Patent Publication Number: US-6209776-B1

Title: Flyback transformer device and process for preparing same

Description:
This is a division of application Ser. No. 08/110,775 filed Aug. 23, 1993 now U.S. Pat. No. 5,396,696. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a flyback transformer device for use in television receivers and various display devices, and more particularly to the structure of a flyback transformer device wherein leads of electronic components are fixedly connected by electric welding to terminal pieces provided upright on a coil bobbin and a process for preparing the device. 
     BACKGROUND OF THE INVENTION 
     Flyback transformer devices  70  having coils provided in layers generally comprise, as shown in FIG. 23, a plurality of divided coils  74  wound around a coil bobbin  71 , and pairs of terminal pieces  73  provided upright at opposite ends of the bobbin  71 . A diode, resistor or like electronic component  6  is connected between each pair of opposed terminal pieces  73 ,  73 . 
     Each of leads  63 ,  63  extending from opposite sides of the electronic component  6  is electrically fixedly connected to the terminal piece  73  conventionally by shaping the terminal piece  73  in a Y-form as illustrated, placing the outer end of the lead  63  on the Y-shaped portion of the terminal piece  73 , crimping the Y-shaped portion to fix the lead  63  in this state and thereafter soldering the crimped portion by dipping (see, for example, Unexamined Japanese Utility Model Publication HEI 1-105383). 
     Another method of mounting electronic components on a coil bobbin has been proposed as shown in FIG. 24. A lead  63  is connected to a terminal piece  73   a  with a solder  66  as shown in FIG. 25 by bending the outer end  63   a  of the lead  63  to an L-shape, fitting the lead end  63   a  in a cavity  65  in a post  71   a  of the coil bobbin at one side of the terminal piece  73   a  to preliminarily fix the lead  63  as held in contact with the terminal piece  73   a  and thereafter dipping the fixed portion in solder (Unexamined Japanese Patent Publication SHO 63-15668 and Examined Japanese Utility Model Publication hei 2-1171). 
     However, the conventional method of mounting electronic components with use of Y-shaped terminal pieces requires the work of fixing the lead by crimping the terminal piece and therefore has the problem of being complex and necessitating cumbersome work. 
     On the other hand, the method wherein cavities are formed in the coil bobbin not only requires a device for bending leads and a device for inserting the lead into the cavity but also makes the die for producing bobbins complex in configuration to result in an increased cost. Another problem is also encountered in that the coil bobbin becomes larger. 
     Further when solder dipping is resorted to for connection, the solder dipping device requires labor for maintenance. This leads to an increase in manufacturing cost. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide the structure of a flyback transformer device wherein the leads of electronic components are fixedly connected to terminal pieces of a coil bobbin by electric welding although this has not been practiced, and a process for preparing the device so as to overcome all the problems described above. 
     The leads of electronic components can be connected to the terminal pieces of the coil bobbin by electric welding firmly with great ease. This simplifies the production process and leads to an automated connecting procedure. 
     Another object of the invention is to provide a process for preparing a flyback transformer device which includes the steps of producing a coil bobbin having upright terminal pieces, winding a coil conductor around the coil bobbin, twining an end portion of the wound coil conductor around one of the terminal pieces, fixing a lead of an electronic component to another one of the terminal pieces by spot welding, and soldering the twined portion of the coil conductor around the terminal piece by dipping. 
     After the coil conductor end portion has been preliminarily fixed to the terminal piece by the conductor twining step of the process, the solder dipping step ensures a mechanical and electrical connection between the coil conductor and the terminal piece. 
     Another object of the invention is to provide an apparatus for preparing flyback transformer devices which apparatus comprises an electronic component feeder, a lead cutter, a bobbin feed position determining mechanism, an electronic component transfer mechanism and an electric welder. The electronic component feeder feeds a component supply tape having a plurality of electronic components arranged at a specified pitch by paying off the tape longitudinally thereof by the specified pitch to send the components one after another to a lead cutting position. The lead cutter cuts off the electronic component in the lead cutting position at outer ends of leads to separate the component from the supply tape. The bobbin feed position determining mechanism feeds a coil bobbin toward a predetermined welding position to position a terminal piece of the coil bobbin in the welding position. 
