Abstract:
A circuit breaker cover is provided with a spring loaded pushbutton assembly that is self-captivated within the cover, thereby enabling the assembly and operation of the pushbutton unit without the need for additional hardware or fixation devices. The pushbutton unit is pivotally arranged within the cover and spring biased against a stop surface in the cover. A top-down assembled, self-captivated pushbutton unit provides for improved manufacturability of the host device, which may be but is not limited to a standard circuit breaker, a rotary circuit breaker, a switch, or a disconnect device. Host devices utilizing such pushbutton units are employed in residential, commercial, industrial or utility applications, and may be employed in single device enclosures or in electrical distribution panels.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to a pushbutton assembly for actuating a trip mechanism of an electrical disconnect device, and, more particularly, to a pushbutton assembly for a circuit breaker where the pushbutton assembly is spring biased and self-captivated within the circuit breaker cover.  
         BACKGROUND OF THE INVENTION  
         [0002]    Pushbutton devices have the general function of providing an interface for the purpose of actuating an auxiliary system behind a panel front. One such auxiliary system is the trip system of a circuit breaker, and one such panel front is a circuit breaker cover. As the push surface of the pushbutton is depressed, a drive surface on the pushbutton is set in motion to produce work. In the instance of a circuit breaker, the work produced results in the tripping of the trip system, or trip latch, and subsequent opening of the circuit breaker contacts, thereby disconnecting the protected circuit from the power source.  
           [0003]    Pushbutton devices can be employed in many types of electrical disconnect devices, such as, but not limited to; conventional circuit breakers, current limiting circuit breakers, rotary circuit breakers, and disconnect switches. However, pushbutton devices are not limited to circuit breakers, but can also be employed in other systems, such as; control devices, pilot lights, sensors, and auxiliary switches. The industries that pushbuttons can be used in are varied, and include, but are not limited to, the utility, industrial, commercial, residential, and automotive industries.  
           [0004]    Trip test buttons for circuit breakers include “twist to trip”, “slide to trip”, and “push to trip” arrangements. U.S. Pat. No. 3,671,890 entitled “Manually Operable Molded Case Circuit Breaker With Special Trip Testing Means” describes a “twist to trip” arrangement. U.S. Pat. No. 4,740,768 entitled “Manual Trip Operator for Molded Case Circuit Breaker” describes a “slide to trip” arrangement. However, for ease of actuation, some applications require the use of a “push to trip” arrangement. U.S. Pat. No. 4,982,173 entitled “Rotatable Trip Test Assembly For Molded Case Circuit Breakers” describes a “push to trip” arrangement incorporating a pushbutton device for use in a circuit breaker that includes a reset spring that is molded integrally with the pushbutton unit. The described pushbutton device is captivated between the circuit breaker cover and auxiliary cover by a ball and socket arrangement, where half of the socket is defined by the circuit breaker cover and the other half by the auxiliary cover. Removal of the auxiliary cover from the circuit breaker cover disturbs the captivation arrangement.  
           [0005]    It would be beneficial to provide a pushbutton device in a “push to trip” arrangement that is easy to actuate and is self captivated in the circuit breaker cover so that removal of an auxiliary cover does not disturb the captivation arrangement.  
         SUMMARY OF INVENTION  
         [0006]    In an exemplary embodiment of the present invention, a pushbutton assembly is self-captivated in a circuit breaker cover, or midcover, thereby enabling the cover or midcover to be removed without disturbing the captivation of the pushbutton unit. Whether the cover or midcover is in place or not, the self-captivated pushbutton is completely operable and can actuate the trip latch components of the circuit breaker operating mechanism. The pushbutton assembly includes a pushbutton unit and a reset spring. The pushbutton unit is pivotally arranged within the circuit breaker midcover, and is held in a self-captivated arrangement with the circuit breaker midcover by the action of the two end legs of the reset spring. One leg of the reset spring is captivated by the circuit breaker midcover, and the other by the pushbutton unit, thereby resulting in a bias force that securely captivates the pushbutton unit in the midcover. A drive surface at the end of an extension leg on the pushbutton unit provides the means for actuating a trip system, and a stop arm on the pushbutton unit interacts with a stop surface on the circuit breaker midcover to limit the reset motion of the pushbutton under the bias of the reset spring. The moment arm of the pivotally arranged pushbutton offers a mechanical advantage not available with linearly actuated arrangements.The pushbutton unit can be fabricated from any material suitable for the application, such as, but not limited to; polyethylene, polypropylene, polystyrene, polyester, polyvinyl chloride, acrylics, nylons, spandex-type polyurethanes, polyamides, polycarbonates, fluorocarbons, cellulosics, or other thermoplastic plastics, or similar such materials.  
