Abstract:
A swivel plug is disclosed to have each metal conducting plug element of the front plug body provided with a male coupling end and each terminal of the rear plug body provided with a female coupling end pivotally coupled to the male coupling end of the respective metal conducting plug element, which female coupling end having a coupling hole with a tapered periphery, which male coupling end having a split protrusion inserted into the coupling hole of the female coupling end expanded into radial spring arms that pressed on the tapered periphery of the coupling hole.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     a. Field of the Invention  
         [0002]     The present invention relates to a plug and more particularly, to a swivel plug.  
         [0003]     b. Description of the Related Art  
         [0004]     A conventional electric plug  1 , as shown in  FIG. 1 , has the metal conducting blades  11  axially extended from the front side of the housing  12 . This design of electric plug  1  requires much vertical installation place.  FIG. 2  illustrates another structure of electric plug that requires less vertical installation space. As illustrated, the electric plug  2  comprises a housing  22 , two metal conducting blades  21  perpendicularly extended out of the bottom side of the housing  22 , a pull ring  24  coupled to the housing  22  for pulling by hand to remove the metal conducting blades  21  from the electric socket. U.S. Pat. No. 5,567,181 discloses a similar design. This design of electric plug provides handle means to facilitate grasping. However, pulling the pull ring or handle means causes a concentration of stress. Because the housing is slightly softened when the internal circuit is bearing a load to produce heat, pulling the pull ring or handle means may cause damage to the housing. Is this design is employed to an electric plug having two metal conducting blades and one grounding prong, pulling the pull ring or handle means may bias the housing, thereby increasing pulling resistance, and much effort should be employed to remove the electric plug from the electric socket. Further, this design of electrical plug still requires much horizontal installation space.  
         [0005]     FIGS.  3 ˜ 4  show a three prong swivel plug constructed according to U.S. Pat. No. 5,658,152. According to this design, the contacts  32  of the front female plug portion and the contacts  31  of the rear male plug portion each have a laterally extending protrusion  321  or  311 . The laterally extending protrusions  321  of the front female plug portion are respectively coupled to the laterally extending protrusions  311  of the contacts  31  of the rear male plug portion. This contact connection arrangement greatly reduces the height of the housing of the swivel plug. However, the contact side is unstable, not suitable for transmitting a big current. When transmitting a big current, a high temperature will be produced due to unstable contact between the contacts.  
         [0006]     U.S. Pat. No. 6,663,396, issued to the present inventor, disclosed an electric plug having horizontal/vertical installation modes. According to this design, as shown in  FIGS. 6 and 7 , rivets  511 ,  512  are used to pivotally connect the conducting blades  41 ,  42  to the metal terminals  51 ,  52 , for enabling the front housing  4  to be turned relative to the rear housing  5  about an axis X-X between two positions within 90 degrees. Referring to  FIGS. 7C and 7D , when a grounding prong  43  and a grounding terminal  53  are added to the electric plug, the distance D between the two adjacent pivots  511 ,  531  is too short to meet the related safety code.  FIGS. 8A and 8B  show the rivet  511  fastened to the conducting blade  41  and the respective metal terminal  51 . Because there is a limitation to the height H of the conducting blade  41  and the metal terminal  51  (normally limited to about 5˜6 mm), the size of the heads and shaft of the rivet  511  must be relatively constrained, i.e., the heads and the shaft of the rivets  511  must not surpass 5 mm and 2 mm respectively. However, a relatively bigger rivet provides a relatively greater contact area and a relatively stronger retaining force. According to the embodiment shown in  FIG. 8B , the rivet  511  provides a strong retaining force to join the conducting blade  41  and the metal terminal  51 . However, it requires much effort to turn the conducting blade  41  relative to the metal terminal  51 . According to the embodiment shown in  FIG. 8C , a spring washer  512  is mounted on the rivet  511  and stopped between one head of the rivet  511  and the metal terminal  51 . The use of the spring washer  512  prevents locking of the conducting blade  41  to the metal terminal  51 , however it relatively increases the assembly time and cost. Further, because the heads of the rivet  511  respectively protruding over the conducting blade  41  and the metal terminal  51 , thereby increasing the combined thickness T 1  or T 2 .  
         [0007]     Therefore, it is desirable to provide a swivel plug that eliminates the drawbacks of the aforesaid prior art designs.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a swivel plug, which has the blades (and grounding prong, if any) directly coupled to the respective terminals without the use of external rivet or pivot means to save the space and the manufacturing cost. It is another object of the present invention to provide a swivel plug, which greatly increases the contact area between the blades and grounding prong and the respective terminals, assuring positive conductivity and stable connection. It is still another object of the present invention to provide a swivel plug, which requires less installation space. It is still another object of the present invention to provide a swivel plug, which meets local electrical safety code.  
