Patent Publication Number: US-7581972-B2

Title: Busbar connection system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of the filing date under 35 U.S.C. § 119(a)-(d) of European Patent Application No. EP 07 015 898.5, filed Aug. 13, 2007. 
   FIELD OF THE INVENTION 
   The present invention is directed to a busbar connection system and an electrical system comprising such a busbar connection system. 
   BACKGROUND 
   Busbar connection systems are commonly used in particular in electrical power distribution systems in order to distribute electrical power from a power source to a number of electrical devices. Such an electrical power distribution system usually comprises at least two conductors which are spaced apart from each other in a predetermined distance for being connected to a number of electrical devices. Each of the electrical devices comprises at least two pluggable connectors in order to respectively connect to one of the conductors. The pluggable connectors of every device are spaced apart from each other in the predetermined distance of the two conductors of the electrical power system. The conductors are typically realized as vertical strip conductors spaced apart a predetermined distance, such as about 25 mm. Due to manufacturing tolerances, the distance between the conductors can have a variation of more than about 1 mm. However, known standard busbar systems allow only for a very small variation, e.g., 0.1 to 0.15 mm, in the predetermined distance. The conductors and the connectors therefore have to be produced and installed with high accuracy, which results in high manufacturing costs. 
   SUMMARY 
   Accordingly, it is an object of the invention to provide an improved busbar connection system which can be used with a less accurately manufactured pair of conductors while providing reliable electrical connections. 
   This and other objects are achieved by a busbar connection system comprising at least two pluggable connectors spaced apart from each other a predetermined distance. Each of the pluggable connectors has an opening for receiving a conductor. At least one contact member for contacting the conductor is provided inside each of the openings. The contact member is rotatable about an axis in a direction transverse to a mating direction of the conductors. At least one urging member engages the contact member and biases the contact member in the direction transverse to the mating direction of the conductors. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partially exploded perspective schematic view of a busbar connection system comprising two pluggable connectors; 
       FIG. 2  is a schematic top view of the busbar connection system of  FIG. 1  shown without housings wherein each of the connectors are connected to conductors which are spaced apart a distance which is greater than a predetermined distance; 
       FIG. 3  is a schematic top view of the busbar connection system of  FIG. 1  shown without housings wherein each of the connectors are connected to conductors which are spaced apart is distance which is smaller than a predetermined distance. 
       FIG. 4   a  is a perspective front view of a single connector of a busbar connection system according to the previous figures shown without a housing. 
       FIG. 4   b  is an enlarged detailed view of  FIG. 4   a.    
       FIG. 5  is a partially exploded perspective view from behind of the single connector of  FIGS. 4   a - 4   b  shown with the housing, which has not yet been fixed to the connector. 
       FIG. 6   a  is a perspective view of the connector of  FIGS. 4   a - 5  from the back side showing the housing fixed to the connector. 
       FIG. 6   b  is a perspective view of the connector of  FIGS. 4   a - 5  from the bottom showing the housing fixed to the connector. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     FIG. 1  shows a perspective schematic view of an exemplary busbar connection system  2  according to the invention. The busbar connection system  2  comprises two pluggable connectors  4  which are fixed side by side via respective fixtures  24  and screws  26  to a printed circuit board  18 . Alternatively, the fixtures  24  may be fixed by press-fit contacts or soldering to the printed circuit board  18 . Each of the connectors  4  has a U-shaped form with an opening  7  which opens to a front facing away from the printed circuit board  18 . A contact member  8  is arranged on each side of each of the openings  7  basically extending over their entire height. Each of the contact members  8  has a curved form with an arcuate contact zone  12  protruding into the opening  7 . The connectors  4  are covered by respective housings  20 , which are made of plastic. Two guiding tracks  22  are arranged on the rear top of each of the housings  20 . The guiding tracks  22  are arranged to accommodate corresponding protrusions (not visible) which are formed on a top of a rear part  8   c  of each of the contact members  8  in order to fix the contact members  8  to the housing  20 , as shown in  FIG. 2 . 
   An electrical conductor  6  is arranged in front of each of the connectors  4 . The conductor  6  is typically 3 mm wide and at least 15 mm in depth and can have a length (height) of up to several meters. The conductors  6  of this type are typically used in power distribution systems, where several electrical devices such as the printed circuit boards  18  are arranged over one another, each of the electrical devices comprising the busbar connection system  2  for receiving electrical power from the conductors  6 . Each of the conductors  6  may be introduced into the opening  7  of the connector  4  in order to establish electrical connection between the contact member  8  and the conductor  6 . 
