Patent Publication Number: US-2007103811-A1

Title: Filtration arrangment for electronic enclosure

Description:
PRIORITY  
      This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/716,040, filed Sep. 9, 2005, which application is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD The present disclosure relates to filtration for electronic enclosures, and in particular, relates to filtration and the removal of contaminants from within hard disk drives.  
     BACKGROUND  
      Hard disk drives and other electronic equipment are often placed within enclosures to provide a clean environment that is necessary for optimal operation of the equipment. For example, hard disk drives normally contain at least one inflexible platter or disk coated with magnetic material that is positioned within an enclosure. The disk is rapidly spun and a magnetic read/write head “flies” a few microns above the disk. It is desirable to position the head as close as possible to the disk without touching it order to provide a high capacity drive.  
      Contaminants, including particles, gases, and liquids within the hard disk drive enclosure, can act to reduce the efficiency and longevity of the hard drive. These contaminants can gradually damage the drive, cause deterioration in performance, and in certain situations can even cause sudden and complete drive failure. Contaminants can, for example, enter the electronic enclosure from an external manufacturing environment, which can contain certain contaminants, and materials incorporated into the disk drive which give off particulates and gases.  
      One particular concern regarding electronic enclosures is that contaminants from outside of the electronic enclosure can enter the enclosure. When a disk drive is in operation, the air in the drive enclosure heats up which creates an increase in air pressure in the enclosure, and when a disk drive ceases to be in operation, the air in the enclosure cools down and creates a decrease in pressure in the enclosure. As a result of these changes in pressure, some disk drives have a breather hole to allow air to move into and out of the drive to equalize the pressure inside the drive with atmospheric pressure.  
      If particulate or chemical contaminants are present in the exchanged air, the interior of the enclosure will become contaminated. In one arrangement that may be employed to limit the potential for contaminants being introduced from outside of the drive is to configure the drive so that it is completely sealed from the atmosphere. In such an arrangement, the interior of the drive is typically filled with an inert, low molecular weight gas, such as helium. The inert, low molecular weight gas expands less than air for a given temperature increase, so that the pressure inside the drive does not build excessively with temperature increases.  
      However, even where the electronic enclosure is sealed, organic vapors and other contaminants can be generated inside electronic enclosures during normal operating conditions. For example, when the temperature exceeds 150° F., organic acids and organic vapors can be formed that damage electronic components. Such temperatures can be achieved by simply leaving the computer in the trunk of a car on a hot day. It is important that these contaminants generated within the enclosure be efficiently captured or removed in order to prevent deterioration of the electronic equipment.  
      The rotation of the disk within a disk drive tends to generate gas flow currents within the drive. In some applications, a filter is placed within these currents. However, the filter in such an arrangement is only exposed to a portion of the total gas current. Moreover, when an electronic enclosure is sealed and filled with an inert, low molecular weight gas, the lower mass density of the gas cause the I current to have lower inertia than a similar current of air. Because a filter necessarily restricts gas flow to some extent, a gas flow of low molecular weight, low inert gas will not tend to flow as readily through a filter as air, and may instead be prone to flowing around the filter. In practice, this results in lower contaminant removal effectiveness.  
      Therefore, a need exists for a filtration arrangement for use in an electronic enclosure, and in particular, a filtration arrangement that improves filtration performance in sealed and unsealed electronic enclosures.  
     SUMMARY  
      The present disclosure is directed to a filtration arrangement for use inside of an electronic enclosure, such as a hard disk drive enclosure containing a rotating disk. The filtration arrangement provides filtration of gases circulating within the electronic enclosure. The filtration arrangement generally comprises a channel formed about a portion of the periphery of a rotating member, such as a disk. Gas currents generated by the rotating member enter the channel at an upstream aperture.  
      While in the channel, the gas current and any contamination entrained within the current is contained within the channel and is isolated from the rotating disk. The gas current exits the channel through a filter placed at a downstream aperture of the channel. The channel limits the ability of the gas to bypass the filter. The above summary is not intended to describe each embodiment of the present disclosure. 
    
    
     DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a top cross-sectional view of a filter arrangement according to present disclosure.  
       FIG. 2  is a side cross-sectional view of the filter arrangement of  FIG. 1  along line A-A in  FIG. 1 .  
       FIG. 3  is a perspective, sectioned view of the filter arrangement of  FIG. 1  taken along line A-A in  FIG. 1 . 
    
