EP0010461A1 - Anti-microphonic coaxial cable to function at a high temperature - Google Patents

Anti-microphonic coaxial cable to function at a high temperature Download PDF

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Publication number
EP0010461A1
EP0010461A1 EP19790400610 EP79400610A EP0010461A1 EP 0010461 A1 EP0010461 A1 EP 0010461A1 EP 19790400610 EP19790400610 EP 19790400610 EP 79400610 A EP79400610 A EP 79400610A EP 0010461 A1 EP0010461 A1 EP 0010461A1
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EP
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Prior art keywords
core
coaxial cable
beads
cable
cable according
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EP19790400610
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German (de)
French (fr)
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EP0010461B1 (en
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Georges Melet
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B11/00—Communication cables or conductors
    • H01B11/18—Coaxial cables; Analogous cables having more than one inner conductor within a common outer conductor
    • H01B11/1834—Construction of the insulation between the conductors
    • H01B11/1856—Discontinuous insulation

Definitions

  • the invention relates generally to coaxial cables which are used in electronics techniques for transmitting electrical signals of very low intensity and applies more particularly to those of these cables which operate in medium hostile and high temperature.
  • Such a coaxial cable known per se is shown in FIG. 1 and consists of two electrodes, namely a central core 1 and an outer braid 3 separated by a dielectric medium 2 surrounding the central core.
  • the central core 1 is generally made of sometimes tinned red copper
  • the dielectric 2 is made of a material with high resistivity such as Teflon
  • the external conductive braid 3 is generally made of sometimes silvery red copper.
  • This antimicrophonic protection in itself known, however, has the disadvantage that it does not overcome the electric charges induced by the friction phenomena developing between the core 1 and the dielectric 2; on the other hand, when it comes to making a coaxial cable working in the middle hostile with vibrations and in particular at a high temperature of the order of several hundred degrees Celsius as is the case for the transmission of measurements from a nuclear reactor core, it is then impossible to use such a intermediate plastic envelope and the problem of microphonic protection of the cable is then completely called into question.
  • the coaxial cables undergo a transformation essentially concerning their dielectric, which then consists of a number of high density ceramic beads, generally in pure alumina, strung on the core of the cable and covered by an outer stainless steel braid.
  • Fig. 1 shows such a coaxial cable for high temperature of a type known per se.
  • a coaxial cable comprising a central core 1 of stainless steel or copper covered with stainless steel on which beads 2, made of pure alumina, constituting the dielectric are strung.
  • the pearls 2 preferably have the shape of a portion of a cylinder limited by respectively convex and concave end surfaces so as to be able to fit perfectly into each other.
  • the second electrode of this cable consists of an outer braid 3, also made of stainless steel and which may comprise several layers.
  • the present invention specifically relates to an antimicrophonic coaxial cable which can operate in a hostile environment and in particular at high temperature, without having the drawbacks of the prior art.
  • the coaxial cable also includes a certain number of metallic intermediate pieces threaded on the core and placed between each of the consecutive beads, which gives it a certain complementary flexibility.
  • the metallic coating of the friction surfaces can be produced in two different ways.
  • the metallic coating of said surfaces is produced by means of a deposit made on the parts of the surface thereof which are in contact with the core, the braid and / or the intermediate pieces, said deposit possibly being constituted for example by an alloy of molybdenum and manganese obtained from a pulverulent solution in an appropriate solvent which is left to dry and which is fixed by a treatment at a high temperature oven to make the combination of the alloy with the alumina surfaces of the pearls.
  • the metallic coating of the friction surfaces consists of rings and metal sleeves which are crimped directly around the pearls or which are forced into their central orifice.
  • an advantageous variant of the invention consists in using said metallic sheaths threaded d ⁇ the central orifice of each pearl to constitute at the same time the spacers making the desired spacing between two consecutive pearls.
  • the cable further comprises intermediate pieces which consist of spherical stainless steel balls 4 two in number between two consecutive beads 2 of pure high density alumina provided with a central channel 5.
  • intermediate pieces consist of spherical stainless steel balls 4 two in number between two consecutive beads 2 of pure high density alumina provided with a central channel 5.
  • external lateral 6 and internal 7 surfaces as well as the hemispherical portions 8 of the entry holes of channel 5 are covered with a metallization with a thickness of 3 / 100th of a mm of an alloy of molybdenum and manganese deposited in the presence of a mask as follows.
  • the mixture of molybdenum and manganese is carried out in a solvent such as toluene or benzene in powder solution.
  • a solvent such as toluene or benzene in powder solution.
  • This mixture is then deposited by brush, spray gun or stencil on the surfaces to be covered and then allowed to dry for about a quarter of an hour until the solvent has completely evaporated.
  • the pearls thus treated are placed in an oven under humid hydrogen and the temperature is raised to 1500 ° C. to obtain the combination of the alloy with the constituting allumine of the pearls.
  • the operation of combining the alloy with alumina requires approximately 45 minutes on average.
  • the assembly can then take place with the pearl thus treated, of course taking the usual precautions to maintain the necessary insulation between the conductive parts.
  • the steel balls 4 are pierced with a diametrical orifice 0.85 mm in diameter which thus allows the passage of the core 1 and the positioning of the alumina beads 2 between them.
  • the dimensions of the different consecutive pieces provide great flexibility to the cable without causing, and this is very important, the slightest abrasion of the bearing surfaces of the balls 4 on the beads 2. It may also be noted that the core 1 does not touch the internal surfaces of the alumina beads 2 which further limits the risk of abrasion:
  • FIG. 3 there are also the main constituent elements of a coaxial cable according to the invention and the corresponding elements which carry the same numbers of reference as in the previous example.
  • the intermediate pieces 4 consist of small cylinders 4 of stainless steel pierced along their axis with an orifice allowing the passage of the steel core 1 and are thus threaded onto said core 1 alternately with the pearls 2.
  • the edges 10 of the intermediate cylinders 4 as well as the outer edges 11 of the beads 2 have a rounded or hemispherical shape, since the presence of sharp angles would deteriorate the metal coating deposited on the dielectric 2.
  • the different previous conditions mean that neither the intermediate pieces 4, nor the outer ringed tube 3 come into contact with the ceramic constituting the pearls 2. In this embodiment it may sometimes be desirable to divide the intermediate elements 4 into two parts to give more flexibility to the entire cable.
  • Fig. 4 shows an embodiment of the second embodiment of the invention in which the metallic coating of the pearls 2 is constituted, as regards the external surface, by a stainless steel ring 12 mounted hot or by any other known means on the dielectric and shown in more detail in FIG. 5; the metallic coating of the central orifices as well as the spacers 4 are produced using sleeves 13, one of which is more particularly shown in FIG. 6, the sleeves 13 being made of a stainless steel cylinder force-fitted at very low temperature (in liquid nitrogen for example) inside the central orifices 5 of the alumina beads 2.
  • the sleeves 13 are made of stainless steel and fitted after fitting the rings 12; they are drilled right through along their axis with an orifice 14 intended for the passage of the stainless steel core 1 of the coaxial cable (fig. 6).
  • the electrode external 3 is also constituted by a ringed tube made of stainless steel and each alumina pearl 2 is a disc pierced along its axis with a hole whose diameter is equal to the external diameter of the steel sheaths 13.
  • Fig. 7 finally shows a very interesting variant of the invention in which we manage to further improve the electrical qualities of the cable while eliminating the intermediate parts.
  • the dielectric 2 the form of spherical or (ellipsoidal) alumina balls which are metallized on all their surface portions in contact with the core 1 or the braid 2 of stainless steel as well as the neighboring pearls .
  • the metallized parts are shown in reinforced lines. This configuration, which is easier to manufacture since it requires only one component, offers, in addition to its antimicrophonic qualities, the advantage of eliminating any capacitive effect which occurs from the other variants between the metallized external faces of the spacers and the metallic sheath.
  • a coaxial cable according to the invention has been the subject of a comparative test with a cable of known type as shown in FIG. 1 in which the alumina beads had no particular metallic protection on their surface part in connection with the core and the outer braid.
  • the cable sample was placed in a shielded enclosure and rigidly fixed at two points.
  • a mechanical device gave the cable an alternating movement with an amplitude of 4 mm, the period of which was 2 seconds.

