FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to a cable on-line transfer device, and more particularly to a soldering method for sealing the cable on-line transfer device.  
         BACKGROUND OF THE INVENTION  
         [0002]    The coaxial cable is generally used to transmit audio and video signals between a transmitter and a receiver of the cable television, video monitor, or AV system. The cable is often provided with an on-line transfer device capable of tapping, wave enhancing, or decoding. The online transfer device has a metal housing, which is externally provided with at least one input connector and one or more output connectors, and is internally provided with a circuit board and an electronic element. The metal housing is generally formed of a metal receiving seat, and a metal cover which is joined with the metal receiving seat by tin soldering, so as to prevent the signals from being affected by the electromagnetic interference, or to prevent the signals from interfering other electronic devices.  
           [0003]    The conventional soldering method for sealing the metal housing is defective in design in that it is time-consuming, and that the tin lumps formed on the metal housing undermine the esthetic effect of the transfer device, and that the tin solder is prone to break or cut by something sharp, and further that the metal housing is often tainted by the soldering flux and is cleansed with a stain remover which contains the volatile material hazardous to human health.  
         SUMMARY OF THE INVENTION  
         [0004]    The primary objective of the present invention is to provide a novel soldering method for sealing an on-line transfer device of cable. The method of the present invention is free of the deficiencies of the prior art soldering method described above.  
           [0005]    The method of the present invention includes a first step in which a fusing area between the receiving seat and the cover of the housing is furnished with an appropriate amount of a soft solder. The cover is then heated for a short period of time such that the heat is transmitted to melt the soft solder. The molten soft solder forms an annular seam. Finally, the receiving seat and the cover are united together by soldering.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 show an exploded view of a transfer device housing of a first preferred embodiment of the present invention.  
         [0007]    [0007]FIG. 2 show a pre-soldering schematic view of the transfer device housing of the first preferred embodiment of the present invention in combination.  
         [0008]    [0008]FIG. 3 shows a post-soldering schematic view of the transfer device housing of the first preferred embodiment of the present invention.  
         [0009]    [0009]FIG. 4 shows a pre-soldering schematic view of a transfer device housing of a second preferred embodiment of the present invention in combination.  
         [0010]    [0010]FIG. 5 shows a post-soldering schematic view of the transfer device housing of the second preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]    As shown in FIG. 5.  1 - 3 , a transfer device housing of the first preferred embodiment of the present invention is formed of a receiving seat  10  and a cover  20  which is joined with the receiving seat  10 . The receiving seat  10  is a hollow rectangular case and is provided in the bottom with a rectangular opening  11 . The receiving seat  10  has a hollow interior for containing the electronic components of the transfer device. The receiving seat  10  is provided in the outer surfaces of the long sides thereof with a plurality of cable connectors  12 . The receiving seat  10  is further provided in the frame edge of the bottom side thereof with an inner protruded edge  14  and an outer protruded edge  15  which is greater in length than the inner protruded edge  14 . The cover  20  is shaped and dimensioned to cap the opening  11  of the receiving seat  10  and is provided in the outer edge of the inner side thereof with a rectangular inner protruded ring  21 , a rectangular outer protruded ring  22 , and an annular slot  23  located between the inner and the outer protruded rings  21  and  22 . The cover  20  is united with the receiving seat  10  to form together a housing  30  such that the outer protruded edge  15  of the receiving seat  10  circumvents the outer edge of the cover  20 , and that the inner protruded edge  14  of the receiving seat  10  is inserted into the annular slot  23  of the cover  20  to press against the inner protruded ring  21  of the cover  20 , with the inner protruded edge  14  remaining a distance away from the outer protruded ring  22 . As a result, there is a solder space  24  in the annular slot  23  of the cover  20 .  
