Abstract:
The present invention provides a circuit interrupting device which can test the conditions of the components in the circuit interrupting device (i.e., the end-of-life test) through the depression of a test button. The circuit interrupting device also possesses reverse wiring protection, including the ability to cutoff power on the user accessible plugs of the face plate when the device is reverse wired or miswired. The circuit interrupting device contains a test button, a reset button, and a series of circuits (including, but not limited to, a main control circuit, an end-of-life detection circuit, and a reset/trip circuit). A depression of the test button generates a simulated fault, which is detected by the main control circuit. When the components in the main control circuit work properly, a control signal is generated by the main control circuit and transmitted to the end-of-life detection circuit to activate the reset/trip circuit and generated an indication signal. After the indication signal is displayed, the reset button is able to be depressed, which sends a signal to the end-of-life detection circuit, which in turn forwards the signal to the reset/trip circuit to reestablish the electrical continuity of the circuit interrupting device.

Description:
RELATED APPLICATIONS  
       [0001]     The present application is a Continuation-In-Part (CIP) of U.S. patent application Ser. No. 11/362,039, filed on Feb. 27, 2006, which claims the priority of U.S. Provisional Patent Application Ser. No. 60/656,090, filed on Feb. 25, 2005, which are herein incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a circuit interrupting device which is capable of testing the conditions of the components in the circuit interrupting device (i.e., the end-of-life test) upon a depression of a test button. The circuit interrupting device also possesses a reverse wiring protection, including the ability to cutoff power on the user accessible plugs of the face plate when the device is reverse wired or miswired. The circuit interrupting device contains a test button, a reset button, and a series of circuits (including, but not limited to, a main control circuit, an end-of-life detection circuit, and a reset/trip circuit). A depression of the test button generates a simulated fault, which is detected by the main control circuit. When the components in the main control circuit work properly, a control signal is generated by the main control circuit and transmitted to the end-of-life detection circuit to activate the reset/trip circuit and generated an indication signal. After the indication signal is displayed, the reset button is able to be depressed, which sends a signal to the end-of-life detection circuit, which in turn forwards the signal to the reset/trip circuit to reestablish the electrical continuity of the circuit interrupting device.  
       BACKGROUND OF THE INVENTION  
       [0003]     Circuit interrupting devices, such as ground fault circuit interrupters (“GFCIs”), arc fault circuit interrupters (“AFCIs”), and circuit breakers, have been widely used by consumers since 1970s. Nowadays, due to household safety concerns, there are needs for GFCIs with extra safety features. According to new UL standards under 943A which was implemented on Jul. 28, 2006, a GFCI is required not only to have reverse wiring protection, but also to be able to provide a user with indications when the GFCI has reached the end of its service life and is no longer capable of providing ground fault protection, and cutoff electricity on the user accessible plug of the GFCI. That is because for most of the GFCIs currently available on the market, when their service life ends, resetting by pressing the reset button is still possible, which gives the users a false sense of security that they are still under proper protection of the GFCI, while in fact the GFCIs&#39; capability of sensing a ground fault and cutting off the electricity due to a ground fault has been compromised. Thus, when a ground fault occurs, the GFCI is unable to provide any protection, which can result in fatal electric shocks.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention provides a circuit interrupting device, such as a ground fault circuit interrupter, an arc fault circuit interrupter, an immersion detection circuit interrupter, an appliance leakage circuit interrupter, or a circuit breaker. The circuit interrupting device contains a test button; a series of circuits including a main control circuit, an end-of-life detection circuit, and a reset/trip circuit; and a reset button. When the circuit interrupting device is properly wired with power on and at a tripped state, a depression of the test button generates a simulated fault which can be detected by the main control circuit. When the components in the main control circuit work properly, a control signal is generated by the main control circuit and transmitted to the end-of-life detection circuit to activate the reset/trip circuit, which in turn can generate an indication signal. The preferred indication signal is a sound, such as a clatter sound “da”. A depression of the test button also can perform a reverse wiring test, i.e., if the circuit interrupting device is reverse wire, a depression of the test button would not generate a simulated fault to be detected by the main control circuit, which, in turn, would not generate the indication signal.  
         [0005]     After the indication signal is displayed, the reset button is able to be depressed to reestablish the electrical continuity of the circuit interrupting device. If the components in the series of circuits do not work properly, the depression of the test button does not allow the fault signal to be generated and passed through the series of circuit which results in no production of the indication signal, and the reset button is not able to be depressed so that no electrical continuity can be reestablished.  
         [0006]     The main control circuit is capable of detecting a fault. The main components in the main control circuit includes a differential transformer and a leakage current detection chip (IC 1 ), such as an RV4145 chip manufactured by National Semiconductor.  
         [0007]     The end-of-life detection circuit comprises an end-of-life detection chip (IC 2 ).  
         [0008]     The reset/trip circuit comprises a silicon controlled rectifier (SCR), and a solenoid coil with an iron core inside the solenoid coil.  
         [0009]     The test button contains a metal piece which is located underneath the test button, and a conductive pin which is located below the metal piece. The conductive pin is embedded in a conductive spring, which is adapted to electrically connected to one of a pair of power input terminals; and the metal piece is adapted to electrically connected to another one of the pair of power input terminals, so that when the test button is depressed, the metal piece is in contact with the conductive pin, which generates the simulated fault when the circuit interrupting device is properly wired. The simulated fault is generated through the use of a resistor, which is located at an electrical path between the conductive spring and one of the pair of the input terminals.  
         [0010]     The test button can also mechanically trip the circuit interrupting device, so that when the circuit interrupting device is not at the tripped state, the depression of the test button will forcibly break the electrical continuity of the circuit interrupting device.  
