Abstract:
A housing body contains the fuse body therein. The fuse body is formed with an opening and a retaining projection arranged in the vicinity of the opening. A cover body is formed with a locking piece adapted to engage with the retaining projection so that the cover body closes the opening. A rigidity-reduced portion is formed in the cover body, so that the cover body can be flexed substantially without flexing the locking piece, at least when the locking piece engages with the retaining projection.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to a fuse used for protecting an automotive electric circuit or the like, and more particularly to an improved fuse in which a fuse body is housed and held in a housing provided with a cover.  
           [0002]    [0002]FIGS. 6 and 7 show a related-art fuse used for protecting an electric circuit in an automobile or the like.  
           [0003]    A fusible link  1  is a so-called plug-in type fuse, and comprises a fuse body  2  made of a metal sheet, a housing  3  which is made of an insulative resin, and has the fuse body  2  housed and held therein (the fuse body  2  is inserted into the housing  3  through a rectangular upper opening), and a cover  4  which is made of an insulative resin, and covers the upper opening in the housing  3 .  
           [0004]    As shown in FIG. 7, the fuse body  2  includes a strip-like fusible conductor  10  having a melting portion  10   a , and a pair of female terminals  11  and  11  which are formed respectively at both ends of the fusible conductor  10 , and can be fittingly connected respectively to mating tab terminals  15  formed on a circuit provided at a fuse receiving portion  13 . This fuse body  2  is formed into an integral construction, using a metal sheet.  
           [0005]    The cover  4  includes a lid  5  in the form of a generally rectangular plate, and a pair of locking pieces  6  extending downwardly respectively from opposite end edges of the lid  5 , and this cover  4  is molded into an integral construction, using a transparent plastic material. Retaining projections  7  are formed on and project respectively from those side walls (peripheral wall) of the housing  3  corresponding respectively to the locking pieces  6 . When the pair of elastic locking pieces  6  are retainingly engaged with the retaining projections  7 , respectively, the cover  4  is locked to the housing  3  in such a manner that this cover  4  covers the upper opening in the housing  3 .  
           [0006]    As shown in FIG. 7, the fusible link  1  is mounted in the fuse receiving portion  13  formed at an electric connection box such as a relay box, and the fuse body  2  is electrically connected to the mating tab terminals  15 . A fuse guide wall  14  for supporting the housing  3  is formed at the fuse receiving portion  13 , and this fuse guide wall  14  serves to guide the mounting insertion of the fusible link  1 , and also serves to prevent the fusible link  1  from being displaced out of position after the fusible link  1  is mounted.  
           [0007]    In recent years, electric connection boxes have increasingly been required to have a compact and lightweight design and a reduced cost, and in this connection fuses also have been required to have a compact and lightweight design.  
           [0008]    Therefore, for example, when a fuse body  22  as well as a housing  23  has a compact design (a reduced height) as in a fusible link  21  shown in FIG. 8, this fusible link  21  can be much more reduced in size and weight as compared with the fusible link  1  shown in FIG. 7.  
           [0009]    And besides, since the fusible link  21  has the compact design and the reduced height, a cover of an electric connection box can be reduced in height, so that the compact and lightweight design of the electric connection box is also achieved.  
           [0010]    In the fuse body  22 , secondary (subsequent) short-circuit or the like must be prevented when a fusible conductor  28  melts, and therefore it is difficult to further reduce the distance between a pair of female terminals  29 .  
           [0011]    Therefore, horizontal dimensions and shapes of the fuse body  22  and housing  23  are substantially the same as those of the fuse body  2  and housing  3  of the fusible link  1 , and a cover  24  has the same shape as that of the cover  4 , and the cover  24  is locked to the housing  23  by locking pieces  26  retainingly engaged respectively with retaining projections  27  formed on and projecting from a peripheral wall of the housing  23 .  
           [0012]    However, when the fusible link  21  is to be mounted in the fuse receiving portion  13  formed at the electric connection box such as a relay box, as shown in FIG. 8, the locking pieces  26  interfere with an upper edge of the fuse guide wall  14 , so that this fusible link  21  can not be mounted in the proper position in the fuse receiving portion  13 .  
           [0013]    Therefore, it is necessary to take countermeasures such as the reduction of the height of the fuse guide wall  14  and the formation of notches for preventing the interference. However, such countermeasures for the fuse guide wall  14  will incur a change of a mold for molding an electric connection box body and a complicated construction of the mold, so that the cost greatly increases.  
           [0014]    When the locking pieces  26  of the cover  24  are shortened so as to prevent the interference thereof with the upper edge of the fuse guide wall  14 , each locking piece  26  is less elastically deformed when it slides over the retaining projection  27 . Incidentally, when each retaining projection  27  is reduced in height so that the locking piece  26  can easily slide over the retaining projection  27 , a sufficient retaining force can not be obtained, and the cover  24  can be easily disengaged from the housing.  
