Patent Publication Number: US-6700082-B1

Title: Trip actuator for a circuit breaker

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is related to commonly assigned, U.S. patent application Ser. No. 10/185,858, filed Jun. 27, 2002, entitled “Circuit Breaker”. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to electrical switching apparatus. More specifically, the invention provides a circuit breaker having a trip mechanism that is actuated when a contactor terminal cover is opened. 
     2. Description of the Related Art 
     The need to ensure that current cannot flow to electrical equipment while that equipment is being serviced has long been recognized. One proposal to meet this need is described in U.S. Pat. No. 4,468,531, issued to J. H. Postlehwait et al. on Aug. 28, 1984. This patent describes a safety shield assembly for precluding access to the line and load stabs of a circuit breaker when that circuit breaker is disconnected from the stabs for servicing. 
     U.S. Pat. No. 5,572,396, issued to D. Robinson on Nov. 5, 1996, describes an electric service safety disconnect apparatus with over voltage and over current protection. The apparatus includes a circuit breaker having a plunger that moves between a retracted, closed position and an extended, open position. When in the open position, a lock may be passed through an aperture in the plunger, preventing the plunger from moving to a closed position. 
     There is a need to ensure that, any time electrical equipment is accessed for servicing, current to that electrical equipment is automatically cut off. 
     SUMMARY OF THE INVENTION 
     The present invention provides an apparatus for automatically tripping a circuit breaker upon opening the cover of electrical components mounted on either the line side or the load side of a circuit breaker. Such components include contactors, motor starters, etc. 
     The apparatus includes a plunger protruding from the housing of the circuit breaker, where it will be depressed by the opening of the cover of electrical equipment connected adjacent to the circuit breaker. A rod extends from the plunger to a location adjacent to the trip mechanism of the circuit breaker, where the rod engages the latch within this trip mechanism. Pushing the plunger will thereby rotate the latch of the circuit breaker, thereby releasing the carrier within the circuit breaker to move under spring bias to a position wherein the circuit breaker&#39;s movable contact is moved away from the fixed contact, thereby opening the circuit breaker. 
     The present invention provides continued protection from current throughout the entire servicing of the equipment. As long as the cover to the equipment is open, the plunger will remain depressed, and the latch of the circuit breaker will remain in the trip position. Therefore, if someone were to attempt to close the circuit breaker using its operating handle, the latch would fail to hold the carrier in the closed position, so that the circuit breaker would open as soon as the operating handle was released. 
    
    
     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 isometric view of a circuit breaker in accordance with the present invention. 
     FIGS. 2A-2B, when placed end-to-end, form a cross sectional view along lines  2 — 2  of one pole of the circuit breaker of FIG. 1 with the operating handle assembly in the OFF position. 
     FIG. 3 is an isometric view, similar to the cross sectional view of a portion of FIG.  2 A and FIG. 2B, but with the operating handle assembly cut away to show the blocking disk. 
     FIG. 4 is a reverse cross sectional view along lines  4 — 4  of one pole of the circuit breaker of FIG. 1 with the operating handle assembly in a blocking position. 
     FIG. 5 is a view similar to FIG. 4, but with the operating handle assembly in a snap close position. 
     FIG. 6A is an isometric view of the carrier mechanism of FIG.  2 A. 
     FIG. 6B is an isometric view, similar to FIG. 6A, but with the latch member removed to show the carrier spring. 
     FIG. 6C is an isometric view, similar to FIG. 6B, but with the carrier cover removed. [please confirm that FIGS. 6A-6C are PRIOR ART] 
     FIG. 7 is an exploded isometric view of three circuit breaker poles and two trip actuators for each pair of the circuit breaker poles. 
     FIG. 8 is an isometric view of the push-to-trip pushbutton of one of the trip actuators of FIG.  7 . 
     FIG. 9 is an isometric view of one of the trip actuators engaging one of the circuit breaker poles of FIG.  7 . 
     FIG. 10 is an isometric front view of a circuit breaker, and its associated contactor, having a trip mechanism activated by the contactor&#39;s bus bar cover, according to the present invention. 
     FIG. 11 is an isometric view of an actuation button for a trip mechanism according to the present invention. 
     FIG. 12 is a partially exploded, isometric front view of a circuit breaker and its associated contactor, having a trip mechanism activated by the contactor&#39;s bus bar cover, according to the present invention. 
     FIG. 13 is an isometric view of the trip mechanism of a circuit breaker, and its associated trip actuator bar. 
     FIG. 14 is a trip actuator bar according to the present invention. 
     Like reference numbers denote like elements throughout the drawings. 
    
    
     DETAILED DESCRIPTION 
     The present invention provides an apparatus for tripping a circuit breaker upon the opening of a cover of electrical equipment in close proximity to the circuit breaker. The manner in which the present invention trips the circuit breaker is best understood through an explanation of the trip mechanism of a circuit breaker with which the present invention may be used. 
