Abstract:
A sealed structure for an electronic device, the sealed structure includes a base, a concave cover enclosing electronic components of the electronic device when the cover is fitted to the base, and a gasket-like sealing member that fits between edge portions of the cover and the base to seal the enclosure. A rib portion is formed on at least one of either the cover or the base so as to prevent the sealing member from protruding from the edge portions of the cover and base, thus providing an improved seal.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sealed structure for an electronic device, and more particularly, to a sealed structure for a magnetic disk drive unit. 
     2. Description of Related Art 
     Electronic devices are typically built in such a way as to bring related components together in order to enable the device to function effectively, or, increasingly, to make the device as a whole more compact. In either case, the design or layout of the components is accommodated within a substantially rectangular or box-like housing. In such cases, depending on the type of electronic device involved the housing must often be sealed with a high degree of precision. 
     For example, in the case of a magnetic disk drive, in which the recording and reproduction of information to and from a rotary disk-like recording medium occurs in an interval between a surface of the disk and a magnetic head, that interval is very small, that is, on the order of microns. As the density with which information is being recorded to and reproduced from recording media continues to increase, head-to-disk intervals on the order of sub-microns are being sought. 
     The need for head-to-disk spacing accurate to the micron or sub-micron level means that any degradation in the quality of the seal of the magnetic disk drive such as would allow dust particles and the like into the interior of the device has the potential to disrupt the stability of the head as it floats over the surface of the disk, potentially causing the head and the rotating disk to come into contact with each other and causing head crashes and other undesirable events. 
     Thus, magnetic disk drives in particular require properly sealed structures. In order to further an understanding of the problem the present invention attempts to solve as well as of the invention itself, a description will now be given of the conventional magnetic disk drive sealed structure with reference to FIGS. 1 through 6. 
     FIG. 1 is a disassembled perspective view of a conventional magnetic disk drive. FIG. 2 is a partial perspective cross-sectional view of a conventional magnetic disk drive. FIG. 3 is a plan view showing a conventional magnetic disk drive prior to the installation of the cover. FIG. 4 is a partial cross-sectional view of a conventional magnetic disk drive, illustrating a case in which the packing is properly mounted. FIG. 5 is a partial cross-sectional view of a conventional magnetic disk drive, illustrating a case in which the packing is deformed and protrudes beyond the contact surfaces. FIG. 6 is a partial cross-sectional view of a conventional magnetic disk drive, illustrating a case in which the packing has collapsed to one side. 
     As shown for example in FIGS. 1 and 2, a conventional magnetic disk drive  1  may have a disk-like recording medium (hereinafter disk or magnetic disk) mounted on a motor assembly not shown in the drawing, an actuator  4  that supports a head  3 , and other electronic components not shown in the drawings, all mounted atop a base  5 . The base  5  is in turn covered by a cover  6  having a substantially concave structure capable of accommodating the electronic components therewithin, the base  5  and the cover  6  forming a single unit. 
     In order to seal the space enclosing the actuator  4  and other electronic components inside the concave structure that is the cover  6 , as shown in FIGS. 1 and 3, a thin sheet of packing  7  made of rubber and having a through-hole portion  7   a  corresponding to the concave shape of the cover is inserted between the cover  6  and the base  5 , specifically between the respective contact surfaces  6   a  and  5   a  thereof. It should be noted that, in these and other diagrams, the packing  7  may be given a mesh design as necessary in order to distinguish it from other components. 
     When assembling the magnetic disk drive  1 , for example, double-sided adhesive tape  8  cut to a shape identical to that of the packing  7  is adhered to the packing  7 , such that the adhesive force of the tape  8  contacts the packing  7  against the flange-like contact surface  6   a  of the cover  6 . The cover  6  is then positioned on the base  5  with the contact surface  6   a  facing downward, to achieve a state depicted in FIG. 4, which is essentially an enlarged view of a portion A of FIG.  2 . Thereafter the cover  6  and the base  5  are formed into a single unit by a tightening member not shown in the diagram. 
     At this time, a restorative force generated by the compressive deformation of the packing  7  due to the tightening of the tightening member securely contacts the packing  7  against both the cover  6  and the base  5 , thus sealing the actuator  4  and other components. 
