Patent Publication Number: US-2013252483-A1

Title: Connecting structure for electronic devices

Description:
BACKGROUND 
     The present invention is related to a connecting structure for electronic devices. The connecting structure can connect together electronic devices having different pitches in contact-to-contact. 
     Patent Document 1 discloses an electronic devices connecting structure which gains high reliability by ensuring the electric connection of electronic devices. As  FIG. 20  shows, in this connecting structure, a pair of busbars  501 ,  503  and a semiconductor light emitting element (LED)  505 , which is a light source, are assembled to a housing. The busbars  501 ,  503 , which have a flat plate-like shape and which are the divided two busbars, have an electric wire connecting portion  507 , a Zener diode connecting portion  509 , a resistor connecting portion  511 , and an LED connecting portion  513 . The resistor connecting portion  511  includes press contact blades  515 ,  515  which are given individually to the busbars  501 ,  503  which are the divided two busbars. The Zener diode connecting portion  509  includes a single press contact blade  517  given to the busbar  501  and a single press contact blade  519  given to the busbar  503 . 
     A Zener diode  521  is electrically connected to the busbar  501  at a lead portion  523  and to the busbar  503  at a lead portion  525  so that the Zener diode  521  is connected in parallel to the pair of busbars  501 ,  503  at a downstream side of a resistor  527 . In this configuration, the Zener diode  521  protects the LED from a failure caused by an abrupt large voltage applied to the circuit by static electricity in a direction in which a forward electromotive force flows in the diode. The Zener diode  521  also disrupts the continuity in the circuit in a direction in which a backward electromotive force flows in the diode so as to protect the LED from a failure. 
     [Patent Document 1] JP-A-2007-149762 
     SUMMARY 
     The conventional connecting structure for electronic devices needs the two types of busbars  501 ,  503  on which the connecting portions which are different in dimensions so as to match the shapes and sizes of the electronic devices. The connecting portions include the press contact blades  515 ,  515 , the press contact blade  517 , and the press contact blade  519 . In addition, only the through-hole electronic devices having the lead portions can be mounted in the connecting structure, leading to a problem that surface mount electronic devices which have found many applications and hence have become inexpensive in recent years cannot be connected to the same construction. The electronic devices include the Zener diode  521  and the resistor  527 . 
     It is therefore one advantageous aspect of the present invention to provide a connecting structure which enables the connection of a plurality of types of surface mount electronic devices having different contact-to-contact pitches, external shapes and sizes with busbars of one type. 
     According to one advantage of the invention, there is provided a connecting structure for electronic devices, the connecting structure comprising:
         a plurality of busbars arranged parallel to each other with a space therebetween, wherein   each of the busbars has a terminal part,   the terminal part has at least two pairs of contact elastic pieces,   each of the pairs of the contact elastic pieces consists of two contact elastic pieces arranged laterally,   the pairs of the contact elastic pieces are vertically arranged so as to form layers,   each of the contact elastic pieces of the busbars is configured to elastically come in contact with one of contact portions of at least one of electronic devices, and   at least two of the contact elastic pieces disposed in same one of the layers are elastically come in contact with the contact portions of the electronic device respectively, when the one of the electronic devices is attached to the connecting structure.       

     The connecting structure may be configured such that: the electronic devices include a first electronic device and a second electronic device, two of the busbars are provided in the connecting structure, each of the busbars includes a pair of contact members arranged laterally, an end part of each of the contact members is branched to form two of the contact elastic pieces, four of the contact elastic pieces are arranged in each of two layers, two of the contact elastic pieces which are adjacent with each other are configured to be come in contact with a pair of the contact portions of the first electronic device respectively in one of the two layers, and two of the contact elastic pieces between which at least one of the contact elastic pieces is arranged are configured to be come in contact with a pair of the contact portions of the second electronic device respectively in the other of the two layers. 
     The connecting structure may be configured such that: each of the busbars is formed by being bent a plate into a U-shape so that each of the busbars includes a pair of side walls disposed in parallel to each other, and the contact elastic pieces are formed by punching the side walls. 
     The connecting structure may be configured such that: the one of the electronic devices is a semiconductor light emitting element, a light emitting portion of the semiconductor light emitting element is disposed between two of the busbars, and reflecting surface are formed on each of side surfaces of the busbars between which the light emitting portion is disposed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of two busbars which are used in a connecting structure for electronic devices according to a first embodiment of the invention. 
         FIG. 2  is a perspective view of a housing which accommodates the busbars shown in  FIG. 1 . 
         FIG. 3  is a perspective view of one of the busbars shown in  FIG. 1 . 
         FIG. 4A  is a plan view of the busbars shown in  FIG. 1 . 
         FIG. 4B  is a sectional view of the busbars taken along the line indicated by arrows A, A in  FIG. 4A . 
         FIG. 4C  is a sectional view of the busbars taken along the line indicated by arrows B, B in  FIG. 4A . 
         FIG. 5A  is a perspective view of a semiconductor light emitting element. 
         FIG. 5B  is a perspective view of a Zener diode. 
         FIG. 6  is a drawing which depicts a busbars assembling step in the connecting structure according to the first embodiment of the invention. 
