Patent GB-568541-A (GB)
Title: Improvements relating to coded track signalling systems for railways and the like
IPC: B61L23/16
Filed: 1943-05-27
Abstract: 568,541. Railway signalling systems.. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd., MAcGREGOR, R. M., and COLEY, J. P. May 27, 1943, No. 8459. [Class 105] In a track circuit the rails are interrupted at a predetermined point X by insulation bridged by an impedance, whereby coded rail current giving a cab signal in accordance with the signal next ahead, as distinct from the normal action in which the cab signal corresponds with that of the signal on entry to the section being run through, is received only when the train reaches that point. As shown in Fig. 1, track-circuit current is supplied to the rails of section BC by a transformer T1 under the control of a relay COR and the control relays SCHR, SCDR for the signal SC governing entrance to the section CD ahead. The rail 1 is interrupted at a point X with insulation 3 bridged by an impedance L so that only when this point is passed will the relay COR, normally energized from the rails through a transformer T2, be de-energized. Assuming the signal SC is in its caution aspect, due to the signal control relays SCHR and SCDR being respectively energized and de-energized, the rail current in section BC at first will be supplied by the transformer T1 as energized over a 180-interruption contact of a coder 180CT, front contact 5 of the signal control relay SCHR, and front contact 6 of the relay COR, but when the train reaches the point X, the relay COR closes its back contact 6, whereby the transformer Tl is energized over a 75- interruption contact 4 of coder 75CT, a back contact of the relay SCDR, a front contact 8 of the relay SCHR and back contact 6 of the relay COR. Thus, when the train enters and proceeds along section BC, the rail current is at first of 180 -interruption rate and so in accordance with the entrance signal SB in the clear aspect when the train entered the section, but when the point X is reached, the rail current is changed to 75-interruption rate in accordance with the caution aspect of the entrance signal SC of the section ahead. Fig. 2 shows an arrangement in which the block sections such as AC comprise an overlap section AT and a section BT, the latter being interrupted at the point X by insulation 3 bridged by an impedance L ; the signals are automatically controlled by the rail current through code-following relays ACFR ' and associated relays FSR, BSR, ADR, these relays also controlling the supply of rail current to the rear section, the current being relayed to the overlap section AT by a code-following relay BCFR. Assuming sections AT, BT, CT are unoccupied, 180-code in section CT operates code-following relay CCFR to energize relays FSR, BSR, CDR, whereby 180-code is applied to section BT by the energization of transformer T2 over the 180-interruption contact of coder 180CT and front contacts 14, 13, 15 of relays BSR, FSR, CCOR, the latter being energized from the rails of the section through a transformer T1. The current in section BT is relayed to section AT. Contacts 10, 11, 12 of the relays FSR, BSR, CDR light the proceed lamp G of the signal SC and the signal SA is similarly energized. If now a train enters section AT, the relays ACFR, FSR, BSR, ADR will be de-energized so that the stop lamp R of signal SA will be lit over back contact 16 of relay FSR. While the train proceeds through section AT 180-code will still be supplied to the rails for cab signalling. When the train enters section BT the relay BCFR will drop, whereby steady energy will be applied to section AT over back contact 17 of relay BCFR. This will cause relays ACFR and FSR to be energized, but the signal SA will continue in its stop aspect but now over front contact 16 of relay FSR and a back contact of relay BSR. The 180-code continues to be supplied to section BT, but when the point X is reached, this current is then supplied over a back contact 15 of relay CCOR (deenergized when point X is reached) and front contacts 18, 19, 20 of relays CDR, BSR, FSR. When the train enters section CT the signal SC changes to the stop aspect and no rail current is supplied to section BT, since the relays FSR, BSR, CCOR are de-energized; section AT is supplied with steady energy over back contact 17 of relay BSFR. When the train enters section DT, steady energy is supplied to the rails of section CT so that relay FSR is energized, whereby 75-code is applied to section BT over contact of coder 75CT, back contact 14 of relay BSR, front contacts 13, 15 of relays FSR, CCOR. If when the train passes from section AT to section BT the signal SC is in the caution aspect, the 180-code which is being supplied over front contacts 14, 13, 15 of relays BSR, FSR, CCOR is changed to 75-code supplied over back contact 18 of relay CDR, front contacts 19, 20 of relays BSR, FSR and back contact 15 of relay CCOR, this last relay being de-energized when the train passes the point X. An arrangement is also described, Fig. 3 (not shown), in which the increased track current when the point X is passed causes a relay to be energized, whereby coded rail current corresponding to the clear aspect of a signal located at point X continues to be applied for cab signalling after the signal has been passed and put to the stop aspect.