Abstract:
A lead wire connection structure includes: a terminal including a terminal main body having a through hole, and a connection part extending from one end of the terminal main body; and a lead wire having one end connected to the connection part. Herein, a pair of elastic holding parts extending from both opposite side edges of the terminal main body holds both side surfaces of a nut. Moreover, an internal thread hole of the nut and the through hole are coaxially arranged. The lead wire connection structure is obtained at low manufacturing cost, that is, the lead wire connection structure is obtained in a short processing time at low material cost and manufacturing facility cost.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based on Japanese Patent Application No. 2013-201848 filed with the Japan Patent Office on Sep. 27, 2013, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The disclosure relates to a lead wire connection structure, for example, a lead wire connection structure to be incorporated in a relay socket. 
       BACKGROUND 
       [0003]    Heretofore, various electric lead wire connection structures for a relay socket have been known. For example, JP 2000-100540 A discloses a method for manufacturing an electric component including a lead wire and an electrically conductive fitting. This method includes: forming a lead wire guide hole, which is a through hole, in the electrically conductive fitting in a thickness direction of the electrically conductive fitting; inserting the lead wire into the lead wire guide hole; applying an external pressure to the electrically conductive fitting to deform the lead wire guide hole; and connecting the lead wire and the electrically conductive fitting to each other. 
         [0004]    In the method for manufacturing the electric component, the electrically conductive fitting is subjected to burring for forming an internal thread hole in a flange on the electrically conductive fitting. 
         [0005]    However, the burring results in increase in manufacturing cost because of the following reasons. In order to perform the burring, a metal material for the electrically conductive fitting is required to be thick, so that material cost increases. Further, the burring requires a large and expensive manufacturing facility and a long processing time. 
       SUMMARY 
       [0006]    In view of the circumstances described above, one or more embodiments of the disclosure provide a lead wire connection structure obtained at low manufacturing cost, that is, a lead wire connection structure obtained in a short processing time at low material cost and manufacturing facility cost. 
         [0007]    In one or more embodiments, a lead wire connection structure according to the disclosure includes: a terminal including a terminal main body having a through hole, and a connection part extending from one end of the terminal main body; and a lead wire having one end connected to the connection part. Herein, a pair of elastic holding parts extending from both opposite side edges of the terminal main body holds both side surfaces of a nut. Moreover, an internal thread hole of the nut and the through hole are coaxially arranged. 
         [0008]    According to one or more embodiments of the disclosure, the nut is held by the elastic holding parts of the terminal. Therefore, burring does not need to be performed, and the connection part of the terminal is easily bent while screw tightening torque is ensured. Hence, the lead wire connection structure is obtained at low manufacturing cost, that is, the lead wire connection structure is obtained in a short processing time at low material cost and manufacturing facility cost. 
         [0009]    Moreover, in the case where the lead wire is incorporated in a housing of an electronic device, the nut and the terminal can be simultaneously positioned. Therefore, workability is improved in the lead wire connection structure. 
         [0010]    In one or more embodiments of the disclosure, the nut may be formed into a quadrilateral shape as seen in a planar view. 
         [0011]    According to one or more embodiments, the opposite side surfaces of the nut are parallel with each other. Therefore, the nut is easily held in the lead wire connection structure. 
         [0012]    Particularly, when the nut is formed into a quadrilateral shape as seen in a planar view, a bottom surface of the terminal main body can be entirely supported with the nut, so that an area supported with the nut is widened. Therefore, since the terminal main body is not plastically deformed in a thickness direction, the terminal can be entirely formed of a thinner metal material, so that material cost can be saved. 
         [0013]    In one or more embodiments of the disclosure, the connection part may be bent with respect to the terminal main body. 
         [0014]    According to one or more embodiments, a floor area of the terminal and nut is reduced. Thus, a space for housing the terminal and the nut can be reduced and space efficiency can be improved in the lead wire connection structure. 
         [0015]    In one or more embodiments of the disclosure, the nut may have engagement grooves formed on the opposite side surfaces thereof, and the elastic holding parts of the terminal may be engaged with the engagement grooves. 
