Abstract:
A multipole electrical switchgear apparatus comprises a drive mechanism equipped with a pole shaft and a plurality of breaking modules. Each module comprises a vacuum cartridge moved by a movable rod articulated on a transmission lever. The pole shaft is linked to the transmission levers by means of a connecting rod. This common connecting rod gives the kinematic transmission system a great strength. Furthermore, it enables switchgear apparatuses having variable distances between breaking modules to be produced inexpensively, based on a standard pole shaft. Finally, it enables differentiation of the switchgear apparatuses to be delayed.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The invention relates to a multipole electrical switchgear apparatus, and in particular to a multipole switchgear apparatus comprising vacuum cartridges.  
           [0002]    The document EP 0,346,603 describes a three-pole electrical switchgear apparatus comprising three identical polar breaking modules arranged side by side on a frame. Each module comprises a vacuum cartridge equipped with an operating rod movable in translation. A spring-loaded drive mechanism of known type comprising a pole shaft drives the operating rods of the three vacuum cartridges. Each operating rod is connected to the pole shaft by means of an independent connecting rod system proper to the corresponding breaking module. This connecting rod system is composed of a transmission lever arranged between two connecting rods, one of the connecting rods connecting the lever to a crank of the pole shaft and the other connecting rod connecting the lever to the operating rod of the vacuum cartridge. In practice, the vacuum cartridges of the different poles are liable to be subjected to different forces when either opening or closing takes place. When opening takes place, the contacts of a cartridge may be slightly welded, or on the contrary the electromagnetic forces induced by the currents on the contacts may tend to separate the contacts of one of the cartridges more violently. When closing takes place, in particular if it takes place on a short-circuit for one of the poles, one of the contacts may be subjected to very strong repulsion forces. On account of these different stresses on the rods of the vacuum cartridges of the different poles, the pole shaft is subjected to high torsion stresses, directly transmitted by the independent connecting rod systems of the different poles. There is then a risk of large dynamic torsional strain of the pole shaft, resulting in non-simultaneous closing or opening of the different cartridges. To counteract this risk, the pole shaft then has to be over-dimensioned so as to give it an additional torsional strength. Moreover, the switchgear apparatus does not enable the distance between the vacuum cartridges of the different poles to be easily varied. It is true that construction in identical and independent breaking modules would theoretically allow any arbitrary arrangement. However, a different pole shaft corresponds to each distance between poles, since the cranks of the pole shaft have to be spaced the same distance from one another as the cartridges. The pole shaft happens to be a particularly expensive part, all the more so as its torsional strength is critical. Furthermore, the necessity of providing different pole shafts for each distance between axes makes it impossible to design the mechanism as a functional unit pre-assembled in the plant independently from the breaking modules. The architecture hardly favors delayed differentiation of the different models of a switchgear apparatus range.  
         OBJECT OF THE INVENTION  
         [0003]    One object of the invention is to achieve a multipole electrical switchgear apparatus with independent polar breaking modules enabling simultaneous operation of the different modules. Another objective is to increase the modularity of a multipole switchgear apparatus with independent polar breaking modules, enabling the distance between poles to be changed at low cost. Another objective is to obtain an architecture enabling standardized functional sub-assemblies to be stocked and assembled at the last moment to meet the customer&#39;s requirements.  
           [0004]    According to the invention, these objectives are achieved by means of a multipole electrical switchgear apparatus comprising:  
           [0005]    a support;  
           [0006]    a drive mechanism equipped with a pole shaft rotating around a first geometric axis fixed with respect to the support;  
           [0007]    a plurality of breaking modules, each module comprising:  
           [0008]    a pair of separable contacts comprising at least one movable contact;  
           [0009]    a movable rod securedly affixed to the movable contact;  
           [0010]    a transmission lever pivoting around a second geometric axis parallel to the first geometric axis, said second geometric axis being common to all the breaking modules and fixed with respect to the support;  
           [0011]    means for connecting the transmission lever to said rod;  
           [0012]    comprising in addition a single connecting rod connecting the pole shaft to the transmission levers of the different breaking modules, the connecting rod being articulated on the one hand on at least two coaxial cranks of the pole shaft, defining a third geometric axis of pivoting parallel to the first geometric axis, and on the other hand on pivots ensuring pivoting of each transmission lever with respect to the connecting rod around a fourth geometric axis of pivoting parallel to the first geometric axis and common to all the breaking modules.  
