Patent GB-563284-A (GB)
Title: Improvements relating to railway traffic controlling apparatus
IPC: B61L19/06
Filed: 1942-10-20
Abstract: 563,284. Railway signalling systems. TOMLINSON, A. V. (Union Switch & Signal Co.). Oct. 20, 1942, No. 14682. [Class 105] In a central traffic control system for railway traffic in either direction over a stretch of single track subdivided into block sections with a head-block signal for each direction governing entrance to the end sections of the stretch, and with a signal for each intermediate section for each direction, the setting of the head-block and intermediate signals for the desired direction is effected by supplying a checking code to the track circuit at the entrance end of the entrance section and relaying this code through the other sections of the stretch in succession, to set the signals for the opposite direction to " stop." The reception of this code at the exit end of the stretch causes code of a substantially different frequency to be relayed from the exit end to the entrance end, the reception of this latter code at the entrance clearing the entrance headblock signal. The checking code described has frequency of 20 per minute, the other codes being of usual 75 and 180 frequencies. The Specification gives a complete circuit diagram showing the invention applied to known C.T.C. circuit arrangements. The circuits are shown as conditioned for west-bound traffic and are traced in detail for the change-over, described below, for east-bound traffic between passing sidings from signals 4RA, 4RB at the west end of insulated section 3T, Fig. 1e, to signal 9R, the entrance to the siding section (not shown) to the east of section 9LT, Fig. 1k, over intermediate section 4RT, Fig. 1f, 13T, Fig. 1g, and other intermediate sections 12T, 11T, 10T (not shown). Each block in the stretch includes at least two track circuits. In each circuit, to allow feed of coded energy in either direction as required, a code-feeding transformer 4 is connected across the rails at each end of every section. At most locations (as in Figs. 1f, 1g, 1k) a track relay transformer 33 is connected in series with the code-feed transformer, and serves to energize a code-following track relay, such as 4RTR, 4RATR, Fig. 1f, or 9LATR, 9LTR, Fig. 1k, through a full-wave rectifier 34. At certain locations a limiting resistor 7 is included in series with transformer 33 and a neutral or polarized direct-current track relay is connected across the rails, such as 4RTRAR, Fig. 1f, or 9LTRA, Fig. 1k. Coded A.C. energy is supplied from a source BX, CX over the appropriate contact CT20, CT75 or CT180 of a code transmitter CT of known kind (not shown) and during supply of this code the secondary winding of transformer 33 is short-circuited, as by contact 13ATR, Fig. 1f. Certain sections are provided with track batteries TB in series with resistors 6 to supply the track with direct current superposed on the coded A.C. current, this direct current being controlled, as by repeating relay contacts such as 13ATRAPR, Fig. 1f, which effect pole-changing, to provide for approach locking of switches, overlap control at ends of sidings, and control of visible or audible indications of train movements in usual way. Change over from west-bound to eastbound traffic, or vice versa, is initiated by energizing the appropriate direction selecting (HSR) relay, RHSR relay for east-bound, LHSR for west-bound traffic. The appropriate relay may be operated in known way selectively, by code, or, as described, by hand lever (not shown), directly controlling the relay circuits. To establish east-bound traffic between signals 4R, 9R, lever-controlled relay 4RHSR, Fig. 1e, is energized, and its pick-up de-energizes, at contact 61, west-bound locking relay 4RWFR, Fig. 1f, and supplies 20 code to section 4RT over contact CT20, back contact 63 of eastbound locking relay 4REFR, front contact 65 of relay 4RHSR and transformer 4, which is alternately energized and shunted by contact CT20. At the same time the supply of 7.5 code (used in west-bound traffic) is stopped by release of contact 4RWFR in the lead from contact CT75 to transformer 4. During the " on periods of the 20 code, the secondary winding of transformer 33 is shunted over wire 68, front contact 69 of relay 4RHSR, back contact 71 of relay 4REFR, a second CT20 contact moving in synchronism with the first, and wire 73. During the " off " period of 20 code, the second CT20 contact closes the circuit from transformer 33 secondary through rectifier 34 so that " proceed " code may be received by the code-following relay 4RTR, when this code is supplied later. The 20 code supplied to section 4RT is passed to code-following relay 4RATR and contact 45 of this relay, Fig. 1g, relays the 20 code via transformer 4 into the track of section 13T at the end J of which west-bound signal 13 is situated. The 20 code is picked up, through transformer 33 and rectifier 34, by code-following relay 13TR, contact 46 of which supplies D.C. at 20 code frequency from source B,C to the primary of a transformer 5 through relays 13FSAR, 13BSAR alternately. Both these relays are sufficiently slow-release to remain picked up on 20 and higher code frequencies. Relay 13SR is, therefore, de-energized at open contact 78 of relay 13FSAR. Relay 13HR is connected alternately to opposite ends of transformer 5 secondary by the " mechanical rectifier " contact 47 of relay 13TR, but is designed to release on 20 code. Relays 13HR, 13HPR release and signal 13 therefore displays its most restrictive indication. Note the separate circuit diagram for signal 13 at lower left-hand corner of Fig. 1g. The 20 code is relayed through the sections of succeeding blocks (not shown) in a manner similar to that described above, setting the west-bound signals en route to their most restrictive indication. Ultimately, 20 code is supplied to section 9LT, Fig. 1k, over the code-following contact of relay 10ATR of the preceding section 10T, Fig. 1j (not shown). Relay 9LTR follows this code and its contacts supply D.C. current to relays 9LFSAR, 9LBSAR which remain energized, and to relay 9LHR, which does not energize on 20 code. Signal 9R therefore indicates " stop." Release of relays 9LHR, 9LHPR closes the circuit of east-bound locking relay 9LEFR, the energization of which opens the circuit of the previously energized west-bound locking relay 9LWFR at contact 53. A contact of relay 9LEFR closes a shunt circuit for secondary winding of transformer 33 so that relay 9LTR ceases to operate and relays 9LFSAR, 9LBSAR release. Relay 9LEFR, however, remains energized over a stick contact bridging the contacts of these two relays. Another contact of relay 9LEFR removes the shunt from primary winding of transformer 4 and connects this winding to a contact CT75 for supplying 75 code to the right-hand end of section 9LT. Code is relayed back over the stretch, in a manner analogous to that described above, the code being fed at the right-hand end of each section and picked up by a code-following relay at the left end. Thus, during " off intervals of 20 code, relay 9LATR follows the 75 code and relays this into section 10T, Fig. 1j (not shown), causing signal 10 (not shown) governing east-bound entrance to that section to indicate. " caution." With the signal relays 10HR, 10HPR, Fig. 1j (not shown), engaged to give this indication, contact is closed to relay 180 code into the next section, instead of 75 code, and 180 code is then relayed throughout the remainder of the stretch, so that remaining east-bound signals up to and including the 4R entrance signals, give the " clear " indication. The 180 code is relayed to section 4RT, Fig. 1f, over contact 13ATR and when relay 4RTR is energized in response, relays 4RFSAR, 4RBSAR, 4RHR, 4RHPR and 4RDR pick up in turn. (The DR relays throughout the system pick up only on 180 code through a decoding unit 35). Contacts of relays 4RHR, 4RHPR complete the circuit of east-bound traffic locking relay 4REFR. Pick up of this relay cuts off supply of 20 code at contact 63, Fig. If, and completes the circuit of relay 4RAHR at contact 96, Fig. 1e, leading to the clearing of signal 4R. Provision for following moves in the intermediate blocks of the single-track stretch is made in known manner by the use of directional stick relays (SR). The operation above described assumes the stretch unoccupied. The Specification describes the traffic reversal before a train is completely out of the " OS " section, to minimize loss of time with " meeting trains, The invention dispenses with all control line wires except those for the C.T.C. coded line circuit and a pair of approach locking wires for the passing siding section: