GB440566A - Improvements in electric discharge tubes - Google Patents

Abstract

440,566. Discharge apparatus. TRIGGS, W. W., 57, Lincoln's Inn Fields, London.-(Naamlooze Vennootschap Machinerieen-en Apparaten Fabrieken Meaf; 30, Croeselaan, Utrecht, Holland) June 30, 1934, No. 19389. [Class 39 (i)] In a tube having an apertured screen separating an anodic space from the remainder of the tube and in which the cross-section of the apertures is small compared with that of the discharge path so that at a predetermined current density within the normal working range of the tube the potential drop across the tube increases with increasing current, the apertures are extended in tubular form near to the anode surface. In the form shown, a metal member B carries a front portion which may be porous and provided with several tortuous passages or may be a member having tubular projections F. To facilitate starting the member B may be connected to the anode A through a resistance, or through a semi-conducting support L, or the member B may be a semi-conductor and may be connected to the anode A or its lead directly. The diameters of the aperture and of its tubular extension should be of the order of the mean free path of the filling and the distance of the screen from the anode should be a few times the mean free path. The tube may be used as a constant current device, or as a lamp, in which case a ballast resistance is unnecessary. A point-like light source is obtained due to the constriction of the discharge by the screen. The cathode may be thermionic or may be a mercury pool with, if necessary, an exciting anode, in which case the tube temperature is kept constant by thermostatic control. Specification 404,455 is referred to.