Patent ID: 6194832
Filing Date: 2001-02-27
Classification: H01J

Abstract:
A metal-halide discharge lamp comprising:a ceramic discharge vessel (4), said discharge vessel having two tubular end portions (6a, 6b);a plug (11) closing each of said tubular end portions;an electrically conductive and weldable lead-through or feed-through (9, 10; 20, 30, 35) which passes through each said plug in a vacuum-tight manner (11);an electrode (14) secured to each lead-through and being located in the interior of the discharge vessel (4);wherein at least one said plug is formed of axially stacked layers or strata (11a-11d; 21a-21f), each of said layers or strata comprising a cermet having a metal content, in which the metal content of the cermet in the layers or strata increases in a direction outwardly from a layer or stratum disposed interiorly with respect of the end portions of the discharge lamp, andwhereinat least one said plug (11) in at least one end portion (6a) comprises:at least four axially placed layers or strata, an outermost layer or stratum (11d, 21f, 31f) comprising at least 50%, by volume, of a metal, the remainder being a ceramic,said metal being weldable;a weld (19) connecting said lead-through (9) to said outermost layer or stratum (11d) in a vacuum-tight manner; andwherein an innermost layer or stratum (11a, 21a) of the plug (11) is connected in a vacuum-tight manner by a direct sinter connection to a respective end portion (6a, 6b) of the discharge vessel which is devoid of a glass melt material or a ceramic melt material.