Abstract:
In a water-proof structure for an opening of a device case, which includes a packing installed in a peripheral groove around a cover and compressed between the inner periphery of the opening and the groove when the cover is inserted into the opening, the packing is configured to have a flat contact surface in contact with the bottom of the groove and have a cross section having a width larger than the height, and the cross section of the packing also has a flat bottom or an inner side to fit the groove bottom that is also flat in a cross section while the outer side has a convex shape so that the whole cross section has a D-shaped form, in order to prevent degraded sealing capability or improper installation due to twist of the packing in the groove.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Stage Application of International application No. PCT/JP2010/053825 filed on Mar. 9, 2010, and published in Japanese as WO 2010128606 A1 on Nov. 11, 2010. This application claims priority to Japanese Application No. 2009-113544 filed May 8, 2009 and Japanese Application No. 2009-155269 filed Jun. 30, 2009. The disclosures of the above applications are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a structure for achieving waterproofness of an opening and closing portion such as a connector cover portion, a battery cover portion or the like in a case of a device. 
         [0004]    2. Description of the Conventional Art 
         [0005]    In a compact electronic device such as a cellular phone, a digital camera or the like, there is a structure which is provided with a connector connection portion and a battery insertion portion for inputting and outputting data and charging, and a cover is detachably fitted to an opening portion which is provided as the connector connection portion or the battery insertion portion in the device case. Further, a gap between the case opening portion and the cover mentioned above has been conventionally sealed by an O-ring, thereby achieving waterproofness. 
         [0006]      FIG. 26  shows the conventional waterproof structure mentioned above, reference numeral  100  denotes a case of a compact electronic device, reference numeral  101  denotes an opening portion which is provided in the case  100 , and reference numeral  200  denotes a cover which is detachably fitted to the opening portion  101 . An installation groove  201  is peripherally provided in an outer peripheral surface of the cover  200 , and an O-ring  202  is installed to the installation groove  201 . The O-ring  202  is a packing which is made of a rubber-like elastic material having a circular cross section, and is structured such as to achieve a waterproof function by being interposed in a compressed state between an inner surface (an inner peripheral surface) of the opening portion  101  and a bottom surface of the installation groove  201  of the cover  200  in a state in which the cover  200  is fitted to the opening portion  101  of the case  100  (refer, for example, to the following patent documents). 
         [0007]    However, in accordance with the conventional waterproof structure, in a process of fitting the cover  200  to the opening portion  101  as shown in  FIG. 26(B)  from a state in which the opening portion  101  is opened by detaching the cover  200  as shown in  FIG. 26(A) , the O-ring  202  is twisted by friction with the inner surface of the opening portion  101  and the bottom surface of the installation groove  201 , and there is a risk that a sealing performance (a waterproof performance) by the O-ring  202  is deteriorated. 
         [0008]    Further, at a time of winding the O-ring  202  in the installation groove  201  of the cover  200 , torsion tends to be caused in the O-ring  202 , and there is a risk that the sealing performance (the waterproof performance) is deteriorated by poor installation. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention is made by taking the point mentioned above into consideration, and a technical problem thereof is to prevent reduction of a waterproof performance and poor installation due to torsion of a packing within an installation groove. 
       MEANS FOR SOLVING THE PROBLEM 
       [0010]    As a means for effectively solving the technical problem mentioned above, a waterproof structure in accordance with the first aspect of the present invention is a structure in which a packing is installed to an installation groove which is peripherally provided in an outer peripheral surface of a cover, and the packing is compressed between an inner surface of an opening portion and a bottom surface of the installation groove by fitting the cover to the opening portion of a case of a device, the structure being characterized in that the packing has a flat shape at a close contact surface with the bottom surface of the installation groove, and a cross sectional diameter in a width direction of the packing is made larger than a cross sectional diameter thereof in a height direction. 
         [0011]    Further, a waterproof structure in accordance with the second aspect of the present invention is a structure in which a packing is installed to an installation groove which is peripherally provided in an outer peripheral surface of a cover, and the packing is compressed between an inner surface of an opening portion and a bottom surface of the installation groove by fitting the cover to the opening portion of a case of a device, the structure being characterized in that the packing has a flat cross sectional shape at a close contact surface with the bottom surface of the installation groove, that is, an inner peripheral surface in accordance that the installation groove has a flat cross sectional shape at its bottom surface, has a circular arc shaped convex surface at an outer periphery surface at the opposite side, and is formed to have a D-shaped cross section as a whole. 
         [0012]    Further, a waterproof structure in accordance with the third aspect of the present invention is a structure in which a packing is installed to an installation groove which is peripherally provided in an outer peripheral surface of a cover, and the packing is compressed between an inner surface of an opening portion and a bottom surface of the installation groove by fitting the cover to the opening portion of a case of a device, the structure being characterized in that a fitting groove extending in an extending direction of the installation groove is formed in the bottom surface of the installation groove, and a fitting projection capable of fitting to the fitting groove is formed on the packing. 
         [0013]    Further, a waterproof structure in accordance with the fourth aspect of the present invention is the waterproof structure of an opening and closing portion of a device case as described in the third aspect mentioned above, the structure being further characterized in that the packing has a flat cross sectional shape at a close contact surface with the bottom surface of the installation groove, that is, an inner peripheral surface in accordance that the installation groove has a flat cross sectional shape at its bottom surface, has a circular arc shaped convex surface at an outer periphery at the opposite side, and is formed to have a D-shaped cross section as a whole, and the fitting projection is formed on an inner peripheral surface of the packing formed to have the D-shaped cross section. 
