Abstract:
A structure for preventing an incorrect advance of screws capable of reliably preventing incorrect screw advance with a simple configuration is provided. The incorrect screw advance preventing structure of the present disclosure includes: a first member having a screw hole in which a screw thread corresponding to the screw is formed; and a second member having an opening provided in a position opposed to the screw hole, and a slope part that rises from a peripheral edge of the opening toward the first member. In this structure, a tip of a long screw which is inadvertently inserted is guided in a predetermined direction by the slope part. Therefore, it is possible to prevent the tip of the screw from reaching an area to be protected, or let the tip of the screw move away from the area to be protected.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation-in-part application of international patent application No. PCT/JP2011/001647, filed Mar. 18, 2011, which claims priority to Japanese Patent Application No. 2010-089102, filed on Apr. 8, 2010. The foregoing applications are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates to a structure for preventing an incorrect advance of screws. More specifically, the present disclosure relates to a structure, provided on a housing of electronic equipment, for preventing a tip of a screw from advancing toward a component that should be protected when an incorrect screw longer than the normal length is inserted. 
         [0004]    2. Description of the Related Art 
         [0005]    Japanese Laid-Open Patent Publication No. 11-294436 (this publication is called “Yamaguchi” hereafter) discloses a structure which prevents an incorrect insertion of a screw. In Yamaguchi, when an incorrect screw (component 4 in FIG. 1 of Yamaguchi) is screwed, the insertion of the screw is prevented when a tip of the screw reaches a blind hole (component 8). As a result, the screw inserting portion (component 53) is forced to rotate in a plane perpendicular to the insertion direction. However, this rotation is intercepted by a rotation intercepting component (component 54). As a result, advance of the screw can be stopped. 
       SUMMARY 
       [0006]    The present disclosure provides a structure for preventing an incorrect advance of screws which can reliably prevent an incorrect screw advance, with a simple configuration. 
         [0007]    The structure of the present disclosure includes: a first member having a screw hole in which a screw thread corresponding to the screw is formed; and a second member having an opening provided in a position opposed to the screw hole, and a slope part that rises from a peripheral edge of the opening toward the first member. 
         [0008]    According the structure of the present disclosure, it can reliably prevent incorrect advance of screws with a simple configuration. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1A  is a top view of a structure for preventing an incorrect advance of screws according to an embodiment of the present disclosure; 
           [0010]      FIG. 1B  is a front view of the above structure; 
           [0011]      FIG. 1C  is a bottom view of the above structure; 
           [0012]      FIG. 1D  is a left side view of the above structure; 
           [0013]      FIG. 2A  is a partial enlarged view of  FIG. 1A ; 
           [0014]      FIG. 2B  is a cross-sectional view taken along a line A-A′ in  FIG. 2A ; 
           [0015]      FIG. 3  is a perspective rear view of a plasma display  11  having the structure  1  for preventing an incorrect advance of screws shown in  FIG. 1 ; 
           [0016]      FIG. 4  is an enlarged view of the plasma display  11 , in which a dashed rectangle shown in  FIG. 3  is enlarged; 
           [0017]      FIG. 5  is a rear view of the plasma display  11  with a back cover being removed; 
           [0018]      FIG. 6  is a perspective view of a part of the plasma display  11  with a back cover being removed; 
           [0019]      FIGS. 7A and 7B  are side views illustrating a state where an incorrect screw is inserted in an instant structure; 
           [0020]      FIG. 8  is a side view illustrating a state where an incorrect screw is inserted in a modified structure; and 
           [0021]      FIG. 9  is a side view illustrating a state where a screw is inserted in another modified structure. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Hereinafter, embodiments will be described in detail with reference to the drawings. It should be noted that a detailed description more than a necessity may be omitted. For example, a detailed description of well-known matters or an overlapping description of substantially same configurations may be omitted. This is to avoid an unnecessarily redundant description below and to facilitate understanding of a person skilled in the art. 
         [0023]    It should be noted that the inventors provide the accompanying drawings and the following description so that a person skilled in art can fully understand the present disclosure, and this is not intended for limiting the definition of the subject matter defined by the claims. 
