Disc drive top cover having an over-molded top pole

Abstract

A disc drive has a top cover formed from a moldable material by an injection molding process and a metal top pole piece over-molded within the top cover. A voice coil motor assembly includes a voice coil attached to an actuator arm of the disc drive, a bottom pole mounted to a base plate of the drive, and a magnet attached to the bottom pole, wherein the coil is positioned adjacent to the permanent magnet between the bottom pole and the top pole piece once the top cover is attached to the base plate. The top cover may be molded from a reinforced polymer material. The metal top pole piece may include a protruding mounting surface that is secured to an actuator arm bearing shaft to provide a metallic anchor between the bearing shaft and the molded top cover.

What is claimed is:  
     
         1 . A disc drive comprising: 
 a base plate supporting a data storage disc rotatably mounted on a drive motor and an actuator arm mounted adjacent the disc for selectively positioning a transducer over the disc;    a top cover attached to the base plate to define an internal environment of the disc drive, wherein the top cover is formed from a moldable material by an injection molding process, and wherein the top cover includes a metal top pole piece over-molded within the top cover during the injection molding process; and    a voice coil motor assembly having a voice coil attached to the actuator arm, a bottom pole mounted to the base plate, and a magnet attached to the bottom pole, wherein the coil is positioned adjacent to the magnet between the bottom pole and the top pole piece over-molded within the top cover.    
     
     
         2 . The disc drive according to  claim 1  wherein the moldable material is a reinforced polymer.  
     
     
         3 . The disc drive according to  claim 2  wherein the polymer is reinforced with carbon fibers.  
     
     
         4 . The disc drive according to  claim 2  wherein the polymer is reinforced with steel fibers.  
     
     
         5 . The disc drive according to  claim 1  wherein: 
 the actuator arm is pivotably connected to a bearing shaft attached to the base plate; and  
 the metal top pole piece includes a pole body and a mounting surface extending from the pole body, wherein the mounting surface is secured to a top end of the bearing shaft to provide a metallic anchor between the bearing shaft and the molded top cover.  
 
     
     
         6 . The disc drive according to  claim 5  wherein the mounting surface of the metal top pole piece has a thickness that is smaller than a thickness of the pole body.  
     
     
         7 . The disc drive according to  claim 5  wherein: 
 the base plate includes a threaded hole aligned with an opening in the top cover for attaching the top cover to the base plate with a fastener; and  
 the metal top pole piece includes an outer flange extending from the pole body, wherein the outer flange includes a hole aligned with the opening in the top cover to provide a reinforced contact point between the base plate and the molded top cover.  
 
     
     
         8 . The disc drive according to  claim 7  wherein the outer flange of the metal top pole piece has a thickness that is smaller than a thickness of the pole body.  
     
     
         9 . The disc drive according to  claim 1  wherein the over-molded metal top pole piece is fully supported by the top cover and is not directly connected to the bottom pole.  
     
     
         10 . The disc drive according to  claim 9  wherein the over-molded metal top pole piece does not extend within the internal environment of the disc drive.  
     
     
         11 . The disc drive according to  claim 10  wherein a thickness of the molded top cover is greater than a thickness of the over-molded metal top pole piece so that a top surface of the top pole piece is embedded within the molded top cover below a top surface of the molded top cover.  
     
     
         12 . A top cover for a disc drive, wherein the disc drive includes a base plate supporting an actuator arm mounted adjacent a data storage disc for selectively positioning a transducer over the disc, the disc drive further including a voice coil motor assembly having a voice coil attached to the actuator arm, a bottom pole mounted to the base plate and a magnet attached to the bottom pole, the top cover comprising: 
 a cover portion formed from a moldable material by an injection molding process, wherein the cover portion is adapted for attachment to the base plate to form an internal environment of the disc drive; and    a metal top pole piece over-molded within the cover portion during the injection molding process, the metal top pole piece including a pole body adapted to be aligned over the bottom pole when the cover portion is attached to the base plate.    
     
     
         13 . The top cover according to  claim 12  wherein the moldable material is a reinforced polymer.  
     
     
         14 . The top cover according to  claim 13  wherein the polymer is reinforced with carbon fibers.  
     
     
         15 . The top cover according to  claim 13  wherein the polymer is reinforced with carbon fibers.  
     
     
         16 . The top cover according to  claim 12  wherein the disc drive actuator arm is pivotably supported by a bearing shaft attached to the base plate, and wherein the top cover further comprises: 
 a mounting surface extending from the pole body of the metal top pole piece, wherein the mounting surface is over-molded within the cover portion and is adapted for attachment to the bearing shaft to provide a metallic anchor between the bearing shaft and the cover portion.  
 
     
     
         17 . The top cover according to  claim 16  wherein the top cover further comprises: 
 an opening defined in the cover portion, the opening adapted for attaching the cover portion to the base plate of the disc drive; and  
 an outer flange extending from the pole body of the metal top pole piece, wherein the outer flange is over-molded within the cover portion and includes a hole aligned with the opening defined in the cover portion, and wherein the outer flange is adapted to provide a reinforced contact point between the cover portion and the base plate of the disc drive.  
 
     
     
         18 . A disc drive having a base plate supporting an actuator arm mounted adjacent a data storage disc for selectively positioning a transducer over the disc and a voice coil motor assembly having a voice coil attached to the actuator arm, a bottom pole mounted to the base plate and a magnet attached to the bottom pole, the disc drive further comprising: 
 a top cover attached to the base plate to define an internal environment of the disc drive; and    means for supporting a top pole piece in alignment above the bottom pole of the voice coil motor assembly so that the top pole piece does not extend into the internal environment of the disc drive.    
     
     
         19 . The disc drive according to  claim 18  wherein the means for supporting the top pole piece includes injection molding the top cover from a moldable material and over-molding the top pole piece within the top cover.  
     
     
         20 . The disc drive according to  claim 19  wherein the moldable material is a reinforced polymer.