Patent GB-839260-A (GB)
Title: Improvements in railway train control and cab-signalling systems
IPC: B61L3/22
Filed: 1957-02-01
Abstract: 839,260. Train control and cab-signalling systems. FORGES ET ATELIERS DE CONSTRUCTIONS ELECTRIQUES DE JEUMONT. Feb. 1, 1957 [Feb. 17, 1956], No. 3571/57. Class 105. In a train control and cab-signalling system, current impulses of repetition frequency indicative of the prescribed speed of a vehicle over a section of track are transmitted under the control of the track relays in an existing track circuit in accordance with traffic conditions in adjoining sections of track, through a cable laid along the track section and the impulses are picked up by inductive pick-up devices carried on the vehicle and utilized for giving an indication as regards the manual control of the speed of the vehicle or for automatically effecting such speed control of the vehicle. The impulsecarrying circuit may be remote controlled from a central office. When the speed control is made automatic a frequency comparator compares the frequency of the impulses received with a locally-generated frequency proportional to the speed of the vehicle, the differential output of the comparator being applied to effect the automatic control of speeds and stops of the vehicle. In the case of manual control, the received frequency is applied to give an indication on a frequency meter. As shown, the section LA, e.g., has a length greater than the normal braking distance FA of a vehicle and the impulse generator 3A feeds the transmission cable 8A at a point P which corresponds to the braking distance FA before the signal S, so that the impulses i travel from the point P along the cable 8A in both directions as impulses i and i2 returning to the other pole of the generator 3A by conductor 18A, or by conductor 19A through contacts of a relay 27A and in either case through contacts 20 under the control, e.g., of a central office. The relay 27A may be supplied with energizing current over a contact 16 of the track relay 6 of the ahead section L or over a contact 16A of the track relay 6A of the section LA. The contacts of and the relay 27A itself are on the ahead side of the point P. Vehicle V in the section LB will receive, by its pick-up coils 29, impulses circulating in cable 8B, and these impulses are amplified in amplifier 33 to feed a small synchronous machine 30 and a frequency comparator 31 to which is also fed impulses from a source 32 generating impulses proportional to the speed of the vehicle and if this latter speed is at its correct prescribed value, the arm 34 of the comparator remains in its neutral position shown. If the speed of the vehicle is too low, the arm 34 moves to the right and feeds the circuit 36 arranged to produce automatic acceleration of the vehicle. If the speed of the vehicle is too high, the arm 34 will move left and feed the circuit 35 arranged to slow down and brake the vehicle automatically. Thus the speed of the vehicle in each track section is controlled automatically by the normal frequency of the impulses which circulate in the section cable, 8, 8A, 8B. Assuming signal S is at " Stop " or " Danger " and signal SA at " Caution," of the contacts 16, 16A track relays controlled by the signal positions, contact 16A would be closed and contact 16 would be open. On the vehicle entering the section LA, track relay 6A would be de-energized and contact 16A opened, resulting in the de-energization of relay 27A which interrupts the impulse circuit through conductor 19A, but the circuit through conductor 18A remains closed and the vehicle continues to travel at its normal speed precribed by impulses il. When it passes point P its pick-up no longer receives impulses and the synchronous machine 30 continues to revolve as an alternator by virtue of its stored-up inertia in a flywheel 30A and feeds a frequency to the comparator gradually decreasing down to zero, and the output of the comparator fed to the control circuit 35 slows down the vehicle to a complete stop in front of the " Danger " signal S. When the signal S changes to " Caution " or " Clear " the energizing winding of relay 27A is completed at contact 16 and the current impulses i2 are restored and the pick-up 29 will restart the vehicle to gain speed in proportion as the synchronous machine 30 accelerates to its prescribed normal speed. The cables such as 8A are arranged to be displaceable laterally to interrupt impulse reception to obtain a local slow-down of the vehicle, e.g. during repair work on a section.