Patent GB-743540-A (GB)
Title: Improvements relating to block signalling systems for railways and the like
IPC: B61L23/12
Filed: 1953-04-16
Abstract: 743,540. Railway signalling systems. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd., MACKEAN, L. G., SYKES INTERLOCKING SIGNAL CO., Ltd., W. R., and KING, V. S. April 14, 1954 [April 16, 1953], No. 10416/53. Class 105. In a railway block signalling system having block instruments of the three position type operated by code signals, a timing device at the train receiving end B of the section is set into operation on receipt of a " Train-on-line " code from the train despatching end A when the train enters the section at A and after an interval of time and the train not yet having arrived at B, the device renders the apparatus at B responsive to a " Release wanted " code from A to unlock the B signalling instrument which, when operated, transmits an " Acceptpermissive 1 " code to A permitting the entry of a following train into the section at A. In the system to be described the coding apparatus at A and B are substantially the same except that to give priority of A over B in case both should attempt to initiate a code simultaneously the relays governing the first impulse transmitted from the two stations have different operating times. The relays of a transmission relay group are each operated by the respective signalling and traffic directional control functions and operate master transmission relays which energize the line positively or negatively. Line relays associated with rectifiers pick up on the positive or negative impulses to operate repeater relays which control the functions at each signal box. Correct code operation is checked and at the end of each code a check-back that the code has been received is provided resetting the equipment ready for transmission or reception of further codes. A coding chain of relays, Fig. 5 (not shown), energize respective bus lines, Fig. 6 (not shown), the polarities of which are stored by code storage relays and are checked against the relay initiating the transmission and, if in order, the equipment is reset. At the receiving station a code delivery relay is picked up at the end of a code and in conjunction with the code storage relays selects the appropriate receiving relay (Fig. 8A, not shown). The signalling instruments are such that the A commutator cannot be moved from one position to another without the co-operation of B operating the B instrument and each instrument has a bell key for transmitting bell signals between the two stations which are connected by two line wires over which the codes are transmitted. A track circuit rail circuit combination is provided at A and B so that as a train passes out of the section a rail circuit relay, normally released, picks up followed by the track circuit relay releasing. After A has offered a train to B by bell signals in the usual way and if B can accept the train he acknowledges the bell signals and A then presses a " release wanted push-button resulting in the transmission of a code to B to unlock the B signalling instrument and to operate a buzzer to indicate that the B commutator can be operated which is then turned to the " accept line clear " position resulting in the transmission. of the relevant code to A and illuminating the B commutator indicator to show that a release code has been sent to A to unlock the A instrument and to illuminate the A commutator indicator showing that the commutator can now be operated into the " Despatch line clear " position resulting in the extinction of the commutator indicator and the A instrument indicator showing " line clear " permitting the clearing of the section entrance signal and the transmission of a code to B to extinguish the B commutator indicator and operate the B instrument indicator to " line clear ". Entry of the train into the section restores the signal to " danger " and changes the A instrument indicator to " Train on line " and transmits a code to B to change the instrument indicator to "Train on line and to initiate operation of the timing device which consists in a relay BTOLJR, Fig. 11B, which at the end of its time period of energization closes a contact and which if its energization circuit should be interrupted before the end of the period, returns to its normal unoperated position. The timing relay is controlled by relay BJS picked up on the closure of the front contact BRJR1 when a receiving relay BRJR (not shown) picks up in response to the receipt of a " Train on line " code from A and relay BJS sticks over its front contact BJS1 and at front contact BJS2 starts off the timing relay BTOLJR. The stick circuit of relay BJS includes in series back contacts on code transmission relays BTLR (operated for transmitting " accept permissive 1 " code; BTNR (operated for transmitting " accept permissive 2 " code and on a receiving relay BRPR (operated on receipt of a " Train out of section " code from A). At the end of the time period a " permissive release