Patent GB-299304-A (GB)
Title: Improvements in or relating to railway control systems
IPC: B61L3/22
Filed: 1928-10-03
Abstract: 299,304. General Railway Signal Co., (Assignees of Hailes, W. D.). Oct. 22, 1927, [Convention date]. Selective. distant control and signalling systems. -Each section of insulated track rails is supplied with a cyclic series of current impulses forming a distinctive code for each signal to be transmitted according to the traffic conditions and each train carries decoding apparatus for continuously controlling signals and traincontrol devices according to the coded impulses received by means of coils in inductive relation to the track rails. Coded current is supplied only to the rails of an occupied block. Each cycle of cyclic code currents is preferably followed by a blank period during which the decoding device is restored to its normal condition if the blank period exceeds a predetermined time interval. The decoding apparatus comprises a relay which is energized while current is on the rails during a code cycle and a series of slowrelease relays two or more of which are consequentially energized according to the number of code impulses received and remain energized if the current-off period is of less than the predetermined length. The decoding relays control slow-release relays appropriate to each signal to be received and these control the circuits to the different signal lamps and the train-control device. The retaining relay for the most restrictive signal has a greater slowrelease time than the other similar relays to prevent de-energization of the said signal during a momentary energization of another signal. Stick-relays partly controlling the signalling circuits are maintained by a circuit including the front contact of the corresponding slow-release, repeater relay. Fig. 1 shows the track equipment comprising track relays TR across the entrance ends of insulated sections H - - K to the exit end of each of which energy is constantly supplied from a battery 4 and alternating current is also intermittently supplied from the secondary of a transformer T, the primary of which is in series with the contacts of the adjacent track relay and a line relay LR controlled from the section in advance and with coding-contacts 7, 8, 9 made and broken by the motor M. The motor M and the track rails of a section are energized only while the coding-motor relay CMR is excited, that is, while a train occupies that section and shunts the trackrelay. The energy supplied to transformer T is preferably alternating current and the coding-motor M makes and breaks each of the contacts 7, 8, 9 so as to send over each of them a cyclic code current comprising a series of short impulses followed, generally, by a longer blank interval or a series of short breaks and a longer interval of unbroken current, Several forms of code current are described in detail in the Specification. One arrangement of train-carried apparatus including a decoding device and lamp signals R, Y, Y/G, G and a whistle AWV and brake-control valve EPV is shown in Fig. 2, and alternatives operable by other codes are described and shown in the Specification. Coils 12 are carried in inductive relation to the track rails 1 and the current impulses induced therein energize a transformer 15, connected to a filter circuit F and an amplifier A from which current is supplied to a coding primary relay CPR, the armatures of which are lifted while control current is on the track rails and are dropped when no such current is supplied. The relay CPR is quick to pick up and also to release, and its armatures thus follow the make and break of the code current. Armature 16 when attracted supplies current to decoding relays R<1>, R<2>, armature 17 when attracted and released controls the circuits to decoding relays R', R<6> and R<3>, R<5> respectively. Each of the last four relays has also a holding circuit, which includes armature 22 of relay R<2> and equalizing resistances 21. Each decoding relay picks up its armatures quickly but drops them at a predetermined time after current is cut off from the coils. For intervals of 0.2 sec. duration of code-current impulses the relays R', R<2> have time lags of 0.3 and 0.8 sec. respectively and relays R<3> R<6> each have a lag of 0.1 sec. in the example given. The initial closing of the circuit in the cyclic code transmission causes the pick up of the relays R<1>, R<2> simultaneously and the following breaks and makes cause the successive pick-up of the relays R<3> - - R<6> or as many of these as correspond to the code signal transmitted. The energized relays remain so until relay R<2> drops away which will occur 0.6 sec. after the last break of the code current; by this time lag, the relays remain energized during transmission of the impulses of a cycle and drop away during a prolonged blank period between impulses. The armatures of relays CPR, R', R<2>, R<4>, R<6>, control repeater relays Y rep, Grcp &c. appropriate to each signal, these relays having each very slow releasing armatures. Relay R.rep has a lag of 6 secs. and the other repeating relays 5 secs. This provides that no signal shall be extinguished momentarily by reason of passing short dead rail sections such as occur at points and that two signals shall not be shown simultaneously. Quickrelease stick-relays R<stk>, &c. are controlled by the repeater relays and control in turn a relay EPVR controlling the electromagneticvalve magnet EPV for actuating the break pipe venting valve, and contacts in the lamp circuits. An acknowledging switch Ack is provided by which the driver may prevent application of the brakes after receipt of a restrictive signal of which he is warned by the whistle- AWV, by closing the contact 21<1> within the five seconds interval before the relay EPVR drops its armatures. A resetting contact Res is provided for restoring the apparatus after a brake application has been made and is preferably placed so as to be inaccessible while the train is in motion.