Metal halide lamp containing ThI.sub.4 with added elemental cadmium or zinc
US4360756A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 13, 1979 |
| Grant date | Nov 23, 1982 |
| Priority date | — |
| Expiry date | Nov 13, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J61/26
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
In a high intensity metal halide discharge lamp utilizing thorium in conjunction with a transport cycle for electrode activation, a getter, preferably cadmium or zinc is added to the lamp fill for the purpose of reducing the concentration of free iodine during operation. By so doing, deposition of thorium on the electrode tip during operation is assured and performance and maintenance are improved. The quantity of getter may include a portion supplied as a corrective measure to scavenge excess iodine released during manufacture, and another portion providing a long-term buffering capacity for capturing iodine released during the lamp's life by reaction of the dose, particularly ScI.sub.3 and ThI.sub.4, with the SiO.sub.2 of the lamp envelope.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.