EP0126668B1 - Rotating anode x-ray tube - Google Patents

Rotating anode x-ray tube Download PDF

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Publication number
EP0126668B1
EP0126668B1 EP84400848A EP84400848A EP0126668B1 EP 0126668 B1 EP0126668 B1 EP 0126668B1 EP 84400848 A EP84400848 A EP 84400848A EP 84400848 A EP84400848 A EP 84400848A EP 0126668 B1 EP0126668 B1 EP 0126668B1
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EP
European Patent Office
Prior art keywords
anode
cathode
hollow
hollow anode
tube according
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP84400848A
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German (de)
French (fr)
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EP0126668A1 (en
Inventor
Jacques Le Guen
André Plessis
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Thales SA
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Thomson CSF SA
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Publication of EP0126668A1 publication Critical patent/EP0126668A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H01J35/08—Anodes; Anti cathodes
    • H01J35/10—Rotary anodes; Arrangements for rotating anodes; Cooling rotary anodes
    • H01J35/101—Arrangements for rotating anodes, e.g. supporting means, means for greasing, means for sealing the axle or means for shielding or protecting the driving
    • H01J35/1017—Bearings for rotating anodes
    • H01J35/103—Magnetic bearings

Definitions

  • the invention relates to an X-ray tube with a rotating anode, in which the rotation of the anode is effected by magnetic bearings.
  • High power X-ray tubes generally use a rotating anode, the rotation of which is still very commonly ensured by mechanical bearings. Given the high rotational speed, which can reach 20,000 revolutions per minute, these mechanical bearings exhibit rapid wear, and are frequently the cause of the decommissioning of X-ray tubes.
  • An important improvement consists in mounting the rotating anode with magnetic bearings. These generally include electromagnets mounted two by two in opposition, which create magnetic fields under the influence of which a rotor, integral with the rotating anode which it ensures rotation, is kept in equilibrium; the rotating anode and the mechanical parts which accompany it in rotation, thus no longer have mechanical contact with the rest of the X-ray tube.
  • thermo-emissive cathodes mechanically linked to the rotating anode; these electrons being captured by fixed anodes.
  • One of the main difficulties is then to supply, to these rotated cathodes, the energy necessary to raise their temperature to a level sufficient to meet the laws of thermoelectronic emission.
  • This patent application describes the arrangement of an X-ray tube with a rotating anode, provided with magnetic bearings and means for flowing, without contact, the anode current.
  • a rotating anode secured to a rotor is mounted on magnetic bearings.
  • the rear of the rotor has two cathodes rotating around an axis, on which an anode is arranged.
  • the cathodes comprise windings cooperating during the rotation of the rotary anode, with a plurality of excitation coils; these excitation coils being distributed over the periphery of the tube and inducing in the rotating windings, the heating voltage of the cathodes.
  • Another French patent application published under No. 2,494,497, also describes an X-ray tube, comprising a rotating anode with magnetic bearings, and means for discharging the anode current without contacts.
  • An auxiliary cathode is placed in the central position of the anode, and a heating filament, in a fixed position, is placed in front of the auxiliary cathode.
  • An auxiliary anode in the form of a tube or ring surrounds the heating filament and collects the electrons emitted by the auxiliary cathode.
  • One of the drawbacks of this solution is that the dimensions of the heating filament are limited by the diameter of the auxiliary ring anode, and therefore it is difficult to obtain the desired heating power.
  • heating intended to flow an anode current is obtained by a combination of much simpler means, which do not have the above-mentioned drawbacks.
  • the present invention relates to an X-ray tube with a rotating anode mounted on magnetic bearings, making it possible to flow the anode current without contact; this being obtained in the X-ray tube according to the invention in a simpler and less expensive way than according to the prior art, thanks in particular to the use of a thermo-emissive cathode and a new arrangement making it possible to heat it by thermal rays.
  • an X-ray tube comprising a rotating anode mounted on magnetic bearings and at least one device intended to drain the anode current from the tube, is characterized in that this device comprises in a fixed position a hollow anode, inside of which a cathode is coupled in rotation to the rotating anode, the hollow anode being associated with heating means external to the hollow anode, the hollow anode being connected to the positive pole of the high voltage, the cathode being electrically connected to the rotating anode so as to ensure the passage of the anode current.
  • the X-ray tube 1 shown in FIG. 1, comprises a vacuum-tight envelope 2-3, constituted in the nonlimiting example described by an insulating central part 2 and, by end parts 3 formed by thin metal shirts; a main cathode 5 carried by the insulating central part 2, is intended to supply an electron beam (not shown) whose impact on a rotating anode 6 causes X-radiation.
  • the rotating anode 6 is carried by a metal shaft 7, integral with a rotor 8; this rotor 8 forms with. a stator 9 located outside the casing 2-3, a motor ensuring the rotation of the rotary anode 6 around a longitudinal axis 10.
  • the shaft 7 is also secured at its ends 4, to rotating parts 11, 12, conical in the nonlimiting example described, and which constitute the suspended parts of magnetic bearings 11-13, 12-14; active parts 13, 14 of these magnetic bearings being located outside the envelope 2-3.
  • guard bearings 25 situated opposite the ends 4 of the shaft 7, with which these bearings 25 are in contact only in the event of failure of the magnetic suspension .
  • the tube 1 also includes a device 40, represented in a frame in dotted lines, located inside the envelope 2-3 and intended, in operation, to drain the anode current from the tube 1.
  • a device 40 represented in a frame in dotted lines, located inside the envelope 2-3 and intended, in operation, to drain the anode current from the tube 1.
  • This device 40 comprises a metal axis 15 extending the shaft 7 along the longitudinal axis 10, on the side of the rotor 8, and carrying a cathode 16.
  • the cathode 16 of spherical shape, in the nonlimiting example described, is centered on the longitudinal axis 10; it is electrically connected by the metal axis 15 and the shaft 7 to the rotating anode 6, and is in operation brought to the same potential as the latter.
  • a hollow anode 17, also of spherical shape in the non-limiting example described, is held in a fixed position and centered around the cathode 16, by a metal support 18 secured to an insulating support 19.
  • the hollow anode 17 comprises a hole 20 intended for the passage of the metal axis 15, thus allowing the movement of the cathode 16, which is coupled in rotation to the rotating anode 6; the rotation of the cathode 16 taking place inside the hollow anode 17, and, like that of the rotating anode 6, around the longitudinal axis 10 according to arrow 29.
  • a heating filament 21 supported in a conventional manner by means not shown and connected to two sealed bushings 22, 23, which is provided with the insulating support 19; the latter also vacuum-tight, has a third bushing 24, electrically connected to the metal support 18 of the hollow anode 17.
