GB679232A - Improvements in or relating to free tripping overload electric switches - Google Patents

Abstract

679,232. Automatic circuit-breakers. IGRANIC ELECTRIC CO., Ltd. June 27, 1950. [June 27, 1949] No. 16034/50. Class 38 (v). A free-tripping, overload-responsive switch has a rectilinearly-movable element which when released moves the pivots of a contact-carrying switch member to open the contacts. The switch has a fixed contact 11 and a moving contact on the switch member 14 which is pivoted at 14a to the rectilinearly-movable element 15. The latter is biased downwardly by a spring 16 but is normally held in its uppermost position, Fig. 2, by a current-carrying bimetal strip 18, the free end of which engages a portion 15d of the element 15. The free end of the member 14 is connected by a snap-acting, over-centre spring 25 to an arm 23c on a toggle member 23 which is pivoted at 23b. The switch is closed by moving the operating lever 24 to the dottedline position, Fig. 2, the forked end 24a of the lever which engages a pin 28 on the member 23, turning the member 23 clockwise about its pivots 23b to move the arm 23c down to a position where the spring 25 snaps over-centre and causes the free end of the switch member 14 to move down to close the contacts. If an overload occurs, the bimetal strip distorts, releasing the element 15, which moves downwardly carrying with it the pivoted end of the member 14. The member 14 strikes against projections 10c on the walls of the switch housing 10, causing it to move into the tripped position, Fig. 3. The member 23 is now relieved of much of the tension of the spring 25, so that a light spring 29 is able to move the member 23 into the position of Fig. 3 where the lever 24 is in a central position indicating that the switch has tripped, and a projection 23d of the member 23 abuts the underside of an extension 15c of the element 15. To reset the switch, the lever 24 is restored to the "off" position shown in full lines in Fig. 2. This movement of the lever 24 turns the member 23 anticlockwise about its pivot 23b so that the projection 23d moves the element 15 up to the position where it is latched by the strip 18, the contacts remaining open during this operation. The projections 10c are so situated in relation to the pivots 14a in their lower position, that retention of the lever 24 in the "on" position does not prevent the tripping of the switch. The switch is opened manually by moving the lever 24 to its "off" position, so moving the spring 25 over-centre to open the contacts. The operating lever 24 may be provided with a dust boot 30. The bracket 18b supporting the bimetal strip 18 has an arm 18c engaged by a screw 21 for current-setting purposes.