Abstract:
A Ground Fault Circuit Interrupter (GFCI) interrupts the flow of current through a pair of lines extending between a source of power and a load. The GFCI includes a circuit breaker, a relay circuit including a solenoid, a latch circuit, and a fault detecting circuit packaged in a circuit assembly. The GFCI is adaptable for a quick connect of a load input cord by a user, allowing for various configurations of cords to be utilized on site, the cord easily connected from the device being protected to the GFCI at the point of use. The GFCI circuit assembly includes a load input section having cable securement jaws for connection of the load input cable terminal ends.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application is related to, claims the earliest available effective filing date(s) from (e.g., claims earliest available priority dates for other than provisional patent applications; claims benefits under 35 USC §119(e) for provisional patent applications), and incorporates by reference in its entirety all subject matter of the following listed application(s) (the “Related Applications”) to the extent such subject matter is not inconsistent herewith; the present application also claims the earliest available effective filing date(s) from, and also incorporates by reference in its entirety all subject matter of any and all parent, grandparent, great-grandparent, etc. applications of the Related Application(s) to the extent such subject matter is not inconsistent herewith: 
         [0002]    U.S. provisional patent application 61/842,999 entitled “A Manual Reset Ground Fault Circuit Interrupter (GFCI) With a Quick Connect Load Input”, naming Victor V. Aromin and Chepur P. Rau as inventors, filed 4 Jul. 2013. 
       FIELD OF USE  
       [0003]    The present invention relates generally to electrical safety devices and more particularly to a ground fault circuit interrupter (GFCI) having a connection feature that allows for on-site quick engagement of Load input cords. 
     
    
     DESCRIPTION OF PRIOR ART (BACKGROUND) 
       [0004]    Conventional electrical appliances typically receive alternating current (AC) power from a power supply, such as an electrical outlet, through a pair of conducting lines. The pair of conducting lines, often referred to as the line and neutral conductors, enable the electrical appliance, or load, to receive the current necessary to operate. 
         [0005]    The connection of an electrical appliance to a power supply by a pair of conducting lines creates a number of potentially dangerous conditions. In particular, there exists the risk of ground fault and grounded neutral conditions in the conducting lines. A ground fault condition occurs when there is an imbalance between the currents flowing in the line and neutral conductors. A grounded neutral condition occurs when the neutral conductor is grounded at the load. A ground fault condition is extremely dangerous and can result in serious injury. 
         [0006]    Ground fault circuit interrupters are well known in the art and are commonly used to protect against ground fault and grounded neutral conditions. In general, GFCI devices sense the presence of ground fault and grounded neutral conditions in the conducting lines, and in response thereto, open at least one of the conducting lines between the power supply and the load to eliminate the dangerous condition. In U.S. Pat. No. 5,177,657, to M. Baer et al, there is disclosed a ground limit interrupter circuit which interrupts the flow of current to a pair of lines extending between a source of power and a load. The ground fault interrupter circuit includes a circuit breaker comprising a normally open switch located in one or both of the lines, a relay circuit for selectively closing the normally open switch, an electronic latch circuit operable in first and second bi-stable states and a fault sensing circuit for sensing the presence of a fault condition in at least one of the lines. The electronic latch circuit causes the relay circuit to close the normally open switch and maintain the normally open switch in its closed position when the electronic latch circuit is in the first bi-stable state. 
         [0007]    The electronic latch circuit also causes the relay circuit to permit the normally open switch to return to its normally open condition when the latch circuit is in its second bi-stable state. A fault sensing circuit senses the presence of a fault condition in at least one of the lines and causes the electronic latch to latch in its second state upon detection of the fault condition. 
         [0008]    In U.S. Pat. No. 5,418,678 to T. M. McDonald, there is disclosed an improved ground fault circuit interrupter (GFCI) device which requires manual setting following initial connection to an AC power source or termination of to power source interruption. The improved GFCI device utilizes a controlled switching device which is responsive to a load power signal for allowing the relay contact sets of the GFCI device to be closed only when power is being made available at the output or load terminals. The controlled switching device preferably comprises an opto-isolator or other type of switching device which provides isolation between the GFCI input and output terminals when the relay contact sets are open. The improved GFCI device may be incorporated into portable units, such as plug-in or line cord units, for use with unprotected AC receptacles. 
