GB651565A - Improvements in or relating to electro-hydraulic actuators - Google Patents

Abstract

651,565. Control of motors. BRITISH MESSIER. Ltd. Dec. 9, 1948, No. 31933. [Class 38(iii)] [Also in Group XXIX] In a unit comprising a hydraulic jack or other reversible hydraulic apparatus and three pumps, the latter are driven by a reversible compound Direct Current motor M, the reversal of which operates a selector valve to extend or retract the jack, (see Group XXIX). To extend the jack, button 66 is pressed which both releases button 65, and completes a circuit over a limit switch 69, operated through a push rod by the jack, to energize a coil 75 in a reversing relay 63 and so close a three pole swich 76, 77 and 78. One end of the series winding 60 is permanently connected to the positive line and one end of the interpole winding 61 is connected by the switch to the negative line. The armature having in series with it a starting resistance 88 which is " cut out " when coil 87. connected to the negative end of the interpole winding 61 and the armature, is energized. When the jack reaches the limit of its travel it operates switch 69 to de-ener-. gize coil 75 and stop the motor. To retract the jack, button 65 is pressed and both automatically releases button 66 and energizes a coil 93 to close another three pole switch to reverse the direction of current through the armature and interpole winding 61 to reverse the motor, which upon completion of the jack stroke is stopped upon operation of another limit switch 68.