  • the high voltage necessary for the operation of the tube 1 is supplied in a known manner by a high voltage generator 31.
  • a positive + HT output of this high voltage is connected to the end portions 3, as well as to the third crossing 24, to be applied to the hollow anode 17;
  • a negative output - HT of the generator 31 is connected in a conventional manner by a fourth bushing 35 to the main cathode 5, the latter also comprising in known manner and not shown, heating connections.
  • the heating filament 21 heats the hollow anode 17, which constitutes a practically closed enclosure in which the cathode 16 is heated in its turn as in an oven, by the thermal radiation of the hollow anode 17.
  • the device 40 may include, as in the nonlimiting example described, a partially shown thermal reflector 32, enveloping the heating filament 21.
  • the cathode 16 electrically connected to the rotating anode 6 then generates electrons which are captured by the hollow anode 17, which is connected to the positive + HT pole of the high voltage; the intensity of the electronic current thus generated is the same as that of the electron beam emitted by the main cathode 5, towards the rotating anode 6.
  • the anodic current of the tube 1 is thus passed with a small difference in voltage between the polarity positive + HT of the high voltage, and the value + HT 'established at the rotating anode 6.
  • the thermal energy supplied by the heating filament 21 is transferred via the hollow anode 17 to the cathode 16 to constitute the energy necessary for the extraction of the electrons.
  • This energy transfer can be made more efficient by appropriate adaptations of the cathode and hollow anode 16, 17, and by the use of a second voltage source, as explained with reference to Figure 2; for better clarity of this FIG. 2, the representation of the X-ray tube according to the invention is limited in order to better show the device 40.
  • the cathode 16 can be hollow as in the example shown in Figure 2, where it has the shape of a sphere; this form may be different as explained in the following description.
  • the cathode 16 has a wall 26, having a small thickness e, and preferably consisting of a refractory material such as tantalum or thoriated tungsten; this wall 26 can also be covered on its outer surface 33, to increase the emissivity in electrons, of lanthanum boride for example (not shown).
  • the hollow anode 17 is formed by two half-spheres 27, 28 assembled made of graphite, pyrolitic graphite for example, or also of a refractory material such as tungsten or molybdenum.
  • the X-ray tube according to the invention comprises a power source constituted by a low-voltage DC generator 45.
  • a positive output V + of this low voltage generator 45 is connected to the hollow anode 17 and also to the positive pole of the high voltage + HT; a negative output -V being it connected to one of the ends of the heating filament 21, to the bushing 23 for example.
  • the DC voltage delivered by this low voltage generator 45 determines, between the heating filament 21 and the hollow anode 17, a potential difference.
  • the hollow anode 17, being positive with respect to the heating filament 21 is subjected to the bombardment of electrons emitted by this filament; this electron bombardment of the hollow anode 17 causes the latter to have a high temperature which determines its thermal radiation in the direction of the cathode 16.
  • This latter mode of heating the hollow anode 17 can be used either alone or combined with that previously described, the heat shield 32, not shown in FIG. 2, which can be kept in this variant.
  • the hollow anode 17 is made of graphite
  • its outer surface 34 is preferably covered with a highly reflective metal deposit (of the so-called mirror-polished type for example) .
  • its external surface 34 can also be reflective (mirror-polished), its internal surface 36 being covered with a material (not shown) with high thermal radiation power.
  • This description constitutes a nonlimiting example of an X-ray tube according to the invention, capable of flowing the anode current from the tube 1, without contact between the fixed parts and the rotating parts of this tube.
  • a device 40 notably includes an electron-emitting cathode 16, which receives the electron extraction energy thanks to the radiation of a hollow anode 17 intended to capture these electrons.
  • the shape of this cathode 16 and of this hollow anode may be different from that shown in FIGS. 1, 2, the main thing being that the cathode 16, integral with the rotating anode 6, is located in an enclosure, heated, constituting a hollow anode 17. Nevertheless, the shapes of the hollow anode 17 and of the cathode 16 are preferably adapted so that their surfaces 36, 33, facing each other, are at a distance D as constant as possible.
  • the hollow anode 17 and the cathode 16 can also have a conical or cylindrical shape as shown in FIG. 3.
  • This arrangement of the hollow anode 17 and the cathode 16 also makes it possible to use heating means different from those constituted by the heating filament 21 and of low-voltage generator 45; the heating of the cathode 16 being obtained by the thermal radiation of the hollow anode 17. It should also be noted that the combination of means of the device 40 can also be located at one or the other of the ends 3 of the 'envelope 2-3 or simultaneously at these two ends.
  • the device 40 can also be adapted to different positions as shown in the nonlimiting example of FIG. 4, where this device, already explained, is represented by a rectangle in dotted lines.
  • FIG. 4 shows an X-ray tube 1 according to the invention, the magnetic bearings 11-13, 12-14 of which are situated on the same side of the rotating anode 6.
  • the tube 1 its envelope is made up of a metal end part 3, and of an insulating part 2, on the side of which are contained the rotating anode 6 and the main cathode 5.
  • the part of metal end 3 being brought to earth potential, as well as the magnetic bearings 11-13,12-14 and the rotor 8, by conventional means and not shown; the guard bearings 25 being arranged around a fixed shaft 39, disposed in the rotor 8 along the longitudinal axis 10.
  • the rotor 8 rotates the rotary anode 6 around the longitudinal axis 10, by means of an insulating shaft 38, the latter being made of a refractory material and highly electrical insulator, such as for example alumina , or ceramic as in the example described.
  • the device 40 serving to drain the anode current is in the immediate vicinity of the rotating anode 6, to which it is mechanically and electrically connected thanks to the metal axis 15; cathode 16, not shown in FIG. 4, being coupled in rotation to the rotating anode 6 as previously explained.
  • the internal electrical connections (not shown), necessary for the device 40 are routed, out of the tube 1, by a sheath 37 made of a refractory material with very low coefficient of expansion, such as for example alumina or ceramic ; these internal connections leading to the crossings 22, 23, 24 of the base 19.
  • the operation of the device 40 remains, in this arrangement, the same as previously explained, as well as its external electrical connections not shown in FIG. 4; an exception however being that in this last version, the end part 3 is at ground potential, and is therefore no longer connected to + HT.
  • An X-ray tube 1 according to the invention is applicable to all fields of radiology, to which it provides a simple, reliable and economical solution, by means of the device 40 serving to flow the anode current without contact.

