EP0075471B1 - Traversée électrique et méthode de fabrication de celle-ci - Google Patents

Traversée électrique et méthode de fabrication de celle-ci Download PDF

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Publication number
EP0075471B1
EP0075471B1 EP82304933A EP82304933A EP0075471B1 EP 0075471 B1 EP0075471 B1 EP 0075471B1 EP 82304933 A EP82304933 A EP 82304933A EP 82304933 A EP82304933 A EP 82304933A EP 0075471 B1 EP0075471 B1 EP 0075471B1
Authority
EP
European Patent Office
Prior art keywords
layer
stress
bushing
conductor
insulation layer
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
EP82304933A
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German (de)
English (en)
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EP0075471A1 (fr
Inventor
Joel Leigh Fritsche
William Trevor Link
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.)
Raychem Corp
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Raychem Corp
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Filing date
Publication date
Application filed by Raychem Corp filed Critical Raychem Corp
Priority to AT82304933T priority Critical patent/ATE18823T1/de
Publication of EP0075471A1 publication Critical patent/EP0075471A1/fr
Application granted granted Critical
Publication of EP0075471B1 publication Critical patent/EP0075471B1/fr
Expired legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B17/00—Insulators or insulating bodies characterised by their form
    • H01B17/26—Lead-in insulators; Lead-through insulators
    • H01B17/28—Capacitor type

