Abstract: A control system for a variable displacement pump or pumps driven by a vehicular engine for supplying pressurized fluid to implement actuators via implement control valves. Included is a servomechanism comprising a servoactuator section coupled to each variable displacement pump for varying the per cycle displacement thereof, a servovalve section for operating the servoactuator section by fluid pressure from a fixed displacement pump, and a control section for actuating the servovalve section. The servomechanism control section has a control piston displaced by variable fluid pressures from the variable displacement pumps against the effect of at least two springs. The springs are so arranged that their spring constant changes as the control piston travels to a predetermined position intermediate the opposite extreme positions thereof, in order to make possible the constant torque control of each variable displacement pump for the effective use of the engine output horsepower.

Abstract: A control system for a variable displacement pump or pumps driven by a vehicular engine for supplying pressurized fluid to implement actuators via implement control valves. The engine has several output conditions each with a different output torque characteristic. The control system includes a servomechanism comprising a servoactuator section coupled to the pump for varying the per cycle displacement thereof, a servovalve section for operating the servoactuator section by fluid pressure from a fixed displacement pump, and a control section for actuating the servovalve section. The servomechanism control section is fluid operated from a torque control valve, which delivers a controlled degree of fluid pressure from the fixed displacement pump to the control section in order to correspondingly vary the torque requirement of the variable displacement pump.

Abstract: Disclosed herein is a device for controlling displacement of a variable displacement hydraulic pump comprising a displacement control system for receiving a discharge pressure of the variable displacement hydraulic pump and a discharge pressure of a fixed displacement hydraulic pump to control the displacement of the variable displacement hydraulic pump.

Abstract: The invention relates to a supply circuit supplying two pressure-using members in parallel, by means of a power-regulated variable displacement pump. Manipulators, associated to the distributors controlling said pressure-using members are fed with a fluid whose pressure can vary as a function of the speed driving the pump and are of a potentiometric type. The invention finds an application in the supply circuit of a hydraulic shovel.

Abstract: A mechanism is provided for connecting the output shaft of a wind turbine with a load rod, such as the rod of a downhole pump. The mechanism includes a drive train which converts the rotating output of the shaft to a variable amplitude reciprocating output having a frequency varying with the speed of the shaft. A control assembly adjusts the drive train to maintain the amplitude of the reciprocating output proportional with the square of the wind velocity.

Abstract: A pump control assembly (16) controls the displacement of a pump (11) and provides a standby pressure (87) that is greater than the difference (96) between the load pressure and the pump discharge pressure. A valve mechanism (38) provides a predetermined pressure signal to a valve member (23) for adding a force to the valve member to provide a control signal to an actuating member (17) which adjusts the pump's flow and pressure to a standby condition. The pump control assembly provides a more precise control of the standby position while eliminating large, bulky springs.

Abstract: A control apparatus for several drive assemblies, which consist of hydrostatic drive units, is described. The hydraulic pumps of the hydrostatic drives are driven by means of a common prime mover and are controlled in terms of output. The output control device consists of an adjusting piston, which is connected with the control element of the hydraulic pumps and upon both sides of which pressure acts, and of a spool valve which controls the pressure action on both pressure chambers at the front surfaces of the adjusting piston and upon which, on one side, the working pressure of the pumps acts and upon which, on the other side, an adjustable spring acts.

Abstract: A spherical gear pump comprises a housing with a first longitudinal axis, a spherical seat, an inlet and outlet adjacent the seat, inlet and outlet passages communicating with the inlet and outlet and adapted for connection to a source of liquid and a liquid load. A hemispherical gear is rotatively mounted within the seat and includes a plurality of peripherally spaced radial gear teeth and a drive shaft for rotation about the first axis. A hemispherical cam is adjustably positioned within the spherical seat having an arc less than 180.degree., and radial cam surfaces facing the spherical gear. A plurality of separate symmetrical radial gear teeth are pivotally mounted within and between the teeth of the spherical gear with each separate gear tooth having a radial top wall centrifugally biased against the cam surfaces on rotation of the spherical gear and a bottom wall adapted for pivotal movements within planes passing through the first axis on rotation of the separate gear teeth over the cam surfaces.

