Abstract: A meter-out load sensing hydraulic system controlling one or more motors, supplied by a variable displacement pump through a directional control valve. The compensating means of the pump senses pressure and flow on the discharge or return side of the motor to determine the pump cam plate position. The signal line connecting this discharge side of the motor to the compensating means is also supplied with a low pressure signal flow which causes the pump to standby at a low pressure level in a neutral valve position or when metering down a gravity load.

Abstract: An improved power steering apparatus includes a variable displacement pump. During a steering operation, a flow control valve effects operation of a motor assembly to vary the displacement of the pump as a function of variations in the demand for power steering fluid. Upon initiation of a steering operation, the displacement of the pump must be quickly increased to enable it to satisfy the impending demand for power steering fluid. Therefore upon initial rotation of a steering wheel, a steering controller restricts a flow of fluid to operate the motor assembly independently of the flow control valve. The displacement of the pump can thus increase before the flow control valve can be actuated during an initial portion of a steering operation.

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: The invention is an integrated hydraulic control circuit for actuating the thrust reversers and variable exhaust nozzle on high preformance gas turbine engine powered aircraft. The hydraulic circuits for both systems are integrated into a single housing and are served by common elements. The circuit for the deployment and stowage of the thrust reverser buckets is hydraulically sequenced inhibiting the application of hydraulic power to the actuators prior to withdrawal of the locking pin. In a like manner, the thrust reversers must be fully retracted before the locking pin is deployed. The hydraulic circuit for the thrust reversers also includes a pressure compensating circuit which reduces the pressure applied to thrust reverser actuators with the thrust reversers in the stowed position.

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: Disclosed is a device for controlling or measuring operational parameters of an axial piston machine. The tilting plate which engages and adjusts the stroke of the piston is provided with two opposite pivot pins supported in fixed bearings. At least one pivot pin is provided with a shearing stress sensor preferably in the form of a magnetoelastic feeler which produces electrical signals the pulsation of which is indicative of rotational speed and the magnitude of the signal is proportional to pressure applied by the pistons and thus to the delivery of the machine. A second sensor is coupled to the tilting plate to indicate the angular displacement of the latter. The output signals from the sensors are separated into the pressure dependent signals, frequency dependent signals and angular displacement signals which upon multiplication are applied to a programmable data processing unit.

Abstract: For operating the rollers and the steam chest in a laundry flatwork ironer a hydraulic system is provided which includes a hydraulic motor for driving the rollers, hydraulic cylinder-and-piston units for raising the steam chest, and a pump for operating the motor and the cylinder-and-piston units. Valves between the pump and the motor are selectively operable to establish low pressure standby operation of the pump with the hydraulic motor off, or low speed operation of the motor to jog the rollers or higher speed operation of the motor to drive the rollers at a speed appropriate for laundry flatwork. Other valves between the pump and the cylinder-and-piston units are selectively operable to raise the steam chest, reduce the cylinder pressure after the steam chest has been raised, and to increase the cylinder pressure whenever laundry flatwork is in the ironer.

Abstract: A compensated fluid flow control of a positive load, which automatically maintains a relatively constant pressure differential across a control orifice of a direction and flow control valve and which permits the variation in the level of this pressure differential in response to an external control signal, while this pressure differential is maintained constant at each specific level.

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: A fluid control system (10) for controlling the torque of a fluid motor (22) and varying the flow to the fluid motor (22) has a mechanism (56) to control the torque and flow in proportion to the operator's input to a pilot operated control valve (16) that controls the fluid motor (22). The mechanism (56) controls the torque and flow of the fluid motor (22) during both acceleration and deceleration of the fluid motor (22). The fluid control system eliminates the need for special, complicated control valves.

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 control for a variable displacement motor and operable in either direction of rotation of the motor (10) and which acts on a servo cylinder (55) to set the position of a wash plate (50). The control includes a signal-setting valve (65) operable in response to the rate of fluid flow through the motor by sensing a pressure drop in a closed circuit line to the motor to set a variable control signal and the variable control signal is applied to the displacement-setting mechanism (56,55) for the motor to have a decrease in motor displacement related to an increase in the rate of fluid flow through the motor.

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 pressure control valve is provided for controlling both the low and high pressure ranges of a variable displacement pump in addition to the pressure control valve used for adjusting the variable displacement member of the variable displacement pump.

