Patent GB-349081-A (GB)
Title: Improvements in or relating to traffic control signals
IPC: G08G1/082
Filed: 1930-02-20
Abstract: 349,081. Road-traffic signalling systems. AUTOMATIC TELEPHONE MANUFACTURING CO., Ltd., Strowger Works, SMITH, S. R., Rock House, Old Swan, both in Liverpool, PREIST, T. P., 104, Deveroux Drive, Poulton, Wallasey, Cheshire, and SAXBY, R. N., 36, Millersdale Road, Mossley Hill, Liverpool. Feb. 20, 1930, No. 5723. [Class 118 (ii).] In a traffic control system employing stepby-step mechanisms at a plurality of signalling points operated in synchronism by impulses from a control station, a synchronizing signal is sent to all the mechanisms at predetermined intervals to cause them to take up corresponding positions so that if any box is out of step it is restored automatically to correct setting. The individual stepby-step mechanisms may be operated manually. The control box CIP comprises a motor M driving a commutator 10 one segment of which is connected directly to earth the others being connected to earth through a resistance so that once during each revolution of the commutator an increased current impulse will flow over the control lead 11 common to all the signalling stations. The electrical impulses over line 11 are insufficient to operate the marginal relay MG but operate an impulsing relay IP, closing a circuit over contacts ip1, mg2 for the driving magnet STM which steps its wipers 1a .. 5a accordingly. The banks 1a .. 4a are multipled to the banks 1b .. 4b of a manually set switch MOS, the position of the wipers 1b .. 4b being indicated by semicircular plates 13 .. 16, Fig. 4, mounted on sleeve shafts integral with the corresponding wipers and giving a representation of the relative times of illumination of the various signals controlled thereby. Operation. When the wiper 1a reaches the marked contact in the bank 1b a relay A operates, locks up over contacts a1 b2 and operates over contacts a3, a4, the red main-road lamp RM, and the common amber lamp AM respectively. When wiper 2a reaches the marked contact in bank 2b, relay B operates, locks up over contacts b1, c2, lights the green main-road lamp GM over contacts b3 and the red cross-road lamp RC over contacts b4 and releases relay A to extinguish lamps RM, AM. Wiper 3a similarly causes relay C to operate and lock up over contacts c1, d2, release relay B, and operate over contacts c3, c4 respectively, the red cross-road lamp RC and the amber lamp AM. Operation of relay D similarly illuminates the green cross-road lamp GC over contact d3 and the red main-road lamp RM, the subsequent operation of relay A releasing relay D to recommence the cycle. At the completion of a revolution of the commutator 10 corresponding to one-half a revolution of the stepping switch 1a .. 5a the increased impulse over the line 11 operates the marginal relay MG in series with IP opening the normal impulsing circuit at contacts mg2. A relay HR is energized over contacts mg1 and the bank 5a and interacts with the driving magnet STM to home its associate wipers should they not already be there. The phase difference between each signalling station is effected by rotating the plates 13 .. 16 and the fixed plate 17, Fig. 4, for each station as a whole, so that the duration of each signal in a cycle is constant for all stations. Manual operation. A switch HC rotated by hand will energize the relays A .. D consecutively, the impulsing circuit and the marking circuits over wipers 1b .. 4b being broken at the contacts HC1, HC2 of the switch HC. For use with alternating current a full wave metal rectifier at the control station supplies the current for the impulsing circuits, a full wave metal rectifier at each signalling station providing the current for the controlling relays and driving magnets. For the homing circuits a half-wave rectifier is used, the resultant impulses at mains frequency being used to step the switches to home position. The impulsing device may be provided with interrupted springs operated consecutively by cams. For a slow stepping period of the switches 1a .. 5a the impulsing circuit would be connected over one pair of interrupted springs, and for faster stepping the line 11 would be connected over two or more interrupted springs in series, different combinations of interrupted springs enabling various speeds to be obtained. The stepping switches are immersed in oil and the relay contacts controlling the lamp circuits may be constructed as mercury switches of the enclosed bulb type.