Arrangement for controlling the speed of a hydraulic motor

Claim 1

In combination with a hydraulic motor having a movable member with a pair of opposite faces to be alternatingly impinged by pressure fluid to move the movable member in one and the opposite direction, a control arrangement for controlling the hydraulic motor comprising a source of pressure fluid; a pair of conduit means for feeding pressure fluid from said source onto said opposite faces, or to discharge pressure fluid therefrom; first valve means interconnected with said conduit means for controlling the direction of movement of said movable member; second valve means interconnected with said conduit means for controlling the speed of the movable member in dependence on the position thereof and comprising a throttle valve in one of said conduit means and having a valve slide movable between a plurality of positions respectively controlling the amount of pressure fluid passing therethrough, a pressure reducing valve upstream of said throttle valve in said one conduit, and a proportional magnet connected to said valve slide for moving the same between the positions thereof; a first inductively operated position transducer connected with said proportional magnet into a feed-back position control circuit; a first electrical control device coordinated with said feedback position control circuit; control means actuated by said movable member for influencing the change of the speed of the latter in dependence on the position thereof, said control means including at least a second inductively operating position transducer for indicating the actual value of displacement of said movable member, said control means forming part of a second feedback circuit.