Patent Publication Number: US-8988174-B1

Title: Tripping mechanisms for two-pole circuit breakers

Description:
BACKGROUND 
     This application relates to tripping mechanisms for two-pole circuit breakers. Example embodiments include ground fault circuit interrupt two-pole residential circuit breakers, arc fault circuit interrupt two-pole residential circuit breakers, and combination arc fault and ground fault circuit interrupt two-pole residential circuit breakers. 
     SUMMARY 
     In a first aspect, a two-pole circuit breaker is provided that includes an electronic pole disposed between a first mechanical pole and a second mechanical pole. The first mechanical pole includes a first armature, and the second mechanical pole includes a second armature. The first and second armatures each are adapted to rotate in a first plane. The electronic pole includes a trip mechanism having a first trip arm disposed adjacent the first armature and a second trip arm disposed adjacent the second armature. The first trip arm and the second trip arm are each adapted to rotate in a second plane substantially orthogonal to the first plane. 
     In a second aspect, an electronic pole is provided for use with a two-pole circuit breaker having a first mechanical pole and a second mechanical pole. The electronic pole includes a solenoid and a trip mechanism coupled to the first mechanical pole and the second mechanical pole. The trip mechanism includes a first trip arm having a first solenoid interface and a second trip arm having a second solenoid interface disposed adjacent the first solenoid interface. The solenoid is adapted to engage the first solenoid interface and the second solenoid interface to common trip the two-pole circuit breaker. 
     In a third aspect, a trip mechanism is provided for a two-pole circuit breaker that includes a first mechanical pole having a first armature adapted to rotate in a first plane, and a second mechanical pole having a second armature adapted to rotate in the first plane. The trip mechanism includes a first trip arm disposed adjacent the first armature and a second trip arm disposed adjacent the second armature. The first trip arm and the second trip arm are each adapted to rotate in a second plane substantially orthogonal to the first plane. 
     Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features of the present invention can be more clearly understood from the following detailed description considered in conjunction with the following drawings, in which the same reference numerals denote the same elements throughout, and in which: 
         FIGS. 1A-1C  are diagrams of an example two-pole circuit breaker in accordance with this invention; 
         FIGS. 2A-2D  are diagrams of example internal components of a mechanical pole in accordance with this invention; 
         FIGS. 3A-3C  are diagrams of an example tripping mechanism in accordance with this invention; 
         FIGS. 4A-4E  are diagrams illustrating an example operation of tripping mechanisms in accordance with this invention; 
         FIGS. 5A-5C  are diagrams illustrating an example operation of a first mechanical pole in accordance with this invention; and 
         FIGS. 6A-6C  are diagrams illustrating an example operation of a second mechanical pole in accordance with this invention. 
     
    
    
     DETAILED DESCRIPTION 
     Two-pole circuit breakers, such as residential two-pole circuit breakers, have two electrical branches or poles through which electrical power is provided to one or more loads. For example, in the United States, residential two-pole circuit breakers typically provide 240 volts instead of 120 volts to devices or appliances such as electric dryers, water heaters, well pumps, and/or electric ranges. Previously known two-pole circuit breakers typically include an electronic pole disposed between first and second mechanical poles. A trip bar typically extends through the electronic pole and communicates with the first and second mechanical poles. 
     If an overcurrent or short circuit is sensed in one pole, the faulted mechanical pole unlatches, and the pole trips. In addition, the electronic pole may include an arc fault or a ground fault detector circuit that continuously monitors current flowing in each mechanical pole. If an arc fault or a ground fault occurs in either mechanical pole, the detector circuit activates a single wound solenoid to trip and unlatch the faulted mechanical pole. As the faulted mechanical pole unlatches, the trip bar rotates, and the rotation causes the other mechanical pole to trip and unlatch. 
     Such a previously known electrical/mechanical tripping mechanism seeks to ensure that when either mechanical pole trips, the other pole also trips, known as a “common trip.” A two-pole circuit breaker that does not common trip could potentially be a safety concern to end users, and must be avoided. Previously known two-pole circuit breakers that include a trip bar, however, have numerous disadvantages. 
     In particular, use of a trip bar may require several production instructions during manufacture, and special fixtures may be needed to ensure that the trip bar is correctly assembled. In addition, key features of the trip bar may have very tight tolerances that need close monitoring to ensure that required drawing specifications are satisfied. 
     Moreover, during assembly of the circuit breaker, numerous components within the circuit breaker typically must be precisely aligned to properly align the trip bar. Improper trip bar alignment could result in binding conditions that prevent the trip bar (and therefore the circuit breaker) from properly operating. As a result, previously known two-pole circuit breaker designs often require substantial monitoring of the trip bar during assembly. Apparatus and methods in accordance with this invention provide a tripping mechanism for a two-pole circuit breaker that common trips, but that does not include a trip bar. 
     Referring to  FIGS. 1A-1C , an example two-pole circuit breaker  10  in accordance with this invention is described. Example circuit breaker  10  includes an electronic pole  12  disposed between a first mechanical pole  14 L and a second mechanical pole  14 R, and a handle tie bar  16  coupled to first and second handles  18 L and  18 R, respectively, on first mechanical pole  14 L and second mechanical pole  14 R, respectively. Handle tie bar  16  may be used to simultaneously operate first and second handles  18 L and  18 R, respectively, to turn circuit breaker  10  ON and OFF. First mechanical pole  14 L includes a first armature  20 L disposed adjacent a first mechanical pole aperture  26 L. Second mechanical pole  14 R includes a second armature  20 R disposed adjacent a second mechanical pole aperture  26 R. 
     As shown in  FIGS. 1B-1C , electronic pole  12  includes a trip mechanism  30  (described in more detail below) that has a first trip arm  32 L having a first trip arm end  34 L, and a second trip arm  32 R having a second trip arm end  34 R. First trip arm  32 L extends from a first aperture  36 L of electronic pole  12 , and second trip arm  32 R extends from a second aperture  36 R of electronic pole  12 . 
     As described in more detail below, first trip arm end  34 L is adapted to extend into first mechanical pole aperture  26 L adjacent first armature  20 L, and second trip arm end  34 R is adapted to extend into second mechanical pole aperture  26 R adjacent second armature  20 R. In addition, electronic pole  12  optionally includes a pigtail  38  which may be used to connect a neutral conductor (not shown) in circuit breaker  10  to a load center or panel board neutral bar (not shown). 
     Referring now to  FIGS. 2A-2D , example components and operation of first mechanical pole  14 L and second mechanical pole  14 R are now described. In particular,  FIG. 2A  illustrates example internal components of first mechanical pole  14 L. First mechanical pole  14 L includes first handle  18 L, first armature  20 L disposed on a first armature pivot  22 L, a first cradle  40 L disposed on a first cradle pivot  42 L, a first moveable bus  44 L that includes a first moveable contact  46 L and is coupled via a first spring  48 L to first cradle  40 L, and a first stationary bus  50 L that includes a first stationary contact  52 L disposed opposite first moveable contact  46 L. A first compression spring  56 L biases first armature  20 L in a clockwise direction about first armature pivot  22 L. First armature  20 L includes a first projection  58 L. 
     First moveable bus  44 L is connected to a first bi-metal strip  54 L by a first flexible conductor  60 L. A first load terminal  62 L is connected to a top end of first bi-metal strip  54 L, and also is coupled to a first short-circuit sensing element  64 L. As described in more detail below, first bi-metal strip  54 L and first short-circuit sensing element  64 L are used to provide overcurrent and instantaneous tripping functions, respectively. A first channel  66 L directs any arc discharge gas resulting from a short circuit away from first mechanical pole  14 L. First cradle  40 L includes a first end  68 L disposed adjacent first projection  58 L of first armature  20 L, and a first cradle feature  70 L adjacent first armature  20 L. 
     First handle  18 L is coupled to an upper end of first moveable bus  44 L, and may be used to selectively turn first mechanical pole  14 L ON and OFF, and thereby selectively CLOSE and OPEN, respectively, first moveable contact  46 L and first stationary contact  52 L. In particular, moving first handle  18 L to the ON position causes first moveable bus  44 L to move in a clockwise direction, which causes first moveable contact  46 L and first stationary contact  52 L to CLOSE. In contrast, moving first handle  18 L to the OFF position causes first moveable bus  44 L to move in a counter-clockwise direction, which causes first moveable contact  46 L and first stationary contact  52 L to OPEN. 
     A latch system of first mechanical pole  14 L activates when first handle  18 L is moved from the OFF position to the ON position. In particular, as first handle  18 L is rotated towards the ON position, first cradle  40 L rotates counter-clockwise. As first cradle  40 L rotates, first end  68 L rotates past first projection  58 L of first armature  20 L. First armature  20 L rotates clockwise towards first cradle  40 L as a result of first compression spring  56 L pushing on the top of first armature  20 L, and first projection  58 L of first armature  20 L passes under first end  68 L of first cradle  40 L. When first handle  18 L is released, first cradle  40 L rotates clockwise until first end  68 L of first cradle  40 L engages first projection  58 L of first armature  20 L, latching first mechanical pole  14 L ON. 
     Although not shown in  FIG. 2A , persons of ordinary skill in the art will understand that second mechanical pole  14 R includes the same components as first mechanical pole  14 L, albeit with “R” reference number designations. That is, second mechanical pole  14 R includes second handle  18 R, second armature  20 R disposed on second armature pivot  22 R, a second cradle  40 R disposed on a second cradle pivot  42 R, a second moveable bus  44 R that includes a second moveable contact  46 R and is coupled via a second spring  48 R to second cradle  40 R, and a second stationary bus  50 R that includes a second stationary contact  52 R disposed opposite second moveable contact  46 R. A second compression spring  56 R biases second armature  20 R in a clockwise direction about second armature pivot  22 R. Second armature  20 R includes a second projection  58 R. 
     Second moveable bus  44 R is connected to a second bi-metal strip  54 R by a second flexible conductor  60 R. A second load terminal  62 R is connected to a top end of second bi-metal strip  54 R, and also is coupled to a second short-circuit sensing element  64 R. As described in more detail below, second bi-metal strip  54 R and second short-circuit sensing element  64 R are used to provide overcurrent and instantaneous tripping functions, respectively. A second channel  66 R directs any arc discharge gas resulting from a short circuit away from second mechanical pole  14 R. Second cradle  40 R includes a second end  68 R disposed adjacent second projection  58 R of second armature  20 R, and a second cradle feature  70 R adjacent second armature  20 R. 
     Second handle  18 R is coupled to an upper end of second moveable bus  44 R, and may be used to selectively turn second mechanical pole  14 R ON and OFF, and thereby selectively CLOSE and OPEN, respectively, second moveable contact  46 R and second stationary contact  52 R. In particular, moving second handle  18 R to the ON position causes second moveable bus  44 R to move in a clockwise direction, which causes second moveable contact  46 R and second stationary contact  52 R to CLOSE. In contrast, moving second handle  18 R to the OFF position causes second moveable bus  44 R to move in a counter-clockwise direction, which causes second moveable contact  46 R and second stationary contact  52 R to OPEN. 
     A latch system of second mechanical pole  14 R activates when second handle  18 R is moved from the OFF position to the ON position. In particular, as second handle  18 R is rotated towards the ON position, second cradle  40 R rotates counter-clockwise. As second cradle  40 R rotates, second end  68 R rotates past second projection  58 R of second armature  20 R. Second armature  20 R rotates clockwise towards second cradle  40 R as a result of second compression spring  56 R pushing on the top of second armature  20 R, and second projection  58 R of second armature  20 R passes under second end  68 R of second cradle  40 R. When second handle  18 R is released, second cradle  40 R rotates clockwise until second end  68 R of second cradle  40 R engages second projection  58 R of second armature  20 R, latching second mechanical pole  14 R ON. 
       FIG. 2B  illustrates an enlarged view of select components of first mechanical pole  14 L in the latched ON configuration. In particular, a first surface  72 L of first end  68 L makes engaging contact with a first top surface  74 L of first projection  58 L, preventing further clockwise rotation of first cradle  40 L. In the latched ON configuration, first moveable bus  44 L is adjacent first stationary bus  50 L, and first movable contact  46 L and first stationary contact  52 L are CLOSED. 
     First mechanical pole  14 L remains latched ON until first handle  18 L is moved to the OFF position, or until an overload condition or a short circuit condition causes the latch mechanism to disengage and trip first mechanical pole  14 L. As described in more detail below, in embodiments in which two-pole circuit breaker  10  also includes ground fault and/or arc fault circuit detection functions, a ground fault and/or an arc fault also cause the latch mechanism to disengage and trip first mechanical pole  14 L. 
     During an overload condition, current flowing through the breaker causes first bi-metal strip  54 L to heat up and deflect, which causes first armature  20 L to rotate in a counter-clockwise direction about first armature pivot  22 L. As first armature  20 L rotates, first top surface  74 L pulls away from first surface  72 L, decreasing the overlap area of the two surfaces, as shown in  FIG. 2C . If the overcurrent condition persists, first bi-metal strip  54 L continues to heat up and deflect, first armature  20 L further rotates about first armature pivot  22 L, and the surface area overlap between first top surface  74 L and first surface  72 L continues to decrease. 
     When the surface area overlap decreases to about zero, first cradle  40 L rotates clockwise about first cradle pivot  42 L, and first extension spring  48 L rotates first moveable bus  44 L counter-clockwise to separate first moveable contact  46 L from first stationary contact  52 L, unlatching first mechanical pole  14 L. In the unlatched OFF configuration, first movable contact  46 L and first stationary contact  52 L are OPEN, as shown in  FIG. 2D . 
     Likewise, during a short-circuit condition, current flowing through the breaker causes a magnetic field of first short-circuit sensing element  64 L to increase, which causes first armature  20 L to rotate in a counter-clockwise direction about first armature pivot  22 L, and the surface area overlap between first top surface  74 L of first armature  20 L and first surface  72 L of first cradle  40 L decreases to about zero. As a result, first cradle  40 L rotates clockwise about first cradle pivot  42 L, and first extension spring  48 L rotates first moveable bus  44 L counter-clockwise to separate first moveable contact  46 L from first stationary contact  52 L, unlatching first mechanical pole  14 L. In the unlatched OFF configuration, first movable contact  46 L and first stationary contact  52 L are OPEN, as shown in  FIG. 2D . 
     Referring now to  FIGS. 3A-3C , an example trip mechanism assembly  30  in accordance with this invention is described. As described above, trip mechanism  30  is disposed in electronic pole  12  of circuit breaker  10 . In particular, as shown in  FIG. 3A , a circuit board  80  is adapted to be mounted in electronic pole  12  (not shown), and includes a recess  82  adapted to receive trip mechanism  30 . A solenoid  84  is disposed on circuit board  80 , and includes a plunger  86  having a tip  88  adjacent recess  82 . Trip mechanism  30  includes first trip arm  32 L and second trip arm  32 R disposed between a top element  102  and a bottom element  104 . 
     In addition, as shown in  FIG. 3B , first trip arm  32 L includes first trip arm end  34 L, a first trip arm journal  110 L, and a first trip arm tab  112 L, and second trip arm  32 R includes second trip arm end  34 R, a second trip arm journal  110 R, and a second trip arm tab  112 R. First trip arm end  34 L includes a first armature interface  114 L and a first cradle interface  116 L, and second trip arm end  34 R includes a second armature interface  114 R and a second cradle interface  116 R. First trip arm tab  112 L includes a first trip arm interface  118 L, a first solenoid interface  120 L and a first trip arm interface surface  122 L, and second trip arm tab  112 R includes a second trip arm interface  118 R, a second solenoid interface  120 R and a second trip arm interface surface  122 R. 
     Bottom element  104  includes a first post  124 L for slidingly receiving first trip arm journal  110 L, and a second post  124 R for slidingly receiving second trip arm journal  110 R. Top element  102  securingly attaches to bottom element  104 , and constrains first trip arm  32 L and second trip arm  32 R. First trip arm  32 L is adapted to rotate about first post  124 L, and second trip arm  32 R is adapted to rotate about second post  124 R. As first trip arm  32 L rotates (e.g., counterclockwise), first trip arm interface  118 L engages second trip arm interface surface  122 R, causing second trip arm  32 R to rotate in an opposite (e.g., clockwise direction), and vice-versa. Likewise, as second trip arm  32 R rotates (e.g., clockwise), second trip arm interface  118 R engages first trip arm interface surface  122 L, causing first trip arm  32 L to rotate in an opposite (e.g., counter-clockwise direction), and vice-versa. 
     Bottom element  104  also may include side posts  126 L,  126 R,  128 L and  128 R for positioning and securing trip mechanism  30  in complementary journals (not shown) in electronic pole  12 . Persons of ordinary skill in the art will understand that alternative techniques may be used to position and secure trip mechanism  30  in electronic pole  12 . As shown in  FIG. 3C , trip mechanism  30  is disposed in recess  82  of circuit board  80 . Tip  88  of solenoid  84  plunger  86  is disposed adjacent first solenoid interface  120 L and second solenoid interface  120 R. 
       FIGS. 4A-4E ,  5 A- 5 C and  6 A- 6 C illustrate the operation of two-pole circuit breaker  10 . In particular,  FIG. 4A  illustrates electronic pole  12  coupled between first mechanical pole  14 L and second mechanical pole  14 R to form two-pole circuit breaker  10 .  FIG. 5A  illustrates a side internal view of first mechanical pole  14 L, and  FIG. 6A  illustrates a side internal view second mechanical pole  14 R. To simplify the drawings, only a few components of electronic pole  12 , first mechanical pole  14 L and second mechanical pole  14 R are shown. 
     In particular,  FIG. 4A  illustrates a top view of portions of electronic pole  12 , first mechanical pole  14 L and second mechanical pole  14 R, with trip mechanism  30  disposed in electronic pole  12 , first trip arm end  34 L disposed in first mechanical pole  14 L between first cradle  40 L and first armature  20 L, and second trip arm end  34 R disposed in second mechanical pole  14 R between second cradle  40 R and second armature  20 R. In the latched ON configuration shown in  FIG. 4A , first trip arm end  34 L does not make engaging contact with first cradle  40 L or first armature  20 L, and second trip arm end  34 R does not make engaging contact with second cradle  40 R or second armature  20 R. 
     As shown in  FIG. 5A , first surface  72 L of first end  68 L makes engaging contact with first top surface  74 L of first projection  58 L, first moveable bus  44 L is adjacent first stationary bus  50 L, and first movable contact  46 L and first stationary contact  52 L are CLOSED. Likewise, as shown in  FIG. 6A , second surface  72 R of second end  68 R makes engaging contact with second top surface  74 R of second projection  58 R, second moveable bus  44 R is adjacent second stationary bus  50 R, and second movable contact  46 R and second stationary contact  52 R are CLOSED. 
     As shown in  FIGS. 4B and 5B , if an overcurrent or short circuit occurs on first mechanical pole  14 L, current flowing through the breaker causes first bi-metal strip  54 L to heat up and deflect, which causes first armature  20 L to rotate in a counter-clockwise direction about first armature pivot  22 L. As first armature  20 L rotates, first cradle feature  70 L engages first cradle interface  116 L, which causes first trip arm  32 L to rotate in a clockwise direction about first trip arm journal  110 L. 
     As first trip arm  32 L rotates in a clockwise direction, first trip arm interface  118 L engages second trip arm interface surface  122 R (not shown), causing second trip arm  32 R to rotate in a counter-clockwise direction about second trip arm journal  110 R. As shown in  FIGS. 4B and 6B , as second trip arm  32 R rotates, second armature interface  114 R engages second armature  20 R, causing second armature  20 R to rotate in a counter-clockwise direction about second armature pivot  22 R. Thus, rotation of first armature  20 L in a first plane, causes first trip arm  32 L and second trip arm  32 R to rotate in a second plane substantially orthogonal to the first plane, which in turn causes second armature  20 R to rotate in the first plane. 
     Referring to  FIGS. 5B and 6B , as first armature  20 L continues to rotate in a counter-clockwise direction about first armature pivot  22 L, second armature  20 R continues to rotate in a counter-clockwise direction about second armature pivot  22 R. First top surface  74 L pulls away from first surface  72 L, and second top surface  74 R pulls away from second surface  72 R. 
     When the surface area overlap for first mechanical pole  14 L and second mechanical pole  14 R decrease to about zero, first cradle  40 L rotates clockwise about first cradle pivot  42 L, and first extension spring  48 L rotates first moveable bus  44 L counter-clockwise to separate first moveable contact  46 L from first stationary contact  52 L, unlatching first mechanical pole  14 L, as shown in  FIGS. 5B-5C . In the unlatched OFF configuration, first movable contact  46 L and first stationary contact  52 L are OPEN, as shown in  FIG. 5C . As also shown in  FIG. 5C , an upper end of first cradle feature  70 L engages first trip arm end  34 L so that first armature interface  114 L remains engaged with first armature  20 L. 
     Likewise, second cradle  40 R rotates clockwise about second cradle pivot  42 R, and second extension spring  48 R rotates second moveable bus  44 R counter-clockwise to separate second moveable contact  46 R from second stationary contact  52 R, unlatching second mechanical pole  14 R, as shown in  FIGS. 6B-6C . In the unlatched OFF configuration, second movable contact  46 R and second stationary contact  52 R are OPEN, as shown in  FIG. 6C . As also shown in  FIG. 6C , an upper end of second cradle feature  70 R engages second trip arm end  34 R so that second armature interface  114 R remains engaged with second armature  20 R. 