   As shown in  FIG. 2 , the connectors  4  are fixed to the printed circuit board  18  via the fixtures  24  and the screws  26  which extend through respective holes  27  in the fixtures  24 . Each of the connectors  4  comprises two of the contact members  8  inversely facing each other with the conductor  6  introduced into the opening  7  between them from the front (bottom of  FIG. 2 ). Each of the contact members  8  is formed from a metal strip. The rear part  8   c  of each of the contact members  8  is bent in an angle of more than about 180° with respect to a middle part  8   b.  An arcuate contact zone  12  is formed from the front part  8   a  of each of the contact members  8  in order to contact the conductor  6 . The rear part  8   c  of each of the contact members  8  is fixed to the fixture  24 . The middle part  8   b  and the front part  8   a  are not fixed to the fixture  24  and thus they can move in a plane extending parallel to the printed circuit board  18 . Due to its bent shape, each of the contact members  8  executes a resilient force on the conductor  6  if it is introduced in between two of the contact members  8 . Between the contact zone  12  and the distal end  8   d  of each of the contact members  8 , a curved sacrificial zone  14  is formed in order to cause any electrical arcs, which may occur when the conductor  6  is pulled out from the connector  4  while power-on thereby interrupting the electrical current, to occur at the sacrificial zone  14  in order to avoid that the contact zone  12  is damaged by the electrical arcs. 
   In the middle part  8   b  of each of the contact members  8  a stop  16  is formed in order to maintain a predetermined distance between the contact members  8 . The stop  16  may be formed protruding out of the contact member  8  by cutting out and bending a section of the contact member  8 . The stop  16  causes a predetermined gap between the contact members  8  even if none of the conductors  6  are introduced between them. This facilitates introducing the conductor  6 . 
   The contact members  8  of the connectors  4  are arranged so that in an idle state, in which none of the conductors  6  are introduced into the connectors  4 , planes A, which extend vertically between the contact members  8  of each of the connectors  4  parallel to the contact members  8  and the insertion direction of the conductor  6 , are spaced apart in a predetermined distance D 0 . A typical value for said distance D 0  is about 25 mm. 
   An urging member clasps the contact members  8  of each of the connectors  4 . In the embodiment shown in  FIG. 2  the urging member is a clip  10  made of stainless steel which clasps the contact members  8  from behind, i.e. from the side opposite to the side where the contact member  8  is introduced. However, alternative urging members, such as springs, can be used as well. Each of the clips  10  basically has a U-shape, which envelopes and contacts the rear parts  8   c  of the contact members  8  and opens to the front side. The contact members  8  extend through the opening. At its front end, the clip  10  comprises two front portions  11  which are bent inwardly in order to contact the contact member  8  in the contact zone  12 . The clip  10  is resiliently biased executing a force on the contact zones  12  of the contact members  8  in order to urge the contact members  8  in a direction of each other onto the conductor  6 , respectively. 
   As a distance D 1  between the conductors  6  is larger than the predetermined distance D 0 , the contact members  8  and the clip  10  are shifted from an initial position to the outside in order to adjust for the difference between the distance D 1  and the predetermined distance D 0 . A typical value for the distance D 1  is about 26.5 mm. This shifting can be performed by resiliently bending the metal connection between the rear part  8   c  of each of the contact members  8  and the fixture  24 . Alternatively, the rear part  8   c  may be fixed to one of the fixtures  24  so that the contact members  8  are rotatable around an axis which is positioned in the middle between the contact members  8  and extends perpendicular to the circuit board. Due to the urging force executed by the clip  10  onto the contact members  8 , a reliable electrical connection between the contact zone  12  of the contact members  8  and the conductor  6  is ensured. In a particular embodiment, the contact members  8  and the clips  10  are configured to permit compensating for a deviation of the distance D 1  between the conductors  6  from the predetermined distance D 0  of up to about 2 mm. 