     Referring to the figures, FIG. 1 shows the exemplary three-phase molded case circuit breaker  2  including an electrically insulated housing  3  comprising a molded base  4  and a similarly molded cover  6  for each of three poles. The molded base  4  and molded cover  6  form a molded case  8  for each of the three poles. For the three poles, three load terminals  10 , 12 , 14  and three line terminals  16 , 18 , 20  are provided, where load terminal  10  is related to line terminal  16 , load terminal  12  is related to line terminal  18 , and load terminal  14  is related to line terminal  20 . A common or ganged handle assembly  22  manually opens and closes the exemplary three-phase circuit breaker  2 . 
     Referring to FIGS. 2A-2B, each pole of the circuit breaker  2  includes the molded base  4 , a load terminal, such as  10 , a line terminal, such as  16 , a first circuit breaker mechanism  24 , a second circuit breaker mechanism  26 , and an operating handle assembly  28  for the pole, which handle is shown in the OFF position. A first U-shaped link  30  is disposed from the operating handle assembly  28  to the first circuit breaker mechanism  24 , and a second link U-shaped  32  is disposed from the operating handle assembly  28  to the second circuit breaker mechanism  26 . The first circuit breaker mechanism  24  includes a first set of separable contacts  34  (shown open), a first operating mechanism  36  for moving the first separable contacts  34  between the open position and a closed position (shown in FIG.  5 ), and a first trip mechanism  38  cooperating with the first operating mechanism  36  for moving the first separable contacts  34  from the closed position to the open position thereof. Similarly, the second circuit breaker mechanism  26  includes a second set of separable contacts  40  (shown open) in series with the first separable contacts  34  between the line terminal  16  and the load terminal  10 , a second operating mechanism  42  for moving the second separable contacts  40  between the open position and a closed position (shown in FIG.  5 ), and a second trip mechanism  44  cooperating with the second operating mechanism  42  for moving the second separable contacts  40  from the closed position to the open position thereof. 
     The single operating handle assembly  28  of the circuit breaker pole is advantageously tied to the two circuit breaker mechanisms  24 , 26  (through first and second secondary pivots  158 , 160  as discussed below) by the links  30 , 32 , respectively. In the exemplary embodiment, the two circuit breaker mechanisms  24 , 26  are housed in series in the single pole molded case  8  and are arranged for operation in the same direction, with the “load” side of the first mechanism  24  being electrically connected to the “line” side of the downstream second mechanism  26 . Thus, the upstream mechanism  24  provides the line terminal  16  of this pole and the downstream mechanism  26  provides the load terminal  10  of the pole. 
     The first and second links  30 , 32  engage the first and second operating mechanisms  36 , 42  to move the first and second separable contacts  34 , 40 , respectively, between the corresponding closed and open positions thereof responsive to the ON and OFF positions, respectively, of the operating handle assembly  28 . 
     Disposed within the molded case  8  are first and second arc chutes  46 , 48 , which are operatively associated with the first and second separable contacts  34 , 40 , respectively. The first set of separable contacts  34  includes a fixed contact  50  and a movable contact  52 . Similarly, the second set of separable contacts  40  includes a fixed contact  54  and a movable contact  56 . The first arc chute  46  is operatively associated with a first arc runner  58  extending from the first fixed contact  50 . Similarly, the second arc chute  48  is operatively associated with a second arc runner  60  extending from the second fixed contact  54 , and a third arc runner  62 , which is electrically interconnected (through a bimetal element  70  as discussed below) with the load terminal  10 . A fourth arc runner  64  is operatively associated with and provides an electrically conducting path between the two arc chutes  46 , 48 . 
     The circuit breaker mechanisms  24 , 26  are provided within the molded case  8  for interconnection between the line terminal  16  and the load terminal  10  as discussed below. The first circuit breaker mechanism  24  includes the first fixed contact  50  and the first movable contact  52 , and the second circuit breaker mechanism  26  includes the second fixed contact  54  and the second movable contact  56 . The fixed contacts  50 , 54  are preferably welded on the arc runners  58 , 60 , respectively. 
     The exemplary first and second trip mechanisms  38 , 44  include magnetic trip coils  66 , 68 , respectively, to provide corresponding instantaneous magnetic trip functions. Although two trip coils  66 , 68  are shown, the invention is applicable to circuit breakers employing a single trip coil (not shown). Also, the second trip mechanism  44  further includes the bimetal element  70  to provide a thermal trip function. The bimetal element  70  has an input or free end  72  electrically interconnected by a flexible shunt  74  with the second movable contact  56  through a corresponding second movable contact arm  76 . The bimetal element  70  also has an output or base  77 , which is electrically interconnected by a flexible shunt  78  with a load conductor  80  of the load terminal  10 . Another flexible shunt  82  electrically connects a first movable contact arm  84  to the fourth arc runner  64  and to the input of the second magnetic trip coil  68 . Preferably, the bimetal element  70  also includes an adjustment screw  83  to adjust a thermal trip threshold thereof. The movable contacts  52 , 56  are suitably plated (e.g., silver) on the respective movable contact arms  84 , 76 , which are movably operable relative to the respective fixed contacts  50 , 54  depending on the status of the corresponding circuit breaker mechanisms  24 , 26 . The movable contact arm  76 , for example, has the movable contact  56  adapted for engagement with the corresponding fixed contact  54 . Similarly, the movable contact arm  84  has the movable contact  52  adapted for engagement with the corresponding fixed contact  50 . 
