Abstract:
An apparatus and method of manufacturing a low cost disc drive base plate that incorporates a platform portion and one or more over-molded disc drive structural components. The platform portion of the base plate is stamped or fine blanked from sheet metal and defines a centrally located depression for receiving over-molded structural components of the disc drive. The structural components of the disc drive are over-molded using a polymer or plastic insert molding process to the platform portion of the base plate. The use of a stamped platform portion having over-molded structural components significantly reduces conventional manufacturing costs and allows for the design of a disc drive having greater positional accuracy then that obtained with current disc drive technology.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of priority of U.S. Provisional Patent Application Serial No. 601130,281 entitled “LOW COST OVER-MOLDED BASE PLATE FOR HARD DISC DRIVES,” filed Apr. 21, 1999. 
    
    
     FIELD OF THE INVENTION 
     This application relates to magnetic disc drives and more particularly to low cost base plates having over-molded structural components and to a method for forming low cost base plates having over-molded structural components. 
     BACKGROUND OF THE INVENTION 
     Disc drives are data storage devices that store digital data in magnetic form on a rotating storage medium on a disc. Disc drives have an outer framework that includes a base plate and top cover. The base plate is essentially a platform to which disc drive components are secured and is of a size and shape to mount the disc drive to the chassis of the computer. The top cover of the disc drive cooperates with the base plate to form an internal sealed compartment for housing other components of the disc drive. 
     Typically, the base plate is composed of aluminum or steel and is formed through either a metal die-casting or extrusion process. Die-casting the base plate is well-known in the disc drive art, involving the addition of molten aluminum or steel, forced under pressure, into a mold conforming to the appropriate size and shape of a disc drive base plate. Once formed, the plate undergoes post machining operations to reach required industry size tolerances. The base plate is then e-coated to remove silicon-based agents used in the die casting process and seal the porous die cast metal. Finally, numerous pre-fabricated and inventoried components of the disc drive are installed onto the base plate. These components include but are not limited to the filter bracket, crash-stops, latching devices, mounting bosses, sound attenuation devices and shock protection features. 
     Forming a base plate by extrusion entails that the aluminum or steel substrate be extruded through a base plate shaped die. Extrusion, like die-casting, requires costly post machining operations to bring the base plate within industry sizing tolerances, and also requires the installation of the pre-fabricated inventoried components to the base plate. Extrusion, however, unlike die-casting, does not require the e-coating step and is, therefore, typically considered the preferred method for forming the base plate. 
     The die-casting and extrusion techniques for forming the base plate require that pre-fabricated disc drive components be installed onto the machined base plate. The components are manufactured separately from each other and are assembled onto the base plate using various forms of fastening techniques, such by screws, nuts, clips or press fits. The process of installing the pre-fabricated components onto the base plate is costly and time consuming for the following reasons: (1) each pre-fabricated component part, feature or assembly requires its own manufacturing cost attributed to materials, labor, energy and shipping resources; (2) each pre-fabricated component incorporates tightly toleranced location features for locating the component to the base plate, where the location features are designed for and maintained through costly quality control programs; (3) each individual pre-fabricated component is inventoried, tracked, inspected and stored for the base plate manufacturing process; (4) each fastening technique used to fasten a pre-fabricated component to the base plate has its own cost attributed to material and labor; and (5) each fastening technique requires that pre-fabricated components be secured to the base plate in an ordered fashion, i.e., require costly “balanced manufacturing lines” that incorporate additional work stations and workers. 
     Accordingly, a need exists in the art to minimize expenses of, and time lost during, the manufacture of conventional disc drive base plates. 
     SUMMARY OF THE INVENTION 
     Against this backdrop the present invention has been developed. The present invention is a low cost disc drive base plate having a platform portion and at least one structural component of the disc drive over-molded to the platform portion. 
     In accordance with one embodiment of the present invention, the low cost base plate for the disc drive includes a platform portion having a top surface and bottom surface. A disc drive structural component is over-molded onto the platform portion to secure the structural component to the platform portion. 
     The present invention may also be implemented as a base plate including the platform portion with two or more over-molded structural components. The structural components may be over-molded to either the top or bottom surface of the platform portion. 
     The present invention can further be implemented as a method for manufacturing a low cost base plate for use in a disc drive. The method typically has the steps of forming a platform portion of the base plate and then over-molding a preferably plastic disc drive structural component to the platform portion so as to fasten the structural component to the platform portion. 