         [0009]    In U.S. Pat. No. 4,816,957 to L. F. Irwin there is disclosed an adapter unit comprising a moisture resistant housing within which is carried an improved, self testing ground line fault interrupter device. The improved device is electrically interconnected with a connector carried externally of the adapter housing so that the unit can be plugged directly into a standard duplex outlet of an existing circuit. The apparatus includes circuitry that automatically tests the operability of the device when it is plugged into a duplex outlet without the need for manual manipulation of test buttons or other overt action by the user. 
         [0010]    In U.S. Pat. No. 4,578,732 to C. W. Draper et al there is disclosed a wall socket type ground fault circuit interrupter baying a pair of sockets, a reset button and a test button that are accessible from the front of the interrupter. The interrupter has latched snap-acting contacts and a novel latching relay structure for releasably maintaining the snap-acting contacts in a circuit making position. The snap-acting contacts permit all of the components including the monitoring toroids and the power supply to be respectively located and connected at the load side of the snap-acting contacts so that all of the circuits of the interrupter are de-energized when the contacts snap to a circuit opening position. The snap-acting contact mechanism and relay are provided with structures which provide the interrupter with a trip-free mode of contact actuation and accordingly a tease-proof snap-acting contact operation. 
         [0011]    One drawback of GFCI devices of the type described above is that the GFCI device generally includes a large solenoid to selectively open and close the switching device. Specifically, the solenoid generally requires a constant supply of line voltage (approximately 120 volts) in order to switch and sustain the solenoid in its energized state. As a consequence, the solenoid acts as a large power drain source. In addition, the constant supply of line voltage to the solenoid causes the solenoid to heat up significantly and potentially burn out. 
         [0012]    Moreover, the devices of the type described above do not include a feature for the on-site quick connection of load input cords. 
       BRIEF SUMMARY  
       [0013]    The foregoing and other problems are overcome, and other advantages are realized, in accordance with the presently preferred embodiments of these teachings. In accordance with one embodiment the invention is directed towards a single universal GFCI adaptable for a quick connect of a load input cord by a user. The device may be sold without a load input cord, allowing for various configurations of cords to be utilized on site, the cord easily connected from the device being protected to the GFCI at the point of use. The GFCI circuit assembly including a load input section having cable securement jaws for connection of load input cable terminal ends. 
         [0014]    Components and circuit traces mounted and or adhered to the Printed Circuit Board (PCB) of the GFCI are configured to minimize PCB packaging density while simultaneously maximizing distances between component and circuit traces to conform to required safety standards, e.g., UL840, to prevent electric arcing and dielectric breakdown. 
         [0015]    The GFCI constructed according to this invention further includes: a circuit breaker having a switch located in one of said lines, said switch having a first position in which the source of power in its associated line is not connected to the load and a second position in which the source of power in its associated line is connected to the load. The switch being in a normally open configuration and prior to use the GFCI having to be manually reset to connect the power to the load, and 
         [0016]    a relay circuit for selectively moving said switch to said first open position after a manual reset or ground fault, said relay circuit including a solenoid operable in either an energized state or a de-energized state, said solenoid setting said switch in said first open position when in its de-energized state and maintaining said switch in said first open position until manually reset, and 
         [0017]    a latch circuit operable in first and second bi-stable states, said latch circuit allowing said solenoid to switch from its energized state (first bi-stable state) to its de-energized state (second bi-stable state) and remain in its de-energized state until manually reset, and 
         [0018]    a fault detecting circuit for detecting the presence of a fault condition in at least one of said lines extending between the power and the load and for causing said latch circuit to latch in its second bi-stable state, allowing said solenoid to switch from its energized state to its de-energized state, upon detection of said fault condition. 
         [0019]    The GFCI circuit arrangement further includes movable contact arms that are mechanically biased to keep the contacts in a normally open position. The contact arms may take the form of a contact-carrying bar mounted in a cantilever fashion by flexible supporting legs that provide the bias to a normally open position. An elongated actuating member is arranged to reciprocate adjacent the contact-carrying bar when manually energized through an appropriate push button. When pushed, the actuating member pushes the moveable contact arm ends to engage stationary contact arms thereby connecting the source of power to the load. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0021]      FIG. 1  is a schematic circuit diagram of an embodiment of a ground fault circuit interrupter (GFCI) employing the principles of subject invention as shown in  FIG. 2-5 ; 
           [0022]      FIG. 2  shows a top plan view of an embodiment of the GFCI employing the principles of subject invention described herein; 
           [0023]      FIG. 3  shows a bottom plan view of the GFCI of  FIG. 2  employing the principles of subject invention described herein; 
           [0024]      FIG. 4  shows a side view of an GFCI of  FIG. 2  employing the principles of subject invention described herein; 
           [0025]      FIG. 5  illustrates an exploded view of the GFCI of the present invention as embodied in a GFCI Enclosure having a 90 degree male receptacle power source input contained in a single enclosure; 
           [0026]      FIG. 6  illustrates the moveable contact arms utilized in subject invention including at one end a flexible projection utilized to secure a load input cable: 
           [0027]      FIG. 7  illustrates a partial view of the GFCI of  FIG. 2  showing the contact arm engagement with a load input cord: 
           [0028]      FIG. 8  illustrates an exploded view of the bottom housing of the GFCI enclosure of  FIG. 5  showing the channels utilized for seating of the load input cord exposed ends; 
           [0029]      FIG. 9  illustrates an assembled GFCI enclosure of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Referring now to the drawings and more particularly to  FIG. 1 , there is shown a ground fault circuit interrupter (hereinafter GFCI) circuit schematic of the GFCI constructed according to the teachings of the present invention, the GFCI being represented generally by reference numeral  100 . As will be discussed in detail below, GFCI  100 , is a manual reset type GFCI circuit, and must be manually set upon connection to a power source to protect a load from ground fault condition. Consequently, upon a ground fault condition, or upon a loss of power to GFCI  100  it can be manually reset to protect against further ground fault conditions. 
         [0031]    GFCI  100  includes a circuit breaker  110 , a fault detection circuit  120 , a latch circuit  130 , a relay circuit  140 , and a test circuit  150 . Circuit breaker  110  includes a pair of single-pole, double-throw switches SW 1  and SW 2  which are located in the line and neutral conductive lines, respectively, between a power source and a load. Circuit breaker  100  acts to selectively open and close the pair of conductive lines. Switches SW 1  and SW 2  can be positioned in either of two connective positions. In the first connective position, which is illustrated in  FIG. 1 , switches SW 1  and SW 2  are positioned such that the power source is not connected to the load, in a normally open position. In the second connective position, which is the opposite position illustrated in  FIG. 1 , switches SW 1  and SW 2  are positioned such that the power source is connected to the load. This condition occurs subsequent to the GFCI being connected to a power source and being manually reset. 
         [0032]    Fault detection circuit  120  acts to detect both ground fault and grounded neutral conditions in the conductive lines when switches SW 1  and SW 2  are in their second connective position. Fault detection circuit  120  comprises a sense transformer T 1 , a grounded neutral transformer T 2 , capacitors C 1 , C 4  and C 5 , resistors R 2  and R 3  and a ground fault interrupter chip U 1 . Transformer T 1  and T 2  are preferably transformers sold by Magnetic Metals Corporation, Camden, N.J. and compatible with Low Power Controller U 1 . Low Power Controller U 1  is preferably that sold by Fairchild Semiconductor, model No. RV4145A. 
         [0033]    Sense transformer T 1  senses the current differential between the line and neutral conductive lines, and upon the presence of a ground fault condition, transformer T 1  induces an associated output from its secondary windings. Grounded neutral transformer T 2  acts in conjunction with transformer T 1  to sense the presence of grounded neutral conditions and in turn, induce an associated output. The AC signal from the secondary winding of transformer T 1  is coupled to chip U 1 . 
         [0034]    Fault detection circuit  120  further provides the capability to prevent fault detection in response to low level faults, line disturbances, and electrical noise. Circuit  120  acts to set a minimum fault current at which Fault Detection Circuit  120  provides an output to latch circuit  130 . Low Power Controller U 1  serves to amplify the fault signal generated by transformer T 1  and provide an output pulse on pin  5  to activate latch circuit  130 . 
         [0035]    Latch Circuit  130  acts to take the electrical signal produced by fault detection circuit  120  upon the detection of a ground fault or grounded neutral condition and, in turn, creating a short across solenoid K 1  and effectively de-energizing it. Latch circuit  130  comprises a silicon controlled rectifier SCR 1  operable in either a conductive or a non-conductive state, and a noise suppression capacitor C 2  to prevent narrow pulses from firing the SCR 1 . In the preferred embodiment, SCR 1  has a high dV/dt rating to ensure that line noise does not falsely trigger SCR 1 , and the SCR 1  has a gate drive requirement of less than 200 uF. 
         [0036]    Relay circuit  140  acts to selectively position switches S 1  and S 2  to their first connective positions when a short occurs across K 1 , thereby indicating a ground fault or ground neutral condition has occured. Relay circuit  140  comprises a solenoid K 1 , capacitor C 3 , resistor R 6 , silicon rectifier CR 1 , and Resistors R 4 , R 5 , R 7 , R 8 . Solenoid K 1  is ganged to the circuit breaker contacts of switches S 1  and S 2  and is responsible for selectively controlling the connective position of switches S 1  and S 2 . Before power is applied to GFCI  100 . SW 1  and SW 2  are in the first connective position, normally open, as illustrated in  FIG. 1 , where the power source is not connected to the load. Upon power being applied to GFCI  100 , SW 1  and SW 2  still remain in the normally open position. Only after switches SW 1  and SW 2  are manually reset via a reset switch (not shown) solenoid SOL 1  positions switches SW 1  and SW 2  in their second connective position (closed) and the source is no connected to the load. Switches SW 1  and SW 2  will remain in their second connective position until either the source of power is removed from GFCI  100  or a ground fault or ground fault neutral condition occurs. A constant voltage of 28 volts is applied to solenoid K 1  subsequent to K 1  being energized after a manual reset. A voltage divider network of resistors R 4 , R 5 , R 5 , R 7 , and R 8  and silicon rectifier CR 1  provide a voltage drop to keep solenoid K 1  Energized. 
         [0037]    Test circuit  150  provides a means of testing whether circuit  100  is functioning properly. Test circuit  150  comprises a current limiting resistor R 1  having a value of 15 Kohms and a test switch SW 3  of conventional push-in type design. When SW 3  is depressed to energize test circuit  150 , resistor R 1  provides a simulated fault current to transformer T 1  which is similar to a gonad fault condition. 
         [0038]    Referring, to  FIG. 2  there is shown a top plan view of a GFCI Printed Circuit Board (PCB)  10 . The GFCI PCB  10  includes solenoid  14  encased in frame  12 , plunger  22 , moveable contact arms  18 , actuating member  20 , stationary contact arms  16 , and transformer  24 . Further dispersed on GFCI  10  are the circuit components as illustrated in  FIG. 1 . It is understood that the arrangement of the circuit components from  FIG. 1  onto the GFCI PCB of  FIGS. 2 and 3  can be an arrangement that allows for the quick connect features of the present invention to be arranged on the GFCI PCB  10 , and which allows for the minimization of PCB packaging density while simultaneously maximizing distances between component and circuit traces to conform to required safety standards, e.g., UL840, to prevent electric arcing and dielectric breakdown. 
         [0039]    In the preferred embodiment, solenoid  14  and frame  12  are positioned at one end of GFCI PCB  10 , and transformer  24 , encapsulating transformers T 1  and T 2  are positioned at the opposite can of GFCI PCB  10 . Movable contact arms  18  are positioned parallel to each other on opposite sides of frame  12  and extend longitudinally to contact points  18 C 3  which are movable by actuating member  20  positioned transverse and forward to transformer housing  24 . Stationary contact arms  16 , having at one end contact point  16 A for engagement with contact point  18 C 3 , extend in longitudinal alignment with contact arms  18  in the direction of transformer housing  24 , and are positioned parallel to each other on opposite sides of transformer housing  24 . 