     However, in the case of the magnetic disk drive  1  described above, for example as shown in FIG. 3, at points A and B the distances L 1  and L 2  from the outer edge of the disk  2  to the outer edge of the base  5  are small in comparison to other areas, as can be seen in FIG.  5 . Reducing the distances L 1  and L 2  in this manner, however, is unavoidable if the intent is to make the magnetic disk drive  1  more compact. 
     However, at points at which distances are small, the widths W 1  of the cover  6  contact surface  6   a  (the flange surface) and the base  5  contact surface  5   a  that contacts the contact surface  6   a , which in turn means that widths W 2 , W 3  of the packing  7  positioned between the base  5  and the cover  6  decreases as well. As a result, when positioning the cover  6  atop the base  5  a slight misalignment arises, such that when the packing  7  is compressed as shown in FIG. 5 the packing  7  protrudes beyond the flange-like contact surface  6   a  of the cover  6  and the contact surface  5   a  of the base  5 . In this case, a predetermined restorative force of the packing  7  does not extend to the base  5  and the cover  6  and accordingly the seal formed by the packing  7  is inadequate and thus the sealing of the electronic components is also poor. Such lapses in quality can cause the packing to collapse to one side as shown in FIG. 6 or take on other extreme deformations, degrading the quality of the seal even further. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an improved and useful sealed structure for an electronic device in which the above-described disadvantage is eliminated. 
     The above-described object of the present invention is achieved by a sealed structure for an electronic device, the sealed structure comprising: 
     a base; 
     a concave cover enclosing electronic components of the electronic device when the cover is fitted to the base; and 
     a gasket-like sealing member that fits between edge portions of the cover and the base to seal the enclosure, 
     a rib portion being formed on at least one of either the cover or the base so as to prevent the sealing member from protruding from the edge portions of the cover and base. 
     According to this aspect of the invention, the sealing member can perform its designated sealing function because the sealing member can be prevented from protruding from the contact surface area, making it possible to provide an electronic device sealed structure with an improved seal. 
     Moreover, by providing the rib on either the inner periphery or the outer periphery of the sealing member, an improved seal can still be attained with relatively less processing of the rib as compared to a case in which ribs are provided on both sides of the sealing member. 
     Additionally, providing the rib on the outer periphery of the sealing member is advantageous in those areas where the contact surface area is restricted and it would therefore be difficult to provide a rib on the inner periphery of the sealing member. Moreover, providing the rib on the outer periphery restricts any protrusion of the sealing member outward therefrom, thus securely preventing degradation of the seal. 
     Additionally, by providing a rib at discrete, non-continuous, intermittent points along the periphery of the sealing member, an improved seal can still be attained with relatively less processing than is the case when the rib is provided continuously along the periphery of the sealing member. 
     In this case, providing the rib in such a way as to alternate between inner and outer periphery positioning, so that there is no overlap between the inner periphery and the outer periphery of the ribs, has the advantage of reducing the processing required to form the rib. 
     It should be noted that, in the sealed structure for an electronic device according to the present invention, by providing the rib at only those regions at which the contact surfaces are narrow (that is, the distance between the inner periphery and outer periphery is relatively small) and which can therefore be expected to be points at which the risk of the sealing member protruding outward from the structure is greatest, an improved seal can still be attained with only partial provision of the rib and thus with reduced processing as compared to a full rib extending the length of the periphery of the sealed structure. 
     It will be appreciated by those of ordinary skill in the art that such regions of reduced contact surface area can be determined easily as a matter of design. 
     Additionally, in the sealed structure for an electronic device according to the present invention, the side of the rib that contacts the sealing member has a slanted surface and the side of the sealing member that contacts the rib has a surface slanted in reverse to that of the rib, so that a deformation of the sealing member in a direction of a width thereof can be more securely restricted so as to provide an improved seal. 
     Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a disassembled perspective view of a conventional magnetic disk drive; 
     FIG. 2 is a partial perspective cross-sectional view of a conventional magnetic disk drive; 
     FIG. 3 is a plan view showing a conventional magnetic disk drive prior to the installation of the cover; 
     FIG. 4 is a partial cross-sectional view of a conventional magnetic disk drive, illustrating a case in which the packing is properly mounted; 
     FIG. 5 is a partial cross-sectional view of a conventional magnetic disk drive, illustrating a case in which the packing is deformed and protrudes beyond the contact surfaces; 
     FIG. 6 is a partial cross-sectional view of a conventional magnetic disk drive, illustrating a case in which the packing has collapsed to one side; 
     FIG. 7 is a partial cross-sectional perspective view of the magnetic disk drive according to a first embodiment of the present invention, with the cover removed; 
     FIG. 8 is a partial perspective view of the magnetic disk drive according to the first embodiment of the present invention, for the purpose of illustrating the state in which the packing is mounted therein; 
     FIG. 9 is a partial cross-sectional perspective view of the magnetic disk drive according to a second embodiment of the present invention, with the cover removed; 
     FIG. 10 is a partial perspective view of the magnetic disk drive according to the second embodiment of the present invention, for the purpose of illustrating the state in which the packing is mounted therein; 
     FIG. 11 is a partial cross-sectional perspective view of the magnetic disk drive according to a third embodiment of the present invention, with the cover removed; and 
     FIG. 12 is a partial perspective view of the magnetic disk drive according to the second embodiment of the present invention, for the purpose of illustrating the state in which the packing is mounted therein. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A description will now be given of embodiments of the present invention, with reference to the accompanying drawings. It should be noted that identical or corresponding elements in the embodiments are given identical or corresponding reference numbers in all drawings, with detailed descriptions of such elements given once and thereafter omitted. 
     It should be noted that, for illustrative purposes only, the electronic device referenced in the following description is a conventional magnetic disk drive. Moreover, the basic structure of such a magnetic disk drive is identical to that of the conventional magnetic disk drive  1  described above, including a magnetic disk  2  mounted on a motor assembly not shown in the diagram, an actuator  4  that supports a head  3  and which, together with other electronic components not shown in the diagram, are arranged atop a base  5 . The base  5  is covered by a cover  6  having a concave shape for accommodating the various electronic components (see for example the portion in FIG. 8 with reference numeral  6   b ), with the base  5  and the cover  6  forming a single unit. In order to seal the space that encloses the actuator  4  and the other electronic components, a thin, sheet-like packing  7  (sealing member) made of an elastic material such as rubber is disposed between the contact surfaces  6   a  and  5   a  of the cover  6  and the base  5 , respectively, the packing  7  having a through-hole portion  7   a  corresponding to the concave portion of the cover  6 . 
     A description will now be given of a sealed structure for a magnetic disk drive according to a first embodiment of the present invention, with reference to FIG.  7  and FIG.  8 . 
     A magnetic disk drive  10  is provided with a rib  12  disposed along an entire length of an outer periphery of the base  5 , and on this point differs from the magnetic disk drive  1  described above. 
     The rib  12  has an inner wall  12   a  that slants progressively outward toward a top of the wall  12   a  (see FIG.  8 ). Additionally, as can be seen in FIG. 7, a plurality of inwardly projecting tab projections  14  having hole portions  14   a  are formed at intervals along an outer edge of the base  5  in place of the rib  12 . 
     As can be seen in FIG. 8, the packing  7  disposed opposite the rib  12  has an outer surface  7   b  slanted at an angle exactly opposite that of the inner wall  12   a  of the rib  12 . A thickness of the packing  7  is set so that, for example, a width W 1  at a point A of the packing  7  is smaller than a width W 4  of the contact surface  6   a  including the width of the rib  12 . Additionally, a height of the packing  7  is formed to a predetermined height so as to exceed a height H of the rib  12  at least in a state in which the packing  7  is compressed between the cover  6  and the base  5  at assembly, the packing at this time compressedly deforming so as to generate a restorative force so as to produce a seal of predetermined strength. 
     It should be noted that, as with the conventional art, two-sided adhesive tape  8  not shown in the drawing is adhered to a top surface of the packing  7 . Additionally, the projecting tab portions  14  are formed to the same height as the rib  12 , so that a top surface  14   b  of the projecting tab portions  14  formed a flush surface with an upper surface  12   b  of the rib  12 . 