           [0015]    When the locking pieces  26  are shortened, and therefore are less elastically deformed, there are anxieties that the cover  24  can not be easily fitted on the housing, and that each locking piece  26  is damaged at its proximal end portion on which an excessive force acts.  
         SUMMARY OF THE INVENTION  
         [0016]    It is therefore an object of this invention to provide a fuse having a compact and lightweight design while being provided with a cover having locking pieces which are prevented from damage.  
           [0017]    In order to achieve the above object, according to the invention, there is provided a fuse, comprising:  
           [0018]    a fuse body, provided with a fusible element;  
           [0019]    a housing body, containing the fuse body therein, and formed with an opening and a retaining projection arranged in the vicinity of the opening; and  
           [0020]    a cover body, formed with a locking piece adapted to engage with the retaining projection so that the cover body closes the opening,  
           [0021]    wherein a rigidity-reduced portion is formed in the cover body, so that the cover body can be flexed substantially without flexing the locking piece, at least when the locking piece engages with the retaining projection.  
           [0022]    In such a configuration, even when the locking piece is short, the cover body itself is elastically deformed at the rigidity-reduced portion so that the locking piece can be displaced in the disengaging directions respectively relative to the retaining projection.  
           [0023]    Since an excessive force will not act on the locking piece which is displaced so as to slide over the corresponding retaining projection, damage to the locking pieces is prevented.  
           [0024]    Therefore, there can be obtained the compact and light-weight fuse provided with the cover body having the relatively short locking piece.  
           [0025]    Preferably, the rigidity-reduced portion is a recessed portion formed in a face of the cover body to be opposed to the opening.  
           [0026]    In such a configuration, merely by forming the recessed portion in the cover body, the rigidity-reduced portion which enables the elastic deformation of the cover body can be easily formed. Further, by suitably determining the width and depth of the recessed portion, the retaining force of the locking piece can be arbitrarily adjusted.  
           [0027]    Preferably, the locking piece includes a pair of locking pieces, which are arranged symmetrically with respect to the rigidity-reduced portion.  
           [0028]    Preferably, the fusible element is exposed through the opening, in a case where the cover body does not close the opening. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]    The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein:  
         [0030]    [0030]FIG. 1 is an exploded, perspective view of a fuse according to a first embodiment of the present invention;  
         [0031]    [0031]FIG. 2 is a perspective view of a cover of the fuse, showing an inner side thereof;  
         [0032]    [0032]FIGS. 3A and 3B are partly cross-sectional, front views explanatory of a mounting operation of the cover on a housing;  
         [0033]    [0033]FIG. 4 is a partly cross-sectional view showing a condition in which the fuse is mounted in a fuse receiving portion;  
         [0034]    [0034]FIG. 5 is a perspective view of a cover of a fuse according to a second embodiment of the present invention;  
         [0035]    [0035]FIG. 6 is a perspective view of a related-art fuse;  
         [0036]    [0036]FIG. 7 is a partly cross-sectional view showing a condition in which the related-art fuse is mounted in a fuse receiving portion; and  
         [0037]    [0037]FIG. 8 is a cross-sectional view explanatory of problems encountered when the related-art fuse is formed into a compact design. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]    Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.  
         [0039]    As shown in FIG. 1, a fusible link  31  according to a first embodiment is a so-called plug-in type fuse, and comprises a fuse body  32  made of a metal sheet, the housing  33  which is made of an insulative resin, and has the fuse body  32  housed and held therein (the fuse body  32  is inserted into the housing  33  through a rectangular upper opening  45 ), and the cover  34  which is made of an insulative resin, and covers the upper opening  45  in the housing  33 .  
         [0040]    As shown in FIG. 1, the fuse body  32  includes a strip-like fusible conductor  40  having a melting portion  40   a , and a pair of female terminals  41  which are formed respectively at both ends of the fusible conductor  40 , and can be fittingly connected respectively to tab (male) terminals  15  formed on a circuit provided at the fuse receiving portion  13 . This fuse body  32  is formed into an integral construction, using a metal sheet.  
         [0041]    As shown in FIGS. 1 and 2, the cover  34  includes a lid  35  in the form of a generally rectangular plate, and a pair of locking pieces  36  extending downwardly respectively from opposite end edges of the lid  35 , and this cover  34  is molded into an integral construction, using a transparent plastics material. The locking pieces  36  of the cover  34  are much shorter than the locking pieces  6  of the cover  4  shown in FIG. 6.  
