Patent Publication Number: US-6710687-B2

Title: Test button assembly for circuit breaker

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to power distribution equipment and, more particularly, to a test button assembly for a circuit breaker. 
     2. Description of the Related Art 
     Circuit breakers and other power distribution equipment are well known in the relevant art. Circuit breakers are typically configured to interrupt current upon the occurrence of one or more predetermined conditions. For instance, circuit breakers may trip in the event of an overcurrent condition or an under-voltage condition, and they additionally trip in the event of a ground fault or an arc-fault condition if configured to do so. Protection from ground faults and arc faults typically is provided by circuitry within the circuit breaker that is operatively connected with a trip unit of the circuit breaker. 
     In order to ensure the continued proper and safe operation of such circuit breakers, the ground fault and arc fault detection circuitry is desirably tested on occasion. The testing of such ground fault and arc fault circuitry typically involves the closing of a pair of contacts within a testing circuit that simulates the fault condition. Upon closing of the contacts and simulation of the fault condition, a successful test of the fault detection circuitry will result in the trip unit of the circuit breaker performing a trip operation. The circuit breaker can then be reset. While such testing circuitry has been generally effective for its intended purpose, such testing circuitry has not, however, been without limitation. 
     Circuit breakers generally are designed in such a fashion to minimize the space occupied thereby. As such, the contacts that are closed in order to test ground fault and arc fault circuitry typically have been mounted directly onto a main printed circuit board of the circuit breaker. In some instances the contacts have been configured as leaf springs that protrude from the main printed circuit board and are deflected into contact with one another in order to close the ground fault or arc fault protection circuit. 
     The deflection of such leaf spring contacts undesirably results in forces and torques being applied to the main printed circuit board. Since numerous other circuitry components of the circuit breaker are mounted on the main printed circuit board, such forces and torques can result in breakage or other failure of the main printed circuit board and thus the circuit breaker. 
     Additionally, since such contacts are disposed internally within the circuit breaker, some type of linkage or other motion transfer mechanism must be provided which operatively extends between the contacts and the exterior of the circuit breaker to permit the contacts to be closed from the exterior of the circuit breaker. Such linkages and the like occupy additional space within the circuit breaker and are often less than fully reliable in closing the contacts of the protection circuitry. Such contacts and linkages additionally have been relatively expensive to incorporate into a circuit breaker. 
     It is thus desired to provide an improved test button assembly for a circuit breaker that overcomes these and other shortcomings of previously known test button designs. 
     SUMMARY OF THE INVENTION 
     Accordingly, an improved test button assembly for use in a circuit breaker includes a frame and a button member, with the button member being pivotably mounted on the frame. A pair of microswitches are mounted on a printed circuit board that is disposed on the frame. The button member is alternately engageable with the two microswitches, with one of the microswitches being connectable with a ground fault protection circuit, and the other microswitch being connectable with an arc fault protection circuit. In an alternate embodiment, a common electrical contact is mounted on the button member, and a pair of contacts are mounted on the frame, with the common contact being alternately engageable with each of the contacts mounted on the frame. The contacts mounted on the frame are connected with the ground fault and arc fault protection circuits. 
     Accordingly, an aspect of the present invention is to provide an improved test button assembly that is relatively less expensive to manufacture and incorporate into a circuit breaker than previously known test button systems. 
     Another aspect of the present invention is to provide an improved test button assembly that is relatively more reliable in function than previously known test button systems. 
     Another aspect of the present invention is to provide an improved test button assembly that is modular in nature. 
     Another aspect of the present invention is to provide an improved test button assembly that is configured such that the operation thereof imparts generally no forces or torques to a main circuit board of the circuit breaker. 
     Another aspect of the present invention is to provide an improved test button assembly for a circuit breaker that occupies minimal space within the circuit breaker. 
     Another aspect of the present invention is to provide an improved circuit breaker that employs an improved test button assembly. 
