Abstract: The present invention relates to the use of two different sealing means in a directional spool valve. On the one hand side, a pressure guide element is provided at the spool so as to make sure that the pressure medium can only flow in radial direction against a seal located in the housing. The second sealing means may be of different design. It is possible that a spool seat surface provided on the spool and moveable against the force of a spring is used, said spool seat surface being adapted to cooperate with a stationary seat surface provided at the housing; alternatively a plurality of control bores is provided in the housing in the area of a port, said bores having a relatively small diameter d, and wherein a seal located the spool is used for opening and closing said bores so that no damage of the seal can occur. It is also possible to make use of the last mentioned sealing principle by itself.

Abstract: The object of the invention is to improve the position and feed or advance regulation of a hydraulic drive which is controlled by a proportional valve. In a first compensation circuit the flow characteristic of the proportional valve is linearized to obtain very small feed rates and a high control amplification. In a second compensation circuit the positioning error of the drive arising from the necessary overlapping of the proportional valve is compensated.

Abstract: For the drive of a vehicle having at least one driven axle, in particular a rail vehicle, a secondarily controlled hydrostatic drive is provided which is connected to a pressure network with impressed pressure. The respective travelling direction and the acceleration and retardation is set at a desired value pickup or generator which is part of a speed control circuit. The circuit arrangement according to the invention solves the problem of avoiding slipping of the drive wheels on acceleration and retardation. In addition, the determined acceleration and retardation values can be superimposed to avoid inadmissible wheel slip and obtain optimum accelerations and retardation operations. For this purpose the circuit arrangement employs a ramp former to which as control voltage various voltages proportional to different operating parameters are supplied, in particular a voltage dependent on the speed of rotation.

Abstract: Hydrostatic drives for wave generating apparatus in swimming pools require a large amount of energy. A hydrostatic drive for the wave generating apparatus is provided which allows that part of the kinetic energy of the rearwardly moving water to be transformed into hydraulic energy, which in turn is used to impart onto the water a forward movement.

Abstract: For detecting the pressures occurring at a control valve pressure pickup cells are provided and for processing the pressure measuring signals evaluating electronics are provided which together with the pressure pickup cells is arranged on an intermediate plate associated with the control valve. With this arrangement signals may be formed which monitor and control the mode of operation of the consumer governed by the control valve. By arranging the components necessary for the control circuit on the intermediate plate a standardized design is made possible in which the constructional expenditure is greatly reduced.

Abstract: A load-independent control device for hydraulic users has an initial position in which a control line transmitting a load pressure is connected with a tank. The control device has a control valve for the user and a switching valve, which can be controlled independently of the control valve, and has a cutoff position as well as a through position, in which it connects with the control line transmitting the load pressure to the tank.

Abstract: A hydraulic system is provided for powering a steering unit, a trailer brake and an auxiliary power unit from a single pump. A control circuit ensures that the hydraulic trailer brake and/or the power steering unit on the vehicle will operate on a preferential basis over the auxiliary power unit. The hydraulic control circuit has two priority valves connected in series. The upstream priority valve has a priority position in which it makes the pump fluid available to a supply line for the common priority flow for the steering and braking apparatus and a non-priority position for powering the auxiliary power unit. The common priority flow is passed through the second or downstream priority valve for priority powering of the power steering circuit.

Abstract: The invention relates to a seat valve in which a ball-shaped valve element is held in a sleeve which has control edges which cooperate with an opening arranged between the valve seats and connected to a connection. On switching over of the valve element from one valve seat to the other a positive switching overlap of the seat valve is achieved and with relatively small ball diameters large flow rates can be controlled.

Abstract: A control system for a hydraulic lift driven by a variable displacement pump is disclosed. It is comprised of a blocking valve which may be opened at least for lowering movement of the hydraulic lift. A control device is provided for opening and closing the blocking valve and for regulating the volumetric flow from a pump line to an operating line leading to the hydraulic lift, and the flow from the hydraulic lift to a tank line leading to a tank. In addition, a load indicating line is provided which transmits the load pressure. The control device is comprised of a servo valve with three valve positions, and is further comprised of an actuator unit which opens and closes the blocking valve. The servo valve regulates the volumetric flow to and from the hydraulic lift. The load registering line is connected to the operating line, and in the initial position of the control device the load registering line is connected via the servo valve to the tank.

Abstract: A control motor for a servo valve is provided. The control motor comprises a control element which can carry out a pivotal movement due to an electric input signal supplied to said motor. The movement of the control element causes a corresponding change of hydraulic resistances and, as a consequence, changes in hydraulic output signals of an hydraulic amplifier actuated by said motor.

