Patent GB-627867-A (GB)
Title: Improvements relating to intermittent inductive train control systems
IPC: B61L3/12
Filed: 1946-10-23
Abstract: 627,867. Railway signalling systems. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd., PETER, L. H., and SHIPP, D. G. Oct. 23, 1946, No. 31426. [Class 105] In a railway signalling system with intermittent inductive type control of the locomotive apparatus by track cores with windings tuned to a particular one of one or more frequencies, the locomotive receiver apparatus is of the normally-balanced magnetic bridge type the energizing winding of which is fed with currents of the one or more frequencies. The action is that on passing a track core the receiver is briefly unbalanced for all fluxes except that of the one particular frequency to which the track core is tuned and the fluxes of the other frequencies then arising in the normally fluxless " cross " arm of the magnetic bridge cause brief energization of relays tuned to such other frequencies. Fig. 2 shows a signalling system in which the signal aspects R, Y, YY, G at the entrance to an occupied section and the succeeding sections to rear cause the track inductor 1 to be open circuited, and then tuned to frequencies f<SP>3</SP>, f<SP>2</SP>, f<SP>1</SP> by a signal contact 4 bridging appropriate contacts. The locomotive apparatus is shown in Fig. 1 and comprises a multi-frequency motor generator 10 feeding a normally balanced magneticbridge type inductor 5 and an inductor 6 with a suitably disposed auxiliary core and secondary winding 17 which feeds a relay F<SP>1</SP>A responsive only to frequency f<SP>1</SP> and a relay F responsive to all the frequencies f<SP>1</SP>, f<SP>2</SP>, f<SP>3</SP>. In the magnetic bridge inductor 5 the cross " arm of the bridge has a secondary winding 11 feeding relays F<SP>1</SP>, F<SP>2</SP>, F<SP>3</SP> respectively responsive to frequencies f<SP>1</SP>, f<SP>2</SP>, f<SP>3</SP>. Accordingly on passing a signal at aspect G i.e. with the track inductor tuned to frequency f<SP>1</SP>, the locomotive inductor 5 will have currents of frequencies f<SP>2</SP> f<SP>3</SP> induced in the " cross " arm winding 11 since the track inductor will act as a plain iron for these frequencies but for frequency f<SP>1</SP> will act as a bucking winding, a plain iron causing an unbalance of flux distributions in the bridge. Thus the relays F<SP>2</SP>, F<SP>3</SP> will be briefly energized to pick up relay GR over back contact a of relay F<SP>1</SP> and front contacts a of relays F<SP>2</SP>, F<SP>3</SP>. A single stroke bell 14 is energized over front contacts d of relays F<SP>2</SP>, F<SP>3</SP>. The pick up circuit for relay GR includes front contact a of relay F<SP>1</SP>A and front contact C of a relay MR. The locomotive inductor 6 which passed the track inductor shortly previous to the magnetic-bridge inductor 5 passing thereover had the flux corresponding to frequencies f<SP>2</SP>, f<SP>3</SP> diverted from it secondary winding 17 but as frequency f<SP>1</SP> was effective the relays F<SP>1</SP>A, F were not affected. At a YY aspect (track inductor tuned to frequency f<SP>2</SP>) the prior passage of locomotive inductor 6 briefly drops relay F<SP>1</SP>A (since there is now no bucking effect as regards frequency f<SP>1</SP>) to open at its contact a the stick circuit for relay GR and to sound the single stroke bell 14 at its contact b. The magnetic-bridge inductor 5 follows shortly thereafter and as f<SP>2</SP> is now the bucking frequency the relays F<SP>1</SP>, F3 are briefly energized thereby picking up the relay YYR and sounding the single stroke bell. Thus at passage of a YY signal there are two strokes on the bell. A similar action arises for the Y aspect. At the R aspect the locomotive inductor 6 has all flux diverted from the winding 17 and accordingly the relays F<SP>1</SP>A, F drop and open the stick circuit of relay MR whereby a braking is initiated unless an acknowledgment key 22 is pressed. As regards the bridge inductor 5 all the relays F<SP>1</SP>, F<SP>2</SP>, F3 are briefly energized but no cab signal relay GR, YYR or YR is picked up ; thus the cab signal R is energized over back contacts of these last relays.