    
    
     These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a disc drive incorporating a low cost base plate in accordance with a preferred embodiment of the present invention. 
     FIG. 2 illustrates a perspective separate view of a platform portion of the present invention. 
     FIG. 3 illustrates a perspective separate view of a top surface of the platform portion shown in FIG. 2 incorporating over-molded structural components of the disc drive. 
     FIG. 4 illustrates a perspective separate view of a bottom surface of the platform portion incorporating over-molded structural components of the disc drive. 
     FIG. 5 is a flow chart of a method of manufacturing a low cost base plate having over-molded components in accordance with a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     A disc drive  100  constructed in accordance with a preferred embodiment of the present invention is shown in FIG.  1 . The disc drive  100  includes a base plate  102  to which various structural components  104  and  105  (FIGS. 3 and 4) of the disc drive  100  are mounted. A top cover  106 , shown partially cut away, cooperates with the base plate  102  to form an internal, sealed environment for the components of the described below disc drive  100 . 
     Enclosed within the disc drive  100 , shown in FIG. 1, is a spin drive motor  108  which rotates one or more information storage discs  110  at a constant high speed. Information is written to and read from tracks on the information storage discs  110  through the use of an actuator assembly  112 , which rotates about a bearing shaft assembly  113  positioned adjacent the discs  110 . The actuator assembly  112  includes a plurality of actuator arms  114  which rotate over the surfaces of the information storage discs  110 , with one or more flexures  116  extending from each of the actuator arms  114 . Mounted at the distal end of each of the flexures  116  is a head  118  which includes an air bearing slider enabling the head  118  to fly in close proximity above the corresponding surface of the associated disc  108 . 
     A platform portion  120  of the base plate  102  of the preferred embodiment of the present invention is shown in FIG.  2 . The base plate  102  has a platform portion  120  that includes a top surface  122  and bottom surface  124  (FIG.  4 ). The platform portion  120  is generally of rectangular shape and is preferably formed by a method such as stamping or fine blanking. The platform portion  120  is preferably formed from metal or other like material. The platform portion  120  generally acts as a structural foundation for the over-molded structural components  104  and  105  of the base plate  102 . 
     A centrally defined depression  126  in the platform portion  120  of the base plate  102  accommodates one or more over-molded structural components  104  and  105  as is shown in FIGS. 3 and 4. An aperture  128  for mounting the spin motor  108  (FIG. 1) and an aperture  130  for mounting the actuator assembly  112  (FIG. 1) are defined within the centrally located depression  126  of the platform portion  120 . Notches  132  along the edges  133  of the platform portion  120  act as mounting features between the platform portion  120  of the base plate  102  and the top cover (not shown). 
     Several structural components  104  and  105  in accordance with a preferred embodiment of the present invention are over-molded to the platform portion  120  of the base plate  102 , as shown in FIGS. 3 and 4. The over-molded structural component  104  is around, over and through the aperture  128  and extends over both the top and bottom surfaces  122  and  124  respectively of the platform portion  120 . The structural component  104  forms a crash-stop  134  and a ramp loading device  136  on the top surface  122  of the platform portion  120  (FIG. 3) and a mounting boss  138  on the bottom surface  124  of the platform portion (FIG.  4 ). 
     FIG. 4 shows several additional disc drive structural components  105  that have been over-molded to the bottom surface  124  of the platform portion  120  of the base plate  102 . These structural components  105  include mounting rails  142  for mounting the base plate  102  to the computer chassis (not shown) and spaced support rails  144  for mounting the PC board (not shown) to the bottom of the base plate  102 . The mounting boss  138  receives a screw (not shown) to fasten the PC board in place. 
     Over-molding the disc drive structural components  104  and  105  to the platform portion  120  is preferably accomplished utilizing a polymer insert molding process, although other over-molding processes are understood to be within the scope of the present invention. Polymer insert molding provides a consistent mechanism accurately positioning the structural component on the platform portion of the base plate. One preferred type of polymer for use in the insert molding process is a thermo-set plastic. 
     The structural components  104  and  105  that can be over-molded to the platform portion  120  of the base plate  102  generally include any plastic component, part or feature of a disc drive that is secured either directly to the base plate or indirectly through another over-molded structural component to the base plate. Thus, it should be understood that the over-molded structural components shown in FIGS. 3 and 4 are exemplary for illustrative purposes only and that other over-molded components capable of being fastened to the base plate are within the scope of the present invention. 
