Patent GB-163597-A (GB)
Title: Improvements in automatic train control systems
IPC: B61L3/18
Filed: 1920-06-01
Abstract: 163,597. Dodgson, F. L. June 1, 1920. Electrical systems, automatic; track apparatus actuating signals on trains and for stopping trains.- In an automatic train control system the speed of a following train is controlled in accordanoe with the distance between it and the train ahead and also in accordance with the speed of the train ahead. In the arrangement shown in Fig. 1, traffic moves to the right over track rails 1, 2 which are divided into sections A, B, C by insulating joints 3 in the track rail 1. Each section has a battery 4 and track relays 5, 5<1> &c. Insulated sections RA, RB &c. of a contact rail correspond to the track sections and sources such as the transformers T', T<2>, capable of giving variable voltages, are connected between the sections RA, RC, &c. and the continuous track rail 2. A rotary drum switch O, Fig. 2, operated though a distance varying inversely as the speed of the train, is provided for each section; each switch is operated by an electric motor and is retained in its operated position by a detent 28 moved by the electromagnet 30 into engagement with the ratchet wheel 25. When the motor is de-energized and the detent is released, the drum is restored to its initial position by a weight 24. When a train enters the section C, Fig. 2, and leaves the section B, the armature of the track relay 5<2> drops, and that of the relay 5<1> is raised. The relay 32 then closes the circuit of the motor and a maintaining circuit for its own winding. The motor operates the switch until the train reaches the end of the section C and enters section D. The solenoid 30 is then energized to lock the drum and the circuit of the motor is broken by the track relay 5<2>. If the train is travelling quickly. the drum switch is therefore only moved a short distance. When the train leaves section D, the detent 28 is withdrawn. When there is no train upon the track shown in Fig. 1, the full winding of the transformer T<3> is connected across the section RA and the track rail 2. If a train is on section D, the relay 5<3> will drop its armatures and connect in circuit with the section RA, only the part of the transformer winding between the leads 53<3>, 55<3>. If a train is on section C, a smaller winding still is connected in circuit, while if the train is on section B no voltage at all can be supplied to the section RA. These connections are modified under certain conditions by the drum switch. If the train entering section C is travelling so fast that it cannot be stopped by an immediate application of the brakes until it has passed the end of section E, a higher voltage may be applied to the conductor rail sections RA, RB; in these circumstances the drum O will only move to its first position while the train travels over the section C. This connects the wires 35<2>, 43<2> to the wire 141<3> and allows the full transformer voltage to be applied to the rail sections RA, RB. If the train is travelling at a speed such that it must pass the section D before it can be stopped, the drum is moved to the second position in which high voltage is applied to the section RA and medium voltage to the section RB. At lower speeds the switch drum 0 does not vary the track connections. The train carries a switch 68 responsive to the electrical conditions of the track, and a switch 80 responsive to the speed of the train. The brake valve 87 is controlled by a solenoid 88, the core 89 of which, when the solenoid is de-energized, falls against the action of a dash-pot 92 to apply the brake. Governor mechanism G, driven from an axle, operates the switch 80. The switches 68, 80 have arc contacts 69, 81 which work over sets of contacts 84, the sets being connected by conductors 85. A warning signal, such as a whistle W, is provided and is operated by the de-energization of the solenoid 95; this permits the valve 96 to drop to make connection to the whistle from the reservoir 98 of compressed air. When the train is travelling over a section supplied with the highest voltage from the transformers on the track, the switch arc 69 occupies the position shown in contact with all its fixed contacts 84. The arc 81 actuated by the speed responsive mechanism may therefore be moved to its highest position, in which it is in contact only with one of its fixed contacts, without operating the whistle W and brake valve 87. If the track section is supplied with a lower voltage, less current flows through the solenoid 64 and the arc contact 69 moves downwards making contact with only two or one of the fixed contacts. The arc contact 81 can then only rise as far as the middle or lowest of its contacts without operating the whistle and brake valve. Recording devices may be associated with the brake solenoid 88 to enable a record to be made of the automatic operations.