Abstract:
An electrical connection box has upper and lower casing and locking components for locking the casings together in an assembled condition. An array of bus bars are mounted upright in the interior space of the casings. At least one of the casings has abutments pressing on the bus bars to maintain the bus bars in position. The bus bars urge the casings apart against the restraint of the locking components.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to electrical connection boxes containing bus bars, particularly electrical boxes suitable for use in vehicles, for example automobiles. 
     2. Description of the Related Art 
     U.S. Pat. No. 5,624,280 discloses an electrical branch joint box having identical upper and lower casings in which an array of upright sheet bus bars is mounted, with terminals of the bus bars projecting through the casings into connector sockets at the exterior face of the casings. The casings have mutually engageable snap-fit locking components, to lock them together in the assembled condition with the bus bars held between them. 
     FIGS. 8 and 9 of the drawings illustrate diagrammatically a problem which arises with casings of electrical connection boxes having snap-fit locking components. In FIG. 8, the box  51  has an upper casing  52  and a lower casing  53 . Wires and the like are accommodated in each of the upper and lower casings  52 , 53 . Locking projections  54  are formed at the lower edge of the outer side surface of the upper casing  52 . At the upper edge of the inner side surface of the lower casing  53 , there are locking recesses  55  in which the projections  54  fit. Fitting of the projections  54  in the recesses  55  allows the upper and lower casings  52 , 53  to be fixedly joined to each other. 
     However, as shown in FIG. 9, the projection  54  is able to enter the recess  55  owing to its elastic deformation in a direction shown by an arrow F. To allow this reliably, it is necessary to provide a predetermined clearance amount C between the projection  54  and a part of the recess  55 . Accordingly, there is looseness or play between the upper casing  52  and the lower casing  53  in correspondence to the length of the clearance C. As a result, due to vibrations generated during travel of a vehicle, the projection  54  and the recess  55  rub against each other to generate abnormal sounds. 
     In an electrical connection box having vertical bus bars disclosed in Japanese Laid-Open Patent Application No. 7-135717, two casing are joined by fitting them together, as illustrated in FIG. 9, and the resulting looseness between the two casings causes the vertical bus bars accommodated in the box to loosen. Therefore, vibration of the electrical connection box due, for example, to vibration of a vehicle, increases the risk that electrical contacts between tabs of the vertical bus bars and electric components connected to the tabs become defective. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an electrical connection box capable of minimizing or preventing looseness between assembled upper and lower casings and looseness of the bus bars included between the upper and lower casings. 
     According to the invention, there is provided an electrical connection box having an upper casing, a lower casing and mutually engageable locking components on the upper and lower casings for locking the casings together in an assembled condition, the inner sides of the casings defining an interior space when in the assembled condition. A plurality of bus bars are mounted upright in the interior space. At least one of the casings has at least one abutment pressing on the bus bars, when the casings are in the assembled condition and the locking components are engaged, in a manner that maintains the bus bars in desired positions and causes the bus bars to urge the casings apart against the restraint of the locking components. 
     The abutment or abutments pressing the bus bars are preferably projections or narrow rib-like bars, achieving contact with the bus bars at a small area, in order to provide a pressing force eliminating looseness and play. 
     In a preferred embodiment the bus bars have main longitudinal body portions of flat shape arranged upright in an array alongside each other and extending parallel to each other in a longitudinal direction, and the box has a plurality of the abutments in the form of longitudinal members each extending across the array of bus bars perpendicularly to the longitudinal direction of the bus bars, the members being spaced apart along the length of the bus bars. 
     In the invention, the reaction force generated by the engagement of the abutment or abutments and the bus bars urges the upper and lower casings apart. This prevents looseness or play at the locking components even though a clearance is provided between the locking components. The natural resilience and/or flexibility of the material of the casings permits the locking components to engage each other, while also allowing the bus bars to press the casings apart so as to eliminate looseness. Therefore, it is possible to prevent looseness between the upper and lower casings. The engagement force between the upright bus bars and the abutment or abutments thus also acts to prevent the bus bars from being loose in the casings. Thus, the bus bars can be reliably and securely placed at predetermined positions in the casings. The casings are typically made of a suitable electrically insulating plastic material having an inherent slight deformability. 
     If a plurality of abutments are arranged to act on the bus bars and extend transversely to the bus bar array and are disposed at predetermined intervals over the entire length of the bus bars, the array of bus bars are uniformly pressed in position, and the casings are urged apart in a balanced manner. 
