Abstract:
An electronic device includes: a first case and a second case; a gasket sandwiched between the first case and the second case, the gasket having an elasticity and being formed on the edge of the first case; and an electronic component accommodated in the first and second cases; wherein the gasket has a first side surface facing inward and a second side surface facing outward, and the first side surface has a first angle with respect to an imaginary line which is perpendicular to a direction in which the first case is joined to the second case, the second side surface has the second angle with respect to an imaginary line which is perpendicular to a direction in which the first case is joined to the second case, and the first angle is different from the second angle when the first case is disjoined to the second case.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2009-131233, filed on May 29, 2009, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    A certain aspect of the embodiments discussed herein relates to an electronic device, a housing, and a gasket. 
       BACKGROUND 
       [0003]    A gasket is provided that prevents water from entering through the gap between a first case and a second case. The gasket is elastic, and is disposed in a groove that is provided in one of the first and second cases. The gasket is pressed by the other of the first and second cases, and water-tightness is thereby provided between the first and second cases. 
         [0004]    [Patent Document] Japanese Laid-open Patent Publication No. 2008-218633 describes an example of the related art. 
         [0005]    The gasket is disposed in the groove and thereafter the first and second cases are joined together. There is a risk of the gasket becoming skewed from the desired position when the first and second cases are joined. In that case, there is a risk that the water-tightness provided by the gasket will be degraded. If care has to be taken to maintain the position of the gasket when joining the first and second cases, there is a risk of the efficiency with which the joining operation is performed becoming degraded. 
       SUMMARY 
       [0006]    According to an aspect of an embodiment, an electronic device includes: a first case and a second case; a gasket sandwiched between the first case and the second case, the gasket having an elasticity and being formed on the edge of the first case; and an electronic component accommodated in the first and second cases; wherein the gasket has a first side surface facing inward and a second side surface facing outward, and the first side surface has a first angle with respect to an imaginary line which is perpendicular to a direction in which the first case is joined to the second case, the second side surface has the second angle with respect to an imaginary line which is perpendicular to a direction in which the first case is joined to the second case, and the first angle is different from the second angle when the first case is disjoined to the second case. 
         [0007]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0008]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  is an exploded perspective view of a cellular phone; 
           [0010]      FIG. 2A  is a view of a front case; 
           [0011]      FIG. 2B  is a view of a rear case; 
           [0012]      FIG. 3A  is a sectional view along a line IIIA-IIIA in  FIG. 2B ; 
           [0013]      FIG. 3B  is a view of the portion shown in  FIG. 3A  when the rear case and the front case have been joined; 
           [0014]      FIGS. 4A and 4B  are views illustrating a first modification; and 
           [0015]      FIGS. 4C and 4D  are views illustrating a second modification. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0016]    A cellular phone will be described as an example of an electronic device. 
         [0017]      FIG. 1  is an exploded perspective view of a cellular phone. The cellular phone includes rear cases  10  and  60 , a display unit  20 , front cases  30  and  80 , and a printed circuit board  70 . The display unit  20  has a display  22 . The display unit  20  is housed in the rear case  10  and the front case  30 . A plurality of keys  82  are provided on the front case  80 . The printed circuit board  70  is housed in the rear case  60  and the front case  80 . Contacts that are switched on and off in response to operation of the keys  82  are provided on the printed circuit board  70 . The front cases  30  and  80  have hinge portions  34  and  84 , respectively. The front cases  30  and  80  are pivotably coupled through the hinge portions  34  and  84 . The display unit  20  and the printed circuit board  70  are electronic components. 
         [0018]      FIGS. 2A and 2B  are views of the front case  30  and the rear case  10 , respectively. In  FIG. 1 , a front panel  39  is fixed to the front side of the front case  30 . The front case  30  has an opening  31  through which the display  22  is exposed. A plurality of engagement holes  32  and through-holes  33  are formed around the opening  31 . A plurality of engagement portions  12  that engage in the engagement holes  32  are formed on the rear case  10 . Also, a plurality of screw holes  13  that correspond to the through-holes  33  are formed in the rear case  10 . The rear case  10  and the front case  30  are joined to each other with the display unit  20  therebetween, so that the display unit  20  is housed in the rear case  10  and the front case  30 . The rear case  10  and the front case  30  are made of a synthetic resin. 
