Patent GB-825828-A (GB)
Title: Improvements in or relating to electrical signalling systems for rail traffic-control
Inventor: PREIST THOMAS WILLIAM
IPC: B61L21/06
Filed: 1955-01-06
Abstract: 825,828. Railway signalling systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. Jan. 31, 1956 [Jan. 6, 1955], No. 374/55. Class 105. In a railway traffic control system particularly for haulage in mines, sets of signals are provided at respective controlled route junctions each set being governed by individual control equipment operated through a vehicle operated switch detector by an approaching vehicle and the control equipments at a junction are interlocked by equipment common thereto such that the right-of-way granted to one approach is only cancelled by the vehicle, having passed the junction, actuating a switch cancellor. Each signal set may be controlled by a relay set and the signals of a set may be interlocked by a cancel and guard relay group, both the relay sets and relay groups being the same for all types of junction and the relay group becoming effective on operation of the cancellor to cancel the right-of-way given to the approach and to reset the relay group to the " at rest " condition. As described each signal set is governed by its relay set so conditioned that if right-of-way is to be withheld from an approach, it causes an amber signal to be produced in addition to a red signal to inform the driver of the approaching vehicle that the detector operation has been registered. The detector and cancellor are direction-sensitive for doubletrack or bi-directional single-track working. Right-of-way is automatically allocated in cyclic order to trains by the control equipment in accordance with traffic movements recorded by the detectors and cancellors. The cancellation of a registration is effected by a cancellor operated by the return of the train in the opposite direction. The train movements may be put under the control of a signalman or despatcher in which case a supervisory counterpart of each set of signals is fitted at the control position and a " calling on " key provided for each detector. The appearance of an amber light indicates the location of every call for right-of-way and the signalman can decide the order of precedence of waiting trains. When the appropriate calling-on key is depressed both the track and supervisory indicators change to green and the circuit arrangements then prevents the release of a further train until the appropriate cancel key has been operated. Fig. 2 is the circuit diagram showing how three control groups are interlocked to give protection to the track layout shown in Fig. 3. One locomotive works in each district A, B and a third is held in the garage C. On a train approaching signals A, of which the red is showing, and operating the detector A, the right-hand winding of relay AD, Fig. 2, is energized and (f.c. AD1) front contacts AD1 provide a holding circuit over (b.c. AL2) (back contacts AL2) and f.c. AD2 provides a holding circuit on the left-hand winding of relay AD from positive potential over b.c. CA1. For automatic operation the call-on keys KDA &c. are short-circuited so that at f.c. AD3 relay AS is picked up over the chain of back contacts BL3, CL3. At f.c. AD4 relay ARD is picked up and at f.c. ARD1 lights the amber light A. At the make-before-break contacts AS1 relay AL is picked up in series with relay X over b.c. Y1, relay X providing a holding circuit over f.c. XI. At f.c. AL1 relay ARL is picked up and at f.c. ARL1 extinguishes the amber and red lights A and R and lights the green lamp G. At f.c. X2 slowto-operate relay Y is picked up and opens contact Y1, ensuring that relays X and AL are fully operated before contacts Y1 open. Locomotive A may now move towards the pit shaft and since no other locomotive follows from district A assuming one locomotive per district, the green light remains. Should locomotive B from district B now pass and operate director B, relays BD and BS operate to light the amber B light (not shown) to bring the locomotive B to a halt, the circuit for relay BL being opened at contacts AS1. On the return journey inbye of locomotive A it closes temporarily cancel key A to pick up relay CA which at b.c. CA1 opens the holding circuit over f.c. AD2 thereby releasing relay AD since the other holding circuit is open at b.c. AL2, and at f.c. CA2 slow-operating relay (e.g. 40 m/s. delay) CB is picked up to close at f.c. CB1 the holding circuit over f.c. BD2 for relay BD. This short delay period enables relay AD to fall away followed by relays AS and AL, the contacts AS1 being restored to pick up relay BL in series with relay X, this latter not being released. When cancel key A opens relay CA drops away and at f.c. CA2 relay CB is de-energized and after a delay drops away, so that b.c. CA1 makes before f.c. CB1 breaks and ensures that the holding circuits potential over contacts AD2 and BD2 &c. is not disconnected for more than the 40 m/s. delay whatever the length of the closure period of the cancel key, due to locomotive or manual action. If now locomotive B having gained access to the pit shaft wishes to enter the garage C, e.g. to refuel before returning to district B, it will pass and operate cancel key C thereby releasing relays BD, BS and BL and restoring contacts BS1 to normal thereby opening the energizing circuit of relay X which drops away followed by relay Y. As locomotive B moves out from the garage, it operates detector C and lights the tail light red indicator C(T) to hold a second locomotive if present in the garage, and also lights the green lamp G of signal C, and retains the red aspect of signal C(T) on a second red lamp which is extinguished only by the operation of the cancel key B. These two red lamps are connected in parallel with the green and amber lamps of the main signals C. Tail protection could alternatively be provided by using a red lamp extinguished and a green lamp lighted on operation of the cancel key B. Applications of the system to various haulage schemes are described including the use of non-interlocked signals or " free " signals operated by trainactuated detectors and cancellors. Reference has been directed by the Comptroller to Specification 694,306.