Plastic and nonmetallic article shaping or treating: processes – With printing or coating of workpiece – Coating or impregnating workpiece before molding or shaping...
Patent
1986-05-22
1987-10-27
Lowe, James
Plastic and nonmetallic article shaping or treating: processes
With printing or coating of workpiece
Coating or impregnating workpiece before molding or shaping...
264254, 264263, 264278, B24C 4514
Patent
active
047028734
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of molding the insulating covering of a long organic electrical insulator. Such an insulator includes a central insulating member, such as a solid or hollow rod, and its ends have metal end fittings.
The central rod is made of laminated material constituted by resin-coated fibers, and it is covered with an insulating covering in the form of a sheath which is generally provided with fins. The covering material is a hot-vulcanizable elastomer such as EPM, EPDM, silicone rubbers, polyurethanes, or the like, and it may be impregnated with inorganic material (alumina, silica, etc. . . ).
The invention relates in particular to insulators which are more than 0.50 meter long, and which may be up to two or three meters long. If a rod of this length is placed in a mold, and elastomer is injected at a pressure of up to 500 bars, it is observed that the rod bends under the effect of the pressure of the material and the various flows filling the mold cavity. This leads to large variations in the thickness of the the covering from one end of the rod to the other. To ensure that there is a covering of a minimum thickness on the rod at all points along its length, one solution would be to increase quite considerably the quantity of elastomer that is injected. However, this has drawbacks: it increases insulator weight, vulcanization time, and cost.
Another solution has thus been sought in which the rod is held in place inside the mold during injection.
British Pat. No. 599 570 describes a method of injection molding an insulating covering on a metal insert in the form of a very thin pin. The covering material is thermoplastic, in other words it is heated to its softening or melting point and it is injected into a cold mold.
A series of very thin rods is provided in the mold which hold the metal insert in place throughout the filling of the mold by the thermoplastic material, and which are automatically retracted when the mold is completely full.
For an organic insulator, the problem posed is much more complex. Firstly the rod has a modulus of elasticity which is four or five times less than that of the above-mentioned metal insert. It thus has a greater tendency to bend than the metal insert. Further, in order for the elastomer covering to adhere properly to the surface of the rod, it is necessary to treat the rod prior to injection with adherization agents, which is not the case with a metal insert.
Furthermore, the covering material is hot vulcanized, which means that it is injected at an average temperature of about 100.degree. C. into a hot mold whose temperature is about 180.degree. C. to 200.degree. C.
If the arrangement of the above-mentioned British patent were implemented, metal supports at mold temperature would come into contact with the adherization agents on the surface of the rod, and would immediately degrade them. This would lead to defects in the adherence of the covering on the rod which would to totally unacceptable for medium and high tension insulators.
The present invention aims to avoid these drawbacks.
The present invention provides a method of molding the insulating covering of an organic electrical insulator which includes a central rod of composite material having adherization agents on its surface, the said insulating covering being made of a hot vulcanized elastomer material, in which method retractable supports are provided in the mold for the said rod, the method being characterized by the fact that the said rod is provided with protective sleeves at least in the region of its surfaces that bear against the said supports, the thickness of the sleeves being less than the thickness of the said covering and the material of the sleeves being directly bondable to the material of said covering during vulcanization of said covering material, in that the material for the said covering is then injected, and in that the said supports are retracted at the end of injection and before vulcanization of the said covering.
The sleeves are advantageously made of an el
REFERENCES:
patent: 1163701 (1915-12-01), Stiarns
patent: 1837142 (1931-12-01), Bailey
patent: 2979431 (1961-04-01), Perrault
patent: 3044127 (1962-07-01), Alden
patent: 3089199 (1963-05-01), Halacsy
patent: 3090999 (1963-05-01), Karns
patent: 3259680 (1966-07-01), Schilke
patent: 3363040 (1968-01-01), Aoki
patent: 4102973 (1978-07-01), Hanning
patent: 4107451 (1978-08-01), Smith, Jr.
patent: 4243628 (1981-01-01), Herold
patent: 4470786 (1984-09-01), Sano et al.
patent: 4561625 (1985-12-01), Weaver
Ceraver S.A.
Lowe James
LandOfFree
Method of manufacturing a composite insulator does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of manufacturing a composite insulator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of manufacturing a composite insulator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1271114