GB673596A - Improvements in and relating to electric insulating bushings and glass therefor - Google Patents

Abstract

673,596. Bushings. BRITISH THOMSONHOUSTON CO., Ltd. Aug. 2, 1950 [Aug. 17, 1949], No. 19305/50. Class 36. [Also in Group XXIII] An insulating bushing comprises a glass insulator consisting of 56-62 per cent SiO 2 , 19.5-24 per cent B 2 O 3' 2-3 per cent Li 2 O, 4.5-7 per cent Na 2 O, 1-4 per cent K 2 O, 3-8 per cent Al 2 O 3 , 0.1-1 per cent CaO, 3-7 per cent PbO, and 0.5-1 per cent MnO 2 , (see Group XXIII), and co-operating terminals consisting of an alloy of 41-43 per cent Ni and 57-59 per cent Fe embedded in part in the glass. A typical bushing, as shown in Fig. 1, includes a hollow threaded stud 1 joined, e.g. by brazing, with a collar 2 embedded in the glass insulator 3, and a lower collar 4 embedded in the glass. The collar 4 is also mounted on the apparatus 5 by welding &c. and serves to mount the bushing. A metal tube 6 passing through the insulator is held by a thimble 7 and may act as a conduit for a conductor fixed to the stud 1. Thimble 7 and shield 8 shield portions of collars 2 and 4 from contact with the glass during casting, thus permitting expansion and contraction of the bushing ports without damage. In Fig. 2, terminal studs 9, 10, 11 have collars 12, 13, 14, the rims of which are embedded in the insulator 15, shields such as 7 being provided. Basal collar 16 also has a flange embedded in the glass and a flange 17 joined to the port 18, e.g. the container of a capacitor or transformer &c.