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  • X-Ray Techniques (AREA)

Description

L'invention concerne un tube radiogène à anode tournante, dans lequel la rotation de l'anode s'effectue grâce à des paliers magnétiques.The invention relates to an X-ray tube with a rotating anode, in which the rotation of the anode is effected by magnetic bearings.

Des tubes radiogènes de forte puissance utilisent généralement une anode tournante, dont la rotation est encore très couramment assurée grâce à des paliers mécaniques. Etant donné la vitesse de rotation élevée, qui peut atteindre 20 000 tours par minute, ces paliers mécaniques présentent une usure rapide, et sont fréquemment la cause de la mise hors service de tubes radiogènes.High power X-ray tubes generally use a rotating anode, the rotation of which is still very commonly ensured by mechanical bearings. Given the high rotational speed, which can reach 20,000 revolutions per minute, these mechanical bearings exhibit rapid wear, and are frequently the cause of the decommissioning of X-ray tubes.

Une amélioration importante consiste à monter l'anode tournante avec des paliers magnétiques. Ceux-ci comportent généralement des électroaimants montés deux à deux en opposition, qui créent des champs magnétiques sous l'influence desquels un rotor, solidaire de l'anode tournante dont il assure la rotation, est maintenu en équilibre ; l'anode tournante et les pièces mécaniques qui l'accompagnent en rotation, n'ont ainsi plus de contact mécanique avec le reste du tube radiogène.An important improvement consists in mounting the rotating anode with magnetic bearings. These generally include electromagnets mounted two by two in opposition, which create magnetic fields under the influence of which a rotor, integral with the rotating anode which it ensures rotation, is kept in equilibrium; the rotating anode and the mechanical parts which accompany it in rotation, thus no longer have mechanical contact with the rest of the X-ray tube.

Ceci pose un nouveau problème qui réside en ce que l'anode, étant mécaniquement isolée du reste du tube, elle l'est également électriquement ; aussi sa connexion à la haute tension du tube, et l'écoulement du courant anodique sont imparfaitement réalisés à ce jour. Des solutions proposées sont souvent des systèmes à frotteurs ou à billes, donc mécaniques, et l'on perd de ce fait une partie de l'avantage du système à paliers magnétiques, à savoir l'absence totale de frottements mécaniques.This poses a new problem which resides in that the anode, being mechanically isolated from the rest of the tube, it is also electrically; also its connection to the high voltage of the tube, and the flow of the anode current are imperfectly realized to date. Solutions proposed are often friction or ball systems, therefore mechanical, and one thereby loses part of the advantage of the magnetic bearing system, namely the total absence of mechanical friction.

'Une autre solution, qui permet l'écoulement du courant anodique sans contact mécanique, utilise l'émission d'électrons générés par des cathodes thermo-émissives liées mécaniquement à l'anode tournante ; ces électrons étant captés par des anodes fixes. L'une des principales difficultés est alors de fournir, à ces cathodes mises en rotation, l'énergie nécessaire à élever leur température à un niveau suffisant pour répondre aux lois de l'émission thermo-électronique.Another solution, which allows the flow of the anode current without mechanical contact, uses the emission of electrons generated by thermo-emissive cathodes mechanically linked to the rotating anode; these electrons being captured by fixed anodes. One of the main difficulties is then to supply, to these rotated cathodes, the energy necessary to raise their temperature to a level sufficient to meet the laws of thermoelectronic emission.

A ce jour, cette difficulté est tournée grâce à des solutions relativement complexes et onéreuses, consistant par exemple à utiliser des phénomènes d'induction pour transférer à ces cathodes l'énergie nécessaire à leur chauffage. Une telle solution est décrite dans unè demande de brevet français publiée sous le N° 2 494 496.To date, this difficulty has been overcome thanks to relatively complex and expensive solutions, consisting for example of using induction phenomena to transfer to these cathodes the energy necessary for their heating. Such a solution is described in a French patent application published under No. 2,494,496.

Cette demande de brevet expose l'agencement d'un tube à rayons X à anode tournante, muni de paliers magnétiques et de moyens pour écouler, sans contact, le courant anodique. Dans' cette demande de brevet, une anode tournante solidaire d'un rotor, est montée sur des paliers magnétiques. Pour évacuer le courant anodique, l'arrière du rotor comporte deux cathodes tournant autour d'un axe, sur lequel est disposée une anode. Les cathodes comportent des enroulements coopérant durant la rotation de l'anode tournante, avec une pluralité de bobines d'excitation ; ces bobines d'excitation étant réparties sur la périphérie du tube et induisant dans les enroulements en rotation, la tension de chauffage des cathodes.This patent application describes the arrangement of an X-ray tube with a rotating anode, provided with magnetic bearings and means for flowing, without contact, the anode current. In this patent application, a rotating anode secured to a rotor is mounted on magnetic bearings. To remove the anode current, the rear of the rotor has two cathodes rotating around an axis, on which an anode is arranged. The cathodes comprise windings cooperating during the rotation of the rotary anode, with a plurality of excitation coils; these excitation coils being distributed over the periphery of the tube and inducing in the rotating windings, the heating voltage of the cathodes.

La mise en oeuvre de cette solution est compliquée et la rend coûteuse ; d'autre part, des problèmes de fiabilité peuvent se présenter du fait des températures élevées auxquelles sont exposés, les enroulements tournants. En effet, ces enroulements doivent comporter des isolants électriques capables de supporter ces températures et, qui ne dégazent pas ; ceci posant un problème technologique encore mal résolu.The implementation of this solution is complicated and makes it expensive; on the other hand, reliability problems may arise due to the high temperatures to which the windings are exposed. In fact, these windings must include electrical insulators capable of withstanding these temperatures and which do not degas; this posing a still poorly resolved technological problem.

