Overrunning bearings are machine parts with specific characteristics. There is no contact between the inner and outer ring in one direction or direction of rotation. In the other direction of rotation there is contact between the inner and outer ring. If an overrunning bearing changes direction, the bearing disengages. An overrunning bearing can be used to create an index movement, as an overrunning clutch or as a fully mechanical device preventing reverse rotation.
Overrunning bearings are also referred to as overrunning clutches and are also supplied in the size of a needle bearing. This type consists of a thin-walled outer shell with a special design inside, plastic cages, reaction springs and needle rollers. They have the ability to transfer torque in one direction of rotation and are radially space-saving. There are versions with and without a supporting bearing ring.
Overrunning clutches shift very precisely because there is permanent contact between the shaft, needles and outer ring, since each needle is pressed individually by a spring. High switching frequencies are possible due to the low mass and the resulting low moment of inertia of the needles. The friction torque is low in the overrunning direction.
Overrunning clutches can be used in many applications, for example in indexing shift mechanisms and devices preventing reverse rotation. The main function can be both engaging and overrunning.