Patent Document

PRIORITY CLAIM 
   This application is a continuation of application Ser. No. 10/434,101 filed May 9, 2003 now U.S. Pat. No. 7,184,250 which claims benefit from U.S. Patent Application Ser. No. 60/378,647, filed on May 9, 2002 entitled “GFCI With Reversible Line/Load Wiring Capability”, the entire contents of which is incorporated herein by reference. 
   CROSS REFERENCE TO RELATED APPLICATIONS 
   Related subject matter is disclosed in U.S. patent application Ser. No. 10/032,064, filed on Dec. 31, 2001 entitled “Ground Fault Circuit Interrupter (GFCI) With A Secondary Switch Contact Protection”, the entire contents of which is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention generally relates to ground fault circuit interrupter (GFCI) devices. More particularly, the invention relates to a GFCI device that isolates the face terminals from the load side and prevents an initial miswiring of the GFCI from the load side. 
   BACKGROUND OF THE INVENTION 
   GFCI devices are designed to trip in response to the detection of a ground fault condition at an AC load. Generally, the ground fault condition results when a person comes into contact with the line side of the AC load and an earth ground at the same time, which is a situation that can result in serious injury. The GFCI device detects this condition by using a sensing transformer to detect an imbalance between the currents flowing in the line and neutral conductors of the AC supply, as will occur when some of the current on the line side is being diverted to ground. When such an imbalance is detected, a solenoid activates a latched circuit breaker within the GFCI device to an open condition, thereby opening both sides of the AC line and removing all power from the load. 
   Some GFCIs include a lockout feature that prevents the GFCI from operating if the solenoid fails to operate. For example, in U.S. Pat. No. 6,381,112 to DiSalvo, which is incorporated by reference herein, a GFCI is provided with a permanent lockout feature which prevents the GFCI from being reset if the solenoid fails to operate or if an open neutral condition exists. However, having a permanent lockout, which prevents the GFCI from operating, can be undesirable. For example, if a homeowner is entertaining guests in the kitchen, a power interrupt can occur requiring the GFCIs to be reset. If a GFCI connected to an appliance is locked out, the homeowner may have to use an extension cord to connect an appliance to a non-GFCI receptacle. In front of guests, this can prove to be embarrassing and inconvenient to the homeowner. 
   GFCIs can also include an LED to provide a trip indication as disclosed in U.S. Pat. No. 4,568,997, to Bienwald et al., the contents of which are incorporated herein by reference herein, This type of receptacle includes test and reset pushbuttons and a lamp or light-emitting diode (LED) which indicates that the circuit is operating normally. When a ground fault occurs in the protected circuit, or when the test button is depressed, the GFCI device trips and an internal circuit breaker opens both sides of the AC line. The tripping of the circuit breaker causes the reset button to pop out and the LED to be extinguished, providing a visual indication that a ground fault has occurred. In order to reset the GFCI device, the reset button is depressed in order to close and latch the circuit breaker, and this also causes the LED to illuminate once again. However, the GFCI disclosed in the Bienwald et al. patent does not provide an indication of a defective solenoid. 
   In addition to ground fault detection/protection, protection for the receptacle terminals of the GFCI is also needed. Specifically, the conventional GFCI device has a set of load terminals that are shared with the receptacle terminals leading to the face of the GFCI. Typically, the AC source is connected to the line terminals while the downstream load devices are connected to the load terminals. However, if the GFCI is miswired, this poses a problem. When the load terminals are connected to an AC source, the receptacle terminals are powered. The installer would be under the impression that the GFCI was operating correctly. However, the installer would be unaware that the GFCI is not providing ground fault protection even when a fault condition is detected. Thus, while tripping the latching mechanism in response to a miswiring condition, only the downstream devices are open. Devices plugged into the GFCI receptacle are still connected to AC power since the face terminals are directly connected to the line/load terminals. 
   It is therefore desirable to provide a latching mechanism that does not share the contacts between the receptacle terminals and the load terminals. 
   It is also desirable to provide a protection device that is not permanently disabled when the solenoid fails. 
   It is also desirable to provide a protection device that provides protection from miswiring, and permanently disables a miswiring prevention device once the protection device is correctly wired. 
   SUMMARY OF THE INVENTION 
   The above and other objectives are substantially achieved by a system and method employing a ground fault circuit interrupter (GFCI) in accordance with the principles of the present invention. 
   According to an embodiment of the present invention, an apparatus and method for preventing the miswiring of a protection device is employed. The protection device includes line terminals and load terminals. The protection device further includes a latching mechanism, adapted to move between a closed state which establishes electrical contact between said line and load terminals, and an open state which prevents electrical contact between said line and load terminals; and an initial reset prevention mechanism, adapted to prevent said latching mechanism from being set in said closed state until power is applied to said line terminals. 
