Abstract:
A hard disk drive with a multiple disk stack normally utilizes disk separator plates near the disk surfaces to reduce wind induced vibrations in the disks and the read/write heads. The manufacturing methods currently used to make these separator plates, metal casting and machining, or injection molded plastic, or extruding and machining, or cold forging tends to be expensive and creates unwanted weight and bulk without the desired precision. Stamping disk separator plates from metal provides exceptional dimensional control at reduced cost, but cannot readily provide the thicknesses required. Stamping and extruding the offsets, or stamping and folding the offsets, is a manufacturing process that provides the required dimensions for the offsets, and dimensional control and reduced cost.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a division of application Ser. No. 13/893,107 filed May 13, 2013 for DISK SEPARATOR PLATES AND METHOD OF MAKING DISK SEPARATOR PLATES FOR HARD DISK DRIVES. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to disk separator plates for reducing airborne noise and vibration in hard disk drives, and more particularly, pertains to methods of manufacturing disk separator plates. 
         [0004]    2. Description of Related Art 
         [0005]    It has been common practice for hard disk drives (HDD) to incorporate disk separator plates in order to reduce vibration caused by wind created by the rotating disk surfaces. This generates undesired noise in the hard disk drive assembly. It is thought that the disk separator plates should cover a maximum of the disk surfaces in order to minimize these vibration effects. It has been experimentally proven that the main airflow in a hard disk drive assembly, which is tangential to the circumferential edge of the rotating disks causes vortexes to be created between the airflow fluid layers, causing disk flutter and vibration of the magnetic reading heads during operation, thereby increasing noise and decreasing HDD performance. 
         [0006]    The use of disk separator plates in hard disk drives has become common place. This increased use of disk separator plates in a hard disk drive increases the cost of the disk drive because of the increased raw materials required, and the secondary manufacturing operations required to make the disk separator plates, after initial stamping, forging, extrusion or casting. 
         [0007]      FIG. 1  illustrates the environment in which disk separator plates of the present invention, also known as air damper plates disk damages, and anti disks, are utilized in a hard disk drive  9  which has a housing  11  with side walls  15  and  13  and a top enclosing the housing (not shown). 
         [0008]    Contained within the housing  11  is the actuator drive assembly  17 . An actuator  19 , along with actuator arms  21  that carry read/write heads ( 22 ) are part of the drive assembly. A disk separator plate  25  is mounted over a top disk  23  to the side walls  15  and  13 , or in any other convenient manner, to the housing  11  of hard disk drive  9 . Besides being mounted over a disk stack  23 , the disk separator plates are mounted between each of the disks in the disk stack, as will be explained hereinafter. 
         [0009]    The shape and construction of the disk separator plates in the prior art are quite varied, although they have a common purpose of reducing airflow induced vibration. 
         [0010]      FIG. 2  illustrates a disk separator plate  27  which is manufactured by casting and then machining to provide the correct thickness and flatness of the offset structures  31 ,  29 ,  32 , and  33  which are used to hold the disk separator plate to the housing of a hard disk drive. Pins  30  and  34  are inserted into the casting or are machined from the casting as secondary operations. These pins mate with corresponding holes in the next separator plate in the stack, or in the drive base. 
         [0011]      FIG. 3  illustrates a disk separator plate  35  that is manufactured by injection molding a plastic material. The plastic separator plate  35  has offset structures  37 ,  38  and  39  formed in the molding process. 
         [0012]      FIG. 4  shows a disk separator plate  41  which is manufactured by extrusion and then milled or turned to reduce the main disk separator plate thickness  44  and establish the offset structures  42 ,  45 ,  46  required for mounting the disk separator plate to the housing of a hard disk drive. Boss  43  is milled from the extrusion to provide location alignment by nesting with an opposing separator plate or a drive base. 
         [0013]    Each of these manufacturing processes has considerable shortcomings with respect to cost for the manufacturing methods used to produce metal disk separator plates. Furthermore, the ability to produce separator plates to precise dimensional control is difficult for each of the above described methods of manufacture. 