         [0019]    A gasket  40  is molded together with the rear case  10 , and is thereby bonded to the rear case  10 . The gasket  40  is elastic, and is for example made of a thermoplastic elastomer. That is, the rear case  10  and the gasket  40  are made of different materials and molded together. The gasket  40  is in the form of a continuous ring that extents along the rim of the rear case  10 . When the rear case  10  and the front case  30  are joined, the gasket  40  is sandwiched therebetween. The gasket  40  functions to waterproof the space inside the rear case  10  and the front case  30 . The gasket  40  will be described in more detail below. 
         [0020]      FIG. 3A  is a sectional view along the line IIIA-IIIA in  FIG. 2B .  FIG. 3B  is a view of the portion shown in  FIG. 3A  when the rear case  10  and the front case  30  have been joined.  FIG. 3A  shows the state before the rear case  10  and the front case  30  are joined. That is,  FIG. 3A  shows the position of the gasket  40  when the rear case  10  and the front case  30  are separate from each other. 
         [0021]    As shown in  FIG. 3A , the gasket  40  is bonded to a bonding surface  14  of the rear case  10 . The gasket  40  has a projecting shape, and includes side portions  41  and  42 , a top portion  45 , and a bonding portion  48 . The side portions  41  and  42  are on opposites sides of the top portion  45 . The tip of the gasket  40  is higher than an abutment surface  18 . The side portion  41  is on the outer side, and the side portion  42  is on the inner side, with respect to the rear case  10 . 
         [0022]    The side portions  41  and  42  have different inclination angles α and β, respectively. The inclination angle α is smaller than the inclination angle β. The sum of the inclination angles α and β is, for example, but not limited to, 120 degrees to 167 degrees. The inclination angles α and β are defined with respect to an imaginary line L that is perpendicular to a direction D in which the front case  30  is joined to the rear case  10 . The inclination angles may be equal to or greater than 90 degrees. A recess  49  is provided on the side-portion- 41  side. The recess  49  reduces the distance between the side portions  41  and  42 . 
         [0023]    A curved portion  43  is provided between the side portion  41  and the top portion  45 . A curved portion  44  is provided between the side portion  42  and the top portion  45 . The curved portions  43  and  44  have different radii of curvature. The radius of curvature of the curved portion  43  is smaller than that of the curved portion  44 . 
         [0024]    The bonding portion  48  is bonded to bonding surfaces  14  and  15 , which are surfaces of the rear case  10 . In this way, a sufficient contact area between the bonding portion  48  and the rear case  10  is obtained. However, the surface of the rear case  10  to which the gasket  40  is bonded is not limited to this form. For example, the gasket may be bonded to a curved surface that is concave as viewed from the gasket side. 
         [0025]    As illustrated in  FIG. 3B , when the rear case  10  and the front case  30  have been joined, the abutment surface  18  abuts a pressing surface  38  of the front case  30 , and the gasket  40  is pressed by the pressing surface  38  and bent toward the inside of the rear case  10 . The gasket  40  abuts the pressing surface  38  mainly at the side portion  41  and the top portion  45 . The gasket  40  is elastic, and therefore exerts pressure on the rear case  10  and the front case  30 , thereby providing water-tightness between the rear case  10  and the front case  30 . 
         [0026]    Because of the different inclination angles α and β, the gasket  40  tends to be bent toward a particular side when the rear case  10  and the front case  30  are joined. Also, because the curved portions  43  and  44  have different radii of curvature, the gasket  40  tends to be bent toward a particular side. Moreover, the recess  49  reduces the distance between the side portions  41  and  42  so that the gasket  40  is easily bent. Every part of the gasket  40 , which is in the form of a ring as described above, is bent inward when the rear case  10  and the front case  30  are joined. 
