Patent GB-817299-A (GB)
Title: Railway train control and cab signalling apparatus
IPC: B61L3/08
Filed: 1956-12-03
Abstract: 817,299. Train control and cab-signalling apparatus. FORGES ET ATELIERS DE CONSTRUCTIONS ELECTRIQUES DE JEUMONT. Dec. 3, 1956 [Jan. 21, 1956], No. 36864/56. Class 105. Train control and cab-signalling apparatus for indicating on a railway vehicle that a specific operation such as reduction of speed or stopping or for automatically effecting such operations comprises on the vehicle a first source of current of frequency proportional to the speed of the vehicle, a second source of current of frequency variable in proportion to the desired rate of decrease of speed of the vehicle, e.g. after passing a distant signal at " caution " aspect, and set into effective operation by a receiver responsive to the state of the successive track circuits and a frequency comparator to compare the two frequencies, the differential output of which is used to provide an aural or visual indication of a desired operation to be performed by the driver or automatically to effect such operation. As shown in Fig. 3, a synchronous motor 30 coupled to a flywheel 30A is driven, by a generator 32, the output frequency of which is proportional to the vehicle speed, until a magnetic receiver contact 28 in the driving circuit is opened as the receiver passes over a co-operating magnet on the track, energized when the distant signal is at " caution " whereupon the machine 30 continues to rotate and functions as an alternator, the frequency output of which gradually decreases in a manner adjusted to represent the desired rate of speed reduction, the two frequencies being now compared in a frequency comparator 31 the differential output controlling a movable contact 34. On observing the distant signal at " caution '' the driver will reduce speed sufficiently to stop before reaching the home signal, the two frequencies being then approximately equal and contact 34 remains central. If the braking is insufficient, the frequency of generator 32 is the higher and contact 34 moves to energize the warning circuit 36 to give a " slow down " visual or aural warning indication. If the braking is too hard, the frequency of the machine 30 is the higher and contact 34 moves to energize the circuit 35 to give an indication to the driver to maintain speed or accelerate. To restart the vehicle after stopping the contact 28 must be remade manually. The apparatus shown in Fig. 4 is subordinated to the track circuit signal impulse currents which are picked up by means of pick-up windings 29 from the track rails and applied to the comparator 31 and to the synchronous motor 30 through a polarity detector 33 in the form of a polarized relay 37 and a frequency multiplier 38. As the distant signal SA, Fig. 2, is at " caution " or " line clear," the vehicle V not having entered the section FA, the line 11 is connected to the source 26 and relay 27 maintains the reversing switch 12 in the position shown to feed normally polarised impulses to the track circuit 1, 2 from the generator 34 and maintain the track relay 6A operated. If, in these conditions, the speed of the vehicle is too low, the contact 34 will move to energize the control circuit 35 which is arranged for increasing the speed. If the speed is too high the contact 34 will move to energize the control circuit 36 which is arranged for reducing the speed and for causing the brakes to operate. The frequency of the track impulses may be adapted to the profile of the track, the local conditions &c. or the frequency furnished by the source 3A may be lowered to obtain automatically a slowing down of the vehicle, e.g. if constructional work is being done on the track. If the home signal S is at " danger " the relay 6 is correspondingly de-energized, and passing of the distant signal SA at " caution " will de-energize relay 6A causing relay 27 to drop away and reverse the polarity of the track impulses resulting in the dropping of the armature of the polarized relay 37, Fig. 4, interrupting the feed to the motor 30 and so cause it to operate as an alternator with decreasing frequency output, causing comparator contact 34 to energize the control circuit 36 to produce a braking of the vehicle to stop. If during this braking period track relay 6 closes its contacts relay 27 will re-establish normal track impulse polarity resulting in operation of polarized relay 37 and feeding of the synchronous motor 30, causing it to accelerate, and feeding the comparator 31 causing the contact 34 to move to energize the control circuit 35 to effect automatic starting and acceleration of the vehicle to its normal speed. In Fig. 2 the braking distance FA coincides with the length of a section. The modification when the distance FA is smaller than the length of a section (Fig. 5, not shown) is also described. The operation of the circuits 35 or 36 may be recorded on a recording band which will show whether the driver has kept to the correct rate of slow-down at the particular part of the journey.