| 摘要 |
A low-cost, self-activating ferrofluid seal apparatus particularly useful as an exclusion seal with computer-disc-drive spindles, which seal apparatus comprises an annular, axially-polarized permanent magnet and first and second pole pieces in a magnetic-flux relationship with each side of the magnet and the one end of the pole pieces extending into a close, noncontacting relationship with the surface of a shaft element to be sealed to form a radial gap with the surface of the shaft and ferrofluid in the radial gap to effect a single-stage ferrofluid seal and wherein the annular permanent magnet has a thickness of not more than about 25 mils and the annular magnet has an energy product of about 1.8x106 gauss-oersteds or greater and the ferrofluid comprises a low-vapor-pressure ferrofluid having a magnetic saturation of at least 200 gauss or more.
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