Abstract: High pressure cutoff controls are useful for variable displacement hydraulic pumps for reducing power losses at high pressure levels. Some operators, however, believe that they get more work from pumps not having the high pressure cutoff control. The subject on-off high pressure cutoff control includes an on-off valve disposed in a pilot passage connected to an output port of a pump and to an end of a high pressure cutoff valve. The on-off valve is selectively movable between a first position at which pressurized fluid passes through the pilot passage to the end of the high pressure cutoff valve to prevent it from functioning as a high pressure cutoff valve. Thus, an operator has the option of operating the hydraulic pump with or without the high pressure cutoff control.

Abstract: This invention relates to a variable capacity pump controller for an industrial vehicle such as a shovel loader using a static hydraulic driving system. In a hydraulically driven vehicle equipped with a variable capacity hydraulic pump (P), the controller of the invention includes variable throttle devices (11, 13) (21, 24), (31, 35), (41, 46) which are disposed in pilot hydraulic circuits (10, 12), (20, 22), (30, 32), (40, 42) of a pump capacity control cylinder (C) for controlling the capacity hydraulic pump (P) and operate in such a manner as to change the operation speed of the pump capacity control cylinder (C) in accordance with the oil pressure of a main hydraulic circuit (S). According to this construction, the variable throttle device operates in such a manner as to open a check valve or a throttle valve in the pilot circuit of the pump capacity control cylinder when the hydraulic driving main circuit is at a high pressure.

Abstract: A power limiter control for a variable displacement axial piston pump monitors systems flow and automatically adjusts pump displacement proportionally as the pressure of working fluid changes to maintain a substantially constant power output as the working fluid output reaches a set maximum power.

Abstract: A fuel injection pumping apparatus for supplying fuel to a compression ignition engine has a low pressure pump which supplies fuel to a high pressure pump by way of a throttle. The high pressure pump has a piston for varying the timing of delivery of fuel. A first fixed orifice connects the outlet of the low pressure pump to the cylinder containing the piston and a second fixed orifice connects the cylinder with a drain by way of a variable orifice. In parallel with the second fixed orifice is a bypass valve including a valve member responsive to the pressure applied to the piston and which with increasing pressure opens to allow fuel to escape through a further fixed orifice from downstream of the second fixed orifice.

Abstract: The flow controlling device for a hydrostatic pump has a servo-piston (12) for adjusting the actuating element (11) of the adjustable pump (10) which is acted upon by a control pressure. The latter is controlled by a regulating valve (22) which is acted upon by a pressure differential across a measuring throttle (16) arranged in the delivery line (15) of the pump. Moreover, a pressure spring (23) acts on the regulating valve against the higher pressure. An external pressure supply (26) (pressurized reservoir) is provided for preparing the control pressure. To obtain an accurate, rapid flow control, even for low operating pressures, a connection line (76, 71) connecting the high-pressure side of delivery line (15) to the control pressure connector of the servo-piston (12) is provided, which contains a fixed throttle (72). Alternatively, the regulating valve may be replaced by two spatially separate valves, a flow regulator (80) and a pressure regulator (81).

Abstract: A feedback apparatus according to the present invention elastically interconnects the swashplate of a variable displacement hydraulic unit with the valve spool of a hydraulic unit displacement control, and is constructed such that a predetermined spring preload force is developed. A feedback spring extends along the valve spool and is surrounded by an elongated housing coupled with the swashplate. Axially movable spring guides are interposed between opposite ends of the spring and a flange formed at each end of the housing. A suitable spacer is positioned between the spring and at least one of the spring guides to compress the spring to a length representative of the desired preload.

Abstract: A hydraulic axial piston pump has a rotating cylindrical barrel which defines pumping chambers and pistons reciprocating in the pumping chambers. A swash plate controls the length of travel of the pistons. During a part of each rotation of the barrel a piston will draw fluid into its complementary pumping chamber and during another part of each such rotation the piston will force fluid under pressure out of its complementary pumping chamber. Each chamber has an inlet valve which is closed when the pressure in the chamber exceeds the inlet pressure. Each chamber also has an outlet valve which is closed when the pressure in the outlet exitway exceeds the pressure in the chamber. High pressure fluid from the chambers is fed to shoes that ride on the swash plate to provide a fluid cushion between the shoes and the swash plate thus reducing friction.