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  • Communication Cables (AREA)
  • Insulated Conductors (AREA)
  • Measuring Temperature Or Quantity Of Heat (AREA)

Abstract

1. Noise-suppressed coaxial, cable, of the known type comprising between the core (1) and the external sheath (3) an insulation of high-density ceramic beads (2) threaded on the cable core, characterized in that all contact surfaces between the beads and the core, between the beads and the external sheath, and between adjacent beads, are provided with a conductive metallic lining, said lining being in particular continuous on the cable core.

Description

L'invention se rapporte d'une manière générale aux câbles coaxiaux que l'on utilise dans les techniques de l'électronique pour transmettre des signaux électriques d'intensité très faible et s'applique plus spécialement à ceux de ces câbles qui fonctionnent en milieu hostile et à température élevée.The invention relates generally to coaxial cables which are used in electronics techniques for transmitting electrical signals of very low intensity and applies more particularly to those of these cables which operate in medium hostile and high temperature.

Un tel câble coaxial en soi connu, est représenté sur la fig. 1 et se compose de deux électrodes à savoir une âite centrale 1 et une tresse extérieure 3 séparées par un milieu diélectrique 2 entourant l'âme centrale. L'âme centrale 1 est généralement constituée en cuivre rouge parfois étamé, le diélectrique 2 est composé d'un matériau à haute résistivité tel que le téflon et la tresse externe 3 conductrice est généralement en cuivre rouge parfois argenté.Such a coaxial cable known per se, is shown in FIG. 1 and consists of two electrodes, namely a central core 1 and an outer braid 3 separated by a dielectric medium 2 surrounding the central core. The central core 1 is generally made of sometimes tinned red copper, the dielectric 2 is made of a material with high resistivity such as Teflon and the external conductive braid 3 is generally made of sometimes silvery red copper.

