Abstract: A pilot operated pressure relief valve unit has a main valve having a main piston movable between two control spaces interconnected by a passage provided with a nozzle; one of the control spaces is constituted by two separate control chambers delimited by corresponding areas of the main piston whereby one of the chambers is directly connected to the pilot valve and the other control chamber is connected to the pilot valve via a nozzle.

Abstract: A radial piston pump has a housing bounding a suction chamber therein and provided with a plurality of pressure ports spaced from one another in circumferential direction of this housing, and with at least one suction port. A plurality of valve units spaced from one another in the circumferential direction of this housing are provided, each of which includes a pressure valve element located in a respective one of the pressure ports and a sleeve member mounted in the same pressure port radially outwardly of the pressure valve element so as to form, together with the latter, a pressure chamber inwardly of and communicating with the pressure port. A plurality of circumferentially extending channels are formed in this housing and intersect the respective pressure chambers.

Abstract: An electrode-position control for arc furnaces includes a hydraulic cylinder-and-piston unit 1 having a cylinder chamber 43 and a piston 1 connectable with an electrode 4 to be moved; a control valve 8; a first pressure conduit 14, 15 which connects the control valve 8 with a source of pressure fluid, and a working conduit 17, 18 which connects the valve 8 with the chamber 43; a pre-selectable two-way valve 5, 6 in each of the conduits 14, 15; 17, 18 a second pressure conduit 34, 33, 17, 42 connecting the chamber 43 directly with the source; and a pre-selectable two-way valve 7 arranged in the second pressure conduit 34, 33, 17, 42 in parallel to the control valve 8, the valve 7 being closed when the valves 5, 6 are open, and vice versa.

Abstract: A radial piston pump comprises a housing bounding a suction chamber therein and at least one valve piston unit mounted in the housing. The valve piston unit includes a pressure valve defining a pressure chamber, a movable piston having an axial passage operatively communicating the suction chamber with the pressure chamber, and a suction valve located in the axial passage of the piston. The suction valve is operative for opening and closing the axial passage of the piston so as to establish and interrupt the above communication, respectively. The piston performs a suction stroke and a working stroke, and a valve member of the suction valve is open during the suction stroke of the piston. The valve member has such a mass that it is opened by an accelerative force produced during the above suction stroke of the piston. The piston is moved by an eccentric mounted on a rotatable shaft, which eccentric has a circumferential groove operatively communicating the suction chamber with the axial passage of the piston.

Abstract: A gerotor machine has a housing and a displacement unit in the housing. The displacement unit includes an inner gear wheel rotatable about an axis, and an outer gear wheel which has an axis circularly displaceable about the axis of rotation of the inner gear wheel. The gear wheels bound a plurality of displacement chambers therebetween. A plurality of recesses are formed between the teeth of one of the gear wheels, and each of the recesses has two circumferentially spaced control edges at one axial end of the one gear. The housing is provided with a plurality of control openings which are located relative to the axis of the one gear at a radial distance corresponding to that of the recesses. The control edges of the recesses of the one gear cooperate with the control openings of the housing and are operative for communicating the control openings with the chambers of the displacement unit.

Abstract: The radial pump preferably for use in connection with a hydraulic clamping device includes a plurality of pumping elements enclosed in a housing and cooperating with a corresponding pluraity of discharge valves. A multiway control valve controls the delivery of pressure fluid to a load port in such a manner that during the actuation of the load the outlet of all discharge valves are united to deliver the entire flow of pressure fluid into the load port, whereas when the load is maintained under a constant pressure, only one pumping element delivers discharged fluid via a single discharge valve into the load port and the remaining pumping elements deliver their output into the reservoir.

Abstract: A hydraulic control arrangement with a feedback device for positioning an implement comprises a positioner including a fluid operated cylinder and piston unit, the piston of which is connected by a plurality of linkage elements to the implement. A first pump delivers through a pressure line fluid under pressure into the cylinder. A two-port three-position valve is interposed in the pressure line movable from a neutral position in which the fluid fed by the first pump is directed to a reservoir, to two operating positions to opposite sides of the neutral position, and in which one of the operating positions fluid fed by the first pump passes into the cylinder and in the other of the operating positions fluid from the cylinder can flow to the reservoir. A pair of pilot chambers are arranged at opposite ends of the valve for moving the latter from the neutral to either of the working positions. A second pump provides fluid under pressure for operating the valve.