     FIG. 3  shows a sectional top view of the same busbar connection system  2  shown in  FIG. 2 . The same reference signs designate the same features which will not be discussed in detail again. In the embodiment shown in  FIG. 3  the distance D 2  between the conductors  6  is smaller than the predetermined distance D 0 . A typical value for the distance D 2  is about 23.5 mm. As the distance D 2  of the conductors  6  is smaller than the predetermined distance D 0 , the contact members  8  of each of the connectors  4  are shifted to the inside in order to adjust for the smaller distance D 2 . This shifting can be performed by resiliently bending the metal connection between the rear part  8   c  of each of the contact members  8  and the fixture  24 . Alternatively, the rear parts  8   c  may be fixed to the fixture  24  so that they are rotatable around an axis which is positioned in the middle between the contact members  8  and extends perpendicular to the printed circuit board  18 . A reliable electrical connection between each of the conductors  6  and the contact zones  12  of the contact members  8  is ensured by the force executed by each of the clips  10  urging the contact zones  12  of the contact members  8  in the direction of the conductor  6 . 
   As shown in  FIGS. 4   a - 4   b,  the contact members  8  are enveloped and clasped by the clip  10 . At its two front ends the clip  10  comprises the front portions  11  which are bent inwardly in order to contact the contact member  8  in the contact zone  12 . At each of the front portions  11  two protrusions  28  are formed at the edge bent inwards, respectively. In the contact zones  12  of each of the contact members  8 , where the clip  10  contacts the contact member  8 , five grooves  30  are formed. The grooves  30  run horizontally and are arranged in a vertical row on top of each other. The two protrusions  28  of each of the front portions  11  are inserted into the highest and the lowest of the grooves  30  of the contact member  8 , respectively. As the clip  10  is resiliently biased this secures the clip  10  to the contact members  8 . At the front side of each of the fixtures  24 , a slot  36  is formed for accommodating part of the housing  20  when attached to the connector  4 . At the back side of the fixtures  24 , an edge  34  is formed for engaging with an appropriate hook of the housing  20 . 
   As shown in  FIG. 5 , the housing  20  comprises the guiding tracks  22  at its rear top in order to accommodate the guiding rails  9  which are formed at the top of the rear part  8   c  of each of the contact members  8 . The guiding rails  9  will be inserted into the guiding tracks  22  when the housing  20  is pushed over the contact members  8  and the clip  10 . This will secure the rear parts  8   c  of the contact members  8  to the housing  20  and thus enhance the stability of the connector  4 . At the bottom of the housing  20  two resilient hooks  32  are formed inversely opposite to each other facing to the outside. When the housing  20  is pushed over the contact members  8  and the clip  10 , the hooks  32  will engage with the edges  34  at the back of the fixtures  24 , respectively, in order to secure the housing  20  to the fixture  24 . This prevents the housing  20  from dropping off of the connector  4 . 
     FIGS. 6   a - 6   b  show the connector  4  of  FIGS. 4   a - 5  from the back side and from the bottom, respectively, wherein the housing  20  has been fixed to the connector  4 . The housing  20  covers the top and the sides of the contact members  8  and the clip  10 , but it is open to the back side. A bottom section  38  of the housing  20  is introduced into the slots  36  formed at the front side of each of the fixtures  24 . The hooks  32  formed at the bottom of the housing  20  engage with the edges  34  at the back side of the fixtures  24 . The guiding rails  9  on top of the rear parts  8   c  of the contact members  8  (not visible) are introduced into the guiding tracks  22  formed in the top of the housing  20 . This arrangement provides a very stable configuration and allows a considerable large contact force to be executed on the conductor  6  in order to ensure a reliable electrical connection. 
   The busbar connection system  2  according to an exemplary embodiment of the invention, as described above, allows deviations in the distance between at least two of the conductors  6  from the predetermined distance D 0  to be absorbed. In order to ensure a reliable electrical connection, the clip  10  urging the contact members  8  against the conductor  6  is used in order to provide a necessary contact force even in a worst case situation. The busbar connection system  2  comprising the connectors  4  according to the invention can be produced easily and at low costs as the essential components can be formed conveniently from flat metal strips. The invention facilitates the assembly of electrical systems, particularly electrical power distribution systems, since larger tolerances in the distance between the conductors  6  are allowed. This reduces the cost for producing such an electrical system. 
   The foregoing illustrates some of the possibilities for practicing the invention. Many other embodiments are possible within the scope and spirit of the invention. It is, therefore, intended that the foregoing description be regarded as illustrative rather than limiting, and that the scope of the invention is given by the appended claims together with their full range of equivalents.