Diagram shows the actions of the clutch and spring
When the magnetic coil is energized it becomes magnetic, drawing the armature plate over to make contact. At this point the spring is tensioned while no other parts are moving.This minimizes friction and possible looseness. Clutch is engaged.
When power to the coil is cut it loses its magnetism. The armature plate is no longer drawn over and the spring pulls it back in place to restore the gap. Clutch is now disengaged.
Principles of Operation
When power to the magnetic coil is cut the magnetic field on the yoke collapses and the plate is no longer attracted. It is pulled back by the spring and motion transmission is cut.
When the magnetic coil is energized the yoke is magnetized and draws the armature plate over. This causes friction between the lining on the yoke and the armature, and the clutch is engaged.
Actions of the brake and spring: