Abstract:
The present invention discloses a power plug providing leakage protection comprising a casing, reset button and test button provided to the surface of the top of the casing; wherein movable springs respectively connected to power supply live wire and neutral wire pins are fixedly provided to the bottom part of a circuit board, movable contact points have separate electrical connections with free ends of the movable springs, stationary contact points corresponding to the movable contact points are provided to the circuit board and connected to a loading power supply cable; and a tripping device capable of contacting or disconnecting the movable and stationary contact points is provided inside the casing. The present invention is safe; has strong protective performance, simple structure, and reasonable design, and is safe, suited for mass production, and able to detect a power cable leakage failure and promptly sever the loaded connection with the power supply.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a national phase entry under 35 U.S.C. §371 of International Application No. PCT/CN2010/000059, filed Jan. 13, 2010, published in Chinese, which claims priority from CN 200920057724.4, filed May 27, 2009, all of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a power plug having a leakage protection function, i.e., ground fault circuit interrupter (abbreviated as GFCI), and refers in particular to a power plug having a leakage protection function that is installed onto a household appliance such as an air conditioner, a refrigerator, or a television. 
         [0003]    At present, people connect household appliances to the utility power supply via power plugs; the majority of power plugs that are currently commercially available are structured so as to comprise a casing, two or three externally exposed pins and a power cable wire connected to the pins being installed onto the casing, such that a direct and fixed connection is made between the power cable wire of the power plug and a power contact on a circuit board inside the appliance, thus forming an electrical connection. When there is a need to use a household appliance, the pins of the power plug need only be inserted into the socket to achieve a connection between the household appliance and the utility power supply. Because the interior of such power plugs does not possess a leakage protection structure, pulling the pins out creates a leakage failure with a live wire, neutral wire, and ground wire; the live, neutral, and ground wires encounter a leaking fault, and a short-circuiting failure occurs between the live and neutral wires on the output terminal of the power plug, and the household appliance suffers direct damage. There have already appeared a number of power plugs having leakage protection functions; despite the ability thereof to cut off the power supply when a failure occurs in order to act to protect the household appliance, these power plugs have at present a relatively more complicated internal structure, which is not suited for mass production, and thus there is a need to solve the above problems. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    To overcome the above-described technical deficiencies, the present invention provides a power plug having a leakage protection function, which is safe and has strong protective performance, has a simple structure and reasonable design, is suited for mass production, and is able during use to detect a power cable leakage failure and to promptly sever the loaded connection with the power supply. 
         [0005]    The power plug having a leakage protection function comprises a casing, a reset button and a test button being provided to the surface of the top of the casing; a power supply live wire pin, neutral wire pin, and ground wire pin being provided to the bottom of the casing; a circuit board being provided to the interior of the casing; and a leakage protection circuit for detecting a cable leakage failure on the output of the power source being provided onto the circuit board; wherein a pair of movable springs for separate electrical connections with the power supply live wire plug and the neutral wire plug are fixedly provided to the bottom of the circuit board, movable contact points of the separate electrical connections being on the free ends of the pair of movable springs, and a pair of stationary contact points corresponding to the movable contact points being provided on the circuit board, such that the stationary contact points are connected with the power supply cable for the connection load; and wherein a tripping device capable of contacting or disconnecting the movable contact points and stationary points is provided inside the casing, the tripping device comprising a rod that is fixedly connected to the reset button, such that a rod reset spring that is disposed on the rod is fixed to a trip board on the free ends of the pair of movable springs and is provided to the stationary armature and movable armature inside the trip coil, the lower end of the rod being slidably connected to the movable armature and a locking bit being provided on the rod, and the trip board being provided with a bayonet of the locking bit, which can lock the rod in after the stationary armature has attracted the movable armature. 
         [0006]    The casing is constituted of a front-top cover, a rear-top cover, and a lower cover for fastening the front-top cover and rear-top cover together, the reset button and test button being provided in holes on the top surface of the rear-top cover and exposed to the exterior; the power supply live wire pin, neutral wire pin, and ground wire pin perforate holes in the lower surface of the lower cover and extend outwardly. 
         [0007]    One end of the movable armature stretches out of the trip coil, that end being provided with an annular groove; the lower end of the rod is provided with a longitudinal slot that slidably interlocks with the annular groove. 
         [0008]    A protective shield is fixedly provided to the bottom of the circuit board, the trip coil being fixed into the protective shield, and an opening through which the movable armature perforates being arranged on the protective shield; a pair of fixed ears are disposed on the top of the protective shield, one end of each of the pair of movable springs being fixed to the pair of fixed ears, and a pin fixation board is fixedly provided to the bottom of the protective shield, jacks for fixing the pins being provided on the pin fixation board. 
         [0009]    The trip board is provided with two connection blocks, fixation holes being arranged on the connection blocks; the free ends of the movable springs are inserted into and locked into the fixation holes and cause the trip board to be fixed to the end parts of the two movable springs, the movable contact points being provided on the connection blocks and electrically connected to the movable springs. 
         [0010]    The bottom surface of the test button is provided with a U-shaped metal pin and test reset spring; the bottom of the circuit board corresponding to the U-shaped metal pin is provided with two test solder joints, which together with the U-shaped metal pin constitute a simulation test switch. 
         [0011]    The leakage protection circuit comprises a trip coil, two zero-sequence transformers, a control chip, and a silicon controlled rectifier; a metal ring of the zero-sequence transformer is disposed on the power supply cable of the connection load, such that a secondary coil of the zero-sequence transformer is connected to the input end of the control chip, the input end of the control chip is connected with the control gate of the silicon controlled rectifier, and the cathode of the silicon controlled rectifier is connected with one end of the trip coil. 
         [0012]    The advantageous effects of the present invention are (1) when there is an inadvertent leakage failure while the household appliance is in use, when the leakage current reaches 4˜6 mA, then the power supply can be cut off, thus acting to protect the household appliance; (2) when any one phase of the power supply live wire or neutral wire experiences circuit break, the power supply can be cut off, thus acting to protect the household appliance; and (3) the present invention has a relatively simple interior structure and a reasonable design, and is easily mass-produced. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a three-dimensional drawing of the present invention; 
           [0014]      FIG. 2  is a complete exploded view of the present invention; 
           [0015]      FIG. 3  is a plan view of the present invention; 
           [0016]      FIG. 4  is a cut-away view in the A-A direction of  FIG. 3 ; 
           [0017]      FIG. 5  is a three-dimensional exploded view of the present invention; 
           [0018]      FIG. 6  is a three-dimensional exploded view of  FIG. 5  after the lower cover is removed; 
           [0019]      FIG. 7  is a three-dimensional drawing of the tripping device of the present invention; 
           [0020]      FIG. 8  is a three-dimensional drawing of  FIG. 7  after the reset button and test button are removed; 
           [0021]      FIG. 9  is a three-dimensional drawing of  FIG. 8  after the covers are removed; 
           [0022]      FIG. 10  is a three-dimensional drawing of  FIG. 9  after the trip board is removed; 
           [0023]      FIG. 11  is a coordinated view between the movable armature and stationary armature of the present invention; and 
           [0024]      FIG. 12  is a schematic circuitry diagram of the leakage protection circuit of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    The following combines the drawings with an embodiment of the present invention to provide a more detailed description. 
