Abstract:
A power distribution box and a method for producing a PDB include molding a lower cover with an integrated protector plate such that a unitary structure is formed. A busbar is inserted into a bottom side of a frame, and a lower cover is attached to the frame from the bottom side, thereby capturing the busbar between the frame and the lower cover. Integrating the protector plate into the lower cover eliminates a molding process, an assembly process, and adds structural integrity to the lower cover without the addition of extra structural support members, thereby reducing material use and the weight of the assembled device.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a power distribution box and a method for producing a power distribution box. 
       BACKGROUND 
       [0002]    Power distribution boxes (PDB&#39;s) are used in various electric and electronic systems, including passenger and commercial vehicles, were there commonly used as fuse boxes. A PDB may consist of a number of different components such as a lower cover, a busbar and a frame, and may be assembled using a “top-down” or “bottom-up” method. Examples of PDB&#39;s using these assembly methods are described, for example, in the patent U.S. Pat. No. 7,371,080 issued to Masters et al. on 13 May 2008, which is hereby incorporated herein by reference. As described in Masters et al. the addition of a separate protector plate to separate wires from the electrically conducting surfaces of the busbar complicates assembly of the PDB. 
         [0003]    In addition, a separately molded protector plate requires retaining features so that it can be attached to a lower cover, and additional retaining features so that it can be attached to the frame. Depending on the particular application for the PDB, it may need to meet certain structural strength requirements. Because the protector plate is a separate piece, it does not contribute significantly to the strength of the lower cover, and the lower cover may need to be constructed with a number of structural reinforcements. Therefore, a need exists for a PDB wherein a protector plate does not need to be separately assembled to a lower cover or frame, thereby eliminating the need for an assembly step, and eliminating separate retaining features provided on the mating components. A need also exists for a PDB having a protector plate that can add structural integrity to a lower cover, thereby helping to eliminate additional structural support members, leading to reduced overall weight and wall thickness for the lower cover. 
       SUMMARY 
       [0004]    At least some embodiments of the present invention include a power distribution box (PDB) having a bottom-up construction and including a frame including a top side, a bottom side, and a plurality of frame apertures disposed therethrough. A busbar is connectable to the bottom side of the frame and has a plurality of busbar terminals extending upwardly for insertion into corresponding apertures in the frame. A lower cover has an integrated protector plate and together they form a unitary structure. The lower cover is connectable to the frame from the bottom side of the frame and includes a plurality of cover apertures therethrough for receiving wires to be inserted into corresponding frame apertures. The integrated protector plate has a plurality of wire protecting features for inhibiting contact between the busbar and wires disposed through the lower cover and retained by the frame. 
         [0005]    At least some embodiments of the present invention include a PDB having a bottom-up construction and including a frame including a top side, a bottom side, a plurality of frame apertures disposed therethrough, and a plurality of wire retaining features. Each of the wire retaining features is configured to retain a corresponding wire inserted from the bottom side of the frame. A busbar is disposed on the bottom side of the frame and has a plurality of busbar terminals extending upwardly through corresponding frame apertures. A lower cover is disposed on the bottom side of the frame and includes a plurality of cover apertures therethrough for receiving wires to be retained by the frame. The lower cover further includes an integrally molded protector plate having a plurality of wire protecting features for inhibiting contact between the busbar and wires disposed through the lower cover and retained by the frame. 
         [0006]    At least some embodiments of the present invention include a method for producing a PDB including molding a lower cover with an integrated protector plate, inserting a busbar into a frame from a bottom side of the frame and attaching the lower cover to the frame from the bottom side of the frame. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  shows an exploded view of a PDB in accordance with embodiments of the present invention; 
           [0008]      FIG. 2  shows a bottom view of a lower cover of a PDB in accordance with embodiments of the present invention; 
           [0009]      FIG. 3  shows a perspective view of the lower cover shown in  FIG. 2 ; 
           [0010]      FIG. 4  shows the lower cover illustrated in  FIG. 3  with a busbar attached; and 
           [0011]      FIG. 5  shows a cross-sectional view of the lower cover and busbar shown in 
           [0012]      FIG. 4  assembled with a frame and wedge. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0014]      FIG. 1  shows a power distribution box (PDB)  10  in accordance with an embodiment of the present invention. The PDB  10  includes a frame  12 , a busbar  14 , and a lower cover  16 . A plurality of wires  18  are shown below the lower cover  16 , and as explained in more detail below, are configured to be inserted through a bottom side  17  of the lower cover  16  and apertures in the lower cover  16  and apertures in the frame  12  where they are retained by wire retaining features. As discussed in more detail below, wire retaining features in a frame, such as the frame  12 , may engage the wire itself—e.g., insulation on the outside of the wire—or it may engage a terminal on an end of the wire; in either case, the effect is that the wire is retained within the frame. The frame  12  includes a top side  20  and a bottom side  22 . A plurality of frame apertures  24  (for clarity, not all of the apertures are labeled) are disposed through the top and bottom sides  20 ,  22 . 