   According to another embodiment of the present invention, a protective device having source and load terminals between a conductive path and face terminals is provided. The protective device includes a latching mechanism, adapted to be operable between a first state in which said latching mechanism permits electrical contact between said source load terminals and said load terminals and a second state in which said contact is broken; and a sensing circuit, adapted to selectively place the latching mechanism in said second state upon detection of a ground fault condition to electrically isolate said face terminals from said source and load terminals. a device is connected between hot and neutral conductors of an AC line. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a perspective view of an example of a ground fault circuit interrupting (GFCI) device in accordance with an embodiment of the present invention; 
       FIG. 2  is another perspective view of the ground fault interrupting device shown in  FIG. 1  in accordance with an embodiment of the present invention; 
       FIG. 3  is a perspective view of an example of the ground fault circuit interrupting device shown in  FIG. 1  having an indicator in accordance with an embodiment of the present invention; 
       FIG. 4  is a schematic diagram illustrating an example of the circuitry of the ground fault circuit interrupting device of  FIG. 1  in accordance with an embodiment of the present invention; 
       FIGS. 5-7  are perspective views illustrating examples of positions of a locking plate of the ground fault circuit interrupting device shown in  FIG. 1  in accordance with an embodiment of the present invention; 
       FIGS. 8-10  are cross sectional views illustrating examples of positions of the locking plate, a latching plate and a reset pin of the ground fault circuit interrupting device of  FIG. 1  in accordance with an embodiment of the present invention; 
       FIG. 11  is a schematic diagram illustrating an example of the circuitry of ground fault circuit interrupting device of  FIG. 3  in accordance with an embodiment of the present invention; 
       FIG. 12  is a schematic diagram of an example of a ground fault circuit interrupting (GFCI) device in accordance with another embodiment of the present invention; 
       FIG. 13-16  are views illustrating examples of positions of a locking plate in the GFCI of  FIG. 12  in accordance with an embodiment of the present invention; 
       FIGS. 17A and 17B  are cross sectional views illustrating examples of positions of a initial reset prevention arrangement that can be used with a GFCI in accordance with an embodiment of the present invention; and 
       FIGS. 18A and 18B  are cross sectional views illustrating examples of positions of a another initial reset prevention arrangement that can be used with a GFCI in accordance with an embodiment of the present invention. 
       FIGS. 19-26  are drawings showing various positions of the switch contacts for the circuit of  FIG. 4  in accordance with an alternative embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a perspective view of an example of a ground fault circuit interrupting (GFCI) device  10  in accordance with an embodiment of the present invention. The GFCI device  10  comprises a housing  12  having a cover portion  14  and a rear portion  16 . The GFCI also includes an inner housing  13  (See  FIG. 5 ) when the cover portion  14  is removed from the rear portion  16 . The cover portion  14  and rear portion are removably secured to each other via fastening means such as clips, screws, brackets, tabs and the like. The cover portion includes plugin slots (also known as face receptacles)  18  and  20  and grounding slots  22 . It will be appreciated by those skilled in the art that plugin slots  18  and  20  and grounding slots  22  can accommodate polarized, non-polarized, grounded or non-grounded blades of a male plug. The male plug can be a two wire or three wire plug without departing from the scope of the present invention. The GFCI receptacle  10  further includes mounting strap  24  having mounting holes  26  for mounting the GFCI receptacle  10  to a junction box (not shown). At the rear wall of the housing  12  is a grounding screw  28  for connecting a ground conductor (not shown). 
   A test button  30  extends through opening  32  in the cover portion  14  of the housing  12 . The test button is used to activate a test operation, that tests the operation of the circuit interrupting portion disposed in the GFCI receptacle  10 . The circuit interrupting portion, to be described in more detail below, is used to break electrical continuity in one or conductive paths between the line and load side of the GFCI receptacle  10 . A reset button  34  extends through opening  36  in the cover portion  14  of the housing  12 . The reset button  34  is used to activate a reset operation, which reestablishes electrical continuity in the open conductive paths. 
   Rear portion  16  has four screws, only two of which are shown in  FIG. 1 . Load terminal screw  38  is connected to a neutral conductor and an opposing load terminal screw  37  (See  FIG. 2 ) is connected to the hot conductor. Line terminal screw  40  is connected to the neutral conductor and an opposing line terminal screw  39  (See  FIG. 2 ) is connected to the hot conductor. It will be appreciated by those skilled in the art that the GFCI receptacle  10  can also include apertures proximate the line and load terminal screws  37 ,  38 ,  39  and  40  to receive the bare end of conductors rather than connecting the bare end of the wires to the line and load terminal screws. 