         [0024]      FIGS. 1A to 1D  illustrate a structure for preventing an incorrect advance of screws according to an instant example (this structure is referred to as “preventing structure  1 ” hereafter).  FIGS. 2A and 2B  are enlarged views of major parts of the structure shown in  FIG. 1 . Specifically,  FIG. 1A  is a top view,  FIG. 1B  is a front view,  FIG. 1C  is a bottom view, and  FIG. 1D  is a left side view. Further,  FIG. 2A  is a partial enlarged view of  FIG. 1A , and  FIG. 2B  is a cross-sectional view taken along a line A-A′ shown in  FIG. 2A . 
         [0025]    The preventing structure  1  is a member for receiving a screw for fastening another member. When an incorrect screw having a length longer than a designed value is inserted, the structure  1  prevents the tip of the screw from advancing toward a component to which this screw should not be contacted. The preventing structure  1  includes an upper plate part  5 , a lower plate part  6  facing the upper plate part  5 , and a vertical plate part  7  connecting the upper plate part  5  and the lower plate part  6 . In the instant example, the upper plate part  5 , the lower plate part  6 , and the vertical plate part  7  are integrally formed of a single metal plate by bending the metal plate. 
         [0026]    Referring to  FIG. 1A , screw holes  2  into which screws are to be screwed are formed in the upper plate part  5 . Referring to  FIG. 1C , openings  4  are formed in the lower plate part  6  at positions opposing the screw holes  2  (see  FIG. 1A  also). In the instant example, each of the openings  4  is a circular hole, and no screw thread is formed on the inner periphery of the opening  4 . Referring to  FIG. 1D , a sloping guide part  3  is formed by bending, toward the upper plate part  5 , a portion of the lower plate part  6  near its outer edge. The sloping guide part  3  has a slope which rises from a peripheral edge of the opening  4  toward the upper plate part  5  (see  FIG. 2B  also), and approaches the upper plate part  5  as the distance from the opening  4  increases. 
         [0027]    Hereinafter, the dimensions of the screw hole  2 , the opening  4 , and the sloping guide part  3 , and the positional relationship between them will be described in detail. 
         [0028]    In the instant example, the inner diameter of the opening  4  is designed smaller than the inner diameter of the screw hole  2 , and larger than the outer diameter of a tip of a screw having a screw thread conforming to the screw hole  2 . The center of the opening  4  does not coincide with the center of the screw hole  2 , and is deviated toward the vertical plate part  7 . Accordingly, the center axis B passing through the center of the screw hole  2  (which substantially coincides with the center axis of the screw having the screw thread conforming to the screw hole  2 ) does not coincide with the center axis C passing through the center of the opening  4 . 
         [0029]    Since the inner diameter of the opening  4  is smaller than the inner diameter of the screw hole  2 , and the center of the opening  4  deviates from the center of the screw hole  2  to the vertical plate part  7  side, the opening  4  side of the sloping guide part  3  comes beneath the screw hole  2  as shown in  FIG. 2A  and  FIG. 2B . 
         [0030]    For simplicity, holes other than the screw holes  2  and the openings  4  are not shown in  FIG. 1 . However, holes for attaching the preventing structure  1  to a housing of electronic equipment may be formed in the lower plate part  6 , for example. 
         [0031]    [Utilization of the Structure  1 ] 
         [0032]      FIG. 3  is a rear perspective view of a plasma display  11  having the preventing structure  1  shown in  FIG. 1 . This figure shows the view of the plasma display  11  when a back cover is removed.  FIG. 4  is an enlarged view of a dashed rectangle portion shown in  FIG. 3 . 
         [0033]    A plasma display  11  has a display section for displaying an image. A back cover  12  covers the entirety of the back surface of the plasma display  11 . The back cover  12  is screwed to the housing. A pair of handles  13  provided near the upper corners of the back surface of the plasma display  11  is for carrying the plasma display  11 . The handles  13  are screwed together with the back cover  12  onto the housing of the plasma display  11  by screws  14 . 
         [0034]    As shown in  FIG. 4 , a pair of screw holes are formed in the handle  13  at the position which contacts the outer surface of the back cover  12 . Likewise, each of the back cover  12  and the housing of the plasma display  11  have screw holes formed near their end edge. By using these screw holes, the housing of the plasma display  11 , the back cover  12 , and the handle  13  are screwed together with the screws  14 . Each of the screw holes in the housing of the plasma display  11  for attaching the handle  13  is equivalent to the screw hole  2  of the preventing structure  1  described above. Hereinafter, this is described in detail. 
