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: 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: A device for the positioning of an adjustment element dependent upon a desired level and the actual level, particularly for the adjustment of a hoist gear train of a tractor, a combine or the like, has an operating circuit 10, which has a multi-way valve 3 pressure-operated in two directions, and a control circuit 29 for the operation of the multi-way valve, connected to a pressure source 19, which is connected to two control devices 11, 12 of the multi-way valve. Circuit 29 has two adjustable series-connected throttles 22, 24, connected to one of the two control devices. The first throttle 24 is also connected to a tank 7 and the second throttle 22 is also connected to pressure source 19. Both throttles have the same maximum flow-through cross section, and are adjustable in the same manner. Third and fourth throttles 27, 28 are provided, one being between the pressure source and control device 11, and the other between the control device and tank 7.

Abstract: The invention provides a support unit for drivers' cabs which actively compensates for any relative movement between chassis and cab by providing at least one support cylinder which is axially rigidly mounted on the chassis with its support piston and flexibly supported on the cab by its cylinder, the cylinder forming a movement-producing unit with a directional control valve whose body alternately connects the front side of the support piston to the pressure side of a constant-pressure circuit or to a non-pressurized outlet and is attached to the cab.

Abstract: A utility vehicle with a self-contained driver compartment and with spring and damping elements by which the driver compartment is elastically supported on the rest of the vehicle mass. Located centrally between the driver compartment and the rest of the vehicle there is provided a guide arrangement which guides the driver compartment in all its motions relative to the rest of the vehicle and which consists of a vertical guide as well as two rotating guides coupled with it, their pivot axes being in the vehicle's longitudinal direction and transverse to it.