         FIG. 7  is a drawing which depicts similarly an electronic devices assembling step. 
         FIG. 8  is a drawing which depicts similarly a housing assembling step. 
         FIG. 9  is a drawing which depicts similarly an electric wire holder assembling step. 
         FIG. 10  is a perspective view of an LED unit which uses the connecting structure according to the first embodiment of the invention. 
         FIG. 11A  is a plan view of an LED unit according to a modified example. 
         FIG. 11B  is a sectional view of the LED unit taken along the line indicated by arrows C, C in  FIG. 11A . 
         FIG. 11C  is a sectional view of the LED unit taken along the line indicated by arrows D, D in  FIG. 11A . 
         FIG. 12  is an enlarged view of a main part of the LED unit shown in  FIG. 11C . 
         FIG. 13  is a perspective view of a busbar according to a modified example in which lateral side walls are partially cut to be erected. 
         FIG. 14A  is a perspective view showing two busbars like the busbar shown in  FIG. 13  as being aligned side by side. 
         FIG. 14B  is a plan view of the busbars like the busbar shown in  FIG. 13  as being aligned side by side. 
         FIG. 15  is a drawing which depicts a busbars assembling step in a connecting structure for electronic devices according to a second embodiment of the invention. 
         FIG. 16  is a drawing which depicts similarly an electronic devices assembling step. 
         FIG. 17  is a drawing which depicts similarly a housing assembling step. 
         FIG. 18  is a drawing which depicts similarly an electric wire holder assembling step. 
         FIG. 19  is a perspective view of an LED unit which uses the connecting structure according to the second embodiment of the invention. 
         FIG. 20  is a perspective view of a conventional connecting structure for electronic devices. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLIFIED EMBODIMENTS 
     Hereinafter, an embodiment of the invention will be described by reference to the drawings. 
       FIG. 1  is a perspective view of two busbars which are used in a connecting structure for electronic devices according to a first embodiment of the invention, and  FIG. 2  is a perspective view of a housing which accommodates the busbars shown in  FIG. 1 . 
     A connecting structure for electronic devices  11  according to the first embodiment of the invention has two busbars  13  having the same shape shown in  FIG. 1  as a main part of the configuration thereof. These two busbars  13  are accommodated in a housing  15  shown in  FIG. 2  for use. 
     The two busbars  13  each have a terminal portion  19  which is formed at one end  17  thereof and are disposed parallel to each other with a space defined therebetween. The terminal portion  19  has at least a pair of contact elastic pieces  23 ,  24  which are disposed parallel to each other horizontally. The contact elastic pieces  23 ,  24  each include several vertically arranged contact elastic elements. The contact elastic elements include a pair of upper and lower contact elastic elements  23   a,    23   b / 24   a,    24   b  in this embodiment. In a sense, the upper contact elastic elements  23   a,    24   a  of the contact elastic pieces  23 ,  24  form an upper pair of contact elastic elements which are disposed parallel to each other horizontally, and the lower contact elastic elements  23   b,    24   b  thereof form a lower pair of contact elastic elements which are disposed parallel to each other horizontally. These contact elastic elements  23   a,    24   a,    23   b,    24   b  can be brought into elastic contact with pairs of contact portions  21  of a plurality of types of electronic devices  11 . The number of the types of electronic devices  11  is two in this embodiment. 
     In this embodiment, as described above, one busbar  13  has the pair of contact elastic pieces  23 ,  24  which are each caused to branch into a substantially Y-shape so that the one busbar  13  has the two pairs of contact elastic elements  23   a,    24   a,    23   b,    24   b  in total towards distal ends of the contact elastic pieces  23 ,  24 . In the four upper contact elastic elements  23   a,    24   a,    23   a,    24   a  of the busbars  13  which are disposed parallel to each other, electric contact portions  45  of the two adjacent contact elastic elements  24   a,    23   a  of the busbars  13  are connected to a pair of contact portions  21  of a semiconductor light emitting element  25 , which is a first electronic device  11  disposed between the two busbars  13  (refer to  FIG. 4 ). In the four lower contact elastic elements  23   b,    24   b,    23   b,    24   b  of the busbars  13  which are disposed parallel to each other, electric contact portions  45  of the two contact elastic elements  24   b,    24   b  of the busbars  13 , which are disposed spaced apart from each other so as to hold the contact elastic element  23   b  of the busbar  13  therebetween, are connected to a pair of contact portions  21  of a Zener diode  27 , which is a second electronic device  11  which is disposed below the semiconductor light emitting element  25  between the two busbars  13  (refer to  FIG. 4 ). 
       FIG. 3  is a perspective view of one of the busbars  13  shown in  FIG. 1 . 
     Part of the busbar  13  projects out of a housing  15  in such a state that the busbar  13  is mounted in the housing  15 . In this embodiment, a side of the housing  15  from which part of the busbar  13  projects is referred to as a “rear” and an opposite side thereto is referred to as a “front.” A press contact blade  31  is provided at a rear end of the busbar  13  for establishing an electric contact between the busbar  13  and a conductor of a covered electric wire by cutting a covering thereof. Continuously formed forwards of the press contact blade  31  are a rear abutment piece  33 , rear elastic legs  35 , front elastic legs  37  and front abutment pieces  39 . 
