Patent GB-845228-A (GB)
Title: Improvements relating to block working for railway signalling systems
IPC: B61L23/12
Filed: 1957-09-03
Abstract: 845,228. Block working systems. WESTING- HOUSE BRAKE & SIGNAL CO. Ltd., and TILLOTSON, P. Sept. 5, 1958 [Sept. 3, 1957], No. 27740/57. Class 105. In a block working system for the control of rail traffic over a stretch of track the block line extending between the ends of the block is open-circuited at each end when the entry of a train into the block is detected by a track circuit and a last vehicle detector positioned at one end of the block, and maintained in that open circuit condition until the exit of the train is detected by a similar track circuit and last vehicle detector positioned at the other end of the block. Fig. 1 indicates a stretch of track extending between positions A and B, AT and BT are insulated track sections at each end of the stretch with shunting track relays ATR and BTR respectively of which only the contacts are shown. AD and BD represent track side last vehicle detectors which produce signals when influenced by co-operating equipment mounted on the last vehicle of the train. The block line (Fig. 2, not shown), includes at each end the normally closed contact means ALVD and BLVD, Figs. 3a and 3b. In entering the block in the direction A-B the train releases relay ATR (not shown), thereby breaking the held circuit of relay AFM at front contact ATR2 thereby open-circuiting the the block line at f.c. AFM4, the open-circuited block line releases relays AZR and BZR (not shown) removing the earth connections from the detector lines 1 and 2 at f.c. (front contacts) AZR1, AZR2, BZR1 and BZR2. In addition, via b.c. (back contact) ATR2 relay ACOR is energized and via its f.c. ACOR1 the last vehicle detector AD is energized which produces a signal to reverse the polar stock relay ADR. Via f.c. ADR1 condenser AC2 is discharged through the pick-up coil of repeater relay ADRP which holds over its f.c. ADRP1. The pick-up circuit for relays AF and BG is completed over b.c. AFM2, f.c. ADRP2, b.c. ATR3, detector line 1, f.c. BTR3, f.c. BTR4, detector line 2, b.c. ATR4 and f.c. ADRP5, relay AF holds over f.c. AF1 and relay BG over f.c. BG1 and b.c. BDRP1. When the train passes out of track circuit AT, relay ATR is energized, switching-off the last vehicle detector by releasing relay ACOR and switching the detector line across the pick-up coil of relay AG. The block line is broken at contact means ALVD at b.c. AF3 and f.c. AFM4 and at BLVD at b.c. BG3, and remains in this condition until the train arrives at track circuit BT. On arrival the sequence of operations is as described for position A and relays BF and AG are operated in series over the detector line. At position A relay AG holds over f.c. AG1 and operates relay AFM over f.c. ADRP3, f.c. AF2 and f.c. AG2, relay AFM holds over its fc. AFM3. On operating relay AFM opens the hold circuits of relays, AF, AG and ADRP at its b.c. AFM2 and by discharging condenser AC1 through relay ADR via AFM1 reverses the relay to its original position. The switching means ALVD returns to its normally made condition. At position B relay BF prepares a circuit for relay BFM which is energized at f.c. BTR2 when the train clears the track circuit BT. Relay BFM holds over its f.c. BFM3 and returns the relays BG, BF, BDRP and BDR to their normal condition as described for position A and the switching means BLVD is returned to its normally made condition. Specification 796,439 is referred to.