Abstract:
A circuit interrupter including a housing, separable main contacts within the housing, and an operating mechanism within the housing and interconnected with the contacts. A trip mechanism is disposed within the housing and includes a rotatable trip bar assembly that, when selectively rotated, generates a tripping operation. The trip bar assembly includes an attaching structure which interconnects with an accessory trip member. The accessory trip member causes the trip bar assembly to rotate and generate a tripping operation when the accessory trip member is moved in a first direction. The accessory trip member is configured to enable flexing of the accessory trip member in a second direction opposite of the first direction.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to circuit interrupters generally and, more specifically, to those kinds of circuit interrupters having a trip bar assembly that rotates during a tripping operation. 
     2. Description of the Prior Art 
     Molded case circuit breakers and interrupters are well known in the art as exemplified by U.S. Pat. No. 4,503,408 issued Mar. 5, 1985, to Mrenna et al., and U.S. Pat. No. 5,910,760 issued Jun. 8, 1999 to Malingowski et al., each of which is assigned to the assignee of the present application and incorporated herein by reference. 
     A continuing industry objective with respect to many types of circuit interrupters is to be able to reduce the size and/or footprint of the interrupter housing while at the same time providing the same or improved performance capabilities. A major advantage of creating such a “smaller package” is that it provides increased flexibility in installation. However, a consequence of this objective is that the internal space constraints of such interrupters have become much more limiting, posing certain design obstacles that need to be overcome. 
     Circuit interrupters include trip mechanisms that can be activated in a variety of manners so as to set in motion a tripping operation to open the contacts of the interrupter. These trip mechanisms often employ a rotatable trip bar assembly that, when selectively rotated, releases a portion of the operating mechanism to thereby generate a tripping operation. 
     Such circuit interrupters advantageously provide for automatic circuit interruption that causes the trip bar assembly to rotate when an overcurrent condition is sensed. This automatic interruption may be thermally, magnetically, or otherwise based. In addition, such circuit interrupters often enable a tripping operation to be manually initiated by implementation of a push-to-trip member which, when pressed, contacts and rotates the trip bar assembly. 
     Circuit interrupters may also advantageously have accessory devices, such as an undervoltage release (UVR) or a shunt trip, connected thereto. Such accessory devices can likewise initiate a tripping operation, and typically do so by contacting and rotating an accessory trip lever on the trip bar assembly that then causes the trip bar assembly to rotate. However, because of the required positioning and size of such an accessory trip lever, the lever sweeps through a relatively large range of motion within the circuit interrupter whenever any type of tripping operation occurs. Therefore, it is difficult to employ such an accessory trip lever within a circuit interrupter having the aforementioned internal space constraints. Internal components of such a circuit interrupter may obstruct the rotational movement of the accessory trip lever and undesirably prevent the trip bar assembly from sufficiently rotating in certain circumstances. 
     One problem associated with accessory trip lever obstruction is encountered when a bimetal is used to implement a thermal tripping operation. The bimetal reacts to current flowing therethrough, with the temperature of the bimetal being proportional to the current magnitude. As current magnitude increases, the heat buildup in the bimetal has a tendency to cause a bottom portion thereof to deflect (bend). When non-overcurrent conditions exist, this deflection is minimal. However, above a predetermined current level, the temperature of the bimetal will exceed a threshold temperature whereby the deflection causes the bottom portion to make contact with a thermal trip member of the trip bar assembly. This contact forces the trip bar assembly to rotate and generate a tripping operation. 
     Under certain circumstances, such as a short circuit condition or the presence of excessively high currents, the bimetal can quickly heat up to a higher temperature, causing the bimetal to deflect faster and to a greater extent than normal under overcurrent conditions. This enhanced deflection has a tendency to cause greater rotation of the trip bar assembly than what is necessary in order to generate a tripping operation, the movement of which can be hindered by the aforementioned obstruction of an accessory trip lever. Unfortunately, by preventing the trip bar assembly from continuing to rotate in this situation, an obstruction can prevent the bimetal from fully and properly deflecting, thereby undesirably causing the bimetal to “take a set.” Such an event can destroy the calibration of the bimetal and prevent it from being properly calibrated thereafter. 
     Therefore, it would be advantageous if a way existed by which an accessory device tripping operation could be conveniently and effectively implemented within a circuit interrupter having internal space constraints. In particular, it would be advantageous if a way existed by which to accommodate for an aforementioned obstruction of an accessory trip lever while, at the same time, enabling the trip bar assembly to continue to rotate during a tripping operation. 
     SUMMARY OF THE INVENTION 
     The present invention provides a circuit interrupter that meets all of the above-identified needs. 
     In accordance with the present invention, a circuit interrupter is provided which includes a housing, separable main contacts within the housing, and an operating mechanism within the housing and interconnected with the separable main contacts. A trip mechanism is disposed within the housing and includes a rotatable trip bar assembly that, when selectively rotated, generates a tripping operation causing the operating mechanism to open the contacts. The trip bar assembly includes an attaching structure which interconnects with an accessory trip member. The accessory trip member causes the trip bar assembly to rotate and generate a tripping operation when the accessory trip member is moved in a first direction. The accessory trip member is configured to enable flexing of the accessory trip member in a second direction opposite of said first direction. 
     This and other objects and advantages of the present invention will become apparent from a reading of the following description of the preferred embodiment taken in connection with the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an orthogonal view of a molded case circuit interrupter embodying the present invention. 
     FIG. 2 is an exploded view of the base, primary cover, and secondary cover of the circuit interrupter of FIG.  1 . 
     FIG. 3 is a side elevational view of an internal portion of the circuit interrupter of FIG.  1 . 
     FIG. 4 is an orthogonal view of the trip bar assembly of the circuit interrupter of FIG.  1 . 
     FIG. 5 is another orthogonal view of the trip bar assembly of the circuit interrupter of FIG. 1 showing how the accessory trip levers are inserted. 
     FIG. 6A is an orthogonal view of the attaching structures of the trip bar assembly of the circuit interrupter of FIG.  1 . 
     FIG. 6B is another orthogonal view of the attaching structures of the trip bar assembly of the circuit interrupter of FIG.  1 . 
     FIG. 7A is an orthogonal view of an accessory trip lever of the trip bar assembly of the circuit interrupter of FIG.  1 . 
     FIG. 7B is an orthogonal view of the lower lever portion of an accessory trip lever. 
     FIG. 7C is an orthogonal view of the upper lever portion of an accessory trip lever. 
     FIG. 8 is an orthogonal view of the trip bar assembly of the circuit interrupter of FIG. 1 depicting the insertion of an accessory trip lever. 
     FIG. 9 is an orthogonal view depicting the locking in of an inserted accessory trip lever. 
     FIG. 10A is an orthogonal side view of the trip bar assembly of the circuit interrupter of FIG.  1 . 
     FIG. 10B is another orthogonal side view of the trip bar assembly with an accessory trip lever bent to the right. 
     FIG. 10C is another orthogonal side view of the trip bar assembly with an accessory trip lever bent to the left. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and FIGS. 1 and 2 in particular, shown is a molded case circuit interrupter or breaker  10 . A detailed description of the general structure and operation of circuit beaker  10  can be found in U.S. patent application Ser. No. 09/386,126, the disclosure of which is incorporated herein by reference. Briefly, circuit breaker  10  includes a base  12  mechanically interconnected with a primary cover  14 . Disposed on top of primary cover  14  is an auxiliary or secondary cover  16 . When removed, secondary cover  16  renders some internal portions of the circuit breaker available for maintenance and the like without requiring disassembly of the entire circuit breaker. Base  12  includes internal phase walls  20 ,  21 , and  22 . Holes or openings  23 A are provided in primary cover  14  for accepting screws or other attaching devices that enter corresponding holes or openings  23 B in base  12  for fastening primary cover  14  to base  12 . Holes or openings  24 A are provided in secondary cover  16  for accepting screws or other attaching devices that enter corresponding holes or openings  24 B in primary cover  14  for fastening secondary cover  16  to primary cover  14 . Holes  25 , which feed through secondary cover  16 , primary cover  14 , and into base  12  (one side showing holes  25 ), are provided for access to electrical terminal areas of circuit breaker  10 . Holes  26 A, which feed through secondary cover  16 , correspond to holes  26  that feed through primary cover  14  and base  12 , and are provided for attaching the entire circuit breaker assembly onto a wall, or into a DIN rail back panel or a load center, or the like. Surfaces  29  and  30  of secondary cover  16  are for placement of labels onto circuit breaker  10 . Primary cover  14  includes cavities  31 ,  32 , and  33  for placement of internal accessories of circuit breaker  10 . Secondary cover  16  includes a secondary cover handle opening  36 . Primary cover  14  includes a primary cover handle opening  38 . A handle  40  (FIG. 1) protrudes through openings  36  and  38  and is used in a conventional manner to manually open and close the contacts of circuit breaker  10  and to reset circuit breaker  10  when it is in a tripped state. Handle  40  may also provide an indication of the status of circuit breaker  10  whereby the position of handle  40  corresponds with a legend (not shown) on secondary cover  16  near handle opening  36  which clearly indicates whether circuit breaker  10  is ON (contacts closed), OFF (contacts open), or TRIPPED (contacts open due to, for example, an overcurrent condition). Secondary cover  16  and primary cover  14  include rectangular openings  42  and  44 , respectively, through which protrudes a top portion  46  (FIG. 1) of a button for a push-to-trip actuator. Also shown are load conductor openings  48  in base  12  that shield and protect load terminals  50 . Although circuit breaker  10  is depicted as a four phase circuit breaker, the present invention is not limited to four-phase operation. 
