A device used toconnect two coaxial shafts or a shaft to a freely moving part that is seated on the shaft. An over running clutch transmits rotary motion and torque from a driving member to a driven member in one direction only.

There are over running versions of positive clutches, including adaptations of the ratchet and jaw types, there are also overrunning friction clutches, with circular cylindrical and eccentric rollers and with self-tensioning helical springs.

Overrunning clutches are used to prevent a reverse transmission of motion in a kinematic loop, such as motion from the driving wheel of a bicycle to the pedals.

They are used to convert a rocking motion to a rotary motion, for instance, in the pulse type of continuously variable transmissions, or to impart to a slowly rotating shaft a faster rotation in the samedirection, as, for example, in mechanisms for high-speed shifting in metal cutting machines.

Other applications include winding mechanisms and arresting devices, where reverse shaft rotation must be prevented.