US Patent 6945536 Oil seal

A two liquid type oil seal 10 having a first seal 13 and a second seal 14, is provided with a communication hole 16 in the first seal 13. The communication hole 16 communicates a space 24 defined by the first and second seals 13, 14 and a crank shaft 2, with a gap 25 between an outer casing 11 and the first seal 13. Negative pressure induced in the space 24 is eliminated by sucking air from the outside through the communication hole 16 while lubrication oil having entered into the space 24 is removed from a groove 15 which is formed in the first and second seals 13, 14, thereby it is possible to restrain the first and second seals 13, 14 from being worn.