         [0011]     Underneath the reset button there is a flexible switch (K 3 ), which contains a first conductive piece and a second conductive piece. The first conductive piece of the K 3  is adapted to be coupled to the reset button and the second conductive piece of the K 3  is adapted to be connected to a printed circuit board. The first conductive piece of the K 3  is further adapted to electrically connect to a power input source; and the second conductive piece of the K 3  is adapted to electrically connected to a first input end of the IC 2 . The depression of the reset button, coupled with the flexible switch (K 3 ) can also perform a reverse wiring test, i.e., when the circuit interrupting device is reverse wired, the device cannot be reset.  
         [0012]     The end of life detection circuit further comprises a triode or transistor (Q 1 ). One end of the Q 1  is electrically connected to an output end of the IC 2  and the other end is to the SCR, so that when the IC 2  outputs a signal to the Q 1 , this signal can be further emitted to SCR to activate the reset/trip circuit.  
         [0013]     The IC 2  comprises a first simulation switch (K 1 ) and a second simulation switch (K 2 ). Both the K 1  and the K 2  are operatively connected to the first input end of the IC 2 . When the K 3  is closed, the K 1  and the K 2  are closed to allow a reset signal to be transmitted to the Q 1 .  
         [0014]     The IC 2  further comprises a plurality of inverters and a NAND gate. A second input end of the IC 2  is adapted to receive a control signal from the main control circuit. The second input end is operatively connected to the plurality of inverters and the NAND gate to control open/close of the K 1  and/or the K 2 . When the control signal is received, the open/close of the K 1  and/or K 2  outputs the control signal to the reset/trip circuit to activate the reset/trip circuit and generate the indication signal.  
         [0015]     The IC 2  further comprises a time delay circuit capable of configuring a time frame to control the open/close of the K 1  and/or the K 2 .  
         [0016]     The IC 2  further comprises a third input end which receives a common collector voltage (Vcc) from a power input source. The Vcc is generated after an alternating current (AC) from the power input source passes through a diode bridge (D 1 -D 4 ) to be converted to a direct current (DC), and further passes through a resistor, a diode, and a capacity to be converted to the Vcc.  
         [0017]     The present invention also provides a ground fault circuit interrupter which comprises a housing; a tripping device positioned in a base of the housing; a printed circuit board positioned in the base of the housing; and a pair of output conductors positioned in an insulated middle support, each of the output conductors contains a pair of fixed contacts.  
         [0018]     The printed circuit board further comprises a first pair of flexible metal pieces having a first end and a second end. The first pair of flexible metal pieces is operationally connected to the power source input terminals. The first end of each of the first pair of flexible metal pieces passes through a differential transformer and is operationally connected to a hot input line or a neutral input line; the second end of each of the first pair of flexible metal pieces has a movable contact. A second pair of flexible metal pieces has a first end and a second end. The first end of each of the second pair of flexible metal pieces is operationally connected to a hot power output terminal or a neutral power output terminal. The second end of each of the second pair of flexible metal pieces has a movable contact point. The movable contact of each of the first pair of flexible metal pieces and the movable contact of each of the second pair of flexible metal pieces are capable of connecting/disconnecting to each of the fixed contacts on the pair of output conductors.  
         [0019]     The present invention further provides an end-of-life detection chip (IC 2 ) in an end-of-life detection circuit of a circuit interrupting device. The IC 2  comprises a plurality of pins; a first simulation switch (K 1 ) and a second simulation switch (K 2 ); a plurality of inverters; and a NAND gate. The plurality of pins comprises a first pin receiving a control signal from a main control circuit when the main control circuit detects a fault and the components of the main control circuit works properly; a second pin receiving a reset signal when a reset button is depressed; and a third pin outputting the control signal and/or the reset signal to a reset/trip circuit. The first pin is operatively connected to the plurality of inverters and the NAND gate to control the open/close of the K 1  and/or the K 2 . When the control signal is received by the first pin, the open/close of the K 1  and/or the K 2  outputs the control signal via the third pin to the reset/trip circuit to activate the reset/trip circuit and generate an indication signal. The K 1  and the K 2  are further operatively connected to the second pin. When the reset signal is received by the second pin, the K 1  and the K 2  are closed, which allows the reset signal to be output via the third pin to the reset/trip circuit to reestablish an electrical continuity of the circuit interrupting device.  
         [0020]     The control signal is sent from an output end of a leakage current detection chip (IC 1 ) in the main control circuit to said the pin of said IC 2 . The second pin of the IC 2  is electrically connected to a flexible switch (K 3 ) in the end-of-life detection circuit. The K 3  has a first conductive piece and a second conductive piece. The first conductive piece of the K 3  is adapted to be coupled to the reset button and said second conductive piece of said K 3  is adapted to be connected to a printed circuit board; wherein said first conductive piece of said K 3  is adapted to electrically connect to a power input source; and wherein said second conductive piece of said K 3  is adapted to electrically connected to said second pin of said IC 2 .  
         [0021]     The third pin of the IC 2  is electrically connected to a first end of a triode/transistor (Q 1 ) and a second end of the Q 1  is adapted to be electrically connected to the reset/trip circuit; whereby when said IC 2  receives said control signal from said first pin or said reset signal from said second pin, said control signal or said reset signal is output via said third pin to said Q 1 , and to said reset/trip circuit.  
         [0022]     The present invention further provides a method for testing a circuit interrupting device (such as a ground fault circuit interrupter (GFCI), which comprises the steps of: (1) when the circuit interrupting device is powered and at the tripped state, depressing the test button on the circuit interrupting device; and (2) if the indication signal (such as a sound) is displayed, depressing the reset button to reset the circuit interrupting device. The display of the indicating signal indicates that the components of the circuit interrupting device work properly. If the indication signal is not displayed, the circuit interrupting device may contain some components which do not work properly, and the user should consider to replace the circuit interrupting device with a new one.  
