Control Flow Instability to Reduce Disk Flutter and Half Frequency Whirl

Abstract

To reduce the whirling air vortices which are normally formed at the disc tip, the outer edge of the disc surface may be gradually thinned down to a sharp tip. An alternative approach, the disc tip is gradually reduced in width and rounded at its outer edge. A flow obstruction may be incorporated in the shroud adjacent the edge of the disc tip. This obstruction may comprise a small substantially rectangular insert extending from the inner edge of the housing. Or, the inner surface of the portion of the housing adjacent the ends of the disc may incorporate grooves therein. These grooves, which are roughly herringbone in shape, and would have their center near either the edge of disc in a single disc environment or mid-way between the disc in a two disc environment.

1 . A method comprising at least one of:
 i.) controlling air flow instability; and   ii.) reducing air vortices, wherein the air flow instability and the air vortices are at least one of:
 a.) adjacent to a disc tip of a recording disc; and 
 b.) between two adjacent recording discs. 
   
     
     
         2 . The method as in  claim 1 , further comprising reducing pressure changes at the disc tip by reducing interaction of the air vortices adjacent to at least one of the disc tip and air vortices between the two adjacent recording discs. 
     
     
         3 . The method as in  claim 1 , wherein reducing air vortices is accomplished by modifying at least one of the recording disc design and the adjacent recording discs design. 
     
     
         4 . The method as in  claim 1 , wherein reducing air vortices is accomplished by at least one of:
 i.) tapering the recording disc to a sharp tip;   ii.) reducing the recording disc width to a rounded end;   iii.) establishing an air flow obstruction on a shroud, the shroud situated adjacent to the disc tip;   iv.) establishing a groove on the shroud;   v.) roughened the shroud; and   vi.) establishing an airfoil at a trailing end of the recording disc, with the trailing end of the recording disc being a thinnest portion of the recording disc.   
     
     
         5 . The method as in  claim 4 , wherein the air flow obstruction comprises a substantially rectangular shape extending from the shroud. 
     
     
         6 . The method as in  claim 4 , wherein the groove is herringbone in shape, and has a center near the edge of the recording disc, or midway between the two adjacent recording discs. 
     
     
         7 . The method as in  claim 1 , wherein reducing air vortices is accomplished by establishing a width of the recording disc that is not finite. 
     
     
         8 . The method as in  claim 1 , wherein controlling air flow instability is accomplished by controlling an interaction of the air vortices adjacent to the disc tip and the air vortices between the two adjacent recording discs. 
     
     
         9 . The method as in  claim 8 , wherein the interaction of the air vortices has a period of two disc revolutions. 
     
     
         10 . The method as in  claim 1 , wherein reducing air vortices comprises preventing formation of air vortices, or breaking up air vortices into smaller air vortices or local air vortices. 
     
     
         11 . The method as in  claim 1 , further comprising at least one of reducing flutter of the recording disc and half frequency whirl, for stabilizing a storage medium. 
     
     
         12 . The method as in  claim 1 , wherein the recording disc and the two adjacent recording discs are utilized with a hard disc drive. 
     
     
         13 . A method comprising reducing pressure changes adjacent to a disc tip of a recording disc. 
     
     
         14 . The method as in  claim 13 , wherein reducing pressure changes is accomplished by reducing interaction of air vortices adjacent to at least one of the disc tip and air vortices between two adjacent discs. 
     
     
         15 . The method as in  claim 13 , wherein reducing pressure changes is accomplished by modifying the recording disc design. 
     
     
         16 . The method as in  claim 13 , wherein reducing pressure changes is accomplished by at least one of:
 i.) tapering the recording disc to a sharp tip;   ii.) reducing the recording disc width to a rounded end;   iii.) establishing an air flow obstruction on a shroud, the shroud situated adjacent to the disc tip;   iv.) establishing a groove on the shroud;   v.) roughened the shroud; and   vi.) establishing an airfoil at a trailing end of the recording disc, with the trailing end of the recording disc being a thinnest portion of the recording disc.   
     
     
         17 . The method as in  claim 16 , wherein the air flow obstruction comprises a substantially rectangular shape extending from the shroud. 
     
     
         18 . The method as in  claim 16 , wherein the groove is herringbone in shape, and has a center near the edge of the recording disc, or midway between two adjacent recording discs. 
     
     
         19 . The method as in  claim 13 , wherein reducing pressure changes is accomplished by establishing a width of the recording disc that is not finite. 
     
     
         20 . The method as in  claim 13 , wherein the recording disc is utilized with a hard disc drive.