         [0014]    The plastic injection molding process has special problems associated with it. The method produces voids and anisotropies in the product. The plastic plates are distorted when clamped. The plates are not as clean as required. The surface finish is not as smooth as required. 
         [0015]    The major problem with the metal disk separator plates is the cost of manufacturing such plates. 
         [0016]      FIG. 5  illustrates a side cross-section of a stack of disk separator plates  49 ,  51 ,  53 , which are fastened to the enclosure  47  of a hard disk drive by a hold down bolt  55 . The stack of disk separator plates illustrated is designed to cover the portions of the disks not swept by the use of the recording heads (not shown) which would rotate in the space between disk separator  49  and  51 ,  51  and  53 , and  53  and the base  54  of housing  47 . Hub  57  is the center around which the disks rotate. 
         [0017]    The offsets  56 , which are designed to provide the correct amount of separation between the disk separators  49 ,  51 , and  53 , and the base  54  of the hard disk drive are created as part of the separator plate during the manufacturing process. As can be seen by the structure of the offset  56  of separator plate  49 , for example, the machining required after initial manufacturing is significant and increases the cost of each separator plate. The amount of metal required to make forged, fully machined, or extruded and machined disk separator plates is large because the starting thickness is at least that of the full offset height. The main plate thickness of the separator plate must be created by removing material. 
         [0018]    Although flat stamped disk separator plates provide the best dimensional control, of all these manufacturing processes, at a minimum manufacturing cost, the stamping process cannot create the thickness, or material reduction required in a typical offset at the mounting points for the disk separator plate. 
         [0019]    Accordingly, the present invention provides a method for manufacturing disk separator plates using disk stamping techniques which reduce raw material content and secondary manufacturing operations, while providing the necessary offset heights, required at the offset points, used for mounting the separator plates to the hard disk drive. 
       SUMMARY OF THE INVENTION 
       [0020]    Making a disk separator plate by stamping and then extruding the offsets to a desired dimension, offset forming, or folding and making layers of material to obtain desired offset structure heights, provides a disk separator plate that is dimensionally controlled, has less debris, less weight and is less expensive to make than disk separator plates made by traditional methods. Extruded offsets are designed to nest into opposing counterbores to provide location alignment in-plane. This eliminates the need for additional alignment pins and holes, freeing up space and enabling more compact designs. Folded offsets also provide for precise alignment of the separator plates, as needed, by the extension of pins in the offset structures or by use of pins in the drive base. These pins mate with corresponding holes in mating parts. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The exact nature of this invention, as well as the objects and advantages thereof, will become readily apparent from consideration of the following specification in conjunction with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof and wherein: 
           [0022]      FIG. 1  is an illustration of a hard disk drive with a disk separator plate located therein; 
           [0023]      FIG. 2  is a perspective illustration of a prior art separator plate; 
           [0024]      FIG. 3  is a perspective illustration of a prior art separator plate; 
           [0025]      FIG. 4  is a perspective illustration of a prior art separator plate; 
           [0026]      FIG. 5  is a side view illustration of a stack of prior art separator plates assembled in a hard disk drive; 
           [0027]      FIG. 6  is a side view of a hard disk drive with separator plates, according to the present invention; 
           [0028]      FIG. 7  is a perspective illustration of a disk separator plate according to the present invention; 
           [0029]      FIG. 8  is a perspective illustration of disk separator plates according to the present invention; 
           [0030]      FIG. 9  is a perspective illustration of separator plate offsets, according to the present invention; 
           [0031]      FIG. 10  is a perspective illustration of a disk separator plate, according to the present invention; 
           [0032]      FIG. 11  is a perspective illustration of the counterbore in a disk separator plate, according to the present invention; 
           [0033]      FIG. 12  is a schematic illustration of the nesting of two disk separator plates, according to the present invention; 