         [0023]     Also, if the circuit interrupting device is not at the tripped state, the user should forcibly depress the test button to mechanically trip the circuit interrupting device.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The detailed description will refer to the following drawings in which like numerals refer to like elements, and in which:  
         [0025]      FIG. 1  is an exploded view illustrating the structure of an exemplary ground fault circuit interrupter (GFCI) that provides an end of life test which is triggered by the depression of the test button.  
         [0026]      FIG. 2  is the front view of the exemplary GFCI of  FIG. 1 .  
         [0027]      FIG. 3  is the front view of the exemplary GFCI of  FIG. 1  with the front lid removed.  
         [0028]      FIG. 4  illustrates exemplary relationships among the components of the circuit board of the exemplary GFCI of  FIG. 1 .  
         [0029]      FIG. 5A  is a partial cross-sectional view along the C-C line in  FIG. 3 , where the GFCI is illustrated to be in a reset and start configuration.  
         [0030]      FIG. 5B  is a partial cross-sectional view along the C-C line in  FIG. 3 , where the GFCI is illustrated to be in a normal working configuration.  
         [0031]      FIG. 5C  is a partial cross-sectional view along the C-C line in  FIG. 3 , illustrating the trip status of the GFCI after a test button is depressed.  
         [0032]      FIG. 5D  is a partial cross-sectional view along the C-C line in  FIG. 3 , illustrating the GFCI being forcibly tripped after the test button is depressed.  
         [0033]      FIG. 6  is a partial cross-sectional view along the A-A line in  FIG. 3 , illustrating the GFCI being tripped after the test button is depressed; and  
         [0034]      FIG. 7  illustrates a schematic view of exemplary circuit connections of the control circuit of the exemplary GFCI of  FIG. 1 .  
     
    
     DETAILED DESCRIPTION  
       [0035]     The present invention describes a circuit interrupting device, which includes, but is not limited to, a ground fault circuit interrupter (GFCI), an arc fault circuit interrupter (AFCI), an immersion detection circuit interrupter, an appliance leakage circuit interrupter, or a circuit breaker. The preferred circuit interrupting device is a GFCI.  
         [0036]     The following experimental designs and result are illustrative, but not limiting the scope of the present invention. Reasonable variations, such as those occur to reasonable artisan, can be made herein without departing from the scope of the present invention. Also, in describing the invention, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected. It is to be understood that each specific element includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.  
         [0037]      FIG. 1  illustrates an exemplary circuit interrupting device, i.e., a ground fault circuit interrupter (GFCI), that provides an end of life test.  FIG. 2  is the front view of the exemplary GFCI of  FIG. 1 .  FIG. 3  is the front view of the exemplary GFCI of  FIG. 1  with the front lid removed. The GFCI includes a housing and a circuit board  18  that is located inside the housing. The circuit board  18  is capable of detecting whether the GFCI has come to the end of its service life by pressing a test button.  
         [0038]     The housing includes a front lid  2 , an insulated mid-level support  3 , and a base  4 . A metal grounding installation board  1  is located between the front lid  2  and the insulated mid-level support  3 . The circuit board  18  is located between the insulated mid-level support  3  and the base  4 .  
         [0039]     As shown in  FIG. 1  and  FIG. 2 , power output sockets  5 ,  6 , a reset button hole  8 -A, a test button hole  7 -A, and a status indicating light hole  30 -A are located on the front lid  2 . A reset button  8  and a test button  7  are located in the reset button hole  8 -A and the test button hole  7 -A, respectively. The reset button hole  8 -A and the test button hole  7 -A penetrate through the metal ground installation board  1  and the insulated mid-level support  3  and make contact with the components on the circuit board  18 . An indicator light G is embedded in the status indicating light hole  30 -A. Four clamp hooks  2 -A are located on the side of the front lid  2  to be used for fastening a groove  4 -B on the base  4 .  
         [0040]     The metal grounding installation board  1  is grounded through a ground screw  13 -A (as shown in  FIG. 1  and  FIG. 2 ) and wires. Grounding pieces  11 ,  12  are located on the metal ground installation board  1  at locations corresponding to the ground holes of the power output sockets  5 ,  6  of the front lid  2 .  
         [0041]     As shown in  FIGS. 1 and 3 , a hot power output conductor  14  and a neutral power output conductor  13  are installed on the two sides of the insulated mid-level support  3 . At the two ends of the power output conductors  13 ,  14 , gripping wing pieces  60 ,  61 ,  62 ,  63  are arranged at the places corresponding to the hot and neutral holes of the power output sockets  5 ,  6  on the front lid  2 . Fixed contacts  15 ,  52  and  16 ,  53  are arranged on the power output conductors  13  and  14 , respectively, to form two pairs of fixed contacts “ 15 ,  16 ” and “ 52 ,  53 .” 
         [0042]     A green indicator light G is also soldered onto the insulated mid-level support  3 . The green indicator light G is embedded inside the status indicating light hole  30 -A on the front lid  2 . The two ends of the green indicator light G are connected to the hot and neutral wires of the GFCI power output (as shown in  FIG. 7 ) to indicate the status of the GFCI.  
         [0043]     As shown in  FIG. 1 , the base  4  is used to accommodate the insulated mid-level support  3  and the circuit board  18 . A pair of hot and neutral power input wiring screws  9 ,  10  and a pair of hot and neutral power output wiring screws  109 ,  110  are installed symmetrically on the two sides of the base  4 .  
         [0044]     The circuit board  18 , which is installed inside the housing, is capable of supplying power to or cutting off power from the power output sockets  5 ,  6  of the front lid  2  and the power output wiring screws  109 ,  110  on the two sides of the base  4 , detecting whether the GFCI has come to the end of its service life, issuing warning signals, and performing a forcible mechanical release.  
