Abstract: A hydraulic actuator arrangement has a pair of double acting actuator devices coupled together for movement in unison. Each device has two control valves respectively operable to cause the device to move in opposite directions. The four control valves are resiliently coupled so that both actuator devices are normally energised simultaneously. Each control valve has an associated pressure relief valve so that failure of any one of the control valves permits the pressures on either side of the associated actuator device to be equalized.

Abstract: A steering worm shaft in operational connection with a steering wheel and communicating with an axially slidably arranged steering gear nut, which gear nut affects an additional gear member, for example, by means of a toothing, and simultaneously functions as a servo-piston or is at least fixedly connected to a servo-piston within a housing, which contains a cylinder space; the servo piston dividing a cylinder space into two operational spaces, which are separated from each other, and the steering gear nut at its outer cover is provided with an outwardly extending, axially directed lever in an area remote from the sealing area of the servo-piston; the axial width of the lever corresponding at least with the lift of the servo-piston and engaging an axial-parallel groove in the housing to allow the lever to perform a minute tilting movement relative to the housing when the steering gear nut, due to friction and rise of the worm gear nut during a rotation of the steering worm shaft, is also set into rotation, wh

Abstract: A device for elevating the boom of a side crane has a double acting valve provided in a hydraulic circuit so as to permit natural lowering of the boom of the side crane under its own weight as well as forcible raising and lowering hydraulically, and also so as to maintain the boom without need of further fluid supply from a pump in its forcibly lowered or lifted state for a long period of time through the trapping of hydraulic fluid within the boom cylinders on both the lifting and lowering sides thereof.

Abstract: A double-acting user has a first and an oppositely acting second pressure-fluid compartment. A source of pressure fluid receives fluid from a fluid reservoir. A first conduit has one section communicating with the first compartment of the user, and another section communicating with the source of pressure fluid. A second conduit communicates with the reservoir. A control valve is interposed in the first conduit and is movable between a first position in which it connects the sections of the first conduit with one another and a second position in which it connects both of the sections of the first conduit with the second conduit. A pressure-reducing and limiting valve has a first port communicating with the second compartment of the user, a second port communicating with the reservoir, a third port communicating with that section of the first conduit which in turn communicates with the source, and a pressure-limiting arrangement which serves to limit the fluid pressure in the second compartment of the user.

Abstract: A hydraulic pressure fluid control system for controlling the displacements of a double-acting servo motor wherein a servo assisting valve mechanism comprises in addition to the control pistons for controlling and maintaining the pressures in the working chambers of the servo motor and the coil springs which place a predetermined minimum force to act on the pistons, spring retainers and further coil springs concentric and codirectional with the first coil springs arranged such that upon a movement of the input member of the system, a predetermined threshold force must be met before the input member directly couples with and controls the movements of the control pistons, the biasing of the coil springs and the further coil springs establishing the threshold value.

Abstract: The steering wheel controlled valve operator in a fluid power steering system, is mechanically held in a neutral position by centering springs associated with fluid pressure controlled reaction pistons yieldably resisting movement of the control valve by the valve operator. Check valves opened in response to suction pressure, conduct fluid in by-pass relation to the control valve between a servo motor chamber and a return fluid line, the control valve connecting both servo motor chambers to the return line in the neutral position.