Il est également connu qu'un tel câble présente ce que l'on appelle l'effet microphonique lorsqu'il est soumis même de façon très faible aux contraintes engendrées par un régime vibratoire. En effet, dans ce cas, les glissements relatifs qui existent entre les trois éléments rappelés précédemment, entraînent des frottements qui sont générateurs de charges électriques d'autant plus grandes que le diélectrique est plus parfait. Ces charges créent un champ électrique qui par induction crée des courants venant se superposer aux signaux électriques que le câble est précisément chargé de véhiculer et perturbe d'une façon parfois inacceptable la réception sure du signal à transporter. Pour lutter contre ce phénomène, on a envisagé de placer entre le diélectrique 2 et la tresse 3, une enveloppe en matériau plastique chargée en carbone qui, étant par conséquent semiconducteur, limite le niveau des charges électriques engendrées et permet l'écoulement de celles-ci dans la tresse 3 avec laquelle il est en contact. Cette protection antimicrophonique en soi connue a toutefois l'inconvénient qu'elle ne permet pas de s'affranchir des charges électriques induites par les phénomènes de friction se développant entre l'âme 1 et le diélectrique 2 ; d'autre part, lorsqu'il s'agit de réaliser un câble coaxial fonctionnant en milieu hostile présentant des vibrations et notamment à une température élevée de l'ordre de plusieurs centaines de degrés Celsius comme c'est le cas pour la transmission de mesures en provenance d'un coeur de réacteur nucléaire, il est alors impossible d'utiliser une telle enveloppe plastique intermédiaire et le problème de la protection microphonique du câble est alors totalement remis en cause.It is also known that such a cable exhibits what is called the microphonic effect when it is subjected even very weakly to the stresses generated by a vibratory regime. In fact, in this case, the relative slippages which exist between the three elements mentioned above, cause friction which generates electrical charges the larger the dielectric is more perfect. These charges create an electric field which by induction creates currents which are superimposed on the electrical signals which the cable is precisely responsible for conveying and disturbs in a sometimes unacceptable manner the safe reception of the signal to be transported. To combat this phenomenon, it has been envisaged to place between the dielectric 2 and the braid 3, an envelope made of plastic material charged with carbon which, being therefore semiconductor, limits the level of the electric charges generated and allows the flow of these Ci in the braid 3 with which it is in contact. This antimicrophonic protection in itself known, however, has the disadvantage that it does not overcome the electric charges induced by the friction phenomena developing between the core 1 and the dielectric 2; on the other hand, when it comes to making a coaxial cable working in the middle hostile with vibrations and in particular at a high temperature of the order of several hundred degrees Celsius as is the case for the transmission of measurements from a nuclear reactor core, it is then impossible to use such a intermediate plastic envelope and the problem of microphonic protection of the cable is then completely called into question.

D'une façon générale d'ailleurs, pour supporter des températures de plusieurs centaines de degrés centigrades, les câbles coaxiaux subissent une transformation concernant essentiellement leur diélectrique, lequel est alors constitué d'un certain nombre de perles en céramique à haute densité, généralement en alumine pure, enfilées sur l'âme du câble et recouvertes par une tresse extérieure en acier inoxydable. La fig. 1 représente un tel câble coaxial pour haute température d'un type connu en soi.In general, moreover, to withstand temperatures of several hundred degrees centigrade, the coaxial cables undergo a transformation essentially concerning their dielectric, which then consists of a number of high density ceramic beads, generally in pure alumina, strung on the core of the cable and covered by an outer stainless steel braid. Fig. 1 shows such a coaxial cable for high temperature of a type known per se.

Sur cette fig. 1, on a représenté un câble coaxial comportant une âme centrale 1 en acier inoxydable ou en cuivre recouvert d'acier inoxydable sur lequel sont enfilées des perles 2, en alumine pure, constituant le diélectrique. Comme on voit sur la fig. 1, les perles 2 ont de préférence la forme d'une portion de cylindre limitée par des surfaces d'extrémités respectivement convexes et concaves de façon à pouvoir s'emboîter parfaitement les unes dans les autres. La deuxième électrode de ce câble est constituée d'une tresse extérieure 3, également en acier inoxydable et pouvant comporter plusieurs couches.In this fig. 1, there is shown a coaxial cable comprising a central core 1 of stainless steel or copper covered with stainless steel on which beads 2, made of pure alumina, constituting the dielectric are strung. As seen in fig. 1, the pearls 2 preferably have the shape of a portion of a cylinder limited by respectively convex and concave end surfaces so as to be able to fit perfectly into each other. The second electrode of this cable consists of an outer braid 3, also made of stainless steel and which may comprise several layers.

Jusqu'à présent, de tels câbles qui de par leur constitution peuvent résister aux hautes températures, n'ont pas pu être munis de dispositifs antimicrophoniques.Until now, such cables which by their constitution can withstand high temperatures, have not been able to be fitted with antimicrophonic devices.

