Patent GB-233775-A (GB)
Title: Improvements relating to railway signalling apparatus
IPC: B61L5/18
Filed: 1924-02-14
Abstract: 233,775. Peter, L. H., Edmonds, C. H. W., and Westinghouse Brake & Saxby Signal Co., Ltd. Feb. 14, 1924. Lamp signals.-In light signals of the kind in which a number of differently coloured lamps may be lighted singly to give different signal indications in the usual way, and may also be lighted in combinations to give signals of intermediate significance, the signals are operated by alternating current and the circuits of the individual signals which are to be operated simultaneously are inductively linked together, the arrangements being such as to ensure that if one lamp of a combination fails, the other is automatically extinguished. Fig. 2 shows three lamps R, Y, G, controlled by relays Ar, Ay, Ag supplied from leads 1, 4. When relay Ar is de-energized, the primary circuit of a transformers Tr is closed through arm 2 of relay Ar and contact 3, and the lamp R in the secondary circuit is lit. When relay Ar is energized, and relays Ay, Ag de-energized a circuit is closed through armature 6 of relay Ay, contact 7, and the primary 24 of a transformer Ty. The circuit of the primary 29 of a transformer Tg is broken at arm 9 of relay Ag. The secondaries 25,30 of the transformers Ty, Tg, and lamps Y, G are permanently connected in series. Under the above conditions, the secondary 25 is energized, but the secondary 30 and lamp G being short-circuited through conductor 26 and an arm 13 of relay Ay. lamp Y alone is lighted. When the relays Ar, Ay, Ag are all energized, the primary circuit 29 is energized, the circuit of primary 24 being broken at contact 7. The secondary 30 is thus energized, but winding 25 and lamp Y being short-circuited through arm 19 and contact 32, lamp G alone is lighted. A combination signal by the simultaneous lighting of lamps Y, G is given when relays Ar, Ay are energized and relay Ag is de-energized. Circuit is thus closed over arm 9, contact 34..conductor 35 and half the primary winding 24. The voltage induced in secondary 25 is thus sufficient to light lamps Y, G in series, the secondary 30 being short-circuited through arm 19 and contact 36. Owing to this series connection, if lamp Y fails, lamp G is extinguished. A simplified form of the above arrangement is described in which the transformers Tr, Ty, Tg are omitted, and lamps R, Y, G are in parallel circuits adapted to be closed singly and directly through the arms 2, 6, 9 of the relays Ar, Ay, Ag when operated as described above for single illumination. In this case, when relays Ar, Ay are energized and relay Ag is de-energized to give simultaneous illumination of lamps Y, G, arm 9 breaks the direct circuit through lamp G and closes a circuit through the primary of a transformer. At the same time, arms 13, 19 of relays Ay, Ag connect the lamps Y, G in series with one another and the secondary of the transformer. A further arrangement without relays is described, in which the three lamps are arranged in the secondary circuits of corresponding transformers, the primary windings of which can be singly and selectively energized. To give a combined signal, an additional primary winding common to two transformers is provided. Energization of this winding results in simultaneous energization of the secondaries of the two transformers and of the corresponding lamps. Fig. 4 shows another arrangement in which the lamps G, Y, R can be singly and selectively energized through leads 44, 43g, 45, 43y, and 46, 43r respectively. Lamps G, Y can be simultaneously energized in parallel through heads 48, 51 connected to the mid-points of inductances 49, 50..The current passes in opposite directions through the two portions of each of the impedances, so that the resultant impedance is negligible. If lamp Y fails, the lower portions of impedances 49, 50 are de-energized, and under these conditions the impedances of the upper portions are sufficient to prevent energization of lamp G. A simpler form of this arrangement is described in which the impedance, 50 is omitted.