Definitions

  • This invention relates to an electrical bushing and to a method of manufacturing such electrical bushing.
  • Electrical bushings are used to conduct high voltage electrical power safely from a power line into an electrical apparatus such as switchgear or transformers.
  • the metal housing of such electrical equipment is an electrical ground and must be insulated from the high voltage power being conducted into the electrical equipment, generally through an opening in the housing.
  • Electrical bushings provide, as minimum features, a conductor for high voltage power, insulation means and means for mounting the bushing in electrical equipment.
  • Electrical bushings frequently comprise an electrical conductor surrounded by metal cylinders of decreasing length at predetermined spacings from the conductor.
  • the spacings between the conductor and the innermost cylinder and between each cylinder are filled with insulation material.
  • insulation material can be of phenolic impregnated paper, cast epoxy or polyester or resin.
  • Such bushings are difficult to manufacture as the insulation must be void-free. This is difficult to achieve and can involve casting of the insulation material under vacuum conditions.
  • Other electrical bushings comprise an electrical conductor, a first layer of insulation surrounding the conductor, a ground plane and a stress-grading material surrounding the insulation, a flange for mounting the bushing to the electrical equipment or apparatus with which it is to be used and an outer insulating layer.
  • the stress-grading material can extend a predetermined distance from the ground plane.
  • the insulation of the first layer can be, for example, a cured epoxy resin, or the like.
  • a typical bushing of this type is disclosed in U.S. Patent No. 3 646 251 to Friedrich. It is important that the insulation layer, the interface between the insulation and stress grading material, and the interface between the insulation and the conductor be void-free.
  • U.S. Patent No. 3 312 776 discloses a bushing in which resinous insulation material is cast around a stress shield and the conductor, the conductor being encompassed by a metallic braid.
  • an electrical bushing comprising:
  • an electrical bushing comprising the steps of:
  • This invention thus provides an electrical bushing and a method of manufacture thereof utilising void-free insulation without the need for casting a void-free layer of epoxy, or similar resin on an electrical conductor. Furthermore, the electrical connection and the mechanical connection of the bushing to the electrical apparatus are separated.
  • the electrical bushing of this invention can be used in high voltage applications of up to about 69 kilovolts, typically of 15, 35 or 69 kilovolts.
  • the electrical conductor of the bushing can be a metal cylinder, either solid or hollow, capable of carrying electric current.
  • the conductor is preferably of copper or other highly conductive metal such as aluminium, silver plated copper and the like.
  • the electric conductor is adapted for use with switchgear, transformers and the like. Use of the bushing permits high voltage electric power to be conducted through the grounded metal casing of such electrical apparatus.
  • the electric conductor of the bushing is provided with suitable termination means to permit it to be connected to the incoming power line and to the electric circuit of the electrical apparatus with which it is used.
  • the conductor can be provided at one end with a flattened terminal plate to which the power line can be bolted.
  • the other end of the conductor can be in the shape of a plug to be inserted into a mating socket in the electrical apparatus.
  • the means used for connecting the conductor to the power supply and to the electrical circuit of the equipment is not critical and any convenient means can be used.
  • the first insulation layer is positioned over an intermediate length, for example a central region, of the electrical conductor so as to leave the end regions uninsulated, i.e. not covered by the first layer of insulation.
  • the first layer of insulation can be resilient or non-resilient, and may comprise a layer of void-free thermoplastic, preferably polymeric, material.
  • void-free is meant material that is relatively free of voids and contains essentially no voids greater than about 0.007 inch (0.018 cms), preferably none greater than about 0.005 inch (0.013 cms).
  • the material of the first layer should have a dielectric strength of at least 200 Volts/mil (78 kilovolts/cm) and preferably at least 300 volts/mil (118 kilovolts/cm).
  • the material when it is polymeric, it can be, for example, polyethylene, ethylene-propylene copolymer or ethylene or propylene-diene terpolymers, polyacrylates, silicone polymers and epoxy resins.
  • the polymer can contain the usual additives, such as stabilisers, antioxidants, anti-tracking agents and the like.
  • compositions for use as high voltage insulating material are described in U.S. Patents Nos. 4,001,128 to Penneck, 4,100,089 to Cammack, 4,189,392 to Penneck and 4,219,607 to Cammack et al, and U.K. Patents Nos. 1,337,951 and 1,337,952 of Penneck.
  • the thickness of the first insulation layer depends on the voltage to be applied to the bushing and the dielectric properties of the particular material, e.g. polymer composition used.
