GB310329A - Improvements in cathode ray and like tubes - Google Patents

Abstract

310,329. Westinghouse Lamp Co., (Assignees of Slack, C. M.). April 23, 1928, [Convention date]. Vacuum tubes.-The window of a cathode-ray or like tube for the passage of electrons or ions consists of vitreous material of not more than a few thousandths of an inch in thickness. The material for the window may be glass, such as lime glass, boro-silicate glass or glass known by the registered Trade Mark, " Pyrex," quartz or non-porous porcelain. The thickness of the window is about 0.00025 inch, or in the case of a small window 0.0001 inch; details of the absorption of energy at different voltages are given. As shown, the window 14 is formed by drawing in a part of the envelope to form a bulbous part. The window may be formed on the closed end of a short length of tube which is subsequently sealed to the envelope. The thickness of the window increases gradually from the centre outwards, and the thickness may be further reduced by etching with a weak solution of hydrofluoric acid. The thickness of the window may be determined by the voltage required to cause cathode rays to pass through. The surface of the window inside the envelope may be coated with a thin film of conducting material connected with the anode 3 so as to prevent the accumulation of a negative charge on the window. The outer surface of the bulbous part below the window is coated with a strengthening and shielding material such as shellac to prevent heating of the glass by impact of stray electrons. The cathode 2 consists of a coil of tungsten or molybdenum mounted within a focusing cup 8 and surrounded bv an electrostatic shield 9 in the form of a split tube of nickel, monel metal, or chrome-iron. The anode consists of a copper tube having a flared end 15 and supported by a split collar 13 of chrome-iron or other metal. In a modification the anode is of cup shape, and has a central aperture for the passage of cathode rays. In another arrangement the bulbous part extends outwards, and is surrounded by a tubular shield of metal or fibre. Specification 251,635 is referred to.