Slotted electrode for high intensity discharge lamp

Abstract

Operation of an HID lamp may be improved by forming a glow generating recess on an exterior side the electrode. The lamp may be of standard construction with a light transmissive lamp envelope having a wall defining an enclosed volume. At least one electrode assembly is extended in a sealed fashion from the exterior of the lamp through the lamp envelope wall to be exposed at an inner end of the electrode assembly to the enclosed volume. A metal halide lamp fill is enclosed with an inert fill gas. The inner end of the electrode is formed with a recess having a least spanning dimension S and a recess depth of D where S is greater the electron ionization mean free path but less than twice the cathode fall plus negative glow distances, throughout the glow discharge phase of starting, for the chosen fill gas composition and pressure (cold).

Description

Technical field [0001] The present invention relates to electric lamps, and in particular to high-intensity discharge lamps. More particularly, the present invention relates to electrodes used in high intensity discharge lamps. Background technique [0002] It is common for arc discharge lamps to have an electrode with a large head formed on the inner end of the rod. For example, many metal halide high-intensity discharge lamps use electrodes that have straight tungsten bars wound with a coil to form a head. During operation, the wrapped head provides a larger area from which hot electrons are emitted, resulting in a more durable electrode during operation at lower temperatures. Unfortunately, the large head is difficult to heat at the beginning and the light start may be lost. If the wound head is too large, then spotmode arc attachment may occur, especially when no emitter material is used, which reduces the steady state operation of the lamp. The coil-wound electrode may also ...

AI Technical Summary

Problems solved by technology

However, unless it happens to be a special lamp and electrode situation, the structure in Eggers has similar starting difficulties under the condition of large tip area

In Altmann's US6211615 a cooling structure similar to Eggers is also disclosed, but there is still no mention of the need for special lamps and electrodes to improve starting

Also, none of these disclosures disclose the special electrode, lamp and ballast conditions required to achieve improved steady state maintenance without dot attachment

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