Patent Publication Number: US-6981896-B2

Title: Plug inner frame with twisted blades

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a plug inner frame with twisted blades to reduce the manufacture cost. 
   2. Description of the Related Art 
   A plug is a necessary element to all kinds of computers, electric appliances, etc and thus plays an important role in daily life. A typical plug generally comprises two or three blades or prongs manufacture, a wire is attached to an end of each blade, and the blades are then embedded into an inner frame. The semi-product comprised of the wires and the blades embedded in the inner frame is then placed into a mold for subsequent injection molding to form the final plug with a housing. 
   Most advanced countries require each blade of the plug to be partially wrapped by an insulating layer at an exposed section thereof, thereby avoiding electric shocks in case that the plug is loosened. The insulating layer is generally made of plastic material and wraps a portion of the exposed section of the blade by means of injection molding. However, the insulating layer is apt to be disengaged from the smooth metal surface of the blade as a result of poor bonding force therebetween. Thus, the insulating layer would slide easily, and sometimes may even fall. The blade is then exposed again and thus could cause an electric shock. 
     FIG. 1  of the drawings illustrates a conventional plug blade  1  including an enclosed section  11  and an exposed section  12 . The exposed section  12  includes a wider front section  121  and a narrower rear section  122  having a transverse through-hole  123 . Plastic material is filled to a face of the narrower rear section  122  and flows through the transverse through-hole  123  to the other face of the narrower rear section  122 . An insulating layer is formed on the narrower rear section  122  after hardening of the plastic material. The bonding force between the insulating layer and the narrower rear section  122  is improved, and the time for filling the plastic material is reduced.  FIG. 2  shows another conventional plug blade  1  that is substantially identical to that of the plug blade  1  in  FIG. 1 , except that the upper and lower faces of the narrower rear section  122  are respectively flush with those of the wider front section  121 . 
   However, an end of a wire must be inserted into and thus embraced by an end of each blade of the plug before subsequent procedure. The blades must face the same direction when proceeding with this wire-inserting procedure in an associated wire-inserting machine. In some countries, the blades of a plug are twisted such that the wire-inserting grooves of the blades face different directions. The current wire-inserting machine could not proceed with the wire-inserting procedure on the plugs with twisted blades. The manufacture cost is largely increased when seeking a solution to this end. In addition, a fault (generally a shallow recess) is formed on a surface of the insulating layer after hardening of the plastic material. The appearance of the plug is thus adversely affected. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a plug inner frame with twisted blades to reduce the manufacture cost. 
   Another object of the present invention is to provide a plug inner frame with twisted blades having an aesthetic appearance. 
   A plug inner frame in accordance with the present invention comprises a frame in the form of a block and at least two blades securely held by the frame. Each blade includes an enclosed section and an exposed section. Each blade includes an end having a wire-receiving groove. A neck is defined between the wire-receiving groove and the exposed section. The neck of each blade is so twisted that the wire-receiving grooves of the blades face the same direction. 
   Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a conventional plug blade. 
       FIG. 2  is a perspective view of another conventional plug blade. 
       FIG. 3  is a perspective view of a first embodiment of a plug inner frame in accordance with the present invention. 
       FIG. 4  is a perspective view of a second embodiment of the plug inner frame in accordance with the present invention. 
       FIG. 5  is a perspective view of a third embodiment of the plug inner frame in accordance with the present invention. 
       FIG. 6  is a perspective view of a fourth embodiment of the plug inner frame in accordance with the present invention. 
       FIG. 7  is a perspective view illustrating a raw material for the plug blade. 
       FIG. 8  is a perspective view illustrating a semi-product of the plug blade in FIG.  7 . 
       FIG. 9  is a perspective view illustrating the semi-product of  FIG. 8  having an insulating layer formed thereon. 
       FIG. 10  is a perspective view of a final plug made from the plug inner frame in FIG.  3 . 
       FIG. 11  is a perspective view of a final plug made from the plug inner frame in FIG.  6 . 
       FIG. 12  is a perspective view of a final plug made from the plug inner frame in FIG.  4 . 
       FIG. 13  is a perspective view of a final plug made from the plug inner frame in FIG.  5 . 
       FIG. 14  is a perspective view of a fifth embodiment of the plug inner frame in accordance with the present invention. 
       FIG. 15  is a perspective view of a sixth embodiment of the plug inner frame in accordance with the present invention. 
       FIG. 16  is a perspective view of a seventh embodiment of the plug inner frame in accordance with the present invention. 
       FIG. 17  is a perspective view of an eight embodiment of the plug inner frame in accordance with the present invention. 
       FIG. 18  is a perspective view illustrating another raw material for the plug blade. 
       FIG. 19  is a perspective view illustrating a semi-product of the plug blade in FIG.  18 . 
       FIG. 20  is a perspective view illustrating the semi-product of  FIG. 19  having an insulating layer formed thereon. 
       FIG. 21  is a perspective view of a final plug made from the plug inner frame in FIG.  14 . 
       FIG. 22  is a perspective view of a final plug made from the plug inner frame in FIG.  17 . 
       FIG. 23  is a perspective view of a final plug made from the plug inner frame in FIG.  15 . 
       FIG. 24  is a perspective view of a final plug made from the plug inner frame in FIG.  16 . 
       FIG. 25  is a perspective view of an embodiment modified from the semi-product of the plug blade of FIG.  9 . 
       FIG. 26  is a perspective view of an embodiment modified from the semi-product of the plug blade of FIG.  20 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 7  illustrates a raw material of a plug blade  22  for manufacturing a plug inner frame ( FIGS. 3 and 6 ) of a final plug in accordance with the present invention. The plug blade  22  includes an enclosed section  221  to be enclosed by a housing (not labeled, see  FIGS. 3 and 6 ) and an exposed section  222 . The exposed section  222  includes a wider front section  223  and a narrower rear section  224 . A transverse through-hole  226  extends from a face of the narrower rear section  224  to the other face of the narrower rear section  224 . A reinforcing guide slot  227  is defined in the narrower rear section  224  and communicated with the transverse through-hole  226 . Also, the reinforcing guide slot  227  extends from a face of the narrower rear section  224  to the other face of the narrower rear section  224 . The enclosed section  221  includes a shallow recess  225  in a front end thereof for filling plastic material into the narrower rear section  224 . The faces of the narrower rear section  224  are lower than those of the wider front section  223 , and two lateral sides of the narrower rear section  224  are lower than those of the wider front section  223 . 
   A wire-receiving groove  228  is defined in a rear end of the enclosed section  221 . A neck  229  is formed between the wire-receiving groove  228  and the exposed section  222 . 
   The neck  229  of the plug blade  22  in  FIG. 7  is twisted to form a plug blade  22  shown in  FIG. 8  such that the wire-receiving groove  228  faces upward for allowing easy insertion of an end of a wire. Next, an insulating layer  220  is formed on the narrower rear section  224 , as shown in FIG.  9 . It is achieved by means of filling molten plastic material into the narrower rear section  224  via the shallow recess  225 . The molten plastic material flows from a face to the other face of the narrower rear section  224  via the transverse through-hole  226  and the slot  227 . The insulating layer  220  is formed after hardening of the plastic material. 
   Next, two of the plug blades  22  in  FIG. 8  can be placed into a mold, and plastic material is injected into the mold to form an inner frame  2  comprising a frame  21  in the form of a plug and two plug blades  22  securely held by the frame  21 , best shown in FIG.  3 .  FIG. 10  is a perspective view of a final plug  3 A made from the plug inner frame  2  in  FIG. 3  after an injection molding procedure. Alternatively, the plug blade  22  in  FIG. 9  can be used to form an inner frame  2 C shown in FIG.  6 . The inner frame  2 C includes a frame  21 C, two blades  22 C, and a grounding prong  4 A.  FIG. 11  is a perspective view of a final plug  3 B made from the plug inner frame  2 C in  FIG. 6  after an injection molding procedure. 
     FIG. 25  illustrate an embodiment modified from the embodiment of  FIG. 9 , wherein the hole in the exposed section  222  in  FIG. 9  is omitted, and the wire-receiving groove  228  is in the form of a circle. The plug blade  22  in  FIG. 25  can be used to form an inner frame  2 A shown in FIG.  4 . The inner frame  2 A includes a frame  21 A and two blades  22 A.  FIG. 12  is a perspective view of a final plug  3 C made from the plug inner frame  2 A in  FIG. 4  after an injection molding procedure. Alternatively, the plug blade  22  in  FIG. 25  can be used to form an inner frame  2 B shown in FIG.  5 . The inner frame  2 B includes a frame  21 B, two blades  22 B, and a grounding prong  4 .  FIG. 13  is a perspective view of a final plug  3 D made from the plug inner frame  2 B in  FIG. 5  after an injection molding procedure. 
