Abstract:
The invention relates to a low voltage circuit breaker which comprises a contact system for a principal current and an arc extinction chamber. An arc transmitting element is disposed between the contact system for the principal current and the arc extinction chamber. Said arc transmitting element comprises at least one arc guiding element which makes it possible to direct said arc in a certain manner to the arc extinction chamber.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is the US National Stage of International Application No. PCT/DE2003/002883, filed Aug. 28, 2003 and claims the benefit thereof. The International Application claims the benefits of German application No. 10250950.6 filed Oct. 25, 2002, both applications are incorporated by reference herein in their entirety.  
       FIELD OF THE INVENTION  
       [0002]     The invention relates to a low voltage circuit breaker which comprises a contact system for a principal current and an arc extinction chamber. An arc transmitting element is disposed between the contact system for the principal current and the arc extinction chamber.  
       BACKGROUND OF THE INVENTION  
       [0003]     It is known that the size, particularly the width of contact systems for the principal current of low voltage circuit breakers depends on a nominal current for which the low voltage circuit breakers have been designed. The higher this nominal current, the wider is the embodiment of the corresponding contact systems for a principal current. A disadvantage here is the fact that on the basis of strongly defined proximity effects for wider contact systems for a principal current, a complicated arc extinction behavior is exhibited because the arc predominantly occurs at the edge of the wide contact systems for a principal current and accordingly predominantly dwells in the edge zone of the arc extinction chamber allocated to the contact systems for a principal current. As a result, the cooling effect of the arc extinction chamber is only used in a limited manner. This leads to the fact that the arc is extinguished relatively late and the danger arises that ionized circuits may escape from the arc extinction chamber. This burning off or down of the arcs in the edge zone occurs both during interruptions in the nominal current zone and during short-circuit interruptions of this low voltage circuit breaker.  
         [0004]     In order to make possible an explicit transmission of arcs into arc extinction chambers, it is known from DE 35 39 673 A1 that an arc-conductive piece of a ferromagnetic material must be allocated to a contact system for a principal current by means of which the arcs are to be explicitly transmitted to the arc extinction chamber. The disadvantage of this arrangement is the fact that additional components must be provided which are directly connected to the contact systems for a principal current. This complicates the structure of the low voltage power switch and low manufacturing and/or assembly tolerances already lead to a failure when the arcs are conducted away.  
         [0005]     In addition, it is known in the case of a low voltage circuit breaker according to said type that provision must be made for an arc guiding element on the arc transmitting element which makes it possible to direct said arc in a defined manner to the arc extinction chamber (U.S. Pat. No. 6,417,474 B1).  
         [0006]     Publication U.S. Pat. No. 4,885,441 describes an arc transmitting element with an arc guiding element in which the arc guiding element has two running edges running at different angles to a center line of the arc transmitting element in which case the running edges extend away from an edge zone in the direction of a middle zone of the arc transmitting element.  
       SUMMARY OF THE INVENTION  
       [0007]     It is the object of the invention to ensure the transmission of the arc to the middle zone of the arc extinction chamber.  
         [0008]     According to the invention, this object of the invention is achieved by the claims. Because said arc transmitting element disposed between the contact system for a principal current and the arc extinction chamber comprises at least one arc guiding element which, in particular, has several running edges running at different angles to a center line of the arc transmitting element extending in the direction of a top side of the arc extinction chamber which extend away from an edge zone in the direction of a middle zone of the arc transmitting element and as a result of the fact that the arc guiding element is formed crown-shaped and has several prongs formed ray-shaped to the center line, it is advantageously achieved, independent of the point of origin of the arc, that the arc is directed away from the contact systems for a principal current to be protected against burning down, and that a shorter arc extinction period is reached. This results in decreasing the stress on both the contact systems for a principal current, on the one hand, and the arc extinction chamber, on the other hand, because these basically can now, by means of a defined start-up by the arc, convert their arc extinction capacity with a high degree of effectiveness. It has been proven that by providing simple arc guiding elements to the arc transmitting element, it is possible to direct the arcs in a defined manner. Changes to the contact system for the principal current itself need not be made so that the modifications according to the invention are only limited to the arc transmitting element alone. As a result, the solution according to the invention is very simple and can therefore also be implemented cost-effectively in mass-produced low voltage circuit breakers.  
         [0009]     In a preferred embodiment of the invention provision is made so that at least one arc guiding element extends at an angle to an imagined vertical line of the arc transmitting element away from an edge zone in the direction of a middle zone. —This advantageously results in the fact that the arc is directed via at least one arc guiding element approximately into the middle of the arc extinction chamber so that the desired arc extinction effect can be very securely achieved.  
         [0010]     In a further preferred embodiment of the invention provision is made so that the arc guiding element has at least one running edge basically running parallel to the arc transmitting element. —As a result of this an optimum arc position can be controlled within the arc extinction chamber in a defined manner. —The running edge can be formed by a sharp-edged transition of a step.  
         [0011]     In a preferred embodiment of the invention provision is made so that the running edges basically run parallel to the arc transmitting element. —As a result of this an optimum arc position can be controlled within the arc extinction chamber in a defined manner. —The running edges can be formed by a sharp-edged transition of a step in each case.  
         [0012]     In addition, in a preferred embodiment of the invention provision is made so that the arc guiding element particularly has several running edges running at different angles to the imagined vertical line. —By means of such a ray-shaped system of the running edges on the arc transmitting element, the arc is directed safely into the middle zone of the arc extinction chamber independent of the point of origin of the arc.  
         [0013]     In further preferred embodiments of the invention there is provision for the arc guiding element to be non-positively connected to the arc transmitting element. As a result the arc guiding element can be embodied in a simple fashion. This only requires the manufacturing of an arc guiding element with a simple design —for example, as a stamped part —and the fixing of this arc guiding element to the arc transmitting element —for example, by means of welding. In the case of a correspondingly selected system of ray-shaped prongs of the stamped part, the running edges can be determined for the arc in a simple way. This particularly allows the different sizes of the arc extinction chambers can be adapted easily. The ray-shaped prongs preferably have two running edges for the arcs running at right angles to one another which run from the edge zone of the arc transmitting element into the middle of the arc extinction chamber. As a result, depending on the point of origin and the intensity, it is possible to direct said adapted arc to the arc extinction chamber.  
         [0014]     The arc guiding element connected non-positively to the arc transmitting element in addition offers the advantage that a bigger cooling body is available in the zone of the arc transmitting element which favorably influences the extinction behavior of the arc extinction chamber.  
         [0015]     At least one section of a wire, particularly a steel wire can also serve as an arc guiding element.  
         [0016]     According to a further preferred embodiment of the invention provision can be made for at least one arc guiding element being embodied as a profile part stamped from the plane of the arc transmitting element. This simplifies manufacturing of an arc transmitting element that features arc guiding elements.  
         [0017]     At least one end plate of a stack of extinction sheets can be used advantageously as an arc transmitting element.  
         [0018]     Further preferred embodiments of the invention can be found in the other features mentioned in the dependent claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     Other advantageous further developments of the invention are explained below on the basis of the accompanying drawings. They are as follows:  
         [0020]      FIG. 1  partial sectional view through a low voltage circuit breaker;  
         [0021]      FIG. 2  view from above of an arc transmitting element;  
         [0022]      FIG. 3  sectional view through the arc transmitting element;  
         [0023]      FIG. 4  enlarged detailed view of the arc transmitting element and  
         [0024]      FIG. 5  schematic perspective view of an arc transmitting element. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]      FIG. 1  shows part of a sectional view of an arc extinction chamber  10  of a low voltage circuit breaker  12 . The low voltage circuit breaker  12  is embodied for a relatively high nominal current, for example, 1000 A.  
         [0026]     A contact system for a principal current  14  of the low voltage circuit breaker  12  comprises a fixed principal contact  16  with a contact facing  18  as well as a movable principal contact  20  with a contact facing  22 . If required, these principal contacts  16  and  20  are provided repeatedly in a parallel system. The higher the nominal current, the wider is —according to the view into the paper plane —the embodiment of the contact system for a principal current.  
         [0027]     The principal contacts  16  and  20  are used for the arc-free transmission of the permanent current of the low voltage circuit breaker  12  in the closed state of the principal contacts  16  and  20 .  
         [0028]     The contact system for a principal current  14  also comprises a fixed blow-out contact  24  with a contact facing  26  and a movable blow-out contact  28  with a contact facing  30 . Arc horns  32  or  34  are allocated to the blow-out contacts  24  and  28 .  
         [0029]     An insulating coupling  36  serves for connection to a driving arrangement and reset device (not shown) in order to open and close the contact system for a principal current  14 .  
         [0030]     The arc extinction chamber  10  comprises a housing  38  which encloses an inner space  40  serving an arc extinction. In the inner space  40 , a stack of extinction sheets  41  consisting of extinction sheets  42 ,  43  is arranged in a known way. An arc transmitting element  44  limits the inner space  40  of its fixed contact side. In principle, the arc transmitting element  44  is embodied plate-shaped and carries on its side facing the inner space  40 , an arc guiding element  46  whose structure will be explained in greater detail below on the basis of the following drawings. The arc gases (switching gases) formed in the course of the extinction process escape from the arc extinction chamber  10  through an outlet  50 , provided on the top side, subdivided into passages  48 ; said gases escaping in the direction of the arrows  52 . In addition, a further switching gas damper can be arranged at the top side of the arc extinction chamber  10 .  
         [0031]     The arc guiding element  46  is arranged in the vicinity of the arc transfer points from the arc horn  32  to the arc transmitting element  44 .  
         [0032]      FIG. 2  shows a view from above of an arc transmitting element  44  which clearly shows the arrangement of the arc guiding element  46  on the arc transmitting element  44 . The arc guiding element  46  is arranged non-positively as an additional part on the surface of the arc transmitting element  44  and spot welded to it or joined using a similar method. According to a further embodiment, the arc guiding element  46  can be stamped from the plane of the arc transmitting element  44 .  
         [0033]     The arc guiding element  46  comprises running edges  54  which form the side limit of ray-shaped prongs  56 . In this case, the running edges  54  run at different angles in each case to an imagined vertical line  58  through the arc transmitting element  44 . In this case, the running edges  54  are embodied in such a way that they run from a bottom edge zone in the direction of the top middle zone of the arc transmitting element  44 .  
         [0034]     The sectional view in  FIG. 3 , as well as the enlarged detailed view in  FIG. 4 , show that the running edges  46  are formed by steps  60  running basically vertically to the plane of the arc transmitting element  44  so that there is a sharp-edged transition  62  on the surface of the arc guiding elements  46 .  
         [0035]      FIG. 5  in a perspective view again shows the plastic protrusion of the arc guiding element  46  on the arc transmitting element  44 . This results in an embodiment of the running edges  54  as sharp-edged transitions  62  of the steps  60 .  
         [0036]     The number of arc guiding elements  46  as well as the number of running edges  54  can be adapted to the design of the low voltage circuit breaker  12 , particularly to the arc extinction chamber  10 .  
         [0037]     The ray-shaped running edges  54  running from the edge zones of the arc extinction chamber  10  into the middle zone of the arc extinction chamber  10  lead to the arcs originating in the edge zone at the contact system for a principal current  14  being safely directed into the middle zone of the arc extinction chamber  10  where these are extinguished particularly effectively. Because of the system of an arc guiding element  46  in the transfer zone of the arc horn  32  on the arc transmitting element  44 , the arcs can be directed particularly well into the middle zone of the arc extinction chamber  10 .  
         [0038]     Each one of the two end plates  43  of the stack of extinction sheets  41  can be used as an arc transmitting element and as a result be provided with an arc guiding element.  
         [0039]     According to further embodiments which are not shown, instead of the shown arc guiding element  46  which either has a crown-shaped or neck-shaped embodiment, provision can also be made for the running edges  54  being formed from welded-on individual elements, for example, steel wire or the like. However, the system of a relatively large additional part which embodies a plurality of running edges  54 , at the same time, leads to an embodiment of an additional mass which has a cooling effect on the arcs at a very early point in time for the switching-off process of the low voltage circuit breaker  12  so that a further improvement of the extinction behavior is achieved.