         [0042]    Retaining projections  46  are formed on and project respectively from upper portions of those side walls (peripheral wall) of the housing  3  corresponding respectively to the locking pieces  36 . When the pair of locking pieces  36  are retainingly engaged with the retaining projections  46 , respectively, the cover  34  is locked to the housing  33  in such a manner that this cover  34  covers the upper opening  45  in the housing  33 .  
         [0043]    As shown in FIG. 2, rigidity-reduced portions  37  are formed at an inner surface of the lid  35 , and these rigidity-reduced portions  37  enable the lid  35  to be elastically deformed so that the locking pieces  36  can be displaced in disengaging directions relative to the retaining projections  46 , respectively.  
         [0044]    In this embodiment, the rigidity-reduced portions  37  are defined respectively by notch grooves formed by notching part of a reinforcing rib  38  formed on the inner surface of the lid  35  at a peripheral edge portion thereof.  
         [0045]    Namely, two portions of the reinforcing ribs  38 , disposed on a centerline S passing between the pair of locking pieces  36  on the lid  35 , are notched to provide the notch grooves, respectively, and as a result the rigidity-reduced portions  37 , which are lower in rigidity than those portions having the remaining reinforcing rib  38 , are formed at the opposite end edge portions, respectively. Therefore, the lid  35  can be elastically deformed about the centerline S.  
         [0046]    Next, the procedure of assembling the fusible link  31  of this embodiment will be described with reference to FIGS. 3A and 3B.  
         [0047]    First, the fuse body  32  is inserted into the housing  33  through the upper opening  45 , and is housed and held in this housing as shown in FIG. 3A.  
         [0048]    Then, the cover  34  is put on the housing  33  to cover the upper opening  45 , and the outer surface of the lid  35  is pressed, thereby bringing the locking pieces  36  into retaining engagement with the retaining projections  46 , respectively.  
         [0049]    At this time, the locking pieces  36  on the cover  34  are hardly elastically deformed in the disengaging directions relative to the retaining projections  46 , respectively, since these locking pieces  36  are very short as described above. However, the lid  35  itself is elastically deformed at the rigidity-reduced portions  37  as shown in FIG. 3B, so that the locking pieces  36  can be displaced in the disengaging directions (left and right directions in this figure) respectively relative to the retaining projections  46  formed on and projecting from the peripheral wall of the housing  33 .  
         [0050]    Therefore, since an excessive force will not act on each locking piece  36  which is displaced so as to slide over the corresponding retaining projection  46 , damage to the locking pieces  36  is prevented.  
         [0051]    Accordingly, there can be obtained the compact fusible link provided with the cover  34  having the short locking pieces  36 .  
         [0052]    When the fusible link  31 , having the short locking pieces  36 , is mounted in a fuse receiving portion  13  (as same as that shown in FIGS. 7 and 8) formed at an electric connection box such as a relay box, the locking pieces  36  will not interfere with an upper edge of a fuse guide wall  14  as shown in FIG. 4, and this fusible link can be mounted in a proper position in the fuse receiving portion  13 .  
         [0053]    Therefore, it is not necessary to take countermeasures such as the reduction of the height of the fuse guide wall  14  and the formation of notches for preventing the interference, and a change of a mold for molding the electric connection box body and a complicated construction of the mold will not be incurred, so that the cost will not greatly increase.  
         [0054]    Therefore, the fusible link  31  of this embodiment can be much more reduced in size and weight as compared with the related-art fusible link  1  shown in FIG. 6, and particularly as a result of the reduction of the height, a cover of the electric connection box can be reduced in height, so that the compact and lightweight design of the electric connection box can also be achieved.  
         [0055]    The constructions of the fuse body, housing, cover, lid, locking pieces, rigidity-reduced portions, etc., of the fuse of the invention are not limited to the constructions of the above embodiment, but can take various constructions on the basis of the subject matter of the invention.  
         [0056]    For example, as second embodiment, a rigidity-reduced portion  57 , provided at a cover  54  of FIG. 5, is defined by a notch groove formed in a generally-rectangular plate-like lid  55  and extending along a centerline S passing between a pair of locking pieces  36  on the lid  55 . This lid can be elastically deformed about the centerline S. Of course, the cross-sectional shape of the notch groove and so on can take various shapes.  
         [0057]    In the above embodiment, although the fuse body  32  of the fusible link  31  is of such a construction that the pair of female terminals  41  are formed integrally with the opposite ends of the fusible conductor  40 , the fuse body may be of such a construction that so-called screw-fastening terminals are connected integrally to the opposite ends of the fusible conductor  40 , respectively.  
         [0058]    The fusible conductor may be of such a construction that it has a first melting portion and a second melting portion.