Patent GB-153873-A (GB)
Title: Automatic train control system
IPC: B61L3/12
Filed: 1920-11-12
Abstract: 153,873. General Railway Signal Co., (Assignees of Howe, W. K.). Nov. 12, 1919, [Convention date]. Electrical systems, automatic; track apparatus for stop-ping trains.-Means under control of the driver may be used to prevent the operation of the brakes due to an impulse received from a track apparatus at a caution signal. A time limit switch prevents the continuous use of this device so as to put the apparatus out of action. Another brake-venting valve is opened if two track devices are passed in. less than a predetermined time interval. Both the brake-venting valves may be controlled by one relay Q, Fig. 2. Fig. 2 shows one form of train-apparatus controlled by electromagnetic induction between a core L having a magnetizing coil 8 and a secondary coil 9, each of which is in series with a battery and a relay coil X, R. The yoke T on the track is wound with a coil which is short-circuited by the armature of a relay 6 in a circuit controlled by the usual track relay, the arrangement being such that the passage of the yoke L over the yoke T when the coil 5 is short-circuited does not affect the relays X, R, but on passing a yoke T with an open-circuited coil, the relays X, R open their contacts momentarily and de-energize the relay Q and the magnet R. The circuit of the service application magnet 53 is normally completed over the contact 71 of relay Q; the driver may close the contacts 23 in parallel with the contacts 71 so as to prevent de-energization of magnet 53 if he observes the signal. The contact 23 is closed by the lever 18, which simultaneously open the valve V to supply pressure to the capacity 29 and cylinder 31 through a restricted channel 28, so that, after a predetermined time, the piston 32 is moved against the action of the spring 33 and the pistonrod head 35 opens the contact 36; this ensures that the driver shall not hold or fix the lever 18 permanently to close contacts 23. A modified hold-off appliance includes a spring-pressed plunger moved against air pressure in a cylinder fitted with an adjustable outlet and a one-way ball valve inlet. On de-energization of the magnet 53, air under pressure passes from the capacity 60 through the valve EPV to the cylinder 44 and the piston 45 moves the rack-rod 43 to set the driver's valve E to " service " position. The pressure on piston 45 is such that the driver may exert sufficient force to hold the valve E at running position, if desired. By means of the adjustable inlet 59 and outlet 50, this pressure is maintained for the desired period of time. The piston is free on the piston-rod so that the valve may normally be used freely. The speed-controlled brake application is made by the de-energization of the magnet 85 controlling the emergency brake valve by the simultaneous opening of contacts 88, 76. The former is opened at each track device which causes variation in the current relays X, R, and the latter is opened after a brief interval which allows contact 88 to re-close and is then maintained open during a predetermined interval after such impulse is received, so that if, during that interval, a second impulse is received to open the contact 88, the magnet 85 is de-energized. The relays X, R control an electro-magnet P which normally holds closed the valve 77, but on de-energization of magnet P the valve is lifted by fluid pressure and air escapes from the chamber 79 through the valve 82 faster than it enters the chamber through the valve 78 from the main reservoir. The upward movement of the valve 77 is controlled by a small escape orifice 84 in the upper end of the valve casing, and at the end of its travel the contact 76 is opened. This delay allows time for the closure of contact 88 of relay Q. The magnet P is of such strength as will close the valve 77 only after a predetermin.ed reduction of pressure below it, and the outlet 82 and inlet 78 from the reservoir are adjusted to bring about the required reduction in the desired time. The track members are spaced apart on the track according to the allowable speed. The pressure tending to open the valve acts on a greater area after the initial opening of the valve than when it is closed, so that the piston 77 must move a full stroke. In a modification of the apparatus for operating the driver's valve, the magnet 53 is strong enough to close the valve against reservoir pressure and the time-control is omitted. In order to necessitate co-operation of a second person in re-setting the apparatus after operation owing to failure to close the contacts 23, the earth connexion of the magnet 53 is passed through a contact opened on de-energization of the magnet in parallel with a contact 116, Fig. 6, which may be closed by say, the fireman. This contact may be closed by the screw and nut gear 142, 144 shown in Fig. 6, or by a spring-pressed plunger. A contact 123 in the circuit of the magnet 53 is opened by the spring- operated dash-pot-controlled lever 119 at a predetermined time after the operating means for the contact 116 is moved from its normal position; this prevents the permanent or prolonged displacement of the re-setting device.