         [0035]      FIG. 5  shows a rear view of the plasma display  11 .  FIG. 6  is a perspective view and an enlarged view of  FIG. 5 .  FIG. 6  differs from  FIG. 5  that it shows screws  14  screwed in each of the screw holes  2 . 
         [0036]    The preventing structure  1  is arranged so that the lower plate part  6  is positioned at the display section side of the plasma display  11 , and upper plate part  5  is positioned behind the lower plate part  6 . As shown in  FIG. 6 , the preventing structure  1  is fixed by screwing the lower plate part  6  to the housing. When the back cover  12  is attached, the outer surface of the upper plate part  5  contacts the inner surface of the peripheral edge of the back cover  12 . 
         [0037]    A plurality of wide flexible cables  15  are arranged on the peripheral edge of the plasma display  11 . The flexible cables  15  are used for transmission of video signals in the plasma display  11 , specifically a transmission between a plasma panel and a plasma panel controlling circuit provided on the rear edge side of the plasma panel. The flexible cable  15  has flexibility, but might be shorted or damaged when a sharp object such as the tip of the screw  14  contacts this cable. In the vicinity of the flexible cables  15 , the screw holes  2  are arranged, for screwing the screws  14  after covering the housing with the back cover  12 . The screws  14  shown in  FIG. 6  are normal-length screws (correct screws) for attaching the handle  13  to the housing. Accordingly, even when each screw  14  is completely tightened (screwed), the tip of the screw  14  does not reaches the flexible cables  15 , the sloping guide part  3  nor the opening  4 . 
         [0038]    However, at the time of attaching the handle  13 , if an incorrect screw longer than the design length is inadvertently inserted into the screw hole  2  and the advance direction of the incorrect screw deviates toward the inner side of the plasma display  11 , the tip of the incorrect screw might contact with the flexible cables  15 . In order to prevent such contact between the incorrect screw and the flexible cables  15 , the preventing structure  1  is utilized. 
         [0039]    Specifically, the preventing structure  1  is arranged such that the sloping guide part  3  is positioned on the side where an area that should be protected exists, so that a component inside this area is protected from being damaged by an inadvertent insertion of a long screw (hereinafter such area is referred to as “protection area”) is present. That is, the preventing structure  1  is attached to the housing so that the opening  4  and the protection area are arranged on the opposite side of the sloping guide part  3  between them. Further, considering the possibility that the incorrect screw might penetrate the opening  4  when a very large torque is applied, the protection area may be arranged in a space on the outer side of the lower plate part  6  (the space on the side opposite to the upper plate part  5 ) and at least not at a position opposing the opening  4 . 
         [0040]    [Incorrect Screw Advance Preventing Function] 
         [0041]      FIGS. 7A and 7B  are side views illustrating the state where the incorrect screw is inserted in the preventing structure  1 . Specifically,  FIG. 7A  shows the state where the tip of the incorrect screw  16  is contacted with the sloping guide part  3 , and  FIG. 7B  shows the state where the tip of the incorrect screw  16  is inserted in the opening  4 . 
         [0042]    The incorrect screw  16  is a screw whose nominal diameter (outer diameter) and screw pitch are equal to those of the screw  14  that is a normal screw, but the nominal length (length of the screw excluding the screw head) is considerably longer than that of the screw  14 . For example, when the normal screw  14  has a nominal diameter of 4 mm, a screw pitch of 0.7 mm, and a nominal length of 12 mm, the nominal length of the incorrect screw  16  is 40 mm or longer. In the international standard for safety of products, it is obligated that, when a screw having a length ten times longer than its nominal diameter is inadvertently inserted, this screw should be apart by at least a predetermined distance from an internal dangerous area (area that might cause ignition and/or smoking when damaged, such as a current-carrying portion). Thereby, in the instant example, the nominal length defined in the international standard is assumed as an exemplary length of the incorrect screw. 
         [0043]    When the incorrect screw  16  having the nominal length considerably longer than the normal length is inserted in the screw hole  2 , first, the tip of the incorrect screw  16  contacts with the sloping guide part  3  as shown in  FIG. 7A . This is because the sloping guide part  3  is arranged under the screw hole  2  as shown in  FIG. 2B  for example. 