Abstract: An apparatus for regulating the speed of internal combustion engine of a hydrostatic system. A fuel control means acts to control the quantity of fuel delivered to the engine responsive to the immediate hydraulic flow demanded by operation of the hydrostatic system. The speed of the engine is set to one of a plurality of discrete levels in response to the required flow being within one of a corresponding plurality of preselected ranges.

Abstract: A control system for a hydrostatic power transmission having a variable displacement hydraulic pump (2) and a hydraulic actuator (3) connected in a closed or semi-closed circuit, wherein the displacement of the pump or the delivery thereby is adjustable in accordance with a manipulated variable of an operating lever (13). A control unit of the system (16) is operative to calculate a hydraulic pump displacement command (X) on the basis of a manipulated variable signal (X.sub.

Abstract: A variable capacity pump delivers fluid at full displacement until both the main high pressure system and the lube system are satisfied. The main system pressure is regulated by a valve connected to the pump discharge while the lube pressure is regulated by a valve disposed in fluid communication with the overflow of the main system valve. The lube system valve establishes fluid pressure for the lube system and directs excess fluid to the displacement control for the pump whereby pump displacement is decreased when both systems are satisfied.

Abstract: An apparatus for controlling both pump displacement of a variable displacement hydraulic pump and the quantity of fuel delivered to an internal combustion engine for the purpose of delivering a requested hydraulic flow at a highly efficient operating point. The apparatus includes an underspeed control means for reducing pump displacement in response to the operating speed of the engine lugging below a desired operating speed. Additionally, a fuel control means operates to reduce the quantity of fuel delivered to the engine in response to the operating speed of the engine rising above the desired operating speed.

Abstract: A variable displacement rotary piston pump has a rotor splined to a driven shaft, a plurality of radially directed cylinders, each having a slidable piston fitted therein, a pumping ring surrounding the rotor and mounted eccentrically of the axis of the rotor with which the pistons maintain contact and are caused to move within the cylinders, a piston return ring engageable with notches formed on the pistons and an eccentric mounted for rotation to which the pumping ring is secured having an actuator pin whose movement determines the position of the pumping ring with respect to the rotor, thereby regulating the flow rate of the pump. The pump destrokes above the idle speed of the engine from which it is driven and limits the flow rate of the pump. A venturi orifice establishes a differential pressure which is applied across a flow control valve, which directs hydraulic fluid at discharge pressure to one or the other of two control pistons thereby adjusting the eccentric position.

Abstract: A variable displacement pump has a swashplate controlled by a pair of pistons. A shuttle valve communicates the highest pressure pump workport to an operator-controlled displacement control valve. A pressure-responsive override valve is connected in series between the displacement control valve and the pistons. When an override pressure is achieved, the override valve blocks communication of the control valve with the pair of pistons and communicates the pump workports directly to the pistons for rapid destroking.

Abstract: A power regulation device for a hydraulic pump includes a slidable piston having a first end face with a first diameter and a second, opposite end face with a smaller diameter, the second end face being biased by operating fluid pressure from the hydraulic pump and the first end face being biased by an adjustable fluid pressure for controlling the operation of the hydraulic pump; a compression spring which biases the piston in a direction against that of the adjustable fluid pressure; a measuring spring, one end of which biases the piston in the same direction as the compression spring; a power valve having a control slider member which is biased in one direction by the other end of the measuring spring and by the operating fluid pressure from the pump and in the opposite direction by a compression spring, the control slider member including a transverse channel for supplying the adjustable fluid pressure to the first end face of the piston during idling and normal operations and for connecting the adjustable

Abstract: An arrangement for regulating supply flow and limiting supply pressure of an adjustable pump, has a flow regulating valve, a control spring and a throttling element for controlling the flow regulating valve and arranged so that a primary pressure takes place upstream and a secondary pressure takes place downstream of the throttling element so as to form a pressure differential, an adjusting member operative for adjusting the pump and controllable by the throttling element, a servo element operative for forming communication with a pressureless space in the event when the supply pressure exceeds a predetermined value so that the pump is adjusted back to a smaller supply, as second throttling element arranged to bring the secondary pressure to the flow regulating valve, and a third throttling element arranged to vary the secondary pressure, connected in series with the servo valve, and first operating when the latter is open.

