Patent Publication Number: US-8993908-B2

Title: Moving contact-carrying carriage and electrical cut-off device equipped with such carriage

Description:
This application claims priority from French patent application serial no. 11/57714 filed Sep. 1, 2011. 
     FIELD OF THE INVENTION 
     The present invention relates to a moving contact-carrying carriage for an electrical cut-off device, said carriage comprising at least one seat arranged to receive a moving contact associated with a return means, and said carriage being intended to be coupled with an actuator mechanism belonging to said device. 
     The invention also relates to an electrical cut-off device provided with a control module associated with at least one cut-off module corresponding to a phase of an electrical network, this cut-off module including at least one moving contact associated with at least one pair of fixed contacts, said moving contact being carried by a carriage coupled with an actuator mechanism controlled by said control module so as to be moved between at least one switched-off position in which the moving contact is distant from the fixed contacts and the electrical circuit is open, and a switched-on position in which the moving contact is resting on the fixed contacts and the electrical circuit is closed. 
     BACKGROUND OF THE INVENTION 
     To move the moving contacts from the open or switched-off position to the closed or switched-on position in electrical cut-off devices such as switches, fuse switches, commutators, reversing switches, circuit breakers or similar appliances, the moving contacts are arranged on or carried by a carriage. This carriage is generally made of a single molded or injection-molded part out of synthetic or composite material and is used to operate simultaneously the moving contacts of the different cut-off modules that equip a same cut-off device in function of the number of phases of the electrical network. The whole of the constraints suffered by the carriage, such as heating, continuous mechanical stress, occasional high-intensity mechanical stress, etc., lead inevitably to deformations or even breakages of the carriage. Switching several phases with a same moving carriage also poses insulation problems between the phases. These various constraints limit the technical performances of such a carriage. 
     SUMMARY OF THE INVENTION 
     The present invention aims to remedy these disadvantages by offering a new design for a moving contact-carrying carriage that can be fitted on any kind of electrical cut-off device in which the moving contacts are closed by pressing them on the fixed contacts, this carriage being arranged to bear without deformation both continuous mechanical stress under high temperature conditions, for example of the order of 100° C., and exceptional mechanical stress, in particular in case of contact areas welding, in order to increase the electrodynamic and mechanical endurance of the electrical cut-off device equipped with such carriage. 
     To that purpose, the invention relates to a carriage of the kind indicated in the preamble, characterized in that it comprises at least one insulating support comprising said seat and at least one supporting structure surrounding said insulating support so as to form around it a load-absorbing belt. 
     The supporting structure comprises advantageously at least one connecting part intended for coupling said carriage with the actuator mechanism belonging to said device, this connecting part being preferably positioned in a front section of said insulating support and passing transversally through said seat in order to rest on the moving contact on the side opposite to its return means when said moving contact is mounted in said carriage. 
     In a preferred embodiment, the supporting structure comprises furthermore a metallic profile extending over the lateral sides and on the rear of said insulating support and the connecting part comprises at least one metallic shaft passing through said insulating support and the side ends of said metallic profile. 
     The insulating support can comprise at least two superposed parts, among which a body in which said moving contact is seated, and a base in which said return means is seated at least partly, said seat extending from said body to said base. 
     In the preferred embodiment, the carriage comprises several seats arranged in parallel to accommodate several moving contacts insulated from each other, these seats can have different depths so as to offset said moving contacts in space. 
     If the carriage is symmetrical with respect to a centerline, then the seats are offset two by two symmetrically with respect to said centerline so as to form stages. 
     Also to that purpose, the invention relates to a cut-off device of the kind indicated in the preamble, characterized in that said carriage comprises at least one insulating support comprising said seat and at least one supporting structure surrounding said insulating support so as to form around it a load-absorbing belt, as defined above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention and its advantages will be better revealed in the following description of an embodiment given as a non limiting example, in reference to the drawings in appendix, in which: 
         FIG. 1  is a perspective view of an example of an electrical cut-off device according to the invention comprising a control module associated with three cut-off modules, in which the last cut-off module is open, 
         FIG. 2  is a cross-sectional view of a cut-off module of the device of  FIG. 1  in switched-on position, 
         FIG. 3  is a perspective view of a moving contact-carrying carriage entering in the design of the device of  FIG. 1 , 
         FIGS. 4A and 4B  are cross-sectional views of the carriage of  FIG. 3 , respectively along the AA and BB section axes, and 
         FIG. 5  is an embodiment variant of the carriage of  FIG. 3  corresponding to a higher current rating. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , the electrical cut-off device  1  object of the invention is usually made of a control module  2  associated with one or several cut-off modules  3  corresponding each to a phase of an electrical network. In the illustrated example, the device  1  is a three-phase device and comprises three cut-off modules  3 . Each cut-off module  3  comprises in a known manner an insulating housing  30  inside of which at least two fixed contacts  4  forming a pair are seated, extending outside of said housing by means of connection terminals  40 , and at least one moving contact  5  carried by a carriage  8  coupled with an actuator mechanism  6  controlled by the control module  2  in order to be moved between at least one switched-off position in which it is distant from the fixed contacts and the electrical circuit is open, and a switched-on position in which it is resting on the fixed contacts and the electrical circuit is closed. The control module  2  may be actuated manually by means of a handle  20  and/or automatically by means of a motorization (not represented). In the represented example, the cut-off device  1  comprises splitting chambers  7  located above the fixed contacts  4  and the moving contact  5  to capture, stretch, cool down and extinguish the electric arc generated by the current at every status change of said device. 
     This cut-off device  1  must be able to establish and cut off currents I called normal or fault currents having a value from 0 to 10 In, In being the value of the rated current that can flow continuously through the device. This device must also be able to establish and if necessary cut off short-circuit currents whose value that can reach 100 to 300 times the rated current In, without breakage or deformation of the carriage  8 . 
     The solution of the invention is described in reference to an electrical device  1  whose cut-off modules have a specific internal architecture, which is the subject of another patent application filed simultaneously, but it can of course apply to any internal architecture according to the state of the art. In the example represented in  FIGS. 1 and 2 , the fixed contacts  4  and the moving contact  5  are arranged to form a current loop having an omega shape that is symmetrical with respect to a centerline A merged with the displacement axis Fd of the moving contact  5 , in which the Laplace forces, also called compensation efforts Fc, generated by the current circulating in the current loop, are acting. The conductive parts that form the fixed contacts  4  are rigidly attached to the housing  30 , bent substantially with an S-shape, arranged in opposition and separated by a free central space. The conductive part that forms the moving contact  5  has a width larger than the free space between the two fixed contacts  4  in order, in the switched-on position, to be pressed against the fixed contacts  4 . Each of these conductive parts has a contact area C located in a plane inclined with respect to the centerline A. 
     The solution of the invention is also described in reference to an electrical device whose moving contact is in fact made of a set  5 ,  5 ′ of several parallel moving contacts  5 A-C,  5 A-F offset in space allowing to stagger in time the approach of the moving contacts on the fixed contacts  4 , which is also the subject of another patent application filed simultaneously, but it can of course apply to the devices according to the state of the art comprising one or several moving contacts for each pair of fixed contacts. In the example represented in  FIGS. 1 and 2 , the number of moving contacts per set depends on the rating of the rated current In.  FIGS. 3 and 5  illustrate two embodiment variants of a set of moving contacts, of which a first set  5  includes five moving contacts  5 A-C and corresponds to a rating of 250 A with a peak value of 50 to 75 kA, and a second set  5 ′ includes twelve moving contacts  5 A-F and corresponds to a rating of 1600 A with a peak value of 120 to 150 kA. The sets  5 ,  5 ′ are symmetrical with respect to the centerline A of the cut-off device  1  and comprise one or two central moving contact(s)  5 A, which are different from the other lateral moving contacts  5 B-F. In the set of  FIG. 3 , the central moving contact  5 A is centered on a centerline B and in the set of  FIG. 4 , the two central moving contacts  5 A are symmetrical with respect to the centerline B. Each central moving contact  5 A is larger and/or positioned ahead of the other ones in order to be the first to approach the fixed contacts  4  to establish the current, and the last to leave the fixed contacts  4  to cut off the current. It is subjected to the electric arc and therefore acts as a spark arrestor. 
     The lateral moving contacts  5 B-C and  5 B-F are made each of a conductive part having the shape of a metallic blade that is symmetrical with respect to the centerline A and provided laterally with two contact areas C. They may have identical dimensions or not. They are at least identical two by two symmetrically with respect to the centerline A. 