         [0015]    The busbar  14  includes a plurality of busbar terminals  26  (also for clarity, not all of the terminals are labeled) extending upwardly for insertion into corresponding apertures  24  in the frame  16 . The horizontally extending member  28  of the busbar  26  includes a pair of apertures and is configured for connection to a power source, such as a vehicle battery. The lower cover  16  includes an integrated protector plate  30 , which forms a unitary structure with the rest of the lower cover  16 . In particular, the protector plate  30  is integrally molded with the rest of the lower cover  16  in a single mold. This provides a number of advantages over PDB&#39;s that use a two-piece, snap-together assembly. First, as previously noted, the protector plate  30  is made in the same mold as the rest of the lower cover  16 , thereby eliminating the need for a second mold and a second molding process. 
         [0016]    In addition to eliminating a mold, a separate molding process and an assembly process, the integrated protector plate  30  does not need to be attached to the frame  12  separately from the lower cover  16 . In fact, retaining features  32  on the lower cover  16  which cooperate with mating features  33  on the frame  12  are the only connections that need to be used to keep the frame  12  attached to the lower cover  16 . Therefore, retaining features do not need to be molded into the integrated protector plate  30  such as, for example, the snap-in retaining features shown in  FIG. 1  of the Masters et al. reference. In addition to the retaining features  32 , the lower cover  16  also includes a mounting flange  34 , which can be used, for example, to mount the PDB  10  to a surface under the hood or in the trunk of a vehicle. 
         [0017]      FIG. 2  shows a lower cover  36  in accordance with another embodiment of the present invention. Similar to the lower cover  16  shown in  FIG. 1 , the lower cover  36  includes a mounting flange  38 , and also includes a mounting clip  40 . The lower cover  36  includes walls  42 ,  44 ,  46 ,  48 , which extended downwardly from cover apertures  50  (which, for clarity, are not all labeled in the drawing figure). The walls  42 - 48  extend downwardly beyond the cover apertures  50  sufficiently such that wires, such as the wires  18  shown in  FIG. 1 , can be bundled within the walls  42 - 48 . This is one of the functions of a lower cover, such as the lower cover  36 —i.e., it allows wires that may be spaced relatively far apart from one another to be bundled, and potentially dressed with tape, placed in a conduit, etc., and then routed out of the lower cover, for example, through a wire takeout  52 . Therefore, even in a top-down design (as opposed to the bottom-up design of the present invention) a lower cover serves the important purpose of allowing the PDB to be flush mounted on a surface while providing an egress for the bundled wires. 
         [0018]    Also shown in  FIG. 2  is a dimension (t) representing the thickness of the wall  44 . Another of the advantages of having an integrally molded, integrated protector plate, such as the protector plate  30  shown in  FIG. 1 , is that it adds structural integrity to a lower cover. It may therefore be possible to reduce the thickness of the walls of the lower cover while still achieving the required strength. For example, in some automotive applications it may be necessary to mold a lower cover with walls having a thickness greater than 1.3 mm. Embodiments of the present invention, however, utilizing the additional strength of the integrated protector plate, may have wall thicknesses between 1.0 mm and 1.3 mm, and in the embodiment shown in  FIG. 2 , the walls  42 - 48  have a thickness (t) no greater than 1.0 mm. 
