Abstract: A constructional unit comprising a hydraulic machine having a drive or driven shaft and of a support by which the hydraulic machine is held with the interposition of material which deadens solid-conducted noise. Low noise emission of the hydraulic machine is obtained in the manner that the support extends over the hydraulic machine in particular in the direction towards the shaft and that the hydraulic machine is supported on the support via material which deadens solid-conducted noise, present between its outer wall surface and the support. In this way the noise emission can be reduced in a simple manner.

Abstract: A control arrangement for at least one hydraulic consumer in which the consumer can be controlled with respect to direction and speed via a directional control valve device, in which two consumer lines lead from the directional control valve device to the consumer, each of which consumer lines can be connected to a pump and a tank respectively via a directional control valve piston and a metering restrictor and in which a throttle valve having a servo-piston is associated with each consumer line. The consumer is to be held free of leakage oil in a given position.

Abstract: The present invention provides for a control apparatus for independently operating at least two users. The users can be the tilt cylinders and the lift cylinders of a loader. The control apparatus provides for the adjustment of the control valves and for the adjustment of the pressure control apparatus of the variable displacement pump means in dependency of each other. In accordance with the invention, the control position of the control spool of the control valve controlling the user with the largest load provides for a measure (or for the adjustment) of the pressure control device of the variable displacement pump. In this manner an extremely effective and economic operation of the hydraulic system comprising the control apparatus and the users is obtained.

Abstract: The invention relates to a drive for a press, in particular for a sheet metal forming press, the press including a press ram which can be moved up and down and a hydraulic movable counter support. The counter support can be moved in a forward stroke in the direction towards the press ram via at least one hydraulic cylinder by a first hydrostatic machine, and in a return stroke by the press ram. In known presses, during the return stroke of the counter support, the pressure medium is displaced from the hydraulic cylinder while a predetermined pressure is maintained by means of a pressure relief valve (pressure limiting valve) or a throttle valve (flow control valve). The balance sheet of energy of such a drive of such a press is to be improved. This is achieved by providing that the first hydrostatic machine is a pressure controlled machine, preferably an axial piston machine. Preferably, the axial piston machine can be swiveled in both directions, i.e. pivoted towards both sides.

Abstract: The present invention provides a method for pressure control of an adjustable pump for a hydraulic system including at least a load. Depending on the size of the system, i.e. the servo cylinder, hydrostatic machine and the line tubing, the fluid volume contained in the system between the adjustable pump and the low pressure side of the load is largely different. In controlling the load pressure in such a system, for example a press or a molding machine for plastic material, a pressure controller adaptively and automatically adjusts the damping factor of the controller and thus the controlling quality independent of the fluid volume of the system to a constant value. It is a benefit of the invention that all adjusting operations of the pressure controller are eliminated which have been necessary heretofore to obtain an appropriate control of the fluid system.

Abstract: A safety circuit for a servo-hydraulic regulating system for the hydraulic control and actuation of load units, such as operating tools on utility vehicles and agricultural machines. The controlling of the load unit is effected via a proportional valve which is actuated in dependence upon a pair of output signals of a measuring bridge in such a way that, in the event of a balanced measuring bridge, it assumes a neutral setting in which the operating line running to the load unit or emanating from the load unit is blocked. In order to prevent the lifting gear from executing a regulating reaction if the measuring bridge is out of tune when the servo-hydraulic regulating system is switched on, a safety valve arrangement is provided in the operating line.

Abstract: The invention relates to a hydraulic drive apparatus having a cylinder. Said cylinder comprises a piston movably mounted in a working chamber, a piston rod which is guided towards the outside through a cylinder head and a wear resistant primary seal and a leakage free secondary seal. Both said seals act between the cylinder head and the piston rod, with the primary seal being closer to the working chamber than the secondary seal. Further, a leakage oil conduit is provided between the primary seal and the secondary seal. Such a hydraulic drive apparatus is to be improved such that the cylinder will hold or maintain a load in a certain position even if the pump is switched off for a long period of time. This is achieved by providing that the leakage oil conduit can be subjected to the load holding pressure by switching a valve.

Abstract: A hydraulic actuator including a single cylinder body which defined therein a pressure chamber in which a first piston with a piston rod and a second piston with a piston rod are independently movably inserted, a first working member secured to the first piston rod, a second working member secured to the second piston rod, and pressurized fluid inlet and outlet ports provided in the cylinder body to be connected to the pressure chamber.

Abstract: A hydrostatic radial pocket bearing for a servo cylinder is described, particularly for a high performance testing cylinder, of the kind as used, for example, in test rig or simulation technology. The radial pocket bearing is suitable for the highly precise regulation of the piston and for receiving large transverse forces acting on the piston rod. An even number of bearing pockets is uniformly distributed over the bearing periphery and fed from a source of pressure fluid by way of associated preliminary throttles connected to pressure supply conduits and by way of an associated connecting conduit. The preliminary throttles are formed by the bearing gap between a supply orifice and at least one outlet groove in an opposite bearing pocket, the bearing pocket being in the form of a reentrant depression either in the fixed or in the moving bearing portion.

Abstract: The present invention relates to a hydraulic secondary control system comprising a hydrostatic machine as a secondary unit which is connected to a pressure line in which an impressed pressure of approximately constant value is generated by a hydrostatic machine as a primary unit. The volume capacity of the secondary unit determines the torque delivered to a load and the torque needed by the load determines the speed of the secondary unit. When the desired speed and thus the volume capacity of the secondary unit is too high, the capacity exceeding the capacity of the primary unit supplying the pressure line, the pressure breaks down. To prevent this, the present invention provides to calculate a permissible capacity as defined by the rotary angle for the secondary unit in accordance with the nominal quantities of the primary and secondary unit.

Abstract: A poppet valve comprising a ball supported within an axial bushing, the ball being urged onto the valve seat by an operating element and being lifted off the valve seat by the force of a spring, wherein pressure is applied to the ball surface within the valve seat, is characterized in that the end of the bushing facing the valve seat protrudes in tangential direction beyond the periphery or equator of the ball and defines together with the ball surface in this region a space for fluid flow inversion to thereby further improving the lifting aid achieved by the bushing with respect to a further decrease of the switching delay together with an increase of the flow rate while maintaining the same flow losses as prior art poppet valves with such bushing.

Abstract: An apparatus for adjusting the pressure of working fluid provided to the load or user via a hydraulically actuatable control valve is provided. The apparatus includes a comparator that compares a given or desired control pressure for the control valve with the predominant present load pressure. The resulting pressure differential is used to re-adjust the control valve or to re-adjust a pressure compensator positioned upstream of the control valve with respect to the direction of the flow of working fluid flowing to the user.

Abstract: The present invention relates to a noise dampening assembly of a hydraulic machine and a drive motor, and provides for a structure comprising a block, in which the hydraulic machine is mounted by means of noise dampening elements.

Abstract: Closed loop control circuit for a variable hydraulic pump the output flow of the pump being variable by control means and the pump including at least two closed loop controllers actuating the control means, wherein at least one hydraulic switching element is provided which automatically connects to the control means the closed loop controller providing the highest or the lowest pressure.

Abstract: The invention relates to a hydraulic system for hydraulic operators for delivering pressurized fluid to a blower drive means and to the hydraulic operators of a hydraulic machine, comprising a variable delivery pump, control valves connecting the hydraulic operators and the blower drive means to the pump, a temperature responsive pressure valve for setting a temperature-proportional control pressure in the pressure line between the blower drive means and the respective control valve, wherein the control valve is subjected to the pressure in the control line in a sense to open the control valve, and a flow volume regulator associated to the variable delivery pump which regulator is subjected via a load sensing line by the load pressure occuring at the hydraulic operators or in the blower drive means depending on which pressure is higher.

Abstract: The present invention relates to a valve assembly for the supply of users in hydraulic control systems with pressurized fluid for the load pressure (LS) independent control of several simultaneously actuated hydraulic users wherein the ratio of the partial flows once set is maintained at undersupply of the system with the pressurized fluid. When the demand of the users exceeds the maximum output flow of the variable displacement pump, the (high) priority users receive the demanded quantity whereas the low priority users receive a reduced quantity by switching the control pressure for the low (i.e. no) priority users via a directional control valve and a pressure relief valve to a lower pressure level. Only when undersupply of the entire system occurs, i.e. when the maximum output flow of the variable displacement pump is no more sufficient despite the limitation of the control pressure for the low priority users, then the presently flowing partial flows of all users are reduced proportionally.

Abstract: A nozzle resistance controlled by a piezoelectric element comprises a housing having a longitudinal bore, a piezoelectric element located in the longitudinal bore, a baffle plate supported by the piezoelectric element, a nozzle body located in the longitudinal bore such, that the bore extending through the nozzle body ends with one end adjacent to the baffle plate, and a chamber defined by the longitudinal bore and connected to the other end of the bore. The chamber is connected to a fluid supply device.

Abstract: A valve arrangement for a hydraulic transmission circuit, in particular for a change-under-load transmission with a clutch valve arrangement for controlling at least one clutch and/or start-up clutch with the aid of a pressure-regulating valve whose normal position can be influenced mechanically by a clutch pedal. The pressure-measuring area of the pressureregulating valve is connected to a control valve whose piston, acted on by the clutch pedal, can be brought, against the force of a spring placed between the pressure-regulating valve and the control valve, first of all out of a position that relieves the pressure-measuring area of load into a floating position in which the pressure-measuring area is connected to the pressure-regulating valve outlet. Then, and after traversing a certain path, it can be brought into contact with the valve body of the pressure-regulating valve.

Abstract: An engine brake for a multicylinder internal combustion engine includes valves that can be periodically opened briefly, in each case outside the exhaust stroke. In the vicinity of the applicable valve drive, a hydraulic piston is provided that is triggered synchronously with the engine rpm via an associated control line by a hydraulic pressure distributor fed by a pump. To improve the accuracy of control over the entire engine rpm range, the various valves are assigned a central positive displacement pump that runs synchronously with the camshaft rpm and whose outlet line leads to the hydraulic pressure distributor, which has a distributor disk. In engine braking operation, an alternating connection of the applicable control line to either the pump outlet line or a low-pressure region of the hydraulic control circuit is effected synchronously with the engine rpm by means of the distributor disk.

Abstract: A digital electronic control apparatus for controlling at least one electronic control element comprises. The apparatus comprises first and second pulse width modulated output signal generators, the frequency of the second signal being different from the first. The second pulse width modulated signal is provided as a function of a digital value determined by at least one of a characteristic and operating condition of the at least one electronic control element. An AND-gate receives the first and second pulse width modulated signals and is capable of producing an output signal for controlling the at least one electronic control element a first and second pulse width modulated signal having a first frequency.