Abstract:
Projections are provided in gaps between each wire opening for electric wire main bodies of a flat cable in a connection box to clamp and hold the flat cable. Stronger holding force is easily attained with smaller body size of the connection box for a flat cable. Various flat cables with deferent wire diameter are accepted in the same size connection box. The operation for assembling the connection box and the flat cable is facilitated.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to an electric wire holding structure for a connection box to protect the joint portion of a flat cable and terminals against external tensile force loaded on the flat cable, juxtapositionally combined in one with a plurality of electric wire main bodies and connected to terminals in a connection box body such a joint box body or the like and clamped at the connecting portions of the flat cable by the joint box body.  
           [0003]    2. Description of the Related Art  
           [0004]    [0004]FIG. 5 is showing one embodiment of an electric wire holding structure of a conventional connection box (joint box).  
           [0005]    A joint box body  43 , made of synthetic resin, includes a base  41 , a cover  42  and pressure contact terminals  44  made of a conductive metal inside. Intermediate position along the length of electric wires  26  is connected to the terminal  44  and the electric wire  26  extends out of gaps between the base  41  and the cover  42  and is formed into wave-like shape by three positions of a rib  24  provided on the base  41  for strain-relief, a rib  25  provided on the cover  42  for strain-relief and a wire opening  45  to protect joint portions of electric wires  26  and terminals  44  against external tensile force loaded on the electric wires  26  by cutting off transmitting the tensile force to the joint portion.  
           [0006]    A joint box  46  is provided mainly with the joint box body  43  and the pressure contact terminals  44 , connecting a plurality of the electric wires  26  reciprocally inside the joint box body  43 . The juxtapositionally terminal combined type with the same number of terminals  44  as the joints of the electric wires  26  may be used.  
           [0007]    The electric wires  26  is round type insulated electric wire which is round shape cross section conductive wire, covered with insulating resin to have round shape cross section. The pressure contact terminal  44  consists of a blade (not shown) cutting the insulation of the electric wires  26  and a slot (not shown), continuous to the blade, holding and connecting the conductive portion of the electric wires  26 . Instead of the pressure contact terminal  44 , a laser beam welding terminal or a crimp contact terminal which is crimp-contacted at the conductive portion, removed the insulation of the electric wires  26  at intermediate portion on the length direction, can be used.  
           [0008]    The joint box body  43  is formed in thin wall thickness rectangular solid shape and the base  41  and the cover  42  are jointed with thin hinges (not shown) on the side of each edge to be open-close free as an example. The ribs  24  (strain relief) as a part of the base  41  are provided at the both of front and back sides of the pressure contact terminals  44 , mounted on almost center of the base  41 . The ribs  25  (strain relief) are provided closely at outer side of the ribs  24  on the cover  42 . Each ribs  24 ,  25  extends long along radius direction of the electric wires  26  to form juxtaposed plural electric wires  26  in wavelike shape simultaneously.  
           [0009]    The wire openings  45  are provided closely outer side of the ribs  25  on the cover  42  in the both of front end and back end side of the joint box body  43 . In this description, front and back are defined along the length of the electric wires  26 . The wire openings  45  are to become round shape openings to be combined by each semicircle opening, formed opposite each other on the perpendicular walls of the base  41  and the cover  42  when the cover  42  closed.  
           [0010]    After connecting the electric wires  26  to the terminals  44 , owing to close the cover  42  to the base  41 , the electric wires  26  are pushed down to the bottom surface of the base  41  by the ribs  25  on the cover  42  and are formed in clank shape between the ribs  24  on the base  41  and the wire openings  45 . Therefore, very stronger tensile force, loaded on the electric wires  26 , enlarges friction force between the electric wires  26  and each ribs  24 ,  25 . Then, electric connection is kept in good condition because the loaded tensile force on the electric wires  26  is caught by the each ribs  24 ,  25  and transmission of the tensile force to the joint portion of the electric wires  26  and terminals  44  is prevented.  
           [0011]    This structure cannot be applied only on the joint box  46  but also on connection boxes, such a pressure contact connector which includes with base portion, cover portion and pressure contact terminals.  