   In an embodiment of the present invention rear portion  16  also contains an aperture  42  (See  FIG. 2 ) for accessing the internal portion of the GFCI receptacle  10  for testing during the manufacturing process. Specifically, the aperture  42  provides access to a locking plate  58 . The aperture  42  is sealed prior to shipping of the GFCI receptacle  10  to distributors. 
     FIG. 3  is a perspective view of an example of a ground fault circuit interrupting (GFCI) device  11  having an indicator in accordance with an embodiment of the present invention. Specifically, GFCI device  11  is similar in operation to the GFCI  10  except GFCI device  11  has an alarm indicator  44  for providing an indication to a user that GFCI device  11  is not providing ground fault protection, or in other words, GFCI device  11  is operating as a normal receptacle. 
   Alarm indicator  44  comprises a dual color lamp which provides a first color when a first filament is activated and a second color when a second filament is activated. In an embodiment of the present invention, the alarm indicator  44  illuminates to provide a green color when the GFCI receptacle  11  is operating normally and providing GFCI protection. In another embodiment of the present invention, the alarm indicator  44  illuminates to provide a flashing red color when the GFCI receptacle  11  is operating as a normal receptacle and not providing ground fault protection. It should be appreciated by those skilled in the art that although the alarm indicator is described as being a dual filament lamp, two separate single filament lamps, a single lamp having a single filament, or a buzzer, or any other suitable indicator such as a colored lamp can be used to provide an alarm indication without departing from the scope of the present invention. 
     FIG. 4  is a schematic diagram illustrating an example of the circuitry of the ground fault circuit interrupting device of  FIG. 1  in accordance with an embodiment of the present invention. In accordance with this embodiment, the GFCI device  10  is provided with a latching mechanism  46 , sensing circuit  48 , solenoid  50 , solenoid plunger  52 , latching plate  54  (See  FIG. 8 ), reset pin  56  (See  FIG. 8 ), locking plate  58 , locking spring  60 , secondary contacts  62 , neutral conductor  64 , hot conductor  66 , a transformer arrangement  68  comprising sensing transformer  68 A and ground transformer  68 B, and a control circuit  70 . 
   GFCI device  10  is structured and arranged to prevent an initial miswiring of the GFCI. That is, as described in more detail below, prior to shipping the device for use, the locking plate  58  is pressed downward to engage a projection on the back of plunger  52  and makes contact with secondary contacts  62  to thus close the secondary contacts  62 . The reset button  34 , when depressed, cannot engage with the latching plate  54  via the reset pin  56  and through aperture  55  (See  FIGS. 8-10 ) in the latching plate  54 . When the GFCI receptacle  10  is connected to the line side, the secondary contacts power the solenoid  50 , causing solenoid plunger  52  to release locking plate  58  and position latching plate  54  so that the reset pin  56  can engage with the edge of the latching plate  54  forming the opening  55  when the reset button  34  is depressed. 
     FIGS. 5-7  are perspective views illustrating examples of positions of the locking plate  54  in accordance with an embodiment of the present invention. In  FIG. 5  the cover portion  14  of the housing  12  is removed to expose the internal housing  13  of the GFCI  10 . The locking spring  60 , secondary contacts  62 , solenoid plunger  52  and solenoid  50  are shown. The locking spring  60  is in an extended or release position and is not exerting pressure. 
   In  FIG. 6 , the locking plate  58  is shown in a released or extended position. The locking spring  60  (See  FIG. 5 ) holds the locking plate  58  up, thus preventing aperture  59  of the locking plate  58  from engaging with the projection  53  of the plunger  52  or from making contact with the secondary contacts  62  and closing the secondary contacts  62 . 
   In  FIG. 7 , the locking plate  58  is shown as being in the down position and engaged with the projection  53  on the plunger  52  and, thus closing the secondary contacts  62 . That is, an aperture  59  in the locking plate  58  interlocks with the projection  53  on the plunger  52  and holds the locking plate  58  in a position in which the locking plate  58  makes contact with and closes the secondary contacts  62 . When the reset button  34  is depressed and the locking plate  58  is in a locked state, the reset pin  56  cannot engage with the latching plate  54  because the plunger  52  positions the latching plate  54  such that the reset pin  56  passes through opening  55  freely. The locking plate  58  will remain in this position until the GFCI receptacle  10  is powered from the line side. As can be appreciated from the schematic in  FIG. 4 , the load terminals  37  and  38  are electrically isolated from the remainder of the circuit when the latching mechanism  46  is in the open state as shown in  FIG. 4 . However, as is also shown, the secondary contacts  62 , when closed by the locking plate  58 , provide a path which enables the solenoid to be powered from the power source connected to the line terminals  39  and  40  and move the plunger  52  in the direction of “A”, thereby removing the projection  53  of the plunger  52  from the aperture  59  and releasing the locking plate  58 . Accordingly, the spring  60  raises the locking plate  58  upward and out of contact with secondary contacts  62 , thus opening the secondary contacts  62 . 
