Electro-mechanical remote control for hydraulic gears and pumps

870,516. Electric remote-control systems. DREHMASCHINENWERK LEIPZIG VEB. Aug. 2, 1957, No. 24486/57. Drawings to Specification. Class 40 (1). In an electro-mechanical remote-control system for continuously variable hydraulic pumps or transmissions comprising a shiftable member for varying the delivery volume or output speed, the displacement of this member is effected by a geared servomotor controlled by electric means comprising a master potentiometer and a controlled potentiometer operated by the geared servomotor, the electrical circuit incorporating a two-way centre zone relay in a bridge circuit, and a contactor causing the servomotor to run when the bridge is unbalanced until balance has been restored. The displacement of the shiftable member is effected through a threaded spindle and nut, and a clutch is incorporated in the motor drive shaft and controlled by a hand lever for disengaging the reduction gearing of the servomotor from the motor drive shaft for the purpose of changing over to auxiliary manual control by a hand wheel mounted on the spindle. The controlled potentiometer is preferably driven from the drive shaft through a gear tain, a gear-wheel carrying a scale to provide a dial being directly connected with the controlled potentiometer. The master potentiometer may be housed in a casing separate from the switch box containing the other electrical control elements and be built into a control panel.