Patent GB-493863-A (GB)
Title: Improvements relating to railway signalling systems
IPC: B61L23/16
Filed: 1937-04-15
Abstract: 493,863. Railway signalling systems. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. April 15, 1937, No. 10815. Convention date, June 10, 1936. [Class 105] An automatic signalling system with approach-lit signals and lamp-failure relays has the lamp-failure relays energized by a checking circuit when the lamps are intact but not alight. For instance, the lamp-failure relay has an additional high-resistance winding in series with the lamp the current being sufficient to energize the relay but not to light the lamp. The system shown in Fig. 1 uses searchlight signals with circuit-controller contacts 7, 8 operated by the vane mechanism to energize a signal repeater relay when the green or yellow roundel is in position. With the signal SB having the roundel G in position the signal repeater relay SR<B> is energized and effects a normal energization of the winding 6 of the rear signal S<A> by a circuit from a pole X, through approach-lighting relay ALR<B>, over front contacts of the signal repeater relay SRB, of the track relay TRA and of the lampfailure or light-out relay LOR<A>. This light-out relay LOR<A> is energized from apoleX, through the lamp LA, and the high-resistance winding 9. The lamp is not sufficiently energized to be alight. When a train enters the section extending up to the signal 8 <A> the approach-lighting relay ALRA is dropped by the opening of a track relay contact similar to contact 20 of the track relay TRA and thereupon the lamp L<A> is lit by current from the pole X, over wires 26, 27, back contact 29 of the approach lighting relay ALRA, and low-resistance winding 10 of the light-out relay LORA. Thus the clear signal shows. When the train passes into section AB the track relay TRA drops and therefore the winding 6 of the signal mechanism S<A> is deenergized so that the roundel R comes into position. The circuit-controller contacts 7, 8 cause the signal repeater relay SR<A> to drop and a back contact 28 of this relay continues the lighting of the lamp LA through the lowresistance winding 10 of the light-out relay LOR<A> so that the danger signal shows. Other back contacts of the signal repeater relay SRA cause the winding of the rear signal to be reversely energized thereby placing its caution roundel Y in position so that a train approaching such signal would receive an approach-lit caution signal. If the filament of the lamp L<B> breaks then the light-out relay LOR<B> drops and its open front contact 17 breaks the circuit to winding 6 of this signal SB which thereupon places its roundel R in position and its circuit-controller contacts 7, 8 de-energize the signal repeater relay SR<B>. This causes the rear signal S<A> to place its roundel Y in position so that a train approaching such rear signal SA would receive an approach-lit caution signal and would thus be in readiness to pull up at the dark signal S<B> which is required to be regarded as a stop signal. The opening of the front contact 17 of the light-out relay (consider the relay LORA) in addition de-energizes the ahead approach lighting relay (ALRB) whereby the lamp of the ahead signal (S<B>) is lit. In the arrangement shown in Fig. 5 main and auxiliary searchlight signals S<A>1, S<A>2 are provided at each location A whereby G/R, Y /G, Y /R and R /R indications are given. The light-out relay LOR<A> is arranged in the circuit of the lamp L<A>1 of the main signal S<A>1. A front contact 121 of the light-out relay LOR<A> is included after the pole X in the circuits for the windings 6 of the signal mechanisms and therefore on failure of the main signal lamp the vanes of the two signals move to bring the roundels R into position. Figs. 3-4 (not shown) show an arrangement in which a failure of the main signal lamp sets only the auxiliary signal to the R indication but lights the lamp of such auxiliary signal and therefore gives a stop aspect. Normally alternating current from a transformer 35 is used for the lighting but on power failure a direct current source EA is placed in circuit by the back contacts of a " power-off " relay POR<A>. In the case of approach-lit multi-lamp colour-light signals giving G/R, Y/G, Y/R, R/R indications that particular main signal lamp which is alight or conditioned for approach lighting is inserted in the circuit of the light-out relay. The dropping of the light-out relay may condition only the auxiliary signal to the R indication, Figs. 6, 7 (not shown), or if a G or Y indication was being given by the main signal may give a stop indication at such location and set the rear signals to a condition corresponding to the section of such defective signal being occupied, Figs. 8, 9 (not shown).