Abstract: A variable displacement pump has a swashplate controlled by a pair of pistons. A shuttle valve communicates the highest pressure pump workport to an operator-controlled displacement control valve. A pressure-responsive override valve is connected in series between the displacement control valve and the pistons. When an override pressure is achieved, the override valve blocks communication of the control valve with the pair of pistons and communicates the pump workports directly to the pistons for rapid destroking. A neutral bypass valve is formed out of a sleeve of the displacement control valve to bypass control pressure to sump when the displacement control valve is in neutral. A pressure-reducing valve limits the pressure acting on the stroke control valve to limit response rates and reduce erosion. The override valve includes orifices which, in intermediate positions, provide flow rate control of the fluid flow to the swashplate control pistons.

Abstract: A circuit pressure control system for a hydrostatic power transmission having a variable-displacement hydraulic pump driven by a prime mover, a hydraulic actuator for actuating a load and a displacement adjusting mechanism for the hydraulic pump. The hydraulic pump and actuator are connected together in closed or semi-closed circuit, and the displacement adjusting mechanism is actuated by a signal indicative of the operating lever manipulated variable and a signal indicative of the actual displacement of the hydraulic pump to control the speed of the hydraulic actuator.

Abstract: A civil machine having a flow-rate controller which applies a preset signal instead of a normal flow-rate signal to a variable type hydraulic pump when delivery pressure of the hydraulic pump exceeds a preset pressure value. The normal flow-rate signal corresponds to the position of an operating lever. The preset signal has a value of minimum flow rate to hold a working tool in a certain posture. With this control system, pressure loss and temperature rise in hydraulic operating oil as well as fuel consumption of the machine can be reduced and cycle time of the work can be improved.

Abstract: A control system for variable displacement hydraulic pumps for use in a hydraulically operated construction vehicle having a fixed displacement hydraulic pump, a plurality of reducing valves operatively interlocked with work implement control valve units of the vehicle disposed on the delivery sides of the variable displacement pumps, control sections for controlling respective flow rate of the variable displacement pumps and equipment for exerting delivery pressures of both the fixed and variable displacement pumps and output pressure of the reducing valve on the control units. The control system exhibits three control functions, i.e., flow control for varying the angle of the swash plate of the variable displacement pump in proportion to the manipulating position of the respective work implement controlling valve, constant torque control in proportion to the delivery pressures of the variable displacement pumps, and cut-off control for reducing relief losses.

Abstract: A hydrostatic drive system includes a hydraulic motor driven by a variable displacement axial piston pump with alternative intake and output ports. A charge pump generates a charge pressure which is communicated only to the pump intake port via a charge valve unit. The pump displacement is controlled by a swashplate which is moved by servo pistons which receive fluid from a displacement control valve. A three check valve unit communicates the higher of pump intake, outlet and charge fluid pressures to an inlet of the displacement control valve.

Abstract: A variable displacement pump control system comprising a variable displacement pump having a movable element for controlling pump displacement, a hydraulic motor for moving the movable element, and a transducer for producing an electric signal corresponding to the actual position of the movable element. A comparator compares the electrical signal from the transducer and an electrical signal corresponding to the desired displacement of the pump and produces an error signal. A control operates in response to the error signal to meter fluid flow from the pump output to the hydraulic motor. The control comprises a relief valve, a compensator valve and a servo valve. The servo valve is preferably a single-stage valve that includes damping orifices to provide stability.

Abstract: A pressure compensated pump which supplies fluid to a common header has an automatic pressure compensator adjustment mechanism which adjusts the pressure setting of the pressure compensator in response to changes in the displacement of the pump, such that the compensator pressure setting of the pump is reduced when the displacement of the pump increases to increase pump flow and the pressure setting is increased when the displacement of the pump decreases to reduce pump flow.

Abstract: A distributor pump type fuel injection system for a diesel engine wherein the pump is driven by the engine and the control of the timing and metering of fuel being delivered to each cylinder of the engine is controlled by a single electromagnetic solenoid device. The control system includes a distribution head for distributing pulses of fuel to each cylinder, the control of the fuel to the cylinder, both metering and timing, being controlled by the above-mentioned single electromagnetic control device. The fuel system includes a metering chamber and a timing chamber, the two chambers being separated by a free piston. In the control system to be described, fuel is premetered into the metering chamber, the quantity of fuel therein being controlled by the duration of energization of the control valve during the metering portion of the cycle. The time of injection of the premetered fuel is similarly under the control of the control valve and is initiated upon energization of the control valve.

