Abstract:
A seal is formed between bypass walls and a cover for a disk drive to improve control and regulation of airflow in the disk drive. The seal is formed with a gasket comprising a bead of form-in-place gasket between the upper edge of the bypass wall and the cover. The seal also may be formed between the cover and the slit shroud, spoiler, and filter. Minimum compression of the gasket is required to form the seal.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates in general to controlling air flow circulation in disk drives and, in particular, to an improved system, method, and apparatus for controlling and sealing airflow around bypass walls in disk drives. 
         [0003]    2. Description of the Related Art 
         [0004]    Controlling the circulation of air flow within disk drives significantly impacts their performance. Some types of disk drives are equipped with an aerodynamic architecture that utilizes a bypass channel to control, regulate, and advantageously circulate the air flow. Disk drives with full bypass channels employ designs that have intentional air flow leakage along some portions of the air flow path, such as a cooling slot that is adjacent the voice coil motor (VCM), air filter implementation, and a gap between the edges of the bypass channel walls and the cover of the disk drive. Advantages for intentional leakage include enhancement of certain overall flow circulation parameters inside the disk drive and increased cooling capacity for the VCM. 
         [0005]    However, one disadvantage for any type of air flow leakage is the loss in air flow efficiency inside the bypass channel itself. In particular, there is a loss of valuable air pressure build up due to leakages and surface friction as the airflow is bypassed through the channel and reintroduced into the disk stack. In particular, leakage through the gap between the bypass channel and the cover amounts to a significant pressure drop on the order of about 200 Pa, even though the separation between the components is at a realistic manufacturing tolerance of approximately 0.65 mm. This parameter, along with data indicating that sufficient air flow circulation and cooling of VCMs are satisfactory based on some designs, suggest that a reduction in air flow losses between the bypass channel and cover would be desirable. 
       SUMMARY OF THE INVENTION 
       [0006]    Embodiments of a system, method, and apparatus for controlling and sealing airflow around bypass walls in disk drives. For example, a gasket such as a bead of form-in-place gasket (FIPG) may be used to seal between the upper edge of the cover and the bypass wall. The invention may be readily extended to seal between the cover and the slit shroud, spoiler, filter, etc. Some embodiments do not require a compression ratio to form an adequate seal, but only a minimum compression from line contact to a low compression amount that only slightly reduces a thickness of the gasket. This readily satisfied requirement avoids causing an adverse effect such as distortion in the disk drive assembly, e.g., of the arm-to-disk position. 
         [0007]    The invention has several advantages, including the ability to increase the usable air pressure in disk drives which can increase the air flow rate through a recirculation filter. In addition, an increase in the air flow potential that can be returned to the disk stack assists in momentum and power recovery. 
         [0008]    The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the present invention, taken in conjunction with the appended claims and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    So that the manner in which the features and advantages of the present invention, which will become apparent, are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof that are illustrated in the appended drawings which form a part of this specification. It is to be noted, however, that the drawings illustrate only some embodiments of the invention and therefore are not to be considered limiting of its scope as the invention may admit to other equally effective embodiments. 
           [0010]      FIG. 1  is a plan view of one embodiment of a disk drive constructed in accordance with the present invention; 
           [0011]      FIG. 2  is an isometric view of the disk drive of  FIG. 1  and is constructed in accordance with the present invention; 
           [0012]      FIG. 3  is a bottom view of one embodiment of disk drive cover constructed in accordance with the invention; and 
           [0013]      FIG. 4  is a sectional side view of the disk drive and cover of  FIGS. 1-3  and is constructed in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Referring to  FIGS. 1-4 , one embodiment of a system, method, and apparatus for an information storage system comprising a magnetic hard disk file or drive  111  for a computer system having an internal seal that is constructed in accordance with the invention is shown. Drive  111  has an outer housing including a base  113  and top cover  114  ( FIGS. 3 and 4 ). The housing contains a disk pack having at least one media disk, e.g., a magnetic disk  115 . The disks  115  are rotated (see arrow  205 ) by a spindle motor assembly having a central drive hub  117 . An actuator  121  having one or more parallel actuator arms  125  is movably or pivotally mounted to base  113  about a pivot assembly  123 . A controller  119  also is mounted to base  113  for selectively moving the arms  125  relative to disks  115 . 
         [0015]    In the embodiment shown, each arm  125  has extending from it at least one cantilevered load beam and suspension  127 . A magnetic read/write transducer or head is mounted on a slider  129  and secured to a flexure that is flexibly mounted to each suspension  127 . The read/write heads magnetically read data from and/or magnetically write data to disk  115 . The level of integration called the head gimbal assembly (HGA) is the head and the slider  129 , which are mounted on suspension  127 . 
         [0016]    Suspensions  127  bias the air bearing surface of the slider  129  against the disk  115  to cause the slider  129  to fly at a precise distance from the disk. A voice coil  133  moves within a conventional voice coil motor magnet assembly  134  and also is mounted to arms  125  opposite the suspensions and head gimbal assemblies. Movement of the actuator  121  (indicated by arrow  135 ) by controller  119  moves the head gimbal assemblies along radial arcs across tracks on the disk  115  until the heads settle on their respective target tracks. The head gimbal assemblies operate in a conventional manner and typically move in unison with one another. 
