RUBO ELETTRICO A SCARICA A DISTRIBUZIONE DEL CALORE CONTROLLATA

The end or ends of the discharge tube of a high pressure sodium or metallic halogenide vapour lamp, esp. one working in the free atmosphere, is (are) provided at the coldest point or points of the discharge chamber, with an axially displaceable, heat insulating sleeve of ceramic material or aluminium. The sleeve is filled with a heat insulating packing of ceramic wool. The difference between the highest and the lowest temp. of the tube wall is reduced to the min. The optimal cold spot temp is maintained and the vapour pressure is held constantly at a value ensures a good yield of light with a good colour. The lamp can be made smaller and since the vapour layer is reduced, the efficiency of the lamp is increased.