Electric lamp and discharge devices – With luminescent solid or liquid material – With gaseous discharge medium
Reexamination Certificate
1998-07-16
2001-01-09
Day, Michael H. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
With gaseous discharge medium
C313S493000, C315S108000
Reexamination Certificate
active
06172452
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to a low pressure mercury vapor discharge lamp using amalgam and, more particularly, to a low pressure mercury vapor discharge lamp that controls the amalgam temperature and improves the luminous efficiency.
BACKGROUND OF THE INVENTION
In a general type of low pressure mercury vapor discharge lamp, such as a light-bulb-shaped fluorescent lamp comprising an outer housing accommodating a fluorescent tube whose inner surface is covered with a phosphor, the mercury vapor pressure in the tube is controlled at a proper value by using an amalgam in order to prevent deterioration of luminous efficiency at a high temperature. In this case, the luminous efficiency depends on the temperature of the amalgam. The luminous efficiency will deteriorate when the amalgam temperature exceeds the proper value. In other words, the problem with the general low pressure mercury vapor discharge lamp is how to control the upper limit of the amalgam temperature.
In order to solve the above problem, a low pressure mercury vapor discharge lamp with amalgam temperature control is suggested, and this is accomplished in the prior art by covering the outer surface of a slender pipe containing amalgam with a heat radiation auxiliary component of a resin whose heat conductivity is better than that of the air. A further preferable example is disclosed in Japanese Laid-Open Patent Application (Tokukai-Sho) No. 61-225753, which discloses a low pressure mercury vapor discharge lamp in which a heat radiation auxiliary component covering a slender pipe contacts a housing, and the heat of the slender pipe is dissipated through the cover to the open air side.
Such a conventional low pressure mercury vapor discharge lamp comprises a slender pipe containing an amalgam. The outer surface of the pipe is covered with a heat radiation auxiliary component of a resin whose heat conductivity is better than that of the air, and the heat radiation auxiliary component is contacted with a housing. There is not, however, a sufficient difference between the temperature of the space in the housing and of the housing's inner surface in contact with the heat radiation auxiliary component, and the temperature of the amalgam container at the steady lighting of the lamp. Therefore, the heat of the amalgam container is not fully radiated, an the overheating of the amalgam cannot be fully controlled.
As such, there remains an opportunity to improve the low pressure mercury vapor discharge lamp. In particular, there exists a need for a low pressure mercury vapor discharge lamp that controls the amalgam temperature at a proper value and improves the luminous efficiency.
SUMMARY OF THE INVENTION
This invention aims to solve the above-mentioned problem by providing a low pressure mercury vapor discharge lamp that controls the amalgam temperature at a proper value and improves the luminous efficiency.
A low pressure mercury vapor discharge lamp of this invention comprises a fluorescent tube having an amalgam container containing amalgam to control mercury vapor pressure at a steady lighting, a holder holding both ends of the fluorescent tube, a lighting circuit to light the fluorescent tube, a case accommodating the lighting circuit, and a base for the case. The amalgam container and the base are connected to each other by a heat conductive component. The heat conductivity K of the heat conductive component is preferably at a value of K≧200 (W·m
−1
·K
−1
) at 100° C. Preferable radiation efficiency can be obtained as the heat conductivity is high.
In the configuration, the heat of the amalgam container can be conducted via the heat conductive component to the base for radiation, so that the overheating of the amalgam can be fully controlled. As a result, the mercury vapor pressure can be controlled at a proper value, and the luminous efficiency can be improved.
It is preferable that the low pressure mercury vapor discharge lamp further comprises a globe to accommodate the holder and to compose an outer housing with the case.
It is preferable in the low pressure mercury vapor discharge lamp that the heat conductive component comprises a metallic material.
It is preferable in the low pressure mercury vapor discharge lamp that the metallic material is at least one material selected from the group consisting of gold, silver, copper and aluminum.
It is preferable in the low pressure mercury vapor discharge lamp that the heat conductive component comprises a heat conductive silicone rubber material.
It is also preferable in the low pressure mercury vapor discharge lamp that the heat conductive component comprises carbon (graphite).
The above features and advantages of the invention will be better understood from the following detailed description taken into conjunction with the accompanying drawing.
REFERENCES:
patent: 4794301 (1988-12-01), Misono et al.
patent: 5274305 (1993-12-01), Bouchard
patent: 5912536 (1999-06-01), Michiels et al.
patent: 61-225753 (1986-10-01), None
Iida Shiro
Itaya Kenji
Nakano Kenji
Yukawa Masao
Day Michael H.
Matsushita Electronics Corporation
Morrison & Foerster / LLP
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