Patent Publication Number: US-8968010-B2

Title: Press-fit type connector terminal

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a press-fit type connector terminal to be inserted into an electrically conductive through-hole formed through a printed circuit board. 
     2. Description of the Related Art 
     Various press-fit type connector terminals have been suggested. For instance, there is a terminal contact section having a needle-eye, C-shaped, N-shaped or Σ-shaped cross-section. 
     Japanese Patent Application Publication No. 2004-134275 has suggested a press-fit type connection terminal including a head to which a cable is connected, and a body to be inserted into a through-hole formed through a substrate. The body is centrally formed with a hole extending in a length-wise direction thereof, and the body is formed with a plurality of slits extending from an inner wall to an outer wall of the body. The hole is filled with electrically conductive adhesive. 
     Japanese Patent Application Publication No. 2007-157469 has suggested a press-fit type terminal including a press-fit section, a terminal base, and a male terminal. The press-fit section includes a contact having a shape which is readily able to make contact with a through-hole, and a compression section composed of elastic material. The compression section is inserted into an opening of the contact, and the compression section exerts an elastic force on the contact such that the contact is compressed into the through-hole. 
     Since a maximum current which can run through the above-mentioned press-fit type connector terminal is dependent on a size of the press-fit type connector terminals, it is necessary to enlarge a size of them in order to make it possible to cause a higher amount of current to run therethrough. However, a through-hole of a printed circuit board into which a contact section of a press-fit type connector terminal is inserted has an upper limit in an inner diameter thereof in dependence on a thickness of the printed circuit board. If a through-hole were designed to have an inner diameter over the upper limit, contact defectiveness between the through-hole and a press-fit type connector terminal tends to occur, resulting in reduction in contact reliability. 
     Thus, for instance, Japanese Patent Application Publication No. 2005-135698 has suggested a press-fit type connector terminal including a wide terminal branched at a distal end thereof into a plurality of sub-terminals to be inserted into through-holes, in order to allow a large amount of current to run therethrough. 
     The conventional press-fit type connector terminals suggested in the above-mentioned Publications Nos. 2004-134275 and 2007-157469 are difficult to allow a large amount of current to run therethrough. Furthermore, since they are designed to have an outer diameter greater than an inner diameter of a through-hole of a printed circuit board, and make electrical contact with a through-hole by inserting the press-fit section having low elasticity into a through-hole, there are caused problems that a printed circuit board is whitened due to a contact pressure exerted by the press-fit section onto a through-hole, and a metal plated on an inner surface of a through-hole is peeled off. Since whitening of a printed circuit board means molecular destruction of components of which the board is composed, the molecular destruction induces not only degradation in electrical insulation of a printed circuit board and deterioration in a withstand voltage, but also an increase in a resistance of a circuit pattern. 
     The press-fit type connector terminal suggested in the above-mentioned Publication No. 2005-135698 is able to allow a large amount of current to run therethrough, because it has a wide terminal branched at a distal end thereof into a plurality of sub-terminals to be inserted into through-holes. However, since each of the sub-terminals to be inserted into a through-hole of a printed circuit board is needle-eye shaped, the press-fit type connector terminal cannot absorb a dimensional tolerance caused between a through-hole and each of the sub-terminals, resulting in degradation in contact reliability. 
     SUMMARY OF THE INVENTION 
     In view of the above-mentioned problems in the conventional press-fit type connector terminals, it is an object of the present invention to provide a press-fit type connector terminal which is capable of allowing a large amount of current to run therethrough without an increase in a diameter of a through-hole of a printed circuit board, reducing a force by which the press-fit type connector terminal is inserted into a through-hole, preventing a contact section from being plastically deformed, preventing a printed circuit board from being whitened, and presenting superior contact reliability. 
     In the first aspect of the present invention, there is provided a press-fit type connector terminal including a pin section in the form of a flat plate, and a plurality of contact sections situated continuous to a front end of the pin section. Each of the contact sections include a contact piece in the form of a barrel or a spindle surrounding an imaginary center line, the contact piece being formed with a slit extending substantially parallel to the imaginary center line, and the connector terminal is comprised of a single bent metal plate having elasticity. 
     In the press-fit type connector terminal in accordance with the present invention, since a plurality of the contact sections continuous to a front end of the pin section being in the form of a flat plate are arranged in series, it is possible to allow a large amount of run to through the press-fit type connector terminal without an increase in a diameter of a through-hole of a printed circuit board. 
