Abstract:
A silver contact structure for conductive blades aims at providing an increased contact area between a silver contact and a conductive blade so that the silver contact may be fixed more securely without breaking off. The conductive blade has a fastening section running through which has a non-circular and irregular cross section to increase the horizontal frictional force so that the silver contact is less likely to break off and may result in a longer service life. The contact area between the silver contact and the conductive blade also increases, thus enhancing the heat dissipation.

Description:
[0001]     This application is a Divisional of co-pending application Ser. No. 10/802,749, filed on Mar. 18, 2004, the entire contents of which are hereby incorporated by reference and for which priority is claimed under 35 U.S.C. § 120. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a silver contact structure for conductive blades and particularly to a technique that employs a novel conductive blade structure to increase the strength of silver contacts and heat dissipation.  
       BACKGROUND OF THE INVENTION  
       [0003]     Conventional techniques for fabricating silver contacts often encounter some problems, notably:  
         [0004]     Silver contacts are usually used in switches to establish conductive connections. When in use, the silver contact receives a strike from a connection leg to form the connection contact of the switch. The instant the switch is connected, the silver contact generates great heat. If the heat is not dispersed smoothly, the contact could melt and result in damage to the switch. The switch could malfunction and its service life will be shortened.  
         [0005]     To remedy this problem, a technique has been disclosed in R.O.C. patent publication No. 448454 entitled “Method for fastening silver contacts of conductive blades”. It punches a fastening hole on a conductive blade that is concave on the upper side and convex on the lower side. Extra material for the conductive blade is extruded to form an extended wedging flange. The fastening hole has screw threads formed therein to provide a horizontal frictional force so that the silver contact is less likely to break off. Finally, the top section of the silver wire is formed as a flange through an upper mold, and a lower die is deployed to ram the wedging flange towards the fastening hole so that the silver wire is filled and wedged securely in the fastening hole. The aforesaid technique can fix the silver contact more securely without breaking loose. The flange increases the heat dissipation area of the silver contact. However, in the design of switches, the interval between the movable contact and the closed circuit contact has to comply with safety regulations (for instance under European safety regulations the interval is 3 mm), the flange will affect the interval between the movable contact and the closed circuit contact, hence the relative positions of the elements in the switch have to be rearranged.  
         [0006]     Referring to  FIG. 1 , to further resolve the problems set forth above, an injection forming approach was proposed to embed the silver contact when the conductive blade is formed by injection. Such a design does not create a flange, and the positions of the elements in the switch do not need to be rearranged. However, embedding by injection forming requires fabricating new molds to suit the different contact sizes of various switches. The manufacturing processes cannot be modularized. As a result, manufacturing costs are increased. Moreover, such an approach does not increase the heat dissipation area between silver contact and conductive blade.  
       SUMMARY OF THE INVENTION  
       [0007]     The primary object of the invention is to solve the aforesaid problems. The invention provides a structure to increase the contact area between the silver contact and the conductive blade. The conductive blade has a fastening section which has a non-circular and irregular horizontal cross section. In addition, the conductive blade has fixing zones that connect to each other and an end formed with a chamfered angle. The non-circular and irregular horizontal cross section of the fastening section can increase the horizontal frictional force. The end provides a retaining force when the silver contact is struck by the connection leg. Both features mentioned above help to fasten the silver contact more securely without loosening. Moreover, the contact area of the silver contact increases, which also increases the heat conduction area and provides improved heat dissipation.  
         [0008]     The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a cross section of a conventional silver contact.  
         [0010]      FIG. 2  is a perspective view of a first embodiment of the conductive blade of the present invention.  
         [0011]      FIG. 3  is a perspective view of a first embodiment of a first upper die of the invention.  
         [0012]      FIGS. 4A, 4B  and  4 C are schematic views of the fabrication process of the first embodiment of the invention.  
         [0013]      FIG. 5  is a perspective view of a second embodiment of the conductive blade of the present invention.  
         [0014]      FIG. 6  is a top view of the second embodiment of the conductive blade of the present invention.  
         [0015]      FIGS. 7A through 7F  are schematic views of the fabrication process of the second embodiment of the invention.  
         [0016]      FIG. 8  is a cross section of a third embodiment of the present invention.  
         [0017]      FIG. 9  is a cross section of a fourth embodiment of the present invention.  
         [0018]      FIG. 10  is a cross section of a fifth embodiment of the present invention.  
         [0019]      FIG. 11  is a cross section of a sixth embodiment of the present invention.  
         [0020]      FIG. 12  is a cross section of a seventh embodiment of the present invention.  
         [0021]      FIG. 13  is a cross section of an eighth embodiment of the present invention.  
         [0022]      FIG. 14  is a block diagram of the fabricating process for the first embodiment of the invention.  
         [0023]      FIG. 15  is a block diagram of the fabricating process for the second embodiment through to the eighth embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     Please refer to  FIGS. 2, 3 ,  4 -A,  4 -B,  4 -C and  14  for a first embodiment of the invention. On a conductive blade  10 , there is a fastening section  11  corresponding to the location of a silver contact  17 . The fastening section  11  has a non-circular horizontal cross section. Fabrication of the first embodiment includes the following steps in the order of A: stamping a blank, and B: planting a silver wire.  
         [0025]     Step A: stamping a blank. First, form the non-circular and irregular fastening section  11  on the conductive blade  10  by stamping through a first upper die  20 . The fastening section  11  has a size about the width of the flange disclosed in R.O.C. patent publication No. 448454 “Method for fastening silver contacts of conductive blades”. In this embodiment, a striking surface is added to the silver contact  17  so that the conductive properties are improved without increasing the amount of silver consumed. The first upper die  20  has extension angle  18 , which is formed in a saw shape. Thus after the conductive blade  10  has been stamped by the first upper die  20 , the contact area between the fastening section  11  and the silver contact  17  increases to improve heat dissipation. Moreover, when the silver contact  17  is wedged in the fastening section  11 , the fastening section  111  provides a horizontal frictional force to prevent the silver contact  17  from moving horizontally.  
         [0026]     Step B: planting a silver wire. Place the conductive blade  10  on a first lower die  21 ; place a silver wire  16  in the fastening section  11 ; press and fill the silver wire  16  in the fastening section  11  through a third upper die  23  to form the silver contact  17 .  
         [0027]     Refer to  FIGS. 5, 6   s    7 -A through  7 F and  15  for a second embodiment of the silver contact  17   a . The fastening section  11   a  formed on the conductive blade  10   a  has a first fixing zone  15   a  and a second fixing zone  19   a  that connect each other. The area adjacent to the juncture of the first and the second fixing zones  15   a  and  19   a  forms an end  121  with a chamfered angle. The process for fabricating the conductive blade  10   a  includes the following steps in the order of C: stamping a blank; D: stamping the blank for a second time; and E: planting a silver wire.  
         [0028]     Step C: stamping a blank through a first upper die  20   a  on the conductive blade  10   a  to form a first fixing zone  15   a . The first upper die  20   a  has a punch end  201   a  which has an extended angle  18   a . In this embodiment, the extended angle  18   a  is tapered at the lower end with the outer side formed in a saw shape.  
         [0029]     Step D: stamping the blank for a second time. Form a second fixing zone  19   d  on the conductive blade  10   a  that is smaller than the first fixing zones  15   a  through a second upper die  22  smaller than the first upper die  20   a . The second upper die  22  is a cylinder.  
         [0030]     Step E: planting a silver wire. Place the conductive blade  10   a  on a first lower mold  21 ; place a silver wire  16  in the fastening section  11   a  which consists of the first fixing zone  15   a  and the second fixing zone  19   a ; press and fill the silver wire  16  in the fastening section  11   a  through a third upper die  23  to complete the fabrication of the silver contact  17   a . The first fixing zone  15   a  has one end forming an end  121  with a chamfered angle on the peripheral side.  
         [0031]     Refer to  FIGS. 8 and 9  for the conductive blades  10   b  and  10   c  of the third and fourth embodiments. In the third embodiment, the first fixing zone  15   b  is a conical trough with a tapered lower end, and the second fixing zone  19   b  is a circular trough with the inner side formed in a saw shape. In the fourth embodiment, the first and second fixing zones  15   c  and  19   c  are all formed in a saw shape, and the first fixing zone  15   c  is a conical trough with a tapered lower end. The fabrication process for the silver contact (not shown in the drawings) is substantially same as the one previously discussed, namely including A: stamping a blank; B: stamping the blank for a second time; and C: planting a silver wire to form the silver contact (not shown in the drawings).  
         [0032]     Refer to  FIGS. 10 through 13  for a fifth through eighth embodiment of the conductive blades  10   d ,  10   e ,  10   f  and  10   g  of the invention. The conductive blades  10   d ,  10   e ,  10   f  and  10   g  have respectively, a first, second and third fixing zone  15   d ,  19   d  and  14   d . The fabrication process for the fifth embodiment includes C: stamping a blank; D: stamping the blank for a second time; and E: planting a silver wire.  
         [0033]     Step C: stamping the blank. Form a first fixing zone  15   d  and a third fixing zone  14   d  on an upper end and a lower end of the conductive blade  10   d  that constitute a conical trough with a tapered end towards the horizontal center of the conductive blade.  
         [0034]     Step D: stamping the blank for a second time. Form a second fixing zone  19   d  on the conductive blade  10   d  that is smaller than the first fixing zone  15   d  and the third fixing zone  14   d . In the fifth embodiment, only the first fixing zone  15   d  has the peripheral side formed in a saw shape.  
         [0035]     Step E: planting a silver wire (not shown In the drawings). Place the silver wire in the fastening section  1  id that consists of the first, second and third fixing zones  15   d ,  19   d  and  14   d . Press and fill the silver wire (not shown in the drawings) into the fastening section  1   d . Fabrication processes of the sixth embodiment ( FIG. 11 ) and the seventh embodiment ( FIG. 12 ) are substantially similar to the one previously discussed. However, in the sixth embodiment, only the third fixing zones  14   e  ( FIG. 11 ) is formed in a saw shape, while in the seventh embodiment only the second fixing zone  19   f  ( FIG. 12 ) is formed in a saw shape. In the eighth embodiment, the first, second and third fixing zones  15   g ,  19   g  and  14   g  are all formed in a saw shape.  
         [0036]     While the preferred embodiments of the invention have been set forth for the purpose of disclosure, modifications to the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments that do not depart from the spirit and scope of the invention.