         [0014]    Further, a waterproof structure in accordance with the fifth aspect of the present invention is the waterproof structure of an opening and closing portion of a device case as described in the third aspect mentioned above, the structure being further characterized in that the packing is formed to have a crucial cross sectional shape while having a fitting projection at an inner peripheral side fitting to the fitting groove, a seal projection at an outer peripheral side coming into close contact with an inner surface of the opening portion, and seal projections at both sides in a width direction, in accordance that the installation groove has a flat cross sectional shape at its bottom surface. 
         [0015]    Further, a waterproof structure in accordance with the sixth aspect of the present invention is a structure in which a packing is installed to an installation groove which is peripherally provided in an outer peripheral surface of a cover, and the packing is compressed between an inner surface of an opening portion and a bottom surface of the installation groove by fitting the cover to the opening portion of a case of a device, the structure being characterized in that the packing has a flat shape at a close contact surface with the bottom surface of the installation groove, and a close contact surface with an inner surface of the opening portion is constructed by a peak portion and inclined surfaces at both sides thereof. 
         [0016]    Further, a waterproof structure in accordance with the seventh aspect of the present invention is a structure in which a packing is installed to an installation groove which is peripherally provided in an outer peripheral surface of a cover, and the packing is compressed between an inner surface of an opening portion and a bottom surface of the installation groove by fitting the cover to the opening portion of a case of a device, the structure being characterized in that the packing has a flat cross sectional shape at a close contact surface with the bottom surface of the installation groove, that is, an inner peripheral surface in accordance that the installation groove has a flat cross sectional shape at its bottom surface, has a shape provided with a peak portion and inclined surfaces at both sides thereof at an outer peripheral surface at the opposite side, and is formed to have a pentagonal cross sectional shape as a whole. 
         [0017]    Further, a waterproof structure in accordance with the eighth aspect of the present invention is the waterproof structure of an opening and closing portion of a device case as described in the sixth or seventh aspect mentioned above, the structure being further characterized in that the inclined surface at a cover inserting direction side is a relatively gentle slope, and the inclined surface at the opposite side to the cover inserting direction is a relatively steep slope, in the inclined surfaces at both sides of the peak portion of the packing. 
         [0018]    Further, a waterproof structure in accordance with the ninth aspect of the present invention is the waterproof structure of an opening and closing portion of a device case as described in the sixth or seventh aspect mentioned above, the structure being further characterized in that the inclined surface at a cover inserting direction side is a relatively gentle slope, and the inclined surface at the opposite side to the cover inserting direction is a relatively steep slope, in the inclined surfaces at both sides of the peak portion of the packing, and the peak portion of the packing is deviated from a center portion in the width direction of the packing toward the opposite side to the cover inserting direction. 
         [0019]    In the waterproof structure in accordance with the first aspect of the present invention having the structure mentioned above, since the packing has the flat shape at the close contact surface with the bottom surface of the installation groove, and the cross sectional diameter in the width direction is set to be larger than the cross sectional diameter in the height direction, seating on the bottom surface of the installation groove is stabilized in comparison with the conventional O-ring which tends to roll, and the packing is hardly twisted even by being exposed to a load in the twisting direction, whereby it is possible to effectively prevent reduction of a waterproof performance. 
         [0020]    Further, in the waterproof structure in accordance with the second aspect of the present invention, since the packing has the flat cross sectional shape at the close contact surface with the bottom surface of the groove, that is, the inner peripheral surface in accordance that the installation groove has the flat cross sectional shape at its bottom surface, has the circular arc shaped convex surface at the outer periphery surface at the opposite side, and is formed to have the D-shaped cross section as a whole, seating on the bottom surface of the installation groove is stabilized in comparison with the conventional O-ring which tends to roll, and the packing is hardly twisted even by being exposed to a load in the twisting direction, whereby it is possible to effectively prevent reduction of the waterproof performance. 
         [0021]    Further, in the waterproof structure in accordance with the third, fourth or fifth aspect of the present invention, since the fitting projection formed on the packing is fitted to the fitting groove formed in the bottom surface of the installation groove, the packing is constrained within the installation groove in accordance with the fitting, and the package is hardly twisted even by being exposed to a load in the twisting direction, whereby it is possible to effectively prevent reduction of the waterproof performance. In accordance with the structure of the fourth aspect, since the inner peripheral surface of the packing has the flat cross sectional shape, seating on the bottom surface of the installation groove is stabilized. In accordance with the structure of the fifth aspect, since the seal projections protruding to both sides in the width direction come into close contact with the bottom surface of the installation groove, seating on the bottom surface of the installation groove is stabilized. Further, since the width in the axial direction of the seal projection at the outer peripheral side coming into close contact with the inner surface of the opening portion is set to be smaller than the width in the axial direction of a whole of the packing, compressive reaction force in an installed state is set to be smaller. 