     Pressure connection blades may be formed on the vertical bus bars so that by pressing an electrical wire against the pressure connection blades of adjacent or spaced bus bars, the bus bars can be electrically connected to each other. Such an arrangement makes it easy to electrically connect the bus bars and to design or alter a bus bar circuit. It is also easy to prevent the electric wire from being separated from the pressure connection blade as the bus bars are prevented from loosening. Accordingly, the reliability of the connection between electrical wires and the bus bars is improved. 
     The invention extends to use of the electrical connection box in a vehicle, for example, an automobile. 
     In this specification, including the claims, the directional terms “upper”, “lower”, etc. are used solely for convenience and clarity of description and definition. It is to be understood that the electrical connection box of the invention can be assembled and used in any orientation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the invention will now be described by way of non-limitative example with reference to the accompanying drawings, in which: 
     FIG. 1 is an exploded perspective view of an electrical connection box which is an embodiment of the invention; 
     FIG. 2 is an exploded perspective view from below of the electrical connection box of FIG. 1; 
     FIG. 3 is a sectional view on line  3 — 3  of FIG. 1; 
     FIG. 4 is a sectional view showing the assembled state of the electric connection box of FIG. 1; 
     FIG. 5 is a sectional view of a part of FIG. 4 enlarged; 
     FIG. 6 is a perspective view of a vertical bus bar of the box of FIG. 1, enlarged; 
     FIG. 7 is a perspective view showing an example of a modification of the bus bar circuit in the box of FIG. 1; 
     FIG. 8 is an exploded perspective view illustrating generally a problem of an electrical connection box having locking components; and 
     FIG. 9 is a partly enlarged sectional view taken along a line  9 — 9  of FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIGS. 1 and 2, an electric connection box  11  embodying aspects of the invention has an outer case constructed of an upper casing  12  and a lower casing  13  and an array  14  of bus bars housed in the assembled casings  12  and  13 . The upper casing  12  and the lower casing  13  are one-piece molded parts made of synthetic resin and formed to attach to each other. More specifically, locking projections  12   a  are formed on outer side surfaces of the upper casing  12 , and on inner side surfaces of the lower casing  13  there are molded shapes providing locking recesses  13   a  capable of receiving and locking in a snap-fit manner with the respective projections  12   a , to securely attach the upper and lower casings  12 , 13 . The material of the upper and lower casings  12 , 13  in this embodiment is PPT (polypropylene+talc). 
     The array  14  of the bus bars is comprised of ten bus bars  15   a - 15   j  each consisting of a one-piece metal plate or sheet lying upright. The bus bars  15   a - 15   j  have similar shapes and configuration and are formed by punching and bending sheet metal. As shown in FIG. 6, each of the bus bars  15   a - 15   j  includes body  21 , a plurality of tab terminals  22 , a plurality of projections  21   a  and a plurality of pressure connection blades  23 . The tab terminals  22  project from the upper side (as defined in FIG. 1) of the body  21  at regular intervals. The pressure connection blades  23  project at regular intervals from the lower side of the body  21 , and each is spaced along the body  21  at a position between longitudinal positions of adjacent tab terminals  22 . No connection blade  23  is formed at a longitudinal position corresponding to that of the tab terminal  22 . The tab terminals  22  and the connection blades  23  are alternately formed along the body  21 . A plurality of projections  21   a  are provided at regular intervals on the lower side of the body  21  at longitudinal positions corresponding to the longitudinal positions of the tab terminals  22  positions. The length of the lower edge of each projection  21   a  is greater than the width of a ridge or bar  27  of the lower casing  13 . 
     As shown in FIG. 1, a plurality of connector-receiving housings  24  for installation of components are formed integrally on the upper side of the upper casing  12 . As shown in FIG. 2, grooves  25  that accommodate the bus bars  15   a - 15   j  are formed on the lower side of the upper casing  12 . These grooves  25  are parallel with one another and spaced at regular intervals. 
     As shown in FIG. 1, bus bar accommodation grooves  26  are formed on the upper side of the lower casing  13  at positions corresponding to the grooves  25 . On the upper surface of the lower casing  13 , ridges or bars  27  extend perpendicularly to the grooves  26 . These ridges or bars  27  are formed at regular intervals and are substantially parallel with one another. The ridges or bars  27  are at positions corresponding to the positions of the projections  21   a  of the bus bars  15   a - 15   j  when assembled in the grooves  26 . 
