Abstract:
A power distribution center (PDC), such as those used in automotive vehicle electrical systems, has device for pivotally connecting a power supply terminal with the PDC such that pivoting movement of the terminal relative to a PDC housing inserts the terminal through an aperture formed in the housing and into contact with a bus bar retained within the housing. The pivoting connection between the terminal and the PDC allows the terminal to be securely connected with the bus bar without the need for any tools, and provides a degree of alignment to guide the terminal into the aperture. It also provides leverage so that a worker can easily generate sufficient force to insert the terminal into connection with the bus bar in the presence of a force resisting insertion, such as may be generated by a spring clamp or other device for urging the terminal into contact with the bus bar. According to another feature of the invention, a spring element is provided to urge the terminal into contact with the bus bar to ensure effective electrical contact therebetween.

Description:
FIELD OF THE INVENTION 
     This invention relates in general to power distribution centers such as those used in automotive vehicle electrical systems, and more specifically to such a power distribution center having improved means for connecting a power supply cable thereto. 
     BACKGROUND OF THE INVENTION 
     Power distribution centers (PDCs) are commonly used in automotive vehicles to simplify electrical system wiring by eliminating multi-branch wiring and consolidating fuses, relays, and other electrical components in a single location. A PDC typically comprises a housing having a plurality of integrally formed external receptacles for receiving electrical connectors, fuses, relays and other circuit components. A bus bar is contained within the housing and is supplied with electrical power from the vehicle alternator and/or battery by a power supply cable. The bus bar has a plurality of blade-like extensions which project into some or all of the receptacles in order to make electrical contact with and distribute power to the components inserted therein. 
     In one known type of PDC, the power supply cable is secured into electrical connection with the bus bar by a nut and bolt. The bolt is inserted through a hole in a flat section of the bus bar and through an eyelet terminal at the end of the cable, then the nut is threaded over the bolt and tightened to urge the eyelet terminal into contact with the bus bar with sufficient normal force to achieve electrical connection therebetween. An example of such a PDC is disclosed in U.S. Pat. No. 5,088,940. 
     There are significant problems associated with a nut and bolt connection of the type described above. If either the bolt or the nut has stripped or otherwise defective threads, the resulting connection may be poor. The relatively small surface area of contact between the terminal and the bus bar may not dissipate heat effectively, leading to undesirable heating at the contact surfaces. Also, threading the nut onto the bolt requires that a tool be used and that the nut be tightened to the correct degree, thus adding to the time and cost involved in the assembly work. 
     SUMMARY OF THE INVENTION 
     It is an objective of this invention to provide a reliable and secure electrical connection between a power supply cable and a power distribution center (PDC). 
     It is another objective of this invention to provide a PDC that may be connected with a power supply terminal by a quick and a simple assembly process. 
     In general, these objectives are achieved by a PDC having means for pivotally connecting a terminal with the PDC such that pivoting movement of the terminal relative to the housing inserts the terminal through an aperture formed in the housing and into contact with the bus bar. The pivoting connection between the terminal and the PDC allows the terminal to be securely connected with the bus bar without the need for any tools, and provides a degree of alignment to guide the terminal into the aperture. It also provides leverage so that a worker can easily generate sufficient force to insert the terminal into connection with the bus bar in the presence of a force resisting insertion, such as may be generated by a spring clamp or other means for urging the terminal into contact with the bus bar. 
     In a first embodiment of the invention, the pivoting connection is provided by a fulcrum disposed on the PDC housing adjacent one end of the aperture. The terminal snaps into engagement with a terminal cover such that a blade portion of the terminal projects downwardly from the cover. The terminal cover has a projection at one end which is inserted beneath the underside of the fulcrum, and the joined terminal and terminal cover is then pivoted downwardly about the fulcrum to insert the blade through the aperture. Latching means may be provided to secure the terminal cover in proximity with the housing to thereby avoid inadvertent removal of the terminal from the inserted position. The lever may also be shaped so as to substantially cover the terminal and the aperture to protect against the entry of contamination into the housing through the aperture. 
     According to a second embodiment of the invention, a fulcrum is formed integrally with the portion of the bus bar immediately below the aperture. This fulcrum may take the form of a simple hole formed through the bus bar. The terminal is formed with a short projection extending from the upper edge of the blade, and this projection is inserted through the hole in the bus bar such that the engagement between the projection and the hole creates a pivot point. The terminal is rotated about the pivot point to move the end of the terminal opposite from the projection downwardly toward the housing, thus urging the blade of the terminal downwardly through the aperture and into electrical connection with the bus bar. This is a very simple and inexpensively fabricated configuration, achieving the pivoting effect with a minimum number of parts. 
