The two shafts connected by the SWP-D type non-retractable short universal coupling will cause changes in the relative position of the two shafts due to manufacturing and installation errors, deformation after load, and the influence of temperature changes, which often cannot be strictly guaranteed. Centering.According to whether the coupling has elastic elements, whether it has the ability to compensate various relative displacements, that is, whether it can maintain the connection function and the purpose of the coupling under the condition of relative displacement, the coupling can be divided into rigid couplings, Flexible couplings and couplings.The main types, characteristics and functions of the coupling and its role in the transmission system. Remarks: Rigid couplings can only transmit motion and torque, and do not have other functions including flange couplings, sleeve couplings, and clamps. Flexible couplings such as shell couplings and flexible couplings without elastic elements can not only transmit motion and torque, but also have different degrees of axial, radial and angular compensation performance, including gear couplings, Flexible couplings with elastic elements such as universal couplings, chain couplings, slider couplings, diaphragm couplings, etc., which can transmit motion and torque; have different degrees of axial, radial, Angular compensation performance; it also has different degrees of damping and buffering effects, improving the working performance of the transmission system, including various non-metal elastic element flexible couplings and metal elastic element flexible couplings, various elastic couplings The structure is different, the difference is large, and the role in the transmission system is also different. The coupling transmits motion and torque, and overload protection.Flexible couplings also have different degrees of compensation performance, including pin type, friction type, magnetic powder type, centrifugal type, hydraulic type and other couplings.