pilot line. The pressure regulator valve eliminates the power wasting pressure differential which normally exists between the pump output and the fluid motor demand in demand compensated hydraulic systems.

Abstract: A hydraulic system having fluid flow feedback from a fluid motor to a demand control valve which operates to change pump output to compensate for motor demand includes a pressure amplifier between the feedback system and the valve. The pressure amplifier includes a chamber with a piston therein which is slidable to connect or block pump output fluid flow to the valve in response to feedback pressure variations from the motor.

Abstract: Apparatus of a fluid system of a work vehicle for controlling the fluid delivered to work elements of the vehicle in response to the load exerted on the fluid system by the work elements.

Abstract: An improved drive system includes a pair of hydrostatic transmissions which are driven by a common engine or prime mover and are drivingly connected with different tracks of a vehicle. The input to output speed ratios of the hydrostatic transmissions are simultaneously varied by operating a single speed control valve to port control fluid pressure to pressure responsive secondary or control motors in pump and motor actuators of the hydrostatic transmissions. A pair of charge pumps are provided to charge the hydrostatic transmissions and provide control fluid. If the fluid pressure output of either of the charge pumps falls below a predetermined level, a control arrangement reduces the control fluid pressure transmitted to the pump and motor actuators by the speed control valve to deswash or destroke both of the transmissions. The control arrangement also short circuits the hydrostatic loops interconnecting the pump and motor units. In addition, the brakes of the vehicle are engaged to stop the vehicle.

Abstract: Fluid is selectively, controllably delivered at substantially common rates from separate respective variable displacement pumps in response to a load pressure signal acting on a single pump control valve serving said pumps.

Abstract: Apparatus of a fluid system of a work vehicle for controlling the fluid delivered to parallel work elements of the vehicle in response to the load exerted on the fluid system by the work elements.

Abstract: An auxiliary hydraulic front wheel drive including a pair of variable displacement pressure and flow compensated motors each connected to individual wheels; the auxiliary drive utilizes a pressure compensated pump source of the existing hydraulic system on the vehicle. The primary accessories run by said pump maintain a priority flow over the auxiliary drive motors since the pressure compensating level of the motors is set slightly below that of the pump.

Abstract: A load responsive direction and flow control valve for use in fluid power load responsive system. The valve maintains a selected constant flow level for control of both positive and negative loads, irrespective of the change in the load magnitude or change in the fluid pressure, supplied to the valve. When controlling positive or negative loads the valve maintains a constant pressure differential across a flow control metering orifice utilizing a single control slide member, first by throttling fluid entering the inlet chamber and then by throttling the fluid leaving the outlet chamber. The valve may be used with fixed displacement pumps, fixed displacement pumps equipped with differential pressure relief valves, with variable displacement pumps equipped with pressure compensators and variable displacement pumps equipped with differential pressure compensators.

Abstract: This disclosure relates to a fluid transmission for automatically varying the drive ratio in accordance with the load placed thereon and includes a pump unit and a motor unit and wherein the pump unit is of a variable displacement with the displacement thereof being automatically adjustable in accordance with the pressure of the fluid output thereof and the input speed of the pump unit. The pump unit is of the radial piston type and includes a race member engaged by the pistons for controlling the displacement thereof. The race member has a cylindrical race surface and is mounted for tilting movement wherein in a neutral position the pistons have zero displacement and wherein when the race member is tilted, the displacement of the pistons increases.

Abstract: An improved differential pressure regulator valve for a hydrostatic transmission control system wherein the valve regulates high fluid pressure versus low fluid pressure and produces a pressure differential that in turn controls the transmission. The regulator valve includes a valve body whose bore is in communication with both first and second sets of fluid inlet and outlet ports, with the valve bore containing a spool assembly that includes first and second cooperating spool members, with the second spool member being operable to control the fluid flow between the first inlet and outlet ports or the second inlet port and the first outlet port. Means, including a passage connecting the first outlet port with a spool port, fluidly unbalances the second spool member by applying the pressure of fluid in the first outlet port to one end of the second spool member in opposition to the biasing action of a regulating spring.

Abstract: A demand compensated hydraulic system includes a pump responsive to a pressurized fluid in a demand feedback pilot line. The pilot line is connected to sense fluid demand between a hydraulic motor and an associated control valve which is closed by servo feedback from the motor. A dither is connected to the pilot line to continuously oscillate the pressurized fluid in the pilot line to prevent the occurrence of a situation wherein the flow across the control valve is sufficient to prevent the pump from going to a stand-by condition while being insufficient to operate the motor to close the valve to thereby cause the pump to go into the standby condition.

Abstract: A first pump and a second pump have respective mechanical inputs and are operative when the mechanical inputs are driven at constant speed for pumping fluid at an adjustable volumetric flow rate and at a constant non-adjustable volumetric flow rate, respectively, the maximum volumetric flow rate of the first pump being at least as great as that of the second pump. Connecting conduits connect the first pump in hydraulic circuit with an hydraulic consumer. An adjusting mechanism is provided for adjusting the volumetric flow rate of the first pump. A control arrangement is provided for bringing the second pump into and out of hydraulic circuit with the consumer in dependence upon the operation of the adjusting mechanism.

Abstract: A load responsive hydraulic system uses a signal supply restrictor, a synthetic signal generator and a unique directional control valve to provide a signal fluid having a pressure magnitude which is at a predetermined value above the load actuating pressure of the system and which is called a synthetic signal pressure. The effective output of the system's pump is controlled by the difference between the pressure of the pump and the pressure magnitude of this synthetic signal pressure. During pressure operation of the system, the directional control valve applies the synthetic signal pressure to the pump control mechanism; and during standby operation, the control valve applies a signal fluid to the pump control mechanism whose pressure magnitude is not increased by the synthetic signal generator.

Abstract: A time saving automatic hydraulic control for that sequence in operations in which a grab excursioning out of sight of the operator, is sequentially lowered open to engage work material, closed to pick up a load, and then hoisted with its load and emptied. A logic circuit is activated to stop the lowering within an adjustable timed period after initial work engagement to provide desired penetration of the work material by the grab followed by a minimal time for grab closing to provide an adjustable constancy of loads and a positive sequential control for the lowering and hoisting modes.

Abstract: A motor-pump unit is used in combination with an existing hydraulic power transmission system to create an additional or auxiliary hydraulic power circuit.

Abstract: Apparatus which regulates the pressure and the rate of flow of fluid supplied by a variable-delivery radial piston or vane pump whose output can be changed by moving a ring-shaped slide block transversely of the rotor. The slide block is engaged by a relatively small piston which is subjected to fluid pressure corresponding to that at the outlet of the pump, and by a relatively large piston which is disposed opposite the smaller piston and is subjected to fluid pressure which is controlled by a regulating valve receiving pressurized fluid from the outlet. The outlet is connected with a set of first consumers, such as hydraulic cylinder and piston units, and the pressure of fluid which is delivered to first consumers can be regulated by a set of series- or parallel-connected pilot valves one of which is permanently connected with the regulating valve and the others of which are connectable to the regulating valve only by discrete two-way valves which can be opened by remote control.

Abstract: A closed loop hydraulic control system for a piston type fluid actuator maintains an average pressure on the piston during all operating conditions of the actuator. The system includes a first pump which controls the actuator and a makeup pump which supplies additional fluid to compensate for fluid losses in the system. An average pressure maintaining valve sums the fluid pressure on each side of the actuator and supplies additional fluid from the makeup pump to maintain a predetermined average pressure on the actuator piston.

Abstract: 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 together with a venturi manifold which function together to normally establish a selected pressure differential in a pair of supply conduits for determining instant operating conditions for the transmission. In order to automatically regulate displacement of each pump unit in response to engine or prime mover speed as determined by load conditions, an underspeed actuator valve unit includes a piston which is hydraulically responsive to the differential pressure in order to adjust the effective moment arm for a lever which controls displacement of the pump unit.

