Electrostatic shield to reduce wall damage in an electrodeless high intensity discharge lamp
US5438235A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 5, 1993 |
| Grant date | Aug 1, 1995 |
| Priority date | — |
| Expiry date | Oct 5, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J65/048
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An electrostatic shield is provided between the induction coil and the arc tube of an electrodeless HID lamp. In one embodiment, the shield is a transparent glass cylinder coated with a thin, transparent, conductive layer of tin oxide. In another embodiment, the electrostatic shield is a conductive, transparent tin oxide coating applied to either the inner or outer surface of an outer light-transmissive jacket surrounding the arc tube. The tin oxide layer is discontinuous so as to minimize currents induced in the conductive tin oxide layer by the induction coil. The thickness of the tin oxide layer is sufficient to make it conductive and form an approximately equipotential surface, thereby shielding the arc tube and plasma discharge from intense electric fields, reducing arc tube wall damage and increasing lamp life. In addition, tin oxide functions as an infrared reflector which returns infrared radiation to the arc tube, resulting in higher efficacy. Other advantages of the electrostatic shield include: a lower color temperature, further improving efficacy; and a lower rate of free iodine formation in lamps employing metal iodide fills, further reducing wall damage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.