Abstract:
An electrical busbar arrangement has provision for connecting a single feeder cable to a plurality of branch cables within an insulating housing. A branch port is provided for each branch cable, and a spring-loaded slidable support plate is arranged to receive the branch cable and to retain it in an aperture thereof. The support plate moves within a cable holder that is driven by a rotatable cam by means of a switch. Operation of the switch between OFF and ON positions is effective to move the branch cable into and out off contact respectively with the busbar. The switches of each port are selectively operable independently of each other. In this way, branch cables may be independently and selectively mounted in the housing and brought into electrical connection with and disconnected from the busbar.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to an electrical interconnection arrangement, which finds particular, though not exclusive, application in providing connection to a busbar having a current capacity greater than 30 A, preferably greater than 50 A, more preferably greater than 100 A. Capacities of 250 A or 400 A may be encountered in practice of the present invention. 
   It is known, for example, from Brazilian Patent Number P19706273, to provide for the electrical connection of a plurality of cables, for example, branch or tap cables, to a single feeder cable, using a busbar mounted in an insulating housing. In this patent, an array of metal support plates is slidably mounted, under the reaction of return springs, within a plastics housing. The support plates are apertured, and can be raised against the action of the springs by a screwdriver such that the apertures are aligned with respective inlet apertures of the housing so that conductors of the cables can be passed thereinto and secured in place in contact with a common busbar retained within the housing. 
   BRIEF SUMMARY OF INVENTION 
   In accordance with one aspect of the present invention, there is provided a switchable electrical interconnection arrangement comprising: 
   a busbar of greater than 30 A current capacity mounted in an electrically insulating housing; 
   means for electrically connecting a feeder cable to the busbar within the housing; 
   at least one connecting means mounted in the housing for making electrical connection to a respective branch cable that is receivable within the housing; and 
   a switching arrangement mounted within the housing for selectively making electrical connection between the or each branch cable and the busbar, the switching arrangement comprising a switch moveable between an ON and an OFF position whereby a cam is rotatably driven so as to make and break electrical contact between an associated branch cable and the busbar. 
   In accordance with another aspect of the present invention, there is provided Switchable electrical interconnection arrangement of greater than 30 A current capacity comprising: 
   an electrically insulating housing having a first electrical conductor secured therein and an apertured chamber for receiving a second (“branch”) electrical conductor; 
   wherein the chamber contains:
         (a) a resiliently-biased support plate having an aperture that is alignable with the chamber aperture for receiving the second electrical conductor;   (b) an electrically-insulating cable holder having first and second interconnecting channels therein for receiving said first and second electrical conductors respectively, and being arranged to receive the support plate slidably mounted therewithin: and   (c) a switching member that is movable between ON and OFF positions in which electrical contact is made and broken respectively between the first and second electrical conductors;       

   wherein the support plate is movable by an external force from a first position, against its resilient biasing, so as to slide within the cable holder to a stop position therewith such that further movement causes both the support plate and the cable support to move within the insulating housing thereby substantially to bring into alignment the apertures of the support plate and the housing to permit introduction of the second electrical conductor into the second channel of the cable holder within the housing; 
   wherein removal of the external force allows the support plate to move back to a second position, under the action of the resilient biasing, thereby to retain the second conductor within the second channel of the cable support; and 
   wherein the switching member is movable between its OFF position in which the cable holder is retained spaced apart from the first electrical conductor, and its ON position in which the support plate and the cable holder are moved, under the restoring force of the resilient biasing, to a third position in which the second channel of the cable holder encompasses the second electrical conductor, thereby effecting electrical connection between the first and second electrical conductors 
   The arrangement is preferably such as to exert a gripping or clamping force on the branch cable conductor of at least 10 Kgf, preferably 15 to 40 Kgf. 
   Thus, the electrical interconnection arrangement of the present invention is switchable such that even with the second conductor mechanically secured within the housing, electrical connection with the first conductor can be controlled by the switching member. 
   Although the switchable electrical interconnection arrangement of the present invention finds application to connect a single insertable second conductor with the retained first conductor of the housing, it finds especial application when the housing has a plurality of associated support plates, cable holders and switching members, whereby one, two or more second electrical conductors may be selectively brought into electrical connection with the first electrical conductor, in the form of an elongate busbar. 
   Advantageously, a camming arrangement interconnects the or each switching member with its associated cable holder, and these components may be mounted on a common support shaft. Rotation of the cammed switching member can then be arranged to produce reversible sliding movement of the cable holder to make and break electrical connection between the first and second electrical conductors. 
   In a preferred embodiment, the housing is provided with a pair of busbars to enhance the electrical connection with the one or more second electrical conductors. 
   Thus, in accordance with the present invention, branch or tap cables, i.e. the second conductors, may be introduced or removed selectively from the arrangement, without interference with any of the other second conductors, and this can be done whilst electrical connection to the first electrical conductor is interrupted for the selected tap cable whilst maintaining electrical connection to other branch cables. 
   The insulating housing may be made of a plastics or polymeric material. The housing may be constructed so as to have a total of ten cable ports for each electrical phase. One of the ports may be arranged to receive a feeder cable, whilst the remaining nine ports may be used for branching tap cables. Another option is to include two separately insulated electrical phases in the same arrangement, in which two ports will receive different feeder cables while the eight remaining ports will be divided into two groups of four to provide for up to four branching tap cables for each of the feeder cables. 
   The switching ability of the present electrical interconnection arrangement thus facilitates the selective connection and disconnection of tap cables without removing them physically. 
   A switchable electrical interconnection arrangement in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a switchable busbar arrangement; 
       FIGS. 2   a - 2   f  are exploded views showing components of the arrangement of  FIG. 1 ; 
       FIG. 3  is a partial cut away view of the arrangement of  FIG. 1 ; 
       FIG. 4  is a front view of part of the arrangement of  FIG. 1  in the ON position; 
       FIG. 5  is a perspective view corresponding to  FIG. 4 ; 
       FIG. 6  is a front view of the arrangement of  FIG. 4  in an OFF position; 
       FIG. 7  is a section along the line A-A of  FIG. 1 , showing one of the connection ports in the OFF position; 
       FIG. 8  is a view corresponding to that of  FIG. 7  in the ON position, and 
       FIG. 9  is a perspective view of a modified switchable busbar arrangement. 
   

     FIG. 1  shows a ten port switchable busbar interconnection arrangement  2  that has an insulating polymeric housing  4  that is arranged to receive a single feeder cable (not shown) at an end port  6 , and that has provision for receiving up to nine branching tap cables (not shown) in respective ones of identical tap ports  8 , which are electrically insulated from each other. 
   DETAILED DESCRIPTION 
   Referring to  FIGS. 1 and 2   a , the housing  4  is of a substantially rectangular configuration that is divided into ten cable-receiving chambers  10  with dividing walls  12  projecting therefrom. The walls  12  have longitudinally-aligned apertures  14  through which an upper support shaft  16  passes for mounting components of the arrangement as hereinafter described. 
   Two conductive, copper, bars  18  ( FIG. 2   b ) are secured longitudinally within the plastic housing  4  and extend through each of the chambers  10 , as can be seen in  FIGS. 7 and 8 . The bars  18  comprise the busbars of the arrangement  2 . 
   As can be seen from  FIGS. 1 and 2   a , each chamber  10  of the housing  4  has an aperture  20  in the side wall thereof for receiving the stripped end of an electrical cable. 
   Since each of the tap ports  8  and associated chambers  10  separated by a pair of dividing walls  12  are identical, the following description will be made in respect of a single set of these components. 
   Referring to  FIGS. 3 and 2   c , a short shaft  22 , extending transversely to the conductive bars  18 , is located in the housing  4  at the lower end of the chamber  10 , and serves to retain the lower end  24  of a tension spring  26 , whose upper end  28  engages the aperture  29  of a support plate  30 , the plane of which lies substantially parallel to the aperture  20  of the chamber  10 . Although as shown in  FIG. 2   c , the upper end of the support plate  20  is bent over to form a hook  32 , a preferred embodiment of the support plate is shown at  34  in  FIG. 2   d , which instead has an aperture  36  at its upper end beyond a pair of shoulders  37 , beyond its aperture  38 . 
   A cable holder  40 , shown in detail in  FIG. 2   e , is slidably mounted within the chamber  10  and has a generally U-shaped upper channel  42  that can be aligned with the support plate aperture  38  and the housing aperture  20  for receipt of an electric cable  43  transversely therein (see  FIGS. 7 and 8 ). The cable holder  40  also has a pair of downwardly-extending lower channels  44  for receiving respective ones of the busbars  18  of the arrangement  2  (see  FIGS. 7 and 8 ). A dividing wall  46  that extends longitudinally of the housing  4 , is slotted at  47  to receive the support plate  34  slidably therewithin. The upwardly-extending side walls of the cable holder  40  have respective oval apertures  48 , by means of which the cable holder  40  is mounted on the longitudinally-extending upper shaft  16  of the housing  2  as hereinafter described. The facing inner surfaces of the cable holder  40  adjacent the apertures  48  are each provided with a pair of stops  50 ,  52  for the purpose discussed below. 
   The final component within each chamber  10  of the arrangement  2  is a switching member  54  (shown in detail in  FIG. 2   f ) that has a pair of spaced apart limbs  56  at one end that are apertured so as rotatably to mount the member  54  on the upper housing shaft  16 . A cam  58  extends outwardly from each of the limbs  56  for engagement within the apertures  48  of the cable holder  40 . 
