Patent GB-234883-A (GB)
Title: Improvements relating to railway signalling apparatus
IPC: B61L5/18
Filed: 1924-02-29
Abstract: 234,883. Peter, L. H., and Westing- house Brake & Saxby Signal Co., Ltd. Feb. 29, 1924. Miniature signals or indicators and the like.- In railway signalling an indication of the particular signal operative is transmitted to a distance by corresponding variation in phase or magnitude of alternating current. The signal S, Fig. 1, has two control windings 1, 2 supplied with A.C., the current through winding 2 being controlled from a signal cabin &c. One end of winding 1 is connected to one terminal of an indicator I, and an intermediate point of the winding 1 is connected through conductor 5, contacts 6, 7, and then through one or other of the contact points 8, 9, 10 and conductor 4 to the other terminal of indicator I. The indicator I is a power-factor meter giving one of four different indications according to whether the indication current has a unity, lagging, or leading power-factor or is zero. Contact 7 is operated in conjunction with the signal S, for example, it may be operated by a signal spectacle having three positions bringing correspondingly differently coloured discs in front of a lamp. Contact points 8, 9, 10 are respectively connected to conductor 4 through inductive resistance 11, non-inductive resistance 12, and condenser 13 giving respectively lagging, unity, and leading power factor. The indicator I shows which of the three signalling positions is operative, and also the open position of contact 6 when no signal is being given. In a modification, the direct connection between coil 1 and indicator I is replaced by a connection between coil 1 and the mid-point of coil 2, and a connection between indicator I and the mid-point of an inductive bridge across the leads supplying coil 2. In the, alternative method of indicating the signal condition by variation in magnitude of the indicating current, the contact 7 is arranged to connect the indicator to different points in a transformer winding, which may be the winding 1, the resistances 11, 12 and condenser 13 being omitted. The indicator in this case is, of ammeter or voltmeter type. Applications of both methods to signals having three different lamps are described. In there, the single contact 7 is replaced by contacts individual to the lamps, and these may be operated by thermosensitive or other relays. Fig. 7 shows a further modification in which the indicating current is rectified. The indicator l is of direct current type arranged to give four different indications with, respectively, zero current, normal strength current of one polarity, normal strength current of reversed polarity, and current of decreased strength. One terminal of a transformer 33 is connected through a rectifier 35 to a fixed contact 8, the other terminal being connected through a rectifier 38 direct to a fixed contact 10, and through a resistance 40 to a fixed contact 9. Midpoint of winding 2 is connected to a contact 6 in series with the contact 7 which co-operates with the points 8, 9, 10. Indicator I is connected between the midpoints of winding 33 and a bridging inductance 15 across the leads supplying winding 2. The contacts 6. 7 are operated in conjunction with the signal as before. The rectifiers 35, 38 which are preferably of the type described in Specification 194,653. [Class 38 (ii), Electric currents, Converting &c.], are arranged to suppress different halves of the alternating current. Normal strength current is thus supplied of one polarity to contact 8 and of reverse polarity to contact 10, and current of reduced strength to contact 9. The invention is also applicable to multiple aspect signals in which lamps are used singly and in combination.