     The electronic component transfer mechanism transfers the electronic component as cut off from the supply tape by the cutter toward the welding position and positions the lead of the component alongside the terminal piece of the bobbin in the welding position. The electric welder comprises a welding head movable toward or away from the welding position, and a pair of electrode pieces projecting from the welding head for holding therebetween the terminal piece of the coil bobbin and the lead of the component in the welding position. 
     With the apparatus described, the electronic component feeder, lead cutter, bobbin feed position determining mechanism, electronic component transfer mechanism and electric welder are related to one another and operate concurrently to produce the flyback transfer device within a short cycle time. 
     More specifically, the component supply tape is paid off by the feeder at the specified pitch in the longitudinal direction to feed electronic components one after another to the lead cutting position. When one electronic component is set in the lead cutting position, the lead cutter operates at the same time to cut off the component at the outer ends of leads and separate the component from the supply tape. The electronic component separated from the supply tape is transported by the component transfer mechanism from the lead cutting position toward the predetermined welding position. At this time, the coil bobbin is set in the predetermined welding position by the bobbin feed position determining mechanism. 
     Accordingly, when the component is set in the welding position by the transfer mechanism, the component has its lead positioned on the terminal piece of the coil bobbin in the welding position while being held by the transfer mechanism. 
     In this state, the electric welder operates, the welding head moves toward the welding position, and the pair of electrode pieces are positioned at opposite sides of the terminal piece and the lead. The terminal piece and the lead are thereafter held from opposite sides between the pair of electrode pieces. Simultaneously with this, current is passed across the electrode pieces, whereby the lead is joined to the terminal piece by spot welding. 
     With the production apparatus described, the welder operates with the component lead positioned alongside the bobbin terminal piece by the transfer mechanism to electrically weld the lead to the terminal piece. This eliminates the need to preliminarily fix the lead to the terminal piece. Accordingly, the terminal piece can be shaped merely in the form of a rod, and there is no need to form lead inserting cavities in the bobbin which are conventionally necessary, nor is it necessary to bend the leads of electronic components. As a result, it is possible to compact the flyback transformer device and to reduce the manufacturing cost of the device. 
     Moreover, the step of electrically welding the lead to the terminal piece is executed almost simultaneously with the step of positioning the lead alongside the bobbin terminal piece by causing the component transfer mechanism to hold the component. This results in a shorter cycle time than the conventional method wherein the lead is preliminarily fixed to the terminal piece and thereafter soldered thereto. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 ( a ), ( b ) and ( c ) are a plan view, side elevation and front view, respectively, showing a coil bobbin in a flyback transformer device of the invention; 
     FIGS. 2 ( a ), ( b ) and ( c ) are a plan view, side elevation and front view, respectively, showing a high-tension coil as provided on the coil bobbin; 
     FIGS. 3 ( a ), ( b ) and ( c ) are a plan view, side elevation and front view, respectively, showing a plurality of electronic components as welded to the coil bottin. 
     FIG. 4 is a diagram showing a spot welding step; 
     FIG. 5 is an enlarged side elevation showing a terminal portion as soldered by dipping; 
     FIG. 6 is an overall front view showing an apparatus embodying the invention for preparing flyback transformer devices; 
     FIG. 7 is an enlarged fragmentary front view of the same; 
     FIG. 8 is a plan view of the same; 
     FIG. 9 is a front view showing the construction of an electronic component feeder; 
     FIG. 10 is a plan view of the same; 
     FIG. 11 is a side elevation of a lead cutter; 
     FIG. 12 is a perspective view of a component receiving member; 
     FIG. 13 is a front view for illustrating a path of movement of electronic components; 
     FIG. 14 is a front view of an electronic component transfer mechanism; 
     FIG. 15 is a side elevation partly broken away of the same; 
     FIG. 16 is a side elevation of an electric welder; 
     FIG. 17 is a front view of the same; 
     FIG. 18 is a plan view showing the internal construction of a welding head; 
     FIG. 19 is a front view of the same; 
     FIG. 20 is an enlarged front view showing a lead of the electronic component as positioned on a terminal piece of the coil bobbin; 
     FIG. 21 is an enlarged front view showing the lead and the terminal piece as held between electrode pieces of the welder; 
     FIG. 22 is a perspective view showing the flyback transformer device to be prepared by the production apparatus of the invention; 
     FIG. 23 is a perspective view showing a conventional flyback transformer device; 
     FIG. 24 is a view a lead preliminarily fixing step in a conventional method of producing the flyback transformer device; and 
     FIG. 25 is a view showing a soldering step of the method. 
