GB559181A - Improvements relating to windows in the envelopes of vacuum tubes - Google Patents

Abstract

559,181. Thermocouplers; glass/metal seals. GRAVES, A., ALLTOOLS, Ltd., TOMES, G. A. R., and CINEMA-TELEVISION, Ltd. Aug. 19, 1942, No. 11681. [Classes 36 and 53] [Also in Groups XL and XXIII] A static vacuum thermocouple comprises a highly-evacuated vessel 10 formed with an aperture, a thermocouple 36 mounted in the vessel with its hot junction opposite the aperture, and a window 12 consisting of a thin film of approximately soap-bubble thickness of a vitreous material such as ordinary glass, high silicate glass, or fused quartz; the window being fused or welded at its edges to the material of the vessel at the boundaries of the aperture. The window material is first blown into a bubble. The rim of the aperture of a glass vessel is then softened with the aid of a blow pipe and the softened rim brought into contact with the bubble. This causes a small piece of the bubble to become attached to the rim. In a modified process, a piece of the bubble is picked up between the aperture and the end of a glass tube of the same diameter. Heat is then applied round the junction to fuse the parts together, and after this the tube is cut short near the window. The vessel may be made of a metal such as copper, multiple seals being then used to weld the window to the vessel. The window may be reinforced on the outside or the inside. A mask 25 may be inserted between the thermocouple and the window and may support the window. The vessel may be double walled or enclosed in an outer casing, the outer wall or casing being provided with a window 28 opposite the thin window of the inner wall or casing. The thermocouple may be as described in Specifications 559,182 and 559,183.