Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1994-12-07
1998-03-10
Gray, Jill
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
264278, 264279, 2642791, 361127, 428373, 428375, 428377, 428392, 428367, 428395, 428408, D02G 300
Patent
active
057259526
DESCRIPTION:
BRIEF SUMMARY
This application claims the benefit under 35 U.S.C. .sctn.120 of the filing date of international application no. PCT/GB 93/01210, filed Jun. 8, 1994, published as WO93/26016 Dec. 23, 1993.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to composite, for example electrically insulating, articles, including electrical insulators per se, and in particular to reinforced polymeric insulators.
Although the invention is preferably concerned with articles that perform a solely insulating function, and the ensuring description, for convenience, will relate mainly thereto, it is to be understood that in general the composite, for example, electrically insulating articles may also or alternatively perform other functions. Thus, the article may be a surge arrester, which for most of its time acts as an insulator but which, on the application of an over-voltage thereto, becomes conducting, in order to divert a surge of electrical power, from a lightning strike on associated electrical equipment for example, to earth. Broadly, however, the invention relates to composite articles whether electrically insulating or conductive.
2. Description of the Prior Art
Electrical insulators for use at voltages in excess of about 1 kV, and typically at 24 kV, can be formed from (i) porcelain, which has good electrical properties but is heavy and brittle, thus having low resistance to vandalism; (ii) glass fibre rod impregnated with an epoxy resin, which is of lighter weight but generally has inferior electrical performance to porcelain in outdoor applications, or must be environmentally sealed; or (iii) solid polymeric material, which combines the advantages of light weight and good electrical performance but has poorer load bearing properties. Furthermore, polymeric tubing and/or sheds (annular extensions) may be added to porcelain or glass fibre rods, or incorporated into polymeric insulator, for enhanced performance. Reference is hereby made to GB-A-1 292 276, US-A-4 045 604, GB-A-1 530 994, GB-A-1 530 995 and EP-A-0 253 622 (all to Raychem) and to GB-A-1 313 609 (BICC) for examples of such insulators and components.
One disadvantage of the use of glass (or other) fibre in the construction of an insulator is the possibility of moisture wicking along the fibre and thus providing an electrical short circuit between the terminals, usually one at each end, of the insulator that make electrical connection therewith. Such material however can provide high mechanical strength.
SUMMARY OF THE INVENTION
In general, it is an object of the present invention to provide a method of making a composite article of high strength that contains fibres, in such a way as to avoid, or at least reduce, the risk of moisture flowing along the fibres.
It is also an object of the present invention to provide an electrical insulator that provides the advantages of glass (or other high strength) fibre and of polymeric material, and to do so in a relatively inexpensive manner, whilst obviating, or at least reducing, the problem of moisture flowing from one end of the insulator to the other.
Thus, in one aspect, the present invention provides a method of making a composite article, the article comprising yarn enclosed within outer fusible material, wherein material, is disposed in a mould, and the temperature of the fusible material being at least equal to, and preferably above, the temperature at which the blocking material fuses, thereby to cause the blocking material to melt and flow between and around the strength fibres of the yarn so as completely to enclose the fibres therewithin, and such that the blocked yarn is completely enclosed within the outer fusible material.
The term yarn is used to mean a plurality of fibres, which may be mono- or multi- filament fibres, and is considered to be synonymous with strand, tow, thread or tape.
By "fusible" is meant a material that flows on becoming hot and which either cures under the influence of the heat or solidifies on cooling, and thus includes thermoplastic and ther
REFERENCES:
patent: 5298301 (1994-03-01), Midgley et al.
patent: 5389442 (1995-02-01), Arroyo et al.
STN Access No. 86(8):122238(abstract of Cattanach et al., J. Polym. Eng., vol. 6, No. 1-4, 1986, pp. 345-362).
STN Access No. 86(5):62182 (abstract of Gore et al., Mater, Eng., vol. 103, No. 3, Mar. 3, 1986, pp. 47-50).
STN Access No. 85(12)181377 (abstract of Chang et al., Compos. Sci. Technol., vol. 24, No. 1, 1985, pp. 61-79).
Patent Abstracts of Japan, P field, vol. 14, No. 240, May 22, 1990, P. 115 P 1051 (abstract if appl'n No. 02-62506 (NTT)).
Bennett Jeffrey
Mackevich Jeffry
Thornley David William Maute
Winfield Philip Roland
Burkard Herbert G.
Chao Yuan
Gray Jill
Raychem Limited
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