Abstract: A fluid pressure system has a reservoir and a variable delivery pump having an inlet connected to the reservoir and an outlet. A control valve connected to a control motor and feedback line with the feedback line adapted to control the fluid flow to and from the control motor to vary the pump displacement, to maintain the pressure at the pump outlet at a difference above the pressure in the feedback line. A control valve is adapted to control the fluid flow between the outlet, the load motor and the reservoir. The control valve is adapted to control the fluid flow between the load motor, the reservoir and a control line and is operable in a neutral position to block off the pump outlet from the load motor and to connect said control line to the reservoir. The control valve is operable to another position which connects said load motor to the control line before the pump outlet is connected to the load motor.

Abstract: A method of controlling an internal combustion engine (14) having a power control (15) and a variable hydrostatic transmission (16, 17) including a hydraulic pump (16) driven by the internal combustion engine, and a hydraulic engine (17) connected therewith.By automatic adjustment of the power control (15) and the ratio (E) of the hydrostatic transmission (16, 17) independently of each other according to a predetermined mathematical control function (FIG. 1) which describes a desired relationship between power and rotational speed of the internal combustion engine, a specific discrete power output is delivered between zero load and full load only at an associated discrete rotational speed of the internal combustion engine.

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 hdydrostatic load sense vehicle steering system which directs fluid from a source to a hydrostatic steering circuit that includes a steering controller, and to an auxiliary circuit. Fluid control means responds to fluid pressures in a pilot circuit to direct priority flow to the steering circuit and excess flow to the auxiliary circuit. The pilot circuit includes a first pilot conduit that communicates with a load sense port of the steering controller. The steering controller controls fluid pressures in the pilot circuit in accordance with the condition of the steering circuit. A second pilot conduit communicates a pressure signal in accordance with the condition of the auxiliary circuit to the fluid control means. The second pilot conduit also communicates through a bleed orifice with the load sense port of the steering controller. When the controller is in neutral, it directs the pilot fluid from its load sense port to a reservoir.

Abstract: A torque absorbing coupling for a hydrostatic steering system which a hydrostatic steering controller responds to operation of a steering wheel to direct flow from a source to a steering motor. The coupling minimizes the possibility of a high reaction torque being felt by the operator who turns the steering wheel more rapidly than the system can deliver flow and pressure to the controller to levels which are sufficient to effect steering as demanded by the operator. The coupling is provided between the steering wheel and the controller's metering unit, and operates to absorb reaction torques over a time interval, and thereby delays transmission of those reaction torques to the operator over that time interval, to provide the system with an additional time interval to increase flow and pressure to the levels demanded.

Abstract: A hydraulic excavator is disclosed which includes two sets of manual control valves for selectively placing a pair of variable displacement pumps in and out of communication with hydraulically driven components such as propelling motors, arm cylinders and boom cylinders. In order to minimize the per-cycle displacement of the pumps when same are discommunicated from all the driven components, a sensing valve is provided which is pilot operated from the sets of manual control valves. When all the manual control valves are in neutral, the sensing valve directs pressurized fluid from a charging pump to a pump-displacement adjustment mechanism thereby causing same to reduce the per-cycle displacement of the pumps to a minimum.

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: A power output control device for a pump having a delivery adjuster, is formed of a housing including a control piston attacked at one end with the output medium of the pump and having means for controlling the pump adjuster; a two-armed rocking lever is supported in the housing for movement parallel to the axis of the control piston, one arm of the lever being biased by a governor spring having a progressive biasing force while the other arm of the lever acts on the control piston against the force of pressure medium; an additional biasing spring thrusts against the other arm of the lever and a first setting screw adjusts the biasing force of the additional biasing means and a second setting screw adjusts the biasing force of the governor spring by adjusting the position of the pivot point of the two-armed rocking lever.

Abstract: A priority flow control system in which the priority feature is obtained by progressively lowering the pressure differential of nonpriority valves, once the maximum pump output is reached, so that all of the system valves always retain their compensated proportional flow feature.

Abstract: A hydraulic valve mechanism has a housing with first and second bores, a control valve element in the first bore, a pressure compensation valve in the second bore, and a non-return valve cooperating with motor parts, wherein control edges for direction control are arranged on the control valve element only at one side of throttle means, the non-return valve is also arranged in the second bore of the housing, and the longitudinal valve element of the pressure compensation valve also forms a closing member of the non-return valve.

