GB461334A - Improvements in or relating to electric discharge tubes - Google Patents

Abstract

461,334. Discharge apparatus. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. Aug. 19, 1935, No. 23253. Convention date, Oct. 29, 1934. [Class 39 (i)] In an electric discharge tube the wall of which is wholly or partly of glass, at least part of the glass wall is divided into a plurality of layers.and the pressures in the cavities between the layers are constant and form, from the exterior to the interior of the tube, a constantly increasing or decreasing series. The wall is thus enabled to withstand internal or external pressure without excessive bulk or curvature. The layers may have different thicknesses and the same or different radii of curvature, including plane and inwardly curving surfaces. The curvature and thickness may vary throughout the same layer, especially in the edge zone to obtain stability. One or more layers may be coated with a layer of material affording protection against splintering such as gelatine, and highly refractive substances such as carbon disulphide or Canada balsam may be introduced into one of the cavities to provide an optical system. In one example, Fig. 1, the wall of a discharge tube has five layers 5 sealed to the stem 3, the inner space being evacuated and the pressures in the intermediate spaces 7 forming an increasing series. In a cathode-ray tube, Fig. 2, only the end of the tube is formed of layers 9, so that the fluorescent layer may be applied to a practically plane surface. The remaining frusto-conical portion 11 of the envelope may be made of ferrochromium, ceramic material or thick glass, and when of conductive material or provided with a conductive coating may be connected to earth or fixed potential through capacitative or inductive means. The end layers 9 are sealed to extensions 13 on a thickened portion 12 of the wall. Exhaust tubes are provided for each cavity, which may be of glass but are preferably of metal and contain solder which when melted runs into kinks or cavities in the tubes to seal them after pumping. The invention is applicable also to photoelectric cells, lamps and X-ray tubes. To avoid subjecting the layers to excessive pressures during pumping, all the cavities may be connected to a common pump, through capillary tubes whose resistances are adjusted so that each cavity attains its correct pressure during the exhaust period. One or more substances having a measurable vapour pressure may be introduced into one of the cavities. Specification 312,507, [Class 39 (i)], is referred to.