GB606279A - Improvements in controllers for reversible electric motors - Google Patents

Abstract

606,279. Controllers; control of motors. DICKINSON, S. Dec. 24, 1946, No. 31897/45. [Class 38(iii)] Continuous reversals; travelling between predetermined limits.-In order to obtain repeated reversals of an electric motor with a time delay between each reversal, a controller is provided comprising a motor-driven screw shaft 5 bearing a nut 13 upon which is resiliently mounted a rod 42 adapted to actuate switches 45 and 46 for stopping the motor when the nut approaches the limits of its travel in either direction. A switch 28 is adapted to re-start the motor and move the nut 13 to the left a predetermined period after the motor has been stopped by the switch 46, and a switch 57 similarly effects restarting of the motor in the reverse direction after stoppage by the switch 45. When the nut 13 moves to the end of its travel, towards the right for example, a cam 37 engages a head 38 of a catch 30 and raises it clear of a bar 34. Substantially at the same time the rod 42 actuates the switch 46. The release of the catch 30 causes a spring 35 to drive a piston 21 towards the right at a rate controlled by the setting of the screw 24, and, after an interval, a rod 26 engages the switch 28. With the nut 13 moving to the left, an arm 39 engages the head 38 and draws the catch and piston assembly back until the catch drops into position on the bar 34. Similar operation obtains when the nut approaches the end of its travel in the left-ward direction. The number of revolutions made by the motor between each reversal may be adjusted by altering the distance between the mountings for the limit switches 45 and 46. The shaft 5 may be coupled to the motor through a clutch which disengages on overload. The limit and reversing switches may be directly connected in the motor circuit, or may control contactors therein.