Abstract:
A miniature circuit breaker has an arc fault detector and a ground fault detector each with its own test circuit. Test switches for the two test circuits are mounted on a printed circuit board and share a common test contact formed by a flat U-shaped leaf spring. The common test contact is deflected into engagement with another test contact for one or the other of the two test switches by a remotely mounted common test button through a common test actuating member which is moved generally rectilinearly by rocking the common test button.

Description:
RELATED APPLICATION 
     Commonly owned, concurrently filed application entitled “Circuit Breaker with Common Test Button for Separate Testing of Ground Fault and Arc Fault Function” and bearing Ser. No. 09/496,566. 
     FIELD OF THE INVENTION 
     This invention relates to circuit breakers provided with two test circuits, such as a ground fault test circuit and an arc fault test circuit, and a single, dual function test button for selectively activating switches in the test circuits which are remote from the common test button. 
     BACKGROUND INFORMATION 
     Circuit breakers provide overcurrent and short circuit protection for electric power systems. In the small circuit breakers, commonly referred to as miniature circuit breakers, used for residential and light commercial applications, such protection is typically provided by a thermal-magnetic trip device. Such a device includes a bimetal which is heated and bends in response to a persistent overcurrent condition thereby unlatching a spring powered operating mechanism which opens the separable contacts of the circuit breaker to interrupt current flow in the protected power system. An armature attracted by the sizable magnetic forces generated by a short circuit also unlatches, or trips, the operating mechanism. 
     In many applications, the miniature circuit breaker also provides ground fault protection. An electronic circuit detects leakage of current to ground and generates a ground fault trip signal. This signal energizes a shunt trip solenoid which unlatches the operating mechanism, typically through actuation of the thermal-magnetic trip device. 
     Recently, there has been considerable interest in also providing protection against arcing faults. Arcing faults are intermittent high impedance faults which can be caused for instance by worn insulation, loose connections, broken conductors, and the like. Because of their intermittent and high impedance nature, arcing faults do not generate currents of sufficient instantaneous magnitude or sufficient average current to rigger the thermal-magnetic trip device. Consequently, separate electrical circuits have been developed for responding to arcing faults. 
     Ground fault protection circuits and arc fault protection circuits typically include test circuits for affirming their continued operability. Currently, separate test switches, each with its own test button, are provided for performing the ground fault and arc fault tests. However, the molded cases of the miniature circuit breakers have been standardized for interchangeable use in load centers. There is limited space available in the standardized miniature circuit breakers for all of the additional circuitry required for ground fault and arc fault protection, let alone the test circuits. 
     U.S. patent application Ser. No. 09/069,355 filed on Apr. 29, 1998 discloses a miniature circuit breaker with a common rocker button which is rotated in one direction to actuate the ground fault test circuit, and the opposite direction to actuate the arc fault test circuit. The ground fault and arc fault test circuits are mounted on a common printed circuit board (PCB) and each has a spring contact arm projecting from the printed circuit board and which is deflected into contact with a common flexible contact extending between them by a separate finger on the common rocker button to actuate the associated test circuit. This arrangement works fine for circuit breakers where the circuit board is in close proximity to the common rocker button so that the spring contact arms can be directly engaged by the rocker button. 
     Unfortunately, on other miniature circuit breakers, the printed circuit board on which the test circuit is implemented is spaced from the test button so that the above-described direct engagement between a common rocker button and test switches is not possible. 
     There is a need, therefore, for improved miniature circuit breakers having both ground fault and arc fault test circuits. 
     More particularly, there is a need for such circuit breakers with a common test button which can separately actuate the ground fault and arc fault test circuits even though and the associated actuating switches are not in close proximity to the common test button. 
     SUMMARY OF THE INVENTION 
     These needs and others are satisfied by the invention which is directed to a circuit breaker which includes a molded housing containing electronic trip means having a first test circuit with a first test switch including a first test contact, and a second test circuit with a second test switch including a second test contact spaced from the first test contact. A common test contact associated with both the first and second test contacts is positioned between them. The circuit breaker also has a dual test switch actuating assembly which includes a common test button mounted in the molded housing remotely from the test switches. This common test button is coupled to a common actuating member which is moved by the common test button, preferably generally rectilinearly, between a first test position and a second test position. In the first test position, either the first test contact or the common test contact is deflected by the common actuating member into engagement with the other to actuate the first test switch in the first test circuit. In the second test position, either the second test contact or the common test contact is deflected by the common actuating member into engagement with the other to actuate the second test switch and thereby activate the second test circuit. The circuit breaker further includes bias means biasing the actuating member and also the common test button to a neutral position between the first and second test positions. 
     Preferably, the common test button is pivotally mounted for rotation in a first direction to move the actuating member against the bias means to the first test position and for rotation in a second direction opposite the first direction to move the actuating member against the bias means to the second test position. 
     In a preferred embodiment of the invention, the bias means comprises a cantilevered spring member engaging the actuating member and extending laterally relative to the generally rectilinear movement of the actuating member. Most preferably, the actuating member is a molded member and the cantilevered spring member is integrally molded with the actuating member. In the exemplary embodiment of the invention, the integrally molded cantilever member terminates in a tip which seats in recess in the molded housing. The tip rotates in this recess as the actuating member moves generally rectilinearly. 
     Preferably, the electronic circuits include a printed circuit (PCB). The first and second switch contacts are mounted on the printed circuit board and the common spring contact comprises an electrically conducting leaf spring secured at a first end to the PCB and deflectable at a second end in the first direction of the generally rectilinear movement of the actuator to engage the first switch contact. This common electrically conductive leaf spring is deflectable in the second direction of the generally rectilinear movement of the actuator to engage the second switch contact. Preferably, the first switch contact and the second switch contact arc electrically conductive leaf springs mounted on the PCB and deflectable with the common test contact. 
     Finally, the common test leaf spring is an elongated U-shaped flat member with two ends adjacent to one another. This shape allows for required deflection without overstressing while minimizing the amount of space occupied on PCB. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which: 
     FIG. 1 is an exploded, fragmentary, isometric view of a circuit breaker incorporating the invention. 
     FIG. 2 is an isometric fragmentary view of the circuit breaker of FIG. 1 partially assembled. 
     FIG. 3 is an elevational view of pertinent parts of the circuit breaker shown in the neutral position. 
     FIG. 4 is similar to FIG. 3 showing the parts in position for testing the ground fault detector of the circuit breaker. 
     FIG. 5 if a view similar to FIG. 3 illustrating the parts and position for testing the arc fault circuit of the circuit breaker. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention will be described as applied to a single pole miniature circuit breaker of the type commonly used in residential and light commercial applications. However, it will be evident to those skilled in the art that the invention is also applicable to other types of circuit breakers, as well. 
     Referring to FIG. 1, the circuit breaker  1  has a housing  3  which is assembled from molded sections composed of electrically insulating material and includes a base  5  and a cover  7 . The circuit breaker includes the conventional thermal-magnetic trip mechanism (not shown) which provides protection from overcurrents and short circuits, as is well known. In addition, an electronic trip circuit  9 , which provides protection from ground faults and arc faults, is implemented on a printed circuit board  11 . The electronic trip circuit  9  includes a ground fault test circuit  13  and an arc fault test circuit  15 . A ground fault test switch  17  energizes the ground fault test circuit  13  when actuated. Similarly, an arc fault test switch  19  energizes the arc fault test circuit  15  when energized. The ground fault test switch  17  includes a ground fault fixed test contact  21  mounted on the printed circuit board  11  while the arc fault test switch  19  also includes a fixed test contact  23  mounted on the printed circuit board and spaced in parallel relation to the ground fault fixed test contact  21 . The ground fault test switch  17  and arc fault test switch  19  share a common moveable contact  25  which is positioned between the contacts  21  and  23 . The common switch contact  25  is a U-shaped electrically conductive leaf spring having a first leg  27  terminating in a first end  28  secured to the printed circuit board  11  and a deflectable, free second leg  29 . The ground fault fixed test contact  21  and the arc fault fixed test contact  23  are each L-shaped with a first leg  31  and  33 , respectively, fixed to the printed circuit board and with second, deflectable legs  35  and  37 , respectively, cantilevered outward as to form leaf springs which straddle the second leg  29  of the U-shaped common switch contact. The ground fault test switch  17  and the arc fault test switch  19  are alternatively actuated by a dual test switch actuating assembly  39 . This assembly  39  includes a common actuating member  41 , which, as can be seen from FIG. 2, is guided for rectilinear reciprocal movement in a slot  43  molded into the base  5 . The common actuating member  41  has on its lower end an elongated projection  45  forming a groove  47  which is engaged by the free end  49  of the second leg  29  of the common switch contact  25 . 
     The common actuating member  41  is reciprocally moved within the slot  43  by a common test button  51 . This common test button  51  is seated in a recess  53  in an escutcheon  55  molded on the housing  3 . The test button is pivotally mounted on a pin  57  molded in the recess  53  and an opposed pin  59  on a cap  61 . The common test button  51  has an actuating arm  63  which supports a drive pin  65  offset from the pivot access formed by the pins  57  and  59 . The drive pin  65  engages a notch  67  in the upper end of the common actuating member  41 . Integrally molded with the common actuating member  41  is a cantilevered spring member  69 . This spring member has a projection  71  extending laterally from the free end which is captured in a groove  73 , within the recess in the base  5 . Alternatively, the spring could be a separate item such as, for example, a leaf spring or a helical spring. 
     The circuit breaker is assembled by positioning the printed circuit board  11  within the base  5 . The common test button  51  is mounted in the recess  53  on the pivot pin  57 . The pin  71  on the spring member  69  is then inserted in the groove  73  and the common actuating member  41  is then slid into the slot  43 . As this occurs, the groove  47  engages the free end  49  of the leg  29  of the U-shaped common switch contact  25  and the notch  67  is engaged by the drive pin  65 . The cover  7  is then secured to the base  5 . The assembled circuit breaker is then tested and any required adjustments to the thermal-magnetic trip can be made by insertion of a tool through the unoccupied portion of the recess  43  adjacent the cover  7 . When final adjustments have been made, the cap  61  is inserted into the remaining open space of recess  53  with the pin  59  engaging the common test button  51  and with a hook  75  on a cantilevered finger  77  engaging the cover  7 . 
     The spring member  69  biases the common actuating member  41  to the neutral position shown in FIG. 3 in which the common switch contact  25  is in a relaxed position in which it is centered between the arc fault fixed test contact  21  and the ground fault fixed test contact  23 . Rocking the common test button  51  counterclockwise raises the common actuating member  41  to the ground fault test position shown in FIG. 4 in which the common switch contact  25  is lifted into contact with the second leg  35  of the ground fault fixed test contact  21 , thereby initiating test of the ground fault detector in the electronic trip circuit  9 . Upon release of the common test button  51 , the spring member  69  returns the common actuating member  41  and therefore the test button  51  to the neutral position shown in FIG.  3 . 
     For testing the arc fault detector in the electronic trip circuit  9 , the common test button  51  is rotated clockwise to the position shown in FIG. 5 in which the common switch contact  25  is rotated downward to make electrical contact with the second leg  37  of the arc fault fixed test contact  23 . Again, upon completion of the test, the spring member  69  returns the common actuating member  41  and common test button  51  to the neutral position shown in FIG.  3 . 
     While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.