Abstract: An aircraft hydraulic control system includes a pump system, a fluid circuit, and a controller. The pump system includes a hydraulic pump and a ram air turbine assembly. The fluid circuit delivers hydraulic fluid to the hydraulic pump and receives the hydraulic fluid output from the hydraulic pump. The controller is in signal communication with the hydraulic pump. The controller determines a rotational frequency of a ram air turbine included in the ram air turbine assembly, and controls the hydraulic pump so as to control the flow of hydraulic fluid in the fluid circuit. The flow of hydraulic fluid in the fluid circuit controls a fluid pressure of the aircraft.

Abstract: A pumping system includes a first variable displacement pump having a first inlet and a first outlet. The first outlet is fluidically connected to a system outlet. A first actuator is mechanically coupled to a first displacement mechanism of the first variable displacement pump A second variable displacement pump includes a second inlet and a second outlet. The second outlet is fluidically connected to the system outlet. The pumping system also includes a second actuator mechanically coupled to a second displacement mechanism of the second variable displacement pump. An electrohydraulic servo valve is hydraulically connected to the first and second actuators. An electronic engine controller is in communication with the electrohydraulic servo valve and is configured to send electrical current to the electrohydraulic servo valve to drive the first actuator and the second actuator.

Abstract: A pump, comprising a rotor axially located between a fluid inlet section and a fluid outlet section, wherein the rotor is configured to rotate about a center axis, a stator surrounding the rotor, wherein the stator includes an inner diameter surface and an outer diameter surface, wherein the inner diameter surface includes a groove surrounding the stator and concentric about the center axis, and a ring surrounding the stator, wherein the ring is adjacent to the groove and defines a gap between an outer diameter of the surface and an inner surface of the ring, wherein the ring includes a ring mass and the stator includes a stator mass, and the ring mass is substantially equal to the stator mass.

Abstract: A variable flow hydraulic device having a plurality of cylinders for varying a flow of hydraulic fluid between a reservoir and a load, the device comprising: a housing having the plurality of cylinders with a plurality of corresponding pistons; an input port of the housing fluidly connected to each cylinder of the plurality of cylinders, the input port facilitating introduction of the hydraulic fluid to said each cylinder; a first output port of the housing connected to said each cylinder, the first output port facilitating the ejection of the hydraulic fluid from said each cylinder, the first output port configured for fluidly coupling said each cylinder to the load; a respective flow control valve for said each cylinder, and a fluid pressure sensing device coupled between downstream of the first output port and said respective flow control valve.

Abstract: A hydraulic system for a working machine includes a hydraulic pump to output an operation fluid, a hydraulic device to be operated by the operation fluid, an operation member to be operated, a first operation valve to regulate a pressure of the operation fluid in accordance with operation of the operation member, and a pressure supplying portion to supply a first counteracting pressure of the operation fluid against a first operation pressure, the first operation pressure being a pressure of the operation fluid regulated by the first operation valve.

Abstract: A hydrostatic valve arrangement for flushing pressure medium from a working line of a hydraulic circuit includes a flushing valve with a first flushing connection for connecting to a first working line and an output connection for connecting to a pressure medium sink. The arrangement also includes a pressure valve arranged in a pressure medium flow path of the arrangement from the output connection in the direction of the pressure medium sink. The pressure valve has a valve body on which a force equilibrium is formed. The force equilibrium includes a pressure equivalent that acts on the valve body in a direction that blocks the pressure medium flow path and an opening pressure that acts in a direction that opens the pressure medium flow path and is dependent on the pressure at the output connection. The arrangement further includes an adjusting device for shifting the force equilibrium.

Abstract: The invention provides a construction machine in which the load torque at the time of engine start-up can be reduced even when the engine stops against the will of the operator. A hydraulic excavator includes a control device (35) having a pump displacement control section (37) and an unload control section (38). The pump displacement control section (37) makes the displacement of a hydraulic pump (16) variable to a minimum displacement by controlling a regulator device (20) when the speed of an engine (14) detected by a speed sensor (41) becomes equal to or less than a preset low speed N3 at the time of driving of the engine (14). The unload control section (40) controls an unloading valve (24) to the open position at the time of start-up of the engine (14).