         [0045]      FIG. 4  illustrates exemplary relationships among the components of the circuit board  18 . As shown in  FIG. 1  and  FIG. 4 , a flexible neutral power input metal piece  50  and a flexible hot power input metal piece  51  are located on the circuit board  18 . One end of the flexible neutral power input metal piece  50  is bent 90 degrees downwards and penetrates through a differential transformer  19 . This end of the flexible neutral power input metal piece  50  is soldered onto the circuit board  18  and connected to the neutral power input wiring screw  9  through an input wiring piece  24 . Similarly, one end of the flexible hot power input metal piece  51  is also bent 90 degrees downwards and penetrates through the differential transformer  19 . This end of the flexible hot power input metal piece  51  is soldered onto the circuit board  18  and connected to the hot power input wiring screw  10  through an input wiring piece  25 . The neutral power input wiring screw  9  is connected to a neutral wire inside a wall through a conductive wire. The hot power input wiring screw  10  is connected to a hot wire inside the wall through a conductive wire.  
         [0046]     A movable contact  54  is located on the opposite end of the flexible neutral power input metal piece  50 . A movable contact  55  is located on the opposite end of the flexible hot power input metal piece  51 . The movable contacts  54 ,  55  respectively correspond to fixed contacts  52 ,  53  on the power output conductors  13 ,  14  located on the insulated mid-level support  3  (as shown in  FIG. 3 ). Two flexible neutral output metal pieces  20 ,  21  are located above and on the sides of the circuit board  18 . One end of the flexible neutral output metal piece  20  is soldered onto the circuit board  18 , together with the neutral power output terminal  80 , and is connected to the neutral power output wiring screw  109  located on the base  4 . The movable contact  22  is located on the opposite end of the flexible neutral output metal piece  20 . Similarly, one end of the flexible hot output metal piece  21  is soldered onto the circuit board  18 , together with the hot power output terminal  81 , and is connected to the hot power output wiring screw  110  located on the base  4 . The movable contact  23  is located on the opposite end of the flexible hot output metal piece  21 . These movable contacts  22 ,  23  respectively correspond to fixed contacts  15 ,  16  on the neutral power output conductor  13  and the hot power output conductor  14  (as shown in  FIG. 3 ). The movable contacts and the fixed contacts on the flexible power input metal pieces  50 ,  51  and the power output conductor  13 ,  14  together constitute two groups of four pairs of power switches, e.g., “ 54  and  52 ,” “ 22  and  15 ,” “ 55  and  53 ,” and “ 23  and  16 .” 
         [0047]     The differential transformer  19 , also located on the circuit board  18 , is capable of detecting a leakage current. As shown in  FIG. 7 , a hot wire (“HOT”) and a neutral wire (“WHITE”) penetrate through the differential transformer  19 . When an electrical current leakage occurs in a power supply loop, the differential transformer  19  outputs a voltage signal to an electric current detection control chip IC 1  (e.g., model number RV4145 manufactured by National Seminonductor). The electric current detection control chip outputs a control signal to turn on a tripping device to trip the devices on the circuit board  18  so as to interrupt the power output.  
         [0048]      FIG. 5A  is a partial cross-sectional view along the C-C line in  FIG. 3 , where the GFCI is illustrated to be in a reset and start configuration. As shown in  FIG. 1 ,  FIG. 4  and  FIG. 5A , the tripping device, which is located on the circuit board  18 , may enable the flexible power input metal pieces  50 ,  51  and the power output conductors  13 ,  14  to be connected or disconnected, thus supplying power to or cutting off power from the flexible power output metal pieces  20 ,  21  and the power output terminals  80 ,  81  through the power output conductors  13 ,  14 . The tripping device includes a tripper  28 , a locking member  30 , a locking spring  34 , a tripping lever  37 , and a solenoid coil  26 , i.e., solenoid coil (SOL).  
         [0049]     The tripper  28  may have a cylindrical body and is located below the reset button  8 . The left side and the right side of the tripper  28  extend outwardly to form lifting arms. The flexible power input metal pieces  50 ,  51  and the flexible power output metal pieces  20 ,  21  are located on the upper part of the lifting arms on both sides of the tripper  28  and can move up and down with the tripper  28 . As shown in  FIG. 4 , the movable contact  54  on the flexible neutral power input metal piece  50  and the movable contact  22  on the flexible neutral output metal piece  20  cross each other at a position above the side lifting arm of the tripper  28 . Similarly, the movable contact  55  on the flexible hot power input metal piece  51  and the movable contact  23  on the flexible hot output metal piece  21  cross each other at a position above the side lifting arm of the tripper  28 .  
         [0050]     A longitudinal central through hole  29  is formed on top of the tripper  28  and is embedded in a reset directional lock  35 , which is equipped with a reset spring  91  and embedded at the bottom of the reset button  8 . The reset directional lock  35  has a blunt end and is movable in a vertical direction in the central through hole  29 . A circular recessed locking slot  36  is formed in the lower part of the reset directional lock  35  close to the bottom of the reset directional lock  35  to form a groove. A movable “L”-shaped locking member  30  made of a metal material is arranged in the lower part of tripper  28  and penetrates through the tripper  28 . A through hole  31  is formed on the horizontal side of the locking member  30 . The locking member  30  is movable through the through hole  31  in a horizontal direction between an aligned position (in which the through hole  31  of the locking member  30  is aligned with the blunt end of the rest directional lock  35  to allow the rest directional lock  35  to pass through) and a misaligned position (in which the circular recess locking slot  36  of the directional lock  35  is locked into the through hole  31  of the locking member  30 ). A circular slot  33  is formed between the side wall of tripper  28  and the inner side of the locking member  30 . The locking spring  34  is arranged in the circular slot  33 . The solenoid coil  26  with a built-in movable iron core  42  is arranged outside of the side wall of the locking member  30 . The movable iron core  42  inside the solenoid coil  26  faces the side wall of the locking member  30 . A protective shield  41  is arranged above the solenoid coil  26 . One end of the insulated mid-level support  3  presses against the protective shield  41 .  