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: An adjusting arrangement for a hydraulic pump with a variable flow quantity, having an operating cylinder located in a neutral position through the intermediary of a positively-acting resetting device, the piston of which is adjustable dependent upon the actual discharge pressure and dependent upon a parameter proportional to the actual discharge flow quantity into a position corresponding to the rated discharge flow quantity with consideration being given to the limiting value for maximum power output, maximum discharge pressure, maximum discharge flow quantity and, as required, the flow direction. An electronic control arrangement receives electrical signals corresponding to the rated discharge flow quantity and the actual discharge flow quantity and the actual pressure, which processes these signals under calculation of the actual power output and the actual pressure, and generates corresponding setting signals for the adjustment of the operating cylinder.

Abstract: The present invention is directed to a simplified viscosity compensating circuit which utilizes a viscosity sensitive capillary and a flow restriction means in series therewith to regulate the pressure at a particular point in a control circuit in response to a change in viscosity of the control fluid. Such viscosity compensation in the circuit is utilized to either maintain a uniform pressure at the circuit output or off-set an adverse condition caused by a change in viscosity of the control fluid.

Abstract: A hydraulic circuit for a so called feathering control of a variable displacement pump in which displacement of the variable displacement pump is controlled to a minimum when every actuator in a system is not in operation thereby keeping a power loss to a minimum. The hydraulic circuit includes a jet flow sensor for detecting a dynamic pressure of fluid. The jet flow sensor is disposed in a circuit for connecting a system pressure line to a reservoir and is adapted to convert static pressure of the fluid to dynamic pressure thereof. This detected dynamic pressure is introduced into a servo mechanism for the variable displacement pump for effecting feathering control.

Abstract: An hydraulic control system is disclosed which comprises a fluid reservoir (14), a variable displacement pump (12) having a fluid input connected to the reservoir and a fluid output, and a fluid pressure actuated displacement of the pump. A control valve (18) is connected to the fluid output of the variable displacement pump and to the reservoir and is adapted to control the flow of fluid to a fluid actuated device. The control valve includes means (44, 50, 52, 54, 56) for regulating flow of a signal fluid provided either by a constant displacement pump (46) or a pressure actuated flow control valve (47).

Abstract: A regulating device is provided for an aggregate of several pumps driven by a primary source at least one of which is adjustable and with a constant volume auxiliary control pressure pump driven by the same primary source in the delivery line of which a restrictor is located with the pressure gradient in front of and following the restrictor acting on the control pressures of an hydraulically regulated discharge valve in a drain line connected to the delivery line of the auxiliary pump, the drain line being connected in front of the restrictor, adjusting means connected to each adjustable pump and a control pressure line to which all adjusting means are connected, branching off from the drain line ahead of the discharge valve.

Abstract: A hydraulic system includes a primary function control valve connected to the output of a highly responsive variable displacement pump and having a power-beyond port connected for supplying fluid to a secondary function control valve. The secondary function control valve has a power-beyond port connected to a displacement controller which is responsive to the flow for increasing or decreasing the displacement of the pump respectively in response to decreases and increases in power-beyond flow from the secondary function control valve.

Abstract: A control means for a variable displacement pump (12) driven by an engine (10) and having a servo-cylinder (78) determining the displacement of the variable pump (12). A charge pump (14) is driven by the engine (10) and supplies charge pressure to the variable pump (12) through an orifice (40). Pilot conduits (42,44) on each side of the orifice (40) sense the pressure drop due to flow and relay the resulting signals to each end of a metering spool (52) in a speed control valve (46), which is arranged to control the pressure in the servo-cylinder (78). A spring (90) biases the servo-cylinder (78) toward an extreme position for the variable pump (12) and opposes the pressure directed to the servo-cylinder (78) by the speed valve (46) in order to provide a smooth transition between the extreme positions for pump displacement.

Abstract: A windmill control system having lever means, for varying length of stroke of the pump piston, and a control means, responsive to the velocity of the wind to operate the lever means to vary the length of stroke and hence the effective displacement of the pump in accordance with available wind energy, with the control means having a sensing member separate from the windmill disposed in the wind and displaceable thereby in accordance with wind velocity.