     FIGS. 8-10  are cross sectional views illustrating examples of positions of the locking plate  58 , a latching plate  54  and a reset pin  56  in accordance with an embodiment of the present invention. In  FIG. 8 , the locking plate  58  is shown as being engaged with the projection  53  of the plunger  52  via the aperture  59 . The locking plate  58  makes contact with secondary contacts  62 , thus closing them. Locking spring  60  is compressed and exerts pressure against the locking plate  58 , but cannot move locking plate  58  upwards because locking plate  58  is held in place by projection  53 . In addition, latching plate  54  is positioned to prevent the reset pin  56  from engaging with the latching plate  54 . That is, the latching plate  54  is positioned to allow the reset pin  56  to freely pass through the latching plate  54  when the reset button is depressed without engaging with the latch plate  54 . 
   In  FIG. 9 , the GFCI receptacle  10  is powered from the line side. The secondary contacts  62  which are closed, power the solenoid  50 , which drives the plunger  52  forward in the direction of “A”. This releases the projection of the plunger  52  from the aperture  59 , and also pushes the plunger  52  against the latching plate  54  to position the opening  53  slightly out of alignment with the reset pin  56 . The locking spring  60  urges the locking plate  58  upward, thus forcing the locking plate into an extended or non-contacting position. The secondary contacts  62  open and remove power from the solenoid  50 . 
   As shown in  FIG. 10 , the GFCI receptacle  10  is in a state of normal operation. That is, the locking plate  58  and locking spring  60  are in an extended position, the secondary contacts are open, and the reset pin  56  is able to engage with the edges of the latch plate  54  forming the aperture  53 , thus allowing the upper shoulder  57  of the reset pin  56  to contact and thus engage with the underside of latching plate  54  when the reset button is depressed. Although not shown specifically, the spring  60  can thus urge the reset button upward along arrow “UP”, thus drawing the latch plate  54  and latch block  63  upward. The latch block  63  thus closes the contacts of latching mechanism  46  to thus provide electrical connection between the line terminals  39  and  40 , and their respective load terminals  37  and  38  and face terminals “hot face” and “neutral face”. 
   Referring now to  FIG. 1  and the operation of the GFCI receptacle  10  in a ground fault state. The GFCI receptacle  10  is disabled upon detection of a current imbalance. Specifically, the sensing circuit  48  selectively places the solenoid  50  in a ground fault state in response to an imbalance of current flow in the AC receptacle. While the solenoid  50  is shown here as being a solenoid, other devices such as piezoelectric components and micro electromechanical systems (MEMS) may be used. It can also be seen that the latching mechanism  46  is connected to the sensing circuit  48  and is placed in series with a plurality of conductive paths between opposing terminals of the receptacle. Specifically, the latching mechanism  46  breaks a plurality of conductive paths leading from side line terminals  39  and  40  to side load terminals  37  and  38  of the GFCI device  10  when the solenoid  16  is placed in the ground fault state. 
   The latching mechanism  46  is structured such that plugins  18  and  20 , the face receptacles, are isolated from the line terminals  39  and  40  and the load terminals  37  and  38 . Thus if the GFCI  10  is miswired and/or in a tripped position, plugins  18  and  20  will not be powered. A detailed description of the operation of latching mechanism  46  can be found in U.S. Provisional Patent Application Ser. No. 60/378,647, referenced above. Latching mechanism  46  provides improved safety while maintaining a relatively low level of complexity with regard to conventional approaches. The latching mechanism  46  has an internal structure that breaks the conductive paths between the side A terminals and the side B terminals and also disconnects a face receptacle hot terminal  256  and a face receptacle neutral terminal  258  from the conductive paths. Specifically, the face receptacle hot terminal  256  is connected to a fifth switch contact  234  and the face receptacle neutral terminal  258  is connected to a first switch contact  226 . Both switch contacts  226  and  234  are selectively placed in the conductive paths. Thus, by selectively placing the switch contacts  226  and  234  in the conductive paths, the face hot terminal  256  and the face neutral terminal  258  can be isolated from the conductive paths as well as the side A and B terminals  39  and  40  and  37  and  38  when a current imbalance is detected. The latching mechanism  46  thus provides improved safety while maintaining a relatively low level of complexity with regard to conventional approaches. The state of switch contacts  222 ,  224 ,  225 ,  230 ,  232  and  233  as shown in  FIG. 4  indicates that the solenoid  50  has entered the ground fault state, due to depression of the test button or due to an actual ground fault. However, when the solenoid  50  is not in the ground fault state and the latching mechanism has been properly reset so that second switch contact  222  and third and fourth dual-switch contacts  224 ,  225  are closed to first switch contact  226 , and sixth switch contact  230  and