Patent Publication Number: US-2023163536-A1

Title: Connection structure of shielded terminal and shielded electrical wire

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority from Japanese Patent Application No. 2021-190346, filed on Nov. 24, 2021, with the Japan Patent Office, the disclosure of which is incorporated herein in its entirety by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a connection structure of a shielded terminal and a shielded electrical wire 
     BACKGROUND 
     A connector for a coaxial cable described in JP H9-120870 includes a coaxial cable including an outer conductor, a terminal for an outer conductor including an outer conductor receiving portion, and a cover member including an outer conductor support portion. The outer conductor of the coaxial cable is received inside the outer conductor receiving portion of the terminal for an outer conductor, and the outer conductor receiving portion is received inside the outer conductor support portion of the cover member. By performing compression bonding on the outer conductor support portion, the outer conductor, the terminal for an outer conductor, and the cover member are connected in a manner that allows electricity to flow. 
     SUMMARY 
     In the technique described above, the outer conductor, the terminal for an outer conductor, and the cover member are bonded via only friction resistance caused by the compression bonding strength of the outer conductor support portion. Accordingly, when the coaxial cable is pulled, the coaxial cable may be moved in the axis direction relative to the terminal for an outer conductor and the cover member. 
     The connection structure of a shielded terminal and a shielded electrical wire of the present disclosure has been made in light of the foregoing and is directed at improving the bonding performance from compression bonding. 
     A connection structure of a shielded terminal and a shielded electrical wire according to the present disclosure includes: a shielded electrical wire including a shield layer; and a shielded terminal including an outer conductor connected to the shield layer, wherein the outer conductor is formed by assembling a first shell including an electrical wire connection portion that comes into contact with an outer circumference of the shield layer, and a second shell including a compression bonding portion that is crimped to an outer circumference of the electrical wire connection portion, and wherein a catch portion that catches on an outer circumferential surface of the shield layer is formed in the electrical wire connection portion. 
     According to the present disclosure, the bonding performance from compression bonding can be improved. 
     The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a shielded terminal and a shielded electrical wire forming a connection structure according to a first embodiment as seen from diagonally up and back. 
         FIG.  2    is a side cross-sectional view of the shielded terminal and the shielded electrical wire. 
         FIG.  3    is a perspective view of a state with a second shell removed as seen from diagonally up and back. 
         FIG.  4    is a perspective view of a state with a second shell removed as seen from diagonally down and back. 
         FIG.  5    is a cross-sectional view taken along line A-A of  FIG.  2   . 
         FIG.  6    is a cross-sectional view taken along line B-B of  FIG.  2   . 
         FIG.  7    is a perspective view of a state before a first shell is bent as seen from diagonally down and back. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. 
     Firstly, embodiments of the present disclosure will be listed and described. 
     (1) A connection structure of a shielded terminal and a shielded electrical wire according to the present disclosure includes: a shielded electrical wire including a shield layer; and a shielded terminal including an outer conductor connected to the shield layer, wherein the outer conductor is formed by assembling a first shell including an electrical wire connection portion that comes into contact with an outer circumference of the shield layer, and a second shell including a compression bonding portion that is crimped to an outer circumference of the electrical wire connection portion, and wherein a catch portion that catches on an outer circumferential surface of the shield layer is formed in the electrical wire connection portion. According to the configuration of the present disclosure, by the catch portion catching on the outer circumferential surface of the shield layer, relative movement between the shielded electrical wire and the outer conductor is prevented. This can improve the reliability of the bonding performance from compression bonding. 
     (2) Preferably, the catch portion is an opening edge of a through hole that extends through the electrical wire connection portion from an outer circumferential surface to an inner circumferential surface. According to this configuration, the outer circumferential portion of the shield layer enters into the through hole, and the shield layer catches on the catch portion of the opening edge of the through hole. Also, in the process of forming the catch portion, cut and raising and other similar bending processing is unnecessary. Thus, manufacturing costs can be reduced. 
     (3) Preferably, a plurality of the electrical wire connection portions are disposed at intervals in a circumferential direction. According to this configuration, each electrical wire connection portion is displaced in the radial direction independently of the other electrical wire connection portions and is pressed against the outer circumferential surface of the shield layer. Thus, the catch portion can deeply dig into the shield layer. 
     (4) Preferably, the compression bonding portion includes a crimping portion that extends in a circumferential direction from a substrate portion while supported on only one side, and an engagement projection that engages with an engagement hole of the electrical wire connection portion is formed on an extending end portion of the crimping portion. According to this configuration, relative movement between the first shell and the second shell can be prevented by the locking action of the engagement projection of the crimping portion and the engagement hole of the electrical wire connection portion. 
     (5) With the configuration of (4), preferably, the engagement projection digs into the shield layer. According to this configuration, relative movement between the compression bonding portion and the shield layer can be prevented. 
     (6) Preferably, the compression bonding portion includes a crimping portion that extends in a circumferential direction from a substrate portion while supported on only one side, the compression bonding portion is crimped at an outer circumferential edge portion of the crimping portion to give a maximum amount of deformation, and the catch portion is disposed in a region pressed by an outer circumferential edge portion of the crimping portion. According to this configuration, the catch portion can effectively dig into the shield layer. 
     DETAILED EMBODIMENTS OF PRESENT DISCLOSURE 
     First Embodiment 
     The present embodiment is an implementation of the present disclosure and is described below with reference to  FIGS.  1  to  7   . Note that the present invention is not limited to these examples and is defined by the scope of the claims, and all modifications that are equivalent to or within the scope of the claims are included. In the first embodiment, regarding the front and back directions, the forward direction of the X axis in  FIGS.  1  to  4    is defined as the front direction. Regarding the left and right directions, the forward direction of the Y axis in  FIGS.  1  and  3  to  6    is defined as the right direction. Regarding the up and down directions, the forward direction of the Z axis in  FIGS.  1  to  6    is defined as the up direction. 
     A connection structure of the first embodiment includes a shielded terminal  10  and a shielded electrical wire  60 . The shielded terminal  10  and the shielded electrical wire  60  are connected via compression bonding in a manner that allows electricity to flow and together form a shielded conductive path. As illustrated in  FIGS.  1  and  2   , in a side view of the shielded terminal  10  and the shielded electrical wire  60  as seen from the side, the shielded terminal  10  has a shape bent in an L-shape. As illustrated in  FIG.  2   , the shielded terminal  10  is formed by assembling together an inner conductor  11  bent in an L-shape, a dielectric  12  enclosing the inner conductor  11 , and an outer conductor  20  enclosing the inner conductor  11  and the dielectric  12 . The lower surface in the internal space of the dielectric  12  can be opened and closed via a cover portion  13 . The inner conductor  11  is housed inside the dielectric  12  with the cover portion  13  in an opened state. 
     As illustrated in  FIGS.  2  to  4   , the outer conductor  20  is formed by assembling a first shell  21  including a metal plate member and a second shell  22  including a metal plate member separate from the first shell  21 . In a state before the inner conductor  11  and the dielectric  12  are assembled with the outer conductor  20 , the first shell  21  is formed in the shape illustrated in  FIG.  7   . The orientation in terms of the up-and-down direction and front-and-back direction of the shape of the first shell  21  will be described on the basis of state illustrated in  FIGS.  2  to  4    in which the inner conductor  11  and the dielectric  12  have been assembled together. 
     The first shell  21  is a single component and includes a cylindrical portion  23  with its axis orientated in the up-and-down direction and an arc portion  24  that is contiguous with the lower end portion of the cylindrical portion  23 . The arc portion  24  extends downward coaxially with the cylindrical portion  23  from a substantially semi-circular region on the front side at the lower end of the cylindrical portion  23 . An extending portion  25  with a plate-like shape and orientated with its thickness direction corresponding to the up-and-down direction extends backward from a back end side region at the lower edge of the cylindrical portion  23 . 
     The first shell  21  includes an angular enclosing portion  26 . The angular enclosing portion  26  includes the extending portion  25  described above, the substrate portion  27 , and a left and right pair of side plate portions  28 . The substrate portion  27  extends backward from a bend portion  29  of the front end portion at the lower edge of the arc portion  24 . The thickness direction of the substrate portion  27  corresponds to the up-and-down direction. The left and right side plate portions  28  are orientated with their thickness direction corresponding to the left-and-right direction and extend upward like walls from the left and right side edges of the substrate portion  27 . The side plate portions  28  are arranged at the back of the back end edges of the arc portion  24  with a gap therebetween. The extending portion  25  is located above the substrate portion  27 . 