         [0044]    When the incorrect screw  16  is further screwed from the state where its tip is in contact with the sloping guide part  3 , the tip of the incorrect screw  16  is guided leftward along the slope of the sloping guide part  3  to the opening  4  as shown in  FIG. 7A . As described above, the opening  4  is a through-hole having no screw thread formed therein, and is designed so that its inner diameter is smaller than the nominal diameter of the incorrect screw  16 , and is larger than the outer diameter of the tip of the incorrect screw  16 . Therefore, as shown in  FIG. 7B , the tip of the incorrect screw  16  fits into the opening  4 , and thereby unfavorable advance of the incorrect screw  16  is stopped. As a result, the incorrect screw  16  is prevented from contacting the flexible cables  15 . The inner diameter of the opening  4  may be smaller than the nominal diameter of the incorrect screw  16 , and the outer diameter of the tip of the incorrect screw  16 . Thereby, when a torque which is not very large is applied to the incorrect screw  16 , the incorrect screw  16  keeps spinning and will not be inserted in the opening  4 . Therefore, a person can notify that this screw is an incorrect screw. On the other hand, when an excessive torque is applied, the incorrect screw  16  fits into the opening  4 , and thereby unfavorable advance of the incorrect screw  16  is stopped. 
         [0045]    Further, since the tip of the incorrect screw  16  shifts leftward as shown in  FIG. 7A  guided by the sloping guide part  3 , the tip of the incorrect screw  16  fits into the opening  4  with its center axis of the incorrect screw  16  being tilted. This has following advantages. First, since the sloping guide part  3  exists, the incorrect screw  16  that is contacted with the sloping guide part  3  is guided to the opening  4 . That is, by existence of the sloping guide part  3 , the incorrect screw  16  is prevented from advancing toward the flexible cables  15 . Further, in the instant example, since the center of the opening  4  does not coincide with the center of the screw hole  2  and a portion of the sloping guide part  3  is located directly beneath the screw hole  2 , the tip of the incorrect screw  16  irresistibly contact with the sloping guide part  3 . Further, when the tip of the screw  16  is inserted to the opening  4 , the incorrect screw  16  is tilted. Therefore, even when a force in the screw insertion direction is applied to the incorrect screw  16  which is fitted to the opening  4 , not all of the force is applied in the vertical direction. That is, since the incorrect screw  16  is tilted, some of the insertion torque applied in the vertically downward direction is converted into horizontal direction components. As a result, it is possible to prevent the preventing structure  1  from being applied an excessive load. Further, even when an excessive torque is applied to the incorrect screw  16  in the state shown in  FIG. 7B , it is possible to prevent the incorrect screw  16  from being contacted with the flexible cables  15 . That is, if an excessive torque is applied, the incorrect screw  16  may cut off the inner surface of the opening  4  and penetrates the opening  4 , however, since the advancing direction of the tip of the incorrect screw  16  turns to the side opposite to the flexible cables  15  (turns leftward in  FIG. 7B ), the advancing direction of the incorrect screw  16  can be limited to a direction that the incorrect screw  16  does not contact with the flexible cables  15 . 
         [0046]    The insertion direction of the incorrect screw  16  may be limited by the angle of the center axis of the screw hole  2 . 
         [0047]    In the above example, the center axis of the opening  4  is deviated to the side opposite to the sloping guide part  3  with respect to the center axis of the screw hole  2 , however, the center axis of the screw hole  2  and the center axis of the opening  4  may be coaxial with each other. 
         [0048]    Further, the dimension of the opening  4  is not limited to the above-described dimension. The dimension of the opening  4  may be determined by performing an appropriate insertion experiment in accordance with the hardness of material, tightening torque, nominal diameter, and nominal length of a possible incorrect screw  16 , or the hardness of material of the sloping guide part  3 . 
         [0049]    The geometry of the opening  4  is not limited to a circle, as long as the tip of the incorrect screw  16  does not contact the flexible cables  15 . For the purpose of fitting the tip of the incorrect screw  16  to the opening  4 , the opening  4  may be a polygon such as hexagon or octagon, for example. However, if the opening  4  is circular, it is desirable because the pressing force is dispersed to the whole periphery of the opening  4  when the tip of the incorrect screw  16  fits into the opening  4 . 
