Patent GB-323893-A (GB)
Title: Improvements relating to selecting switches such as used in automatic telephone systems
IPC: H01H67/12
Filed: 1928-12-14
Abstract: 323,893. Siemens Bros. & Co., Ltd., Petithory, E. A., and Forceville, E. A. Dec. 14, 1928. Automatic exchange selectors.-In a co-ordinate selector having a movable carriage and a wiper carrier transversely movable thereon, the carriage is moved by the action of an electromagnet on a ratchet which engages a projection on the carriage, whilst the wiper carrier is moved by a magnet mounted on the switch base with an elongated armature capable of engaging a ratchet carried by the wiper carrier in all positions of the carriage. Figs. 2 and 3 illustrate such a switch set and restored by ratchet drive, whilst the. switch in Figs. 8 and 9 is returned to normal by a spring. A bare-wire multiple is employed, arranged in breadth and depth. The carriage 4 in Figs. 2 and 3 is moved by the action of magnet 13 on a ratchet bar 6 (Fig. 5) which is bent over at 6<a> (Fig. 3) and during the initial movement is held by spring 8 so that its lower side (Fig. 5) engages with a projection 5 of the carriage 4. The first series of impulses operate magnet 13 and at each energization link 11 moves bar 6 to the right, allowing one of its teeth to slide over the projection 5. When 13 de-energizes bar 6 is pulled back by spring 35 and carries the carriage one division, over-movement being prevented by pins 29 acting against stops 30. A spring-pressed roller 32 engages semicircular grooves 36 cut in guide bar 2 and prevents the carriage being returned as bar 6 is moved to the right on the energizations of 13. The next train of impulses energizes magnet 15, and armature 16 which runs the whole breadth of the switch engages with groove 41 to move the pawl 18<a>, taking the wiper carrier 14 into the multiple bank. At the first step off normal a stop passes into slot 28 on bar 2 to prevent motion of the carriage whilst the wipers are in the bank. Backward movement of 14 with 18<a> is prevented by roller 34. When the connection is released magnet 10 operates throwing over with its armature extension 21 the pawl so that end 18b engages rack 14 (instead of 18<a>) and moving spring 8 so that the upper side of ratchet bar 6 (Fig. 5) engages the projection 5. The circuit of magnet 15 is intermittently made and at each de-energization the rack 14 is moved by pawl 18<b> one step out of the multiple, roller 34 preventing riding back with the pawl as before. -When the carrier is in its normal position, the stop is removed from slot 28 and the circuit of 13 is intermittently made. Rack 6 interacts with projection 5 and at each energization of 13 steps the carriage back one division, riding back of the carriage with the rack being prevented by roller 32 as before. When the carriage reaches normal, magnet 10 de-energizes, leaving the switch ready for further use. Figs. 8 and 9 illustrate a spring-returned switch. The primary movement is completed by the interaction of magnet 22 with rack 24, the rack being returned to normal after every pulse by spring 28. Three such racks are provided, one of which faces in the direction opposite to 24 and all three are pivoted about 25. The two racks without lateral movement act as holding and stopping pawls respectively. Secondary movement is effected by armature 17 of magnet 18 acting on pawl 10, groove 16 being cut in the pawl to allow 17 to engage the pawl in all positions of the carriage as before. Over-stepping is prevented by stop 21 and riding-back by pawl 9. During both setting movements the band 6 unwinds from drum 8 and winds up a spring enclosed therein. When the connection is released magnet 34 pulls up, removing the pawl. 9 from the wiper carrier by the action of its armature extension 13 on pawl extension 12 and withdrawing by its armature 33 the three toothed racks out of engagement with the carriage. The wiper carrier restores and on reaching its normal position is unlocked as before from the guide bars 3, 3<b> along which the carriage is pulled into its normal position. Specifications 262,207 and 322,652 are referred to.