High speed ball bearing for dental or medical handpieces

Abstract

A bearing assembly for use in a medical, surgical, or dental handpiece that enables spindle rotation for a supported rotary tool at high speeds. The bearing assembly incorporates annular gap shields at each axial end to prevent contaminate ingress and to retain lubricating grease within the bearing assembly to avoid re-lubrication after each use or sterilization cycle.

1 . A medical, surgical, or dental handpiece bearing assembly comprising:
 an outer ring defining an outer raceway and an inner ring defining an inner raceway; said inner and outer rings defining a radial distance between said inner and outer rings;   a first shield proximate a first axial end of said bearing assembly and extending from and integral with one of said inner and outer rings towards the other of said inner and outer rings;   a second shield proximate a second axial end of said bearing assembly and extending from one of said inner and outer rings towards the other of said inner and outer rings;   wherein said second shield is snap fit with one of said inner and outer rings to interlock said second shield and said ring together; said second shield being comprised of an engineering plastic of an amorphous polyetherimide to withstand temperatures of approximately 134° C.;   wherein said first and second shields each have a length equal to at least about 50% of the radial distance between said inner and outer rings;   a plurality of balls installed between said inner and outer rings and positioned to contact said inner and outer raceways;   a retainer positioned between said inner and outer rings defining a plurality of pockets which receives said balls, said retainer comprising an engineering plastic having a base material selected from either a polyamide-imide (PAI) or a polyetheretherketone (PEEK) to withstand repeated sterilization, autoclaving, and application temperatures without degradation of mechanical properties; and   a lubricating grease being disposed between the first shield and the second shield, adjacent to the plurality of balls, the lubricating grease comprising a mineral base oil with polyurea thickener.   
     
     
         2 . The bearing assembly of  claim 1  wherein said second shield is mounted to an outer diameter axial surface of said inner ring, an inner diameter axial surface of said outer ring, or an outer diameter axial surface of said outer ring; said inner or outer ring defining a groove which receives said second shield. 
     
     
         3 . The bearing assembly of  claim 1  wherein said first and second shields extend substantially the full radial distance between said inner and outer rings. 
     
     
         4 . The bearing assembly of  claim 1  wherein said engineering plastic of the second shield further includes glass filler. 
     
     
         5 . The bearing assembly of  claim 1  wherein the material for the retainer includes carbon fillers. 
     
     
         6 . The bearing assembly of  claim 5  wherein said carbon fillers comprise graphite and/or carbon fibers. 
     
     
         7 . The bearing assembly of  claim 5  where in the carbon is present in amounts greater than, or equal to, about 10% by weight. 
     
     
         8 . The bearing assembly of  claim 1  wherein the material for the retainer comprises fillers, said fillers including fluoropolymer particles, and wherein said fluoropolymer is a polytetrafluoroethylene. 
     
     
         9 . The bearing assembly of  claim 8  wherein the fluoropolymer particles are present in amounts greater than, or equal to, about 1% by weight. 
     
     
         10 . The bearing assembly of  claim 1  wherein said plurality of balls are supported in an angular contact configuration. 
     
     
         11 . The bearing assembly of  claim 1  wherein one of said inner and outer rings has a relieved configuration; and wherein said retainer has a one-piece configuration fully encompassing the equator of each of said plurality of balls. 
     
     
         12 . The bearing assembly of  claim 1  wherein said first shield is integrally formed with said outer ring and said second shield snap fits with said outer ring. 
     
     
         13 . The bearing assembly of  claim 1  wherein said lubricating grease has a viscosity of at least about 110 centristrokes at approximately 104 degrees Fahrenheit. 
     
     
         14 . The bearing assembly of  claim 2  wherein said second shield is mounted to an outer diameter surface of said outer ring. 
     
     
         15 . The bearing assembly of  claim 1  wherein the engineering plastic of said second shield is a material which remains as a barrier and preserves shield integrity at temperatures of approximately 134 degrees Centigrade and exposure to steam. 
     
     
         16 . The bearing assembly of  claim 1  wherein the thermal expansion properties of the engineering plastic of said second shield maintain a mechanical interlock at temperatures of approximately 134 degrees Centigrade and exposure to steam. 
     
     
         17 . The bearing assembly of  claim 1  wherein said second shield is mounted to an inner diameter surface of said outer ring. 
     
     
         18 . The bearing assembly of  claim 1  wherein said second shield is mounted to an outer diameter surface of said outer ring. 
     
     
         19 . A medical, dental, or surgical handpiece containing a driven member and incorporating at least one bearing assembly of  claim 1  to support said driven member. 
     
     
         20 . The medical, dental, or surgical handpiece of  claim 19  wherein said handpiece comprises a head defining a cavity housing said driven member; said cavity including upper and lower recesses axially opposite said driven member with each recess receiving one of said bearing assemblies; and each of said bearing assemblies orientated in said recesses such that said second shield faces axially inward toward said driven member.