           [0034]      FIG. 13  is a perspective illustration of stacked disk separator plates, according to the present invention; 
           [0035]      FIG. 14  is a perspective illustration of stacked disk separator plates, according to the present invention; 
           [0036]      FIG. 15  is a perspective illustration of a disk separator plate, according to the present invention; 
           [0037]      FIG. 16  is a perspective illustration of stacked disk separator plates, according to the present invention; 
           [0038]      FIG. 17  is a perspective illustration of a disk separator plate, according to the present invention, before an offset structure is formed; 
           [0039]      FIG. 18  is a perspective illustration of a disk separator plate, after the offset structure is formed; 
           [0040]      FIG. 19  is a perspective illustration of a disk separator plate with an alternate offset, according to the present invention; 
           [0041]      FIG. 20  is a perspective illustration of the offset assembly of  FIG. 19 ; 
           [0042]      FIG. 21  is a perspective illustration of the offset assembly of  FIG. 20  in a finished state; and 
           [0043]      FIG. 22  is a perspective illustration of stacked disk separator plates utilizing the offset assembly of  FIG. 21 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0044]      FIG. 6  illustrates a stack of separator plates  61 ,  63 ,  65 , manufactured according to the present invention, attached to a housing  59  of a hard disk drive. The upper separator plate  61  and the lower separator plate  65  create the required offset between separator plates  61  and  63 ,  63  and  65 , and  65  and the base  66  respectively, by offset forming the ends of the separator plate  61  and  65  a certain distance to create the offset  71  for separator plate  61  and the offset  73  for separator plate  65 . The center separator plate  63  is not bent and has no offset. The stack of separator plates  61 ,  63 , and  65 , is assembled on a standoff  68  which is part of the frame  59  of the hard disk drive housing. The stack is fastened down by a fastening bolt  67 . 
         [0045]    The disks (not shown) that rotate in the spaces between the separator plates  61  and  63 ,  63  and  65  and  65  and the base  66 , are attached to a rotating spindle  69 , in a manner well known. 
         [0046]    Manufacturing the separator plates of  FIG. 6  by stamping and then forming the ends to create a standoff has proven to be a less expensive method of manufacturing, while at the same time producing a more accurately dimensioned disk of separator plates. Moreover, much less raw material is required since the raw material thickness is close to the smaller plate tip thickness  72 , instead of the larger offset thickness  71 . 
         [0047]      FIG. 7  illustrates a disk separator plate manufactured by stamping the shape of the plate  75  out of a preferred metal such as aluminum, along with the tabs  77 ,  81 ,  79 . The offset on the tabs is formed by offset forming, essentially two right angle bends. Pins  76  and  82  are extruded during stamping to provide location alignment. 
         [0048]      FIG. 8  illustrates two disk separator plates mounted together. A top plate  75  is mounted to a bottom plate  83  to create a gap  80  within which a disk rotates. The tabs  85 ,  89 , and  87  are joined together so that the alignment pins and holes  76  and  78 , line up. 
         [0049]      FIG. 9  schematically illustrates the offset bends  84  and  86  in the upper disk separator plate  75  and the lower disk separator plate  83  that create the respective tabs  85 A and  85 B. These tabs are mated together to form tab  85 . 
         [0050]    Besides creating offsets in the stamped plates by offset forming, the present invention creates offsets by extrusion from thinner raw material. Extrusion of an offset boss is illustrated in  FIG. 10 , which shows a disk separator plate  91  having tabs with extruded offset bosses  93 ,  97 , and  95  which create the offset structure. It is contemplated that the top face of the disk separator plate around the perimeter of the offset boss  93  has a counterbore  101  with a diameter slightly larger than the extruded boss ( FIG. 11 ) to provide location alignment with the separator plate above. 
         [0051]      FIG. 12  schematically illustrates how two extruded offset bosses nest. The top plate  105  with offset boss  107  is supported by the bottom plate  103  with offset boss  109 , nesting offset boss  107  in the counterbore  111 . 
         [0052]    It is contemplated that rather than creating a counterbore in the face of a separator plate around each offset boss, the extruded offsets could be made larger in diameter than the apertures through the boss. 
         [0053]      FIG. 13  illustrates three separator plates  113 ,  115 , and  117  each having extruded bosses as offsets  119 ,  121 , and  123  respectively. The aperture  125  through offset boss  119 , for example, has a smaller diameter than the external diameter of offset boss  119 , as do each of the other separator plates  115  and  117 . The result is the three separator plates can be simply stacked one on top of the other, with the bottom of the boss of one plate  119  sitting on the top surface of disk separator plate  115 , and the bottom of offset boss  121  sitting on the top surface of separator plate  117 . 
         [0054]    A slight variation of this construction is illustrated in  FIG. 14 , which shows separator plates  127 ,  129 , and  131  having offset bosses  133 ,  135 , and  137  that are extruded and then flared in a slightly upside-down V-shaped cross section with the top of the boss being smaller in diameter than the bottom. Thus, separator plate  127  with a V-shaped extruded offset boss  133  has a larger diameter at its base than at the top. The aperture  139  which passes through boss  133  has a smaller diameter than the top of boss  133 . As a result, the separator plates  127 ,  129 ,  131  all have the same footprint and each sit on top of the separator plate below it. These V-shaped offset bosses allow use of the full offset height when large aperture  139  lead-in radii are required to generate enough material volume to create the required offset height. Without the flare, bosses  133  and  135  would recess into the apertures and reduce the stack height. 
         [0055]    The present invention also contemplates the creation of offsets in stamped metal disk separator plates by double internal tabs. As shown in  FIG. 15 , a disk separator plate  141  has the tab internally cut  143  to create legs  144  and  146 . These legs are then bent again at top surface  141  of the disk to create the offset and bent at the end of the legs to create feet  145 ,  147 . These feet extend beyond the diameter of the aperture  143 . 
         [0056]    This permits stacking of the disk separator plates as illustrated in  FIG. 16 . Disk separator plate  141  is stacked on disk separator plate  149 , which is, in turn, stacked on disk separator plate  157 . The offset legs of disk separator plate  141  rest on the top surface of disk separator plate  149  because of the feet  147  and  145  created by the bend in the legs  144 ,  146 . The feet of disk separator plate  149 , feet  155  and  153  sit on the top surface of disk separator plate  157 . The feet  161 ,  163  of disk separator plate  157 , sit on top of another disk separator plate, or a fastening protrusion on the frame of a disk drive. 
         [0057]    The present invention also contemplates the creation of offsets by folding tabs in parallel. As illustrated in  FIG. 17 , a disk separator plate  165  is stamped from a metal to create the shape of the disk separator plate, as well as a tab configuration  167 . This tab configuration will create the offset required. Two overlapping folds accurately align the apertures  169 ,  171 , and  173  in the tab  167 .  FIG. 18  shows the tab  167  after the parallel folds are completed. Aperture  173  is on the bottom, aperture  171  is in the middle, as the result of first bend  177 . Aperture  169  is on top, as the result of second bend  165 . Aperture  169  can also be pierced through all three layers after folding. Offset height can be reduced as required by corning the three folded tabs during stamping. 
         [0058]    The present invention also contemplates the creation of offsets in a stamped disk separator plate by attaching a separate piece formed around a fastening tab of the stamped separator plate. 
         [0059]      FIG. 19  illustrates a disk separator plate  181  having a fastening tab with an aperture  189  and a ridge  183  on the tab. A bent clip  185 , having an aperture  187  in the top and bottom legs of the clip, is formed to fit over the tab so the apertures  187  and  189  align, as illustrated in  FIG. 20 . Upon alignment, the clip  185  is crimped and/or corned to the tab of disk separator plate  181  to create the required offset height, as illustrated in  FIG. 21 . 
         [0060]    Disk separator plates manufactured in  FIGS. 19-21  can be stacked as shown in  FIG. 22 . Disk separator plate  193  with its offset clip  195  is stacked on top of disk separator plate  197  with its offset  199 . The apertures  201  of both offsets align with considerable precision. Disk separator plates using an attached offset can be easily stacked to any required height.