Patent GB-148381-A (GB)
Title: Improvements in or relating to automatic traffic-controlling systems for railways
IPC: B61L3/22
Filed: 1920-07-09
Abstract: 148,381. Day, A. van T. Oct. 18, 1916, [Convention date]. Electrical systems, automatic; track apparatus actuating signals on trains and for stopping trains.-Railway traffic is controlled by the transmission of current from the track rails to amplifying-appartus carried on the vehicle, the amplified current being employed to govern signalling and retarding means on the vehicle. In the system shown in Fig. 1, one side of a low-frequency traction generator 3 is earthed on the track rails 15 through an impedance bond 2, and the other is connected to the transmission line 5 which supplies the motor 9 on the train 10. The motor windings M of the rotary converters 11<a>, 12<b>, 13<a>, 14<b>, &c., are connected between the conductor 5 and the track, and the generator windings G are connected across the track to supply alternate frequencies of one hundred and one hundred and fifty. A coil 16 in inductive relation to the track is carried at the front of the train and is connected to parallel circuits including the primaries 19<a>, 19<b> of the transformers 20<a>, 20<b>. The transformer secondaries 21<a>, 21<b> are connected to the grids of electron amplifiers 24a, 24<b> and to potentiometers 22<a>, 22<b>. The plate circuits of the amplifiers include telephonic amplifiers magnets 33<a>, 34<a>, 33<b>, 34<b>, which act upon microphone cells 35a, 35b connected on the primary sides of amplifiers 36<a>, 36<b>. The secondary sides are connected to relay magnets 38<a>, 38<b>. All the circuits associated with the transformer 20<a> are tuned by variable capacities to respond to a frequency of one hundred, and those, associated with the transformer 20<b> are tuned to respond to a frequency of one hundred and fifty. When the tiack is clear far enough in front of the train to enable both frequencies to be supplied, both magnets 38<a>, 38<b> are energized and close contacts 39a, 39b to enable the battery 40 to energize the brake-control magnet 42 and to operate visual signals directly. The track currents may be amplified by amplifiers 69 before they are supplied to the transformers. The coil 16 may be replaced by a coil wound on a hollow cylindrical laminated core surrounding the first axle, and the impedances of the other axles may be increased by providing them with similar cores; or current may be collected by contact brushes bearing on the rails as far as possible in advance of the train; or the brushes may collect from the wheels, the axles may be surrounded by magnetic cores; or the wheels may be insulated from the axles and so serve as collectors. Several frequencies may be employed, the sequence of rotary converters being repeated through successive portions of the continuous track. The contacts controlled by the amplified track currents may be connected in circuit with electro-magnet windings as sliown in Fig. 5. The closure of the first contact 39a enables the solenoid 46<a> to lift its core 48<a> to which is attached the solenoid 46h in circuit with the next contact arm 39<b>. This arrangement is repeated so that the movement of the cross-bar on the last core is equal to the sum of the movements of the cores into their respective solenoids. The elevation of tiie cross-bar therefore depends on the number oftrack currents received, and one end 49 may indicate on a scale the clear length of track in front of the train, and the other end 50 may be used in any automatic arrangement for controlling a warning-signal or retarding means; it may, for instance, be in electric contact with a sleeve operated by a centrifugal governor geared to an axle.