GB190821398A - Improvements in Apparatus for Electrically Operating or Controlling Railway or Tramway Points, Bars, Frogs, Signals and such like Appliances. - Google Patents

Abstract

21,398. Edmonds, C. H. W., and McKenzie & Holland. March 26,1909. Switches. - For automatically placing a highresistance in the circuit of an electric motor used to operate railway points, signals, and like appliances, when too great a current flows, due for example to the motor sticking, an electromagnetic switch is employed having two windings and normally closed contacts short-circuiting the highresistance winding, the armature when attracted opening the short circuit and placing the windings in series, until the abnormal current is reduced The switch is enclosed in a box 1 provided with an inspection window 26. The high-resistance coil 4 and the low-resistance coil 3 are mounted on a common core and attract a pivoted armature 6, which lifts a guided spring-retracted rod 9 linked to the contact-carrying member 11. The contact is composed of carbon or other blocks 17 a attached to a conducting bridge-piece 13 carried on a spring plate or strip 14, which is bolted or screwed to the lever 11. Separate fixed contacts 18<a> are mounted in an insulating manner and connected to the ends of the high-resistance coil. The arrangement is shown diagrammatically in Fig. 3. If the motor 28, which is controlled in the ordinary way by a reversing-switch N R, sticks or otherwise takes an excessive current from the battery 27, the attraction due to the low-resistance winding 3 opens the short circuit 17, 17<a> round the high-resistance winding 4, .and the switch remains in its displaced condition until the current is reduced. The movement of the switch may be made to ring a bell, mechanically or electrically.