Abstract:
A connector includes a base connector and a cylindrical member. The base connector has a cylindrical projection to penetrate through an outside wall of an attachment subject. The cylindrical member is fitted with the cylindrical projection and has a cavity.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to a connector for providing a wiring outside an electric apparatus and, more particularly, to a connector that complies with a pressure-resistant/explosion-proof standard. 
       RELATED ART 
       [0002]    Electric apparatus to be installed in dangerous places etc. where a flammable gas or vapor of a flammable liquid exists or may exist are required to be provided with a countermeasure against an explosion, and related standards are established. A typical explosion-proof structure of an explosion-proof standard is a pressure-resistant/explosion-proof structure (symbol d). 
         [0003]    In the pressure-resistant/explosion-proof structure (symbol d), an electric apparatus which may become an ignition source is placed in an explosion-proof, fully-closed chamber so that even if an explosion occurs inside the chamber the explosion, does not reach the outside of the chamber. This structure is required to be strong enough to withstand an internal explosion and to be able to prevent a flame occurring inside from igniting what is located outside through a gap between joining surfaces of the chamber. As long as a chamber satisfies the above requirements, no restrictions are imposed on an electric apparatus incorporated therein. The case of an electric apparatus itself may such as to satisfy the above requirements. 
         [0004]    For example, if an electric apparatus  30  to which an antenna  32  is connected (see  FIG. 5A ) should satisfy the requirements of the pressure-resistant/explosion-proof structure (symbol d), designing is done so that the region enclosed by a boundary  41  and containing also the antenna  32  satisfies the standard. More specifically, a pressure-resistant/explosion-proof structure (symbol d) can be realized by a pressure-resistant/explosion-proof chamber that contains the region enclosed by the boundary  41 . If the case of the electric apparatus  30  itself excluding an antenna connection portion satisfies the requirements, as shown in  FIG. 5B  a pressure-resistant/explosion-proof structure (symbol d) can easily be realized by using a pressure-resistant/explosion-proof chamber  42  that is attached to the case of the electric apparatus  30 . 
       PRIOR ART DOCUMENTS 
     Patent Documents  
       [0005]    [Patent document 1] JP-A-9-182284 
         [0006]    On the other hand, assume a case that as shown in Fig. SC the antenna  32  is connected to the electric apparatus  30  by an antenna extension cable  34  to dispose the antenna  32  at a place where high sensitivity can be attained. To satisfy the requirements of the pressure-resistant/explosion-proof structure (symbol d) by the same approach as shown in  FIG. 5A , designing should be done so that the region enclosed by a boundary  43  and containing the antenna extension cable  34  and the antenna  32  in addition to the electric apparatus  30  satisfies the standard. 
         [0007]    In this case, one approach is to construct a pressure-resistant/explosion-proof chamber that contains the antenna extension cable  34 , the antenna  32 , and the electric apparatus  30 . If the case of the electric apparatus  30  itself excluding an antenna extension cable connection portion satisfies the requirements, another approach is possible in which a pressure-resistant/explosion-proof chamber that contains the antenna extension cable  34  and the antenna  32  is constructed and attached to the case of the electric apparatus  30 . 
         [0008]    However, the antenna  32  may be connected to the electric apparatus  30  by an antenna extension cable  34  that is as long as several tens of meters. In such a case, it is very difficult to adapt a pressure-resistant/explosion-proof chamber to the shape of a path of the antenna  32  and the antenna extension cable  34 . This approach is not practical in terms of cost and the number of steps necessary for installation. 
       SUMMARY 
       [0009]    Exemplary embodiments of the invention provide a connector which can realize a pressure-resistant/explosion-proof structure of an electric apparatus easily at a low cost in the case where a wiring is provided outside the electric apparatus. 
         [0010]    A connector includes: 
         [0011]    a base connector having a cylindrical projection to penetrate through an outside wall of an attachment subject; and 
         [0012]    a cylindrical member which is fitted with the cylindrical projection in a state that a cavity is formed. 
         [0013]    The cavity may be filled with a resin. The cylindrical member may be fitted with the cylindrical projection through a threaded mechanism. 
         [0014]    The base connector may be of a water-proof type. The base connector may have a generally truncated-cone-shaped external form. 
         [0015]    The cylindrical projection and the cylindrical member may be monolithically formed. 
         [0016]    According to the exemplary embodiments of the invention, it is possible to realize a pressure-resistant/explosion-proof structure of an electric apparatus easily at a low cost in the case where a wiring is provided outside the electric apparatus. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIGS. 1A-1C  are views showing use forms of a connector according to an embodiment. 
           [0018]      FIG. 2  is a schematic sectional view showing an example configuration of the connector according to the embodiment. 
           [0019]      FIGS. 3A and 3B  are views showing a general-purpose water-proof high-frequency connector and a cylindrical member. 
           [0020]      FIGS. 4A and 4B  are views showing a state that the connector is connected to a case of an electric apparatus or a pressure-resistant/explosion-proof chamber. 
           [0021]      FIGS. 5A-5C  are views for explaining a related-art pressure resistant/explosion-proof structure. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    An embodiment of the present invention will be hereinafter described with reference to the drawings.  FIG. 1A-1C  show use forms of a connector  100  according to the embodiment. Components etc. having the same ones in  FIGS. 5A-5C  are given the same reference numerals as the latter.  FIG. 1A-1C  show examples of manners for realizing a pressure-resistant/explosion-proof structure (symbol d) using the connector  100  which complies with the pressure-resistant/explosion-proof standard. 
         [0023]    In the example of  FIG. 1A , the connector  100  is attached to the case of an electric apparatus  30  and used for connecting an antenna  32  to the electric apparatus  30 . In the example of  FIG. 1B , the connector  100  is attached to the case of the electric apparatus  30  and used for connecting an antenna extension cable  34  to the electric apparatus  30 , The examples of  FIGS. 1A and 1B  correspond to a case that the case itself of the electric apparatus  30  satisfies the pressure-resistant/explosion-proof standard. In the example of  FIG. 1C , the connector  100  is attached to a pressure-resistant/explosion-proof chamber  47  which contains the electric apparatus  30 , and is used for connecting an antenna extension cable  34  to a cable  35  which is connected to the electric apparatus  30 . 
         [0024]    It is assumed that the electric apparatus  30  is required to satisfy the requirements of the pressure-resistant/explosion-proof structure (symbol d). In the configuration of Fig. IA in which the antenna  32  is directly connected to the connector  100 , because of the use of the connector  100  which complies with the pressure-resistant/explosion-proof standard, a boundary  44  which contains the electric apparatus  30  and the connector  100  is regarded as a pressure-resistant/explosion-proof chamber, whereby a pressure-resistant/explosion-proof structure (symbol d) is realized. 
         [0025]    Likewise, in the configuration of  FIG. 1B  in which the antenna  32  is connected to the connector  100  via the antenna extension cable  34 , a boundary  45  which contains the electric apparatus  30  and the connector  100  is regarded as a pressure-resistant/explosion-proof chamber, whereby a pressure-resistant/explosion-proof structure (symbol d) is realized. 
         [0026]    In the configuration of  FIG. 1C  in which the antenna extension cable  34  is connected to the connector  100  which is attached to the pressure-resistant/explosion-proof chamber  47 , a boundary  46  which contains the pressure-resistant/explosion-proof chamber  47  and the connector  100  is regarded as a pressure-resistant/explosion-proof chamber, whereby a pressure-resistant/explosion-proof structure (symbol d) is realized, 
         [0027]    In the embodiment, the connector  100  which complies with the pressure-resistant/explosion-proof standard serves as part of the boundary  44 ,  45 , or  46 , whereby the electric apparatus  30  comes to satisfy the requirements of the pressure-resistant/explosion-proof structure (symbol d). The antenna extension cable  34  and the antenna  32  are regarded as being located outside the application range of the pressure-resistant/explosion-proof structure (symbol d). Therefore, the antenna extension cable  34 , its length, and the antenna  32  can be selected freely. 
         [0028]      FIG. 2  is a schematic sectional view showing an example configuration of the connector  100  according to the embodiment, which is a bulkhead type high-frequency connector with a fringe. The connector  100  is a combination of an existing, general-purpose water-proof high-frequency connector  10  shown in  FIG. 3A  and a cylindrical member  20  shown in  FIG. 3B . A cavity which is formed in the cylindrical member  20  when it is combined with the high-frequency connector  10  is filled with a resin  21  that forms a cemented joint to satisfy the pressure-resistant/explosion-proof standard. Since a connector which complies with the pressure-resistant/explosion-proof standard is constructed using, as a base, an existing, general-purpose water-proof connector, the embodiment makes it possible to realize connectors that comply with various kinds of pressure-resistant/explosion-proof standards easily at a low cost. 
         [0029]    The general-purpose water-proof high-frequency connector  10  has a cylindrical projection  11 , and the connector  100  is attached to the case of the electric apparatus  30  or the pressure-resistant/explosion-proof chamber  47  in such a manner that the projection  11  penetrates through its outside wall. The cylindrical member  20  is attached to the projection  11  so as to surround it without forming any gaps. For example, the cylindrical member  20  may be manufactured easily by plating a cylindrical brass member. 
         [0030]    For example, the cylindrical member  20  may be attached to the general-purpose water-proof high-frequency connector  10  by means of a threaded portion  29  formed on the inside circumferential surface of the cylindrical member  20  and a threaded portion  13  formed on the outer circumferential surface of the projection  11  of the general-purpose water-proof high-frequency connector  10 . 
         [0031]    The threaded portions  13  and  29  are formed so that a cavity having a length L is formed in the cylindrical member  20 , As described above, this cavity serves as a resin filling space and is filled with the resin  21  which will set to become an insulating material. The resin  21  may be a two-liquid thermosetting silicone potting material, for example. The length L should be greater than or equal to a length that is required by a resin-related part of the explosion-proof standard. 
         [0032]    The outer circumferential surface of the cylindrical member  20  is formed with a threaded portion  28  to be used for fixing the connector  100  to the case of the electric apparatus  30  or the pressure-resistant/explosion-proof chamber  47  using a flat washer  24 , a washer  25 , and a nut  26 . 
         [0033]    The connector  100  is electrically connected to internal circuits of the electric apparatus  30  by the cable  35  and electrically connected to the antenna  32  or the antenna extension cable  34  by a plated core wire  12 . The core wire  12  is surrounded by a dielectric  14  such as a carbon fluoride resin or the like to form a coaxial structure. 
         [0034]    Instead of the cable  35 , a harness, another connector, an adaptor, or the like may be used to connect the connector  100  to the electric apparatus  30 .  FIGS. 2 and 3  show, in a simplified manner, the configuration of the water-proof connector  100 , and it may have a hermetic internal structure. Where an existing connector is used which has a space that can be filled with the resin  21  having a necessary thickness, the connector  100  can be constructed without combining the cylindrical member  20 . 
         [0035]    Since the connector  100  employs the general-purpose water-proof high-frequency connector  10 , an O-ring  19  is used as a countermeasure against water penetration from outside the connector  100  and an O-ring  18  is used as a countermeasure against water penetration into the case of the electric apparatus  30  or the pressure-resistant/explosion-proof chamber  47 . Typical examples of the high-frequency connector  10  are a SNC connector, an SMA connector, 7 mm connector, 3.5 mm connector, 2.92 mm connector, 2.4 mm connector, 1.85 mm connector, 1.0 mm connector, a INC connector, and an N connector; However, the high-frequency connector  10  is not limited to them. 
         [0036]      FIG. 4A  shows a state that the connector  100  is connected to the case of the electric apparatus  30  or the pressure-resistant/explosion-proof chamber  47 . In this example, the connector  100  is connected to the case of the electric apparatus  30  or the pressure-resistant/explosion-proof chamber  47  using screws  16  that are inserted in screw holes that are formed through the fringe of the general-purpose water-proof high-frequency connector  10  and the washers and nut  24 - 26 . Alternatively, either the screws  16  or the washers and nut  24 - 26  may be used. 
         [0037]    It is desirable that the screws  16  be of such a type as to require a special tool for their disengagement (e.g., Tors screws) so that the screws  16  cannot be removed from the outside using pliers, nippers, or the like. 
         [0038]    In the embodiment, since the cavity of the cylindrical member  20  is filled with the resin  21  to the extent that the resin  21  has a thickness that is equal or more than a thickness that fills a chamber of the cemented joint of the pressure-resistant/explosion-proof chamber, a boundary B can be regarded as a boundary of a pressure-resistant chamber (see  FIG. 4B ) when the connector  100  is attached to the case of the electric apparatus  30  or the pressure-resistant/explosion-proof chamber  47 . Therefore, basically an explosion-proof structure can be realized without being affected by the structure of the water-proof high-frequency connector  10  itself which is located outside the boundary B and serves as a base of the connector  100 . 
         [0039]    As a result, although in the embodiment the connector  100  is constructed using the high-frequency connector  10  as a base, connectors that satisfy a pressure-resistant/explosion-proof standard can be constructed using various kinds of existing connectors that are not a high-frequency connector or a water-proof connector. 
         [0040]    Incidentally, explosion-proof standards require that a connector be subjected to a steel ball drop test. To reduce impact of this test, as shown in  FIG. 4A  the connector  100  according to the embodiment employs the water-proof high-frequency connector  10  whose fringe is shaped like a truncated cone that forms an angle  0  with the attaching direction (signal transmission direction). 
         [0041]    For example, assume that impact that occurs when a steel ball having a weight 1 kg is dropped perpendicularly to the signal transmission direction (in FIG. 4A, in the horizontal direction) from a height 0.7 m is F (N). The impact F′ (N) acting perpendicularly on a slant surface having the angle θ is given by: 
         [0000]        F′=F cosθ,
 
         [0000]    which is smaller than in the case of normal incidence. If θ is equal to 45°, the impact of the steel ball dropped is much decreased to about 70%. The angle θ can be set freely. 
         [0042]    In general, a hemisphere formed at the tip of a heavy weight used in steel ball drop tests has a diameter 25 mm. Therefore, the impact acting on the connector  100  in a steel ball drop test is decreased further if the length, in the signal transmission direction, of that portion of the connector  100  which projects outward from the case of the electric apparatus  30  or the pressure-resistant/explosion-proof chamber  47  (see  FIG. 4A ) is shorter than 25 mm. 
         [0043]    The embodiment makes it possible to realize a pressure-resistant/explosion-proof structure of an electric apparatus easily at a low cost because as described above a boundary that can be regarded as a boundary of an explosion-proof chamber is formed by using the connector  100  which is a combination of the general-purpose water-proof high-frequency connector  10  and the cylindrical member  20 . 
         [0044]    More specifically, an existing connector is worked to form a threaded portion for attachment of a cylindrical member to be used for filling of a resin that forms a cemented joint, whereby the existing connector can be used as a base of a connector which satisfies a pressure-resistant/explosion-proof standard. As a result, a pressure-resistant/explosion-proof connector can be manufactured easily at a very low cost. A pressure-resistant/explosion-proof connector can be manufactured by using a base connector that is selected from a wide variety of existing connectors according to a use, which means increase in the degree of freedom in selection of components. Furthermore, it is not necessary to develop a new pressure-resistant/explosion-proof connector.