Patent GB-304830-A (GB)
Title: Improvements relating to apparatus for the control of railway traffic
IPC: B61L7/08
Filed: 1927-10-27
Abstract: 304,830. Westinghouse Brake & Saxby Signal Co., Ltd., (Union Switch & Signal Co.). Oct. 27, 1927. Selective distant-control systems ; tell-tale apparatus.-Signals or other traffic controlling devices located along the track are controlled by means of selector devices selectively operated by code currents from a distant point of control. Track circuits may be used for a joint control dependent upon traffic conditions. Indications may be given at the point of control to show the operation of the traffic controlling-devices, and of the passage of trains, by means of selector mechanism which includes means for storing the indication of a subsequent operation until the preceding one has been completely transmitted. Fig. 1 shows signals W, E at a loop road selectively controlled from a cabin apparatus, shown at the right side of the figure, which includes code-current transmitters K<1>, K<2>, K<3> and indicating lamps controlled by selector mechanisms S<4>- - S<7> actuated bv code currents transmitted from the distant apparatus by the discs K<4> - - K<7> driven bv the motor M. All code currents are transmitted over the lines 4, 5, and relays N, L operate polechanging contacts to reverse the connection from the line wires 4, 6 and battery 25 to the coils 10 which operate the code selectors S<1> - - S' which close circuits from local sources of energy, the terminals of which are indicated by B, B<1>, C, C<1>. Signals W, E are normally at " stop " and are set to clear by energization of selectors S<1>, S<2> respectively and are reset, if required, from the cabin, by operation of selector S<2>. A contact 16, closed by the first movement of any selector energizes a relay and prevents sending of code currents while any selector is operative. Signals E, W are controlled by stick-relays F<1>, F<3> respectively which are energized by selector contacts over a circuit including a back-contact, 34, 38, of the other relay; the stick-circuit includes the closed contact of selector S<2> and a front contact 41, 43 of the energized relay, and is broken to restore the signal to " stop " by operation of the selector S<2> by the transmitter K<2>. Indications of the movements of signals to " clear " and " stop " and of the passage of a train in either direction over insulated rail-sections to which relays r<1>, r<2> are connected are controlled by indication relays G<6>, G<7,> G<4>, G<5> respectively. Each signal, just before reaching its " clear " position actuates a switch arm T<w>, TE, to close a contact 46 in a circuit over a front contact of the energized relay F<1>, F<3> controlling the signal to relay G<6>; a similar circuit to relay G' is closed over back-contacts of both signal relays just before a signal reaches its " stop " position. The armatures of relays r<1>, r<2> are interconnected and in series with the armatures of a slow releasing relay k and with relays G<4>, G<5> so that one of these relays G<4> is energized momentarily only when a train passes over and beyond both insulated rail sections travelling eastwards, the other relay responding only to traffic in the other direction. Stick circuits are provided for all indicating relays, and are opened when the controlled selector reaches its set position and opens contact 21. Each relay G<4> .. G' closes a circuit from source B and wire 100 over the contacts 20 in series to relay j, which closes a stick-circuit over contacts 22 in series and is thus maintained energized until the required selector is set. Relay i also closes a circuit to the motor M which drives the selector driving-shaft, to which are geared a number of driving discs each of which is fitted with a magnetic clutch energized by an electromagnet P<4> - - P<7>, through which the appropriate selector contact-disc K<4> - - K<7> and the means for operating contacts 20, 21, 22 are driven. The first movement from normal of any disc K<4> - - K' energizes relay f which opens the circuit of relay N and prevents its operation while code currents are being sent to the line wires from discs K<4> - - K'. The selectors S<4> - - S<7> in the cabin, when set, energize lamps 134, 138 showing the position of the signals and lamps 145, 146 indicating passage of a train past the signals. The latter indications are maintained over stick-contacts of relays H<4>, H<5> until manually reset by operation of a key Z. An audible signal 156 is energized when codedcurrent is received by relay g through a one-way contact 152. A detailed description is given of a signalling system (Fig. 6 of the drawings, not shown) for a single-track railway with passing- loops and, if desired, intermediate signals. The signals for several sections are controlled from a cabin over one pair of transmission wires for code currents to selectors suitably situated along the track which may occupy several operative positions and make contacts appropriate to the desired signal indications. The signals are further controlled by track-relays and by line-relays which are in turn dependent upon traffic conditions and the position of signals along the length of track ahead of the signal concerned. In order to avoid the superimposition of code currents on the line wires due to simultaneous transmission of indications of the operation of signals or the passage of trains, arrangements are provided at each selector by which, while one indication is being transmitted any other, or others, controlled by that selector is stored until the first is completed. Arrangements are also made for storing the transmission of indications of operations controlled by the different selectors along the track. These arrangements are illustrated in Fig. 7 (not shown).