     Both of the magnetic trip coils  66 , 68  are preferably active and provide instantaneous magnetic trip functions for the respective circuit breaker mechanisms  24 , 26 . In this manner, the most effective current limiting capability is provided. Since the magnetic trip coils  66 , 68  act independently and since common activation currents are very difficult to achieve, a common trip actuator  206  (FIG. 7) is employed between the two circuit breaker mechanisms  24 , 26 . 
     Although the exemplary embodiment employs a single bimetal element  70  with the second circuit breaker mechanism  26 , a bimetal element (not shown) may alternatively be employed with the first circuit breaker mechanism  24 . Although one bimetal element is preferred, two bimetal elements (not shown) may be employed with both circuit breaker mechanisms  24 , 26 . 
     The first magnetic trip coil  66  is electrically interconnected between the line terminal  16  and the first fixed contact  50  by a line conductor  86  of the line terminal  16  at one end and the first arc runner  58  at the other end of the coil  66 . The second magnetic trip coil  68  is electrically interconnected between the first movable contact  52  and the second fixed contact  54  by the flexible shunt  82  at one end and the second arc runner  60  at the other end of the coil  68 . 
     An electrical circuit between the line terminal  16  and the load terminal  10  is formed by the series combination of the line conductor  86  from the line terminal  16 , the first magnetic trip coil  66 , the first arc runner  58 , the first fixed contact  50 , the first movable contact  52  (in the closed position of FIG.  5 ), the first movable contact arm  84 , the flexible shunt  82 , the second magnetic trip coil  68 , the second arc runner  60 , the second fixed contact  54 , the second movable contact  56  (in the closed position of FIG.  5 ), the second movable contact arm  76 , the flexible shunt  74 , the bimetal element  70 , the flexible shunt  78 , and the load conductor  80  to the load terminal  10 . 
     The first arc chute  46  is electrically positioned between: (a) the arc runner  58  for the first fixed contact  50  at the output of the first magnetic trip coil  66 , and (b) the arc runner  64  and the input of the second magnetic trip coil  68 . The second arc chute  48  is electrically positioned between: (a) the arc runner  60  for the second fixed contact  54  at the output of the second magnetic trip coil  68 , and (b) the arc runner  62  and the output or base  77  of the bimetal element  70 . The arc chutes  46 , 48  include a plurality of conventional spaced deionization plates  88 , 90 . 
     The exemplary circuit breaker  2 , thus, employs a series arrangement of the two circuit breaker mechanisms  24 , 26 . The interruption performance of the circuit breaker  2  is determined by the “current limitation of series arcs,” which provides two arcs in series, thereby having twice the resistance of a single arc. In the exemplary embodiment, IEC 898 component circuit breaker mechanisms are employed. This exemplary configuration allows for a UL 480 VAC (and perhaps a 600 VAC) device capable of 65 kA interruption in an 18 mm per pole width. 
     The enhanced current limiting capability provided by the circuit breaker  2  increases the likelihood for Type 2 protection. Such protection provides that equipment so classified can be returned to regular service after exposure to its listed short circuit withstand. No part or component within the system requires replacement prior to continued operation. 
     Also referring to FIG. 3, the operating handle assembly  28  includes an operating handle  92  (FIG. 2A) and a blocking disk  94  (FIG.  3 ), both of which are co-pivotally mounted by a pivot mechanism  96  related to the molded base  4 . The secondary pivots  158 , 160  include a spring (not shown) which biases the operating handle  92  toward the OFF position of FIG.  2 A. The blocking disk  94  is preferably molded to include a first portion  98  and a second portion  100 . The first portion  98  (and, thus, the second portion  100  and the blocking disk  94 ) is biased to resist counter-clockwise rotation with respect to FIGS. 2A-2B and  3 . The bias may be provided by employing cantilever spring member  102  having a first end  104  disposed from the first blocking disk portion  98  and a second end  106  loaded against a surface  108  of the molded base  4 . Alternatively, a torsion spring (not shown) may be employed. 