Abstract: A variable displacement pump is controlled throughout a broad range of operating conditions between a maximum pressure, low flow rate combination and a minimum pressure, high flow rate combination even when the pump is driven by a power limited prime mover. Different relief valves set at different operating pressures are automatically selectably connected to a control port of the pump in response to the actual flow rate of the fluid pumped by the pump reaching different flow rate set points.

Abstract: A fluid power pumping apparatus having a control system for limiting the power loading thereon to the power available from a motor (126) driving the apparatus, includes a variable displacement rotating piston pump (122). A compensating valve assembly (128) of a type known in the prior art is mounting on the pump. The compensating valve controls flow volume through the pump in response to pressure at an outlet (130) of the compensating valve. The outlet is connected to a variable pressure relief valve (134). The relief pressure of the relief valve varies according to the position of a cam (140) which is connected to the swash plate of the pump. The relief pressure of the variable pressure relief valve and the control pressure on the compensating valve are both at their maximums when the pump is at a minimum flow condition and vice versa.

Abstract: A torque control system for variable delivery pumps receiving torque from an engine employs a signal related to an engine torque available at each engine speed setting to control the torque, and thus the amount of engine power that is absorbed by the variable delivery pumps. In a low-power regime, wherein the fuel injected into the engine is less than maximum, torque control is effected by comparing the available torque with an amount of torque that would be available at maximum fuel injection. In a high-power regime, wherein the fuel injected is at least a predetermined value, torque contol is effected by comparing the available torque with an amount of torque that is available at a combination of a set engine speed and an actual engine speed. A bias circuit biases the stable speed operating point a small amount below the maximum speed, whereby improved fuel economy is attained.

Abstract: A variable displacement hydrostatic unit (11) includes a swashplate (23), the position of which is controlled by a servo piston (73). A multiple mode control (33) is disclosed, including a main valve member (63) and a secondary valve member (65), both of which are attached to a linkage member (61) by which movement of a manual control handle (47) actuates the main and secondary valve members. The flow of control pressure from a charge pump (21) ot the servo piston (73) is controlled by a pair of solenoid valves (83,85) having two control conditions. In one, control pressure flows through the main valve member (63) to give a normal operating mode (FIG. 6), while in the other control condition, control pressure flows through the secondary valve member (65) to provide a secondary operating mode (FIG. 7).

Abstract: A control device for a variable displacement hydrostatic machine having a stroke-volume regulator which is responsive to an actuating pressure. The control device includes a booster pump. The delivery pressure of the machine is the actuating pressure unless the delivery pressure of the machine is insufficient in which case the actuating pressure is a feed pressure produced by the booster pump. The control device includes a plurality of delivery-pressure lines and a proportioning pressure regulator having an outlet pressure which is proportionally reduced relative to the intake pressure connected between each delivery-pressure line and the stroke-volume regulator.

Abstract: A flow metering device designed to variably control the discharge from a variable displacement pump by detecting changes in momentum of the flowing fluid, which are proportional to the mass flow rates. The rate of discharge from the pump is then accurately controlled to a prescribed rate without being influenced by changes in viscosity of the fluid or where cavitation, bubbling, or the like occurs in the flow.

Abstract: A control system (33, 41) is disclosed of the type used to control the displacement of a variable displacement pump (11) having stroking cylinders (25, 27). The control system includes a pair of ON-OFF electromagnetic valves (49, 51) and a proportional valve (85). When a first direction of operation is selected, a first direction command signal (43) is transmitted to the first ON-OFF valve (40) such that control pressure from the charge pump (17) flows through the valve (49), then through the proportional valve (85) and through the valve (51) to the reservoir (75) until the proportional valve (85), in response to an increasing displacement signal (47), moves from its minimum displacement position (FIG. 1) toward a position corresponding to the desired displacement of the pump.

Abstract: A hydraulic control system that comprises a hydraulic pressure line, a hydraulic fluid control mechanism and a lag network coupling the pressure line to the control mechanism for restricting flow of hydraulic flow therethrough, and thereby delaying and damping response of the control mechanism to fluid pressure fluctuations at the hydraulic line. The lag network comprises check valve that includes a flow passages interconnecting the hydraulic line and the control mechanism, a valve element, and a spring resiliently urging the valve element to close the passage, such that resistance to fluid flow increases as fluid flow decreases between the hydraulic pressure line and the control mechanism. Preferably, a pair of such check valves are connected in parallel between the hydraulic pressure line and the control mechanism for controllably restricting fluid flow in both directions.

Abstract: A stroke detection correcting system for variable displacement type compressors comprises a variable displacement type compressor including a plurality of working pistons operatively connected to an internal combustion engine and variable in stroke, a stroke detecting device for detecting the operation stroke of the working pistons, a switching device for changing the switching mode when the stroke of each working piston is in a given range previously set, and a correcting circuit for correcting the detected value from the stroke detecting device on the basis of a predetermined value in accordance with the changing of the switching mode of the switching device. This makes it possible to correct the detected value from the stroke detecting device on the basis of the actual operation stroke of the working piston to provide a substantially correct stroke value, regardless of an error of attachment of and a deterioration with age of the stroke detecting device.

Abstract: A control load such as a cylinder or the like is driven at a constant speed by controlling the flow rate of a variable delivery pump. The control mode is switched to the pressure control to keep the stop pressure constant on the basis of an increase in pressure when the control load stops. A remaining delivery amount which will be necessary to raise the delivery pressure to an object stop pressure when the load stops and an excess delivery volume due to the operation time lag when it is assumed that the delivery by the pump is stopped at the present time are predicted. When they coincide, the delivery amount of the pump is set to zero and the control mode is switched to the pressure control. On the other hand, the product of a load volume and a fluid compressibility is calculated from the increase in pressure when the load stops. The feedback gain of the pressure control is controlled on the basis of the calculated value of this product.

Abstract: A control load such as a cylinder or the like is driven at a constant speed by controlling the flow rate of a variable delivery pump. The control mode is switched to the pressure control to keep the stop pressure constant on the basis of an increase in pressure when the control load stops. A remaining delivery amount which will be necessary to raise the delivery pressure to an object stop pressure when the load stops and an excess delivery volume due to the operation time lag when it is assumed that the delivery by the pump is stopped at the present time are predicted. When they coincide, the delivery amount of the pump is set to zero and the control mode is switched to the pressure control. On the other hand, the product of a load volume and a fluid compressibility is calculated from the increase in pressure when the load stops. The feedback gain of the pressure control is controlled on the basis of the calculated value of this product.

Abstract: A control system and method for chemical injectors includes a controller which outputs multiple feed set point signals and associated driver signals, each set point signal defining a desired injection capacity for a chemical injector and the associated driver designation signal designating the injector to receive the set point signal. A driver assembly is associated with each injector. The driver assembly receives a capacity signal from the injector which defines the volumetric injection capacity of the injector, compares the capacity signal to the feed set point signal, and outputs a drive signal to adjust the volumetric injection capacity of the injector. An adjustment assembly is provided for receiving the drive signal and positioning a stop to limit the reciprocal motion of the piston of the injector, thereby adjusting the volumetric injection capacity of the injector.

Abstract: An apparatus for controlling a variable displacement type hydraulic pump including an engine as a driving power source is disclosed. The subject invention detects the number of revolutions of the engine and the pressure of hydraulic oil delivered from the hydraulic pump, and sets a pump absorption torque characteristic which decreases in relation to the number of revolutions of the engine. The inclination angle of a swash plate in the pump is detected with reference to the pump absorption torque characteristic and the pressure of hydraulic oil delivered from the pump, and the swash plate in the pump can be controlled so as to assure its inclination angle; the number of revolutions of the engine can be reduced without the absorption torque of the hydraulic pump exceeding the allowable torque of the engine. When the controlled apparatus is utilized, the number of revolutions of the engine can be optimally reduced and fuel consumption cost reduced correspondingly.

Abstract: A control for a variable displacement pump in which a displacement control element is made responsive to a load sensing valve and a pilot pressure relief valve. A control fluid is supplied to the pressure relief valve and the load sensing valve and the control pressure fluid controls the working pressure fluid which operates the stroking piston for the pump.

Abstract: The invention provides a variable output pump of the gerotor type in which one rotor meshes in two side by side annulii which can be aligned for maximum output and turned in opposite directions to be non-aligned for minimum output. The movement is effected by a gear train displaced by a rack which is hydraulically operated by pump pressure. Hence high pressure displaces the rack to result in lower output against lower pressure. A variation is described in which a control spool diverts fluid to either side of the piston according to need and this is displaced in one direction by the derived fluid pressure and in the other direction additionally by spring pressure transferred from the piston position by a lever system. This can give desired pump output/speed results at reduced power consumption.

