This standard specifies the types and parameters, technical requirements, test methods, inspection rules, and signs of LM, LMD, LMS, LMZ-I and LMZ-II plum-shaped elastic couplings (hereinafter referred to as couplings). , packaging and storage. This standard is applicable to the transmission shaft system connecting two coaxial shafts. It has certain compensation for the relative offset of the two shafts and general vibration reduction performance. .