     The operating mechanisms  36 , 42  further include carrier mechanisms  110 , 112 , respectively. As shown in FIGS. 6A-6C, the carrier mechanism  110  of the first operating mechanism  36  includes a base portion  114  and a cover portion  116 . The base and cover portions  114 , 116  are secured together by two sets of fingers  118 , 120  of the base portion  114 , which engage the cover portion  116  at respective openings  122 , 124  thereof. The movable contact arm  84  is pivotally mounted to the carrier mechanism  110  by pivots  125  and  126 , which are pivotally mounted in an opening  128  of the base portion  114  and an opening  129  of the cover portion  116 , respectively. 
     The carrier mechanism  110  also includes a latch member  130  and a spring  132 . The latch member  130  is pivotally mounted to the carrier mechanism  110  by a post  134 , an upper end of which extends through an opening  136  of the cover portion  116 . A lower end  135  (shown in FIGS. 4 and 5) of the post  134  extends through a corresponding opening  135 A (shown in FIGS. 4 and 5) of the carrier base portion  114 . In turn, the lower post end  135  is pivotally mounted in an opening (not shown) of the molded base  4  of FIG.  3 . The carrier mechanism  110  further includes a channel  137  formed in the base portion  114  and the cover portion  116 . The channel  137  has a first end  138  and an opposite second end  140 . As discussed below, the pivotally mounted latch member  130  is employed for releasing the carrier mechanism  110  in response to a trip condition of the circuit breaker  2 . 
     As shown in FIGS. 2A-2B, the channel  137  accepts a U-shaped link  142  with an end  143  being disposed in the first end  138  of the channel  137  of the first carrier mechanism  110 . Similarly, a U-shaped link  144  having an end  145  is disposed in the first end  138  of the channel  137  of the second carrier mechanism  112 . As discussed below, the links  142 , 144  provide linkages from the respective carrier mechanisms  110 , 112  through the secondary pivots  158 , 160  to the operating handle assembly  28 . 
     Referring again to FIGS. 6A-6C, the spring  132  has an opening  146 , a first end  148  and a second end  150 . The post  134  of the latch member  130  passes through the spring opening  146 . A bend portion  149  proximate the first spring end  148  engages a notch  152  of the carrier base portion  114 , and the second spring end  150  engages a surface  153  of the movable contact arm  84  in order to bias such arm clockwise with respect to FIG.  6 C. The link  142  is engaged by the hook member  156  of the latch member  130 , which permits the carrier mechanism  110  to rotate with the operating handle assembly  28 . The carrier spring  132  further interacts with the molded base  4  to provide counterclockwise (with respect to FIG. 2A) bias to open the carrier mechanism  110  upon release of the latch member  130 . [please confirm] 
     A spring (not shown) associated with the secondary pivot  160  (FIG. 2B) biases the operating handle  92  off and biases the upper portion of the latch member  130  clockwise (with respect to FIG. 6A) to hold the link end  143  in the first end  138  of the channel  137 . [please confirm] As discussed below, the latch member  130  is adapted to pivot counter-clockwise with respect to FIG. 6A in response to a trip condition to release the link end  143  toward the second end  140  of the channel  137 . Hence, the latch member  130  releases the link  142  in response to a trip condition. 
     Referring to FIGS. 2A-2B and  3 - 5 , the operating handle  92  has an OFF position (FIG.  2 A), an ON position (shown in phantom line drawing in FIG.  2 A), and first and second intermediate positions (shown in FIGS. 3 and 4, and FIG. 5) between the OFF and ON positions. As shown in FIGS. 2A,  4  and  5 , the operating handle assembly  28  is rotated counter-clockwise (with respect to FIG. 2A) toward the ON position (as shown in phantom line drawing in FIG.  2 A). The operating handle assembly  28 , in turn, drives the operating mechanisms  36 , 42  through the links  30 , 32 , which rotate the secondary pivots  158 , 160 , respectively, counter-clockwise (with respect to FIGS.  2 A- 2 B). The pivots  158 , 160  are pivotally mounted to the molded base  4  by respective pins  162 , 164 . The opposite secondary pivot ends  163 , 165  of the links  142 , 144  are pivotally mounted in openings of the pivots  158 , 160 , respectively. Similarly, first ends of the links  30 , 32  are pivotally mounted in corresponding openings of the operating handle assembly  28 , and second ends of the links  30 , 32  are pivotally mounted in corresponding openings of the respective pivots  158 , 160 . 
     As shown with the operating mechanism  36 , the first secondary pivot  158 , in turn, drives the link  142 , which drives the carrier mechanism  110  clockwise (with respect to FIG. 2A) about the post  134 . As discussed above in connection with FIGS. 6A-6C, the carrier mechanism  110  carries the movable contact arm  84  having the movable contact  52  disposed at the free end thereof. Solely with this arrangement, as disclosed above, the slower that the user rotates the operating handle assembly  28  into the ON position, the slower the carrier mechanism  110  drives the movable contact arm  84 , in order to contact the fixed contact  50  with the movable contact  52 . It will be appreciated that the second operating mechanism  42 , the second secondary pivot  160 , the links  32  and  144 , the second carrier mechanism  112 , and the second separable contacts  40  operate in an analogous manner. 