           [0007]    The pushbutton device of the present invention has the functional characteristics of “push” actuation, pivotal motion, linear or rotary resultant action, and self-captivation. As described, the pushbutton device can be employed in electrical disconnect devices, such as, for example, safety switches, and conventional and rotary circuit breakers, and the distribution equipment that such disconnect devices are employed in. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0008]    [0008]FIG. 1 illustrates a perspective view of an electrical distribution panel incorporating the present invention;  
         [0009]    [0009]FIG. 2 illustrates a perspective view of an electrical circuit breaker incorporating the present invention;  
         [0010]    [0010]FIG. 3 illustrates an exploded perspective view of the electrical circuit breaker of FIG. 2 with the circuit breaker covers removed;  
         [0011]    [0011]FIG. 4 illustrates a cutaway side view of the electrical circuit breaker of FIG.  2  showing the internal electrical components;  
         [0012]    [0012]FIG. 5 illustrates an exploded perspective view of a circuit breaker midcover and a pushbutton device;  
         [0013]    [0013]FIG. 6 illustrates a partial perspective view of the circuit breaker midcover and pushbutton device of FIG. 5 in a partially assembled state;  
         [0014]    [0014]FIG. 7 illustrates a partial perspective view of the circuit breaker midcover and pushbutton device of FIG. 5 in a fully assembled state;  
         [0015]    [0015]FIG. 8 illustrates a partial perspective view of the circuit breaker midcover and pushbutton device of FIG. 5 in a fully assembled and actuated state;  
         [0016]    [0016]FIG. 9 illustrates a partial side view of the circuit breaker midcover and pushbutton device of FIG. 5 in a quiescent state; and  
         [0017]    [0017]FIG. 10 illustrates a partial side view of the circuit breaker midcover and pushbutton device of FIG. 5 in an actuated state. 
     
    
     DETAILED DESCRIPTION  
       [0018]    Distribution Panel Generally  
         [0019]    An electrical distribution panel, well known to one skilled in the art of electrical distribution, is depicted generally in FIG. 1, is fully described in commonly assigned U.S. patent application Ser. No. 09/560,226 entitled “Electrical Distribution Panel With Split Neutral Bus” filed Apr. 28, 2000, functions generally to distribute protected power from a common main source to a plurality of branch circuits, and is described generally below.  
         [0020]    Referring to FIG. 1, an electrical distribution panel  100  includes a panel base  102 , a panel cover  104  and an interior assembly  106 . The panel base  102  and panel cover  104  generally make up the panel housing  108  of distribution panel  100 . The interior assembly  106  is attached to panel base  102  by suitable fasteners, not shown, through mounting holes  110 . Upstanding supports  112  are integral to interior assembly  106  and provide attachment surfaces  114  for attachment of panel cover  104 , which is secured to the attachment surfaces  114  by suitable fasteners, not shown, through holes  116  in panel cover  104 .  
         [0021]    Interior assembly  106  includes main support  118  for mechanically supporting a main circuit device, such as but not limited to a circuit breaker  200  that is fully described below, at least one busbar  120  for connecting circuit breaker  200  to a plurality of branch circuit connections  122 , a ground connector  124  for providing an electrical ground connection within the distribution panel  100 , and a neutral connector  126  for providing an electrical neutral connection within the distribution panel  100 . Power distribution to a plurality of branch circuits, not shown, is made through the plurality of branch circuit connections  122 .  
         [0022]    Circuit Breaker Overview  
         [0023]    A circuit breaker  200  incorporating the present invention is depicted in the perspective view of FIG. 2 and the exploded view of FIG. 3. Base  212  and midcover  214  captivate cassette  216 , trip unit  218  and operating mechanism  220  by fasteners, not shown, through holes  222 . Cassette halves  216   a,b  are secured by fasteners, not shown, and are positionally located in pocket  224  of base  212 . Pushbutton  300  extends through opening  302  of top cover  304  and is described in more detail below. Top cover  304  is secured to midcover  214  by fasteners, not shown, through holes  306 .  
         [0024]    For simplicity and clarity, where more than one element of the same type is present, only one will be referenced, but the reader will readily recognize that the single reference pertains to more than one element of the same type. Here, for example, there are three cassettes  216  and three pockets  224 . Each cassette  216  is positionally located in an associated pocket  224 . Reference is made to a cassette  216  and a pocket  224 , but the reader will readily recognize that three cassettes  216  and three pockets  224  are present. Also for simplicity and clarity, reference will only be made to a three phase circuit breaker, but the reader will recognize that the present invention is equally applicable to single phase, two phase or multi-phase electrical switching devices of any kind.  
         [0025]    Extending through opening  226  of escutcheon  228  on midcover  214  is operating handle  230 , which is operatively connected to movable contact arm  232  by operating mechanism  220  and link  234 , best seen by referring to FIG. 4. Handle  230  enables the opening and closing of electrical contacts  236   a,b,c,d,  best seen by referring to FIG. 4.  