     The moving contacts  5 A-C,  5 A-F of a same set  5 ,  5 ′ are carried by a carriage  8  object of the present invention. In the illustrated example, the carriage  8  comprises several separated and parallel seats  80 , arranged for receiving the moving contacts  5 A-C,  5 A-F and insulating them from each other. Each moving contact is associated in its seat  80  with a return means  65 , for example in the form of a compression spring, arranged to exert a determined pressing force on the moving contact when it is pressed against the fixed contacts  4  in the switched-on position. The seats  80  have different depths so that the lateral moving contacts  5 B-C,  5 B-F are offset two by two with respect to the protruding central moving contact  5 A and form stages E 1 , E 2 , etc. The stroke from one stage to another may be equal or not. 
     The carriage  8  comprises an insulating support  81  in which the seats  80  are provided, as well as a supporting structure  9  surrounding the insulating support  81  to form around it a load-absorbing belt. In the represented example, the insulating support  81  is made of two superposed parts that define a body  82  in which the moving contacts  5 A-C,  5 A-F are seated, insulated from each other by the walls of the seats  80 , with an axial freedom of movement, and a base  83  on the bottom of which the return means  65  are resting. The seats  80  extend between the base  83  and the body  82  and come out of said body laterally and symmetrically with respect to the centerline A to let the contact areas C stand out. The central seat  80  extends up to the front of the insulating support  81  taking into account the boss  50  that prolongs the central moving contact  5 A in order to serve as a spark arrestor. The body  82  and the base  83  are held assembled by said supporting structure  9 . Of course, any other embodiment of said insulating support  81  that would allow achieving the same functionality is conceivable. 
     In the represented example, the supporting structure  9  comprises a preferably metallic flat profile  90  extending over the lateral sides and on the rear of the insulating support  81  like a belt. It furthermore comprises a connecting part  91  in the form of a preferably metallic shaft passing through the insulating support  81  at the front and linked mechanically with the side ends of the profile  90  to close the belt. This connecting part  91  passes transversally through at least one of the seats  80  and preferably the central seat to rest against at least and preferably the central moving contact  5 A, on the side opposite to its return means  65 . The connecting part  91  forms a joint B 2  that allows coupling the carriage  8  with the actuator mechanism  6  as explained below and thus transmits directly the driving efforts of said mechanism, in particular when switching off to open the electrical circuit, to the central mobile contact  5 A that is the last leaving the fixed contact  4 . Of course, any other embodiment of said supporting structure  9  that that would allow achieving the same functionality is conceivable. 
     In the represented example, the actuator mechanism  6  of the set  5 ,  5 ′ of moving contacts comprises a drive shaft  60  linked in rotation with the handle  20  by means of a (non visible) angle transmission and/or controlled by a second (non represented) element fitted in the square bore  61 . A system converting the rotary movement of the drive shaft  60  into a translation movement allows moving the carriage  8  along centerline A. This movement conversion system comprises a couple of jointed rods  62 ,  63 , but any other equivalent means is conceivable. The first rod  62  is fixed to the drive shaft  60  and coupled in rotation with the second rod  63  by means of a first joint B 1 . The second rod  63  is coupled in rotation with the carriage  8  by a second joint B 2  defined by the connecting part  91 . The carriage  8  is guided in translation with respect to housing  30  by means of rails, ribs or any other equivalent means in which the protruding ends of the connecting part  91  that form the joint B 2  or any other complementary shape are circulating. 
     This description shows clearly that the invention allows reaching the goals defined, in particular the design of the moving contact-carrying carriage allows dissociating the moving contacts insulation function from the mechanical resistance function of the carriage, and assigning them to two different but complementary parts, adapted to the assigned function as well in the choice of the materials as in their shape. The achieved result is an increase of the technical characteristics of such a carriage and of its lifetime, contributing favorably to prolong the endurance of the electrical cut-off device. 
     The present invention is not restricted to the examples of embodiment described, but extends to any modification and variant which is obvious to a person skilled in the art while remaining within the scope of the protection defined in the attached claims. The carriage of the invention has been described in reference to a multi-moving contact version, but it can also be provided for a single-moving contact version. In any case, it is necessary to provide one carriage per cut-off module or per phase.