     Referring now to FIG. 3, a longitudinal section of a side elevation, partially broken away and partially in phantom, of circuit breaker  10  is shown having a load terminal  50  and a line terminal  52 . There is shown a plasma arc acceleration chamber  54  comprising a slot motor assembly  56  and an arc extinguisher assembly  58 . Also shown is a contact assembly  60 , an operating mechanism  62 , and a trip mechanism  64  including a rotatable trip bar assembly  122 . Although not viewable in FIG. 3, each phase of circuit breaker  10  has its own load terminal  50 , line terminal  52 , plasma arc acceleration chamber  54 , slot motor assembly  56 , arc extinguisher assembly  58 , and contact assembly  60 . Reference is often made herein to only one such group of components and their constituents for the sake of simplicity. 
     Each contact assembly  60  is shown as comprising a movable contact arm  78  supporting thereon a movable contact  80 , and a stationary contact arm  82  supporting thereon a stationary contact  84 . Each stationary contact arm  82  is electrically connected to a line terminal  52  and, although not shown, each movable contact arm  78  is electrically connected to a load terminal  50 . Also shown is a crossbar assembly  86  which traverses the width of circuit breaker  10  and is rotatably disposed on an internal portion of base  12  (not shown). Actuation of operating mechanism  62  causes crossbar assembly  86  and movable contact arms  78  to rotate into or out of a disposition which places movable contacts  80  into or out of a disposition of electrical continuity with fixed contacts  84 . 
     Operating mechanism  62  comprises a handle arm or handle assembly  92  (connected to handle  40 ), a configured plate or cradle  94 , an upper toggle link  96 , an interlinked lower toggle link  98 , and an upper toggle link pivot pin  100  which interlinks upper toggle link  96  with cradle  94 . Lower toggle link  98  is pivotally interconnected with upper toggle link  96  by way of an intermediate toggle link pivot pin  102 , and with crossbar assembly  86  at a pivot pin  90 . Provided is a cradle pivot pin  104  which is laterally and rotatably disposed between parallel, spaced apart operating mechanism support members or sideplates  106 . Cradle  94  is free to rotate (within limits) via cradle pivot pin  104 . A main stop bar  112  is laterally disposed between sideplates  106 , and provides a limit to the counter-clockwise movement of cradle  94 . 
     In FIG. 3, operating mechanism  62  is shown for the ON disposition of circuit breaker  10 . In this disposition, contacts  80  and  84  are closed (in contact with each other) whereby electrical current may flow from load terminals  50  to line terminals  52 . 
     Operating mechanism  62  will assume the TRIPPED disposition of circuit breaker  10  in certain circumstances. The TRIPPED disposition is related to an opening of circuit breaker  10  caused by a manual tripping operation, an accessory tripping operation (as described below), or the thermally or magnetically induced reaction of trip mechanism  64  to the magnitude of the current flowing between load conductors  50  and line conductors  52 . A detailed description of the manual tripping operation and the automatic operation of trip mechanism  64  can be found in U.S. patent application Ser. No. 09/386,126. Whatever the nature of a tripping operation, it is initiated by a force causing trip bar assembly  122  to rotate clockwise (overcoming a spring force biasing assembly  122  in the opposite direction) and away from an intermediate latch  114 . This unlocking of latch  114  releases cradle  94  (which had been held in place at a lower portion  116  of a latch cutout region  118 ) and enables it to be rotated counter-clockwise under the influence of tension springs (not shown) interacting between the top of handle assembly  92  and the intermediate toggle link pivot pin  102 . The resulting collapse of the toggle arrangement causes pivot pin  90  to be rotated clockwise and upwardly to thus cause crossbar assembly  86  to similarly rotate. This rotation of crossbar assembly  86  causes a clockwise motion of movable contact arms  78 , resulting in a separation of contacts  80  and  84 . 