         [0022]    Further, in the waterproof structure in accordance with the sixth aspect of the present invention, since the close contact surface with the bottom surface of the installation groove in the packing has the flat shape, seating on the bottom surface of the installation groove is stabilized in comparison with the conventional O-ring which tends to roll, and the packing is hardly twisted even by being exposed to a load in the twisting direction, whereby it is possible to effectively prevent the reduction of the waterproof performance. Further, since the close contact surface with the inner surface of the opening portion of the case is constructed by the peak portion and the inclined surfaces at both sides thereof, the compressive reaction force becomes smaller in comparison with the structure in which the close contact surface with the inner surface of the opening portion is formed into the circular arc shaped convex surface, in the case that a collapsing margin is fixed, whereby it is possible to reduce press-fit resistance at a time of fitting the cover to the opening portion of the case, and abrasion of the packing. Therefore, it is possible to prevent poor installation of the packing and torsion of the packing within the groove on the basis of repeated opening and closing motions of the cover or the like, it is further possible to reduce the press-fit resistance at a time of fitting the cover to the opening portion of the case, and it is possible to suppress reduction of the waterproof performance due to the abrasion. 
         [0023]    Further, in the waterproof structure in accordance with the seventh aspect of the present invention, since the packing has the flat cross sectional shape at the close contact surface with the bottom surface of the installation groove, that is, the inner peripheral surface in accordance that the installation groove has the flat cross sectional shape at its bottom surface, seating on the bottom surface of the installation groove is stabilized in comparison with the conventional O-ring which tends to roll, and the packing is hardly twisted even by being exposed to a load in the twisting direction, whereby it is possible to effectively prevent the reduction of the waterproof performance. Further, since the packing has the cross sectional shape provided with the peak portion and the inclined surfaces at both sides thereof at the outer peripheral surface at the opposite side to the inner peripheral surface, and is formed to have the pentagonal cross sectional shape as a whole, the compressive reaction force becomes smaller in comparison with the structure in which the close contact surface with the inner surface of the opening portion is formed into the circular arc shaped convex surface, in the case that a collapsing margin is fixed, whereby it is possible to reduce press-fit resistance at a time of fitting the cover to the opening portion of the case, and abrasion of the packing. Therefore, it is possible to prevent poor installation of the packing and torsion of the packing within the groove on the basis of repeated opening and closing motions of the cover or the like, it is further possible to reduce the press-fit resistance at a time of fitting the cover to the opening portion of the case, and it is possible to suppress reduction of the waterproof performance due to the abrasion. 
         [0024]    Further, in the waterproof structure in accordance with the eighth or ninth aspect of the present invention, friction resistance of the packing with the inner surface of the opening portion of the case becomes smaller in a cover inserting direction and larger in the opposite direction thereto. Further, since surface pressure of the packing with respect to the inner surface of the opening portion of the case more rapidly rises at the opposite side to the cover inserting direction than the peak portion, resistance against intruding pressure of water from the external is increased. Accordingly, the cover can be fitted easier to the opening portion of the case, the cover can be firmly fitted so as to hardly fall away from the opening portion of the case, and it is possible to further improve the waterproof performance. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0025]      FIG. 1  is a perspective view showing a first embodiment of a waterproof structure of an opening and closing portion of a device case in accordance with the present invention; 
           [0026]      FIG. 2  shows a state in which a packing is installed to a groove in the first embodiment, in which  FIG. 2(A)  is a front view and  FIG. 2(B)  is a side view in which a part of the packing is cut; 
           [0027]      FIG. 3  shows an example of the packing in accordance with the first embodiment, in which  FIG. 3(A)  is a front view and  FIG. 3(B)  is a cross sectional view along a line B-B in  FIG. 3(A) ; 
           [0028]      FIG. 4  is a cross sectional view showing a part of the packing in  FIG. 3  in an enlarged manner; 
           [0029]      FIG. 5  is a cross sectional view showing in an enlarged manner a state in which a cover is fitted to an opening portion of a case, in the first embodiment; 
           [0030]      FIG. 6  is an explanatory view showing a process of fitting the cover to the opening portion of the case, in the first embodiment; 
           [0031]      FIG. 7  is a cross sectional view of a substantial part showing a second embodiment of the waterproof structure of the opening and closing portion of the device case in accordance with the present invention; 
           [0032]      FIG. 8  shows a state in which a packing is installed to a groove in the second embodiment, in which  FIG. 8(A)  is a front view and  FIG. 8(B)  is a side view in which a part of the packing is cut; 
           [0033]      FIG. 9  shows the packing in accordance with the second embodiment, in which  FIG. 9(A)  is a front view and  FIG. 9(B)  is a cross sectional view along a line B-B′ in  FIG. 9(A) ; 
           [0034]      FIG. 10  is a perspective view showing a state in which the packing is installed to a packing installation groove, in the second embodiment; 
           [0035]      FIG. 11  is a cross sectional view of a substantial part showing a third embodiment of the waterproof structure of the opening and closing portion of the device case in accordance with the present invention; 
           [0036]      FIG. 12  is a cross sectional view showing shapes of a cover and a packing in the third embodiment; 
           [0037]      FIG. 13  is a perspective view showing a state in which the packing is installed to a packing installation groove in the third embodiment; 
           [0038]      FIG. 14  is a perspective view showing a fourth embodiment of the waterproof structure of the opening and closing portion of the device case in accordance with the present invention; 
           [0039]      FIG. 15  is a cross sectional perspective view showing a state in which a packing is installed to a groove in the fourth embodiment; 
           [0040]      FIG. 16  shows an example of a cover to which the packing is installed, in the fourth embodiment, in which  FIG. 16(A)  is a plan view,  FIG. 16(B)  is a back view, and  FIG. 16(C)  is a side view; 
           [0041]      FIG. 17  shows the other example of the cover to which the packing is installed, in the fourth embodiment, in which  FIG. 17(A)  is a plan view,  FIG. 17(B)  is a back view, and  FIG. 17(C)  is a side view; 
           [0042]      FIG. 18  is a cross sectional view showing a concrete example of the packing in accordance with the fourth embodiment; 
           [0043]      FIG. 19  is an explanatory view showing a process of fitting the cover to an opening portion of a case in the fourth embodiment; 
           [0044]      FIG. 20  is a cross sectional perspective view showing a state in which a packing is installed to a groove, in a fifth embodiment of the waterproof structure of the opening and closing portion of the device case in accordance with the present invention; 
           [0045]      FIG. 21  is a cross sectional view showing an example of the packing in accordance with the fifth embodiment; 
           [0046]      FIG. 22  is an explanatory view showing a process of fitting a cover to an opening portion of a case, in the fifth embodiment. 