   As mentioned above with reference to  FIG. 1 , the left hand port  6  of the arrangement  2  is for receipt of a feeder cable, and as such the contents of its chamber  10  differ from that of the chambers  10  of the tap ports  8 . A feeder cable connection device  60 , shown in detail in  FIG. 2   g  comprises a metal body  62  that contains a compression spring  64  at its lower end. A shear head screw  66  is threadedly engaged at the upper end of the device  60  and is connected to an inner pressure plate  68 . With the connection device  60  retained within the insulating housing  4 , a feeder cable can be introduced through the feeder port aperture  20 , so as to extend through the body  62 , wherein it is tightened by means of the screw  66  and pressure plate  68  against the spring  64 . After the connection is made, the screw  66  may be covered by a protective insulating cap  67 . The device  60  is located transversely in the housing  4  between the busbars  18 , and this tightening action not only secures the feeder cable within the device  60 , but also ensures good electrical contact, against the returning action of the spring  64 , of the feeder cable onto the pair of spaced apart busbars  18 . 
     FIG. 2   h  shows a modification of the feeder cable connection device  60 , wherein the resilience for retaining the cable is provided by flexibility of the body of the device  70 . 
   In operation of the switchable electrical interconnection arrangement, a feeder electric cable is stripped of its insulation at one end, and the bare conductor is inserted into the aperture  20  of the port  6  so as to pass through the body  62  of the connecting device  60 . The screw  66  is tightened up to its shear point, thereby ensuring good electrical connection between the feeder cable and the pair of busbars  18 . 
   Whilst a branching tap cable may be connected into its aperture  20  of the tap port  8  with its switching member  54  in the ON or OFF position, connection is preferred, for safety reasons, to be made with it in the OFF position, abutting the stops  52  of the cable holder  40 . In this position, as shown in  FIGS. 6 and 7 , the cams  58  of the switching member  54 , which extend into the apertures  48  of the cable holder  40 , have raised the cable holder  40  such that the upper shoulders thereof project above the upper surfaces of the projections  12 , and the branch cable channel  42  is in a raised position. The support plate  34  may then be raised, by means of its aperture  36 , for example by levering a screwdriver over the top of the housing  4  above the aperture  20 , against the resistance of the spring  26 , so as to dispose the support plate aperture  38  in alignment with the housing aperture  20  and with the channel  46 . In this position, the stripped end of a tap cable conductor  43  can be inserted so as to lie along the channel  46  of the cable holder  40 . Release of the screwdriver then allows the support plate  34  to return downwards under the action of the spring  26  until the tap conductor  43  in the channel  42  is urged against the cable holder dividing wall  46  (see  FIG. 7 ). Thus, in this position the tap cable is mechanically securely retained within the housing  4  and is electrically separated from the busbars  18 . 
   In order to make electrical connection between the branch cable and the busbars  18 , and thus with the feeder cable, the switching member  54  is moved over from the OFF position shown in  FIG. 7 , to the ON position shown in  FIG. 8 , abutting the stops  50  of the cable holder  40 . Owing to the eccentric mounting of the cams  58  within the oval apertures  48  of the cable holder  40 , this movement allows the support plate spring  26  to pull both the support plate  34  and the cable holder  40  downwardly in the tap chamber  10 , and to bring the branch cable  43  lying in the channel  42  of the cable holder  40  down into contact with the pair of busbars  18 , which are now sitting within the channels  44  and straddled by the cable holder  40 . It will be appreciated, that the upper surface of the dividing wall  46  of the cable holder  40  lies below the bottom of the channels  44  thereof, to allow this interengagement, which is enhanced by the return force of the support plate spring  26 , which is still under tension. 
   It will be appreciated that by reversing the movement of the switching member  54 , the cable holder  40 , owing to the movement of the cams  58  within the holder apertures  48 , is again pulled upwards in the chamber  10  until the switching member  54  again abuts the OFF stop  52 . 
   It will also be appreciated, that each of the nine tap ports  8  may be operated independently of each other, so that appropriate ones of the branch cables  43  may be introduced or removed, and connected or disconnected, independently of the others. 
     FIG. 9  shows a modified switching arrangement  70 , in which ten chambers of the housing  72  are divided into two groups  74 ,  74   a  of five chambers each. Each group  74 ,  74   a  can receive one feeder cable, for example of different phases, in a respective end port  76 ,  76   a  and can accommodate up to four branch cables in the remaining ports. The ports and other components of the arrangement  70  may be substantially as described above for the feeder and branch ports respectively of the arrangement  2 . It will be appreciated that the busbars of the arrangement  70  will be approximately half the length of the busbars  18  of the arrangement  2 , since they will be serving respective groups  74 ,  74   a  of the housing chambers, and will be insulated from each other. 
   It will be appreciated that fewer or more than eight branch ports may be provided by the switchable electrical interconnection arrangement of the invention.