     A pivot lever  166  is pivotally mounted to the molded base  4  by a pin  168 . The pivot lever  166  includes a first arm  169  having a first end  170  adapted for engagement with the movable contact arm  84 , and a second arm  171  having a second end  172  adapted for engagement with the operating handle assembly  28 . The first end  170  of the pivot lever  166  carriers a U-shaped hook member  174  pivotally disposed thereon. The hook member  174  has a J-shaped hook  176  (shown in FIG.  3 ), which hook is adapted for engagement with the movable contact arm  84 , and a J-shaped pivot end  178 , which is pivotally mounted in an opening  179  of the first arm  169 . 
     In order to eliminate the dependency between the movable contact arm  84  and the operating handle assembly  28 , the hook  176  of the hook member  174  initially hooks the movable contact arm  84  (as shown in FIG.  4 ). The pivot end  178  of the hook member  174  is inserted into the first or free end  170  of the pivot lever  166 . The pivot lever  166  pivots about the pin  168  and translates the hook member  174  and the movable contact arm  84  movement up to the operating handle assembly  28 . The second or handle end  172  of the pivot lever  166  interacts with the blocking disk  94  (FIG. 5) of the operating handle assembly  28 , which disk rotates about the same center as the operating handle  92 , but is allowed independent movement. 
     This independent movement of the operating handle  92  and the blocking disk  94  of the operating handle assembly  28  provides a resetable snap close function. As shown in FIGS. 3 and 4, the blocking disk  94  includes two diameters or surfaces  180 , 182  having an abrupt radius transition or surface  184  therebetween. The blocking disk  94  is continuously biased clockwise (with respect to FIGS. 2A and 3) and counter-clockwise (with respect to FIGS. 4 and 5) by the spring  102 . This forces the large diameter  182  to block the handle end  172  of the pivot lever  166  from clockwise rotation (with respect to FIGS. 2A and 3, and, thus, from counter-clockwise rotation with respect to FIG.  4 ). As shown in the blocking position of FIG. 4, the pivot lever  166  and the hook member  174  block the movable contact arm  84  from rotating with the carrier mechanism  110  as the operating handle assembly  28  is turned (clockwise with respect to FIG. 4) to the ON position of the operating handle  92  (shown in phantom line drawing in FIG.  4 ). 
     As shown in FIGS. 4 and 5, this blocking condition (FIG. 4) exists until the operating handle assembly  28  is further turned clockwise (with respect to FIG. 5) toward the ON position of the operating handle  92  (shown in phantom line drawing in FIG.  5 ), at which time the blocking disk  94  is forced to rotate with the operating handle assembly  28  by the dowel or extension  186  (FIG. 4) of the operating handle  92 , which dowel engages the radius or surface  188  of the blocking disk  94 . As the blocking disk  94  is rotated further counter-clockwise with respect to FIGS. 2A and 3 by the operating handle dowel  186 , the blocking disk  94  rotates clockwise with respect to FIGS. 4 and 5 against the bias of the spring  102 . As shown in FIG. 5, this rotation causes the large diameter  182  of the blocking disk  94  to abruptly transition to the smaller diameter  180  at the end portion  190  of the handle end  172  of the pivot lever  166 . 
     The line of force exerted through the drive lines  142 , 144  on the respective secondary pivots  158 , 160  passes through the pivot center of such pivots as the operating handle  92  approaches the ON position. The previous clockwise bias (with respect to FIGS. 2A-2B) of the secondary pivots  158 , 160  changes to a counterclockwise bias (with respect to FIGS.  2 A- 2 B), which tends to keep the operating handle  92 , as connected through the links  142 , 144 , in the ON position. 
     The first surface or large diameter  182  of the blocking disk  94  blocks the end  190  of the pivot lever  166  as the operating handle assembly  28  is moved from the OFF position (FIG. 2A) toward the intermediate non-blocking position (FIG. 5) thereof. That large diameter  182  releases the pivot lever end  190  to the second surface or small diameter  180  as the operating handle assembly  28  is moved to the intermediate position (FIG. 5) thereof. As shown in FIG. 4, the hook member  174  of the pivot lever  166  blocks movement of the movable contact arm  84  when the large diameter  182  blocks the pivot lever end  190 . In turn, the hook member  174  of the pivot lever  166  releases (FIG. 5) the movable contact arm  84  when the large diameter  182  releases the pivot lever end  190  as the operating handle assembly  28  is moved to the intermediate position (FIG. 5) thereof, thereby allowing movement of the movable contact arm  84  and the movable contact  52  toward the fixed contact  50  in response to the bias of the carrier mechanism spring  132  (FIGS.  6 A- 6 C). 