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described in detail with reference to the drawings. 
     (Construction of Flyback Transformer Device) 
     FIGS. 1 ( a ), ( b ) and ( c ) show the appearance of a coil bobbin  71  for use in a flyback transformer device of the invention, and FIGS. 2 ( a ), ( b ) and ( c ) show a high-tension coil  74  as provided around the coil bobbin  71  of FIG.  1 . As illustrated, the coil  74  comprises a coil conductor  75  as wound in layers with an insulating film  76  interposed between the layers. With the present embodiment, the high-tension coil is formed in six layers. Opposite ends of conductor portion of each layer are preliminarily fixed as twined around terminal pieces  72 . 
     FIGS. 3 ( a ), ( b ) and ( c ) show six diodes  6   a  and one limiting resistor  6   b  as mounted on the coil bobbin  71  having the high-tension coil formed therearound. With reference to these drawings, each diode  6   a  extends between and is electrically welded to a pair of terminal pieces  72 ,  72  corresponding thereto, while the limiting resistor  6   b  has a lead electrically welded to another terminal piece  72  and a lead soldered to an eyelet terminal  78 . 
     (Process for Preparing Flyback Transformer Device) 
     With reference first to FIGS. 1 ( a ) to ( c ), metal terminal pieces  72  are implanted upright on posts  77  of a coil bobbin  71 . Used as the terminal piece  72  in the present embodiment is a brass core wire which is plated with tin. 
     With reference to FIGS. 2 ( a ) to ( c ), a coil conductor  75  is next wound in six layers around the bobbin  71  with an insulating film  76  interposed between the layers. At this time, opposite ends of the conductor portion  75  of each layer are preliminarily fixed as twined around terminal pieces  72 . The number of layers in the high-tension coil differs depending on the type of coil. 
     As shown in FIGS. 3 ( a ), ( b ) and ( c ), diodes  6   a  and a limiting resistor  6   b  are mounted. With reference to FIG. 4, the outer end of lead  63  of each diode  6   a  is held to the terminal piece  72  by being clamped between a pair of welding electrodes  40 ,  40 , and a current of several milliamperes is passed between the electrodes to melt the surfaces of the terminal piece  72  and lead  63  and join them together by spot welding. The terminal piece  72  and the lead  63  of the diode  6   a  thus joined together by spot welding have a sufficient joint strength and are also electrically connected together. As already stated, one lead end of the limiting resistor  6   b  is spot-welded to the terminal piece  72  in the same manner as above, while the other lead end is preliminarily fixed to an eyelet terminal  78  as engaged therewith. 
     After the diodes  6   a  and the limiting resistor  6   b  have been mounted in place in this way, the spot welds between the terminal pieces  72  and the leads  63  of the diodes  6   a , the coil conductor portions  75  twined around other terminal pieces  72  and the connection between the lead of the resistor  6   b  and the eyelet terminal  78  are dipped in a solder bath (not shown) at the same time for soldering, whereby the welded portions of the terminal pieces  72  and leads  63  and the conductor twined portions are covered with solder  67  as shown in FIG.  5 . Although the coil conductor  75  is covered with an insulating coating, the coating is removed by the heat of solder when dipped in the solder bath, so that the conductor  75  and the terminal piece  72  are electrically connected together. The spot weld between the terminal piece  72  and the lead  63  of each diode  6   a  is further reinforced with the solder. The lead of the resistor  6   b  is connected to the eyelet terminal  78  electrically more reliably also by the solder. 