    
     DETAILED DESCRIPTION  
      The present disclosure is directed to a filter arrangement for use inside an electronic enclosure, such as a hard disk drive enclosure containing a rotating disk. The filter arrangement provides filtration of gases circulating within the enclosure. Referring now to the figures, an embodiment of the invention is described detail with reference to the drawings, wherein like reference numbers represent parts and assemblies throughout the several views.  
      Referring to  FIG. 1 , a top cross-sectional view of a disk drive  20  is shown. Disk drive  20  includes a housing  22 , a magnetic disk  24 , a magnetic read/write head  24  around at least a portion of the circumference of disk  24 . In one embodiment, wall  32  extends around about half of the circumference of disk  24 . In another embodiment, wall  32  extends around more than half of the circumference of disk  24 . In yet another embodiment, wall  32  extends around less than half of the head  26 , and a magnet  28 .  
      A gas  52  is contained within housing  22  and generally entrained contaminants. Contaminants within gas  52  may include organic such as in direction A indicated in  FIG. 1 , by connection to a drive motor (not shown) through hub  30 . Magnetic read/write head  26  is positioned in close proximity to magnetic disk  24 , but is not in contact with magnetic disk  24 . As shown in the cross-sectional view of disk drive  20  in  FIG. 2 , housing  22  includes bottom region  34 , top region  36 , first side region  38 , and second side region  40 . As see in  FIG. 1 , housing  22  defines an end region  42  that includes a curved side  44  defining a relatively uniform clearance with disk  24  around at least a portion of the circumference of disk  24 . In another embodiment, curved surface  44  is formed separately from housing  22 . Housing  22 , magnetic disk  24 , magnetic read/write head  26 , magnet  28 , and hub  30  are constructed and operated in a manner known to those of skill in the art. Wall  32  is located between curved surface  44  and magnetic disk  24  includes embodiments of wall  32  are possible. In the embodiment shown in  FIGS. 1 and 2 . Wall  32  defines a first surface  46  that faces toward disk  24  and a second surface  48  that faces toward curved surface  44 . Wall  32  is configured so that the clearance with the circumference of disk  24  is relatively shall but wall  32  does not touch disk  24 . In the embodiment shown in  FIGS. 1, 2  and  3 , wall  32  extends between bottom region  34  and top region  36  of housing  22 . In another embodiment, wall  32  extends partially between bottom region  34  and to region  36  of housing  22 .  
      Channel  50  is formed between second surface  48  of wall  32  and curved surface  44  of housing  22 . Channel  50  defines an entry aperture  54  and an exit aperture  56 . Channel  50  may comprise many different embodiments. In the embodiment shown in  FIGS. 1, 2 , and  3 , channel  50  is bounded by bottom region  34  and top region  36  of housing  22 . In the embodiments shown in  FIGS. 3 , curved surface  44  and second surface  48  are generally separated by equal distances, forming a channel  50  of uniform width. However, surfaces  44  and  48  may be configured to be separated by a variable distance, forming a channel  50  of varying width.  
      Filter  58  is located within channel  50 , Filter  58  may be located anywhere in channel  50 . In the embodiment shown in  FIGS. 1, 2 , and  3 , filter  58  is located proximate to discharge aperture  56  of channel  50 . Filter  58  may also comprise  1  any different embodiments. In one embodiment, filter  58  comprises an activated carbon filter. In another embodiment, filter  58  comprises polytetrafluoroethylene (PTFE).  
      In yet another embodiment, filter  58  comprises a dessicant. In a further embodiment, filter  58  may comprise an adsorbent recirculation filter (ARF). Another embodiment of filter  58  is a solid recirculation filter (SRF). Filter  58  preferably forms a close fitting connection with at least curved surface  44  and second surface  48 . In operation, when magnetic disk  24  rotates in direction A, the rotation tends to induce currents  60  within the gas  52  present within disk drive  20 . Currents  60  of gas  52  proceed in the same general direction as the rotation of magnetic disk  24 . The velocity of currents  60  is related to the velocity of the surface of magnetic disk  24  at the circumference of magnetic disk  24 , currents  60  will also tend to be greatest. Because for a given rate of rotation of disk  24 , the greatest velocity of disk  24  will be near the circumference of magnetic disk  24 . As currents  60  of gas  52  flow through channel  50 , they will encounter filter  58  proximate to discharge aperture  56 . Because gas  52  is constrained within channel  50 , gas  52  must pass through the filter  58  before exiting through discharge aperture  56  of channel  50 . This has the advantage of minimizing the amount of gas  52  that can bypass or flow around filter  58 , and thereby increases the effectiveness of filter  58  in removing contaminants from gas  52 .