Abstract: The invention relates to a driving unit for a feed pump, particularly for a crude oil feed pump which is suitable for recovery of energy. The delivery flow of a hydraulic variable displacement pump, in particular a pump of the axial piston type is used to perform the upstroke of the pump piston. A directional valve control means is provided to deliver the liquid volume displaced under pressure in the downstroke of the pump piston through the pump in the same direction of flow as for the upstroke. The pressurized fluid may either pass to a reservoir, wherein the pump drives a motor for supplying electrical energy back to the electric supply, or, respectively, may load a hydraulic accumulator which is connected to the suction port of the pump for performing the upstroke of the pump piston for which the accumulator is discharged, wherein the remaining torque only has to be supplied by the drive motor.

Abstract: A proportional solenoid operated pressure regulating valve is disclosed. First and second metering spools are respectively mounted for movement inside first and second control spools. Each metering spool responds to a fluid pressure being controlled at a respective operating port.

Abstract: A hydraulic pump of the type in which a cam ring and rotor are mounted within a rotor chamber formed between a cover and housing fixedly mounted together. An adjustment screw extends into the rotor chamber transverse to the axis of rotation for adjusting the level of the cam ring. Two pairs of bolts, and only two pairs, extend parallel to the rotation axis at a given radius from that axis to fix together the housing and cover. The distance between the pair of bolts on either side of the adjustment screw and at the pressure region are less than the distance betwen the bolts of the opposite pair at the suction region. Further the angle .beta. between an x-x axis transverse to both the adjustment axis and the rotation axis and the radii of the pair of bolts on either side of the adjustment screw is between 60.degree. and 75.degree. and the angly .gamma. between the x-x axis and the radii of the other pair of bolts is between 25.degree. and 40.degree.

Abstract: A device for controlling an adjustable arm 1 has an operating circuit 10 including a movable valve 3 with two control mechanisms 11, 12 bidirectionally actuated by pressure. A control circuit to activate the movable valve is connected to a pressure source 19, to the two control mechanism 11, 12, and to an adjustable throttle 22 attached to one of the two control mechanism 12. The control circuit also includes an adjustable throttle 24, series connected adjustable throttles 27, 28 attached to the other control mechanism 11 and a fifth adjustable throttle 57. The fifth throttle is used to create an additional actual value input. An adjustable control valve 53 employs the desired and actual value inputs supplied by the adjustable throttles in various ways by interconnecting the throttles with the control devices and a pressure ratio valve 45 so that the system responds to applied force, position or both.

Abstract: The present invention relates to a rotary piston machine comprising a housing which consists of a flange housing, an intermediate housing and an end housing. The flange housing has a flange extending there from landing the machine on a suitable support. A shaft is rotatively supported within the housing, and a rotor is fixedly mounted on the shaft and adapted to rotate together with the shaft. A hollow gear for farming compressing chambers is also located within the housing for cooperation with the rotor. A commutator is fixedly mounted within the flange housing means and is adapted to supply pressure medium to and to remove pressure medium from the compressing chambers.

Abstract: A pressure responsive flow divider valve for servo-powered steering devices comprises a flow control valve having three ports to divide the fluid flow delivered by a pump between a pair of partial volumes, one flowing to the steering valve and the other flowing to a further hydraulic load. When the steering device is not operated, the further load is primarily supplied with fluid, while the flow to the load is reduced, but the steering valve is fully supplied when the steering device is actuated. The valve comprises a valve member which is actuated in response to pressure to change the cross section of the throttle in the flow control valve so that the steering valve is supplied with a relatively small volume of fluid when the steering device is not operated, whereas the valve member is shifted by a pressure increase when the steering device is actuated to supply an increased fluid flow to the steering valve as required. The valve according to the invention allows to reduce energy to drive the pump.

Abstract: A hydrostatic machine having a rotor mounted in a housing and having a leakage oil connection, the leakage oil being conducted before discharge to the tank through predetermined housing portions in order to heat the central part of the housing during the start-up phase of the machine.

Abstract: In the supply of a power-assisted steering and an additional hydraulic system with fluid the power-assisted steering has priority so that when the steering is actuated the influx of fluid to the hydraulic system is correspondingly throttled by a priority valve. When a leak occurs in the hydraulic system, the influx of fluid to the hydraulic system is completely shut off when the oil level in the reservoir drops to a lower limit value. The closure of the priority valve is effected by a switch valve which is disposed in one of the control pressure lines of the priority valve and which is rendered currentless on response of the sensor for the fluid level.

Abstract: A servovalve includes a flow-control valve connectable between a source of fluid pressure and a load and having a spool displaceable between an open position permitting fluid flow between the load and the source and a closed position axially offset therefrom and blocking such flow. A pilot valve has an impact plate and a pair of nozzles operatively axially oppositely effective on the spool and oppositely flanking the plate. Thus when the plate is closer to one of the nozzles than to the other the spool is axially displaced into one of its positions and when the plate is closer to the other nozzle the spool is urged axially oppositely. A solenoid-type servomotor is connected to the impact plate to move same between the nozzles so that when it is close to one nozzle it blocks flow therefrom and allows pressure to build up on the corresponding end of the spool, while the other nozzle is opened to reduce pressure at the corresponding spool end.

Abstract: An apparatus for controlling the movement of a movable element as a working circuit (10) with a directional control valve (3) equipped to control devices (11, 12) which can be pressure activated in two directions. A control circuit (29) which can be connected to a fluid source (19) is used to activate the directional control valve for which the control circuit is connected to the two control devices and has an adjustable first choke (24) connected to one of the two control devices (12), a second choke (22) which is similarly adjustable and connectable to the same control device, and third and fourth adjustable chokes (27, 28) which are connectable to the other of the two control devices (11). The first and third chokes are connectable further to a storage tank (7) and the second and fourth chokes are further connectable to a pressure source. A proportioning pressure valve (45) can be connected to the other of the two control devices (11). The first and third chokes are connected to a pilot valve (38).

Abstract: A three chambered solenoid-actuated directional control valve in which a spool is reciprocally mounted for movement within a valve housing. The housing and spool define the three chambers with one adapted to be connected to a pump for supplying hydraulic fluid, the second adapted for connection to a first load and the third adapted to connection to a second load. A solenoid is reciprocally mounted for movement along the direction of the bore for actuating the spool with a rod fixedly mounted to the armature of the solenoid. At least one groove is formed between the outer surface of the armature and the inner bore of the valve housing for conducting flow of hydraulic fluid between a recess at the end of the solenoid adjacent the three chambers and the end remote therefrom. A throttle in the form of a single cross wall having either a groove or bore extending therethrough dampens movement of the armature to reduce pressure peaks during switching. Throttle grooves are also provided on the lands of the spool.

Abstract: A piston for a hydraulic piston machine in which a piston body receives a ball in a space defined at one end of thereof. A bearing dish supports the ball in the space with an O-ring engaging the recess to seal the bottom surface of the bearing dish. Preferably the bearing dish is formed with a steel support layer, a bronze layer cast onto the steel support layer, and a plastic layer supporting the ball.

Abstract: A hydraulic system for operating a pressurizable load off a pressure source having a high-pressure side and a low-pressure side has a main valve having a load side connected to the load and a source side connected to both sides of the source and displaceable between one position permitting flow from the source to the load and another position for opposite flow. Respective fluid-operated actuators displace the valve into its positions. A controller has an input side connected to the high-pressure sides of the source at the source side of the valve and an output side connected to the load at the load-side of the valve and with the sump at the source side of the valve. This controller also is connected to the actuators for pressurizing same alternately and thereby moving the valve between its positions.