     Accordingly, an aspect of the present invention is to provide a test button assembly for a circuit breaker, the circuit breaker including a first protection system and a second protection system, the circuit breaker including a case formed with a receptacle, in which the general nature of the test button assembly can be stated as including a frame, a button member, the button member being mounted on the frame, the button member being movable with respect to the frame, a first contact, the first contact being disposed on the frame, the first contact being structured to be electrically conductively connected with the first protection system, a second contact, the second contact being disposed on the frame, the second contact being structured to be electrically conductively connected with the second protection system, a common contact, the common contact being operatively connected with the button member, the common contact being movable by the button member to be electrically conductively connectable with the first contact, the common contact being movable by the button member to be electrically conductively connectable with the second contact, and the test button assembly being a discrete unit that is structured to be received in the receptacle and mounted to the case of the circuit breaker as a single assembly. 
     Another aspect of the present invention is to provide a test button assembly for a circuit breaker, the circuit breaker including a first protection system and a second protection system, the circuit breaker including a case formed with a receptacle, in which the general nature of the test button assembly can be stated as including a frame, a first microswitch, the first microswitch being disposed on the frame, the first microswitch being structured to be electrically conductively connected with the first protection system, a second microswitch, the second microswitch being disposed on the frame, the second microswitch being structured to be electrically conductively connected with the second protection system, a button member, the button member being mounted on the frame, the button member being movable with respect to the frame, the button member being operatively engageable with the first microswitch, the button member being operatively engageable with the second microswitch, and the test button assembly being a discrete unit that is structured to be received in the receptacle and mounted to the case of the circuit breaker as a single assembly. 
     Another aspect of the present invention is to provide a circuit breaker the general nature of which can be stated as including a case, a trip unit, the trip unit being disposed within the case, a line conductor, a load conductor, the line and load conductors being electrically conductively connectable with one another, the trip unit being operative to electrically conductively connect and disconnect the line and load conductors, a first protection system, the first protection system being operatively connected with the trip unit, a second protection system, the second protection system being operatively connected with the trip unit, a test button assembly, the test button assembly including a first microswitch, the test button assembly including a second microswitch, the test button assembly including a support, the first microswitch being mounted on the support, the second microswitch being mounted on the support, the support being disposed on the case, the first microswitch being operatively connected with the first protection system, and the second microswitch being operatively connected with the second protection system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A further 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 a schematic cut-away view of an improved circuit breaker in accordance with the present invention that incorporates an improved test button assembly in accordance with a first embodiment of the present invention; 
     FIG. 2 is a sectional view as taken along line  2 — 2  of FIG. 1; 
     FIG. 3 is a sectional view as taken along line  3 — 3  of FIG. 2; 
     FIG. 4 is a top plan view of a switch assembly of the first embodiment; 
     FIG. 5 is a view similar to FIG. 3, except depicting a button member of the first embodiment operatively engaged with a first microswitch of the first embodiment; 
     FIG. 6 is view similar to FIG. 5, except depicting the button member operatively engaged with a second microswitch of the first embodiment; 
     FIG. 7 is a sectional end view of an improved test button assembly in accordance with a second embodiment of the present invention; 
     FIG. 8 is a sectional view as taken along line  8 — 8  of FIG. 7; 
     FIG. 9 is a view similar to FIG. 8, except depicting a common contact of the second embodiment electrically conductively engaged with a first contact of the second embodiment; 
     FIG. 10 is view similar to FIG. 9, except depicting the common contact electrically conductively connected with a second contact of the second embodiment. 
    
    
     Similar numerals refer to similar parts throughout the specification. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A circuit breaker  4  in accordance with the present invention is illustrated schematically in FIG.  1 . The circuit breaker  4  is advantageously configured to include a test button assembly  8  in accordance with a first embodiment of the present invention. The test button assembly  8  is employed for the testing of protection circuitry of the circuit breaker  4 . The test button assembly  8  is advantageously of a modular configuration, as will be set forth more fully below. 
     The circuit breaker  4  includes a case  12 , a trip unit  16 , a first protection system  20 , a second protection system  24 , a first conductor  28 , and a second conductor  32 . The trip unit  16 , the first protection system  20 , and the second protection system  24  are disposed within the case  12 . The first conductor  28  and the second conductor  32  each extend between the interior of the case  12  and the exterior thereof. As is well known in the relevant art, the first and second conductors  28  and  32  may be line and load conductors, respectively, and include contacts  30  and  34 , respectively. The contacts  30  and  34  are engaged with one another (not shown in FIG. 1) such that the first and second conductors  28  and  32  are electrically conductively connected with one another during normal operation of the circuit breaker  4 . The contacts  30  and  34  are disengaged from one another by the trip unit  16  upon the occurrence of one or more specified conditions to disconnect the first and second conductors  28  and  32  from one another, all in a known fashion. The first and second conductors  28  and  32  are intended to be connected with a line and a load, as is well understood in the relevant art. 
     The trip unit  16  can include one or more of any of a wide variety of trip systems such as thermal trip systems, magnetic armature trip systems, under-voltage trip systems, and the like in a well understood fashion. The first and second protection system  20  and  24  can likewise each be any of a variety of protection systems such as ground fault protection systems and arc fault protection systems. As can be understood from FIG. 1, the first and second protection systems  20  and  24  are each operatively connected with the trip unit such that upon the occurrence of a specified condition, either or both of the first and second protection systems  20  and  24  will trigger the trip unit  16  to disconnect the first and second conductors  28  and  32  in order to interrupt the current through the circuit breaker  4  in a well understood fashion. 
     As can further be understood from FIG. 1, the case  12  is formed to include a receptacle  36 . The test button  8  is advantageously received in the receptacle  36  and is thereby disposed on the case  12 . As such, the test button assembly  8  advantageously is not mounted on either of the first and second protection systems  20  and  24  or on a main printed circuit board (not explicitly depicted in FIG. 1) upon which the first and second protection systems  20  and  24  may be mounted. 
     As can be understood from FIGS. 2 and 3, the test button assembly  8  includes a frame  40 , a button member  44 , and a switch assembly  48 . The button member  44  and the switch assembly  48  are both mounted on the frame  40 , whereby the test button assembly  8  is modular in nature and can be readily mounted onto the case  12  of the circuit breaker  4 . As used herein, the term “modular” and variations thereof refers to a condition in which multiple components or parts are connected with one another in such a fashion that the components or parts together form a discrete unit or module that can be handled and employed as a single assembly. In the context of the test button assembly  8 , the test button assembly  8  is a discrete unit or module that can be mounted as a single assembly on the circuit breaker  4  by slidingly receiving the test button assembly  8  in the receptacle  36  of the case  12 , as will be set forth more fully below. 
     The frame  40  includes a base  52 , a pair of parallel and spaced apart walls  56  extending from the base  52 , and a pair of legs  60  that each include a locking tab  64  and that extend away from the base  52 . The base  52  and the walls  56  together are generally U-shaped. The legs  60  extend away from the base  52  in a direction opposite the walls  56 . 
     The button member  44  includes a pair of axially aligned pins  68  that are pivotably mounted in correspondingly sized and positioned holes (not shown) formed in the walls  56 . In the embodiment of the test button assembly  8  depicted in the accompanying figures, the button member  44  does not itself include a spring or other structure to bias the button member  44  to a particular position, and rather is free to pivotably float. It is understood, however, that such a spring or other biasing structure could be added to the test button assembly  8  without departing from the concept of the present invention. 
     During mounting of the test button assembly  8  to the case  12 , the test button assembly  8  is translated toward the case  8  to receive the legs  60  in the receptacle  36 . The engagement of the locking tabs  64  with the walls of the receptacle causes the legs  60  to deflect generally toward one another. The receptacle  36  terminates at a pair of opposed ledges  72 . As the test button assembly  8  further slidingly received in the receptacle  36 , the locking tabs  64  ultimately move past the ledges  72 , and the legs  60  spring back into the position depicted in FIG. 3 so that the test button assembly  8  snaps into place. 
     As can be understood from FIG. 2, the case  12  also includes a pair of stops  76  formed on the interior of the receptacle  36  for engagement with the base  52 . It thus can be seen that the locking tabs  64  function as mounting structures that permit the test button assembly  8  to be lockably engaged with the case  12 . Moreover, the test button assembly  8 , being of a modular configuration, is received in the receptacle  36  and is thus mounted on the case  12  as a discrete unit. While the ledges  72  and the stops  76  together fixedly retain the test button assembly  8  within the receptacle  36 , it is understood that other structures and assembly methodologies may be employed to retain the test button assembly  8  in the receptacle  36 . 
     As can be understood from FIGS. 2 and 3, the switch assembly  48  includes a generally planar support  80 , a first microswitch  84 , and a second microswitch  88 . The switch assembly  48  further includes a first wire  112 , a second wire  116 , and a common wire  120  that extend from the support  80 . The support  80  may be any of a wide variety of structural support members and may be a small printed circuit board. It can be seen that the support  80  is received in a pair of confronting notches  92  (FIG. 2) formed in the walls  56 . 
     The first and second microswitches  84  and  88  are substantially identical to one another, although such identity is not essential to the operation of the test button assembly  8 . The first microswitch  84  includes a first plunger  94 , a first terminal  96 , and a second terminal  100 . Similarly, the second microswitch  88  includes a second plunger  102 , a first terminal  104 , and a second terminal  108 . As is understood in the relevant art, the first plunger  94  is movable and is operable to change the first microswitch  84  between an open condition in which the first and second terminals  96  and  100  are electrically conductively disconnected from one another and a closed condition in which the first and second terminals  96  and  100  are electrically conductively connected together. The first plunger  94  is spring biased to the open condition. The second plunger  102  is similarly movable and operable to change the second microswitch  88  between open and closed positions in which the first and second terminals  104  and  108  are disconnected and connected together, respectively. The second plunger  102  is spring biased to the open condition. The first and second microswitches  84  and  88  may, for instance, each be a Mechanical Keyswitch B3F-1000 sold by Omron Electronics, Inc., of Schaumburg, Ill., USA, although other switches from other manufacturers may be employed without departing from the concept of the present invention. 
     As can be understood from FIG. 4, the first terminal  96  of the first microswitch  84  is electrically conductively connected with the first wire  112 . The first wire  112  is electrically conductively connected with the first protection system  20 . Similarly, the first terminal  104  of the second microswitch  88  is electrically conductively connected with the second wire  116 . The second wire  116  is electrically conductively connected with the second protection system  24 . It can further be seen that the second terminals  100  and  108  are electrically conductively connected with one another and with the common wire  120 . 
     It thus can be understood that when the button member  44  is moved into operative engagement with the first microswitch  84 , as is depicted generally in FIG. 5, the first plunger  94  is depressed by the button member  44  which places the first microswitch  84  in the closed condition in which the first and second terminals  96  and  100  are connected with one another. Such a circumstance closes the circuit of the first protection system  20  which, if in proper operating condition, triggers the trip unit  16  to separate the first and second conductors  28  and  32 . Similarly, when the button member  44  is in operative engagement with the second microswitch  88 , as is generally depicted in FIG. 6, the second plunger  102  is depressed by the button member  44  which electrically conductively connects the first and second terminals  104  and  108  which closes the circuit of the second protection system  24 . If the second protection system  24  is in proper operating condition it triggers the trip unit  16  to separate the first and second conductors  28  and  32 . In such fashion, the first and second protection systems  20  and  24  can be tested. 
     It can be seen from FIG. 3 that the first, second, and common wires  112 ,  116 , and  120  extend from the support  80  through a hole  124  formed in the base  52  for connection with the appropriate components of the circuit breaker  4 . It is understood, however, that in other embodiments of the test button assembly  8 , the first, second, and common wires  112 ,  116 , and  120  may be routed in a different fashion and thus may not extend through any such hole  124 . 
     It thus can be seen that the test button assembly  8  is of a modular configuration and can be received in the receptacle  36  and secured therein by the engagement of the locking tabs  64  with the ledges  72  and the engagement of the base  52  with the stops  76 . With the test button assembly  8  installed as such, the first, second, and common wires  112 ,  116 , and  120  can be electrically conductively connected with appropriate components within the circuit breaker  4  such that the first microswitch  84  is operatively connected with the first protection system  20  and the second microswitch  88  is operatively connected with the second protection system  24 . The test button assembly  8  is relatively small in physical size, with the size thereof being generally dictated by and limited by the size of the first and second microswitches  84  and  88 . Depending upon the availability of other microswitches, the test button assembly  8  can be configured to be even more compact than that explicitly depicted herein. 
