U.S. Philips Corporation

Andreas S Geven

Antonius J Driessen

Jean J Heuvelmans

Peter Arend Seinen

Christoffel Wijenberg

Max L Renardus

Hui-Meng Chow

Jan A Stoffels

Patricius W Lepelaars

Johan Liebe

Henricus L Vogels

Jeroen C Langevoort

Jan R deBie

Harald R Dielis

At least one of the electrodes (6a) has a coil (60a) of a refractory metal which is electrically connected to current supply conductors (7a, 7a') which extend to outside the discharge vessel. The coil (60a) has a central portion (61a) which is coated with an electron-emitting material and an end portion (62a, 62a) on either side thereof, which end portions are covered with a protecting material which is mainly formed by one or more oxides of calcium and/or magnesium.

Low-pressure discharge lamp with filament having protective coating

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

A high-pressure discharge lamp of the invention includes a ceramic discharge vessel (10) in which a first and a second electrode (40a, 40b) are arranged and which encloses a discharge space (11 ) which is provided with a filling containing a metal halide. The discharge vessel (10) has a central zone (20) between the electrodes (40a, 40b) and a first and a second cylindrical end zone (30a, 30b) which each surround a current supply conductor (50a, 50b) connected to a respective electrode (40a, 40b). At least the first end zone (30a) has a diameter smaller than the smallest diameter of the central zone (20). The current supply conductor (50a) through the first end zone (30a) has a halide resistant portion (51a) which faces the discharge space (11) and a portion (52a) permeable to hydrogen and oxygen and facing away from the discharge space (11). The halide resistant portion (51a) extends through the first end zone (30a) over a distance that is at least the inner diameter D of the first end zone (30a) augmented by 2 mm. Furthermore, the current supply conductor (50b) through the second end zone (30b) has a halide resistant portion (51b) which faces the discharge space (11). The construction allows for a sufficient reduction of the amount of hydrogen and oxygen in the discharge vessel (10), while corrosive attack of the current supply conductors (50a, 50b) by halides is prevented.

High-pressure discharge lamp

In the high-pressure sodium discharge lamp according to the invention, the electrodes (17) are surrounded by a hollow cylindrical body (18), which limits an annular space accommodating an electron emitter (19). The cylindrical body (18 l ) extends against the current conductor (6) supporting the electrode (17). Means for screening the electron emitter (19) are provided at the end of the annular space facing the electrode tip (20). A shield (21) extends from against the electrode tip (20) laterally beyond the hollow cylindrical body (18).

High-pressure sodium discharge lamp comprising a discharge arc shielding

The invention relates to a high-pressure discharge lamp having a discharge envelope (3) with a ceramic wall provided with at least one electrode (4). The electrode (4) comprises a rod (41) which is connected to a tubular lead-through member (40) and on which an emitter-containing element (42) is arranged. By means of a screening body (43), the emitter-containing element (42) is screened on its outer side. According to the invention, the screening body (43) extends with a constant cross-section from the tubular lead-through member (40) to the end of the emitter-containing element (42) facing the discharge path. Thus, an improved temperature control is obtained within the discharge envelope (3) during operation of the lamp.

High-pressure discharge lamp with shielded electrode

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Eindhoven, Netherlands

Andreas S Geven