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

Abstract: A variable speed engine (10) drives a tractive effort drive train (12) and fixed and variable displacement pumps, (14 and 16) arranged to supply fluid pressure to a hydraulic work system (24). The displacement of the variable pump (16) is determined by a control ram (42) and a conduit (44, 53, 74) interconnects the variable pump output and the control ram (42). An engine speed control valve (60) and a system pressure compensator valve (46) interposed in series in said conduit (44, 53, 74). The two valves (60 and 46) maintain the variable pump (16) at full output except when low engine speed and high system pressure exists simultaneously.

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: 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: A hydraulic apparatus for changing flow rate by displacing the flow rate changing member of a variable displacement hydraulic pump accommodated in a casing for eliminating any surplus and leaked oil and diminished kinetic energy loss comprises an actuator, a flow rate control valve, a resilient member accommodated in the casing to urge the flow rate changing member toward the direction where the flow rate of the hydraulic pump is increased, first and second sliding members slidably received in first and second cylinder chambers, respectively, provided in the casing to urge the flow rate changing member toward the direction where the flow rate of the hydraulic pump is decreased, a first fluid conduit having one end connected with an outward port of the hydraulic pump and the other end connected with a rear port of the actuator, a second fluid conduit having one end connected with a fore port of the actuator and the other end connected with an inlet port of the hydraulic pump through the flow rate control valve

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

Abstract: 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 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: PCT No. PCT/US79/00920 Sec. 371 Date Oct. 29, 1979 Sec. 102(e) Date Oct. 29, 1979 PCT Filed Oct. 29, 1979A steering system (36) for vehicles (10) in which a device (90) is provided for circulating fluid through the system when operating in a cold environment. The system includes a hand metering unit (58) which is connected to opposite ends of a pilot operated steering valve (42) through a pair of pilot lines (60,62). A pressure reducing valve (94) maintains a continuous flow of fluid to the pilot lines (60,62) at a first predetermined pressure level. A pressure responsive valve (94) positioned between the hand metering unit (58) and a reservoir (40) intermittently passes pilot control fluid, returned to the hand metering unit (58) from the pilot actuation of the steering valve (42), to the reservoir (40) in response to the pressure of such returned fluid reaching a second slightly higher predetermined pressure level such as occurs when the fluid in the system is cold.

Abstract: A hydrostatic-transmission control system for fork-lift trucks and like industrial vehicles has at least one variable-displacement hydrostatic motor driving wheels on opposite sides of the vehicle and supplied by a pump having a control element for varying its displacement under the control of an operator. The prime mover, e.g. a gasoline engine or electric motor, drives the pump. The control system comprises means whereby, for low and average output speeds of the transmission consisting of a combination of the pump and motor, the control of the transmission ratio is a function only of the operator-set position of the aforementioned element whereas, for the highest output speeds, the ratio is controlled by both the position of this element and by a further parameter, usually the output speed of the prime mover.

Abstract: A variable displacement pump is compensated to provide a relatively constant predetermined flow of hydraulic fluid under pressure to an open-center hydrostatic steering system, as the speed of the engine driving the pump varies, and a relief valve by-passes the steering system whenever the steering system would normally reduce the flow to hydraulic apparatus connected in series with and downstream of the steering system.

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: A hydraulic pumping arrangement for pumping a liquid to a hydraulic system, which comprises pumping means for pumping the liquid, swash means including a variable swash member which enables the liquid output of the pumping means to be infinitely varied between minimum and maximum, a first piston-and-cylinder arrangement for increasing the position of the swash member to increase the liquid output of the pumping means, a second piston-and-cylinder arrangement for decreasing the position of the swash member to decrease the liquid output of the pumping means, control means for controlling the flow of liquid for the second piston-and-cylinder arrangement, switching means operative to pass liquid from the system to the control means at a first condition in the system and operative to stop liquid from the system passing to the control means at a second condition in the system, and valve means for isolating the pumping arrangement from the system and from a main pump normally supplying liquid to the system, the cont

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: 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 power steering system is disclosed which selectively controls the flow of fluid to a steering motor and an auxiliary device, and may have as its source of pressurized fluid either a fixed displacement pump, a variable displacement pump, or a load sensing pump. The system includes a steering control valve disposed between the pump and the steering motor, and an externally pilot operated flow control valve, specifically, a priority valve, disposed between the pump and the steering control valve, such that the entire system flow enters the priority valve.

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 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 hydraulic system and control valve assembly therefor characterized in that it provides a two wheel pressure compensated hydraulic drive for mobile equipment in forward or rearward direction at any speed up to maximum as determined by the operation of the control valve assembly. Said control valve assembly is further characterized in that it incorporates an override for the pressure compensating means to achieve steering control by decreasing the rate of flow of fluid to either wheel motor or to achieve braking action in conjunction with a counterbalance valve in the motor return circuit by decreasing the rate of flow of fluid to both wheel motors.

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

Abstract: A hydraulic drive control system for driving a generator or alternator or the like at a constant RPM regardless of variations in the output load or the input load comprising a driven pump having a variable volume and variable pressure output connected in a closed system to a hydraulic motor which will maintain a constant RPM output, regardless of the RPM's of the driving means, which is coupled to the device to be driven. Connected between the pump and the motor is a volume control line having a volume control valve which insures that the volume of fluid to the hydraulic motor will be constant thus providing a constant line RPM output of the driving motor, and a pressure regulating line connected between said pump and said motor to regulate the pump pressure output to insure that the motor RPM is constant although the load on the motor may vary. The volume control valve regulates hydraulic fluid between the pump and motor regardless of the pressure and volume output of the pump.

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

Abstract: An hydraulic system is disclosed for driving a plurality of hydraulic power units, such as warping and retaining winches on ships, each connected to an hydraulic supply network with a constant network pressure. Each hydraulic power unit is adjustable for torque output and a volume regulating device controls the amount of hydraulic fluid supplied to each unit. The torque adjustment and the volume regulation are interconnected to simultaneously control both operating parameters.

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

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