Importance

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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. A first control line leads from the second pump to one of the pilot chambers and a fixed throttle cooperating with an operator adjustable throttle is located in the first control line. The arrangement includes also a feedback device comprising a second control line leading from the second pump to the other pilot chamber and a second fixed throttle cooperating with a second adjustable throttle is located in the second contial line. The flow-through cross-section of the second adjustable nozzle is adjusted by engagement with one of the linkage elements.

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First Claim