Incandescent light bulb with variable pitch coiled filament
US6690103B1 · kind B1 · utility
Inventor
Key dates
| Filing date | May 4, 2000 |
| Grant date | Feb 10, 2004 |
| Priority date | — |
| Expiry date | May 4, 2020 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01K1/14
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An incandescent light bulb includes a lamp envelope, a coiled filament with a predetermined amperage rating disposed inside the lamp envelope, and current supply wires that electrically connect a pair of opposite terminal ends of the filament to a power supply. The power supply has a predetermined nominal voltage range for causing a current to flow through the filament sufficient to heat the same to a temperature at which it emits visible light. In one arrangement the filament has a pair of end segments and a central segment between the end segments. The end segments of the filament have a first pitch which is smaller than a second pitch of the central segment of the filament. With this configuration, more of the length of the coil will be heated to the maximum operating temperature while avoiding peak temperature areas that lead to failures. The variable pitch of the filament increases the brightness of the light bulb without decreasing its life.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.