Patent GB-868052-A (GB)
Title: Improvements in or relating to vehicle-operated or other vehicle signalling systems
IPC: B61L3/12
Filed: 1956-06-27
Abstract: 868,052. Track and train interacting apparatus. SIEMENS & GENERAL ELECTRIC RAILWAY SIGNAL CO. Ltd., BARKER, P. J., and RIDDLE, H. J. N. June 27, 1957 [June 27, 1956], No. 19941/56. Class 105. [Also in Group XL (a)] In a railway signalling system apparatus carried by the train includes a magnetron the anode of which is provided with an A.C. supply and the change in direct current component of the anode current (the magnetron acting as a rectifier) when the train passes a particular point along the track causing a change in the magnetic field in which the magnetron lies is used to actuate a means, e.g. an electromagnetic relay energized by the anode current and arranged on operation to close a front or back contact in its energizing circuit. In a modification the anode is fed by a D.C. supply and an alternating field component is injected into the magnetic field in which the magnetron lies and the alternating current component resulting in the anode circuit is passed to the relay, e.g. through a rectifier so that the relay is operated by a change in the anode current component. The magnetrons may be placed on the railway track or in the path of any vehicle so that the magnetic field in which the magnetron lies is varied by the passage of a vehicle and in this respect two magnetrons arranged to be successively passed by the vehicle may be used in an axle counting-in and counting-out system. Multianode magnetrons may be used having symmetrically-spaced anodes around an elongated thermionic cathode (see Group XL (a)) with anode currents equal in the absence of electromagnetic fields or in the presence of a field symmetrical about the cathode. In an apparatus as illustrated in Figs. 10 and 11 for detecting or counting the passage of the wheels of a train past a specified position, two single-anode magnetrons 38, 39 are disposed in magnetic fields parallel to the cathodes and produced between polepieces 36, 37 and 40, 41 by adjacent pairs of three permanent magnets 31, 32, 33 spaced along the track and the fields of which are adjustable to the desired values by auxiliary magnets 43, 44 pivotable about the ends thereof on brackets 45 secured to a member 42 to which also are connected at their lower ends the magnets 31, 32, 33 and the polepieces 37, 41 to provide a good magnetic path between them. The magnets 31, 32, 33 and polepieces 36, 37, 40, 41 and the member 42 are carried by an insulating board 48. Each of the lower polepieces 37, 41 is embraced by a coil 46, 47 energized to provide magnetic bias. The magnetrons or the coils 46, 47 are excited by A.C. current. The upper ends of the magnets and upper polepieces lie slightly below the top of the rail 34 and the gaps between these members and the rail are such that the magnetic field therein is normally low and increases in the presence of a train wheel to increase the fields in which the magnetrons lie, a wheel creating by its passage an impulsive variation in the A.C. component of the anode current of each magnetron, the sequence of the variations from the two magnetrons being used temporarily to operate sequentially two relays to control the axle counting device.