Patent GB-254412-A (GB)
Title: Intermittent inductive train control system
IPC: B61L3/12
Filed: 1925-04-07
Abstract: 254,412. Howe, W. K. April 7. 1925. Electrical systems, automatic; track apparatus for stopping trains.-In an inductive traincontrol system of the general type described in Specification 1513,873, in which the control is determined by the time interval between successive impulses received by train-carried arrangements as the train passes a suitably spaced pair of track devices, the spacing of each pair of track devices is such that no automatic brake application occurs if the speed in passing one pair of devices is not more than would allow the train to be brought to a stop within the section if the brakes were applied at the next pair. A rotary train-carried timing device is used, preferably driven from a constant speed motor through a slipping clutch. To allow running in either direction, two train-carried devices are provided at opposite sides of the vehicle, co-operting with two correspondingly disposed sets of track devices, the proper train-carried device being switched in automatically according to the direction of rotation of the vehicle wheels. The track devices T have U-shaped cores 6 provided with windings which are opened or closed according to traffic conditions bv line relavs 8 under control of track relays, not shown, in the usual way. Each train device comprises a U-shaped core 25 one leg being provided with a primary winding P and the other with a secondary winding S. The automatic switching device comprises an insulated bridging contact 60 carried by an arm frictionally mounted on the axle 54 of the vehicle wheels and moved thereby into contact with one or other of two stops 61, 62. The timing device comprises a constant-speed motor 29 energized from a battery 32 and serving to drive a contact disc 50 carried by centrifugal governor arms 49, and also, through a slipping clutch 34 and gearing 37, 39, an insulated contact arm 40 normally held stationary in contact with a strip 85 by a stop 41 forming the armature of a normally energized magnet CS. When the magnet CS is momentarily de-energized, arm 40 is released and makes one rotation in a predetermined time. Brake control is effected by a normally energized device K the circuit of which includes stick-contacts 28 so that its circuit is permanently broken by momentary de-energization, and the brakes are applied. The train circuits are energized from a source, not shown, the pole connections of which are indicated by B, N. A control relay C is normally energized from pole B, over stick contact 63, winding C, contact 60 and one or other of the secondaries S to pole N. A circuit is also closed from pole B, over contact 63, and a repeater relay R to pole N. Relay R when .energized closes a circuit from pole B over relay contact 100, conductor 77, contacts 28 winding K, contact disc 50 and primary windings P to pole N. An alternative circuit is also normally closed from pole B over arm 40, contact 85, switch 87, contacts 28, winding K, &c. as above. A circuit is also normally closed from pole B over contact 100, conductor 74 and winding CS. The arrangement is such that the change of flux on passing the first track device T under danger conditions causes an impulse in the secondary S which de-energizes relay C, with consequent deenergization of relay R. This interrupts one circuit through device K, the other being intact whilst arm 40 is on strip 85. Magnet CS is, however, de-energized, releasing arm 40, but before the arm leaves strip 85 a pick-up circuit is closed from pole B, over arm 40, strip 85, switch 87, conductor 77, contact 100 of de-energized relay R, contact 88, winding C, &c., so that relays C, R are re-energized. Circuit of device K is thus maintained energized, the net effect of the first impulse being to release arm 40. On receipt of a second impulse on passing the next track device, a similar de-energization of relays C. R occurs. If the time interval is such that arm 40 has not returned to contact strip 85, both circuits through device K are broken and the brakes are applied. After a brake application, device K can be re-energized by closure of the switch 87, shunting stick contacts 28. Switch 87 is enclosed in a sealed box, is accessible only from the ground, or is otherwise arranged to impose penalty. Track devices may be arranged to effect control at permanent hazards irrespective of traffic conditions as in Specification 153,873. The spacing of the track devices along a track section in accordance with the main feature of the invention is explained in detail with the aid of a speed-curve diagram.