         [0026]    Operating mechanism  220  is of a type well known to one skilled in the art. An example of such an operating mechanism is depicted generally in FIG. 3, is fully described in commonly assigned U.S. patent application Ser. No. 09/516,475 entitled “Circuit Interrupter Operating Mechanism” filed Mar. 1, 2000, and functions generally to open and close electrical contacts  236   a,b,c,d  by actuation of operating handle  230 .  
         [0027]    Trip unit  218  is of a type well known to one skilled in the art and is depicted generally in FIGS. 2 and 3. An example of such a trip unit is fully described in commonly assigned U.S. Pat. Nos. 4,589,052, 4,728,914, and 4,833,563, and functions generally to initiate a trip action within the actuator  264  after receiving a trip signal from current sensors  238 .  
         [0028]    Trip unit  218  is operatively connected to current sensors  238  by pins  240  and sockets  242 , and to operating mechanism  220  by actuator  264 , shown in phantom in FIG. 2, to effectuate the opening of contacts  236   a,b,c,d  upon the occurrence of an abnormal overcurrent condition.  
         [0029]    An example of an actuator  264  is shown generally in phantom in FIG. 2, is fully described in commonly assigned U.S. patent application Ser. No. 09/518,899 entitled “Fast Acting High Force Trip Actuator” filed Mar. 6, 2000, and functions generally to transfer the trip action to the operating mechanism  220  after receiving a trip signal from the trip unit  218 .  
         [0030]    Current sensor and current transformer  238  is shown generally in FIGS. 3 and 4 and is well known to one skilled in the art of current sensing. A representative example of such a current sensor and current transformer  238  is fully described in commonly assigned U.S. Pat. Nos. 4,589,052, 4,728,914, and 4,833,563, and functions generally to power up trip unit  218  and provide trip unit  218  with a signal representative of the circuit current in the protected circuit.  
         [0031]    Referring to FIG. 4, which depicts a cutaway side view of cassette  216  and current sensor  238  in base  212 , electrical connections between the protected circuit, not shown, and circuit breaker  200  are made through load terminal  244  on load side  246  of circuit breaker  200 . Electrical connections between the power source, not shown, and circuit breaker  200  are made through line terminal  248  on line side  250  of circuit breaker  200 .  
         [0032]    Referring to FIGS. 2, 3 and  4 , circuit breaker  200  includes operating handle  230  for driving operating mechanism  220  to manually open and close electrical contacts  236   a,b,c,d.  Contact  236   a  is carried by elongated fixed contact arm  252 , contacts  236   b,c  are carried by elongated movable contact arm  232 , and contact  236   d  is carried by elongated fixed contact arm  254 . FIG. 4 also shows movable contact arm  232   a,  depicted in phantom, following an opening action by trip unit  218  and operating mechanism  220 . Fixed contact arm  252  extends through opening  256  of cassette  216  to terminate in line terminal  248 , which is accessible through an opening, not shown, in line side  250  of base  212 . Obviously, each phase of the multi-phase circuit breaker would have separate conductors per phase, not shown. Operating mechanism  220  is operatively connected to contact arm  232  by link  234 , rotor  258 , and connecting pins  260   a,b.    
         [0033]    The current path through circuit breaker  200  in the closed position is best seen by referring to FIG. 4. Under quiescent operating conditions, the current from the power source enters circuit breaker  200  through line terminal  248  (and other line terminals on adjacent phases not shown), and exits through load terminal  244  (and other load terminals on adjacent phases not shown). Between line terminal  248 , and load terminal  244 , the current path consists of; fixed contact arm  252 , electrical contacts  236   a  and  b,  movable contact arm  232 , electrical contacts  236   c  and  d,  fixed contact arm  254 , and sensor strap  262 . Sensor strap  262  passes through and provides primary current signal to current sensor  238 , which is operatively connected to trip unit  218  by pins  240  and sockets  242 . Fixed contact arm  254  is mechanically and electrically connected to sensor strap  262  by a fastener, not shown. Sensor strap  262  passes through current sensor  238  to terminate in load terminal  244 , which is accessible through an opening, not shown, in load side  246  of base  212 .Arc chute, or arc extinguishing assembly  270 , is removably captivated within cassette  216  by molded detail  272  that is integral to cassette  216 . Arc plates  274 , are typically, but not necessarily, arranged substantially parallel to one another, have tabs  276  that are captivated in corresponding slots in plate supports  278 . Exhaust baffle  280  is removably captivated within cassette  216  by molded slot, not shown, that is integral to cassette  216 . Holes in exhaust baffle  280 , not shown, provide for the passage of arc effluent generated from a short circuit interruption condition. The arc effluent passing through exhaust baffle  280  on line side  250  of circuit breaker  200  will exit base  212  through terminal chamber  282 . The arc effluent passing through exhaust baffle  280  on load side  246  of circuit breaker  200  will exit base  212  through vent channel  284 , shown in phantom in FIG. 4.  
