Patent Publication Number: US-6218993-B1

Title: Stretchable antenna for mobile phones

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to a gain structure of a stretchable antenna for mobile phones, and especially to a gain structure of a stretchable rod antenna capable of increasing capability of signal receiving and emitting in cooperation with a coil antenna when the rod antenna is stretched. 
     2. Description of the Prior Art 
     A conventional antenna for mobile phones is divided mainly into two kinds; they are the quarter-wave and the half-wave antennas. The quarter-wave antennas have lower impedance in servo linking, and do not need using of impedance transformers, but they are inferior to the half-wave antennas in the capability of signal receiving and emitting. The half-wave antennas have higher impedance, and need using of impedance transformers in the interior of their mobile phones. 
     In the recent years, mobile phones tend to be minimized. Half-wave antennas have higher impedance and need impedance transformers which occupy larger space in their mobile phones; other redundant parts used further increase their costs. Lengths of half-wave antennas generally are hard to suit modern pocket mobile phones; such lengths are disproportional to the main bodies after assembling. In view of this, pocket mobile phones generally use quarter-wave antennas or quarter-wave coil antenna; however, quarter- wave antennas are evidently insufficient in the capability of signal receiving and emitting even when the rods of antennas as radiators are fully stretched. 
     In a U.S. patent “Antenna device for portable equipment” U.S. Pat. No. 5,757,325 granted to Saldell, an impedance transformer is evidently used. 
     In another U.S. Pat. No. 5,661,495 granted to Saldell, a technique is disclosed to use a switching device to separate a quarter-wave antenna when the antenna is retracted; however, it is still insufficient in the capability of signal receiving and emitting. 
     In another U.S. Pat. No. 5,771,023, a coil antenna for broad bands is disclosed, wherein, a broadband antenna is formed by connecting two coil antennas respectively with a rod antenna. 
     A U.S. Pat. No. 5,650,789 provides a retractable antenna for an indoor wireless telephone set, of which two coil antennas are respectively used at the end of a rod antenna and the telephone set. The coil antenna at the end of the rod antenna is electrically broken when the latter is stretched out, but can make a fixed coil antenna on the surface of an engaging seat form electromagnetic coupling with the coil antenna at the end of the rod antenna for signal receiving and emitting when the rod antenna is retracted. This patent still cannot increase capability of signal receiving and emitting by using a quarter-wave antenna. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a gain structure of a stretchable antenna for mobile phones, wherein, a coil antenna is provided in a connecting member on the telephone set. The coil antenna is connected with a metallic conductive block normally. A spring sheet is connected on an end thereof with the metallic conductive block, while the other end thereof contacts the electric circuit board in the telephone set. A rod antenna which can be stretched and contracted and is provided with a metallic bottom end sleeve is not electrically connected when it is contracted, and has the metallic bottom end sleeve connected to the metallic conductive block to get gain in capability of signal receiving and emitting when it is stretched. The above stated structure of antenna can thus suit a quarter-wave coil antenna and a quarter-wave rod antenna on a miniature mobile phone. 
     The present invention will be apparent in its novelty and features after reading the detailed description of the preferred embodiment thereof in reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an analytic perspective view showing the elements of a preferred embodiment of the present invention; 
     FIG. 2 is a sectional view showing the embodiment of FIG. 1 after assembling; 
     FIG. 3 is a sectional view showing retracting state of the rod antenna of the embodiment of FIG. 2; 
     FIG. 4 is a sectional view showing stretching state of the rod antenna of the embodiment of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 and 2, the present invention is provided generally with a connecting member  10  connectable to a mobile phone. The connecting member  10  normally is formed from non-electrically conductive material and is provided with a first inner bore  11  of suitable size smaller than the diameter of a second connecting inner bore  12  and a third inner bore  13  (opened downwardly) of the connecting member  10 . Diameter of the third inner bore  13  is slightly larger than that of the second connecting inner bore  12 . A through hole  14  is provided on the top surface of the connecting member  10  in communication with the first inner bore  11 , the diameter of the through hole  14  is slightly larger than that of a rod antenna. The lower section of the whole connecting member  10  is provided with a connecting portion  15 . 
     The first inner bore  11  stated above can accept insertion of a coil antenna  20  which is a quarter-wave antenna for suiting a miniature mobile phone. A metallic conductive block  30  is mounted at the inner bottom of the first inner bore  11 , so that one end of the coil antenna  20  is abutted on the inner top surface of the first inner bore  11 ; while the other end thereof is abutted on the upper surface of the metallic conductive block  30 . The metallic conductive block  30  is provided with a central hole  31  with a diameter larger than that of the rod antenna and is provided with a radial hole  32 . 
     A spring sheet  40  has its top folded end  41  inserted into the radial hole  32  of the metallic conductive block  30 , and has the other end thereof extended for a suitable length to abut on the internal electric circuit board  90  (FIGS.  3  and  4 ). A hole  16  and a slit  17  are provided for extending of the spring sheet  40  therethrough respectively on the connecting member  10  between the first inner bore  11  and the second connecting inner bore  12  as well as on the connecting portion  15  of the connecting member  10 . 
     The coil antenna  20 , the metallic conductive block  30  and the spring sheet  40  in the assembled gain structure can have the connecting portion  15  forcedly connected in a hole in a connecting seat  71  provided on the top of the mobile phone  70  as shown in FIGS. 3 and 4. The hole is provided therein with an insulation lining  72  to be tightly connected with the connecting portion  15  of the connecting member  10 . 
     In order to make sure of the contact of the spring sheet  40  with the internal electric circuit board  90 , in the preferred embodiment, the bottom end of the spring sheet  40  is folded into a beveled section  42 , and then is folded from this section  42  into an even more beveled shorter section  43 , another section  44  folded back to the beveled section  42  is formed on the end of the shorter section  43 . Thereby, the shorter section  43  and the folded back section  44  form therebetween a pressing point  45  which protrudes out of the connecting portion  15  of the connecting member  10  and has a specific distance from the vertical main body of the spring sheet  40  for elastic stretching. Thereby, when the connecting member  10  is inserted into the insulation lining  72  in the connecting seat  71  of the mobile phone  70 , the pressing point  45  of the whole spring sheet  40  will be pressed by the fact that it is the most protruding end. Hence the spring sheet  40  is moved rightwards as of FIGS. 3 and 4 under pressing force about the top folded end  41  until the bottommost point  46  formed between the beveled section  42  and the shorter section  43  contacts the internal electric circuit board  90 . In this mode of connection, the pressing point  45  of the whole spring sheet  40  is forced to abut against the insulation lining  72 , and the bottommost point  46  under a slight down pressing force assures contact with the internal electric circuit board  90 . 
     A quarter-wave rod antenna  50  can be mounted in the above stated connecting member  10  of a minimized mobile phone, as a normal antenna, it can be enveloped by injection molding by an insulation coating  52  over the nickel-chromium wire  51  thereof, and is provided with a top cap  53 . The rod antenna  50  of the present invention is slipped over by a metallic bottom end sleeve  60  provided with a central hole  61  for insertion of a partial section of the rod antenna  50 . The metallic bottom end sleeve  60  fits the central hole  31  of the metallic conductive block  30  and the second connecting inner bore  12 . The metallic bottom end sleeve  60  is further provided with a bottom  62  fitting the third inner bore  13 . The shank of the whole rod antenna  50  can thereby freely stretch and contract in the topmost through hole  14  and other related internal holes. 
     Referring to FIG. 3, when the rod antenna  50  is retracted, the whole rod antenna  50  is not electrically connected by virtue that it does not contact with any connecting member. At this time, the mobile phone  70  does signal receiving and transmitting through the coil antenna  20  having been electrically connected. When the rod antenna  50  is in the state as shown in FIG. 4, the metallic bottom end sleeve  60  thereof is pressed into the central hole  31  of the metallic conductive block  30  to make electric connection therewith to get the gain of ¼+¼ wavelengths in signal receiving and transmitting. 
     The mobile phone  70  can thus suit the minimized quarter-wave coil antenna plus quarter-wave rod antenna. When the rod antenna  50  is stretched out, a gain of half-wavelength can be obtained, so that the minimized mobile phone  70  can have strengthened capability of signal receiving and emitting.