Abstract:
The electricity transmission device comprises prolonged rigid conductors made of copper, and also a connector comprising a network of flexible elements, such as brazed tubes with cooling channels for the conductors, that enables angular displacements between the successive segments and therefore gives a flexibility absorbing small displacements of the device. A lifting manoeuvre system is associated with the segments. The segments may be joined to other elements of the device through connections with jaws enabling slipping.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS OR PRIORITY CLAIM 
     This application is a national phase of International Application No. PCT/EP2007/051236, entitled “DEVICE FOR TRANSPORTING ELECTRICITY AT HEAVY CURRENT AND HIGH FREQUENCY”, which was filed on Feb. 9, 2007, and which claims priority of French Patent Application No. 06 50490, filed Feb. 10, 2006. 
     DESCRIPTION 
     Technical Field and Prior Art 
     The subject of this invention is a device for transmission of electricity at high current and high frequency. 
     Although there are many types of electricity conducting devices, all known devices designed for use at high currents and high frequencies use large rigid conducting elements usually made in the form of elongated copper bars or plates. 
     Difficulties occur in some applications in which the conducting device is required to connect a power supply device to an instrument that can move slightly or can be displaced. This situation arises in vitrification devices in which electrical current is used to supply power to the electromagnetic induction means arranged around a crucible and that is designed to melt material that will be placed in it, and in which the crucible can sometimes be moved. In the vitrification of radioactive waste application, the crucible is behind a biological protection wall that the conducting device must pass through without clearance to prevent ionising radiation leaks, and the dilemma arises of how to place a conducting device with rigid elements with an imposed position and an imposed orientation at the location of the crossing through the wall, but which must be variable to follow the displacements of the instrument to which the conducting device is connected behind the wall, the problem being particularly difficult because this instrument can only be placed by remote manipulation means that are not sufficiently precise to prevent positioning errors. 
     In its most general form, the invention relates to an electricity transmission device comprising at least one electricity conducting element made essentially from an elongated rigid section, the conducting element comprising two segments separated by a connection composed of flexible electricity conducting elements, characterised in that it comprises a joint support device for the two segments; and the flexible elements are metallic tubes brazed onto the segments of the conducting element. 
     The flexible elements conduct electricity between segments at the price of a loss of energy; this lost is modest due to the shortness of the flexible elements. 
     Therefore the flexible elements form a hinge in the middle of the conducting device which deforms without breaking, following the displacements of the instrument. The joint segments support element prevents accidental excessively different displacements of segments while they are being manipulated, which would cause breakage of the flexible elements joining them together. 
     The combination of largely rigid metal tubes to join segments and the joint segments support is justified in the very frequent situation in which segments have to be cooled by a liquid; the tubes are then used not only for the electric connection, but also for the hydraulic connection by joining channels of segments through which this liquid circulates. 
     Prior art (for example GB-A-2 051 461) illustrates rigid electrical conductors joined by metallic braids or very flexible elements but are not leak tight and therefore do not allow cooling liquid to circulate from one segment to the next. In this case, flexible ducts have to be added with much more complicated connectors than simple brazing. 
     Other more particular arrangements of the invention are used to apply it to the technical context for crossing through a biological protection wall into which a portion of the device has to be embedded with no clearance. It may be in the form of the third segment provided with cooling channels, said cooling channels being made on the surface of the third segment and with a wave shape, the third segment comprising ionising radiation screens aligned with straight line portions of cooling channels, an electromagnetic shielding cover comprising an outside adjustment surface that surrounds the third segment, and a filling material that extends between the third segment and the electromagnetic shielding cover. 
     Other arrangements are used to move the instrument associated with tension or compression of the device rather than bending. Thus, it will be possible for the conducting element to comprise at least one third segment (possibly corresponding to the third segment mentioned above) extended with another of the segments, and a connector for connecting segments comprising jaws pressing said segments prolonging each other together. 
     It is also useful to allow for the possibility of disassembling successive segments of the transmission device provided with cooling channels: they are then advantageously provided with separable connectors, and even more advantageously with valves self-closing in the disassembled state. 
    
    
     
       Other arrangements, possibly more secondary, will also become clear after reading the following description with reference to the figures, in which: 
         FIG. 1  shows a preferred application of the invention, 
         FIG. 2  shows a rigid segment of the device, 
         FIG. 3  shows the flexible portion of the device, 
       and  FIGS. 4 and 5  show mechanical, electrical and hydraulic connections of segments to cooled conductors. 
     
    
    
     In one envisaged main application, the electricity transmission device, as shown in  FIG. 1 , comprises a rigid portion  1  passing through a biological protection wall  2  through holes in the wall provided for the passage of various transmissions or various object transfers between the chamber delimited by the biological protection wall  2  and the outside. The rigid portion  1  is connected to an electricity supply  3 . As shown in  FIG. 2 , it comprises one or several conducting elements  4  (two in this case) in the form of elongated plates made of copper, and separated from each other by an intermediate insulating sheet  5 . The conducting elements  4  are provided with cooling channels  6  with projecting relief on their outside surface. The cooling channels  6  are sinuous and more precisely are composed of baffles  7  separating straight portions  8 . The copper screens  9  are connected to conducting elements  4  along the alignment of the straight portions  8 , and they project with the same relief as the cooling channels  6  on the conducting elements  4 . This arrangement makes it possible to have copper screens  9  stop the ionising radiation that would pass through the biological protection wall  2 , following straight portions  8  of the cooling channels  6 , particularly when the cooling liquid that would usually pass through them has been drained. The cooling channels  6  end up on the connecting end pieces  10  that will be described later and extend in a direction transverse to the conducting elements  4 . The rigid portion  1  also comprises a polymer shell  11  formed from two assembled halves surrounding the conducting elements  4  to fill in the remainder of the section of the hole in the biological protection wall  2  in which the rigid portion  1  is engaged; finally, an electromagnetic shielding cover  12  surrounds the assembly. 
     One important element of the invention is located in another portion of the electricity transmission device, which connects the rigid portion  1  already described on the other side of the protection wall  2 , to a vitrification crucible  14  that may be displaced by a small distance. This other portion that is shown in  FIG. 3 , is a flexible portion  13  that comprises two successive segments  15  and  16  attached by a flexible connector  17 . Like the rigid portion  1 , each of the segments  15  and  16  comprises a pair of conducting elements  18  made of elongated copper plates and an intermediate insulating sheet  19  that separates them. The conducting elements  18  are also provided with cooling channels  20  extending longitudinally along them and that finish at the far ends of the segments  15  and  16  on connectors  21  corresponding to the connectors  10  already encountered, and at the ends of segments  15  and  16  facing each other, on junction channels  22  extending transverse to the conducting elements  18 . 
     The junction ducts  22  are connected to each other by flexible metallic tubes  23  (made of stainless steel or copper) that are used as a mechanical, electrical and hydraulic junction between segments  15  and  16 , allowing electricity and water to pass through the cooling channels  20 . The number of flexible tubes  23 , their arrangement and length are determined so as to minimise the inductance of the segment. No other part electrically connects the segments  15  and  16 . The essential property of the flexible tubes  23  is to resist bending produced by the angular displacement of the segments  15  and  16  with respect to each other and therefore to absorb position variations of the vitrification crucible  14 . The electrical insulation between the fluid tubes  23  connected to the corresponding conductors  18  is maintained by intermediate insulating sheets  19  that project from the conducting elements  18  and separate them from each other over part of their length. In any case, a sufficient spacing between the flexible tubes  23  may be chosen to eliminate any risk of creating electrical arcs by making sure that the inductance of the line is not increased excessively. It is also observed that bending of flexible tubes  23  within moderate limits does not break the brazing through which they are assembled to the junction channels  22 . Segments  15  and  16  are surrounded by electromagnetic shielding covers  24  that also extend around the flexible tubes  23  and include portions overlapping each other, thus preventing any leak of the electromagnetic flux to the outside. 
