초록 ▼

A ferrofluid rotary-shaft seal apparatus of extended seal life particularly adapted for use as an exclusion seal with a computer-disc-drive spindle, which seal apparatus comprises: an annular permanent magnet; first and second pole pieces of unequal length at the one end, and which one end of each p

A ferrofluid rotary-shaft seal apparatus of extended seal life particularly adapted for use as an exclusion seal with a computer-disc-drive spindle, which seal apparatus comprises: an annular permanent magnet; first and second pole pieces of unequal length at the one end, and which one end of each pole piece extends into a close, noncontacting relationship with the surface of the shaft, to form a small-gap width and a large-gap width between the one end of the pole piece and the surface of the shaft; and a ferrofluid in the small- and large-gap widths to form a ferrofluid O-ring seal at each gap width, whereby, during rotation of the shaft, the ferrofluid at the small-gap width evaporates and forms an air gap, while the ferrofluid at the large-gap width provides extended seal life.

대표청구항 ▼

In a method for extending the seal life of a ferrofluid, rotary-shaft seal apparatus, which, in sealing a rotary shaft, comprises: (a) surrounding the rotary shaft with an annular permanent magnetic having one end and another end and having poles of opposite polarity at each end; (b) surrounding the

In a method for extending the seal life of a ferrofluid, rotary-shaft seal apparatus, which, in sealing a rotary shaft, comprises: (a) surrounding the rotary shaft with an annular permanent magnetic having one end and another end and having poles of opposite polarity at each end; (b) surrounding the rotary shaft with first and second, magnetically permeable, pole-piece elements in a magnetic-flux relationship with one and the other ends of the permanent magnet, each pole piece having a one end and another end; (c) extending the one end of each pole piece into a close, noncontacting relationship with the surface of the rotary shaft, to form first and second gaps therebetween of defined length; and (d) retaining magnetically, in the first and second gaps, a ferrofluid to form at least two liquid O-ring seals on the surface of the rotary shaft, to effect sealing of the rotary shaft, the improvement which comprises preferentially evaporating ferrofluid from one of the gap lengths by changing the defined gap lengths, to provide for unequal first and second gap lengths, whereby the ferrofluid will evaporate preferentially from the smallest gap length, while the ferrofluid in the largest gap length will provide a seal of extended seal life, in comparison to a seal wherein the gap lengths are smaller and equal.