         [0012]    The soldering method of the present invention involves a first step in which a soft solder  40  is applied by the web fed press on the fringe of the inside of the slot  23  such that the soft solder  40  is corresponding in location to the solder space  24 . The soft solder  40  contains tin and lead and has a melting point of about 200 degrees in Celsius. The cover  20  is then located in the opening  11  of the receiving seat  10 , as shown in FIG. 2. With the cover  20  facing downward, the housing  30  is heated for about two seconds on a hot plate which is previously heated to have a temperature higher than 200 degrees in Celsius. As the heat is transmitted to the bottom of the housing  30 , the solder ointment  40  is caused to melt rapidly. The molten solder  40  is dispersed by the capillary action into the interstices between the receiving seat  10  and the cover  20 , especially between the inner protruded edge  14  and the inner protruded ring  21 . The solder residue is deposited in the bottom of the solder space  24 . Now referring to FIG. 3, an annular soldering strip  41  is formed in the bottom of the solder space  24  after the molten solder is cooled and solidified. In the meantime, a filling layer  42  is formed by the molten solder which is dispersed into the interstices. The receiving seat  10  and the cover  20  are thus securely joined together. In other words, the housing  30  is hermetically sealed off to minimize the effect of electromagnetic interference. It must be noted here that the heating process of the present invention is benign to the structural integrity of the electronic components which are contained in the receiving seat  10 .  
         [0013]    As shown in FIGS. 4 and 5, a housing  50  of the second preferred embodiment of the present invention is formed of a metal receiving seat  60  and a metal cover  70 , which are electroplated with nickel. The receiving seat  60  is a hollow rectangular case with an opening  61  facing downward and is provided in the inner edge of the bottom fringe thereof with an annular shoulder  62 . The cover  70  is shaped and dimensioned to join with the opening  61  such that the outer edge of the inner side of the cover  70  is in contact with the shoulder  62 . The cover  70  is provided in proximity of the outer edge of the inner side thereof with a rectangular protruded ring  71 , which is inserted into the receiving seat  60  and has an inclined outer side slanting inward to form with the wall of the receiving seat  60  an acute angle of  15  degrees or so. As a result, an annular acute angle space  72  is formed between the protruded ring  71  and the peripheral wall of the receiving seat  60 .  
         [0014]    The soldering method of the second preferred embodiment of the present invention includes a first step in which a solder ointment  80  is applied by the web fed press on the upper portion of the inclined side of the protruded ring  71  of the cover  70 . In the meantime, a soldering flux ointment  81  is applied by the web fed press on the lower portion of the inclined side of the protruded ring  71  of the cover  70 . Thereafter, the cover  70  is located in the opening  61  of the receiving seat  60 . The housing  50  is then dipped into a vessel containing the molten tin for about two seconds. The dipping depth is corresponding to the thickness of the cover  70 . The molten tin is kept at a temperature of 230° C. or so. As a result, the solder  80  is melted to disperse by the capillary action and the earth gravitation into the narrow end of the acute angle space  72 , in which the molten solder  80  is mixed with the molten flux  81  to form a mixture. The mixture is then dispersed by the capillary action into the interstices between the receiving seat  60  and the cover  70 , with the residue being deposited in the bottom end of the acute angle space  72  to form an annular soldering strip  82 , as shown in FIG. 5. A filling layer  83  is formed in the interstices between the receiving set  60  and the cover  70 . The housing  50  is thus hermetically sealed off. The soldering quality is enhanced by the flux  81 . The receiving seat  60  and the cover  70  are electroplated with a nickel layer to promote the flowing of the molten solder. After the dipping of the housing  50  into the molten tin, the underside of the housing  50  is not tainted with tin.  
         [0015]    The present invention is cost-effective, free of the solder taint and the solder lumps, thereby resulting in the production of the value-added product.
A soldering method is designed to seal an on-line transfer device of cable such that a housing of the device is sealed off to prevent the electromagnetic interference. The method includes a first step in which a fusing portion between a receiving seat and a cover of the housing is furnished with a soft solder. The cover is heated to cause the soft solder to melt to flow into the fusion portion, so as to fuse the receiving seat and the cover together. The housing of the device is free of the soldering marks or lumps.