Patent GB-268897-A (GB)
Title: Improvements relating to the automatic control of electric switches
IPC: H01H75/04
Filed: 1926-01-14
Abstract: 268,897. Pailin, G., and Pailin, Ltd., F. Jan. 14, 1926. Automatic circuit-breakers; protective arrangements.-An automatic overload circuitbreaker of the kind which automatically recloses a pre-adjusted number of times (if the overload does not meanwhile disappear) and thereafter is prevented from further automatic reclosure, ccmprises two mechanical spring relay arrangements (i) that associated with the shaft d, h for determining the time-intervals between which the reclosures shall occur and (ii) that associated with the shaft 4 and including a pawl-andratchet 6, 2 for determining the number of times an auxiliary switch supplying closure current to the circuit-breaker, shall be re-closed on the overload. A rod a associated with the moving parts of the circuit-breaker assumes the position shown in Fig. 3 when the circuit-breaker is in the closed position. When rising to this position a pin f on a lever c loose on the shaft d drives a toothed sector e. This in turn, drives a toothed wheel g on the spindle hand strains a spring v Fig. 1, which, when the rod a descends corresponding to the open position of the switch, slowly drives back the sector e together with a pair of relatively-adjustable cam wheels 32, 27, Figs. 1 and 7, of which 32 serves as an indicating plate, carries a stop 33 and is formed with a recess 34. A projection 28 on the cam wheel 27, when in engagement with a roller 40 on a spring-controlled lever 38, serves to hold the auxiliary control switch (controlled by links connected with the shaft 39) in the off position. When, however, after a time determined by the relative setting of the projection 28 and the recess 34 which rotate together under the action of the spring v, the roller drops into the recess 34, the auxiliary switch is moved to the closed position. The reclosure action is as follows. When the circuit-breaker opens on overload the rod a descends and allows the spring relay, just described, to return the cam parts under retardation produced by a train of wheels o, p, i, Fig. 1, and an escapement. At the same time, the rod a swings the bell-crank lever x, Fig. 3, in a clockwise direction, frees the pawl 6 from a fixed projection 5 so that, under the action of the springs 3, it mav come into driving connection with the ratchet wheel. Consequently, the wheel is driven round through the distance of one tooth and the spring 7 of the second mechanically relay is stressed. Meanwhile, the cam wheels 32, 27 have rotated under the action of the spring v to such a position that the roller 40 has dropped into the slot 34 thereby closing the auxiliary switch and supplying closing current to the circuit-breaker. In closing, again, the rod a rewinds the spring v and lifts the bellcrank lever x so as to free the pawl again, whereupon the ratchet wheel rotates under theactions of the spring 7 and retarded by gearwheels and an escapement, and if the overload goes off for a sufficiently long interval the ratchet wheel will rotate to its initial position. This position is adjustable (to determine the number of reclosures that may take place on a persistant overload) by means of a pin 20 fixed in one or other of a number of holes in an indicating plate 22, Figs. 1 and 7, and engaged by a projection 19 carried on a cam plate 18 fixed on the shaft 4. With persistent overload, the ratchet wheel is notched round step-by-step with each opening movemnt of the circuit-breaker and, after say three reclosures, the cam 18 is rotated sufficiently to bring a recess 50 in it opposite a roller 25 on a spring-controlled three-armed lever 23. The roller thereupon enters the recess and the arm 41 engages the stop projection 33 thereby preventing the cam wheels from returning and preventing the roller 40 from entering the recess 24. Consequently, the current-breaker cannot again be automatically reclosed. It mav be reclosed, however, by hand or distant solenoid control of a lever 43 which positively removes the projection 41 from engagement with the stop 33.