Browse Prior Art Database

Methods to Equalize Pressure in Sealed Disk Drives

IP.com Disclosure Number: IPCOM000121969D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Apuzzo, NA: AUTHOR [+4]

Abstract

Disclosed is a method to equalize the pressure difference which may occur in a hermetically sealed disk file which incorporates a spindle motor having rotary ferrofluid seals.

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Methods to Equalize Pressure in Sealed Disk Drives

      Disclosed is a method to equalize the pressure difference
which may occur in a hermetically sealed disk file which incorporates
a spindle motor having rotary ferrofluid seals.

      To prevent debris generated by the spindle motor from
contaminating the heads and disks inside a disk drive, rotary
ferrofluid seals are typically employed.  However, if the file is
hermetically sealed, then the pressure within the motor volume can be
higher or lower than the internal file pressure.  This pressure
difference can exceed the "burst" pressure of the rotary fluid seals,
resulting in seal failure.  To achieve an equilibration of pressure
we propose two possible solutions.

      As shown in the figure, the motor volume is connected to a
bellows (or membrane), which resides within the disk file volume.  If
the bellows is designed to exhibit a small spring constant, then the
pressure difference between the motor and HDA volumes will be
negligible.  The correct choice of non-permeable bellows material
prevents internal motor contaminants (particulate and vapor) from
entering the HDA.

      Similarly, the bellows shown could be replaced with a
particulate filter to prevent debris from entering the disk file
volume.  Vapor entry may be minimized by a diffusion limited path.