Une autre demande de brevet français, publiée sous le N° 2 494 497, décrit également un tube à rayons X, comportant une anode tournante à paliers magnétiques, et des moyens pour évacuer le courant anodique sans contacts. Une cathode auxiliaire est disposée en position centrale de l'anode, et un filament chauffant, en position fixe, est disposé en face de la cathode auxiliaire. Une anode auxiliaire en forme de tube ou anneau entoure le filament chauffant et capte les électrons émis par la cathode auxiliaire. L'un des inconvénients de cette solution est que les dimensions du filament chauffant sont limitées par le diamètre de l'anode auxiliaire en anneau, et par suite, il est difficile d'obtenir la puissance de chauffage désirée.Another French patent application, published under No. 2,494,497, also describes an X-ray tube, comprising a rotating anode with magnetic bearings, and means for discharging the anode current without contacts. An auxiliary cathode is placed in the central position of the anode, and a heating filament, in a fixed position, is placed in front of the auxiliary cathode. An auxiliary anode in the form of a tube or ring surrounds the heating filament and collects the electrons emitted by the auxiliary cathode. One of the drawbacks of this solution is that the dimensions of the heating filament are limited by the diameter of the auxiliary ring anode, and therefore it is difficult to obtain the desired heating power.

Dans la présente invention, un chauffage destiné à écouler un courant anodique, est obtenu grâce à une combinaison de moyens beaucoup plus simples, qui ne présentent pas les inconvénients ci-dessus mentionnés.In the present invention, heating intended to flow an anode current is obtained by a combination of much simpler means, which do not have the above-mentioned drawbacks.

La présente invention concerne un tube radiogène à anode tournante montée sur paliers magnétiques, permettant d'écouler sans contact le courant anodique ; ceci étant obtenu dans-le tube radiogène selon l'invention d'une manière plus simple et moins onéreuse que selon l'art antérieur, grâce notamment à l'utilisation d'une cathode thermo-émissive et un agencement nouveau permettant de la chauffer par rayonnement thermique.The present invention relates to an X-ray tube with a rotating anode mounted on magnetic bearings, making it possible to flow the anode current without contact; this being obtained in the X-ray tube according to the invention in a simpler and less expensive way than according to the prior art, thanks in particular to the use of a thermo-emissive cathode and a new arrangement making it possible to heat it by thermal rays.

Selon l'invention, un tube radiogène, comportant une anode tournante montée sur paliers magnétiques et au moins un dispositif destiné à écouler le courant anodique du tube, est caractérisé en ce que ce dispositif comporte en position fixe une anode creuse, à l'intérieur de laquelle une cathode est couplée en rotation à l'anode tournante, l'anode creuse étant associée à des moyens de chauffage extérieurs à l'anode creuse, l'anode creuse étant reliée au pôle positif de la haute tension, la cathode étant électriquement reliée à l'anode tournante de manière à assurer le passage du courant anodique.According to the invention, an X-ray tube, comprising a rotating anode mounted on magnetic bearings and at least one device intended to drain the anode current from the tube, is characterized in that this device comprises in a fixed position a hollow anode, inside of which a cathode is coupled in rotation to the rotating anode, the hollow anode being associated with heating means external to the hollow anode, the hollow anode being connected to the positive pole of the high voltage, the cathode being electrically connected to the rotating anode so as to ensure the passage of the anode current.

L'invention sera mieux comprise grâce à la description qui suit et aux quatre figures annexées dont :

  • la figure 1 représente schématiquement un tube radiogène conforme à l'invention ;
  • la figure 2 montre plus particulièrement des moyens du dispositif destiné à écouler le courant anodique du tube selon l'invention ;
  • la figure 3 montre une variante du dispositif destiné à écouler le courant anodique ;
  • la figure 4 montre schématiquement une variante du tube radiogène selon l'invention.
The invention will be better understood thanks to the description which follows and to the four appended figures, of which:
  • Figure 1 schematically shows an X-ray tube according to the invention;
  • FIG. 2 shows more particularly means of the device intended to drain the anode current from the tube according to the invention;
  • FIG. 3 shows a variant of the device intended to drain the anode current;
  • Figure 4 schematically shows a variant of the X-ray tube according to the invention.

Le tube radiogène 1 selon l'invention, montré sur la figure 1, comporte une enveloppe 2-3 étanche au vide, constituée dans l'exemple non limitatif décrit par une partie centrale isolante 2 et, par des parties d'extrémités 3 formées par des chemises métalliques de faible épaisseur ; une cathode principale 5 portée par la partie centrale isolante 2, est destinée à fournir un faisceau d'électrons (non représenté) dont l'impact sur une anode tournante 6 provoque le rayonnement X.The X-ray tube 1 according to the invention, shown in FIG. 1, comprises a vacuum-tight envelope 2-3, constituted in the nonlimiting example described by an insulating central part 2 and, by end parts 3 formed by thin metal shirts; a main cathode 5 carried by the insulating central part 2, is intended to supply an electron beam (not shown) whose impact on a rotating anode 6 causes X-radiation.

L'anode tournante 6 est portée par un arbre 7 métallique, solidaire d'un rotor 8 ; ce rotor 8 forme avec. un stator 9 situé à l'extérieur de l'enveloppe 2-3, un moteur assurant la rotation de l'anode tournante 6 autour d'un axe longitudinal 10. L'arbre 7 est également solidaire à ses extrémités 4, de parties tournantes 11, 12, coniques dans l'exemple non limitatif décrit, et qui constituent les parties en suspension de paliers magnétiques 11-13, 12-14 ; des parties actives 13, 14 de ces paliers magnétiques étant situées à l'extérieur de l'enveloppe 2-3. A l'intérieur de cette enveloppe sont disposés des roulements de garde 25, situés en vis-à-vis des extrémités 4 de l'arbre 7, avec lequel ces roulements 25 ne sont en contact qu'en cas de défaillance de la suspension magnétique.The rotating anode 6 is carried by a metal shaft 7, integral with a rotor 8; this rotor 8 forms with. a stator 9 located outside the casing 2-3, a motor ensuring the rotation of the rotary anode 6 around a longitudinal axis 10. The shaft 7 is also secured at its ends 4, to rotating parts 11, 12, conical in the nonlimiting example described, and which constitute the suspended parts of magnetic bearings 11-13, 12-14; active parts 13, 14 of these magnetic bearings being located outside the envelope 2-3. Inside of this envelope are disposed guard bearings 25, situated opposite the ends 4 of the shaft 7, with which these bearings 25 are in contact only in the event of failure of the magnetic suspension .

