GB1277224A - Electric switch mechanisms - Google Patents

Abstract

1277224 Automatic circuit breaker SIEMENS AG 25 Sept 1969 [25 Sept 1968] 47356/69 Heading H1N The linkage of an automatic circuit breaker is arranged so that the moment of the force acting on a pivoted latched lever 13 remains substantially constant from the time the contacts first engage. A handle 1 forms a toggle with a link 10, being moved overcentre into engagement with a stop 3 to close the contacts 4, 5. The lower end of the link 10 is coupled to a pivoted contact lever 6 by link 11 and to a pivoted latched lever 13 by link 19. In the open position (Fig. 2) link 19 lies above pivot 17 of the latched lever 13 so that opening spring 8 acts, through the linkage, to bias the lever 13 anticlockwise against a stop 18; this allows the latch to return to its retaining position. When handle 1 is moved towards the closed position (Fig. 1) joint 20 moves downwards past pivot 17 so that the moment of force on latched lever 13 is reversed bringing it into engagement with the latch 12. When the contacts first engage the force on the lever 13 increases abruptly and thereafter falls as the linkage 10, 11 moves towards the straight position. Since the joint 20 is still moving downwards, however, the lever arm is increasing and therefore the moment of the force remains substantially constant as does the pressure at the latch. Upon overload an electromagnet (not shown) is de-energized to release an armature 22 which strikes an arm 15 of the latch to release it. Lever 13 then turns clockwise allowing joint 20 to move to the left to release the toggle 1, 10. The springs return the mechanism and operating handle 1 to the condition of Fig. 2 automatically.