         [0019]      FIG. 3  shows a perspective view of the lower cover  36  shown generally from the top. Similar to the lower cover  16 , which had integrated protector plate  30 , the lower cover  36  shown in  FIG. 3  includes an integrally molded protector plate  54  forming a unitary structure with the rest of the lower cover  36 . The integrated protector plate  54  includes a number of wire protecting features, which are generally configured as horizontal surfaces—see, for example, surfaces  56 ,  58 ,  60 ,  62 . The surfaces  56 - 62  do not represent all of the wire protecting features of the integrated protector plate  54 ; however, they can be used to illustrate how the protector plate helps to inhibit wires, such as the wires  18  shown in  FIG. 1 , from undesirably contacting a busbar, which can lead to chafing of the insulation on the wires. This is explained in more detail with regard to  FIG. 4 . Also shown in  FIG. 3 , are retaining features  64 , which are used to connect the lower cover  36  to a frame  70  (see  FIG. 5 ), and a recessed portion  66 , which is configured to hold a cassette that will be attached to a power source, such as a vehicle battery. 
         [0020]    Turning to  FIG. 4 , the lower cover  36  is shown with a busbar  68  superimposed over the integrated protector plate  54 . As shown in  FIG. 4 , the horizontal surfaces  56 - 62  of the integrated protector plate  54  overlap the edges of the busbar  68  such that wires coming up through the lower cover  36  will not be chafed or cut by the edges of the busbar  68  as they continue through to the frame  70 , which is shown in  FIG. 5 . Turning to  FIG. 5 , a cross-sectional view of the lower cover  36  is shown as taken through the cut line  5 - 5  shown in  FIG. 4 , but with a frame  70  attached to the lower cover  36 . On top of the frame  70  is a wedge  72  which, among other things, helps to retain wires, such as the wires  18  shown in  FIG. 1 , when they are inserted through the lower cover  36  and into the frame  70 . In particular, the frame  70  includes a number of wire retaining features, commonly referred to as “terminal lock fingers”,  74 , which retain wires inserted through frame apertures  76 . The terminal lock fingers  74  are of the type discussed above—i.e., they retain the wires by engaging with terminals on the respective ends of the wires. 
         [0021]    As shown in  FIG. 5 , the wedge  72  includes wedge tabs  78 , which are disposed adjacent the terminal lock fingers  74  to keep them from being displaced laterally, so that the inserted wires (not shown in  FIG. 5 ) will not be released. Thus, in order to release wires inserted through the frame apertures  76  and retained by the terminal lock fingers  74 , it is necessary to remove the wedge  72  from the top of the frame  70 , thereby creating a space adjacent to the terminal lock fingers  74  whereby they can be displaced laterally so that terminals on the ends of the wires can be released and the wires removed. One of the horizontal surfaces  80  of the integrated protector plate  54 , which acts as a wire protecting feature, is shown in  FIG. 5  adjacent portion of the busbar  68 , which is illustrated by the vertically oriented terminals  82 . 
         [0022]    In addition to providing the wedge tabs  78 , the wedge  72  is configured to receive a number of fuses, which, in the embodiment shown in  FIG. 5 , are J-case fuses  84 . In some configurations of a PDB, a busbar, such as the busbar  68 , will be attached to a power source such as a vehicle battery, and then wires, such as the wires  18  shown in  FIG. 1 , will be attached to various vehicle accessories. Then, when a fuse connects the busbar and one of the wires, the accessory has a fused power supply. Also shown in  FIG. 5  is a cassette  86  inserted into the cavity  66  ( FIG. 3 ), and which contains terminal posts  88 ,  92  for connection to a power source such as a vehicle battery. 
         [0023]    As described in detail above, having an integrally molded protector plate, such as the integrated protector plates  30  ( FIGS. 1) and 54  ( FIG. 3 ), provides a number of advantages over snap-together configurations. One of the advantages, as discussed above, is the increased structural strength of a lower cover having an integrated protector plate. Returning to  FIG. 1 , it is shown that the lower cover  16  includes a first portion  92  and a second portion  94 . The first portion  92  includes structural supports  96 , which, in the embodiment shown in  FIG. 1 , are transverse members extending across a width of lower cover  16  from a first wall  98  to a second wall  100 . In contrast, the second portion  94 , which contains the integrated protector plate  30 , has no such transverse structural supports, and it does not need them to maintain the required strength for the application. Thus, in addition to reducing wall thickness, integrating a protector plate into a lower cover allows for a reduction in the support structures molded into the lower cover, and can even reduce the weight of the assembled PDB. 
         [0024]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.