Patent GB-190706135-A (GB)
Title: Improvements in and relating to Signalling Systems for Railways and the like.
Filed: 1907-03-13
Granted: 1908-03-05
Abstract: 6135. British Thomson-Houston Co., [General Electric Co.]. March 13. Auiomatic systems; electric railways, signalling on.-In an automatic electric system of signalling on electric railways employing the rails as electrically continuous conductors for power current and signalling- current, high-frequency alternating current of different phase in adjacent sections is employed for signalling, and track relays of special construction responding only when energized by two currents of different phase are used. A further modification for the purpose of economizing energy is carried out by the use of normally open transformer circuits which are closed by relays, the circuits of which are also normally open and are closed by an approaching train ; this modification is not included in the system shown in Fig. 1, in which the transformers E', E<2>, E<3>, E<4> are shown with their circuits always closed and energizing the track rails A. The rails A are electrically continuous, and the impedance which they offer to the high-frequency signalling-current is sufficient to divide the line into block sections with a small overlap, which may be reduced by suitably designed transformers, relays, &c. Each transformer is supplied from one phase of a three-phase generator D, and its secondary is connected to the rails at the end of the block ; one coil of each of the relays F<1>, F<2>, F<3>, &c. is connected to the centre of the blocks, so that these coils receive currents of different phase from the transformers on either side. If the track is clear, the resultant current in these coils is out of phase with the current in the primary supply circuit which supplies the other coil of the relay. The two field coils of the twophase relays shown are therefore energised with currents of different phase and produce a torque on the short-circuited moving coil to close the local circuit. If, owing to the presence of a train or a broken rail, one transformer is unable to energize the relay winding, the current in the two field coils will be of the same phase and no torque will be produced. With a train H between the transformer E<4> and the relays F<5>, F<6>, the coils of these relays receive current only from the transformer E<3>, which produces a torque in the relay F<6> since its two windings are then supplied from different phases of the supply current ; but the relay F<5> receives current in its two windings from one phase only, and the local circuit to the signal G<3> is opened and the signal goes to 'danger' and remains so until the train passes to such a point beyond the transformer E<3> that it can energize the relay F<6>, which is de-energized when the train is close thereto. In the modified system described in the Specification 'home' and 'distant' signals are used, the ' distant' being operated by mechanism energized through contacts carried by the 'home' signals. A construction of relay suitable for the systems described is shown in Fig. 3. Two conducting- disks I', I<2> carry the local circuit contacts and are pivoted to move between the poles of C-shaped cores. Two such cores J are placed on opposite sides of the disks and are energized by coils K connected to the track rails. Each disk has two other C-shaped cores on opposite sides of the core J, the relay F<1> having the two cores L' energized by the coil M'which are supplied directly from the linewires, the two coils being connected so as to produce a combined action on the disks I' and to rotate it if the currents in the coils J, M<1> are of different phase. Specification No. 12,235, A.D. 1904, is referred to.