Le tube 1 comporte également un dispositif 40, représenté dans un cadre en traits pointillés, situé à l'intérieur de l'enveloppe 2-3 et destiné, en fonctionnement, à écouler le courant anodique du tube 1.The tube 1 also includes a device 40, represented in a frame in dotted lines, located inside the envelope 2-3 and intended, in operation, to drain the anode current from the tube 1.

Ce dispositif 40 comporte un axe métallique 15 prolongeant l'arbre 7 selon l'axe longitudinal 10, du côté du rotor 8, et portant une cathode 16. La cathode 16 de forme sphérique, dans l'exemple non limitatif décrit, est centrée sur l'axe longitudinal 10 ; elle est électriquement reliée par l'axe métallique 15 et l'arbre 7 à l'anode tournante 6, et se trouve en fonctionnement portée au même potentiel que cette dernière.This device 40 comprises a metal axis 15 extending the shaft 7 along the longitudinal axis 10, on the side of the rotor 8, and carrying a cathode 16. The cathode 16 of spherical shape, in the nonlimiting example described, is centered on the longitudinal axis 10; it is electrically connected by the metal axis 15 and the shaft 7 to the rotating anode 6, and is in operation brought to the same potential as the latter.

Une anode creuse 17, également de forme sphérique dans l'exemple non limitatif décrit, est maintenue en position fixe et centrée autour de la cathode 16, par un support métallique 18 solidaire d'un support isolant 19. L'anode creuse 17 comporte un trou 20 destiné au passage de l'axe métallique 15, permettant ainsi le mouvement de la cathode 16, laquelle est couplée en rotation à l'anode tournante 6 ; la rotation de la cathode 16 s'effectuant à l'intérieur de l'anode creuse 17, et, comme celle de l'anode tournante 6, autour de l'axe longitudinal 10 selon la flèche 29.A hollow anode 17, also of spherical shape in the non-limiting example described, is held in a fixed position and centered around the cathode 16, by a metal support 18 secured to an insulating support 19. The hollow anode 17 comprises a hole 20 intended for the passage of the metal axis 15, thus allowing the movement of the cathode 16, which is coupled in rotation to the rotating anode 6; the rotation of the cathode 16 taking place inside the hollow anode 17, and, like that of the rotating anode 6, around the longitudinal axis 10 according to arrow 29.

Autour de l'anode creuse 17 est disposé un filament chauffant 21, supporté d'une manière classique par des moyens non représentés et relié à deux traversées 22, 23 étanches, dont est muni le support isolant 19 ; ce dernier également étanche au vide, comporte une troisième traversée 24, électriquement reliée au support métallique 18 de l'anode creuse 17.Around the hollow anode 17 is disposed a heating filament 21, supported in a conventional manner by means not shown and connected to two sealed bushings 22, 23, which is provided with the insulating support 19; the latter also vacuum-tight, has a third bushing 24, electrically connected to the metal support 18 of the hollow anode 17.

Le filament chauffant 21, constitué dans l'exemple non limitatif décrit en tungstène, est destiné à élever la température de l'anode creuse 17. A cette fin, le filament 21 est chauffé par effet JOULE, et les deux traversées 22, 23 auxquelles il aboutit dans le tube 1 sont reliées à une source de tension classique, telle qu'un transformateur 30 par exemple.The heating filament 21, constituted in the nonlimiting example described in tungsten, is intended to raise the temperature of the hollow anode 17. To this end, the filament 21 is heated by JOULE effect, and the two bushings 22, 23 at which it ends in the tube 1 are connected to a conventional voltage source, such as a transformer 30 for example.

La haute tension nécessaire au fonctionnement du tube 1 est fournie de manière connue par un générateur haute tension 31. Une sortie positive + HT de cette haute tension est reliée aux parties d'extrémités 3, ainsi qu'à la troisième traversée 24, pour être appliquée à l'anode creuse 17 ; une sortie négative - HT du générateur 31, est reliée d'une manière classique par une quatrième traversée 35 à la cathode principale 5, cette dernière comportant également de manière connue et non representée, des connexions de chauffage.The high voltage necessary for the operation of the tube 1 is supplied in a known manner by a high voltage generator 31. A positive + HT output of this high voltage is connected to the end portions 3, as well as to the third crossing 24, to be applied to the hollow anode 17; a negative output - HT of the generator 31, is connected in a conventional manner by a fourth bushing 35 to the main cathode 5, the latter also comprising in known manner and not shown, heating connections.

En fonctionnement, le filament chauffant 21 chauffe l'anode creuse 17, laquelle constitue une enceinte pratiquement close dans laquelle la cathode 16 est chauffée à son tour comme dans un four, par le rayonnement thermique de l'anode creuse 17. Pour limiter les pertes thermiques, le dispositif 40 peut comporter ainsi que dans l'exemple non limitatif décrit, un reflecteur thermique 32 partiellement représenté, enveloppant le filament chauffant 21.In operation, the heating filament 21 heats the hollow anode 17, which constitutes a practically closed enclosure in which the cathode 16 is heated in its turn as in an oven, by the thermal radiation of the hollow anode 17. To limit losses thermal, the device 40 may include, as in the nonlimiting example described, a partially shown thermal reflector 32, enveloping the heating filament 21.