     Further, it should be noted that, for ease of explanation, the dimensions shown in FIG. 8 differ slightly from actual dimensions. 
     When the cover  6  is to be installed on the base  5  (on which base the actuator  4  and other electronic components are mounted), initially the packing  7  is installed on the flange-like contact surface  6   a  of the cover via double-sided adhesive tape  8 . Next, a hole portion  17  formed in a step-like fixing portion  15  on the cover  6  is aligned with the hole portion  14   a  in the projecting tab portion  14  and a bottom surface  15  of the fixing portion contacted with the top surface  14   b  of the projecting tab portion  14 , and at the same time the cover  6  is positioned atop the base  5  in such a way that the outer slanted surface  7   b  of the packing  7  slidingly contacts the inner wall  12   a  of the rib  12 . By further inserting a fixing member such as a screw  13  into the hole portion  17  and the hole portion  14   a  so as to join the fixing portion  15  and the projecting tab portion  14 , the cover  6  and the base  5  are formed as a single unit. 
     At this time, the force with which the fixing member is attached seals the fixing portion  15  of the cover  6  against the projecting tab portion  14  of the base  5 , and, at the same time, leaves a gap between the upper surface  12   b  of the rib  12  and the contact surface  6   a  of the cover  6 . At this time the packing  7  squeezed between the contact surfaces  6   a  and  5   a  is compressively deformed to a thickness T that is slightly larger than the height H of the rib  12 . Additionally, the outer slanted surface  7   b  of the packing  7  comes into contact with the inner wall  12   a  of the rib  12 , thus restricting the protrusion of the packing  7  outside the area of the contact surfaces  6   a  and  5   a  (that is, to the right side of FIG.  8 ). Additionally, since the outer slanted surface  7   b  of the packing  7  is pressed closely against and positioned by the inner wall  12   a  of the rib  12 , deformation of the packing  7  toward an exterior is almost completely forestalled. Similarly, the packing  7 , having as it does a predetermined width W 4 , does not protrude inwardly from the region of the contact surfaces  6   a ,  5   a  (that is, to the left in FIG.  8 ). 
     Accordingly, the predetermined restorative force created by the compressive deformation of the packing  7  by the fixing member provides a secure seal between the cover  6 , the base  5  and the packing  7 , thus sealing the actuator  4  and other components within the space formed by the cover  6  and the base  5 . 
     As can be appreciated, the sealed structure for the magnetic disk drive  10  according to the first embodiment of the present invention provides the rib  12  around only an outer edge of the base  5 , thus maintaining an improved seal for the magnetic disk drive  10  while requiring relatively little processing as compared to a case in which the rib  12  is provided on both an inner and an outer edge of the base  5 . 
     Further, as shown in FIG. 8, a mount portion  5   b  for mounting a magnetic disk  2  is formed on the base  5 , on the inside of the inner surface of the packing  7 . In the present embodiment, an outer edge of the mount portion  5   b  and the inside surface of the packing  7  are separated from each other. However, even if the outer edge of the mount portion  5   b  and the inside surface of the packing  7  contact each other the outer edge of the mount portion  5   b  performs the function of a rib positioned on the inside of the packing  7 , thus preventing the packing  7  from protruding inwardly from the region of the contact surfaces  6   a ,  5   a . As a result, an improved sealed structure for the magnetic disk drive  10  can still be attained even without the provision of a rib on the inside of the packing  7 . 
     It should be further noted that with respect to the first embodiment of the present invention as described above, the rib  12  need not be positioned along the outer edge of the base  5  but may be positioned inward of the outer edge as well, so long as the rib  12  remains to the outside of the packing  7 . Additionally, the inner surface  12   a  of the rib  12  and the outer surface  7   b  of the packing  7  need not be slanted. Further, the rib  12  may also be provided on an inner periphery of the packing  7  instead of an outer edge of the base  5 . 
     A description will now be given of a sealed structure for a magnetic disk drive according to a second embodiment of the present invention, with reference to FIG.  9  and FIG.  10 . 