     Furthermore, since each of the contact sections is in the form of a barrel or a spindle being able to elastically enlarge or reduce a diameter thereof, the contact piece defining the contact section can be elastically deformed to be inserted into a through-hole when each of the contact sections is inserted into a through-hole of a printed circuit board. Hence, each of the contact sections no longer exerts an excessive compression force (contact pressure) onto an inner surface of a through-hole. Accordingly, it is possible to reduce a force with which the press-fit type connector terminal is inserted into a through-hole formed through a printed circuit board, prevent the contact sections from being plastically deformed when the press-fit type connector terminal is inserted into a through-hole, prevent a printed circuit board from being whitened, and further prevent a plated surface of a through-hole from being degraded. Furthermore, since the contact piece inserted into a through-hole makes contact with an inner surface of the through-hole, keeping a force with which the contact piece enlarges a diameter thereof, by virtue of elasticity thereof, it is possible to prevent occurrence of contact defectiveness, and provide superior contact reliability. 
     In addition, since the press-fit type connector terminal in accordance with the present invention can be formed by bending a single metal plate having elasticity, it is possible to reduce a number of parts and reduce fabrication costs. 
     In the second aspect of the present invention, there is provided a press-fit type connector terminal including a pin section in the form of a flat plate, and a plurality of contact sections situated continuous to a front end of the pin section. Each of the contact sections include a plurality of “&lt;”-shaped or arcuate contact pieces extending around an imaginary center line and outwardly protruding so as to surround the imaginary center line, and the connector terminal is comprised of a single bent metal plate having elasticity. 
     In the press-fit type connector terminal in accordance with the present invention, since a plurality of the contact sections continuous to a front end of the pin section being in the form of a flat plate are arranged in series, it is possible to allow a large amount of run to through the press-fit type connector terminal without an increase in a diameter of a through-hole of a printed circuit board. 
     Furthermore, since each of the contact sections is in the form of a barrel being able to elastically enlarge or reduce a diameter thereof, a plurality of the contact pieces defining the contact section can be elastically deformed to be inserted into a through-hole when each of the contact sections is inserted into a through-hole of a printed circuit board. Hence, each of the contact sections no longer exerts an excessive compression force (contact pressure) onto an inner surface of a through-hole. Accordingly, it is possible to reduce a force with which the press-fit type connector terminal is inserted into a through-hole formed through a printed circuit board, prevent the contact sections from being plastically deformed when the press-fit type connector terminal is inserted into a through-hole, prevent a printed circuit board from being whitened, and further prevent a plated surface of a through-hole from being degraded. Furthermore, since each of the contact pieces inserted into a through-hole makes contact with an inner surface of the through-hole at a plurality of sites, keeping a force with which the contact piece enlarges a diameter thereof, by virtue of elasticity thereof, it is possible to prevent occurrence of contact defectiveness, and provide superior contact reliability. 
     In addition, since the press-fit type connector terminal in accordance with the present invention can be formed by bending a single metal plate having elasticity, it is possible to reduce a number of parts and reduce fabrication costs. Comparing the “&lt;”-shaped contact piece to the arcuate contact piece, the arcuate contact piece tends to have a higher yield strength, and hence, does not degrade until it deforms in a relatively much degree. Thus, the arcuate contact piece is superior to the “&lt;”-shaped contact piece for enhancing repeatability with which the press-fit type connector terminal is inserted into and pulled out of a through-hole. 
     The press-fit type connector terminal may be designed to further include an inner shaft section situated in the contact section and continuous with at least one of the pin section and the contact piece. 
     By so designing the press-fit type connector terminal, since the inner shaft section is surrounded by a plurality of the contact pieces in the contact section, it is possible to insert the press-fit type connector terminal perpendicularly to a printed circuit board when the press-fit type connector terminal is inserted into a through-hole of the printed circuit board, ensuring enhancement in contact reliability by virtue of the contact pieces facing one another. 
     It is preferable that the contact pieces are equally spaced away from adjacent ones. 
     By so designing the contact pieces, each of the contact pieces makes contact with an inner surface of a through-hole at a plurality of sites at an equal pitch, keeping a force for enlarging a diameter thereof, ensuring that contact reliability can be enhanced. 
     The inner shaft section may be designed to be formed at an outer surface thereof with a protrusion protruding towards the contact pieces. 
     By so designing the inner shaft section, it is possible to prevent the excessive deformation of the contact pieces caused by reduction in a diameter of the contact pieces, by virtue of the protrusion, when the contact section of the press-fit type connector terminal is inserted into a through-hole formed through a printed circuit board, ensuring that repeatability with which the press-fit type connector terminal is inserted into and pulled out of a through-hole can be enhanced. 
     It is preferable that the press-fit type connector terminal further includes C-shaped binders arranged around distal and proximal ends of the contact piece so as to surround the imaginary center line. 
     By designing the press-fit type connector terminal to further include the C-shaped binders, it is possible to stably arrange a plurality of the contact pieces, ensuring that contact reliability can be enhanced. 
     It is preferable that the press-fit type connector terminal further includes a tapered inclining section at a distal end of the binder situated at a distal end of each of the contact pieces. 
     By designing the press-fit type connector terminal to further include the tapered inclining section, since the tapered inclining section continuous to a distal end of the binder makes contact with an inner surface of a through-hole at an opening of the through-hole, and then, is guided into the through-hole when the contact section of the press-fit type connector terminal is inserted into the through-hole of a printed circuit board, ensuring insertability of the contact section into a through-hole can be enhanced. 
