GB191124164A - Improvements in or connected with Luminescent Tubes for Rare Gases. - Google Patents

Abstract

24,164. Soc. l'Air Liquide (Soc. Anon. pour l'Etude et 1'Exploitation des ProcÚdÚs G. Claude). Nov. 28, 1910, [Convention date]. Vacuum tubes.-A lighting-tube containing neon or a similar gas has electrodes the surface areas of which exceed 1À5 square decimetres per ampere, to avoid excessive heating of the electrodes and consequent rapid occlusion of the gas by metallic deposits on the tubes. At long intervals during use, additional gas is introduced through a valve from a bottle, which for the purpose of purifying the gas contains lithium or the like, or coco-nut charcoal, the bottle being in the latter case immersed in liquid air when the valve is opened. A pressure gauge may be connected to the tube. Variations in the current in the intervals between the admissions of gas may be prevented by an automatically - adjustable or other resistance or inductance. To expel occluded gas from the electrodes while the tube is being rinsed out with gas as described in Specification 5589/11, the electrodes are heated by means of a large current, or by wrapping asbestos paper or the like round the tube in their vicinity. A receptacle containing charcoal and communicating with the tube may be heated at the beginning of the exhaustion, being then allowed to cool slowly to atmospheric temperature; after this, the final charge of gas is admitted and the receptacle is cooled by liquid air. The gas used may be carefully dried to prevent the formation of hydrogen in the tube. The reddish tint of neon is diminished by using a high currentdensity, say one ampere for a tube of 45 mm. diameter. A tube 6 metres long with alternating current requires 800 volts. Short tubes may be used with low-pressure continuous current, extra current being used for starting. The tube may be of silica, and the electrodes of carbon, iron, copper, or aluminium. Lamps of high power may be used in conjunction with mercury-vapour lamps. The Specification as open to inspection under Section 91 (3) (a) states also that the electrodes may be kept out of contact with the tube by means of glass beads. This subject-matter does not appear in the Specification as accepted.