The present invention relates to an oil seal for use between two relatively movable members and, more particularly, to a seal which serves to recover oil leakage with a pumping effect, the oil seal being provided at the sides of a differential gear used for the transmission system of motor vehicles. 
An oil seal is provided to a rotation shaft for recovering oil.  To restrict frictional resistance between the rotation shaft and the oil seal, the oil seal makes a line-contact with the shaft at the inner face of the shaft.  Portions of the seal positioned beside the line-contact at the inner face have a bevel surface which becomes greater further from the surface of the shaft as they become closer to openings at the edges of the oil seal.  Ribs are provided at a bevel at a side corresponding to a space without oil, each rib presenting an angle of attack against the positive and negative rotation directions of the shaft.  When oil goes beyond the line-contact position from an oil-containing space during the rotation of the shaft, the oil can be recovered by the pumping function of the ribs. 
Various structures of the ribs in such an oil seal have been proposed in U.S. Pat.  Nos.  3,504,920, issued Apr. 7, 1970, 3,923,315, issued Dec. 2, 1975 and 3,934,888 issued Jan. 27, 1976.  However, the conventional oil seals cannot sufficiently recover oil to prevent oil leakage.