         [0009]     To achieve these and other objects of the present invention, the swivel plug comprises a front plug body, the front plug body comprising a housing, and a plurality of metal conducting plug elements fastened to and partially extended out of the housing of the front plug body, the metal conducting plug elements each having a coupling end; and a rear plug body, the rear plug body comprising a housing coupled to the housing of the front plug body and turnable relative to the housing of the front plug body between a horizontal position and a vertical position, and a plurality of terminals, the terminals each having a coupling end respectively pivoted to the coupling ends of the metal conducting plug elements of the front plug body; wherein the coupling end of one terminal and the coupling end of the respective metal conducting plug element include a female coupling end and a male coupling end, the female coupling end having a coupling hole, the coupling hole having a tapered periphery, the male coupling end having a split protrusion protruded from one side thereof and inserted into the tapered coupling hole of the respective female coupling end, the split protrusion being expanded into at least one radial spring arm pressed on the tapered periphery of the respective coupling hole. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is an elevational view of an electric plug according to the prior art.  
         [0011]      FIG. 2  is an elevational view of another structure of electric plug according to the prior art.  
         [0012]      FIG. 3  is an exploded view of a three prong swivel plug constructed according to U.S. Pat. No. 5,658,152.  
         [0013]      FIG. 4  is a schematic drawing showing the connection between contacts according to U.S. Pat. No. 5,658,152.  
         [0014]      FIG. 5  is a sectional view taken in an enlarged scale along line  5 - 5  of  FIG. 4 .  
         [0015]      FIG. 6  is an exploded view of an electric plug having horizontal/vertical installation modes according to U.S. Pat. No. 6,663,396.  
         [0016]     FIGS.  7 A˜D are schematic drawings showing connection between conducting blades and metal terminals according to U.S. Pat. No. 6,663,396.  
         [0017]      FIG. 8   8 A˜ 8 C are schematic drawings showing riveting structure between conducting blade and metal terminal according to the prior art.  
         [0018]      FIG. 9  is a sectional view of a swivel plug according to the present invention.  
         [0019]      FIG. 10  is a schematic drawing showing the front plug body turned relative to the rear plug body between two positions within 90 degrees according to the present invention.  
         [0020]      FIG. 11  is a schematic drawing showing the structure of the housing of the front plug body and the structure of the housing of the rear plug body according to the present invention.  
         [0021]      FIG. 12  is an enlarged view of a part of the present invention, showing the connection between the blades and grounding prong and the respective terminals.  
         [0022]      FIG. 13  is a schematic drawing showing the connection between the lade and the respective terminal according to the present invention (I).  
         [0023]      FIG. 13A  is a sectional view taken in an enlarged scale along line  13 A- 13 A of  FIG. 13 .  
         [0024]      FIG. 14  is a schematic drawing showing the connection between the blade and the respective terminal according to the present invention (II).  
         [0025]      FIG. 15  is a schematic drawing showing the connection between the blade and the respective terminal according to the present invention (III).  
         [0026]      FIG. 16  is a schematic drawing showing the connection between the blade and the respective terminal according to the present invention (IV).  
         [0027]      FIG. 17  is a schematic drawing showing the connection between the blade and the respective terminal according to the present invention (V).  
         [0028]      FIG. 18  is a schematic drawing showing the connection between the blade and the respective terminal according to the present invention (VI).  
         [0029]      FIG. 19  is a schematic drawing showing the connection between the blade and the respective terminal according to the present invention (VII).  
         [0030]      FIG. 20  is a top view of  FIG. 19 .  
         [0031]      FIG. 21  is an elevational view of the swivel plug according to the present invention.  
         [0032]      FIG. 22  is an elevational view of an alternate form of the swivel plug according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]     Referring to FIGS.  9 ˜ 11 , a swivel plug is shown comprised of a front plug body  6  and a rear plug body  7 . The front plug body  6  and the rear plug body  7  each comprise a respective housing  60  or  70 . As shown in  FIG. 11 , the housing  60  of the front plug body  6  has a rear coupling portion  601 ; the housing  70  of the rear plug body  7  has a front coupling portion  701  fitting and pivotally connected to the rear coupling portion  601  of the housing  60  of the front plug body  6 .  