         [0017]    The disks  115  define an axis  201  of rotation  205  and a radial direction  207  relative to the axis  201 . The disks  115  have a downstream side  213  wherein air flows away from the disks  115 , and an upstream side  215  wherein air flows toward the disks  115 . The drive  111  also has a bypass channel  219  located in the housing  113  for directing the air flow generated by rotation of the disks  115  from the downstream side  213  of the disks  115  to the upstream side  215  of the disks  115 . In this way the airflow substantially bypasses the actuator  121 . 
         [0018]    In the embodiment shown, the bypass channel  219  is located between an outer perimeter  217  of the housing  113  and the actuator  121 , such that the bypass channel  219  completely circumscribes the actuator  121 . The elements that define the bypass channel  219  may be integrally formed (e.g., cast) with the base  113 . In disk drive designs where there is insufficient space to implement a full bypass channel, the bypass channel  219  may be interrupted and is known as a partial bypass. Furthermore, in order to help the bypass airflow negotiate substantial angular changes (channel bends), one or more turning vanes may be placed in those areas. 
         [0019]    The embodiment shown also comprises a slit shroud  300 . The slit shroud  300  is designed to be integrated and work with the bypass channel  219 . The bypass channel  219  includes inner and outer walls  301 ,  303  that define the conduit for the airflow. At least one opening  305  ( FIG. 2 ) is formed in the inner wall  301  adjacent the actuator  121 . The slit shroud  300  may be mounted to the housing adjacent the actuator  121  for maintaining planar shrouding of the media disks  115  and inhibit axial turbulent velocity components with respect to the actuator  121 . The slit shroud  300  has a wall feature  307  that is located in and closes the opening  305  when fully installed ( FIG. 1 ) at the inner wall  301  of the bypass channel  219 . The wall feature  307  is complementary to the inner wall  301  and, in one embodiment, flush with it as well for contiguous airflow through the conduit and to reduce drag. 
         [0020]    In one embodiment, the wall feature  307  of the slit shroud  300  and the inner wall  301  of the bypass channel  219  extend in an axial direction (e.g., vertically) from the housing. The wall feature  307  and the opening  305  may span a linear gap of approximately 1 mm to 20 mm. For example, a typical 3.5-inch server class drive the gap may comprise about 5 mm. As shown in the drawings, the opening  305  may comprise a flat rectangular hole, and the wall feature  307  may comprise a flat rectangular panel that completely covers opening  305 . 
         [0021]    As shown in the illustrated embodiment of  FIG. 2 , the opening  305  in the inner wall  301  of the bypass channel  219  is located on the upstream side  215  (reference  FIG. 1 ) of the media disks  115 . The opening  305  separates the inner wall  301  into an upstream portion  309  and a downstream portion  301 . The downstream portion  301  may extend from the downstream side  213  of the media disk  115  and around the actuator  121  opposite the media disk  115 . The upstream portion  309  is located only directly adjacent the upstream side  215  of the media disks  115 , such that the downstream portion  301  is much longer than the upstream portion  309 . 
         [0022]    As shown in the embodiment of  FIGS. 1 and 2 , the downstream portion  301  may be shortened to provide room for a spoiler  321 . Like slit shroud  300 , spoiler  321  may be configured to flushly span a gap in the inner wall  301  but adjacent downstream side  213 . 
         [0023]    In some disk drive embodiments, a load/unload ramp is required for suspensions  127 . For those applications, the slit shroud  300  is slidingly installed relative to suspensions  127  (i.e., parallel to the planes defined by suspensions  127 ) to prevent damage to the components of the drive. If no load/unload ramp is required, the slit shroud  300  (i.e., wall feature  307 ) may be installed directly downward (i.e., axially) into opening  305  by motion perpendicular to the planes defined by suspensions  127 . 
         [0024]    One or more elements that define the bypass channel  219  also comprise top surfaces that are parallel to each other. For example, inner wall  301  (e.g., including the downstream and upstream portions) may be configured with a top surface  401  ( FIGS. 1 and 2 ) that extends for its entire distance. Depending on the embodiment, the top surface  401  may include adjacent top surfaces  403 ,  405  on slit shroud  300  and spoiler  321 , respectively. The one or more top surfaces  401 ,  403 ,  405 , are parallel and thus flush with each other in the axial direction to provide a uniform, circumferential surface that extends around the actuator assembly area. The exterior walls  303  are provided with similar top surfaces  421  ( FIG. 2 ) and have an external seal gasket  422  ( FIGS. 3 and 4 ) to prevent an uncontrolled exchange of air with the external environment to minimize contamination sources. 
         [0025]    As shown in  FIG. 3 , the top cover  114  has an interior surface  409  provided with a gasket  411  that is configured and designed to form a seal against the one or more top surfaces  401 ,  403 ,  405  when the top cover is installed on the enclosure  113 . In one embodiment, the gasket  411  comprises a thin bead of material, such as form-in-place gasket (FIPG), that fills and seals the designed axial gap that would otherwise be located between top cover  114  and top surfaces  401 ,  403 ,  405 . The gasket  411  may comprise the same material as the external seal gasket used on the external walls  303 . 
         [0026]    While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.