     It is preferable that the press-fit type connector terminal further includes a shoulder having a portion protruding beyond an outer surface of the contact section, the shoulder being situated between the pin section and the contact section. 
     By designing the press-fit type connector terminal to further include the shoulder, since it is possible to exert a compression force on the shoulder having a portion protruding beyond an outer surface of the pin section, in order to insert the contact section into a through-hole formed through a printed circuit board, ensuring that workability with which the contact section is inserted into a through-hole formed through a printed circuit board can be enhanced. 
     It is preferable that the metal plate includes a first area for forming the pin section, the first area being in the form of a flat plate, a second area for forming a plurality of the contact sections, the second area being continuous to a front end of the first area, and a third area for forming a plurality of the inner shaft sections, the third area being continuous to a front end of the second area, the second area being substantially rectangular, having a width smaller than the same of the first area, and including a plurality of slits extending in parallel with a longitudinal axis of the first area, the third area being band-shaped and having a width smaller than the same of the second area. 
     By so designing the metal plate, it is possible to form the press-fit type connector terminal by folding the third area around a fold line longitudinally extending in the third area, folding the third area by 180 degrees towards the second area around the fold line, and bending the second area such that the second area surrounds the third area, ensuring that a fabrication yield can be enhanced. 
     The metal plate may be designed to includes a first area for forming the pin section, the first area being in the form of a flat plate, and a second area for forming a plurality of the contact sections, the second area being continuous to a front end of the first area, the second area being substantially rectangular, and having a width smaller than the same of the first area. 
     By so designing the metal plate, it is possible to readily form the press-fit type connector terminal including a plurality of the contact sections being in the form of a barrel or a spindle, continuous to a front end of the pin section being in the form of a flat plate. 
     The metal plate may be designed to include a first area for forming the pin section, the first area being in the form of a flat plate, a second area for forming a plurality of the contact sections, the second area being continuous to a front end of the first area, a third area for forming a plurality of the inner shaft sections, the third area being continuous to a front end of the second area, and a fourth area for forming the shoulder, the fourth area being located between the first area and the second area, the second area being substantially rectangular, having a width smaller than the same of the first area, and including a plurality of slits extending in parallel with a longitudinal axis of the first area, the third area being band-shaped and having a width smaller than the same of the second area. 
     By so designing the metal plate, it is possible to form the shoulder by bending the metal plate, ensuring that an efficiency in steps for fabricating the press-fit type connector terminal can be enhanced. 
     The metal plate may be designed to further include a band-shaped third area for forming an inner shaft section, the third area having a width smaller than the same of the second area, the third area being situated continuous to a front end of the second area or between the first area and the second area. 
     By so designing the metal plate, it is possible to readily form the press-fit type connector terminal including the inner shaft section within the contact section being in the form of a barrel or a spindle. 
     The third area may be designed to include a fifth area for forming a protrusion, the fifth area protruding beyond the third area in both width-wise and thickness-wise directions of the third area, the protrusion being formed at an outer surface of the inner shaft section and protruding towards the contact piece. 
     By so designing the metal plate, it is possible to readily form the protrusion at an outer surface of the inner shaft section, protruding towards the contact pieces. 
     The advantages obtained by the aforementioned present invention will be described hereinbelow. 
     The present invention provides the press-fit type connector terminal which is capable of allowing a large amount of current to run therethrough without an increase in a diameter of a through-hole of a printed circuit board, reducing a force by which the press-fit type connector terminal is inserted into a through-hole of a printed circuit board, preventing a contact section from being plastically deformed when inserted into a through-hole of a printed circuit board, preventing a printed circuit board from being whitened, and presenting superior contact reliability. 
     The above and other objects and advantageous features of the present invention will be made apparent from the following description made with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the press-fit type connector terminal in accordance with the first embodiment of the present invention. 
         FIG. 2  is a perspective view of the press-fit type connector terminal illustrated in  FIG. 1 , viewing in a different angle from  FIG. 1 . 
         FIG. 3  is a front view of the press-fit type connector terminal illustrated in  FIG. 1 . 
         FIG. 4  is a right-side view of the press-fit type connector terminal illustrated in  FIG. 1 . 
         FIG. 5  is a bottom view of the press-fit type connector terminal illustrated in  FIG. 1 . 
         FIG. 6  is a partial cross-sectional view showing the press-fit type connector terminal illustrated in  FIG. 1 , before inserted into a through-hole formed through a printed circuit board. 
         FIG. 7  is a partial cross-sectional view showing the press-fit type connector terminal illustrated in  FIG. 1 , after having been inserted into a through-hole formed through a printed circuit board. 
         FIG. 8A  is a view illustrating a developed metal plate from which the press-fit type connector terminal illustrated in  FIG. 1  is fabricated. 
