High-pressure discharge lamp with stabilized arc
AssigneePatent-Treuhand-Gesellschaft fur elektrische Gluhlampen mbH
InventorsWolfgang Pabst, Manfred Rehmet
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Abstract
To improve the arc stability of a high-pressure arc discharge lamp, typically a xenon arc lamp, the cathode (4) has an essentially conical end portion (9), terminating in a roughly flat, or slightly rounded tip (10). The cathode is covered with a carbide layer (11) decreasing in thickness towards the tip (10) and, preferably, leaving a zone (12) adjacent the tip and extending over about one-third of the end zone (9) free from carbide. The carbide has a lower melting temperature than the tungsten of the electrode, and leaving the tip free from carbide prevents deterioration of the electrode due to melting of the carbide material, in operation of the lamp.
Claims20
High-pressure arc discharge lamp (1) having
- a transparent vessel (2);
- two facing electrodes (3, 4), a first electrode (3) and a second electrode (4) forming a cathode,
- and wherein the cathode (4) comprises an essentially cylindrical body (8) of high-temperature resistant material doped with an electron-emitting material, said electrode having an end portion (9) of reduced diameter and terminating in a tip (10, 10'),
- a cover layer of a carbide of the metal of the electrode coating the outside of the cylindrical body at least in the region of the end portion (9) of reduced diameter (9),
- and wherein, in accordance with the invention,
- the thickness dimension of the carbide cover layer (11) is small with respect to the diameter of the cylindrical body (8) of the cathode (4) and decreases towards the tip (10) of the electrode.
Dependencies are inferred from the claim text.