Skeleton oil seal is a typical representative of oil seal. Generally speaking, oil seal refers to framework oil seal. The function of oil seal is to isolate the parts that need to be lubricated in the transmission parts and the output parts, so as not to let the lubricating oil leak. The skeleton is like the steel bar in the concrete component, which plays a reinforcing role and keeps the shape and tension of the oil seal. According to the structure, it can be divided into single lip framework oil seal and double lip framework oil seal. The secondary lip of double lip framework oil seal plays a dust-proof role to prevent external dust and impurities from entering into the machine. According to the framework type, it can be divided into inner framework oil seal, exposed framework oil seal and assembled oil seal. According to the working conditions, it can be divided into rotating framework oil seal and reciprocating framework oil seal. Widely used in gasoline engine crankshaft, diesel engine crankshaft, gearbox, differential, shock absorber, engine, axle and other parts.