Browse Prior Art Database

Enhanced Compact Magnetic Fluid Seal

IP.com Disclosure Number: IPCOM000105629D
Original Publication Date: 1993-Aug-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Cossette, LA: AUTHOR [+2]

Abstract

A method for increasing the magnetic forces acting on the magnetic fluid in a magnetic fluid exclusion seal is disclosed. Alignment of seal features can effectively increase the magnetic forces without the need to modify a seal's design.

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This is the abbreviated version, containing approximately 87% of the total text.

Enhanced Compact Magnetic Fluid Seal

      A method for increasing the magnetic forces acting on the
magnetic fluid in a magnetic fluid exclusion seal is disclosed.
Alignment of seal features can effectively increase the magnetic
forces without the need to modify a seal's design.

      A typical rotary magnetic fluid seal (Fig. 1) consists of a
permanent magnet 1 which creates a completed magnetic circuit through
the air gap 2 between the shaft 3 and the pole pieces 4.  By
controlling the gap dimension, an intense magnetic field is
generated, which retains the magnetic fluid, thereby forming a low
drag hermetic seal.

      The trend in disk drives is driven by small size and higher
speeds, which may induce higher centrifugal forces causing the fluid
to spin off.  An increase in the magnetic retention forces would
counter the centrifugal forces and avoid any spin-off.  Roseinweig
(1971) increased the magnetic forces by focusing the magnetic field
in one point; this practice was achieved by tapering the poles.  The
magnetic forces can be maximized for any seal pole geometry and seal
gap through the addition of shaft or hub features that are aligned
with one or more poles of the seal.  The addition of shallow notches
above or below a seal pole on the shaft of an inner diameter seal
modifies the magnetic flux distribution/gradients, yielding higher
magnetic forces in the seal pole/shaft gap.  Corresponding features
on the mating hub of an outer diameter seal...