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 control motor for a servo valve which includes pole screws defining an armature space, first and second coils supported by the pole screws, respectively, a soft metal armature which is resiliently mounted to a thin walled tube and a permanent magnet which polarizes the armature. An annular body carrying said pole screws and providing for a magnetic path between the pole screws and the permanent magnet.

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 servovalve includes a flow-control valve connectable between a source of fluid pressure and a load and having a spool displaceable between an open position permitting fluid flow between the load and the source and a closed position axially offset therefrom and blocking such flow. A pilot valve has an impact plate and a pair of nozzles operatively axially oppositely effective on the spool and oppositely flanking the plate. Thus when the plate is closer to one of the nozzles than to the other the spool is axially displaced into one of its positions and when the plate is closer to the other nozzle the spool is urged axially oppositely. A solenoid-type servomotor is connected to the impact plate to move same between the nozzles so that when it is close to one nozzle it blocks flow therefrom and allows pressure to build up on the corresponding end of the spool, while the other nozzle is opened to reduce pressure at the corresponding spool end.

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 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.