EP0027061B1 - Lightning arrester device allowing an external short-circuiting and corresponding protection assembly - Google Patents

Lightning arrester device allowing an external short-circuiting and corresponding protection assembly Download PDF

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Publication number
EP0027061B1
EP0027061B1 EP80400986A EP80400986A EP0027061B1 EP 0027061 B1 EP0027061 B1 EP 0027061B1 EP 80400986 A EP80400986 A EP 80400986A EP 80400986 A EP80400986 A EP 80400986A EP 0027061 B1 EP0027061 B1 EP 0027061B1
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EP
European Patent Office
Prior art keywords
external casing
elastic
fusible element
arrester
metal
Prior art date
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
EP80400986A
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German (de)
French (fr)
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EP0027061A1 (en
Inventor
Jacques Cholley
François Guichard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Industrielle de Tubes et Lampes Electriques Cie (CITEL)
CITEL SAS
Original Assignee
Industrielle de Tubes et Lampes Electriques Cie (CITEL)
CITEL SAS
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Publication date
Priority claimed from FR7924916A external-priority patent/FR2466854A1/en
Priority claimed from FR8012962A external-priority patent/FR2484695A1/en
Application filed by Industrielle de Tubes et Lampes Electriques Cie (CITEL), CITEL SAS filed Critical Industrielle de Tubes et Lampes Electriques Cie (CITEL)
Publication of EP0027061A1 publication Critical patent/EP0027061A1/en
Application granted granted Critical
Publication of EP0027061B1 publication Critical patent/EP0027061B1/en
Expired legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T4/00—Overvoltage arresters using spark gaps
    • H01T4/10—Overvoltage arresters using spark gaps having a single gap or a plurality of gaps in parallel
    • H01T4/12—Overvoltage arresters using spark gaps having a single gap or a plurality of gaps in parallel hermetically sealed
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T1/00—Details of spark gaps
    • H01T1/14—Means structurally associated with spark gap for protecting it against overload or for disconnecting it in case of failure

