This kind of oil seal has a special structure, which is different from ordinary oil seal. It is generally composed of outer ring and inner ring. The outer ring is a bit like our common framework oil seal, but it is also specially designed, such as positioning, dust-proof, oil storage and other structures. Its special place is the internal slip ring. When working, the slip ring rotates with the rotating shaft, and the sealing lip is only matched and rubbed with the slip ring. The characteristic of the box oil seal is its strong anti pollution ability, which can be used in the occasions with heavy pollution, such as heavy truck axle, concrete machinery, agricultural machinery, etc.

The service life of the box type oil seal is generally longer than that of the ordinary oil seal, so the replacement cycle is longer, and it is also suitable for the occasion where the oil seal is difficult to be replaced. The box type oil seal also has the biggest advantage, that is, the processing requirements for the shaft are greatly reduced. It can be seen from the structure in the figure that the sealing lip is not in contact with the shaft surface, so the surface roughness and surface hardness requirements of the shaft are greatly reduced compared with ordinary oil seals. So the whole processing cost will also be reduced.