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: The invention relates to a vane pump having input and output slot means. Either the input slot means or the output slot means are designed such that for a movement of the cam ring into a position of zero excentricity the area of overlap between the input slot means and the output slot means is increased.

Abstract: The invention relates to a hydraulic vane type pump and to a radial piston pump. The cam ring of said pumps is adapted for horizontal and vertical movement. So as to achieve stable operating conditions for the pump at least within a certain range, a single-piece support body is mounted within the vertical adjustment screw so as to avoid a change in the level of height when the cam ring is moved axially.

Abstract: In a directional seat valve all the valve seat components disposed axially adjacent each other in the housing bore are held between two closure screws and for assembling the valve the movable valve elements are supported via the valve actuating pin on a punch. By turning the closure screws the valve seat components can be adjusted in the axial direction so that the actuating pin has a predetermined spacing with respect to the housing end side of the valve. An advantage resides in that in the assembly of the valve itself a constant dimension can be set between the actuating pin and the housing and consequently an adjustment on subsequent attachment to the actuating means dispensed with, in particular an adjustment of the actuator cooperating with the actuating pin.

Abstract: For a drive system comprising a hydrostatic adjustable machine an electrical control is provided with which the actuator of the machine is driven so that for acceleration, retardation and braking, i.e. when the machine moves from motor mode to pump mode, a predetermined operating behavior of the machine necessarily results. The particular input desired value for the speed is transformed so that suddenly occurring abrupt acceleration, retardation and braking operations are avoided and in particular on abrupt entry of desired values increased safety against operating errors is achieved.

Abstract: A secondarily controlled hydrostatic machine with variable volume is connected to a line with impressed system pressure which is fed by a primary unit. By switching over the primary unit the secondary unit is subjected to a displacement amount which results in as large as possible a pivot angle of the secondary unit to obtain the highest possible efficiency. The switching over takes place in dependence upon an upper and lower switching point corresponding to the desired pivot angle range of the secondary unit.

Abstract: Into the housing of a multiway valve a pressure balance is incorporated, the end of the control piston subjected to the load report pressure facing a housing recess in which the load report pressure obtains while the opposite end of the control piston is subjected to the supply pressure and in the opposite sense to the supply pressure to the force of a spring. The valve has a simple structure.

Abstract: The switching time in opening and closing a valve is determined by a closing throttle and an opening throttle which both together are arranged in series with a check valve. For closing the valve the check valve is opened thus making the opening throttle ineffective so that the closing speed is solely determined by the cross-section of the closing throttle. For opening the valve the check valve is closed so that the control pressure is decreased across the opening throttle defining a desired opening speed.

Abstract: A reservoir loading valve accomplishing a pressure protection of the reservoir circuit comprises a pre-control valve subject to the pressure of the control circuit and which controls depending on this pressure a switching valve the piston of which in turn controls the connection between a pump and a working hydraulic and the reservoir circuit. The reservoir circuit is supplied with pressure fluid through a blind bore and a transverse bore in the piston of the switching valve, while a flow control orifice is provided in the blind bore and controls the size of the flow of volume flowing to the reservoir circuit. When the reservoir is loaded and the working hydraulic circuit is connected, the piston of the switching valve will be displaced by the high pressure delivered by the pump into a position in which the connection between the pump and the reservoir circuit is completely interrupted.

Abstract: A hydraulically operated two-way seat type valve includes a housing a forming valve seat, and a locking body displaceable in the housing and cooperating with the valve seat. A cover is mounted on the housing. An actuating piston for actuating the locking body of the valve is guided in the cover. The piston has two opposing piston-shaped extensions one of which is secured to the locking body whereby a non self-closing valve can be switching into the self-closing valve.

Abstract: A control motor for a servo valve which includes pole screws defining an armature space, first and second spools or coils supported by the pole screws, respectively, a soft metal armature which is resiliently mounted to a thin walled tube and a samarium cobalt permanent magnet. The permanent magnet polarizes the armature so that when the spools or coils are energized, the armature will move toward one of the coils and away from the other coil.

Abstract: A method and apparatus for adjusting the working depth of a soil-moving (soil-working, tilling) machine carried by a tractor includes adjusting the position of the machine in relation to the tractor in dependence upon a traction signal and upon a position signal. The traction signal corresponds to the traction produced on the machine in the soil and the position signal corresponds to the position of the machine in relation to the tractor. A portion of the traction signal above a certain cut-off frequency and a portion of the position signal below the same cut-off frequency or below a lower one are utilized in the adjusting control.