           [0013]    According to one embodiment, the movable rod is, in each module, connected to the connecting rod by means of a link pivoting around a fifth geometric axis parallel to the first geometric axis. A simple and advantageous geometric arrangement is thus obtained, ensuring a geometric transmission to a pole shaft situated at the height of the vacuum cartridges, while enabling the connecting rod to work in traction when closing of the contacts takes place. Preferably, the movable rod is connected to the connecting rod, in each module, by means of a link pivoting around a fifth geometric axis. The lever effect in this configuration enables the amplitude of the movement transmitted to be reduced and the forces to be geared down, which is particularly favorable when the contacts only have a small opening and closing travel, as is the case in particular for vacuum cartridges.  
           [0014]    Preferably, the connecting rod is arranged so as to be solicited in traction when closing takes place. Closing is the sequence of movement where the forces transmitted by the connecting rod are the greatest. By making the connecting rod work in traction in this sequence, the strains on the connecting rod are limited. When opening takes place, the connecting rod is solicited in compression but the forces are relatively lower, so that the risks of deformation of the connecting rod out of its plane by buckling are avoided.  
           [0015]    Preferably, the connecting rod comprises a metal plate shaped in such a way that its quadratic moment with respect to an axis perpendicular to a plane containing the third and fourth axes is high. The strength of the connecting rod in flexion in a plane containing the third and fourth axes enables any risk of delay on opening or closing of one of the pairs of contacts to be avoided.  
           [0016]    According to a preferred embodiment, the connecting rod comprises a metal plate comprising two V-shaped arms, each V-shaped arm comprising a convergent end supporting a bearing for articulation with one of the cranks of the pole shaft, and a divergent end, the divergent ends of the two V-shaped arms being connected to one another by a base supporting bearings for articulation with the levers of the breaking modules.  
           [0017]    According to one embodiment, the means for connecting the transmission lever to said movable rod comprise an insulating arm. This arrangement ensures insulation between the contacts and the mechanism which is accessible to operators.  
           [0018]    According to one embodiment, the means for connecting the transmission lever to said movable rod comprise:  
           [0019]    a contact pressure spring having two ends;  
           [0020]    a first support means of a first end of the spring, securedly affixed to the lever;  
           [0021]    a second support means of a second end of the spring, securedly affixed to the movable rod;  
           [0022]    a mechanical connection between the first support means and the lever, performing full transmission of the movement of the lever in the closing direction and not performing transmission of the movement in the opening direction.  
           [0023]    Preferably, each breaking module comprises a frame equipped with support bearings enabling pivoting of the transmission lever around the second axis of pivoting. The breaking modules can then be pre-assembled and tested in the plant before being assembled with the mechanism and connecting rod. This contributes to improving delayed differentiation.  
           [0024]    Preferably, the connecting rod makes an angle close to a right angle with the transmission levers, and the movable rods work in translation in a plane appreciably parallel to the connecting rod. In other words, the geometric plane defined by the second and fourth geometric axes on the one hand and the geometric plane defined by the third and fourth geometric axes on the other hand make an angle of close to 90° between them, whereas the movable rod is parallel to the plane containing the third and fourth axes.  
           [0025]    The invention is particularly well suited to a configuration wherein each breaking module comprises a vacuum cartridge forming an enclosure housing the separable contacts. However, it could be adapted to other breaking principles, provided that the opening and closing travel of the contacts is small. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    Other advantages and features will become more clearly apparent from the following description of a particular embodiment of the invention, given for non-restrictive example purposes only and represented in the accompanying drawings in which:  
         [0027]    [0027]FIG. 1 represents an exploded view of a switchgear apparatus according to an embodiment of the invention, showing in particular a drive mechanism and breaking modules;  
         [0028]    [0028]FIG. 2 represents a cross-sectional view of the switchgear apparatus of FIG. 1, in the open position;  
         [0029]    [0029]FIG. 3 represents a perspective view of a kinematic transmission system connecting the mechanism to the breaking modules;  
         [0030]    [0030]FIG. 4 represents a side view of the kinematic system, in the closed position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0031]    With reference to FIGS. 1 and 2, a three-pole switchgear apparatus  10  comprises a drive mechanism  12  and three identical breaking modules  14 ,  16 ,  18 , arranged side by side on the same side of a partition  20  separating the modules from the drive mechanism  12 . The partition  20  is formed by a metal plate having three windows  22 ,  24 ,  26  and is supported by a second metal plate  28  forming a bracket and acting as support base. The partition  20  is at earth potential and performs electrical protection of people.  
         [0032]    The drive mechanism  12  can be of any known type comprising a pole shaft. It can for example be a mechanism of the type described in the document EP-A-0,222,645, equipped with a loading and closing sub-assembly comprising a closing spring, and with an opening sub-assembly comprising an opening spring. The essential thing with respect to the present invention is that the mechanism comprises an output shaft, which can also be called pole shaft. In the embodiment, the mechanism  12  is fixed to a support frame  30  and equipped with a pole shaft  32  supported by bearings  34  fixed to the frame  30 . The frame is itself fixed to the partition  20 .  
         [0033]    As illustrated in FIG. 3, the pole shaft  32  comprises two double cranks  36 ,  38  which pass through the wall of the frame via apertures and enable articulation to be achieved between the pole shaft  32  and a transmission rod  40 . The transmission rod  40  is formed by a flat part forming two double V-shaped arms  42 ,  44 , spaced apart from one another and joined at their divergent ends by a base  46 . Each V-shaped arm  42 ,  44  supports, at its convergent end, a pair of flanges  50 ,  52  provided with coaxial bores, forming bearings. The cranks  36 ,  38  also comprise coaxial bores forming bearings, so that a pivoting link of the hinge type is obtained between the double cranks  36 ,  38  of the pole shaft  32  and the transmission rod  40  by insertion of spindles  54  in the corresponding bores of the double cranks  36 ,  38  and of the double flanges  50 ,  52 . The base  46  supports three pairs of flanges  60 ,  62 ,  64  provided with coaxial bores, forming bearings. By insertion of spindles  66 , these flanges enable a hinge type link to be achieved with three double levers  70 ,  72 ,  74  belonging to the three polar modules  14 ,  16 ,  18  of the apparatus and passing through the windows  22 ,  24 ,  26  of the partition  20 .  
         [0034]    As the three breaking modules are identical, only the module  18  will be described. As illustrated in FIG. 2, the module  18  comprises a vacuum cartridge  80  supported by a frame  82 . The frame  82  is fixed to the wall  20  and to the support base  28 , so that the frame  30 , the metal plates  20 ,  28  and the frames  82  of the three poles together form a support assembly  83  for the other parts of the apparatus. Two connecting strips  84 ,  86 , fixed to the frame  82 , are designed to electrically connect the cartridge  80  to a busbar (not represented). The generic expression ‘vacuum cartridge’ designates in this case a sub-assembly of known type comprising a cylindrical body  88  forming an enclosure wherein a relative vacuum prevails and which houses a pair of separable contacts  90 ,  92  connected to the connecting strips  84 ,  86 . The body  88  is itself divided into a central insulating section  94  made of insulating material, a first metallic end section constituting a first closing flange  96 , and a second metallic end section constituting a second closing flange  98 . The contact  92  is stationary and is connected to the second flange  98 . The other contact  90  forms an axial end of a rod  100  movable in translation along its axis and passing through the body  88  of the cartridge via an orifice of the flange  96 . A sealing bellows  102  brazed onto the rod  100  and onto the internal wall of the first flange  96  allows an axial movement of the rod  100  and of the movable contact  90  in translation with respect to the stationary contact  92 , while preserving the vacuum prevailing in the enclosure. Electrical connection of the rod  100  to the busbar is achieved by means of a flexible electrical connection  104 , one of the ends of this connection also constituting the connecting strip  84 .  
         [0035]    Outside the enclosure, the rod  100  is connected to the double lever  74  by means of an insulating arm  110 . The insulating arm comprises a body made of plastic material  112  overmolding on the one hand the head of a first threaded rod  114 , and on the other hand the head of a second threaded rod  116  situated in the axial extension of the first rod  114 . The first threaded rod  114  is screwed into a tapped blind hole situated at the end of the rod  100  of the cartridge  80 . A tubular adjusting nut  118  is screwed onto the second threaded rod  116 . The nut  118  supports at one end a support seat  120  for one end of a contact pressure spring  122 . The other end of the spring  122  bears on a second support seat  124 , which rests on a bar  126 . The bar comprises a bore  128  forming a guide sheath through which the tubular nut  118  passes. The bar  126  rotates freely in the lateral spindles  130  supported by the arms of the lever  74 . The guide sheath  128  allows both translation of the nut  118  parallel to its axis and free rotation thereof. The nut  118  comprises a shoulder resting on the bar part  126  opposite the second support seat  124 . The two arms of the double lever  74  pivot around a spindle  132  supported by the frame  82 . The three breaking modules  14 ,  16 ,  18  of the apparatus  10  being arranged side by side, the pivoting spindles  132  of the levers  70 ,  72 ,  74  are aligned and parallel to the pole shaft  32 . The levers  70 ,  72 ,  74  are parallel.  
