In practical application, according to the magnitude of the transfer torque, the coupling can be divided into three categories: heavy, medium and light.
Heavy duty universal coupling is usually used in metallurgical machinery, heavy machinery, petroleum machinery, engineering machinery, lifting machinery.
The universal coupling of medium and light is often used in vehicles such as automobiles, machine tools and light machinery.
Small universal coupling is mainly used for transmission movement, and is generally used for precision machinery and control mechanism. How to choose the appropriate coupling and what precautions should be taken in use?

1、 Select coupling application
1. due to manufacturing, installation, load deformation and temperature change, it is difficult to keep the two shafts in strict alignment after installation and commissioning.
10. The displacement and offset CI in Y direction are to some extent. When the radial displacement is large, the sliding coupling can be selected, and when the angular displacement of the intersecting two shafts is large, the universal coupling can be selected. In the process of working, flexible coupling should be selected when there is a large relative displacement between the two shafts.
2. the working speed of coupling and the centrifugal force caused.
For high speed transmission shaft, coupling with high balance precision, such as diaphragm coupling, should be selected, but coupling with eccentric slider should not be selected.
3. the magnitude and nature of torque to be transmitted, as well as the requirements for buffering and damping.
For high power heavy load transmission, gear coupling can be selected; for transmission with high impact load or requiring eliminating torsional vibration of shaft system, high elastic coupling, such as tire coupling, can be selected.
4. the working speed of coupling and the centrifugal force caused.
For high speed transmission shaft, coupling with high balance precision, such as diaphragm coupling, should be selected, but coupling with eccentric slider should not be selected.
5. the magnitude and direction of relative displacement of the two axes
After installation and commissioning, if it is difficult to align the two shafts strictly or there will be a large additional relative displacement of the two shafts during the work, flexible coupling shall be selected. For example, when the radial displacement is large, the slider coupling can be selected, and the universal coupling can be selected for the connection with the larger angular displacement or the intersection of two shafts.
6. reliability and working environment of coupling.
The non lubricated coupling, usually made of metal components, has high reliability; without lubrication coupling, its performance is easily affected by lubrication performance and may pollute the environment. Coupling with non-metallic elements such as rubber is sensitive to temperature, corrosion medium, strong light, etc., and is easy to aging.
7. manufacture, installation, maintenance and cost of coupling.
According to the requirements of convenience performance, the coupling with convenient installation, simple maintenance and low cost should be selected. For example, the rigid coupling is not only simple in structure, but also easy to install and dismantle, and it is suitable for low speed and large rigid transmission shaft. Ordinary non-metallic elastic coupling (such as elastic sleeve coupling, elastic column coupling, quincunx elastic coupling, etc.) is widely used in general medium and small power transmission because of its good comprehensive performance.

2、 Precautions for coupling use
1. the coupling shall not have deflection and radial displacement beyond the specified axis line, so as to avoid affecting its transmission performance.
2. after the universal coupling is installed, it is required to check all fastening screws for normal operation. If it is found to be loose, it must be screwed again according to the specified torque so that it can be loosened for several shifts.
3. the sliding surface, shaft and bearing of universal coupling must be lubricated. Generally, 2 # lithium-based grease for industrial use or 2 # molybdenum disulfide calcium base grease shall be used. In general, it shall be filled once for 500 hours continuously, and oil shall be added once for two months in discontinuous operation. If the operation is under high temperature, it must be refueled once a week. When filling, screw off the oil hole on the bearing end face and inject it with high-pressure oil gun until it overflows Out.
4. during daily maintenance of coupling, if any normal wear phenomenon such as indentation is found, it shall be replaced in time; no crack is allowed to occur in the coupling. If there is any crack, it shall be replaced (it can be knocked by small hammer and judged by sound); when maintenance and cleaning, the cross shaft shall be adjusted 180 ° to achieve the alternate use of the bearing neck stress.
5. the tooth width contact length of gear coupling shall not be less than 70%, and the axial displacement length shall not be greater than 5mm.
6. the tooth thickness of gear coupling is worn. When the tooth thickness of lifting mechanism exceeds 15%, and the wear of the operating mechanism exceeds 25%, it shall be scrapped, and if there is any broken tooth, it shall be scrapped.
7. if the elastic ring of the pin coupling and the sealing ring of the gear coupling are damaged due to aging, it should be replaced timely.
8. during the operation, it is necessary to observe whether the universal coupling has abnormal radial swing and bearing heating, and find that these phenomena should be repaired in time.