Patent GB-605152-A (GB)
Title: Improvements in or relating to automatic telephone or like selectors
IPC: H01H63/20
Filed: 1945-12-17
Abstract: 605,152. Automatic exchange switches. ERICSSON TELEPHONES, Ltd., and CROWE, D. C. Dec. 17, 1945, No. 34062. [Class 40 (iv)] An automatic selector switch has a brush carriage moved in one direction by a spring and restored in the opposite direction against the tension of the spring, the movement being controlled through a pinion engaging a rack on the carriage. The carriage 2, Fig. 1, which may carry two sets of wipers 6, 12, turns about a pivot 3 and is urged in the direction of the arrow by a spring 4. When it moves, however, a rack 17 attached to it turns a pinion 16, Fig. 2, and shaft 15, the extent of rotation being determined by the received digits. The shaft 15 carries a sleeve 18 which rotates with it but can slide longitudinally and which is formed with a worm 19 at one end and an abutment 20 at the other. When a tens digit is received, a magnet 30 steps a sliding carriage 23 along the appropriate distance by means of a pawl 28 and ratchet 27, and thereby withdraws a stop 21 from engagement with the abutment 20. The brush carriage is consequently turned by the spring 4, Fig. 1, and as shaft 15, Fig. 2, is rotated by the rack 17 the worm 19 works along the rack 22 until the abutment 20 again reaches the stop 21. The speed of this movement is controlled by a governor 57 and is adjusted so as to lag slightly behind the rate of receipt of the impulses. Each revolution of shaft 15 allows the wipers to pass over ten terminal contacts and thus after receipt of the tens digit the wipers are set at the commencement of the group containing.the desired outlet. The units impulses energize magnet 41 to actuate a feed .pawl 40 and the first impulse steps a detent 39 into mesh with a toothed wheel 36 fixed to shaft 15. At the same time tens magnet 30 is energized to disengage the stop 21 from abutment 20 and leave rotation of the shaft 15 dependent on detent 39. Each subsequent units impulse first advances detent 39 into engagement with a wheel 37 which is capable of an angular displacement of one tooth relative to wheel 36. The shaft 15 therefore rotates a corresponding amount and at the end of each impulse the detent 39 moves back into engagement with the next tooth of wheel 36. Consequently, the shaft 15 is rotated one tooth space of wheel 36 for each impulse after the first and the brushes are stepped forward to the corresponding set of contacts. When the desired contacts are reached, one of magnets 60, 61, Fig. 1, is energized to draw an arcuate member 62, .63 outwards and through push rods 65, 66 to press the wiper blades into engagement with the terminal contacts. Wiper 7 may be constantly in engagement if the switch is required to hunt. When the mechanism is to be restored, release magnets 31, 43, Fig. 2, are energized to lift the retaining and feed pawls 28, 29, 40, 42 and allow the'carriages 23, 38 to return to their original positions, and at the same time to actuate bell-cranks 44, 45 which tilt a frame 47 and lift a pinion into engagement with a constantly rotating crown wheel 50. This drives the shaft 15 in the reverse direction and restores the brush carriage to its original position. When this is reached, the member 18 engages a cranked member 56 and opens contacts 55 to de-energize the magnets 31, 43. A number of switch mechanisms, as shown in Fig. 1, are mounted above each other in a rack with their axes 3 aligned. The bank contact assemblies 67, 68 are hung on arcuate racks and consist of a number of vertically aligned groups as shown in Fig. 4. Each such assembly comprises a series of multipling strips 84 with which the appropriate bank contacts 69 ... 79 in each switch are integrally formed. These are secured on and spaced by an insulating panel 82 and the whole assembly is held between insulating panels 85, 86. Brackets 88 are used for hanging the assembly in position on the rack. If it is required to receive a number of preliminary impulses before the wiper carriage moves, a crank member 54, Fig. 2, may engage a stop on the sleeve member 18 until it is tripped by a stud 89 on carriage 23 at the first impulse of the tens digit. Any desired circuit may be set up over wiper 34 and contacts 35. Provision is made for up to four such preliminary impulses, but if less than this number is to be received, the carriage 23 can be made to hunt until it reaches the fifth contact at which point the member 54 is tripped, ready for receipt of the tens impulses. In a modification of the switch described, the fixed disc or cup of the governor is free to rotate unless held by a magnet energized by contacts operated by member 18. If any tendency then exists for the 'carriage 23 to lag behind the received impulses, the governor is rendered temporarily inffective.