Patent GB-228171-A (GB)
Title: Improvements relating to railway signalling apparatus
IPC: B61L23/16
Filed: 1925-01-22
Abstract: 228,171. Westinghouse Brake & Saxby Signal Co., Ltd., (Assignees of Grondahl, L. O.). Jan. 24, 1924, [Convention date]. Electrical s y s t e m s, automatic.-In an automatic signalling system the signal indications are controlled by thermosensitive relays operating in conjunction with unidirectional current-carrying devices. The unidirectional current devices may be as described in Specification 194,653, [Class 38 (ii), Electric currents, Converting &c.]. The track rails 1, 1<a> are divided by insulating joints 2 into sections AB, BC &c. and each section is provided with three lamp or other signals G<A>, R<A>, Y<A>, G<B> &c. and five thermo-sensitive relays F<A>, H<A>, J<A>, K<A>, L<A>, &c. Alternating current is supplied from a generator D through lines 3, 3<a> and transformers 10. Each relay comprises a, thermo-sensitive element 9 the resistance of which decreases with rise of temperature, and a heater 8. A terminal d common to the heaters 8 of relays J<A>, K<A> is connected to the rail 1<a> through heater 8 of relay L<A>. The outer ends of these heaters are respectively connected to rail 1 through unidirectional current devices 4, 5 which are oppositely disposed, so that relay JA is energized by track current of one polarity, and relay K<A> by the reversed current. When one or other of the relays J<A>, K<A> is energized, current is supplied from transformer secondary 13 through heater 8 of relay HA, sensitive element 9 of the energized relay, and corresponding lamp GA or Y<A>. Current for lamp R<A> is supplied from transformer secondary 12 through conductor 23, resistance, 24, lamp R<A>, and heater 8 of relay F<A>. When relay HA is energized consequent on energization of either of the relays J<A>, K<A> and lamps G<A>, YA, current is supplied through resistance 24 and element 9 of relay H<A> from transformer secondary 11, and the proportions are selected and adjusted so that voltage drop in resistance 24 due to secondary 11 opposes and neutralizes the drop due to secondary 12. thus lamp R<A> is extinguished and relay F<A> de-energized. Track current is supplied from secondary 14 through element 9 of relay LA and a unidirectional current device 6, or from secondary 15 through element 9 of relay FA and unidirectional device 7, the devices 6. 7 being oppositely disposed so that current of opposite polarity is supplied from the secondaries 14, 15. A vehicle V ahead of section AB de-energizes relays J<A>, K<A>, L<A> so that lamps G<A>, Y<A> are also de-energized. Relay H<A> is also de-energized, so that lamp RA gives a danger indication and relay F<A> is energized. Current of " reversed " polarity is therefore supplied to section AB from the secondary 15. This current selectively energizes relay K<B> and gives a caution indication at lamp Y<B>. Relay H<B> is also energized so that lamp R<B> is extinguished and relay F<B> de-energized. Relay L<B> being energized, current of normal polarity is supplied to section BC from secondary 14. This current selectively energizes relay J<C>, giving a proceed signal at lamp G<C>. Relay H<C>, together with lamp R<C> and relay F<C> are de-energized, and current of normal polarity is therefore supplied to the section behind BC.