     According to another feature of the present invention, a spring member is co-located with the connection portion of the bus bar directly below the aperture to urge the terminal blade and connection portion into contact with one another in order to create sufficient normal force between the two elements to ensure good electrical contact. 
     In a first embodiment, the spring member comprises a flat contact plate having upper and lower edges bent into curved spring portions. The spring member is flattened somewhat and inserted into the housing from below so that the spring portions push against a vertical wall formed on the inside of the housing adjacent the aperture and the contact plate is biased into contact with the bus bar connection portion. Insertion of the terminal blade through the aperture causes the blade to slide between the bus bar connection portion and the spring member, deflecting the spring member slightly and thus generating the desired normal force. 
     In another embodiment, the normal force is generated by a spring clamp having first and second parallel plates biased toward one another and which fits around the flat contact portion of the bus bar. Insertion of the terminal blade downwardly through the aperture causes the blade to slide between the contact portion of the bus bar and one of the plates of the clamp. 
     In a third embodiment, a spring clamp is formed integrally with the connection portion of the bus bar by bending an end of the bus bar back on itself to form two parallel contact plates connected along a vertical edge by a spring loop which biases the plates toward one another. Insertion of the terminal blade through the aperture urges the blade between the contact plates. A additional spring clamp may also be provided to supplement the normal force of the clamp formed with the bus bar, the spring clamp fitting over and around the bus bar contact plates. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a power distribution center (PDC) according to the present invention; 
     FIG. 2 is a perspective view of a lever according to the present invention; 
     FIG. 3 is a cross-sectional view of the lever with a power supply terminal installed therein according to the present invention; taken along line  3 — 3  of FIG. 1; 
     FIG. 4 is a cross-sectional view of the lever and terminal taken along line  4 — 4  of FIG. 1; 
     FIG. 5 is a side view of the power distribution center illustrating the lever in a raised, pre-contact position; 
     FIG. 6 is a side view illustrating the lever in an inserted, electrical connect position; 
     FIG. 7 is a partial perspective view of a modified spring clamp and bus bar; 
     FIG. 8 is a cross-sectional view of the modified spring clamp and bus bar mounted within a power distribution center housing; 
     FIG. 9 is an exploded perspective view of a PDC according to a second embodiment of the invention; 
     FIG. 10 is a partial cross-sectional view taken along line  10 — 10  of FIG. 9 illustrating the terminal partially inserted into contact with the bus bar; and 
     FIG. 11 is a partial cross-sectional view taken along line  10 — 10  of FIG. 9 showing the terminal fully inserted into contact with the bus bar. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As seen in FIG. 1, a power distribution center (PDC)  10  comprises a substantially hollow housing  12 , an electrically conductive bus bar  14  which is inserted into the housing from below, a power supply terminal  16  attached to a cable  18 , and a lever  20  for receiving the terminal and pivotally engaging the housing in a manner to be described in greater detail hereinbelow. Although the PDC  10  illustrated is of a type typically used in conjunction with the electrical system of an automotive vehicle, the present invention is not limited to automotive PDC applications, but rather may be beneficially practiced in relation to any PDC in which it is desired to provide a quick, positive, and tool-free connection between the PDC and an electrical cable. 
     The housing  12  is preferably injection molded from an electrically non-conductive thermoplastic material and has a plurality of receptacles  22  formed on upper surfaces thereof for receiving various electrical circuit components such as fuses and relays (not shown), as is well known in the art. The housing  12  has various latch features  24  molded integrally therewith for securing the housing to a mating lower housing (not shown) for enclosing the bottom of the PDC  10  and/or a cover (not shown) for protecting the upper surface of the housing. 
     An aperture in the form of a slot  26  is formed through the upper surface of the housing  12 , and a pair of parallel support plates  28  extend from the surface of the housing adjacent one end of the slot. A fulcrum bar  30  extends between the upper ends of the support plates  28  such as to be oriented parallel with the upper surface of the housing  12  and perpendicular to the long axis of the slot  26 . A pair of latching holes  32  are formed in the surface of the housing  12  adjacent the end of the slot  26  opposite from the fulcrum bar  30 . 
     The bus bar  14  is formed from a thin piece of electrically conductive metal such as tin-plated copper and comprises two elongated bus arms  34  connected by a crosspiece  35 . A plurality of finger-like contacts  36  extend upwardly from each of the bus arms  34 . The PDC  10  is assembled by inserting the bus bar  14  upwardly into the interior of the housing  12 , the bus bar being securely retained therein in a conventionally known manner such as locking tabs (not shown) formed on the interior of the housing and which engage locking holes  38  formed at several locations on the bus bar  14 . When the bus bar  14  is installed in the housing  12 , the contacts  36  project upwardly into the respective receptacles  22  of the housing  12  in order to make electrical connection with the various circuit components when they are inserted into their receptacles. Prior to installing the bus bar  14  in the housing  12 , adapters  40  (only one of which is shown) having female features at both ends may be placed over the bus bar contacts  36  where necessary to properly mate with male terminals of the electrical components. 
