GB426899A - Glow discharge tube for signalling purposes - Google Patents

Abstract

426,899. Discharge lamps. BARON, H., 231, Strand, London.-(Telephonwerke Albisrieden Akt.-Ges.; Albisrieden, Zurich, Switzerland) March 15, 1934, No. 8226. [Class 39 (i)] Discharge lamps for signalling have the cathode surface 4 on which the glow forms so inclined that extraneous light falling on the cathode is reflected on to the internally or externally blackened sides of the envelope 1. The cathode is conical with an apex angle of 90‹ or less and the anode 5 ring - shaped with an aperture equal to or less than the section at the anode 5 of the double cone on which the cathode 4 lies so that all light passing downwards through the anode falls on the blackened envelope and is not reflected upwards out of the lamp. Signalling with the lamp in sunlight is thus facilitated. The upper side of the cathode may be coated with electro-positive material such as potassium, sodium, rubidium, caesium, barium or strontium. The tube is filled with neon and argon, 3-30 per cent of helium being added to neutralize wall charges. To facilitate starting, a point 8 on the anode 5 approaches the cathode. To reduce instability due to the photo-electric action of extraneous light, a filter absorbing short wavelengths but passing the long wavelengths emitted by the lamp is placed in front of the tube. The wall of the tube may form the filter or may be coated with a varnish &c. The anode lead 6 passes through the cathode and is screened by a glass tube 7.