Abstract: A hydraulic system comprising a full flow supercharged variable displacement pump and a fixed displacement charge pump adapted to be driven by the same prime mover as the variable displacement pump for supplying fluid to the variable displacement pump. An orifice is provided in the supply line to the variable displacement pump, a circuit is provided from a point downstream of the orifice to tank pressure, and a feedback valve is provided in series with the circuit. The feedback valve comprises a pair of mutually and oppositely adjustable flow restrictions in series with said circuit. The restrictions are connected to the displacement varying means to vary them equally and oppositely in proportion to the movements of the displacement varying means.

Abstract: A warm-up valve in a load responsive hydraulic system which connects the pump discharge pressure with the pump compensator while bypassing to reservoir a partial capacity of the pump. When proper reservoir temperature is reached, a thermostatically controlled solenoid closes the warm-up valve causing the pump to return to low pressure standby.

Abstract: A regulating device for a hydrostatic drive unit such as a hydropiston pump is provided with an adjusting piston designed as a differential piston, connected with the final control element of the drive unit and/or the pump and under pressure from both sides, and with a control valve controlling the pressure exerted on the adjusting piston in the pressure spaces in front of the end faces and with a control pressure gauge piston arranged in a sliding manner in the housing and on which the working pressure of the drive unit and/or feed pressure of the pump is exerted, and which lies against a lever, which is connected through a flexible coupling with the adjusting piston and is supported on this latter and is forced against it by a spring and actuates the control valve, in which case the control valve is located in the adjusting piston crosswise to its longitudinal axis, characterized in that the lever is designed as an angle lever and that the spring is located in the adjusting piston and lies against the secti

Abstract: A hydraulic fluid drive for a land motor vehicle having front and rear drive wheels. An internal combustion engine drives a pair of positive displacement pumps. A first pump is connected to hydraulic motors that drive the front wheels of the vehicle. A second pump is connected to a hydraulic motor that drives a rear steerable wheel of the vehicle. A manually operated control is used to adjust the speed and torque of the motors for the front wheels. A front and rear wheel drive equalizing control operates in response to differences in hydraulic fluid pressure supplied to the front and rear hydraulic motors to equalize the fluid pressure pumped to the front and rear hydraulic motors so as to maintain the torque and speed of the front and rear wheels substantially constant. A foot operated lever is used to operate the control for the first pump for changing the supply of fluid pressure to the front wheel motors.

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.

Abstract: A liquid fuel injection pumping apparatus includes a rotary distributor member housed in a sleeve mounted in a body. The distributor member is movable in an axial direction and mounts a pumping plunger in a transverse bore. An inclined surface is formed on the plunger for co-operation to limit the outward movement of the plunger, with an inclined surface on a part in the form of a strip. The strip rotates with the distributor member but is restricted against axial movement. Hence axial movement of the distributor member varies the amount of outward movement of the plunger and hence the amount of fuel which can be supplied by the apparatus.

Abstract: A signal bleed-down valve in a load responsive system which is positioned in the sensing line between the pump compensator and control valve. The valve in the absence of sufficient pilot pressure opens the pump compensator to drain. Otherwise, the valve is controlled by pilot flow across a fixed orifice in the spool which creates a pressure drop acting against a spring, and moves the valve spool to a position metering the pilot flow so as to maintain a constant flow level across the valve spool regardless of the pressure level.

Abstract: A fluid control cirucit for selectively varying the displacement of a variable displacement pump (P), such as the type employed in a hydrostatic transmission, comprises a primary control circuit connecting a pressurized fluid source (10) with the pump (P) and adapted to be actuated to selectively vary the displacement of the pump (P) between minimum and maximum values. A separate override control circuit is connected to the primary control circuit to override it to selectively vary the displacement of the pump (P).

Abstract: A control for a variable displacement pressure compensated pump in which pressurized control fluid regulates the setting of a sequence valve to set the maximum output pressure of the pump and also set the displacement of the pump. The sequence valve is a two-stage device which utilizes a sequence poppet stage and cone stage. When working fluid pressure exceeds the setting of the sequence valve, the cone stage spills to reduce the displacement of the pump. If the pressure is not reduced fast enough the sequence poppet spills to more rapidly reduce the displacement of the pump.