     FIG. 9 is a partial cross-sectional perspective view of the magnetic disk drive according to a second embodiment of the present invention, with the cover removed. FIG. 10 is a partial perspective view of the magnetic disk drive according to the second embodiment of the present invention, for the purpose of illustrating the state in which the packing is mounted therein. 
     As shown in FIG. 9, a rib  18  is formed selectively along the outer edge of the base  5  of the magnetic disk drive  16  at portions A, B where a width of the contact surfaces  6   a  and  5   a  of the cover  6  and the base  5  narrows. Additionally, the rib  18  is further divided into discrete, noncontinuous portions  18   a ,  18   b.    
     The rib  18 , like the rib  12  of the magnetic disk drive  10  described above, has slanted inner surfaces  18   a - 1 ,  18   b - 1  which slant outward toward the top of the rib. A distance L 3  separating the ribs  18   a ,  18   b  is determined with reference to the elasticity, width and depth of the packing  7 , and is small enough so that the packing  7  does not protrude outward from the gap L 3  when the packing is compressed during positioning of the cover  6  on the base  5 . 
     It should be noted that, just as is shown in FIG. 7, in FIG. 9 as well it can be seen that a plurality of projecting tab portions  14  in which hole portions  14   a  are formed are provided on an outer edge of the base  5 . A detailed description of the purpose of the projecting tab portions  14  and the corresponding fixing portions  15 , which, as described above, serve to align the cover  6  and the base  5 , is unchanged for this and subsequent embodiments of the present invention and omitted hereinafter. 
     It should be noted that the packing  7 , in correspondence to the rib  18 , as shown in FIG. 10, has an outer surface  7   b  slanted at an angle exactly opposite that of the inner wall  12   a  of the rib  12 , that is, slanted inward towards a bottom of the packing  7 . 
     When the cover  6  is mounted on the base  5  (on which base  5  the actuator  4  and other electronic components are mounted), the packing  7  is first mounted on the flange-like contact surface  6   a  of the cover  6 . Next, the cover  6  is positioned atop the contact surface  5   a  of the base  5  in such a way that the inner surface  7   b  of the packing  7  slidingly contacts the inner wall  12   a  of the ribs  18   a ,  18   b . The cover  6  is then fixedly mounted on the base  5 . 
     At this time, the packing  7 , which is squeezed between the contact surfaces  6   a ,  5   a  by the force with which the fixing member is attached, though it may compressively deform, is nevertheless restricted from protruding outwardly beyond the region of the contact surfaces by the rib portions  18   a  and  18   b . In particular, the outer slanted surface  7   b  of the packing  7   c  comes into contact with the inner walls  18   a - 1  and  18   b - 1  of the rib portions  18   a ,  18   b , so deformation of the packing  7  toward an exterior (that is, to the right in FIG. 10) is almost completely forestalled. It should further be noted that the above-described gap L 3  between rib portions  18   a ,  18   b  is set to be small, such that no packing protrudes through this gap. Additionally, the outer slanted surface  7   b  of the packing  7  contacts and is positioned by the inner walls  18   a - 1  and  18   b - 1  of the rib portions  18   a  and  18   b , so the packing  7  does not protrude inwardly from the region of the contact surfaces  6   a ,  5   a  (that is, to the left in FIG.  10 ). 
     Accordingly, the predetermined restorative force created by the compressive deformation of the packing  7  by the fixing member provides a secure seal between the cover  6 , the base  5  and the packing  7 , thus sealing the actuator  4  and other components within the space formed by the cover  6  and the base  5 . 
     As can be appreciated, the sealed structure for the magnetic disk drive  16  according to the second embodiment of the present invention selectively provides the noncontinuous rib  18  around an outer edge of the base  5  at those regions at which the contact surfaces are narrow and which can therefore be expected to be points at which the risk of the sealing member protruding outward from the structure are greatest, thus maintaining an improved seal for the magnetic disk drive  10  while requiring relatively little processing as compared to a case in which the rib  12  is provided on both an inner and an outer edge of the base  5 . 
     Next, a description will be given of a sealed structure for a magnetic disk drive according to a third embodiment of the present invention, with reference to FIGS. 11 and 12. 