     Over-molding disc drive structural components  104  and  105  to the platform portion  120  of the disc drive base plate  102  provides several advantages over die-cast or extruded base plates. These advantages include: (1) the elimination of fasteners and manufacturing stations required to install discrete pre-fabricated disc drive components to the die-cast or extruded base plate; (2) the elimination of purchasing and inventorying the discrete pre-fabricated disc drive components required for a die-cast or extruded base plates; (3) the elimination of tight tolerance positioning and sizing of the platform portion; (4) the elimination of tight tolerance positioning and sizing of the discrete pre-fabricated components of the disc drive; (5) the elimination of having to die cast/extrude the platform portion of the base plate with mounting rails for mounting the base plate to the computer chassis or spaced rails for mounting the PC board to the bottom of the base plate; (6) the elimination of the need for much of the manufacturing space required for the assembly of the components onto the die-cast or extruded base plates; and (7) the elimination of post machining operations required in the use of die-cast or extruded base plates. 
     A method for manufacturing a base plate  102  in accordance with the preferred embodiment of the present invention by over-molding the disc drive structural components  104  and  105  onto a platform portion  120  is shown in FIG.  5 . In step  146 , a platform portion  120  of the base plate  102  is formed by processes such as stamping or fine blanking. In step  148 , the platform portion thus formed is placed in a mold cavity having recesses for one or more over-molded structural component on the base plate. In step  150 , the mold is closed and a polymer is injected into the recesses to form over-molded structural components  104  and  105  on the platform portion. Finally, in step  152 , the mold is opened and the completed base plate having over-molded structural components  104  and  105  fastened to it is removed. 
     In summary, the present invention is a low cost base plate (such as  102 ) for a disc drive (such as  100 ). The low cost base plate includes a platform portion (such as  120 ) having a top surface (such as  122 ) and a bottom surface (such as  124 ). A disc drive structural component (such as  104  and  105 ) is over-molded onto the platform portion (such as  120 ) to secure the structural component (such as  104  and  105 ) to the platform portion (such as  120 ). The structural component (such as  104  and  105 ) may be formed from a polymeric material. One example of a structural component (such as  104  and  105 ) is a spaced support rail (such as  144 ). 
     Two or more disc drive structural components (such as  104  and  105 ) may be over-molded to the platform portion (such as  120 ) of the base plate (such as  102 ), where one or more of the structural components (such as  104 ) may be over-molded to the top surface (such as  122 ) of the platform portion (such as  120 ) and one or more of the structural components (such as  105 ) may be over-molded to the bottom surface (such as  124 ) of the platform portion (such as  120 ). 
     The top surface (such as  122 ) of the platform portion (such as  120 ) may define a centrally located depression (such as  126 ) for receiving over-molded structural components (such as  104 ) of the disc drive (such as  100 ). The centrally located depression (such as  126 ) may also include a first aperture (such as  128 ) for mounting the spin motor (such as  108 ) and a second aperture for mounting an actuator assembly (such as  112 ). The structural components (such as  104 ) may be positioned within the centrally located depression (such as  126 ) or may be located on the bottom surface (such as  124 ) of the platform portion (such as  120 ). 
     The present invention is also a method for manufacturing a base plate (such as  102 ) for a disc drive (such as  100 ), where a platform portion (such as  120 ) is formed and a structural component (such as  104  and  105 ) is over-molded to the platform portion (such as  120 ) so as to fasten the structural component (such as  104  and  105 ) to the platform portion. The platform portion (such as  120 ) may be formed from sheet metal by stamping or fine blanking. 
     The method for manufacturing a base plate for a disc drive may further include over-molding two or more disc drive structural components (such as  104  and  105 ) to the platform portion (such as  120 ) of the base plate (such as  102 ). These structural components (such as  104  and  105 ) may be over-molded to the top or bottom surface (such as  122  and  124  respectively) of the platform portion. 
     It will be clear that the present invention is well adapted to attain the ends and advantages mentioned as well as those inherent therein. While a presently preferred embodiment has been described for purposes of this disclosure, numerous changes may be made which will readily suggest themselves to those skilled in the art For example, other over-molded structural components not disclosed in the detailed specification are also envisioned to be within the scope of the present invention, these over-molded components may include but are not limited to: filter brackets, locating features, sound attenuation devices, shock protection features and flexible circuit routing structures. Accordingly, all such modifications, changes and alternatives are encompassed in the spirit of the invention disclosed and as defined in the appended claims.