U.S. Philips Corporation

Philips Electronics North America Corporation

Hui-Meng Chow

Jean J Heuvelmans

Paul D Goodell

Susan McGee

Andreas S Geven

Jose Azevedo

Willem Van Erk

Patricius W Lepelaars

Henricus L Vogels

Jeroen C Langevoort

Martin F Willemsen

An electric gas discharge lamp includes an electrode having a tip portion comprised by a mesh body carrying an emitter material. The mesh body in a favorable embodiment is circular cylindrical and is attached via an electrically conductive thermal isolator to a conductive feed-through, such as a hollow ferrule, extending through a seal of the lamp vessel. As compared to a continuous walled tip portion of similar shape and material, the mesh body has a lower mass and heat capacity, and can therefore be operated at higher temperatures without increasing the temperature of the seal area. The higher operating temperature of the tip portion promotes greater electron emission from the emitter material, and therefore a lower cathode fall. A lower cathode fall enables the lamp to be operated at higher lamp currents for greater light output. The mesh body also has the capability to reduce sputtering from the electrode through improved adhesion of the emitter material to the tip portion and faster attainment of its nominal operating temperature as compared to a smooth continuous walled body. In a favorable embodiment, the lamp is a low pressure discharge lamp having an inside diameter of less than about 5 mm.

Gas discharge lamp having an electrode with a low heat capacity tip

A low-pressure discharge lamp of the invention is provided with a gas-tight discharge vessel (10) which contains an ionizable filling. Electrodes are arranged inside At least one of the electrodes has a tungsten coil (20.sub.A) which is electrically connected to current supply conductors (30.sub.A, 30.sub.A ') which extend to outside the discharge vessel (10). The coil (20.sub.A) has a central zone (21.sub.A) covered with an electron-emitting material (22.sub.A) and, on either side, boundary zones (23.sub.A, 23.sub.A ') between the central zone (21.sub.A) and respective current supply conductors (30.sub.A, 30.sub.A '). The boundary zones (23.sub.A, 23.sub.A ') having a covering (24.sub.A, 24.sub.A ') of a protective material, comprising a ceramic material having a specific resistance less than 1000 .mu..OMEGA..cm.

Low-pressure discharge lamp

The low-pressure discharge lamp is discolsed having a lamp vessel into which hollow cylindrical electrodes enter, between which a discharge path extends. At least one of the electrodes has a tube at a distance from an end thereof, the tube extending in the discharge path. The tube is connected to the electrode by electrically conductive means and is coated with electron emissive material. The surface area of the material of the means in cross-section is at most 25% of the surface area of the material of the electrode in cross-section.

Low-pressure discharge lamp having hollow electrodes

The high-pressure metal halide discharge lamp has tungsten electrodes in a light-transmitting lamp vessel which is closed in a vacuumtight manner. The electrodes comprise an emitter which is distributed throughout their mass and is formed by a first oxide chosen from hafnium oxide and zirconium oxide and by a second oxide chosen from yttrium oxide, lanthanum oxide, cerium oxide and scandium oxide, and are substantially free from thorium oxide. The lamp retains its initial light output to a high degree throughout its life.

High-pressure metal halide discharge lamp with electrodes substantially

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Briarcliff Manor, NY, United States of America

Hui-Meng Chow