CA1067971A - Composite structures and heat recoverable articles - Google Patents
Composite structures and heat recoverable articlesInfo
- Publication number
- CA1067971A CA1067971A CA237,196A CA237196A CA1067971A CA 1067971 A CA1067971 A CA 1067971A CA 237196 A CA237196 A CA 237196A CA 1067971 A CA1067971 A CA 1067971A
- Authority
- CA
- Canada
- Prior art keywords
- article
- substrate
- heat
- longitudinal axis
- sheds
- 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
Links
Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G15/00—Cable fittings
- H02G15/02—Cable terminations
- H02G15/06—Cable terminating boxes, frames or other structures
-
- 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
- H01B17/32—Single insulators consisting of two or more dissimilar insulating bodies
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H85/00—Protective devices in which the current flows through a part of fusible material and this current is interrupted by displacement of the fusible material when this current becomes excessive
- H01H85/02—Details
- H01H85/04—Fuses, i.e. expendable parts of the protective device, e.g. cartridges
- H01H85/05—Component parts thereof
- H01H85/165—Casings
Landscapes
- Insulating Bodies (AREA)
- Cable Accessories (AREA)
- Insulators (AREA)
- Inorganic Insulating Materials (AREA)
- Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
Abstract
ABSTRACT
Disclosed is a heat-recoverable hollow article for use in covering a substrate. The article, which may be a shedded insulator, has at least one open end and has a plurality of outwardly extending portions. Each portion extends round at least part of the periphery of the article and is such that, on partial recovery of the article around and into contact with the substrate, it will be inclined to the longitudinal axis of the article.
Disclosed is a heat-recoverable hollow article for use in covering a substrate. The article, which may be a shedded insulator, has at least one open end and has a plurality of outwardly extending portions. Each portion extends round at least part of the periphery of the article and is such that, on partial recovery of the article around and into contact with the substrate, it will be inclined to the longitudinal axis of the article.
Description
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The present invention relates to composite structures and heat-recoverable articles and to a process for their manufacture, and more particularly relates to insulators.
In the high voltage fi21d insulators ( or insulating units~ may he used, for example, to support overhead power lines, the insulators being either under compression or under tension, or, in the case of, for example, post insulators in sub-stations and bushings on transformers and switchgear, to provide a satisfactory leakage distance between those 10 parts of the equipment that are at a high potential and those parts which are earthed. The outer surface of an insulator used as indicated above is generally provided with a number of sheds to increase the creepa~e distan~e and flash~over volta~e and to reduce leakage currents. The sheds also 15 provide a number of protected areas which-help to improve the overall performance of the insulator.
; In the pastS insulators of the above type have j` generally been fabricated from an~insulating material such s as porce~ain or, in the~case of suspension insulators, glass.
j~ 20 me smaller units, for example 33 KV post insulators and 11 and 33 KV bushings for transformers and switchgear, are fabrlcatea as single units, the bushings being hollow to allow them to receive the metal component at high potential.
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Ae the size increases, the manufacture of one-piece insulators ~ 25~ bèoomes~more di~ficult and insu1ators are normally manufactured j~ in a~number of separate units which, in the case of bushings and post~insulators, are generally cemented together to form ~: :
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the complete structure and, in the case of suspension in-sulators, are generally connected by metal fittings which are cemented to the glass or ceramic. Although insulators made as indicated above are advantageous in that relatively inexpensive starting materials are used, they have the disadvantage that they are expensive to manufacture, heavy, and relatively fragile.
Recently, proposals have been made to make insulators from plastics materials. me most commonly used materials have been epoxy resins, and the insulators, or insulator components, have been made by a casting or moulding process.
Thus, for example, British Patent Specification No. 1,345,566 in the name of General Electric Co., published 30th January, 1974, described a method in which a central rod and the desired number of sheds are integrally moulded from a plastics material.
` 15 Such an integral moulding method is, however, only practicable when the plane of the sheds is perpendicular to the longitudinal axis of the insulator as incIined sheds would, for example, .
impede the opening of the mould and would almost certainly be damaged~~uring opening of the mould, and although insulators having such perpendicular sh~ds are useful in some circumstances, there are cases where their use would be most undesirable. ~hus, for example, where an insulator is to be used outdoore, it is ~esir ble that the sheds should be inclined in a downward direction, suitably at an angle of 15 to 30 to the horizontal, so that rain will run off and the under~side of the sheds will remain relatively dry.
Previous proposal~s for manufacturing insulators ~: :
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with inclined sheds from plastics materials have, because of the difficulties mentioned above, all involved the separate moulding of individual sheds or shedded insulator portions, and the assemb~y of a number o:E separate units to form the complete insulator. Thus, for example, in the case of sus-pension insulators, the individual sheds may be cemented to a glass fibre core to build up an insulator o~ the desired rating.
The sheds to be used in this way may, if desired, be heat-shrinkable, as described in British Patent Specification No.
10 1,292,276 in the name of Raychem Limited, published 11th October, 1972. Even when heat-shrinkable sheds are used, however, the manufacture and installation of a number of separate sheds is inevitably time-consuming and may lead to undesired variations in quality in the final product.
~5 The present invention provides a composite structure which comprises a substrate having applied to the outer surface thereof a hollow heat-recoverable article having at least one open end and two or more outwardly extending portions which extend a~ound at least part of the periphery of the article and are inclined to the longitudinal axis of the composite structure.
me invention also provides a method for making a com-p~site structure which method comprises positioning a hollow : heat-recoverable article, which article has at least one open 25 ~ end and has two or more outwardly extending portions which : extend round at least part of the periphery of the article, around a support member the exterior dimensions of which support member:are greater than the interior d:;mensions .:
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that the article would have i~ reco~ered in the absence o~ a ~ubstrate, and heating to cause the article to reco~er into contact with the support member such that two Qr more o~ the outwardly extending portions are inclined to the longitudinal : 5 axis o~ the article.
The invention also provides a method of co~ering a s~bstrate comprising:
po~itioning round the su~strate a heat-recoverable hollow article having at lea~t one open end and two or more outwardly extendin~ portions which e~tend round at least a part of the periphery of the article ~nd are :; ~uch that, on partial recovery of the article around and i~to co~tact with the substrate, the~ will be in-clined to the longitudinal a~i~ o~ the article; and heat-recovering the article into contact ~ith the : substrate.
~he invention further pro~ides a heat-recoverable hollow article ~or ~se in covering a substrate~ whioh artiole has at leaæt one open end and two or more outwardly e~tending - 20 portions which e~tend round at lea~t part o~ the periphery oi the arti¢le and are such that, on partial reco~e~y of the artiole around a ~bstrate, they ~rill be inclined to the longi~
tudinal: axis o~ the artiole, and a proces~ for making a heat-recoverable hollow article, whi¢h process compri~es ~orming a ~: 25 hollow art~cle having at least one open end and two or more outward}y exte~ding portions whioh e~tend round at lea~t part of the periphery of the article and are ~ubstantiall~ perpendicular 5 _ 1~;797:~
to the longitudinal ~xis of the article~ and enlarging the inner dimensions o~ the article to co~vert it to a heat-recoverable state in which two or more outwa:rdly eætending portions are such that, on partial recovery of the article around a substrate, they will be inclined to the longitud.inal axis of the arti~le.
~ he inve~tion also prov:ides a heat-recoverable article ^~hich comprises an elo.ngate hollow member havi~g at least one open end and two or more ~heds which e~tend outwardly in a generally radial direction from the hollow member and are incllned to the longitudinal axis o~ the hollow member, the article be~ng such that, if the article were recovered into contact with a substrate haYing outer dimensions such that it can just be received in the hollow mem~er, the ~aid sheds would be inclined to the longitudinal a~i~ o~ the hollow member, and ~uch that on substrate-free reco~ery the said sheds would be substantially perpendicular to the longitudinal a~i~ o~ the hollow member. In use, .the article may be re~overed into contac~ wi~h any substrate which has ~xterior dlmensions greater than the interior dimensions that the hollow member wo~ld have i~ recovered in the absencs of a substrate such that on recove~y of the article into oontact with the substrate the said sheds are inclined to the longitudinal a~i8 ~of the hollow bodyO
The in~ention ~urther provide~ a process for the manu-facture of a heàt-reooverable article, which comprises ~orming 25 an artiole comprising an elongate hollow member having at lea~t one open end and two or more sheds which e~ten~ ou~wardly in a generally radial direction from the hoIlow member and substantially perpendioular to the l~ngitudinal axi8 0~ the hollow memb~r, ~,, 1, 5a 6~7~7~
enlarging the inner dimensions o~ the article to aonvert it to a heat-recoverable state in which at lea~t two said sheds are inclined to the longitudinal axis of the hollow member and in which the article is such that, if the article were recovered into contact with a substrate having outer dimensions such that it can just be received in the hollow member~ the said at least two sheds would be incl.ined to the longitudinal axis o~ the hollow member.
~he in~ention also rovides a composite structure whic~
comprises a substrate having applied to the outer surface thereo*
a heat-recoverable article com.prising an elongate hollow member havin$ at least one open e~d and two or more sheds ~hich extend ; outwardl~ i~ a generall~ radial direction from the hollow member and are inclined to the longitudinal axis o~ the composite ~; 15 structure, the article being such that, if the substrate were removed and the article were fully recovered, the said æheds i~
the ~ully recovered article would be substantially perpendicular to the longitudinal a~is o~ the holIow member, and a method of making a composite structure which comprises positioning around a substrate a heat-recoverable article comprising an elongate `~ hollow member having at least o~e open end and two or ~ore sheds which e~tend outwardly in a generaIly radial direction ~rom the hollow member and are inclined to ~he longitudinal a~i~ oi the hollow member, the exterior dimension~ of the substrate being greater than the interior dimen~ions th~t the hollow member would have i~ recovered in the absence of a substrate ~uch that , , on recovery oi the article into ¢ontact with the sub~tr~te the 5b -, . , . .: . , . .. . .. ., , .. . . . . . . : . ..
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~aid sheds are inclined to the longi-tudinal a~is of the hollow member and the article bein~ ~uch that on sub~trate-~ree recovery the said sheds would be substan-tially perpendicular to the longitudinal a~is of the hollow member, and heating to cause the article to recover into contact with the substrate~
In this specification~ a heat~reco~erable articls iæ an article at least part o~ which has been changed from an original - ~ubstan^tially heat-stable configuration to a dimensionally heat-unstable eonfiguration and tends to move in the direction of the original con~iguration on the application of heat alo~eO ~he ori~inal dimensionally heat-stable ~orm ma~ be a transient form . in a continuous process in which, ~or example, an e~truded tube;: i9 exp~ndsd~ whilst hot, to a dimension~lly heat-u~stable form,but in other applications a prefo~ed dimensionally heat-stable article is deformed to a dimensionally heat-unstable ~orm i~ a separate stage, Tha heat-reco~erable arti~le i~ preferabl~ in-dependently dimensionally heat-unstable~ that is, it pre~erably doe~ no-t require the presence of another member to hold it in a `~ dimen~ionally heat-un~table state~ Alternati~ely, however~ the 20 heat-recoverable article may compri~e, for example, an ela~tomeric or resiliently-recoverable member ~hich is held in a dimensio~-ally heat-unstable ~tate by 2~other member, ~or e~ample by a member whi~h, upon heating weakens and thus allows the elasto-meric member to recoverO
25 ~ :In thi~ ~pecifioatio~, an outwardly ex~ending por~ion is ~aid~to be perpendicular to the longitudinal axi~ o~ the hollow artiele~if~ B straight line ~rom the outermost extremity o~ the outwardly e~tending por~ion and perpe~dicular to the longitudinal ~is pas~eæ along the sur~ace 5c .. . . . .
~ " ' ' ~. '. . ' ' ' . ' . ' . ' ' ' "' .. ' " . . .
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of or through the outwardly extending portion, while an l'inclinedl' outwardly extending portion may be defined as an outwardly ex-tending portion which is not perpendicular to the longitudinal axis of the article. It will of course be obvious that any minor protuberances or bumps on the surface o~ an outwardly extending portion should be ignored when considering whether or not that outwardly extending portion i9 perpendicular to the longitudinal axis. Thus, in other words, an outwardly extending portion may be said to be substantially perpendicular to the longitudinal axis of the hollow article if it is such that a mould split only longitudinally could be removed from the article in a direction substantially perpendicular to the longitudinal axis with substantially no deformation of the outwardly extending portion.
In the case where an outwardly extending portion is, in the dimensionally stable state of the article, substantially symmetrical about a plane perpendicular to the longitudinal axis of the article (as, ~or example, in a symmetrical shed3, the above definitions can be simplified. Thus, in this case, the outwardly extending portion may be said to inclined to the longitudinal axis of the article if an ima~inary lin~ joining the outer extrêmity, or the centre of the outermost surface, of that portion-to the centre of the inner extremity meets the longitudinal axis at an àngle ~ther than 90, while, if said angle is approximately 90, the outwardly extending portion may be said to be perpendicular to the longitudinal axis.
If at least the outer surface of the composite structure of~the invention comprises an electrical insulating material, the composite structure may be used as an insulator, and the use ~: ' 7~7~
of appropriate non-tracking materials may render such an in-sulator suitable for high-voltage work. Although the structure, when made of appropriate materials, is particularly suitable for use as an insulator, however, it may also be used for other purposes readily apparent to those skilled in the art. Thus, for example, it may be used as a pulley, or a reel for accommodating thread or rope, provided that the outwardly extending portions are inclined in appropriate directions. However it is used, the composite structure of the invention has the advantage that, as it can be made from a single heat-recoverable component which includes all the desired outwardly extending portions, its manufacture is simpler and less time-consuming than the manu-facture of, for examplei an insulator from a plurality of in-dividual heat-shrinkable sheds, and can be carried out by less skilled workmen.
Each outwardly extending portion in theiarticle of the invention extends round at least part of the periphery of the ; article. If the outwardly extending portions are sheds of elec trically insulating material, these sheds are advantageously continuous, extending round the entire periphery of the article.
~or other uses, however, outwardly extending portions which extend round only part of the periphery may be suitable, provided that each outwardly extending portion extends round the article by such an amount that the desired distortion of the outwardly extending portions occurs on heat-recovery. Where the outwardly extending portions extend round only part of the periphery of the article the article may, if desired, be made in a wrap-around form, a longitudinal seam being made in the article after, e.g., mould-ing. Such a wrap around article might, for example~ find use in 1~6~797~
the wea~ing industr~. The outwardlg e~tending portion~ in the article of the invention are preferably inte~ral with (that is, formed in one piece with) the remainder o~ the article.
I~ de~ired, one or more o~ the outwardly e~tending portions in the article of the invention may extend helici~lly round the longitudi~al a2i~ o~ the article and there may be situations where it is advantageous that all the outwardly e~tendi~g portions are provided by a æingle helic~l outwardly extending member, ~hus, the i~ve~tio~ also provides a modificatio~ of the compo~ite ~tructure, method~ heat-recoverable article i~d process of the invention wherei~ a isingle helical outwardly extendlng member iæ
used instead o~ the outwardly extendi~g portion~.
The inner ~urface o~ the article o~ the i~entio~ may be shaped to facilitate escape o~ air during heat-recovery o~
. 15 the article from between the central por~io~ ther~o~ i~nd a su~strate ~uch as an eleotrical insulator srou~d which the artisle is - -being reoo~ered. ~o this end, ~or example, the inner ~ur~ace ~ .
of the central portion may have at lei~s~t one longitudinallg e~tending - deformity therein~
: ~he hollow article ueed in acoordi~nce with the inventi~
exists, ~rom:the time o~ its ma~ufacture to the time ~hen it has , : fina-1~ beeu i~ætalled on the support member~
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in at least three different states. mese are the substantially heat-stable state in which it is formed, a first heat-recoverable state, wherein its internal dimensions are large enough for it to be slipped over the support member, and a second heat-recoverable state wherein it has been recovered around the support member but is prevented by the support member from recovering completely to its original heat-stable state. In the second state it is said to be partially re-covered or to exhibit "unresolved recover~''. As will be well known to those skilled in the art, a body may be converted to a heat-recoverable, or heat-unstable, state by heating it, deforming the hot body, and cooling while maintaining the deforming force. Alternatlvely, deformation may be carried out without 'heating, but a greater deforming force will then generally be required. The heat-recoverable body will maintain its deformed dimensions until it is heated to a~temperature (the recovery temperature~ at which it recovers, or attempts to recover, to its original dimensions.
When the hollow article used in accordanc~ with the ~o invention is in its heat-stable state, the outwardly exte~ding portions are substantially parpendicular to the longitudinal axis of the article, and the~article can thus readily be moulded.
; ~ ~When the heat-stable article is expanded to the first heat-recovera~le state, the outwardly extending portions may, if the degree of expànsion is relatively small, remain substantially ~-perpendicular to the'longitudinal axls. Generally, however, th'e stresses exerted on the outwardly extending portions as _ .. ; ,` : : .
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a result of their inner dimensions being expanded while the outer dimensions remain substantially unaltered will cause the outwardly extending portions to "flip over", so that they are inclined to the longitudinal axis at an angle that is determined by the dimensions of the article before and after expansion~ On partial recovery of the article from the first heat-recoverable state to the second heat-recoverable state, the outwardly extending portion~ will, if they were substan-tially perpendicular to the longitudinal axis in the first heat-recoverable state, "flip over" so that they are inclined to the longitudinal axis or, if they were inclined to the axis in the first heat-recoverable state, will remain inclined to the axis although at an angle that is somewhat closer to the perpendicular. Again, the angle at which the outwardly extending portions are inclined to the longitudinal axis will depend on the dimensions of the article in the heat-stable ~: state and its dimensions in the partially recovered state.
~î The desired angle of inclination of the outwardly extending portions in the composite structure of the : 20 invention will, of course, d~pend on the use to which the .~i composite structure is to be put. If, for example, th~
j composite structure is to be used in highly polluting , conditions as a non-tracking insulator for high voltage ,,! ~ electrical~components tin which case the outwàrdly extending 25~ portlons will, of course, be sheds~, the angle at which the optlmum~working voltages are obtained will depend on the : dlmensions of`the insulator, the operating voltage and the wettlng characterlstics of the outer surface of the insulator, ~f ~ 1 0 -~067~
and can readily be determined by those skilled in the art.
For some high voltage applications it has been found advantageous to use sheds inclined at an angle of 15 to 30 to the perpendicular (75 to 60 to the longitudinal axis).
In some instances, the direction in which the out-wardly extendin~ portions t'flip over" may be irrelevant, the important factor merely being that these portions should, in the final composite structure, be inclined to the longitudinal axis of the structure. In many cases, however, the direction of inclination is important. Thu~, for example, in an insulator, all the sheds should normally be inclined in the same direction while, in the case of a pulley or reel, each first outwardly extending portion is advantageously inclined in a direction opposite to that of each second shed.
When the direction of inclination is important, the outwardly extending portions must either be so constructed that they inevitably "flip over" in the right direction, or the movement away from the perpendicular must be controlled so that it takes place in the desired direction. This can readily be done by mechanical means. Thus, for example, comb~
like means may be used, the means having a number of suitably spaced teeth or plates which can be brought into abutting relationship with the outwardly extending portions so that movement in the wrong dixection is prevented. Where, of cour~e, the "flipping over" takes place durlng expansion from the heat-stable state to the first heat-recoverable state, the direction of in~lination in~the first heat-recoverable state will remaln unchanged on partial recovery of the article to :: :
,, .. .. .. .. "., . ~ . , . . . .. , .. , ~ . ,., . . ..... ~
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the second heat-recoverable state, and this has the advantage that the direction of inclination can be predetermined by the manufacturer of the heat-recoverable article, and that the installation of the heat-recoverable article on the support member is particularly simple.
The hollow article used according to the invention, which in the heat-recoverable state, may have plastic or elastic memory, may comprise any material which may have been cross-linked by chemi-cal means or irradiation or by a combination thereof and that may be converted to a heat-recoverable state, the nature of the material being dictated by the use to which the composite structure is to be put. Thus, for example, when the composite structure i5 to be used as a high-voltage insulator, at least ~he outer surface of the composite structure should normally comprise a non-tracking elec-trically insulating material. A non-tracking material may be defined as one which has an initial tracking voltage of more than 3 KV when tested in accordance with ASTM-D2303-64T ~wetting agent Triton X-100), a tes~ method which uses the inclined plane liquid contamination test and is designed to represent service exposure of insulators under polluting conditions. Examples of non-tracking materials which may be converted to a heat-recoverable state are given in British Patent Specifications Nos. 1,292,276, published October 11, 1972, 1,284,081, 1,284,082, both pub-lished August 2, 1972, 1,303,432 published August 17, 1973, 1,337,951, and 1,337,952 bo~h published November 21, 1973, all in the name of Raychem Limited. The article of the invention may be moulded by, for exampIe, compression transfer or injection moulding, andJ when any superfluous material has been remo~led, - 12 -~
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may be expanded by any desired method, either automatic or manual.
The exact nature of the support member in the composite structure of the invention will also depend on the use to which the structure is to be put. ~hus, when the composite structure is to be used an an insulator, the support member advantageously comprises a fibre-reinforced electrically insulating material;
details of suitable electrically insulating materials are given, for example, in British Patent Specification ~o. 1,292,276.
Alternatively, there may be situations where the heat-recoverable - article itself is to provide insulation for an electrical ~` component, and in that case the support mer~ber may comprise an electrically conductive material, for example an electrical component such as a cable. It will be understood that the invention is in no way limited by the shape or nature of the support member or of the material from which it is made, and that the support member may comprise any object or objects that are capable of preventing complete recovery of the heat-recoverable ; article.
If ~esire~, an adhesive may be used to bond the heat-. ~
~, recoverable article to the support member used in the composite structure of the invention and/or at least part of the surface of the article which is to contact the support member or `substrate may be provided with a stress-grading material or 25 ~ layer, that is, a material or la~er which can act to reduce the electrical~stress which may exist in various areas of a high voltage component, for example, at the end of the screen of a high voltage~cable. As~sultable adhesives there may be - : :
. ~ . , ' .' ' . ' ' . : ' , ' ., , , " ,: , ' ;' ' , " . . . . ` " . : ". , , ' ' . . ' : ' ~ . ' ~L~16797~
mentioned, for example, epoxy resins (either hot or cold cured~
and polyesters, which resins and polyesters may be used with or without fillers, and silicone-contalning adhesives, especially those with non-tracking properties. Other suitable adhesive compositions include those comprising .
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a copolymer of a hydrocarbon containing at least one polymerisable double bond and a compound containing a polymerisable double bond together with one or more carboxylic acid groups, which carboxylic acid groups may be in the form of a derivative, for example an es*er or an anhydride. As examples of such copolymers there may be mentioned ethylene/vinyl acetate copolymers, ethylene/ethyl acrylate copolymers, methyl vinyl ether/malei~ anhydride copolymers and, preferably, alkyl esters of methyl vinyl/maleic anhydride copolymers. A stress grading material or layer is suitably a material or layer with linear or preferably, non-linear electrical resistance properties and may have form stability or comprise a substantially non-crystalline material (for example a mastic-like material~ which has a viscosity of not more than 10 3 cp at 25 C. Examples of suitable stress-grading materials are given in DOS 2,344,067 published April 11, 1974 and DOS 2,413,475 published January 2, 1975, both in the name of Raychem Limited. The aspects of stress-grading and anti-tracking ma~ be combined in an article or structure of the invention as described in Canadian Patent Application No.
237~197 filed October 7, 1975 in the name of R.J.T. Clabburn and R.J. Penneck.
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The invention will now be described, by way of example only, with , reference to the accompanying drawings, in which:
~igure 1 is a cross-section through a hollow article provided with sheds to be used for making an electrical insulator;
Figure 2 is an enlarged cross-section through a portion of a shed;
Figure 3 shows the article of ~igure 1 in an expanded, heat .. ~ .
;- ~ recoverable form;
; Flgure 4 shows the article~of Figure 2 recovered round a substrate;
Figure 5 shows another article according to the invention recovered . ::
round a mandrel3~and Flgures 6 and ? are plots of results obtained according to Example 2.
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The Figures are not drawn to scale.
Referring now to the drawingsl Figure 1 shows a hollow article 1 of electrically insulating material which comprises a central tubular portion 2 and a plurality of sheds 3. The sheds 3 are integral with the tubular portion 2, and each shed 3 extends round the entire periphery of the tubular portion 2. Each shed 3 is perpendicular to the longitudinal axis of the tubular portion 2 and is thus such that a longi-tudinally split mould can be removed from the hollow article 1 in a direction substantially perpendicular to the longi-tudinal axis of the tubular portion 2 without substantial ; deformation of the sheds 3.
:
As is clear from Figure 2, the angle of inclination x o~ a shed 3 is the acute angle between the longitudinal axis 4 o~ the article and the imaginary line 5 joining the outer extremity 6 of the shed and the centre point 7 of the inner extremity of the shed. In the article of Figure 1, the sheds are substantlally norma~l to the longitudinal axis, the angle between that axis and the~imaginary line 5 being approximately 90 (for example 90 * about 5~.
Flgure~3 shows the article of Figure 1 in a heat-recoverable form. As can be~ seen from the drawing, the ~; inner diameter of the tubular portion 2 has been expanded, causing the sheds 3 to "flip over" to a state in which ~ they are inclined at an angle x to the longitudinal axis.
~ :
~ ~The article o~ Figure 3 may be positioned around a substrate :
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(shown diagrammatically at 8~ and heated to cause it to shrink into close contact with the substrate. The angle of inclination x' of the sheds after shrinking is greater than x but, because the outer diameter of the substrate 8 is greater than the inner diameter of the article in the "as-moulded form" illustrated in Figure 1, the sheds are still inclined and do not return completely to the perpen~ular state shown in Figure 1.
m e following Examples illustrate the in~ention.
Example 1 An article was moulded in the form shown in Figure 1, the inner diameter a of the tubular portion 2 being 5.71 cm. and the distance b (measured perpendicular to the longitudinal axis~
betwe~n the outer extremity of each shed and the inner surface of the tubular portion was 2.54 cm. The sheds, which were symmetrical about a plane perpendicular to the longitudinal axis, were perpendicular to that axis.
In the expanded form shown in Figure 3 (the first heat-recoverable state~, the inner diameter a~ of the tubular portion
~0~7~
The present invention relates to composite structures and heat-recoverable articles and to a process for their manufacture, and more particularly relates to insulators.
In the high voltage fi21d insulators ( or insulating units~ may he used, for example, to support overhead power lines, the insulators being either under compression or under tension, or, in the case of, for example, post insulators in sub-stations and bushings on transformers and switchgear, to provide a satisfactory leakage distance between those 10 parts of the equipment that are at a high potential and those parts which are earthed. The outer surface of an insulator used as indicated above is generally provided with a number of sheds to increase the creepa~e distan~e and flash~over volta~e and to reduce leakage currents. The sheds also 15 provide a number of protected areas which-help to improve the overall performance of the insulator.
; In the pastS insulators of the above type have j` generally been fabricated from an~insulating material such s as porce~ain or, in the~case of suspension insulators, glass.
j~ 20 me smaller units, for example 33 KV post insulators and 11 and 33 KV bushings for transformers and switchgear, are fabrlcatea as single units, the bushings being hollow to allow them to receive the metal component at high potential.
:
Ae the size increases, the manufacture of one-piece insulators ~ 25~ bèoomes~more di~ficult and insu1ators are normally manufactured j~ in a~number of separate units which, in the case of bushings and post~insulators, are generally cemented together to form ~: :
:: :
~C~6797~
the complete structure and, in the case of suspension in-sulators, are generally connected by metal fittings which are cemented to the glass or ceramic. Although insulators made as indicated above are advantageous in that relatively inexpensive starting materials are used, they have the disadvantage that they are expensive to manufacture, heavy, and relatively fragile.
Recently, proposals have been made to make insulators from plastics materials. me most commonly used materials have been epoxy resins, and the insulators, or insulator components, have been made by a casting or moulding process.
Thus, for example, British Patent Specification No. 1,345,566 in the name of General Electric Co., published 30th January, 1974, described a method in which a central rod and the desired number of sheds are integrally moulded from a plastics material.
` 15 Such an integral moulding method is, however, only practicable when the plane of the sheds is perpendicular to the longitudinal axis of the insulator as incIined sheds would, for example, .
impede the opening of the mould and would almost certainly be damaged~~uring opening of the mould, and although insulators having such perpendicular sh~ds are useful in some circumstances, there are cases where their use would be most undesirable. ~hus, for example, where an insulator is to be used outdoore, it is ~esir ble that the sheds should be inclined in a downward direction, suitably at an angle of 15 to 30 to the horizontal, so that rain will run off and the under~side of the sheds will remain relatively dry.
Previous proposal~s for manufacturing insulators ~: :
.
~L~67~37~
with inclined sheds from plastics materials have, because of the difficulties mentioned above, all involved the separate moulding of individual sheds or shedded insulator portions, and the assemb~y of a number o:E separate units to form the complete insulator. Thus, for example, in the case of sus-pension insulators, the individual sheds may be cemented to a glass fibre core to build up an insulator o~ the desired rating.
The sheds to be used in this way may, if desired, be heat-shrinkable, as described in British Patent Specification No.
10 1,292,276 in the name of Raychem Limited, published 11th October, 1972. Even when heat-shrinkable sheds are used, however, the manufacture and installation of a number of separate sheds is inevitably time-consuming and may lead to undesired variations in quality in the final product.
~5 The present invention provides a composite structure which comprises a substrate having applied to the outer surface thereof a hollow heat-recoverable article having at least one open end and two or more outwardly extending portions which extend a~ound at least part of the periphery of the article and are inclined to the longitudinal axis of the composite structure.
me invention also provides a method for making a com-p~site structure which method comprises positioning a hollow : heat-recoverable article, which article has at least one open 25 ~ end and has two or more outwardly extending portions which : extend round at least part of the periphery of the article, around a support member the exterior dimensions of which support member:are greater than the interior d:;mensions .:
~CI 6~79~
that the article would have i~ reco~ered in the absence o~ a ~ubstrate, and heating to cause the article to reco~er into contact with the support member such that two Qr more o~ the outwardly extending portions are inclined to the longitudinal : 5 axis o~ the article.
The invention also provides a method of co~ering a s~bstrate comprising:
po~itioning round the su~strate a heat-recoverable hollow article having at lea~t one open end and two or more outwardly extendin~ portions which e~tend round at least a part of the periphery of the article ~nd are :; ~uch that, on partial recovery of the article around and i~to co~tact with the substrate, the~ will be in-clined to the longitudinal a~i~ o~ the article; and heat-recovering the article into contact ~ith the : substrate.
~he invention further pro~ides a heat-recoverable hollow article ~or ~se in covering a substrate~ whioh artiole has at leaæt one open end and two or more outwardly e~tending - 20 portions which e~tend round at lea~t part o~ the periphery oi the arti¢le and are such that, on partial reco~e~y of the artiole around a ~bstrate, they ~rill be inclined to the longi~
tudinal: axis o~ the artiole, and a proces~ for making a heat-recoverable hollow article, whi¢h process compri~es ~orming a ~: 25 hollow art~cle having at least one open end and two or more outward}y exte~ding portions whioh e~tend round at lea~t part of the periphery of the article and are ~ubstantiall~ perpendicular 5 _ 1~;797:~
to the longitudinal ~xis of the article~ and enlarging the inner dimensions o~ the article to co~vert it to a heat-recoverable state in which two or more outwa:rdly eætending portions are such that, on partial recovery of the article around a substrate, they will be inclined to the longitud.inal axis of the arti~le.
~ he inve~tion also prov:ides a heat-recoverable article ^~hich comprises an elo.ngate hollow member havi~g at least one open end and two or more ~heds which e~tend outwardly in a generally radial direction from the hollow member and are incllned to the longitudinal axis o~ the hollow member, the article be~ng such that, if the article were recovered into contact with a substrate haYing outer dimensions such that it can just be received in the hollow mem~er, the ~aid sheds would be inclined to the longitudinal a~i~ o~ the hollow member, and ~uch that on substrate-free reco~ery the said sheds would be substantially perpendicular to the longitudinal a~i~ o~ the hollow member. In use, .the article may be re~overed into contac~ wi~h any substrate which has ~xterior dlmensions greater than the interior dimensions that the hollow member wo~ld have i~ recovered in the absencs of a substrate such that on recove~y of the article into oontact with the substrate the said sheds are inclined to the longitudinal a~i8 ~of the hollow bodyO
The in~ention ~urther provide~ a process for the manu-facture of a heàt-reooverable article, which comprises ~orming 25 an artiole comprising an elongate hollow member having at lea~t one open end and two or more sheds which e~ten~ ou~wardly in a generally radial direction from the hoIlow member and substantially perpendioular to the l~ngitudinal axi8 0~ the hollow memb~r, ~,, 1, 5a 6~7~7~
enlarging the inner dimensions o~ the article to aonvert it to a heat-recoverable state in which at lea~t two said sheds are inclined to the longitudinal axis of the hollow member and in which the article is such that, if the article were recovered into contact with a substrate having outer dimensions such that it can just be received in the hollow member~ the said at least two sheds would be incl.ined to the longitudinal axis o~ the hollow member.
~he in~ention also rovides a composite structure whic~
comprises a substrate having applied to the outer surface thereo*
a heat-recoverable article com.prising an elongate hollow member havin$ at least one open e~d and two or more sheds ~hich extend ; outwardl~ i~ a generall~ radial direction from the hollow member and are inclined to the longitudinal axis o~ the composite ~; 15 structure, the article being such that, if the substrate were removed and the article were fully recovered, the said æheds i~
the ~ully recovered article would be substantially perpendicular to the longitudinal a~is o~ the holIow member, and a method of making a composite structure which comprises positioning around a substrate a heat-recoverable article comprising an elongate `~ hollow member having at least o~e open end and two or ~ore sheds which e~tend outwardly in a generaIly radial direction ~rom the hollow member and are inclined to ~he longitudinal a~i~ oi the hollow member, the exterior dimension~ of the substrate being greater than the interior dimen~ions th~t the hollow member would have i~ recovered in the absence of a substrate ~uch that , , on recovery oi the article into ¢ontact with the sub~tr~te the 5b -, . , . .: . , . .. . .. ., , .. . . . . . . : . ..
~67g7~
~aid sheds are inclined to the longi-tudinal a~is of the hollow member and the article bein~ ~uch that on sub~trate-~ree recovery the said sheds would be substan-tially perpendicular to the longitudinal a~is of the hollow member, and heating to cause the article to recover into contact with the substrate~
In this specification~ a heat~reco~erable articls iæ an article at least part o~ which has been changed from an original - ~ubstan^tially heat-stable configuration to a dimensionally heat-unstable eonfiguration and tends to move in the direction of the original con~iguration on the application of heat alo~eO ~he ori~inal dimensionally heat-stable ~orm ma~ be a transient form . in a continuous process in which, ~or example, an e~truded tube;: i9 exp~ndsd~ whilst hot, to a dimension~lly heat-u~stable form,but in other applications a prefo~ed dimensionally heat-stable article is deformed to a dimensionally heat-unstable ~orm i~ a separate stage, Tha heat-reco~erable arti~le i~ preferabl~ in-dependently dimensionally heat-unstable~ that is, it pre~erably doe~ no-t require the presence of another member to hold it in a `~ dimen~ionally heat-un~table state~ Alternati~ely, however~ the 20 heat-recoverable article may compri~e, for example, an ela~tomeric or resiliently-recoverable member ~hich is held in a dimensio~-ally heat-unstable ~tate by 2~other member, ~or e~ample by a member whi~h, upon heating weakens and thus allows the elasto-meric member to recoverO
25 ~ :In thi~ ~pecifioatio~, an outwardly ex~ending por~ion is ~aid~to be perpendicular to the longitudinal axi~ o~ the hollow artiele~if~ B straight line ~rom the outermost extremity o~ the outwardly e~tending por~ion and perpe~dicular to the longitudinal ~is pas~eæ along the sur~ace 5c .. . . . .
~ " ' ' ~. '. . ' ' ' . ' . ' . ' ' ' "' .. ' " . . .
~C~6~97:~L
of or through the outwardly extending portion, while an l'inclinedl' outwardly extending portion may be defined as an outwardly ex-tending portion which is not perpendicular to the longitudinal axis of the article. It will of course be obvious that any minor protuberances or bumps on the surface o~ an outwardly extending portion should be ignored when considering whether or not that outwardly extending portion i9 perpendicular to the longitudinal axis. Thus, in other words, an outwardly extending portion may be said to be substantially perpendicular to the longitudinal axis of the hollow article if it is such that a mould split only longitudinally could be removed from the article in a direction substantially perpendicular to the longitudinal axis with substantially no deformation of the outwardly extending portion.
In the case where an outwardly extending portion is, in the dimensionally stable state of the article, substantially symmetrical about a plane perpendicular to the longitudinal axis of the article (as, ~or example, in a symmetrical shed3, the above definitions can be simplified. Thus, in this case, the outwardly extending portion may be said to inclined to the longitudinal axis of the article if an ima~inary lin~ joining the outer extrêmity, or the centre of the outermost surface, of that portion-to the centre of the inner extremity meets the longitudinal axis at an àngle ~ther than 90, while, if said angle is approximately 90, the outwardly extending portion may be said to be perpendicular to the longitudinal axis.
If at least the outer surface of the composite structure of~the invention comprises an electrical insulating material, the composite structure may be used as an insulator, and the use ~: ' 7~7~
of appropriate non-tracking materials may render such an in-sulator suitable for high-voltage work. Although the structure, when made of appropriate materials, is particularly suitable for use as an insulator, however, it may also be used for other purposes readily apparent to those skilled in the art. Thus, for example, it may be used as a pulley, or a reel for accommodating thread or rope, provided that the outwardly extending portions are inclined in appropriate directions. However it is used, the composite structure of the invention has the advantage that, as it can be made from a single heat-recoverable component which includes all the desired outwardly extending portions, its manufacture is simpler and less time-consuming than the manu-facture of, for examplei an insulator from a plurality of in-dividual heat-shrinkable sheds, and can be carried out by less skilled workmen.
Each outwardly extending portion in theiarticle of the invention extends round at least part of the periphery of the ; article. If the outwardly extending portions are sheds of elec trically insulating material, these sheds are advantageously continuous, extending round the entire periphery of the article.
~or other uses, however, outwardly extending portions which extend round only part of the periphery may be suitable, provided that each outwardly extending portion extends round the article by such an amount that the desired distortion of the outwardly extending portions occurs on heat-recovery. Where the outwardly extending portions extend round only part of the periphery of the article the article may, if desired, be made in a wrap-around form, a longitudinal seam being made in the article after, e.g., mould-ing. Such a wrap around article might, for example~ find use in 1~6~797~
the wea~ing industr~. The outwardlg e~tending portion~ in the article of the invention are preferably inte~ral with (that is, formed in one piece with) the remainder o~ the article.
I~ de~ired, one or more o~ the outwardly e~tending portions in the article of the invention may extend helici~lly round the longitudi~al a2i~ o~ the article and there may be situations where it is advantageous that all the outwardly e~tendi~g portions are provided by a æingle helic~l outwardly extending member, ~hus, the i~ve~tio~ also provides a modificatio~ of the compo~ite ~tructure, method~ heat-recoverable article i~d process of the invention wherei~ a isingle helical outwardly extendlng member iæ
used instead o~ the outwardly extendi~g portion~.
The inner ~urface o~ the article o~ the i~entio~ may be shaped to facilitate escape o~ air during heat-recovery o~
. 15 the article from between the central por~io~ ther~o~ i~nd a su~strate ~uch as an eleotrical insulator srou~d which the artisle is - -being reoo~ered. ~o this end, ~or example, the inner ~ur~ace ~ .
of the central portion may have at lei~s~t one longitudinallg e~tending - deformity therein~
: ~he hollow article ueed in acoordi~nce with the inventi~
exists, ~rom:the time o~ its ma~ufacture to the time ~hen it has , : fina-1~ beeu i~ætalled on the support member~
~ . -.~ .
.
~:
, :
:~ ~ j - - 8 ~
~ .
in at least three different states. mese are the substantially heat-stable state in which it is formed, a first heat-recoverable state, wherein its internal dimensions are large enough for it to be slipped over the support member, and a second heat-recoverable state wherein it has been recovered around the support member but is prevented by the support member from recovering completely to its original heat-stable state. In the second state it is said to be partially re-covered or to exhibit "unresolved recover~''. As will be well known to those skilled in the art, a body may be converted to a heat-recoverable, or heat-unstable, state by heating it, deforming the hot body, and cooling while maintaining the deforming force. Alternatlvely, deformation may be carried out without 'heating, but a greater deforming force will then generally be required. The heat-recoverable body will maintain its deformed dimensions until it is heated to a~temperature (the recovery temperature~ at which it recovers, or attempts to recover, to its original dimensions.
When the hollow article used in accordanc~ with the ~o invention is in its heat-stable state, the outwardly exte~ding portions are substantially parpendicular to the longitudinal axis of the article, and the~article can thus readily be moulded.
; ~ ~When the heat-stable article is expanded to the first heat-recovera~le state, the outwardly extending portions may, if the degree of expànsion is relatively small, remain substantially ~-perpendicular to the'longitudinal axls. Generally, however, th'e stresses exerted on the outwardly extending portions as _ .. ; ,` : : .
~l~67~7~
a result of their inner dimensions being expanded while the outer dimensions remain substantially unaltered will cause the outwardly extending portions to "flip over", so that they are inclined to the longitudinal axis at an angle that is determined by the dimensions of the article before and after expansion~ On partial recovery of the article from the first heat-recoverable state to the second heat-recoverable state, the outwardly extending portion~ will, if they were substan-tially perpendicular to the longitudinal axis in the first heat-recoverable state, "flip over" so that they are inclined to the longitudinal axis or, if they were inclined to the axis in the first heat-recoverable state, will remain inclined to the axis although at an angle that is somewhat closer to the perpendicular. Again, the angle at which the outwardly extending portions are inclined to the longitudinal axis will depend on the dimensions of the article in the heat-stable ~: state and its dimensions in the partially recovered state.
~î The desired angle of inclination of the outwardly extending portions in the composite structure of the : 20 invention will, of course, d~pend on the use to which the .~i composite structure is to be put. If, for example, th~
j composite structure is to be used in highly polluting , conditions as a non-tracking insulator for high voltage ,,! ~ electrical~components tin which case the outwàrdly extending 25~ portlons will, of course, be sheds~, the angle at which the optlmum~working voltages are obtained will depend on the : dlmensions of`the insulator, the operating voltage and the wettlng characterlstics of the outer surface of the insulator, ~f ~ 1 0 -~067~
and can readily be determined by those skilled in the art.
For some high voltage applications it has been found advantageous to use sheds inclined at an angle of 15 to 30 to the perpendicular (75 to 60 to the longitudinal axis).
In some instances, the direction in which the out-wardly extendin~ portions t'flip over" may be irrelevant, the important factor merely being that these portions should, in the final composite structure, be inclined to the longitudinal axis of the structure. In many cases, however, the direction of inclination is important. Thu~, for example, in an insulator, all the sheds should normally be inclined in the same direction while, in the case of a pulley or reel, each first outwardly extending portion is advantageously inclined in a direction opposite to that of each second shed.
When the direction of inclination is important, the outwardly extending portions must either be so constructed that they inevitably "flip over" in the right direction, or the movement away from the perpendicular must be controlled so that it takes place in the desired direction. This can readily be done by mechanical means. Thus, for example, comb~
like means may be used, the means having a number of suitably spaced teeth or plates which can be brought into abutting relationship with the outwardly extending portions so that movement in the wrong dixection is prevented. Where, of cour~e, the "flipping over" takes place durlng expansion from the heat-stable state to the first heat-recoverable state, the direction of in~lination in~the first heat-recoverable state will remaln unchanged on partial recovery of the article to :: :
,, .. .. .. .. "., . ~ . , . . . .. , .. , ~ . ,., . . ..... ~
.. ' ' !. ~ ' .` ' . ' ' ~ ~ i ; ; ' ' '' - ' : . ' . , ' ' ,` ., ', ' : . ' . ' ; : ' . . . . ', . . ' .:, : , 9~
the second heat-recoverable state, and this has the advantage that the direction of inclination can be predetermined by the manufacturer of the heat-recoverable article, and that the installation of the heat-recoverable article on the support member is particularly simple.
The hollow article used according to the invention, which in the heat-recoverable state, may have plastic or elastic memory, may comprise any material which may have been cross-linked by chemi-cal means or irradiation or by a combination thereof and that may be converted to a heat-recoverable state, the nature of the material being dictated by the use to which the composite structure is to be put. Thus, for example, when the composite structure i5 to be used as a high-voltage insulator, at least ~he outer surface of the composite structure should normally comprise a non-tracking elec-trically insulating material. A non-tracking material may be defined as one which has an initial tracking voltage of more than 3 KV when tested in accordance with ASTM-D2303-64T ~wetting agent Triton X-100), a tes~ method which uses the inclined plane liquid contamination test and is designed to represent service exposure of insulators under polluting conditions. Examples of non-tracking materials which may be converted to a heat-recoverable state are given in British Patent Specifications Nos. 1,292,276, published October 11, 1972, 1,284,081, 1,284,082, both pub-lished August 2, 1972, 1,303,432 published August 17, 1973, 1,337,951, and 1,337,952 bo~h published November 21, 1973, all in the name of Raychem Limited. The article of the invention may be moulded by, for exampIe, compression transfer or injection moulding, andJ when any superfluous material has been remo~led, - 12 -~
: ~ .
~C~679~
may be expanded by any desired method, either automatic or manual.
The exact nature of the support member in the composite structure of the invention will also depend on the use to which the structure is to be put. ~hus, when the composite structure is to be used an an insulator, the support member advantageously comprises a fibre-reinforced electrically insulating material;
details of suitable electrically insulating materials are given, for example, in British Patent Specification ~o. 1,292,276.
Alternatively, there may be situations where the heat-recoverable - article itself is to provide insulation for an electrical ~` component, and in that case the support mer~ber may comprise an electrically conductive material, for example an electrical component such as a cable. It will be understood that the invention is in no way limited by the shape or nature of the support member or of the material from which it is made, and that the support member may comprise any object or objects that are capable of preventing complete recovery of the heat-recoverable ; article.
If ~esire~, an adhesive may be used to bond the heat-. ~
~, recoverable article to the support member used in the composite structure of the invention and/or at least part of the surface of the article which is to contact the support member or `substrate may be provided with a stress-grading material or 25 ~ layer, that is, a material or la~er which can act to reduce the electrical~stress which may exist in various areas of a high voltage component, for example, at the end of the screen of a high voltage~cable. As~sultable adhesives there may be - : :
. ~ . , ' .' ' . ' ' . : ' , ' ., , , " ,: , ' ;' ' , " . . . . ` " . : ". , , ' ' . . ' : ' ~ . ' ~L~16797~
mentioned, for example, epoxy resins (either hot or cold cured~
and polyesters, which resins and polyesters may be used with or without fillers, and silicone-contalning adhesives, especially those with non-tracking properties. Other suitable adhesive compositions include those comprising .
.
:.
:: : :
: : : :
~ 13a -~ 67,~37~L
. . .
a copolymer of a hydrocarbon containing at least one polymerisable double bond and a compound containing a polymerisable double bond together with one or more carboxylic acid groups, which carboxylic acid groups may be in the form of a derivative, for example an es*er or an anhydride. As examples of such copolymers there may be mentioned ethylene/vinyl acetate copolymers, ethylene/ethyl acrylate copolymers, methyl vinyl ether/malei~ anhydride copolymers and, preferably, alkyl esters of methyl vinyl/maleic anhydride copolymers. A stress grading material or layer is suitably a material or layer with linear or preferably, non-linear electrical resistance properties and may have form stability or comprise a substantially non-crystalline material (for example a mastic-like material~ which has a viscosity of not more than 10 3 cp at 25 C. Examples of suitable stress-grading materials are given in DOS 2,344,067 published April 11, 1974 and DOS 2,413,475 published January 2, 1975, both in the name of Raychem Limited. The aspects of stress-grading and anti-tracking ma~ be combined in an article or structure of the invention as described in Canadian Patent Application No.
237~197 filed October 7, 1975 in the name of R.J.T. Clabburn and R.J. Penneck.
.
The invention will now be described, by way of example only, with , reference to the accompanying drawings, in which:
~igure 1 is a cross-section through a hollow article provided with sheds to be used for making an electrical insulator;
Figure 2 is an enlarged cross-section through a portion of a shed;
Figure 3 shows the article of ~igure 1 in an expanded, heat .. ~ .
;- ~ recoverable form;
; Flgure 4 shows the article~of Figure 2 recovered round a substrate;
Figure 5 shows another article according to the invention recovered . ::
round a mandrel3~and Flgures 6 and ? are plots of results obtained according to Example 2.
` --~6~67~7:~L
The Figures are not drawn to scale.
Referring now to the drawingsl Figure 1 shows a hollow article 1 of electrically insulating material which comprises a central tubular portion 2 and a plurality of sheds 3. The sheds 3 are integral with the tubular portion 2, and each shed 3 extends round the entire periphery of the tubular portion 2. Each shed 3 is perpendicular to the longitudinal axis of the tubular portion 2 and is thus such that a longi-tudinally split mould can be removed from the hollow article 1 in a direction substantially perpendicular to the longi-tudinal axis of the tubular portion 2 without substantial ; deformation of the sheds 3.
:
As is clear from Figure 2, the angle of inclination x o~ a shed 3 is the acute angle between the longitudinal axis 4 o~ the article and the imaginary line 5 joining the outer extremity 6 of the shed and the centre point 7 of the inner extremity of the shed. In the article of Figure 1, the sheds are substantlally norma~l to the longitudinal axis, the angle between that axis and the~imaginary line 5 being approximately 90 (for example 90 * about 5~.
Flgure~3 shows the article of Figure 1 in a heat-recoverable form. As can be~ seen from the drawing, the ~; inner diameter of the tubular portion 2 has been expanded, causing the sheds 3 to "flip over" to a state in which ~ they are inclined at an angle x to the longitudinal axis.
~ :
~ ~The article o~ Figure 3 may be positioned around a substrate :
::
~6797~L
(shown diagrammatically at 8~ and heated to cause it to shrink into close contact with the substrate. The angle of inclination x' of the sheds after shrinking is greater than x but, because the outer diameter of the substrate 8 is greater than the inner diameter of the article in the "as-moulded form" illustrated in Figure 1, the sheds are still inclined and do not return completely to the perpen~ular state shown in Figure 1.
m e following Examples illustrate the in~ention.
Example 1 An article was moulded in the form shown in Figure 1, the inner diameter a of the tubular portion 2 being 5.71 cm. and the distance b (measured perpendicular to the longitudinal axis~
betwe~n the outer extremity of each shed and the inner surface of the tubular portion was 2.54 cm. The sheds, which were symmetrical about a plane perpendicular to the longitudinal axis, were perpendicular to that axis.
In the expanded form shown in Figure 3 (the first heat-recoverable state~, the inner diameter a~ of the tubular portion
2 was 8.38 cm. and the distance bg was 2.00 cm. me a~gle of inclination x was 60. In the second heat recoverable form shown in Figure 4 the distance a~ was 8.0~ cm, the distance bS9 was 2.03 cm. and the angle of inclination x9 was 80Q.
} e 2 Experiments~were~carried out to investigate the way in which the angle of inclination of an outwardly extending portion in an article according to the invention varies with the degree ; of~expansion of the article.
:
~ 16 -~7~71 A number of parts were moulded from electrically insulating material. me parts were identical, each consisting of a central tubular portion 9 (see Figure 5~ having an overall length of 16.5 cm and outer diarneter of 2.2 cm and provided with 4 integral symmetrical sheds 10, the distance between adjacent sheds being approximately 2.54 cm. In the "as-mouldedl' article, each of the sheds was perpendicular to the longitudinal axis 11 of the tubular-portion.
Each of the parts was then heated in a glycerine tank at 160C and expanded to a heat-recoverable state by means of a Teflon~ mandrel. On such expansion, the sheds "~lipped over" so that they were no longer perpendicular to the longitudinal axis of the tubular portion, and the angle a (see Figure 5 of the accompanying drawings~ between the "upper" surface of each shed - 15 and the longitudinal axis of the tu~ular portion was determined by measuring the shed diameter ~SoD~ the shed length ~S~L~) and the outer diameter (S.D.~ of the tubular portion, the angle being calculated according to the equation sin a = SoD~ ~ O.D.
2 x S.L.
~! 20 In some cases the parts, having been expanded once J were expanded again, the angle a being determined for each of the expanded states. Thus in T~ble I, which is set out below and indicates the internal dimensions of the expanded parts, state D, wherein the internal diameter was 3.02 cm, was obtained by expanding a part with an "as moulded" internal di~neter of 1.90 cm .! :
~ to a state A, in which it has an internal diameter of 2.54 cm, and s : :
s ~ ~ *~Trade~mark. - 17 -, , 1~6797~
then expanding furthier to an internal diameter of 3.02 cm.
The expanded parts were then recovered in an air oven at 170C round appropriate mandrels, and the angle a was determined for each of the recovered states. Again, in some cases a part, having been partially recovered once, was removed from the mandrel in question and recovered further round a mandrel of smaller diameter.
The internal diameters of the various states obtained on expansion and recovery are indicated in Tables I and II
respectively, while the dimensions measured in each of the states are given in Tables III and IV, Table III referrin~ to the states obtained on expansion, and Table IV referring to those obtained on recovery. Tables V and VI are similar to Tables I and II, but show the shed angles obtained in states A to F and A2 to F2.
In thie parts before expansion the internal diameter 1.D was 1.90 cm, S.D. was 6.5 cm, O.D was 2.2 cm and S.L. was 2.1 + 0.1 cm.
Table~I - Expansion.
amitl internal - ~ ~
_ 2.54 ______ }~a~ ., 3~75 _ _ 1.90 A B C
_ ~ ___ E
~able II - Recovery Initial internal ~iameter (cm9 ~ ; ~ ~ _ _3~03 _ 2,54 _1.90 - ~ 3.75 F2 E2 C2 ~ 3.02 ~ _ _ , :~6797~L
Table III - Expansion A B C D E F
OD(cm~ 2.9 3.4 4,1 ~ r~~~ 4.1 3.9 . ._ . . . ___ . .. ,. .
~cm~6.6 6.5 6.1 6.7 6.1 6.2 .. _.__ ... . ..... _ _ .. _ . . -. __ tcm~2.0 2.0 2.0 2.0 2.0 2.0 . ........ _ _ . ., .. ..... _ : a 68 51 30 .. 30 35 Table IV - Recovery `: A2 B2 C2 D2 E2 R2 . _ 2.-9 2.8 2.8 2.9 ~ 2 3~4 __ .. , _ _ .__ __ 'D(cm~6,7 6.7 6.7 6.7 6.6 6.4 ~ S L . . _- . . . .~ . . _ .~ ' tcm~2.0 2.0 2.0 2.0 2.0 2.0 . . ... __ . , __ a 72 77 77 72 68 49 ., . . . . . --- __~ . .. ~-~ . - .__ Table V - Expansion ! Initial internal Expanded lnternal diameter -~ diameter (cm~ _ _ _ ~ r-------____ , 2.54 3.~2 3.75 :~ .. _ . _ , _ 1.90 68 51 30 2.54 56 30
} e 2 Experiments~were~carried out to investigate the way in which the angle of inclination of an outwardly extending portion in an article according to the invention varies with the degree ; of~expansion of the article.
:
~ 16 -~7~71 A number of parts were moulded from electrically insulating material. me parts were identical, each consisting of a central tubular portion 9 (see Figure 5~ having an overall length of 16.5 cm and outer diarneter of 2.2 cm and provided with 4 integral symmetrical sheds 10, the distance between adjacent sheds being approximately 2.54 cm. In the "as-mouldedl' article, each of the sheds was perpendicular to the longitudinal axis 11 of the tubular-portion.
Each of the parts was then heated in a glycerine tank at 160C and expanded to a heat-recoverable state by means of a Teflon~ mandrel. On such expansion, the sheds "~lipped over" so that they were no longer perpendicular to the longitudinal axis of the tubular portion, and the angle a (see Figure 5 of the accompanying drawings~ between the "upper" surface of each shed - 15 and the longitudinal axis of the tu~ular portion was determined by measuring the shed diameter ~SoD~ the shed length ~S~L~) and the outer diameter (S.D.~ of the tubular portion, the angle being calculated according to the equation sin a = SoD~ ~ O.D.
2 x S.L.
~! 20 In some cases the parts, having been expanded once J were expanded again, the angle a being determined for each of the expanded states. Thus in T~ble I, which is set out below and indicates the internal dimensions of the expanded parts, state D, wherein the internal diameter was 3.02 cm, was obtained by expanding a part with an "as moulded" internal di~neter of 1.90 cm .! :
~ to a state A, in which it has an internal diameter of 2.54 cm, and s : :
s ~ ~ *~Trade~mark. - 17 -, , 1~6797~
then expanding furthier to an internal diameter of 3.02 cm.
The expanded parts were then recovered in an air oven at 170C round appropriate mandrels, and the angle a was determined for each of the recovered states. Again, in some cases a part, having been partially recovered once, was removed from the mandrel in question and recovered further round a mandrel of smaller diameter.
The internal diameters of the various states obtained on expansion and recovery are indicated in Tables I and II
respectively, while the dimensions measured in each of the states are given in Tables III and IV, Table III referrin~ to the states obtained on expansion, and Table IV referring to those obtained on recovery. Tables V and VI are similar to Tables I and II, but show the shed angles obtained in states A to F and A2 to F2.
In thie parts before expansion the internal diameter 1.D was 1.90 cm, S.D. was 6.5 cm, O.D was 2.2 cm and S.L. was 2.1 + 0.1 cm.
Table~I - Expansion.
amitl internal - ~ ~
_ 2.54 ______ }~a~ ., 3~75 _ _ 1.90 A B C
_ ~ ___ E
~able II - Recovery Initial internal ~iameter (cm9 ~ ; ~ ~ _ _3~03 _ 2,54 _1.90 - ~ 3.75 F2 E2 C2 ~ 3.02 ~ _ _ , :~6797~L
Table III - Expansion A B C D E F
OD(cm~ 2.9 3.4 4,1 ~ r~~~ 4.1 3.9 . ._ . . . ___ . .. ,. .
~cm~6.6 6.5 6.1 6.7 6.1 6.2 .. _.__ ... . ..... _ _ .. _ . . -. __ tcm~2.0 2.0 2.0 2.0 2.0 2.0 . ........ _ _ . ., .. ..... _ : a 68 51 30 .. 30 35 Table IV - Recovery `: A2 B2 C2 D2 E2 R2 . _ 2.-9 2.8 2.8 2.9 ~ 2 3~4 __ .. , _ _ .__ __ 'D(cm~6,7 6.7 6.7 6.7 6.6 6.4 ~ S L . . _- . . . .~ . . _ .~ ' tcm~2.0 2.0 2.0 2.0 2.0 2.0 . . ... __ . , __ a 72 77 77 72 68 49 ., . . . . . --- __~ . .. ~-~ . - .__ Table V - Expansion ! Initial internal Expanded lnternal diameter -~ diameter (cm~ _ _ _ ~ r-------____ , 2.54 3.~2 3.75 :~ .. _ . _ , _ 1.90 68 51 30 2.54 56 30
3.02 35 ., ...... ____ ._ ~. .__ ', ! - 19 -! - `
. . . .. . .
~67~7~
Table VI - Recovery ._ .
Initial internal Recovered internaL diameter diameter (cm~ _ . . ~. .
3.02 2.54 2022 ._ __ . , . .
.- 3.75 , 49 68 77 3.02 72 77 .: 2.54 _ 72 , . __ It can be seen from Tables V and VI that, within the limits of experimental error, the shed angle for a part is dependent only on the internal diameter of that part, the same angle a being obtained for a given diameter whether that dia~eter is the result of expansion from a smaller diameter or recovery from a larger one. If the average shed angle and percentage expansion : - (actual internal ~iameter - "as moulded" internal diameter~ x 100 b l'as moulded" internal diameter ."
are calculated for each internal diameter, the values yiven in .! Table VII are obtained.
. Table VII
_ , ~ , ,'. ~ ~ .
Internal diameter Average shed % Expan~ion ~l : (cm3 . angle ... ~ . . - , .. - _ 1 . 90 so o 2.22 75 15.8 i 2.54 69 33.7 . 3.02 52 59.
3.75 32 97.5 ~ ~.... ,.. ____ ____ : ~ - 20 -:
,,.'.''..,'"',''"'''"'"'.,' '' '' ' ' " ;''~'"' '';"' ~ ',"". ."' ;' ( ` ~L0~i7~71 Plots of these values against the internal diameter are shown in Figures 6 and 7.
. . . .. . .
~67~7~
Table VI - Recovery ._ .
Initial internal Recovered internaL diameter diameter (cm~ _ . . ~. .
3.02 2.54 2022 ._ __ . , . .
.- 3.75 , 49 68 77 3.02 72 77 .: 2.54 _ 72 , . __ It can be seen from Tables V and VI that, within the limits of experimental error, the shed angle for a part is dependent only on the internal diameter of that part, the same angle a being obtained for a given diameter whether that dia~eter is the result of expansion from a smaller diameter or recovery from a larger one. If the average shed angle and percentage expansion : - (actual internal ~iameter - "as moulded" internal diameter~ x 100 b l'as moulded" internal diameter ."
are calculated for each internal diameter, the values yiven in .! Table VII are obtained.
. Table VII
_ , ~ , ,'. ~ ~ .
Internal diameter Average shed % Expan~ion ~l : (cm3 . angle ... ~ . . - , .. - _ 1 . 90 so o 2.22 75 15.8 i 2.54 69 33.7 . 3.02 52 59.
3.75 32 97.5 ~ ~.... ,.. ____ ____ : ~ - 20 -:
,,.'.''..,'"',''"'''"'"'.,' '' '' ' ' " ;''~'"' '';"' ~ ',"". ."' ;' ( ` ~L0~i7~71 Plots of these values against the internal diameter are shown in Figures 6 and 7.
Claims (26)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A heat-recoverable hollow article for use in covering a substrate which article has at least one open end and has two or more outwardly extending portions which extend round at least part of the periphery of the article and are such that, on partial recovery of the article around and into contact with the substrate, they will be inclined to the longitudinal axis of the article.
2. An article as claimed in claim 1, wherein each outwardly extending portion extends around the entire periphery of the article.
3. An article as claimed in claim 1 or claim 2, wherein each outwardly extending portion is integral with the remainder of the article.
4. An article as claimed in claim 1, wherein the said outwardly extending portions are substantially perpen-dicular to the longitudinal axis of the article.
5. An article as claimed in claim 1, which is made of electrically insulating material.
6. An article as claimed in claim 5, wherein each outwardly extending portion is a shed.
7. An article as claimed in claim 5 or claim 6, at least the outer surface of which is made of a non-tracking electrically insulating material.
8. An article as claimed in claim 6 suitable for use in covering an electrical insulator which article includes a longitudinal central portion having a plurality of sheds extending outwardly therefrom.
9. An article as claimed in claim 8, wherein the inner surface of the central portion has at least one longitudinally extending deformity therein to facilitate escape of air from between the central portion and the insulator during heat-recovery of the article.
10. An article as claimed in claim 8, wherein the inner surface of the article is shaped to facilitate escape of air from between the central portion and the insulator during heat-recovery of the article.
11. An article as claimed in claim 5, wherein at least a part of the surface of the article which is to contact the substrate comprises, or is provided with a layer of , a stress-grading material.
12. An article as claimed in claim 1, wherein at least a part of the surface of the article which is to contact the substrate is provided with an adhesive.
13. A process for the manufacture of a heat-recoverable hollow article, which comprises forming a hollow article having at least one open end and two or more outwardly extending portions which extend round at least part of the periphery of the article and are substantially perpendicular to the longitudinal axis of the article, and enlarging the inner dimensions of the article to convert it to a heat-recoverable state in which two or more outwardly extending portions are such that, on partial recovery of the article around a substrate, they will be inclined to the longitudinal axis of the article.
14. A heat-recoverable hollow article for use in covering a substrate which article has at least one open end and has two or more outwardly extending portions which extend round at least part of the periphery of the article and are such that, on partial recovery of the article around and into contact with the substrate, they will be inclined to the longitudinal axis of the article, and are such that, on substrate free recovery of the article, they will be substantially perpendicular to the longitudinal axis of the article.
15. A composite structure which comprises a substrate having applied to the outer surface a hollow heat-recoverable article having at least one open end and two or more outwardly extending portions which extend around at least part of the periphery of the article and are inclined to the longi-tudinal axis of the composite structure.
16. A composite structure as claimed in claim 15, wherein the substrate is of an electrically insulating material.
17. A composite structure as claimed in claim 16, wherein the substrate is a fuse body, bush or insulator post.
18. A composite structure as claimed in claim 15, wherein the outwardly extending portions are inclined in the same direction to the longitudinal axis of the article.
19. A method of covering a substrate comprising:
positioning round the substrate a heat-recoverable hollow article having at least one open end and two or more outwardly extending portions which extend round at least a part of the periphery of the article and are such that, on partial recovery of the article around and into contact with the substrate, they will be in-clined to the longitudinal axis of the article; and heat-recovering the article into contact with the substrate.
positioning round the substrate a heat-recoverable hollow article having at least one open end and two or more outwardly extending portions which extend round at least a part of the periphery of the article and are such that, on partial recovery of the article around and into contact with the substrate, they will be in-clined to the longitudinal axis of the article; and heat-recovering the article into contact with the substrate.
20. A composite structure which comprises a sub-strate which has had heat-recovered into contact with the outer surface thereof a heat-recoverable hollow article having at least one open end and two or more outwardly extending portions which extend round at least a part of the periphery of the article and are such that, on partial recovery of the article around and into contact with the substrate, they will be inclined to the longi-tudinal axis of the article.
21. A method of making a composite structure which comprises positioning a hollow heat-recoverable article, which article has at least one open end and has two or more outwardly extending portions which extend round at least part of the periphery of the article, around a support member the exterior dimensions of which support member are greater than the interior dimensions that the article would have if recovered in the absence of a substrate, and heating to cause the article to recover into contact with the support member such that two or more of the outwardly extending portions are inclined to the longitudinal axis of the article.
22. A heat-recoverable article which comprises an elongate hollow member having at least one open end and two or more sheds which extend outwardly in a generally radial direction from the hollow member and are inclined to the longi-tudinal axis of the hollow member, the article being such that, if the article were recovered into contact with a substrate having outer dimensions such that it can just be received in the hollow member, the said sheds would be inclined to the longitudinal axis of the hollow member, and such that on substrate-free recovery the said sheds would be substantially perpendicular to the longitudinal axis of the hollow member.
23. A heat-recoverable article as claimed in claim 22, wherein the sheds are all inclined in the same direction.
24. A process for the manufacture of a heat-recoverable article, which comprises forming an article end and two or more sheds which extend outwardly in a generally radial direction from the hollow member and substantially per-pendicular to the longitudinal axis of the hollow member, en-larging the inner dimensions of the article to convert it to a heat-recoverable state in which at least two sheds are inclined to the longitudinal axis of the hollow member and in which the article is such that, if the article were recovered into contact with a substrate having outer dimensions such that it can just be received in the hollow member, the said at least two sheds would be inclined to the longitudinal axis of the hollow member.
25. A composite structure which comprises a substrate having applied to the outer surface thereof a heat-substrate article comprising an elongate hollow member having at least one open end and two or more sheds which extend out-wardly in a generally radial direction from the hollow member and are inclined to the longitudinal axis of the composite structure, the article being such that, is the substrate were removed and the article were fully recovered, the said sheds in the fully recovered article would be substantially perpen-dicular to the longitudinal axis of the hollow member.
26. A method of making a composite structure which comprises positioning around a substrate a heat-recoverable article comprising an elongate hollow member having at least one open end and two or more sheds which extend outwardly in a generally radial direction from the hollow member and are in-clined to the longitudinal axis of the hollow member, the exterior dimensions of the substrate being greater than the interior dimensions that the hollow member would have if recovered in the absence of a substrate such that on recovery of the article into contact with the substrate the said sheds are inclined to the longitudinal axis of the hollow member and the article being such that on substrate-free recovery the said sheds would be substantially perpendicular to the longitudinal axis of the hollow member, and heating to cause the article to recover into contact with the substrate.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB43536/74A GB1530994A (en) | 1974-10-08 | 1974-10-08 | Composite structures of heat-recoverable articles |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1067971A true CA1067971A (en) | 1979-12-11 |
Family
ID=10429196
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA237,196A Expired CA1067971A (en) | 1974-10-08 | 1975-10-07 | Composite structures and heat recoverable articles |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5851367B2 (en) |
| AU (1) | AU503587B2 (en) |
| CA (1) | CA1067971A (en) |
| DE (1) | DE2544992A1 (en) |
| FR (1) | FR2287756A1 (en) |
| GB (1) | GB1530994A (en) |
| IT (1) | IT1043227B (en) |
| NO (1) | NO141529C (en) |
| ZA (1) | ZA756232B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2170360B (en) * | 1979-03-12 | 1988-10-12 | Lapp Insulator Co | High voltage resistant members and method for producing same |
| US4312123A (en) * | 1979-03-12 | 1982-01-26 | Interpace Corporation | Methods of making high voltage electrical insulators and oil-less bushings |
| EP0017677A1 (en) * | 1979-04-24 | 1980-10-29 | BBC Aktiengesellschaft Brown, Boveri & Cie. | Process for joining oblong bodies by means of memory-shape alloy connection elements |
| GB8312892D0 (en) * | 1983-05-11 | 1983-06-15 | Raychem Ltd | Electrical insulator |
| GB8923408D0 (en) * | 1989-10-17 | 1989-12-06 | Raychem Ltd | Electrical insulator |
| ES2170901T3 (en) * | 1996-07-31 | 2002-08-16 | Pirelli Cavi E Sistemi Spa | PROCEDURE FOR THE MANUFACTURE OF A PROFILE INSULATION COATING IN THE FORM OF A FIN. |
| JPWO2018003312A1 (en) * | 2016-06-30 | 2019-04-18 | リンテック株式会社 | Semiconductor processing sheet |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1640768A1 (en) * | 1968-02-24 | 1971-02-11 | Kabel Metallwerke Ghh | Method for producing an end termination for high voltage cables and lines |
| FR1583206A (en) * | 1968-04-12 | 1969-10-24 | ||
| GB1292276A (en) * | 1968-09-04 | 1972-10-11 | Raychem Ltd | Improvements in and relating to insulators |
| DE2142283B2 (en) * | 1971-08-24 | 1972-12-07 | Feiten & Guilleaume Kabelwerke AG, 5000 Köln | CABLE END CLOSURE |
| GB1434719A (en) * | 1972-09-01 | 1976-05-05 | Raychem Ltd | Heat recoverable products |
| US3808352A (en) * | 1972-10-26 | 1974-04-30 | Minnesota Mining & Mfg | Elastomeric terminal insulator and stress cone and conductor terminated therewith |
-
1974
- 1974-10-08 GB GB43536/74A patent/GB1530994A/en not_active Expired
-
1975
- 1975-10-01 ZA ZA00756232A patent/ZA756232B/en unknown
- 1975-10-07 NO NO753375A patent/NO141529C/en unknown
- 1975-10-07 CA CA237,196A patent/CA1067971A/en not_active Expired
- 1975-10-07 AU AU85525/75A patent/AU503587B2/en not_active Expired
- 1975-10-08 DE DE19752544992 patent/DE2544992A1/en active Granted
- 1975-10-08 IT IT28103/75A patent/IT1043227B/en active
- 1975-10-08 FR FR7530786A patent/FR2287756A1/en active Granted
-
1980
- 1980-07-11 JP JP55094927A patent/JPS5851367B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2287756B1 (en) | 1981-08-21 |
| AU8552575A (en) | 1977-04-21 |
| AU503587B2 (en) | 1979-09-13 |
| JPS5851367B2 (en) | 1983-11-16 |
| DE2544992C2 (en) | 1987-08-20 |
| NO141529C (en) | 1980-03-26 |
| ZA756232B (en) | 1976-10-27 |
| DE2544992A1 (en) | 1976-04-22 |
| FR2287756A1 (en) | 1976-05-07 |
| NO141529B (en) | 1979-12-17 |
| GB1530994A (en) | 1978-11-01 |
| NO753375L (en) | 1976-04-09 |
| IT1043227B (en) | 1980-02-20 |
| JPS5635313A (en) | 1981-04-08 |
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