Patent Publication Number: US-8529293-B2

Title: Coaxial connector

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a coaxial connector and particularly to reduction in height of a coaxial connector. 
     So-called angle-type coaxial connectors for connecting coaxial cables at a given angle to terminals mounted on a circuit board have been widely used in communication devices and the like. Use of such coaxial connectors enables height reduction with the electronic devices incorporating circuit boards. 
     A coaxial connector of this kind comprises a receptacle and a plug that engage with each other. Typically, the receptacle comprises a central contact projecting like a pin in engagement direction while the plug comprises a central contact including a two-leaf spring portion, and the spring portion of the central contact of the plug pinches the pin-like central contact of the receptacle to achieve electric connection. 
     However, this kind of contact structure involving the central contact required a length of spring longer than a given length along the engagement direction to be secured for the spring portion in order to provide the leaf spring portion of the central contact of the plug with spring characteristics sufficient to achieve a high-reliability connection with the receptacle. Accordingly, reducing the height of the coaxial connector in engagement direction was impossible. 
     Thus, JP 6-5158 U, for example, describes a coaxial connector where, as illustrated in  FIG. 10 , a receptacle  1  comprises a flat receptacle central contact  2  perpendicular to the engagement direction, and a plug central contact  4  of a plug  3  in the form of a spring is brought into contact with the receptacle central contact  2 . 
     SUMMARY OF THE INVENTION 
     However, because the plug central contact  4  is so shaped as to be routed from a contact portion with the flat receptacle central contact  2  in the engagement direction, reducing the height of the coaxial connector in engagement direction is difficult. 
     In addition, because the coaxial connector described in JP 6-5158 U has a plug external contact  5  that engages with and comes into contact with the outer periphery of a receptacle external contact  6 , and because an engagement length longer than a given length is required to secure the engagement of the plug external contact  5  and the receptacle external contact  6  without allowing displacement, the height of the coaxial connector necessarily increases. 
     Further, because the receptacle external contact  6  is exposed at the outer periphery of the receptacle  1  during disengagement, not only are foreign matters allowed to attach to that periphery, but external forces may be directly applied to the receptacle external contact  6 , making the coaxial connector unreliable. 
     An objective of the present invention is to overcome the above problems associated with the prior art and provide a coaxial connector enabling height reduction and increased reliability. 
     A coaxial connector according to the present invention comprises: 
     a receptacle having an engagement hole formed inside; and 
     a plug engaging with the receptacle along an engagement axis, 
     wherein the receptacle includes an annular receptacle external contact of which an inner peripheral surface is exposed inside the engagement hole, and a receptacle central contact having a receptacle central contact portion exposed in a direction perpendicular to the engagement axis inside the engagement hole, 
     wherein the plug includes a plug external contact engaging with the inside of the engagement hole of the receptacle so as to be in contact with the inner peripheral surface of the annular receptacle external contact when the plug engages with the receptacle, and a cantilever-shaped plug central contact having an extension extending in a direction perpendicular to the engagement axis and a plug central contact portion positioned so as to be in contact with the receptacle central contact portion inside the engagement hole when the plug engages with the receptacle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a receptacle used in a coaxial connector according to an embodiment 1 of the invention. 
         FIGS. 2A ,  2 B, and  2 C are a top plan view, a side view, and a front view respectively illustrating a receptacle used in the coaxial connector according to the embodiment 1. 
         FIG. 3  is a cross section taken along line A-A of  FIG. 2A . 
         FIG. 4  is a perspective view of a plug used in the coaxial connector according to the embodiment 1. 
         FIGS. 5A ,  5 B,  5 C, and  5 D are a top plan view, a side view, a bottom view, and a front view respectively illustrating a plug used in the coaxial connector according to the embodiment 1. 
         FIG. 6  is a cross section of a structure of the coaxial connector according to the embodiment 1. 
         FIG. 7  illustrates steps following which a receptacle external contact portion is produced according to the embodiment 1. 
         FIG. 8  is a perspective view of a receptacle member used in a coaxial connector according to an embodiment 2. 
         FIGS. 9A ,  9 B, and  9 C are a top plan view, a side view, and a front view respectively illustrating a receptacle member used in the coaxial connector according to the embodiment 2. 
         FIG. 10  is a cross section of a structure of a conventional coaxial connector. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention will be described below based on the appended drawings. 
     Embodiment 1 
       FIGS. 1 and 2  illustrate a receptacle  11  used in a coaxial connector according to an embodiment 1 of the invention. The receptacle  11  comprises a receptacle external contact  12 , a receptacle insulator  13  and a receptacle central contact  14 . 
     The receptacle external contact  12  has a an engagement hole  15  having a substantially annular shape as a whole for engagement with a plug described later, which engagement hole  15  exposes therein an inner peripheral surface  16  of the receptacle external contact  12 . The central axis of the engagement hole  15  coincides with an engagement axis C for the receptacle  11  and the plug. Both lateral sides of the receptacle external contact  12  are folded toward the bottom side of the receptacle  11  so as to hold the integrally provided receptacle insulator  13 . 
     The receptacle central contact  14  is a strip that is bent into the shape of a step, with one end portion protruding frontward from the receptacle  11  at the bottom thereof. The other end of the receptacle central contact  14  leads to a vicinity of the surface of the receptacle  11  in the engagement hole  15  and is exposed as a receptacle central contact portion  17  lying in a plane and in a direction perpendicular to the central axis of the engagement hole  15  or the engagement axis C for the receptacle  11  and the plug. 
     As illustrated in  FIG. 3 , the receptacle insulator  13  covers the outer periphery of the annular receptacle external contact  12  and projects into the engagement hole  15  from the bottom side of the receptacle  11  without touching the inner peripheral surface  16  of the receptacle external contact  12 . The receptacle insulator  13  thus holds the receptacle central contact  14 . 
     There is formed in the inner peripheral surface  16  of the receptacle external contact  12  an annular receptacle external contact portion  18 . The receptacle external contact portion  18  is a recess formed in the inner peripheral surface  16  of the receptacle external contact  12 , so that the external contact of the plug fitted to the inside of the engagement hole  15  comes into contact therewith for engagement. 
       FIGS. 4 and 5  illustrate a plug  21  used in the coaxial connector according to the embodiment 1. The plug  21  comprises a plug external contact  22 , a plug insulator  23  and a plug central contact  24 . 
     The plug external contact  22  comprises an arc-shaped plug external contact portion  25  having its center at the engagement axis C for engagement with the receptacle  11 . The plug external contact portion  25  comes into contact with the annular receptacle external contact portion  18  in the engagement hole  15  of the receptacle  11  as the plug  21  is fitted into the receptacle  11  and has a shape in cross section outwardly projecting so as to engage with the recessed receptacle external contact portion  18 . 
     The plug external contact  22  comprises an extension  26  extending from the engagement axis C for engagement with the receptacle  11  in a direction perpendicular to the engagement axis C. The extension  26  comprises a cable connecting portion  27  near its other end, to which an external conductor of a coaxial cable is connected. 
     As illustrated in  FIG. 5C , the plug central contact  24  is secured through the plug insulator  23  to the plug external contact  22  near the middle portion of the extension  26  of the plug external contact  22  and extends therefrom to a vicinity of the engagement axis C for engagement with the receptacle  11  substantially parallel to the extension  26  of the plug external contact  22 , so that the plug central contact  24  is shaped like a cantilever. The plug central contact  24  comprises a plug central contact portion  28  at the free end of the cantilever positioned close to the engagement axis C for engagement with the receptacle  11 . The plug central contact portion  28  comes into contact with the receptacle central contact portion  17  as the plug  21  engages with the receptacle  11  to achieve electric connection. 
     Because the plug central contact  24  is thus shaped like a cantilever extending substantially in parallel to the extension  26  of the plug external contact  22 , a sufficient length of spring can be secured to provide the plug central contact  24  with spring characteristics sufficient to establish a highly reliable connection between the plug central contact portion  28  and the receptacle central contact portion  17  as the plug  21  and the receptacle  11  engage. 
     As illustrated in  FIG. 5C , the plug external contact portion  25  is shaped into an arc having a segment removed in a direction in which the plug central contact  24  extends. Thus, the plug central contact portion  28  is located inside the arc-shaped plug external contact portion  25 , whereas the plug central contact  24  extends through a portion where the plug external contact portion  25  does not exist. 
     The plug central contact  24  further has a cable connecting portion  29  formed near a portion at which the plug external contact  24  is secured to the plug external contact  22  for connection to a central conductor of an axial cable. 
     The plug insulator  23  secures the plug central contact  24  to the plug external contact  22  in the middle portion of the extension  26  of the plug external contact  22  and is provided on the bottom surface of the extension  26  to prevent short-circuiting between the plug external contact  22  and the plug central contact  24 . 
     Next, the operations of the coaxial connector according to the embodiment 1 will be described. 
     As illustrated in  FIG. 6 , it is supposed that the plug external contact  22  of the plug  21  has been previously connected with the external conductor of an axial cable  31  while a cable connecting portion  29  of the plug central contact  24  has been previously connected with the central conductor of the axial cable  31 . It is also supposed that the receptacle  11  is mounted on a circuit board of an electric device, not shown. 
     When the plug external contact portion  25  of the plug external contact  22  of the plug  21  is pushed into the engagement hole  15  of the receptacle along the engagement axis C for engagement, the outwardly projecting arc-shaped plug external contact portion  25  comes into contact with the recessed receptacle external contact portion  18  to establish electric connection between the plug external contact portion  25  and the receptacle external contact portion  18  while the plug external contact portion  25  engages with the recessed receptacle external contact portion  18 . 
     Upon the plug external contact portion  25  engaging with the receptacle external contact portion  18 , the plug central contact portion  28  of the plug central contact  24  comes into contact with the receptacle central contact portion  17  exposed and lying in a plane and in a direction perpendicular to the engagement axis C inside the engagement hole  15  of the receptacle  11 . Now, the cantilever-like plug central contact  24  possesses given spring characteristics secured by the sufficient length of spring, so that a highly reliable connection can be established between the plug central contact portion  28  and the receptacle central contact portion  17 . 
     Thus, the external conductor of the axial cable  31  is electrically connected to the receptacle external contact  12  through the plug external contact  22 , the plug external contact portion  25 , and the receptacle external contact portion  18  sequentially, and the central conductor of the axial cable  31  is electrically connected to the receptacle central contact  14  to the plug central contact  24 , the plug central contact portion  28 , and the receptacle central contact portion  17  sequentially. 
     Because the plug central contact  24  is shaped like a cantilever extending perpendicularly to the engagement axis C, a sufficient length of spring can be secured regardless of the height in the direction along the engagement axis C while the receptacle central contact portion  17  is so exposed as to lie in a plane and in a direction perpendicular to the engagement axis C, reduction in height of the axial coaxial connector can be attained while establishing a highly reliable connection at the same time. 
     When, in particular, the receptacle  11  and the plug  21  are engaged, the plug central contact  24  has a substantially flat shape extending in a direction perpendicular to the engagement axis C as illustrated in  FIG. 6 , while the contact plane in which the plug central contact portion  28  formed at the end of the plug central contact  24  is in contact with the receptacle central contact portion  17  lies so close in height to the extension of the plug central contact  24  that, it may be said, the contact plane lies substantially in the same plane as the extension of the plug central contact  24 . Such a configuration serves to further help reduce the height of the coaxial connector. 
     Further, the configuration where the receptacle external contact portion  18  is formed in the inner peripheral surface of the engagement hole  15  and the receptacle central contact portion  17  is positioned inside the engagement hole  15  greatly reduces the chance of foreign matters, etc. attaching to the receptacle external contact portion  18  and the receptacle central contact portion  17  and, hence, the chance of unforeseen external forces being applied thereto, thus increasing the reliability in the coaxial connector. 
     Further, the receptacle insulator  13  covering the outer periphery of the annular receptacle external contact  12  minimizes the positional shift of the receptacle external contact  12  and thereby eliminates the chance of the engagement becoming loose and unstable even when the engagement length is short or when engagement and disengagement are repeated a number of times, thus enabling production of a highly reliable coaxial connector. 
     The receptacle  11  may be produced by integrally molding the receptacle external contact  12 , the receptacle insulator  13 , and the receptacle central contact  14  using injection molding method or the like. Thus, the receptacle external contact  12 , the receptacle central contact  14  and the receptacle insulator  13  can be placed in a still closer contact with each other, and the strength of the receptacle  11  as a whole can be increased. 
     Similarly, the plug  21  may be produced by integrally molding the plug external contact  22 , the plug insulator  23 , and the plug central contact  24  using injection molding method or the like. Thus, the plug external contact  22 , the plug central contact  24  and the plug insulator  23  can be placed in a still closer contact with each other, and the strength of the plug  21  as a whole can be increased. 
     The receptacle external contact portion  18  of the receptacle external contact  12  may be formed by bending but may be more readily formed by pressing a sheet. For example, an annular recess  33  as illustrated in  FIG. 7  is formed in a metal sheet  32 , a material for forming the receptacle external contact  12 , by pressing the metal sheet, followed by burring to make an opening  34  at the center of the annular recess  33  and a rise  35  around the opening  34 . The rise  35  is formed so that the annular recess  33  is positioned in the inner periphery. The recess  33  of the rise  35  thus formed is the receptacle external contact portion  18  while the opening  34  is the engagement hole  15 . 
     Embodiment 2 
       FIGS. 8 and 9  illustrate a receptacle member  41  used in a coaxial connector according to an embodiment 2. The receptacle member  41  is produced by integrally forming a first receptacle  42 , which has the same configuration as the receptacle  11  according to the embodiment 1 illustrated in  FIGS. 1 and 2 , and a second receptacle  43 , one close to the other. 
     The receptacle member  41  comprises a receptacle external contact  44 , a receptacle insulator  45  and two receptacle central contacts  46  and  47 . 
     The first receptacle  42  comprises a receptacle external contact  44 , a receptacle insulator  45 , and a receptacle central contact  46 ; the second receptacle  43  comprises a receptacle external contact  44 , a receptacle insulator  45 , and a receptacle central contact  47 . The receptacle  43  comprises a receptacle external contact  44  and a receptacle central contact  47  integrally formed with the receptacle external contact  12  through a receptacle insulator  45 . 
     The first receptacle  42  and the second receptacle  43  have the same inner structure as the receptacle  11  according to the embodiment 1 except that the receptacles  42 ,  43  share the receptacle external contact  44  and the receptacle insulator  45 . 
     The first receptacle  42  comprises an engagement hole  48 , an annular receptacle external contact portion  49  formed in the inner peripheral surface of an engagement hole  48 , and a receptacle central contact portion  50  exposed in a plane and in a direction perpendicular to an engagement axis C 1  inside the engagement hole  48 . 
     Likewise, the second receptacle  43  comprises an engagement hole  51 , an annular receptacle external contact portion  52  formed in the inner peripheral surface of the engagement hole  51 , and a receptacle central contact portion  53  exposed in a plane and in a direction perpendicular to an engagement axis C 2  inside the engagement hole  51 . 
     The receptacle member  41  may be produced by integrally molding the receptacle external contact  44 , the receptacle insulator  45 , and the two receptacle central contacts  46 ,  47  using injection molding method or the like. Thus, the receptacle central contact  44 , the receptacle central contacts  46 ,  47 , and the receptacle insulator  45  can be placed in a still closer contact with each other, and the strength of the receptacle  41  as a whole can be increased. 
     The first receptacle  42  and the second receptacles  43  are each fitted with the plug  21  as illustrated in  FIGS. 4 and 5 . Specifically, the plug  21  engages with the first receptacle  42  along the engagement axis C 1  while the plug  21  engages with the second receptacle  43  along the engagement axis C 2 . 
     This completes a two-core coaxial connector. 
     The outer periphery of the annular receptacle external contact portion  49  in the first receptacle  42 , while the outer periphery of the annular receptacle external contact portion  52  in the second receptacle  43  are each covered by the receptacle insulator  45 , and the plug  21  engages with the engagement hole  48  of the first receptacle  42  and the engagement hole  51  of the second receptacle  43 , which enhances the freedom with which the first receptacle  42  and the second receptacle  43  are positioned and permits free designing according to the use. 
     A three-core or multi-core coaxial connector may be produced in like manner. 
     The present invention enables production of a coaxial connector as illustrated in  FIG. 6  wherein, with the plug fitted in the receptacle, the height of the receptacle along the engagement axis C from the bottom surface of the receptacle to the top surface of the plug can be reduced to as small as about 1 mm. 
     Therefore, the coaxial connector of the invention produces great advantageous effects when used in cell phones and other like electronic devices of which a thinner design is required. Further, being coaxial, the connector of the invention may be most suitably used for transmission of image signals of high quality images, transmission of broadband signals for cell phones or the like.