     As shown in FIG. 5, once the abrupt radius transition  184  rotates past the end portion  190  to the recessed portion  192  of the pivot lever handle end  172 , the pivot lever  166  is, then, allowed sufficient counter-clockwise (with respect to FIG. 5) motion and the movable contact arm  84 , which was previously held stationary by the hook member  174 , snaps to close the movable contact  52  onto the fixed contact  50 . During the blocking operation (FIG.  4 ), the movable contact arm  84  pivots counter-clockwise (with respect to FIGS. 6A-6C) in the carrier mechanism  110  and, thus, the closing force for the separable contacts  34  is directed clockwise with respect to FIG. 2A (and counter-clockwise with respect to FIG. 5) due to the carrier spring  132 . 
     In the exemplary embodiment, the snap close function (from FIG. 4 to FIG. 5) is provided with the hook member  174 , the carrier mechanism  110  and the movable contact arm  84 . Since no blocking function is provided with the exemplary second carrier mechanism  112  and its movable contact arm  76 , the second separable contacts  40  close before the first separable contacts  34 . 
     As the circuit breaker  2  is turned OFF or trips open, the dowel  186  (FIG. 4) of the operating handle  92  rotates the pivot lever  166  (clockwise with respect to FIG. 4) to clear the large diameter  182  of the blocking disk  94 . Once this has occurred (FIG.  4 ), the bias (shown as counter-clockwise in FIG. 4) of the spring  102  drives the blocking disk  94  back to its original position (FIG.  3 ), thereby resetting it for another close operation. 
     The interaction between the operating handle assembly  28  and the pivot lever  166  also advantageously acts as a position ON indication. In the event that the separable contacts  50 , 52  have welded closed, when turning the operating handle  92  to the OFF position, the pin  186  (FIG. 4) engages the second arm  171  of the pivot lever  166 , which is prevented from rotating through hook member  174 . Hence, it is not possible to bring the operating handle assembly  28  back to the position of FIG. 4 without the application of excessive force. 
     FIG. 7 shows the circuit breaker  2  of FIG. 1 constructed by stacking three single pole circuit breakers  200 , 202 , 204 , which employ two trip actuators  206 , 208  therebetween. The circuit breakers  202 , 204  are preferably identical to the circuit breaker  200  as discussed in connection with FIGS. 2A-2B,  3 - 5 ,  6 A- 6 C and  9  herein. As shown in FIG. 8, each of these trip actuators, as shown with actuator  206 , has a push-to-trip pushbutton  210 , which is engaged by one of the trip actuators  206 , 208  of FIG.  7 . The push-to-trip pushbutton  210  is disposed through an opening  212  formed between adjacent molded bases  4  of the single pole circuit breakers  200 , 202 . The trip actuator  206  extends toward the face of the exemplary circuit breaker  2  and engages the manual trip button  210  (FIG. 8) to facilitate manual trip testing. 
     Referring again to FIG. 2A, the latch member  130  of the carrier mechanism  110  is adapted to pivot (counter-clockwise with respect to FIG. 2A) in response to various trip conditions, in order to release the end  143  of the link  142  toward the second end  140  of the carrier channel  137  and, thus, trip the circuit breaker mechanism  24  and, in turn, the circuit breaker  2 . As shown in FIG. 6A, the upper end projection  214  of the latch member  130  of circuit breaker  202  is adapted for engagement by a projection  216  (shown in phantom line drawing in FIG. 6A) of the trip actuator  206 , which is external to the circuit breakers  200 , 202  of FIG.  7 . In a related manner, an upper end projection  242  (FIG. 2B) of the latch member  220  of the second carrier mechanism  112  of circuit breaker  202  is adapted for engagement by a projection  222  (FIG. 7) of the trip actuator  206 . 
     Referring to FIGS. 7 and 9, the upper end  215  of the latch member  220  of the second carrier mechanism  112  is adapted for engagement by a projection  219  of the trip actuator  206 . In a related manner, the upper end  218  of the latch member  130  of the first carrier mechanism  110  is adapted for engagement by a projection  217  of the trip actuator  206 . Manual movement (as shown by arrow  224  of the push-to-trip pushbutton  210  from the left to the right of FIG. 9) (i.e., from the bottom right to the top left of FIG. 8 as shown by arrow  226 ) rotates the latch members  130 , 220  clockwise (with respect to FIG. 9, and counter-clockwise with respect to FIG. 6A for latch member  130 ). For example, in the first circuit breaker mechanism  24 , the hook member  156  of the latch member  130  releases the link end  143 . In turn, the carrier mechanism  110  rotates clockwise (with respect to FIG. 5, and counter-clockwise with respect to FIG. 6A) under the bias of spring  132  and the link end  143  (FIG. 2A) moves toward the second end  140  of the channel  137 . 
