GB985179A - Improvements in and relating to electric motor drive arrangements - Google Patents

Abstract

985,179. Control of motors; controllers; camoperated switches. DUNKERMOTOREN PRAZISIONS-KLEINSTMOTOREN-G.m.b.H. Aug. 16, 1961 [Aug. 18, 1960], No. 29518/61. Headings H2B and H2J. In a portable tool, motor 2 drives output shaft 5 through shaft 2a, threaded spindle 4, nut 6, and spring-plates 5a, and, if the output torque becomes excessive, nut 6 rotates relatively to the spindle 4 and moves thereon in the axial direction, sleeve 7 being carried therewith and spring 8, 9 compressed. Resilient arm 10a enters groove 7b to open contacts 10 in series with the motor. Simultaneously, detent 14a engages groove 7c to prevent return movement of the sleeve 7 until push-button 12 is released. When the motor has stopped, the nut 6 is returned to its initial position by the spring 8, and, when the push-button 12 is released to open contacts 13 in series with the motor, sleeve 7 returns to its orginal position to re-close contacts 10. It is therefore necessary to re-actuate the pushbutton 12 before the motor 2 can again be placed in operation. The transmissible torque is adjusted by displacing arm 10a axially in relation to the groove 7b. This is effected by means of threaded collar 15 engaging slide 11 which supports arm 10a and detent spring 14. In another arrangement, a single switch 40 serves both for normal on-off control of the motor and for disconnecting it when the torque becomes excessive. Thus, when excessive torque causes the nut to move relatively to the spindle, flange 6c engages sleeve 7 so that projection 44a passes from peripheral portion 7a on to portion 7b. Lever 44 turns to open contacts 40 whereby the nut is spring-returned to its initial position. The sleeve 7 is held, however, by engagement of projection 44a with edge 7c until pushbutton 52 is released and levers 44, 50, are spring-returned to their original positions. Axial displacement of slide 39 effects adjustment of the transmissible torque.