Metal halide lamp having open tungsten coil electrodes

Details Metal halide lamp having open tungsten coil electrodes Metal halide lamp having open tungsten coil electrodes

1976-04-30

1978-08-08

Demeo, Palmer C.

Electric lamp and discharge devices

With support and/or spacing structure for electrode and/or...

For plural electrodes of discharge device

313218, 313229, H01J 61068, H01J 6118

Patent

active

041059085

ABSTRACT:
In a metal halide lamp of the sodium-scandium-thorium iodide type utilizing tungsten electrodes without emission mix, lumen depreciation during life results primarily from blackening of the arc tube wall by electrode sputtering during the glow-to-arc transition phase of lamp start-up. The glow-to-arc transition is speeded up by a lower glow-to-arc transition voltage which is achieved by using electrodes comprising an open tungsten wire coil on a tungsten shank, the coil comprising two layers of a composite wire made by open-winding a 2 mil overwind on a 4 mil core and then close-winding two layers of the composite wire on the shank. This decreases sputtering at starting and improves lamp maintenance.

REFERENCES:
patent: 2171234 (1939-08-01), Freeman
patent: 2441863 (1948-05-01), Zabel
patent: 2765420 (1956-10-01), Martt
patent: 3313974 (1967-04-01), Koury et al.
patent: 3937996 (1976-02-01), Cap
patent: 3979624 (1976-09-01), Liu et al.

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