GB814681A - Improvements in railway signalling track circuits - Google Patents

Abstract

814,681. Railway track circuits. FORGES ET ATELIERS DE CONSTRUCTIONS ELECTRIQUES DE JEUMONT. Oct. 19, 1956 [Dec. 17, 1955], No. 31906/56. Class 105. In a railway track circuit signalling system employing electrically continuous rails both for power and signalling currents, the rails of each track circuit are fed with periodic signalling current impulses, e.g. A.C. or peak impulses, each track circuit being identified by a specific impulse frequency or by respectively phased impulses of the same frequency and pick-up devices for the signalling currents in the rails are coupled to control at least one relay through an energy accumulating device in such a way that the relay or relays is/are responsive only to the impulses appertaining to the section and is/are unaffected by the traction power currents circulating in the rails. As shown in Fig. 1, time phased unidirectional or alternating current impulses are fed from the impulse generators 3, 3A, e.g. electronic impulse generators, into the rails 1, 2 and circulate in opposite directions indicated by the arrows i and suffer attenuation due to ballast leakages. Pick-up coils 4, 5 such as the coil 4, Fig. 5, on a magnetic core 20 associated with a rail 1, are associated with the rails 1, 2 at a desired distance from the generator 3, the coils 4, 5 being so connected that the currents induced therein by the signalling currents in the rails are additive, but the currents due to the traction currents in the rails tend to neutralize each other. The currents in the coils 4, 5 are fed through a receiver device 7 which may take the form of an intermittently conducting electronic valve and a capacity, synchronized to the generator 3 as by a polyphase line 12, and applies its output to a relay 6 Similarly the receiver 7A fed by pick-up coils 4A, 5A in the adjacent section is synchronized to the generator 3A by a phase of the polyphase line 12 different from that of the generator 3 and receiver 7. Adjustable phase-shifters 14, 14A may be used in the control circuits of the receivers 7, 7A. The operation of the circuit in the presence of a shunting axle 15 is such that the effective track sectional length LA extends beyond the point of connection of generator 3A and overlaps the adjacent section by a length m. The signalling currents in the pick-up devices 4, 5 may be supplemented by currents derived from the voltage between the rails 1, 2. In a two-way traffic system separate sets of pick-up devices are provided for each traffic direction and are associated with corresponding track relays. Alternatively, a plurality of separate pick-up windings may be disposed at the opposite extremities of the section and connected so that the signal currents are additive and the traction currents cancel each other and in this case the impulses are fed to the rails at the centre of the section, the result being a better definition of the length L.