La cathode 16 électriquement reliée à l'anode tournante 6, génère alors des électrons qui sont captés par l'anode creuse 17, laquelle est reliée au pôle positif + HT de la haute tension ; l'intensité du courant électronique ainsi généré est la même que celle du faisceau d'électrons émis par la cathode principale 5, vers l'anode tournante 6. Le courant anodique du tube 1 est ainsi écoulé avec une faible différence de tension entre la polarité positive + HT de la haute tension, et la valeur + HT' établie au niveau de l'anode tournante 6. Cette disposition permet au trajet anode creuse-cathode 17, 16 de présenter une faible impédance qui permettrait sous une faible tension, le passage d'un courant électronique d'une intensité très supérieure à celle nécessaire en utilisation courante ; ceci permettant de ne perturber en aucun cas le fonctionnement du tube 1. Il est à remarquer de plus, que la puissance dissipée sous forme de chaleur au niveau de l'anode creuse 17, par l'impact des électrons qui constituent le courant anodique, contribue à favoriser l'émission électronique de la cathode 16.The cathode 16 electrically connected to the rotating anode 6 then generates electrons which are captured by the hollow anode 17, which is connected to the positive + HT pole of the high voltage; the intensity of the electronic current thus generated is the same as that of the electron beam emitted by the main cathode 5, towards the rotating anode 6. The anodic current of the tube 1 is thus passed with a small difference in voltage between the polarity positive + HT of the high voltage, and the value + HT 'established at the rotating anode 6. This arrangement allows the hollow anode-cathode path 17, 16 to have a low impedance which would allow under low voltage, the passage an electronic current of an intensity much higher than that necessary in current use; this making it possible in no case to disturb the operation of the tube 1. It should also be noted that the power dissipated in the form of heat at the level of the hollow anode 17, by the impact of the electrons which constitute the anode current, contributes to promoting the electronic emission from cathode 16.

Ainsi l'énergie thermique fournie par le filament chauffant 21, est transférée par l'intermédiaire de l'anode creuse 17 à la cathode 16 pour constituer l'énergie nécessaire à l'extraction des électrons. Ce transfert d'énergie peut être rendu plus efficace par des aménagements appropriés de la cathode et de l'anode creuse 16, 17, et par l'utilisation d'une seconde source de tension, ainsi qu'il est expliqué en référence à la figure 2 ; pour une meilleure clarté de cette figure 2, la représentation du tube radiogène selon l'invention est limitée afin de mieux montrer ie dispositif 40.Thus, the thermal energy supplied by the heating filament 21 is transferred via the hollow anode 17 to the cathode 16 to constitute the energy necessary for the extraction of the electrons. This energy transfer can be made more efficient by appropriate adaptations of the cathode and hollow anode 16, 17, and by the use of a second voltage source, as explained with reference to Figure 2; for better clarity of this FIG. 2, the representation of the X-ray tube according to the invention is limited in order to better show the device 40.

Dans le but de diminuer l'énergie nécessaire à l'extraction des électrons, la cathode 16 peut être creuse ainsi que dans l'exemple montré par la figure 2, où elle a la forme d'une sphère ; cette forme pouvant être différente ainsi qu'il est expliqué dans la suite de la description. La cathode 16 compte une paroi 26, ayant une épaisseur e faible, et constituée de préférence par un matériau réfractaire tel que du tantale ou du tungstène thorié ; cette paroi 26 pouvant également être recouverte sur sa surface extérieure 33, pour augmenter le pouvoir émissif en électrons, de borure de lanthane par exemple (non représenté).In order to reduce the energy required for the extraction of electrons, the cathode 16 can be hollow as in the example shown in Figure 2, where it has the shape of a sphere; this form may be different as explained in the following description. The cathode 16 has a wall 26, having a small thickness e, and preferably consisting of a refractory material such as tantalum or thoriated tungsten; this wall 26 can also be covered on its outer surface 33, to increase the emissivity in electrons, of lanthanum boride for example (not shown).

Dans l'exemple non limitatif décrit, l'anode creuse 17 est formée par deux demi-sphères 27, 28 assemblées constituées en graphite, en graphite pyrolitique par exemple, ou encore par un matériau réfractaire tel que le tungstène ou le molybdène.In the nonlimiting example described, the hollow anode 17 is formed by two half-spheres 27, 28 assembled made of graphite, pyrolitic graphite for example, or also of a refractory material such as tungsten or molybdenum.

Afin d'augmenter encore l'efficacité du chauffage de l'anode creuse 17, et par là celui de la cathode 16, le tube radiogène selon l'invention comporte une source d'alimentation constituée par un générateur basse tension continue 45.In order to further increase the heating efficiency of the hollow anode 17, and thereby that of the cathode 16, the X-ray tube according to the invention comprises a power source constituted by a low-voltage DC generator 45.

Une sortie positive V+ de ce générateur basse tension 45 est reliée à l'anode creuse 17 et également au pôie positif de la haute tension + HT; une sortie négative -V étant elle reliée à l'une des extrémités du filament chauffant 21, à la traversée 23 par exemple. La tension continue délivrée par ce générateur basse tension 45 détermine, entre le filament chauffant 21 et l'anode creuse 17, une différence de potentiel. Par cette différence de potentiel, l'anode creuse 17, étant positive par rapport au filament chauffant 21, est soumise au bombardement d'électrons émis par ce filament ; ce bombardement électronique de l'anode creuse 17 provoque à cette dernière une température élevée qui détermine son rayonnement thermique en direction de la cathode 16.A positive output V + of this low voltage generator 45 is connected to the hollow anode 17 and also to the positive pole of the high voltage + HT; a negative output -V being it connected to one of the ends of the heating filament 21, to the bushing 23 for example. The DC voltage delivered by this low voltage generator 45 determines, between the heating filament 21 and the hollow anode 17, a potential difference. By this difference in potential, the hollow anode 17, being positive with respect to the heating filament 21, is subjected to the bombardment of electrons emitted by this filament; this electron bombardment of the hollow anode 17 causes the latter to have a high temperature which determines its thermal radiation in the direction of the cathode 16.

Ce dernier mode de chauffage de l'anode creuse 17 peut être utilisé soit seul, soit conjugué avec celui précédemment décrit, l'écran thermique 32, non représenté sur la figure 2 pouvant être conservé dans cette variante.This latter mode of heating the hollow anode 17 can be used either alone or combined with that previously described, the heat shield 32, not shown in FIG. 2, which can be kept in this variant.