     As shown in FIG. 2A, the lower end  228  of the first latch member  130  is adapted for engagement by the armature  230  of the first coil  66  of the first magnetic trip circuit. Under predetermined instantaneous current conditions (e.g., greater than about three, seven or twenty times rated current), the current flowing through the coil  66 , from the line terminal  16  to the load terminal  10 , causes the armature  230  to move to the right on FIG. 2A, engage the lower end  228  of the latch member  130 , and rotate the latch member  130  counter-clockwise (with respect to FIGS. 2A and 6A, and clockwise with respect to FIG.  9 ). In a related manner, the lower end  232  of the second latch member  220  is adapted for engagement by the armature  234  of the coil  68  of the second magnetic trip circuit. 
     As shown in FIG. 3, the bottom end  236  of the second latch member  220  is adapted for engagement by a shuttle member  238  of the bimetal element  70  of the thermal trip circuit. Under thermal trip conditions, the free end  72  of the bimetal element  70  moves to the right of FIG.  3 . In response, the shuttle member  238 , which engages the bottom end  236  of the second latch member  220 , rotates the latch member  220  counter-clockwise (with respect to FIGS.  2 B and  3 ), in order to trip the second circuit breaker mechanism  26 . 
     As shown in FIG. 9, the trip actuator  206  includes the projections  216  and  222 , which respectively engage the upper end projection  214  of the first latch member  130  of the first circuit breaker mechanism  24  and the corresponding upper end projection  242  (shown in FIG. 2B) of the second latch member  220  of the second circuit breaker mechanism  26  of the circuit breaker  202 . Similarly, the second trip actuator  208  includes projections  244 , 246 , which engage the upper end projections (not shown) of the latch members (not shown) of the two circuit breaker mechanisms (not shown) of the third circuit breaker  204  of FIG.  7 . 
     As shown in FIG. 7, the circuit breaker  200  is adapted for operation as a first pole of the circuit breaker  2 . The trip actuator  206  includes the projections  217 , 250  and  219 , 252 , which are adapted to interface the two carrier mechanisms  110 , 112  of the first pole formed by the circuit breaker  200 . The trip actuator  206  also includes the projections  216 , 222 , which are adapted to interface the two carrier mechanisms (not shown) of the second pole formed by the circuit breaker  202 . It will be appreciated that the second trip actuator  208  operates in an analogous manner with respect to the other two adjacent circuit breakers  202 , 204 . 
     The projections  216 , 222 , 244 , 246  of the trip actuators  206 , 208  cooperate with the four carrier mechanisms  110 , 112  of the circuit breakers  202 , 204 , in order to provide a cascading trip of the four sets of separable contacts  34 , 40 . For example, in response to a thermal trip, magnetic trip or manual trip of the circuit breaker mechanism  24  of the circuit breaker  202 , the carrier mechanism  112  rotates clockwise (with respect to FIG. 5, and counter-clockwise with respect to FIG.  6 A). As shown in FIG. 6A, the cover portion  116  of the carrier mechanism  112  of the circuit breaker  202  has a projection  248 , which engages the projection  216  (shown in phantom line drawing) of the trip actuator  206 . In turn, movement of the trip actuator  206  (toward the upper left of FIG. 7) causes the projection  222  to engage the upper end projection  242  (shown in FIG. 2B) of the second latch member  220  and, thereby, trip the second circuit breaker mechanism  26  of the circuit breaker  202 . 
     The trip actuators  206  and  208  also include respective projections  217 , 219  (as discussed above in connection with FIG. 9) and  221 , 223 , which cooperate with the four carrier mechanisms  110 , 112  of the circuit breakers  200 , 202 , in order to manually cause the cascading trip of the four sets of separable contacts  34 , 40 . 
     The trip actuators  206  and  208  further include respective finger projections  250 , 252  and  254 , 256 , which cooperate with the four carrier mechanisms  110 , 112  of the circuit breakers  200 , 202 , in order to provide the cascading trip of the four sets of separable contacts  34 , 40 . As shown in FIG. 9, in response to a thermal trip, magnetic trip or manual trip of the first circuit breaker mechanism  24  of the circuit breaker  200 , the carrier mechanism  112  rotates clockwise (with respect to FIG. 9, and counter-clockwise with respect to FIG.  6 A). This causes the movement of the trip actuator  206  to the right of FIG. 9 as shown by the arrow  224 . In turn, the movement of the projection  219  moves the upper portion  215  of the latch member  220 , which causes the trip of the circuit breaker mechanism  26  of the circuit breaker  200 . Also, the movement of the projections  216  and  222  respectively moves the upper end projection  214  of the latch member  130  of the first circuit breaker mechanism  24  and the upper end projection  242  of the latch member  220  of the second circuit breaker mechanism  26  of the circuit breaker  202 . Further, the circuit breaker  202  causes the movement of the trip actuator  208  through the projections  254 , 256 , thereby moving the projections  244 , 246  to cause the trip of the circuit breaker mechanisms  24 , 26 , respectively, of circuit breaker  204 . 
     Thus, as discussed above, a manual or magnetic trip of one of the six circuit breaker mechanisms  24 , 26  (or a thermal trip of one of the three circuit breaker mechanisms  26 ) of the circuit breakers  200 , 202 , 204  causes the trip of the other five circuit breaker mechanisms. 
     Referring to FIGS. 10 and 12, it is often desirable to close couple mount various devices to either the line side or the load side of the circuit breaker. FIGS. 10 and 12 illustrate such a device mounted to the line side of the circuit breaker. The device  258  may be a contactor, motor starter, or any other electronic device typically mounted to the line side of a circuit breaker. As shown in FIG. 12, bus bars  260  connect each of the line terminals  16 ,  18 ,  20  of the circuit breaker  2  with one of three sections of the contactor  258 . Cover  262 , which is pivotally mounted at pivot  264  to the circuit breaker&#39;s housing  3 , prevents accidental contact with the exposed portions of the bus bars  260 , the line terminals  16 , 18 , 20  or the device terminals  282 , which are connected to the other end of the bus bar  260  externally to the housing  259  of the contactor  258 . 
     Contactors such as the contactor  258  are commonly utilized in conjunction with circuit breakers to provide a manual means of energizing and de-energizing the load. Whenever a pair of contacts are opened or closed, there is some arc in between the contacts during the time that they are open, but not sufficiently far apart to prevent the arcing. Circuit breakers are designed to interrupt overcurrents, and have a limited number of actuations before they become unusable. Repeatedly subjecting the contacts to such arcing, and the heat created by the arc erodes the surface of the contacts, until the contacts eventually become unusable. Therefore, use of a contactor to manually control the flow of current instead of the circuit breaker saves wear and tear on the contacts of the more complex circuit breaker, by using the contactor, which is designed for repeated current interruption. Additionally, many contactors are designed to open the contacts in response to the opening of the switch at the time period within the alternating current phase likely to cause the least amount of erosion. 
     One example of the many different contactors that may be utilized in conjunction with the above-described circuit breaker is described in U.S. Pat. No. 5,559,426, and incorporated herein by reference. This contactor includes three sets of fixed and corresponding movable contacts, corresponding to a three-phase alternating current system. The movable contacts are spring-biased towards their open position, and may be held in their closed position against the spring bias by a magnetic coil. Both a direct current waveform and a smaller alternating current ripple waveform are applied through the coil. When the stop switch is opened, the coil voltage drops to zero. When the alternating current waveform reaches zero, the current within the coil will exponentially decay towards zero. Therefore, once the current within the coil decays below the minimum level required to hold the movable contacts in their closed position, the contacts are opened. An over travel gap between the opening mechanism and movable contacts ensures that each movable contact is moved away from its corresponding fixed contact at a point in time when current flowing through that movable contact is substantially zero. Therefore, arcing is minimized within the contactor. 
     Ideally, one wishing to service any portion of the circuit breaker, contactor, or any other upstream or downstream electronic equipment, will use the contactor to open the circuit, ensuring that there is no current flow within the circuit. However, if one were to rotate the cover  262  from its closed position of FIG. 10 to its open position of FIG. 12, the circuit breaker  2  would be tripped, as described below. 
     Referring to FIG. 14, a plunger trip rod  266  of the present invention is illustrated. The plunger trip rod  266  includes a plunger  268  at its top end, an upper trip branch  270 , located within the upper portion  272  of the plunger trip rod  266 , and a lower trip branch  274  within the lower portion  276  of the plunger trip rod  266 . The upper and lower trip branches  270 ,  274  preferably protrude substantially perpendicular to the plunger trip rod  266 , and in some preferred embodiments may extend from both sides  278 ,  280  of the plunger trip rod  266 . The plunger trip rod  266  may also include the push to trip button  210 , as described above in conjunction with the trip actuator  206 . 
     Referring back to FIGS. 10,  11 , and  13 , it can be seen that the lower trip branch  274  interacts with the upper end projection  214  of the latch  130 . Therefore, when the cover  262  is rotated from the closed position of FIG. 10 to the open position of FIG. 12, the lower trip branch  274  will push downward on the upper end projection  214 , thereby tripping the circuit breaker. Likewise, the upper trip branch  270  will interact with the upper end projection  242  (FIG.  2 B), also pushing down on the upper end projection  242  to trip the circuit breaker upon the opening of the cover  262 , and consequent depression of the plunger  268 . The plunger  268  protrudes from the housing  3  in close proximity to the cover  262 , so that cover  262  will depress the plunger  268  when the cover  262  is opened even to a small degree. It is therefore unlikely to open the cover  262  a sufficient distance to access the buses without depressing the plunger  268  and tripping the breaker. 
     While a specific embodiment of the invention has 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 appended claims and any and all equivalents thereof.