Patent GB-313626-A (GB)
Title: Improvements relating to electrical insulators
IPC: H01B17/36
Filed: 1929-06-15
Abstract: 313,626. Associated Electrical Industries, Ltd., (Assignees of Miller, F. H., and Jackson, R. P.). June 16, 1928, [Convention date]. Insulators. - An electric insulator for high-voltage transmission-line service comprises a tension rod or tube 2 formed of organic or fibrous insulating material such as wood, paper or cloth impregnated with a binder such as alurite. The tube 2 is formed with frusto-conical ends enclosed in caps 8, and preferably tapers from the centre to the ends as shown in Fig. 1. A porcelain tube 3, adapted to contain an oil filling 25 or the like, surrounds the rod 2. The tube 3 has a silica-glaze coating 10, and, near its ends, metallic glaze bands 12 are applied in the wet state, the tube being then fired to a temperature such as to fuse the silica glaze. The glaze bands 12 are preferably formed from chloro-platinic acid suspended in essential oils such as lavender cloves and spice, or from silver nitrate mixed with a reducing agent such as sugar, silver oxalate, nickel or copper formate, or copper acetate. The caps 8 carry studs 14 on which are mounted caps 15 for the tube 3, cushioning gaskets 17 and end caps 18. The caps 18, preferably of thin sheet metal such as copper, are apertured for the studs 14 and are soldered to the caps 8, and the side wall portions 23 of the caps 18 are soldered to the glaze-bands 12. Flexibility is provided for by forming the caps 18 with annular ridges 21 as shown in Fig. 1. The tube 3 may contain oil, dry air or inert gas, the oil being poured in through a hole in the cap 18 which is then closed by solder. The gaskets 17 are formed by corrugated split metal rings. The solder seals on the caps 18 are protected by nuts 28 on the studs 14, and by the side walls 29 of the caps 15, respectively. As shown in Fig. 2, an electrostatic stress distribution hood 30 may be mounted between washers 31, 32 beneath a clevis 33, on the upper stud 14. The clevis 33 may mount the insulator on a mainsupporting tower or pole cross-arm. The lower stud 14 carries a conductor clamp or an insulator between the lower stud and the conductor. In a modified construction, the sealing caps 18 are omitted, the main caps being slidable on the tube ends and the tube hermetically sealed by cylindrical diaphragms soldered to the caps and to the metal glaze films 12. In a further modification shown in Fig. 5, copper caps 60 are formed with cup portions 61 to engage the tube ends 7, the cap 60 having lateral flanges 62 with edges 63 flared to form pockets for solder, as shown. Clamps 65 are interlocked against the sides of the cups 61 by bolts 67, fitted with nuts 68, passing through lugs 66 on the clamps 65. Terminal bolts 69, 70 are adapted to receive clevis and eyemembers 71, 72 respectively. At the upper end of the insulator, a hood 73, held in position on the clamps 65 by a washer 74 and the clevis 71, seals the spaces between the members 65 against moisture. End webs 75 on the members 65 and side webs fit against the hood 73. To drain moisture from the lower end of the insulator a hood 73 is formed with an opening 77 in one of the webs 75. Both hoods 73 have flanges 78, the upper hood having riveted to the flanges 78 an electrostatic-stress-distributor 79, the lower hood carrying a torus 80 riveted to the flange 78.