Patent GB-599040-A (GB)
Title: Improved means for signalling on railways
IPC: B61L3/12
Filed: 1945-09-12
Abstract: 599,040. Railway signalling apparatus. FLETCHER, K. A., and BURNS, Ltd., J. Sept. 12, 1945, No. 23562. [Class 105] Cab signals and cabin indication of the position of a train are transmitted by shortwave oscillators (50-500 cms.) preferably through dipole antennae transversely arranged on the locomotive and on the track the signals being given by the increase of anode current on approach to trackside signal locations such increase of anode current operating relays included in the anode circuits of the locomotive and track oscillators. The track transmitters are energized in accordance with the trackside signal but the locomotive transmitters are continuously in,operation; neon lamps are included in the various anode circuits to give warning of failure of the transmission by their extinction. At a homesignal thera are two near-spaced track dipoles which give an increasing current on a locomotive to show by a warning milliameter with a reddened scale section when the danger limit point is reached. Different frequencies are used for the Distant, Home and Clear signal indications and these frequencies are stabilized by filters. Fig. 1 shows a track arrangement of a dipole A for Distantsignal, two near-spaced dipoles C, D for Home signal, and a dipole E for Clear signal, energized through filters J from short-wave oscillators F, G, G<1>, H, which may be of the Colpitts or Barkhausen-Kurz types, fed by power packs K. Cabin indications of the approach of a train are shown by the lighting of lamps 19 on a miniature diagram Fig. 4, when the increasing anode current eventually causes a relay 17, Figs. 1 and 3, to close a contact. A neon lamp 14, alight so soon as the cabin switch 13 is closed to energize the track oscillator, denotes that the apparatus is in effective condition. The filaments of the oscillator valves are kept permanently alight. The locomotive carries three dipole Q, R, S, Fig. 2, energized by oscillators T, U, V with associated relays W, X, Y to give the Home, Distant, and Clear signals when increased anode current on approach to a track signalling point causes operation of a particular one of these relays. Fig. 6 shows the electrical interlocking of the relays. Normally the relays are inoperative being energized only by normal anode current and consequently a Clear signal lamp is lit from a battery 28 over back contacts 25, 29, 30 of relays Y, X, W. A Distant signal lamp is lit from battery 28 over back contact 34 of relay W and front contact 32 of relay X when approach to a Distant'signal track dipole A causes increased anode current in the oscillator U associated with relay X. The relay X thereafter retains its contacts by the normal oscillatory anode current so that this signal continues to be shown. Similarly on approach to a Home signal track dipole C increased anode current in the oscillator T associated with relay W causes a Home signal lamp to be lit from battery 28 over front contact 35 of relay W. A brake or a propulsion-power cut-off relay 2, Fig. 2, may also be operated by the Home signal relay W. When a Clear signal is transmitted to a train from a track dipole E the energization of the Clear signal relay Y cancels the Home signal or Distant signal indication by opening the circuit of the relay X or W at back contact 26 of relay Y and thereafter the Clear signal is given over back contacts 25, 29, 30 on departure from dipole E. A Colpitts oscillator is shown in Fig. 7 as having a neon lamp 23 in its anode circuit to denote effective operation of the valve and as being coupled through a coaxial feeder 12 to the locomotive dipole antenna, Fig. 8. The oscillators have their connectors arranged as plug-in units.