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The coupling is normally the softest element in the drive line, literally – but by no means the weakest link of the chain. Its configuration plays a decisive role for the functional capability of the driving and driven machine and for the reliability and lifetime of the entire drive system. The optimum adjustment of the coupling to the connected machine units is especially important in all cases where failures and breakdowns are not allowed to occur. 

Couplings transmit torque in drive systems. But they are able to do more. These are the three essential functions of a coupling.

Stiffness describes the ability of a body to resist elastic deformation. The transmission of power would not be possible without stiffness. However, there are events which should not be transmitted, such as torque peaks and shock loads. In order for a system to withstand such loads, it is damped. Engineers are confronted with the challenge to tune stiffness and damping in a vibratory system in such a way that reliable operation, essentially free of load peaks, is ensured.