Browse Prior Art Database

New-Class of Filters for Sealed Disk Drives

IP.com Disclosure Number: IPCOM000122924D
Original Publication Date: 1998-Jan-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Chang, CJ: AUTHOR [+3]

Abstract

Disclosed is a new class of filters suitable for disk drives, in particular those having low profiles. It utilizes the viscous pumping of fluid by the boundary layer on the rotating disk drives. Disk drive filters described in prior art based on a pressure differential available in the bulk flow, outside the disk boundary layers. As the disk drive design moves toward lower overall height, the spacings between disks and between disk and cover become smaller. Consequently, the relative effectiveness of the viscous pumping by the disk boundary layer becomes increasingly important.

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New-Class of Filters for Sealed Disk Drives

      Disclosed is a new class of filters suitable for disk drives,
in particular those having low profiles.  It utilizes the viscous
pumping of fluid by the boundary layer on the rotating disk drives.
Disk drive  filters described in prior art based on a pressure
differential available  in the bulk flow, outside the disk boundary
layers.  As the disk drive  design moves toward lower overall height,
the spacings between disks and  between disk and cover become
smaller.  Consequently, the relative effectiveness of the viscous
pumping by the disk boundary layer becomes  increasingly important.

      The flow pattern is the space between the disks and cover is
for the flow to move outward along the disk and return inward along
the cover.  Viscous effects are confined to thin layers of fluid, the
boundary layers, on the solid surface.  For the flow geometry defined
by a rotating disk and a corresponding cover, the thickness of the
boundary layer is a function of the disk rotational rate only;
independent of the  radial distance from the axis of rotation.  The
thickness of the boundary  layer on the rotating disk is 3 (v/&Omega)
where v is the kinetic viscosity of the fluid and is the rotational
speed of the disk. There is  also boundary layer of comparable
thickness on the cover.  The relative  importance of the viscous
effect on the flow increases as the spacing between disk and cover,
H, reduces.  In the limit of H = 6 v/, the two  boundary layers on
the disk and cover merge so that the bulk flow ceases ...