     The terminal  16  is stamped from a flat sheet of electrically conductive metal and comprises an electrical contact portion taking the form of a flat blade  42  and a cable connection portion  44  which is crimped around the core wire of the power supply cable  18 . A small hole  46  is formed through the blade  42  adjacent its upper edge. 
     The lever  20  is formed from an electrically non-conductive material such as thermoplastic and is a generally rectangular, substantially hollow box having parallel side walls  20   a,b . A hinge finger  48  extends from one end of the lever  20  and has a concave upper surface. Latch tabs  50  extend downwardly from each side wall  20   a,b  adjacent the end opposite the hinge finger  48 . Short grip ledges  52  extend outwardly from the upper surface of the lever  20  above the latch tabs  50 . 
     As best seen in FIG. 2, the underside and the second end of the lever  20  are substantially open. A first interior wall  54  runs the full length of the lever  20  and is parallel to the side walls  20   a, b . A second interior wall  56  runs from the closed end of the lever  20  to a point short of the open end to leave a relatively wide chamber  58  adjacent the open end. A small lock arm  60  projects inwardly from the outer wall of the lever  20  adjacent the open end and has a series of teeth  60   a  projecting from the end thereof. A small slot  62  is formed in the upper surface of the lever  20  immediately above the lock arm  60 . A retaining tab  64  projects inwardly from the long interior wall  54  adjacent the first end of the lever  20 , as best seen in FIG. 3. A tie strap  66  is attached to the lever  20 , preferably by a living hinge, and has a plurality of parallel lock ridges  68  projecting from one surface and a large rectangular bump  70  projecting from the other surface. 
     A spring clamp  72  (see FIG. 1) is formed from a sheet of spring steel or the like and comprises first and second parallel clamp plates  74  connected along their lower edges by a spring loop  76  that biases the plates into contact with one another. The edges of the clamp plates  74  opposite the spring loop  76  are flared outwardly, away from one another. When assembled, the spring clamp  72  is slid upwardly over the crosspiece  35  of the bus bar  14  to sandwich the crosspiece between the clamp plates  74 . The normal force generated by the spring clamp is sufficient to hold the clamp in connection with the crosspiece. When the bus bar  14  is installed within the housing  12 , the crosspiece  35  and spring clamp  72  are positioned directly below and parallel with the slot  26 . 
     During assembly of an automotive vehicle, the PDC  10  is usually installed in the vehicle (typically in the engine compartment) prior to being connected to the power supply cable  18 . To prepare for connection of the power supply cable  18 , the terminal  16  is first inserted upwardly into the lever  20  such that the retaining tab  64  on the interior wall  54  of the lever snaps into engagement with the hole  46  in the blade  42  (see FIG. 3) and the connection portion  44  of the terminal is disposed within the chamber  58  adjacent the open end of the lever  20 . The tie strap  66  is then wrapped around the underside of the lever  20  such that the bump  70  juts upwardly into the chamber  58  to support the terminal connection portion  44 , and the free end of the strap is inserted upwardly between the side wall  20   b  and interior wall  54  of the lever so that the teeth  60   a  of the lock arm  60  engage the ridges  68  on the strap and the tip of the strap projects through the slot  62  in the top of the lever (see FIG.  4 ). Engagement between the teeth  60   a  of the lock arm  60  and the ridges  68  on the tie strap  66  prevent the strap from loosening. 
     To mate the lever/terminal assembly with the housing, the hinge finger  48  extending from the end of the lever  20  is inserted beneath the fulcrum bar  30 , with the opposite end of the lever raised so that the terminal blade  42  is clear of the upper surface of the housing  12 , as seen in FIG.  5 . In this pre-contact position, the terminal blade  42  is directly above and aligned with the slot  26 . 
     The joined lever  20  and terminal  16  are then pivoted downwardly to insert the terminal blade  42  through the slot  26  and between the spring clamp plates  74 , which are positioned directly below and parallel with the slot  26  (see FIG.  6 ). The flared upper edges of the clamp plates  74  guide the blade  42  between the plates such that the blade is in parallel contact with the crosspiece  35  of the bus bar  14 . The mating lower housing which encloses the bottom of the PDC prevents the spring clamp from being pushed off the crosspiece by the blade. Alternatively, a lock could be provided within the PDC for holding the spring clamp in position, or a conventional latch mechanism could be placed on the spring clamp and crosspiece. The inward pressure supplied by the spring clamp  72  urges the blade  42  into contact with the crosspiece  35  with sufficient force to ensure good electrical connection therebetween. 