         [0050]    Instead of the opening  4 , a recess that is not a through-hole may be formed. Alternatively, a screw thread may be formed in the opening  4 . However, a through-hole having no screw thread is favorable in a sense that the processing is facilitated. 
         [0051]    [Modifications] 
         [0052]      FIG. 8  is a side view of a modified structure for preventing an incorrect advance of screws. 
         [0053]    In the structure shown in  FIG. 8 , an opening  17  having an inner diameter larger than the inner diameter of the screw hole  2  is formed in the lower plate part  6 . In this structure, the tip of the incorrect screw  16  is guided to the opening  17  by the sloping guide part  3 , and then penetrates the opening  17 . Such a structure can be applied when a component which should be protected (such as flexible cables  15  or the like) is not present in the space beneath the opening  17  and therefore the incorrect screw  16  does not contact the protecting component even when it penetrates the opening  17 . Or, it can be applied when the incorrect screw  16  is not likely to be come close to the protecting component even when it penetrates the opening  17 . 
         [0054]      FIG. 9  is a side view illustrating a state where a screw is inserted in another modified structure for preventing an incorrect advance of screws. 
         [0055]    In the structure shown in  FIG. 9 , when a screw  18  is screwed into the screw hole  2 , at least a tip of the screw  18  is entering an opening  19 . This structure is achieved by adjusting the interval between the upper plate part  5  and the lower plate part  6 , and the length of the screw  18 . A screw thread may be formed on an inner periphery of the opening  19 , and the tip of the screw  18  may be screwed into the opening  19 . Alternatively, the tip of the screw  18  may be just brought into contact with the inner periphery of the opening  19 . In the structure shown in  FIG. 9 , the screw  18  bridges the upper plate part  5  and the lower plate part  6  to reinforce the screw receiving member comprising the upper plate part  5 , the lower plate part  6 , and a vertical plate part  7 . As a result, the rigidity of the screw receiving member is increased, thereby improving the resistance to thermal deformation or the like. 
         [0056]    In the above-described example, the upper plate part  5 , the lower plate part  6 , and the vertical plate part  7  are integrally formed by same member. However, these parts may be formed by different members. Alternatively, some or all of the upper plate part  5 , the lower plate part  6 , and the vertical plate part  7  may be formed integrally with the housing. However, the above described preventing structure is favorable when the upper plate part  5 , the lower plate part  6 , and the vertical plate part  7  are integrally formed by the same member. The reason is as follows. In such integrated configuration, the strength is not strong enough because an excessive torque may be applied by the incorrect screw  1  to the lower plate part  6 , with a contact point between the upper plate part  5  and the incorrect screw  16  being a fulcrum point  6 . On the other hand, in terms of cost, it is advantageous to integrally form the upper plate part  5 , the lower plate part  6 , and the vertical plate part  7  by the same member. In the instant preventing structure, unfavorable advance of the incorrect screw  16  is prevented by the sloping guide part  3  and the opening  4 , or by the guide part  3  and the opening  17 , even when an excessive torque is applied to the incorrect screw  16 . Accordingly, the structure of this modified example is suitable for such integrated plates, and is beneficial in terms of cost. 
         [0057]    In the above-described example, the slope of the sloping guide part  3  is plane. Instead, this may be curved. Further, two or more sloping guide parts  3  may be provided. 
         [0058]    The preventing structure of the above disclosure is applicable to electronic equipment such as a plasma display. 
         [0059]    The above examples have been described above as illustrative examples of the technology in the present disclosure. For that, the accompanying drawings and the detailed description have been provided. 
         [0060]    Therefore, the constituent elements described in the accompanying drawings and the detailed description may include not only constituent elements essential for solving the problems but also constituent elements non-essential for solving the problems, in order to illustrate the technology described above. Thus, these non-essential constituent elements should not be readily recognized as being essential, due to these non-essential constituent elements being described in the accompanying drawings and the detailed description. 
         [0061]    Furthermore, since the embodiments described above are intended to illustrate the technology in the present disclosure, various changes, substitutions, additions, omissions, and the like can be made within the scope of the claims and the scope of equivalents thereof.