Patent GB-739380-A (GB)
Title: Improvements in or relating to automatic overload electric switches
IPC: H01H73/30
Filed: 1952-08-01
Abstract: 739,380. Automatic circuit-breakers; snap-action switches. IGRANIC ELECTRIC CO., Ltd. Aug. 1,1952 [auk. 3, 1951], No. 19510/52. Class 38 (5). In a switch having a member manually movable to " on " and " off " positions to snap the contacts " on " and " off," movement to the " on " position cocks a biased reset element which remains cocked in spite of further movements of the manual member, the contacts opening independently of the manual member upon overload and the element being released on overload to restore the member to " off '' position. In one form, Figs. 1 and 2, the manual operating member 16 is connected by a compression spring 36 to a contact arm 28 pivoted at 32 to a slider 34 (the biased reset element) and co-operating with a fixed contact 24. The slider 34 has a hole slidably receiving the end 20 of member 16 and is normally retained in its set position, Fig. 1, by a pivoted latch 44 having a tooth 52 engaging a lug 54 on the slider, which is urged upwards by a spring 58 compressed between a lug 60 on slider 34 and a lug 62 on a trigger 56 which is retained in the Fig. 1 position by the tip of a bimetal strip 72. The contacts may ordinarily be opened and closed by movement of knob 18 on member 16 but may be opened on overload, even though the knob is held down. On overload, the strip 72 deflects to the right to release the trigger 56 which is moved down by spring 58, a lug 80 pushing contact arm 28 over-centre to open the contacts. Further, a lug 68 on trigger 56 engages the end 70 of latch 44 which is deflected to release slider 34 which moves upwards taking member 16 and trigger 56 with it to the Fig. 2 position. Depression of knob 18 reengages tooth 52 with slider 34, but trigger 56 is only reset if the strip 72 has returned to its normal position in which case the contacts reclose. If, however, strip 72 has not returned, trigger 56 continuues to move down and the lug 80 holds the contacts open. In a modification, Fig. 6, the trigger 156 is pivoted at 160 and is urged downwardly by a spring 158 against the tip of a bimetal 172 so that when released it moves down and a lug 180 opens the contacts. The slider 134 has a tooth 154 normally engaged by a surface 152 on a plate 133 and has a cam 170 engaged by a part of the trigger, so that downward movement of the trigger causes leftward movement of the tip of slider 134 to disengage 152, 154 and free the slider. Upward movement of operating member 116 raises the trigger 156 by means of a lug 182. In a further modification, Figs. 11 and 14, the trigger 256 is pivoted at 260 and its tip normally engages the end of a bimetal 272. A bolt 255 acted on by a spring 258 is pivoted in a recess 267 in trigger 256 and has a surface 252 normally engaging over a tooth 254 on a slider 234. Downward movement of trigger 256 on release thereof causes leftward sliding movement of bolt 255 to disengage 252, 254 and release the slider. In a further form, Fig. 17, the over-centre spring 36 is replaced by a spring plunger 340 acting on the surface of the contact arm 328 above or below the pivot 330 of the arm, depending on the position of member 316. The trigger is pivoted at 360 and has a lug 344 normally overlying the tip of the slider 334. Release of trigger 356 causes a lug 380 to open the contacts against the action of plunger 340, and slider 334 is released.