Abstract:
A mold structure for molding a circuitry comprises a cavity to which a plurality of bus bars are juxtaposedly inserted provided with gap portions to which a resin material to be injected therethrough; and a plurality of holder pins provided on the respective gap portions and arranged alternatively in the juxtaposition direction of the plural bus bars to hold the respective bus bar to be inserted therebetween.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method of forming or molding a circuitry by molding a resin on a plurality of bus bars inserted at a small pitch (at small intervals) in a mold, and the present invention also relates to a mold structure used in this molding method. 
     A circuitry, having bus bars, is used in an internal circuit of an electric part such as a connector. This circuitry is produced by inserting a plurality of bus bars into a mold and then by injecting a resin into the mold to form a resin-molded portion. As a result, the resin-molded portion holds the bus bars in such a manner that the adjacent bus bars are kept out of contact with each other. 
     FIGS. 4 and 5 show a related method of molding such a circuitry. A mold  1  has a cavity portion  3  in which a plurality of bus bars  2  are held in a juxtaposed manner. Holder pins  4  are provided in the cavity portion  3 , and these holder pins  4  hold the plurality of bus bars  2  at small intervals in such a manner that the bus bars will not contact with one another. The holder pins  4  are arranged substantially on a common straight line in a direction of juxtaposition of the bus bars  2 . 
     In this method, the bus bars  2  are juxtaposed in the cavity portion  3  of the mold  1  in such a manner that each bus bar  2  is inserted between the associated holder pins  4 , and then the mold is clamped, and then molten resin is injected into the cavity  1  through a gate (not shown). The molten resin thus injected flows in between the bus bars  2 , and is solidified to form resin-molded portions  5 , and each resin-molded portion  5 , formed between the associated adjacent bus bars  2 , holds these bus bars  2  out of contact with each other, as shown in FIG.  5 . 
     In the above molding method, however, the holder pins  4  and the bus bars  2  are arranged so densely that the resin can not easily flow in between the bus bars  2 , and therefore the resin-molded portions  5  are liable to be formed with insufficient length (short shot). And besides, since the holder pins  4  are arranged such that each of the bus bars  2  is held at two juxtaposed points on a common line perpendicular to an extending direction of the bus bars  2 , each holder pin  4  functions as a rotational fulcrum for the associated bus bar  2 , so that the bus bars  2  are liable to be turned as indicated by arrows in FIG.  6 . This results in a problem that the adjacent bus bars  2  are brought into contact with each other. Furthermore, since the holder pins  4  are arranged on a common line, the holder pins  4  are disposed close to one another as shown in FIG.  7 . Therefore, the whole of each holder pin  4 , including its base portion  4   a , can not be made thick, and therefore the holder pin  4  has a reduced strength, and is liable to be broken. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a method of molding a circuitry in which a short shot of a molded resin is prevented, and bus bars are prevented from being turned, and holder pins have an increased strength. Another object of the present invention is to provide a mold structure suitably used in this molding method. 
     In order to achieve the above objects, there is provided a mold structure for molding a circuitry comprising: a cavity to which a plurality of bus bars are juxtaposedly inserted provided with gap portions to which a resin material to be injected therethrough; and a plurality of holder pins provided on the respective gap portions and arranged alternatively in the juxtaposition direction of the plural bus bars to hold the respective bus bar to be inserted therebetween. 
     In the mold structure, each of the bus bars is held by both sides of the holder pins at two different points in an extending direction thereof. 
     In the mold structure, each of the holder pins has a large-diameter base portion, and the holder pins are arranged such that the base portions of any adjacent holder pins are overlapped in an extending direction of the bus bars. 
     Since the holder pins are arranged alternatively, the adjacent holder pins are sufficiently spaced from each other. Therefore, the holder pins and the bus bars are not arranged densely, and the resin can easily flow in between the bus bars, so that the short shot of the resin is prevented. And besides, the adjacent holder pins are contacted respectively with right and left sides of the bus bar at two different points in the extending direction thereof to thereby hold the bus bar, and therefore the bus bar will not be turned, and the bus bars will not be brought into contact with each other. Furthermore, the adjacent holder pins are sufficiently spaced from each other, and therefore the holder pins can be made thick to have an increased strength. 
     According to the present invention, there is also adopted a method of molding a circuitry, in which a plurality of bus bars are juxtaposed with predetermined intervals, comprising the steps of: preparing a mold structure comprising a cavity, and a plurality of holder pins provided with the predetermined intervals and arranged alternatively in the juxtaposition direction thereof; inserting the plural bus bars juxtaposedly into the cavity through respective spaces between the holder pins; injecting a resin material into respective spaces between the bus bars through the cavity; and solidifying the resin material to keep the bus bars out of contact with each other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a plan view of a mold used in one preferred embodiment of the present invention; 
     FIG. 2 is a plan view showing a condition in which each bus bar is inserted between holder pins; 
     FIG. 3 is a side view showing the operation of the holder pin; 
     FIG. 4 is a plan view of a mold used in a related method; 
     FIG. 5 is an enlarged plan view of a portion of FIG.  4 . 