         FIG. 8B  is a view viewing in a direction indicated with an arrow P shown in  FIG. 8A . 
         FIG. 9  is a perspective view of the press-fit type connector terminal in accordance with the second embodiment of the present invention. 
         FIG. 10  is a front view of the press-fit type connector terminal illustrated in  FIG. 9 . 
         FIG. 11  is a right-side view of the press-fit type connector terminal illustrated in  FIG. 9 . 
         FIG. 12  is a bottom view of the press-fit type connector terminal illustrated in  FIG. 9 . 
         FIG. 13  is a perspective view of the press-fit type connector terminal in accordance with the third embodiment of the present invention. 
         FIG. 14  is a front view of the press-fit type connector terminal illustrated in  FIG. 13 . 
         FIG. 15  is a right-side view of the press-fit type connector terminal illustrated in  FIG. 13 . 
         FIG. 16  is a bottom view of the press-fit type connector terminal illustrated in  FIG. 13 . 
         FIG. 17A  is a view illustrating a developed metal plate from which the press-fit type connector terminal illustrated in  FIG. 13  is fabricated. 
         FIG. 17B  is a view viewing in a direction indicated with an arrow Q shown in  FIG. 17A . 
         FIG. 18  is a perspective view of the press-fit type connector terminal in accordance with the fourth embodiment of the present invention. 
         FIG. 19  is a front view of the press-fit type connector terminal illustrated in  FIG. 18 . 
         FIG. 20  is a right-side view of the press-fit type connector terminal illustrated in  FIG. 18 . 
         FIG. 21  is a bottom view of the press-fit type connector terminal illustrated in  FIG. 18 . 
         FIG. 22  is a perspective view of the press-fit type connector terminal in accordance with the fifth embodiment of the present invention. 
         FIG. 23  is a perspective view of the press-fit type connector terminal in accordance with the sixth embodiment of the present invention. 
         FIG. 24  is a perspective view of the press-fit type connector terminal in accordance with the seventh embodiment of the present invention. 
         FIG. 25  is a perspective view of the press-fit type connector terminal in accordance with the eighth embodiment of the present invention. 
         FIG. 26  is a perspective view of the press-fit type connector terminal in accordance with the ninth embodiment of the present invention. 
         FIG. 27  is a perspective view of the press-fit type connector terminal illustrated in  FIG. 26 , viewing in a different angle from  FIG. 26 . 
         FIG. 28  is a front view of the press-fit type connector terminal illustrated in  FIG. 26 . 
         FIG. 29  is a right-side view of the press-fit type connector terminal illustrated in  FIG. 26 . 
         FIG. 30  is a bottom view of the press-fit type connector terminal illustrated in  FIG. 26 . 
         FIG. 31  is a cross-sectional view taken along the line A-A shown in  FIG. 28 . 
         FIG. 32A  is a view illustrating a developed metal plate from which the press-fit type connector terminal illustrated in  FIG. 26  is fabricated. 
         FIG. 32B  is a view viewing in a direction indicated with an arrow B shown in  FIG. 32A . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     The press-fit type connector terminal  100  in accordance with the first embodiment of the present invention is explained hereinbelow with reference to  FIGS. 1 to 8 . 
     As illustrated in  FIGS. 1 to 5 , the press-fit type connector terminal  100  is formed by bending a single metal plate  110  (see  FIGS. 8A and 8B ) having elasticity. 
     The press-fit type connector terminal  100  includes a pin section  11  in the form of a flat plate, a plurality of contact sections  113  continuous to a front end of the pin section  111 , and a shoulder  112  situated between a front end of the pin section  111  and the contact sections  113  and being in the form of a flat plate. 
     Each of the contact sections  113  includes a plurality of “&lt;”-shaped contact pieces  13  extending along an imaginary center line  113   c  and outwardly protruding so as to surround the imaginary center line  113   c.    
     An inner shaft section  114  continuous to the contact piece  113  stands coaxially with the imaginary center line  113   c  in each of the contact sections  113 . In each of the contact sections  113 , a plurality of the contact pieces  13  is arranged around the inner shaft section  114  having a U-shaped cross-section such that the contact sections  113  are equally spaced away from adjacent ones. Each of the contact sections  113  is entirely in the form of a barrel. Each of the contact sections  113  being in the form of a barrel around the inner shaft section  114  is able to elastically enlarge and reduce a diameter thereof. As best illustrated in  FIG. 7 , protrusions  115  protrude towards the contact pieces  13  from an outer surface of the inner shaft section  114 . 
     Each of the contact sections  113  is formed at both distal and proximal ends of the contact pieces  13  with C-shaped binders  116  and  117  surrounding the inner shaft section  114 . The binder  116  situated at front ends of the contact pieces  13  has a tapered inclining section  118  at a front end thereof. The rectangular shoulder  112  situated between the pin section  111  and the contact sections  113  and being in the form of a flat plate has a surface extending in parallel with a direction in which the contact sections  113  are arranged. The shoulder  112  has opposite ends  112   a  located beyond outer surfaces of the contact pieces  113  located at left and right ends of a line of the contact sections  113 . A tapered connector  119  is situated between each of the contact sections  113  and the shoulder  112 . The connector  119  has a width reducing towards the contact section  113 . 
     The pin section  111  being substantially rectangular and being in the form of a flat plate is perpendicularly folded in the vicinity of a front end  111   a  in a length-wise direction L thereof. The shoulder  112 , the connector  119  and the contact sections  113  are arranged continuous to the front end  111   a . Thus, a direction in which the contact sections  113  are inserted into through-holes of a printed circuit board and the length-wise direction L of the pin section  111  are perpendicular to each other. A distance between the opposite ends  112   a  of the shoulder  112  is greater than a length of the pin section  111  measured in a width-wise direction W thereof. 
     As illustrated in  FIGS. 6 and 7 , since a plurality of the contact pieces  13  defining the contact section  113  elastically deforms such that they come close to the inner shaft section  114 , and is inserted into a through-hole  21  when the contact section  113  is inserted into the through-hole  21  plated with a metal  22  and formed through a printed circuit board  20 , it is possible to reduce a force with which the contact section  113  is inserted into the through-hole  21 . Furthermore, since the contact section  113  no longer exerts an excessive compression force (contact pressure) onto an inner surface of the through-hole  21 , a plated surface of the through-hole  21  is not degraded, and it is possible to prevent the printed circuit board  20  from being whitened. In addition, even if the pin section  111  were inclined, the contact pieces  13  would be difficult to be elastically deformed, because the contact pieces  13  make contact with the inner shaft section  114 . 
     Furthermore, since the contact pieces  13  defining the contact section  113  having been inserted into the through-hole  21  equally makes contact with an inner surface of the through-hole  21  at a plurality of sites, keeping a force by which the contact pieces  13  enlarge a diameter thereof, contact defectiveness would not occur, and superior contact reliability is provided. In addition, a plurality of the contact sections  113  continuous to the pin section  111  being in the form of a flat plate allows a large amount of current to run therethrough without an increase in a diameter of the through-hole  21  of the printed circuit board  20 . 
     In addition, as illustrated in  FIGS. 1 and 2 , since C-shaped binders  116  and  117  surround the inner shaft section  114  at distal and proximal ends of each of the contact pieces  13 , the contact pieces  13  can be stably arranged both when the contact section  113  is inserted into the through-hole  21  and after the contact section  113  was inserted into the through-hole  21 , as illustrated in  FIGS. 6 and 7 , ensuring that contact reliability can be enhanced. 
     Since the press-fit type connector terminal  100  is designed to have the protrusions  115  protruding towards the contact pieces  13 , at an outer surface of the inner shaft section  114 , it is possible to prevent, by virtue of the protrusions  115 , the excessive deformation of the contact pieces  13  which is caused by the shrinkage in a diameter of the contact section  113  when the contact section  113  is inserted into the through-hole  21  formed through the printed circuit board  20 , as illustrated in  FIG. 6 . Thus, it is possible to enhance the repeatability with which the press-fit type connector terminal  100  is inserted into and pulled out of the through-hole  21 . 
     Furthermore, since the press-fit type connector terminal  100  is designed to include the tapered inclining section  118  at a distal end of the binder  116  situated at a distal end of each of the contact pieces  13 , when the contact section  113  is inserted into the through-hole  21  of the printed circuit board  20 , as illustrated in  FIG. 6 , the tapered inclining section  118  situated at a distal end of the binder  116  makes contact with an inner surface of the through-hole  21  at an opening of the through-hole  21 , and then, is guided into the through-hole  21 , ensuring insertability of the contact section  113  into the through-hole  21  can be enhanced. 
     Though each of the contact pieces  13  is designed to be “&lt;”-shaped, each of the contact pieces  13  may be designed to be arcuate. 
     The press-fit type connector terminal  100  is formed by bending a single metal plate  110  having elasticity, illustrated in  FIGS. 8A and 8B . As illustrated in  FIGS. 8A and 8B , the metal plate  110  formed by pressing includes a substantially rectangular first area  120  for forming the pin section  111 , a substantially rectangular fourth area  121  for forming the shoulder  112 , continuous to a front end of the first area  120 , a plurality of sixth areas  122  each for forming the tapered connector  119 , continuous to a front end of the fourth area  121 , a plurality of second areas  123  each for forming the contact section  113 , continuous to a front end of each of the sixth areas  122 , and a plurality of third areas  124  each for forming the inner shaft section  114 , continuous to a front end of each of the second areas  123 . 