Abstract: A control load such as a cylinder or the like is driven at a constant speed by controlling the flow rate of a variable delivery pump. The control mode is switched to the pressure control to keep the stop pressure constant on the basis of an increase in pressure when the control load stops. A remaining delivery amount which will be necessary to raise the delivery pressure to an object stop pressure when the load stops and an excess delivery volume due to the operation time lag when it is assumed that the delivery by the pump is stopped at the present time are predicted. When they coincide, the delivery amount of the pump is set to zero and the control mode is switched to the pressure control. On the other hand, the product of a load volume and a fluid compressibility is calculated from the increase in pressure when the load stops. The feedback gain of the pressure control is controlled on the basis of the calculated value of this product.

Abstract: An electrohydraulic system for control of a variable output pump includes a microprocessor-based controller receiving inputs from condition sensors coupled to the pump and command inputs from a remote master controller. The controller supplies outputs to an electrohydraulic valve for metering hydraulic fluid to a pump control port and thereby controlling pump operation in any one of a number of preselected and prestored pump control modes. A hydromechanical valve is connected in parallel with the electrohydraulic valve for controlling pump operation in the event of electrical malfunction or failure. Circuitry connected between the pump condition sensors and the control computer prevents aliasing errors due to mismatch between the computer sampling frequency and pump speed. A pump torque sensor measures pump input shaft torque.

Abstract: A control circuit and specific embodiments thereof are provided using a four-port infinitely variable pilot operated pressure-compensator spool valve and a three-port infinitely variable pilot operated load sense spool valve in series to regulate the output pressure of a variable displacement radial piston pump. The valves are so constructed that both must be correctly positioned to put the pump into full stroke, while either valve can de-stroke the pump. The three-port valve is pilot controlled between the load sense pressure and the outlet pressure, while the four-port valve is controlled between the pump inlet and outlet pressures. A check valve and orifice are positioned between the two control valves and the crankcase control line of the pump to assist in stabilizing the pump output. A relief valve is provided on the crankcase line to minimize output spikes. In an alternative embodiment, a single three-port valve is controlled between the inlet and outlet pressures of the pump.

Abstract: An apparatus and method for manufacturing plural component materials, especially rigid urethane structures, from reactive components. The system includes a source of a first component, a source of a second component, a sprayer for mixing the components and for dispensing the mixture therefrom, and a delivery system for delivering the components to the sprayer. The delivery system is designed to continuously recirculate the components from their respective sources to the sprayer and back to the sources and includes positive displacement piston pumps simultaneously driven by a single motor. The system further includes means for calibrating the rates of flow of the components in the delivery system and a chopper to direct reinforcing glass fibers into the component mixture dispensed from the sprayer.

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: A variable displacement piston pump of the type in which the hydraulic pressure in a pressure chamber of an output flow variable element is controlled by a proportional electro-hydraulic control valve to control the displacement of the variable element against a spring to vary the output flow within a range between a maximum output flow and a full cut-off and the output pressure or both the output pressure and the output flow of the pump are controlled electro-hydraulically through a closed loop.

Abstract: A rotary fluid energy converter which can be used either as a hydraulic pump or as a motor, can recover energy with high efficiency. The converter has a spring for biasing a pintle, which supports a torque ring, in one direction, and a hydraulic actuator for moving the pintle in the opposite direction against the action of the spring. A high pressure fluid used in the converter is introduced into the actuator via a pressure-compensating valve to maintain the pressure of this fluid at the pressure set for the valve at all times.

Abstract: An arrangement for operating a diesel-hydraulic drive on a construction machine in limit-load control with a microprocessor controller in which the installed hydraulic power is greater than the rated output of the diesel engine. Upon thermal and/or diesel-engine overload the hydraulic power which can be taken off is reducible; in the case of non-output loading, after a selectably predetermined time the diesel engine can be switched to idling speed of rotation and hydraulic displacement pumps can be operated with minimum delivery oil quantity; and the adjustable hydraulic displacement pumps can be adjusted in accordance with selectably predeterminable output curves.

Abstract: An adjustment mechanism for changing the timing of fluid flow to or from the combustion chamber of an internal combustion engine wherein an axially displaceable support body 15 displaces a plunger 10 tangentially relative to a camshaft 2 which reciprocates the plunger 10.

Abstract: The invention relates to a pump assembly having a pump with reversible and adjustable controls, the pump controls having a neutral nonflow position and varying positions in opposite directions for effecting corresponding varying rates of flow in the opposite directions. The pump controls include a control valve for the adjusting function which is cooperable with resetting apparatus.

Abstract: A servo-mechanism includes a piston and cylinder unit controlled by a valve coupled in known manner by a linkage means to a movable control element to provide closed loop servo operation to position the piston and cylinder unit piston rod according to the position of the movable element. The movable element is fast with an annular gear segment of an epicyclic gear mechanism of which the sun gear forms a main control input and the planet pinion carrier forms an override input. The mechanism is of utility in an hydraulic transmission of the variable stroke pump/fixed stroke motor type, the overrride input being actuable by a pump port pressure limit sensor.

Abstract: A pump stroke is matched to the operating speed of a high speed windmill. The windmill drives a hydraulic pump for a control. Changes in speed of a wind driven shaft open supply and exhaust valves to opposite ends of a hydraulic actuator to lengthen and shorten an oscillating arm thereby lengthening and shortening the stroke of an output pump. Diminishing wind to a stall speed causes the valves to operate the hydraulic cylinder to shorten the oscillating arm to zero. A pressure accumulator in the hydraulic system provides the force necessary to supply the hydraulic fluid under pressure to drive the actuator into and out of the zero position in response to the windmill shaft speed approaching and exceeding windmill stall speed.

Abstract: A variable displacement, pressure compensated, axial piston pump has an electrohydraulic servo valve connected to the pressure compensator mechanism to enable the pressure setting of the mechanism to be changed from a remote location.

Abstract: The device of this invention has a variable capacity pump, a channel through which the discharged fluid from the pump passes toward an actuator, a variable choke located in the channel and pressure detecting means which detects the pressure difference on opposite sides of the variable choke. The pump varies its volume in relation with the pressure difference detected by the pressure detecting means. The opening area of the channel is varied by the variable choke in relation with the pressure of the fluid being supplied to the actuator, namely the pressure of the fluid flowing downstream of the variable choke. The device of this invention may also have an auxiliary variable choke located in the channel. The auxiliary variable choke can control the amount of fluid being supplied to the actuator in response to the operating condition of the actuator.

Abstract: A pressure and delivery regulating device for an adjustable pump includes a directional control valve connected in a discharge conduit and to a control conduit branching from the discharge conduit between the pump and the directional control valve. The control conduit leads to a setting piston for the adjustment of the pump. The directional control valve is controlled by a solenoid which in turn is controlled by a control system consisting of a regulating circuit, a delivery limiting circuit and a control circuit for the solenoid. The output signal from the regulating circuit controls a desired delivery value signal supplied to the delivery limiting circuit. A follow-up circuit connected between the regulating circuit and the delivery limiting circuit corrects the regulating signal and a circuit for producing a direction dependent signal from the actual pressure provides a damping of the regulating circuit.

Abstract: In the pressure regulation of a variable displacement pump very high pressures can build up in the pump delivery line if at the consumer no discharge of the fluid takes place, for example the piston of a servo motor moves against a stop. A pressure regulation of the pump is then only possible via the inner losses of the pump. Consequently, although the pressure can be built up rapidly it can only be reduced very slowly. According to the invention the pressure reduction is via a bypass which is controlled by the control valve of the variable displacement pump and which connects the pressure side of the pump to a tank discharge when the control valve is driven in the sense of a reduction of the pump pressure. According to the invention a very rapid pressure reduction is obtained so that the variable displacement pump can again be pressure controlled.

Abstract: An anti-plug control for a drive to prevent jamming of a driven working element in response to an overload wherein said drive includes a hydrostatic transmission having a variable displacement unit and a fixed displacement unit connected in closed circuit. A servo control cylinder is connected to a swash plate of the variable displacement unit for causing positioning thereof. A normally closed pressure-responsive valve monitors the pressure in the high pressure side of the closed circuit and is openable when the pressure reaches a predetermined value to deliver fluid from the closed circuit to the servo control cylinder and modify the displacement of the variable displacement unit to increase the speed of the working element to attempt clearing the overloaded condition of the working element.

Abstract: A variable displacement pump system including a pressure compensator for operating a pump adjusting mechanism to vary the displacement by applying hydraulic fluid to the pump adjusting mechanism and a spring biased piston applying a yielding force to the pump adjusting mechanism opposing the pressure compensator. A load sensing valve senses the pressure of the load to which fluid is supplied from the pump through a system valve and applies this load pressure to work in unison with the spring biased piston for purposes of urging the pump towards its maximum displacement.