     The terminal portion  19 , which is disposed at the one end  17  (the front end) of the busbar  13 , is continuously provided with the front abutment piece  39  which lies on a back side of  FIG. 3  via a connecting portion  41  (refer to  FIG. 4A ). The press contact blade  31 , the rear abutment piece  33 , the rear elastic legs  35 , the front elastic legs  37 , the front abutment pieces  39  and the terminal portion  19  are punched altogether out of a sheet of metal through sheet metal working and are then bent into a shape shown in  FIG. 3 . The terminal portion  19  of the busbar  13  is bent into a U-shape so that a pair of lateral side walls  43  become parallel to each other, and the contact elastic pieces  23 ,  24  are formed in the corresponding lateral side walls  43  through punching. A main body of the busbar  13  is bent into the U-shape, and the two pairs of contact elastic elements  23   a,    24   a,    23   b,    24   b  are formed at the distal ends of the contact elastic pieces  23 ,  24  which are formed so as to branch into the substantially Y-shape through punching in the pair of lateral side walls  43  of the busbar  13  which face each other, whereby the elastic contact construction having a number of electric contact portions  45  can be fabricated compact with ease. 
       FIG. 4A  is a plan view of the busbars  13  shown in  FIG. 1 ,  FIG. 4B  is a sectional view of the busbar  13  taken along the line indicated by arrows A, A in  FIG. 4A ,  FIG. 4C  is a sectional view of the busbar  13  taken along the line indicated by arrows B, B in  FIG. 4A ,  FIG. 5A  is a perspective view of the semiconductor light emitting element  25 , and  FIG. 5B  is a perspective view of the Zener diode  27 . 
     In one busbar  13 , the pair of contact elastic pieces  23 ,  24  are formed so as to be parallel to each other. The contact elastic pieces  23 ,  24  are each caused to branch into the substantially Y-shape so as to have the pair of contact elastic elements  23   a,    23   b / 24   a,    24   b  which are formed towards the distal end thereof. In other words, the contact elastic elements  23   a,    24   a  form the upper pair of contact elastic elements and the contact elastic elements  23   b,    24   b  form the lower pair of contact elastic elements. The electric contact portions  45  formed at respective distal ends of the contact elastic elements  23   a,    24   a,    23   b,    24   b  so as to project therefrom are each formed into a triangular shape whose apex is configured as a contact point. As is shown in  FIG. 4A , the two busbars  13  are disposed parallel to each other with a space defined therebetween. According to this configuration, in each of the busbars  13  which are disposed parallel to each other, four electric contact portions  45  are provided to be disposed at the distal ends of the contact elastic elements  23   a,    24   a,    23   b,    24   b.  Thus, in the two busbars  13 , eight electric contact portions  45  in total are provided to be disposed at the distal ends of the two pairs of contact elastic elements  23   a,    24   a,    23   b,    24   b,  as is shown in  FIG. 4C . Upper part seating portions  47  are formed on the busbars  13  so as to face the four upper electric contact portions  45  of the four upper contact elastic elements  23   a,    24   a,    23   a,    24   a  of the busbars  13  which are disposed parallel to each other. In addition, lower part seating portions  49  are formed on the busbars  13  so as to face the four lower electric contact portions  45  of the four lower contact elastic elements  23   b,    24   b,    23   b,    24   b  of the busbars  13  which are disposed parallel to each other. 
     The semiconductor light emitting element  25  is mounted between the upper part seating portions  47  and the corresponding four upper electric contact portions  45  of the four upper contact elastic elements  23   a,    24   a,    23   a,    24   a.  The Zener diode  27  is mounted between the four lower electric contact portions  45  of the four lower contact elastic elements  23   b,    24   b,    23   b,    24   b  and the corresponding lower part seating portions  49 . As is shown in  FIG. 5A , the semiconductor light emitting element  25  is a surface mount electronic device  11  on one surface of which a pair of contact portions  21  are provided. In addition, as is shown in  FIG. 5B , the Zener diode  27  is also a surface mount electronic device  11  on one surface of which a pair of contact portions  21  are provided. 
     As is shown in  FIG. 4C , the semiconductor light emitting element  25  is brought into abutment with the upper part seating portions  47  on a back side thereof with the side where the contact portions  21  are provided oriented towards the electric contact portions  45  of the upper adjacent contact elastic elements  23   a,    24   a.  The Zener diode  27  is brought into abutment with the lower part seating portions  49  on a back side thereof with the side where the contact portions  21  are provided oriented towards the electric contact portions  45  of the lower adjacent contact elastic elements  23   b,    24   b.    
     In this embodiment, a contact-to-contact pitch of the semiconductor light emitting element  25  is smaller than a contact-to-contact pitch of the Zener diode  27 . Namely, the two electronic devices  11  have different contact-to-contact pitches. In this embodiment, the two types of electronic devices  11  having the different contact-to-contact pitches are allowed to be mounted in the electronic devices connecting construction for electronic devices  11  at the same time. Namely, as is shown in  FIG. 4C , in the four upper contact elastic elements  23   a,    24   a,    23   a,    24   a  of the busbars  13  which are disposed parallel to each other, the electric contact portions  45  of the adjacent contact elastic elements  24   a,    23   a  are in contact with the pair of contact portions  21  of the semiconductor light emitting element  25 . In the four lower contact elastic elements  23   b,    24   b,    23   b,    24   b  of the busbars  13  which are disposed parallel to each other, the electric contact portions  45  of the two adjacent contact elastic elements  24   b,    24   b  of the busbars  13 , which are disposed spaced apart from each other so as to hold the contact elastic element  23   b  of the busbar  13  therebetween, are in contact with the pair of contact portions  21  of the Zener diode  27 . 
     Namely, in  FIG. 4C , the semiconductor light emitting element  25  is connected to the second leftmost electric contact portion  45  and the third leftmost electric contact portion  45  in the upper electric contact portions  45  of the busbars  13  which are disposed parallel to each other. In addition, the Zener diode  27  is connected to the first leftmost electric portion  45  and the third leftmost electric portion in the lower electric contact portions  45  of the busbars  13  which are disposed parallel to each other. However, the Zener diode  27  can also be connected to the second leftmost electric contact portion  45  and the fourth leftmost electric contact portion  45 . In this embodiment, the contact-to-contact pitch of the Zener diode  27  used is double the contact-to-contact pitch of the adjacent electric contact portions  45 . However, a Zener diode  27  can also be used which has a contact-to-contact pitch which is three times the contact-to-contact pitch of the adjacent electric contact portions  45 . As this occurs, a pair of contact portions  21  of the Zener diode  27  are connected to the first leftmost electric contact portion  45  and the fourth leftmost electric contact portion  45 . 
     Next, assembling steps of the connecting structure for electronic devices  11  will be described. 
       FIG. 6  is a drawing which depicts a busbars assembling step in the connecting structure for electronic devices  11  according to the first embodiment of the invention,  FIG. 7  is a drawing which depicts similarly an electronic devices assembling step,  FIG. 8  is a drawing which depicts similarly a housing assembling step,  FIG. 9  is a drawing which depicts similarly an electric wire holder assembling step, and  FIG. 10  is a perspective view of an LED unit  53  which uses the connecting structure for electronic devices  11  according to the first embodiment of the invention. 
     The connecting structure for electronic devices  11  can preferably be adopted for an LED unit  53 , for example. In application of the connecting structure for electronic devices  11  to the LED unit  53 , as is shown in  FIG. 6 , the two busbars  13  are mounted in the housing  15 . 
     Two busbar accommodation compartments  55  are formed in the housing  15 . In each of the busbar accommodation compartments  55 , a rear wall  57  is formed at a rear thereof, and a pair of holding grooves  59  are formed on inner wall surfaces which lie forwards of the rear wall  57 . In the busbar  13  inserted into the busbar accommodation compartment  55 , the rear wall  57  is held by the rear abutment piece  33  and the rear elastic legs  35 , so that the busbar  13  is mounted in the housing  15  while being restricted from being dislodged therefrom. 
     As is shown in  FIG. 7 , an LED mounting opening portion  61  and a diode mounting opening portion  63  are formed in a front side of the housing  15  so as to be disposed vertically. The semiconductor light emitting element  25  is inserted into the LED mounting opening portion  61  with the contact portions  21  oriented downwards. The Zener diode  27  is inserted into the diode mounting opening portion  63  with the contact portions  21  oriented upwards. By the electronic components being inserted into the housing  15  in the ways described above, as is shown in  FIG. 4C , the contact portions  21  thereof are connected to the corresponding electric contact portions  45 . In addition, a resistor mounting opening portion (not shown) is formed in a bottom side of the housing, and the resistor  28  is inserted thereinto. By this configuration, the resistor  28  is held by the front abutment pieces  39  and the front elastic legs  37  of the busbar  13  disposed on a near side, and electric contact portions of the front elastic legs  37  are connected a pair of contact portions of the resistor  28  (refer to  FIG. 1 ). 
     Here, the LED unit  53  according to this embodiment needs a circuit in which resistors  28  are provided, respectively, between the semiconductor light emitting element  25  and the Zener diode  27  and between an anode terminal and a cathode terminal. Then, as  FIG. 7  shows, a cutaway portion  16  is formed between the pair of front abutment pieces  39  and the pair of front elastic legs  37  of the near side busbar  13 , whereby the resistor  28  mounted in the near side busbar  13  is connected with the semiconductor light emitting element  25  and the Zener diode  27  in series. 
     As  FIG. 8  shows, the housing  15  in which the semiconductor light emitting element  25  and the Zener diode  27  are mounted is mounted, in turn, in a lens cover  65 . A housing inserting opening portion  67  is formed in a rear end face of the lens cover  65 . In the housing  15  inserted into the lens cover  65 , the press contact blades  31  project rearwards in an interior of the lens cover  65 . 