Pour cette variante et dans le cas précédemment mentionné où l'anode creuse 17 est en graphite, sa surface extérieure 34 est préférentiellement recouverte d'un dépôt métallique très réflecteur (du type dit poli-miroir par exemple).; quand l'anode creuse 17 est en matériau réfractaire, sa surface extérieure 34 peut être également réflectrice (poli-miroir), sa surface intérieure 36 étant recouverte d'un matériau (non représenté) à haut pouvoir de rayonnement thermique.For this variant and in the previously mentioned case where the hollow anode 17 is made of graphite, its outer surface 34 is preferably covered with a highly reflective metal deposit (of the so-called mirror-polished type for example) .; when the hollow anode 17 is made of refractory material, its external surface 34 can also be reflective (mirror-polished), its internal surface 36 being covered with a material (not shown) with high thermal radiation power.

Cette description constitue un exemple non limitatif d'un tube radiogène selon l'invention, capable d'écouler le courant anodique du tube 1, sans contacts entre les parties fixes et les parties tournantes de ce tube. Ceci est obtenu grâce à un agencement nouveau de ce tube radiogène, dans lequel un dispositif 40 comporte notamment une cathode 16 émettrice d'électrons, laquelle reçoit l'énergie d'extraction des électrons grâce au rayonnement d'une anode creuse 17 destinée à capter ces électrons. La forme de cette cathode 16 et de cette anode creuse peut être différente de celle montrée par les figures 1, 2, l'essentiel étant que la cathode 16, solidaire de l'anode tournante 6, soit située dans une enceinte, chauffée, constituant une anode creuse 17. Néanmoins, les formes de l'anode creuse 17 et de la cathode 16 sont de préférence adaptées pour que leurs surfaces 36, 33, en vis-à-vis, soient à une distance D aussi constante que possible.This description constitutes a nonlimiting example of an X-ray tube according to the invention, capable of flowing the anode current from the tube 1, without contact between the fixed parts and the rotating parts of this tube. This is obtained by virtue of a new arrangement of this X-ray tube, in which a device 40 notably includes an electron-emitting cathode 16, which receives the electron extraction energy thanks to the radiation of a hollow anode 17 intended to capture these electrons. The shape of this cathode 16 and of this hollow anode may be different from that shown in FIGS. 1, 2, the main thing being that the cathode 16, integral with the rotating anode 6, is located in an enclosure, heated, constituting a hollow anode 17. Nevertheless, the shapes of the hollow anode 17 and of the cathode 16 are preferably adapted so that their surfaces 36, 33, facing each other, are at a distance D as constant as possible.

Ainsi, par exemple l'anode creuse 17 et la cathode 16 peuvent également comporter une forme conique, ou cylindrique comme montré par la figure 3.Thus, for example the hollow anode 17 and the cathode 16 can also have a conical or cylindrical shape as shown in FIG. 3.

Cet agencement de l'anode creuse 17 et de la cathode 16 permet également d'utiliser des moyens de chauffage différents de ceux constitués par le filament chauffant 21 et de générateur basse tension 45 ; le chauffage de la cathode 16 étant obtenu par le rayonnement thermique de l'anode creuse 17. Il est aussi à remarquer que la combinaison de moyens du dispositif 40, peut également être située à l'une ou l'autre des extrémités 3 de l'enveloppe 2-3 ou simultanément à ces deux extrémités.This arrangement of the hollow anode 17 and the cathode 16 also makes it possible to use heating means different from those constituted by the heating filament 21 and of low-voltage generator 45; the heating of the cathode 16 being obtained by the thermal radiation of the hollow anode 17. It should also be noted that the combination of means of the device 40 can also be located at one or the other of the ends 3 of the 'envelope 2-3 or simultaneously at these two ends.

Il est enfin à remarquer que le dispositif 40 peut également s'adapter à des positions différentes comme montré dans l'exemple non limitatif de la figure 4, où ce dispositif déjà explicité est représenté par un rectangle en traits pointillés.Finally, it should be noted that the device 40 can also be adapted to different positions as shown in the nonlimiting example of FIG. 4, where this device, already explained, is represented by a rectangle in dotted lines.

La figure 4 montre un tube radiogène 1 selon l'invention dont les paliers magnétiques 11-13, 12-14 sont situés d'un même côté de l'anode tournante 6.FIG. 4 shows an X-ray tube 1 according to the invention, the magnetic bearings 11-13, 12-14 of which are situated on the same side of the rotating anode 6.

Dans cette version du tube 1, son enveloppe est constituée d'une partie d'extrémité 3 métallique, et d'une partie isolante 2, du côté de laquelle sont contenues l'anode tournante 6 et la cathode principale 5. La partie d'extrémité 3 métallique étant portée au potentiel de la terre, ainsi que les paliers magnétiques 11-13,12-14 et le rotor 8, par des moyens classiques et non représentés ; les roulements de garde 25 étant disposés autour d'un arbre fixe 39, disposé dans le rotor 8 selon l'axe longitudinal 10.In this version of the tube 1, its envelope is made up of a metal end part 3, and of an insulating part 2, on the side of which are contained the rotating anode 6 and the main cathode 5. The part of metal end 3 being brought to earth potential, as well as the magnetic bearings 11-13,12-14 and the rotor 8, by conventional means and not shown; the guard bearings 25 being arranged around a fixed shaft 39, disposed in the rotor 8 along the longitudinal axis 10.

Le rotor 8 entraîne en rotation l'anode tournante 6 autour de l'axe longitudinal 10, par l'intermédiaire d'un arbre isolant 38, ce dernier étant constitué en un matériau réfractaire et hautement isolant électrique, comme par exemple de l'alumine, ou de la céramique ainsi que dans l'exemple décrit.The rotor 8 rotates the rotary anode 6 around the longitudinal axis 10, by means of an insulating shaft 38, the latter being made of a refractory material and highly electrical insulator, such as for example alumina , or ceramic as in the example described.

