Abstract: Rigid electrical insulator including a soda-lime glass dielectric with an average thickness of 10 to 15 mm, exhibiting a substantially parabolic stress curve, wherein the maximum value of the surface compression stresses at any point in the part falls within the range of 30 to 80 MPa, while the maximum value of the internal tensile stresses at any point in the part falls within the range of 15 to 40 MPa.

Abstract: An electrical insulator offering reduced sensitivity to pollution comprises a body of a glass or porcelain dielectric material with a semiconductor outside coating. This coating mainly consists of zinc oxide with at least one further metal oxide added to it to make its voltage-current characteristic non-linear, such that I=kV.sup..alpha. where I is current, V is voltage, k and .alpha. are coefficients, and the value of .alpha. is between 20 and 50. The coating is between 0.05 and 0.5 mm thick. The further metal oxide is advantageously selected from bismuth, manganese, cobalt, chromium and antimony oxides.

Abstract: The ends of a fiber-reinforced resin rod are inserted through sealing grommets into cavities of respective end fittings; the end fittings of the assembly are placed in accurately spaced end moulds; the rod is encased in intermediate half shells; an insulator covering is moulded around the rod by filling the half shells; and the end fittings are then fixed to the rod by embedding or swaging.

Abstract: A tempered glass dielectric material for use as an electrical insulator is thermally tempered to produce surface compression between 200 MPa and 400 MPa. At least part of the material is then chemically tempered under conditions of temperature and duration such that the surface compression due to the thermal tempering is reduced by between 50% and 80%. The chemical tempering is effected by applying to the relevant part of the material, at ambient temperature, a solution containing alkaline salts. This solution is dried and the material then heated for several hours at a temperature between 300.degree. C. and 500.degree. C. The solution has the following composition (in percentage by weight):______________________________________ H.sub.2 O 70% to 90% Starch 2% to 10% KNO.sub.3 4% to 12% K.sub.2 HPO.sub.4 + KCl + K.sub.2 SO.sub.

Abstract: The invention relates to line insulators made of organic material. Such an insulator comprises a bar (7) of high tensile strength, a protective sheath (8) made of an elastomer material, a plurality of fins (4) and an anchor fitting (2) at each end. In accordance with the invention, at least one inner part of the insulator is semiconductive along the whole length which separates the anchor fittings (2); this part may be constituted either by the sheath (8) itself or by the bar (7) and the bedding material in said fittings. Application, in particular, to line insulators intended for use in highly polluted zones.

Abstract: An insulator comprising a plurality of fins (1) or one-piece groups of fins made of elastomer and having sleeves (2) disposed end-to-end. The fins surround a central member (3) and are vulcanized. The fins form a water-tight tube whose cohesion is ensured at least by vulcanizing intermediate elastomer portions (5) which are inserted raw between vulcanized fins or one-piece groups of fins and adhere to the facing surfaces of the said sleeves by virtue of their subsequent vulcanization.

Abstract: The invention relates to line insulators made of organic material. Such an insulator comprises a bar (7) of high tensile strength, a protective sheath (8) made of an elastomer material, a plurality of fins (4) and an anchor fitting (2) at each end. In accordance with the invention, at least one inner part of the insulator is semiconductive along the whole length which separates the anchor fittings (2); this part may be constituted either by the sheath (8) itself or by the bar (7) and the bedding material in said fittings. Application, in particular, to line insulators intended for use in highly polluted zones.