US 5,471,110 A · High pressure discharge lamp having filament electrodes

Abstract

A high pressure discharge lamp having a discharge vessel with opposing end chambers includes discharge electrodes each consisting of an open elongate filament of refractory metal wire having a plurality of succesive coil turns extending transverse to the longitudinal axis of the discharge vessel. The filament electrodes are dimensioned so that the discharge arc which terminates thereon is sufficiently retracted into the end chamber of the discharge vessel so that the fill constituents condense on a region of the discharge vessel which is primarily axially between the filament electrodes. In a favorable embodiment, the lamp is a metal halide lamp in which the electrode and the discharge sustaining fill is free of thoria and its compounds.

Claims34

Dependent claims

A high pressure discharge lamp comprising a discharge vessel having opposing end chambers and a longitudinal axis, a discharge sustaining filling within said discharge vessel, and a pair of opposing discharge electrodes arranged in said end chambers and between which an arc discharge is maintained during lamp operation, characterized in that:

said discharge electrodes each consist of an open elongate filament of refractory metal wire having a plurality of successive coil turns extending transverse to the longitudinal axis of said discharge vessel and on which the discharge arc terminates during lamp operation, and
the dimensions of the electrode and the spacing of the coil turns from the end chamber being selected such that the discharge arc sufficiently heats the end chamber during lamp operation so that the fill constituents primarily condense on the discharge vessel at a location axially between the discharge electrodes with (i) the discharge vessel oriented vertically in a gas filled outer envelope and (ii) with the discharge vessel being free of a heat conserving end coat and free of a sleeve thereabout.

A high pressure discharge lamp, comprising:

a) an outer envelope;
b) a discharge vessel within said outer envelope, said discharge vessel consisting of fused silica and including a tubular body portion of substantially constant cross section defining a longitudinal axis of the discharge vessel, seals at each end sealing the discharge vessel in a gas-tight manner, and end chambers of continuously reducing cross-section extending between said tubular body portion and each of said seals, said end chambers each including an end wall lying on the longitudinal axis of the discharge vessel;
c) a discharge electrode mounted in each end chamber between which an arc discharge is maintained during lamp operation, each discharge electrode being free of thoria and comprising a filament of refractory metal wire having a plurality of successive open coil turns extending transverse to the longitudinal axis, said filament being dimensioned such that said discharge arc terminates thereon within about 2 mm of the end wall of the discharge vessel;
d) a discharge sustaining filling within said discharge vessel, said discharge sustaining filling being free of metals of low work function which are pyrolitically decomposable and subject to plating out on said electrodes during lamp operation;
and
e) means for supporting said discharge vessel within said outer envelope and for connecting said discharge electrodes to a source of electric potential outside of said lamp envelope.

3 more elements

A metal halide discharge lamp, comprising:

a) an outer envelope sealed in a gas-tight manner;
b) a discharge vessel arranged within said outer envelope, said discharge vessel comprising (i) a body of fused silica having a tubular portion of substantially constant cross section defining a longitudinal axis of the discharge vessel, opposing planar seals sealing the discharge vessel in a gas-tight manner, and end chambers of continuously reducing cross-section extending between said tubular portion and each of said seals, (ii) a discharge electrode mounted in each end chamber between which an arc discharge is maintained during lamp operation, each discharge electrode comprising a filament of refractory metal wire having a plurality of successive coil turns extending transverse to the longitudinal axis, said discharge electrodes being free of thoria, (iii) conductive feed-throughs connected to each filament and extending through a respective seal in a gas-tight manner, and (iv) a discharge sustaining filling within said discharge vessel comprising mercury, a rare gas and one or more metal halides, said discharge sustaining filling being free of metals of low work function which are pyrolitically decomposable and subject to plating out on said electrodes during lamp operation;
c) a light transmissive sleeve arranged about said discharge vessel;
and
c) frame means for supporting said sleeve and discharge vessel within said outer envelope and for connecting said feed-throughs to a source of electric potential outside of said lamp envelope.

2 more elements

Dependencies are inferred from the claim text.

High pressure discharge lamp having filament electrodes

Life of this patent

High pressure discharge lamp having filament electrodes

Life of this patent

Abstract

Claims34