     As  FIG. 9  shows, an electric wire holder  69  is inserted into the lens cover  65  in which the housing  15  is mounted from the housing inserting opening portion  67 . U-shaped electric wire holding grooves  71  are formed at two locations over three external surfaces of the electric wire holder  69 . A covered electric wire  29  is bent into a U-shape to be mounted in each of the electric wire holding grooves  71 . Horizontal press contact blades entrance slits  73  are formed in a front side of the electric wire holder  69  so as to straddle the corresponding electric wire holding grooves  71 . In this configuration, when the electric wire holder  69  is inserted into the lens cover  65 , the press contact blades  31  of the busbars  13  which project rearwards in the interior of the lens cover  65  enter the corresponding press contact blade entrance slits  73 , whereby the press contact blades  31  and conductors of the electric wires  29  are connected together. 
     When the electric wire holder  69  is inserted into the lens cover  65 , locking claws  77  provided on lateral sides of the electric wire holder  69  so as to project therefrom are locked in corresponding locking holes  75  formed in lateral side portions of the lens cover  65 , whereby the dislodgement of the housing  15  from the lens cover  65  and the electric wire holder  69  from the lens cover  65  is restricted. The LED unit  53  shown in  FIG. 10  is completed by the housing  15  and the electric wire holder  69  being mounted in the lens cover  65 . 
     In this way, in the connecting structure for electronic devices  11  of the first embodiment, the two busbars  13  having the terminal portions  19  are disposed parallel to each other with the space defined therebetween, and the terminal portion  19  includes the pair of contact elastic pieces  23 ,  24  each having the pair of contact elastic elements  23   a,    23   b / 24   a,    24   b  which face each other vertically. In other words, the contact elastic element  23   a  of the busbar  13  and the contact elastic element  24   a  of the other busbar  13  form the upper pair of contact elastic elements which face each other horizontally, and the contact elastic element  23   b  of the busbar  13  and the contact elastic element  24   b  of the other busbar  13  form the lower pair of contact elastic elements which face each other horizontally. Then, in the upper four contact elastic elements  23   a,    24   a,    23   a,    24   a  of the busbars  13  which are disposed parallel to each other, the electric contact portions  45  of the two adjacent contact elastic elements  24   a,    23   a  of the busbars  13  are connected to the pair of contact portions  21  of the semiconductor light emitting element  25  which is disposed between the two busbars  13 . In addition, in the lower four contact elastic elements  23   b,    24   b,    23   b,    24   b  of the busbars  13  which are disposed parallel to each other, the electric contact portions  45  of the contact elastic elements  24   b,    24   b  of the busbars  13  which are disposed spaced apart from each other so as to hold the contact elastic element  23   b  of the busbar  13  therebetween are connected to the pair of contact portions  21  of the Zener diode  27  which is positioned below the semiconductor light emitting element  25  between the two busbars  13 , whereby the electronic devices  11  having the different contact-to-contact pitches, external shapes and sizes can be connected together. 
     In addition, the two busbars  13  are disposed parallel to each other with the space defined therebetween, and each busbar  13  has the pair of contact elastic pieces  23 ,  24  which are each caused to branch into the substantially Y-shape so that each contact elastic piece  23 / 24  has the pair of contact elastic elements  23   a,    23   b / 24   a,    24   b  which are provided towards the distal end thereof while facing each other vertically. In other words, each busbar  13  has the two upper and lower pairs of contact elastic elements  23   a,    24   a,    23   b,    24   b  which face each other horizontally. Thus, each busbar  13  has the four electric contact portions  45  and the two busbars  13  have the eight electric contact portions  45  in total. By adopting this configuration, in the four upper contact elastic elements  23   a,    24   a,    23   a,    24   a  of the two busbars  13  which are disposed parallel to each other with the space defined therebetween, the electric contact portions  45  of the two adjacent contact elastic elements  24   a,    23   a  of the busbars  13  can be connected to the semiconductor light emitting element  25  whose size and contact-to-contact pitch are small. In addition, in the four lower contact elastic elements  23   b,    24   b,    23   b,    24   b  of the two busbars  13 , the two contact elastic elements  24   b,    24   b  of the busbars  13  which are disposed spaced apart from each other so as to hold the contact elastic element  23   b  of the busbar  13  therebetween can be connected to the Zener diode  27  whose size and contact-to-contact pitch are large. 
     Next, modified examples made to the connecting structure for electronic devices  11 . 
       FIG. 11A  is a plan view of an LED unit  53  according to a modified example,  FIG. 11B  is a sectional view of the LED unit  53  taken along the line indicated by arrows C, C in  FIG. 11A , and  FIG. 11C  is a sectional view of the LED unit  53  taken along the line indicated by arrows D, D in  FIG. 11A .  FIG. 12  is an enlarged view of a main part of the LED unit  53  shown in  FIG. 11C . 
     In a connecting structure for electronic devices  11  according to this modified example, one of electronic devices  11  is a semiconductor light emitting element  25 , and a light emitting portion  79  thereof is disposed between two busbars  13 A. On the other hand, in the two busbars  13 A, a reflecting surface  83  is formed on each of lateral side wall surfaces  81  which face each other across the light emitting portion  79 . 
