GB301914A - Improvements relating to railway traffic controlling apparatus - Google Patents

Abstract

301,914. Westinghouse Brake & Saxby Signal Co., Ltd., (Assignees of Bossart, P. N.). Dec. 8, 1927, [Convention date]. Track apparatus actuating signals on trains.- In train controlling apparatus of the intermittent inductive type in which track magnetic members at signalling positions on the track influence apparatus on the trains, the train apparatus comprises an arrangement of magnetic cores and air gaps the reluctances of which are. adjusted to be balanced or unbalanced in the manner of a Wheatstone bridge dependent upon the co-operation of the track devices. One arrangement is shown in Fig. 2 in which a coil 1 energized from a highfrequency generator G produces flux in two circuits, one including the air gaps 4, 6, the other the air gap 12 and the gap between the poles 2, 8. An unbalanced flux threads the coil 9 and serves to energize the relay R by means of a tuning condenser 10, transformer T, amplifier 23, transformer K and rectifier 22. At a danger signal, the coil 17 on the track core, in a tuned circuit including a capacity 18 and an air-core reactor 19 of low power factor, is open circuited at contact 20 and the core 16 forms an additional magnetic shunt across the poles 2, 8 of the train apparatus which is adjusted that no resultant flux passes through coil 9 so that the relay R is de-energized and remains so since the circuit includes the contact 11. The cores are formed of an iron having a high initial permeability and the magneto motive force of the coil 1 is kept low. By this means the reluctance of the core 16 may be arranged to be a substantial fraction of that between the poles 2, 8 and the apparatus is practically unaffected by passage over casual masses of iron, such as track rails, which are of less permeability. It is preferred to use a high frequency current, for example, one with a frequency of 1000 cycles per second and to laminate the cores of the apparatus in order to take advantage of the skin effect produced in casual masses of iron. It is also preferred to arrange the capacity 18 near the track core 16 and the reactor 19 near the controlling relay J since if, then, the leads become short-circuited, the closed circuit is not tuned but is of a high impedance, and reacts as if on open circuit.