     The first shell  21  includes an upper surface electrical wire connection portion  30 , and a lower surface electrical wire connection portion  31 , and a left and right pair of side surface electrical wire connection portions  32 . These four electrical wire connection portions  30 ,  31 , and  32  have a plate-like shape and extend, while supported at only one side, backward from the back end of the angular enclosing portion  26 . The upper surface electrical wire connection portion  30  includes a flat plate, is orientated with its thickness direction corresponding to the up-and-down direction, and is contiguous with the back end of the extending portion  25 . The lower surface electrical wire connection portion  31  includes a curved plate curved in an arc shape, is disposed below the upper surface electrical wire connection portion  30  orientated its thickness direction corresponding to the up-and-down direction, and is contiguous with the back end of the substrate portion  27 . The pair of left and right side surface electrical wire connection portions  32  each include a curved plate curved in an arc shape, are orientated with their thickness direction corresponding to the left-and-right direction, and are contiguous with the back ends of the side plate portions  28 . 
     These four electrical wire connection portions  30 ,  31 , and  32  are arranged in the circumferential direction centered on the axis of the front-and-back direction with a slit  34  orientated in the front-and-back direction formed between each. The four electrical wire connection portions  30 ,  31 , and  32  are disposed forming a tube-like shape. A shield layer  63  of the shielded electrical wire  60  described below is housed in the space enclosed by the four electrical wire connection portions  30 ,  31 , and  32 . The four electrical wire connection portions  30 ,  31 , and  32  are disposed in a non-contact positional relationship, and thus can be individually displaced in the radial direction (in the direction toward and away from the outer circumferential surface of the shielded electrical wire  60 ) independently of the other electrical wire connection portions  30 ,  31 , and  32 . 
     A rectangle through hole  35  is formed in the front end portion of each one of the four electrical wire connection portions  30 ,  31 , and  32 . All of the through holes  35  formed in the four electrical wire connection portions  30 ,  31 , and  32  are disposed at the same position in the front-and-back direction. The through holes  35  formed in the four electrical wire connection portions  30 ,  31 , and  32  are disposed at intervals in the circumferential direction. One through hole  35  is formed in the upper surface electrical wire connection portion  30 . A pair of the through holes  35  spaced apart in the left-and-right direction (circumferential direction) are formed in the lower surface electrical wire connection portion  31 . A pair of the through holes  35  spaced apart in the up-and-down direction (circumferential direction) are formed in both the left and right side surface electrical wire connection portions  32 . 
     The through holes  35  are each formed in a window-like shape via a pressing process and extend through from the outer surface to the inner surface of the electrical wire connection portions  30 ,  31 , and  32 . The inner surfaces of the electrical wire connection portions  30 ,  31 , and  32  are surfaces that face the outer circumferential surface of the shielded electrical wire  60 . The opening edges of the through holes  35  on the inner surfaces of the electrical wire connection portions  30 ,  31 , and  32  are each formed in right angle edge-like shape via a pressing process and each correspond to a portion that functions as a catch portion  36  (see  FIG.  5   ). All of the edges of the opening edges of the through holes  35  function as the catch portions  36 . 
     An engagement hole  37  with a rectangular opening is formed in the lower surface electrical wire connection portion  31 . The engagement hole  37  is formed in a window-like shape via a pressing process and extends through from the outer surface to the inner surface of the lower surface electrical wire connection portion  31 . The engagement hole  37  is disposed further back than the through holes  35 . The opening area of the engagement hole  37  is greater than the opening area of one through hole  35 . 
     As illustrated in  FIG.  4   , the second shell  22  is a single component including a shielding portion  40  and a compression bonding portion  44 . The shielding portion  40  includes an upper surface plate portion  41  orientated with its thickness direction corresponding to the up-and-down direction and a left and right pair of side surface plate portions  42  extending downward from the left and right side edges of the upper surface plate portion  41 . The shielding portion  40  has the function of closing the gap in the angular enclosing portion  26  of the first shell  21 . 
     The compression bonding portion  44  includes a wire barrel portion  45  and an insulation barrel portion  46 . The wire barrel portion  45  includes a plate-like front side base portion  47  extending backward from the back end of the upper surface plate portion  41  and a left and right pair of front side crimping portions  48  extending downward from the left and right side edges of the plate-like front side base portion  47 . The insulation barrel portion  46  includes a plate-like back side base portion  49  extending backward from the back end of the plate-like front side base portion  47  and a left and right pair of back side crimping portions  50  extending downward from the left and right side edges of the plate-like back side base portion  49 . An engagement projection  51  is formed on the extending end edge of each one of the left and right front side crimping portions  48 . A positioning projection portion  52  is formed on the extending end edge of the back side crimping portion  50  on the left side, and a positioning recess portion  53  is formed on the extending end edge of the back side crimping portion  50  on the right side. 
     As illustrated in  FIGS.  5  and  6   , the shielded electrical wire  60  includes a coaxial cable including a core wire  61 , a cylindrical insulating cover  62  that encloses the core wire  61  in a concentric manner, the shield layer  63  that covers the outer circumferential surface of the insulating cover  62 , and a cylindrical sheath  64  that encloses the shield layer  63 . At the front end of the shielded electrical wire  60 , the front end portion of the core wire  61  projects forward from the front end surface of the insulating cover  62 . Further back from the front end of the insulating cover  62 , the sheath  64  is peeled out and the shield layer  63  is exposed. The exposed portion of the shield layer  63  encloses the outer circumferential surface of the insulating cover  62 . The front end of the exposed portion of the shield layer  63  is located at a position slightly back from the front end of the insulating cover  62 . The shield layer  63  is made of a braided wire, metal foil, or the like and has flexibility and plasticity. 
     Next, the process of assembling the shielded terminal  10  and the process of connecting the shielded terminal  10  and the shielded electrical wire  60  will be described. First, the back end portion of the inner conductor  11  is bonded to the front end portion of the core wire  61  of the shielded electrical wire  60 . The back end portion of the inner conductor  11  and the front end portion of the shielded electrical wire  60  are arranged in a line with the axis orientated with the front-and-back direction. Next, with the first shell  21  in a state with the shape illustrated in  FIG.  7   , the dielectric  12  is housed inside the cylindrical portion  23  and the arc portion  24  from below the first shell  21 . Next, with the cover portion  13  opened, the front end portion of the inner conductor  11  is housed inside the dielectric  12 . After the inner conductor  11  is housed, the cover portion  13  is closed. 
     The connection portion of the inner conductor  11  and the core wire  61  is housed inside the back end portion of the dielectric  12 , the front end surface of the insulating cover  62  and the back end surface of the dielectric  12  are brought close together into a positional relationship in which they face one another in the front-and-back direction or a state in which they are in contact in the front-and-back direction. The back end portion of the dielectric  12  projects backward from the opening on the back surface side of the arc portion  24 . The upper surface of the back end portion of the dielectric  12  is covered by the extending portion  25 , and the upper surface portion of the shield layer  63  is covered by the upper surface electrical wire connection portion  30 . The back end of the upper surface electrical wire connection portion  30  is located at a position further forward than the front end of the sheath  64 . 
     Thereafter, the substrate portion  27  is rotated 90° up and back with the bend portion  29  as the fulcrum, overlapping the substrate portion  27  with the back end portion lower surface of the dielectric  12 . Via the rotation, the left and right side plate portions  28  are displaced and cover the left and right outer surface of the back end portion of the dielectric  12 , and the angular enclosing portion  26  is formed by the extending portion  25 , the substrate portion  27 , and both of the side plate portions  28 . The angular enclosing portion  26  encloses the back end portion of the dielectric  12  and the connection portion of the inner conductor  11  and the core wire  61 . 
     Via the rotation of the substrate portion  27 , the lower surface electrical wire connection portion  31  and the left and right side surface electrical wire connection portions  32  are positioned covering the lower surface portion of the shield layer  63  and the left and right side surface portions. The back end of the lower surface electrical wire connection portion  31  and the back ends of the side surface electrical wire connection portions  32  are located at positions further forward than the front end of the sheath  64 . The shield layer  63  is enclosed in the up, down, left, and right directions by the four electrical wire connection portions  30 ,  31 , and  32 . The shield layer  63  is exposed to the outer circumferential surface side of the electrical wire connection portions  30 ,  31 , and  32  through the slits  34  between the four electrical wire connection portions. 
     Next, the second shell  22  is assembled together with the first shell  21  and the shielded electrical wire  60  from above. Upon assembly, the shielding portion  40  is placed over the angular enclosing portion  26  from above and attached, and the compression bonding portion  44  is placed over the back end portion of the first shell  21  and the front end portion of the sheath  64  from above and attached. The shielding portion  40  covers and hides the gap between the left and right side edges of the extending portion  25  and the upper edges of the left and right side plate portions  28 . In this manner, the back end portion of the dielectric  12  is shielded around the entire periphery. The wire barrel portion  45  of the compression bonding portion  44  covers the shield layer  63  and the four electrical wire connection portions  30 ,  31 , and  32 , and the insulation barrel portion  46  covers the front end portion of the sheath  64 . 
     From this state, the wire barrel portion  45  and the insulation barrel portion  46  are crimped and decreased in diameter to compression bond the compression bonding portion  44  to the shielded electrical wire  60 . In this compression bonded state, the wire barrel portion  45  presses against the four electrical wire connection portions  30 ,  31 , and  32 , displacing each one inward in the radial direction and bringing each one into close contact with the outer circumferential surface of the shield layer  63 . In this manner, the shield layer  63  and the outer conductor  20  are connected in a manner that allows electricity to flow. The insulation barrel portion  46  is crimped to the outer circumferential surface of the sheath  64 . In this manner, the shielded terminal  10  and the shielded electrical wire  60  are held in a state of being bonded together in a manner that allows electricity to flow. 
     The front end portion of the wire barrel portion  45  presses against the front end portions of the electrical wire connection portions  30 ,  31 , and  32  stronger than it presses against other portions and strongly presses against the outer circumferential surface of the shield layer  63 . The front end portions of the electrical wire connection portions  30 ,  31 , and  32  that are strongly crimped by the wire barrel portion  45  are the portions where the through holes  35  are formed. Thus, since the electrical wire connection portions  30 ,  31 , and  32  are strongly pressed against the outer circumferential surface of the shield layer  63 , portions of the shield layer  63  deform and enter into the through holes  35 . The portions of the shield layer  63  that enters inside the through holes  35  are strongly pressed against the edge-like catch portions  36  of the opening edges of the through holes  35 . Thus, between the shield layer  63  and the catch portions  36 , a catch is formed in the front-and-back direction and the circumferential direction. When the shield layer  63  is strongly pulled, for example, backward relative to the outer conductor  20 , the portions of the shield layer  63  that have entered into the through holes  35  press against the catch portions  36 , and the catch portions  36  dig into the outer circumferential surface of the shield layer  63 . This catching and digging-in allows misalignment (relative displacement in the front-and-back direction and the circumferential direction) between the shield layer  63  and the electrical wire connection portions  30 ,  31 , and  32  to be prevented. In other words, the bonding strength from the compression bonding portion  44  via the catching action of the catch portions  36  is increased, and the reliability of the function of holding the shielded terminal  10  and the shielded electrical wire  60  in a connected state is improved. 
     Also, as illustrated in  FIGS.  2  and  6   , the engagement projections  51  of the wire barrel portion  45  engage with the engagement hole  37 , extend through the shield layer  63 , and dig into the insulating cover  62 . The engagement between the engagement projections  51  and the engagement hole  37  restricts the relative movement in the front-and-back direction between the wire barrel portion  45  and the lower surface electrical wire connection portion  31 . The engagement projections  51  digging into the insulating cover  62  restrict the relative movement in the front-and-back direction (axis direction) and the left-and-right direction (circumferential direction) between the outer conductor  20  and the shielded electrical wire  60 . In this manner, the outer conductor  20  and the shielded electrical wire  60  are reliably bonded together. 
     The connection structure of the shielded conductive path according to the present first embodiment includes the shielded electrical wire  60  including the shield layer  63  and the shielded terminal  10  including the outer conductor  20  connected to the shield layer  63 . The outer conductor  20  is formed by assembling the first shell  21  and the second shell  22 . The first shell  21  includes the electrical wire connection portions  30 ,  31 , and  32  that come into contact with the outer circumference of the shield layer  63 . The second shell  22  includes the compression bonding portion  44  that is crimped to the outer circumference of the electrical wire connection portions  30 ,  31 , and  32 . The catch portions  36  that catch on the outer circumferential surface of the shield layer  63  are formed on the electrical wire connection portions  30 ,  31 , and  32 . By the catch portions  36  catching on the outer circumferential surface of the shield layer  63 , relative movement between the shielded electrical wire  60  and the outer conductor  20  is prevented. This can improve the reliability of the bonding performance from compression bonding. 
     The catch portions  36  are opening edges of the through holes  35  that extend through from the outer circumferential surface to the inner circumferential surface of the electrical wire connection portions  30 ,  31 , and  32 . The outer circumferential portion of the shield layer  63  enters into the through holes  35 , and the shield layer  63  catches on the catch portions  36  of the opening edges of the through holes  35 . Also, in the process of forming the catch portions  36 , cut and raising and other similar bending processing is unnecessary. Thus, manufacturing costs can be reduced. 
     Also, in a case where electrical wire connection portions are a single tube-like portion continuous in the circumferential direction, the amount of deformation in the radial direction of the electrical wire connection portions is insufficient and the amount of deformation at each portion around the circumferential direction is uneven. Thus, the catch portions cannot be strongly pressed against the outer circumferential surface of the shield layer  63 . As a countermeasure, the plurality of electrical wire connection portions  30 ,  31 , and  32  are disposed at intervals in the circumferential direction. According to this configuration, each one of the electrical wire connection portions  30 ,  31 , and  32  can be displaced in the radial direction independently of the other electrical wire connection portions  30 ,  31 , and  32 . In other words, the presence of the other electrical wire connection portions  30 ,  31 ,  32  does not restrict the displacement amount in the radial direction of each one of the electrical wire connection portions  30 ,  31 , and  32 . Accordingly, the catch portions  36  of the electrical wire connection portions  30 ,  31 , and  32  are strongly pressed against the outer circumferential surface of the shield layer  63 , allowing them to deeply catch in the shield layer  63 . 
     The compression bonding portion  44  includes the front side crimping portions  48  extending in the circumferential direction from substrate portion  27  while supported on only one side, and the engagement projections  51  that engage with the engagement hole  37  of the lower surface electrical wire connection portion  31  are formed in the extending end portions of the front side crimping portions  48 . According to this configuration, relative movement between the first shell  21  and the second shell  22  can be prevented by the locking action of the engagement projections  51  of the front side crimping portions  48  and the engagement hole  37  of the lower surface electrical wire connection portion  31 . Relative movement between the compression bonding portion  44  and the shield layer  63  can be prevented due to the engagement projections  51  digging into the shield layer  63 . 
     The compression bonding portion  44  includes the front side crimping portions  48  extending in the circumferential direction from substrate portion  27  while supported on only one side, and the compression bonding portion  44  is crimped at the front end portions of the outer circumferential edges of the front side crimping portions  48  to give the maximum amount of deformation. The catch portions  36  are disposed in the regions that are pressed by the front end portions of the front side crimping portions  48 , or in other words at the front end portions of the electrical wire connection portions  30 ,  31 , and  32 . According to this configuration, the catch portions  36  can effectively catch in the shield layer  63 . 
     Other Embodiments 
     The catch portion may be formed via a cut and raise method, a hammering method, or the like. 
     The electrical wire connection portion may be a single tube-shaped portion that is continuous in the circumferential direction with no break. 
     The electrical wire connection portion may not include an engagement hole. 
     A configuration may be used in which an engagement projection portion does not dig into a shield layer. 
     The catch portions may be disposed in regions corresponding the back edge portion and the side edge portion of the front side crimping portions, or may be disposed in regions distanced from the outer circumferential edge portions of the front side crimping portions, in other words regions corresponding to the central portion of the front side crimping portions. 
     From the foregoing, it will be appreciated that various exemplary embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various exemplary embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims.