Abstract: A multi-stage hydraulic actuator including a cylinder body having an outer cylinder and an inner cylinder provided in the outer cylinder, first and second pistons inserted in the outer cylinder to independently move and provided with first and second working members, and third and fourth pistons inserted in the inner cylinder to independently move and provided with third and fourth working members.

Abstract: A hydraulic control circuit for building machinery includes a hydraulic cylinder to operate a tool. To stabilize vibrations of the tool around the pitch axis, a hydraulic accumulator is provided to be connected to a pressure source via a fill line. A shut-off valve is disposed in the fill line, which valve is subjected to the pressure in the accumulator such that in operating the cylinder the accumulator is loaded to a pressure corresponding to the load pressure. The system is very simple in structure and fluid losses are eliminated.

Abstract: A circuit for limiting a static and/or dynamic pressure load in a hydraulically actuated use device which is controlled in a closed control circuit by means of a directional control valve and a mechanically or hydraulically releasable blocking device. Aa pressure control valve is arranged between the use device and the pressure relief valve and being adapted to discharge a hydraulic fluid from the use device to a tank when a predetermined hydraulic pressure in the use device is exceeded. The output port of the pressure relief valve is connected to a hydraulic control line is adapted to hydraulically connect the pressure relief valve to a control side of the control valve.

Abstract: A vane pump or a vane motor is here specified, having a variable displacement volume. The vane pump has a vane rotor and an annular stator that surrounds the rotor eccentrically and that is stabilized by means of a piston arrangement for adjusting the eccentricity that determines the displacement volume. The piston arrangement includes at least one pendulum piston that is acted upon by a pressure medium, the pendulum piston being guided in a sealed manner in a housing bore by a piston head that delimits a control space. To simplify the assembly and to decrease manufacturing costs while simultaneously improving the sealing action and increasing the peripheral life of the guide surfaces, plastic rings, which are composed of wear resistant, sliding material, or are prestressed radially, to guide the piston in the piston bore and to seal the control space are embedded, inserted or emplaced in the piston head.

Abstract: A hydraulic drive is actuated by a CNC means via an electrically actuable valve. The pressure applied to the hydraulic drive or the force excerted by the hydraulic drive is supplied in the form of a signal to a pressure control means or a force control means. The output signal of the pressure- or force control means is supplied via a switch means--shortly prior to reaching the desired position value of the drive--to the electrically operated valve as a control signal. Simultaneously, the output signal of the switch means, which can be supplied to the valve, is interrupted, wherein the switching range shortly prior to reaching the desired position value is smaller than the admissible differential value, determined by the CNC means, i.e.

Abstract: A cheek plate for a vane pump is provided which is made of an aluminum alloy. The cheek plate has a first or casing face which faces towards the casing of the pump when installed in the pump. A second or rotor face of the cheek plate faces the rotor when the cheek plate is installed in the pump. The cheek plate further includes a first radially outwardly located pressure control passage configuration, a second pressure control passage configuration located radially inwardly with respect to the first pressure control passage configuration. A first radially outwardly suction control passage configuration located diametrically opposite to the first pressure control passage configuration and a second suction control passage configuration located radially inwardly with respect to the first suction control passage configuration. The first and second pressure control passage configurations and the first and second suction control passage configurations extend between the casing face and the rotor face.

Abstract: A multiway valve, which includes a piston slide valve and at least five control chambers, of which a middle chamber comprises an intake chamber for a pressure medium, chambers adjacent the middle chamber are connected to actuators, and chambers outside the adjacent chambers are connected to a reservoir at a preset pressure level wherein, in the area of piston guide gaps formed between the intake chamber and actuator chambers, a first annular space is provided, which in a middle position of the position slide valve, in which an intake of the pressure medium source and connections of the actuators are closed, is connected by ducts in the piston slide valve to a reduced pressure level source.

Abstract: The invention relates to a variable displacement pump supplying fluid to a number of consumers. The pump control for adjusting the delivery rate is actuated by a signal which is produced by the respective highest loaded consumer. The signal is provided by a valve, in particular a pressure compensating valve which is associated with the consumer, and which valve opens a spool land when the valve becomes positioned at its control end range. A pressure signal from any pressure fluid source is delivered through the land to the pump controller. The control, according to the invention, offers a broad variety of possibilities for arranging the pressure compensation valve at various locations, engaging the valve by a variety of pressure differences, and using a number of pressure fluid sources of provide for the signal pressure to actuate the pump controller.

Abstract: A valve system is provided for the load-independent control of a plurality of simultaneously operated hydraulic consumers, i.e. regardless of variations in load pressure. Fluid flow in a consumer line to each consumer passes across a compensating flow control valve, i.e. a compensator. The valve piston thereof being displaceable to the open position by a pressure downstream of a flowmeter against the opposing resistance offered by a spring and by the respective maximum load pressure of the consumers at a time. The actual highest load pressure is also available at a regulator for the common variable displacement supply pump feeding the consumers.

Abstract: A first cylinder chamber of a hydraulic cylinder is connected to a pair of variable displacement pumps of which the first one is connected to a reservoir and second one is connected to the second cylinder chamber. This allows to bias the piston by a hydraulic force acting on either side of the piston corresponding to the direction of motion. This is obtained by adjusting the delivery volume of both the pumps such that the volume supplied is larger than the volume drained. Metering the difference of both the delivery volumes results in the desired biasing counter-pressure.

Abstract: A radial piston engine is provided having recesses in the area of movement of the rollers, adapted to receive roller sections on both roller end faces. For guiding the roller end faces, oppositely located guide surfaces are milled in the cylinder block for said rollers.

Abstract: A circular piston engine or machine is provided having a rotor with outer teeth and fixedly connected for rotation with the shaft. The rotor cooperates with an outer gear having inner teeth. The outer gear is supported by the housing at its outside and the user ports extend axially in the control housing.

Abstract: A control circuit includes a microprocessor, a table store and an amplifier stage to control a controlled device which has a non-linear or linear, but discontinuous response curve. To obtain a linear response curve of the controlled device the table store is loaded with a response curve map in operating the controlled device. Thereafter the data loaded in pairs in the table store are inversely read-out and used as a control signal for the controlled device. The table store thus allows to linearize the response curve of the controlled device. In addition the data may be modified. According to the invention any correcting means to obtain an ideal response of the controlled device is eliminated. The invention provides for an optimum performance, smallest possible expenditure of circuitry and shortest possible control time.

Abstract: Amplifier units for controlling valves, in particular proportional solenoid valves, comprise a number of components such as an end stage, a power supply, a control electronics and possibly a closed loop control including signal inputs for desired and actual values. The control electronics generates a desired positioning characteristic for each type of valve. According to the invention, the control electronics is replaced by a programmable component including a read-only-memory in which the amplifier is associated to a particular type of valve by loading the read-only-memory with valve specific data which specify a particular type of valve. The invention allows to manufacture and to stock non-programmed amplifiers of identical structure. To make an amplifier unit ready for use a particular program is loaded to suit the amplifier to the valve type.

Abstract: The invention refers to a hydraulic system comprising at least a variable displacement pump and at least a consumer. Means are provided to generate electrical limit signals when at least one of the consumers, preferrably a load leading consumer indicates the need for an increased delivery rate or when the variable displacement pump indicates a hydraulic under-supply. In response to the limit signals generated by the consumer need or the pump are varied in a control circuit to adjust the control signals delivered to the servo devices of the hydraulic systems such that the pump control is optimized and that the flow rates to the consumers are decreased in the mode of under-supply. In addition very simple electrical circuits are disclosed to substantially reduce the expenditure of the system.

Abstract: For a load independent control of a plurality of simultaneously actuable hydraulic users, a throttle valve (pressure compensator) is assigned to the control valve of each user at a location downstream with respect to the metering orifice formed by said control valves; said throttle valve is subjected in opening direction to the pump pressure and in closing direction, via a shuttle valve, either to a load pressure of the respective user or to a pressure which is determined by the highest load pressure occurring for one of said users. Said highest load pressure which is reported by a shuttle valve chain is supplied as control pressure to a pressure reducing valve, the input side thereof being connected with the pressure line of the pump and the output side thereof being connected to control lines leading to the throttle valves assigned to the individual control valves and to the control line for the pump control.

Abstract: A control motor for a servo-valve includes elements of a control motor including a yoke, permanent magnet, control coil and armature mounted to one another. An output member transmits the pivotal movements of the armature. A frequency dependent passive electric dampening means is formed as an annular disc, and located adjacent the control means to compensate for non-linearities in frequency response.

Abstract: A pilot controlled sequence valve having a pilot valve and a main valve is provided. This sequence valve is preferably used for switching on and switching off a charging operation of a hydraulic accumulator. The displacement volume of the main spool of the main valve is directed via an orifice to the tank when the switching into the pressureless circulation occurs.

Abstract: An automatic control including a memory is provided to be loaded with positional data for the automatic control of a cycle of motions of preferably a plurality of power members. The speed reading the data in and out is freely selectable. Accordingly programming a cycle of motions may be performed in a slow motion process, whereas the speed of reading out the data is selected such that an optimum operational speed is obtained. In addition to the automatic speed control a manual control is provided to interrupt the cycle motion of the automatic control to manually adjust the position or the power member. In returning to the automatic control the further cycle of motion is taken up again where it has been interrupted.

Abstract: A device is disclosed for the selective clamping of an axially moveable or rotatable cylindrical shaft. The device disclosed may be either of a spring actuated-pressure release or a pressure actuated spring release embodiment. A clamping sleeve is located coaxially surrounding the cylindrical shaft to be immobilized. The clamping sleeve is separated into clamping elements at one end by longitudinal slots in the generally cylindrical sleeve. An actuating element is also arranged coaxially to the cylindrical body and the clamping sleeve and is mounted exterior to the clamping sleeve. The clamping elements are located radially inwardly from the actuating element and are separated therefrom by a series of bearings. The bearings engage the actuating element and the clamping elements through matched sets of inclined ramp elements. Each clamping element is provided with a set of bearings and ramp elements.