Patent GB-190706133-A (GB)
Title: Improvements in and relating to Signalling Systems for Railways and the like.
Filed: 1907-03-13
Granted: 1908-01-09
Abstract: 6133. British Thomson-Houston Co., [General Electric Co.]. March 13. Automatic systems; electric railways, signalling on.-In an automatic electric system of signalling on electric railways in which the track rails are continuous and serve as conductors for both the power and signalling current, alternating current of only one frequency is employed for the signalcontrolling circuits, all of which are normally open. An approaching train sets its signals to 'clear,' if the track is clear, by momentarily closing a rail contact, shown on the drawings as a short insulated rail section bridged by conductors, in the circuit of a self-holding relay controlling either the primary or secondary circuit of the transformers at the entrance end of the sections which supply energy to the track relays at the exit end of the sections. The circuits of transformers for advance sections may also be controlled by contacts on the signal for controlling ' home ' and distant' signals or three-position signal arms. No reactance bonds are used to separate block sections of the rails. Three systems are described: in the first system only 'home' signals are used; in the second system, the ' home ' signals are provided with contacts controlling directly the distant' signal operating- devices. The third system is shown diagrammatically in Fig. 3. Any suitable type of relay, source of energy, contact-maker, or other apparatus may be substituted for that indicated in the Figure. The trains move in the direction shown by the arrow. A train passing over a track contact similar to the rail J, but not shown on the drawing, closes a circuit from the upper pole of the battery g, magnet G', the upper rail A, train axles, and rail contact J to the lower pole of the battery g. The magnet G<1> draws its three armatures and the armature m<2> closes the selfholding circuit, which may be arranged to include contacts on the signal arm to ensure that the magnet is de-energized when the signal is operated to 'clear.' The armature m<1> breaks the. circuit of the coil f<1> of the two-phase motor relay F<1> and makes the circuit of the secondary coil of the transformer E', which also passes through the contacts h' on the home signal H<1>. The transformer E<1> energizes the rails A through the resistance e<1>, which is introduced to protect the transformer from excessive short-circuit currents when the train is over the part of the rail to which they are connected. The coil f<1> of the relay F<2> at the exit end of the section is thus energized, if the section is clear and if the rails are unbroken throughout, and the short-circuited coil f is moved to close the contacts of the relay, thereby completing the circuit from the source of energy i, signal - operating mechanism I', armature m<3> of the magnet G<1> on its upper contact, and the contacts of the relay F<2>. The signal H<1> is thus moved to 'clear' and breaks the circuit to the transformer E<1> at the lower contacts h'. Just before breaking this circuit, the contact closes the circuit to transformer E<2> at the upper contacts h<1>, and this transformer supplies energy to keep the relay F<2> energized, and to energize the relay (not shown) of the next section to the left of the Figure if that section is clear,' thereby closing the circuit from the left-hand pole of the battery i<2> through conductor 1, track relay (not shown), conductor 2, armature m<3> of magnet G<2> on its back contact, contacts h of signal H<1>, and operating-mechanism M of distant signal L to the battery i<2>. The distant signal is thus driven to ' clear.' The opening of the circuit of the transformer before the train reaches it prevents the large short - circuit current which would otherwise be taken from the transformer. The home signal H<2> is not operated by the closure of the relay F' because its circuit is broken at the armature m<3> of the relay G<2>. The distant signal in the rear of the train is also not operated, its circuit being broken at the back contact of armature m<3> of relay G'. The signals H<1>, L having been cleared, remain so until the train reaches the contact section J. This contact shortcircuits the relay magnet A' and the armatures drop. The armature m<3> opens the operating- circuit of the signal H', which returns by gravity and opens the circuit of the distant signal operating-mechanism M and of the transformer E<2> at the contact h<1>, and so de-energizes the relay F' which drops its armature. The closed contact J at the same time energizes the magnet G<2>, which closes the circuit to the transformer as described with reference to the magnet G', but the relay F' is not energized, its circuit being broken at the contact m<1>.