         [0036]    The kinematic system connecting the pole shaft  32  to the rods  100  of the three breaking modules  14 ,  16 ,  18  thus comprises a single connecting rod  40  between the pole shaft  32  and the three double levers  70 ,  72 ,  74  of the breaking modules, and is extended in each module by an insulator  112 , one of whose ends slides in a sheath  128  rotating with respect to the double lever  70 ,  72 ,  74 , and the other of whose ends is secured to the rod  100  of the cartridge  80 . This kinematic system enables five geometric axes of parallel rotation to be defined: a first geometric axis  140  of pivoting of the pole shaft, a second geometric axis  142  of pivoting of the levers  70 ,  72 ,  74 , a third geometric axis  144  of pivoting of the connecting rod with respect to the cranks of the pole shaft, a fourth geometric axis  146  of pivoting of the connecting rod with respect to the levers, and a fifth geometric axis  148  of pivoting of the bars  126  with respect to the levers  70 ,  72 ,  74 . The first axis  140  and the second axis  142  are both fixed with respect to the support  83 , the other axes being mobile during the opening and closing sequences.  
         [0037]    Strictly speaking, the movement imparted on the rod  100  of the cartridge  80  by this mechanism without any play between the moving parts would not be perfectly straight with respect to the frame  82 . However, the angle between the lever  70 ,  72 ,  74  and the rod  100  is always very close to a right angle, and the travel of the rod  100  of the cartridge between its open position and its closed position does not exceed a few millimeters, which corresponds to an angle of rotation of the lever not exceeding a few degrees, so that in the absence of play, the scope of radial movement of the rod  100  would be about one hundredth of its axial travel. In the embodiment described, this radial movement is absorbed by the clearances existing between the various elements of the kinematic system, in particular at the level of the spindles  130 ,  132 . However, if a larger travel was desired, it would be possible to guide the bar  126  in an oblong of the lever  90 ,  92 ,  94 .  
         [0038]    The kinematic system operates in the following manner. When the contacts are separated and the mechanism is open, the kinematic system is initially in the position represented in FIG. 2. When closing takes place, the closing spring of the mechanism  12  drives the pole shaft  32  counterclockwise over a travel of more than 50°. The connecting rod  40  transmits this movement uniformly to the three double levers  70 ,  72 ,  74 . In each of the breaking modules, the double lever pivots clockwise around the spindle  132 , driving the bar  126  which compresses the spring  122  by means of the support seat  124 . The closing force is then transmitted by the spring  122  to the movable contact  90  via the seat  120 , the nut  118  and the insulating arm  110 . The kinematic system is then in the closed position of FIG. 4, the contacts being closed.  
         [0039]    When opening takes place, the opening spring of the mechanism  12  drives the pole shaft clockwise over a travel of more than 50°. The connecting rod  40  transmits this movement uniformly to the three double levers  70 ,  72 ,  74 . In each of the breaking modules, the double lever pivots counterclockwise around the spindle  132  in FIG. 4, directly driving the bar  126 , the nut  118 , the insulating arm  110  and the rod  100  of the movable contact, until the open position of FIG. 2 is reached.  
         [0040]    The single connecting rod  40  has a high quadratic moment with respect to an axis perpendicular to the geometric plane containing the axes of pivoting of the connecting rod with respect to the pole shaft and the double levers. Although the structure of the connecting rod has been lightened to reduce its weight, the base  46  keeps the required strength. In other words, the forces applied to the connecting rod in its plane are not liable to induce a notable flexion of the connecting rod. Consequently, the connecting rod  40  gives the kinematic system a great strength, so that even if the forces to be applied to the different cartridges are different, their movement will nevertheless be simultaneous. By construction, the pole shaft  32  itself has a very great torsional strength, so that the two hinges joining the connecting rod  40  to the pole shaft  32  can be spaced apart which contributes to increasing the strength of the kinematic system even further.  
         [0041]    The connecting rod is manufactured by being cut out from a sheet metal plate. The levers are also made of metal plate. The electrical insulation is achieved in each breaking module by means of the insulating arms. It should be noted that the insulating part  112  of the arm is shaped as a skirt so as to achieve optimum insulation.  
         [0042]    To modify the distance between the axes of the polar modules, the connecting rod and, if necessary, the wall  20 , which are very inexpensive parts, simply have to be changed. Each specific connecting rod has a base of a different length and especially flanges  60 ,  62 ,  64  of variable number and locations. The distance between the flanges  50 ,  52  performing the hinge link with the cranks of the pole shaft on the other hand remains constant. The pole shaft  32  thus remains identical whatever the distance between the axes of the polar modules, which means that the mechanism  12  can be pre-assembled in the plant and forms a functional unit for the whole of the range. In like manner, the breaking modules  14 ,  16 ,  18  are identical whatever the distance between axes chosen. This enables assembly of the apparatus to be deferred until the customer has made his choice.  
         [0043]    Various modifications are naturally possible. The number of modules is not limited to three: the invention applies equally to two-pole, four-pole, or even six-pole or eight-pole apparatuses. The levers  70 ,  72 ,  74  can be single. The drive mechanism can be of any type: with distinct closing and opening springs to enable a closing, loading, opening, closing, opening sequence; or with a single spring enabling closing and opening.