Abstract:
The invention relates to a switching contact arrangement for a power switch, which is characterized in that a plurality of contact levers are pivoted on a contact support ( 30 ) by means of a bearing pin ( 37 ) and that the contact support ( 30 ) is provided with at least three support elements ( 32   a   , 32   b   , 31 ) for radially supporting the bearing pin. In order to simplify production of the contact support, at least three of the support elements ( 32   a   , 32   b   , 31 ) are configured as a one-piece shaped element that forms the contact support ( 30 ). At least one of the support elements can have a metal element ( 31 ) that is at least partially embedded in a plastic shaped element ( 43 ) of the contact support ( 30 ). Said metal element ( 31 ) can be configured as a sheet metal part.

Description:
[0001]     This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/DE02/01250 which has an International filing date of Mar. 28, 2002, which designated the United States of America and which claims priority on German Patent Application numbers DE 101 17 844.1 filed Apr. 4, 2001 and DE 201 18 493.1 filed Nov. 7, 2001, the entire contents of which are hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention generally relates to the field of electrical/power switches, and is preferably applicable to the design configuration of a rigid member which is used as a contact mount for a contact.  
       BACKGROUND OF THE INVENTION  
       [0003]     In a known electrical switch of this type, in which two or more contact levers which form the contact are held on the contact mount by way of a bearing bolt such that they can pivot, the contact mount has at least three supporting elements in order to support the bearing bolt radially (E 0 222 686 B1). The contact mount in this case includes a metal frame, which is formed from two side walls and from two or more bolts which connect the side walls. The metal frame is hinged via a coupling bolt on an insulating coupling element, which is used for coupling the contact mount to a switch drive. Two of the supporting elements, which are associated with the ends of the bearing bolt, are in this case formed by the side walls of the metal frame.  
         [0004]     In order to prevent undesirable radial bending of the bearing bolt for the contact levers with as little complexity in terms of additional material as possible, two intermediate bearings for this contact mount, which are arranged between adjacent contact levers in the axially central region of the bearing bolt, form additional supporting elements by being hinged on the coupling bolt. In this case, aperture openings are required for the contact mount, for the intermediate bearings to pass through to the coupling bolt. Supporting elements which are integrated in this way in addition to the two outer supporting elements in the contact mount must be positioned for installation of the bearing bolt, owing to their capability to pivot about the coupling bolt.  
       SUMMARY OF THE INVENTION  
       [0005]     Against the background of an electrical switch, an embodiment of the invention is based on an object of simplifying the production and installation of the contact mount.  
         [0006]     According to an embodiment of the invention, an object may be achieved in that at least three of the supporting elements are in the form of part of a molding which forms the contact mount and is produced integrally. For the purposes of an embodiment of the invention, the expression an integrally produced molding should be understood as being a part in which two or more functional elements are connected in the course of a molding process, such as a stamping, injection-compression molding, casting, injection molding, compression molding or sintering process, to form a single component which is assembled such that it cannot be disconnected for installation purposes.  
         [0007]     In the case of a refinement such as this, the three supporting elements are integrated rigidly in a predetermined position in the contact mount, as part of it. In this case, the three supporting elements are actually aligned with the axis of the bearing bolt during the production of the contact mount so that no tilting of the bearing bolt caused by tolerance discrepancies will in practice occur during operation of the switch. A bearing bolt which is supported in this way is also subject to only a small maximum amount of bending when high short-circuit or surge currents occur, and thus has a good capability to withstand high short-circuit and surge currents.  
         [0008]     The novel switching contact arrangement may have a large number of contact levers, which are each subject to an individual tolerance discrepancy from a given nominal size, and intermediate bearings, which are possibly likewise subject to an individual tolerance discrepancy from their nominal size, but which may be part of the contact levers, since the number of contact levers is subdivided into subsets. Each of these is arranged axially bounded between two adjacent supporting elements. This axial bounding of the subsets of contact levers limits any axial movement of the contact levers in one subset, owing to the current forces which act between them, to the axial section of the bearing bolt which is bounded by the respective supporting elements. The maximum amount of movement is not greater than the sum of all the individual tolerance discrepancies of the contact levers and of the intermediate bearings, which may be present, in this subset. This makes it possible to geometrically associate the contact levers with contact force springs such that their spring force is not reduced by bending or tilting. The geometrically accurate association between the contact force springs and the contact levers thus also contributes to increasing the capability of the switching contact arrangement to withstand short-circuit and surge currents.  
         [0009]     If the molding is at least partially in the form of a plastic molding, then there is no need for the coupling bolt to have an electrically insulating configuration. The mechanical strength of a plastic molding such as this can be increased by embedding at least one reinforcement element at least partially in the plastic molding. A thermosetting plastic which, for example, has fiber reinforcement is typically used for the plastic molding and a nonmagnetic steel, for example, is used for the reinforcement element. As an alternative to this, other pure plastics or, for example, plastics reinforced by ceramic or glass fibers can also be used for the plastic molding, and other metals or metal sheets can be used for the reinforcement element.  