Abstract: A direction flow control valve for control of positive and negative loads operated by a single pilot valve stage, which automatically maintains a relatively constant pressure differential across valve spool, while controlling positive and negative loads and which permits variation in the level of pressure differential in response to an external control signal, while this pressure differential is maintained constant at each controlled level.

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: In a vehicle having an engine and a cooling system for the engine including means for circulating a coolant through the engine, a fluid motor driven fan disposed in operative relation with the radiator and an engine driven pump operatively connected to the fluid motor, a means for controlling the operation of the cooling system generally consisting of a first means operatively connected to the pump and responsive to an output pressure of the pump above a first predetermined pressure for setting the output pressure of the pump at the first predetermined pressure, and second means operatively connected to the pump and responsive to an output pressure of the pump above a second predetermined pressure and a predetermined temperature of the coolant for setting the output pressure of the pump at the second predetermined pressure.

Abstract: A hydrostatic drive system with an adjustable pump is provided with branch lines from a main delivery line to several consumers, an arbitrarily actuatable switch in each branch line, an adjustable parallel connecting restrictor in each branch line with an adjusting element loaded on one side by pressure from either the main delivery line or the branch line and on the other side by a spring and control pressure and a source of common control pressure furnishing the control pressure to the adjusting element through a check valve.

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 hydrostatic transmission (10) includes a variable displacement pump (12) for driving a fluid motor (14) in first and second directions. First and second high pressure conduits (20,22) connects the pump (12) and motor (14) in a continuous fluid circuit. A control pump (40) supplies make-up fluid to the first and second high pressure conduits (20,22) and simultaneously provides pressurized control fluid to a system control (50) for controlling the operation of the hydrostatic transmission (10). First and second low pressure conduits (24,26) are respectively disposed about the first and second high pressure conduits (20,22) and defines first and second spaces (28,30) therebetween. A pressure control arrangement (32) is connected to the first and second spaces (28,30) to control the maximum pressure level in the spaces (28,30) upon the failure of one of the high pressure conduits (20,22).

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: The hydraulic system has an adjustable pump for delivering pressure fluid to a plurality of loads, multiway control valve assigned to respective loads and means for adjusting the flow of the pressure fluid to the working conditions of the loads, the adjusting device includes measuring throttles provided in the switching passages of respective control valves and a flow regulating device having a differential piston displaceable by the pressure difference at the outlet of the pump and at the outlet of the measuring throttle of the activated control valve. The differential piston controls a branched stream of high pressure fluid from the pump to control an actuator in the form of a cylinder and piston unit mechanically coupled to the adjusting member for the pump.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions, a pump for supplying fluid to said actuator, pilot operated meter-in valve means to which the fluid from the pump is supplied for controlling the direction of movement of the actuator, pilot operated meter-out valve means associated with each opening of the actuator for controlling the flow out of said actuator. The pressure of fluid being supplied to the actuator by the meter-in valve means is sensed and caused to produce a force opposing the movement of the meter-in valve means by the pilot pressure resulting in a smooth and accurate control of the movement of the actuator.

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 closed center programmed valve system having a load sense fluid source for control of the raising and lowering of load means by a raise and a lower normally closed two stage valve assembly. Each of the second stages of the valve assemblies has a poppet with a parabolic contour which is dimensioned to provide substantially linear flow rate change for minimized shock when the respective valve is actuated to the valve closed state. The load sense for the load means is taken from the outlet of the raise second stage without the requirement of a separate actuated valve or land with a load sense signal being applied to the fluid source during the time the raise valve assembly is actuated to the valve open state.

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 self propelled combine having forward main drive wheels and rear steerable wheels. A hydrostatic drive including a variable displacement motor is arranged to drive the main drive wheels. An electronic-hydraulic control system is automatically operable to drive the rear steerable wheels in response to sensing preselected pressure and combine attitude values while automatically varying the displacement of the hydrostatic drive motor to minimize combine speed changes and to provide torque as required under varying loads imposed by hilly terrain or increasing amounts of grain collected in the grain tank of the combine.

Abstract: A load responsive system employing a fixed displacement pump and a variable displacement pump in a parallel circuit as a source of fluid in an open-center load sensing system. The load response control valve includes an unloading spool which is flow responsive in the operative positions of the control valve and maintains a constant .DELTA..rho. across the control valve by dumping the pump flow to reservoir; the control valve .DELTA..rho. being greater than the .DELTA..rho. of the pump compensator means so that the variable displacement pump will remain destroked until the system utilizes the full flow of the fixed displacement pump at which time the variable displacement pump strokes-out upon demand.

Abstract: A "load-plus" valve is oftentimes utilized in the servo-system for a variable displacement pump to maintain pump discharge pressure above a minimum pressure level and above a load pressure in a fluid actuator. Valves of this type normally employ a spring interconnected between a modulating spool and a piston which is responsive to load pressure to modulate a control pressure, controlling the displacement of the pump. Valves of this type thus provide a constant discharge pressure margin over load pressure while also providing the pump's minimum stand-by pressure. However, valves of this type further provide pump packages which are somewhat bulky in design. The improved load-plus valve (22) of this invention provides a spool (49) movable between a first position communicating a control pressure (P.sub.

Abstract: It is common practice to provide the servo-system for a variable displacement pump with a "load-plus" valve to maintain pump discharge pressure above a minimum pressure level and above a load pressure in a fluid actuator connected to the pump in response to the load pressure in the actuator. Systems of this type are normally lacking in a device for ensuring that the prime mover for the pump functions at maximum efficiency. This invention is directed to a pressure and horsepower limiting valve (24) for ensuring such efficiency by modulating a load pressure signal (P.sub.L) communicated to the "load-plus" valve (23).

Abstract: Flow-pressure compensated valves are employed in servo-systems for variable displacement pumps to maintain discharge pressure above a minimum pressure level and above the load pressure in a fluid actuator, during the working range of the pumps. In addition, such systems may also include a horsepower limiting valve for ensuring that the rating or predetermined range of horsepower consumption of the pumps is not exceeded. Prior art systems normally continually bleed-off pump discharge or load pressure signals when such horsepower requirements are exceeded to, thus, effect an undesirable horsepower loss in the system. In addition, control systems of this type normally cannot be packaged in modular form and are not adapted for use with pumps of various capacities and sizes. The improved fluid circuit (10) of this invention includes a horsepower limiting arrangement (39) for blocking communication of an actuator pressure signal (P.sub.

Abstract: A constant pressure system for pumping a coal slurry includes a slurry pump mechanically driven by a hydraulic motor which, in turn, is driven by a hydraulic pump. The output of the hydraulic pump is controlled by a pressure sensitive flow control valve that maintains the hydraulic fluid pressure drop as a constant across the hydraulic motor. The system assures a constant hydraulic motor output torque, driving the slurry pump at a constant delivery pressure.

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 fluid pressure system includes a variable displacement pump and a control spool. The control spool has one end face exposed to pressure in a control chamber and another end face exposed to pump outlet pressure to increase or decrease the displacement of the pump. The control chamber includes a pilot valve which regulates the maximum pressure in the control chamber. A resistance means and a capacitance means is connected to the control chamber in parallel with the pilot valve to make the control spool responsive to the rate of change of pump outlet pressure.

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 "load-plus" valve (34) is oftentimes utilized in the servo-system (20) for a variable displacement pump (11) to maintain pump discharge pressure (P.sub.D) above a minimum pressure level and above a load pressure signal (P.sub.L) generated in a fluid actuator (13). Valves of this type normally include a margin spring (39) for biasing a modulating spool (36) against the opposing force of pump discharge pressure (P.sub.D) to maintain a constant margin over the load pressure signal (P.sub.L) throughout the working range of the system. When the load pressure signal (P.sub.L) exceeds a maximum pressure level, it is normally vented to tank (12), or continuously bled to tank across an orifice, resulting in horsepower losses. The control package employed in systems of this type are also somewhat bulky.

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 variable displacement fluid pump system is provided having a pressure and flow compensated control system with constant torque and viscosity sensing over-ride acting on the control system.

Abstract: A hydraulic system comprising a pair of actuators operable to move a single load, each of which has a fluid inlet, a variable displacement pump including means responsive to a pressure for varying the displacement of the pump, a pilot operated meter-in valve associated with each actuator for supplying fluid from the pump to its respective actuator, and means for sensing the pressures between each meter-in valve and its associated actuator and applying an average of said pressures to said responsive means of said pump.

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.