Abstract: Variable stroke pump apparatus includes a photovoltaic array for providing electrical current to motors, one of which provides for the pumping action of a walking beam, one of which provides for movement of a control unit which varies the length of stroke of the pumping apparatus from a minimum of zero to a maximum, and one of which operates a counterweight for moving the counterweight in response to the pumping load. The apparatus includes mechanical elements which adjust the length of the stroke of the pumping arm, and a control system which controls the length of the pumping stroke in response to the output of the photovoltaic array.

Abstract: Pressure control device comprising a manual valve (VM) associated with a pressure control valve (VRP), includes a first line pressure (P.sub.L), defined by two calibrated jets in series, which are placed on a duct set at zero pressure by the manual valve (VM) being in a first position R. At a second line pressure range (P.sub.L), a duct is fed at line pressure (P.sub.L), the manual valve (VM) is in a second position A. A variation of line pressure (P.sub.L) is assured by a modulating solenoid valve (EVM), which establishes a modulated pressure (P.sub.M) acting on a differential section (.SIGMA.) of said pressure control valve (VRP).

Abstract: A torque control device for an adjustable hydropump is described which is based on an output control device in which the output control is determined as a function of the output pressure of the hydropump and a pressure in a working pressure control line. For this purpose a torque valve is provided whose closure power is determined by a measuring spring or set of springs connected with the pump control member and pretensioned depending on the output setting. The torque valve connects the working pressure control line with the pressureless outlet depending on the pressure in the working pressure control line and the pretension of the measuring spring. The torque valve can be fixed on to the hydropump as a separate unit and the control characteristic can be changed from outside by adjustment of the measuring spring.

Abstract: A hydraulic lifting and lowering system for battery-powered lift trucks includes an electronic control system which reduces or limits operator selected lifting commands in accordance with the current being drawn by an electric motor connected to drive a variable-displacement pump, and in accordance with the state-of-charge of the vehicle battery, to control a proportional valve which meters fluid flow to a lift cylinder.

Abstract: A power control device for an adjustable hydrostatic pump with a lever controlling a control valve piston and a pressure measuring piston loaded with feed pressure acting on said lever to control the pressure feed to a servo piston is provided wherein the pressure measuring piston loaded with feed pressure is mounted in a structural member slidable with the servo piston and slides lengthwise of the lever and the control valve piston is biased by resilient member toward the pressure measuring piston.

Abstract: A fluid operated pump displacement control system is provided wherein a self pressure is defined as a first control signal, and characterized in that an arbitrary switchable second control signal different from the first control signal is added to the first control signal, and a displacement is adapted to be switched to a displacement corresponding to a value of the second control signal as added to the first control signal. Further, a fluid operated pump displacement control system is provided comprising a control circuit connected to respective displacement control devices of variable displacement pumps and adapted to be operated by discharge pressure fluid from a discrete control pump.

Abstract: In order to stabilize the line pressure developed by a line pressure regulator valve and simultaneously control the operation of a variable capacity pump in a manner that the latter exhibits the desired degree of response to changes in the line pressure, a flow restriction is defined in the bore of the valve itself. This flow restriction is defined between the wall of the bore in which the spool is disposed and a portion of the spool which extends between two adjacent lands and which has a diameter which is slightly smaller than that of the bore.

Abstract: In a control device for limiting the maximum permissible input torque or power for a hydraulic pump, a control valve is provided with a first piston area which is acted upon by pressure from a torque sensor. A second piston area effective to more the control valve against a return means is acted upon by pressure from a remote control device so as to reduce the maximum possible input torque and thus create an input torque control device also effective as a power preselecting device.

Abstract: An output control apparatus for a hydrostatic drive in open circuit is described which has a device for regulating the delivery of the hydraulic pump. In addition to conventional output control by way of an output valve, the arrangement of an additional control piston which acts on the spool of the output valve provides the possiblity of adjusting the delivery as a function of the restoring pressure of a load during its working movement in a return direction, with reduced power consumption.

Abstract: A plunger pump wherein the plunger is reciprocable in a barrel by a tappet which is coupled to the plunger by a pressure member. The tappet is reciprocable by a rotary cam in conjunction with a coil spring and is movable axially of the plunger by a first drive having a sleeve surrounding the barrel and having jaws in engagement with complementary jaws of the pressure member. Rotation of the pressure member in response to rotation of the sleeve entails axial movement of the tappet because the latter has threads in mesh with complementary threads of the pressure member whereby the tappet changes the length of forward and return strokes of the plunger. The latter has a control edge which can regulate the volume of outflowing liquid in response to rotation of the plunger on actuation of a second drive having a second rotary sleeve with jaws engaging complementary jaws of the plunger.