GB410033A - Improvements in and relating to methods of and apparatus for producing refractory bodies - Google Patents

Abstract

410,033. Fusing and working silica. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Ellis, A. L. ; 11, Banks Road, Swampscott, and Winckler, G. A. F. ; 29, Clearview Avenue, Worcester, both in Massachusetts, U.S.A.) Nov. 28, 1933, No. 33335. Convention date, Nov. 30, 1932. [Class 56.] Relates to the apparatus described in Specification 364,993 for producing massive articles of refractory material, particularly for forming a silica blank for an astronomical mirror. The present invention consists of means for regulating the rate of feed of the comminuted silica, means for protecting the gas conduits from the abrading action of the silica, means for distributing the silica in the fusion zone, and means for conserving the heat of the fusion zone. The article which is being built up, such as a blank for an astronomical mirror, is contained in an electrically heated furnace consisting of a housing 55, Fig. 1, having resistance heaters 59, 60 on the walls and roof and below the silica blank 61. The burner 58, which deposits the silica, is carried by a support 57 that passes through openings in the housing 55 and rests on rollers 62, 63, 64. The support is a tube through which water or other cooling fluid is circulated, and it encloses the gas supply conduits 65, 66, Fig. 2. An offset joint 67, into which silica becomes packed, is provided at the bend of the conduit 66 and acts as a wear-resisting deflector for the silica powder carried by the stream of hydrogen. The burner 58 is moved to-and-fro over the blank 61 by any suitable mechanism 76, Fig. 1. The burner, as described in the earlier Specification, comprises two groups or bundles of tubes 78 supplied with oxygen and hydrogen respectively. The groups of tubes approach one another at their outlets to prevent concentration of silica near the outer zone of the burner. Deflectors 79, secured to the burner, prevent the silica from depositing in ridges. The device for feeding the silica consists of a drum 85, Fig. 6, having a number of small pockets 86 formed on its surface, and these pockets become filled with the finely divided silica as the drum rotates past a hopper 83. The silica falls from the pockets into the hydrogen conduit, and the rate of feed of the silica is independent of the velocity of the gas stream and the condition of the silica itself. The heat deflector for the fusion zone consists of a conical member 93, Fig. 7, supported by hangers 94 from the flange 96 of the burner jacket 71. The deflector is supported at some distance below the orifices of the burner, but close to the heated area of the article which is being built up.