     Thus, as shown in  FIGS. 4A-4C , an overcurrent or short circuit fault on first mechanical pole  14 L results in a common trip of first mechanical pole  14 L and second mechanical pole  14 R without using a trip bar. Persons of ordinary skill in the art will understand that an overcurrent or short circuit fault on second mechanical pole  14 R likewise results in a common trip of first mechanical pole  14 L and second mechanical pole  14 R without using a trip bar. 
     In addition to tripping on overcurrent or short circuit faults, two-pole circuit breakers in accordance with this invention also may trip on arc faults and/or ground faults. For example, electronic pole  12  may include an arc fault and/or a ground fault detector circuit (not shown) that continuously monitors current flowing in each mechanical pole. Referring to  FIG. 3C , if an arc fault or a ground fault occurs in first mechanical pole  14 L or second mechanical pole  14 R, the detector circuit activates solenoid  84  to trip and unlatch first mechanical pole  14 L and second mechanical pole  14 R without using a trip bar. 
     In particular, referring now to  FIGS. 4D-4E , if an arc fault or a ground fault occurs in first mechanical pole  14 L or second mechanical pole  14 R, the detector circuit activates solenoid  84 , which causes plunger  86  (not shown) and tip  88  to move towards and push against first solenoid interface  120 L and second solenoid interface  120 R. As tip  88  pushes against first solenoid interface  120 L and second solenoid interface, first trip arm  32 L rotates in a clockwise direction about first trip arm journal  110 L, and second trip arm  32 R rotates in a counter-clockwise direction about second trip arm journal  110 R. 
     As shown in  FIGS. 4D-4E ,  5 B and  6 B, as first trip arm  32 L and second trip arm  32 R rotate, first armature interface  114 L engages first armature  20 L, causing first armature  20 L to rotate in a counter-clockwise direction about first armature pivot  22 L, and second armature interface  114 R engages second armature  20 R, causing second armature  20 R to rotate in a counter-clockwise direction about second armature pivot  22 R. Thus, rotation of first trip arm  32 L and second trip arm  32 R in a second plane causes first armature  20 L and second armature  20 R to rotate in the first plane substantially orthogonal to the second plane. 
     As first armature  20 L continues to rotate in a counter-clockwise direction about first armature pivot  22 L, second armature  20 R continues to rotate in a counter-clockwise direction about second armature pivot  22 R. In addition, first top surface  74 L pulls away from first surface  72 L, and second top surface  74 R pulls away from second surface  72 R. 
     When the surface area overlap for first mechanical pole  14 L and second mechanical pole  14 R decrease to about zero, first cradle  40 L rotates clockwise about first cradle pivot  42 L, and first extension spring  48 L rotates first moveable bus  44 L counter-clockwise to separate first moveable contact  46 L from first stationary contact  52 L, unlatching first mechanical pole  14 L, as shown in  FIGS. 5B-5C . In the unlatched OFF configuration, first movable contact  46 L and first stationary contact  52 L are OPEN, as shown in  FIG. 5C . As also shown in  FIG. 5C , an upper end of first cradle feature  70 L engages first trip arm end  34 L so that first armature interface  114 L remains engaged with first armature  20 L. 
     Likewise, second cradle  40 R rotates clockwise about second cradle pivot  42 R, and second extension spring  48 R rotates second moveable bus  44 R counter-clockwise to separate second moveable contact  46 R from second stationary contact  52 R, unlatching second mechanical pole  14 R, as shown in  FIGS. 6B-6C . In the unlatched OFF configuration, second movable contact  46 R and second stationary contact  52 R are OPEN, as shown in  FIG. 6C . As also shown in  FIG. 6C , an upper end of second cradle feature  70 R engages second trip arm end  34 R so that second armature interface  114 R remains engaged with second armature  20 R. 
     Thus, as shown in  FIGS. 4D-4E , an arc fault and/or a ground fault on first mechanical pole  14 L or second mechanical pole  14 R results in a common trip of first mechanical pole  14 L and second mechanical pole  14 R without using a trip bar. 
     In accordance with this invention, dimensions of second armature interface  114 R may be selected to increase the moment arm and reduce the amount of force required to de-latch second armature  20 R. Likewise, dimensions of first armature interface  114 L may be selected to increase the moment arm and reduce the amount of force required to de-latch first armature  20 L. 
     The foregoing merely illustrates the principles of this invention, and various modifications can be made by persons of ordinary skill in the art without departing from the scope and spirit of this invention.