seventh and eighth dual-switch contacts  232 ,  233  are closed to fifth switch contact  234 ; the first conductive path includes the first side A terminal  40 , first side A conductor  64 , first switch contact  226 , second switch contact  222 , third and fourth dual-switch contacts  224 ,  225 , face terminal receptacle neutral  258 , and first side B terminal  38 . Similarly, the second conductive path includes second side A terminal  39 , a second side A conductor  66 , fifth switch contact  234 , sixth switch contact  230 , seventh and eighth dual-switch contacts  232 ,  233 , face terminal receptacle hot  256 , and second side B terminal  37 . While the first and second conductive paths are shown as corresponding to the neutral and hot connections respectively, it will be appreciated that these assignments can readily be reversed without departing from the scope of the present invention. 
   It can further be seen that the latching mechanism  46  is structured such that, in response to a reset button  34 (see  FIG. 19 ) being pressed in the AC receptacle, second switch contact  222  comes into contact with fourth switch contact  225 . The upward movement of second switch contact  222  provides for the second switch contact  222  and third and fourth dual-switch contacts  224 ,  225  making contact with first switch contact  226 . Similarly, the sixth switch contact&#39;s  230  upward movement provides for sixth switch contact  230  coming into contact with eighth switch contact  233 . The upward movement is continued until the sixth switch contact  230  and seventh and eighth dual-switch contacts  232 ,  233  make contact with fifth switch contact  234 . Thus, face receptacle hot and face receptacle neutral terminals  256  and  258  are connected with the conductive paths and can provide power to a load that is plugged into the receptacles. 
   Turning now to  FIGS. 19-26  which are diagrams showing various positions of switch contacts for the circuit of  FIG. 4  in accordance with an alternative embodiment of the present invention. In  FIG. 19 , the reset button  34 , which in an embodiment of the invention is spring loaded, is in an open position.  FIG. 20  which shows the GFCI from a different angle depicts first switch contact  226 , second switch contact  222 , and third and fourth dual-switch contacts  224 ,  225  being open with respect to each other.  FIG. 21  shows the reset button  34  in a closed position while  FIG. 22  shows first switch  226 , second switch contact  222 , and third and fourth dual-switch contacts  224 ,  225  still being open with respect to each other. As shown in  FIG. 23 , as the reset button  34  moves back towards an open position, second switch contact  222  moves upward and comes into contact with fourth switch  225  (see  FIG. 24 ). When the reset button  34  goes back into the open position (see  FIG. 25 ), second switch contact  222  and third and fourth dual-switch contacts  224 ,  225  close with first switch contact  226 . Although not shown in the drawings, the same sequence of events occur for fifth switch contact  234 , sixth switch contact  230 , and seventh and eighth dual-switch  232 ,  233 . 
   It should be noted that the sensing circuit  48  effectively defines an imbalance of current flow as any difference in the amount of current flowing in the candidate paths that rises above a predetermined threshold. 
   To better demonstrate the operation of latching mechanism  46 , the sensing circuit  48  will now be described in greater detail. Generally, it can be seen that the sensing circuit  48  has a transformer arrangement  68 , a control circuit  70  and a test switch  30 . The transformer arrangement  68  generates control signals in response to the imbalance of current flow, while the control circuit  70  is connected to the transformer arrangement  68  and selectively generates a switching signal based on the control signals. The test switch  30  is connected between the line terminal  40  and the load terminal  37  such that the test switch  30  enables manual generation of the imbalance of current flow. 
   Specifically, when the test switch  30  is closed (for example, manually, by an installer of the device), a circuit path is created from the load terminal  38  to the line terminal  40 , which creates an imbalance that is detected by a first (or sense) transformer  68 A. In an embodiment of the invention, the first transformer  68 A detects imbalances in the net flux on the load side e.g. terminals  37  and  38  of the GFCI receptacle  10 , and operates in conjunction with the control circuit  70  to energize the solenoid  50 . 
   Detection of the imbalance condition by the first transformer  68 A and the control circuit  70  causes activation of the solenoid  50  such that the latching mechanism  46  is open as shown in  FIG. 1 . It can be further be seen that a second (grounded neutral) transformer  68 B is also provided to allow the transformer arrangement  68  to measure the change in net flux between the first conductive path  64  and the second conductive path  66 . 
   It can be seen that the control circuit  70  preferably includes an amplifier and trip circuit  72 , a full-wave bridge rectifier  74  and a silicon controlled rectifier (SCR)  76 . The amplifier and trip circuit  72  generate the switching signal, where the bridge rectifier  74  is connected to the line side terminals  39  and  40 . It can be seen that the bridge rectifier  74  provides power to the amplifier and trip circuit  72  and that the SCR  76  selectively energizes the solenoid  50  based on the switching signal. The control circuit  70  preferably includes the components listed in the following table: 
   
     
       
             
             
           
         
             
                 
             
           
           
             
               CAPACITOR C1 
               10 MIC OF AND, 16 VDC ALUM, ELECTROLYTIC 
             
             
               CAPACITOR C2 
               3.3 MIC, 16 VDC ALUM, ELECTROLYTIC 
             
             
               CAPACITOR C3 
               .01 MIC, 50 VDC CERAMIC 
             
             
               CAPACITOR C4 
               .033 MIC, 25 VDC CERAMIC 
             
             
               CAPACITOR C5 
               .01 MIC, 500 VDC CERAMIC 
             
             
               CAPACITOR C6 
               .01 MIC, 50 VDC CERAMIC 
             
             
               CAPACITOR C7 
               470 PIC, 50 VDC CERAMIC 
             
             
               DIODE D1 
               IN4004 
             
             
               DIODE D2 
               IN4004 
             
             
               DIODE D3 
               IN4004 
             
             
               DIODE D4 
               IN4004 
             
             
               DIODE D5 
               IN4004 
             
             
               RESISTOR R1 
               15K OHM, ¼ W CARBON FILM 
             
             
               RESISTOR R2 
               1.5 MED OHM, ¼ W METAL FILM 
             
             
               RESISTOR R3 
               24K OHM, ½ W CARBON FILM 
             
             
               RESISTOR R4 
               200 OHM, ¼ W CARBON FILM 
             
             
               IC 
               RV4145 
             
             
                 
             
           
        
       
     
   