         [0040]    Referring also to  FIG. 3  there is shown a bottom plan view of the GFCI PCB package  10 . The GFCI PCB  10  includes components mounted on a bottom surface of PCB  10 . Also shown in  FIG. 3  are surface traces connecting the top and bottom PCB components. It will be appreciated that the components, and circuit traces shown in  FIG. 3  are strategically arranged to minimize required spacing while simultaneously maintaining arcing and dielectric breakdown prevention distances between each of the components and surface traces. 
         [0041]    As illustrated in  FIG. 2  and  FIG. 4 , GFCI PCB  10  includes a load input section  50  and a source power input section  45 . As illustrated in  FIGS. 5 and 9 , a 90 degree source input plug is illustrated, however, any angular configuration plug, such as an in-line may be utilized with the GFCI PCB  10 . Referring to  FIG. 5  and  FIG. 9 , GFCI PCB may be housed in enclosure  40 , the enclosure having a top  28  and bottom  30 . 
         [0042]    Referring to  FIG. 4 , the GFCI PCB  10  arrangement employs movable contact arms  18  that are mechanically biased to keep the contacts in a normally open position. Referring to  FIG. 6 , the contact arms  18  may take the form of a contact-carrying bar mounted in a cantilever fashion having flexible supporting legs  18 C 2  that provide the bias to a normally open position. In the preferred embodiment, and referring to  FIG. 4 , Flexible supporting, legs  18 C 2  are arranged adjacent to frame  12  of GFCI PCB  10 , and anchored at point  18 A. As illustrated in  FIG. 4 , Flexible Supporting legs  18 C 2  are resiliently flexible, and place contacts  18 C 3  in the normally open position. 
         [0043]    Referring to  FIG. 4 , an elongated actuating member  21  is arranged to reciprocate adjacent the contact-carrying bar  20  when manually energized through an appropriate push button  26 . When pushed, the actuating member  21  pushes the moveable contact arm ends  18 C 3  to engage stationary contact arms  16  thereby connecting the source of power  45  to the load  50 . 
         [0044]    Referring to  FIG. 6 , contact carrying bar  18 C further includes an upward, resiliently flexible projection  18 B and recess  18 C 1 . As illustrated in  FIG. 7 , the quick connect feature of the present invention allows for the stripped end  32 A 1  of cord  32  to slideably engage flexible projection  18 B causing projection  18 B to flex downward. In the preferred embodiment, flexible projection  18 B includes a grooved contact surface  18 B 1  to provide increased contact surface to stripped end  32 A 1 . Stripped end  32 A 1  slideably engages grooved contact surface  18 B 1  up to a point when the end of stripped end  32 A 1  seats within recess  18 C 1 . From point  18 A, legs  18 C 2  are raised to provide legs  18 C 2  with resilient flexibility. 
         [0045]    Referring to  FIG. 8 , bottom housing  30  includes channels  34 , which encase flexible projection  18 B, and recess  18 C 1 . When the components of  FIG. 8  are assembled in enclosure  40  a load input cord  32  can be attached on site. As illustrated in  FIG. 7 and 8 , when the stripped end  32 A 1  engages channel  34  of bottom housing  30 , flexible projection  18 B urges stripped end  32 A downward against the bottom surface of channel  34  locking it in place. Grooved contact surface  18 B 1  further facilitates the locking in place of stripped end  32 A 1 . Stripped end  32 A 1  engages channel  34  through quick connect holes  34 A. 
         [0046]    In the preferred embodiment, the strip requirements of conductive ends  32 A 1  are approximately ⅜ of an inch. Therefore in the preferred embodiment the length of channel  34 , is approximately ⅜ of an inch to ensure conductive ends  32 A 1  are not exposed. In the preferred embodiment, cord  32  is an industry standard 18AWG cord 
         [0047]    It should be understood that the foregoing description is only illustrative of the invention. Thus, various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims.