GB344572A - Improvements in the manufacture of refractory articles - Google Patents

Abstract

344,572. Refractory articles ; discharge apparatus. WESTINGHOUSE LAMP CO., Bloomfield, New Jersey, U.S.A. -(Assignees of Iredell, C. V.; 376, Prospect Street, East Orange, New Jersey, U.S.A.) Dec. 24, 1929, No. 39475. Convention date, Dec. 29, 1928. [Classes 22 and 87 (ii).] Refractory insulating articles are made from powdered refractory material, such as alumina, magnesia, zirconia, thoria, silica, zirconium silicate, magnesium silicate, &c., by adding a normally non-fluid temporary binder of organic waxy material such as paraffin wax or beeswax, moulding the dry mixture to shape under pressure, and firing. The refractory material is preferably prefired to approximately the maximum temperature at which the formed articles are to be used. The wax may be added in solution, the solvent being dried off before the moulding operation. In an. example refractory support members 1, Fig. 4, for the indirectly-heated cathode 2 of vacuum tube apparatus described in Specification 315,375, [Class 39 (i), Electric lamps, Arc. &c.], are formed from a mixture of 98 per cent of alumina which has been prefired for a prolonged period, and 2 per cent of talc. This mixture is milled to pass a 100-mesh screen and the powder is mixed with a solution of 8 grams of paraffin in 200 to 400 c.c. of ether in such proportion as to give about 8 per cent by weight of paraffin to powder. The powder is then air-dried and re-screened. The article is moulded in a press comprising a die 7, Fig. 1, a bottom plunger 17 and a top plunger 13 having a thin extension 16 adapted to enter a boring 19 in the bottom plunger. With the bottom plunger in the position shown, the die is filled with powder and the top plunger is forced down to form the article 1. The top plunger is then raised and the formed article is ejected by upward movement of the bottom plunger 17. The article is then fired in a hydrogen atmosphere at 1500-1650‹ C. Specifications 23071/08, [Class 87, Moulding &c.], and 223,573, [Class 22, Cements &c.], also are referred to.