The labial rubber seal of rotary shaft is the main type of rubber seal of rotary shaft, which is often referred to as oil seal. Flexible lip, usually combined with one or two metal skeletons as support to improve the stiffness of the oil seal, relies on the radial pressure applied to the shaft surface by the sealing lip to prevent fluid leakage. In order to maintain a constant radial pressure, a hoop spring is often added to the lip. According to its movement state, it can be divided into low-speed oil seal and high-speed oil seal; according to the main structure, it can be divided into skeleton type, skeleton-free type and composite type, in which skeleton oil seal can be divided into outer skeleton and inner skeleton, spring and spring-free, with and without auxiliary lip. Oil seals are made of nitrile rubber, fluorine rubber, silicone rubber, acrylic acid rubber and silicone fluorine rubber. This product is widely used in a variety of mechanical equipment, the sealed medium is mainly a variety of mineral lubricants and hydraulic oils.