Abstract: A variable displacement rotary pump includes a tiltable cam plate which varies the pump displacement as a function of the fluid pressure in a control chamber. The pump pumps fluid to a fluid motor via an orifice in an outlet passage. A spool valve meters fluid to the control chamber in response to the differential pressure across the orifice. Pressure on one side of the orifice acts upon the spool valve in a feedback chamber remote from the outlet passage. The orifice is defined by an annular space between the wall of the outlet passage and neck portion of the spool valve. A feedback passage in the spool valve communicates fluid pressure from the one side of the orifice to the feedback chamber. A leakage flow path extends through a bearing to provide for automatic bearing lubrication.

Abstract: A variable displacement pump 1 includes a housing 2 having an inlet port 3 and an outlet port 4. The pump 1 is an axial piston pump having a swash plate 5 which is actuated to different angular positions by an actuating member 7. The torque limit of the pump 1 is controlled by a horsepower control valve 19 and a speed responsive control valve 35, which change the torque limit of the pump 1 in response to changes in the position of the actuating member 7 and in response to changes in the speed of the engine 33. In this manner, the torque limit of the pump 1 for any position of the actuating member 7 closely approximates the maximum available output torque of the engine 33.

Abstract: An arrangement for regulating the output flow and the output pressure of an adjustable pump includes two parallel throttles arranged, respectively, in an output conduit and in a branch conduit; a spring biased multi-way directional control valve is controlled by differential pressure in the branch conduit upstream of the two throttles to adjust the delivery of the pump; manually closed overpressure control valve connects the branch conduit downstream of the corresponding throttle to a tank and a normally open one-way valve connects the output conduit to the branch conduit downstream of the throttles and interrupts the connection as long as the overpressure control valve is open.

Abstract: The invention is an efficient hydraulic motor/pump whose mechanical advantage can be varied while it is operating. Preferred embodiments described include a multi-cylinder reciprocation motor/pump, a variable level power extraction system used with a wave generator, a hydraulic transformer and a hydraulic autotransformer.

Abstract: A hydraulic system includes an actuator and a motor driven pump. A servo-control valve adjusts the displacement of the pump and provides a stable response to pump output pressure variations. The servo-valve is adapted for the addition of a control piston which operates against the spool of the servo-valve to modulate its operation in response to a moderate pressure drop across a restriction placed in the line from the pump to the actuator.

Abstract: Control apparatus 24 for use with a pressure-flow compensated variable displacement pump assembly 10 for saving energy by limiting the power output of the pump 12 to the load requirements, or to the pump drive capacity, comprising a pressure regulated variable orifice means 52 through which the pumped fluid to load flows, the orifice means being responsive to changes in pressure of the pumped fluid from the pump assembly to vary inversely the effective area of the orifice means, the flow compensator 28 of the pump assembly functioning to hold the pressure drop across the orifice means constant so that the flow across the orifice means also varies inversely with the pressure to limit to a preselected value the horsepower supplied by the pump assembly to load.

Abstract: An electronic control system for pressure and flow control of variable displacement pumps consists of a closed loop system of operational amplifiers which provide continuous control of the volume modifying element in the pump. In a variable displacement vane pump application a command flow control signal and a feedback signal representative of the position of the adjustable cam ring in the pump are applied to an integrating amplifier to develop a signal for application to an electro-hydraulic valve in the pressure compensating portion of the pump. A command pressure signal is compared with the control signal to limit the latter to a level, thereby providing pressure control for the pump. Slip compensation is effected in the control system by utilizing a portion of the control signal to provide proportional modification of the command signal.

Abstract: A variable displacement pump has a displacement control cam operably connected to a displacement control cylinder within a pump housing and a pressure and flow sensitive compensating valve is connected to the pump housing for regulating output of the pump. The compensating valve is secured to the pump housing through a spacer block. A lever is disposed partly in the spacer block and partly in a housing of the compensating valve responsive to positioning of the pump cam through a mechanical connection for actuating a sleeve in the compensating valve to incorporate torque-limiting feedback regulation of the pump. An adjustment is operable from an outer surface of the spacer block to limit torsional operation of the lever about a pivot point.