   The state of the latching mechanism  46  as shown in  FIG. 4  indicates that the solenoid  50  has entered the ground fault state, due to depression of the test button  30  or due to an actual ground fault. However, when the solenoid  50  is not in the ground fault state and the latching mechanism  46  has been properly reset so that latching mechanism  46  is closed a first and second path is created connecting the line terminals  39  and  40  to the load terminals  37  and  38  providing power to a load when the GFCI  10  is powered from the line side. 
   It is also important to note that when in the ground fault state, as shown in  FIG. 1 , an alternative current path is provided between the load terminal  37  and the line terminal  40 . Thus, if the AC source is connected to the line side of GFCI receptacle  10  and the test switch  30  is closed, current flows from line side terminal  40 , through resistor R 1 , to the load terminal  37 . Thus, this current path will create an imbalance in the transformer arrangement  68  resulting in the latching mechanism  46  being open. 
     FIG. 11  is a schematic diagram illustrating an example of the ground fault circuit interrupting device of  FIG. 3  in accordance with another embodiment of the present invention. The GFCI receptacle  11  is similar in operation to the GFCI device  10  discussed above except GFCI receptacle  11  includes an alarm indicator  44 , a test switch  30  having primary contacts TS 1  and secondary contacts TS 2 . A detailed description of the operation of the test switch can be found in U.S. patent application Ser. No. 10/032,064, filed on Dec. 31, 2001 entitled “Ground Fault Circuit Interrupter (GFCI) With A Secondary Switch Contact Protection”, which is incorporated herein by reference. 
   When test switch  30  is pressed and closes primary test switch contacts TS 1 , an imbalance is created. The latching mechanism  46  opens and the alarm indicator  44  is extinguished and no longer provides a green colored illumination. Since the latching mechanism  46  is open, the subsequent closing of secondary test switch contacts TS 2  by test switch  30  has no affect on GFCI  11 . 
   In contrast, if the closing of primary test switch contacts TS 1  fails to trip the latching mechanism  46 , secondary test switch contact TS 2  causes a short circuit blowing the fuse F 10  and extinguishing the alarm indicator  44  providing green illumination. However, the alarm indicator  44  illuminates red. Diode DC 10 , resistor R 11  and capacitor together act to flash alarm indicator  44 . The flashing alarm indicator  44  indicates to a user that GFCI  11  is not providing ground fault protection and is only operating as an unprotected receptacle and not as a GFCI. Alarm indicator  44  will only flash red when the latching mechanism fails to trip. Thus, the alarm indicator can also serve to provide an indication of a defective solenoid  50 , or any other component of the GFCI that aids in tripping the latching mechanism  46 . 
     FIG. 12  is a perspective view of an example of a ground fault circuit interrupting (GFCI) device in accordance with another embodiment of the present invention. The GFCI  115  does not contain isolated face terminals and performs ground fault detection in a manner known to those skilled in the art and will be discussed with reference to its novelty. The GFCI  115  includes latching plate  153  (See  FIG. 13 ), secondary contacts  162  and a locking plate  157 . Latching plate  153  is structured and arranged so that a portion of the latching plate passes through a plunger end  151  (See  FIG. 13 ). The portion of the latching plate  153  passing through the plunger end  151  has a curved end. The curved end of the latching plate  153  allows the plunger end  151  to move the latching plate  153  laterally in the direction of “A” and “B”. Proximate its center, latching plate  153  has an aperture  154  to allow reset pin  156  to engage with the latching plate  153  when the reset button  134  is depressed. In a reset prevention state, the latching plate  153  is positioned such that the reset pin  156  freely passes through the latching plate  153 . 
   Locking plate  157  is used to place the GFCI  115  in a reset prevention state. The locking plate can be a pin type device, which is inserted through the aperture  142  during the manufacturing process between the plunger  151  and the secondary contacts  162 , thus closing the secondary contacts  162 . When the GFCI  115  is powered from the load side, there is no power to the solenoid  150 . Therefore, the GFCI  115  remains in a reset prevention state because upper shoulder  149  of the reset pin  156  cannot latch with the bottom surface of the latching plate  153  and reset the GFCI  115 . When the GFCI  115  is powered from the line side, the solenoid is powered and moves the plunger in the direction of “B” slightly misaligning the aperture  154  in the latching plate  153  with the reset pin  156 , thus allowing the upper shoulder  149  of reset pin  156  to contact the lower surface of latching plate  153 , and thus pull latch plate  153  and latch block  159  upward to close the contacts of latching mechanism  178  in a manner similar to that discussed with regard to latch plate  54  and latch block  63 . The locking plate  157  falls and opens the secondary contacts  162 , removing power from the solenoid  150 . 
