Patent Publication Number: US-5898351-A

Title: Multipolar circuit breaker

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an improved multipolar circuit breaker used for a molded-case circuit breaker or an earth-leakage circuit breaker. 
     2. Description of Prior Art 
     In the case of a multipolar circuit breaker having a plurality of poles to be used to break a plurality of circuits, the pole of each circuit is independently provided with a mechanical section such as a cradle or a tripping section and thus, a structure must be used in which, when the tripping section of the pole of any circuit operates, tripping sections of poles of other circuits operate so that the circuits can be broken. 
     Therefore, conventionally, as shown in FIGS. 8 and 9, bottoms of trigger plates 1 of tripping sections of poles are connected to each other by a trigger joint 2 so that, when the trigger plate 1 of any pole is moved and a cradle 3 is tripped due to an overcurrent or the like, tripping is performed also in other poles. 
     However, the engagement amount between the trigger plate 1 and the cradle 3 slightly fluctuates every pole, or even if tripping is performed in one pole, it may not be performed in other poles due to a slight backlash between the trigger plate 1 and the trigger joint 2. Therefore, a severe factory-adjustment must be performed to prevent the above problem. 
     Problems to be Solved by the Invention 
     The present invention is made to solve the above conventional problem and its object is to provide a multipolar circuit breaker which makes it possible to securely operate tripping sections of poles of other circuits when the tripping section of the pole of any circuit operates. 
     SUMMARY OF THE INVENTION 
     Means for Solving the Problem 
     The present invention made to solve the above problem uses a multipolar circuit breaker comprising trigger plates of tripping sections of a plurality of poles connected to each other by a trigger joint, and includes a mechanism for further moving a trigger plate in the tripping direction when the cradle of any pole is tripped from the trigger plate. 
     According to a first embodiment of the invention a protrusion is formed on a cradle and according to a second embodiment of the invention, a protrusion is formed at the trigger plate. 
     These protrusions are provided so as to further move a trigger plate in the tripping direction when it is tripped from a cradle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of the first embodiment of a cradle of the present invention; 
     FIG. 2 is an illustration of a multipolar circuit breaker using the cradle of the first embodiment after removing its front cover in order to show the ON state of the breaker; 
     FIG. 3 is a partial perspective view of FIG. 2; 
     FIG. 4 is a perspective view of FIG. 3 when removing a partition between first and second circuits; 
     FIG. 5 is an illustration of a multipolar circuit breaker of the present invention after removing its front cover in order to show the TRIP-state of the breaker; 
     FIG. 6 is a side view of a trigger plate of the second embodiment; 
     FIG. 7 is a perspective view showing an engagement state between the trigger plate shown in FIG. 6 and the cradle; 
     FIG. 8 is a sectional view of a conventional multipolar circuit breaker under the ON-state; and 
     FIG. 9 is a side view showing the portion of a trigger plate and trigger joint of a multipolar circuit breaker. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention are described below in detail by referring to the accompanying drawings. 
     FIGS. 1 to 7 show an embodiment of the present invention wherein a multipolar circuit breaker provided within a case 4 includes housing tripping sections of two poles of two circuits at the both sides of a partition 6 (see FIG. 3). Also in this case, the trigger plates 1 of the poles are connected to each other by the trigger joint 2, and the partition 6 is provided with an opening 6a so that the trigger joint 2 can be rotated. 
     The multipolar circuit breaker of the present invention, whose internal structure behind by removing a front cover is shown in FIG. 2, is used for the two-circuit two-pole type, in which first and second circuits are constituted in first and second spaces separated by the partition 6 in the case 4. 
     In FIG. 2, only the front first circuit can be seen and the second circuit is present behind the first circuit. Both circuits are respectively provided with a trigger plate 1, cradle 3, fixed contact 11, movable contact 12, and bimetal 13 which bends itself due to overcurrent. 
     The trigger joint 2 is fitted to the bottom of the adjacent two trigger plates 1. A pair of fulcrums 1a for rotatably supporting the trigger plate 1 are set slightly above the trigger joint 2. 
     A reverse-U-type bent portion whose front end 1b engages with the top end of the bimetal 13 in the ON-state (normal state) is formed at the top end of the trigger plate 1. 
     The cradle 3 is supported by a pivot 14 and pulled downward by a spring 15. In the ON-state, however, the front end 3a of the cradle 3 engages with the bottom margin 1e of a hole 1d formed on the trigger plate 1 and stops. 
     In the case of the trigger plate 1, the reverse-U-type bent portion 1c is pulled rightward and rotates clockwise about the fulcrum 1a when the top end of the bimetal 13 is bent rightward due to overcurrent. In this case, the front end 3a of the cradle 3 engaging with the bottom margin 1e of the hole 1d of the trigger plate 1 is tripped from the above engaging state. As a result, the cradle 3 is rotated downward (clockwise) by the action of the spring 15 to separate the moving contact 12 shown in FIG. 2 from the fixed contact 11 by a known toggle mechanism (not illustrated). Thereby, as shown in FIG. 5, breaking of the first circuit, that is, switching of the first circuit to the OFF-state is completed (see FIG. 5). 
     Though not shown in the front view of FIG. 2, a second circuit having the same structure as the illustrated first circuit is provided at the other side of the partition 6 in the case 4. This state is shown by partial perspective views of FIGS. 3 and 4. The bottoms of the trigger plates 1 of the first and second circuits are connected to each other by the trigger joint 2. Therefore, when the trigger plate 1 of the pole of either circuit rotates in the tripping direction, the trigger plate 1 of the other circuit is forcibly rotated. However, because the operation maybe uncertainly performed, conventionally a triggering problem may occur as described hereinabove under the heading &#34;Background of the Invention&#34;. 
     The first embodiment of the present invention is provided with a protrusion 5 at a position slightly above the front end 3a of the cradle 3 of each pole toward the trigger plate 1 as shown in FIG. 1. The protrusion 5, as clearly shown by the perspective view in FIG. 4, is once folded toward the one side and then bounded toward the trigger plate 1 again, and its front end 5a is formed so as to face the side frame portion of the hole 1d of the trigger plate 1 by avoiding the hole 1d. 
     The front end 5a of the protrusion 5, in the ON-state shown in FIG. 2, is kept so as not to contact or press the trigger plate 1 in the ON-state shown in FIG. 2 even when the front end 3a of the cradle 3 contacts the trigger plate 1. However, when the trigger plate 1 of any pole operates and the front end 3a of the cradle 3 disengages and comes to the TRIP-state shown in FIG. 5, the front end 5a of the protrusion 5 provided for the cradle 3 pushes (or strikes) the trigger plate 1 of its own and further deeply moves the trigger plate 1 in the tripping direction. 
     Therefore, the trigger plate 1 of the pole now tripped is greatly moved from the position where the front end 3a of the cradle 3 disengages to thereby also move the trigger plates 1 of the poles of other circuits connected by the trigger joint 2 simultaneously. As a result, even though the engagement amount between the trigger plate 1 and the cradle 3 slightly fluctuates for each pole or there is a slight backlash between the trigger plate 1 and the trigger joint 2, tripping is securely performed in other poles. 
     FIGS. 6 and 7 show the second embodiment of the present invention. In the case of the second embodiment, a protrusion 7 is formed on the trigger plate 1 slightly downward from the engagement position between the trigger plate 1 and the cradle 3 of each pole as shown in FIG. 6. The protrusion 7 does not contact the cradle 3 in the ON-state. However, when the trigger plate 1 of any pole operates, the front end 3a of the cradle 3 disengages and comes to the TRIP-state, the front end 3a of the cradle 3 pushes (or strikes) the protrusion 7 and further deeply moves the trigger plate 1 of the pole in the tripping direction. 
     As a result, the pushed (or struck) trigger plate 1 is more greatly moved than a conventional distance and therefore the trigger plates 1 of other poles connected by the trigger joint 2 are simultaneously also greatly moved. Thus, secure tripping is performed in the poles of other circuits. 
     Advantages of the Invention 
     As described above, the present invention has the advantage that when the tripping section of any pole operates, tripping sections of other poles can securely be operated even if there is a slight backlash between a trigger plate and a trigger joint.