Definitions

  • the present invention relates to the production of a gas arrester intended in particular for the protection of electronic circuits against overvoltages.
  • the invention also relates to the production of protection assemblies using such lightning arresters.
  • gas surge arresters also known as spark gaps, surge protectors or voltage limiters
  • surge arresters of this type when they allow the flow of an amount of energy greater than a threshold, permanently short-circuit to ensure effective protection of the circuit to be protected; when the aforementioned energy threshold is exceeded, the energy being dissipated in the arrester, the latter heats up and its temperature can reach approximately 600 ° C.: it is therefore necessary to establish an important flow path thanks to when the lightning arrester is short-circuited (the resistance must then be less than 1 Q).
  • a surge arrester of this type is for example described in application FR-A-2 384 371: in such a surge arrester, the cylindrical outer envelope of the arrester is metallic and forms one of the electrodes; the other electrode is a metal rod arranged along the axis of said outer casing and mechanically connected thereto by an electrically insulating glass bead.
  • the corresponding arrester for example, in Figures 4 and 5 of this document consists of an outer casing which comprises, in a central part, a metal cylinder and, on either side thereof, two ceramic cylinders themselves terminated by metal end sleeves; each of the three metal parts of the outer envelope is connected to one of the terminals of the device; the outer casing carries an elastic member consisting of two metal strips electrically connected to the central metallic part of said outer casing; said strips are capable of coming into contact with the metal end sleeves and they are kept spaced from their short-circuit position by the interposition of a fusible material disposed at the base of the strips, between these strips and the central metal part of the envelope.
  • Such a lightning arrester is not reliable due to the fact that the fusible element supports a significant elastic force due to its positioning and tends to creep over time; in addition, any error in the dimensioning of the fusible element results in a much greater error in the spacing of the ends of the strips relative to the fixed electrode with which they must come to make a short circuit; it follows that there is an excessive imprecision on the value of the overvoltage which causes the short-circuit.
  • the mechanical resistance of the fusible element means that only a small elastic force remains to ensure the short-circuiting, so that this does not happen mentally.
  • the object of the present invention is to eliminate the drawbacks presented by lightning arresters with external short-circuiting of known types. More specifically, the purpose of the present invention is to describe a lightning arrester device with an external short-circuiting, the overall dimensions of which, although slightly larger than for the arresters with internal short-circuiting, nevertheless remain relatively reduced. Another object of the invention is to describe a lightning arrester device with an external short-circuit capable of being short-circuited for a precise value of overvoltage.
  • the device according to the invention can be used regardless of its orientation because the fuse element used ensures no contact after fusion, said fuse element acting only as a temporary hold as described in the state. of technique.
  • the resistance of the arrester according to the invention after its short-circuiting is of the order of 0.1 ohm, so that the damaged arrester cannot be the seat of a dangerous release of heat.
  • the present invention therefore has as an object a lightning arrester device for protecting a circuit against the effects of an overvoltage, said lightning arrester being constituted by an external envelope defining an enclosure containing an inert gas and forming a first electrode of the lightning arrester , said outer casing containing at least one metal rod forming another electrode and externally carrying at least one elastic metallic member, having, parallel to the outer casing, at least one elastic blade, a first zone of which rests on a fusible element disposed in the vicinity of an end of the outer envelope and carried by it, said first zone of said member being able to come by elasticity, when said fusible element is melted, in electrical contact with the (or one of) the metal rod (s) (s) mentioned above, and of which a second zone, opposite the first, is connected to a metal fixing ring tightened on the outer casing, characterized by the fact that the outer envelope is an entirely metallic cylinder, part of the rods forming another electrode projecting outside of said envelope and being connected to it by an insulator
  • the fusible element consists of an eutectic alloy or close to an eutectic; the metal alloy of the fusible element preferably has a melting point of between 65 ° C and 165 ° C.
  • a so-called "WOOD metal” alloy can be used, having a melting point of 70 ° C.
  • the outer casing is associated with a single other electrode and the elastic member comprises a single elastic strip resting, in its first zone, on the fusible element and connected, in its second zone, to the fixing ring.
  • the outer envelope is associated with two other electrodes and the two elastic members associated with said other electrodes constitute a single part carried by said outer casing, said single part comprising, on the one hand, a fixing ring tightened on the outer casing and, on the other hand, symmetrically on either side of this ring, two elastic blades each pressing on a fusible element carried by the outer casing.
  • the elastic member consists of a cut and folded sheet made of beryllium bronze or beryllium copper.
  • the dimensioning of the elastic member is provided so that said member allows without any difficulty the passage of energy, which must pass through the arrester in the event of a short-circuit, which is generally achieved by using a blade of a few millimeters in width and a few tenths of a millimeter in thickness.
  • the metal outer shell of the arrester according to the invention is advantageously made of nickel-plated steel and the rods forming the electrodes are advantageously made of an iron-nickel-cobalt alloy called "KOVAR" allowing the soldering of the glass bead which ensures the connection mechanical between the outer casing and the considered electrode.
  • KVAR iron-nickel-cobalt alloy
  • the fusible element is a patch, which is disposed between the outer casing and the elastic member, with which said patch is associated, and which is bonded to one of these two elements.
  • the fusible element has the form of a ring surrounding the outer envelope, said ring being centered on the metal sleeve which encloses the insulator by which the rod forming the electrode is maintained, with which the elastic member associated with said ring.
  • the fusible element is a ball welded or wedged between the elastic member and the outer casing.
  • the outer envelope of the arrester of a arrester device has been designated by 1; this outer casing consists of a metal cylinder having a bottom 1a in the central area of which there is an outer rod 1b which constitutes the first surge arrester terminal.
  • the outer casing 1 is connected by a solder 2 to a sleeve 3 made of an iron-nickel-cobalt alloy called "KOVAR".
  • the sleeve 3 is engaged in the outer casing 1 until it bears against a shoulder 4.
  • a rod 5 is arranged, which projects outside the arrester and the end of which 5a constitutes the second electrode of the arrester, this second electrode being opposite the bottom 1 inside the outer casing 1.
  • the rod 5 is connected to the sleeve 3 by a glass bead 6 and it is produced in the same metal as the machon 3.
  • the glass bead 6 constitutes a plug, which isolates from the outside the zone of the envelope 1 where the electrode 5a is disposed, this zone constituting an enclosure, where there is a rare gas , such as argon, under reduced pressure; into the atmosphere of this enclosure, a material is introduced intended to reduce the starting voltage of the arrester.
  • the arrester which has just been described is well known in the state of the art and corresponds to the embodiments of FIGS. 1 and 3.
  • the elastic member 7 comprises a ring 7a, which elastically encloses the outer envelope and which, if desired, can be connected to it by a soldering point after its installation.
  • the ring 7a is integral with an elastic blade 7b, the end of which which is opposite to the blade 7a, is folded at right angles to form a return 7c.
  • the elastic member 7 is made of beryllium bronze by cutting and folding a sheet of 0.2 mm thick; in the example described, the outer casing 1 and its sleeve 3 have an axial length of approximately 15 mm, the ring 7a has an axial length of approximately 5 mm, the elastic blade 7b has a length of approximately 9 mm and the 7c square return has a length about 3 mm; the width of the strip 7b and of the square return 7c is 2 mm and the diameter of the arrester is approximately 5 mm.
  • a fusible element 8 which consists of a square patch with a side of 2 mm and a millimeter in thickness.
  • This patch can be glued to the face of the elastic blade 7b, which faces the envelope 1, in order to ensure easy installation. Due to the elasticity of the blade 7b, the pad 8 is applied against the outer casing 1 and the end of the square return 7c is then, as shown in Figure 1, about 1 mm from the rod 5 If the arrester is subjected to an overvoltage, an arc is established between the electrode 5a and the outer envelope 1 of the arrester and this arc causes the outer envelope 1 to heat up.
  • the nature of the metal from which the patch 8 is made is made, as a function of the energy threshold that the surge arrester must allow to pass without short-circuiting.
  • FIG. 3 represents another embodiment of the arrester device according to the invention; in this embodiment, the surge arrester itself is identical to that which has been described for FIG. 1, that is to say that all the elements bearing references between 1 and 6 inclusive are the same as for the embodiment of Figure 1.
  • the elastic member of the arrester is also the same as the elastic member 7 shown in Figures 1 and 2. The only difference comes from the particular embodiment of the fusible element, which is associated with the elastic blade 7b of the member 7.
  • the fuse element designated by 18 is constituted by a metal ring disposed around the projecting part of the sleeve 3.
  • the ring 18 comes to bear against the shoulder that constitutes the border of the cylindrical lateral wall of the envelope 1 and the ring 18 is held against this border by the return at right angles 7c to the elastic member 7.
  • the elastic member 7 is put in place on the outer casing 1, positioning it so that the angle return 7c maintains the ring 18 in position.
  • the operation of this embodiment is the same as that which has been described for the embodiment of FIG. 1, the fusion of the ring 18 causing the arrester to short-circuit by contact between the return angle 7c and rod 5.
  • FIGS. 4 and 5 which illustrate another variant of the preferred embodiment of the invention, it can be seen that the outer casing of the arrester of the device according to the invention has been designated by 21; said outer casing consists of a metal cylinder which, at each of its former rémity t, is connected by a solder 22 to a sleeve 23 made of an iron-nickel-cobalt alloy called "KOVAR".
  • the sleeve 23 is engaged in the outer casing 21 until it bears against a shoulder 24.
  • each of the sleeves 23 is arranged a rod 251, 252 which projects outside the arrester; the ends 251a, 252a of the two rods 251 and 252 respectively constitute the two electrodes inside the external envelope 21.
  • the two rods 251 and 252 are each connected to their sleeve 23 by a glass bead 26; they are made of the same metal as the sleeves 23.
  • the glass bead 26 constitutes a plug, which isolates from the outside the zone of the envelope 21, where the electrodes 251 a and 252a are arranged, this zone constituting an enclosure where there is a rare gas, such as argon, under reduced pressure; into the atmosphere of this enclosure, a material is introduced intended to reduce the starting voltage of the arrester.
  • the arrester which has just been described, is well known in the state of the art.
  • a metal part designated by 27 as a whole has been put in place.
  • the part 27 comprises, in its central zone, a ring 27a, which elastically encloses the outer envelope 21 and which, if desired, can be connected to it by a weld point after its installation.
  • On either side of the ring 27a are two elastic members 271 and 272 symmetrical with respect to the ring 27a; each of these elastic members 271 and 272 consists of an elastic blade 271 b and 272b respectively, each elastic blade having its end, which is opposite to the ring 27a, folded at right angles to constitute in return 271e c and 272c respectively.
  • Piece 27 is made of beryllium bronze by cutting and folding a sheet of 0.2 mm thick; in the example described, the outer casing 21 and its sleeves 23 have an axial length of 16 mm, the ring 27a has an axial length of approximately 5 mm, the elastic blades 271b and 272b have a length of approximately 6 mm and the square returns 271c and 272c have a length of about 3 mm; the width of the blades 271 b and 272b and the corresponding square returns is 2 mm and the diameter of the arrester is approximately 6 mm.
  • a fusible element 28 which consists of a square patch with a side of 2 mm and a thickness of 1 mm. This patch can be glued to the faces of the elastic blades 271b and 272b which are opposite the envelope 21, in order to ensure easy installation. Due to the elasticity of the blades 271 b and 272b, the pellets 28 are applied against the outer casing 21 and the ends of the angled returns 271 c and 272c are then, as shown in Figure 4, about 1 mm rods 251 and 252 respectively.
  • an arc is established inside the arrester between this electrode and the outer casing 1 and this arc causes the outer casing 21 to heat up.
  • the temperature from the outer casing 21 rises sufficiently, the melting point of the metal of which the pellets 28 are made is reached; the pellets 28 melt and the elastic blades 271 b and 272b approach the envelope 21 due to their elasticity; in this movement the ends of the square returns 271 c and 272c come into contact with the rods 251 and 252 respectively, which simultaneously puts the two electrodes of the arrester in short circuit.
  • this simultaneous short-circuiting of the two electrodes 251 and 252 is particularly advantageous because, usually, on three-pole surge arresters having an internal short-circuiting, only the electrode which is subjected to the overvoltage short-circuits the outer envelope, the other electrode keeping a high ignition voltage; it follows that, in the prior art, the surge arrester becomes asymmetrical which is often harmful to the protected circuit. On the contrary, the three-pole arrester according to the invention, which has just been described, allows the simultaneous short-circuiting of the two electrodes with the outer casing.
  • the nature of the metal from which the chip 28 is made is chosen, as a function of the energy threshold that the arrester must allow to pass without short-circuiting.

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Description

La présente invention a trait à la réalisation d'un parafoudre à gaz destiné notamment à la protection des circuits électroniques contre les surtensions. L'invention a également trait à la réalisation d'ensembles de protection mettant en oeuvre de tels parafoudres.The present invention relates to the production of a gas arrester intended in particular for the protection of electronic circuits against overvoltages. The invention also relates to the production of protection assemblies using such lightning arresters.

