Bearing assembly with integrated ferrofluid seal

A bearing assembly with an integrated ferrofluid seal, which bearing assembly comprises:

• (a) a magnetically permeable bearing assembly adapted to surround a rotatable shaft and having an inner race secured to the shaft and a spaced-apart outer race to define an annular raceway therebetween, ball-bearing cages in the raceway, and ball bearings retained in the ball-bearing cage in the raceway, to provide for the rotation of the inner and outer races relative to one another;
• and
• (b) a single-stage ferrofluid seal apparatus in the raceway positioned generally closely adjacent the ball bearings, the ferrofluid seal apparatus comprising
• (i) a single magnetic pole piece having a one and another end, one end radially extending into a close noncontacting relationship with the surface of the inner or outer race to define a small radial gap,
• (ii) an annular, axially-polarized, polymeric or ceramic permanent magnet having a radially disposed one end and another end relative to the axis of said shaft, the permanent magnet having an L-shaped sectional configuration the one end of the permanent magnet extending toward said radial gap to form an air gap with said surface, said other end of said pole piece being in contact with the permanent magnet between arms of the L-shaped configuration, the permanent magnet material having an energy product of from about 1.1 to 6.5 million gauss-oersteds, and acting as a magnetic insulating housing about the other end of the pole piece, and
• (iii) ferrofluid retained in the radial gap by magnetic flux of the permanent magnet, to provide a ferrofluid exclusion seal with said surface of the inner or outer race, and whereby the magnetic flux circuit passes between the pole piece, the ferrofluid in the radial gap, the surface of the race, the air gap, and the permanent magnet.