Specifications

RailCorp Infrastructure Engineering Manual – Signalling

Maintenance Manual

Electric Point Machine Westinghouse Style M70 MKIII TMG E1583

4.5 Circuit Controller

4.5.1 Description

The circuit controller shown in Figure 4.5.1, comprises of two sets of sealed contacts

for the points detector and two sets of snap action motor contacts.

The detector contacts are operated by both a roller, which follows the cam surface cut

into the lock box above which the circuit controller is mounted, and the detector lever

assembly, which operates through a roller, and lever assembly. The detector lever

assembly overrides the lock box roller to ensure that detection is dependent on the

position of both the lock box and the switch blades, proving that the points are in the

correct position and locked.

The motor control switches (one for each direction of operation) are operated by the

lock box roller through a toggle mechanism, which gives a snap action. As soon as the

motor circuit is cut, the switch applies a "snub" to the motor, which stops it abruptly,

thus avoiding impact at the end of the traverse.

4.5.2 Adjustment of Detector Push Rods

When a detector roller is touching the bottom of its recess, the associated push-rod

should allow the detector switch roller (at the far end of the push- rod) to rest clear

(10.4 mm max) of the 45 degree step in the rod. Adjustment of this clearance is by

means of the hexagon domed nut and lock nut on the threaded end of the push-rod.

4.6 Point Contactor

4.6.1 Description

The point contactor, shown in Figure 4.6.1, is a plug-connected interlocked 50 volt

D.C. magnetic stick relay which actuates 3 sets of normal and 3 sets of reverse

contacts. The point contactor determines the direction of the motor by switching to the

appropriate field winding. To protect the contacts from foreign matter which may

disrupt operation, the unit is sealed by a protective plastic cover.

4.6.2 Removal

The point contactor is simply removed by unplugging the lead and loosening the two

screws at the base.

4.7 Motor Protection Unit and Rectifier

4.7.1 Description

The motor protection unit, shown in Figure 4.7.1, is located on the mounting plate of

the terminal board. It is designed to protect the motor and the friction clutch in the

event that an obstruction prevents movement of the throw mechanism by cutting the

motor circuit when operation takes abnormally long. The motor circuit is reconnected

automatically by restoring the points lever to its original position.

Issue Date: 1 December 2009 Uncontrolled when Printed