         [0034]    Vent channels  284  are shown generally in phantom in FIG. 4, are fully described in commonly assigned U.S. patent application Ser. No. 09/366,473 entitled “Bottom Vented Circuit Breaker Capable of Top Down Assembly Onto Equipment” filed Aug. 3, 1999, and function generally to provide a passage for the arc effluent to travel from the inside of cassette  216  to the outside of circuit breaker  200  during an abnormal overcurrent condition.  
         [0035]    Pushbutton Assembly  
         [0036]    Referring to FIGS. 5, 6, and  7 , pushbutton unit  300  includes a push surface  320 , a first leg  322  with a pivot  324  disposed at the end thereof, a second leg  326  with a drive surface  328  disposed at the end thereof, a support arm  330  concentric with pivot  324 , and an engagement surface  332 . Alternatively, pushbutton unit  300  may have an engagement surface  332  with a side wall  332   a.  Reset spring  340  includes a spring body  340   a,  a first spring leg  340   b,  and a second spring leg  340   c.  Midcover  214  includes a pivot pocket  334 , an engagement surface, or bridging wall,  336 , and a stop surface, or restraining wall,  338 .  
         [0037]    The assembly of pushbutton unit  300  and reset spring  340  to midcover  214  is accomplished by first placing spring body  340   a  over support arm  330  and rotating reset spring  340  to orient first and second spring legs  340   b  and  c  as shown in FIG. 6. The pushbutton assembly of pushbutton unit  300  and reset spring  340  is next assembled to midcover  214  by inserting pivots  324  into pivot pockets  334  while hooking first spring leg  340   b  under engagement surface  336  of midcover  214 . Second spring leg  340   c  is then hooked under engagement surface  332  of pushbutton unit  300  to complete the captivation of reset spring  340 . Allowing pushbutton unit  300  to rotate under the bias of reset spring  340  results in pushbutton unit  300  rotating in a clockwise direction (a first direction), illustrated by arrow A, until the end of second leg  326  of pushbutton unit  300  engages stop surface  338  of midcover  214 . In the assembled condition, or quiescent condition, the bias force of reset spring  340  serves to self-captivate pushbutton unit  300  in midcover  214 .  
         [0038]    Alternative Embodiment of Pushbutton Assembly  
         [0039]    The above described pushbutton assembly includes a pushbutton unit  300  and a reset spring  340 . However, reset spring  340  may also be made integral with pushbutton unit  300 , thereby providing a unitary pushbutton and spring arrangement that is self-captivated within the midcover  214 . Selection of a suitable thermoplastic material, such as from the list provided above, will enable such an integral pushbutton arrangement to function as a resettable pushbutton, and in accordance with the teachings of the present invention be self-captivating.  
         [0040]    Pushbutton Operation  
         [0041]    Referring to FIGS. 8, 9, and  10 , pushing on push surface  320  of pushbutton unit  300  rotates pushbutton unit  300  in a clockwise direction (a second direction) about pivot  324 , illustrated by arrow B, in opposition to the bias force of reset spring  340 . As pushbutton unit  300  continues to rotate clockwise about pivot  324 , drive surface  328  engages outer leg  350  of trip latch  352  to rotate trip latch  352  clockwise about latch pivot  354 , as shown in FIG. 10. Rotation of trip latch  352  serves to trip operating mechanism  220 , thereby resulting in the separation of contacts  236   a - d  to disconnect the protected circuit as discussed above. Release of pushbutton unit  300  allows pushbutton unit  300  to return to its quiescent position under the bias force of reset spring  340 , as shown in FIG. 9. Throughout the clockwise and return counterclockwise motion of pushbutton unit  300 , pushbutton unit  300  remains self-captivated in midcover  214  whether top cover  304  is attached or not.  
         [0042]    Alternative Embodiment of Pushbutton Action  
         [0043]    The above described action of pushbutton unit  300  results in rotational motion of trip latch  352 . However, it will be appreciated that the scope of the present invention also encompasses translational motion of a trip latch (or other driven member). Since drive surface  328  of pushbutton unit  300  rotates in a clockwise direction about pivot  324  when push surface  320  is pushed, see FIG. 10, it has motion in both the negative-X and negative-Y directions, see FIGS. 9 and 10 for sign convention. Thus, by incorporating an appropriate cam surface on a trip latch (or other driven member), either rotational or translational motion of the trip latch can result, and the decision to use one or the other arrangements is simply a matter of design choice.  
         [0044]    While this invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.