Patent GB-378928-A (GB)
Title: Improvements in or relating to electric selective relays
IPC: G08C19/20
Filed: 1931-04-20
Abstract: 378,928. Electric selectors. WHITBY, E., 33, Cropthorne Court, Maida Vale, London, PEDLER, I. A. D., 5, Hampstead Road, Brislington, SELSTON, E. J., York House, Morley Road, Staple Hill, both in Bristol, LESTER, L. R., Rest Harrow, Old Bracknell, Berkshire, and NEWMAN, A. J., Northacre, Stoke Hill, Stoke Bishop, Bristol. April 20, 1931, No. 11692. [Class 40 (iv).] A selector for use in an electric remote control system in which current impulses cause the stepping round of a multicontact electromagnetic switch at the receiving station to a position corresponding to the number of impulses received, is arranged so that after this position has been reached a setting-back member momentarily closes a contact device arranged in series with the closed contacts of the selected circuit, the continued motion of the setting-back member then returning the rotary member of the selective relay to its normal position of rest. As shown in the Figure, current impulses received in the electromagnet 33 cause the attraction of the armature 2 and the stepping round of the rotary member 10 by means of a pawl 4 eangaging ratchet plate 3. The contact arm 12 carried by the plate 10 is then moved into engagement with a selected contact of a series 13 in accordance with the number of current impulses received in the electromagnet 33. Immediately the member 10 commenced to move contacts 14 were brought into engagement by the insulating projection 17 attached to the upper contact being raised out of the recess 8 in the periphery of the plate 10 and the circuit of a motor 23 completed, the motor 23 driving a setting-back member 26 on a plate 24 through gearing 20, 21, 22. The setting-back disc 24 is arranged to rotate at a considerably slower speed than the impulse-driven selecting disc 10 so that the latter has time to reach the selected contact 13 to prepare a selected circuit such as 32, 321 or 3211 which is completed by contacts 28 which are closed for a short time as a cam projection 25 on the setting-back disc engages an insulating projection 30 carried by the upper contact blade 28. The continued motion of the disc 24 causes the arm 26 to engage behind an arm 9 on the disc 10 to carry this disc round to the normal position shown in which position the circuit of the motor 23 is broken at contacts 14. If desired, arrangements may be made to accelerate the motor 23 after the engagement of the contacts 28 in order that the apparatus may be quickly restored to its normal position in readiness for a subsequent operation. To prevent incorrect operation by fault impulses the disc 10 has to be moved through an angle # before reaching the first of the contacts 13 and the angle alpha through which the disc 24 turns before engaging contacts 28 is made smaller so that in the case of one or even of a small number of fault impulses the apparatus is restored to normal without completing any circuit. The contacts 13 are made wide enough to cover a number, for example, three, steps of the ratchet so that a desired switching operation may be effected even with one impulse less or more than the required number.