     Precautions are taken to prevent the flexible connector  17  being broken by a clumsy manipulation. Segments  15  and  16  are also connected by a pulley block  26  provided with a swing arm  27  at the ends of which segments  15  and  16  are suspended by articulated connections comprising a tab  40  fixed to the corresponding segment  15  or  16  and a bolted pin  41  (only one of which is shown). When the flexible portion  13  has to be moved, it is raised by a remote manipulation machine not shown gripping the pulley block  26 : the swing arm  27  is balanced as a function of the masses of the subassemblies  15  and  16  of the flexible portion  13  connected to the segments, they remain at the same level and the flexible tubes  23  are practically unloaded. Segments  15  and  16  are also provided with stands  28  to keep them at an identical and invariable height on a common support when the conducting portion  13  is released. When the segments  15  and  16  are put into place, the swing arm  27  is disassembled and removed by unscrewing the bolted pins  41  so that the position and the shape of the flexible segment  13  can be adjusted. 
     We will now describe other elements of the device regarding the connection between the rigid portion  1  and the flexible portion  13 . Refer to  FIGS. 4 and 5 . One of the conducting elements  4  of the rigid portion  1  comprises a protuberance  21  fitted with a tab support  31  on the side of this conducting element  18 , through a side face  30 . Thus, the flexible portion  13  may be fixed longitudinally and transversely in contact with the rigid portion  1 , the position of which is invariable. 
     The electrical junction between the rigid portion  1  and the flexible portion  13  is obtained by a vice  32  comprising a mobile jaw  33  and a fixed jaw  34  bearing on the external faces of the conducting elements  4  and  18 . The mobile jaw  33  is conducting and creates the electrical connection between corresponding conducting elements  4  and  18  and that are not directly connected to each other; it overlaps these conducting elements  4  and  18  and remains separate from them, and can be disassembled; the fixed jaw  34  is fixed to the protuberance  29 . A clamping bolt  35  holds them close to each other when it is tight, by pressing the mobile jaw  33  into contact with the conducting elements  4  and  18 . When it is loose, the mobile jaw is released and the conducting elements  4  and  18  can be separated. The clamping bolt is at the same electrical potential as the fixed jaw  34  and the protuberance  29 , but is electrically separated from the mobile jaw  33  through an insulating dish  37  between the mobile jaw  33  and a nut  36  of the clamping bolt  35 . A sleeve  37  surrounds the stem of the clamping bolt  35  and comprises a support collar on the protuberance  29 . 
     Therefore, electricity is transmitted through the protuberance  29  for a pair of a conducting elements  4  and  18  and through the conducting jaw  33  for the other pair of conducting elements. A movement of the vitrification crucible  14  within the defined limits is felt by conductors  18  of the flexible portion  13  slipping on the lateral face  30  of the protuberance  29  or on the conducting jaw  33 , without the contact being broken and conduction being interrupted, and by bending of the flexible connector  17  as already mentioned, for a horizontal or vertical displacement. 
     The end pieces  10  and  21  of the portions  1  and  13  are attached by curved connectors  38  that can easily be connected onto end pieces  10  and  21  by a remote manipulated tool. The connectors  38  are flexible and an electrical insulation covers their entire outside face. Advantageously, they are placed on the same side of the segments so that they can be put into place and removed more easily. They comprise rings  39  that fit onto end pieces  10  and  21  creating a click fit that releases valves not shown in the end pieces  10  and  21  and in the connectors  38  to open the channel communication. These valves close automatically when the connectors  38  are removed, therefore closing the channels and preventing leaks. Such systems are known in the field of hydraulic connections, so they will not be described further herein.