         [0034]     Referring to  FIG. 12  and FIGS.  9 ˜ 11  again, the front plug body  6  further comprises a positive pole blade  61 , a negative pole blade  62 , and a grounding prong  63 . The blades  61 , 62  and the grounding prong  63  are respectively fastened to the inside of the housing  60  of the front plug body  6  and extended out of the housing  60  through a respective hole  602  in the housing  60 . The rear plug body  7  further comprises a positive pole terminal  71 , a negative pole terminal  72 , and a grounding terminal  73  respectively connected to a respective conductor in a power cord  8 . The blades  61 , 62  and the grounding prong  63  are respectively pivoted to the positive pole terminal  71 , negative pole terminal  72  and grounding terminal  73  of the rear plug body  7  by a respective pivot  67 . The pivots  67  are axially aligned in a line X-X. The blades  61 , 62  and the grounding prong  63  may be variously embodied to meet the related electric codes of different countries. According to the embodiment shown in  FIGS. 10 and 12 , the blades  61 , 62  and the grounding prong  63  are perpendicularly extended out of the bottom side of the housing  60  of the front plug body  6 . Alternatively, the blades  61 , 62  and the grounding prong  63  can be made extended out of the front side of the housing  60  of the front plug body  6  in horizontal with the housing  60 . Further, the grounding prong  63  is an angled prong having a longitudinal part  631  and a transverse part  632 . The longitudinal part  631  and the transverse part  632  can be so made that the longitudinal part  631  has one end pivoted to the grounding terminal  73  and the other end formed integral with one end of the transverse part  632 . Alternatively, the longitudinal part  631  and the transverse part  632  can be so made that the longitudinal part  631  has one end pivoted to the grounding terminal  73  and the other end terminating in a plug portion  6311  fastened to a retaining hole  6321  in one end of the transverse part  632  (see  FIG. 12 ).  
         [0035]     In order to achieve good electric conductivity and positive connection, the blades  61 , 62  and grounding prong  63  and the terminals  71 , 72 , 73  must be specially designed. As shown in  FIGS. 13 and 14 , the blade  61  has the rear end (the end to be pivoted to the respective terminal  71 ) stamped, thereby forming a split protrusion  611  and an axial hole  612  at the bottom side of the split protrusion  611 . The protrusion  611  has radial crevices  613  (see  FIG. 13A ). The terminal  71  has a coupling hole  712  for receiving the split protrusion  611 . The coupling hole  712  has a tapered periphery  711 . After insertion of the split protrusion  611  of the blade  61  into the coupling hole  712  of the terminal  71  (see  FIG. 14 ), an upper die A and a bottom die B are attached to the split protrusion  611  at the top and bottom sides respectively (see  FIG. 15 ) and then pressed to expand the radial crevices  613  of the split protrusion  611 , and therefore the split protrusion  611  forms a plurality of radial spring arms  614  that are pressed on the tapered periphery  711  within the coupling hole  712  of the terminal  71  (see  FIG. 16 ). Thus, the blade  61  is pivoted to the terminal  71  without an external rivet or pivot means. Further, the coupling hole  712  of the terminal  71  has a vertical section  713  at the bottom side of the tapered periphery  711  that prevents locking of the blade  61  to the terminal  71 . The connection between the other blade  62  or grounding terminal  63  and the respective terminal  72  or  73  is achieved in the same manner.  
         [0036]     As an alternate form of the present invention, the terminals  71 , 72 , 73  are made having the aforesaid split protrusion  611  and the blade  61 , 62  or grounding prong  63  is made having the aforesaid coupling hole  712  with a tapered periphery  711 .  
         [0037]     Further, a recessed hole  615  (see  FIG. 17 ) or through hole  616  (see  FIG. 18 ) may be formed in the bottom side of the radial crevices  613 . Further, a tapered hole  617  may be formed in between the axial hole  612  and the through hole  616  (see  FIG. 19 ). The tapered hole  617  having a diameter made gradually reduced from the axial hole  612  toward the through hole  616 .  FIG. 20  is a top view showing the radial spring arms  614  extended out and pressed on the tapered periphery  711  within the coupling hole  712  (not shown) of the terminal  71 .  
         [0038]      FIG. 21  is an elevational view of the swivel plug according to the present invention. As illustrated, the front plug body  6  is coupled to the rear plug body  7  and turnable relative to the rear plug body  7  between a horizontal position and a vertical position, and the rear plug body  7  has a power cord  8  extended out of the rear side.  FIG. 22  is an elevational view of an alternate form of the swivel plug according to the present invention. According to this embodiment, the rear plug body  7  has an electric socket  9  formed in the rear side.  
         [0039]     As indicated above, the connection between the blade or grounding prong and the respective terminal is achieved by stamping to reduce the manufacturing cost. Because the radial spring arms of the blade (or grounding prong) are pressed on the tapered periphery within the coupling hole of the respective terminal, the contact area between the blade (or grounding prong) and the respective terminal is relatively increased. Because no external rivet or pivot means is used, the total height is relatively reduced. Because the split protrusion of the blade (or grounding prong) is processed into radial spring arms that are pressed on the tapered periphery with the coupling hole of the respective terminal, the blade (or grounding prong) can be freely turned relative to the respective terminal without falling when maintained in close contact with the respective terminal.  
         [0040]     A prototype of angle-adjustable plug has been constructed with the features of FIGS.  9 ˜ 22 . The angle-adjustable plug functions smoothly to provide all of the features discussed earlier.  
         [0041]     Although particular embodiments of the present invention have been shown and described, it will be understood that various modifications and changes could be made thereunto without departing from the spirit and scope of the invention disclosed.