Patent GB-383219-A (GB)
Title: Improvements in and relating to machines for shaping articles of silica or the like
IPC: C03B23/07
Filed: 1932-06-24
Abstract: 383,219. Fusing and working silica. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Hooper, 1. F. ; 33, Avon Street, Saugus, Niedergesass, B. F. ; 15, Colonial Avenue, and Devers, P. K. ; 6, Pierce Road, both in Lynn, both in Massachusetts, U.S.A.) June 24, 1932, No. 17928. Convention date, June 24, 1931. [Class 56.] A method of making articles from fused silica, particularly insulators for sparking plugs, consists in heating a zone of an elongated portion of the material until it is plastic, exerting endwise pressure on the portion to produce an enlargement of the heated zone, moulding the enlargement to produce a desired configuration, forming a channel through the portion, and then separating the shaped portion from the body of the material. A machine for carrying out the method comprises an horizontal spider 12, Fig. 2, mounted on a pedestal 13 and secured to a sleeve 16 which is rotated step by step. Chucks 11 are carried by guides 10 mounted on the spider, and they are rotated continuously by a gear wheel 18 secured to a shaft 17 which is journalled in the sleeve 16. Burners 146 are arranged to direct oxyhydrogen flames into the silica, and the shaping mechanisms are brought into operation by cams when the chucks arrive at the different operating positions. In use, a length 9 of silica tubing is placed in a chuck, and at the first operating-station, the chuck is opened by an arm 125 and the tube 9 is allowed to slide downwards until it is stopped by a plate 118, Fig. 21, which is raised to the desired position. The chuck then locks, the plate 118 descends, and the chuck is moved to the next operating-station. Here a part of the silica tube is heated by oxyhydrogen burners until the heated zone is plastic, and then a head 15, Fig. 22, is raised and exerts endwise pressure on the silica until an enlargement 153 is formed at the heated zone. At the same time, a pin 133, Fig. 2, carried by the hedd 15 enters the bore of the silica tube. The head is rotated relatively to the tube so that the pin maintains the bore and ensures that it is of the required diameter. A similar pin may be provided at each of the succeeding stations, but in some cases the pin may be dispensed with and the bore maintained by means of compressed air. At the next two stations, the enlargement 153 is shaped by means of rollers 139, Fig. 23, of metal or highly refractory material such as zerconia, and at the next two stations the lower portion of the silica is tapered by means of rollers 151, Fig. 26, and the bottom is shaped. The lower parts of the rollers may be heated, while the upper parts 152 are left cool in order to provide a relatively cold or rigid seating for the enlargement 153. At the next station, the upper part of the shaped silica is indented or grooved by a wheel 163, Fig. 28, which is brought into contact with the heated skin of the silica. Finally, the shaped article is broken off the length of tubing by a hammer, a supporting-wheel being brought into contact with the groove formed by the wheel 163. Certain parts of the mechanism are cooled by water which is circulated through troughs 174, 175, Fig. 2, by pipes 179.