Patent GB-456781-A (GB)
Title: Improvements relating to railway traffic controlling apparatus
IPC: B61L3/22
Filed: 1935-09-11
Abstract: 456,781. Railway signalling systems. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd., 82, York Road, King's Cross, London.- (Assignees of Failor, C. W. ; 107, Elmore Road, Forest Hills Borough. Pennsylvania, U.S.A.) Sept. 11, 1935, No. 25261. Convention date, Sept. 12, 1934. [Class 105] A railway signalling system with wayside or cab signals controlled in accordance with ahead traffic conditions by code current in the rails has codes consisting of cycles comprising one or more time intervals of current supply separated by a time interval or intervals of non-supply and the codes are made distinctive by the duration of the cycle, the intervals of supply, and the intervals of non-supply, all being varied ; the decoding means is responsive to the intervals both of supply and non-supply and assumes a signal-determining condition which is maintained so long as the code persists. Fig. 3 shows a wayside signal control system in which four codes are used for the control of such signals and a further code, not effecting any change in the wayside signals or in the code applied to rear sections, is used to cancel a level-crossing signal as soon as the train has passed the crossing. The section with the level-crossing is formed as a cut section with the code repeated at the cut point e<1> save when the further part-section e<1> f is occupied. The track-circuit feed of adjacent sections is of opposite polarity so that a breakdown of the insulation between two sections prevents the track relay being wrongly held up (closing its normal contact) by the current of an adjacent section. The track relays such as TR follow the code and by means of slow-release decoding relays TP, TPA, H, HA effect the lighting of different lamps in the signals such as Se and the application of a less restrictive code to the rear section. When a train is in the first portion e e<1> of the cut section, the track relay TR remains de-energized and its back contact 12 maintains relay TPA energized and relay TP de-energized. The relays H, HA, are therefore de-energized and in turn therefore the signal control relays D, DD, DDD are deenergized. The relays D, DD have repeater relays DP, DDP which are also therefore de-energized. Accordingly, the signal S<e> gives an RR indication by the upper and lower lamps R being lit respectively over back contacts 29, 31 and 32, 34 of the relays DP, DDP. The level crossing signal came into action when its relay XR was de-energized by reason of the front contact 24 of the relay H being opened. The back contacts 38, 36 of relays DP, DDP apply code 2 to the section at the rear of point e over the coding contact 2 of the continuously operating code motor CT. When the train is in the exit portion e<1> f of the cut section, the relay TR<1> is de-energized thereby de-energizing the relays TP<1>, TPA<1> so that back contacts 21, 19 of the relay TPA<1> respectively energize a code motor CT<1> and apply a code 1 from the coding contact 1 to the rear portion e e<1> of the cut section. This code 1 consists of short " on " and " off current intervals so that the track relay TR oscillates and energizes both the slow relays TP, TPA which therefore remain up and thus the relay H is energized to close its contact 24 thereby energizing the relay XR to cancel the level-crossing signal. Since the relays D, DD, DDD remain de-energized there is no change at the signal Se nor in the code applied to the section at the rear of point e. When the train has left the cut section e f and entered the ahead section, the action is to apply code 2 to the feed end f of the section e f and thus the intermediate track relay TR<1> oscillates so energizing the slow relays TP<1>, TPA<1> which remain up and thereby cause the code to be repeated over the front contact 12 of the relay TR<1> and the front contact 19 of the relay TPA<1>. This repeated code causes the track relay TR to oscillate and as this code 2 has a short " on " and a long " off " interval, the relay TP will drop during the long interval and therefore its contact 23 will oscillate. The oscillations of the contact 23 will energize the relay H and the relay D (the latter over front contact 41 of relay H). Accordingly, the signal Se gives a YR indication by the lighting of upper lamp Y over front contact 29 of relay DP, front contact 44 of relay D, and back contact 46 of relay DDP, and by the lighting of the lower lamp R over front contact 32 of relay DP, front contact 50 of relay D, and back contact 52 of relay DDP. Code 3 given by contact 3 of the code motor CT is now applied to the rear section over back contact 56 of relay DDP and front contact 38 of relay DP. Thus, as the train progresses, codes 3, 4 and 5 will in turn be applied to the section e f. Code 3 has long " on " and short " off " intervals and thus relay TPA will drop during the long " on " interval so that its contact 58 oscillates and thereby energizes the relays HA, DD. Relay D drops since the armature 23 of relay TP no longer oscillates. Accordingly, the signal S<e> gives a YY indication, the upper lamp Y being lit over back contact 29 of relay DP and front contact 31 of relay DDP, and the lower lamp Y being lit over back contact 32 of relay DP and front contact 34 of relay DDP. Code 4 consists of long " on " and long " off " intervals and therefore the armatures 23, 58 of the two relays TP, TPA will oscillate thereby energizing the relays H, D, HA, DD. Accordingly, the signal Se gives a GY indication, the upper lamp G being lit over front contacts 29, 44, 46, 68 of relays DP, D, DDP, DD, and the lower lamp Y being lit over front contacts 32, 50, 52 of relays DP, D, DDP, and back contact 71 of relay DDD. Code 5 consists of a long " on," a short " off," a short " on," and a long off " interval. The relay TPA will not drop during the short " on " interval and thus remains up for the total time of the short " off," the short " on " and the long " off intervals (it of course drops during the long on " interval) ; thus the relay TPA remains up sufficiently long for the relay HA to drop and therefore this relay HA oscillates and therefore the relay DDD is energized (over front contact 99 of relay DD). Accordingly, the signal S<e> gives a GG indication, the upper lamp G being lit over front contacts 29, 44, 46, 68 of relays DP, D, DDP, DD and the lower lamp G being lit over front contacts 32, 50, 52, 71 of relays DP, D, DDP, DDD. Cab signals may be given by a similar arrange ment of de-coding relays operated by a codefollowing relay which is energized by the rail current through inductor collector windings and an amplifier. The track-circuit current may be an alternating or direct current and the cancellation of the level-crossing signal may be effected by the presence of sustained (uncoded) current in the track circuit of the rear portion of the cut section such sustained current being applied over a back contact of a slow-acting track-relay repeater relay TP<1>, Fig. 8 (not shown), of the further portion of the cut section. The repeating of the code at the cut point is effected by the oscillating armature of the track relay and is applied over a front contact of the trackrelay repeater relay. Slow pick-up relays may be used thereby avoiding the use of the oscillating armatures in the de-coding relays.