     Although the terminal piece  72  used in the present invention has a rectangular cross section, this is not limitative, but the section can be circular, or elliptical or otherwise shaped as desired. 
     In the case of the flyback transformer device described, the lead of the diode  6   a  can be fixedly connected to the terminal piece  72  easily by spot welding. This facilitates automation of the connecting procedure, further leading to the advantage of obviating the need, for example, to bend the diode lead to an L-form. Further with such a type of devices that coil bobbins of different sizes are used, the diode mounting step can be easily executed using a jig for cutting the leads of diodes to a suitable length immediately before mounting, so that the diodes need not be worked on in advance. 
     Furthermore, the coil conductor twining step preliminarily fixes the end of the conductor  75  to the terminal piece  72 , the step of joining the lead  63  of the diode  6   a  to the terminal piece  72  by spot welding secures the diode  6   a  to the terminal piece  72 , and the solder dipping step mechanically and electrically connects the coil conductor  75  to the terminal piece  72  simultaneously with establishment of a mechanical and electrical connection between the lead  63  of the diode  6   a  and the terminal piece  72 . These steps are therefore advantageous in effecting a sequence of operations automatically. 
     (Construction of Apparatus for Preparing Flyback Transformer Device) 
     Next, a production apparatus for acutally preparing the flyback transformer device of the above construction will be described in detail with reference to the drawings concerned. As shown in FIG. 22, the flyback transformer device  7  having superposed layers and to be prepared by the apparatus includes a coil bobbin  71  for forming a high-tension coil  74  thereon. A plurality of barlike terminal pieces  72  are provided at each end of the bobbin. An electronic component  6 , which is a diode, is provided between the pair of terminal pieces  72 ,  72 . The component  6  has leads  63 ,  63  which are fixedly connected to the respective terminal pieces  72  by electric welding. 
     Overall Construction 
     With reference to FIGS. 6 to  8 , arranged on a frame  90  are an electronic component feeder  1 , lead cutter  2 , electronic component transfer mechanism  3 , electric welder  4  and bobbin feed position determining mechanism  5 . Each of these devices operates under the control of a control unit  8  having a microcomputer. A welding power source device  81  is connected to the welder  4 . Incidentally, two electric welders  4  which are identical inconstruction are provided at opposite sides of the bobbin feed position determining mechanism  5 . 
     A component feed reel  61  for paying off a component supply tape  62  is attached to the left side of the frame  90 . The tape separated from electronic components is guided by a tape discharge guide  92  and a tape discharge chute  9  and collected in a tape container baox  91 . As shown in FIG. 10, the supply tape  62  includes a multiplicity of electronic components  6  arranged at a specified pitch and having leads  63 ,  63  the outer ends of which are fixedly affixed to two tape segments  62   a ,  62   a  extending in parallel. 
     The electronic component feeder  1  operates to pay off the component supply tape  62  from the reel  61  at the pitch of compnents in the longitudinal direction and send the components  6  one after another to a position where the leads are cut by the lead cutter  2 , intermittently by a distance at a time which distance corresponds to the pitch of components arranged. The lead cutter  2  removes the electronic component  6  set in the cutting position from the supply tape  62  by cutting opposite ends of the leads  63 ,  63 . The bobbin feed position determining mechanism  5  holds a coil bobbin  71  on the frame  90  shown in FIG. 7 at a right end portion thereof, transports the bobbin  71  leftward to a position opposed to the electric welders  4  and thereafter repeats an intermittent feed operation to bring opposed pairs of terminal pieces  72 ,  72  one after another to a predetermined position for welding by the electric welders  4 . 
