Electric lamp and discharge devices – Having pressure control of gas or vapor
Reexamination Certificate
2000-06-01
2001-10-30
Day, Michael H. (Department: 2879)
Electric lamp and discharge devices
Having pressure control of gas or vapor
C313S564000, C313S565000, C313S490000
Reexamination Certificate
active
06310437
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to electric lamps and, in particular, to a holder for an amalgam in a gas discharge lamp.
Maintaining mercury vapor pressure equilibrium within a gas discharge lamp such as a fluorescent lamp is necessary to maintain optimum lumen output during extended lamp on periods. In conventional fluorescent lamps, the mercury vapor pressure increases to an optimum pressure allowing the lamp to reach maximum lumen output. As time passes, the mercury vapor pressure increases to a level above the most preferable pressure causing the luminous flux to decrease.
To help maintain the pressure at the optimum pressure, amalgams are introduced to maintain the mercury vapor pressure within an optimal range during lamp operation. Upon lamp ignition, the amalgam is heated which causes mercury to diffuse out of the solid and is released into the lamp as vapor. The amalgam achieves mercury vapor equilibrium during lamp operation by supplying the same amount of mercury atoms to the interior of the lamp envelope as are spent. However, when the lamp is switched off, the decrease in temperature causes the mercury vapor to navigate to and diffuse into the amalgam causing mercury starvation. The lack of mercury vapor in the lamp envelope during off periods results in low lumens at lamp startup. In order to obtain peak lumens upon lamp ignition without any startup time penalty, an adequate dose of mercury vapor is required to remain in the lamp envelope during lamp off periods.
A restricted fixed orifice in an amalgam capsule can be used to reduce the starvation effect for short off times. U.S. Pat. No. 5,828,169 uses such a technique. However, during extended off times, virtually all of the mercury can still return to the amalgam.
SUMMARY OF THE INVENTION
An amalgam holder for a discharge lamp having an exhaust tube and a flare pinched about the tube where the holder includes an extension of the tube or flare having a cavity for an amalgam, the cavity having a mouth; and a cover for the mouth, the cover being thermally actuated.
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Akins William W.
Blau Andrew P.
Borowiec Joseph C.
Lukacs Sandor
Day Michael H.
General Electric Company
Pearne & Gordon LLP
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