Electric discharge lamp
AssigneeThorn Lighting Limited
InventorsDavid Robert Mason, Susan Margaret Cole, Maurice Arthur Cayless, David Osborn Wharmby
Life of this patent
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Abstract
Electric discharge lamps of extended life can be produced or cheaper materials used in their manufacture by providing on the internal surface of the envelope and on the exposed surfaces of internal components a protective coating of a metal phosphate or arsenate glass. External surfaces can also be protected against corrosion in air or in the atmosphere within an outer jacket, where this is employed. The coating may be applied in a liquid medium which, preferably after draining, is warmed to evaporate the medium and thereafter baked to form the vitreous coating.
Claims8
In the method of manufacturing an electric discharge lamp comprising an arc tube, components including spaced electrodes and leads or supports therefor in said tube and a gaseous fill in said tube, the improvement comprising the steps of:
- coating the internal surfaces of the arc tube and the exposed surfaces of said components, which tend to react with said fill during lamp operation, with a solution having dissolved therein a composition selected from metal phosphates and arsenates, said solution being capable of generating on being heated a substantially uniform coating in the form of a potentially vitreous compound;
- and heating said coated surfaces to form thereon a vitreous protective coating of said metal phosphate or arsenate.
Dependencies are inferred from the claim text.