On sait que les parafoudres à gaz, encore dénommés éclateurs, para-surtensions ou limiteurs de tension, sont particulièrement utilisés pour la protection des installations téléphoniques et l'on impose que les parafoudres de ce type, lorsqu'ils permettent l'écoulement d'une quantité d'énergie supérieure à un seuil, se mettent définitivement en court-circuit pour assurer une protection efficace du circuit à protéger; lorsque le seuil d'énergie précité est dépassé, l'énergie étant dissipée dans le parafoudre, celui-ci, s'échauffe et sa température peut atteindre 600°C environ: il est donc nécessaire d'établir une voie d'écoulement importante grâce à la mise en court-circuit du parafoudre (la résistance devant être alors inférieure à 1 Q). Bien entendu, lorsqu'un parafoudre a été ainsi mis en court-circuit, il est nécessaire, pour remettre l'installation en état, de changer ledit parafoudre mais ce remplacement ne représente qu'un inconvénient mineur par rapport à la détérioration, qui serait intervenue, si les circuits à protéger avaient subi l'effet de la surtension, qui a provoqué la mise en court-circuit dudit parafoudre. Un parafoudre de ce type est par exemple décrit dans la demande FR-A-2 384 371 : dans un tel parafoudre, l'enveloppe extérieure cylindrique du parafoudre est métallique et forme l'une des électrodes; l'autre électrode est une tige métallique disposée selon l'axe de ladite enveloppe extérieure et mécaniquement reliée à celle-ci par une perle de verre électriquement isolante.It is known that gas surge arresters, also known as spark gaps, surge protectors or voltage limiters, are particularly used for the protection of telephone installations and it is imposed that surge arresters of this type, when they allow the flow of an amount of energy greater than a threshold, permanently short-circuit to ensure effective protection of the circuit to be protected; when the aforementioned energy threshold is exceeded, the energy being dissipated in the arrester, the latter heats up and its temperature can reach approximately 600 ° C.: it is therefore necessary to establish an important flow path thanks to when the lightning arrester is short-circuited (the resistance must then be less than 1 Q). Of course, when a surge arrester has thus been short-circuited, it is necessary, in order to restore the installation to repair, to change said surge arrester, but this replacement represents only a minor drawback in relation to the deterioration, which would be intervened, if the circuits to be protected had suffered the effect of the overvoltage, which caused the shortening of said surge arrester. A surge arrester of this type is for example described in application FR-A-2 384 371: in such a surge arrester, the cylindrical outer envelope of the arrester is metallic and forms one of the electrodes; the other electrode is a metal rod arranged along the axis of said outer casing and mechanically connected thereto by an electrically insulating glass bead.

Certaines législations prévoient que la mise en court-circuit d'un parafoudre doit s'effectuer à l'intérieur du parafoudre: ce type de mise en court-circuit a l'avantage de ne donner lieu à aucun phénomène à l'extérieur du parafoudre mais il comporte deux gros inconvénients. En effet, en premier lieu, si les conditions réelles d'utilisation viennent à être différentes de celle prévue par les normes, ce qui peut être fréquent, le parafoudre reste extérieurement intact mais intérieurement détérioré et il ne correspond plus aux normes imposées, de sorte qu'il est susceptible, par exemple, de provoquer le passage d'un arc entre ses électrodes pour des tensions considérées comme normales sur un réseau téléphonique en fonctionnement, ou de n'amorcer que pour des tensions très élevées et donc de ne plus protéger le réseau. On risque donc ainsi d'avoir, dans des installations comportant des parafoudres, des parafoudres hors- normes, qui créent des perturbations de fonctionnement importantes mais difficilement repérables. C'est la raison pour laquelle on souhaite que la détérioration d'un parafoudre se traduise par une mise en court-circuit franche, pour que la ligne correspondante soit facilement repérable. En second lieu, lorsqu'un parafoudre à mise en court-circuit intérieure est détérioré, sa résistance chute à une valeur faible mais non nulle (quelques ohms par exemple): il en résulte que, si après détérioration il est traversé par un courant, il constitue une résistance chauffante, dont le dégagement thermique est susceptible d'être dangereux. Dans le cas des parafoudres tripolaires, il convient d'ajouter qu'il est très difficile, voir impossible, d'avoir un parafoudre en court-circuit sur les trois électrodes (en effet, seules deux électrodes sur trois sont en court-circuit).Some legislations stipulate that the short-circuiting of a surge arrester must be done inside the surge arrester: this type of short-circuiting has the advantage of not giving rise to any phenomenon outside the surge arrester but it has two major drawbacks. Firstly, if the actual conditions of use come to be different from that provided for by the standards, which can be frequent, the arrester remains externally intact but internally deteriorated and it no longer corresponds to the standards imposed, so that it is likely, for example, to cause an arc to pass between its electrodes for voltages considered normal on a working telephone network, or to strike only for very high voltages and therefore to no longer protect the network. There is therefore a risk of having, in installations comprising surge arresters, non-standard surge arresters, which create significant operating disturbances which are difficult to identify. This is the reason why it is desired that the deterioration of a surge arrester translate into a frank short-circuiting, so that the corresponding line is easily identifiable. Secondly, when a surge arrester with internal short-circuit is damaged, its resistance drops to a low but not zero value (a few ohms for example): it follows that, if after deterioration it is crossed by a current, it constitutes a heating resistance, the thermal release of which is likely to be dangerous. In the case of three-pole surge arresters, it should be added that it is very difficult, if not impossible, to have a surge arrester short-circuited on the three electrodes (indeed, only two electrodes out of three are short-circuited) .

Pour éviter les inconvénients précités, certaines législations prévoient, au contraire, d'imposer une mise en court-circuit extérieure des parafoudres; dans ce cas, la structure interne du parafoudre n'est pas modifiée lors du passage d'une surtension correspondant à une mise en court-circuit. Un dispositif de ce type a déjà été décrit dans le brevet US-A-4 034 326; le parafoudre correspondant, par exemple, aux figures 4 et 5 de ce document est constitué d'une enveloppe extérieure qui comporte, dans une partie centrale, un cylindre métallique et, de part et d'autre de celui-ci, deux cylindres de céramique eux-mêmes terminés par des manchons d'extrémité métalliques; chacune des trois parties métalliques de l'enveloppe extérieure est reliée à l'une des bornes de l'appareil; l'enveloppe extérieure porte un organe élastique constitué de deux lamelles métalliques reliées électriquement à la partie centrale métallique de ladite enveloppe extérieure; lesdites lamelles sont susceptibles de venir faire contact avec les manchons métalliques d'extrémité et elles sont maintenues écartées de leur position de court-circuit par interposition d'un matériau fusible disposé à la base des lamelles, entre ces lamelles et la partie centrale métallique de l'enveloppe. Un tel dispositif parafoudre n'est pas fiable en raison du fait que l'élément fusible supporte un effort élastique important en raison de son positionnement et a tendance à fluer au cours du temps; de plus, toute erreur sur le dimensionnement de l'élément fusible se traduit par une erreur beaucoup plus importante sur l'écartement des extrémités des lamelles par rapport à l'électrode fixe avec laquelle elles doivent venir faire court-circuit; il en résulte qu'il y a une imprécision excessive sur la valeur de la surtension qui provoque le court-circuit. En outre, dans ce dispositif, au moment de la fusion de l'élément fusible, la résistance mécanique de l'élément fusible fait qu'il ne reste qu'une faible force élastique pour assurer la mise en court-circuit, de sorte que celle-ci ne se produit pas de façon franche.To avoid the aforementioned drawbacks, certain legislations provide, on the contrary, for imposing an external short-circuiting of the surge arresters; in this case, the internal structure of the arrester is not modified during the passage of an overvoltage corresponding to a short-circuiting. A device of this type has already been described in patent US-A-4,034,326; the corresponding arrester, for example, in Figures 4 and 5 of this document consists of an outer casing which comprises, in a central part, a metal cylinder and, on either side thereof, two ceramic cylinders themselves terminated by metal end sleeves; each of the three metal parts of the outer envelope is connected to one of the terminals of the device; the outer casing carries an elastic member consisting of two metal strips electrically connected to the central metallic part of said outer casing; said strips are capable of coming into contact with the metal end sleeves and they are kept spaced from their short-circuit position by the interposition of a fusible material disposed at the base of the strips, between these strips and the central metal part of the envelope. Such a lightning arrester is not reliable due to the fact that the fusible element supports a significant elastic force due to its positioning and tends to creep over time; in addition, any error in the dimensioning of the fusible element results in a much greater error in the spacing of the ends of the strips relative to the fixed electrode with which they must come to make a short circuit; it follows that there is an excessive imprecision on the value of the overvoltage which causes the short-circuit. In addition, in this device, at the time of the melting of the fusible element, the mechanical resistance of the fusible element means that only a small elastic force remains to ensure the short-circuiting, so that this does not happen frankly.

On a également décrit dans le brevet français 2 351 520, un autre type de parafoudre à mise en court-circuit extérieure; notamment, dans la réalisation correspondant à la figure 5, on retrouve une structure voisine de celle définie dans le brevet US-A-4 034 326 c'est-à-dire que le parafoudre est constitué d'une enveloppe extérieure qui porte extérieurement des lamelles élastiques; cependant, pour éviter l'inconvénient provenant du calage des lamelles élastiques dans une zone voisine de leur base, on a proposé dans la demande FR-A-2 351 520, d'utiliser des anneaux de calage mis en place au voisinage des extrémités des lamelles; il était dès lors obligatoire que ces anneaux de calage fusibles ne réalisant pas en permamence un court-circuit entre les électrodes et l'enveloppe extérieure: c'est la raison pour laquelle lesdits anneaux fusibles sont constitués d'une substance diélectrique qui repose sur une zone de l'enveloppe extérieure réalisée en verre ou en céramique. Il en résulte qu'en cas de surtension, l'échauffement généré à l'intérieur d'un tel parafoudre se transmet très mal vers l'élément fusible en raison de la nature même des matériaux utilisés et, en outre, l'anneau fusible n'a pas une fusion franche. En cas de surtension, il se produit donc, avec retard, une fusion pâteuse de l'élément fusible, ce qui permet un affaissement progressif des cales que constituent les anneaux fusibles; de la sorte, par des échauffements successifs dont chacun de devrait pas produire une mise en court-circuit du parafroudre, on peut réaliser un cumul d'affaissements, ce qui amène finalement entre le manchon central et le manchon d'extrémité, un court-circuit, intermittent ou non, mais, en tout cas, non franc. Ce court-circuit peut d'ailleurs se produire au moment d'un échauffement légèrement inférieur à la surtension-seuil dès lors qu'il y a eu antérieurement des affaissements successifs des anneaux fusibles. On constate donc que la parafoudre décrit dans FR-A-2 351 520 ne permet pas une mise en court-circuit fiable pour une valeur précise de surtension.Another type of arrester with external short-circuiting has also been described in French patent 2,351,520; especially in the embodiment corresponding to FIG. 5, there is a structure close to that defined in patent US-A-4 034 326, that is to say that the arrester consists of an external envelope which carries elastic lamellae on the outside; however, to avoid the drawback arising from the wedging of the elastic lamellae in an area close to their base, it has been proposed in application FR-A-2 351 520, to use wedging rings placed in the vicinity of the ends of the slats; it was therefore compulsory that these fusible setting rings did not permanently produce a short circuit between the electrodes and the outer casing: this is the reason why said fusible rings consist of a dielectric substance which rests on a outer envelope area made of glass or ceramic. As a result, in the event of an overvoltage, the heating generated inside such a surge arrester is very poorly transmitted to the fusible element due to the very nature of the materials used and, moreover, the fusible ring does not have a straightforward merger. In the event of an overvoltage, a pasty melting of the fusible element therefore occurs with delay, which allows a progressive collapse of the shims which constitute the fusible rings; in this way, by successive overheating, each of which should not produce a short-circuiting of the surge arrester, it is possible to achieve a plurality of sags, which ultimately leads, between the central sleeve and the end sleeve, to a short- circuit, intermittent or not, but in any case not frank. This short circuit can moreover occur at the time of a heating slightly lower than the threshold overvoltage since there have previously been successive collapses of the fusible rings. It can therefore be seen that the arrester described in FR-A-2 351 520 does not allow reliable short-circuiting for a precise value of overvoltage.

La présente invention a pour but de faire disparaître les inconvénients présentés par les dispositifs parafoudres à mise en court-circuit extérieure de types connus. Plus précisément, la présente invention a pour but de décrire un dispositif parafoudre à mise en court-circuit extérieure, dont l'encombrement, quoique légèrement plus important que pour les parafoudres à mise en court-circuit intérieure, reste néanmoins relativement réduit. Un autre but de l'invention est de décrire un dispositif parafoudre à mise en court-circuit extérieure susceptible de se mettre en court-circuit pour une valeur précise de surtension. De plus, le dispositif selon l'invention, peut être utilisé quelle que soit son orientation car l'élément fusible mis en oeuvre n'assure après fusion aucun contact, ledit élément fusible jouant uniquement un rôle de cale provisoire comme décrit dans l'état de la technique. La résistance du parafoudre selon l'invention après sa mise en court-circuit est de l'ordre de 0,1 ohm, de sorte que le parafoudre détérioré ne peut être le siège d'un dégagement de chaleur dangereux.The object of the present invention is to eliminate the drawbacks presented by lightning arresters with external short-circuiting of known types. More specifically, the purpose of the present invention is to describe a lightning arrester device with an external short-circuiting, the overall dimensions of which, although slightly larger than for the arresters with internal short-circuiting, nevertheless remain relatively reduced. Another object of the invention is to describe a lightning arrester device with an external short-circuit capable of being short-circuited for a precise value of overvoltage. In addition, the device according to the invention can be used regardless of its orientation because the fuse element used ensures no contact after fusion, said fuse element acting only as a temporary hold as described in the state. of technique. The resistance of the arrester according to the invention after its short-circuiting is of the order of 0.1 ohm, so that the damaged arrester cannot be the seat of a dangerous release of heat.

La présente invention a, en conséquence, pour objet, un dispositif parafoudre destiné à protéger un circuit contre les effets d'une surtension, ledit parafoudre étant constitué d'une enveloppe extérieure définissant une enceinte contenant un gaz inerte et formant une première électrode du parafoudre, ladite enveloppe extérieure renfermant au moins une tige métallique formant une autre électrode et portant extérieurement au moins un organe métallique élastique, ayant, parallèle à l'enveloppe extérieure, au moins une lame élastique dont une première zone s'appuie sur un élément fusible disposé au voisinage d'une extrémité de l'enveloppe extérieure et porté par elle, ladite première zone dudit organe pouvant venir par élasticité, quand ledit élément fusible est fondu, en contact électrique avec la (ou l'une des) tige(s) métallique(s) précitée(s), et dont une deuxième zone, opposée à la première, se raccorde à une bague de fixation métallique serrée sur l'enveloppe extérieure, caractérisé par pe fait que l'enveloppe extérieure est un cylindre entièrement métallique, une partie des tiges formant une autre électrode faisant saillie à l'extérieure de ladite enveloppe et lui étant reliée par un isolant disposé annulairement entre l'enveloppe et la tige, et que, pour obtenir une bonne précision de la surtension de mise en court-circuit, d'une part, l'élément fusible est constitué d'un alliage métallique électriquement et thermiquement conducteur à fusion franche et, d'autre part, l'extrémité de la lame de l'organe élastique est pliée en équerre en direction de la tige formant électrode correspondante.The present invention therefore has as an object a lightning arrester device for protecting a circuit against the effects of an overvoltage, said lightning arrester being constituted by an external envelope defining an enclosure containing an inert gas and forming a first electrode of the lightning arrester , said outer casing containing at least one metal rod forming another electrode and externally carrying at least one elastic metallic member, having, parallel to the outer casing, at least one elastic blade, a first zone of which rests on a fusible element disposed in the vicinity of an end of the outer envelope and carried by it, said first zone of said member being able to come by elasticity, when said fusible element is melted, in electrical contact with the (or one of) the metal rod (s) (s) mentioned above, and of which a second zone, opposite the first, is connected to a metal fixing ring tightened on the outer casing, characterized by the fact that the outer envelope is an entirely metallic cylinder, part of the rods forming another electrode projecting outside of said envelope and being connected to it by an insulator annularly disposed between the envelope and the rod, and that , to obtain a good accuracy of the short-circuit overvoltage, on the one hand, the fusible element consists of an electrically and thermally conductive metallic alloy with free fusion and, on the other hand, the end of the blade of the elastic member is bent at right angles to the rod forming the corresponding electrode.

Dans un mode préféré de réalisation, l'élément fusible est constitué d'un alliage eutectique ou voisin d'un eutectique; l'alliage métallique de l'élément fusible a, de préférence, un point de fusion compris entre 65°C et 165°C. On peut utiliser un alliage dit "métal de WOOD", ayant un point de fusion de 70°C et constitué de 50% de bismuth, 25% de plomb, 12,5% d'étain et 12,5% de cadmium; on peut aussi utiliser un alliage dit "de LICHTENBERG" qui fond à environ 100°C et qui est constitué de 50% de bismuth, 20% d'étain et 30% de plomb, ou un alliage qui fond à 140°C et qui est constitué de 58% de bismuth et 42% d'étain, ou encore un alliage qui fond à 240°C environ et qui est constitué de 95% d'étain et 5% d'antimoine, tous les pourcentages ci-dessus indiqués étant des pourcentages en poids.In a preferred embodiment, the fusible element consists of an eutectic alloy or close to an eutectic; the metal alloy of the fusible element preferably has a melting point of between 65 ° C and 165 ° C. A so-called "WOOD metal" alloy can be used, having a melting point of 70 ° C. and consisting of 50% bismuth, 25% lead, 12.5% tin and 12.5% cadmium; one can also use an alloy called "LICHTENBERG" which melts at around 100 ° C and which consists of 50% bismuth, 20% tin and 30% lead, or an alloy which melts at 140 ° C and which consists of 58% bismuth and 42% tin, or an alloy that melts at about 240 ° C and which consists of 95% tin and 5% antimony, all of the above percentages being percentages by weight.

Dans une première variante, l'enveloppe extérieure est associée à une seule autre électrode et l'organe élastique comporte une seule lame élastique s'appuyant, dans sa première zone, sur l'élément fusible et raccordée, dans sa deuxième zone, à la bague de fixation.In a first variant, the outer casing is associated with a single other electrode and the elastic member comprises a single elastic strip resting, in its first zone, on the fusible element and connected, in its second zone, to the fixing ring.

Dans une deuxième variante, l'enveloppe extérieure est associée à deux autres électrodes et les deux organes élastiques associés auxdites autres électrodes constituent une seule pièce portée par ladite enveloppe extérieure, ladite pièce unique comportant, d'une part, une bague de fixation serrée sur l'enveloppe extérieure et, d'autre par, symétriquement de part et d'autre de cette bague, deux lames élastiques appuyant chacune sur un élément fusible porté par l'enveloppe extérieure.In a second variant, the outer envelope is associated with two other electrodes and the two elastic members associated with said other electrodes constitute a single part carried by said outer casing, said single part comprising, on the one hand, a fixing ring tightened on the outer casing and, on the other hand, symmetrically on either side of this ring, two elastic blades each pressing on a fusible element carried by the outer casing.

De façon avantageuse, l'organe élastique est constitué d'une tôle découpée et pliée réalisée en bronze au béryllium ou en cuivre au béryllium. Le dimensionnement de l'organe élastique est prévu de façon que ledit organe permette sans aucune difficulté le passage de l'énergie, qui doit traverser le parafoudre en cas de mise en court-circuit, ce qui est généralement réalisé en utilisant une lame de quelques millimètres de largeur et de quelques dixièmes de millimètres d'épaisseur.Advantageously, the elastic member consists of a cut and folded sheet made of beryllium bronze or beryllium copper. The dimensioning of the elastic member is provided so that said member allows without any difficulty the passage of energy, which must pass through the arrester in the event of a short-circuit, which is generally achieved by using a blade of a few millimeters in width and a few tenths of a millimeter in thickness.

L'enveloppe extérieure métallique du parafoudre selon l'invention est avantageusement réalisée en acier nickelé et les tiges formant les électrodes sont avantageusement constituées en un alliage fer-nickel-cobalt dit "KOVAR" permettant la soudure de la perle de verre qui assure la liaison mécanique entre l'enveloppe extérieure et l'électrode considérée.The metal outer shell of the arrester according to the invention is advantageously made of nickel-plated steel and the rods forming the electrodes are advantageously made of an iron-nickel-cobalt alloy called "KOVAR" allowing the soldering of the glass bead which ensures the connection mechanical between the outer casing and the considered electrode.

Selon un premier mode de réalisation, l'élément fusible est une pastille, qui est disposée entre l'enveloppe extérieure et l'organe élastique, auquel est associée ladite pastille, et qui est collée à l'un de ces deux éléments. Dans un deuxième mode de réalisation, l'élément fusible a la forme d'un anneau entourant l'enveloppe extérieure, ledit anneau étant centré sur le manchon métallique qui renferme l'isolant grâce auquel est maintenue la tige formant électrode, avec laquelle coopère l'organe élastique associé audit anneau. Dans un troisième mode de réalisation, l'élément fusible est une bille soudée ou calée entre l'organe élastique et l'enveloppe extérieure.According to a first embodiment, the fusible element is a patch, which is disposed between the outer casing and the elastic member, with which said patch is associated, and which is bonded to one of these two elements. In a second embodiment, the fusible element has the form of a ring surrounding the outer envelope, said ring being centered on the metal sleeve which encloses the insulator by which the rod forming the electrode is maintained, with which the elastic member associated with said ring. In a third embodiment, the fusible element is a ball welded or wedged between the elastic member and the outer casing.

Pour mieux faire comprendre l'objet de l'invention, on va en décrire maintenant, à titre d'exemples purement illustratifs et non limitatifs, plusieurs modes de réalisation représentés sur le dessin annexé.To better understand the object of the invention, we will now describe, by way of purely illustrative and nonlimiting examples, several embodiments shown in the accompanying drawing.

Sur ce dessin:

  • - la figure 1 représente, en coupe axiale, un dispositif selon le premier mode de réalisation de l'invention, dans lequel le parafoudre comporte une seule électrode et l'élément fusible est constitué d'une pastille métallique;
  • - la figure 2 représente, en perspective, l'organe élastique du dispositif de la figure 1;
  • - la figure 3 représente, en coupe axiale, un autre mode de réalisation du dispositif selon le premier mode de réalisation de l'invention dans lequel l'élément fusible est constitué d'un anneau métallique, l'organe élastique et le parafoudre étant les mêmes que ceux représentés pour le dispositif de la figure 1 ;
  • - la figure 4 représente, en coupe axiale, un dispositif selon l'invention comportant un parafoudre tripolaire ayant une enveloppe extérieure métallique et deux électrodes symétriques, l'élément fusible associé à chaque électrode étant une pastille métallique;
  • - la figure 5 représente, en perspective, l'organe élastique du parafoudre de la figure 4;
On this drawing:
  • - Figure 1 shows, in axial section, a device according to the first embodiment of the invention, in which the arrester comprises a single electrode and the fusible element consists of a metal pad;
  • - Figure 2 shows, in perspective, the elastic member of the device of Figure 1;
  • - Figure 3 shows, in axial section, another embodiment of the device according to the first embodiment of the invention in which the fusible element consists of a metal ring, the elastic member and the arrester being the same as those shown for the device of Figure 1;
  • - Figure 4 shows, in axial section, a device according to the invention comprising a three-pole arrester having a metal outer casing and two symmetrical electrodes, the fuse element associated with each electrode being a metal pad;
  • - Figure 5 shows, in perspective, the elastic member of the arrester of Figure 4;