  • the thickness is generally in the range of about 0.1 cm to about 5.0 cm, preferably in the range of about 0.5 cm to about 2.0 cm.
  • the first layer of insulation can be applied by any conventional technique.
  • One method of applying the insulation layer is to place a dimensionally-recoverable, in particular a heat-shrinkable, tubular article of polymeric material over the conductor and then heating to cause the tube to shrink into intimate contact with the conductor.
  • Heat-shrinkable polymeric tubular articles and methods for their manufacture are known, see for example, U.S. Patent No. 3,086,242 to Cook.
  • Dimensionally-recoverable articles which recover without application of heat are also known, for example, see U.S. Patent No. 4,135,553 to Evans et al.
  • the interface between the insulation layer and the conductor should be void-free, as voids at the interface result in localized electric fields between the conductor and the insulation which cause electrical discharge and ultimately failure of the bushing. Because of imperfections in the surfaces of the metal conductor and the insulation layer, it is difficult to provide a void-free interface between the conductor and the first insulation layer. To obviate this problem, an intermediate conductive layer adhering to the surface of the insulation layer can be used. This conductive layer renders the surface of the insulation layer conductive and any voids between this conductive layer and the conductor will not, in accordance with Faraday's Law, result in destructive electric fields.
  • The-conductive layer is suitably a layer of metal, carbon black, graphite, or other conductive material coated on the inside of the insulation layer.
  • the conductive layer can be applied by vacuum deposition of a metal or coating with a conductive paint, for example, by spraying the paint onto the inner surface of the insulation.
  • a layer of metal, e.g. aluminum foil can be applied over the conductor before the insulation layer is applied. The foil is bonded to the insulation layer in a void-free interface.
  • the stress-grading layer is applied over the first insulation layer.
  • the stress-grading layer can be coextensive with, i.e. can extend the full length of, the insulation layer but is generally shorter so as to extend over an intermediate length, for example a central region, of the first insulating layer, such that the end regions of the first insulation layer extend beyond the stress-grading layer.
  • the stress-grading layer grades the potential between the electrical conductor and ground thereby reducing the resulting electric fields. Ground in this case is the point where the metal housing of the electric apparatus is electrically connected to the bushing. As discussed in more detail below, using the bushing of this invention the apparatus is electrically connected through the flange to the stress control layer of the bushing.
  • the stress-grading layer should extend from the point at which it is connected to ground for a distance sufficient to produce a minimum electric field at each end of the stress-grading layer.
  • Stress-grading materials which can be used are well known. Such materials typically comprise a polymeric, preferably thermoplastic, material having conductive particles dispersed therein.
  • the conductive particles can be, for example, carbon black, particulate graphite, silicon carbide particles and the like.
  • Such materials can be in the form of a paint or solid polymeric materials capable of being formed into shaped articles.
  • An example of a stress-grading material can be found in U.S. Patent No. 3,950,604 to Penneck.
  • the stress-grading material can be applied to the first insulation layer by any convenient technique. If the stress-grading material is in the form of a paint, e.g. a mixture of silicon carbide particles in a liquid curable resin system such as an epoxy resin, the material can be coated on to the surface of the first insulation layer by spraying, brushing or the like.
  • a paint e.g. a mixture of silicon carbide particles in a liquid curable resin system such as an epoxy resin
  • the stress-grading material can be in the form of a dimensionally-recoverable, for example a heat-shrinkable, tubular article, for example, as described in above-mentioned U.S. Patent No. 3,950,604.
  • the stress-grading layer can then be applied, for example, by positioning a heat-shrinkable tubular article over the first insulation layer and heating to cause the tubular article to shrink into intimate contact with the first insulation layer.
  • the flange is electrically grounded and is electrically connected to the stress-grading layer of the bushing to prevent discharge between the metal housing of the apparatus and the electrical conductor.
  • the connection is generally made at about the mid-point of the bushing.
  • Prior methods of connecting a metal flange of a bushing to the insulation layer surrounding an electrical conductor have generally produced a direct mechanical and electrical connection between the centre of the bushing and the flange. This places mechanical stress on the bushing at the same place as the maximum electrical stress which has been found to be disadvantageous. With the present bushing the electrical and mechanical connections of the bushing to the apparatus are separated.
  • the flange is preferably of metal but need not be entirely of metal, for example, it can be primarily of plastic containing a metal element.