Abstract: A radial piston pump has a housing, a shaft mounted for rotation in the housing and including an eccentric provided with a cam track, inlet and outlet ports in the housing, valve means installed in the ports, a plurality of radially reciprocable pistons spaced about the eccentric and each having a radially inner surface in sliding engagement with the cam track, and a layer of synthetic plastic material having a low coefficient of friction on each of the surfaces, so as to reduce friction between the same and the cam track.

Abstract: A flow meter comprises a housing defining a fluid inlet passage and a fluid outlet passage; a piston defining a jacket surface and a base surface is arranged in the housing for reciprocating movement between the two passages; a biasing spring urges the piston into a zero flow position in which the piston interrupts the communication between the two passages; the base surface of the piston faces the inlet passage so that the fluid flow displaces the piston into a flow position; flow distributing means in the form of a partition arranged in the outlet passage has a plurality of slots shaped for adjusting the flow rate between the two passages according to the variation of the spring bias of the moving piston; and an electrical position detector coupled to the piston to generate an electrical signal proportional to the displacement of the piston.

Abstract: A multi-position flow control valve comprises a control piston movable in a boring in two opposite directions. At each end of the boring a pressure chamber is provided accommodating a pressure spring supported on a spring collar that at its end facing the boring has a conical recess. Each recess accommodates a conical projection of a supporting rod that is slidably guided in a blind end bore provided in the control piston. A spring is arranged in the blind end to urge the supporting rod into engagement with the recess in the spring collar. If a pressure fluid is introduced into one pressure chamber, it displaces the piston and compresses the biasing spring in the other pressure chamber whereby the spring biased supporting rods remain in engagement with the recesses in the spring collars.

Abstract: A rotary fluid displacing apparatus operable as pump or motor comprises a housing in which a fluid displacing unit is arranged comprising an annular stator having a plurality of radially inwardly extending teeth and a rotor within the stator and having radially outwardly extending teeth numbering one tooth less than those of the stator, meshing with the teeth of the latter, and forming between the stator and the rotor spaces increasing and decreasing during rotation of the rotor. Flow of fluid into and out of these spaces is controlled by a stationary control plate and a rotary control disc, both of which are formed with a central opening through which a universal-joint shaft extends which, at one end is tiltably connected to a machine shaft mounted in the housing for rotation about a fixed axis.

Abstract: A flow-control valve assembly for connection between a source of fluid under pressure and a fluid-operated load has a main valve and a pilot valve. The main valve defines a continuous flow path having an input end connectable to the source of fluid under pressure and an output end. This valve further has a valve member which defines with the housing of the main valve a plurality of variable flow restrictions, the valve member being displaceable in the main-valve housing between an open position wherein the restrictions are all of maximum flow cross section and a closed position wherein the restrictions are all of minimum flow cross section. A pilot valve has an input side connected to the output end of the continuous flow path through the main valve and an output side connectable to the load.

Abstract: A variable-output pump has an output-adjusting element which is acted upon by a differential piston arrangement having oppositely facing active surfaces of a smaller and of a larger active area. Control fluid is permanently admitted to the smaller active area of the differential piston arrangement to act on the same and urge the output-adjusting element of the pump toward a low-output position. A biasing spring acts against the force of the fluid acting on the smaller surface, and the control fluid is also selectively admitted to the larger surface to urge the adjusting element toward higher outputs. A control slide controls the admission of the control fluid to the larger surface of the differential piston arrangement and has a housing provided with a bore in which a slide is mounted for movement longitudinally of the bore. The slide has an end face acted upon by the control fluid and another end face acted upon by a spring.

Abstract: A fluid machine, particularly a hydraulic pump, has a high pressure side and a low pressure side. A rotor or a pair of cooperating gears are mounted for rotation and have spaced end faces extending transversely of their respective axes of rotation. Walls define at each of these end faces at least one fluid compartment which is open to the respective end face and which communicates via a restricted outflow gap with the low pressure side of the machine, and via a conduit with the high pressure side of the machine. In each conduit a throttle is interposed, and the end faces are subjected from the respective compartments to fluid pressures which permanently tend to equalize with one another, and which therefore tend to axially center the rotor or gears in the event of axial displacement thereof.