         [0027]    When the gasket  40  is bent, the contact area between the front case  30  and the gasket  40  becomes larger than when the gasket  40  is pressed by the front case  30  while remaining erect. As a result, the pressure applied to the front case  30  is reduced and the front case  30  is subjected to less stress. This allows the front case  30  to be thin. The recess  49  prevents the resilient force of the gasket  40  from being too great. 
         [0028]    Next, a gasket whose structure is different from that of the present embodiment will be described. This gasket is not bonded to the rear case, but housed in a groove of the rear case. This gasket has a projecting shape. In order to facilitate the mounting of the gasket in the groove, the width of the groove is made larger than that of the gasket. There is a risk of the gasket becoming skewed from the desired position when the rear case and the front case are joined. If the rear case and the front case are joined in such a condition, there is a risk that the resilient force of the gasket will become less than the expected level. In that case, there is a risk that the water-tightness between the rear case and the front case will be degraded. Moreover, there is a risk of water entering through the gap between the bottom of the gasket and the rear case. If care has to be taken to maintain the gasket in a desired position when joining the front case and the rear case, there is a risk of the efficiency with which the joining operation is performed becoming degraded. 
         [0029]    In contrast, in the present embodiment, the rear case  10  and the gasket  40  are bonded together by being molded together. Therefore, the gasket  40  is fixed in a desired position before assembly, so that it is not necessary to take care to maintain the position of the gasket  40  when joining the rear case  10  and the front case  30 . Therefore, the efficiency with which the joining operation is performed is improved. When the rear case  10  and the front case  30  have been joined, the gasket  40  is bent and water-tightness is obtained. 
         [0030]    Next, modifications will be described. 
         [0031]      FIGS. 4A and 4B  are views illustrating a first modification.  FIGS. 4C and 4D  are views illustrating a second modification. As illustrated in  FIG. 4A , in a gasket  40   a  of the first modification, an inclination angle α 1  of a side portion  41   a  is larger than an inclination angle β 1  of a side portion  42   a . The radius of curvature of a curved portion  43   a  is smaller than that of a curved portion  44   a . As illustrated in  FIG. 4B , after the cases have been joined, the tip of the gasket  40   a  is bent toward the inside. A pressing surface  38   a  has the form of a step. A surface of the pressing surface  38   a  that is perpendicular to a direction D presses the gasket  40   a . The direction D is the direction in which the cases are joined. The gasket  40   a  of the first modification also improves the efficiency with which the joining operation is performed. 
         [0032]    As illustrated in  FIG. 4C , in a gasket  40   b  of the second modification, an inclination angle α 2  of a side portion  41   b  is smaller than an inclination angle β 2  of a side portion  42   b . The radius of curvature of a curved portion  43   b  is larger than that of a curved portion  44   b . A pressing surface  38   b  has the form of a step. A gasket  40   b  is bonded to an abutment surface  18   b  which is flat. As illustrated in  FIG. 4D , after the joining, the gasket  40   b  is bent toward the inside. A portion of the pressing surface  38   b  of a front case  30   b  that is perpendicular to a direction D presses the gasket  40   b . The direction D is the direction in which the cases are joined. As illustrated in  FIG. 4D , a sufficient contact area between the front case  30   b  and the gasket  40   b  is obtained. The gasket  40   b  of the second modification also improves the efficiency with which the joining operation is performed. 
         [0033]    While a preferred embodiment of the present invention has been described in detail, the present invention is not limited to the embodiment. Various modifications and changes are possible without departing from the spirit of the present invention that is set forth in the claims. 
         [0034]    The electronic device is not limited to a cellular phone, and may be, for example, a PDA or a notebook computer. The housing in which the gasket is used may be one that houses something other than electronic components. It is only necessary that the gasket should be bent always toward a particular side, and the gasket may be so designed as to be bent toward the outside of the case. Recesses may be provided on both sides of the gasket. The gasket may be provided in the rear case  60 . 
         [0035]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and condition, nor does the organization of such examples in the specification relate to a showing of superiority and inferiority of the invention. Although the embodiment of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alternations could be made hereto without departing from the spirit and scope of the invention.