GB1452589A - Circuit breaker with handle indicating means - Google Patents

Abstract

1452589 Automatic circuit breakers WESTINGHOUSE ELECTRIC CORP 18 Nov 1974 [28 Nov 1973] 49743/74 Heading H1N A circuit breaker, shown closed in Fig.1, cannot be reset after tripping if the contacts have failed to open, e.g. because of welding, and the position of the handle always gives a true indication of the position of the contacts. For normal operation a projection 33 on the handle 35 engages in a depression on a movable contact arm 29 and an over centre spring 43 maintains tension between the arm and a cradle member 41 which is pivoted on a post 42 at its one end and is latched at 73, 71 at its other end. The cradle member must be latched before the breaker can be closed but an overcurrent acting on a combined thermal and magnetic trip means 25 can release the latch to open the breaker automatically whereupon the handle 35 assumes the intermediate position of Fig.3 and the latch can then be reset by moving the handle towards and beyond the OFF position of Fig.2 (not shown). If the contacts are welded when the breaker is automatically tripped a projecting tab 81 on the cradle member 41 first strikes the contact arm 29 in an attempt to break the weld, failing which the tab lodges against a recess 85 on the arm 29 to block any further movement and following any attempt to relatch the mechanism, Fig.5 (not shown), merely results in the handle 35 restoring to the contacts closed position under the action of the spring 43, Fig.4 (not shown).