     FIG. 18  illustrates another embodiment of a raw material of a plug blade  22  for manufacturing a plug inner frame ( FIGS. 14 and 17 ) in accordance with the present invention. The plug blade  22  includes an enclosed section  221  to be enclosed by a housing (not labeled, see  FIGS. 14 and 17 ) of a final plug and an exposed section  222 . The exposed section  222  includes a wider front section  223  and a narrower rear section  224 . A transverse through-hole  226  extends from a face of the narrower rear section  224  to the other face of the narrower rear section  224 . A reinforcing guide slot  227  is defined in the narrower rear section  224  and communicated with the transverse through-hole  226 . Also, the reinforcing guide slot  227  extends from a face of the narrower rear section  224  to the other face of the narrower rear section. The enclosed section  221  includes a shallow recess  225  in a front end thereof for filling plastic material into the narrower rear section  224 . The faces of the narrower rear section  224  are flush with those of the wider front section  223 , and two lateral sides of the narrower rear section  224  are lower than those of the wider front section  223 . 
   A wire-receiving groove  228  is defined in a rear end of the enclosed section  221 . A neck  229  is formed between the wire-receiving groove  228  and the exposed section  222 . 
   The neck  229  of the plug blade  22  in  FIG. 18  is twisted to form a plug blade  22  shown in  FIG. 19  such that the wire-receiving groove  228  faces upward for allowing easy insertion of an end of a wire. Next, an insulating layer  220  is formed on the narrower rear section  224 , as shown in FIG.  20 . It is achieved by means of filling molten plastic material into the narrower rear section  224  via the shallow recess  225 . The molten plastic material flows from a face to the other face of the narrower rear section  224  via the transverse through-hole  226  and the slot  227 . The insulating layer  220  is formed after hardening of the plastic material. 
   Next, two of the plug blades  22  in  FIG. 20  can be placed into a mold, and plastic material is injected into the mold to form an inner frame  2  comprising a frame  21  in the form of a block and two plug blades  22 , best shown in FIG.  14 .  FIG. 21  is a perspective view of a final plug  3 A made from the plug inner frame  2  in  FIG. 14  after an injection molding procedure. Alternatively, the plug blade  22  in  FIG. 20  can be used to form an inner frame  2 C shown in FIG.  17 . The inner frame  2 C includes a frame  21 C, two blades  22 C, and a grounding prong  4 A.  FIG. 22  is a perspective view of a final plug  3 B made from the plug inner frame  2 C in  FIG. 17  after an injection molding procedure. 
     FIG. 26  illustrate an embodiment modified from the embodiment of  FIG. 20 , wherein the hole in the exposed section  222  in  FIG. 20  is omitted, and the wire-receiving groove  228  is in the form of a circle. The plug blade  22  in  FIG. 26  can be used to form an inner frame  2 A shown in FIG.  15 . The inner frame  2 A includes a frame  21 A and two blades  22 A.  FIG. 23  is a perspective view of a final plug  3 C made from the plug inner frame  2 A in  FIG. 15  after an injection molding procedure. Alternatively, the plug blade  22  in  FIG. 26  can be used to form an inner frame  2 B shown in FIG.  16 . The inner frame  2 B includes a frame  21 B, two blades  22 B, and a grounding prong  4 .  FIG. 24  is a perspective view of a final plug  3 D made from the plug inner frame  2 B in  FIG. 16  after an injection molding procedure. 
   According to the above description, it is noted that the procedure for a current wire-inserting machine needs no change, as the inner frame  2 ,  2 A,  2 B,  2 C in accordance with the present invention with twisted blades  22 ,  22 A,  22 B,  22 C allows the wire-receiving holes  228  to face the same direction. The fault resulting from the formation of the insulating layer is located in a position adjacent to the shallow recess  225  for filling the molten plastic material. Nevertheless, the shallow recess  225  is enclosed by the housing after formation of the whole plug  3 A,  3 B,  3 C,  3 D. Thus, the appearance of the insulating layer is not adversely affected. Further, due to provision of the reinforcing guide slot  227  communicated with the transverse through-hole  226 , the air on the faces of the metal blade can be well expelled, and the molten plastic material flowing randomly on the faces of the metal blades may flow from one face to the other of each metal blade. Thus, the thickness of the insulating layer is more uniform after formation. Further, the overall structure of the plug blade has appropriate rigidity from metal and appropriate softness from the plastic material, thereby having an optimal resistance to bending. The finally formed plugs  3 A,  3 B,  3 C, and  3 D meet requirements of different countries. 
   Although the invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the invention as hereinafter claimed.