         [0016]    According to one or more embodiments, the elastic holding parts are engaged with the engagement grooves, so that positioning work is facilitated. Thus, high positioning accuracy is attained and the nut is less prone to drop off in the lead wire connection structure. 
         [0017]    In one or more embodiments of the disclosure, the engagement grooves may be formed to cut through the side surfaces of the nut. 
         [0018]    According to one or more embodiments, the nut is easily manufactured, and the side surfaces of the nut can be entirely held by the elastic holding parts. Therefore, the nut is less prone to drop off in the lead wire connection structure. 
         [0019]    In one or more embodiments of the disclosure, the elastic holding parts may pinch the side surfaces of the nut to hold the nut. 
         [0020]    According to one or more embodiments, the elastic holding parts pinch the entire side surfaces of the nut to hold the nut. Therefore, the nut is still less prone to drop off in the lead wire connection structure. 
         [0021]    In one or more embodiments of the disclosure, the nut may have chamfered portions formed on at least a pair of edges of the opposite side surfaces thereof, the edges being opposite to each other with the internal thread hole interposed therebetween. 
         [0022]    According to one or more embodiments, the elastic holding parts of the terminal are easily attached to the nut. Therefore, assembling workability is improved. 
         [0023]    In one or more embodiments of the disclosure, the nut may have an annular chamfered portion formed along an opening edge of the internal thread hole thereof, and the terminal main body may have a through hole having a diameter which is equal to or more than an outer peripheral diameter of the annular chamfered portion. 
         [0024]    According to one or more embodiments, even when a screw to be screwed into the internal thread hole is misaligned to some extent, the screw is guided by the annular chamfered portion and is easily screwed into the internal thread hole. Therefore, the assembling workability can be improved. 
         [0025]    In one or more embodiments of the disclosure, the chamfered portions and the annular chamfered portion may be symmetrically formed on top and bottom surfaces of the nut. 
         [0026]    According to one or more embodiments, the nut is easily aligned in the assembling work. Therefore, the assembling workability is further improved. 
         [0027]    An electronic device according to the disclosure includes a cover, a base, and the lead wire connection structure described above. Herein, the lead wire connection structure is housed and disposed in a space formed by the cover and the base. 
         [0028]    According to one or more embodiments of the disclosure, since the nut is held by the elastic holding parts of the terminal, burring does not need to be performed. Hence, the electronic device is obtained at low manufacturing cost, that is, the electronic device is obtained in a short processing time at low material cost and manufacturing facility cost. 
         [0029]    Moreover, in the case where the lead wire is incorporated in the housing of the electronic device, the nut and the terminal can be simultaneously positioned. Therefore, workability is improved in the electronic device. 
         [0030]    In one or more embodiments of the disclosure, the terminal and the nut may be held by an inner surface of the cover and a support plate protruding from a top surface of the base. 
         [0031]    According to one or more embodiments, the terminal and the nut are less prone to drop off in the electronic device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]      FIG. 1A  is a perspective view in which a lead wire connection structure is applied to a relay socket, and illustrates a state that a relay is attached to the relay socket according to one or more embodiments; 
           [0033]      FIG. 1B  is a perspective view and illustrates a state that the relay is detached from the relay socket according to one or more embodiments; 
           [0034]      FIG. 2  is an exploded perspective view of the relay socket illustrated in  FIG. 1B  according to one or more embodiments; 
           [0035]      FIG. 3  is an exploded perspective view of the relay socket illustrated in  FIG. 1B , the relay socket seen from a different angle from that in  FIG. 2  according to one or more embodiments; 
           [0036]      FIG. 4A  is a perspective view of partially enlarged components of the relay socket illustrated in  FIG. 2  according to one or more embodiments; 
           [0037]      FIG. 4B  is an exploded perspective view of the partially enlarged components illustrated in  FIG. 4A  according to one or more embodiments; 
           [0038]      FIG. 5A  is a plan view of the relay socket illustrated in  FIG. 1B  according to one or more embodiments; 
           [0039]      FIG. 5B  is a section view taken along line V-V in  FIG. 5A  according to one or more embodiments; 
           [0040]      FIG. 6  is a perspective view of a partially enlarged section of the relay illustrated in  FIGS. 1A and 1B  according to one or more embodiments; 
           [0041]      FIG. 7  is a perspective view of the partially enlarged section seen from a different angle from that in  FIG. 6  according to one or more embodiments; 
           [0042]      FIG. 8  is a perspective view of partially enlarged components for illustrating an assembling method according to one or more embodiments; 
           [0043]      FIG. 9A  is an exploded perspective view of enlarged main components according to one or more embodiments; 
           [0044]      FIG. 9B  is an exploded perspective view of enlarged main components according to one or more embodiments; 
           [0045]      FIG. 10A  is an exploded perspective view of enlarged main components according to one or more embodiments; 
           [0046]      FIG. 10B  is an exploded perspective view of enlarged main components according to one or more embodiments; 
           [0047]      FIG. 11A  is a perspective view of enlarged main components according to one or more embodiments; 
           [0048]      FIG. 11B  is an exploded perspective view of the enlarged main components according to one or more embodiments; 
           [0049]      FIG. 12  is a perspective view of a partially enlarged section according to one or more embodiments; 
           [0050]      FIG. 13  is a perspective view of the partially enlarged section, the partially enlarged section seen from a different angle from that in  FIG. 12  according to one or more embodiments; 
           [0051]      FIG. 14A  is a perspective view in which the lead wire connection structure is applied to a relay socket, and illustrates a state that a relay is attached to the relay socket according to one or more embodiments; 
           [0052]      FIG. 14B  is a perspective view and illustrates a state that the relay is detached from the relay socket according to one or more embodiments; 
           [0053]      FIG. 15A  is a plan view of the relay socket illustrated in  FIG. 14B  according to one or more embodiments; 
           [0054]      FIG. 15B  is a section view taken along line XV-XV in  FIG. 15A  according to one or more embodiments; 
           [0055]      FIG. 16A  is a perspective view in which the lead wire connection structure is applied to a relay socket, and illustrates a state that a relay is attached to the relay socket according to one or more embodiments; 
           [0056]      FIG. 16B  is a perspective view and illustrates a state that the relay is detached from the relay socket according to one or more embodiments; 
           [0057]      FIG. 17A  is a plan view of the relay socket illustrated in  FIG. 16B  according to one or more embodiments; 
           [0058]      FIG. 17B  is a section view taken along line XVII-XVII in  FIG. 17A  according to one or more embodiments; 
           [0059]      FIG. 18  is an exploded perspective view of the relay socket illustrated in  FIG. 16B  according to one or more embodiments; 
           [0060]      FIG. 19  is an exploded perspective view of the relay socket illustrated in  FIG. 16B , the relay socket seen from a different angle from that in  FIG. 18  according to one or more embodiments; 
           [0061]      FIG. 20A  is a perspective view in which the lead wire connection structure is applied to a relay socket, and illustrates a state that a relay is attached to the relay socket according to one or more embodiments; 
           [0062]      FIG. 20B  is a perspective view and illustrates a state that the relay is detached from the relay socket according to one or more embodiments; 
           [0063]      FIG. 21A  is a plan view of the relay socket illustrated in  FIG. 20B  according to one or more embodiments; and 
           [0064]      FIG. 21B  is a section view taken along line XXI-XXI in  FIG. 21A  according to one or more embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0065]    Description will be given of embodiments in which a lead wire connection structure according to the disclosure is applied to a relay socket  10  as illustrated in  FIGS. 1A to 21B  attached herein. 
         [0066]    In one or more embodiments, as illustrated in  FIGS. 1A and 1B , the relay socket  10  has a configuration that a relay  11  is attachable thereto. Moreover, as illustrated in  FIGS. 2 and 3 , the relay socket  10  includes a cover  20 , a base  30 , and a plurality of lead wires  60  housed and wired in a space formed by the cover  20  and the base  30 . 
         [0067]    As illustrated in  FIG. 2 , the cover  20  is formed into a substantially box shape, and has a positioning recess  21  formed on a center of a top surface thereof. The positioning recess  21  has a plurality of insertion holes  22  formed in a bottom surface thereof and arranged in a lattice form. Each of the insertion holes  22  is formed into a substantially cross shape as seen in a planar view, and has a structure that a contact  70  (which will be described later) can be inserted from below. 
         [0068]    The cover  20  has a plurality of front-to-rear two-level insulation walls  23  formed on opposite side surfaces thereof with a predetermined pitch, and also has a rearward partition wall  24  and a forward partition wall  25  integrally formed in parallel with each other between the insulation walls  23  and  23  (see  FIG. 6 ). Thus, a terminal  80  and a nut  90  (each of which will be described later) can be housed in a space formed by the insulation walls  23  and  23 , the rearward partition wall  24  and the forward partition wall  25 . The rearward partition wall  24  has a notch  24   a  formed on a lower end edge thereof, and the forward partition wall  25  has positioning projections  25   a  and  25   b  formed on an inward surface thereof such that the entire forward partition wall  25  has a substantially E shape as seen in a planar view (see  FIG. 6 ). The insulation walls  23  and  23  have a finger protector  26  integrally formed on upper ends thereof, and the finger protector  26  has a work hole  26   a  which facilitates connecting work and improves safety. The cover  20  has an opening, and engagement latches  27  formed on inner edges of the opening so as to be engaged with the base  30  as will be described later (see  FIG. 3 ). The cover  20  also has screw fixing holes  28  formed in diagonally opposite corners thereof such that the cover  20  is fastened to a different device with screws. 
         [0069]    As illustrated in  FIG. 2 , the base  30  is formed into such a planar shape as to close the opening of the cover  20 , and has a plurality of support plates  31  formed in parallel with one another with a predetermined pitch on a top surface thereof so as to protrude from the top surface. The support plates  31  are inserted along opposite surfaces of the insulation walls  23  and  23  of the cover  20 , and are brought into contact with both lower edges of the nut  90  as will be described later, thereby positioning the nut  90 . As illustrated in  FIG. 3 , the base  30  also has a pair of latch receivers  32  formed on opposite front and rear surfaces thereof, respectively, such that the engagement latches  27  of the cover  20  can be engaged with the latch receivers  32 . The base  30  also has a groove  33  formed on a center of a bottom surface thereof. The groove  33  is formed for slidably attaching a guide rail (not illustrated) formed into a hat shape as seen in a sectional view. The base  30  also has a pair of engagement latches  34  formed on one side edge of the groove  33 , and a mounting groove  35  formed on the other side edge of the groove  33 . The mounting groove  35  is formed for attaching a rail guide member  40  (which will be described later), and is orthogonal to the groove  33 . The mounting groove  35  has a locking hole  35   a  formed in a ceiling surface thereof. 
         [0070]    As illustrated in  FIG. 3 , the rail guide member  40  is formed into such a frame shape as to be slidably attached to the mounting groove  35  formed on the bottom surface of the base  30 , and has an S-shaped spring  41  integrally formed thereinside. When the rail guide member  40  is laterally attached to the mounting groove  35 , a locking projection  42  (see  FIG. 2 ) formed on the S-shaped spring  41  is locked by the locking hole  35   a  formed in the bottom surface of the base  30 . Thus, the rail guide member  40  is prevented from being detached from the base  30 . More specifically, the pair of engagement latches  34  formed on the bottom surface of the base  30  is engaged with one side edge of the guide rail (not illustrated) formed into a hat shape as seen in a sectional shape, and a tip end latch  43  of the rail guide member  40  is engaged with the other side edge of the guide rail. Thus, the base  30  is slidably attached to the guide rail. 
         [0071]    As illustrated in  FIGS. 4A and 4B , each of the lead wires  60  is easily bent, and has first and second ends  61  and  62 . The contact  70  is secured by crimping to and electrically connected to a core wire at the first end  61 , and the terminal  80  for holding the nut  90  is secured by crimping to and electrically connected to a core wire at the second end  62 . If necessary, the contact  70  and the terminal  80  may be electrically connected by soldering to the core wires, respectively. 
         [0072]    The contact  70  has the following structure. That is, a terminal (not illustrated) of the relay  11  is press fitted into between a pair of elastic contact pieces  71  and  72  each of which is formed in such a manner that an electrically conductive metal plate is stamped out by press working and then the stamped plate is bent. Thus, the contact  70  can be electrically connected to the relay  11 . Each of the elastic contact pieces  71  and  72  has a guide tongue piece  73  which is formed by bending and raising a tip end of each elastic contact piece outward. Therefore, even in the state that the contact  70  is housed in the insertion hole  22  of the cover  20 , the terminal of the relay  11  can be easily press fitted into the contact  70  through the guide tongue pieces  73  and  73 . Moreover, the contact  70  is electrically connected to the first end  61  of the lead wire  60  in such a manner that a crimping latch  74  extending from the elastic contact piece  71  is crimped inward. 
         [0073]    The terminal  80  is formed in such a manner that an electrically conductive metal plate is stamped out by press working, as in the contact  70 . More specifically, the terminal  80  has a terminal main body  81  formed into a quadrilateral shape as seen in a planar view, a through hole  82  formed in the terminal main body  81 , and a pair of elastic holding parts  83  extending from centers of both opposite side edges of the terminal main body  81 . The elastic holding parts  83  are bent twice to hold the nut  90  as will be described later. In order to prevent misalignment of the temporarily held nut  90 , the terminal  80  also has positioning tongue pieces  84  formed to extend from the side edges of the terminal main body  81  and bent at an obtuse angle. 
         [0074]    The terminal  80  also has a connection part  85  extending from one of sides thereof other than the sides where elastic holding parts  83  are formed, and an elastic press tongue piece  86  extending from the remaining side thereof. The elastic press tongue piece  86  is formed into a substantially T shape. The connection part  85  is formed of a thin metal plate, and therefore is easily bent. Particularly, the connection part  85  is bent at an obtuse angle with respect to the terminal main body  81 , so that a space for housing the terminal  80  is reduced. Moreover, the connection part  85  has two sets of crimping latches  85   a  protruding from both side edges thereof. When the crimping latches  85   a  are crimped inward, the terminal  80  is electrically connected to the second end  62  of the lead wire  60 . On the other hand, the elastic press tongue piece  86  is bent at a substantially right angle with respect to the terminal main body  81 , and both side edges of the elastic press tongue piece  86  are bent and raised. Thus, locking latches  86   a  are formed. 
         [0075]    The nut  90  is substantially equal in planar shape to the terminal main body  81 , and is slightly smaller in size than the terminal main body  81 . Moreover, the nut  90  has an internal thread hole  91  formed in a center thereof. The nut  90  is press fitted into between the elastic holding parts  83  and  83  of the terminal  80  connected to the lead wire  60 . Thus, the nut  90  is held by the terminal  80 . Herein, the shapes of the terminal main body  81 , through hole  82  and elastic holding parts  83  and  83  are set such that the through hole  82  of the terminal main body  81  and the internal thread hole  91  of the nut  90  can be coaxially arranged. Since the terminal main body  81  and the nut  90  are substantially equal in planar shape to each other, the nut  90  supports the entire bottom surface of the terminal main body  81  even when the terminal main body  81  of the terminal  80  is formed of a thin metal plate. Therefore, even when a screw  50  (which will be described later) is screwed into the internal thread hole  91  of the nut  90 , the terminal main body  81  can be prevented from being plastically deformed and predetermined tightening torque can be ensured. 
         [0076]    Moreover, the positioning tongue pieces  84  are brought into contact with opposite outer side corners of the nut  90 , so that the temporarily held nut  90  can be prevented from being misaligned. 
         [0077]    Herein, the shape of the nut  90  is not limited to a quadrilateral shape as seen in a planar shape, but may be, for example, a right hexagonal shape as seen in a planar view. 
         [0078]    Next, description will be given of a method for assembling the constituent components described above. 
         [0079]    First, the contact  70  and the terminal  80  are connected by crimping to the first end  61  and the second end  62  of the lead wire  60 , respectively, and the nut  90  is held by the elastic holding parts  83  and  83  of the terminal  80 . Then, the rail guide member  40  is slid into and engaged with the mounting groove  35  of the base  30 . Moreover, the locking projection  42  of the rail guide member  40  is locked by the locking hole  35   a  of the base  30  such that the rail guide member  40  is prevented from being detached from the base  30 . 
         [0080]    On the other hand, the cover  20  is positioned with the opening thereof directed upward. Then, the inverted screw  50  having a washer  51  attached thereto is inserted into the space formed by the insulation walls  23  and  23 , the rearward partition wall  24  and the forward partition wall  25 . Herein, a head of the screw  50  is fitted into the work hole  26   a  of the finger protector  26 , and the washer  51  is locked by an opening edge of the work hole  26   a , so that the screw  50  is positioned. Therefore, the assembling work is facilitated. 
         [0081]    As illustrated in  FIG. 8 , next, the terminal  80  and the nut  90  each connected to the lead wire  60  are temporarily fixed in the space formed by the insulation walls  23  and  23 , the rearward partition wall  24  and the forward partition wall  25 . Thus, the connection part  85  of the terminal  80  is engaged with the notch  24   a  of the rearward partition wall  24 , and the inward surface of the nut  90  is brought into contact with the rearward partition wall  24 , so that the nut  90  is positioned. On the other hand, both side surfaces of the nut  90  are positioned by the insulation walls  23  and  23  through the use of the elastic holding parts  83  and the positioning tongue pieces  84 . Moreover, a center of the elastic press tongue piece  86  of the terminal  80  is positioned by the positioning projection  25   a  of the forward partition wall  25 , and an outward surface of the nut  90  is positioned by the positioning projection  25   b  of the forward partition wall  25 . Herein, the locking latches  86   a  formed on both ends of the elastic press tongue piece  86  are locked by the positioning projections  25   b  and  25   b , so that the terminal  80  and the nut  90  are prevented from dropping off. Further, a tip end of a shank of the screw  50  is fitted into the internal thread hole  91  of the nut  90 . Therefore, the screw  50  can be prevented from dropping off and the assembling work is facilitated. 
         [0082]    As illustrated in  FIG. 5B , moreover, since the connection part  85  of the terminal  80  is bent at an obtuse angle with respect to the terminal main body  81 , the space for housing the terminal  80  in the cover  20  can be minimized. Further, an internal partition wall  24   b  extends from the ceiling surface of the cover  20  at the rear side of the connection part  85 . The internal partition wall  24   b  can ensure a high insulating property between the terminal  80  and the contact  70 . 
         [0083]    Then, the base  30  is fitted into the opening of the cover  20 , and the engagement latch  27  of the cover  20  is engaged with the latch receiver  32  of the base  30  such that the cover  20  and the base  30  are prevented from being separated from each other. Thus, the terminal  80  and the nut  90  each of which is connected to the lead wire  60  are housed and disposed in the space formed by the cover  20  and the base  30 . Moreover, both lower side edges of the nut  90  are pressed against the upper ends of the pair of support plates  31  of the base  30 . Therefore, the connection part  85  of the terminal  80  is engaged with the notch  24   a  of the rearward partition wall  24  such that the terminal  80  is prevented from being detached from the cover  20  (see  FIG. 6 ). Further, the locking latch  86   a  of the elastic press tongue piece  86  is locked by the positioning projection  25   b  of the forward partition wall  25  such that the terminal  80  is prevented from being detached from the cover  20  (see  FIG. 7 ). That is, the terminal  80  and the nut  90  are held from above by the notch  24   a  of the rearward partition wall  24  and the positioning projections  25   b  of the forward partition wall  25  in the cover  20 , and are also held from below by the support plates  31  protruding from the top surface of the base  30 . 
         [0084]    As illustrated in  FIG. 8 , particularly, the positioning tongue piece  84  of the terminal  80  is elastically deformed to come into press contact with the opposite surfaces of the insulation walls  23  and  23 . In the cover  20 , thus, the nut  90  is supported with the elastic holding parts  83  and  83  and the positioning tongue pieces  84  and  84 . Therefore, the nut  90  can be supported without wobbling. 
         [0085]    In one or more embodiments, the elastic holding parts  83  and  83  and the positioning tongue pieces  84  and  84  are acted for supporting the terminal  80  and the nut  90 , and are also acted for supporting the cover  20  and the nut  90 . Alternatively, the elastic holding parts  83  and  83  may be acted for supporting the terminal  80  and the nut  90 , and the positioning tongue pieces  84  and  84  may be acted for supporting the terminal  80  and the cover  20 . 
         [0086]    Next, the screw  50  is screwed into the internal thread hole  91  of the nut  90  through the work hole  26   a  of the cover  20 . Thus, the assembling work is finished. 
         [0087]    According to one or more embodiments, since the lead wire  60  is easily bent, the assembling work is facilitated. 
         [0088]    According to one or more embodiments, moreover, the elastic holding parts  83  of the terminal  80  hold the nut  90  such that the nut  90  is prevented from dropping off. Therefore, the assembling work is further facilitated. 
         [0089]    According to one or more embodiments, further, the screw  50  can be accurately set at a predetermined position in such a manner that the head of the screw  50  is fitted into the work hole  26   a  of the finger protector  26 . Therefore, the assembling work for the terminal  80  and the nut  90  is facilitated. 
         [0090]    When the terminal  80  and the nut  90  are positioned in the cover  20 , the tip end of the shank of the screw  50  is fitted into the internal thread hole  91  of the nut  90 , so that the screw  50  can be prevented from dropping off. Therefore, the assembling work is further facilitated. 
         [0091]    As illustrated in  FIG. 9A , one or more embodiments are different in the following point. That is, engagement grooves  92  are formed on opposite outer side surfaces of the nut  90 , and the terminal  80  holds the nut  90  in such a manner that the elastic holding parts  83  are engaged with the engagement grooves  92 . For convenience of the description, the same constituent components are denoted with the same reference signs, and the detailed description thereof will not be given here. 
         [0092]    According to one or more embodiments, the elastic holding parts  83  are engaged with the engagement grooves  92 . Therefore, the nut  90  can be accurately held and is less prone to drop off. 
         [0093]    As illustrated in  FIG. 9B , one or more embodiments are different in the following point. That is, engagement grooves  92  are formed on opposite outer side surfaces of the nut  90  so as to cut through the outer side surfaces, and the terminal  80  holds the nut  90  in such a manner that the elastic holding parts  83  are engaged with the engagement grooves  92 . For convenience of the description, the same constituent components are denoted with the same reference signs, and the detailed description thereof will not be given here. 
         [0094]    According to one or more embodiments, the nut  90  can be accurately held and is less prone to drop off. Moreover, the nut  90  is easily manufactured. 
         [0095]    As illustrated in  FIG. 10A , one or more embodiments are different in the following point. That is, the terminal  80  holds the nut  90  so as to pinch the entire side surfaces of the nut  90  with the elastic holding parts  83 . For convenience of the description, the same constituent components are denoted with the same reference signs, and the detailed description thereof will not be given here. 
         [0096]    According to one or more embodiments, the nut  90  is pinched by the elastic holding parts  83 , and therefore is still less prone to drop off. 
         [0097]    As illustrated in  FIG. 10B , one or more embodiments are different in the following point. That is, engagement grooves  92  are formed on opposite outer side surfaces of the nut  90  so as to cut through the outer side surfaces, and the elastic holding parts  83  of the terminal  80  are engaged with the engagement grooves  92  to pinch the nut  90 . For convenience of the description, the same constituent components are denoted with the same reference signs, and the detailed description thereof will not be given here. 
         [0098]    According to one or more embodiments, the nut  90  can be more accurately and firmly held, and therefore is still less prone to drop off. 
         [0099]    As illustrated in  FIGS. 11A and 11B , one or more embodiments are different in the following point. That is, chamfered portions  90   a  are formed on edges of the top surface of the nut  90 . Moreover, an annular chamfered portion  91   a  is formed on an opening edge of the internal thread hole  91  of the nut  90 . On the other hand, a through hole  82  is formed in the terminal  80  so as to be larger in diameter than the opening edge of the internal thread hole  91  of the nut  90 . 
         [0100]    According to one or more embodiments, the chamfered portions  90   a  allow the elastic holding parts  83  of the terminal  80  to be easily attached to the nut  90 . Unlike the foregoing embodiments, therefore, the elastic holding parts  83  are not necessarily bent twice, but are merely bent once. That is, productivity is improved. 
         [0101]    Moreover, the proximal end of the elastic holding part  83  and the proximal end of the positioning tongue piece  84  do not interfere with the outer peripheral edge of the nut  90 . Therefore, the elastic holding part  83  and the positioning tongue piece  84  are easily bent. That is, the productivity is further improved. 
         [0102]    Further, even when the screw  50  is misaligned, the annular chamfered portion  91   a  guides the screw  50  to the internal thread hole  91 . Therefore, the screw  50  can be screwed into the internal thread hole  91  with certainty. 
         [0103]    Herein, each of the chamfered portion  90   a  and the annular chamfered portion  91   a  is not limited to a C-plane, but may be an R-plane. 
         [0104]    Moreover, the chamfered portions  90   a  and the annular chamfered portion  91   a  may be symmetrically formed on the top and bottom surfaces of the nut  90 . When the chamfered portions  90   a  and the annular chamfered portion  91   a  are formed on the top and bottom surfaces of the nut  90  as described above, the nut  90  is easily aligned in the assembling work. Therefore, assembling workability is improved. 
         [0105]    As illustrated in  FIGS. 12 and 13 , one or more embodiments are different in the following point. That is, a positioning projection  31   a  is formed on the upper end of the support plate  31  of the base  30  to position the inward surface of the nut  90 . For convenience of the description, the same constituent components are denoted with the same reference signs, and the detailed description thereof will not be given here. 
         [0106]    According to one or more embodiments, since the nut  90  can be positioned by the positioning projection  31   a  of the support plate  31 , a tolerance upon incorporating the terminal  80  and the nut  90  in the cover  20  becomes large. Therefore, the relay socket  10  is obtained with improved assembling workability. 
         [0107]    The relay socket  10  to be employed in the disclosure is not limited to the 14-pin relay socket  10  provided with the finger protector  26  having the work hole  26   a  in the first embodiment. As illustrated in  FIGS. 14A to 15B , for example, the lead wire connection structure may be applied to a 14-pin relay socket  10  provided with no finger protector (a second application example). 
         [0108]    Moreover, the relay socket  10  to be employed in the disclosure is not limited to the 14-pin relay socket  10  provided with the finger protector  26  having the work hole  26   a  in the first embodiment. As illustrated in  FIGS. 16A to 19 , the lead wire connection structure may be applied to an 8-pin relay socket  10  provided with a finger protector  26  (a third application example). 
         [0109]    As illustrated in  FIGS. 20A to 21B , further, the lead wire connection structure may be applied to an 8-pin relay socket  10  provided with no finger protector (a fourth application example). 
         [0110]    In the respective application examples described above, for convenience of the description, the same constituent components are denoted with the same reference signs, and the detailed description thereof will not be given here. 
         [0111]    In the foregoing embodiments, the lead wire connection structure is applied to the relay socket; however, the disclosure is not limited to the relay socket. For example, the lead wire connection structure may be applied to a different electronic device. 
         [0112]    Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims.