Abstract: Fluid control circuits employed on construction vehicles to control the actuation of various work cylinders oftentimes include a system for sensing the fluid pressure in the cylinder and communicating such fluid pressure to a control device in signal form to closely control the displacement of a pump, the flow capacity of a pressure compensated flow control valve, or the like. The sensing system is normally associated with the spool of a directional control valve which must travel a substantial distance to effect extension or retraction of the cylinder and normally requires an "anti-rotation" device to insure proper alignment of the various ports and passages. Conventional high pressure systems of this type also pose potential leakage problems.

Abstract: A load sensing controller is disclosed of the type which may be used in a hydrostatic power steering system. The controller housing includes a valving arrangement (29) and a fluid meter (31), through which fluid is delivered to a steering cylinder (15). A controller housing (63) defines a load signal port (25) which is connected to a load sensing flow control valve (39) to vary the rate of fluid delivery to the controller. During normal operation, a steering load signal is sensed downstream of a variable flow control orifice (131) and communicated through a shuttle valve assembly (151) to the load signal port (25). When the steering cylinder is subjected to an overrunning load, an increased load signal is sensed upstream of a variable orifice (136) and the shuttle valve assembly communicates this increased load signal to the load signal port to increase the rate of fluid delivery to the controller to prevent cavitation.

Abstract: The displacement controllers of a first variable displacement pump supplying fluid for hoe and travel functions of an excavator and a second pump supplying fluid for the excavator house swing function are connected to shuttle valves which operate to couple to the controllers the lesser of the power beyond fluid pressures emanating from travel function and swing function control valves. A bypass circuit is arranged to couple power beyond flow from the swing function control valve to join the flow being outputed from the first pump when the pressure of the last-named power beyond flow exceeds the lesser of that emanating from the travel control functions. Lead compensators are provided to make the controllers more responsive to circuit demands and a power limiting valve is provided for automatically connecting pressure for destroking the pumps to relieve engine load when the engine speed falls to a predetermined minimum.

Abstract: Load responsive system controls to vary output flow control of a system pump to control the pressure differential, acting across a control orifice positioned between system pump and a fluid motor. The system controls permit 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: In a load responsive fluid power and control system employing plurality of control valves with positive and negative load compensation, a closed loop pressurized exhaust system supplied with a make-up and fluid exchange pump equipped with an unloading device responsive to positive and negative load system pressures.

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: A pressure compensated pump has a pressure compensator valve connected to a stroking piston. When the discharge pressure exceeds a set maximum the compensator valve connects pressure fluid to the stroking piston to reduce the displacement of the pump. The flow of pressure fluid to the stroking piston is accompanied by a concurrent flow of fluid to case.

Abstract: A load responsive fluid control system in which system pump controls permit variation in the level of pressure differential in response to an external control signal and which uses direction control valves equipped with load responsive variable pressure differential positive load controls.

Abstract: In a load responsive fluid power and control system employing plurality of control valves with positive and negative load compensation, a closed loop pressurized exhaust system supplied with a make-up and fluid exchange pump equipped with an unloading device responsive to positive and negative load system pressures.

Abstract: PCT No. PCT/US79/00968 Sec. 371 Date Nov. 8, 1979 Sec. 102(e) Date Nov. 8, 1979, PCT Filed Nov. 8, 1979An improved load resolver (41) is provided of the type which receives a pair of generally unequal pressure signals (32, 34), and which resolves the pair of pressure signals (32, 34) by blocking the lesser and transmitting the greater. Each pressure signal (32, 34) is sent to the load resolver (41) by a respective control valve (18, 20) in a hydraulic system (10). Prior load resolver structures have required angled or intersecting holes therein or special porting therearound. The improved load resolver (41) comprises a first member (58) having a first, axially extending hole (64) and a second member (72) having second and third axially extending holes (78, 104). The members (58, 72) are fitted within a bore (48) of a control valve body (19).

Abstract: In a fluid throttling pressure compensated valve remote control of position of valve spool in which the total force acting on the spool is directly proportional to displacement of the spool from its neutral position, irrespective of the pressure differential between the pump pressure and the load pressure or the pressure differential between the load pressure and the reservoir pressure.

Abstract: A drive system has an engine that operates a control pump and a hydraulic variable-displacement drive pump having a control element and connected to a hydraulic motor. A servocylinder operates the control element of the drive pump and is pressurized through a control line connected to the control-pump output. A control valve is connected between the control line and the sump of the system and is connected to the hydraulic line between the motor and the drive pump to reduce pressure in the control line when the higher pressure of the line between the drive pump and the motor rises within a predetermined range. Thus it is possible with a substantially constant engine speed to produce a substantially constant output torque, with only the displacement of the pump and pressure in the lines between the pump and the motor varying by appropriate control of the control-line pressure.

Abstract: A method and apparatus for linear and nonlinear control of a hydraulic press is provided with a feedback loop allowing the operation of a variable displacement pump to be selectively controlled with respect to either hydraulic pressure moving a piston in a cylinder, or the velocity of the piston. During controlled movement of the piston, a directional valve blocks a pump compensator so that the pump operates as a fixed displacement pump to provide fast response to feedback signals. Simultaneously, the directional valve connects a proportional pressure controller to a relief valve. During a period when the piston is maintained in fixed position, the directional valve is switched so that the proportional pressure controller now controls the pump compensator and the relief valve is blocked, so that energy consumption is substantially reduced.

Abstract: A variable delivery pump has a pump control mechanism in a housing secured thereto for governing directional flow of fluid through the pump, the pump being adapted to be connected through a closed loop to a motor. A pressure compensating valve is provided in the housing for governing pressure output of the pump, and a pump control cylinder is provided for positioning a flow control cam of the pump in accordance with flow of fluid through the direction control valve and the pressure compensating valve. A cam plate is coaxially connected to a directional control rotatable valve spool of the direction control valve, the cam plate having an outer periphery that is continuously radially variable from a maximum radial point to a minimum radial point for either direction of rotation of the cam from the maximum radial point as the control spool is rotated in either direction from a normal position. The cam plate actuates a cam follower, which in turn actuates a slideable sleeve in the pressure compensating valve.

Abstract: A hydraulic control system for adjusting the displacement of a variable displacement pump or pumps as dictated by pump output pressure and input speed. Driven by the same prime mover as the pump or pumps is a charging pump which communicates with a restrictor adapted to create a differential in the output fluid pressure therefrom, which pressure differential is sensed by a sensing valve for providing a corresponding output fluid pressure. Servo control means provided to the variable displacement pump or pumps communicates with both the restrictor and the sensing valve for adjusting the pump displacement in response to the fluid pressures delivered therefrom. A flow metering valve assembly is connected in a bypass around the restrictor to permit the passage therethrough of the charging pump output fluid at a rate metered in accordance with the variable displacement pump output pressure.

Abstract: A load sensing hydraulic system is disclosed of the type in which a load signal is communicated from downstream of a main flow control orifice to a device which is operable to vary the fluid delivery rate in response to changes in the load signal. Disposed in the load signal conduit is a load signal modulating valve which, in one position, communicates the load signal, substantially unchanged, to the variable fluid source. In another position of the modulating valve, the load signal chamber of the variable fluid source is drained to tank, while in intermediate positions of the modulating valve, a portion of the load signal is communicated to the variable fluid source, and a portion is bled to tank. Modulation of a load signal permits flow control in an hydraulic system, independent of the position or movement of the main spool valve. The input to the modulating valve may be manual or electric, and if electric, may be remote, or may be automatic in response to certain predetermined system conditions.

Abstract: A load responsive fluid power control system using servo type flow control valves and fluid motors supplied by a variable displacement pump. The pump displacement is either regulated by an electro-hydraulic control valve in response to an electrical signal proportional to motor load or the pump displacement is regulated to maintain a constant discharge pressure. The flow of pressurized fluid from the pump is automatically cut off from a servo type valve controlling a negative or aiding load once this load exceeds a certain minimum level and the inlet flow requirement of the actuator is supplied from a low pressure source bypassing the servo valve.

Abstract: Each directional control valve of a load responsive hydraulic system supplies a flow of signal fluid to a work port channel thereof and pressurizes this flow of signal fluid to a predetermined pressure magnitude above the load actuating pressure in the work port channel to provide a synthetic signal pressure. Fluid logic is provided for the selection of the highest synthetic signal pressure from any of the directional control valves and for application of this highest synthetic signal pressure to an effective output operator for the control of the pressure and effective output of the pump.

Abstract: A supply or demand margin valve for use in hydraulic systems having at least one load provided with hydraulic fluid under pressure by a main pump, a pilot pump and at least one control valve for the load. The margin valve includes a valve body having a bore with a spool reciprocally received within the bore. A first port in the body extends to the bore and is adapted to be connected to the pilot pump. A second port in the body extends to the bore and spaced in relation to the first port and is adapted to be connected to a component of a hydraulic system other than a pilot pump. A spring is disposed in the valve body for applying a biasing force to the spool to urge the spool in one direction and a third port is in fluid communication with the pressure responsive surface and is adapted to be connected to a main pump so as to apply a force to the spool to urge the spool in the same direction as the spring.

Abstract: A fluid horsepower control system is adapted to operate a fluid load by output of a variable delivery pump having a control cylinder governed by a pressure compensated variable orifice connected in multiple with a load sense control valve for causing fluid flow to be inversely proportional to pump discharge pressure and maintaining constant drop across the orifice, without requiring mechanical feedback from the variable delivery pump to the load sense control valve.

Abstract: A hydraulic controller for a hydrostatic transmission to control a number of functions of a variable displacement pump or motor of the transmission. A valve includes a spool biased in one direction by a spring and in the opposite direction by fluid pressure in a chamber communicating with the charge pump. A variable orifice communicates the chamber with a drain. The size of the orifice is controlled electrically by a signal representative of swashplate position. Depending upon the pressure of the fluid in the chamber, the valve will directly vary the pressure ported from the charge pump to the standard controller. A needle roller has one end in contact with the end of the spool communicating with the chamber. A high pressure signal is provided via a shuttle valve across the high and low pressure conduits of the transmission to the other end of the needle roller.

Abstract: A control system for a variable displacement pump which powers a load actuator via a selector valve and which has its displacement varied by a pump actuator of the single-acting type. The system includes a load-sensing control valve for selectively communicating the pump actuator with a pressurized fluid source or with a fluid drain in accordance with a differential between the sum of the pump output pressure and the pump actuator pressure and the sum of the load actuator pressure and the force of a spring. Also included is a normally open, cutoff control valve, connected serially with the load-sensing control valve, for placing the pump actuator in communication with a fluid drain in response to the sum of the pump output pressure and pump actuator pressure acting against the force of a spring.

Abstract: A variable displacement pump includes a plurality of pistons and a swash plate arranged therewith, with the swash plate displaced in response to pump discharge manifold pressure for controlling the stroke of the pistons to maintain a predetermined substantially constant pressure with a variable flow of fluid through the pump.

Abstract: A load responsive fluid power control system using servo type flow control valves and fluid motors supplied by a variable displacement pump. The pump displacement is regulated by an electro-hydraulic control valve in response to an electrical signal proportional to motor load or motor load pressure to vary the pump displacement to maintain a controlled constant or variable pressure differential between the pump outlet pressure and motor load pressure or to vary the pressure differential between pump outlet pressure and motor load pressure in response to a signal from a computing device. The pump control also limits maximum and minimum system pressures.

Abstract: A load responsive fluid power control system using servo type flow control valves and fluid motors supplied by a variable displacement pump. The pump displacement is regulated by a control valve in response to the motor load pressure to vary the pump displacement to maintain a constant preselectable ratio between the pump outlet pressure and motor load pressure and to vary the pressure differential between pump outlet pressure and motor load pressure with variation in magnitude of the load. The pump control also limits maximum and minimum system pressures.

Abstract: A load responsive fluid power control system using servo type flow control valves and fluid motors supplied by a variable displacement pump. The pump displacement is regulated by a control valve in response to the motor load pressure to vary the pump displacement to maintain a constant preselectable ratio between the pump outlet pressure and motor load pressure and to vary the pressure differential between pump outlet pressure and motor load pressure with variation in magnitude of the load. The pump control also limits maximum and minimum system pressures.

Abstract: A hydraulic system has a pump whose outlet is connected to a load and which has a pilot port whose pressurization is proportional to the pressure at the outlet. A restriction is provided between the outlet of the pump and the load. A differential valve is provided connected to the conduit between the pump and the load to both sides of the restriction and serves to compare the difference between pressure upstream and downstream of this restriction with a set point so as to depressurize the pilot port of the pump when this difference exceeds the set point. Furthermore, another valve is provided which compares the pressure in the feed conduit downstream of the restriction through yet another set point and also serves to depressurize the pilot port when this downstream pressure exceeds the second set point.

Abstract: The disclosure is directed to a closed center, pressure compensated hydraulic system which uses a multiple section hydraulic control valve in conjuction with a variable output hydraulic pump. The hydraulic control valve has a plurality of independently operable power spools each of which is used to control the flow of hydraulic fluid to a separate hydraulic actuator and load. Each valve section includes an automatic spool positioner which enables the operator to move the valve handle to a preselected position, the power spool thereafter being retained in such position until the actuator completes its stroke. After completion of the stroke, the automatic spool positioner causes the power spool to return to the neutral position. The multiple section hydraulic control valve also includes means for selecting the highest demand or work port pressure, and for controlling the variable output pump as a function of this selected pressure.

Abstract: A pump control assembly for a variable displacement pump has a means connected to a spring for selectively adjusting the preload on the spring for selectively adjusting the minimum pump discharge pressure. An adjustable stop device is provided for selectively adjusting the maximum force exerted on the spring by a piston device which increases the load on the spring for increasing the pump discharge pressure in response to a load pressure signal exceeding a preselected pressure level.

Abstract: A first device for controlling the position of a displacement control member of a variable displacement pump has an actuator connected to the control member and a valve member which is movable between a first position at which a pump discharge pressure signal is in communication with the actuator and a second position at which said pump discharge pressure signal is blocked from communication with the actuator and the actuator is connected to a drain. The valve member has an end substantially continuously exposed to the pump discharge pressure signal and is responsive thereto for biasing the valve member toward one of the first and second positions. A spring apparatus biases the valve member toward the other of said positions in opposition to the biasing force of said pump discharge pressure signal and establishes a preselected minimum discharge pressure.

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. System is powered by a single fixed or variable volume pump. The direction flow control valve is equipped with a load responsive control which automatically regulates pump discharge pressure to maintain either a constant low pressure level or low pressure differential at the motor exhaust. The pump discharge pressure is either regulated by bypassing of excess flow to reservoir, or by a special load responsive control, which varies the pump displacement. Direction control valve may also be equipped with a control responsive to load pressure for controlling negative loads and an inlet pressure throttling control for simultaneous control of multiplicity of loads.

Abstract: A multi-range pressure compensated fluid delivery system gives output flow over at least two pressure ranges. The system comprises a prime mover driven variable displacement pump having an inlet from a source of hydraulic fluid and a delivery outlet. A delivery circuit from the output has at least two work circuits selectively connected thereto. A first of the circuits is operable up to a first pressure and a second of the circuits is operable only up to a second lower pressure. An actuator system controls pump displacement responsive to a pressure applied thereto. A system selectively applies a first signal determined by the first pressure to the actuator system to adjust the operating pressure of the pump. A device reduces the first pressure to the second pressure responsive to connection of the second circuit to the delivery circuit to thereby decrease the maximum compensated pressure setting of the pump.

Abstract: A total fluid power system for an engine powered vehicle includes an engine driven, variable displacement pump, a pair of variable displacement wheel motors and auxiliary functions. Transducers sense engine speed, pump output pressure and motor speeds to supply signals to pump and motor controls which process the signals with operator input signals to maintain pump and motor displacements for optimum engine power usage and desired vehicle performance.

Abstract: A constant pressure at the output of a pressure regulator is adjusted to and maintained at a required value by hydraulic remote control of a sliding valve in operative association with a control cylinder responsive to actual pressure conditions. The position of the piston of the control cylinder is determined both by a pilot pressure and by the pressure prevailing at the output of the regulator.

Abstract: Pressurized fluid is supplied to fluid-driven mechanisms by a variable displacement supply pump through a check valve and a flow control valve. A compensator receiving a pressure feedback signal from the control valve side of the check valve increases pump displacement in response to a pressure signal drop and decreases pump displacement in response to a rise in the signal pressure to compensate for variations in demand. Part of the supply pump output is used to drive a small fluid motor which turns a small pressure signal-amplifying pump connected in parallel with the check valve. The check valve opens to transmit the variable displacement pump output to the driven mechanisms when the control valve is opened.

Abstract: The invention is concerned with an improvement in a hydraulic fluid system of a vehicle which comprises a variable displacement pump; a first work element; and a device for receiving a first load signal from the first work element and controlling the pump discharge responsive thereto. The improvement includes a plurality of second work elements which receive fluid flow from the pump via a common supply line connected to the first work element, said fluid flow not passing via any independent load responsive delivery system, and a load responsive controller having flow restricting means in a signal line which communicates with the common supply line for sensing a load pressure in the common supply line, said load pressure being a maximum load pressure of any of the second work elements and delivering a second load signal representative of the load pressure to combine with the first load signal to control the discharge of the pump to be responsive to the larger of the first and second load signals.

Abstract: A horsepower limiter control for an axial piston pump provides a simple adjustment for setting the maximum horsepower the pump can provide and automatically adjusts the product of working pressure and maximum pump displacement to maintain the set horsepower. The horsepower limiter control operates to reduce the displacement of the pump when working fluid pressure exceeds the setting of the sequence valve.

Abstract: A load responsive fluid power control system using servo type flow control valves and fluid motors supplied by a variable displacement pump. The pump displacement is regulated by a control valve in response to the motor load pressure to vary the pump displacement to maintain a constant preselectable ratio between the pump outlet pressure and motor load pressure and to vary the pressure differential between pump outlet pressure and motor load pressure with variation in magnitude of the load. The pump control also limits maximum and minimum system pressures.

Abstract: A control valve arrangement for regulating a servo pressure which in turn controls the stroke of a variable displacement pump has a control element positioned by means of an operating pressure derived from the pressure at the pump outlet. A solenoid valve is operable to reduce the operating pressure and thereby to position the control element so as to cause the pump stroke to be reduced. Movement of the control element beyond a predetermined position in a pump stroke reducing direction opens a bypass connection which maintains a small cooling flow through the pump.

Abstract: A hydraulic control valve in a closed-center load responsive system having a passage with a check valve therein downstream of the inlet metering and signal passage allowing flow from the signal passage to the load prior to connecting the pressure circuit to the load circuit so as to relieve fluid from the signal circuit to the load circuit as the signal circuit attains a pressure higher than the existing load thus causing flow past the inlet metering whereby the pressure differential in the metering compensates the pump.

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 improved control means for controllably positioning the swash plate in response to a modified load pressure signal.

Abstract: A hydraulic control device for protecting a drive from excess loading conditions includes at least one pump having adjustable members for controlling the quantity of fluid transported by the pump. A pressure-responsive control slide is mounted for movement relative to a housing and is moved towards respective positions, each of which corresponds to a normally loaded condition of the drive by a control pump which generates a pressure force which is indicative of the rpm of the drive at normally loaded conditions. The device further includes an arrangement for securing the control slide when the drive is subjected to loads in excess of the respective normally loaded conditions so that a valve member is permitted to move in response to excess loads relative to the control slide after the latter has been secured in said respective positions by the securing arrangement between switching positions in which the adjustable members are operative to adjust the quantity of fluid being transported by the pump.

Abstract: A tractor-implement hydraulic system having a valve interposed between a cylinder-piston assembly, a reservoir and a variable displacement pressure and flow compensated pump having compensating means is disclosed herein. The valve has a housing which has a bore supporting a valve spool and an inlet chamber and pressure chamber in communication with the valve bore with the inlet chamber being connected to the pump while the pressure chamber is connected to both the cylinder and the compensating means so that the cylinder and compensating means are immediately interconnected when the valve spool is actuated in one direction. The valve housing also has a return passage between the cylinder and the reservoir with a valve therein that normally blocks flow and is opened in response to movement of the valve spool in an opposite direction.

Abstract: A variable displacement pump having a tiltable swash plate including a pair of servo mechanisms for controlling discharge of pump fluid includes a zero displacement positioner for automatically returning the pump swash plate to a central, neutral position to discontinue pumping action if pump pressure is lost or if linkage controlling one of the servo mechanisms should break or otherwise fail.

Abstract: A load sensitive hydraulic system for operating auxiliary equipment on a vehicle with a priority flow control valve to provide priority pressure in operating a regenerative steering circuit of the hydraulic system. The regenerative hydraulic steering circuit provides load sensing and utilizes single source of pressurized fluid which responds to various loads in the hydraulic system. A priority valve assures that the steering demands are met before providing adequate pressure for all other auxiliary functions.

Abstract: A pump control assembly for a variable displacement pump has adjustable biasing means for providing improved control of the pump.

Abstract: An apparatus for converting a hydraulic pressure signal to a mechanical motion in a way such that the amount of physical displacement of an element is directly proportional to the value of a hydraulic signal, the apparatus having a housing having a cylindrical cavity, a diaphragm within the housing dividing the cavity into a first portion and a second portion, the second portion of the cavity having walls configured as a frustocone, the base of the cone being the inner surface of the diaphragm, a shaft slidably positionable in the housing, the inner end of the shaft connecting the diaphragm so that hydraulic pressure applied to the rearward surface of the diaphragm displaces the shaft, the diaphragm contacting the conical walls as it is moved forward by increased hydraulic pressure, decreasing the effective area of the diaphragm such that the displacement of the shaft is substantially directly proportional to the pressure of the hydraulic signal.

Abstract: A pump assembly having at least two variable displacement pumps each having a separate pump control assembly are interconnected for control in response one to the other. Each pump control assembly has first and second biasing means acting on a respective swash plate. The first and second biasing means have interconnecting fluid pathways formed through a pump control housing. Means are provided within the housings for modifying the discharge pressures of the separate pumps to provide a resultant pressure signal for controlling the second biasing means.

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 fluid system of work elements of a work vehicle has first and second fluid circuits each having a pump connected to a work element through a control valve assembly that is operated by a pilot pump. A fluid control means is provided for controllably passing fluid between the first and second fluid circuits in response to control signals passing between said circuits.