Patent GB-519772-A (GB)
Title: Improvements in automatic train control systems
IPC: B61L3/12
Filed: 1938-07-29
Abstract: 519,772. Railway signals. BOOT, J., and GENERAL RAILWAY SIGNAL CO., Ltd. July 29, 1938, No. 22657. [Class 105] Warning signals are given at an outer distant signal, not at clear,. on any train passing at excessive speed and at an inner distant signal on all trains except those passing at a small minimum speed. A location-indicating signal is given in passing any signal point. A timeinterval device measuring, say, two seconds is used in conjunction with spaced track devices. At the outer distant signal, the spacing is' such that only trains passing at over, say, 60 miles per 'hour reach the second track. device before the 2 seconds have elapsed. At the inner distant signal there are three track devices, the distance between the first and second is such that all trains passing at more than, say, six miles per hour reach the second in less than two seconds and the distance between the first and third is such that all trains passing between 25 and 100 miles per hour reach the third in less than two seconds. The third track device is necessary since the train-interval device does not become operative in, say, the first half-second and in that time trains travelling at more than 25 'miles per hour would have passed over the second track device. Relay. R' is energized by current passing through coil S on the traincarried device M and when the latter passes over an unwound track device, or one of which the circuit is open, the current is sufficiently reduced to de-energize relay R<1>. The circuit of relay R<2> is broken at b of relay R<1> and contacts b, d of relay R<2> cause R' to pick up again at once. The holding circuit of a time-interval device RM is broken at contact c of relay R<2> and shortly afterwards a cam OC1 operated by RM closes contacts a, b of OC1 and keeps them closed until the end of the time-interval. Contact b of OC1 causes R<2> to pick up again and contact a of OC1 energizes an indicator 1D on the train. A circuit of relay R<3> is broken when R<1> is de-energized but another circuit through c of a second cam OC2 is not at that time broken. On the completion of the time-interval, the device E returns to its initial position and is held here because the relay R<2> is re-energized. If a second track device with open circuit is reached before the end of the time-interval, R<1> and R<2> are again de-energized and R<3> also is de-energized because its second circuit is broken at c of OC2, the re-setting circuit of R' is also broken at d of OC2 so that R' remains, de-energized. With R' de-energized the restraining circuit of a second indicating device VH and, it may be, a brake control is broken at c, d of relay R'. The apparatus may be reset or its action restrained by means of a handoperated device AK which, when depressed, closes at c, d and b resetting circuits for the relays R<1>, R<2> and R<2> and pneumatically by means of a piston P and a device RS returns the timeinterval device to zero. When the device AK is depressed, it brings VH into operation by breaking its circuit at a. In a modification, a location warning only is given on vehicles passing an outer distant'signal at speed and on all vehicles passing an inner signal at any speed above a small value. Only one indicator 1D is provided and this is controlled by relay R', the device AK is used only to restore the timeinterval device and the latter is restored whether or not an indication has been given. All the track devices are unwound or have open circuits.