         [0026]    With reference to  FIGS. 1 to 11 , the present invention discloses a power plug having a leakage protection function, comprising a casing  1 , a reset button  11  and a test button  12  being provided to the surface of the top of the casing  1 ; a power supply live wire pin  2 , neutral wire pin  3 , and ground wire pin  4  being provided to the bottom of the casing  1 ; a circuit board  5  being provided to the interior of the casing  1 ; and a leakage protection circuit for detecting a cable leakage failure on the output of the power source being provided onto the circuit board  5 ; wherein a pair of movable springs  7  for separate electrical connections with the power supply live wire plug  2  and the neutral wire plug  3  are fixedly provided to the bottom of the circuit board  5 , movable contact points  71  of the separate electrical connections being on the free ends of the pair of movable springs  7 , and a pair of stationary contact points  51  corresponding to the movable contact points being provided on the circuit board  5 , such that the stationary contact points  51  are connected with the power supply cable for the connection load, and such that contacting or disconnecting the movable contact points  71  with the stationary contact points  51  can cause a connection or disconnection between the pins and the power supply cable; and wherein a tripping device  8  capable of contacting or disconnecting the movable contact points  71  and stationary points  51  is provided inside the casing  1 , the tripping device  8  comprising a rod  81  that is fixedly connected to the reset button  11 , such that a rod reset spring  82  that is disposed on the rod  81  is fixed to a trip board  83  on the free ends of the pair of movable springs  7  and is provided to the stationary armature  84  and movable armature  85  inside the trip coil  61 , the lower end of the rod  81  being slidably connected to the movable armature  85  and a lock bit  811  being provided on the rod  81 , and the trip board  83  being provided with a bayonet  831 , which can lock the lock bit  811  of the rod  81  in after the stationary armature  84  has attracted the movable armature  85 . When the present power plug is used, the pins are first inserted into a sock connected to the utility power supply, and thereafter the reset button  11  is pressed and held down by hand, causing the rod  81  to move downward; when pressed to a given position, the surface on the locking bit  811  on the rod  81  is locked into the bayonet  831  on the trip board  83 . When there is a need to use a household appliance, the pin of the power plug must be inserted into the socket, whereupon there is a disconnect between the movable contact points  71  and the stationary contact points  51 , such that when there is a desire to create a connection between the household appliance and the utility power supply, the reset button  11  must be pressed, which causes the rod  81  to move downward, and simultaneously also places pressure on the rod reset spring  82 . When the locking bit  811  on the rod  81  penetrates the bayonet  831  on the trip board  83 , because an electrical current runs through the trip coil  61 , the stationary armature  84  therewithin is made to be magnetic, thus attracting the movable armature  85 ; the movable armature  85  causes the rod  81  to move toward the direction of the stationary armature  84 , causing the locking bit  811  to lock onto the bayonet  831 , whereupon the hand is released. The rod reset spring  82  resets and causes the rod  81  to move upward, and the rod  81  causes the trip board  83  to move upward, and therefore causes the free ends of the movable springs  7  to swing upward, causing the movable contact points  71  to come into contact with the stationary contact points  51 . A connection is thus made between the power supply cable of the connection load and the pins, thereby allowing the utility power supply to pass through the present plug and supply power to the household appliance. 
         [0027]    The casing  1  is constituted of a front-top cover  13 , a rear-top cover  14 , and a lower cover  15  for fastening the front-top cover  13  and rear-top cover  14  together, the reset button  11  and test button  12  being provided in holes on the top surface of the rear-top cover  14  and exposed to the exterior; the power supply live wire pin  2 , neutral wire pin  3 , and ground wire pin  4  perforate holes in the lower surface of the lower cover  15  and extend outwardly. 
         [0028]    One end of the movable armature  85  stretches out of the trip coil  61 , that end being provided with an annular groove  851 ; the lower end of the rod  81  is provided with a longitudinal slot  812  that slidably interlocks with the annular groove  851 . 
         [0029]    A protective shield  9  is fixedly provided to the bottom of the circuit board  5 , the trip coil  61  being fixed into the protective shield  9 , and an opening  91  through which the movable armature  85  perforates being arranged on the protective shield  9 ; a pair of fixed ears  92  are disposed on the top of the protective shield  9 , one end of each of the pair of movable springs  7  being fixed to the pair of fixed ears  92 , and a pin fixation board  10  is fixedly provided to the bottom of the protective shield  9 , jacks for fixing the pins being provided on the pin fixation board  10 . 
