The coupling can be divided into rigid coupling and flexible coupling.
Rigid coupling does not have the capacity of buffering and compensating the relative displacement of two axes, so it requires two shafts to be aligned strictly. However, this kind of coupling has the advantages of simple structure, low manufacturing cost, convenient assembly and disassembly, and convenient maintenance, which can ensure the two shafts to have a high degree of neutral and transfer torque, so it is widely used. Flange coupling, sleeve coupling and jacket coupling are commonly used.
Flexible coupling can also be divided into flexible coupling without elastic element and flexible coupling with elastic element. The former type only has the ability to compensate the relative displacement of two axes, but can not cushion vibration. The common ones are sliding block coupling, tooth type coupling, universal coupling and chain coupling. Because of the elastic element, the latter type has the ability to compensate the relative displacement of two axes, and also has the ability to compensate the relative displacement of two axes It has the function of buffering and reducing vibration, but the torque transmitted is not as good as that of flexible coupling without elastic element due to the limitation of elastic element strength. The common types are elastic sleeve pin coupling, elastic pin coupling, plum shaped coupling, tire coupling, serpentine spring coupling and reed coupling.