From a continous running power source, the driven member can be engaged or disengaged every complete, fractional or multiple revolution.
The example on the next page shows a typical arrangement for this type.
An electrically or pneumatically actuated latch engages the rollers driving cage. The inertia of the driven parts forces the inner race to travel on until it contacts an internal stop. It is during this inner race overtravel that the rollers are taken out of the clamping angle to disconnect the clutch.
Removal of the external latch allows the rollers to go back to driving position. This unit can thus provide a stop in an identical position at each revolution.
A backstop is generally also incorporated to avoid shaft back-rotation.
During selection, it is most important to take into account the dynamic torque i.e. moment of inertia of the driven masses.