         [0010]     One preferred refinement of the novel switching contact arrangement provides for at least one of the supporting elements to have a metal part which is at least partially embedded in the plastic molding.  
         [0011]     A metal part such as this may be part of the reinforcement element, thus at the same time increasing the mechanical strength of that part of the contact mount which forms the supporting element.  
         [0012]     If the metal part is in the form of a metal sheet, for example composed of nonmagnetic sheet steel, a first subregion of which, which has undercuts, is embedded in the plastic molding and a second subregion of which, which is provided with a hole for the bearing bolt, projects out of the plastic molding. This then advantageously allows the cross section of the supporting element to be reduced such that it is no broader than the distance between the contact levers that is required for separation of the contact levers and thus does not lead to any additional broadening of the contact mount.  
         [0013]     A further advantageous refinement of the novel switching contact arrangement provides for supporting elements which contain the metal parts to be at a distance from the coupling element in the axial direction of the bearing bolt if the contact mount is coupled to a switching shaft, which can be rotated using a switch drive, via a metallic coupling element. This makes it possible to avoid accidental energizing and problems relating to the insulation between the contact mount and the switch drive, in a simple manner. In this refinement, the entire available material depth of the contact mount transversely with respect to the bearing bolt can be used for the rigid embedding of a first subregion of a supporting element which is in the form of a metal sheet.  
         [0014]     If a holder for the shielding body is provided on at least one of the supporting elements for a contact mount which is equipped with the shielding body, then this provides additional support for the shielding body against the gas pressure which occurred during switching. In a refinement such as this, side mounting limbs, which rest on the contact mount, are designed to be smaller owing to the reduced load, or may possibly be omitted. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The present invention will become more fully understood from the detailed description of preferred embodiments given hereinbelow and the accompanying drawings, which are given by way of illustration only and thus are not limitative of the present invention, wherein FIGS.  1  to  9  show a number of exemplary embodiments of the novel switching contact arrangement and wherein:  
         [0016]      FIG. 1  shows a schematic section illustration of a low-voltage circuit breaker with a switching contact arrangement which comprises a stationary contact assembly and a moving contact assembly,  
         [0017]      FIG. 2  shows a moving contact assembly with a first embodiment of a contact mount which is at least partially in the form of a plastic molding,  
         [0018]      FIG. 3  shows a reinforcement element, which may be embedded in the plastic molding of the contact mount shown in  FIG. 2 ,  
         [0019]      FIG. 4  shows a second embodiment of a contact mount which is at least partially in the form of a plastic molding, and in which supporting elements in the form of a metal sheet are partially embedded in the plastic molding,  
         [0020]      FIG. 5  shows a section illustration, transversely with respect to the direction of the bearing bolt, through the contact mount shown in  FIG. 4 ,  
         [0021]      FIG. 6  shows a reinforcement element which may be embedded in the plastic molding of the contact mount in  FIG. 4 ,  
         [0022]      FIG. 7  shows a section illustration, transversely with respect to the direction of the bearing bolt, through a contact mount with an embedded reinforcement element as shown in  FIG. 6 ,  
         [0023]      FIG. 8  shows a further section illustration through the contact mount illustrated in  FIG. 4  along the line A-A in  FIG. 5 , and  
         [0024]      FIG. 9  shows the contact lever mount as shown in  FIG. 4  with a shielding body.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     The electrical switch which is shown in  FIG. 1  and is used in low-voltage power supply systems for voltage ranges up to about 1 000 V has a switch pole enclosure  1  in which switching chambers  2  are formed alongside one another, depending on the number of poles required. A switching shaft  4 , which can be rotated by way of a switch drive  3 , is used to operate the switching contact arrangement jointly, each of which includes a stationary contact assembly  5  and a moving contact assembly  6 . For this purpose, two levers  7  which project radially from the switching shaft  4  (see  FIG. 8 ) are coupled to a metallic coupling element which is hinged on the moving contact assembly  6 . The contact assemblies  5 ,  6  are connected in a known manner to externally accessible connecting rails  9 ,  10 . Two exemplary embodiments  6   a  and  6   b  of the moving contact assembly  6  will be explained in the following text with reference to  FIGS. 2 and 3  and, respectively, FIGS.  4  to  9 .  
         [0026]     As can be seen in more detail from  FIG. 2 , the moving contact assembly  6   a  has a contact mount  11  which has a plastic molding  12  in the form of an integrally produced molding, which was formed in the course of a stamping process, with a reinforcement element as shown in  FIG. 3  being embedded in it. The contact mount is mounted in the enclosure  1  (see  FIG. 1 ) such that it can pivot, and can be moved via the switching shaft  4  and by use of the switch drive  3 , of which  FIG. 1  shows only one drive run  15  that is supported on a spring stalk  14  relative to the stationary contact assembly  5  to a connected position and to a disconnected position.  
         [0027]     Two or more contact levers  16 ,  17 , which are arranged parallel to one another, on the contact mount  11  can pivot relative to the contact mount  11  about a bearing bolt  18 . Contact force springs  19  (see  FIG. 1 ) ensure that the contact levers  16 ,  17  are prestressed in the direction of the stationary contact assembly  5 . Flexible conductors  20  in the form of braids or strips are used for connecting the contact levers  16 ,  17  to the lower connecting rail  10  in such a way as to guarantee that the contact levers  16 ,  17  and the contact mount  11  can move without any impediment during the switching movements.  
         [0028]     The number of contact levers  16 ,  17  which are fitted to the contact mount  11  depends on the magnitude of the current which the circuit breaker is intended to carry during operation. As can be seen from  FIG. 2 , of the total of  22  contact levers that are provided,  8  contact levers  16  are designed to be shorter and have only one contact area  21 , which have no leading contact area  22  and no arcing horn  23  in the same way as the other contact levers  17 .  
         [0029]     During operation, all the contact levers are held between side pieces  24   a ,  24   b  of the contact mount  11 , which point transversely with respect to the bearing bolt  18 . These side pieces  24   a ,  24   b , which are provided with holding openings  25   a ,  25   b  for the bearing bolt  18  form a first and a second supporting element for the ends of the bearing bolt, via which the bearing bolt is positioned axially and is supported radially. A part  29   a  or  29   b  of the reinforcement element  13  (see  FIG. 3 ) can extend in each of these side pieces, and has an aperture  27   a  or  27   b , respectively, for the bearing bolt. In the downward direction, the side pieces  24   a ,  24   b  merge into bearing arms  26  for the contact mount  11 .  
         [0030]     The relatively large width of the switching contact arrangement indicates that the section of the bearing bolt which runs between the two side supporting elements  24   a ,  24   b  is subjected to a relatively severe bending load when further forces in addition to the forces of the contact force springs  19  are caused by a heavy current, such as a short-circuit or surge current, when the switching contact arrangement is in the closed state.  
         [0031]     Bending of this section of the bearing bolt is prevented by way of an additional, third supporting element, which supports the bearing bolt axially in the center. This third supporting element is formed by a contact mount rib  28 , which is provided with a holding opening  25   c  (which cannot be seen in the figure) for the bearing bolt  18  and points transversely with respect to the bearing bolt, with a metal part  29   c  (which is completely embedded in the plastic molding  12  and has an aperture  27   c  for the bearing bolt) extending in the rib  28  and being part of the reinforcement element  13  (see  FIG. 3 ).  
         [0032]     Of the second exemplary embodiment  6   b  of the moving contact group,  FIG. 4  shows only a second embodiment  30  of the contact mount. In this contact mount  30 , two supporting elements, which are in the form of metal sheets  31 , are used to radially support that section of the bearing bolt which runs between two supporting elements that are in the form of side pieces  32   a ,  32   b . A first subregion  33  of the two central supporting elements  31  is embedded in the plastic molding  34  of the contact mount  30 , and together with a second subregion  35  of the two central supporting elements  31 , projects out of the plastic molding.  
         [0033]     As can be seen in  FIG. 5 , the metal sheets  31  have undercuts  36  in the first subregion  33  which is embedded in the plastic molding, and these are used to anchor the respective metal sheet in the plastic molding securely even when the bearing bolt is subjected to a high bending load. The second subregion  35 , which is provided with a hole  38  for the bearing bolt  37  to pass through, also has a recess  39 , which is used to hold a shielding body  40  that is not shown in any more detail in  FIG. 9 . As is shown in  FIG. 7 , two reinforcement elements  41 ,  42  may be embedded in the plastic molding of the contact mount, and one of these is illustrated in  FIG. 6 .  
         [0034]     As can be seen from  FIG. 8 , the two metal sheets  31  are at a distance from the metallic coupling element  8  (see  FIG. 1 ) in the axial direction, in order to avoid accidental energizing between the bearing bolt (which is at a low-voltage potential) of the contact levers and the metallic coupling element  8  (which is at ground potential), and thus the switch drive.  
         [0035]     As can be seen from  FIG. 9 , tongues  43  are integrally formed on the shielding body  40 , which protects the pivoting area of the contact mount  30  and further switch parts (which are not shown in any more detail but are arranged underneath the contact areas  21 ,  22  (see  FIG. 1 )) against erosion products that fall out and against condenser switching gases, and these tongues  43  engage in the recesses  39  which are provided on the metal sheets (see also  FIG. 5 ). In consequence, the shielding body  40  is supported against the gas pressure which occurs during switching processes, in such a way that its mounting limbs  44   a ,  44   b , which are held in the side on the contact mount, are less severely loaded.  
         [0036]     Exemplary embodiments being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.