     FIG. 6 is a plan view showing a condition in which each bus bar is inserted between holder pins in the related mold; and 
     FIG. 7 is a side-elevational view showing the related holder pins; 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows one preferred embodiment of a mold  11  of the present invention. This mold  11  has a cavity portion  13 , and a plurality of bus bars  12  are juxtaposed in the cavity portion  13 , and in this condition a resin is molded on the bus bars. A plurality of holder pins  14  are provided in the cavity portion  13 , and these holder pins  14  hold the bus bars  12  inserted in the mold  11  in such a manner that each bus bar  12  is held between the associated adjacent holder pins  14 . The holder pins  14  are so arranged that the bus bars  12  can be juxtaposed to one another at small intervals. 
     As shown in FIG. 3, each holder pin  14  includes a base portion  14   a  of a larger diameter, and a holder portion  14   b  of a smaller diameter formed at a distal end of the base portion  14   a . Each bus bar  2  is inserted between the associated holder portions  14   b , so that the holder pins  14  function to hold the bus bar  12 . The holder pins  14  are arranged alternatively (i.e., a zigzag manner) in a direction of juxtaposition of the bus bars  12  (transversal direction in FIG.  1 ), so that any two adjacent ones of the holder pins  14  are not disposed on a common line in this juxtaposition direction. Therefore, when the bus bar  12  is inserted between the adjacent holder pins  14 , the adjacent holder pins  14  hold the bus bar  12  therebetween in such a manner that these pins  14  are contacted respectively with two different points (portions) of the bus bar  2  spaced from each other in an extending direction of the bus bar  2 . 
     For molding a circuitry of this embodiment, the bus bars  12  are inserted into the cavity portion  13  of the mold  11 . In this inserting operation, each bus bar  12  is inserted between the associated adjacent holder pins  14 . Therefore, each bus bar  12  is held by the adjacent holder pins  14 , so that the bus bars  12  will not be brought into contact with each other. The bus bars  12  are thus held by the holder pins  14 , and in this condition the mold is clamped or closed, and molten resin is injected into the mold  11 . The molten resin thus injected flows in between the bus bars  2  and between the holder pins  14  as shown in a right half portion of FIG. 1, and then is solidified to form resin-molded portions  15 , and each resin-molded portion  15 , formed between the associated adjacent bus bars  12 , holds these bus bars  12  out of contact with each other. 
     In this embodiment, the holder pins  14  for holding the bus bars  12  are arranged alternatively, and therefore any two adjacent ones of the holder pins are not disposed on a common line in the direction of juxtaposition of the bus bars  12 . Therefore, the adjacent holder pins  14  are sufficiently spaced from each other, and the holder pins  14  and the bus bars  12  are not arranged densely. Therefore, the resin can easily flow in between the bus bars  12 , and a short shot of the resin will not occur. 
     As shown in FIG. 2, the adjacent holder pins  14  are contacted respectively with the right and left sides of the bus bar  2  at two different points thereof, spaced from each other in the extending direction thereof the bus bar  2 , to thereby hold the bus bar  2 , and therefore the bus bar  2  will not be turned. Therefore, the contact of the bus bars  2  with each other due to such turning movement is eliminated. And besides, the adjacent holder pins  14  are sufficiently spaced from each other, and therefore the base portion  14   a  can be made so thick that it overlaps the base portion  14   a  of the adjacent holder pin  14 , as shown in FIG.  3 . As a result, the holder pin  14  can be increased in overall strength, and will not be broken. 
     In this embodiment, although the resin is injected into the mold  11 , the resin-molded portions  15  can be formed by an injection blow molding, an extrusion molding or the like. 
     As has been described heretofore, according to the present invention, the holder pins for holding the bus bars are arranged alternatively, and therefore the holder pins and the bus bars are not arranged densely, and the short shot of the resin is prevented. And besides, each bus bar is held at two different points in the extending direction thereof, and therefore the bus bar is prevented from being turned, and therefore will not be brought into contact with the adjacent bus bar, and each holder pin can be made thick to have an increased strength. 
     Although the present invention has been shown and described with reference to specific preferred embodiments, various changes and modifications will be apparent to those skilled in the art from the teachings herein. Such changes and modifications as are obvious are deemed to come within the spirit, scope and contemplation of the invention as defined in the appended claims.