     Each of the second areas  123  is in the form of a rectangle having a width greater than a width of the fourth area  121 , and has a plurality of slits  125  and strips  126  both extending in parallel with a length-wise direction L of the first area  120 . The third area  124  has a width smaller than a width of the second area  123 , and is band-shaped. The third area  124  is centrally formed with a fifth area  127  for forming the protrusion  115 . The fifth area  127  protrudes beyond the third area  124  in both width-wise and thickness-wise directions of the third area  124 . 
     The press-fit type connector terminal  100  illustrated in  FIG. 1  is formed by bending the metal plate  110  illustrated in  FIGS. 8A and 8B  as follows. 
     First, the opposite ends  120   a  of the first area  120  are folded by 180 degrees towards a center of the first area  120  around two fold lines  128  extending in a length-wise direction L of the first area  120 . Thus, the pin section  111  (see  FIG. 1 ) is formed. 
     Then, the third area  124  is folded along a length-wise direction thereof such that the third area  124  has a U-shaped cross-section, to thereby form the inner shaft section  114  (see  FIG. 1 ). Then, the inner shaft section  114  is folded by 180 degrees towards the second area  123  along a fold line  129  extending between the third area  124  and the second area  123 . By folding the third area  124  to have a U-shaped cross-section, the protrusion  115  (see  FIG. 1 ) is formed by the fifth area  127 . 
     Then, each of the strips  126  of the second area  123  is folded in the “&lt;”-shaped form, areas  116 A and  117 A for forming the binders  116  and  117  are folded in the C-shaped form around the inner shaft section  114 , and each of the second areas  123  is folded in the barrel form to surround the inner shaft section  114 . Thereby, there is formed a plurality of the contact sections  113 . Then, as illustrated in  FIG. 1 , the pin section  111  being in the form of a flat plate is perpendicularly folded at a portion which is in the vicinity of the front end  111   a  in a length-wise direction L. 
     The press-fit type connector terminal  100  in accordance with the first embodiment is designed to include the three contact sections  113 . A number of the contact sections  113  is not to be limited to three, but may be determined in dependence on a use thereof and/or conditions in accordance with which the contact sections  113  are employed. 
     Though the press-fit type connector terminal  100  in accordance with the first embodiment is designed to include the inner shaft section  114  in the contact section  113 , the press-fit type connector terminal  100  may be designed not to include the inner shaft section  114  in the contact section  113 . 
     Second Embodiment 
     The press-fit type connector terminals  200 ,  300 ,  400 ,  500 ,  600 ,  700 ,  800  and  900  in accordance with the second to ninth embodiments are explained hereinbelow with reference to  FIGS. 9 to 32B . Parts or elements that correspond to those of the above-mentioned press-fit type connector terminal  100  illustrated in  FIGS. 1 to 8  have been provided with the same reference numerals, and operate in the same manner as corresponding parts or elements in the press-fit type connector terminal  100 , unless explicitly explained hereinbelow. 
     The press-fit type connector terminal  200  in accordance with the second embodiment, illustrated in  FIGS. 9 to 12 , is designed to include a pin section  211  in the form of a flat plate not folded. A direction in which each of the contact sections  113  is inserted into and pulled out of the through-hole  21  (see  FIG. 6 ) of the printed circuit board  20  is in parallel with a length-wise direction L of the pin section  211 . 
     By so designing the pin section  211 , it is possible to perpendicularly connect the press-fit type connector terminal  200  to the printed circuit board  20 . 
     Third Embodiment 
     The press-fit type connector terminal  300  in accordance with the third embodiment, illustrated in  FIGS. 13 to 17 , is designed to include a shoulder  312  having a double-wall structure. Specifically, as illustrated in  FIGS. 17A and 17B , a metal plate  310  from which the press-fit type connector terminal  300  is formed is designed to include a band-shaped fourth area  321  extending in parallel with a width-wise direction (see  FIG. 13 ) of the pin section  111 , between the first area  120  for forming the pin section  111  and the sixth areas  122  each for forming the connector  119 . The shoulder  312  is formed by folding the fourth area  321  around two fold lines  329  extending in parallel with the fold lines  128 . Two areas located outwardly beyond the fold lines  329  define opposite ends  312   a  of the shoulder  312 . The opposite ends  312   a  of the shoulder  312  protrude beyond the contact sections  113  located at right and left ends among the contact sections  113  arranged in a width-wise direction W of the pin section  111 . 
     By so designing the shoulder  312 , the press-fit type connector terminal  300  can be inserted into a through-hole of a printed circuit board by pushing the shoulder  312 . 
     In the press-fit type connector terminal  300 , as illustrated in  FIGS. 13 and 16 , the three contact sections  113  arranged in a width-wise direction W of the pin section  111  are alternately rotated by 180 degrees around the inner shaft section  114 . 
     By so designing the three contact sections  113 , a distance between the adjacent contact sections  113  can be arbitrarily changed merely by changing a position of the fold lines  329 . 
     Fourth Embodiment 
     The press-fit type connector terminal  400  in accordance with the fourth embodiment, illustrated in  FIGS. 18 to 21 , is designed to include a pin section  411  in the form of a flat plate not folded. A direction in which each of the contact sections  113  is inserted into and pulled out of the through-hole  21  (see  FIG. 6 ) of the printed circuit board  20  is in parallel with a length-wise direction L of the pin section  411 . Except for the shape of the pin section  411 , the press-fit type connector terminal  400  has the same structure and functions as those of the press-fit type connector terminal  300  illustrated in  FIG. 13 . 
     By so designing the pin section  411 , it is possible to perpendicularly connect the press-fit type connector terminal  400  to the printed circuit board  20 . 
     Fifth Embodiment 
     The press-fit type connector terminal  500  in accordance with the fifth embodiment, illustrated in  FIG. 22 , is designed to include a pin section  511  and a shoulder  511  in place of the pin section  111  and the shoulder  112 . The pin section  511  and the shoulder  511  are both composed of a metal plate having a thickness greater than the same of a metal plate of which the pin section  111  and the shoulder  112  are composed. 
     By so designing the section  511  and the shoulder  511 , the pin section  511  can have a higher strength, and the press-fit type connector terminal  500  can be inserted into a through-hole with the pin section  511  being horizontally kept. 
     Sixth Embodiment 
     The press-fit type connector terminal  600  in accordance with the sixth embodiment, illustrated in  FIG. 23 , is designed to include a pin section  611  in the form of a flat plate not folded. A direction in which each of the contact sections  113  is inserted into and pulled out of the through-hole  21  (see  FIG. 6 ) of the printed circuit board  20  is in parallel with a length-wise direction L of the pin section  611 . Except a shape of the pin section  611 , the press-fit type connector terminal  600  has the same structure and functions as those of the press-fit type connector terminal  500  illustrated in  FIG. 22 . 
     By so designing the pin section  611 , it is possible to perpendicularly connect the press-fit type connector terminal  600  including the pin section  611  having a high strength, to the printed circuit board  20 . 
     Seventh Embodiment 
     The press-fit type connector terminal  700  in accordance with the seventh embodiment, illustrated in  FIG. 24 , is designed to include a shoulder  712  having a double-wall structure similarly to the shoulder  312  of the press-fit type connector terminal  300  illustrated in  FIG. 13 , in place of the shoulder  512  of the press-fit type connector terminal  500  illustrated in  FIG. 22 , having a single-wall structure. 
     A metal plate of which the shoulder  712  is formed has a thickness greater than the same of a metal plate of which the shoulder  312  is formed. 
     By designing the press-fit type connector terminal  700  to include the shoulder  712 , since the shoulder  712  has an increased thickness, the press-fit type connector terminal  700  can have an increased strength when inserted into a printed circuit board. 
     Eighth Embodiment 
     The press-fit type connector terminal  800  in accordance with the eighth embodiment, illustrated in  FIG. 25 , is designed to include a pin section  811  in the form of a flat plate not folded. A direction in which each of the contact sections  113  is inserted into and pulled out of the through-hole  21  (see  FIG. 6 ) of the printed circuit board  20  is in parallel with a length-wise direction L of the pin section  811 . Except a shape of the pin section  811 , the press-fit type connector terminal  800  has the same structure and functions as those of the press-fit type connector terminal  700  illustrated in  FIG. 24 . 
     By so designing the pin section  811 , it is possible to perpendicularly connect the press-fit type connector terminal  800  to the printed circuit board  20 , and the shoulder  712  can have an increased strength when the press-fit type connector terminal  800  is inserted into the printed circuit board  20 . 
     Ninth Embodiment 
     The press-fit type connector terminal  900  in accordance with the ninth embodiment of the present invention is explained hereinbelow with reference to  FIGS. 26 to 32B . 
     The press-fit type connector terminal  900  is formed by bending a single metal plate  910  (see  FIGS. 32A and 32B ) having elasticity. 
     The press-fit type connector terminal  900  includes a pin section  911  in the form of a flat plate, and a plurality of contact sections  913  continuous to a front end of the pin section  911 . 
     Each of the contact sections  913  includes a contact piece  93  being in the form of a barrel surrounding an imaginary center line  913   c . The contact piece  93  is formed at a surface thereof with a slit  94  extending substantially in parallel with the imaginary center line  913   c . An inner shaft section  114  having a U-shaped cross-section is located in the contact section  913  such that the inner shaft section  114  is continuous with the contact piece  93 . 
     Each of the contact pieces  93  is formed at both distal and proximal ends thereof with C-shaped binders  116  and  117  surrounding the inner shaft section  114  which is coaxial with the imaginary center line  913   c . The binder  116  situated at front ends of the contact pieces  93  has a tapered inclining section  118  at a front end thereof. A shoulder  112  is formed in the vicinity of the contact section  913  in a length-wise direction L of the pin section  911 . The shoulder  112  has opposite ends  112   a  located beyond outer surfaces of the pin section  911  and the contact sections  913 . As illustrated in  FIG. 31 , the inner shaft section  114  is designed to include a plurality of protrusions  115  protruding towards the contact piece  93  from an outer surface of the inner shaft section  114 . 
     The press-fit type connector terminal  900  illustrated in  FIG. 26  is made from the metal plate  910  illustrated in  FIGS. 32A and 32B . As illustrated in  FIGS. 32A and 32B , the metal plate  910  formed by pressing includes a substantially rectangular first area  120  for forming the pin section  911 , a substantially rectangular fourth area  121  for forming the shoulder  112 , continuous to a front end of the first area  120 , a plurality of sixth areas  122  each for forming the tapered connector  119 , each continuous to a front end of the fourth area  121 , a plurality of second areas  923  each for forming the contact section  913 , each continuous to a front end of each of the sixth areas  122 , and a plurality of third areas  124  each for forming the inner shaft section  114 , each continuous to a front end of each of the second areas  923 . 
     Each of the second areas  923  is in the form of a rectangular flat plate. Each of the third areas  124  is band-shaped and has a width smaller than the same of the second area  923 . The third area  124  is centrally formed with a fifth area  127  for forming the protrusion  115 . The fifth area  127  protrudes beyond the third area  124  in both width-wise and thickness-wise directions of the third area  124 . 
     The press-fit type connector terminal  900  illustrated in  FIG. 26  is formed by bending the metal plate  910  illustrated in  FIGS. 32A and 32B  as follows. 
     First, the opposite ends  120   a  of the first area  120  are folded by 180 degrees towards a center of the first area  120  around two fold lines  128  extending in a length-wise direction L of the first area  120 . Thus, the pin section  911  (see  FIG. 26 ) is formed. 
     Then, each of the third areas  124  is folded along a length-wise direction thereof such that each of the third areas  124  has a U-shaped cross-section, to thereby form the inner shaft section  114  (see  FIG. 26 ). Then, the inner shaft section  114  is folded by 180 degrees towards the second area  923  along a fold line  129  extending between the third area  124  and the second area  923 . By folding the third area  124  to have a U-shaped cross-section, the protrusion  115  (see  FIG. 31 ) is formed by the fifth area  127 . 
     Then, each of the second areas  923  is folded in the form of a barrel such that each of the second areas  923  surrounds the inner shaft section  114  (or the imaginary center line  913 ) and the slit  94  (see  FIG. 31 ) faces the side edges  923   a  and  923   b  of each of the second areas  923 . Then, the first area  120  is perpendicularly folded in the vicinity of the front end  911   a  thereof in a length-wise direction L thereof to thereby form the pin section  911 . Thus, the press-fit type connector terminal  900  illustrated in  FIG. 26  is fabricated. 
     The press-fit type connector terminal  900  is used in the same way and has the same functions as the press-fit type connector terminals  100 ,  300 ,  500  and  700  illustrated in  FIGS. 1 ,  13 ,  22  and  24 , respectively, but is structurally different from the press-fit type connector terminals  100 ,  300 ,  500  and  700  in that the contact section  913  of the press-fit type connector terminal  900  includes the contact piece  93  having a non-cut continuous shape without the slit  94 . By including the contact piece  93 , the press-fit type connector terminal  900  makes it possible to increase an area in which the press-fit type connector terminal  900  makes contact with a through-hole of a printed circuit board, and enhance contact reliability. 
     A shape of the contact piece  913  is not to be limited to a barrel. The contact piece  913  may be designed to be in the form of a spindle outwardly protruding arcuately at about a center in a direction in which the imaginary center line  913   c  extends. 
     The press-fit type connector terminal  900  is designed to include the three contact sections  913 . However, the number of the contact sections  913  is not to be limited to three. The press-fit type connector terminal  900  may be designed to include any number of the contact sections  913  in dependence on a use and conditions in accordance with which the press-fit type connector terminal  900  is employed. 
     The press-fit type connector terminal  900  is designed to include the inner shaft section  114  in the contact section  913 . In contrast, the press-fit type connector terminal  900  may be designed not to include the inner shaft section  114 , in which case, the contact section  913  is empty. 
     The above-mentioned press-fit type connector terminals  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ,  800  and  900  are just examples of the present invention. The scope of the present invention is not to be limited to those examples. 
     INDUSTRIAL APPLICABILITY 
     The press-fit type connector terminal in accordance with the present invention can be broadly employed, for instance, in fields of electric/electronic industry and automobile industry as a connector to be inserted into a through-hole formed through a printed circuit board for accomplishing electric connection. 
     While the present invention has been described in connection with certain preferred embodiments, it is to be understood that the subject matter encompassed by way of the present invention is not to be limited to those specific embodiments. On the contrary, it is intended for the subject matter of the invention to include all alternatives, modifications and equivalents as can be included within the spirit and scope of the following claims. 
     The entire disclosure of Japanese Patent Application No. 2012-61040 filed on Mar. 16, 2012 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.