         [0051]     A hole  32  is formed at one end on the top surface of the locking member  30 . The “7”-shaped tripping lever  37  penetrates through the hole  32 . The tripping lever  37  is located directly underneath the test button  7 . A pivot point  28 -A is arranged on the side wall of tripper  28  close to the tripping lever  37 . The tripping lever  37  can rotate around the pivot point  28 -A on the side wall of tripper  28 .  
         [0052]     The tripper  28 , the locking member  30 , the locking spring  34 , and the tripping lever  37  are connected to each other to form an integral body that can move freely.  
         [0053]     As shown in  FIG. 4 , two pairs of position limiting pieces  43 ,  44  as well as  73 ,  74  are arranged on the protective shield  41  of the solenoid coil  26  below the movable contacts of the flexible power input metal pieces  50 ,  51  and below the flexible output metal pieces  20 ,  21 .  
         [0054]      FIG. 7  illustrates a schematic view of exemplary circuit connections of the control circuit of the GFCI. As shown in  FIG. 5A  and  FIG. 7 , a flexible switch K 3 , which is made of a flexible metal material, is located between the bottom of the tripper  28  and the circuit board  18 . The flexible switch K 3  contains two conductive pieces  67 ,  68 , one is coupled to the reset button  8 , and the other is coupled to the printed circuit board  18 . Each of the two conductive pieces has a contact. When the reset button  8  is depressed, the flexible switch K 3  closes. When the reset button  8  is released, the flexible switch K 3  is opened. The flexible switch K 3  is further electrically connected to a power source. An alternating circuit (AC) from the power source passes through a diode bridge (D 1  to D 4 ) to be converted into a direct current (DC). The DC is further converted to a common collector voltage (Vcc) through resistor R 7 , diode D 5 , and capacitor C 8 . The Vcc supplies power to the IC 2  via pin  7 .  
         [0055]     As shown in  FIG. 7 , the two differential transformer  19 , the leakage current detection chip IC 1 , resistors R 2 , R 3 , and capacitors C 2 -C 5  constitute a main control circuit. When a leakage current (such as a ground fault or a simulated fault) occurs, it causes an electrical imbalance between the hot wire (“HOT”) and the neutral wire (“WHITE”) of the differential transformer  19 . The differential transformer  19  immediately outputs a voltage signal to the leakage current detection chip IC 1 . Pin  5  of the leakage current detection chip IC 1  outputs a high level voltage signal.  
         [0056]     The test button  7  and a test resistor R 4  constitute a simulated leakage current generation circuit. One end of the test button  7  is connected to the hot wire (“HOT”). The opposite end of the test button  7  is connected to the neutral wire (“WHITE”) through the test resistor R 4 . When the test button  7  is depressed, the hot and neutral wires have a short and generate a leakage current. If the components of the GFCI work normally, pin  5  of the leakage current detection chip IC 1  outputs a high level signal.  
         [0057]     A silicon controlled rectifier (SCR), the solenoid coil  26  with the built-in iron core  42 , and a capacitor C 7  constitute a reset/trip circuit. One end of the solenoid coil  26  is connected with the hot wire (“HOT”) of the power line input end of the GFCI, and the opposite end of the solenoid coil  26  is connected to the positive end of the silicon controlled rectifier. The negative end of the silicon controlled rectifier is connected to the ground. When the control pole of the silicon controlled rectifier is at a high level voltage, the silicon controlled rectifier is triggered to become conductive. The solenoid coil  26  is energized so that current flows through the solenoid coil  26  to generate an electromagnetic field. The iron core  42  inside the solenoid coil  26  moves to plunge the locking member  30  of the tripping device to display a clatter sound “da.” At this time, the reset button  8  is popped up and the GFCI is tripped. After the displayed of the clatter sound, the reset button  8  can be depressed to allow the GFCI to be reset. When the GFCI is reset, the GFCI&#39;s load output ends, i.e., the power output wiring screws  109 ,  110 , as well as the tri-pronged user accessible power output sockets  5 ,  6  on the face plate of the GFCI all have power output. When the reset button  8  is popped up or when the GFCI is tripped, the power output wiring screws  109 ,  110  and the tri-pronged user accessible power output sockets  5 ,  6  have no power.  
         [0058]     The flexible switch K 3  which are coupled to the reset button  8 , a triode Q 1 , resistors R 7 , R 16 , R 19 , and capacitors C 8 -C 12 , and the end-of-life detection chip IC 2  constitute an end-of-life detection circuit. Pin  1  of the end-of-life detection chip IC 2  is connected to the positive pole of a direct current power supply output by a diode rectification bridge D 1 -D 4  through the resistor R 7 , and generates a regulated direct current power supply (i.e., common collector voltage) Vcc through R 7 , D 5 , C 8 , thus providing power for the end-of-life detection chip IC 2  and the triode Q 1 . Pin  2  of the end-of-life detection chip IC 2  is connected to pin  5  of the leakage current detection chip IC 1  through a resistor R 12  and receives a control signal from the leakage current detection chip IC 1 . Pin  3  of the end-of-life detection chip IC 2  is connected to the ground through parallel connected C 10 , R 16 . Pin  4  of the end-of-life detection chip IC 2  is connected to the ground. Pin  5  of the end-of-life detection chip IC 2  is connected to the ground through parallel connected C 11 , R 19 . Pin  6  of the end-of-life detection chip IC 2  is connected to pin  5  through the capacitor C 12 . C 11 , C 12 , R 19 , which are connected to pin  5 , pin  6  of the end-of-life detection chip IC 2 , may be used to eliminate an instant high level signal output by pin  6  when the GFCI is supplied power and to adjust the setup time of the mono-stable timing circuit. A control signal input pin  7  of the end-of-life detection chip IC 2  is connected to the direct current power supply Vcc through the flexible switch K 3 , which is coupled to the reset button  8 . A control signal output pin  8  of the end-of-life detection chip IC 2  is connected to the base of the triode Q 1 . The collector of the triode Q 1  is connected to the direct current power supply Vcc. The emitter of the triode Q 1  is connected to the control pole of the silicon controlled rectifier through a resistor R 11 , and at the same time, the emitter of the triode Q 1  is also connected to the ground through a resistor R 10  and the capacitor C 9 . The triode Q 1  can be changed to a transistor.  
         [0059]     An embodiment of the end-of-life detection chip IC 2  is an integrated circuit, which includes inverter NOT 1 -NOT 5 , a NAND gate, two electronic simulation switches K 1 , K 2 , a control circuit U 1  that controls the opening or closing of the electronic simulation switch K 1 , and a control circuit U 2  that controls the opening or closing of the electronic simulation switch K 2 . The end-of-life detection chip IC 2 &#39;s internal connection relation is as follows. Pin  2  of the end-of-life detection chip IC 2  is connected to two inverters NOT 1 , NOT 2 , and is further connected to the control circuit U 2  through a delay circuit and a resistor R 8  to control the opening or closing of the electronic simulation switch K 2 . The delay circuit includes R 15 , D 7 , C 10 , R 16 . Pin  2  of the end-of-life detection chip IC 2  is further connected to the control circuit U 1  through a serial connection with a resistor R 17 , two inverters NOT 1 , NOT 4 , a diode D 8 , a resistor R 21 , the NAND gate, the inverter NOT 5 , and a resistor R 20  to control the opening or closing of the electronic simulation switch K 1 .  
         [0060]     The resistor R 8  inside the end-of-life detection chip IC 2  may be used to eliminate noise signals. A diode D 6  controls one way turn-ons of the electronic simulation switch K 1 . The resistor R 9 , the triode Q 1 , and the resistor R 10  constitute an emitter tracker to drive the silicon controlled rectifier. The resistor R 11  and the capacitor C 9  may be used for filtering to eliminate interference signals and noises. R 15 , D 7 , C 10 , and R 16  constitute a time delay circuit capable of configuring a time frame to control the open/close of the K 1  and/or K 2 .  
         [0061]     An embodiment of the end-of-life detection chip IC 2  detects whether a GFCI has come to its end of life as follows. After the hot wire (“HOT”) and the neutral wire (“WHITE”) on the GFCI&#39;s input end are properly connected to the hot and the neutral wires inside the wall, the main power supply may be turned on. An alternate current voltage is applied to a control circuit input line. This alternate current voltage outputs a direct current voltage to the leakage current detection chip IC 1  after being rectified by the diode rectification bridge D 1 -D 4 . At the same time, this direct current voltage provides a work voltage Vcc to pin  1  of the end-of-life detection chip IC 2  through the regulated voltage circuit that includes R 7 , D 5 , C 8 . At this time, pin  1  of the end-of-life detection chip IC 2  is at a high level and pin  2  is at a low level. The electronic simulation switch K 1  inside the end-of-life detection chip IC 2  is in an open state, and the electronic simulation switch K 2  is in a closed state. Since pin  2  of the end-of-life detection chip IC 2  is at a low level, pin  8  of the end-of-life detection chip IC 2  is also at a low level. The triode Q 1  is terminated and the silicon controlled rectifier is not on. No electric current passes through solenoid coil  26  and no electro-magnetic field is generated. The iron core  42  inside the solenoid coil  26  is not activated, neither is the tripping device that includes the tripper  28 , the locking member  30 , and the locking spring  34 .  
         [0062]     At this time, if the reset button  8  is pressed for a reset, since pin  8  of the end-of-life detection chip IC 2  is at a low level, the triode Q 1  is terminated and the silicon controlled rectifier is not on. No electric current passes through the solenoid coil  26  and no electro-magnetic field is generated. The iron core  42  inside the solenoid coil  26  is not activated, neither is the tripping device. Accordingly, the reset button  8  for reset cannot be accomplished. Neither the GFCI&#39;s output end nor the tri-pronged user accessible power output sockets  5 ,  6  have power output. The GFCI is stably connected in the power supply circuit. The test button  7  may need to be pressed first for a test to detect whether the GFCI is still capable of providing ground fault protection against any electrical current leakage and whether the GFCI has come to the end of its service life (see below).  
         [0063]      FIG. 5B  is a partial cross-sectional view along the C-C line in  FIG. 3 , where the GFCI is illustrated to be in a normal working configuration.  FIG. 5C  is a partial cross-sectional view along the C-C line in  FIG. 3 , illustrating the trip status of the GFCI after a test button is pressed.  
         [0064]     Pressing the test button  7  generates a simulated leakage current, so that the electric current that penetrates through the hot wire (“HOT”) and the neutral wire (“WHITE”) of the differential transformer  19  is imbalanced. If the GFCI is intact and has not come to the end of its service life, the differential transformer  19  detects the current leakage and immediately outputs a voltage signal to the leakage current detection chip IC 1 . Pin  5  of the leakage current detection chip IC 1  outputs a high level signal to pin  2  of the end-of-life detection chip IC 2 , which turns from a low level into a high level. Pin  8  of the end-of-life detection chip IC 2  also outputs a high level signal. The triode Q 1  is turned on and the silicon controlled rectifier is triggered to become conductive. The solenoid coil  26  with a built-in iron core  42  is energized so that current flows through the solenoid coil  26  to generate an electro-magnetic field. The iron core  42  inside the solenoid coil  26  moves to push the locking member  30  of the tripping device. An indication signal, such as a “clatter” sound, may be generated from inside the GFCI, indicating that the GFCI is intact, has not come to the end of its service life, and can be safely used.  
