Models 5E, 5F, 5G & 5H Electric Switch Machines: Single ... - Alstom

Theory of Operation2.5.3. Friction ClutchThe friction clutch shown in Figure 2–14 reduces gear mechanism shock and motorburnout. The friction clutch is typically adjusted to slip when motor operating currentexceeds 12 to14 amps for 110V switch machines or 17 to 20 amps for 24V switchmachines. The overload relay, located in the control circuit, opens the switch motorcontrol circuit approximately 3 seconds after the clutch begins slipping. To reset anoverload condition, the switch must be called to the opposite position.The pinion gear of the motor meshing with the bevel gear drives the clutch body. Insideare friction disks compressed against the clutch body. Some disks are engaged with thepinion shaft. Other disks (metal) are engaged with the clutch body. The pinion will bedriven until torque to drive the remainder of the gear train increases enough to causethe friction disks to slip. When the friction disks slip, the clutch body continues to rotatethough the pinion stops.An adjusting nut is provided to increase or decrease the amount of pressure on thefriction disks to the clutch body. The maximum amount of torque that the friction clutchpinion must provide for the switch machine to move the switch points and provide forswitch point pressure is closely related to current draw of the motor.HOLE FOR PINPINIONNOTCH FOR LOCKINGADJUSTING SCREWLOCK NUTSETSCREWBEVEL GEARCASEDRAIN HOLE(KEEP CLEAR)Figure 2-14. Friction ClutchP1293, Rev. Jun/07 2–16 Alstom Signaling Inc.