indication " code is transmitted from B to A by the automatic energization of a transmission relay BTBR, Fig. 4B (not shown), picked up over a front contact of timing relay BTOLJR in series with a back contact of an auxiliary relay BTOLJS, Fig. 11B, picked up over a front contact of relay BTBR and a front contact BTOLJR1 of the time relay so that relay BTOLJS picks up as soon as relay BTBR picks up to initiate the code transmission and sticks over its contact BTOLJS1 when relay BTBR releases at the end of the code transmission. Relay BTOLJR releases upon opening of contact BJS2 when relay BJS releases upon opening of any one of contacts BTLR2, BTNR2 or BRPR1. At front contact BRJR2 the indicator control relay BTOLKR, Fig. 12B, is energized and latched up and over its front contacts BTOLKR3 and BTOLKR4 the indicator is operated to a "Train on line indication and opens its back contact BTOLKR in the pick up circuit of relay BLCR which at front contacts BLCR1 and BLCR2 when operated, complete alternative energizing circuits of reverse polarity for the indicator to operate it into a " line clear " indication. When both relays are released the indicator returns to its central " line blocked " position. The relay BTOLKR releases when its latch coil is energized on receipt of codes " train out of section 1 " or " Train out of section-check" to operate receiving relays BRMA or BRPR (not shown) to close the front contact BRMR2 or BRPR, Fig. 12B. These circuits include front contact BLBR3, proving, when closed, that the commutator is in its normal line blocked position. Assuming that the first train has not arrived at B before relay BTOLJR has completed its operation, the instrument indicators at A and B show " train on line " indications, the A commutator is at " Despatch line clear " and the B commutator at " Accept line clear ". At the end of the time period front contact BTOLJR4, Fig. 12B, closes to illuminate the " Permissive release " indication lamp BPRK and a corresponding code is transmitted to A the receipt of which results in illuminating a " Permissive release " indication and in picking up a receiving relay ARBR (not shown) to enable transmission of a " Release wanted " code by operation of the A " release wanted " push-button. A is prevented from transmitting a code requesting B for another release code until he has received the " Permissive release " indication code signifying that the time delay before a following train may enter the section, has expired. This is effected when the commutator is moved to its " Despatch line clear " position by opening contacts in the energizing circuit of a relay ALBR, Fig. 9A (not shown), similar to relay BLBR, Fig. 9B, controlling the energization of a relay ATLR (not shown) for transmitting the " release wanted " code and providing a pick-up circuit for that relay ATLR closed on picking up of a receiving relay ARBR (not shown). Receipt of the " release wanted " code at B results in picking up of receiving relay BRLR (not shown) which at contact BRLR2, Fig. 12B, energizes a buzzer X. B then moves the commutator towards the " Accept line clear-permissive 1 " position and in so doing closes contacts LC-PER1, Fig. 9B, to close the energizing circuit of the " commutator lock " winding over contact BRLR3 to enable the commutator to continue its movement into the " Accept line clear permissive 1 " position to close contacts to pick up a transmitting relay BTLR (not shown) for transmitting the "Accept permissive 1 " code to A and at contact BTLR2, Fig. 11B, to release relay BJS which in turn terminates the operation of the timing relay BTOLJR, followed by release of relay BTOLJS. Relay BTLR also releases the receiving relay BRLR which stops the buzzer and effects illumination of the commutator indicator. Release of relay BTOLJR at contacts BTOJR4 extinguishes the " Permissive release " indication at B. Receipt of the code " Accept permissive 1 " at A operates a receiving relay ARLR (not shown) to operate a buzzer as at B and illuminate the commutator indicator and A moves the commutator to the " Despatch permissive 1 " position to pick up a transmission relay ATDR1 (not shown) to transmit a code " Accept permissive 1 check " to B and extinguish the commutator indicator at A. Receipt of this code at B picks up a receiving relay BRDR1 (not shown) which at contact BRDR1 releases relay BCKR which at its contact BCKR2, Fig. 12B, extinguishes the commutator indication lamp BCK. Relay BCKR also releases relay BRDR. The instrument indicators at A and B are at " Train on line position ". A now operates the signal lever to display a permissive aspect as the second train enters the section, the signal returns to stop and a " train on line " code is transmitted to B. Receipt of this code at B effects the picking up of the receiving relay BRJR(not shown) which at BRJR1, Fig. 11B, as before energizes relay BJS and energizes the timing device which at contact BRJR4, Fig. 9B, picks up relay BRJS over commutator contacts ACC-PER1-ACC-PER2 which are clo