Patent GB-577725-A (GB)
Title: Improvements relating to railway traffic controlling apparatus
IPC: B61L23/16
Filed: 1944-05-19
Abstract: 577,725. Railway signals. WESTING- HOUSE BRAKE & SIGNAL CO., Ltd. May 19, 1944, No. 9662. Convention date, Aug. 11, 1943. [Class 105] For the control of railway signals a line wire circuit extends through the section and provides two communication channels alternately connected in by a rail-current coding relay and a code-following track relay at the respective ends of the section. In the arrangement shown in Fig. 1 rail current of 75 interruption rate is supplied to section 1T and operates a code-following track relay TR at that rate. A line-wire circuit comprising out and return wires 14, 15 extends through the section and provides for the control of a signal, points, or other railway signal functions at each end of the section by means of a pole-changing relay PCR1, PCR2 at the opposite end of the section, the line wire circuit being alternately first connected in for the energization of a signal relay HDR1 at one end by a battery 19 at the other end and then connected in for the energization of a signal relay HDR2 at the said other end by a battery 18 at the said one end under the control of contacts 20, 21 of a repeater relay CTP for the coder CT and of contacts 8, 9 of the code-following track relay TR. The line wire circuit also includes normally closed contacts 23, 24, 27, 28 of a relay TPR which remains energized so long as coded rail current is received. During the "on" periods of code the signal relay HRD1 is energized with normal or reverse current from the battery 19, in accordance with the position of the contacts 22, 25 of pole-changing relay PCR2, over front contacts 23 of relay TPR., 8 of codefollowing track relay TR, line wire 14, 20 of coder repeater relay CTP, winding of relay HDR1, 21 of coder repeater relay CTP, line wire 15, 9 of code-following track relay TR, 24 of relay TPR. Similarly during the " off " periods of the coded rail current the signal relay HDR2 is normally or reversely energized from battery 18, in accordance with the position of the contacts 26, 29 of pole-changing relay PCR1, over back contacts 20, 21 of the code-repeater relay CTP, the line wires 14, 15, back contacts 8, 9 of the code-following track relay TR and front contacts 27, 28 of the relay TPR which remains up. The relay CTP is adjusted so as to give the same time lag as arises in the code-following track relay TR due to the track circuit characteristics. The arrangement shown in Figs. 2a, 2b is for absolute Permissive Block working in a single line stretch between passing sidings WS, ES, with control by directional stick relays. The single line comprises sections 2T ... 5T with a coder 2-3 CT supplying sections 2T, 3T where they adjoin and a coder 4-5CT similarly supplying sections 4T, 5T. Signals 2S, 4S govern Eastbound traffic through the stretch and signals 5S, 3S govern Westbound traffic through the stretch. When an Eastbound train enters section 2T the track relay 2TR and the relay 2TPR drop whereby the signal relay 2HDR is cut off from the line wires 14, 15 and no battery can be applied at the West end of the line circuit. The dropping of signal relay 2HDR drops its repeater relay 2HPR back contact 36 of which lights the danger lamp R of signal 2S for any following train. Battery power being cut off from the West end of the line circuit causes signal relay 3HDR to drop whereby through back contact 36 of its repeater relay 3HPR the danger lamp R of signal 3S is lit and further the opening of front contact 41 of relay 3HPR prevents a directional stick relay 3SR being picked up so that signal relay 5HDR cannot receive current from its line circuit because contacts 70, 71 of signal repeater relay 3HPR are on their back points and contact 80 of the directional stick relay 3SR is open. This signal relay 5HDR therefore through its repeater relay 5HPR lights the lamp R of signal 5S. Thus the signals 5S, 3S are set against entry of a train into the single track stretch in the opposing direction. As the Eastbound train progresses into section 4T the track relay 4TR and relay 4TPR will drop thereby de-energizing signal relay 4HDR and its repeater relay 4HPR to light the danger lamp R of the signal 4S against a following train. Also due to the time lag of relays 4HDR, 4HPR the directional stick relay 4SR is picked up over back contact 72 of relay 4TPR and front contact 73 of relay 4HPR and thereafter is struck up first over back contact 72 of relay 4TPR and then over back contact 73 of relay 4HPR and its own stick front contact 74. Accordingly when section 2T-3T is vacated'reverse current is applied to the line wire circuit 14, 15 (during the "on" periods of code) from front contact 55 of directional stick relay 4SR, over back contacts 54, 44 of relay 4HPR, front contacts 53, 46 of relay 3TPR, 52, 47 of codefollowing track relay 3TR, line wire 15, 14, front contacts 51, 48 of code-following track relay 2TR, 50, 49 of relay 2TPR and so to winding of signal relay 2HDR which being reversely energized causes signal 2S to display its Y aspect to allow a following train to enter the stretch. The opposing signals 3S, 5S continue to display the danger signal R since signal relay 3HDR continues de-energized by reasons of the open back contact 62 of directional stick relay 4SR and signal relay 5HDR cannot be energized until the directional stick relay 4SR is de-energized to close its back contact 81. When the train vacates the single track stretch the signal relay 4HDR is energized and in turn energizes its repeater relay 4HPR the latter opening its back contact 73 to drop the directional stick relay 4SR. Back contacts 62, 81 of the directional stick relay 4SR then respectively allow signal relays 3HDR, 5HDR to be energized and the system returns to the normal state.