Patent GB-122009-A (GB)
Title: Improvements in and relating to Railway Signalling.
IPC: B61L3/22
Filed: 1918-01-07
Abstract: 122,009. McKenzie, Holland, & Westinghouse Power Signal Co., (Union Switch & Signal Co.). Jan. 7, 1918. Electrical systems, automatic; track apparatus actuating signals on trains and for stopping trains. -Track rail circuits controlling either wayside signals or apparatus on trains or both are supplied with alternating electro motive forces of different and relatively high frequences according to the state of the track ahead and the circuits to the signalling and train controlling apparatus include electron relays responsive selectively to the several frequencies of alternations respectively for the purpose of amplifying the variations in energy transmitted to the train. Each insulated section of track rails is supplied with energy at its forward end, and track signals are controlled by relays connected across the rear ends of the section. Apparatus on trains is controlled by energy derived either by induction from the track rails in a train-carried coil or by conduction through the first pair of train wheels, the receiving circuits including amplifying devices of the vacuum-tube type. Train-stopping apparatus may be made dependent also upon a device which is set according to the speed of the train. Several systems are described in the Specification, in all of which a danger signal is given when the section ahead is occupied by a train which cuts off all energy from the track relays or train circuits; caution signals are operated by current of one frequency only, which serves to energize one of two relays controlling the signal apparatus, and a clear signal is given by energization of both relays when current of two frequencies is supplied to the track rails. Fig. 1 shows a system in which highfrequency generators 4, 4a supply line wires 3, 3<a> along the track, the wires 3 being connected to transformers T permanently supplying the track rails of each section at the forward ends, and the wire 3<a> being connected to transformers T<1> which supply the rail circuits through a contact 10 of relay S. At the rear ends of the sections, transformers 7, 7<a> are connected to the rails and supply relays S, S<1>, which control circuits to signals R, Y, G which may be lamps. The circuits of transformers T and 7 and of relay S are made resonant at the frequency of generator 4 and those of transformers T<1> and 7a and relay S<1> are made resonant at the frequency of generator 4a by the use of condensers. A train V<1> in section D, E, de-energizes both relays S, S<1> so that the circuit of the danger signal R is closed, and the contact 10 is opened. Section CD thus receives current from generator 4 only and relay S of this section is alone energized, and the circuit to the caution signal Y is closed, together with contact 10. Section BC then receives energy from both generators 4, 4<a> and both relays S, S<1> are energized and close the circuit to the clear signal G. Fig. 7 shows a system in which alternate sections permanently receive energy from each source, and inductance bonds M are connected round the insulation 2 and are adjusted so that current passes from an advance section to that in the rear but current (of the other frequency) cannot pass in the opposite sense. In this system, as shown, no track signals are used, but these may be adopted if desired. An alternative form of inductance bond comprises a transformer with a closed secondary circuit including a condenser. Figs. 1 and 7 show train-controlling circuits for actuating signals according to the frequency of current induced in a coil 14 supported in proximity to the track rails which serve as the primary of a transformer. The closed circuit of coil 14 and condenser 15 is tuned broadly to the mean of the two frequencies of generators 4, 4a. In the apparatus shown in Fig. 1, one current amplifying device of the vacuum-tube type is connected in a similarly-tuned circuit with the primaries of two transformers 25, 25<a>, the secondaries of which supply the relays P, P<1> and are tuned to the frequency of the generators 4, 4<a> respectively. In the apparatus shown in Fig. 7, the coil 14 is connected to transformers J, J<1>, the secondaries of which are in closed circuits tuned to the frequency of the generators 4, 4a respectively, and a separate amplifying device supplied each relay P, P<1>. In both systems, the danger signal R<1> is shown when neither relay is energized, and the clear signal G<1> when both are energized. The connexions of the supply mains to the track shown in Fig. 1 are such that a caution signal can be given only by the current of generator 4 energizing the relay P while the relay P<1> is de-energized. A train passing over sections supplied as shown in Fig. 7 may receive a caution signal by current of either frequency, and the circuit of the caution signal Y' is closed when either relay P or P' is energized while the other is deenergized. Fig. 5 shows apparatus for actuating a train-controlling valve which is normally held out of action by an electro-magnet M. The magnet M is de-energized to open the valve according to the state of the track and the speed of the train. The local contacts of the relays P, P<1>, which are arranged as shown in Fig. 7, are connected in series with contact arcs 28, 29 30, with which an arm 27 controlled by the speed governor Q co-operates, to close the circuit to the magnet M. The arc 30 is in circuit under " danger " conditions and the circuit is completed only at low speeds, whereas the circuit through the are- 28 under " clear " conditions is completed at all speeds up to a predetermined maximum. Fig. 6 shows an arrangement of circuits for supplying high-frequency current to the track rails H, H<1> by conversion of low frequency current supplied from mains 3b. The transformer primary T‹ has three secondary windings, of which T<3> supplies low voltage current to the heating filaments of vacuum-tube rectifiers R<1>, R<2>, which rectify the high-voltage current from the coil T<2>, a condenser 39 being added to smooth out the current. The rectified current is supplied through the leads 37, 38 to the plate 40 and filament 35 of the vacuumtube device R<3>, the filament of which is heated by current from the secondary T<4> of transformer T<0>. The grid 41 and filament 35 of the device R<3> are connected to a closed resonant circuit a<2> and this arrangement is such that oscillations of a frequency determined by the constants of the circuits are induced in the circuit of transformer 45, the secondary of which is connected in a tuned circuit to the track rails H, H<1>.