Explain the origin of plum coupling

　　The plum blossom coupling is to install an integral plum blossom-shaped elastic ring between the convex claws of two half couplings of the same shape to realize the connection of the two half couplings.The power is transmitted through the squeezing between the claw and the elastic ring, and the relative deviation of the two shafts is compensated by the elastic deformation of the elastic ring to achieve vibration reduction and buffering.This kind of coupling has been standardized, GB/T5272-2002 has five structural forms: LM type (basic type), LMD type (single flange type), LMS type (double flange type), LMZ-I type ( Split brake wheel type) and LNZ-II (full brake wheel type).There are 14 specifications for each type, the applicable shaft hole diameter d=12-160mm, the shaft hole length L=35-135mm, the nominal torque T=25-25000N.m, the allowable speed [n]=1500- 15300r.min.
　　The cross-section of plum petals is usually circular, which can improve the uniformity of load distribution on the working surface, and can transmit larger torque, but the elasticity is slightly reduced.It can also be made into a rectangular or fan shape.When the coupling is working, the plum petals are squeezed, and only half of the plum petals carry work.Plum-shaped elastic parts are generally made of polyester polyurethane (hardness code a), or cast nylon (hardness code b), the former has a lower bearing capacity than the latter.The semi-coupling and flange connection material is 45 steel or ZG70-500. In the chemical industry, in order to prevent corrosion, the phenolic resin is often used to make the semi-coupling
　　The quincunx-shaped elastic coupling has a simple structure, a small number of parts, a small radial dimension, and no need for lubrication; the elastic element has a high load-bearing capacity under pressure.Except for the double-flange quincunx elastic coupling, the half coupling must be moved axially when replacing the wearing part quincunx elastic part.This kind of coupling has the ability to compensate the relative offset of the two shafts.