     When the terminal  16  is fully inserted to the electrical connect position shown in FIG. 6, the latch tabs  50  on the lever  20  engage the latching holes  32  in the upper surface of the housing  12  to secure the lever and terminal in that position. 
     FIGS. 7 and 8 depict an alternative means for providing the normal force between the terminal blade  42  and the bus bar  14 . In this embodiment, the upper edge of the bus bar crosspiece  35 ′ is bent to one side, and a spring element  78  replaces the spring clamp  72  of the first embodiment. The spring element  78  comprises a flat contact plate  78   a  having upper and lower edges bent into curved spring portions  78   b . A vertical wall  80  is disposed on the interior of the housing  12 , the wall offset a short distance from the slot  26  and extending parallel thereto. A retaining arm  82  extends from the surface of the vertical wall  80  toward the slot  26 . 
     During assembly of this second embodiment of the PDC prior to its installation into the vehicle, the bus bar  14  is inserted into the housing  12  from below, then the spring element  78  is slid upwardly between the vertical wall  80  and the bus bar crosspiece  35 ′. The spring portions  78   b  must be flattened somewhat in order for the spring element  78  to fit into this space, so that the spring portions push against the vertical wall  80  and the contact plate  78   a  is urged into parallel contact with the bus bar crosspiece  35 ′. As the spring element  78  is urged upwardly into its position, the uppermost of the spring portions  78   b  rides up over the retaining arm  82  then snaps over the top of the arm to secure the spring element  78  in position. 
     When the terminal blade  42  is inserted downwardly through the slot  26  in the housing  12  by the pivoting motion described hereinabove, it slides between the bus bar crosspiece  35 ′ and the contact plate  78   a , further flattening the spring element  78  so that the terminal blade  42  is urged firmly into contact with the crosspiece, as seen in FIG.  8 . 
     FIGS.  9 - 11  depict a second embodiment of the invention in which the fulcrum for achieving pivoting engagement with the terminal is integrated with the bus bar, and the terminal itself engages the fulcrum. 
     The housing  84  of this embodiment is substantially similar to the previously described embodiment, except that it does not feature the fulcrum bar  30 , the support plates  28 , nor the latching holes  32  on the upper surface of the housing. 
     The bus bar  86  has a connection portion comprising a first contact plate  88  extending from one end of a bus arm, a second contact plate  90  in parallel contact with the first contact plate, and a spring loop  92  joining the first and second contact plates along their edges and extending upwardly beyond the upper edges of the contact plates. The first and second contact plates  88 , 90  and the spring loop  92  are all formed integrally with the bus arm by a stamping process. 
     A fulcrum hole  94  is formed through the spring loop  92  adjacent its upper end on the side opposite the contact plates  88 , 90 , and the upper end of the spring loop  92  opposite the fulcrum hole  94  is notched to form a gap  96  between the edges of the loop above the contact plates. The upper edges of the contact plates  88 , 90  are flared outwardly. 
     A terminal  98  for use with this embodiment comprises a cable connection portion  100  for crimping onto a cable  18  and a flat blade  102  having a downward sloping upper edge leading to a curved horn  104  projecting outwardly and upwardly from the end of the blade. 
     When the bus bar  86  is installed within the housing  84 , the outwardly flared upper edges of the contact plates  88 ,  90  and the upper end of the spring loop  92  are positioned directly below the slot  26 . To place the terminal  98  in electrical connection with the bus bar  86 , the terminal is tipped downwardly so that the horn  104  may be inserted through the slot  26  and into engagement with the fulcrum hole  94 , as seen in FIG.  10 . The terminal  98  is then pivoted about the point of engagement between the horn  104  and the fulcrum hole  94  to urge the rest of the blade  102  between the contact plates  88 , 90  as seen in FIG. 11. A conventional clamp could be provided on the surface of the housing to secure the terminal and prevent the blade from pivoting out of electrical connection with the contact plates. For example, the clamp could receive the cable connection portion  100 . An additional spring clamp  106  may also be provided, the spring clamp fitting over and around the contact plates  88 , 90  and spring loop  92  to increase the amount of normal force urging the contact plates  88 , 90  into contact with the terminal blade  102 . 
     This embodiment of the invention, when compared with the first embodiment, eliminates the need for a separate lever component and so may be less expensive and quicker to assembly. It should be noted that the fulcrum may be formed integrally with the bus bar while using some other means of providing the normal force urging the terminal into contact with the bus bar, such as the methods shown in FIG. 1 or FIGS. 7 and 8. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.