A coupling is a mechanical element part that connects two shafts together to accurately transmit the power from the drive side to the driven side while absorbing the mounting error (misalignment), etc. of the two shafts.

Here are reasons what is the functions of coupling element: 

> Power is transmitted from the driving side (turning side) to the driven side (turned side).

> Absorbs mounting errors between the axes of the driving side (turning side) and the driven side (turning side).

> Absorbs vibration from the driving side (turning side) and protects surrounding products.

> Does not transfer heat from the motor on the drive side (turning side), etc. to the driven side (turned side).