Patent GB-570134-A (GB)
Title: Improvements relating to railway signalling apparatus
IPC: B61L23/16
Filed: 1941-01-23
Abstract: 570,134. Railway signalling systems. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. Jan. 23, 1941, No. 919. Convention date, Aug. 16, 1940. [Class 105] In a track-circuit railway signalling system for traffic movement in either direction over a single stretch of track, in order that, inter alia, the same apparatus may function for both directions the relays serving as a code repeating relay, a track relay, an approach impulse transmitting relay, and an approach impulse receiving relay for one direction interchange functions so as to operate respectively as the approach impulse transmitting relay, the approach impulse receiving relay, the code repeating relay, and the track relay for the other direction, this interchange of functions being controlled by a direction selector relay operated in known manner. The invention may be applied to the control of wayside signals but is described as giving cab signals in a system having track circuits normally energized by the usual coded track current, but becoming energized with train control code on the approach of a train. Figs. 1a, 1b show identical arrangements at the ends of an insulated track section DE at which wayside signals, shown dotted, would be situated if used. The apparatus is shown in normal condition for east-bound traffic. The various relays are distinguished at the righthand end of the section by prefix 2 or by suffix E replacing suffix D used on Fig. 1a. The direction selector relays DS have neutral contacts 2, 10, 26 and polar contacts 1, 14, 11, 25 moved to the left or normal position for,eastbound, and to the right or reverse position for west-bound frame. Relays DSEM, DSWM repeat, respectively, the normal and reverse positions of relays DS, the circuits of each between source terminals 13, C including a back contact 3 or 4 of the other, neutral contact 2, and polar contact 1 in its normal or reverse position as the case may be. Relay TRD, Fig. 1a, acts as the usual code following track relay for east-bound traffic. Code impulses are supplied to the right-hand end of section DE from a track battery TB under control of front contact 5 of relay 2CR which acts as a coderepeating relay repeating the operation of code transmitter CT180 or CT75 depending on whether decoding relay HE is energized or de-energized as determined by traffic conditions. 180 code is supplied from source terminal B over contact 39 of transmitter CT180 and front contact 41 of relay HE, and 75 code is supplied over contact 46 of transmitter CT75 and back contact 41, the circuit in each case being completed over front contact 44 of relay 2DSEM, wire 45 and relay 2CR to terminal C. The circuit of battery TB includes the secondary of transformer 2TT which, under proper conditions, supplies A.C. impulses coded over contact 5. For east-bound traffic, however, primary winding of transformer 2TT is normally, short-circuited over front contacts 31 of relay 2DSEM and 29 of a relay 2TP. For west-bound trallic this short-circuiting is effected by back contact 31 alone. Relay TRD follows the code, its contact 7 changing the input pole of current supplied to the primary winding of transformer DTD from source terminal B over contacts 10, 11 of relay DS. Transformer DTD has two output windings 8, 9. Contact 13 rectifies the output of winding 9 which is used to energize relay HD. Impulses from winding 8 pass over contact 18 of relay DSEM to relay CRD which operates its contact 20 at code rate and functions as an approach code impulse transmitter as described below. Relay CRD is of polarized direct-current type closing its front contact. 20a when normal current is supplied and its back contact 20b when supplied with reverse current. Arrangement is made so that normal current is supplied when relay TRD is de-energized and contact 7 is down. Thus, when contact 5 of relay 2CR is down contact 20 of relay CRD is up, and vice versa. Front contact 20 thus sends coded impulses from a battery TB to the track, the circuit including the secondary of transformer TTD which, under proper conditions, supplies coded A.C. impulses. As shown, however, the primary of transformer TTD is short-circuited over back contact 21. of relay DSWM. Relay 2TR follows this code and its contacts 15, 16 can, for west-bound traffic, effect control of transformer DTE similar to the control effected by contacts 7,. 13 respectively for east-bound traffic. With contact 11 in normal position shown for east-bound traffic, contacts 15, 16 are, however, ineffective. Relay 2TP (similar to 1TP) is a slow-release repeater of front contact 22 of relay 2TR for east-bound traffic or front contact 23 of relay TRE for west-bound traffic, the circuit of relay 2TP including contacts 25, 26 of relay 2DS. Relay 2TP is thus normally maintained energized for east-bound and west-bound traffic by the operation of relays 2TR, TRE respectively, and de-energizes when relay 2TR or TRE as the case may be is de-energized by occupation of the corresponding track section. For east-bound traffic contact 35 of relay 2TP is without function since its connection with the primary winding of transformer TTE is broken at contact 21 of relay 2DSWM. For west-bound traffic front contact 35 is included in series with front contact 21 in the normal short-circuit of that primary winding, whilst back contact 35 connects terminal BX of A.C. source BX, CX to said winding. Similarly, contact 29 of relay 2TP has no function for west-bound traffic since its' connection with the primary winding of relay 2TT is broken at contact 31 of relay 2DSEM, but for east-bound traffic as shown front contact 29 is included in the short-circuit of said primary winding, whilst back contact 29 connects source terminal BX with the winding over front contact 31. With the track sections unoccupied and the apparatus set as shown, each section is receiving 180 code at the right-hand end via contact 5 of its code-repeating relay 1CR, 2CR, the code being followed by its track relay' (TRD, TRE) and approach control code of the same frequency at its left-hand end via contact 20 of its approach impulse transmitting relay CRD, CRE, the decoding relays HD, HE being consequently picked up. The approach code is followed by its approach impulse receiving relay (1TR, 2TR) and the repeating relay (1TP, 2TP) is consequently held picked up by the periodic closing of contact 22. An east-bound train entering the section to the left of section DE de-energizes relay 1TR releasing relay 1TP and supplying A.C. to the primary of transformer 1TT. This A.C. is transformed to control code by contact 5 of relay 1CR which continues to operate at 180 rate. This control code operates train-carried receiving apparatus to give a "clear" signal. When section DE becomes occupied relay TRD de-energizes, de-energizing relay HD and also relay 2TR which in turn releases relay 2TP. Release of relay 2TP' supplies A.C. to transformer 2TT from which code control impulses are supplied to the exit. end of the section over contact 5 of relay 2CR. If the section to the right of section DE be unoccupied, code is supplied at 180 rate. and a "clear", cab signal is given. If, however, the section be occupied, relay HE will be released by release of relay TRE and the code is supplied at 75 rate, giving a "caution" cab signal. When the sections are cleared, the apparatus returns to the normal condition shown. The functioning of the system for west-bound traffic is also described. For this, the right-hand position of the polar contacts of relays DS, with consequent release of DSEM relays and pick-up of DSWM relays connects (considering section DE) relay CRD to act as a code repeating relay supplied over front contact 48 of relay DSWM. Relay 2TR functions as the track relay, following the code, controlling the input and output of transformer DTE, the winding 8 of which is connected over a front contact of relay 2DSWM, to relay 2CR, said relay thus acting as the approach impulse transmitting relay. Approach code impulses are followed by relay TRD functioning as the approach impulse receiving relay. On de-energizing relay 1TP an A.C. source is connected to transformer TTD which then supplies coded energy to the left-hand end of the section for operation of the train-carried receiving apparatus. Subject to the interchange of relay functions indicated, the described operation of the system for west-bound traffic resembles generally that for east-bound traffic. The system may be adapted for threeblock signalling in place of the two-block signalling described. If wayside signals be used approach lighting may be effected over a backcontact of relay 1TP or 2TP.