GB1464063A - Low-pressure gas discharge lamp - Google Patents

Abstract

1464063 Metal vapour lamps PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 8 July 1975 [11 July 1974 5 June 1975] 28682/75 Heading H1D [Also in Division C1] A low pressure discharge lamp (e.g. Hg or Na with or without luminescent coatings) has a solid filamentary body permeable to the discharge; the body being present over at least half (e.g. 80%) the electrode distance and thinly distributed over the space, the ratio between volumes of body and space being between 3.10<SP>-7</SP> f/# and 3.10<SP>-2</SP> f/# where f is the quotient of the volume and area of the body in microns and # equals 5 microns. The body may be interrupted, as shown into packets 7, 8, 9. The light output of the lamp may be increased without increase of energy consumption by the lamp and stabilizing element. Between 5 x 10<SP>-6</SP> and 5 Î 10<SP>-3</SP> mg. of the body/cubic mm. may be present. Preferably the electrode distance/ cross-sectional diameter of the discharge space is >5. Preferably the density near the axis differs from that near the wall. A reduced near axial density reduces uneven temperature distributions producing mercury or sodium deposits, while an increased near axial density in a circular-cylindrical lamp increases light output. The body may be glass, quartz or metal (e.g. W) wool for example. Metal wool may be provided with insulating material to improve potential distribution, and the wire may be 5 to 100 Ám diameter. The body may be luminescent glass or glas coated with Mn and/or Sb activated calcium halophosphate for example or gehlenite glass for sodium resistance. Excessive absorption may be countered by a surface reflective coating of zirconium oxide, magnesium oxide or barium sulphate. Cooling for optimum efficiency may be by radiation shields on the electrode stems, or alloys in the discharge space (e.g. In or Hg amalgams). The lamp may be U-shaped (Figs. 3, and 4, not shown). Comparative test results are detailed and specify for example, dimensions, pressures, currents and efficiencies. Hg may be with 75% by vol. Ar and 25% by vol. Ne at 2À5 torr, or with 72% by vol. Ne and 28% by vol. He at 4 or 6 torr. A favourable ratio of power supplied/losses in the power supply apparatus is obtained for V/l<7, where V is the operating voltage in volts and l is the electrode separation in ems. Reproduction applications using aperture lamps is mentioned.