On a déjà envisagé, pour des câbles coaxiaux fonctionnant sous tension ou fréquence relativement élevées et utilisant l'air comme diélectrique d'éviter les phénomènes de décharge électrique par étincelles en revêtant partiellement les surfaces des corps d'espacement enfilés sur l'âme du câble en contact avec la tresse d'une couche de métal noble. C'est le cas par exemple des câbles coaxiaux faisant l'objet des brevets allemand n° 702 951 et britannique n° 397 081. Les solutions décrites dans ces brevets sont toutefois inapplicables pour obtenir l'effet antimicrophonique dans les conditions physiques rappelées ci-dessus, et ce pour les deux raisons suivantes :

  • a) les câbles en question sont à diélectrique à air, et les corps d'espacement prévus de place en place ne sont là que pour servir d'entretoise, maintenant l'âme du câble au centre de la tresse ; or, à haute température, et sous rayonnement l'air s'ionise, ce qui perturbe le fonctionnement du câble de façon inacceptable.
  • b) les surfaces en présence et susceptibles de frotter l'une sur l'autre ne sont métallisées que partiellement et, notamment, de façon discontinue entre l'âme et les différents corps d'espacement. Il en résulte que de telles structures ne permettent absolument pas de supprimer les nuisances dues à l'effet microphonique, en particulier lors des torsions du câble qui peuvent engendrer des frottements entre des portions de surfaces isolantes non revêtues et l'une des électrodes métalliques.
It has already been envisaged, for coaxial cables operating under relatively high voltage or frequency and using air as a dielectric, to avoid the phenomena of electrical discharge by sparks by partially coating the surfaces of the spacing bodies threaded on the core of the cable. in contact with the braid of a layer of noble metal. This is the case for example of coaxial cables making the subject of German patents No. 702 951 and British No. 397 081. The solutions described in these patents are however inapplicable to obtain the antimicrophonic effect under the physical conditions mentioned above, for the following two reasons:
  • a) the cables in question are air dielectric, and the spacers provided from place to place are only there to serve as a spacer, keeping the cable core in the center of the braid; however, at high temperature, and under radiation the air ionizes, which disturbs the functioning of the cable in an unacceptable way.
  • b) the surfaces present and likely to rub one on the other are only partially metallized and, in particular, discontinuously between the core and the different spacing bodies. As a result, such structures absolutely do not make it possible to eliminate the nuisances due to the microphonic effect, in particular during twists of the cable which can cause friction between portions of uncoated insulating surfaces and one of the metal electrodes.

La présente invention a précisément pour objet un câble coaxial antimicrophonique pouvant fonctionner en milieu hostile et notamment à haute température, sans présenter les inconvénients de l'art antérieur.The present invention specifically relates to an antimicrophonic coaxial cable which can operate in a hostile environment and in particular at high temperature, without having the drawbacks of the prior art.

Il se caractérise essentiellement en ce que toutes les parties des surfaces des éléments constituant le câble, en contact et pouvant avoir des mouvements relatifs entre elles, sont pourvues d'un revêtement métallique, ledit revêtement étant en particulier continu sur l'âme du câble.It is essentially characterized in that all the parts of the surfaces of the elements constituting the cable, in contact and capable of having relative movements between them, are provided with a metallic coating, said coating being in particular continuous on the core of the cable.

De cette façon en effet, les glissements ou frottements qui peuvent intervenir lorsqu'un tel câble subit des vibrations ou des contraintes mécaniques alternatives, n'engendrent pratiquement plus l'apparition de charges du type électrostatique ou du type piézoélectrique, puisque les glissements relatifs qui interviennent ont lieu entre les deux parties métalliques et non plus entre une partie métallique et un diélectrique et que l'âme est en quelque sorte protégée par une enveloppe métallique continue.In this way, in fact, the slippages or friction which can occur when such a cable undergoes vibrations or alternative mechanical stresses, practically no longer generate the appearance of charges of the electrostatic type or of the piezoelectric type, since the relative slips which occur between the two metal parts and no longer between a metal part and a dielectric and that the core is somehow protected by a continuous metallic envelope.

Dans des modes de mise en oeuvre de l'invention, le câble coaxial comporte également un certain nombre de pièces intercalaires métalliques enfilées sur l'âme et placées entre chacune des perles consécutives, ce qui lui confère une certaine souplesse complémentaire.In embodiments of the invention, the coaxial cable also includes a certain number of metallic intermediate pieces threaded on the core and placed between each of the consecutive beads, which gives it a certain complementary flexibility.

Selon la présente invention, le revêtement métallique des surfaces en frottement peut être réalisé de deux façons différentes.According to the present invention, the metallic coating of the friction surfaces can be produced in two different ways.

Dans un premier mode de mise en oeuvre, le revêtement métallique desdites surfaces est réalisé à l'aide d'un dépôt fait sur les parties de la surface de celles-ci qui sont en contact avec l'âme, la tresse et/ou les pièces intercalaires, ledit dépôt pouvant être par exemple constitué par un alliage de molybdène et de manganèse obtenu à partir d'une solution pulvérulente dans un solvant approprié que l'on laisse sécher et que l'on fixe par un traitement au four à haute température pour réaliser la combinaison de l'alliage avec les surfaces d'alumine des perles.In a first embodiment, the metallic coating of said surfaces is produced by means of a deposit made on the parts of the surface thereof which are in contact with the core, the braid and / or the intermediate pieces, said deposit possibly being constituted for example by an alloy of molybdenum and manganese obtained from a pulverulent solution in an appropriate solvent which is left to dry and which is fixed by a treatment at a high temperature oven to make the combination of the alloy with the alumina surfaces of the pearls.