   This embodiment of the invention will now be discussed with reference to  FIG. 13-16  which are views illustrating examples of positions of a locking plate in the GFCI of  FIG. 12  in accordance with an embodiment of the present invention. In  FIG. 13 , secondary contacts  162  are open and the locking plate  157  is being inserted into the GFCI  115  via the aperture  142 . 
   In  FIG. 14 , the locking plate  157  comprising a pin type device is inserted between the plunger  151  and the secondary contacts  162 , thus closing the secondary contacts  162  and allowing the secondary contacts  162  to power the solenoid  150  if the GFCI  115  is wired from the line side. The latching plate  153 , however, is positioned to allow the reset pin  156  to freely pass through the aperture  154  and thus not engage with the latching plate  153  unless the GFCI  115  is connected to the line side in a manner similar to that discussed above with regard to  FIGS. 4-10 . 
   In  FIG. 15 , the GFCI  115  has been wired to the line side and the plunger  151  moves in the direction of “B” to release the locking plate  157 . IN  FIG. 16 , the plunger  151  moves in the direction of “A” allowing an aperture in the latch plate  153  to be slightly misaligned with the reset pin  156  as shown in  FIG. 16 . 
     FIGS. 17A and 17B  are cross sectional views illustrating examples of positions of an initial reset prevention arrangement that can be used with a GFCI in accordance with another embodiment of the present invention. For conciseness, the details of the reset button, and reset pin are not repeated here. In  FIG. 17 , the locking plate  182  comprises a vertical member  182 A connected to a horizontal member  182 B proximate the center of the horizontal member  182 B. A locking spring  180  is disposed between a portion of the inner housing  113  and an end of the horizontal member  182 B. The locking spring  180  exerts force on the horizontal member  182 B in the direction of “C”. An opposing end of the horizontal member  182 B makes contact with secondary contacts  178  in order to close the secondary contacts  178 . The locking plate  182  is shown in a non-initial reset prevention state. That is, the plunger end  151  does not retain the vertical member  182 A of the locking plate  182  in a position in which the horizontal member  182 B closes the secondary contacts  178  by making contact with the secondary contacts  178 . 
   Referring now to  FIG. 17B , the plunger end  151  is shown retaining the vertical member  182 A of the locking plate  182  which enables the horizontal member  182 B to close the secondary contacts  178 . The latch plate  153  is positioned so that the end of the reset pin (not shown) can freely pass through the opening  154  as discussed above, to prevent resetting. As also discussed above, the locking spring  180  is compressed by an end of the vertical member  182  which exerts force in the direction of “C”. When the GFCI is powered from the line side, the secondary contacts  178  power the solenoid  150  which results in the plunger  151  moving in the direction of “A”, thus releasing the locking plate  182 . Substantially simultaneously, the spring  180  exerts force on the horizontal member  182 B to propel the horizontal member  182 B in the direction of “C” and open the secondary contacts  178 . 
     FIGS. 18A and 18B  are cross sectional views illustrating examples of positions of a another initial reset prevention arrangement that can be used with a GFCI in accordance with an embodiment of the present invention. Referring to  18 B, the solenoid  150  includes a plunger  184  having a vertical member  184 A, a horizontal member  184 B and an aperture  184 C. The vertical member  184 A is connected to the solenoid  150  and to a latching plate  186 , which is similar to latching plate  153  discussed above. The horizontal member  184 B is connected to the vertical member  184 A. In an initial reset prevention state, the pin  191  of locking plate  190  is aligned with and passes through aperture  184 C engages with the upper surface of horizontal member  184 B, and thus closes the secondary contacts  192 . In this position, an aperture  187  in the latching plate  186  is substantially aligned with a reset pin (not shown) to thus allow the reset pin to pass through the aperture  187 . Thus, the reset pin cannot latch with the latching plate  186  and close the latching mechanism (not shown) to reset. The locking spring  188  is compressed and exerts force on the locking plate  190  in the direction of “C”. However, the locking spring  188  cannot pull the locking plate  190  out of the aperture  184 C unless the GFCI is powered from the line side. 
   Referring now to  FIG. 18A , the GFCI has been wired to the line side. The secondary contacts  192  power the solenoid  150  moving the plunger  184  in the direction of “B”. This movement releases the locking plate from aperture  184 C. The locking spring  180  propels the locking plate  190  away from the aperture  184 C and secondary contacts  192  to a position of rest as shown. The release of the locking plate  190  moves the latching plate  186  to slightly misalign the aperture  187  in the latching plate  186  with the reset pin. Thus, the reset pin can engage the latching plate  186  and reset the contacts to a closed state in a manner similar to that discussed above. 
   Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention can be described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification and following claims.

Technology Category: 5