     Referring now to FIGS. 4 and 5, shown is trip bar assembly  122  of trip mechanism  64  of the exemplary embodiment. Assembly  122  includes a trip bar or shaft  140  to which is connected thermal trip bars or paddles  142 , magnetic trip bars or paddles  144 , and accessory trip levers  148 A and  148 B. Trip bar assembly  122  also includes an intermediate latch interface  150  that locks with intermediate latch  114  (FIG. 3) when trip bar assembly  122  has not rotated clockwise during a tripping operation. 
     Circuit breaker  10  includes the ability to provide accessory tripping operations which can cause trip bar assembly  122  to rotate in the clockwise direction and thereby release cradle  94 . Referring now briefly again to FIG. 2, primary cover  14  includes cavities  32  and  33  into which may be inserted internal accessories for circuit breaker  10 . Examples of such conventional internal accessories include an undervoltage release (UVR), and a shunt trip. Each of cavities  32  and  33  includes a rightward opening (not shown) that provides access into base  12  and which faces trip mechanism  64 . In particular, the opening within cavity  32  provides actuating access to accessory trip lever  148 A, and the opening within cavity  33  provides actuating access to accessory trip lever  148 B (see FIG.  4 ). When an appropriate accessory device, located in cavity  33  for example, operates in a conventional manner whereby it determines that a tripping operation of circuit breaker  10  should be initiated, a plunger or the like comes out of the device and protrudes through the rightward opening in cavity  33  and makes contact with a contact surface  160  of accessory trip lever  148 B. This contact causes trip lever  148 B to move to the right, thereby causing a clockwise (when viewed in FIG. 3) rotation of trip bar assembly  122  which leads to the TRIPPED disposition. 
     Internal components of circuit breaker  10 , such as portions of primary cover  14 , may obstruct the rotational movement of the top of an accessory trip lever  148  during clockwise rotation of trip bar assembly  122  during any type of tripping operation (push-to-trip, thermal, magnetic, etc.). This is especially true in a circuit breaker having internal space constraints. Such an obstruction can prevent lever  148  from continuing to rotate in the clockwise direction. In a manner described below, circuit breaker  10  of the present invention ensures that trip bar assembly  122  can continue to sufficiently rotate in the clockwise direction during a tripping operation notwithstanding such obstruction of an accessory trip lever  148 . 
     Referring again to FIGS. 4 and 5, trip bar assembly  122  includes integrally molded attaching devices or structures  166  that connect accessory trip levers  148 A and  148 B to trip bar assembly  122 . Referring now also to FIGS. 6A and 6B, each of the attaching structures  166  of the exemplary embodiment includes an open-ended cavity  168  defined by a front wall  170 , sidewalls  172  and  174 , and a backwall  176 . For purposes described below, front wall  170  includes a groove  178  positioned within cavity  168  and extending from the top of wall  170  to a point above the bottom thereof (see FIG.  8 ). The tops of sidewalls  172  and  174  each define a shoulder  180  and  182 , respectively, for purposes described below. The above-described configuration of attaching structure  166  can be advantageously molded into trip bar assembly  122  without complicated molding processes such as bypass molding or side pull molding. 
     Now referring also to FIGS. 7A,  7 B and  7 C, shown is an accessory trip lever  148  of the exemplary embodiment. Accessory trip lever  148  is comprised of a lower lever portion or accessory lower lever  190 , and an upper lever portion or accessory spring lever  192 . As best seen in FIG. 7B, lower lever portion  190  includes a base  196  connected to a head  198  which defines abutment surfaces  200  and  202 . Base  196  includes a protrusion  204  which, in the exemplary embodiment, is oval in shape. Also connected to base  196  are parallel legs  206  with a cutout  208  therebetween. Legs  206  have abutment regions  206 A for purposes described below. Lower lever portion  190  also includes a front surface  209 . In the exemplary embodiment, lower lever portion  190  is formed of cold-rolled steel of sufficient thickness so as to be substantially rigid. 