Selon un second mode de réalisation de la présente invention, le revêtement métallique des surfaces en frottement est constitué par des bagues et des fourreaux métalliques que l'on sertit directement autour des perles ou que l'on rentre à force dans leur orifice central. Dans ce cas, une variante intéressante de l'invention consiste à utiliser lesdits fourreaux métalliques enfilés dε l'orifice central de chaque perle pour constituer en même temps les pièces intercalaires réalisant l'espacement voulu entre deux perles consécutives.According to a second embodiment of the present invention, the metallic coating of the friction surfaces consists of rings and metal sleeves which are crimped directly around the pearls or which are forced into their central orifice. In this case, an advantageous variant of the invention consists in using said metallic sheaths threaded dε the central orifice of each pearl to constitute at the same time the spacers making the desired spacing between two consecutive pearls.

De toute façon, l'invention sera mieux comprise en se référant aux exemples d'application décrits ci-après, et donnés à titre d'exemples non.limitatifs en se référant aux fig. 2 à 7 ci-jointes sur lesquelles :

  • - la fig. 2 représente un exemple de réalisation du premier mode de mise en oeuvre de l'invention selon lequel les perles de diélectrique sont recouvertes partiellement d'une couche métallique ;
  • - la fig. 3 représente une variante du même mode de mise en oeuvre ;
  • - la fig. 4 représente un exemple de réalisation du deuxième mode de mise en oeuvre de l'invention dans lequel les perles de matériaux diélectriques sont serties de bagues et de fourreaux métalliques ;
  • - la fig. 5 représente le détail d'une bague d'acier inoxydable ;
  • - la fig. 6 représente le détail d'un fourreau d'acier inoxydable utilisé dans le dispositif de la fig. 4 ;
  • - la fig. 7 représente une variante intéressante de l'invention dans laquelle manquent les pièces intercalaires.
In any case, the invention will be better understood by referring to the application examples described below, and given by way of non-limitative examples with reference to FIGS. 2 to 7 attached on which:
  • - fig. 2 shows an embodiment of the first embodiment of the invention according to which the dielectric beads are partially covered with a metallic layer;
  • - fig. 3 shows a variant of the same mode of implementation;
  • - fig. 4 shows an embodiment of the second embodiment of the invention in which the beads of dielectric materials are set with rings and metal sleeves;
  • - fig. 5 shows the detail of a stainless steel ring;
  • - fig. 6 shows the detail of a stainless steel sheath used in the device of FIG. 4;
  • - fig. 7 shows an interesting variant of the invention in which the intermediate pieces are missing.

Sur la fig. 2, on reconnait les principaux éléments déjà mentionnés sur la fig. 1 d'un câble coaxial destiné à travailler à haute température, les éléments correspondants portant les mêmes nombres de référence. Dans l'exemple particulier de la fig. 2, le câble comporte en outre des pièces intercalaires qui se composent de billes sphériques d'acier inoxydable 4 au nombre de deux entre deux perles consécutives 2 en alumine pure à haute densité munies d'un canal central 5. Selon l'invention, les surfaces latérales externes 6 et internes 7 ainsi que les portions hémisphériques 8 des trous d'entrée du canal 5, sont recouvertes d'une métallisation d'une épaisseur de 3/100è de mm d'un alliage de molybdène et de manganèse déposé en présence d'un masque de la façon suivante. Le mélange de molybdène et de manganèse est réalisé dans un solvant tel que le toluène ou le benzène en solution pulvérulente. Ce mélange est ensuite déposé au pinceau, au pistolet ou au pochoir sur les surfaces à recouvrir puis on le laisse sécher un quart d'heure environ jusqu'à évaporation complète du solvant. Ensuite, les perles ainsi traitées sont placées dans un four sous hydrogène humide et on élève la température jusqu'à 1500°C pour obtenir la combinaison de l'alliage avec l'allumine constitutif des perles. Pour un dépôt de l'ordre de 2 à 3/100è de mm, l'opération de combinaison de l'alliage avec l'alumine demande environ 45 minutes en moyenne. Le montage peut alors intervenir avec la perle ainsi traitée en prenant bien entendu les précautions d'usage pour conserver les isolements nécessaires entre les parties conductrices.In fig. 2, we recognize the main elements already mentioned in FIG. 1 of a coaxial cable intended to work at high temperature, the corresponding elements carrying the same reference numbers. In the particular example of FIG. 2, the cable further comprises intermediate pieces which consist of spherical stainless steel balls 4 two in number between two consecutive beads 2 of pure high density alumina provided with a central channel 5. According to the invention, external lateral 6 and internal 7 surfaces as well as the hemispherical portions 8 of the entry holes of channel 5, are covered with a metallization with a thickness of 3 / 100th of a mm of an alloy of molybdenum and manganese deposited in the presence of a mask as follows. The mixture of molybdenum and manganese is carried out in a solvent such as toluene or benzene in powder solution. This mixture is then deposited by brush, spray gun or stencil on the surfaces to be covered and then allowed to dry for about a quarter of an hour until the solvent has completely evaporated. Then, the pearls thus treated are placed in an oven under humid hydrogen and the temperature is raised to 1500 ° C. to obtain the combination of the alloy with the constituting allumine of the pearls. For a deposit of the order from 2 to 3 / 100th of mm, the operation of combining the alloy with alumina requires approximately 45 minutes on average. The assembly can then take place with the pearl thus treated, of course taking the usual precautions to maintain the necessary insulation between the conductive parts.

Dans certains cas il est utile de compléter le dépôt d'alliage molybdène-manganèse par un dépôt d'argent ou de tout autre métal suivant le même processus ; si un nettoyage de la surface des perles s'avère nécessaire on peut opérer par sablage à condition toutefois d'avoir au préalable masqué les parties conductrices métallisées. Dans l'exemple de mise en oeuvre représenté sur la fig. 2 et donné à titre non limitatif, les différents éléments constitutifs du câble coaxial ont les dimensions suivantes :

  • - L'âme est en acier inoxydable 18/8 et a un diamètre de 0,8 mm ;
  • - Le diélectrique constituant les perles 2 est de l'alumine pur à haute densité, le diamètre extérieur de chaque perle étant de 6 mm et le diamètre intérieur de 1 mm ;
  • - Les billes intercalaires 4 sont également en acier inoxydable 18/8 d'un diamètre de 3 mm et la gaine extérieure 3 est un tube annelé également en acier inoxydable 18/8 d'un diamètre extérieur de 8 mm.
In certain cases it is useful to supplement the deposit of molybdenum-manganese alloy by a deposit of silver or any other metal following the same process; if a cleaning of the surface of the pearls proves necessary, it is possible to operate by sandblasting provided, however, that the metallic conductive parts have been masked beforehand. In the example of implementation shown in FIG. 2 and given without implied limitation, the various constituent elements of the coaxial cable have the following dimensions:
  • - The core is made of 18/8 stainless steel and has a diameter of 0.8 mm;
  • - The dielectric constituting the beads 2 is pure alumina at high density, the outside diameter of each bead being 6 mm and the inside diameter of 1 mm;
  • - The intermediate balls 4 are also made of 18/8 stainless steel with a diameter of 3 mm and the outer sheath 3 is a corrugated tube also made of 18/8 stainless steel with an outside diameter of 8 mm.

Les billes d'acier 4 sont percées d'un orifice diamétral de diamètre 0,85 mm qui permet ainsi le passage de l'âme 1 et le positionnement des perles d'alumine 2 entre elles. Les dimensions des différentes pièces consécutives assurent une grande souplesse au câble sans provoquer, et ceci est très important, la moindre abrasion des portées des billes 4 sur les perles 2. On peut noter également que l'âme 1 ne touche pas les surfaces internes des perles d'alumine 2 ce qui limite encore le risque d'abrasion:The steel balls 4 are pierced with a diametrical orifice 0.85 mm in diameter which thus allows the passage of the core 1 and the positioning of the alumina beads 2 between them. The dimensions of the different consecutive pieces provide great flexibility to the cable without causing, and this is very important, the slightest abrasion of the bearing surfaces of the balls 4 on the beads 2. It may also be noted that the core 1 does not touch the internal surfaces of the alumina beads 2 which further limits the risk of abrasion:

Dans le mode de mise en oeuvre représenté sur la fig. 3 on retrouve également les éléments constitutifs principaux d'un câble coaxial selon l'invention et les éléments correspondants qui portent les mêmes nombres de référence que dans l'exemple précédent.In the embodiment shown in FIG. 3 there are also the main constituent elements of a coaxial cable according to the invention and the corresponding elements which carry the same numbers of reference as in the previous example.

Dans cet exemple toutefois, les pièces intercalaires 4 sont constituées par des petits cylindres 4 d'acier inoxydable percés selon leur axe d'un orifice permettant le passage de l'âme d'acier 1 et sont ainsi enfilés sur ladite âme 1 alternativement avec les perles 2. Dans ce mode de mise en oeuvre seuls les bords latéraux externe 6 et interne 7 ainsi que les portions de paroi 9 des perles 2 doivent être métallisés. Pour plus de souplesse dans l'assemblage, les bords 10 des cylindres intercalaires 4 ainsi que les bords externes 11 des perles 2 ont une forme arrondie ou hémisphérique, car la présence d'angles vifs détériorerait le revêtement métallique déposé sur le diélectrique 2. Les différentes conditions précédentes font que ni les pièces intercalaires 4, ni le tube annelé extérieur 3 ne viennent en contact avec la céramique constituant les perles 2. Dans ce mode de mise en oeuvre il peut parfois être souhaitable de diviser les éléments intercalaires 4 en deux parties pour donner plus de souplesse à l'ensemble du câble.In this example, however, the intermediate pieces 4 consist of small cylinders 4 of stainless steel pierced along their axis with an orifice allowing the passage of the steel core 1 and are thus threaded onto said core 1 alternately with the pearls 2. In this embodiment, only the external lateral 6 and internal 7 edges as well as the wall portions 9 of the pearls 2 must be metallized. For more flexibility in assembly, the edges 10 of the intermediate cylinders 4 as well as the outer edges 11 of the beads 2 have a rounded or hemispherical shape, since the presence of sharp angles would deteriorate the metal coating deposited on the dielectric 2. The different previous conditions mean that neither the intermediate pieces 4, nor the outer ringed tube 3 come into contact with the ceramic constituting the pearls 2. In this embodiment it may sometimes be desirable to divide the intermediate elements 4 into two parts to give more flexibility to the entire cable.

La fig. 4 montre une réalisation du deuxième mode de mise en oeuvre de l'invention dans lequel le revêtement métallique des perles 2 est constitué pour ce qui concerne la surface externe par une bague d'acier inoxydable 12 montée à chaud ou par tout autre moyen connu sur le diélectrique et représentée plus en détail sur la fig. 5 ; le revêtement métallique des orifices centraux ainsi que les pièces d'espacement 4 sont réalisés à l'aide de fourreaux 13 dont l'un d'entre eux est plus spécialement représenté sur la fig. 6, les fourreaux 13 étant constitués d'un cylindre d'acier inoxydable emmanché à force à très basse température (dans l'azote liquide par exemple) à l'intérieur des orifices centraux 5 des perles d'alumine 2. Les fourreaux 13 sont en acier inoxydable et emmanchés après le montage des bagues 12 ; ils sont percés de part en part selon leur axe d'un orifice 14 destiné au passage de l'âme en acier inoxydable 1 du câble coaxial (fig. 6).Fig. 4 shows an embodiment of the second embodiment of the invention in which the metallic coating of the pearls 2 is constituted, as regards the external surface, by a stainless steel ring 12 mounted hot or by any other known means on the dielectric and shown in more detail in FIG. 5; the metallic coating of the central orifices as well as the spacers 4 are produced using sleeves 13, one of which is more particularly shown in FIG. 6, the sleeves 13 being made of a stainless steel cylinder force-fitted at very low temperature (in liquid nitrogen for example) inside the central orifices 5 of the alumina beads 2. The sleeves 13 are made of stainless steel and fitted after fitting the rings 12; they are drilled right through along their axis with an orifice 14 intended for the passage of the stainless steel core 1 of the coaxial cable (fig. 6).

Dans la réalisation de la fig. 4, l'électrode externe 3 est également constituée par un tube annelé en acier inoxydable et chaque perle d'alumine 2 est un disque percé selon son axe d'un trou dont le diamètre est égal au diamètre extérieur des fourreaux d'acier 13.In the embodiment of FIG. 4, the electrode external 3 is also constituted by a ringed tube made of stainless steel and each alumina pearl 2 is a disc pierced along its axis with a hole whose diameter is equal to the external diameter of the steel sheaths 13.

La fig. 7 montre enfin une variante très intéressante de l'invention dans laquelle on parvient à améliorer encore les qualités électriques du câble tout en supprimant les pièces intercalaires. On parvient à ce résultat en donnant au diélectrique 2 la forme de billes sphériques ou(ellipsoidales) d'alumine qui sont métallisées sur toutes leurs portions de surface en contact avec l'âme 1 ou la tresse 2 en acier inoxydable ainsi que les perles voisines. Sur la fig. 7, on a représenté quatre perles 2 à 2d dont les deux premières 2a et 2b sur la partie gauche du dessin sont vues en coupe et dont les deux dernières 2c et 2d sur la partie droite, sont vues de face en élévation. Sur cette fig. 7 les parties métallisées sont représentées en 'traits renforcés. Cette configuration, plus facile à fabriquer car elle ne nécessite qu'un seul composant, offre, en plus de ses qualités antimicrophoniques l'intérêt de supprimer tout effet capacitif qui se produit d les autres variantes entre les faces extérieures métallisées des pièces intercalaires et la gaine métallique.Fig. 7 finally shows a very interesting variant of the invention in which we manage to further improve the electrical qualities of the cable while eliminating the intermediate parts. This is achieved by giving the dielectric 2 the form of spherical or (ellipsoidal) alumina balls which are metallized on all their surface portions in contact with the core 1 or the braid 2 of stainless steel as well as the neighboring pearls . In fig. 7, there are shown four beads 2 to 2d, the first two 2a and 2b on the left of the drawing are seen in section and the last two 2c and 2d on the right, are seen from the front in elevation. In this fig. 7 the metallized parts are shown in reinforced lines. This configuration, which is easier to manufacture since it requires only one component, offers, in addition to its antimicrophonic qualities, the advantage of eliminating any capacitive effect which occurs from the other variants between the metallized external faces of the spacers and the metallic sheath.

A titre d'exemple, un câble coaxial selon l'invention a fait l'objet d'un essai comparatif avec un câble de type connu tel que représenté sur la fig. 1 dans lequel les perles d'alumine n'avaient pas de protection métallique particulière sur leur partie de surface en liaison avec l'âme et la tresse externe. L'échantillon de câble était placé dans une enceinte blindée et fixée rigidement en deux points. Un dispositif mécanique imprimai- au câble un mouvement alternatif d'une amplitude de 4 mm doi la période était de 2 secondes. Les mesures, effectuées sur deux échantillons de câble, l'un selon l'art antérieur, l'autre selon l'invention, ont permis de constater une amplitude du signal piézoélectrique qui était de 3,4.10-12 ampère dans le premier cas et seulement de 2,4.10-14 ampère pour un câble coaxial du type antimicrophonique réalisé selon l'invention et conforme au mode de mise en oeuvre de la fig. 4.By way of example, a coaxial cable according to the invention has been the subject of a comparative test with a cable of known type as shown in FIG. 1 in which the alumina beads had no particular metallic protection on their surface part in connection with the core and the outer braid. The cable sample was placed in a shielded enclosure and rigidly fixed at two points. A mechanical device gave the cable an alternating movement with an amplitude of 4 mm, the period of which was 2 seconds. The measurements, carried out on two cable samples, one according to the prior art, the other according to the invention, made it possible to note an amplitude of the piezoelectric signal which was 3.4.10 -12 ampere in the first case and only 2,4.10 -14 ampere for a coaxial cable of the antimicrophonic type produced according to the invention and in accordance with the embodiment of FIG. 4.

Claims (6)

1. Câble coaxial antimicrophonique pouvant fonctionner en milieu hostile et notamment à haute température, du genre de ceux qui comprennent de façon connue entre l'âme et la tresse extérieure un diélectrique constitué de perles en céramique à haute densité enfilées sur l'âme du câble, caractérisé en ce que toutes les parties des surfaces des éléments constituant le câble, en contact et pouvant avoir des mouvements relatifs entre elles, sont pourvues d'un revêtement métallique, ledit revêtement étant en particulier continu sur l'âme du câble.1. Antimicrophonic coaxial cable capable of operating in a hostile environment and in particular at high temperature, of the type which includes in a known manner between the core and the outer braid a dielectric consisting of high density ceramic beads strung on the core of the cable , characterized in that all the parts of the surfaces of the elements constituting the cable, in contact and capable of having relative movements between them, are provided with a metallic coating, said coating being in particular continuous on the core of the cable. 2. Câble coaxial selon la revendication 1, caractérisé en ce que le revêtement métallique desdites surfaces est constitué d'un alliage de molybdène et de manganèse.2. Coaxial cable according to claim 1, characterized in that the metallic coating of said surfaces consists of an alloy of molybdenum and manganese. 3. Câble coaxial selon la revendication 1, caractérisé en ce que le revêtement métallique desdites surfaces est constitué de bagues et de fourreaux métalliques sertis sur lesdites perles.3. Coaxial cable according to claim 1, characterized in that the metal coating of said surfaces consists of rings and metal sleeves crimped on said beads. 4. Câble coaxial selon l'une quelconque des revendications 1 et 2, caractérisé en ce que les perles sont des billes d'alumine pure enfilées de façon jointive sur l'âme et métallisées sur leurs portions de surface en contact avec l'âme, la tresse extérieure et les perles voisines.4. Coaxial cable according to any one of claims 1 and 2, characterized in that the pearls are pure alumina balls strung contiguously over the core and metallized on their surface portions in contact with the core, the outer braid and the neighboring pearls. 5. Câble coaxial selon l'une quelconque des revendications 1 à 3, caractérisé en ce qu'il comporte un certain nombre de pièces intercalaires métalliques enfilées sur l'âme et placées entre chacune des perles consécutives.5. Coaxial cable according to any one of claims 1 to 3, characterized in that it comprises a certain number of metallic intermediate pieces threaded on the core and placed between each of the consecutive beads. 6. Câble coaxial selon les revendications 3 et 5, caractérisé en ce que lesdits fourreaux métalliques sont enfilés à force dans l'orifice central de chaque perle et constituent en même temps les pièces intercalaires.6. Coaxial cable according to claims 3 and 5, characterized in that said metal sleeves are force-fitted into the central orifice of each pearl and at the same time constitute the intermediate pieces.
EP19790400610 1978-09-08 1979-09-04 Anti-microphonic coaxial cable to function at a high temperature Expired EP0010461B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR7825844A FR2435787A1 (en) 1978-09-08 1978-09-08 ANTIMICROPHONIC COAXIAL CABLE THAT CAN OPERATE AT HIGH TEMPERATURE
FR7825844 1978-09-08

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EP0010461A1 true EP0010461A1 (en) 1980-04-30
EP0010461B1 EP0010461B1 (en) 1983-08-24

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003054891A1 (en) * 2001-12-20 2003-07-03 Koninklijke Philips Electronics N.V. Rf system for an mri apparatus, provided with bead-shaped spacers
CN100357747C (en) * 2004-03-22 2007-12-26 摩托罗拉公司 Flexible test cable

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB397081A (en) * 1932-05-10 1933-08-17 Telefunken Gmbh Improvements in or relating to electric cables for use for conveying radio and other very high frequency energy
DE702951C (en) * 1932-12-21 1941-02-20 Porzellanfabrik Kahla insulated high-frequency cables

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB397081A (en) * 1932-05-10 1933-08-17 Telefunken Gmbh Improvements in or relating to electric cables for use for conveying radio and other very high frequency energy
DE702951C (en) * 1932-12-21 1941-02-20 Porzellanfabrik Kahla insulated high-frequency cables

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003054891A1 (en) * 2001-12-20 2003-07-03 Koninklijke Philips Electronics N.V. Rf system for an mri apparatus, provided with bead-shaped spacers
CN100357747C (en) * 2004-03-22 2007-12-26 摩托罗拉公司 Flexible test cable
CN101067636B (en) * 2004-03-22 2010-08-18 摩托罗拉公司 Flexible test cable

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FR2435787A1 (en) 1980-04-04
EP0010461B1 (en) 1983-08-24
FR2435787B1 (en) 1981-11-06
DE2966090D1 (en) 1983-09-29

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