           [0012]    In the electric wires holding structure of connection boxes by ordinary skills, forming the electric wires  26  in wavelike shape by ribs  25 ,  24 , projected upwardly and downwardly on inner surface of the joint box body  43  for strain relieves as tension relaxing parts, has issues to require enough rooms inside and bigger size of the joint box  46 .  
           [0013]    Further, very strong force for closing the cover  42  required to push the electric wires  26  and form the wires in radius direction of the wire with ribs  25  makes assembling of the joint box  46  troublesome. Forming a plurality of electric wires  26  simultaneously in the joint box is more troublesome.  
           [0014]    Adjusting the projecting height of ribs  24 ,  25  is required as lower height rib is for thicker wire and higher height rib is for thinner wire, various kinds of joint box body  43  are necessary for each size of the electric wires  26 . It makes a number of kinds on the joint box body  43  increased and manufacturing and administration costs push up.  
         SUMMARY OF THE INVENTION  
         [0015]    This invention has been accomplished to overcome the above drawbacks and an object of this invention is to avoid increasing outer size and inner room size of connection boxes such a joint box or the like and to provide an electric wire holding structure of a connection box, easily assembled as the cover can be easily closed and unnecessary to change the connection box body for each electric wire size.  
           [0016]    In order to attain the objects, regarding a connection structure having electric wires inserted through a gap between a base and a cover of a connection box body and terminals connected to the electric wires within said connection box, the connection structure comprising opposed projections for clamping connecting portions between each electric wire main body of a flat cable, which constitutes said electric wires, being provided at each end of wire lead-out side of said base and cover, whereby said connecting portions of said flat cable are fixed by clamping with the projection.  
           [0017]    In the above structure, a flat cable by connected plural electric wire main bodies juxtapositionally can be clamped strongly in a connection box body. Therefore, the reliability on electric connection of a flat cable and each terminal is improved, as each projection of the base and the cover holds the tensile force of the flat cable and eliminate the affection of the tensile force to a joint portion of electric wire main bodies and terminals, when a strong external tensile force loaded on the flat cable.  
           [0018]    Further, the inner room size of the connection box body can be shrunk and the connection box size can be miniaturized in the length and radius (vertical) direction of the electric wires because conventional ribs for pressing electric wires is not required and forming the electric wires wave-like inside the connection box body is not required. Manufacturability to close the cover, in other words, manufacturability of assembling the connection box is improved because disuse of forming the electric wires with sharp angle (close to 90 degree) and clamping with large deformation at the flat connecting portions of the flat cable as usual makes the force of closing the cover smaller. Even if the diameter of an electric wire main body changed, the pressing operation of the connecting portions is done by common method and the connection box body can be common use, because of pressing the connecting portions for connecting electric wire main bodies by the projections instead of pressing electric wire main bodies. This allows reducing manufacturing cost and administration cost of the connection boxes.  
           [0019]    Advantageously, each of said projections is formed between respective juxtaposed openings for electric lead-out wires. In this structure, the flat cable can be pressed uniformly at plural positions along juxtapositional direction of electric wire main bodies with the same interval and this allows stronger and more stable holding force for the flat cable and then connection area of the terminals can be protected reliably against the tensile force on the flat cable.  
           [0020]    Advantageously, each of said projections has flat surface at the top end for pressing connecting portions. In this structure, each flat surface at the top end of projections contacts closely the upper and down surfaces of the each connecting portion of the flat cable without gaps between the connecting portions and the top ends. Then, without slipping between the flat cable and the each top ends, pressing the flat cable with constant pressure by each projections along juxtapositional direction of the electric wire main bodies can react on strong tensile force in the whole width of the flat cable when the tensile force loaded on the flat cable.  
           [0021]    Advantageously, one of the projections is formed into convex shape at its top end while the other projection is formed into concave shape at its top end. In this structure, the convex section of the upper-side projections deform the thin connecting portions of the flat cable to push the connecting portions into the concave section of the down side projections and the connecting portions fit into the concave sections. Therefore, the friction force between the connecting portions and the projections is increased and then the holding force of the flat cable is increased to react against stronger tensile force on the flat cable.  
           [0022]    Advantageously, connection structure wherein said convex sections and said concave sections are formed into V-shape or semicircular shape. In this structure, as the connecting portions of the flat cable are deformed to fit tightly into the concave sections by V-shape convex and concave sections of the top ends of projections, the holding force of the flat cable is increased more and reacts strongly against the tensile force on the flat cable. Furthermore, clamping the connecting portions of the flat cable with semicircular shape concave and convex sections prevents to damage the connecting portions and then extends the life of the flat cable.  
           [0023]    The above and other objects, features and advantages of this invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    [0024]FIG. 1 is a front view of a connection box, showing one embodiment of an electric wire holding structure of a connection box according to this invention;  
         [0025]    [0025]FIG. 2 is a (longitudinally) sectional view taken along the line A-A of FIG. 1;  
         [0026]    [0026]FIG. 3 is a longitudinally sectional view of a connection box, showing other embodiment of an electric wire holding structure of a connection box according to this invention;  
         [0027]    [0027]FIG. 4 is a longitudinally sectional view of a connection box, showing more other embodiment of an electric wire holding structure of a connection box according to this invention;  
         [0028]    [0028]FIG. 5 is a longitudinally sectional view of a connection box, showing one embodiment of an electric wire holding structure of a conventional connection box; 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0029]    One embodiment of this invention will now be described with reference to the attached drawings.  
         [0030]    [0030]FIG. 1 (the front view) and FIG. 2 (the sectional view taken along the line A-A of FIG. 1) is showing one embodiment of an electric wire holding structure of a connection box according to this invention.  
         [0031]    In FIG. 1, connecting portions  2 , made of thin insulating resin material, joint a plurality of electric wire main bodies  1  lateral juxtapositionally to make a flat cable  3  (flat circuit body). Each connecting portion  2  of the flat cable  3  is pressed in clamping direction and held at wire openings  7  on the front end of a joint box body (connection box body)  6  by each projection  8 ,  9  of a base  4  and cover  5 .  
         [0032]    A couple of right and left locking projections  10  of the base  4  and flexible engaging flaps  11  of the cover  5  lock the joint box body  6  like an enclosure. As shown in FIG. 2, the rear portions of the joint box body  6  are connected to be open-close free with thin thick hinges  12 , as parts of the joint box body  6 . In this embodiment of the invention, the flat cable  3  is inserted through only the front end side of the joint box body  6  and the front edge of the flat cable  3  is placed near the inside rear end of the joint box body  6 .  
         [0033]    As shown in FIG. 1, the wire openings  7  are given as round shape by combining, in vertical direction, same inner radius semicircular openings  7   a  and  7   b,  formed on the base  4  and the cover  5 . Gaps  14  are formed horizontally connecting juxtaposed plural wire openings  7 , three openings in this embodiment, in the line made by the circle centers of the wire openings  7 . Rectangular shape projections  8 ,  9  are formed opposed vertically to each other in the gaps  14  for pressing the flat cable. The projections  8 ,  9  which top ends have horizontal flat surfaces  8   a  and  9   a  are continued through short steps  15  horizontally to inner radius surfaces of semicircular openings  7   a  and  7   b.    
         [0034]    The projections  8 ,  9 , formed narrow and sharp by the steps  15  in the electric wire radius direction, catch the thin flat connecting portions  2  of the flat cable  3  securely and press the connecting portions  2  with very high pressure force. As shown in FIG. 2, the projections  8 ,  9  are formed wide width, herein as the same width of the wall thickness of a front wall portion  13  along the length of the electric wire. It is possible to use partial area of the inner surface of the semicircular openings  7   a  and  7   b  as the lateral walls of the projections  8 ,  9 , eliminating the steps  15 .  
         [0035]    The flat cable  3  is inserted into the round shape wire opening  7  with small clearance for each round sectional electric wire main body  1  and each electric non-conductive flat connecting portion  2  of the flat cable  3  is placed in each horizontal gap  14  connecting respective wire openings  7 . The connecting portions  2  are clamped and held by opposed up and down projections  8 ,  9  as the upward projections  8  of the base  4  push up the bottom surface of the connecting portions  2  and the downward projections  9  of the cover  5  push down the upper surface of the connecting portions  2 . Therefore, when loaded strong tensile force on the flat cable  3 , friction force between upper and down projections  8 ,  9  and the connecting portions  2  of the flat cable  3  can hold the tensile force and avoid transmitting the force to joint portions of electric wire main body  1  and terminals  17  (FIG. 2) and then the joint portions are protected stably eliminating affection of tensile force on the flat cable  3 .  