     As best seen in FIG. 7C, upper lever portion  192  of accessory trip lever  148  is rectangular in shape and includes a lower end region  210  through which extends an opening  212  that is sized and shaped to correspond to protrusion  204  of lower lever portion  190 . Near its top, upper lever portion  192  includes a contact surface  160  (as described above). In the exemplary embodiment, upper lever portion  192  is formed of stainless spring steel having a thickness of approximately 0.010 inches, and is semi-flexible for reasons discussed below. 
     Accessory trip lever  148  is assembled by inserting protrusion  204  of lower lever portion  190  into opening  212  of upper lever portion  192  in the manner shown in FIG.  7 A. In this configuration, the back surface of portion  192  contacts front surface  209  of portion  190 , with contact surface  160  positioned above head  198  of portion  190 . As shown in FIG. 7A, the width of base  196  of lower lever portion  190  is approximately the same as the width of upper lever portion  192 . 
     Each of accessory trip levers  148 A and  148 B (assembled as shown in FIG. 7A) insert into attaching structures  166  in order to be connected to trip bar assembly  122 . Referring now also to FIG. 8 wherein a portion of front wall  170  of attaching structure  166  is cut away for purposes of illustration, the insertion process begins with the insertion of legs  206  into cavity  168 , and continues until abutment surfaces  200  and  202  abut shoulders  180  and  182 , respectively. During this insertion, protrusion  204  of accessory trip lever  148  is channeled into groove  178  of front wall  170 , resulting in the insertion of lower end region  210  of upper lever portion  192  within cavity  168  and the locking together of lower lever portion  190  and upper lever portion  192 . 
     After insertion of an accessory trip lever  148  as described above, legs  206  of lower lever portion  190  protrude through the bottom of cavity  168 , as shown in FIG.  8 . Referring now also to FIG. 9, legs  206  are then bent outwards and away from each other until abutment regions  206 A of legs  206  abut the bottoms of sidewalls  172  and  174  (see FIG.  6 B), thereby vertically locking accessory trip lever  148  within cavity  168  and providing a secure engagement of lever  148  with trip bar assembly  122 . In order to achieve the aforementioned separation of legs  206 , an arbor press with a V-shaped mandrel may be used. 
     The attachment of an accessory trip lever  148  to an attaching structure  166  enables lever  148  to cause a clockwise rotation of trip bar assembly  122  (when viewed in FIG. 3) when contact surface  160  is contacted by one of the above-described accessory devices during an accessory tripping operation. Referring now also to FIGS. 10A,  10 B, and  10 C, FIG. 10A shows a side view of a completely assembled trip bar assembly  122  without the application of any external forces thereon. When contact surface  160  is first contacted by an accessory device, upper lever portion  192  may slightly bend to the right at an upper bending moment  220  located along the length of portion  192  substantially at the point where it contacts the top of head  198  of lower lever position  190 , as shown in FIG.  10 B. However, the position of upper bending moment  220  makes upper lever portion  192  sufficiently rigid such that further force exerted upon contact surface  160  causes rotation of trip bar assembly  122  which, in turn, initiates a tripping operation. 
     In order to accommodate for an aforementioned obstruction of an accessory trip lever  148 , and yet enable trip bar assembly  122  to continue to sufficiently rotate in the clockwise direction during a tripping operation, trip lever  148  is capable of more substantial bending than that shown in FIG.  10 B. In particular, referring to FIG. 10C, when an obstruction occurs, upper  30  lever portion  192  bends to the left at a lower bending moment  222  located along the length of portion  192  substantially at the point where it contacts attaching structure  166 . Because bending moment  222  is positioned lower along the length of upper lever portion  192  than upper bending moment  220  (FIG.  10 B), portion  192  is afforded greater flexibility when bent to the left than when bent to the right, thereby allowing trip bar assembly  122  to continue to sufficiently rotate in the clockwise direction during a tripping operation notwithstanding an obstruction. 
     As described above, accessory trip lever  148  of the present invention is designed to be sufficiently rigid when force is applied to it in a rightward direction (as viewed in FIG. 10B) and sufficiently flexible when force is applied to it in a leftward direction (as viewed in FIG.  10 C). The positioning of lower lever portion  190  relative to upper lever portion  192 , and the material used for and thickness of upper lever portion  192 , are appropriately selected in order to provide this desired functionality. 
     Although the preferred embodiment of the present invention has been described with a certain degree of particularity, various changes to form and detail may be made without departing from the spirit and scope of the invention as hereinafter claimed.