GB843102A - Improvements in or relating to the manufacture of tubes - Google Patents

Abstract

843,102. Electrophonesis. MULLARD RADIO VALVE CO. Ltd. April 26, 1957 [May 3, 1956], No. 13703/56. Class 41. [Also in Group XXIII] A method of manufacturing a tube of vitreous, aluminous or silicaceous material comprises disposing a straight metal rod 7 as one electrode in a liquid suspension of the material, disposing a second electrode, e.g. a gauze cylinder 3, to surround the rod 7, passing an electric current between the electrodes to deposit electrophonetically a coating of the material on the rod 7, removing the coated rod 7 from the liquid, firing the coating, and removing the rod 7 from the tube of material. The tube may be machined before or after firing, which may be carried out at 1400‹C. in the case of alumina. Where a hard tube is desired, firing is effected at 1600‹C. or above and the tube may be machined before firing or ground after firing. In the illustrated embodiment, the rod 7, which may be a nickel-iron alloy, is rotated about its longitudinal axis during deposition and stirrers 5 are rotated about the gauze 3 by a rotated spindle 6. The gauze 3 rests on an annular electrode 2. The liquid is aluminium hydroxide in methanol, the weight ratio being 2:3. The tube is fired at 1400‹C., machined, and the rod 7 removed by dissolving in acid, e.g. aqua regia. If the firing is to be above 1600‹C., the rod 7 should be molybdenum or tungsten-steel. A molybdenum rod may be removed by dissolving in a sodium hydroxide solution or in a mixture of hydrochloric and sulphuric acids, or the rod 7 may be stretched to reduce its diameter. The method is applicable to suspensions of fine glass or silica.