         [0036]    Clamping the connecting portions  2 , jointing the electric wire main body  1 , by the projections  8 ,  9  instead of the electric wire main body  1  which has conductive body  1   a  of core wire and round shape synthetic resin insulation coating  1   b  on the conductive body  1   a,  allows to hold reliably the flat cable  3  regardless of external diameter size of the electric wire main body  1 . The wire pitch of the electric wire main bodies  1  is required to be placed in the wire openings  7  as the electric wire extending out of a model joint box body  6 . Adjusting the inner radius size of wire openings  7  to receive the maximum wire radius allows one model of joint box body  6  may be used for a various diameter size of electric wire main bodies  1 .  
         [0037]    As shown in FIG. 2, the electric wire main bodies  1  are connected to the pressure contact terminals  17  in almost middle of the joint box body  6 . Each electric wire main body  1  or some electric wire main bodies  1  required to be connected to each other are connected to each pressure contact terminal  17  which are combined juxtapositionally on a conductive board (not shown). Then, for example, electric current supplied on one electric wire main body  1  can be supplied on the other electric wire main body  1 . Placing the center line height of the electric wire main body  1  on the boundary line of the base  4  and the cover  5  in connecting condition of the wire and the terminals  17  is preferable to hold the electric wire main bodies  1  without bending.  
         [0038]    As same as conventional structure, the base  4  consists of a bottom wall  18 , a front wall  13 , a rear wall  19  and two lateral walls and the cover  5  consists of a upper wall  20 , a front wall  13 , a rear wall  21  and two lateral walls. At least, the terminals  17  and the terminal end of the flat cable  3  are placed in the rectangular room  22  formed inside by closing the base  4  and the cover  5 . A joint box (connection box)  23  consists of the terminals  17  and the joint box body  6 , provided with the base  4  and the cover  5 .  
         [0039]    The joint box body  6 , consisting of the base  4  and the cover  5 , is formed shorter in front-rear direction than the conventional joint box body corresponding to the required length to form the electric wire main body  1  wave-likely with plural ribs  24 ,  25  (FIG. 5). Furthermore, unnecessity of upper and down ribs  24 ,  25  and bending the electric wire main body  1  wave-like vertically can make the height of the joint box body  6  smaller.  
         [0040]    Further, as locking projections  10  of the base  4  and flexible engaging flaps  11  of the cover  5  lock the base  4  and the cover  5  with tight fitting and clamp the flat cable  3  at the front wall  13  of the joint box body  6 , the clamping force of the flat cable  3  is kept strongly for a long while and then the joint portion of the electric wire main body  1  and terminals  17  is protected reliably for tensile force on the flat cable  3 .  
         [0041]    [0041]FIG. 3 and FIG. 4 are showing other embodiments of an electric wire holding structure of connection box according to this invention. Compared with above embodiment by FIG. 1 and FIG. 2, the top ends of the projections  27 ,  28  (FIG. 3) and  29 ,  30  (FIG. 4) pressing the connecting portions  2  of the flat cable  3  are formed in V-shape or semicircular shape. As the other structure of these embodiments is the same as the structure shown in FIG. 2, detailed description on the other structure of these embodiments is omitted herein.  
         [0042]    Regarding the structure shown in FIG. 3, a projection  28  of the cover  5  is formed downwardly in convex V-shape and a projection  27  of the base  4  is formed in concave V-shape. A relatively sharp convex V-shape top (convex section)  28   a  of the upper projection  28  and a concave V-shape top (concave section)  27   a  of the downside projection  27  have respectively a front slant wall  31  and a rear slant wall  32  symmetrically on front and rear portions in the length direction of the electric wires. Each projection  27 ,  28  is placed between each wire opening  7  as same as FIG. 1. The front side width of the projection  27 ,  28  between each wire opening  7  is narrow, but the width of the projection  27 ,  28  along the length of electric wires is as same as wall thickness of the front wall  13  as shown in FIG. 3 and is relatively wide to form V-shape slant walls  32 ,  32  with enough length.  
         [0043]    Shutting the cover  5 , the thin plate shape connecting portions  2 , made of synthetic resin, are clamped with pressure and deformed V-shape between the convex V-shape top  28   a  of the upper projection  28  and the concave V-shape top  27   a  of the downside projection  27 . Therefore, the counter force to the tensile force on the electric wire main body  1  is remarkably increased and the joint portion of the electric wire main body  1  and the terminals  17  is protected more reliably not to be affected by the tensile force.  
         [0044]    Regarding the FIG. 4 structure, a projection  30  of the cover  5  is formed downwardly in convex semicircular shape and a projection  29  of the base  4  is formed in concave semicircular shape. The upper projection  30  has a relatively small curved convex semicircular shape top (convex section)  30   a  and the downside projection  29  has a concave semicircular shape top (concave section)  29   a.  In this embodiment, the convex semicircular shape top  30   a  and the concave semicircular shape top  29   a  have respectively a front curved wall  33  and a rear curved wall  34  symmetrically on front and rear portions in the length direction of the electric wires. Each projection  29 ,  30  is placed between each wire opening  7  as same as FIG. 1. The front side width of the projection  29 ,  30  between each wire opening  7  is narrow, but the width of the projection  29 ,  30  along the length of wire is as same as wall thickness of the front wall  13  as shown in FIG. 4 and relatively wide to form semicircular shape curved walls  33 ,  34  with enough length.  
         [0045]    Shutting the cover  5 , the thin plate shape connecting portions  2 , made of synthetic resin, are clamped with pressure and deformed semicircular shape between the convex semicircular shape tops  30   a  of the upper projections  30  and the semicircular shape curved walls  33 ,  34  of the downside projections  29 . Therefore, the counter force to the tensile force on the electric wire main body  1  is remarkably increased and the joint portion of the electric wire main bodies  1  and the terminals  17  is protected more reliably not to be affected by the tensile force.  
         [0046]    A convex trapezoid-like shape top and a concave trapezoid-like shape top instead of the convex V-shape top and the concave V-shape top of the projection  28 ,  27  in FIG. 3 is effected. Further, a slope curved shape instead of the complete arc shape as the convex semicircular shape top and the concave semicircular shape top of the projection  30 ,  29  in FIG. 4 is effected. In short, a hooking part in cross direction for the flat cable is accepted. Furthermore, providing projections  28  with convex V-shape top on the base  4  and projections  27  with concave V-shape top on the cover  5  is effected. Providing projections  30  with convex semicircular shape top on the base  4  and projections  29  with concave semicircular shape top on the cover  5  is also effected.  
         [0047]    Advantageously, although the front wall of the joint box body  6  may hold the flat cable  3  in each of above embodiments, inserting the flat cable  3  through the right and left end walls of the joint box body  6 , the similar projections, such as projections  8 ,  9 ,  27 ,  28 ,  29 ,  30  as mentioned above, provided on said right and left end walls, can hold the flat cable  3  on two positions along the length of the flat cable  3  at same time.  
         [0048]    Preferably, the terminal  17  is effected by not only pressure contact type but also crimp type or welding type. As electric wire joint portions of pressure contact terminals are easily disjointed by tensile force on the cable, above mentioned structure is especially effective for pressure contact type terminals. Opening and shutting the cover  5  and the base  4  without hinges  12  can be used and such structure requires at least two locking projections  10  and flexible engaging flaps  11  (FIG. 1) as locking means on the front and rear walls or on the right and left walls of the joint box body  6 .  
         [0049]    Preferably, the flat cable (flat circuit body) is made of not only the round type electric wire main body  1  but also a flat circuit wire, a printed wire or the like (not shown).  
         [0050]    Advantageously, above mentioned structure can be used not only for the joint box body  6  but also for a base and a cover of a pressure contact connector (not shown) as a kind of a connection box or for flat wire (flat wire harness) holding in an electric connection box (not shown).