     Since the first and second microswitches  84  and  88  include first and second plungers  94  and  102  that are biased to the open condition, the button member  44  need not be separately biased to a neutral position but rather may be permitted to pivotably float while being retained between the walls  56 . Furthermore, the test button assembly  8  is operated without applying any forces or torques to any components of the circuit breaker  4  other than the case  12 . As such, the potential for breakage or other failure of a main printed circuit board or other components of the circuit breaker  4  due to the application of forces or torques thereto is substantially alleviated. 
     It is understood that the test button assembly  8  depicted in the accompanying figures is merely exemplary in nature and can be configured in numerous different fashions without departing from the concept of the present invention. For instance, the notches  92  could be formed in the case  12 , with the support  80  being received in such notches. In such fashion, the frame  40  could be eliminated from the test button assembly  8 . Moreover, the switch assembly  48  could be additionally or alternatively disposed such that the first and second plungers  94  and  102  protrude slightly through correspondingly sized and positioned holes formed in a cover extending over the receptacle  36  such that the first and second plungers  94  and  102  could be manually engaged. Such a configuration would additionally eliminate the need for a button member  44 . Such alternate configurations of the test button assembly  8  could be incorporated into the circuit breaker  4  depicted generally in FIG. 1 without the departing from the concept of the present invention. 
     It is noted, however, that the button member  44  of the present invention is configured to function as a rocker to alternately test the first and second protection systems  20  and  24 . As such, a user can advantageously determine which of the first and second protection systems  20  and  24 , if either, is functioning improperly. If the first and second protection systems  20  and  24  were tested simultaneously, one could not determine whether or not one of the first and second protection systems  20  and  24  was malfunctioning unless both were malfunctioning. 
     A second embodiment of a test button assembly  208  is indicated generally in FIGS. 7-10. The test button assembly  208  includes a frame  240  and a button member  244  that are substantially similar to those of the test button assembly  8 . The test button assembly  208  includes a switch assembly  248 , however, that includes a first bar  282 , a second bar  286 , and a common bar  290 . The first and second bars  282  and  286  are mounted on the frame  240  and are retained in position by a pair of first protrusions  328  and a pair of second protrusions  332 , respectively, formed on the frame  240 . 
     The common bar  290  is a reentrantly formed generally T-shaped member that is made from a single bar of spring wire that is bent to such shape. The common bar  290  is engaged with the button member  244  and biases the button member  244  to a neutral position that is depicted generally in FIG.  8 . 
     It can further be seen that the first bar  282  extends through a first hole  336  and is connected with a first wire  312 . The second bar  286  extends through a second hole  340  and is connected with a second wire  316 . The common bar  290  extends through a third hole  344  and is connected with a common wire  320 . It is understood, of course, that the first, second, and common wires  312 ,  316 , and  320  could be routed in different fashions. The first, second, and common wires  312 ,  316 , and  320  are connectable in a fashion similar to the first, second, and common wires  112 ,  116 , and  120  of the test button assembly  8 . 
     It can be seen from FIG. 9 that the button member  244  is pivotable to a first position in which the common bar  290  is electrically conductively connected with the first bar  282  which completes a first circuit. Similarly, the button member  244  can be pivoted to a second position (FIG. 10) in which the common bar  290  is electrically conductively connected with the second bar  286 , which completes a second circuit. The common bar  290  is alternately electrically conductively connectable with the first and second bars  282  and  286 . 
     It thus can be seen that the test button assembly  208  could be substituted for and have a similar operation to that of the test button assembly  8 . In such fashion, the first wire  312  could be electrically conductively connected with the first protection system  20 , and the second wire  316  could be electrically conductively connected with the second protection system  24 . Moreover, the test button assembly  208  could be incorporated into the circuit breaker  4  depicted generally in FIG.  1 . 
     The test button assemblies  8  and  208  thus are modular in configuration, and the operation thereof generally applies no forces to any components of the circuit breaker  4  other than to the case  12 . The test button assemblies  8  and  208  are relatively inexpensive to manufacture and are reliable in their operation and advantageously do not increase the potential for breakage or other failure of the main circuit board or other components of the circuit breaker  4 . 
     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 the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.