Abstract: A medical fluid injector system (450) is disclosed that may utilize one or more of flow rate determination logic (130), injection volume determination logic (132), display control logic (134), drive ram motion control logic (136), and pressure monitoring logic (138). The flow rate determination logic (130), injection volume determination logic (132), and display control logic (134) each may utilize a concentration input (172, 192, 202) to calculate flow rates, injection volumes, and generate multi-color graphics, respectively, for a simultaneous injection configuration. The drive ram motion control logic (136) may utilize both a target pressure and a monitored pressure to derive a velocity for advancing a drive ram. The pressure monitoring logic (138) may provide a monitored pressure value for the drive ram control logic (136), where this monitored pressure value may be derived from the input power being used to advance a drive ram and the drive ram velocity.

Abstract: In an oil-well-pump driving hydraulic system capable of avoiding occurrence of cavitation, at least a bidirectional variable displacement piston pump, a discharge rate detection portion, a discharge pressure detection portion, and a proportional solenoid control valve are contained as a single unit structure in a same housing as a pump body. The pump body includes: a connection portion provided on a side surface of the housing and to which a pump discharge passage of an external pilot hydraulic circuit is connected; and a second pilot passage that introduces an external pilot pressure from the connection portion to a pilot passage between the discharge passage of the piston pump and the proportional solenoid control valve.

Abstract: A hydraulic actuator is arranged such that the hydraulic actuator operates a swash plate of a hydraulic motor by a first pilot pressure and a second pilot pressure, the first pilot pressure being branched from a high-speed oil passage and applied to the hydraulic actuator for operating the swash plate of the hydraulic motor to a low speed side, the second pilot pressure being branched from a charge pump and applied to the hydraulic actuator for operating the swash plate of the hydraulic motor to a high speed side.

Abstract: First and second mechanical hydraulic valves are disposed between a pump and the cap side chamber of an actuator and the pump and the rod chamber of the pump. The first and second valves are actuated as a result of respective pressure differentials applied across the valves. A controller controls flow from a pump in response to a commanded motion to control movement of the actuator, and cause the valves to open. The valves are disposed in their no-flow positions when the pump is not operative, and when the hydraulic system of off or locked out to hold a load.

Abstract: A hydrostatic drive, in particular a fan drive, with a variable displacement pump is configured to drive at least one hydraulic motor. The variable displacement pump is activated via a pressure regulating valve and a following directional valve predetermining the feed direction, via which valves the control spaces of an actuating cylinder can be acted upon with a control pressure difference. The variable displacement pump is prestressed into a basic position in which the feed volume flow is maximum.

Abstract: A hydrostatic pump (1) with a variable delivery volume can be operated in a closed circuit. An electrically controllable actuator device (4) is provided for the control of the delivery volume of the pump (1). The electrically controllable actuator (4) has an electrically actuatable control valve device (6) which generates a positioning pressure which actuates a positioning piston device (5) which is in an operative connection with a delivery volume control device (3) of the pump. An electrical position feedback circuit (21) of the delivery volume control device (3) is provided and the actuator device (4) is provided with a switchable hydraulic neutral position control system (25), by means of which a restoring movement can be generated that acts on the positioning piston device (5) and places the delivery volume control device (3) into a neutral position.

Abstract: A pump torque control system is capable of preventing hunting due to interference between speed sensing control and control of an engine speed of a prime mover when the temperature of a hydraulic fluid is low. A maximum absorption torque is set in a regulator 31 that controls displacement volumes of hydraulic pumps 2 and 3 based on a deviation between target and actual engine speeds of a prime mover 1. A second modification factor calculating section 45 and a control gain modifying section 49, which are included in a controller 23 that performs speed sensing control to ensure that the maximum absorption torque of the hydraulic pumps 2 and 3 is reduced, change a control gain of the speed sensing control based on a value detected by the hydraulic temperature sensor 34 to ensure that the control gain is reduced as the temperature of the hydraulic fluid is reduced.

Abstract: A hydraulic control system is disclosed, which can minimize the flow rate of a hydraulic fluid being discharged from a variable displacement hydraulic pump by using pilot pressure constantly produced by a pilot pump when a switching valve is in a neutral position, and can adjust the flow rate of the hydraulic fluid being discharged from the variable displacement hydraulic pump by using pressure produced by a pressure generator positioned at the most downstream side of a bypass passage if a separate input signal is applied to the pressure generator when the switching valve is operated.

Abstract: Differential pressures across flow control valves 6a, 6b and 6c are controlled by pressure compensating valves 7a, 7b and 7c to be held at the same value, i.e., a differential pressure &Dgr;PLS, and the differential pressure &Dgr;PLS is maintained at a target differential pressure &Dgr;PLSref by a pump displacement control unit 5. For changing the target differential pressure depending on change in revolution speed of an engine 1, a flow detecting valve 31 is disposed in a delivery line 30a, 30b of a fixed displacement hydraulic pump 30, and a differential pressure &Dgr;Pp across a variable throttle portion 31a of the flow detecting valve 31 is introduced to a setting controller 32. A selector valve 50 operable to shift between a fully closed position and a throttle position is disposed in parallel to the flow detecting valve 31 and is shifted by a control lever 51.

Abstract: A fixed throttle 12 is provided in a delivery line 11a of a fixed pump 11 driven by an engine 9 for rotation together with a hydraulic pump 1, and a differential pressure detecting valve 31 is provided in association with the fixed throttle 12 to detect a differential pressure across the fixed throttle 12 and to output a pressure lower than the detected differential pressure by a predetermined value. The output of the differential pressure detecting valve 31 is introduced, as a signal pressure, to a pressure bearing section 5c of a load sensing valve 5, thereby setting a target differential pressure. With that arrangement, a pressure in link with an engine revolution speed can be directly employed as the set differential pressure of the load sensing valve, and the structure of the load sensing valve can be avoided from being complicated.

Abstract: An apparatus, for controlling a plurality of hydraulic motors and a clutch for driving a drive shaft, can prevent a speed change shock and a load slip of a hydraulic motor as well as making a structure simple. The apparatus includes: a first volume variable hydraulic motor (1), connected to the drive shaft (3) through the clutch (5); a second volume variable hydraulic motor (2), which is always connected to the drive shaft (3); first tilt rotation control means (7, 8), for controlling a tilt rotation amount (a discharge volume cc/rev) of the first hydraulic motor by receiving a drive side pressurized oil (Pac) of the first hydraulic motor; and a zero tilt rotation holding means (10, 10A), for holding the tilt rotation amount of the first hydraulic motor at substantially zero in a state wherein the tilt rotation amount of the first hydraulic motor is controlled to be substantially zero.

Abstract: A travel drive apparatus for a hydraulic drive work vehicle of simple configuration, capable of preventing occurrence of cavitation which is predicted when a work vehicle is decelerated, descends a slope, or is changed from forward travel to reverse travel or from reverse travel to forward travel, and a control method thereof.

Abstract: A differential pressure &Dgr;PLS between a delivery pressure of a hydraulic pump 2 and a maximum load pressure among a plurality of actuators 3a-3c is maintained at a target differential pressure &Dgr;PLSref by pump displacement control means 5. The target differential pressure &Dgr;PLSref is modified depending on an engine rotational speed by introducing a differential pressure &Dgr;Pp across a throttle 50 disposed in a delivery line of a fixed pump 30. An unloading valve 80 has first and second auxiliary control pressure chambers 80e, 80f to which the differential pressure p across the throttle 50 is introduced, and a target differential pressure &Dgr;Pun of the unloading valve is also modified in match with change in the target differential pressure &Dgr;PLSref modified by the operation driver 32. Stable load sensing control is thereby achieved without being affected by the engine rotational speed.

Abstract: A hydraulic drive system wherein differential pressures across flow control valves are controlled by pressure compensating valves to become the same value, i.e., a differential pressure .DELTA.PLS, and the differential pressure .DELTA.PLS is maintained at a target differential pressure .DELTA.PLSref by a pump displacement control system. For modifying the target differential pressure .DELTA.PLSref depending on change in rotational speed of an engine, a flow rate detecting valve is disposed intermediate between delivery lines of a fixed displacement hydraulic pump and a differential pressure .DELTA.Pp across a variable throttle of the flow rate detecting valve is introduced to a setting modifying unit to thereby modify the target differential pressure .DELTA.PLSref. The flow rate detecting valve changes an opening area of the variable throttle depending on the differential pressure .DELTA.Pp depending on the rotational speed of the engine.

Abstract: An overspeed control for a hydrostatic transmission of a mobile machine includes a speed control valve arrangement connected to a fixed displacement pump through a supply line and to a pressure responsive displacement controller of a variable displacement hydraulic pump of the transmission. An overspeed control valve is connected to the supply line and is operative for reducing the fluid pressure level in the displacement controller when the speed control valve arrangement is in an operative position and the rotational speed of the engine exceeds a predetermined level. This reduces the displacement of the variable displacement pump (which acts as a motor in a downhill situation) and thus increasing engine retarding and transmission losses for preventing the positive grade from accelerating the machine, engine and/or the components of the hydrostatic transmission to speeds exceeding their designed limits.

Abstract: A hydraulic drive system includes a first driven hydrostatic machine adjustable in volume and operating as a pump supplying fluid to a supply line for maintaining an impressed pressure therein, a second hydrostatic machine which is adjustable in volume and is connected to the supply line, a valve determining the direction of rotation and the speed of the second machine by adjusting a control flow defining a desired speed value, a signal generator coupled to the second machine for generating a control flow defining an actual value of the speed, a pilot controlled valve for comparing the actual value control flow and the desired value control flow and generating a pressure difference therebetween, and an adjusting cylinder controlled by the pressure difference for setting the pivotal angle of the second machine. To increase the load stiffness and stability of the control system a hydraulic compensating volume is connected to either side of the signal generator.

Abstract: An improved RAM air turbine (30) for the generation of emergency power on an airplane is disclosed. The RAM air turbine has an operational range in which reduced power is produced by a power controller (40) at speeds at which stalling of the RAM air turbine would occur under the control of a governor (16) which adjusts the pitch of the blades (12) of the turbine in combination with a pressure regulator (150) controlling the output of pressurized hydraulic fluid from a variable displacement hydraulic pump (19).

Abstract: A hydrostatic system includes a variable displacement hydraulic motor whose absorption volume is adjusted by a pressure regulator, depending on the rpms generated by the power source driving the system. The apparatus enables the variable displacement motor to fully utilize the drive power avaiable from the power source over a range of operating speeds.

Abstract: An energy regenerative circuit in a hydraulic apparatus wherein when a direction control valve is at the actuator unloaded-side chamber acting position, the discharge fluid line of a variable displacement pump is connected to a fluid tank via the direction control valve, by-pass fluid line change-over valve and by-pass fluid line that has a signal orifice. The by-pass fluid line is connected to a capacity control mechanism of the variable displacement pump via a signal fluid line on the upstream side of the signal orifice. The loaded-side chamber of the actuator is so connected that the pressurized fluid thereof is partly added through the direction control valve to the fluid line through which the pressurized fluid discharged from the variable displacement pump is fed to the loaded-side chamber.

Abstract: A hydraulic drive system to actuate the piston of a cylinder unit comprises a first hydrostatic machine having variable displacement, a second hydrostatic machine mechanically coupled to said first machine and operating as a signal generator either in a pump mode or a motor mode, and a third hydrostatic machine of fixed displacement mechanically coupled to said first machine, which third machine is hydraulically connected to said cylinder unit. In response to zero speed or rotation of the drive system the piston of the cylinder unit may be stopped in any position, or, respectively, raised or lowered. The variable displacement machine may operate as a pump and as a generator in which latter case energy is recovered in lowering a load.

Abstract: A regulator for an adjustable hydrostatic machine (1) having a hydraulic servo controller (4) for continuous variation of the displacement volume, with a valve device (16, 18) for controlling or regulating the servo controller (4) in dependence on the displacement volume and/or working pressure of the hydrostatic machine (1) and a second regulating valve (15) for regulating the servo controller (4) in dependence on the displacement volume, is arranged so that it can be operated without significant regulating losses in the working stream. This is done by providing a third control valve (48), controlled in dependence on the control movement of the servo controller (4), to control the pressure acting on the second regulating valve (15).

Abstract: The present invention is directed to a power control for an automatic transmission which consists of two valves, the first of which is a characteristic valve providing a pressure differential linearly proportional to an input speed signal provided by a prime mover driven fixed displacement pump, and a second valve which is modulated by the pressure differential generated by the first valve and by a pressure feedback proportional to the torque transmitted by the transmission. The power control provides a series of linear control curves proportional to input speed and is useful as either an automotive type control or an anti-stall control, or a combination of both.

Abstract: A control apparatus for a variable displacement pump includes a variable displacement pump having an inlet port and a discharge port driven by an external engine. A piston assembly is provided for varying the amount of displacement of the pump. The control apparatus further includes a switching valve for switching operational fluid which is to be applied to and operates the piston assembly, an additional pump a control pressure a magnitude of which is proportional to the rotational speed of the external engine, a balance piston for transducing the control pressure from the additional pump into a force and for applying the force to one end of the switching valve. A discharge line is provided connecting the discharge port of the variable displacement pump with an external load, and a pilot line is branched off from the discharge line into the switching valve for applying a pressure in the discharge line to the other end of the switching valve.

Abstract: In a positive displacement variable stroke motor, a constant speed variable power drive governor is disclosed which varies stroke instead of driving pressure and hence conserves power through reducing throttling losses. Typically, the control is used on at least one of a plurality of motors all driven from the high pressure manifold of a pressure compensated controlled pump driven by a prime mover. The particular controlled positive displacement variable stroke motor is connected at fluid intake to the high pressure manifold on the high pressure fluid side and discharges to a reservoir on the low pressure fluid side. The controlled motor also drives a small positive displacement pump--typically an in situ charge pump--and produces a discharge through a square edge orifice in an insolated hydraulic control circuit. In response to load changes, a hydraulic amplifier monitors the pressure in the hydraulic control circuit and changes the motor stroke, typically by changing tilt box angle.

Abstract: A composite hydraulic system for a work vehicle which has two separate hydraulic circuits. Included in the composite system are three pumps, two of which supply the two circuits on the vehicle. A third pump transfers hydraulic fluid between the two hydraulic circuits. An engine operates all three pumps simultaneously and means are provided whereby the third pump under certain conditions operates as a motor to provide regeneration.

Abstract: A synchronized mechanical-hydrostatic gearbox with infinitely variable drive ratio including a hydrostatic gear and a following mechanical gear coupled thereto. The hydrostatic gear includes a hydraulic transmission motor with variable displacement which is connected to the mechanical gear. The mechanical gear is made with at least two gear ratio stages and with means adapted for altering the displacement of the hydraulic transmission motor on alteration of the gear ratio of the mechanical gear to an extent corresponding to the gear ratio change. The gear box is intended to be incorporated in a transmission for vehicles, particularly terrain vehicles, preferably driven by an internal combustion engine.

Abstract: A control device for a hydrostatic gear driven by a drive engine, preferably an internal-combustion engine, is described, having an auxiliary pump, which is driven synchronously with the drive engine speed, for the generation of a control pressure which may be adjusted by way of a regulating valve, which is dependent upon the speed of the drive engine and which acts upon the setting mechanism for the hydrostatic gear. A pressure reducing valve ("inch" valve) is thereby provided for the purpose of shutting off the control pressure as a function of an external parameter and also for lowering the control pressure in the case of a load speed reduction of the drive engine ("partial inch" function).

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

Abstract: A hydrostatic drive system has an internal combustion engine, a main pump driven by the engine and having a control element displaceable to vary the pump displacement, a control pump driven by the engine, an output motor having a control element displaceable to vary the motor displacement and having a rotary output, and conduits interconnecting the main pump and output motor for driving of the motor by the pump. A speed-measuring pump is connected to the motor output and produces a pressure differential corresponding to the speed of the motor output. A pump controller is powered by the control pump and connected to the pump control element for adjusting the pump displacement. A motor controller is connected to the motor control element for adjusting the motor displacement.

Abstract: Disclosed is a control arrangement for a hydrostatic drive of the type having a power-driven adjustable pump, a pressure responsive setting cylinder coupled to the pump, a hydraulic motor connected via pressure conduits to the pump and a measuring motor coupled to the hydraulic motor to rotate with a proportional rotary speed. A supply pump is connected in a control circuit including the measuring motor and a nominal or desired value generator in the form of an adjustable throttle by means of which the desired rotary speed of the hydraulic motor is adjusted. Deviations between the actual and desired speeds produce a differential control flow which is fed to the setting cylinder which adjusts the position of an adjusting member of the pump for so long as until the deviation equals zero.

Abstract: A hydraulic drive system including at least one hydraulic actuator, two variable displacement hydraulic pumps each connected to the hydraulic actuator to form a closed circuit therewith and connected in parallel with each other, two prime movers each driving one of the hydraulic pumps, and directional control valves each arranged between the hydraulic actuators and one of the hydraulic pumps. The directional control valves are each operative to shut, when one of the prime movers associated therewith is shut down, the hydraulic pump connected to the shutdown prime mover off the other hydraulic pump and the hydraulic actuator, to thereby prevent the hydraulic pump from being rotated by the pressure fluid delivered by the other hydraulic pump.

Abstract: An apparatus for use in controlling a variable displacement pump in a hydrostatic transmission comprises servo-positioning means for varying the displacement of the variable displacement pump, signal producing means for producing a first signal dependent on the rotational speed of the input shaft of the variable displacement pump and means communicating the first signal dependent on the rotational speed of the input shaft to the servo-positioning means to increase or decrease the displacement of the variable displacement pump as the rotational speed of the input shaft increases or decreases. A second signal dependent on the output pressure of the variable displacement pump is communicated to the servo-positioning means to act in opposition to the first signal to tend to reduce or increase the displacement of the variable displacement pump.

Abstract: Control arrangement for regulating the speed of movement of a hydrostatic energy consumer is provided in which the ratio between pressure supplied and power on the output side is constant, in particular, a piston capable of sliding in a cylinder connected to a pressure main line, characterized in that an initial hydrostatic displacement machine is connected between the pressure main line and the consumer and is coupled with a second hydrostatic displacement machine on the shaft side, the second hydrostatic displacement machine is adjustable with respect to its displacement volume per revolution and is connected on the one hand to the pressure main line and on the other hand to a chamber carrying a lower pressure, where the adjusting element of this second displacement machine is connected with an r.p.m.-regulating device.

Abstract: A control and regulating arrangement for an adjustable hydrostatic unit is provided in which the regulating device has an auxiliary control constant pump in the feed line of which there is a restrictor, in which case the pressure retained in front of the latter acts on a pressure chamber in which a regulating piston capable of sliding against the force of a spring and which influences the position of a regulating piston connected with the final control element of the hydrostatic unit and capable of sliding in a regulating cylinder is capable of sliding, characterized in that the unit is a hydrostatic motor and the auxiliary control pump is connected to its output shaft.

Abstract: A control device for a hydrostatic transmission including apparatus for sensing a speed of a prime mover which powers a variable displacement pump of the hydrostatic transmission and for regulating the displacement of the variable displacement pump in accordance with the speed of the prime mover, is disclosed. The control device also includes apparatus for transmitting a mechanical feedback signal representative of the displacement of the variable displacement pump to the control device to maintain the variable displacement pump at a displacement proportional to the speed of the prime mover.

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: In a control for a hydrostatic drive system with a primary energy source and with an adjustable pump and at least one adjustable consumer of hydrostatic energy and with a pump adjusting piston connected with the adjusting element of the pump and capable of sliding in a pump adjustment cylinder, where the load on the pump adjustment cylinder is regulated by means of a servo control valve, also with a constant pump connected to the drive shaft of the pump, the delivery line of which leads to a restrictor and to which a signal-pressure line is connected in front of the restrictor, where the pressure-signal present in it regulates a relief valve jet, which in turn is located in a control-signal line, the improvement characterized in that an additional restrictor is located in the control-signal line and means are provided for switching the pressure gradient in it to the servo control valve.

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: 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 hydraulic system comprising a reversible variable displacement pump, a hydraulic servo motor for controlling the direction and amount of displacement of the pump, a fluid motor connected in parallel to the pump and adapted to be driven by the pump, a pilot operated directional valve for controlling the position and direction of the servo motor system, and a valve for sensing the displacement of said pump and applying a force to the directional valve opposite to the force of the pilot pressure for moving the valve.

Abstract: A hydraulic motor control system comprises a speed control loop and a pressure control loop which provide closed loop control of a variable displacement chamber space and the mechanical advantage coupling thereof to the motor output shaft. The speed control loop is effective in the speed control mode of operation to maintain a set speed within a given load range. In response to load increases beyond said range, the pressure control loop pre-empts the speed control loop so that the control operates in a constant horsepower mode.

Abstract: In an adjustable axial flow piston pump having a swivellable component such as a swash plate, pressure chambers for swivelling the swivellable component, a lever connected with the swivellable component and supported in the housing of the pump, a final control member mounted in and movable in the lever, a fluid passage in the lever supplying fluid pressure to the control member, a fluid passage in the pump housing connected to the pressure chamber and a fluid passage in the lever connecting the control member and the fluid passages in the housing whereby fluid pressure is delivered through the lever and control means to the pressure chamber.

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.