           [0047]      FIG. 23  is an explanatory view showing surface pressure distribution of the packing in the fifth embodiment; 
           [0048]      FIG. 24  is a cross sectional perspective view showing a state in which a packing is installed to a groove, in a sixth embodiment of the waterproof structure of the opening and closing portion of the device case in accordance with the present invention; 
           [0049]      FIG. 25  is a cross sectional view showing an example of the packing in accordance with the sixth embodiment; and 
           [0050]      FIG. 26  is an explanatory view showing a process of fitting a cover to an opening portion of a case in a waterproof structure of an opening and closing portion of a device case in accordance with a conventional art. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0051]    A description will be given below of preferable embodiments of a waterproof structure of an opening and closing portion of a device in accordance with the present invention with reference to the accompanying drawings. 
       First Embodiment 
       [0052]    First of all, in a perspective view of  FIG. 1 , reference numeral  1  denotes a case of a compact electronic device, and reference numeral  2  denotes a cover which is detachably fitted to an opening portion  11  provided in the case  1 . 
         [0053]    The opening portion  11  provided in the case  1  is structured such that an opening shape is formed as a square shape having round corners. In other words, an inner peripheral surface thereof has flat surface portions and curved surface portions alternately in a peripheral direction. 
         [0054]    The cover  2  is formed in a tabular shape as a whole, and has an insertion portion  21  which can be inserted to the opening portion  11  of the case  1 , and a collar portion  22  which is formed so as to protrude out of an outer end portion of the insertion portion  21  and is opposed to an outer surface  1   a  of the case  1 , as shown in  FIG. 5 . 
         [0055]    An outer peripheral surface  21   a  of the insertion portion  21  of the cover  2  is formed in its projection shape in an inserting direction, to have an approximately similar shape to the opening shape of the opening portion  11  of the case  1 , that is, a square shape having round corners as shown in  FIG. 2 , has flat surface portions and curved surface portions alternately in a peripheral direction, and is a little smaller than the opening portion  11 . Further, an installation groove (also called simply as “groove”, and also called as “packing installation groove”)  23  is peripherally provided in an outer peripheral surface  21   a  of the insertion portion  21 , and the installation groove  23  is formed to have an approximately C-shaped cross section, that is, is constructed by a flat surface shaped bottom surface  23   a  which is in parallel to the outer peripheral surface  21   a  of the insertion portion  21 , and a pair of inner surfaces  23   b  which vertically rise from both sides thereof. 
         [0056]    A packing  3  made of a rubber-like elastic material (a rubber material or a synthetic resin material having a rubber-like elasticity) is installed to the installation groove  23  mentioned above. The packing  3  is molded in an annular shape as shown in  FIG. 3(A) , and a cross section thereof has a D-shape as shown in  FIG. 3(B) . In more detail, in a cross sectional shape shown in  FIG. 4  and  FIG. 5 , an inner peripheral surface  3   a  coming into close contact with a bottom surface  23   a  of the installation groove  23  has a flat shape, and an outer peripheral surface  3   b  which protrudes to an outer side of the installation groove  23  so as to be brought into pressure contact with an inner surface of the opening portion  11  of the case  1  in an appropriate deformed state is formed into a circular arc shaped convex surface. In this case, the inner peripheral surface  3   a  of the packing  3  corresponds to the close contact surface described in the first aspect. 
         [0057]    Further, as shown in  FIG. 4 , a cross sectional diameter L 1  in a width direction of the packing  3  is larger than a cross sectional diameter L 2  in a height direction, that is, a relation of L 2 /L 1 &lt;1 is established. In this case, L 2  is larger than a depth of the installation groove  23 . 
         [0058]    In the structure mentioned above, the cover  2  is structured such that the insertion portion  21  thereof is press fitted to the opening portion  11  of the case  1  via the packing  3 , and the packing  3  is held in a state of being appropriately compressed between the bottom surface  23   a  of the installation groove  23  and the inner peripheral surface  11   a  of the opening portion  11 , thereby closing the opening portion  11  in a sealed state so as to achieve waterproofness. 
