Patent GB-569720-A (GB)
Title: Improvements relating to railway traffic controlling apparatus
IPC: B61L23/16
Filed: 1943-01-27
Abstract: 569,720. Railway signalling systems. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. (Union Switch & Signal Co.). Jan. 27, 1943, No. 1376. [A Specification was laid open to inspection under Sect. 91 of the Acts, Nov. 17, 1943.] [Class 105] The invention relates to railway signalling systems utilizing code impulses transmitted over a line or a track circuit in which both a master code and a feed-back code are given, the feed-back code being generated in response to the master code. According to the invention the track or line circuit is provided at each end with a direct-current source and a polar relay which remains in its last operated position, the sources being of opposite polarity and the polar relays being simultaneously energized first with one polarity from one source and then with the other polarity from the other source. Such a system is shown in Fig. 1, while Fig. 4 shows the adaptation to provide a three-aspect automatic signalling system. As shown in .Fig. 1 a polar stick track relay WTR, ETR is provided at each end of the track section DE together with slow release relays FSA1, HR1, FSA2, HR2, which latter in effect are decoding relays. In the position shown the source WTB reversely energizes the polar track relays WTR, ETR, the circuit including normal contact 16 of a polar relay M and front contact 17 of a slow release repeater relay ETPR energized over normal contact 15 of polar track relay ETR. The polar track relays accordingly set their contacts at reverse whereby repeater relay ETPR is de-energized and polar relay M reversely energized, the latter by current over reverse contact 9 of polar track relay WTR, front contact 11 of slow release FSA1 and reverse winding. At the end of the release period of repeater relay ETPR its back contact 17 closes whereby source ETB energizes the polar track relays WTR, ETR in the normal direction over reverse contact 16 of relay M so that repeater relay ETPR is again energized and the apparatus is returned to the first position. This action continues. It will be noted that the slow release relay FSA1 remains up being energized over normal content 6 of polar relay M (or parallel front contact 7 of relay HR1) and reverse contact 5 of polar track relay WTR. Likewise slow release relay HR1 remains up being energized over front contact 10 of relay FSA1 and normal contact 5 of polar track relay WTR. Entry of a train at D will cause relay WTR .to assume the reverse position if not at the time in that position, also relay ETR will assume the normal position. In due course relays HR1 and then FSA1 drop and on closure of back contacts 12, 11 thereof the reverse contact 9 of polar track relay WTR effects normal energization of relay M. This energizes relay FSA1 over reverse contact 5 of polar, track relay WTR and normal contact 6 of relay M ; on closure of front contact 11 of relay FSA1 the relay M becomes reversely energized whereby relay FSA1 is de-energized and at the end of the release period the relay M is energized in the normal direction over reverse contact 9 of polar track relay WTR back contacts 11, 12 of relays FSA1, HR1. This action of relays FSA1, N6 continues till the departure of the train whereupon the polar track relay ETR is reversely energized and thereafter the circuit functions in the manner first described. The arrangement shown in Fig. 4 is the same as that of Fig. 1 except that a slow lift relay 2HP has been added. With an eastbound train in the section to the right of section DE a relay HR3 will be making its back instead of its front contact 33 and therefore when contact 15 of polar track relay ETR moves to normal positions the track repeater relay ETPR will not be energized until the slow-lift relay 2HP has closed contact 37. This lengthening of the period between the pulses for setting the contact 30 of polar track relay WTR so reduces the mean current to a relay DR that this relay drops its contact 36 thereby to give a Y signal. The R signal is given by back contact 35 of relay HR1 de-energized when section DE itself is occupied. Instead of the two track relays being energized in series they may be energized in parallel by being shunted across the current source at the respective end, Fig. 3 (not shown).