     The electronic component transfer mechanism  3  holds the electronic component  6  removed from the supply tape  62  by the lead cutter  2  and transfers the component  6  rightward to a position opposed to the welders  4  to position its leads  63 ,  63  alongside the respective terminal pieces  72 ,  72  of the bobbin  71  in the welding position. Each of the electric welders  4  comprises a pair of electrode pieces  42 ,  42  projecting from a welding head  41  which is movable toward and away from the welding position. The terminal piece  72  of the coil bobbin  71  in the wedling position and the lead  63  of the component  6  in position are clamped by the electrode pieces  42  from opposite sides. 
     A detailed description will be given of the construction and operation of the component devices or mechanisms of the apparatus. 
     Electronic Component Feeder  1   
     With reference to FIGS. 9 and 10, the component feeder  1  comprises a pair of toothed feed wheels  12 ,  12  for feeding the electronic components  6  on the supply tape  62  to the lead cutting position intermittently by a distance (pitch) at a time, and tape guides  11 ,  11  for guiding the movement of the tape  62  toward an inlet side of the feed wheels. Each of the feed wheels  12  is formed along its periphery with feed teeth  13  resembling sawteeth and engageable with the leads  63  of components  6  on the tape  62 , the pitch of teeth  13  being equal to the pitch of components  6 . 
     As shown in FIG. 10, a shaft  10  carrying the component feed wheels  12  has mounted thereon a ratchet wheel  14  integral with one of the feed wheels  12 . A pawl  15  is in engagement with the tooth of the wheel  14  to provide a ratchet mechanism for rotating the feed wheels  12  toward the component feed direction (clockwise direction) intermittently at a specified pitch. One-way clutch  16  is coupled to the shaft  10  to prevent reverse rotation of the feed wheels  12  and apply a predetermined frictional torque to the wheels  12  when they rotate forward. 
     As shown in FIG. 9, the shaft  10  has further attached thereto a ratchet drive plate  18  for driving the feed wheels  12  toward the component feed direction. The ratchet drive plate  18  is biased by a tension spring  19  toward a direction opposite to the feed direction (i.e., counterclockwise direction). To drivingly rotate the ratchet drive plate  18  in the feed direction, a reciprocating block  102  is attached to a rod of an actuator  17  and carries a push bolt  101  screwed therethrough and bearing at its forward end against an end portion of the drive plate  18 . 
     Accordingly, when the reciprocating block  102  is advanced rightward by the operation of the actuator  17 , the push bolt  101  advances away from the ratchet drive plate  18  at the same time. Consequently, the drive plate  18  rotates counterclock only through a predetermined angle under the action of the tension spring  19 . At this time, the feed wheels  12  remain at rest by being prevented by the ratchet mechanism from rotating counterclockwise with the above-mentioned rotation. The operation of the actuator  17  thereafter retracts the reciprocating block  102  leftward, causing the push bolt  101  to drive the ratchet drive plate  18  clockwise, whereby the feed wheels  12  are rotated clockwise, i.e., toward the component feed direction, through a predetermined angle. 
     As a result, the electronic components on the tape guides  11  are fed to the lead cutting postion, one at a time by the intermittent rotation of the feed wheels  12 . The angle through which the feed wheels  12  are rotated at a time is adjustable by the the position of the push bolt  101  relative to the reciprocating block  102  which position is determined by screwing the bolt, whereby the amount of the tape  62  to be fed at a time can be made to accurately match the pitch of components. 
     Lead Cutter  2   
     The lead cutter  2  comprises, as shown in FIG. 11, an upper blade  22  having a cutting edge at each of two cutting positions and two lower blades  23 ,  23  for cutting the leads  63 ,  63  of the component  6  at their outer end portions. The upper blade  22  is fixed to a lift block  26 , while the lower blades  23 ,  23  are fixedly positioned at a predetermined level. Connected by shafts  27 ,  27  to the lift block  26  is an actuator  25  for driving the block  26  downward, whereby the upper blade  22  engages with the lower blades  23  to cut the leads  63  of the electronic component  6 . 
     Disposed below the lead cutting position is a component receiving member  21  for receiving the component  6  separated from the supply tape, at the base ends of the leads  63 ,  63 . The component receiving member  21  is mounted on the reciprocating block  102  constituting the component feeder  1 ; and is in a stand-by position immediately below the upper blade  22  when to cut the leads as seen in FIG. 9. A ball plunger  24  is coupled to the component receiving member  21 . When tightened up, the ball plunger  24  reliably fixes the receiving member  21  to the reciprocating block  102 . 
     With reference to FIG. 12, the receiving member  21  has a pair of recesses  28 ,  28  spaced apart by a predetermined distance W 1  for the leads  63 ,  63  of the component  6  to fit in. The component  6  is accommodated in the space between the recesses  28 ,  28 . The receiving member  21  is formed in one side thereof opposite to the recessed side ( 28 ) with a pair of recesses  29 ,  29  which are spaced apart by a distance W 2  different from the distance W 1  so as to handle electronic components of different size when mounted as turned upside down on the reciprocating block  102 . 
     To separate off components of different size, the upper blade  22  is removably attached to the lift block  26 , while the position of the lower blades  23  is adjustable according to the width of the upper blade  22 . 
     When the upper blade  22  is lowered from the position shown in FIG. 9 for cutting the lead, the reciprocating block  102  is retracted as stated above to position the component receiving member  21  below the upper blade  22 , and the electronic component separated from the supply tape  62  by cutting falls onto the receiving member  21 . Subsequently, with the advance of the block  102  to rotate the ratchet drive plate  18  counterclockwise, the receiving member  21  moves with the component placed thereon to the broken-line position of FIG. 9 to deliver the component to the electronic component transfer mechanism  3  as shown in FIG.  13 . 
     Electronic Component Transfer Mechanism  3   
     With reference to FIGS. 14 and 15, the electronic component transfer mechanism  3  is attached to a mount plate  93  provided upright on the frame  90  and is reciprocatingly movable horizontally. The mechanism  3  has two pairs of chuck members  32 ,  32  which pairs are spaced apart by a distance in accordance with the. length of the electronic component for gripping the respective leads  63 . 
     Two guide shafts  37 ,  37  extending horizontally in parallel to each other are supported by the mount plate  93 . A reciprocating block  36  is slidable on the guide shafts in engagement therewith. An actuator  38  is disposed between the mount plate  93  and the block  36  for reciprocatingly driving the block  36 . 
     The reciprocating block  36  is provided with a vertical ball screw  33 , which carries a lift block  34  in screw-thread engagement therewith. The ball screw  33  is coupled to a servomotor  30  by pulley means  35 . The ball screw  33  is drivinly rotatable forward or reversely by the servomotor  30 , whereby the lift block  34  is moved upward or downward. The two pairs of chuck members  32 ,  32  are attached to the lift block  34 . An actuator  31  is coupled to the chuck members  32  to open or close these members. 
     With reference to FIG. 13, the advance of the reciprocating block  102  moves the electronic component  6  on the receiving member  21  to below the chuck members  32 ,  32  of the transfer mechanism  3 , whereupon the lift block  34  of the transfer mechanism  3  lowers, causing the chuck members  32 ,  32  to hold the leads  63 ,  63  of the component  6  as indicated in broken lines in FIG.  15 . 
     Next, the lift block  34  rises to raise the component  6 , and the reciprocating block  36  horizontally moves to a position above the welding position of the electric welders  4 . The lift block  34  thereafter lowers, whereby the component  6  held by the chuck members  32 ,  32  is positioned alongside a pair of terminal pieces  72  on the coil bobbin  71  in the welding position as shown in FIG.  20 . 
     With the component transfer mechanism  3  described, the servomotor  30  is used as a drive source for the vertical movement, so that the stop position of the vertical movement can be determined as desired. Furthermore, the use of the ball screw  33  as the drive mechanism assures high positioning precision. 
     Bobbin Feed Position Determining Mechanism  5   
     The bobbin feed position determining mechanism  5  comprises, as shown in FIGS. 7,  8  and  16 , a rail  56  mounted on the frame  90 , a slide base  51  having a pair of arms  52 ,  52  projecting therefrom for embracing the rail  56  from opposite sides, slide drive means  53  for reciprocatingly moving the slide base  51  along the rail  56 , and a bobbin mount shaft  54  supported on the slide base  51  by a support member  55 . The bobbin mount shaft  54  is removably attached to the support member  55  so as to be readily replaceable for handling bobbins of different size. 
     The coil bobbin  71  as fitted to the mount shaft  54  as shown in FIG. 16, is moved from the bottin mounting position shown in FIG. 7 to the welding position shown in FIG. 13 by the operation of the slide drive means  53 . The slide drive means is adapted to reciprocatingly drive the slide base  51  by rotating a ball screw forward or reversely by a servomotor so as to position the bobbin  71 , as mounted on the shaft  54 , in place with high accuracy. 
     The electronic component  6  held by the chuck members  32 ,  32  of the transfer mechanism  3  is lowered toward the coil bobbin  71  set in the welding position as shown in FIG. 13 to position the leads  63  of the component  6  alongside the desired pair of terminal pieces  72  on the bobbin  71  as shown in FIG.  20 . 
     The electric welders  4  to be described below perform a welding operation on the coil bottin  71  transported from the bobbin mounting position to the welding position to connect one electronic component  6  to the coil bobbin  71 . During the following period before the second component  6  is brought to the welding position by the transfer mechanism  3 , the bobbin feed position determining mechanism  5  positions the next pair of terminal pieces  72  to be welded at the welding position by moving the bobbin  71  by a small distance (e.g., 1 mm to 3 mm) equal to the pitch of terminal pieces  72 . 
     After the second component  6  has been welded to the bobbin  71  by the welders  4 , the position determining mechanism  5  similarly repeats the above movement until a predetermined number of pairs of components  6  are completely welded. 
     Electric Welder  4   
     With reference to FIGS. 16 and 17, each of the electric welders  4  has a slide block  49  mounted on the frame  90  and slidable toward or away from the welding position. The welding head  41  is mounted as inclined at a predetermined angle on the slide block  49  by means of a position adjusting block  44 . Two guide shafts  43 ,  43  project downward from the bottom of the welding head  41  and slidably extend through the position adjusting block  44 . A level adjusting screw  45  is provided between the welding head  41  and the position adjusting block  44 . The level of the welding head  41  on the block  44  is adjustable by manipulating the screw  45 . 
     The position adjusting block  44  is connected to the outer end of a rod of an actuator  46  mounted on the slide block  49  as inclined at the same angle as the welding head  41 . The operation of the actuator  46  reciprocatingly moves the position adjusting block  44  and the welding head  41  as inclined. The welding head  41  has projected therefrom the above-mentioned pair of electrode pieces  42 ,  42 . The welding head  41  is moved toward the coil bobbin  71  in the welding position by the operation of the actuator  46 , with the result that the pair of electrode pieces  42 ,  42  are positioned at opposite sides of the lead  63  and the terminal piece  72  in the welding position to hold them. 
     Coupled to the slide block  49  is a position adjusting actuator  47  for horizontally moving the slide block  49  when coil bobbins  71  of different shape are to be handled. For such bobbins, the level adjusting screw  45  is also turned to alter the level of the welding head  41 . 
     The electrode pieces  42 ,  42  are made of a material which is suitably determined in view of electric conductivity, hardness, etc. in accordance with the material of the leads and terminal pieces to be welded. According to the present embodiment, a special alloy is used which is prepared by adding chrominum, zirconium, etc. to copper. 
     FIGS. 18 and 19 show the interior construction of the welding head  41 . A slide body  409  is in engagement with a first arm  407  mounted on the frame  90  and slidable horizontally relative to the arm. The slide body has a second arm  408  projecting therefrom. Thw two electrode pieces  42 ,  42  are attached to the respective arms. 
     Fixed to the first arm  407  is an actuator  48  which has a rod connected by a connecting rod  401  to a pressure shaft  402  at its base end, the shaft  402  extending through the slide body  409 . The pressure shaft  402  has a forward end on which an adjusting screw  400  is screwed. A knob  404  is integral with the head of the screw  400 . A tube  406  projects from a side portion of the slide body  409 . A coiled compression spring  403  is provided between the pressure shaft  402  and the tube  406  for biasing the slide body  409  rightward relative to the pressure shaft  402 . Tension springs  405  provided between the first arm  407  and the pressure shfat  402  bias—this shaft  402  leftward. 
     The first arm  407  is provided with terminals  411 ,  412  for passing current between the pair of electrode pieces  42 ,  42 . These terminals are connected to the aforementioned welding power supply device  81 . A limit switch  410  is provided along the path of movement of the connecting rod  401 . The limit switch  410  is turned on when the pressure shaft  402  is moved rightward by being pulled by the actuator  48 , and current is pased between the pair of electrode pieces  42 ,  42  in response to the resulting ON signal. 
     With the pair of electrode pieces  42 ,  42  arranged at opposite sides of the lead and the terminal piece, the pressure shaft  402  is driven rightward by the actuator  48  against the tension springs  405 , whereupon the slide body  409  is driven rightward through the compression spring  403 , with the result that the left electrode piece  42  projecting from the slide body  409  is brought toward the right electrode piece  42  to clamp the lead and the terminal piece between the two electrode pieces  42 ,  42 . 
     The actuator  48  is further driven also after the slide body  409  has come to a halt to compress the spring  403 . The slide body  409  is pressed rightward by the repellent force of the spring  403 . This pressure acts to press the left electrode piece  42  projecting from the slide body  409  against the right electrode piece  42 . 
     As a result, the lead  63  of the electronic component  6  and the terminal piece  72  of the bobbin  71  in the welding position are held between the pair of electrode pieces  42 ,  42  under pressure as shown in FIG.  21 . Immediately thereafter, the limit switch  410  operates to pass current between the electrode pieces  42 ,  42 . This produces Joule heat due to contact resistance at the portions where the electrode pieces are in contact with the lead  63  and with the piece  72 . The Joule heat joins the lead  63  to the terminal piece  72  by spot welding. 
     With the electric welder  4 , the knob  404  is turned to adjust the initial amount of compression of the spring  403 , whereby the clamping pressure to be exerted by the pair of electrode pieces  42 ,  42  on the lead and terminal piece can be set at a suitable value. 
     When a capacitor type welding power source is used as the power source device  81 , satisfactory results can be obtained by setting the current passing capacity at 2 to 3 kA and current passing time at 1 to 3 msec. More satisfactory results can be expected if a welding power source of the inverter type is used. 
     According to the present embodiment, two electric welders  4 ,  4  are arranged at opposite sides of the wlding position as shown in FIG. 8 to weld the respective leads  63 ,  63  of the electronic component  6 . The two welders need to be energized with a slight time lag therebetween to prevent the electronic compoent from breaking. With the present invention, therefore, a distributor is used to connect a common power supply to the welders  4 ,  4  alternatively. 
     With the apparatus described for preparing flyback transformer devices, electronic components can be connected to coil bobbins with a reduced number of steps. This serves to greatly reduce the production cost of flyback transformer devices. Use of electric welding to make fixed connections eliminates the need for a complex transformer structure for preliminarily fixing the electronic component lead to the terminal piece to realize coil bobbins of reduced size. 
     The above description of embodiments is given for the illustration of the present invention and should not be interpreted as limiting the invention defined in the appended claims or reducing the scope thereof. The construction of the components of the present device and apparatus is not limited to those of the embodiments but can of course be modified variously by one skilled in the art without departing from the sprit of the invention as defined in the claims. 
     For example, with the foregoing electric welder  4 , one of the electrodes  42  is fixed to the welding head  41 , with the other electrode piece  42  made movable to clamp the lead and the terminal piece, whereas the two electrode pieces  42 ,  42  can be driven at the same time for opening or closing.