         [0030]    The trip board  83  is provided with two connection blocks  832 , fixation holes being arranged on the connection blocks  832 ; the free ends of the movable springs  7  are inserted into and locked into the fixation holes and cause the trip board  83  to be fixed to the end parts of the two movable springs  7 , the movable contact points  71  being provided on the connection blocks  832  and electrically connected to the movable springs  7 . 
         [0031]    The bottom surface of the test button  12  is provided with a U-shaped metal pin  121  and test reset spring  122 ; the bottom of the circuit board  5  corresponding to the U-shaped metal pin  12  is provided with two test solder joints, which together with the U-shaped metal pin  121  constitute a simulation test switch TEST. When the test button  12  is pressed down, the U-shaped metal pin  121  instantly comes into contact with the two test solder joints on the circuit board  5 , creating conduction in a test circuit, such that the zero-sequence transformers  62  on the leakage protection circuit generate an electrical leakage test current and the secondary coil thereof generates a sensor signal; the silicon controlled rectifier SCR is triggered to conduct and the trip coil  61  is given a short-circuit connection. The stationary armature  84  loses magnetic force such that the movable armature  85  is released, the locking bit  811  of the rod  81  is separated out from the bayonet  831  by the action of the rod reset spring  82 , and the trip board  83  loses upward pull; gravity then acts to swing the free ends of the movable springs  7  downward, thus disconnecting the movable contact points  71  from the stationary contact points  51 , and therefore disconnecting the power supply cable of the connecting load from the pins. The utility power supply is thereby stopped from supplying power to the household appliance, and the household appliance ceases operating. 
         [0032]    As illustrated in  FIG. 12 , the leakage protection circuit comprises a trip coil  61 , two zero-sequence transformers  62 , a control chip U 1 , and a silicon controlled rectifier SCR; a metal ring of the zero-sequence transformer  62  is disposed on the power supply cable of the connection load, such that a secondary coil of the zero-sequence transformer  62  is connected to the input end of the control chip U 1 , the output end of the control chip  63  is connected with the control gate of the silicon controlled rectifier SCR, and the cathode of the silicon controlled rectifier SCR is connected with one end of the trip coil  61 . When there is an inadvertent leakage failure while the household appliance is in use, when the leakage current reaches 4˜6 mA, a leakage current signal is sensed in the secondary coil of the zero-sequence transformer  62 , the silicon controlled rectifier SCR is triggered to conduction, and the trip coil  61  is given a short-circuit connection; the stationary armature  84  loses magnetic force such that the movable armature  85  is released, the locking bit  811  of the rod  81  is separated out from the bayonet  831  by the action of the rod reset spring  82 , and the trip board  83  loses upward pull. Gravity then acts to swing the free ends of the movable springs  7  downward, thus disconnecting the movable contact points  71  from the stationary contact points  51 , and therefore disconnecting the power supply cable of the connecting load from the pins. The utility power supply is thereby stopped from supplying power to the household appliance, and the household appliance ceases operating. 
         [0033]    Alternatively, when any one phase of the power supply live wire or neutral wire experiences circuit break, the trip coil  61  experiences a circuit break, such that the stationary armature  84  loses magnetic force and the movable armature  85  is released, the locking bit  811  of the rod  81  is separated out from the bayonet  831  by the action of the rod reset spring  82 , and the trip board  83  loses upward pull. Gravity then acts to swing the free ends of the movable springs  7  downward, thus disconnecting the movable contact points  71  from the stationary contact points  51 , and therefore disconnecting the power supply cable of the connecting load from the pins. The utility power supply is thereby stopped from supplying power to the household appliance, and the household appliance ceases operating. 
       INDUSTRIAL APPLICABILITY 
       [0034]    The present invention is a power plug, which possesses a leakage protection function and therefore can be applied to industrial use.