         [0065]     By contrast, if the GFCI has come to the end of its service life and cannot detect a leakage current, pin  5  of the leakage current detection chip IC 1  cannot output a high level signal. Pin  2  of the end-of-life detection chip IC 2  is still at a low level, so is Pin  8  of the end-of-life detection chip IC 2 . The triode Q 1  is not turned on. The silicon controlled rectifier is in a closed state. The reset/trip circuit, which includes the solenoid coil  26  with the built-in iron core  42  and the capacitor C 7 , is not supplied power. No electric current passes through the solenoid coil  26  and no electromagnetic field is generated. The iron core  42  inside the solenoid coil  26  is not activated. No “clatter” sound is generated, which indicates that the GFCI has come to the end of its service life and can no longer be safely used.  
         [0066]     If the GFCI is intact, pin  2  of the end-of-life detection chip IC 2  is at a high level. Driven by the inverters NOT 1 , NOT 2 , this high level signal passes through the delay circuit, which includes R 15 , D 7 , C 10 , R 16 , and generates a control signal to the control circuit U 2  to open the electronic simulation switch K 2 . Similarly, driven by the inverters NOT 3 , NOT 4 , this high level signal triggers the mono-stable timing circuit, which includes the NAND gate and the inverter NOT 5 , and causes the inverter NOT 5  to output a high level signal to the control circuit U 1  to close the electronic simulation switch K 1 .  
         [0067]     When the test button  7  is pressed to test the GFCI and the GFCI has not come to the end of its service life, releasing the test button  7  causes the simulated leakage current to disappear. Pin  5  of the leakage current detection chip IC 1  changes to a low level signal, so does pin  2  of the end-of-life detection chip IC 2 . The electronic simulation switch K 2  automatically closes.  
         [0068]     After hearing the “clatter” sound, a user may press the reset button  8 . Since the flexible switch K 3  is coupled to the reset button  8 , the flexible switch K 3  closes when the reset button  8  is pressed. At this time, switches K 1 , K 2 , K 3  are all in a closed state. Pin  8  of the end-of-life detection chip IC 2  outputs a high level signal. The triode Q 1  is turned on. The silicon controlled rectifier in the reset/trip circuit is triggered to become conductive. The solenoid coil  26  is supplied power so that current flows through the solenoid coil  26  to generate an electro-magnetic field. The iron core  42  inside the solenoid coil  26  moves to push the locking member  30  of the tripping device.  
         [0069]     As shown in  FIG. 5B , the circular recessed locking slot  36  of the reset directional lock  35  embedded at the bottom of the reset button  8  is seized in the through hole  31  of the locking member  30 . When the reset button  8  is released, the tripper  28  moves up to elevate the flexible metal pieces  50 ,  51 ,  20 ,  21  located above the lifting arms on the two sides of the tripper  28 . As a result, the movable contacts  54 ,  55  on the flexible power input metal pieces  50 ,  51  make contact with the fixed contacts  52 ,  53  on the power output conductors  13 ,  14  to power up the output conductors  13 ,  14 . Powering up the output conductors  13 ,  14  in turn allows the flow of electricity to the tri-pronged user accessible power output sockets  5 ,  6  on the face of the GFCI. Also, the movable contacts  22 ,  23  on the flexible output metal pieces  20 ,  21  make contact with the fixed contacts  15 ,  16  on the power output conductors  13 ,  14  to power up the flexible output metal pieces  20 ,  21 , which are in contact with the power output terminals  80 ,  81 . Powering up the flexible output metal pieces  20 ,  21  allows electricity to be output to the power output terminals  80 ,  81  of the GFCI and to the tri-pronged user accessible power output sockets  5 ,  6  on the face of the GFCI. As a result, the GFCI operates normally.  
         [0070]     The mono-stable timing circuit may be set for, e.g., 5 minutes, to keep the electronic simulation switch K 1  in a closed state. After the set time expires, the mono-stable timing circuit is automatically restored to its initial state. The inverter NOT 5  outputs a low level signal, the electronic simulation switch K 1  is automatically opened and the electronic simulation switch K 12  continues to be closed.  
         [0071]      FIG. 6  is a partial cross-sectional view along the A-A line in  FIG. 3 , illustrating the GFCI being tripped after the test button is pressed. As shown in  FIG. 5C ,  FIG. 6  and  FIG. 7 , a metal piece  40  is located below the test button  7 . A conductive pin  72  is located below the metal piece  40 . The conductive pin  72  is embedded in a conductive spring  71 , which is connected to the neutral wire (“WHITE”) through a conductive wire  27 -A and the test resistor R 4 . The metal piece  40  is connected to the hot wire (“HOT”) through a conductive wire  27 -B.  
         [0072]     As shown in  FIG. 5C , when the test button  7  is pressed, the circular recessed locking slot  36  at the bottom of the reset directional lock  35  jumps out of the through hole  31  of the locking member  30 . When the reset button  8  is released, the tripper  28  drops down. The flexible metal pieces  50 ,  51 ,  20 ,  21  located above the two lifting arms of the tripper  28  drop as well to disconnect the movable contacts  54 ,  55  on the flexible power input metal pieces  50 ,  51  from the fixed contacts  52 ,  53  on the power output conductors  13 ,  14 . The fixed contacts  15 ,  16  on the power output conductors  13 ,  14  are disconnected from the movable contacts  22 ,  23  on the flexible output metal pieces  20 ,  21  so that neither the power output conductors  13 ,  14  nor the flexible output metal pieces  20 ,  21  are supplied power. As a result, no power is output to the power output terminals  80 ,  81  of the GFCI or to the tri-pronged user accessible power output sockets  5 ,  6  on the face of the front lid  2  of the GFCI, so that the entire power output of the GFCI is interrupted. Driven by the inverters NOT 1 , NOT 2 , a signal passes through the time delay circuit, which includes R 15 , D 7 , C 10 , R 16 , and generates a control signal to open the electronic simulation switch K 2 . Similarly, driven by the inverters NOT 3 , NOT 4 , this signal triggers the mono-stable timing circuit, which includes the NAND gate and the inverter NOT 5 , and causes the inverter NOT 5  to output a high level signal to close the electronic simulation switch K 1 . When the test button  7  is released, the high level signal from pin  5  of the leakage current detection chip IC 1  disappears. At this time, the output from the inverter NOT 2  changes to a low level signal and the electronic simulation switch K 2  automatically closes.  
         [0073]     In the event that the GFCI has come to the end of its service life and can no longer provide protection against any electrical current leakage, two things may happen. First, pin  5  of the leakage current detection chip IC 1  will not output a high level signal to pin  2  of the end-of-life detection chip IC 2 . Output from the inverters NOT 2 , NOT 5  of the end-of-life detection chip IC 2  is also at a low level. The electronic simulation switch K 1  is in an open state and the electronic simulation switch K 2  is in a closed state. Pin  8  of the end-of-life detection chip IC 2  remains at a low level. The silicon controlled rectifier in the reset/trip circuit is not conductive, no electric current passes through the solenoid coil  26 , and no electromagnetic field is generated. The GFCI may not generate a “clatter” sound. The tripper  28  and the locking member  30  of the GFCI are not activated and the reset button  8  cannot be reset. The second possibility is: pin  5  of the leakage current detection chip IC 1  continues to output a high level signal, so that the negative D 7  pole becomes a high level signal. The electronic simulation switch K 2  remains in an open state, so that the silicon controlled rectifier in the reset/trip circuit cannot be triggered to become conductive. No electric current passes through the solenoid coil  26  and no electro-magnetic field is generated. The reset button  8  cannot be reset, and the user should be reminded to replace GFCI with a new GFCI.  
         [0074]     By first pressing the test button  7  during use, the end-of-life detection chip IC 2  and the leakage current detection chip IC 1  detect whether the GFCI can still provide protection against a current leakage or whether the GFCI has come to the end of its service life. If the GFCI is fully functional, the user may hear a “clatter” sound. When the user presses the reset button  8  to reset, the GFCI&#39;s load output ends and the power output sockets  5 ,  6  on the surface of the GFCI have power output. On the other hand, if the GFCI has come to the end of its service life, the end-of-life detection chip IC 2  does not output a control signal, so that the silicon controlled rectifier in the reset/trip circuit cannot be triggered to become conductive. No electric current passes through the solenoid coil  26  and no electromagnetic field is generated, so that the tripper  28  and the locking member  30  of the GFCI are not activated, thus preventing the reset button  8  from being reset. As a result, the GFCI&#39;s load output ends and the power output sockets  5 ,  6  are not supplied power. During use, a user may press the test button  7  to test the GFCI. If the user does not hear a “clatter” sound and the reset button  8  cannot be reset, the user knows that it is time to replace the GFCI with a new GFCI.  
         [0075]     As shown in  FIG. 5D , the user may mechanically and forcibly cut off power output of the GFCI by pressing the test button  7 . The test button  7  has a tail end which penetrates through the insulated mid-level support  3 , which touches upon the end of the tripping lever  37 . When the service life of the GFCI has ended and the reset button  8  cannot be tripped by using a simulated leakage current, the user can further press down the test button  7  to forcibly trip the GFCI. Pressing the test button  7  pushes the tail end of the test button  7  against the top of the tripping lever  37 , which revolves around a pivot point  28 -B. The side wall of the tripping lever  37  leaves a pivot point  28 -A on the side wall of the tripper  28 . Since the tripping lever  37  penetrates through the hole  32  of the locking member  30 , the tripping lever  37  pulls the locking member  30  and moves it with the tripping lever  37 , causing the circular recessed locking slot  36  at the bottom of the reset directional lock  35  to jump out of the through hole  31  of the locking member  30 . The tripper  28  falls, and the flexible power input metal pieces  50 ,  51  fall as well. The movable contacts on the flexible power input metal pieces  50 ,  51  are disconnected from the fixed contacts on the power output conductors  13 ,  14 . As a result, power output conductors  13 ,  14  are not supplied power. The flexible output metal pieces  20 ,  21  connected to the power output terminals  80 ,  81  are not supplied power, either. Since neither the power output conductors  13 ,  14  nor the power output terminals  80 ,  81  are supplied power, no power is output to the load terminals, i.e., the power output terminals  80 ,  81  of the GFCI, or to the tri-pronged user accessible power output sockets  5 ,  6  on the face of the GFCI front lid  2 .  
         [0076]     The embodiments of the exemplary GFCI described above provide protection against any electrical current leakage. Additionally, when the exemplary GFCI is connected to the hot and neutral wires inside the wall, a user may first press the test button  7  to detect if the GFCI has come to the end of its service life. Specifically, if the GFCI is fully functional and can still provide protection against any electrical current leakage, a “clatter” can be heard, and the reset button  8  can be reset normally. On the other hand, if the GFCI has come to the end of its service life, the end-of-life detection chip IC 2  may prevent the reset button  8  from being reset normally. In addition, when a certain part or accessory inside the GFCI fails during use, especially when the solenoid coil  26  fails to work in a normal manner, the test button  7  may be pressed to forcibly cut off the power output of the GFCI using mechanical means. The exemplary GFCI can be widely applied, is safe and easy to use, thus effectively ensuring the personal safety of the user as well as the safety of appliances.  
         [0077]     While the GFCI that provides an end of life test and a test result prompt has been described in connection with an exemplary embodiment, those skilled in the art will understand that many modifications in light of these teachings are possible, and this application is intended to cover variations thereof. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications.