Patent GB-297945-A (GB)
Title: Improvements relating to railway traffic controlling apparatus
IPC: B61L3/22
Filed: 1927-08-31
Abstract: 297,945. Westinghouse Brake & Saxby Signal Co., Ltd., (Union Switch & Signal Co.). Aug. 31, 1927. Electrical systems, automatic; track apparatus actuating signals on trains.-Alternating current of a commercial frequency, for example, 60 or 100 cycles per second, is supplied to the track rails through a series of contacts which are opened and closed at different frequencies, for example 80, 120 and 180 times per minute, the frequency of interruption or variation of the supply being dependent upon the traffic conditions of the sections ahead and train-carried apparatus controlled by currents induced in coils on the train in relation to the track rails is responsive differently according to the frequency of the interruptions of the current supply. The traincarried apparatus may be tuned mechanically or electrically. One form of mechanically tuned train apparatus is shown in Fig. 1, which shows also the means for supplying energy to the track rails 1, 1<a> from a generator G over the contacts of a home relay H and a line relay L and over one of the contacts 3, 4, 5 opened and closed by the continuously driven cams C', C<2>, C<3> having different numbers of teeth. The state of the track ahead thus determines the frequency of interruption of the supply to the track rails 1, 1<a>. The current induced in the train coils 11, 11<a> passes through an amplifier 13 to a transformer Q, the secondary of which energizes a polarized relay R which oscillates the armature 15 to and fro as each impulse of energy, supplied to the track rails 1, 1<a> increases and decreases in magnitude. The armature 15 closes circuits from the battery D to relay-magnets 19, 20 and transformer T<1>. Transformer T<1> supplies energy through the rectifier J<1> to the relay K<1> which is thus energized so long as current impulses of any frequency are received by the train. In the mechanically tuned oscillators F<3>, F<2> the magnets 19, 20 control a pivoted armature 21, connected by springs 36, 37 to a loaded spring-controlled lever 22 carrying a contact 25. By variation of the loads 22<a> the period of vibration of the lever 22 is adjustable to one of the frequencies of interruption of the track current so that, when current of that frequency is received by the train the contact 25 closes the circuit to the corresponding one of the transformers T<3>, T<2>, rectifier J<3>, J<2>, and relay K<3>, K<2>. The armatures of relays K', K<2>, K<3> control the " proceed " signal 29, " caution " signal 30, slow signal 31, and stop signal 32, the last being energized when no current is received from the track, as when another train is between the track source of supply and the train concerned. In a modification, the relay R supplies energy to three mechanically tuned oscillators each comprising a weighted tongue oscillated by two magnets which are energized alternately. Each energizes a transformer and a relay; by a suitable combination of armature contacts four signal lamps are energized as in the abovedescribed system. Electrically tuned relay circuits comprising inductances 40 and capacities 41 and rectifiers J', J<2>, J<3> for energizing one of three relays K<1>, K<2>, K<3> controlling the lamp signal circuits are supplied with energy at the frequency of the track-circuit current interruptions through a transformer T the primary of which is supplied with current impulses in each half of its windings at each oscillation of the armature relay R. One such apparatus is shown in Fig. 4. The rectifiers may be of the kind described in Specification 257,305, [Class 37, Electricity, Measuring &c.].