Patent GB-190228762-A (GB)
Title: Improvements in or relating to Railway Electric Signal Systems.
Inventor: BOULT ALFRED JULIUS
Filed: 1902-12-30
Granted: 1903-10-15
Abstract: 28,762. Boult, A. J., [Huff, S. W.]. Dec. 30. Signalling between trains; controlling and locking signals; interlocking ; contacts, mechanical; fog and audible signals.-Relates to automatic block signal systems, in which the signal stands normally at danger, and drops to the position indicating safety as the train approaches the signal, provided the track ahead is clear. A mechanical device restores the signal to the danger position as the train passes it. The Figure shows the signals 1, 2 at opposite ends of a section of track 36, 37, 38. The mechanical re-setting devices comprise bars 3<a> fulcrumed at 3<b> and actuating the signal through connections 4. The signal is released by means of a detent 6 actuated by the electromagnet 8. Three main wires 9, 10, 11, co-extensive with the track, are employed. The wire 9 is broken at intervals, at 34, 34<a>, &c., but, whenever a current passes through the wire 10 and the sections 36, 38, 37 of the track, the relays 35. 35<a> complete the circuit through the wire 9. With each signal are associated a battery 13, a signal relay 12 which controls the electromagnet 8, and a switch 19. The electromagnets 23, 23<a> are normally energized by current from the batteries 28, 28<a> connected across the short insulated sections of track 26, 27, 27<a> on opposite sides of the signal. In these circumstances, the armatures 30, 30<a>, pivoted at 3O<x>, 31<x>, are attracted, and the switch arm 19 is thrown against the contact 20, the battery 30 being thus normally placed across the main wires 10, 11. The relay 12 is across the wires 10, 9. The relays 12 are polarized so that they are not responsive to currents from the home battery, but respond to reverse currents sent from a distant station through the distant relay and main wires. When a train x approaches the signal 1, the battery 28 is shortcircuited and the electromagnet 23 de-energized The armature 30 is drawn back by its controlling- spring, and the switch 19 thrown over against the contact 21 so as to disconnect the battery from the main wire 11 and connect the wires 10, 11. Current now flows from the distant battery 13 through the wires 10, 11, and the relays 35 complete the circuit through the wire 9. Current from the distant battery then flows through the distant relay 12, wires 9, 12<a>, home relay 12 (in reverse direction), and through switch 19, main wire 11, and distant switch 19 back to the distant battery. The home relay closes the circuit of the home battery through the electromagnet 8, and the signal drops. Switches 31, 32 open the track wires 10, 11 in rear of the train when the switch 19 is actuated, and thus prevent currents from being received from the signal previously passed. As the train passes the signal, it re-sets the signal mechanically. To prevent the signal from being dropped again as the tail end of the train moves over the section of track 26, 27<a>, contacts 33, 33<a> are provided which bridge over the insulated gap 29 at the time that both the electromagnets 23, 23<a> are de-energized, and consequently maintain the shortcircuit of both batteries 28, 28<a> until the rear wheels of the train have left the section 26, 27<a>. The operations described depend entirely on the absence of wheels on the track between the signals. If wheels are on the track, one or more of the relays 35 will be short-circuited, and the circuit 9 will remain open, thus preventing the sending of current from the distant station to the signal relay. Contacts 41, 42, 43 are opened when the signal drops, so as to prevent waste of current if the train stands on the line adjacent to the signal after it has fallen. A switch 44 is so arranged that it is momentarily closed as the lever 4 rises, but is not closed on the downward movement. An electric detonator 45 is provided, and this detonator is fired if the switch 44 is closed while the contact 41 is also closed. The detonator thus provides an audible signal if the train runs past the signal while it is in the raised or "danger" position.