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 pressure control valve is connected to selectively supply a control pressure signal to shift a relief valve from a first low pressure mode to a second higher pressure mode and for simultaneously supplying the control pressure signal to an associated variable displacement pump for reducing the relatively high output of the pump to a relatively lower output.

Abstract: A load responsive fluid power multiple load control system using load responsive direction and flow control valves in combination with pump control responding to highest system load. Each direction flow control valve is equipped with a single load responsive controller which automatically regulates fluid flow into and out of the fluid motor to maintain a constant pressure in front of a variable flow controlling orifice, during the control of both positive and negative loads. The load responsive controller of each direction control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust.

Abstract: A direction flow control valve for control of positive and negative loads equipped with a load responsive positive load control which automatically regulates valve inlet pressure to maintain a relatively constant pressure differential between inlet pressure and load pressure. The load responsive control of the direction flow control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust.

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 control including a control valve and an override valve for use with a variable displacement pump or motor unit having a pair of strokers into and out of which fluid must be directed to vary the displacement of the unit. The control valve ports fluid from a high pressure source to a first control passage and from a second control passage to a low pressure source, reverses said flow, and terminates said flow. The override valve is interposed between the control passages and the strokes and defines a pair of override passages therein used to direct fluid from one control passage to one stroker and from the other stroker to the other control passage. The override valve is selectively movable between a first position directing such flow therethrough and a second position in which such flow is terminated between the control passages and the strokers.

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 load responsive fluid power multiple load control system using load responsive direction and flow control valves in combination with pump control responding to highest system load. Each direction flow control valve is equipped with a load responsive pressure control which automatically regulates valve inlet pressure to maintain a constant low pressure level at the motor exhaust and a load responsive negative load control to control a constant pressure differential at the motor exhaust. The load responsive control of each direction control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust.

Abstract: A load responsive fluid power multiple load control system using load responsive direction and flow control valves in combination with pump control responding to highest system load. Each direction flow control valve is equipped with a load responsive pressure control which automatically regulates valve inlet pressure to maintain a constant low pressure level at the motor exhaust and a load responsive negative load control to control a constant pressure differential at the motor exhaust. The load responsive control of each direction control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust.

Abstract: A fluid drive assembly has a pump, a variable displacement motor, a fluid circuit connecting the pump to the motor, and an actuator device for controlling the displacement of the motor. The actuator device is movable between a first position at which the displacement of the motor is at a preselected maximum and a second position at which the displacement of the motor is at a preselected minimum. A control system for the fluid drive assembly includes a source of fluid at a first preselected pressure value. A valve device is connected to the source of fluid and to the actuator device for controlling the fluid flow therebetween and is movable between a first position at which the source of fluid is in communication with the actuator device and a second position at which the source of fluid is blocked from communication with the actuator device.

Abstract: Two fluid passages are connected through flow restrictors to a fluid supply. Downstream of the restrictors the fluid supply has a drooping pressure-load characteristic. Venting means for the fluid passages comprises vent openings therein downstream of the restrictors and variable position obstructor means cooperating with vent openings to vary venting and thereby vary fluid pressures in the fluid passages. This forms a mechanical to fluidic translator. Pressures at the translator's outputs are a function of the obstructor's position. This translator forms the transmitter of a servo or remote control or indicator system.Fluid conduits connect these pressure outputs to a fluid to mechanical translator comprising a double acting piston moving in a cylinder whose opposite ends are connected to the fluid conduits. The piston and cylinder form the responder of the system, which may be adjacent the mechanical to fluidic translator and form part of the transmitter.

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: An electro-hydraulic control for a hydrostatic transmission including a variable displacement hydraulic pump and fluid operable servos to vary the displacement of the pump. The electro-hydraulic control is in series between the charge pump and the standard manual controller and determines the maximum pressure of the charge fluid ported to the standard controller. The electro-hydraulic control includes a spool biased toward a first position to port fluid from the charge pump to the standard controller, and biased toward a second position to relieve to tank the pressure of fluid ported to the manual controller. The biasing toward the second direction is accomplished, in part, by pressure in a fluid chamber exerting a biasing force on the spool, the fluid chamber being in communication with drain through a variable orifice which is variable in response to a pressure command signal.

Abstract: A hydraulic system includes a fluid responsive means that controls the effective output of the pump in response to pressurization of signal fluid that is supplied by the pump. The signal fluid is pressurized by flowing through a synthetic signal generator and on into a fluid motor in opposition to the working pressure therein. This signal fluid is directed to the fluid motor by the directional control valve when the directional control valve is in an operating position; and it is directed to a sump by the directional control valve when the directional control valve is in a standby position. The present invention provides pressure actuated means to divert or occlude this signal fluid from the directional control valve except when the directional control valve provides a load sensing flow path which communicates this signal fluid to the fluid motor.

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: A load responsive direction and flow control valve for use in a fluid power load responsive system. The valve maintains a selected constant flow level for control of both positive and negative loads in parallel or series type circuits, irrespective of the change in the load magnitude or change in the fluid pressure, supplied to the valve. When controlling positive or negative loads the valve maintains a constant pressure differential across a flow control metering orifice utilizing a single load responsive controller, first by throttling fluid entering the inlet chamber and then by throttling the fluid leaving the outlet chamber. The load responsive controller blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust.

Abstract: A load responsive fluid power multiple load control system using load responsive direction and flow control valves in combination with pump flow control responding to highest system load. Each direction flow control valve is equipped with a load responsive negative load control. The negative load responsive control of each direction control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust while maintaining a constant pressure in front of a variable flow metering land.

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 vehicle steering system comprises a source of fluid, a hydraulic steering motor actuatable to effect vehicle steering, and a steering control valve in fluid communication with the source of fluid and with the steering motor. The steering control valve is operable to direct fluid from the source of fluid to the steering motor. A metering mechanism is connected in fluid communication with the steering control valve and the steering motor. The metering mechanism is manually operable in accordance with the operator's demand for steering, and a hydraulic system is responsive to demand for steering fluid by the metering means to increase the output flow of the fluid from the source of fluid to the metering means at a pressure sufficient only to effect steering action against a variable load.

Abstract: A pump has a rotatable rotor carrying a plurality of radially-extending pistons bearing at their outer ends on an annular adjustment ring which can be displaced radially in the pump housing by means of a pair of diametrically opposed adjustment cylinders that serve to displace this ring and adjust the stroke of the radial pistons in the rotor. One of the adjustment pistons is of larger diameter than the other and both of the adjustment pistons are spring-biased against the outer periphery of the adjustment ring and both have throughgoing bores so that pressure behind these adjustment pistons is fed to pressure-relief pockets at their inner ends against the adjustment ring. The small-diameter piston is provided in its through-going passage with a pressure-limiting valve which only allows pressure past to its respective pressure-relief pocket when pressure behind the smaller piston exceeds a predetermined minimum which is approximately a tenth of the maximum pump operating pressure.

Abstract: A hydrostatic transmission comprising a closed loop system incorporating a hydraulic pump and a hydraulic motor driven by the pump has an accelerator for the motor drive shaft which sets the maximum delivery pressure of the pump, and control means which acts to vary the relative volume displacement of the pump and the motor to maintain the pump delivery pressure at the maximum value determined by the setting of the accelerator. Thus, the closed loop system maintains a substantially constant maximum pressure throughout the flow range, and since the output torque of the motor drive shaft is proportional to this system pressure a true acceleration control is achieved. The relative value displacement of the pump and the motor may be influenced by the low pressure of delivery of the pump on overrun of the motor shaft and by a spring loaded braking valve adjustable by a pedal control to provide for braking of the motor drive shaft.

Abstract: A load responsive fluid power multiple load control system using load responsive direction and flow control valves in combination with pump control responding to highest system load. Each direction flow control valve is equipped with a load responsive positive load control which automatically regulates valve inlet pressure to maintain a relatively constant pressure differential between pump inlet pressure and load pressure at a first level and a load responsive negative load control which automatically regulates valve inlet pressure to maintain a relatively constant pressure differential between pump inlet pressure and load pressure at a second higher level. The load responsive control of each direction control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust.

Abstract: A hydraulic control system for controlling the flow between a reservoir, a pump having pressure flow compensating means associated therewith and first and second flow control means for controlling flow to first and second fluid operated devices is disclosed herein. The hydraulic control system includes a priority flow control valve which maintains a priority of flow from the pump to the first flow control means based upon the amount of flow required as well as the pressure requirements. The priority flow control valve has a valve spool which is positioned as a function of a biasing spring, as well as the pressure of the fluid from the pump to the first flow control means and the pressure of the fluid in the first fluid operated device. The system is particularly adapted for functions requiring higher pressure than low stand-by system pressure and where one of those functions require priority over the other.

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 is disclosed which combines hydrostatic and implement motors and includes a plurality of hydraulic motors with a variable displacement pump supplying fluid for the motors and a plurality of directional control valves for selectively directing fluid from the pump to the respective motors and includes pressure varying means connected to each of the directional control valves for varying a pilot pressure communicated to vary the displacement of the variable displacement pump in direct relationship to the shifting of the directional control valves.

Abstract: A hydraulic control arrangement for the lifting and lowering of loads is disclosed. The system is illustrated in an industrial truck and includes a multiple element control valve with timing circuitry to eliminate unwanted transient pressure surges during valve actuation. Series-parallel oil flow paths are provided for directing and controlling oil from the load lifting cylinder to the oil reservoir when the load is being lowered.

Abstract: A control system has override for fluid operated work elements served by at least two variable displacement pumps each serving a separate circuit. At least two work elements are served by the first circuit and at least one work element is served by the second circuit. The discharge rate of the first pump is controlled by a signal delivered from a summing valve in response to the pressures of the first and second circuits during operation of a preselected one of the work elements of the first circuit and controlled by a modified pilot pressure signal in response to operation of only the other work element of the first circuit.

Abstract: A control device for a hydrostatic drive, especially for a fork lift truck, in which an engine drives a reversible variable delivery pump which supplies fluid to a fluid motor connected to the drive wheels of the lift truck. A reversible actuator is connected to a control element for the pump and is connected through a reversing valve with a further engine driven pump. The rate of movement of the actuator is controlled in the opposite directions of movement thereof. The truck includes a lift cylinder supplied by a still further engine driven pump, and when the lift cylinder is under pressure, the rate of movement of the actuator is controlled at a still slower speed of movement in at least one direction of movement.

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

Abstract: A fluid drive vehicle has an engine speed control, a fluid drive transmission having a fluid actuator device for moving a control element from its neutral position progressively to increase the drive ratio, and a control system which includes a first fluid circuit which has a control valve movable from a neutral fluid blocking position progressively to increase the flow of pressurized fluid from an auxiliary pump to the fluid actuator device. A fluid responsive servo mechanism moves the control valve from the neutral position while a fluid motor is operative to move the engine speed control from an idling position to increase the engine speed.

Abstract: For automatically terminating the operation of the vibrator in a self-propelled roller compactor when the vehicle is at rest or travelling slowly, a variable displacement pump driving the hydraulic motor of the vibrator is provided with a servo control mechanism including a spring-neutralized linear actuator capable of adjustably varying the per-cycle displacement of the pump by receiving hydraulic fluid pressure from another pump. Provided between the servo control mechanism and the said other pump is an on-off valve which is closed when the vehicle speed becomes less than a predetermined value, with the result that the actuator is neutralized to zero the displacement of the variable displacement pump. The on-off valve can be operated from an operator controlled shift lever, so as to be closed when the lever is in or adjacent a neutral position.

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 variable speed drive system for driving one or, preferably, a plurality of fans at a desired, controllable speed. The fans are rotated by motors in fluid communication with variable displacement pumps. The motors rotate the fans at a speed corresponding to the fluid displacement of the pumps and an adjusting structure operably connected to the pumps regulates the fluid displacement of the pumps so that the fans are driven by the motors at a desired speed. Preferably, the adjusting structure includes a temperature sensor and a pump displacement control responsive to the temperature sensor so that the fluid displacement of the pumps is automatically regulated in response to the temperature of the substance cooled by the fans.

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 closed center control valve for double acting motors having an inlet passage and a pair of control passages is provided with pre-sized restrictions in the control passages to control the flow rate to the motor so that a pre-selected velocity of movement of the motor is achieved.

Abstract: A conveyor drive system employing a constant speed master drive and a slave drive of the hydrostatic, closed loop type in which there are no electrical or hydraulic feedback lines between the master and slave drive unit. The master drive moves the conveyor at a constant speed as load varies and the slave drive unit responds to changes in load on the conveyor to vary the speed of the drive to maintain a constant pull on the conveyor to insure that the slave drive shares its portion of the load with the master drive.

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

Abstract: A load responsive fluid power multiple load control system using load responsive direction and flow control valves in combination with pump control responding to highest system load. Each direction flow control valve is equipped with a load responsive positive load control which automatically regulates valve inlet pressure to maintain a relatively constant pressure differential between pump inlet pressure and load pressure at a first level and a load responsive negative load control which automatically regulates valve inlet pressure to maintain a relatively constant pressure differential between pump inlet pressure and load pressure at a second higher level. The load responsive control of each direction control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust.

Abstract: The present invention relates to an apparatus providing for the co-ordinated driving of a towing vehicle and a towed vehicle equipped with a hydrostatic driving system of its own. The respective driving wheels of the towed vehicle are each driven by a separate hydrostatic transmission and a variable output hydraulic pump coupled to a hydraulic motor which can be driven by output of said hydraulic pump and can be engaged with a driving wheel. The apparatus includes for each respective transmission control circuits having a control device mounted on the towing vehicle. The invention is particularly useful for a cross-country towing vehicle and a towed vehicle in the form of a heavy field artillery gun which for purposes of operating the hydrostatic transmissions is equipped with a reciprocating engine, for instance a gasoline engine, which actuates said transmissions via a dividing gear box.

Abstract: A hydraulic circuit for controlling actuators in a construction vehicle which comprises an engine, a fixed displacement pump driven by said engine, a variable displacement pump driven by said engine, a controlling cylinder connected to the variable displacement pump for controlling the displacement thereof, an orifice provided between the output of the fixed displacement pump and a tank and, an unloading valve connected to the fixed displacement pump and also to the variable displacement pump via a pilot line for selectively unloading an output fluid from the fixed displacement pump when it is open.

Abstract: Programmable hydraulic power controls for an injection molding machine having a proportional-response flow control valve arranged in the main supply line of a variable delivery pump and a feedback line with a control diaphragm linking a point on the supply line behind the flow control valve with the pump control member, and a proportional-response pressure control valve in a branch line to the feedback line, each valve being controlled by a proportional-force electromagnet with a position transducer and electronic feedback loop for position verification in accordance with a nominal program signal fed to the electromagnet.

Abstract: A drive mechanism for a pair of forging or stretching rollers comprising a hydraulic system including a pump, a hydraulic motor and switching means interposed between a main drive motor and the rollers.

Abstract: A steering control system is disclosed of the type utilizing a variable fluid delivery source, such as a variable delivery pump, providing fluid to a steering cylinder, the flow to the steering cylinder being controlled by a steering control valve. The steering control valve includes a first orifice which is variable between a minimum orifice area permitting a minimum system flow and a maximum orifice area corresponding to a maximum system flow. The variable fluid delivery source is maintained at a generally constant level above the steering load as the system flow varies between the minimum and maximum flow rates. Disposed in series flow relationship between the fluid delivery source and the steering control valve is a second valve including a valve member defining a second variable orifice operable to maintain a relatively constant pressure drop across the second valve as the system flow varies between the minimum and maximum flow rates.

Abstract: A demand compensated hydraulic system includes a pump responsive to pressurized fluid in a demand feedback pilot line. The pilot line is connected to sense fluid demand between a hydraulic motor and its associated control valve which is closed by servo feedback from the motor. A flow sensitive device is interposed in an output line connecting the pump and the control valve to sense when the flow decreases until it is insufficient to operate the function. At a predetermined decreased flow rate, the flow sensitive device operates to momentarily connect the demand feedback pilot line to a reservoir to cause the pump to go into a stand-by condition.

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 demand compensated hydraulic system includes a pump responsive to pressurized fluid in a demand feedback pilot line. The pilot line is connected to sense fluid demand between a hydraulic motor and its associated control valve which is closed by servo feedback from the motor. A flow sensitive device is interposed in an output line connecting the pump and the control valve to sense when the flow decreases until it is insufficient to operate the function. At a predetermined decreased flow rate, the flow sensitive device operates to momentarily connect the demand feedback pilot line to a reservoir to cause the pump to go into a stand-by condition.

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

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