Ferrofluid cap seal for spindle motor

Abstract

A hard disk drive spindle motor has a hub, a drive shaft, and a bearing therebetween. The spindle motor also has a ferrofluid seal to prevent any incidental oil emissions from the bearing from entering the drive. A ferrofluid cap is mounted on the axial end of the spindle motor for sealing the ferrofluid seal. The cap is a flat ring and has an elastomeric pad around its outer edge. The pad seats in a recess in the bore of the hub. The cap does not touch the shaft as it rotates with the hub about the shaft. Any excess ferrofluid from the ferrofluid seal is forced radially outward away from the shaft by centrifugal force. The cap contains the excess ferrofluid within the spindle motor and prevents it from entering other areas of the disk drive.

We claim:  
     
         1 . An apparatus, comprising: 
 a hub having a central axis, a bore, an annular recess formed in the bore, and an axial end;    a shaft mounted in the hub concentric with the axis, the hub and shaft being rotatable relative to each other;    a bearing mounted between the shaft and the hub;    a ferrofluid seal mounted axially outboard of the bearing between the shaft and the hub for sealing the bearing in the hub, the ferrofluid seal containing ferrofluid;    a solid ferrofluid cap for sealing the ferrofluid in the hub, the cap having an outer edge mounted in the recess in the bore of the hub axially outboard of the ferrofluid seal, and an axial hole through which the shaft extends, the cap being free of contact with the shaft.    
     
     
         2 . The apparatus of    claim 1   , further comprising an elastomeric seal mounted to the outer edge of the ferrofluid cap for engaging the annular recess in the bore of the hub to form a seal.  
     
     
         3 . The apparatus of    claim 1    wherein the ferrofluid cap is a circular disc, and the outer edge and axial hole of the cap are circular.  
     
     
         4 . The apparatus of    claim 1    wherein the elastomeric seal is molded to the cap.  
     
     
         5 . The apparatus of    claim 1    wherein the ferrofluid cap is free of adhesive bonds with respect to the hub.  
     
     
         6 . The apparatus of    claim 1    wherein the bore of the hub has an annular concave recess for engaging the outer edge of the cap.  
     
     
         7 . A rotational apparatus for a hard disk drive, comprising: 
 a hub having a central axis, a bore, an annular recess formed in the bore, and an axial end;    a shaft mounted in the hub concentric with the axis, the hub and the shaft being rotatable relative to each, other;    a bearing mounted between the shaft and the hub;    a ferrofluid seal mounted axially outboard of the bearing between the shaft and the hub for sealing the bearing in the hub, the ferrofluid seal containing ferrofluid;    a solid ferrofluid cap mounted in the annular recess in the bore of the hub axially outboard of the ferrofluid seal for sealing the ferrofluid in the hub, the cap comprising a circular disc with an outer circumferential edge and an axial hole that is free of contact with the shaft; and    an elastomeric seal mounted to the outer circumferential edge of the ferrofluid cap for engaging the annular recess in the bore of the hub to form a seal.    
     
     
         8 . The rotational apparatus of    claim 7    wherein the elastomeric seal is molded to the cap.  
     
     
         9 . The rotational apparatus of    claim 7    wherein the cap is free of adhesive bonds with respect to the hub.  
     
     
         10 . The rotational apparatus of    claim 7    wherein the bore of the hub has an annular recess for engaging the cap.  
     
     
         11 . A rotational apparatus for a hard disk drive, comprising: 
 a hub having a central axis, a bore with an annular concave recess, and an axial end;    a shaft rotatably mounted in the hub concentric with the axis;    a bearing mounted between the shaft and the hub;    a ferrofluid seal mounted axially outboard of the bearing between the shaft and the hub for sealing the bearing in the hub, the ferrofluid seal containing ferrofluid;    a ferrofluid cap mounted in the annular concave recess in the bore of the hub axially outboard of the ferrofluid seal for sealing the ferrofluid in the hub, the cap comprising a solid circular disc with an outer circumferential edge and an axial hole for remaining free of contact with the shaft;    an elastomeric seal integrally formed on the outer circumferential edge of the cap for engaging the annular concave recess in the bore of the hub to form a seal; and wherein 
 the elastomeric seal is free of adhesive bonds with respect to the hub.