         [0059]    Further, in accordance with the present invention, since the inner peripheral surface  3   a  brought into close contact with the bottom surface  23   a  of the installation groove  23  is flat and the relation of L 2 /L 1 &lt;1 is established, in the packing  3 , resistance at a time when force in a rolling (twisting) direction acts is large. Accordingly, the packing  3  is not twisted on the basis of friction with the inner peripheral surface  11   a  of the opening portion  11  and the bottom surface  23   a  of the installation groove  23 , in a process of fitting the cover  2  to the opening portion  11  as shown in  FIG. 6(B)  from a state in which the opening portion  11  is open as shown in  FIG. 6(A) , and an excellent sealing performance (a waterproof performance) by the packing  3  is secured. 
         [0060]    Further, since the packing  3  is molded in an annular shape as shown in  FIG. 3 , the conventional O-ring tends to be twisted at a time of being fitted onto the insertion portion  21  of the noncircular cover  2  having the flat portions and the curved surface portions alternately in the peripheral direction as shown in  FIG. 1  and  FIG. 2  so as to be wound in the groove  23 . However, in accordance with the present invention, since the packing  3  has the cross sectional shape as shown in  FIG. 4  so as to be hardly twisted, it is possible to effectively prevent the sealing performance (the waterproof performance) from being deteriorated by poor installation. 
       Second Embodiment 
       [0061]    Next,  FIG. 7  to  FIG. 10  show a second embodiment in accordance with the present invention. 
         [0062]    In  FIG. 7  among them, reference numeral  1  denotes a case of a compact electronic device such as a cellular phone or the like, and reference numeral  2  denotes a cover which is detachably fitted to an opening portion  11  which is provided as a connector insertion portion or the like in the case  1 . The opening portion  11  of the case  1  has a square shape having round corners in its opening shape, that is, an inner peripheral surface  11   a  thereof has flat surface portions and curved surface portions alternately in a peripheral direction. The cover  2  is formed in a tabular shape as a whole, and has an insertion portion  21  which can be inserted to the opening portion  11  of the case  1 , and a collar portion  22  which is formed so as to protrude out of an outer end portion of the insertion portion  21  and is opposed to an outer surface  12  of the case  1 . 
         [0063]    An outer peripheral surface  21   a  of the insertion portion  21  of the cover  2  has, in its projection shape with respect to an inserting direction, an approximately similar shape to the opening shape of the opening portion  11  of the case  1 , that is, a square shape having round corners as shown in  FIG. 8 , has flat surface portions and curved surface portions alternately in a peripheral direction, and is a little smaller than the opening portion  11 . Further, an installation groove  23  is peripherally provided in an outer peripheral surface  21   a  of the insertion portion  21  of the cover  2 , and a packing  3  is installed to the installation groove  23 . 
         [0064]    The installation groove  23  is constructed by a bottom surface  23   a  which has a flat cross sectional shape and is in parallel to the outer peripheral surface  21  a of the insertion portion  21  of the cover  2 , and a pair of inner surfaces  23   b  which approximately vertically rise from both sides thereof, and a fitting groove  24  which extends in an extending direction of the installation groove  23  and has a C-shaped cross sectional shape is formed at an intermediate position in a width direction of the bottom surface  23   a.    
         [0065]    The packing  3  is molded in an annular shape as shown in  FIG. 9(A)  by a rubber-like elastic material (a rubber material or a synthetic resin material having a rubber-like elasticity), and is constructed by a main body portion  31  which has a D-shaped cross section, and a fitting projection  32  which is formed on an inner peripheral surface  31  a thereof, as shown in  FIG. 9(B)  and  FIG. 10 . 
         [0066]    In detail, the main body portion  31  of the packing  3  is retained within the installation groove  23 , the inner peripheral surface  31   a  brought into close contact with the bottom surface  23   a  of the installation groove  23  has a flat cross sectional shape, an outer peripheral surface  31   b  protruding out to an outer side of the installation groove  23  so as to be brought into pressure contact with the inner peripheral surface  11   a  of the opening portion  11  of the case  1  in an appropriate deformed state is formed into a convex surface having a circular arc shaped cross section, and slight gaps are provided with respect to the inner surfaces  23   b  of the installation groove  23  so that a filling rate of the main body portion  31  within the installation groove  23  does not become 100% or more even in a state of being compressed between the bottom surface  23   a  of the installation groove  23  and the inner peripheral surface  11   a  of the opening portion  11 . Further, the fitting projection  32  is structured such as to be brought into close contact with and fitted to a fitting groove  24  formed in the bottom surface  23   a  of the installation groove  23 . 
         [0067]    In the waterproof structure in accordance with the second embodiment structured as mentioned above, as shown in  FIG. 7 , the insertion portion  21  of the cover  2  is press fitted into the opening portion  11  of the case  1  via the packing  3  and the main body portion  31  of the packing  3  is held in a state of being appropriately compressed between the bottom surface  23   a  of the installation groove  23  and the fitting groove  24 , and the inner peripheral surface  11   a  of the opening portion  11 , whereby the cover  2  closes the opening portion  11  in a sealed state so as to achieve waterproofness. 
         [0068]    Further, since the packing  3  is bound by the fitting projection  32  being brought into close contact with and fitted to the fitting groove  24  formed in the bottom surface  23   a  of the installation groove  23 , resistance at a time when force F in a rolling (twisting) direction shown in  FIG. 10  acts is large. Therefore, the packing  3  (the main body portion  31 ) is not twisted by friction with the inner peripheral surface  11   a  of the opening portion  11  and the bottom surface  23   a  of the installation groove  23  in a process of fitting the cover  2  to the opening portion  11 , and an excellent sealing performance (a waterproof performance) is secured. 
         [0069]    Further, if the fitting projection  32  is pushed into the fitting groove  24  of the bottom surface  23   a  of the installation groove  23  while pressing the main body portion  31  lightly, at a time of fitting the packing  3  onto the insertion portion  21  of the noncircular cover  2  so as to wind it in the installation groove  23 , the fitting projection  32  is fitted into the fitting groove  24  sequentially. Accordingly, torsion of the packing  3  (the main body portion  31 ) is not caused, and it is possible to effectively prevent the sealing performance (the waterproof performance) from being deteriorated by poor installation. 
       Third Embodiment 
       [0070]    Next,  FIG. 11  to  FIG. 13  show a third embodiment in accordance with the present invention. In this third embodiment, a difference from the previously described second embodiment is cross sectional shapes of the fitting groove  24  and the packing  3 . 
         [0071]    In more detail, the fitting groove  24  formed at an intermediate position in a width direction of the bottom surface  23   a  of the installation groove  23  has an approximately U-shaped cross section, as shown in  FIG. 12  and  FIG. 13 . 
         [0072]    Further, the packing  3  has an inner peripheral side fitting projection  32  which has a convex surface having a circular arc shaped cross section corresponding to the fitting groove  24 , an outer peripheral side seal projection  33  having a cross sectional shape which is 180 degree symmetrical with the fitting projection  32 , and seal projections  34  and  35  at both sides in a width direction having cross sectional shapes which are 90 degree symmetrical with the fitting projection  32  in 90 degree different directions from the fitting projection  32  and the seal projection  33  respectively, in a cross section shown in  FIG. 11  and  FIG. 12 , that is, the packing  3  has an approximately crucial cross sectional shape. 
         [0073]    Further, the fitting projection  32  of the packing  3  is brought into close contact with and fitted to a fitting groove  24  formed in the bottom surface  23   a  of the installation groove  23 , and the seal projection  33  at the outer peripheral side protrudes to the outer side of the installation groove  23  so as to be brought into pressure contact with the inner peripheral surface  11   a  of the opening portion  11  of the case  1  in an appropriate deformed state. Further, the seal projections  34  and  35  at both sides in the width direction are brought into close contact with the inner surfaces  23   b  and  23   b  of the installation groove  23  at their top ends as well as being retained within the installation groove  23 , and their inner peripheral portions are brought into close contact with the bottom surface  23   a  of the installation groove  23 . Since they have a convex surface having a circular arc shaped cross section, slight gaps are formed with respect to the bottom surface  23   a  and the inner surfaces  23   b  of the installation groove  23 , and a filling rate of the packing  3  within the installation groove  23  does not become 100% or more. 
         [0074]    In the waterproof structure in accordance with the third embodiment constructed as mentioned above, as shown in  FIG. 11 , the cover  2  is structured such that the insertion portion  21  is press fitted into the opening portion  11  of the case  1  via the packing  3  and the packing  3  is held in a state of being appropriately compressed between the bottom surface  23   a  of the installation groove  23  and the fitting groove  24 , and the inner peripheral surface  11   a  of the opening portion  11 , thereby closing the opening portion  11  in a sealed state so as to achieve waterproofness. 
         [0075]    Further, since the packing  3  is structured such that the fitting projection  32  at the inner peripheral side is brought into close contact with and fitted to the fitting groove  24  formed in the bottom surface  23   a  of the installation groove  23 , and the top ends of the seal projections  34  and  35  at both sides in the width direction are brought into close contact with the inner surfaces  23   b  and  23   b  of the installation groove  23 , resistance at a time when force F in the rolling (twisting) direction shown in  FIG. 13  acts is large, whereby the packing  3  is not twisted on the basis of friction with the inner peripheral surface  11   a  of the opening portion  11  and the bottom surface  23   a  of the installation groove  23  in a process of fitting the cover  2  to the opening portion  11 , and an excellent sealing performance (waterproof performance) can be secured. 
         [0076]    Further, if the fitting projection  32  is pressed into the fitting groove  24  of the bottom surface  23   a  of the installation groove  23  while pushing lightly the seal projections  33  to  35  at a time of fitting the packing  3  onto the insertion portion  21  of the noncircular cover  2  so as to wind it in the installation groove  23 , the fitting projection  32  is fitted into the fitting groove  24  sequentially. Accordingly, torsion of the packing  3  (the main body portion  31 ) is not caused, and it is possible to effectively prevent the sealing performance (the waterproof performance) from being deteriorated by poor installation. 
         [0077]    In this case, in the present invention, the fitting projection  32  may not be necessarily continuous in an endless shape in the extending direction of the packing  3 , but may be intermittent. In accordance with this, it is not necessary to carry out the work of fitting the fitting projection  32  to the installation groove  24  all over the periphery at a time of installing the packing  3 , and it is possible to prevent air from being included in the fitting groove  24 . 
       Fourth Embodiment 
       [0078]    Next,  FIG. 14  to  FIG. 19  show a fourth embodiment in accordance with the present invention. In a perspective view in  FIG. 14  among them, reference numeral  1  denotes a case of a compact electronic device, and reference numeral  2  denotes a cover which is detachably fitted to an opening portion  11  for inserting a battery or connecting a connector, provided in the case  1 . 
         [0079]    The opening portion  11  provided in the case  1  is structured such that an opening shape is, for example, a square shape having round corners such as an example in  FIG. 14 , or an elliptic shape (not shown). In other words, an inner peripheral surface  11   a  thereof has flat surface portions and curved surface portions alternately in a peripheral direction. 
         [0080]    The cover  2  has a tabular shape as a whole, and has an insertion portion  21  which can be inserted to the opening portion  11  of the case  1 , and a collar portion  22  which is formed so as to protrude out of an outer end portion of the insertion portion  21  and is opposed to an outer surface  1   a  of the case  1 . 
         [0081]    The insertion portion  21  of the cover  2  is formed, in its projection shape with respect to an inserting direction, in an approximately similar shape to the opening shape of the opening portion  11  of the case  1 , for example, a square shape having round corners as an example shown in  FIG. 16 , an elliptic shape as an example shown in  FIG. 17  and the like, that is, has flat surface portions and curved surface portions alternately in a peripheral direction, and is a little smaller than the opening portion  11 . Further, an installation groove  23  is peripherally provided in an outer peripheral surface  21   a  of the insertion portion  21  as shown in  FIG. 15  and  FIG. 16 , and the installation groove  23  has an approximately C-shaped cross section, that is, is constructed by a flat shaped bottom surface  23   a  which is in parallel to the outer peripheral surface  21   a  of the insertion portion  21 , and a pair of inner surfaces  23   b  which vertically rise from both sides thereof. 
         [0082]    A packing  3  made of a rubber-like elastic material (a rubber material or a synthetic resin material having a rubber-like elasticity) is installed to the installation groove  23  of the cover  2 . 
         [0083]    The packing  3  is molded in an annular shape so as to have a pentagonal cross sectional shape. As shown in  FIG. 18 , a height h in a radial direction is larger than a depth d of the installation groove  23 , an inner peripheral surface  3   a  brought into close contact with a bottom surface of the installation groove  23  has a flat shape, both side surfaces  3   c  and  3   d  rising from both ends in the width direction thereof have a vertical flat shape with respect to the inner peripheral surface  3   a,  and an outer peripheral surface which protrudes to an outer side of the installation groove  23  so as to be brought into pressure contact with an inner surface of the opening portion  11  of the case  1  in an appropriate deformed state is constructed by a peak portion  3   e,  and inclined surfaces  3   f  and  3   g  which extend toward both the side surfaces  3   c  and  3   d  from the peak portion  3   e.  The peak portion  3   e  is positioned at the center in the width direction of the packing  3 , and slopes of the inclined surfaces  3   f  and  3   g  at both sides of the peak portion  3   e  are equal to each other. In this case, the inner peripheral surface  3   a  corresponds to “close contact surface with the bottom surface of the installation groove” described in claim the sixth or seventh aspect. 
         [0084]    In a concrete example shown in  FIG. 18 , the packing  3  is structured such that a width w is about 1.1 mm, and a height h is about 1.0 mm, that is, a relation of h/w&lt;1 is established. Further, an angle θ formed by both the inclined surfaces  3   f  and  3   g  is about 74 degree, the peak portion  3   e  is chamfered so as to have a rounded surface in which a radius of curvature is about 0.3 mm, and the corner portions between the inner peripheral surface  3   a  and the side surfaces  3   c  and  3   d  and the corner portions between the side surfaces  3   c  and  3   d  and the inclined surfaces  3   f  and  3   g  are chamfered respectively so as to have rounded surfaces in which a radius of curvature is about 0.2 mm. 
         [0085]    In the fourth embodiment structured as mentioned above, the cover  2  is structured such that the insertion portion  21  is press fitted to the opening portion  11  of the case  1  via the packing  3  and the packing  3  is held in a state of being appropriately compressed between the bottom surface  23   a  of the installation groove  23  and the inner surface  11   a  of the opening portion  11 , thereby closing the opening portion  11  in a sealed state so as to achieve waterproofness. 
         [0086]    Further, in the packing  3 , since the inner peripheral surface  3   a  brought into close contact with the bottom surface  23   a  of the installation groove  23  has the flat shape, resistance at a time when force in a rolling (twisting) direction acts is large, and friction resistance with respect to the inner surface  11   a  of the opening portion  11  on the basis of compressive reaction force is small in addition as mentioned below. Accordingly, the packing  3  is not twisted in a process of fitting the cover  2  to the opening portion  11  as shown in  FIG. 19(B)  from a state in which the opening portion  11  is open as shown in  FIG. 19(A) , whereby an excellent sealing performance (waterproof performance) by the packing  3  is secured. Further, since the relation of h/w&lt;1 is established in the illustrated embodiment, this effectively contributes to the torsion prevention of the packing  3 . 
         [0087]    Further, in this packing  3 , the compressive reaction force becomes smaller, in comparison with the packing  3  having the D-shaped cross section, that is, having the convex surface in the circular arc cross sectional shape at its outer peripheral surface  3   b,  which is described previously and shown in  FIG. 4 . This is because a volume of the outer peripheral portion in the packing  3  in accordance with the present embodiment in which the outer peripheral surface is constructed by the peak portion  3   e  and the inclined surfaces  3   f  and  3   g  at both sides thereof is smaller, in comparison with the packing  3  in which the outer peripheral surface is formed into the circular arc shaped convex surface, as shown by a single dot chain line in  FIG. 18 , in the case that the height h is fixed, whereby an amount of compression becomes smaller in comparison with the packing  3  having the D-shaped cross section if a collapsing margin δ is fixed. Accordingly, friction resistance of the packing  3  with respect to the inner surface  11   a  of the opening portion  11  becomes smaller, and it is possible to reduce press-fit resistance at a time of fitting the cover  2  to the opening portion  11  as shown in  FIG. 19(B)  and abrasion of the packing  3 . 
