Patent GB-284384-A (GB)
Title: Improvements relating to railway signalling systems
IPC: B61L3/22
Filed: 1926-10-25
Abstract: 284,384. Westinghouse Brake & Saxby Signal Co., Ltd., (Union Switch & Signal Co.). Oct. 25, 1926. Electrical systems, automatic. - In an automatic signalling system the signalling current supplied to the track sections is interrupted to constitute a code signal characteristic of traffic conditions in the section, signals on the track or in the cab, or both, being selectively responsive to the code signals. The code signals may be characterized by the durations of the impulses, or by the intervals between successive impulses, or by groups of impulses, each group containing a predetermined number of impulses. As described, the code signals are given under caution and clear conditions. The track, Fig. 1, is divided into insulated sections AB, BC, &c., the sections having similar circuit, &c. arrangements. Each section has a signal S<A>, SB, &c. at the entrance end, and is bridged by a track relay R<A>, &c. fed over the rails from a track battery H<A>, &c. under control of an interrupter D<A>, &c., which in turn is controlled bv a circuit controller E<A>, &c. operated in conjunction with the signal. Associated with each track relay are two slow-acting relays J<A>, K<A>, &c. A battery G<A>, &c. supplies current to the interrupter D<A>, relays J<A>, K<A>, and also to the signal operating mechanism, the signals shown being of three-position semaphore type with separate caution and clear operating circuits. Each interrupter has a pair of contacts 4, 5 oscillated in unison, the former being in the circuit of the interrupter winding to give automatic make-and-break action under control of a pendulum 7 adjusted so that, for example, the contacts make a to-and-fro movement in two seconds. The section to the right of C being occupied by a vehicle B, relay RC is shunted with consequent de-energization of the slow-acting relays JC, k<C> and of the signal-operating mechanism. Signal S<C> therefore indicates danger, and its circuit controller E<C> is open, thus deenergizing the interrupter D<C>, the contacts 4, 5 of which are at rest in the normal or closed position. A continuous current its therefore supplied to section BC from battery H<c> over contact 5 and impedance 3. Relay RB is thus continuously energized, holding its contacts 18, 18<a> closed so as continuously to energize K<B>. A contact 28 is thus closed, energizing the caution circuit of signal S<B> which indicates caution and closes the contact of controller EB. Interrupter DB is thereby energized and a code-signal current at. say two-second intervals is supplied from batterv HB to section AB. Under the abovedescribed conditions, relay K<B> also closes a contact 24 in circuit with the relay JB, but relay JB remains de-energized as its circuit is broken at the back contact 18, 18<b> of relay RB. Intermittent current being supplied to section AB. relay R<A> closes its front contact at two-second intervals and relay K<A>, owing to its slow-acting character, thereby maintains its contacts closed. Each time relay R<A> is de-energized, it closes, through its back contact, the circuit of relay J<A>, which is thus intermittently energized and owing to its slow characteristics maintains its contact closed. With relays J<A>, K<A> both energized, current is supplied from battery G<A> to the clear operating circuit of signal S<A>, which indicates clear " and closes contact of controller E<A> in the circuit of interrupter D<A>, whereby " clear " code current is supplied to, and a " clear " signal given in, the section to the left of A. Where for any reason the distance between adjacent signals is great, the track section may be divided into subsections with repeater relays for the signal current at the junctions. Alternating current may be substituted for the direct current described. Fig. 2 shows a system in which different indications are given by different codes, which differ as regards time intervals. Energy is supplied from an alternator F through supply transformers QA, QB, Q<C>, Each interrupter D<A>, &c. is continuously energized and has an additional contact 38 moving in unison with contacts 4, 5 and adapted to close a circuit at each end of its stroke by co-operation with two electrically connected contacts 38<a>, 38b. Thus, if the pendulum control causes contact 4 to make its to-and-fro movement in, say, two seconds, contact 5 is adapted to close a circuit at two-second intervals, and contact 38 to close a circuit at one-second intervals. Signal current is supplied to the track through transformers T<A>, TB, T<C>, the primaries of which are energized from transformers QA, &c. under control of the contacts 5 or 38 of the timing devices D<A>, &c. in series with the contacts of circuit controller EA, &c. operated in conjunntion with the corresponding signal. The track relays R<A>, &c. control the slow-acting relays J<A>, K<A>, &c. indirectly through corresponding timemeasuring devices UA, UB, U<C>. Each device comprises fixed contacts 75, 76 in the circuits of relays J<A>, &c., K<A>, &c., respectively, and cooperating with a contact 74 operated by a winding 73. The arrangements are such that with winding 73 de-energized, or continuously energized, contact 74 occupies one or other of its extreme positions clear of contacts 75, 76. When winding 73 becomes energized, contacts 74, 76 close one second after the commencement of the energization, and contacts 74, 75 two seconds after. The contacts of relays J<A>, &c., KA, &c. control the signal-operating circuits. The winding 73 is energized, when the corresponding track-relay is de-energized, over the back contact of the relay, the slow-acting relays being energized when the track relay is energized, over the front contact of the track relay and contact 74. With the track to the right of C occupied by a vehicle V, relay R<C> is de-energized, with consequent de-energizations of relays J<C>, K<C>, so that signal SC indicates danger, and contact 45 of controller E<C> is closed. Impulses are thus transmitted to section BC at one-second intervals by the action of contact 38, with a corresponding intermittent energization of relay RB. The winding 73 of device UB is energized over back contact of relay RB long enough to allow contacts 74, 76 of the device to close intermittently and be closed when the front contact of relay RB closes. Relay KB is thus energized to close its contact in the signaloperating circuit so that signal SB indicates caution and the contact 43 of controller EB is closed. Contact 5 of interrupter D<B> is thus operative to cause transmission to the section AB of signalling current at two-second intervals, with corresponding intermittent energization of relay R<A>. The two-second period is sufficient to allow contacts 74, 75 of device U<A> to close intermittently, with energization of both relays J<A>, KA, so that signal S<A> indicates " clear," with closure of contact 43 of controller E<A>. Twosecond impulses are therefore supplied to sections to the left of A, with corresponding " clear " signals. The Specification describes a modification of the arrangement shown in Fig. 1, in which direct current impulses are used, constituting two code signal currents as in Fig. 2. Fig. 4 shows a system using polarized track relays R<A>, &c., each relay having a winding 100 bridges across the track, and a winding 101 constantly supplied with current from the transformer Q<A>, &c. When winding 100 receives current of normal relative polarity, contact 18 moves to the right, closing the circuit of relay K<A>, &c. Current of reversed polarity moves contact 18 to the left, closing the circuit of relay J<A>, &c With winding 100 de-energized, contact 18 occupies a mid-position, and both relays JA, &c., K<A>, &c. are de-energized. The track sections are supplied with signalling current through transformers T<A>, &c., the primary circuits of which include a pole-changer PA, &c. and circuit controller E<A>, &c., both operated in conjunction with the corresponding signal. Controller EA, &c. determines the inclusion in or exclusion from the primary circuit of the corresponding track transformer of contact 5 of the corresponding interrupter D<A>, &c. Each section is bridged at an intermediate point X by a winding 113 of a transformer F<A>, &c. the circuit of the other winding 120 being controlled by contact 38 of the device D<A>, &c. in series with a circuit controller O<A>, &c. operated in conjunction with the corresponding signal. When the circuit of winding 120 is closed, winding 113 is an effective shunt for the track current to the left of point X, but with winding 120 open, this shunt is ineffective. By opening and closing contact 38 of device D<A>, &c. the part of a section to the left of X may be made to receive impulses ' at predetermined intervals, whilst the part to the right is receiving continuous current. This feature is made use of with train-carried apparatus giving cab signals as described below. With the section to the right of C occupied by a vehicle V, relays RC, J<C>, K<C> are de-energized and signal S<C> indicates " danger." Controller EC is closed so as to exclude the contact of device DC from the primary circuit of transformer T<c>, and the pole-changer P<c> is thrown to supply the section B<c> continuously with current of reversed relative polarity. Contact of control O<c> is closed, so that the operation of contact 38 of device DC causes the signal current in the portion BX of the section to be interrupted at one-second intervals. Contact 18 of relay RB is moved to the left with consequent energization of relay JB the contact of which closes a signal-operating circuit whereby signal S<B> indicates " caution.' At the same time controller O<B> opens the circuit of winding 120 of transformer FB, whilst pole-changer PB and controller EB are operated to supply signal impulses of normal relative polarity to the whole section AB, at two-second int