Dans cette version du tube 1 selon l'invention, le dispositif 40, servant à écouler le courant anodique est à proximité immédiate de l'anode tournante 6, à laquelle il est mécaniquement et électriquement relié grâce à l'axe métallique 15 ; la cathode 16, non représentée sur la figure 4, étant couplée en rotation à l'anode tournante 6 ainsi qu'il a été précédemment expliqué.In this version of the tube 1 according to the invention, the device 40, serving to drain the anode current is in the immediate vicinity of the rotating anode 6, to which it is mechanically and electrically connected thanks to the metal axis 15; cathode 16, not shown in FIG. 4, being coupled in rotation to the rotating anode 6 as previously explained.

Les liaisons électriques internes (non représentées), nécessaires au dispositif 40 sont acheminées, pour sortir du tube 1, par un fourreau 37 constitué d'un matériau réfractaire à très faible coefficient de dilatation, comme par exemple de l'alumine ou de la céramique ; ces liaisons internes aboutissant aux traversées 22, 23, 24 de l'embase 19.The internal electrical connections (not shown), necessary for the device 40 are routed, out of the tube 1, by a sheath 37 made of a refractory material with very low coefficient of expansion, such as for example alumina or ceramic ; these internal connections leading to the crossings 22, 23, 24 of the base 19.

Le fonctionnement du dispositif 40 reste, dans cette disposition, le même que précédemment expliqué ainsi que ses connexions électriques extérieures non représentées sur la figure 4 ; une exception toutefois étant que dans cette dernière version, la partie d'extrémité 3 est au potentiel de la terre, et n'est donc plus reliée au + HT.The operation of the device 40 remains, in this arrangement, the same as previously explained, as well as its external electrical connections not shown in FIG. 4; an exception however being that in this last version, the end part 3 is at ground potential, and is therefore no longer connected to + HT.

Un tube radiogène 1 conforme à l'invention est applicable à tous les domaines de la radiologie, auxquels il apporte une solution simple, fiable et économique, grâce au dispositif 40 servant à écouler sans contact le courant anodique.An X-ray tube 1 according to the invention is applicable to all fields of radiology, to which it provides a simple, reliable and economical solution, by means of the device 40 serving to flow the anode current without contact.

Claims (9)

1. A radiation tube, comprising a rotating anode (6) mounted on magnetic bearings, and at least one device (40) conceived to conduct the anode current of the tube (1), characterized in that said device (40) comprised in a fixed position a hollow anode (17), inside which a cathode (16) is rotatably coupled to the rotating anode (6), the hollow anode (17) being associated to heating means (21, 45, 32) outside the anode (17), the hollow anode (17) being connected to the positive pole (+HT) of the high voltage and the cathode (16) being electrically connected to the rotating anode (6), so as to ensure the passage of the anodic current.
2. A radiation tube according to claim 1, characterized in that the heating means (21, 45, 32) comprise a heating filament (21) disposed around the hollow anode (17) for heating it.
3. A radiation tube according to claim 2, characterized in that the heating filament (21) is surrounded by a thermal reflector (32).
4. A radiation tube according to claim 2, characterized in that the heating means (21, 45, 32) further comprise a low voltage generator (45) co-operating with the heating filament (21) and the hollow anode (17) for realising between the latters a potential difference permitting an electron bombardement of the hollow anode (17).
5. A radiation tube according to any one of the preceding claims, characterized in that the hollow anode constitutes a practically closed zone acting as an oven for the heating of the cathode (16).
6. A radiation tube according to any one of the preceding claims, characterized in that the cathode (16) is hollow.
7. A radiation tube according to any one of the preceding claims, characterized in that the hollow anode (17) and the cathode (16) have forms adjusted in such a manner that their inner respectively their outer surfaces (36, 33) are at a constant distance (D).
8. A radiation tube according to any one of the preceding claims, characterized in that the hollow anode (17) and the cathode (16) are spherical.
9. A radiation tube according to any one of the preceding claims, characterized in that the hollow anode (17) and the cathode (16) are cylindrical.
EP84400848A 1983-05-06 1984-04-26 Rotating anode x-ray tube Expired EP0126668B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8307610A FR2545649B1 (en) 1983-05-06 1983-05-06 RADIOGENIC TUBE WITH ROTATING ANODE
FR8307610 1983-05-06

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EP0126668A1 EP0126668A1 (en) 1984-11-28
EP0126668B1 true EP0126668B1 (en) 1987-08-19

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EP (1) EP0126668B1 (en)
DE (1) DE3465550D1 (en)
FR (1) FR2545649B1 (en)

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Publication number Priority date Publication date Assignee Title
JP2539193B2 (en) * 1984-12-20 1996-10-02 バリアン・アソシエイツ・インコーポレイテッド High intensity X-ray source
JPS6276246A (en) * 1985-09-30 1987-04-08 Toshiba Corp Rotary anode x-ray tube
DE3540303A1 (en) * 1985-11-13 1987-05-14 Siemens Ag TURNING ANODE TUBE TUBES
FR2599555A1 (en) * 1986-06-03 1987-12-04 Thomson Cgr Rotating X-ray tube
GB2346007B (en) 1999-01-21 2004-03-03 Imaging & Sensing Tech Corp Getter flash shield
US8284899B2 (en) * 2007-11-21 2012-10-09 Varian Medical Systems, Inc. X-ray tube having a focal spot proximate the tube end
DE102008062671B4 (en) * 2008-12-17 2011-05-12 Siemens Aktiengesellschaft X-ray equipment
WO2013038287A1 (en) * 2011-09-13 2013-03-21 Koninklijke Philips Electronics N.V. X-ray radiation with multiple photon energies

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DE2262757C3 (en) * 1972-12-21 1979-06-21 Siemens Ag, 1000 Berlin Und 8000 Muenchen X-ray rotating anode storage
DE3043046A1 (en) * 1980-11-14 1982-07-15 Siemens AG, 1000 Berlin und 8000 München TURNING ANODE TUBE TUBES
DE3043670A1 (en) * 1980-11-19 1982-07-08 Siemens AG, 1000 Berlin und 8000 München TURNING ANODE TUBE TUBES

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EP0126668A1 (en) 1984-11-28
US4651336A (en) 1987-03-17
FR2545649B1 (en) 1985-12-13
DE3465550D1 (en) 1987-09-24
FR2545649A1 (en) 1984-11-09

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