         [0088]    Further, since the inner peripheral surface  3   a  brought into close contact with the bottom surface  23   a  of the installation groove  23  has the flat shape as mentioned above, the packing  3  is hardly twisted even in the installing process to the installation groove  23 , whereby it is possible to effectively prevent the sealing performance (the waterproof performance) from being deteriorated by poor installation. 
       Fifth Embodiment 
       [0089]    Next,  FIG. 20  to  FIG. 23  show a fifth embodiment in accordance with the present invention. 
         [0090]    In this fifth embodiment, a difference from the fourth embodiment mentioned above exists in a matter that the peak portion  3   e  of the packing  3  is deviated from the center in the width direction toward the opposite side to the cover inserting direction (a side of the collar portion  22  of the cover), as shown in  FIG. 20  and  FIG. 21 . In other words, a distance L 3  in an axial direction between the peak portion  3   e  and the side surface  3   c  at the cover inserting direction side is larger than a distance L 4  in an axial direction between the peak portion  3   e  and the side surface  3   d  at the opposite side to the cover inserting direction, and a slope α of the the inclined surface  3   f  at the cover inserting direction side is a relatively gentle slope, and a slope β of the inclined surface  3   g  at the opposite side to the cover inserting direction is a relatively steep slope, that is, a relation of a α&lt;β is established in the inclined surfaces  3   f  and  3   g  at both sides of the peak portion  3   e.  The other portions can be structured basically the same as the fourth embodiment. 
         [0091]    Therefore, in accordance with this structure mentioned above, similarly to the fourth embodiment, it is possible to effectively prevent torsion of the packing  3 , and it is possible to reduce abrasion of the packing  3 . 
         [0092]    Further, since the friction resistance of the packing  3  with respect to the inner surface  11   a  of the opening portion  11  of the case  1  becomes smaller in the cover inserting direction on the basis of the relation of α&lt;β, press-fit resistance at a time of fitting the cover  2  to the opening portion  11  as shown in  FIG. 22(B)  from a state in which the opening portion  11  of the case  1  is open as shown in  FIG. 22(A)  is further reduced. In addition, since the friction resistance becomes larger in the opposite direction to the cover inserting direction, the cover  2  hardly fall away by accident from the opening portion  11 . 
         [0093]    Further, since the peak portion  3   e  of the packing  3  is deviated from the center in the width direction toward the opposite side to the cover inserting direction, surface pressure P with respect to the inner surface  11   a  of the opening portion  11  of the case  1  is distributed so as to rapidly rise at the opposite side to the cover inserting direction, as shown in  FIG. 23 . Therefore, resistance against pressure of intrusion of water or the like from the external is increased, and it is possible to further enhance the waterproof performance. 
         [0094]    In this case, since there is a risk that the sealing performance is lowered and smooth opening and closing of the cover  2  become hard, if an offset amount of the peak portion  3   e  of the packing  3  is too large, it is desirable to set a ratio of L 3 :L 4  within a range between 1:1 and 5:1. 
       Sixth Embodiment 
       [0095]    Next,  FIG. 24  and  FIG. 25  shows a sixth embodiment in accordance with the present invention. 
         [0096]    In this sixth embodiment, the peak portion  3   e  is positioned at the center in the width direction of the packing  3 , a slope α of the inclined surface  3   f  at the cover inserting direction side is a relatively gentle slope, and a slope β of the inclined surface  3   g  at the opposite side to the cover inserting direction is a relatively steep slope, that is, a relation of α&lt;β is established in the inclined surfaces  3   f  and  3   g  at both sides of the peak portion  3   e.  Therefore, in accordance with the difference of the slopes α and β, a skirt portion  3   h  of the inclined surface  3   g  at the opposite side to the cover inserting direction is formed in a concave surface shape. The other portions can be structured basically the same as the fifth embodiment. 
         [0097]    Further, in accordance with this structure, similarly to the fifth embodiment, it is possible to reduce abrasion of the packing  3  as well as effectively preventing torsion of the packing  3 . Further, the same effect as the fifth embodiment can be obtained on the basis of the relation of α&lt;β. In other words, the friction resistance of the packing  3  with respect to the inner surface  11   a  of the opening portion  11  of the case  1  becomes smaller in the cover inserting direction and becomes larger in the opposite direction to the cover inserting direction. In addition, surface pressure with respect to the inner surface  11   a  of the opening portion  11  of the case is distributed so as to rapidly rise at the opposite side to the cover inserting direction, and resistance against pressure of intrusion of water from the external is increased. 
         [0098]    Further, in accordance with the sixth embodiment, in the case that the width w, the height h, the collapsing margin δ and the like of the packing  3  shown in  FIG. 25  are the same as those of the packing  3  shown in  FIG. 18  and described previously, an amount of compression (compressive reaction force) becomes further smaller in comparison with the packing  3  in  FIG. 18 . Therefore, it is possible to further reduce press-fit resistance at a time of fitting the cover  2  to the opening portion  11  and abrasion of the packing  3 .