Wenderoth, Lind & Ponack
Air-tight sintering furnace for the production of a quartz preform
 This invention relates to a sintering furnace for the production of a quartz preform which can be used for carrying out dehydration, fluorine-addition and/or sintering of a porous quartz soot preform prepared by a flame hydrolysis method such as a VAD method or a OVD method, and in particular, to such a furnace in which joints in a long furnace muffle so long that fabricating it as open body is impossible can be maintained fully gas-tight, so that it is possible to prevent H.sub.2 O, O.sub.2 and other impurities in the air from entering the muffle from outside, and corrosive and poisonous gases in the muffle are prevented from leakage to outside the muffle. This sintering furnace has a muffle of high purity carbon, the inner wall and/or outer wall of which is coated with a gas-impermeable film, which muffle is a cylinder with an axis in the longitudinal direction and divided into a plurality of parts in the longitudinal direction, the parts each having the upper and lower ends finished so as to be flat and abutting adjacent parts sealed by a carbon gasket between them, and further has an air cylinder for pressing the parts together in the axial direction with a uniform force around the circumference of the muffle. 
Sumitomo Electric Industries, Ltd.
C C Y
C03B C03B Y10S
inventional additional additional
Toshimi Shinji Masahide Ichiro
Habasaki Ishikawa Saito Tsuchiya