GB856912A - Improvements in or relating to tubular electric resonance radiation discharge lamps - Google Patents

Abstract

856,912. Discharge lamps. GENERAL ELECTRIC CO. March 27, 1957 [April 9, 1956], No. 9999/57. Addition to 821,321. Class 39(1). A discharge lamp, particularly a fluorescent discharge lamp, according to the parent Specification is modified so that a kidney-shaped crosssection of the lamp is such that the ratio of the curved annular length D between the two ends of the kidney configuration to the maximum wall-to-wall spacing E in the centre thereof is between 2 : 1 and 10 : 1, and that the wall-to-wall spacing decreases from the centre of the kidney configuration towards the ends thereof such that the ratio of the decrease in the spacing to spacing at the centre, i.e. the ratio of (E-F) to E, does not exceed one half and can be 0À21. The or each kidney-shaped cross-section of the lamp is bounded by a convex outer wall 16, a concave inner wall 17 of greater curvature than that of the outer wall 16, two convex edge walls 18, 18<SP>1</SP> of greater curvature than that of the inner wall 17, and outwardly diverging substantially straight wall sections 19 and 19<SP>1</SP>, the radius of curvature of the edge walls 18 and 18<SP>1</SP> being less than that of the inner wall 17 to an extent not exceeding 50% and the straight wall sections 19 and 19<SP>1</SP> being inclined at an angle # of at least 15 degrees to the medial line of the cross-section. The concave inner wall 17 can have a radius of curvature approximately one third that of the convex outer wall 16 and the inclination of the straight wall sections 19 and 19<SP>1</SP> to the medial line of the cross-section can be approximately 27 degrees. The kidney shaped cross-section can extend the full length of the envelope forming a single groove or the envelope can be provided with a plurality of longitudinally spaced indentations or re-entrant grooves arranged on one side only or on diametrically opposite sides and which may alternate on opposite sides and be of unequal length. The lamp, at rated voltage and current values, can have a wall loading in the range of 0À05 to 0À08 watts per sq. cm. and a linear loading of from 20 to 40 watts per 30 cms. length. In a specific example the ratio of the curved annular length D to the maximum wall-to-wall spacing E is approximately 5:1, the wall loading is approximately 0À07 watts per sq. cm., the linear loading is approximately 35 watts per 30 cms. length, and the average current density is approximately 0À2 amps per sq. cm. of the crosssection. The lamp filling comprises one or more rare gases such as argon at a pressure of 0À5 to 5 mms. and mercury vapour at a pressure of 1 to 20 microns. With argon at a pressure of 3 mms. the mercury can be at a pressure of 5-8 microns. A halophosphate phosphor activated with antimony and manganese can be coated on the inside of the lamp envelope and a water-repellent material can be coated on the outside of the envelope to facilitate starting. A polar light distribution pattern and a wall temperature distribution pattern for the lamp are given.