Abstract: The invention refers to a pressure reducing valve including a pilot valve. The main piston of the pressure reducing valve allows to selectively connect a load port to either a port connected to a pressure source or to a port connected to the reservoir. The pilot valve is connected to a control pressure line and to the reservoir. The main piston controlled connection to the reservoir opens within the valve housing into a port connecting the pilot valve to the reservoir. This provides for a substantially simplified construction of the valve since there are only two operating ports and a reservoir port. Furthermore, the main piston is engaged by a spring which is capable of becoming activated such that dynamic stresses resulting from a change from high to low pressure values are avoided which vibrations are detrimental in generating pressure peaks as well as pressure breaks.

Abstract: A pressure-relief valve has a housing forming a chamber extending along an axis and a valve seat centered on the axis and subdividing the chamber into an outer high-pressure compartment and an inner low-pressure compartment. The seat defines generally the only fluid-communication path between the compartments. A pump and a load can be connected to the high-pressure compartment and a sump to the low-pressure compartment. A valve body is formed with a central radially outwardly open main groove, an outer face exposed in the high-pressure compartment, an inner face exposed in the low-pressure compartment, a radially outwardly open control groove offset axially inward from the main groove toward the inner face, and a diametrally throughgoing control bore at the main and control grooves.

Abstract: The electrode of an electric arc melting furnace is adjusted in height by a hydraulic cylinder having an operating chamber which is connected via a servo valve to a hydraulic pressure source or, respectively, to a reservoir. The servo valve is actuated by a control signal which is produced by a comparison of the actual value of the electric arc current and a predetermined desired current value. Additionally, the pressure in the operating chamber of the cylinder is measured and supplied to the control circuit as a feedback value. An important advantage deriving from the present invention is the ability to provide a control of the electrode motion by virtue of the measured pressure even before the electric arc is ignited and to steadily hydraulically support the electrode under any condition of operation. Accordingly, uncontrolled motions of the electrode are prevented which motions might result in an increased danger of breakage, in overcurrents or short-circuits.

Abstract: A hydrostatic machine, in particular of bent axis design comprises a clutch which is provided between the drive shaft and the pistons. The force necessary for clutch engagement is produced by hydraulic pressure forces which are either applied to the pistons or delivered by the pistons depending on whether the machine operates as a motor or as a pump. When the machine neither produces a moment nor receives a moment the clutch is automatically disengaged due to the reduction of the hydraulic pressure forces. According to the invention the clutch helps to prevent hydraulic losses of the machine while running idle and improves the overall efficiency.

Abstract: An apparatus for positioning an adjustable member as a function of a command signal and a control condition, especially for the positioning of a hoisting mechanism on a tractor or the like, comprises an operating circuit and a control circuit. The operating circuit has a bidirectional positionable valve with a valve side and first and second control devices for regulating flow of pressure medium from a supply tank to the adjustable member. The control circuit connects a control pressure medium source to the control devices at first and second junctions and includes adjustable throttles and a flow-regulating valve. A first adjustable throttle is connected between the supply tank and the first junction. The second adjustable throttle is connected between the control pressure medium source and the first junction and in series with the first adjustable throttle.

Abstract: The position control and force control of a device mounted to a tractor, in particular for controlling the depth penetration of a plough, is supplemented by a lowering speed-responsive control to limit the lowering speed to a predetermined maximum value in order to increase safety of operation. Activating and disabling the lowering speed signal takes place in response to operating a mode select switch provided for the position control and force control as well as in response to a high-speed actuation of the mounted device. Furthermore, the lifting and lowering function of the hydraulic jack of the mounted device may be locked to prevent undesired motions of the mounted device when the system is put in operation.

Abstract: In the spool member of a multi-way-valve leakage of pressure fluid from the inlet port to the operating ports and a corresponding pressure increase in a consumer are prevented by annular grooves and radial bores through which pressure fluid leaking from the inlet is discharged to the reservoir. The radial bores are provided in the spool member so that the land relief between the pressure inlet port and the operating port is achieved via the spool member, and the housing of the multi-way-valve may remain unchanged.