GB190412235A - Improvements in Railway Signalling Systems - Google Patents

Abstract

12,235. Thullen, J. C., and Thullen, L. H. May 30. Contacts, electric ; electric railways and tramways, signalling on; signalling between trains.-Relates to block signalling systems in which alternating currents of more than one phase are used for operating the signals. One of the rails is divided into insulated block sections 8, 9, 10, 11. Alternating current flows from a generator or other source by leads 2, 6 to a transformer 4, wound with two secondary coils 18, 22, in which currents of different phase are generated. The same effect may be produced by placing inductive and non-inductive resistances in the circuits of the two coils respectively, or otherwise. The cores of the other transformers 4<1>, 4<11> may be of different forms in order to give secondary currents of different phase from those produced in the transformer 4, but the connections are similar. The current from the coil 22 flows to the two rails 7, 8, and that from the coil 22 to the rails 7, 9, in each case passing through a resistance 21. A relay 30 keeps a local circuit closed and thereby holds down the arm of the signal 34, except when short-circuited by a train on the section. The relay is arranged to operate with either or both of the currents from the coils 18, 22<1>. Two relays may be used for each section, one at each end, either of which may, when short-circuited, allow the local circuit to be broken. In another arrangement, the relay is so constructed as to close the local circuit only when it simultaneously receives a current from the rails and a current of different phase from some other source, such as the coil 22, or a two-phase alternator which replaces the one-phase generator. If the coil 22 is used as the source of the second current, a two-phase alternator may supply consecutive transformers with current of different phase. In electric railways, the circuit through the rails 8, 9, 10, 11 and the secondary coils of the transformers is utilized as a return for the propulsion currents, as well as the rail 7.