     FIG. 11 is a partial cross-sectional perspective view of the magnetic disk drive according to a third embodiment of the present invention, with the cover removed. FIG. 12 is a partial perspective view of the magnetic disk drive according to the second embodiment of the present invention, for the purpose of illustrating the state in which the packing is mounted therein. 
     The sealed structure for the magnetic disk drive  20 , like the sealed structure for the magnetic disk drive  16  according to the second embodiment of the present invention as described above, provides a rib selectively formed at which the contact surfaces  6   a ,  5   a  of the cover  6  and the base  5 , respectively, are narrow (refer to FIG. 3 for an example of such a portion, labeled herein as B). The difference between the present embodiment and the second embodiment is that two ribs  22 ,  24  are formed on the outer periphery of the base  5 , rib  22  being formed along the outer edge of the base  5  and rib  24  being formed on an inner side of the packing, at a distance sufficient to accommodate a width of the packing. Moreover, each of the ribs  22 ,  24  is divided into rib portions  22   a ,  24   a  and  24   b  (see FIG.  11 ). 
     The rib  22  (that is, rib portion  22   a ) has an inner side wall  22   a - 1  that contacts the packing  7  that slants outward toward a top of the rib (to the right in FIG.  12 ), and rib portions  24   a ,  24   b  having outer side walls  24   a - 1 ,  24   b - 1  that slant inward toward a top thereof (to the left in FIG. 12;  24   b - 1  not shown in FIG.  12 ). A distance L 4  separating the ribs  18   a ,  18   b  is determined with reference to the elasticity, width and depth of the packing  7 , and is small enough so that the packing  7  does not protrude inward from the gap L 4  when the packing is compressed during positioning of the cover  6  on the base  5 . 
     The packing  7 , in correspondence to the ribs  22 ,  24 , has outer and inner slanted surfaces  7   b ,  7   c  tapered so as to be narrower at the bottom. 
     When the cover  6  is mounted on the base  5  (on which base  5  the actuator  4  and other electronic components are mounted), the packing  7  is first mounted on the flange-like contact surface  6   a  of the cover  6 . Next, the cover  6  is positioned atop the contact surface  5   a  of the base  5  in such a way that the packing  7  is positioned between the two ribs  22  and  24 . The cover  6  is then fixedly mounted on the base  5 . 
     At this time, the packing  7 , which is squeezed between the contact surfaces  6   a ,  5   a  by the force with which the fixing member is attached, though it may compressively deform, is nevertheless restricted from protruding outwardly (that is, to the right in FIG. 12) beyond the region of the contact surfaces  6   a ,  5   a  by the rib portion  22   a . Additionally, the packing  7  is prevented from protruding inwardly (that is, to the left in FIG. 12) beyond the contact surfaces  6   a ,  5   a  by the rib portions  24   a ,  24   b . It should be noted that the above-described gap between rib portions  24   a ,  24   b  is set to a predetermined distance L 4 , small enough to prevent packing  7  from protruding through this gap. 
     Accordingly, the predetermined restorative force created by the compressive deformation of the packing  7  by the fixing member provides a secure seal between the cover  6 , the base  5  and the packing  7 , thus sealing the actuator  4  and other components within the space formed by the cover  6  and the base  5 . 
     The sealed structure for a magnetic disk drive  16  according to this third embodiment of the present invention, like that of the second embodiment described above, selectively provides the noncontinuous ribs  22  and  24  around an outer edge of the base  5  at those regions at which the contact surfaces are narrow and which can therefore be expected to be points at which the risk of the sealing member protruding outward from the structure are greatest, thus maintaining an improved seal for the magnetic disk drive  20  while requiring relatively little processing as compared to a case in which the rib  12  is provided on both an inner and an outer edge of the base  5 . 
     The above description is provided in order to enable any person skilled in the art to make and use the invention and sets forth the best mode contemplated by the inventors of carrying out the invention. 
     The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope and spirit of the present invention. 
     The present application is based on Japanese Priority Application No. 2000-267620, filed on Sep. 4, 2000, the contents of which are hereby incorporated by reference.