     In the electrical connection box  11  having the above-described structure, as shown in FIGS. 1 to  4 , the bus bars  15   a - 15   j  are accommodated in the grooves  25 , with the tab terminals  22  projecting upwards. The bodies  21  of the bus bars  15   a - 15   j  are perpendicular to the bottom surface of the upper casing  12 . As shown in FIGS. 3 to  5 , the terminals  22  project through through-holes  24   a  formed through the bottom surface of each of the connector housings  24 , while the projections  21   a  and the pressure connection blades  23  are located in rows perpendicular to the longitudinal direction of the bodies  21  of the bus bars. 
     When it is necessary to design a bus bar circuit by electrically connecting different bus bars  15   a - 15   j , an electrical wire  31 , for example a single-core wire, is pressed against the desired pressure connection blades  23  by means of a pressing machine (not shown). The electrical wire is trapped in and electrically contacts the slots of the pressure connection blades  23  (see FIG.  7 ). Thereby, the appropriate bus bars  15   a - 15   j  are electrically connected to one another. Because the pressure connection blades  23  are arranged in rows, the electrical wires  31  can run linearly in a direction perpendicular to the longitudinal direction of the bodies  21 . In the exemplary embodiment shown in FIG. 2, the bus bars  15   a - 15   c  and the bus bars  15   g - 15   i  are electrically connected to each other respectively, by the two wires  31 . 
     In summary, the lower casing  13  is installed on the bottom face of the upper casing  12 . The upper and lower casings  12 , 13  are locked together by fitting the locking projections  12   a  of the upper casing  12  with the respective locking recesses  13   a  of the lower casing  13 . The locking projections components  12   a  and the locking recesses  13   a  have an amount of clearance C (see FIG. 5) to permit them to be fitted together. Upon completion of the attachment of the lower casing  13  to the upper casing  12 , as shown in FIG. 5, the ridges or bars  27  of the lower casing  13  press the projections  21   a  of the bus bars  15   a - 15   j . More specifically, as shown in FIG. 5, upon completion of the attachment of the lower casing  13  to the upper casing  12 , each ridge or bar  27  is higher than the lower edge of the projections  21   a  by a small amount h 1  (about 0.2 mm in the exemplary embodiment). Therefore, each bar  27  is slightly deformed by the projections  21   a  at their contact points. The natural resilience of the material of the casings maintains a tight contact of the bars  27  during use. Consequently, as shown with the arrow V 1  of FIG. 5, the bus bars  15   a - 15   j  are urged upward by the force applied by the bars  27 , and the lower casing  13  is urged downward by the reaction force, as shown with the arrow V 2  of FIG.  5 . Finally, the upper casing  12  is urged upward by the bus bars  15   a - 15   j . Thus the upper and lower casings  12 , 13  are urged apart minimizing or eliminating any play or looseness at the locking components. As FIG. 5 shows, mutually abutting faces of the locking projections  12   a  and the locking recesses  13   a  are pressed together to restrain the casings from moving apart. 
     It is possible to alter the bus bar circuit as desired for a particular use, by cutting off parts of the bus bars  15   a - 15   j . For example the body  21  may be cut at positions shown by broken lines C 1  in FIG. 6, so that the bus bar consists of two electrically divided component parts. Various bus bar circuits can thus be obtained, as shown, for example, in FIG.  7 . 
     When it is necessary to electrically connect non-adjacent bus bars, for example, the bus bars  15   f  and  15   j , a pressure connection blade  23  of each of the bus bars  15   g - 15   i  is cut off, as shown, for example, in FIG. 7, where each blade  23  is cut off at a position shown with broken line C 2  in FIG.  6 . In this case, the wire  31  is connected to the blades  23  of only the bus bars  15   f  and  15   j . Thereby, it is possible to electrically connect the bus bars  15   f  and  15   j  to each other reliably. 
     Accordingly, the following effects can be obtained in this embodiment. 
     (1) Upon fitting of the projection  12   a  on the recess  13   a , the bars  27  press the bus bars  15   a - 15   j  upward, so that the upper and lower casings  12 , 13  are urged apart, to minimize or prevent looseness between the upper casing  12  and the lower casings  12  despite the clearance provided between the locking projection  12   a  and the recess  13   a.    
     (2) The pressure between the ridge or bars  27  and the bus bars  15   a - 15   j  prevents the bus bars  15   a - 15   j  from being loose in the electric connection box  11 . The bus bars are securely held at predetermined positions in the electric connection box  11 . 
     (3) The ridges or bars  27  extend in parallel at regular intervals in a direction perpendicular to the longitudinal direction of the bus bars  15   a - 15   j . Thus, all the bus bars  15   a - 15   j  are pressed by each of the ridges or bars  27 . The upper and lower casings  12 , 13  are urged apart in a balanced manner at a plurality of spaced locations, to minimize or prevent looseness between the upper and lower casings  12 , 13 . 
     (4) Each bus bar  15   a - 15   j  has pressure connection blades  23 . Thus, the bus bars  15   a - 15   j  can be electrically connected to each other in a simple manner through electric wires  31  by pressing the wires  31  against the blades  23 . This eliminates a need for connection terminals for wires which fit on tab terminals  22  in known electrical connection boxes. Thus, it is easy to electrically connect the bus bars  15   a - 15   j . It is also easy to design or alter the bus bar circuit. 
     Further, as the bus bars  15   a - 15   j  are prevented from becoming loose, the risk that an electrical wire  31  will be separated from a blade  23  is reduced. Accordingly, the reliability of the connection between the electric wire  31  and the bus bars  15   a - 15   j  is improved. 
     (5) A plurality of projections  21   a  on each of the bus bars  15   a - 15   j  contact the ridges or bars  27  when properly positioned in the upper casing  12 . Therefore, it is possible to assure the location of the bus bars  15   a - 15   j  in the upper casing, by first assembling the bus bars  15   a - 15   j  and the upper casing  12 , thereby preventing defective positioning of the bus bars  15   a - 15   j . If the projections  21   a  project from the bottom surface of the upper casing  12 , they can be reliably brought into contact with the ridges or bars  27 . Further, because the length of the lower edges of the projections  21   a  is greater than the width of the ridges or bars  27 , the ridges or bars  27  can be reliably brought into contact with the projections  21   a.    
     (6) Each projection  21   a  is at a position corresponding to a longitudinal position of a tab terminal  22 , and is supported by one of the ridges or bars  27 . Thus, even when an insertion force of an electrical component is applied to the tab terminal  22  upon connection of an electrical component, the risk that a tab terminal  22  is depressed in the casings  12 , 13  is minimized. Thus, the risk of defective connection of an electrical component on the tab terminal  22  is substantially reduced. 
     (7) The top of a ridge or bar  27  is higher than the lower edge of a projection  21   a  by a small amount h 1 , for example 0.2 mm, upon locking of the lower casing  13  to the upper casing  12 . If this height h 1  is too large, it may be difficult to fit locking projection  12   a  in the locking recess  13   a . If the height h 1  is too small, the ridge or bar  27  may not be deformed sufficiently for the desired effect. Thus, by setting the height hi to about 0.2 mm in this example, it is possible to deform the ridges or bars  27  reliably, without making fitting of the projection  12   a  in the recess  13   a  difficult. 
     While the invention has been described in conjunction with the exemplary embodiment described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. 
     The following variations are mentioned as examples: 
     (1) The projections  21   a  may be omitted to allow each of the bus bars  15   a - 15   j  to have a more simplified structure, with the ridges or bars  27  contacting the bodies  21  of the bus bars directly. 
     (2) The ridges or bars  27  may be omitted and instead, abutments equivalent to the ridges or bars  27  may be formed on the bottom surface of the upper casing  12  to act as the abutment portions. That is, the abutments may be on the upper casing  12  or the lower casing  13 . 
     (3) The abutment is not limited to the bar  27 . It is possible to form a narrow projection in correspondence to each projection  21   a.    
     (4) The recesses  13   a  may be on the upper casing  12  and the locking projection  12   a  on the lower casing  13 . 
     (5) The bar  27  is higher than the lower edge of the projection  21   a  by a height h 1  of 0.2 mm upon connection of the lower casing  13  on the upper casing  12  and elimination of play at the locking components. However, this height hi is not limited to 0.2 mm, but for example may be in the range of 0.1 to 0.5 mm. 
     (6) The tab terminals  22  may be formed on both sides of the body  21 . That is, each of the bus bars  15   a - 15   j  may have the tab terminal  22  extending vertically upwards and downwards from the body  21 . 
     Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.