Patent GB-978559-A (GB)
Title: Improvements in or relating to train control
Inventor: MALAQUIN ANDRE
IPC: B60L15/20
Filed: 1961-05-09
Abstract: 978,559. Automatic train control systems. SOC. INDUSTRIELLE DE LIAISONS ELECTRIQUES. May 9, 1961, No. 16897/61. Heading B7N. A train braking control apparatus for ensuring that braking is carried out safely between a first predetermined point at the start of a braking zone and a cessation of braking point on or at the end of said zone, comprises means for generating a signal as the train leaves each of a number of equal fractions of the zone, means for counting the number of signals generated, means for comparing the difference between the number of signals counted, i.e. the number of equal fractions passed through by the train and the total number of fractions in the zone, said difference being indicative of the safety speed, with the actual speed of the train and means for controlling the train for maintaining its actual speed below the safety speed. The braking zone fractions are measured by a counting chain No. 1, Fig. 7 (not shown), which initially counts the pulses generated by a wheel operated pulse generator when the train is travelling between two magnetic beacons spaced the prescribed fraction of the braking zone apart. At the end of the counting period the count is stored, the counter issues an output pulse and restores the counting stages to zero, thereafter the counter continues counting the pulses and issues an output pulse and restores its counting stages to zero each time the number of pulses counted equals the initial number stored. The output pulses are counted in a second counter which records the number of equal fractions of the zone passed through. The beacons, Fig. 5, are disposed on the track in positions which depend on the required speed of the train at the end of the braking distance, e.g. beacons BA, BB are used when the train has to stop at signal Si and beacons BD<SP>1</SP> and BD are energized when the speed has to be reduced to 60 km./h. at signal Si. The distance d is always the same fraction of the total length of the zone, e.g. onehundredth thereof, even though braking is carried out over only a portion of the zone. The second counter, Fig. 8, is operated to count another fraction each time contact Z3 is operated by the first counter and is arranged so that only the last counting relay Ll . . . Lq to operate stays picked up. The counting relays have contacts serially connected in a comparing circuit of the type described in Specification 971,823, in which the safety speed, which is a function of the difference between the tota number of fractions in the zone and the number counted is compared with the actual speed measured each time relay Z operates, by a third counting chain, Fig. 9 (not shown). In the arrangement shown in Fig. 10 when the train has to reduce its speed to a set value at the end of the braking zone a third beacon, e.g. BCa, is provided in a position appropriate to that speed. If the train picks up a track current signal at frequency fl indicating slow speed before it reaches beacon BA, a relay contact frl picks up and when the train passes BA relay CB picks up via contacts of a relay A (not shown) which is energized on passing BA. A contact cb3 of relay CB opens the circuit to the second counting chain and thus prevents initiation of braking until relay CB is released on passing beacon BCa. The braking, Fig. 4, is thus delayed until passing beacon BCa and follows curve R until the train speed reaches the required value G at the end of the zone. Where the train is initially required to stop at the end of the zone and this instruction is changed to a slow speed aspect, e.g. after the train has passed beacon BCa, the train commences braking on passing BA as a result of the before-described comparison and in addition to the fractional pulses being counted in the second counting chain, these pulses are also counted in a fourth counting chain, Fig. 13 (not shown). On passing beacon BCa relay CA, Fig. 11, picks up and opens the counting pulse circuit to the fourth counting chain. Assume the change aspect to slow speed signal occurs at time x, Fig. 4, relay contacts fr3, fr4 are picked up by current at a particular frequency in the track circuit and relay CC is energized. Contacts of this relay energize relay CD which on opening its contact cd2 stops further counting in chain No. 2, whereby the train is controlled to a constant speed determined by the last relay in this chain to operate and the counting stages of counting chain number 4, which is provided with means for storing the count, are reduced to zero. The train is controlled to the constant speed until the number of "fractional " pulses counted by chain 4, which immediately starts recounting on being restored to zero, equals the number sorted. On equality being reached, a relay picks up and reconnects the circuit to counter number 2 and braking recommences. Referring to Fig. 4, under this condition the train speed is reduced from D to E along curve F, remains constant from E to F and is reduced to value G at the end of the zone along curve R. Specifications 804,427 and 972,859 also are referred to.