Patent Publication Number: US-8118612-B2

Title: End-processing method of coaxial cable and end-processing structure of coaxial cable

Description:
TECHNICAL FIELD 
     The present invention relates to a method of processing an end of a coaxial cable to which a shield terminal for coaxial cable forming a coaxial connector is electrically and mechanically connected, and also to a end-processing structure of a coaxial cable. 
     BACKGROUND ART 
     Generally, a coaxial cable used for transmitting high-frequency signals as in an antenna wire includes, in outward order from the center, a core wire as a center conductor, an insulator as a dielectric, a metallic tape conductor and a braid as an outer conductor, and an insulative sheath as an outer covering. The coaxial cable of such a construction has a coaxial connector provided at an end thereof so that the coaxial cable can be connected to a mating equipment, a mating coaxial cable or the like. The coaxial connector has a shield terminal for coaxial cable through which the braid is groundedly connected to a mating coaxial connector so as to cutoff electrical noises such as electromagnetic waves and static electricity. 
     With respect to an end-processing structure of a coaxial cable (the structure of connecting a coaxial cable and a coaxial connector together), the following structure has been proposed. Namely, there is carried out an operation in which first, a braid is exposed at an end portion of the coaxial cable, and then the exposed braid is undone, and a connecting conductor portion of the coaxial connector is inserted into a gap between the undone braid and a metallic tape conductor (or an insulator) disposed inside the braid. Then, an operation for press-fastening a metallic sleeve, separate from the coaxial cable and the coaxial connector, at the position of the above exposed braid is effected. By press-fastening the metallic sleeve, the coaxial cable and the coaxial connector are electrically and mechanically connected together (see, for example, Patent Literature 1). 
     In order that the contours of cross-sections of the insulator and the outer conductor are not deformed out of a concentric condition, in other words, in order to satisfy high-frequency characteristics, the above end processing structure has such a structure that the connecting conductor portion of the coaxial connector is inserted into the gap between the braid and the metallic tape conductor (or the insulator) disposed inside the braid. Such a connecting structure also aims at satisfying a predetermined tensile strength of the coaxial cable and the coaxial connector. 
     Incidentally, in the above end processing structure, it is necessary to carry out the operation for once undoing the braid, exposed at the end portion of the coaxial cable, in order to insert the connecting conductor portion of the coaxial connector into the inside of the braid of the coaxial cable. Therefore, the conventional end processing structure has a problem that the efficiency of the operation is affected since the cumbersome operation must be carried out. 
     Furthermore, in the above end processing structure, there is required the production and operation, in which the metallic sleeve separate from the coaxial cable and the coaxial connector is prepared, and is attached. Therefore, the above end processing structure has problems that the number of parts increases and that the efficiency of the operation is affected. With respect to the resolution of the problem that the number of the parts increases, consideration for satisfying the predetermined tensile strength of the coaxial cable and the coaxial connector is necessary. 
     A technique for solving the above problems is disclosed in the following Patent Literature 2. This will be briefly described below. 
     In  FIG. 11 , when a connecting conductor portion  14  of a shield terminal  10  forming a coaxial connector  9  is pushed in a cable-extending direction, an annular braid gathered portion  8  composed of a braid  4  is formed between an insulator  3  and an insulative sheath  5 . The braid gathered portion  8  is formed by causing a gathered portion to be produced at the braid  4  by the pushing-in of the connecting conductor portion  14 . In accordance with the formation of this braid gathered portion  8 , a terminal catching portion  7  in the form of an annular bulge is formed at the insulative sheath  5 . When the terminal catching portion  7  is formed, a coaxial cable  6  which is a feature of Patent Literature 2 is formed. 
     In the condition in which the coaxial cable  6  is formed, the connecting conductor portion  4  is kept inserted between those portions of the insulator  3  and the insulative sheath  5  disposed at the front side of the terminal catching portion  7 . The connecting conductor portion  14  and the braid gathered portion  8  are contacted with each other, and therefore an electrical connection is formed in a provisional condition. 
     When a sheath holding portion  15  and a second sheath holding portion  16  of the shield terminal  10  are press-fastened to hold the insulative sheath  5  of the coaxial cable  6 , a series of operations are completed. The sheath holding portion  15  and the second sheath holding portion  16  are press-fastened on the insulative sheath  5  in a wound condition. At this time, one outer edge portion  18  of the sheath holding portion  15  is press-fastened to be located adjacent to the terminal catching portion  7 . Also, the second sheath holding portion  16  is press-fastened in such a condition that the portion of the insulative sheath  5  disposed at the front side of the terminal catching portion  7  is held between the second sheath holding portion  16  and the connecting conductor portion  14 . 
     When the press-fastening of the sheath holding portion  15  and the second sheath holding portion  16  of the shield terminal  10  is completed, the mechanical fixing is completed, and also the electrical connection of the connecting conductor portion  14  and the braid gathered portion  8  to each other is completed in a complete condition. 
     If a force is applied in a direction of withdrawing of the coaxial connector  9 , the one outer edge portion  18  of the sheath holding portion  15  is caught by the terminal catching portion  7  of the coaxial cable  6 . The coaxial cable  9  is prevented by the terminal catching portion  7  from movement in the withdrawing direction. 
     Reference numeral  2  in the drawings denotes a core wire, reference numeral  11  denotes a dielectric,  12  denotes a shield terminal body,  13  denotes a press-clamping portion and reference numeral  17  denotes a base portion of the press-clamping portion  13 .
     Patent Literature 1: JP-A-2004-55475   Patent Literature 2: JP-A-2006-302722   

     DISCLOSURE OF THE INVENTION 
     Problem that the Invention is to Solve 
     Although the disclosed technique of Patent Literature 2 provides the structure in which the movement of the coaxial connector  9  in the withdrawing direction is prevented by the terminal catching portion  7  of the coaxial cable  6 , there is anxiety about the following point. 
     Namely, the terminal catching portion  7  is the bulged portion of the synthetic resin-made insulative sheath  5 , and besides the one outer edge portion  18  of the sheath holding portion  15  of the metallic shield terminal  10  includes a portion formed into an edge-shape, and therefore if damage such as biting and so on develops though achieving the catching when a strong force is applied, for example, in the direction of withdrawing of the coaxial connector  9 , it is uncertain whether the movement in the withdrawing direction can be positively prevented, and there is anxiety about this point. 
     The present invention has been made in view of the above circumstances, and its object is to provide an end-processing method of a coaxial cable and an end-processing structure of a coaxial cable, in which a catching engagement less liable to invite damage is achieved, and a high tensile strength can be obtained, and also the reliability can be enhanced. 
     Means for Solving the Problem 
     An end-processing method of a coaxial cable according to a first aspect of the present invention provided to achieve the problem is a method including: stripping an intermediate portion of an insulative sheath of the coaxial cable; drawing one insulative sheath toward the other insulative sheath and projecting a braid annularly outwardly from between end portions of the one and the other insulative sheath in association with the drawing to form an annular projecting braid portion; thereafter folding the annular projecting braid portion from its proximal end portion and superposing the folded annular projecting braid portion on the one insulative sheath to thereby form a folded braid portion; and press-clamping and connecting the folded braid portion by a braid press-clamping portion of a shield terminal for coaxial cable which is to be connected to an end portion of the coaxial cable, and also press-clamping and fixing a sheath press-clamping portion of the shield terminal for coaxial cable to the other insulative sheath disposed near to a terminal catching portion formed at the proximal end portion of the folded braid portion. 
     In the present invention having these features, even when a strong force is applied, for example, in a direction of withdrawing of the coaxial connector, the metallic portions are caught and engaged with each other, and therefore damage is much less liable to occur as compared with the catching engagement of a synthetic resin-made portion and a metallic portion with each other. Since damage is less liable to occur, a tensile strength is increased, and also the reliability is enhanced. 
     The end-processing method of the coaxial cable according to a second aspect is a method in the end-processing method of the coaxial cable of the first aspect, wherein a step portion corresponding to the terminal catching portion is formed at a base plate of a press-clamping portion of the shield terminal for coaxial cable, the base plate coupling the braid press-clamping portion to the sheath press-clamping portion. 
     In the present invention having this feature, the area of the portion caught and engaged with the terminal catching portion is increased, and the tensile strength is further increased. And besides, the positioning relative to the folded braid portion, in other words, the positioning relative to the coaxial cable, becomes easier. 
     The end-processing method of the coaxial cable according to a third aspect is a method in the end-processing method of the coaxial cable of the first or second aspect, wherein the sheath press-clamping portion is formed into a rectangular shape  15  smaller in width than the braid press-clamping portion. 
     In the present invention having this feature, the catching engagement less liable to invite damage is sufficiently maintained even when the width of the sheath press-clamping portion is reduced, and the braid press-clamping portion relating to the connection and fixing to the folded braid portion can be increased by an amount corresponding to this width reduction. 
     An end-processing structure of a coaxial cable according to a fourth aspect of the present invention provided to achieve the problem is a structure including: an annular projecting braid portion which is formed by stripping an intermediate portion of an insulative sheath of the coaxial cable and by causing a braid to project annularly outwardly from between end portions of one insulative sheath and the other insulative sheath in association with the drawing of the one insulative sheath toward the other insulative sheath; and a folded braid portion which is formed by folding the annular projecting braid portion from its proximal end portion so as to superpose the folded annular projecting braid portion on the one insulative sheath, wherein the folded braid portion is press-clamped and connected by a braid press-clamping portion of a shield terminal for coaxial cable which is to be connected to an end portion of the coaxial cable, and also a sheath press-clamping portion of the shield terminal for coaxial cable is press-clamped and fixed to the other insulative sheath disposed near to a terminal catching portion formed at the proximal end portion of the folded braid portion. 
     In the present invention having these features, even when a strong force is applied, for example, in a direction of withdrawing of the coaxial connector, the metallic portions are caught and engaged with each other, and therefore damage is much less liable to occur as compared with the catching engagement of a synthetic resin-made portion and a metallic portion with each other. Since damage is less liable to occur, a tensile strength is increased, and also the reliability is enhanced. 
     ADVANTAGE OF THE INVENTION 
     In the present invention according to the first aspect, by achieving the catching engagement less liable to invite damage, there are achieved advantages that the high tensile strength is obtained and that the reliability is also enhanced. 
     In the present invention according to the second aspect, there is achieved an advantage that the tensile strength can be further increased. And besides, there is achieved an advantage that the positioning relative to the coaxial cable can be made easier. 
     In the present invention according to the third aspect, in addition to the above advantages, there is achieved an advantage that the connected condition can be stabilized. 
     In the present invention according to the fourth aspect, by achieving the catching engagement less liable to invite damage, there are achieved advantages that the high tensile strength is obtained and that the reliability is also enhanced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows one embodiment of an end-processing structure of a coaxial cable of the present invention, and (a) is a perspective view of an annular projecting braid portion, (b) is a perspective view of a folded braid portion and (c) is an exploded perspective view of the end-processing structure of the coaxial cable. 
         FIG. 2  is a perspective view showing a coaxial cable before the processing. 
         FIG. 3  is a perspective view showing a condition in which an intermediate portion of an insulative sheath of the coaxial cable is stripped. 
         FIG. 4  is a perspective view showing a condition in which the annular projecting braid portion is formed at the coaxial cable. 
         FIG. 5  is a perspective view showing a condition in which the folded braid portion is formed at the coaxial cable. 
         FIG. 6  is a perspective view showing a condition in which a core wire is exposed. 
         FIG. 7  is a perspective view showing a condition in which an inner terminal is mounted on the core wire. 
         FIG. 8  is a perspective view showing a condition before the coaxial cable is connected to a shield terminal for coaxial cable. 
         FIG. 9  is a perspective view showing a condition in which braid press-clamping portions are press-clamped to the folded braid portion, and also sheath press-clamping portions are press-clamped to the insulative sheath. 
         FIG. 10  is a perspective view showing a condition in which the connection of the coaxial cable and the shield terminal for coaxial cable to each other is completed. 
         FIG. 11  is a cross-sectional view showing a conventional coaxial cable end-processing structure. 
     
    
    
     DESCRIPTION OF THE REFERENCE NUMERALS 
     
         
         
           
               21  coaxial cable 
               22  coaxial connector 
               23  annular projecting braid portion 
               24  folded braid portion 
               25  inner terminal 
               26  shield terminal (shield terminal for coaxial cable) 
               27  dielectric 
               28  core wire 
               29  insulator 
               30  braid 
               31  insulative sheath 
               31   a  one insulative sheath 
               31   b  the other insulative sheath 
               32  end face 
               33  annular outer peripheral edge portion 
               34  proximal end portion 
               35  terminal catching portion 
               36  shield terminal body 
               37  press-clamping portion 
               38  base plate 
               39  braid press-clamping portion 
               40  sheath press-clamping portion 
               41  step portion 
           
         
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Description will be made below with reference to the drawings.  FIG. 1  shows one embodiment of an end-processing structure of a coaxial cable of the present invention, and (a) is a perspective view of an annular projecting braid portion, (b) is a perspective view of a folded braid portion and (c) is an exploded perspective view of the end-processing structure of the coaxial cable. 
       FIG. 2  is a perspective view showing a coaxial cable before the processing,  FIG. 3  is a perspective view showing a condition in which an intermediate portion of an insulative sheath of the coaxial cable is stripped,  FIG. 4  is a perspective view showing a condition in which the annular projecting braid portion is formed at the coaxial cable, and  FIG. 5  is a perspective view showing a condition in which the folded braid portion is formed at the coaxial cable. 
       FIG. 6  is a perspective view showing a condition in which a core wire is exposed,  FIG. 7  is a perspective view showing a condition in which an inner terminal is mounted on the core wire,  FIG. 8  is a perspective view showing a condition before the coaxial cable is connected to a shield terminal for coaxial cable,  FIG. 9  is a perspective view showing a condition in which braid press-clamping portions are press-clamped to the folded braid portion, and also sheath press-clamping portions are press-clamped to the insulative sheath, and  FIG. 10  is a perspective view showing a condition in which the connection of the coaxial cable and the shield terminal for coaxial cable to each other is completed. 
     In  FIG. 1 , reference numeral  21  denotes a coaxial cable. Reference numeral  22  denotes a coaxial connector. As the coaxial cable  21 , there is used one in which an annular projecting braid portion  23  is formed, and this is folded to form a folded braid portion  24 . The coaxial connector  22  includes an inner terminal  25 , a shield terminal (shield terminal for coaxial cable)  26 , and a dielectric  27 . Each construction will be described hereafter with reference to  FIG. 1  to  FIG. 10 . 
     The coaxial cable  21  includes a core wire  28  as a center conductor, an insulator  29  as a dielectric, a metallic tape conductor (not shown) and a braid  30  as an outer conductor, and the insulative sheath  31  as an outer covering (see  FIG. 1  and  FIG. 2 ). The core wire  28  is disposed at the center of the coaxial cable  21 , and the insulator  29  to the insulative sheath  31  are arranged in this order on the outside of this core wire. The core wire  28  to the insulative sheath  31  are already known, and detailed description will be omitted here. 
     The annular projecting braid portion  23 , as well as the folded braid portion  24  formed by folding this annular projecting braid portion  23 , is formed at an end portion of the coaxial cable  21 . The annular projecting braid portion  23  as well as the folded braid portion  24  is disposed and formed at a position spaced a predetermined distance from an end face (see reference numeral  32  in  FIG. 1  and  FIG. 2 ) of the coaxial cable  21 . First, the annular projecting braid portion  23  will be described specifically. The annular projecting braid portion  23  is formed by processing the braid  30 , and is formed into such a shape that annular projecting braid portion  23  projects annularly outwardly from the insulative sheath  31  as shown by (a) in  FIG. 1 . 
     Here, the formation of the annular projecting braid portion  23  will be described. Assume that the end portion of the coaxial cable  21  is, for example, in a condition as shown in  FIG. 2 . First, an intermediate portion of the insulative sheath  31  is stripped as shown in  FIG. 3 , so that one insulative sheath  31   a  and the other insulative sheath  31   b  are formed respectively at the opposite sides of this stripped portion. The one insulative sheath  31   a  is disposed close to the end face  32  of the coaxial cable  21 . The braid  30  is exposed from the above stripped portion. 
     Then, the one insulative sheath  31   a  is drawn toward the other insulative sheath  31   b  as shown in  FIG. 4 . At this time, in association with the drawing, the exposed braid  30  projects annularly outwardly from between end portions of the one insulative sheath  31   a  and the other insulative sheath  31   b . When the braid  30  projects annularly outwardly, the annular projecting braid portion  23  is formed. An annular outer peripheral edge portion  33  of the annular projecting braid portion  23  is a portion formed as a result of folding the braid  30 , and therefore wire elements forming the braid  30  are not loosened. The annular projecting braid portion  23  is formed according to this procedure. 
     In the condition in which the annular projecting braid portion  23  is formed, the most part of the braid  30  except this annular projecting braid portion  23  is covered with the other insulative sheath  31   b , and therefore there is provided the structure in which the annular projecting braid portion  23  itself will not move. When the formation of the annular projecting braid portion  23  is completed, the process then shifts to the step of forming the folded braid portion  24 . 
     In  FIG. 1 ,  FIG. 4  and  FIG. 5 , the folded braid portion  24  is formed by folding the annular projecting braid portion  23  from its proximal end portion  34  so as to superpose this annular projecting braid portion on the one insulative sheath  31   a . The one insulative sheath  31   a  is covered with the folded braid portion  24  (In the drawings, although the whole of the outer surface of the one insulative sheath  31   a  is covered, this covering range is one example.). A distal end of the folded braid portion  24  is formed by the annular outer peripheral edge portion  33  of the annular projecting braid portion  24 , and therefore is in a condition not requiring an end processing. When the proximal end portion  34  of the annular projecting braid portion  23  is bent, a terminal catching portion as designated by reference numeral  35  is formed at the folded braid portion  24 . 
     The folded braid portion  24  is superposed on the one insulative sheath  31   a , and therefore the terminal catching portion  35 , when viewed from the other insulative sheath  31   b , bulges outwardly from the other insulative sheath  31   b , and is formed to provide an annular step. The terminal catching portion  35  is so formed as to function as a portion for catching the shield terminal  26  when a strong force is applied, for example, in a direction of withdrawing of the coaxial connector  22 . 
     When the one insulative sheath  31   a  is drawn toward the other insulative sheath  31   b  at the time of forming the annular projecting braid portion  23 , the insulator  29  is exposed, and when part of this insulator  29  is removed as shown in  FIG. 6 , the core wire  28  is exposed. The inner terminal  25  is electrically and mechanically connected to this exposed core wire  28  as shown in  FIG. 7 . The inner terminal  25  forming the coaxial connector  22  has electrical conductivity, and is formed into a pin-shape as shown in the drawings. 
     In  FIG. 8 , the shield terminal  26  forming the coaxial connector  22  includes a generally tubular shield terminal body  36 , and a press-clamping portion  37  continuously formed at a rear portion of this shield terminal body  36 . The shield terminal body  36  and the press-clamping portion  37  are formed by pressing a metallic thin sheet having electrical conductivity. The dielectric  27  is mounted within the shield terminal body  36  so as to be moved in a forward-rearward direction. The dielectric  27  is formed into such a shape that a distal end portion of the inner terminal  25  can be inserted into a center portion of this dielectric. The illustrated shapes of the shield terminal body  36 , inner terminal  25  and dielectric  27  are given as one example. 
     The press-clamping portion  37  has a base plate  38  continuous with the shield terminal body  36 , and the pair of braid press-clamping portions  39  adapted to be press-fastened at the position of the folded braid portion  24  of the coaxial cable  21  to be electrically and mechanically connected thereto, as well as the pair of sheath press-clamping portions  40  adapted to be press-fastened at a position near to the terminal catching portion  35  of the folded braid portion  24  to be mechanically connected to the other insulative sheath  31   b , are formed at this base plate  38 . Further, a step portion  41  of a generally semi-circular arc-shape corresponding to the terminal catching portion  35  is formed at the base portion  38  at a position between the pair of braid press-clamping portions  39  and the pair of sheath press-clamping portions  40 . 
     The pair of braid press-clamping portions  39  are formed, for example, into a rectangular shape so as to be wound on the folded braid portion  24  of the coaxial cable  21 . Like the pair of braid press-clamping portions  39 , the pair of sheath press-clamping portions  40  are also formed, for example, into a rectangular shape so as to be wound on the other insulative sheath  31   b . The pair of sheath press-clamping portions  40  are formed into the rectangular strip-shape smaller in width than the pair of braid press-clamping portions  39 . 
     Next, the procedure of processing the end of the coaxial cable  21  based on the above construction will be described with reference to  FIG. 8  to  FIG. 10 . 
     In  FIG. 8 , first, the folded braid portion  24  is formed, and thereafter an operation for preparing the coaxial cable  21  having the inner terminal  25  connected and fixed thereto is effected. Also, an operation for preparing the shield terminal  26  having the dielectric  27  mounted therein is effected. The formation of the folded braid portion  24  is effected as described above. 
     Then, in the condition of  FIG. 8 , an operation for inserting the inner terminal  25  into the shield terminal body  36  of the shield terminal  26  as shown in  FIG. 9  is effected. Further, there is effected an operation in which the folded braid portion  24  of the coaxial cable  21  is press-clamped by the pair of braid press-clamping portions  39  of the shield terminal  26  to be electrically and mechanically connected thereto, and also the other insulative sheath  31   b  of the coaxial cable  21  is press-clamped by the pair of sheath press-clamping portions  40  at the position near to the terminal catching portion  35  of the folded braid portion  24  to be mechanically connected thereto. Through these operations, the connection and fixing of the coaxial cable  21  and the shield terminal  26  to each other are completed. 
     Finally, when an operation for sliding the dielectric  27  rearward so as to cause the dielectric  27  to hold the distal end of the inner terminal  25  as shown in  FIG. 10  is effected, the coaxial connector  22  is completely mounted on the end portion of the coaxial cable  21 , and the series of operations for the end processing are completed. 
     As described above with reference to  FIG. 1  to  FIG. 10 , in the structure of processing the end of the coaxial cable  21 , even when a strong force is applied, for example, in the direction of withdrawing of the coaxial connector  22 , the terminal catching portion  35  of the folded braid portion  24  and the pair of sheath press-clamping portions  40  are caught and engaged with each other, and also the terminal catching portion  35  and the step portion  41  of the press-clamping portion  37  are caught and engaged with each other, that is, the metallic portions are caught and engaged with each other, and therefore damage is much less liable to occur as compared with the catching engagement of a synthetic resin-made portion and a metallic portion with each other as in the conventional example. Therefore, the tensile strength can be increased, and also the reliability can be enhanced. 
     In the present invention, various changes can be made in so far as the subject matter of the present invention is not changed. 
     Although the present invention has been described in detail with reference to the specific embodiments, it will be obvious to those skilled in the art that various changes and modifications can be added without departing from the spirits and scope of the present invention. 
     The present application is based on Japanese Patent Application (Patent Application No. 2007-221245) filed on Aug. 28, 2007, and its contents are incorporated herein by reference.