     In this modified example, the light emitting portion  79  of the semiconductor light emitting element  25  is disposed so as to be held between the two busbars  13 A which are disposed parallel to each other with a space defined therebetween. The reflecting surface  83  is formed on each of the lateral side wall surfaces  81  of lateral sides  43  of the two busbars  13 A which hold the light emitting portion  79  therebetween, whereby as  FIG. 12  shows, light emitted from the light emitting portion  79  is reflected by the reflecting surfaces  83  so as to be directed towards a lens  65   a  of a lens cover  65  which is disposed in the direction of emission of light, whereby the light emitted from the light emitting portion  79  can be used effectively. 
     Next, another modified example will be described. 
       FIG. 13  is a perspective view of a busbar  13 B according to a modified example in which lateral side walls  43  are partially cut to be erected,  FIG. 14A  is a perspective view showing two busbars like the busbar  13 B shown in  FIG. 13  as being aligned side by side, and  FIG. 14B  is a plan view of the busbars  13 B so aligned. 
     In a connecting structure for electronic devices  11  according to this modified example, as  FIG. 13  shows, distal end portions and portions lying further rearwards than the distal end portions of lateral side walls  43  of a busbar  13 B are cut to be erected so that a pair of front and rear vertical pieces  85  project on each of the lateral side walls  43 . As with the previous example, two busbars  13 B like the busbar  13 B just described are provided side by side a pair of contact elastic piece  23  of one busbar  13 B and a pair of contact elastic pieces  24  of the other busbar  13 B become parallel to each other, whereby the front vertical pieces  85  and the rear vertical pieces  85  on the lateral side walls  43  of the busbars  13 B are butted up against each other. Facing surfaces of the vertical pieces  85  are configured as reflecting surfaces  83 . 
     By adopting this configuration, as  FIG. 14  shows, a light emitting portion  79  is surrounded around four sides thereof by reflecting surfaces  83  which are formed on a pair of parallel lateral side walls  43  and a pair of reflecting surfaces  83  formed on vertical pieces  85  which are perpendicular to the reflecting surfaces  83  on the lateral side walls  43  and in which a pair of vertical surfaces  85  which are butted up against each other face the other pair of vertical surfaces  85  which are also butted up against each other. According to this configuration, almost no light leakage occurs, thereby making it possible to make effective use of light emitted from the light emitting portion  79 . 
     Consequently, according to the connecting structure for electronic devices  11  of this embodiment, with one type of busbars  13 , two types of surface mount electronic devices  11  having different contact-to-contact pitches, external shapes and sizes can be connected together. 
     In the first embodiment, while the connecting structure for electronic devices  11  has been described which has the two busbars  13  having the same shape as the main part of the configuration thereof, the connecting structure according to the invention is not limited thereto. Therefore, there may be provided a connecting structure which has three or more busbars having the same shape as a main part of the configuration thereof. 
     Referring to  FIGS. 15 to 19 , a two-lamp type LED unit  99  will be described which uses a connecting structure for electronic devices  11 A according to a second embodiment. Like reference numerals will be given to substantially like constituent members to those of the LED unit  53  which uses the connecting structure for electronic devices  11  according to the first embodiment, and the detailed description thereof will be omitted herein. 
     A connecting structure for electronic devices  11 A according to the second embodiment has three busbars  13 C, shown in  FIG. 15 , which have the same shape as a main part of the configuration thereof. The three busbars  13 C are accommodated in a housing  91  for use. 
     The three busbars  13 C each have a terminal portion  19  which is formed at one end  17  thereof and are disposed parallel in three rows while being spaced apart from one another. The terminal portion  19  has at least a pair of contact elastic pieces  23 ,  24  which are disposed parallel to each other horizontally. The contact elastic pieces  23 ,  24  each include several vertically arranged contact elastic elements. The contact elastic elements include a pair of upper and lower contact elastic elements  23   a,    23   b / 24   a,    24   b  in this embodiment. In a sense, the upper contact elastic elements  23   a,    24   a  of the contact elastic pieces  23 ,  24  form an upper pair of contact elastic elements which are disposed parallel to each other horizontally, and the lower contact elastic elements  23   b,    24   b  thereof form a lower pair of contact elastic elements which are disposed parallel to each other horizontally. These contact elastic elements  23   a,    24   a,    23   b,    24   b  can be brought into elastic contact with pairs of contact portions  21  of a plurality of electronic devices  11 A. The number of the electronic devices  11 A is three, and the number of the types of the electronic devices  11 A is two, in this embodiment. 
     One busbar  13  has the pair of contact elastic pieces  23 ,  24  which are each caused to branch into a substantially Y-shape so that the one busbar  13  has the two pairs of contact elastic elements  23   a,    24   a,    23   b,    24   b  in total towards distal ends of the contact elastic pieces  23 ,  24 . In the six upper contact elastic elements  23   a,    24   a,    23   a,    24   a,    23   a,    24   a  of the three busbars  13 C which are disposed parallel in three rows, electric contact portions  45  of the four adjacent contact elastic elements  24   a,    23   a,    24   a,    23   a  of the busbars  13 C are connected to respective pairs of contact portions  21  of two semiconductor light emitting elements  25 , which are first electronic devices  11 A disposed between the three busbars  13 C. In addition, in the six lower contact elastic elements  23   b,    24   b,    23   b,    24   b,    23   b,    24   b  of the busbars  13 C which are disposed parallel in three rows, electric contact portions  45  of the two contact elastic elements  23   b,    24   b  of the busbars  13 C, which are disposed spaced apart from each other so as to hold the two central contact elastic elements  24   b,    23   b  of the central busbar  13  therebetween, are connected to a pair of contact portions  21  of a Zener diode  27 , which is a second electronic device  11 A which is disposed below the two semiconductor light emitting elements  25  between the three busbars  13 C. In the second embodiment, a contact-to-contact pitch of the Zener diode  27  used is three times a pitch defined between contacts of the electric contact portions  45 . 
     Namely, in  FIG. 15 , one of the semiconductor light emitting elements  25  is connected to the second leftmost electric contact portion  45  and the third leftmost electric contact portion  45  in the upper electric contact portions  45  of the busbars  13 C which are disposed parallel in three rows. The other semiconductor light emitting element  25  is connected to the fourth leftmost electric contact portion  45  and the fifth leftmost electric contact portion  45 . In addition, the Zener diode  27  is connected to the second leftmost electric contact portion  45  and the fifth leftmost contact portion  45  in the lower electric contact portions  45  of the busbars  13 C which are disposed parallel in three rows. 
     Next, assembling steps of the connecting structure for electronic devices  11 A will be described. 
       FIG. 15  is a drawing which depicts a busbars assembling step in the connecting structure for electronic devices  11 A according to the second embodiment of the invention,  FIG. 16  is a drawing which depicts similarly an electronic devices assembling step,  FIG. 17  is a drawing which depicts similarly a housing assembling step,  FIG. 18  is a drawing which depicts similarly an electric wire holder assembling step, and  FIG. 19  is a perspective view of the LED unit  99  which uses the connecting structure for electronic devices  11 A according to the second embodiment of the invention. 
     The connecting structure for electronic devices  11 A can preferably be applied, for example, to the two-lamp type LED unit  99 . In order to apply the connecting structure for electronic devices  11 A to the two-lamp type LED unit  99 , as  FIG. 15  shows, the three busbars  13 C are mounted in a housing  91 . 
     Three busbar accommodation compartments  55  are formed in the housing  91 . In each of the busbar accommodation compartments  55 , a rear wall  57  is provided at a rear end thereof, and a pair of holding grooves  59  are formed in inner wall surfaces lying forwards of the rear wall  57 . When the busbar  13 C is inserted in the busbar accommodation compartment  55 , the rear wall  57  is held by a rear abutment piece  33  and rear elastic legs  35  of the busbar  13 C therebetween, so that the busbar  13 C is mounted in the housing  91  while being restricted from being dislodged therefrom. 
     As  FIG. 16  shows, two left and right LED mounting opening portions  61  and a diode mounting opening portion  63  are formed vertically in a front side of the housing  91 . The semiconductor light emitting elements  25  are inserted individually into the LED mounting opening portions  61  in such a state that the contact portions  21  are oriented downwards. The Zener diode  27  is inserted into the diode mounting opening portion  63  in such a state that the contact portions  21  are oriented upwards. By adopting this configuration, the contact portions  21  of the semiconductor light emitting elements  25  and the contact portions  21  of the Zener diode  27  are connected to their corresponding electric contact portions  45 . In addition, a resistor mounting opening portion (not shown) is formed in a bottom side of the housing  91 , and a resistor  28  is inserted thereinto. By adopting this configuration, the resistor  28  is held by front abutment pieces  39  and front elastic legs of the busbar  13 C on a near side therebetween, and electric contact portions of the front elastic legs  37  are connected to a pair of contact portions of the resistor  28 . 
     As  FIG. 17  shows, the two semiconductor light emitting elements  25  and the Zener diode  27  are mounted in the housing  91 , and then, the housing  91  is mounted in a lens cover  95  which includes two lenses  95   a.  A housing inserting opening  97  is formed in a rear end face of the lens cover  95 . In the housing  91  which has been inserted in the lens cover  95 , press contact blades  31  project rearwards in an interior of the lens cover  95 . 
     As  FIG. 18  shows, an electric wire holder  93  is inserted into the lens cover  95  into which the housing  91  has been mounted from the housing inserting opening  97 . U-shaped electric wire holding grooves  71  are formed at three locations on three external sides of the electric wire holder  93 . Covered electric wires  29  are each bent into a U-shape and are mounted individually in the electric wire holding grooves  71  formed laterally outwards. Horizontal press contact blade entrance slits  73  are formed in a front side of the electric wire holder  93  so as to extend over the corresponding electric wire holding grooves  71 . By adopting this configuration, when the electric wire holder  93  is inserted into the lens cover  95 , the press contact blades  31  of the busbars  13 C, which project rearwards in the interior of the lens cover  95 , enter the press contact blade entrance slits  73  so that the press contact blades  31  and conductors of the electric wires  29  are connected to each other. 
     When the electric wire holder  93  is inserted into the lens cover  95 , locking claws  77  provided on lateral sides of the electric wire holder  93  so as to project therefrom are locked in locking holes  75  formed in lateral side portions of the lens cover  95 , whereby the housing  91  and the electric wire holder  93  are restricted from being dislodged from the lens cover  95 . When the housing  91  and the electric wire holder  93  are mounted in the lens cover  95 , the two-lamp type LED unit  99  shown in  FIG. 19  is completed. 
     In this way, in the connecting structure for electronic devices  11 A according to the second embodiment of the invention, the three busbars  13 C each have the terminal portion  19  including the two upper and lower pairs of contact elastic elements  23   a,    24   a,    23   b,    24   b  which face each other horizontally, and the three busbars  13 C are disposed parallel in three rows. Then, In the six upper contact elastic elements  23   a,    24   a,    23   a,    24   a,    23   a,    24   a  of the three busbars  13 C which are disposed parallel in three rows, the electric contact portions  45  of the four adjacent contact elastic elements  24   a,    23   a,    24   a,    23   a  of the busbars  13 C are connected to the respective pairs of contact portions  21  of the two semiconductor light emitting elements  25 . In addition, in the six lower contact elastic elements  23   b,    24   b,    23   b,    24   b,    23   b,    24   b  of the busbars  13 C which are disposed parallel in three rows, the electric contact portions  45  of the two contact elastic elements  23   b,    24   b  of the busbars  13 C, which are disposed spaced apart from each other so as to hold the two central contact elastic elements  24   b,    23   b  of the central busbar  13  therebetween, are connected to the pair of contact portions  21  of the Zener diode  27  which is disposed below the two semiconductor light emitting elements  25  between the three busbars  13 C. Thus, the electronic devices  11 A having the different external shapes, sizes and contact-to-contact pitches can be connected together. 
     In the two-lamp type LED unit  99  according to the second embodiment, the two light emitting semiconductors  25  can still emit light without mounting the Zener diode  27 , thereby making it possible to omit the Zener diode  27  so as to reduce the number of parts to be mounted. 
     According to the connecting structure for electronic devices according to the invention, the surface mount electronic devices having the different contact-to-contact pitches, external shapes and sizes can be connected with the busbars of one type. 
     According to the connecting structure for electronic devices of the present invention, the plurality of busbars each having the terminal portion are disposed parallel to each other with the space defined therebetween, and the terminal portion has at least the two upper and lower pairs of contact elastic elements. Then, any two contact elastic elements of the upper and lower contact elastic elements of the elastic pieces are connected respectively to the pairs of contact portions of the plurality of types of electronic devices which are disposed between the busbars. Thus, the plurality of types of electronic devices having the different contact-to-contact pitches, external shapes and sizes can be connected to electric contact portions which are formed vertically in the terminal portions between the busbars which are disposed parallel to each other. 
     According to the electronic devices connecting portions of the present invention, the busbars each has the pair of contact elastic pieces which are each caused to branch into the substantially Y-shape and the two upper and lower pairs of contact elastic elements are formed at the distal ends of the pair of contact elastic pieces. Thus, by disposing the two busbars like the busbars parallel to each other with the space defined therebetween, in total, eight electric contact portions are disposed on the upper and lower pairs of contact elastic elements with four electric contact portions disposed on each of the upper and lower pairs. By adopting this configuration, in either of the upper and lower pairs, the pair of contact portions of the first electronic device having a smaller contact-to-contact pitch can be connected to the electric contact portions of the adjacent contact elastic elements, while in the other pair, the pair of contact portions of the second electronic device having a larger contact-to-contact pitch can be connected to the electric contact portions of the contact elastic elements which are disposed spaced apart from each other so as to hold at least the electric contact portion of the contact elastic element therebetween. 
     According to the connecting structure for electronic devices of the present invention, the main body of the busbar is formed by being bent into the U-shape, and the two upper and lower pairs of contact elastic elements are formed at the distal ends of the contact elastic pieces which are each caused to branch into the substantially Y-shape in the pair of lateral side walls which face each other through punching. By adopting this configuration, the elastic contact construction having a number of electric contact portions can be fabricated compact with ease. 
     According to the connecting structure for electronic devices of the present invention, the light emitting portion of the semiconductor light emitting element is disposed in such a state that the light emitting portion is held between the two busbars which are disposed parallel to each other with the space defined therebetween. The reflecting surfaces are formed on the lateral side walls of the two busbars which hold the light emitting portion therebetween, whereby light emitted from the light emitting portion is reflected on the reflecting surfaces so as to be directed in the direction of emission of light, thereby making it possible to make effective use of light emitted from the light emitting portion. 
     The present application is based on Japanese Patent Application No. 2010-258229 filed on Nov. 18, 2010 and Japanese Patent Application No. 2011-180846 filed on Aug. 22, 2010, the contents of which are incorporated herein by way of reference. 
     The present invention is extremely useful in providing a connecting structure for electronic devices in which a plurality of types of surface mount electronic devices having different contact-to-contact pitches, external shapes and sizes can be connected to various forms of connecting circuits with one type of busbars.