Patent GB-509066-A (GB)
Title: Improvements in railway signalling devices
IPC: B61L3/20
Filed: 1938-03-11
Abstract: 509,066. Railway signalling - apparatus. SOC. AUXILIAIRE D'ETUDES ELECTROTECHNIQUES. March 11, 1938, No. 7673. Convention date, April 21, 1937. [Class 105] Signals are given on locomotives and at stations or level crossings by means of traincarried A.C. generators of constant frequency giving an electromotive force proportional to the train speed through the excitation being provided by an axle-driven dynamo having a constant field. Fig. 2 shows an arrangement in which the signalling current is applied to the trolley wire 11 supplying the traction current, there being two collecting trolleys 13, 14 spaced as far as possible whereby the intervening impedance 103 of the trolley line causes operation of a differential relay 44, 49 so that the locomotive signals are operated only by ahead conditions and not by rear conditions ; an axle-driven commutator 123 alternately applies the signal current to the trolley line and gives a short-circuit, for the signal-current frequency, between the trolley line and the track, whereby a warning is given to any train in the rear. Fig. 3 shows the apparatus at a level crossing. The warning signal at the crossing comes into action a constant time before the arrival of the train whatever its speed and if the gates are not eventually closed the train is stopped. The gates are locked till the train has passed. With the apparatus in the condition shown in Fig. 3, a short-circuit for the signal current exists between the trolley line 11 and the rails 10 over the wires 59 and 64 since the rejector 63, 67 is rendered non-effective by a secondary winding 66, the circuit of which is closed at contact 71 and includes a galvanometer winding 74. Rejectors 60, 61 and 79, 80 prevent the traction current reaching the apparatus. An approaching train will therefore move the galvanometer needle 82 on to a contact 199 when the current, determined by the speed and distance, reaches a certain value. A winding 205 is thus energized from a battery 84 and closes a contact 211 whereby the warning signal 86 and a holding winding 217 for the contact 211 are energized. In addition, a winding 235 is energized over its own back contact 233 so that this winding is intermittently energized and so vibrates the contacts 71, 77, whereby the signal-current rejectors 63, 67 and 65, 69 are intermittently ineffective and thus the trolley wire 11 is alternately short-circuited to the rails, for signal-frequency current, and connected to the ahead trolley wire 11<1> to operate the apparatus at an ahead level-crossing. As the train approaches nearer to the first level crossing, the galvanometer needle 82 will close a contact 200 whereby a winding 208 is energized and closes a contact 240 to operate a winding 242 which lifts a locking dog 244 from a disc 246 so that a locking dog 248 is now free to drop into a locking notch 249 when the gates are closed (by operating a lever 195) and thereby locks the gates in the closed position; this dog 248 also closes a contact 238, whereby the winding 235 is now steadily energized and thus the contacts 71, 77 'are now respectively steadily open and closed. As the contact 71 is steadily open there is no longer an intermittent shortcircuit from the trolley wire 11 and therefore the locomotive signal current does not increase to the extent required to operate the cab signals. Thus, with the level-crossing gates locked in the closed position, the train proceeds at full speed. When the train is past the levelcrossing and reaches a pair of insulated rails 98, 99, the holding winding 217 is shunted out, whereby a contact 220 is closed to energize a winding 223 by which the locking dog 248 is lifted and the gates can then be restored to the open position. If the train should slow down sufficiently or stop before reaching the crossing, the galvanometer needle 82 would recede to a contact 198, whereby a winding 202 would be energized and open a contact 210 so disconnecting the battery 84 and restoring the apparatus to the unoperated condition. The locking arrangement for the lever 195 can be applied to lock a points lever in either position by providing a second notch 249. The locomotive apparatus comprises a synchronous motor 16 operated by the traction current supply and driving an A.C. generator 15 giving an electromotive force proportional to the speed through its excitation being given by an axle-driven dynamo 23. An axle-driven commutator arm 123 periodically applies, when on a contact segment 125, the A.C. signal current 'from the generator 15 to the trolley wire 11 over a transformer 29, 30, lead 35 (with traction-current rejector 33, 34) and the two branches 37, 39 leading to the two trolleys 13, 14. Assuming a short-circuit on the trolley wire at some distance on the righthand side then due to the impedance of the portion 103 of the trolley wire between the two trolleys 13, 14, the currents in the branches 37, 39 will be unequal and thus the differential galvanometer 44, 49 will operate its needle 50 to the right and' eventually will close a contact 53 to operate a warning signal 57. When the commutator arm 123 is on the contact segment 124, the winding 29 of the transformer is shortcircuited and a short-circuit exists (for the signal current) between the trolley wire 11 and the rails. This short-circuit would effect a signal control on any train in the rear. While the commutator arm 123 is on this segment 124 an additional contact 150 on the arm energizes a winding 146 by which the galvanometer needle 50 is held in its deflected position. The locomotive apparatus also includes signals for failure of the signalling and relay current supplies and breakage in one of the branches to the trolleys.