Abstract: A hydrostatic auxiliary power steering mechanism for motor vehicles is described, in which the steering cylinder power is controlled by a servo mechanism for which a control loop is provided for regulating oil quantity proportional to the turning of the steering wheel. This control loop is connected in parallel to a hand pump driven by the steering wheel. In this way, the transmission ratio of the hand pump can be selected independently of the auxiliary power control loop in such a way that the vehicle remains steerable in all operating conditions. Moreover, there results the possibility of designing the auxiliary power control loop with external feedback in such a way that disturbance variables of a control system comprising the steering valve, the steering cylinders and the steering linkage can be controlled.

Abstract: An off-road vehicle has ground supports on each side which can be simultaneously braked, or independently braked to aid in steering. A braking system includes a brake valve device which feeds high fluid pressure to a pair of reversing valves. The reversing valves deliver the high pressure to respective wheel brake cylinders disposed on opposite sides of the vehicle. The reversing valves and brake valve device are controlled by a common pedal which comprises separately or simultaneously actuable half-pedals. Each half-pedal actuates the brake valve device and a respective reversing valve such that when both half-pedals are depressed the system operates in a dual-sided braking mode, and when only one half-pedal is depressed the system operates in a braked-steering mode. The system can be shifted directly from the dual-sided braking mode to a brake-steering mode by simply releasing one of the half-pedals without having to first release all braking action.

Abstract: A radial piston engine comprising: a housing, an annular cam disk fixedly mounted in said housing, a cylinder block rotatably mounted about an axis with respect to said cam disk, a plurality of bores arranged in said cylinder block in a position radially with respect to said axis of rotation, a plurality of pistons respectively mounted in said bores, and cylindrical rollers for supporting said pistons on said cam disk, said rollers having axes which extend parallel to the axis of rotation of the cylinder block, and wherein said bores of said cylinder block which are adapted to receive and pistons are provided with recesses in the area of movement of said rollers, so as to receive sections of said rollers on both endfaces of said rollers.

Abstract: The invention relates to a radial piston machine comprising height adjustment means, control means and adjustment means all having abutment means designed such that the cam ring of the machine will carry out during its adjustment a substantially rolling movement.

Abstract: With the invention a supply voltage and a control signal are to be supplied via a two-conductor cable to the power stage of a solenoid valve. For this purpose pulse-width modulation is employed, i.e. in a microcomputer the adjusting signal is converted directly as pulse-width-modulated signal via a power stage to an AC voltage. The control signal is obtained from the pulse width in the power stage.

Abstract: A 3/2 proportional control valve is provided with an actuating piston which is subjected to the control pressure set in a pilot valve. The area relationships of the actuating piston are so chosen that at the actuating piston a high pressure gradient obtains and the adjustment dynamics of the regulating piston are increased.

Abstract: A rotary piston engine having a commutator valve in a cooperating connection with the output shaft so as to supply and remove pressure medium to and from tooth chambers. Said engine further comprises passages which end adjacent to the commutator valve in ellipse shaped control openings. The commutator valve is integrally formed with the output shaft and all control channels are in the outer circumference of the commutator valve in the form of grooves which are parallel to the axis. Lands are provided between said grooves. The width of the lands defining said grooves is selected such that the width of the lands changes alternately, one land having a width approximately corresponding to the smaller width of the control ellipse, while the alternate land has a width which is increased by an oversize over the width of the smaller width of said control ellipse.

Abstract: The invention relates to a safety arrangement for a controlled drive which is connected to a conduit with impressed pressure. When the safety arrangement responds the machine is separated via shutoff valves from the inlet and outlet and a via a switchover valve the pivot angle of the machine is set to the maximum value so that the largest possible braking torque can be automatically set.

Abstract: A cylinder unit is supplied with pressurized fluid from a hydraulic machine which is variable in speed and/or displacement. The machine may be operated as a pump and as a motor to increase the pressure or, respectively, to decrease the pressure so that the piston of the cylinder unit may be actuated in both directions and, furthermore, the brake energy is recovered by the machine when the piston is driven through an external load. This results in an increased efficiency of the control apparatus for the cylinder unit avoiding any problems arising from heat.

Abstract: A hydraulic vane-type pump is provided having a venting valve which is located immediately at the pressure space of the pump, i.e., avoiding any additional passage means between the pressure space of the pump and the venting valve.