GB788007A - Motorised drives for screw-operated valves - Google Patents

Abstract

788,007. Control of motors. FIRKINS, Ltd., G. & A., and FIRKINS, G. A. March 12, 1956 [March 12,1955], No. 7296/55. Class 38 (3). [Also in Group XXIX] An axially movable valve actuating spindle has a motor drive, the circuit of which includes two limit switches which operate to stop the motor at the ends of the spindle movement. In one example, Fig. 1, a motor 16 drives through a reduction gear-box 19 a pinion 20 which meshes with the toothed periphery of an actuating nut 21 which engages an external thread on a rotatable but axially fixed sleeve 22 the internal thread of which engages a complementary screw-thread on the valve actuating spindle 10. In operation the actuating nut 21 is held by opposed helical springs 27, 28 between contacts 17, 18 of limit switches in the circuit of the motor 16 and the sleeve 22 effects axial movement of the spindle 10. When the spindle 10 reaches the end of its travel the sleeve 22 is locked and the nut 21 moves axially against one or other of the springs 27, 28 and operates the appropriate limit switch contact 17 or 18 to stop the motor. In another example, Fig. 2 (not shown), only one of the limit switch contacts is operated by the actuating nut which is biased by a helical spring away from a plunger which actuates said contact. The other limit switch contact is operated by a plunger controlled by a crosshead fixed to the actuating spindle.