  • the electrical connection is made between the stress-grading layer and the metal flange by placing an electrical conductor between them in such a manner to exert little force on the stress-grading material to insure minimal mechanical stress on the stress-grading layer and the underlying first insulation layer.
  • the stress-grading layer can be provided with a conductive surface layer with a wire or metal braid being connected between this layer and the metal flange or metal element of a non-metal flange.
  • the mechanical connection between the flange and the conductor comprises an outer rigid insulating layer connecting the flange to the ends of the conductor extending beyond the first insulating layer.
  • This insulation is of a material capable of withstanding forces to which the bushing may be subjected during installation or use. Such forces can be in the range of, for example, a compression force in the axial direction between the conductor and the flange in the order of 4,000 pounds (18,000 Newtons).
  • Materials that can be used in the outer insulating layer include, for example, curable epoxy resins, polyester resins, fibre-reinforced epoxy resins and polyesters, especially glass-fibre reinforced epoxy resins and polyesters, and the like.
  • the cured epoxy resin may be a cycloaliphatic epoxy resin.
  • the material used should be substantially non-tracking and known antitracking additives such as alumina trihydrate can be added to the resin. In the event that a tracking material is used a non-tracking layer can be coated on to the material.
  • the gap that separates the outer rigid insulation layer from the layer of stress-grading material is preferably an air gap, but can be filled with a flexible material such as a silicone resin or gas such as sulfur hexafluoride, if desired.
  • the outer insulation is preferably sealed to the end regions of the first insulation layer to prevent electrical discharge in the gap.
  • the outer insulation is sealed to the conductor to prevent ingress of moisture into the bushing and to provide mechanical connection between the outer insulation layer and the conductor.
  • the stress grading layer may have an additional insulating layer placed on the top of it but not touching the outer insulation, thus providing improved electrical performance.
  • the outer insulation layer can be cast in place over the inner components of the bushing.
  • the cast material e.g. resin wet the conductor and the outer ends of the first insulating layer in order to effect a seal.
  • the gap between the stress-grading layer and the outer insulation can be created by use of a mould release agent applied over the stress-grading material.
  • the outer insulating layer can be preformed in one piece or in segments by casting the material in an appropriate mould or moulds. The insulating layer is then assembled over the inner components of the bushing. The outer insulating layer is sealed to the flange and to the conductor and the first insulation layer by appropriate means, for example, by the in-place casting of a plug of the same type of material as the outer insulating layer. If the outer insulating layer is preformed in segments, the segments are positioned over the bushing components and sealed to each other to form a unitary insulating layer.
  • the insulation layer is a tube of fibre-reinforced plastic with each end secured to the conductor using metal end caps at each end of the insulating tube. The metal end caps are machined to fit tightly between the conductor and insulating tube.
  • the interface between the insulation layer 12 and the stress-grading layer 14 should be void-free.
  • the insulation layer 12 and stress-grading layer 14 can be coextruded in which case a void-free interface is produced. In this embodiment, they are applied as separate heat-shrinkable tubes or sleeves.
  • a layer of grease for example, a silicone grease, to the heat-recovered insulation layer 12 before the stress-grading layer 14 is applied.
  • a hole 5 is drilled through the flange 2 and insulating layer 4. (For purposes of illustration, only one hole is shown, additional holes through the flange, or other configuration, may be provided, if desired).
  • the conductive layer 16, which covers a portion of the surface of the stress-grading layer 14, is a layer of carbon black-containing conductive paint. The use of other conductive layers, for example, a metal plate in the order of 10 mils (0.025 cm) thick is also contemplated.
  • the conductive layer passes under the two shorter sleeves 18 and 20 of stress-grading material and is connected to the stress-grading layer 14.
  • the mechanical connection of the flange to one end of the conductor of the bushing is also shown in Figure 2.
  • Metal flange, 2 is bolted to the electrical apparatus with which it is used (not shown).
  • Metal flange 2 is embedded in outer insulating layer 4.
  • the outer insulating layer is separated from the stress-grading layer 14 of the bushing by air gap 13.
  • the outer insulating layer 4 is sealed to conductor end region 8.
  • the mechanical attachment of the flange to the conductor must be able to withstand an axial load of about 4,000 pounds (18,000 Newtons) and a bending moment of about 3,000 inch-pounds (49,000 Nm) with a deflection of less than about 1°.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Insulators (AREA)
  • Insulating Bodies (AREA)

Claims (19)

1. Traversée électrique comprenant:
(a) un conducteur électrique (6);
(b) une première couche isolante (12) constituée par un matériau d'isolation électrique dépourvu de vides superposé par-dessus une longueur intermédiaire du conducteur (6) avec les parties d'extrémité du conducteur s'étendant au-delà de ladite couche (12);
(c) une couche d'un matériau (14) d'échelonnement des contraintes superposée sur au moins une longueur intermédiaire de la première couche isolante (12);
(d) une couche isolante externe rigide (4) qui est disposée par-dessus la couche (14) de matériau d'échelonnement des contraintes et la première couche isolante (12); et
(e) une collerette (2) montée sur la couche isolante externe (4), la collerette (2) étant reliée électriquement à la couche de matériau (14) d'échelonnement des contraintes de telle sorte que la contrainte électrique à laquelle la traversée est soumise soit dirigée sur une partie de la traversée située entre lesdites régions d'extrémité du conducteur (6), caractérisée en ce que la couche isolante externe (4) est liée rigidement aux parties d'extrémité du conducteur (6) qui s'étendent et est séparée de la couche de matériau (14) d'échelonnement des contraintes par un intervalle (13) tel qu'une contrainte mécanique à laquelle la traversée est soumise soit dirigée en s'éloignant de la couche (14) d'échelonnement des contraintes, sur lesdites régions d'extrémité du conducteur (6).
2. Traversée suivant la revendication 1, caractérisée en ce que ledit intervalle (13) est constitué par de l'air ou un autre gaz.
3. Traversée suivant la revendication 1, caractérisée en ce que ledit intervalle (13) est rempli d'un matériau souple.
4. Traversée suivant l'une quelconque des revendications précédentes, caractérisée en ce que la couche (14) d'échelonnement des contraintes est coextensive avec ladite première couche isolante (12).
5. Traversée suivant l'une quelconque des revendications 1 à 3, caractérisée en ce que la couche (14) d'échelonnement des contraintes s'étend par-dessus la partie du milieu de ladite première couche isolante (12) en laissant des régions d'extrémité de la couche isolante (12) s'étendre au-delà de la couche (14) d'échelonnement des contraintes.
6. Traversée suivant l'une quelconque des revendications précédentes, caractérisée en ce que ladite première couche isolante (12) est une couche d'un matériau élastique.
7. Traversée suivant l'une quelconque des revendications précédentes, caractérisée en ce que la première couche isolante (12) est une couche d'un matériau thermoplastique.
8. Traversée suivant l'une quelconque des revendications précédentes, caractérisée en ce que ladite couche (14) d'échelonnement des contraintes est constituée par un polymère thermoplastique dans lequel sont dispersées des particules conductrices.
9. Traversée suivant l'une quelconque des revendications précédentes, caractérisée en ce que ladite couche isolante externe rigide (4) est constituée d'une résine époxy durcie, de préférence une résine époxy cyclo-aliphatique.
10. Traversée suivant l'une quelconque des revendications précédentes, caractérisée en ce que ladite couche isolante externe rigide (4) est à peu près dépourvue de propriétés de cheminement.
11. Traversée suivant l'une quelconque des revendications précédentes, caractérisée en ce que ladite première couche isolante (12) et/ou ladite couche (14) d'échelonnement des contraintes sont constituées par un élément tubulaire capable de reprendre ses dimensions, de préférence thermo-rétrécissable, en une matière polymère.
12. Procédé de fabrication d'une traversée électrique comprenant des phases consistant à:
(a) appliquer une première couche isolante (12) constituée d'un matériau électriquement isolant dépourvu de vides, par-dessus une longueur intermédiaire d'un conducteur électrique (6) laissant les régions d'extrémité du conducteur s'étendre au-delà de ladite couche (12);
(b) appliquer une couche d'un matériau (14) d'échelonnement des contraintes sur au moins une longueur intermédiaire de la première couche isolant (12);
(c) disposer une couche isolante rigide externe (4) par-dessus la couche de matériau (14) d'échelonnement des contraintes et la première couche isolante (12); et
(d) fixer une collerette (2) sur la couche isolante externe (4), ta collerette (2) étant reliée électriquement à la couche de matériau (14) d'échelonnement des contraintes de telle sorte que la contrainte électrique à laquelle la traversée est soumise soit dirigée sur une partie de la traversée entre lesdites régions d'extrémité du conducteur (6); caractérisée en ce que la couche isolante externe (4) est liée rigidement aux régions d'extrémité en saillie du conducteur (6) et séparée de la couche de matériau (14) d'échelonnement des contraintes par un intervalle (13), de telle sorte que la contrainte mécanique à laquelle la traversée est soumise soit dirigée en s'éloignant de la couche (14) d'échelonnement des contraintes, sur lesdites régions d'extrémité du conducteur (6).
13. Procédé suivant la revendication 12, caractérisé en ce que l'intervalle (13) est rempli d'air ou d'un autre gaz.
14. Procédé suivant la revendication 12, caractérisé en ce que l'intervalle (13) est rempli d'un matériau souple.
15. Procédé suivant l'une quelconque des revendications 12 à 14, caractérisé en ce que ladite couche isolante (12) est appliquée en disposant un élément tubulaire en un matériau isolant polymère capable de reprendre ses dimensions, de préférence thermo-rétrécissable, par-dessus le conducteur (6) et en astreignant ensuite l'élément (12) à reprendre en contact étroit avec le conducteur (6).
16. Procédé suivant l'une quelconque des revendications 12 à 15, caractérisé en ce que ladite couche (14) d'échelonnement des contraintes est appliquée en disposant un élément tubulaire en un matériau polymère d'échelonnement des contraintes, capable de reprendre ses dimensions, de préférence thermo-rétrécissable, par-dessus la première couche isolante (12) et en forçant ensuite l'élément (14) à reprendre en contact étroit avec la première couche isolante (12).
17. Procédé suivant l'une quelconque des, revendications 12 à 14, caractérisé en ce que ladite première couche isolante (12) et ladite couche (14) d'échelonnement des contraintes sont appliquées en disposant un élément tubulaire co-extrudé, capable de reprendre ses dimensions, de préférence thermo-rétrécissable par-dessus ledit conducteur (6) et en forçant ensuite l'élément à reprendre en contact étroit avec le conducteur.
18. Procédé suivant l'une quelconque des revendications 12 à 17, caractérisé en ce que ladite couche isolante externe rigide (4) est liée à la collerette (2) et aux extrémités du conducteur (6) qui s'étendent, par coulage d'une résine durcissable par-dessus les composants internes de la traversée et en durcissant la résine.
19. Procédé suivant l'une quelconque des revendications 12 à 17, caractérisé en ce que la couche isolante externe rigide (4) est pré-formée, puis assemblée par-dessus les composants internes de la traversée et liée à la collerette (2) et aux régions d'extrémité en saillie du conducteur (6).
EP82304933A 1981-09-21 1982-09-20 Traversée électrique et méthode de fabrication de celle-ci Expired EP0075471B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT82304933T ATE18823T1 (de) 1981-09-21 1982-09-20 Elektrische durchfuehrung und deren herstellungsverfahren.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US30423381A 1981-09-21 1981-09-21
US304233 1981-09-21

