The dimension of the coupling, i. e. the maximum radial and axial dimensions, must be within the allowable installation space of the equipment. It should be convenient to install and disassemble, without maintenance, long maintenance period, easy maintenance, replacement of wearing parts, no movement of two shafts, easy adjustment of centering.

It is difficult to adjust the two shafts to the middle of the large machine equipment. It is necessary to use the couplings which are durable and replace the wearing parts. Flexible metal element flexible couplings generally have longer service life than flexible couplings with non-metallic elastic components. Sealed lubrication and the use of non durable couplings will inevitably increase maintenance effort. For the long-term continuous operation and high economic situations, such as metallurgical enterprises in China high speed transmission system of the rolling mill end, is now widely used by gear coupling, gear coupling, although theoretically transfer torque, but must be sealed in order to work under the conditions of good durability and lubrication. And often need to check the sealing conditions, grease or grease lubrication, maintenance workload, increase the auxiliary hours, reduce the effective working time, affect production efficiency. Internationally developed industrial countries have been generally used to use a long life, lubrication and maintenance of the diaphragm does not replace the drum shaped tooth coupling, not only improved economic efficiency, but also to purify the working environment. In the rolling mill transmission system, the elastic movable pin coupling and the fan-shaped block elastic coupling developed by our country are not only provided with the advantages of the diaphragm coupling, but also have good cushioning and vibration damping effect and lower price