Patent Publication Number: US-9431695-B2

Title: Vehicle-mounted replacement antenna

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2013-143163 filed on Jul. 9, 2013, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a vehicle-mounted replacement antenna, and more particularly to such a vehicle-mounted replacement antenna which is attachable to an antenna boss to be mounted in replacement of an existent vehicle-mounted antenna. 
     2. Related Art 
     There has been conventionally widely used a vehicle-mounted monopole antenna detachably screwed into an antenna boss provided on a vehicle roof. The vehicle-mounted monopole antenna includes a slender cylindrical antenna holder incorporating a helical antenna element. The antenna holder has a proximal end provided with a screw shaft portion which is screwed into a screw hole of an antenna boss. For example, Japanese patent application publication Nos. JP-A-2012-169892 and JP-A-2011-228767 disclose conventional vehicle-mounted monopole antennas. 
     The vehicle-mounted monopole antenna is detachably screwed into a screw hole of an antenna boss as described above. Accordingly, when a vehicle is washed by a vehicle washer or the vehicle is parked in a garage having a low ceiling, there is a possibility that the antenna may be broken. However, the antenna can be easily detached from the antenna boss. 
     On the other hand, since the antenna can be easily detached from she antenna boss, she antenna has a high possibility of being thieved when a driver leaves his/her vehicle. 
     SUMMARY 
     Therefore, an object of the disclosure is to provide a vehicle-mounted replacement antenna which can he mounted to a vehicle in replacement of the vehicle-mounted antenna and which is difficult to thieve even when the replacement antenna is kept mounted. 
     The present disclosure provides vehicle-mounted replacement antenna which is mounted on an antenna boss to which a vehicle-mounted antenna is detachably screwed. The vehicle-mounted replacement antenna includes an antenna holder including a cylindrical portion having a proximal end surface formed into an opening, a connecting shaft including a fitting shaft portion rotatably fitted into the cylindrical portion and having two ends, a hook shaft portion provided on one end of the fitting shaft portion and having an outer periphery formed with a ring groove, and a screw shaft portion provided on the other end of the fitting shaft portion and screwable into an existent antenna screw hole of the antenna boss, an antenna element inserted into the cylindrical portion from the opening of the cylindrical portion, and a concealed screw. In the replacement antenna, the cylindrical portion has a screw hole for the concealed screw, extending from an outer surface of the proximal end thereof into a hollow interior thereof. The screw shaft portion is screwed into the existent antenna screw hole so that the connecting shaft is fixed to the antenna boss. The cylindrical portion is caused to cover the connecting shaft from the opening of the proximal end surface thereof. The fitting shaft portion is fitted into the cylindrical portion. The cylindrical portion is fitted with an outer periphery of the existent antenna screw hole, and a distal end of the hook potion is electrically connected to the antenna element. The concealed screw is embedded into the concealed screw hole and a distal end of the concealed screw is pressed against a bottom surface of the ring groove, so that the antenna holder is mounted on the connecting shaft so as to be prevented from rotation, or the concealed screw is screwed into the concealed screw hole, and the distal end of the concealed screw is spaced from the bottom surface of the ring groove and hooked on a side surface of the ring groove, so that the antenna holder is mounted on the connecting shaft so as to be rotatable and unremovable. 
     According to the above-described construction, the concealed screw is embedded into the concealed screw hole, and the distal end of the concealed screw is pressed against the bottom surface of the ring groove, so that the antenna holder is unrotatably mounted on the connecting shaft. Accordingly, the antenna holder can be fixed to the antenna boss in a predetermined position. 
     On the other hand, the concealed screw is embedded into the concealed screw hole and the distal end of the concealed screw is slightly spaced from the bottom surface of the ring groove and is further hooked on a side surface of the ring groove  13   e , whereby the antenna holder is mounted to the connecting shaft so as to be rotatable and unremovable. 
     Accordingly, unless the concealed screw is found, someone else can rotate the antenna holder with the intention of detaching the antenna holder from the antenna boss, but the connecting shaft is not rotated. Accordingly, the connecting shaft is not detached from the antenna boss. As a result, since the connecting shaft cannot be detached from antenna boss, the vehicle-mounted replacement antenna can be prevented from being thieved. 
     In one embodiment, a plurality of the ring grooves is formed along an axis of the connecting shaft. According to this, when the cylindrical portion of the antenna holder is fitted with the outer periphery of the existent antenna screw hole, the concealed screw can be inserted into either one of the ring grooves, even in the case where the gap between the proximal end surface of the cylindrical portion and the distal end surface of the antenna screw hole differs depending upon vehicle types. As a result, the vehicle-mounted replacement antenna is convenient since the antennas of a plurality of vehicle types can be replaced by the vehicle-mounted replacement antenna. 
     In another embodiment, the antenna holder is generally formed into a shark fin shape and the cylindrical portion is formed along a back of the shark fin shape. According to this, the existent antenna can be replaced by a sporty shark fin antenna having a quite different design from the existent antenna. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a perspective view of a vehicle-mounted replacement cement antenna according to a first embodiment and an antenna boss to which the vehicle-mounted replacement antenna is mounted; 
         FIG. 2  is a partially broken side view of the vehicle-mounted replacement antenna and the antenna boss to which the vehicle-mounted replacement antenna is mounted; 
         FIG. 3  is a side view of a connecting shaft of the vehicle-mounted replacement antenna; 
         FIG. 4  is a partially enlarged section of a concealed screw hole and a concealed screw of the connecting shaft; 
         FIG. 5  is also a partially enlarged section of the concealed screw hole and the concealed screw, showing the case where a distal end of the concealed screw is slightly spaced from a ring groove bottom; 
         FIG. 6  is a partially broken side view of the vehicle-mounted replacement antenna mounted to another antenna boss; and 
         FIG. 7  is a partially broken side view of a vehicle-mounted replacement antenna according to a second embodiment and an antenna boss to which the vehicle-mounted replacement antenna is mounted. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments will be described with reference to the accompanying drawings. Referring first to  FIGS. 1 and 2 , a vehicle-mounted replacement antenna  10  of the first embodiment is shown. The antenna  10  includes an antenna holder  11 , a helical antenna element  12 , a connecting shaft  13  and a concealed screw  14 . 
     The antenna holder  11  is made of ABS resin and includes a back formed into an elongated cylindrical portion  11   a  and a thin fin portion  11   b  expanding from the back, thereby being formed into the shape of a shark fin. The fin portion  11   b  is formed to be tapered from a proximal end of the cylindrical portion  11   a . The cylindrical portion  11   a  has a proximal end surface formed into an opening  11   c.  The cylindrical portion  11   a  has a screw hole  11   d  for a concealed screw, extending from an outer surface. of the proximal end to a hollow interior of the cylindrical portion  11   a.    
     The helical antenna element  12  formed into a helical shape is covered by a vinyl cover  15 . An acrylic rod  16  serving as a dielectric is inserted into the antenna element  12 . 
     As shown as an enlarged form in  FIG. 3 , the connecting shaft  13  includes a fitting shaft portion  13   a,  a hook shaft portion  13   b  provided at one of two ends of the fitting shaft portion  13   a  and a screw shaft portion  13   c  provided at the other end of the fitting shaft portion  13   a.  The fitting shaft portion  13   a  has a diameter set so as to be rotatably fitted into the cylindrical portion  11   a  of the antenna holder  11 . The hook shaft portion  13   b  has an outer periphery formed with two ring grooves  13   d  and  13   e.  The screw shaft portion  13   c  is provided with a screw which can be screwed into the existent antenna screw hole of an antenna boss. Further, the hook shaft portion  13   b  has a distal end surface formed with a coin groove  13   f  into which a coin is insertable. 
     The vehicle-mounted, replacement antenna  10  is thus of the antenna holder  11 , the helical antenna element  12 , the connecting shaft  13  and the concealed screw  14  as described above. The antenna  10  will be assembled to an antenna boss  21  mounted on a roof  20  of the vehicle in the following procedure. A base  22  is fixed to the roof  2  and includes a top to which a pivot shaft  23  is assembled. The antenna boss  21  is integrally provided on the pivot shaft  23 . The antenna boss  21  has a three-stage structure including a large-diameter portion  21   a,  a middle diameter portion  21   b  and a small-diameter portion  21   c.  The uppermost small-diameter portion  21   c  is formed with an existent antenna screw hole  21   d.  An existent antenna (not shown) screwed into the existent antenna screw hole  21   d.  is detached, and a suitable coin is inserted into the coin groove  13   f,  so that the screw shaft portion  13   c  of the connecting shaft  13  is rotated thereby to be screwed into the existent antenna screw hole  21   d . As a result, the connecting shaft  13  is fixed to the antenna boss  21 . 
     The helical antenna element  12  and the rod  16  both covered by the cover  15  are inserted from the proximal end opening  11   a  of the cylindrical portion  11   a  thereby so be housed in the cylindrical portion  11   a.  Subsequently, the cylindrical portion  11   a  is caused to cover the connecting shaft  13  from the distal end opening  11   c . The fitting shaft potion  13   a  is then fitted into the cylindrical portion  11   a , and the proximal end of the cylindrical portion  11   a  is fitted with an outer periphery of the middle diameter portion  21   b  of the existent antenna boss  21 . The proximal end of the cylindrical portion  11   a  is caused to abut on an upper end of the large-diameter portion  21   a.  With this, a spring force of the antenna element  12  presses the distal end of the hook shaft portion  13   c  against an end of the helical antenna element  12 . 
     Subsequently, the concealed screw  14  is embedded into the screw hole  11   d  with a tool (not shown), and the distal end of the concealed screw  14  is pressed against the bottom of the ring groove  13   e  at the screw shaft portion  13   c  side, whereby the antenna holder  11  is mounted. to the connecting shaft  13  without being turned, as shown in  FIG. 4 . 
     The vehicle-mounted replacement antenna  10  assembled to the antenna boss  21  can be caused to rise from the roof  20  as shown by an imaginary line in  FIG. 1  or to fall to the roof  20  as shown by solid line in  FIG. 2 . 
     When the vehicle is parked for a long time, the concealed screw  14  embedded into the screw hole  11   d , is turned with a tool in order that the replacement antenna  10  may be prevented from being thieved, as shown in  FIG. 5 . Consequently, the distal end of the concealed screw  13   e  is slightly spaced from the bottom of the ring groove  13   e  and hooked on a side surface of the ring groove  13   e,  with the result that the antenna holder  11  is mounted on the connecting shaft  13  so as to be pivotable and unremovable. 
     According to the vehicle-mounted replacement antenna of the first embodiment, the concealed screw  11   d  is embedded into the screw hole lid, and the antenna holder  11  can be unrotatably mounted on the connecting shaft  13 . Accordingly, the antenna holder  11  can be fixed to the antenna boss  21  in a predetermined position. 
     On the other hand, the distal end of the concealed screw  14  is slightly spaced from the hot tom of the ring groove  13   e  and hooked on the side surface of the ring groove  13   e,  whereby the antenna holder  11  can be mounted to the connecting shaft  13  so as to be rotatable and unremovably. Accordingly, unless the concealed screw  14  is found, someone else can rotate the antenna holder  11  with the intention of detaching the antenna holder  11  from the antenna boss  21 , but the connecting shaft  13  is not rotated. Accordingly, the connecting shaft  13  is not detached from the antenna boss  21 . As a result, since the connecting shaft  13  cannot be detached from antenna boss  21 , the vehicle-mounted replacement antenna can be prevented from being thieved. 
     Further, the existent antenna can be replaced by a sporty shark fin antenna having a quite different design from the existent antenna. 
       FIG. 6  shows another case where the vehicle-mounted replacement antenna  10  is mounted to an antenna boss  25  of another type. The foregoing antenna boss  21  has the three-stage structure including the large-diameter portion  21   a,  the middle-diameter portion  21   b  and the small-diameter portion  21   c.  The uppermost small-diameter portion  21   c  is formed with the existent antenna screw hole  21   d.  On the other hand, an antenna boss  25  as shown in  FIG. 6  has a two-stage structure including a large-diameter portion  25   a.  and a middle-diameter portion  25   b.  The middle-diameter portion  25   b  is formed with an antenna screw hole  25   c.  in order that the antenna holder  11  may be mounted to the antenna boss  25 , the middle-diameter portion  25   b  is fitted into the cylindrical portion ha of the antenna holder  11 . 
     The above-described antenna boss  21  and the antenna boss  25  differ from each other in a gap between the proximal end surface of the cylindrical, portion  11   a  and the distal ends of the existent antenna boss  21   d  or  25   c  in the case where the cylindrical portion  11   a  of the antenna holder  11  is fitted with the outer periphery of the antenna boss  21  or  25 . The gap in the antenna boss  25  is shorter than the gap in the antenna boss  21 . Accordingly, when the cylindrical portion  11   a  is caused to cover the middle-diameter portion  25   b  of the antenna boss  25 , and the end surface of the cylindrical portion  11   a  is caused to abut on the upper end of the large-diameter portion  25   a,  the concealed screw hole lid is opposed to the ring groove  13   d  at the hook shaft portion  13   b  side, so that the concealed screw  14  is embedded into the concealed screw hole  13   d.    
     The two rind grooves  13   d  and  13   e  are thus formed along the axis of the connecting shaft  13 . Accordingly, when the cylindrical portion ha of the antenna holder  11  is fitted with the outer periphery of the existent antenna screw hole  21   d  or  25   d  of the antenna boss  21  or  25 , the concealed screw  14  can be inserted into either the ring groove  13   d  or  13   e  even in the case where the gap between the proximal end surface of the cylindrical portion  11   a  and the distal end surface of the existent antenna screw hole  21   d  or  25   d  differs depending upon vehicle types. As a result, the vehicle-mounted replacement antenna  10  is convenient since the antennas of a plurality of vehicle types can be replaced by the vehicle-mounted replacement antenna 
       FIG. 7  illustrates a vehicle-mounted replacement antenna  30  according to a second embodiment. The vehicle-mounted replacement antenna  30  includes a rod antenna  31  as the antenna element although the vehicle-mounted replacement antenna  10  of the first embodiment includes the helical antenna  12  as the antenna element. The rod antenna  31  is assembled to the antenna holder  32 . 
     The antenna holder  32  includes a flexible portion  32   a  made of rubber-like plastic and a cylindrical portion  32   b  made of an electrically conductive metal. A proximal end of the rod antenna  31  and a bending coil spring  33  are buried in the flexible portion  32   a  by integral molding. The flexible portion  32   a  has a proximal end formed with a fitting recess  32   c  The cylindrical portion  32   b  has a distal end which is fitted into the fitting recess  32   c . The cylindrical portion  32   b  has a proximal end formed into an opening  32   d.  A contact spring  34  is accommodated in the interior of the cylindrical portion  32   b.  Further, the cylindrical portion  32   b  is formed with a screw hole  32   e  for a concealed screw. The cylindrical portion  32   b  has a distal end fitted into the fitting recess  32   c  of the flexible portion  32   a.  The flexible portion  32   a  and the cylindrical portion  32   b  are integrally joined together by welding. 
     In the second embodiment, the cylindrical portion  32   b  is caused to cover the connecting shaft  13  screwed into the existent antenna screw hole  21   d  of the antenna boss  21 , from the opening  32   d . The concealed screw  14  is then screwed into the screw hole  32   e,  and the distal end of the concealed screw  14  is pressed against the ring groove  13   e,  whereby the antenna holder  32  of the vehicle-mounted replacement antenna  30  is fixed to the antenna boss  21 . 
     On the other hand, the distal end of the concealed screw  14  is slightly spaced from the bottom surface of the ring groove  13   e  and is further hooked on a side surface of the ring groove  13   e,  whereby the antenna holder  32  is mounted to the connecting shaft  13  so as to be rotatable and unremovable. Consequently, the vehicle-mounted replacement antenna can be prevented from being thieved. 
     Further, the bending spring  33  is interposed between the rod antenna  31  and the cylindrical portion  32   b.  Accordingly, when an external force is applied to the rod antenna  31 , the flexible portion  32   a  is flexed thereby to prevent the rod antenna  31  from being broken. 
     The foregoing description and drawings are merely illustrative of the present disclosure and are not to be construed in a limiting sense. Various changes and modifications will become apparent to those of ordinary skill in the art. All such changes and modifications are seen to fall within the scope of the appended claims.