Abstract: A fluid operated positioning apparatus includes a multi-position valve operated in response to differential pressure in a fluid control circuit. The control circuit includes two adjustable throttles in series, the junction between the throttles being connected to a control device at one end of the valve. Particular relationships for the throttles are disclosed. Other embodiments include additional throttles for improved control with low pressures.

Abstract: A control valve for a variable displacement pump is improved so that the levelling of the pressure fluctuations of the pump is better and quicker. For this purpose an additional control piston portion on the control piston of the control valve is used. Corresponding to the deflection of the control piston the constriction cross-section set by the control piston portion between the supply connected to the pump pressure line and a passage leading to the control space of the variable pump is varied so that the pressure rise in the control space of the pump and also the pressure drop is accelerated.

Abstract: The invention relates to a priority control means with which the actuation sequence of two servo motors can be automated. For this purpose a priority control valve is provided which on actuation of the higher priority control valve immediately blocks the lower priority servo motor. If the priority servo motor has reached a certain position the associated control valve is automatically switched back so that the actuation of the lower priority servo motor then follows automatically. Via a changeover valve the working pressure of the respective servo motor is furthermore automatically switched to the pump control of an adjustment pump or, with a constant pump, to the load-pressure-dependent pressure control so that a load-dependent regulation takes place.

Abstract: A vehicle, such as a tractor, has an attachment implement, such as a plow. An automatic controller acts upon a power lift of the plow, which moves the plow during operation in trenching position. In a first control, this motion of the plow ensues relative to the tractor, so that the vertical absolute velocity component of the plow becomes approximately zero. The plow is so moved relative to the vehicle that it moves upward during a downward motion of the plow-tractor joint and downward during an upward motion of such joint. The tractor is this completely disconnected dynamically from the plow, so that the pitching vibration behavior of the tractor is not subjected to a negative change due to the moments resulting from the forces of acceleration of the plow and affecting the plow, as is the case with a vehicle having a rigidly connected attachment implement. In a second control, the plow is moved in opposite phase to the tractor to counteract a change of its pitching angle coordinate.

Abstract: In a priority control device the supply flow to the lower-ranking consumer is set by a flow control valve (pressure balance) whose control chamber subjected to the control pressure of the lower-ranking consumer can be relieved of pressure via a proportional valve. The proportional valve is adjusted in dependence upon the load pressure of the priority consumer so that the flow of fluid to the lower-ranking consumer is throttled by the pressure balance when the pressure difference at the priority consumer drops on increased volume flow requirement. The priority control device thus consists of two simply constructed power valves and a small-dimensioned pilot valve.

Abstract: A hydraulic system comprises an accummulator for supplying hydraulic fluid to a load, a variable displacement pump for charging the accummulator and a valve means for adjusting the pump to deliver a high pressure for charging the accummulator and then to a low pressure when the load is supplied with fluid from the accummulator. By this operation, in which the pump is switched between the zero stroke positions of high and low pressure, the losses of the pump are decreased and the lifetime is increased.

Abstract: A casting mold with a feeder, particularly for producing cast iron, includes an exothermically heated feeder mass. The casting material in the cylindrical or slightly conical feeder volume of the feeder mass is kept in a liquid state until termination of the drawing in of casting material by suction into the casting cavity. The feeder volume has dimensions corresponding to the quantity of casting material drawn into the mold cavity to compensate for casting shrinkage, plus a miximum security allowance of 30 percent of the quantity of casting material drawn in. To obtain a feeder mass which is less costly than conventional feeder masses, from the point of view of simpler and more propitious temperature measurements, the feeder mass has an outside shape of a flattened sphere, a flattened ellipsoid or a flattened pear. The smallest diameter is on the side away from the casting being produced. The flattening is provided adjacent to the casting.

Abstract: A parking brake valve cooperates with a spring loaded cylinder which releases a parking brake when pressurized. The valve includes a shaft with an eccentric section, and this shaft may be turned by an actuating lever from a position in which the brake is engaged to a released position. In the released position, the eccentric section of the shaft causes the movement of a control piston, permitting the spring loaded cylinder to be pressurized, releasing the brake. The pressure applied to the spring loaded cylinder is also provided to a radial surface on the shaft, causing the shaft to be friction locked in the released position, despite a spring force applied by a control spring tending to return it to the braking position. If a breakdown occurs in the parking brake system, however, the pressure to the spring loaded cylinder will drop, releasing the friction lock.