En se référant au dessin, et plus particulièrement à la figure 1, on voit que l'on a désigné par 1 l'enveloppe extérieure du parafoudre d'un dispositif parafoudre selon l'invention; cette enveloppe extérieure est constituée d'un cylindre métallique comportant un fond 1 a dans la zone centrale duquel se trouve une tige extérieure 1b qui constitue la première borne de parafoudre. A son extrémité opposée au fond 1a, l'enveloppe extérieure 1 est reliée par une brasure 2 à un manchon 3 réalisé en un alliage fer-nickel-cobalt dit "KOVAR". Le manchon 3 est engagé dans l'enveloppe extérieure 1 jusqu'à mise en appui contre un épaulement 4. Selon l'axe du manchon 3 est disposée une tige 5, qui fait saillie à l'extérieure du parafoudre et dont l'extrémité 5a constitue la deuxième électrode du parafoudre, cette deuxième électrode étant en vis-à-vis du fond 1 a l'intérieur de l'enveloppe extérieure 1. La tige 5 est reliée au manchon 3 par une perle de verre 6 et elle est réalisée dans le même métal que le machon 3. La perle de verre 6 constitue un bouchon, qui isole de l'extérieur la zone de l'enveloppe 1 où est disposée l'électrode 5a, cette zone constituant une enceinte, où se trouve un gaz rare, tel que l'argon, sous pression réduite; dans l'atmosphère de cette enceinte, on introduit un matériau destiné à réduire la tension d'amorçage du parafoudre. Le parafoudre qui vient d'être décrit est bien connu dans l'état de la technique et correspond aux réalisations des figures 1 et 3.Referring to the drawing, and more particularly to FIG. 1, it can be seen that the outer envelope of the arrester of a arrester device according to the invention has been designated by 1; this outer casing consists of a metal cylinder having a bottom 1a in the central area of which there is an outer rod 1b which constitutes the first surge arrester terminal. At its end opposite the bottom 1a, the outer casing 1 is connected by a solder 2 to a sleeve 3 made of an iron-nickel-cobalt alloy called "KOVAR". The sleeve 3 is engaged in the outer casing 1 until it bears against a shoulder 4. According to the axis of the sleeve 3, a rod 5 is arranged, which projects outside the arrester and the end of which 5a constitutes the second electrode of the arrester, this second electrode being opposite the bottom 1 inside the outer casing 1. The rod 5 is connected to the sleeve 3 by a glass bead 6 and it is produced in the same metal as the machon 3. The glass bead 6 constitutes a plug, which isolates from the outside the zone of the envelope 1 where the electrode 5a is disposed, this zone constituting an enclosure, where there is a rare gas , such as argon, under reduced pressure; into the atmosphere of this enclosure, a material is introduced intended to reduce the starting voltage of the arrester. The arrester which has just been described is well known in the state of the art and corresponds to the embodiments of FIGS. 1 and 3.

Dans la réalisation de la figure 1, on voit que, sur l'enveloppe extérieure 1, on a mis en place un organe élastique conducteur désigné par 7 dans son ensemble. L'organe élastique 7 comporte une bague 7a, qui enserre élastiquement l'enveloppe extérieure et qui, si on le désire, peut y être reliée par un point de soudure après sa mise en place. La bague 7a est solidaire d'une lame élastique 7b, dont l'extrémité qui est opposée à la lame 7a, est repliée en équerre pour constituer un retour 7c. L'organe élastique 7 est réalisé en bronze au béryllium par découpage et pliage d'une tôle de 0,2 mm d'épaisseur; dans l'exemple décrit, l'enveloppe extérieure 1 et son manchon 3 ont une longueur axiale d'environ 15 mm, la bague 7a a une longueur axiale d'environ 5 mm, la lame élastique 7b a une longueur d'environ 9 mm et le retour en équerre 7c a une longueur d'environ 3 mm; la largeur de la lame 7b et du retour en équerre 7c est de 2 mm et le diamètre du parafoudre est d'environ 5 mm.In the embodiment of FIG. 1, it can be seen that, on the outer envelope 1, an elastic conducting member designated by 7 as a whole has been put in place. The elastic member 7 comprises a ring 7a, which elastically encloses the outer envelope and which, if desired, can be connected to it by a soldering point after its installation. The ring 7a is integral with an elastic blade 7b, the end of which which is opposite to the blade 7a, is folded at right angles to form a return 7c. The elastic member 7 is made of beryllium bronze by cutting and folding a sheet of 0.2 mm thick; in the example described, the outer casing 1 and its sleeve 3 have an axial length of approximately 15 mm, the ring 7a has an axial length of approximately 5 mm, the elastic blade 7b has a length of approximately 9 mm and the 7c square return has a length about 3 mm; the width of the strip 7b and of the square return 7c is 2 mm and the diameter of the arrester is approximately 5 mm.

Entre la lame élastique 7b et la paroi cylindrique de l'enveloppe extérieure 1 du parafoudre, on dispose un élément fusible 8, qui est constitué d'une pastille carrée de 2 mm de côté et d'un millimètre d'épaisseur. Cette pastille peut être collée sur la face de la lame élastique 7b, qui est en vis-à-vis de l'enveloppe 1, afin d'assurer une mise en place facile. En raison de l'élasticité de la lame 7b, la pastille 8 est appliquée contre l'enveloppe extérieure 1 et l'extrémité du retour en équerre 7c se trouve alors, comme indiqué sur la figure 1, à environ 1 mm de la tige 5. Si le parafoudre est soumis à une surtension, un arc s'établit entre l'électrode 5a et l'enveloppe extérieure 1 du parafoudre et cet arc provoque un échauffement de l'enveloppe extérieure 1. Lorsque la température de l'enveloppe extérieure 1 s'élève suffisamment, on atteint le point de fusion du métal, dont est constituée la pastille 8 et, dans ce cas, la pastille 8 fond et la lame élastique 7b se rapproche de l'enveloppe 1 en raison de son élasticité; dans ce mouvement, l'extrémité du retour en équerre 7c vient en contact avec la tige 5, ce qui met en court-circuit le parafoudre.Between the elastic strip 7b and the cylindrical wall of the outer casing 1 of the arrester, there is a fusible element 8, which consists of a square patch with a side of 2 mm and a millimeter in thickness. This patch can be glued to the face of the elastic blade 7b, which faces the envelope 1, in order to ensure easy installation. Due to the elasticity of the blade 7b, the pad 8 is applied against the outer casing 1 and the end of the square return 7c is then, as shown in Figure 1, about 1 mm from the rod 5 If the arrester is subjected to an overvoltage, an arc is established between the electrode 5a and the outer envelope 1 of the arrester and this arc causes the outer envelope 1 to heat up. When the temperature of the outer envelope 1 rises sufficiently, the melting point of the metal of which the pellet 8 is made is reached and, in this case, the pellet 8 melts and the elastic blade 7b approaches the casing 1 due to its elasticity; in this movement, the end of the square return 7c comes into contact with the rod 5, which short-circuits the arrester.

Bien entendu, con choisit la nature du métal, dont est constituée la pastille 8, en fonction du seuil d'énergie que le dispositif parafoudre doit laisser passer sans se mettre en court-circuit. On pourra, par exemple, utiliser pour réaliser la pastille 8 un alliage fondant à 100°C et constitué de 50% en poids de bismuth, 20% en poids d'étain et 30% en poids de plomb.Of course, con chooses the nature of the metal from which the patch 8 is made, as a function of the energy threshold that the surge arrester must allow to pass without short-circuiting. We can, for example, use to make the pellet 8 an alloy melting at 100 ° C and consisting of 50% by weight of bismuth, 20% by weight of tin and 30% by weight of lead.

La figure 3 représente un autre mode de réalisation du dispositif parafoudre selon l'invention; dans ce mode de réalisation, le parafoudre proprement dit est identique à celui qui a été décrit pour la figure 1, c'est-à-dire que tous les éléments portant des références comprises entre 1 et 6 inclusivement sont les mêmes que pour la réalisation de la figure 1. L'organe élastique du parafoudre est également le même que l'organe élastique 7 représenté sur les figures 1 et 2. La seule différence provient de la réalisation particulière de l'élément fusible, qui est associé à la lame élastique 7b de l'organe 7. En effet, sur la figure 3, l'élément fusible désigné par 18 est constitué par un anneau métallique disposé autour de la partie saillante du manchon 3. L'anneau 18 vient en appui contre l'épaulement que constitue la bordure de la paroi latérale cylindrique de l'enveloppe 1 et l'anneau 18 est maintenu contre cette bordure par le retour en équerre 7c de l'organe élastique 7. En d'autres termes, après avoir positionné l'anneau 18 sur le manchon 3, on met en place l'organe élastique 7 sur l'enveloppe extérieure 1, en le positionnant de façon que le retour en équerre 7c maintienne l'anneau 18 en position. Le fonctionnement de ce mode de réalisation est le même que celui qui a été décrit pour le mode de réalisation de la figure 1, la fusion de l'anneau 18 provoquant la mise en court-circuit du parafoudre par contact entre le retour en équerre 7c et la tige 5.FIG. 3 represents another embodiment of the arrester device according to the invention; in this embodiment, the surge arrester itself is identical to that which has been described for FIG. 1, that is to say that all the elements bearing references between 1 and 6 inclusive are the same as for the embodiment of Figure 1. The elastic member of the arrester is also the same as the elastic member 7 shown in Figures 1 and 2. The only difference comes from the particular embodiment of the fusible element, which is associated with the elastic blade 7b of the member 7. In fact, in FIG. 3, the fuse element designated by 18 is constituted by a metal ring disposed around the projecting part of the sleeve 3. The ring 18 comes to bear against the shoulder that constitutes the border of the cylindrical lateral wall of the envelope 1 and the ring 18 is held against this border by the return at right angles 7c to the elastic member 7. In other words, after having positioned the ring 18 on the sleeve 3, the elastic member 7 is put in place on the outer casing 1, positioning it so that the angle return 7c maintains the ring 18 in position. The operation of this embodiment is the same as that which has been described for the embodiment of FIG. 1, the fusion of the ring 18 causing the arrester to short-circuit by contact between the return angle 7c and rod 5.

En se référant maintenant aux figures 4 et 5, qui illustrent une autre variante du mode préféré de réalisation de l'invention, on voit que l'on a désigné par 21 l'enveloppe extérieure du parafoudre du dispositif selon l'invention; cette enveloppe extérieure est constituée d'un cylindre métallique qui, à chacune de ses ex- trémités, est relié par une brasure 22 à un manchon 23 réalisé en un alliage fer-nickel-cobalt dit "KOVAR". Le manchon 23 est engagé dans l'enveloppe extérieure 21 jusqu'à mise en appui contre un épaulement 24. Selon l'axe de chacun des manchons 23 est disposée une tige 251, 252 qui fait saillie à l'extérieur du parafoudre; les extrémités 251a, 252a des deux tiges 251 et 252 respectivement constituent les deux électrodes à l'intérieur de l'enveloppe extérieure 21. Les deux tiges 251 et 252 sont reliées chacune à leur manchon 23 par une perle de verre 26; elles sont réalisées dans le même métal que les manchons 23. La perle de verre 26 constitue un bouchon, qui isole de l'extérieur la zone de l'enveloppe 21, où sont disposées les électrodes 251 a et 252a, cette zone constituant une enceinte où se trouve un gaz rare, tel que l'argon, sous pression réduite; dans l'atmosphère de cette enceinte, on introduit un matériau destiné à réduire la tension d'amorçage du parafoudre. Le parafoudre, qui vient d'être décrit, est bien connu dans l'état de la technique.Referring now to FIGS. 4 and 5, which illustrate another variant of the preferred embodiment of the invention, it can be seen that the outer casing of the arrester of the device according to the invention has been designated by 21; said outer casing consists of a metal cylinder which, at each of its former rémités t, is connected by a solder 22 to a sleeve 23 made of an iron-nickel-cobalt alloy called "KOVAR". The sleeve 23 is engaged in the outer casing 21 until it bears against a shoulder 24. According to the axis of each of the sleeves 23 is arranged a rod 251, 252 which projects outside the arrester; the ends 251a, 252a of the two rods 251 and 252 respectively constitute the two electrodes inside the external envelope 21. The two rods 251 and 252 are each connected to their sleeve 23 by a glass bead 26; they are made of the same metal as the sleeves 23. The glass bead 26 constitutes a plug, which isolates from the outside the zone of the envelope 21, where the electrodes 251 a and 252a are arranged, this zone constituting an enclosure where there is a rare gas, such as argon, under reduced pressure; into the atmosphere of this enclosure, a material is introduced intended to reduce the starting voltage of the arrester. The arrester, which has just been described, is well known in the state of the art.

Dans cette réalisation, on voit que sur l'enveloppe extérieure 21, on a mis en place une pièce métallique désignée par 27 dans son ensemble. La pièce 27 comporte, dans sa zone centrale, une bague 27a, qui enserre élastiquement l'enveloppe extérieure 21 et qui, si on le désire, peut y être reliée par un point de soudure après sa mise en place. De part et d'autre de la bague 27a se trouvent deux organes élastiques 271 et 272 symétriques par rapport à la bague 27a; chacun de ces organes élastiques 271 et 272 est constitué d'une lame élastique 271 b et 272b respectivement, chaque lame élastique ayant son extrémité, qui est opposée à la bague 27a, repliée en équerre pour constituer en retour 271e c et 272c respectivement. La pièce 27 est réalisée en bronze au béryllium par découpage et pliage d'une tôle de 0,2 mm d'épaisseur; dans l'exemple décrit, l'enveloppe extérieure 21 et ses manchons 23 ont une longueur axiale de 16 mm, la bague 27a a une longueur axiale d'environ 5 mm, les lames élastiques 271b et 272b ont une longueur d'environ 6 mm et les retours en équerre 271c et 272c ont une longueur d'environ 3 mm; la largeur des lames 271 b et 272b et des retours en équerre correspondants est de 2 mm et le diamètre du parafoudre est d'environ 6 mm.In this embodiment, it can be seen that on the outer casing 21, a metal part designated by 27 as a whole has been put in place. The part 27 comprises, in its central zone, a ring 27a, which elastically encloses the outer envelope 21 and which, if desired, can be connected to it by a weld point after its installation. On either side of the ring 27a are two elastic members 271 and 272 symmetrical with respect to the ring 27a; each of these elastic members 271 and 272 consists of an elastic blade 271 b and 272b respectively, each elastic blade having its end, which is opposite to the ring 27a, folded at right angles to constitute in return 271e c and 272c respectively. Piece 27 is made of beryllium bronze by cutting and folding a sheet of 0.2 mm thick; in the example described, the outer casing 21 and its sleeves 23 have an axial length of 16 mm, the ring 27a has an axial length of approximately 5 mm, the elastic blades 271b and 272b have a length of approximately 6 mm and the square returns 271c and 272c have a length of about 3 mm; the width of the blades 271 b and 272b and the corresponding square returns is 2 mm and the diameter of the arrester is approximately 6 mm.

Entre chacune des lames élastiques 271 b et 272b et la paroi cylindrique de l'enveloppe extérieure 21 du parafoudre, un dispose un élément fusible 28, qui est constitué d'une pastille carrée de 2 mm de côté et de 1 mm d'épaisseur. Cette pastille peut être collée sur les faces des lames élastiques 271b et 272b qui sont en vis-à-vis de l'enveloppe 21, afin d'assurer une mise en place facile. En raison de l'élasticité des lames 271 b et 272b, les pastilles 28 sont appliquées contre l'enveloppe extérieure 21 et les extrémités des retours en équerre 271 c et 272c se trouvent alors, comme indiqué sur la figure 4, à environ 1 mm des tiges 251 et 252 respectivement. Si l'une des électrodes du parafoudre est soumise à une surtension, un arc s'établit à l'intérieur du parafoudre entre cette électrode et l'enveloppe extérieure 1 et cet arc provoque en échauffement de l'enveloppe extérieure 21. Lorsque la température de l'enveloppe extérieure 21 s'élève suffisamment, on atteint le point de fusion du métal, dont sont constituées les pastilles 28; les pastilles 28 fondent et les lames élastiques 271 b et 272b se rapprochent de l'enveloppe 21 en raison de leur élasticité; dans ce mouvement les extrémités des retours en équerre 271 c et 272c viennent en contact avec les tiges 251 et 252 respectivement, ce qui met simultanément les deux électrodes du parafoudre en court-circuit.Between each of the elastic blades 271 b and 272b and the cylindrical wall of the outer casing 21 of the arrester, one has a fusible element 28, which consists of a square patch with a side of 2 mm and a thickness of 1 mm. This patch can be glued to the faces of the elastic blades 271b and 272b which are opposite the envelope 21, in order to ensure easy installation. Due to the elasticity of the blades 271 b and 272b, the pellets 28 are applied against the outer casing 21 and the ends of the angled returns 271 c and 272c are then, as shown in Figure 4, about 1 mm rods 251 and 252 respectively. If one of the electrodes of the arrester is subjected to an overvoltage, an arc is established inside the arrester between this electrode and the outer casing 1 and this arc causes the outer casing 21 to heat up. When the temperature from the outer casing 21 rises sufficiently, the melting point of the metal of which the pellets 28 are made is reached; the pellets 28 melt and the elastic blades 271 b and 272b approach the envelope 21 due to their elasticity; in this movement the ends of the square returns 271 c and 272c come into contact with the rods 251 and 252 respectively, which simultaneously puts the two electrodes of the arrester in short circuit.

Il convient d'indiquer que cette mise en court-circuit simultanée des deux électrodes 251 et 252 est particulièrement intéressante car, habituellement, sur les parafoudres tripolaires comportant une mise en court-circuit interne, seule l'électrode qui est soumise à la surtension se met en court-circuit avec l'enveloppe extérieure, l'autre électrode gardant une tension d'amorçage élevée; il en résulte que, dans l'état de la technique, le parafoudre devient dissymétrique ce qui est souvent nuisible au circuit protégé. Au contraire, le parafoudre tripolaire selon l'invention, qui vient d'être décrit, permet la mise en court-circuit simultanée des deux électrodes avec l'enveloppe extérieure.It should be noted that this simultaneous short-circuiting of the two electrodes 251 and 252 is particularly advantageous because, usually, on three-pole surge arresters having an internal short-circuiting, only the electrode which is subjected to the overvoltage short-circuits the outer envelope, the other electrode keeping a high ignition voltage; it follows that, in the prior art, the surge arrester becomes asymmetrical which is often harmful to the protected circuit. On the contrary, the three-pole arrester according to the invention, which has just been described, allows the simultaneous short-circuiting of the two electrodes with the outer casing.

Bien entendu, on choisit la nature du métal, dont est constituée la pastille 28, en fonction du seuil d'énergie que le parafoudre doit laisser passer sans se mettre en court-circuit. On pourra, par exemple, utiliser pour réaliser la pastille 28 un alliage fondant à 100°C et constitué de 50% en poids de bismuth, 20% en poids d'étain et 30% en poids de plomb.Of course, the nature of the metal from which the chip 28 is made is chosen, as a function of the energy threshold that the arrester must allow to pass without short-circuiting. We could, for example, use to make the pellet 28 an alloy melting at 100 ° C and consisting of 50% by weight of bismuth, 20% by weight of tin and 30% by weight of lead.

Claims (9)

1. An overvoltage protection device intended to protect a circuit against the effects of an excess voltage, the said overvoltage protection device being constituted by an external casing defining an enclosure containing an inert gas and forming a first electrode of the overvoltage protection device, the said external casing enclosing at least one metal pin forming another electrode and carrying externally at least one elastic metal device having, parallel to the external casing at least one elastic strip a first zone of which is bearing on a fusible element disposed near one end of the external casing and carried by it, the said first zone of the said device being capable of coming into electric contact by its elasticity when the said fusible element has fused with the (or one of the) above mentioned metal pin (or pins) and a second zone of which, on the opposite side from the first is connected to a metal fixing ring tightly fitted on the external casing, characterised in that, [in the known way], the external casing (1, 21) is a cylinder entirely made of metal, one part of the pins forming another electrode (5, 251, 252) projecting outside from the said casing (1, 21) and being joined thereto by an insulator (6, 26) disposed annularly between casing (1, 21) and the pin (5, 251, 252) and in that, to obtain a good accuracy in the excess voltage producing the short circuit, the fusible element (8, 18, 28) is, on the one hand, constituted of a metal alloy which is an electric and thermal conductor with proper fusion and on the other hand, the end of the strip of the elastic device (7, 27) [comprises at least one elastic strip which has a portion (7b, 271b-272b) substantially parallel to the external casing (2, 21) and whose end (7c, 271 c, 272c)] is folded at right angles towards the pin forming the corresponding electrode (5, 251-252).
2. A device according to Claim 1, characterised in that the fusible element (8, 18, 28) is constituted by a eutectic alloy or approximating to a eutectic alloy.
3. A device according to one of Claims 1 or 2, characterised in that the metallic alloy of the fusible element (8, 18, 28) has a melting point comprised between 65°C and 165°C.
4. A device according to one of Claims 1 to 3, characterised in that the external casing (1) is associated with another single electrode (5) amd that the elastic device (7) comprises a single elastic strip bearing in its first zone on the fusible element (8) and joined in its second zone to the fixing ring (7a).
5. A device according to one of Claims 1 to 3, characterised in that the external casing (21) is associated with two other electrodes (251-252) and that the two elastic devices joined to the said other electrodes (251-252) constitute a single component (27) carried by the said external casing, the said single component (27) comprising a fixing ring (27a) tightly fitted on the external casing (21) and, symmetrically on either side of this ring, two elastic strips (271-272), each bearing on a fusible element (28) carried by the external casing (21).
6. A device according to one of Claims 1 to 5, characterised in that the elastic device (7, 27) is constituted by a cut-out and folded sheet made of beryllium bronze or of beryllium copper.
7. A device according to one of Claims 1 to 6, characterised in that the fusible element is a pellet (8, 28) which is disposed between the external casing (1,21) and the elastic device (7, 27) wherewith the said pellet (8, 28) is associated and which is bonded to one of these two elements.
8. A device according to one of Claims 1 to 6, characterised in that the fusible element has the shape of a ring (18) surrounding the external casing (1), the said ring (18) being centred on the metallic sleeve (3) which encloses the insulator (6) by means of which the pin forming the electrode (5) is held, wherewith there co-operates the elastic device (7) associated with the said ring (18).
9. A device according to one of Claims 1 to 6, characterised in that the fusible element is a ball soldered or wedged between the elastic device (7) and the external casing (1, 21).
EP80400986A 1979-10-05 1980-06-30 Lightning arrester device allowing an external short-circuiting and corresponding protection assembly Expired EP0027061B1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
FR7924916A FR2466854A1 (en) 1979-10-05 1979-10-05 Gas filled lightning arrester with external short-circuit - imposed by spring conductor making contact with electrode after melting of spacer
FR7924916 1979-10-05
FR8012962 1980-06-11
FR8012962A FR2484695A1 (en) 1980-06-11 1980-06-11 Gas filled lightning arrester with external short-circuit - imposed by spring conductor making contact with electrode after melting of spacer

Publications (2)

Publication Number Publication Date
EP0027061A1 EP0027061A1 (en) 1981-04-15
EP0027061B1 true EP0027061B1 (en) 1984-10-10

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BR (1) BR8006402A (en)
DE (1) DE3069411D1 (en)

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US4538201A (en) * 1983-05-02 1985-08-27 International Standard Electric Corporation Surge protector
EP0308553A1 (en) * 1987-09-24 1989-03-29 Semitron Industries Limited Transient suppressor device assembly
JPH0227694U (en) * 1988-08-10 1990-02-22
KR0144463B1 (en) * 1988-10-26 1998-07-15 오오가 노리오 A magnetic disk apparatus
GB2230900A (en) * 1989-04-24 1990-10-31 Semitron Cricklade Ltd Electrical components
FR2659504B1 (en) * 1990-03-09 1994-07-08 Sofycom SAFETY RECEPTACLE FOR TELEPHONE LINE PROTECTION PROTECTOR.
JP3676610B2 (en) * 1999-03-16 2005-07-27 炳霖 ▲楊▼ Chipless surge absorber for converting and absorbing surge energy by dielectric breakdown of air chamber and method for manufacturing the same
ES2491365B1 (en) * 2013-02-04 2015-02-12 Ricardo SEGU CAMPS PROTECTION METHOD FOR ELECTRICAL DEVICES AND PROTECTED ELECTRONIC DEVICE
CN113393987A (en) * 2021-06-03 2021-09-14 中国电力科学研究院有限公司 Arrester core body with insulating layer, arrester body and multi-column parallel arrester

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EP0027061A1 (en) 1981-04-15
DE3069411D1 (en) 1984-11-15

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