Abstract: A hydraulic system is provided in which a single variable displacement pump supplies the hydraulic fluid requirements of both an open center hydraulic circuit and a closed center hydraulic circuit. The hydraulic output from the variable displacement pump is delivered to a pressure compensated flow divider which at all times delivers a priority minimum and constant flow to the open center hydraulic circuit despite variations in pump output pressures. Unless there is a demand for hydraulic flow by a device or devices in the closed center hydraulic circuit, there is no hydraulic flow delivery from the flow divider to the closed center hydraulic circuit, and the variable displacement pump operates at relatively low power input required to supply the demands of the open center hydraulic circuit.

Abstract: A control device for connection between a hydropump and a hydromotor of a hydraulic system, to provide a control pressure for regulating operation of the system, has a valve housing accommodating a displaceable valve member formed to provide a throttling passageway between an inlet and a main outlet of the housing. Fluid flow through the throttle tends to move the valve member to open a connection between the inlet and a control pressure outlet of the housing, against the action of a resilient biasing arrangement and a force produced on the member in dependence upon the control pressure itself. The action of the biasing arrangement, however, is variable, enabling the device to be designed in accordance with a desired fluid-pressure/flow rate relationship.

Abstract: A stepless, preferably hydrostatic, transmission is provided for an internal-combustion engine and the system is controlled by an operating member. A mechanism connects the members to the transmission and the engine so that both the engine and the transmission controls respond to this member. Means is provided for affecting the linkage in response to the torque on the transmission shaft, preferably in dependence upon the pressure in a transmission-fluid line.

Abstract: A variable displacement pump control assembly as for an axial piston pump having a swash plate actuating piston characterized in that the control assembly is embodied in the pump housing to provide a pressure compensated pump, or to provide a pressure compensated pump having an auxiliary modulator to control the pressure applied to the swash plate actuating piston to maintain a predetermined pressure drop across a variable area metering orifice embodied as in a directional control valve for a fluid motor, or to provide a pressure compensated pump having a horsepower modulator with or without the auxiliary modulator, said horsepower modulator providing desired control of horsepower in relation to pump delivery pressure and displacement.

Abstract: A hydraulic control system includes a generating circuit for providing power to a work function. A driving apparatus operates the generating circuit. A control circuit is connected to the generating circuit and the driving apparatus for permitting delivery of power to the work function when the driving apparatus is operating up to a predetermined speed. The control circuit also stops delivery of power to the work function when the driving apparatus runs above the predetermined speed.

Abstract: An improved controller assembly is utilized in a hydrostatic steering system having an engine driven pump with a servomotor which is effective to vary the displacement of the pump upon operation of a pressure responsive valve assembly. The controller assembly includes a housing having a valve chamber with an inlet port which receives fluid from the pump. Upon rotation of a steering wheel, a controller valve member is moved to an actuated position and a metered flow of fluid is conducted from the valve chamber through a motor port to a steering motor. In addition, fluid is conducted from the steering motor through another motor port to the controller valve chamber. The fluid from the steering motor is then discharged from the valve chamber to reservoir or drain through an outlet port. The controller assembly also includes a control port connected in fluid communication with the pressure-responsive valve assembly.

Abstract: An apparatus and method for operating an auxiliary hydraulic load at low noise levels. A pump having a capacity which is sufficiently large to supply the load with the necessary volume of hydraulic fluid at relatively low pump speeds is driven by an engine operating at a speed near its idling speed. Throttle control means control the fuel supply to the engine at a level sufficient to drive the pump while maintaining the engine speed near its idling speed. When the engine speed is increased to a predetermined level in excess of its idling speed, means are provided to maintain the output from the pump at or below a predetermined flow rate to not overload the pump means or the auxiliary load. The pump may include a variable displacement pump or a plurality of fixed displacement pumps with means to vary the pump output in response to the pressure demand from the auxiliary load to maintain the torque input requirements for the pump below a predetermined level.