GB670417A - Improvements in and relating to starting and control arrangements for electric discharge apparatus - Google Patents

Abstract

670,417. Liquid electrode apparatus. BERTELE, H. C. April 19, 1948, No. 10572/47. Class 39 (i). An ignition system for a vapour electric discharge apparatus with a liquid pool cathode comprises an igniting electrode in an insulating sheath which is roughened to give an upward meniscus with the pool liquid, and a ring or shield of arc-resisting metal, e.g. molybdenum or tungsten surrounding the sheath and provided with apertures which permit outward movement of the arc-spot but protect the sheath against radiation from the arc. Fig. 8 shows one form with the starting electrode 9 projecting from its sheath 20 of quartz or alkali free glass and topped by a small disc or plate 22. The shield 12 has notches 13 located at the surface of the mercury pool. The openings 13 may be rectangular perforations giving the shield a continuous lower rim. The shield is preferably supported on the sheath by radial arms or fins 16 which may be formed as shown in Fig. 6 by bending in portions 16a cut from the shield wall 12. The shield may form a depending skirt or cup integral with the disc 22. Two concentric shields 32, 12 (Fig. 10), may be fitted to co-operate in removing the arc-spot in stages. In a further modification (not shown), an auxiliary disc-shaped electrode is mounted on the end of a rod which passes eccentrically through screen 32 without contact and is sealed in the insulating sheath parallel with the starting electrode. Where the pool container or the envelope is of metal the insulating shield is sealed thereto at its base. In some cases the insulating sheath is integral with the pool container. Specification 670,416 is referred to.