Publications (2)

Publication Number Publication Date
EP0075471A1 EP0075471A1 (fr) 1983-03-30
EP0075471B1 true EP0075471B1 (fr) 1986-03-26

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EP82304933A Expired EP0075471B1 (fr) 1981-09-21 1982-09-20 Traversée électrique et méthode de fabrication de celle-ci

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EP (1) EP0075471B1 (fr)
JP (1) JPS58131610A (fr)
AT (1) ATE18823T1 (fr)
DE (1) DE3270131D1 (fr)
GB (1) GB2110479B (fr)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ATE46392T1 (de) 1985-07-19 1989-09-15 Raychem Corp Schmiersystem.
GB8608484D0 (en) * 1986-04-08 1986-05-14 Raychem Gmbh Electrical apparatus
GB8630335D0 (en) * 1986-12-19 1987-01-28 Raychem Gmbh Hv cables
ITVI20060166A1 (it) * 2006-06-05 2007-12-06 Comem Spa Isolatore passante per trasformatori elettrici
CN101669178B (zh) * 2006-12-20 2011-12-14 Abb研究有限公司 套管及用于生产套管的方法
JP6230491B2 (ja) * 2014-06-13 2017-11-15 新日鉄住金エンジニアリング株式会社 電気集塵機用貫通碍子、及び電気集塵機
DE102018206148B4 (de) * 2018-04-20 2023-05-17 Siemens Aktiengesellschaft Steuerelektrode und Durchführung für Mittelspannungsanlagen und Hochspannungsanlagen
SE543113C2 (en) * 2019-02-11 2020-10-06 Hm Power Ab Elastic tubular high-voltage insulating body
DE102020213476A1 (de) * 2020-10-27 2022-04-28 Siemens Energy Global GmbH & Co. KG Durchführungsanordnung sowie Verfahren zu deren Herstellung, Transformator und Verwendung

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1503073A (en) * 1919-05-05 1924-07-29 Steinberger Louis Insulated connecter
GB793974A (en) * 1955-10-28 1958-04-23 British Thomson Houston Co Ltd Improvements relating to electric insulating bushing assemblies
DE1162901B (de) * 1956-10-10 1964-02-13 Westinghouse Electric Corp Durchfuehrung fuer Hochspannung und Verfahren zu ihrer Herstellung
US3312776A (en) * 1966-04-04 1967-04-04 Components For Res Inc Insulated conductor and method of fabricating the same
US3646251A (en) * 1970-12-08 1972-02-29 Westinghouse Electric Corp Electrical bushing having stress-grading layer disposed within solid insulation including a ground layer term inated at each end with a layer of material having a voltage-dependent resistivity
GB1433129A (en) * 1972-09-01 1976-04-22 Raychem Ltd Materials having non-linear resistance characteristics
JPS508513A (fr) * 1973-05-18 1975-01-29
JPS515194A (ja) * 1974-07-02 1976-01-16 Ota Takuo Hikidojo

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Publication number Publication date
GB2110479A (en) 1983-06-15
GB2110479B (en) 1985-10-23
DE3270131D1 (en) 1986-04-30
JPS58131610A (ja) 1983-08-05
ATE18823T1 (de) 1986-04-15
EP0075471A1 (fr) 1983-03-30

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