Electric lamp and discharge devices – With luminescent solid or liquid material – With gaseous discharge medium
Reexamination Certificate
1998-12-02
2001-05-08
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
With gaseous discharge medium
C313S318010, C313S331000, C313S623000, C501S015000, C439S232000
Reexamination Certificate
active
06229257
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fluorescent lamp. More specifically, the present invention relates to a fluorescent lamp having a reduced adverse effect on the environment by improving the glass bulb material and the arrangement to provide an electrode to the fluorescent lamp.
2. Description of the Prior Art
A fluorescent lamp generally has the following configuration. As shown in
FIG. 5
, a conventional fluorescent lamp includes a cylindrical glass bulb
33
whose inner surface is coated with a fluorescent substance
37
. The glass bulb
33
is sealed with stems at both ends of the glass bulb
33
(
FIG. 5
shows only one end of the glass bulb
33
). The stem includes a flare
32
, an exhaust tube
34
, lead wires
35
and a filament coil
36
. The two lead wires
35
are connected to the ends of the filament coil
36
. The glass bulb is evacuated to a vacuum, and mercury and a rare gas are injected through the exhaust tube. Then, the exhaust tube
34
is sealed. A lamp base
38
is attached to the end of the glass bulb
33
with cement
39
. The lead wires
35
are connected to electrodes terminal pins
31
provided in the lamp base
38
.
The glass bulb
33
is formed of a soda-lime glass comprising 10 to 20 wt % of sodium oxide because of its low cost and easy processing. Generally, lead glass containing 4 to 28 wt % of lead oxide is used as a glass material for the stem including the exhaust tube and the flare because it is handled easily in a heating process. Furthermore, the lamp base
38
is formed of aluminum or plastic such as polycarbonate. The cement
39
is formed by using an organic solvent such as phenol.
On the other hand, great attention has been given to environmental issues recently. In response to this tendency, in the field of fluorescent lamps, various efforts to reduce adverse effects on the environment have been undertaken. Recycling of waste lamps, reduction of environmental contaminants and upgrading of the workplace are examples of such efforts.
A variety of approaches have been proposed to pursue recycling of fluorescent lamps so that mercury, soda-lime glass and lead glass can be reused by a recycling treatment. However, there still remains a problem in sorting glass by type, so that the glass materials have not completely been reused yet. As for lamp bases, the cost of recycling is unattractively high, and therefore, waste lamp bases are buried in the earth at present.
The most problematic contaminants are mercury and lead. To tackle problems of mercury, a method for sealing up mercury has been changed. More specifically, a liquid mercury was sealed up by dropping before, whereas other methods associated with use of capsules, alloy, or amalgam are used at present. Thus, the amount of mercury contained is reduced, and the workplace is improved.
However, mercury is contained in a lamp in an amount larger than the amount theoretically necessary for the fluorescent lamp to light.
A larger amount of mercury is necessary partly because mercury is consumed by soda-lime glass generally used for a glass bulb. When the lamp including a glass bulb formed of soda-lime glass lights on, sodium ions in the soda-lime glass diffuse to the surface of the glass bulb while the lamp is on. The diffused sodium ions react with mercury vapor. Alternatively, mercury is fixed to voids formed as a result of the diffusion of sodium ions. Such mercury no longer contributes to discharge. These phenomena consume mercury, and therefore a superfluous amount of mercury, which is larger than an amount necessary for the glow of the lamp, is required to be sealed up in the lamp.
As for lead, a variety of glasses that contain less lead or do not contain lead have been proposed. However, any proposed glasses have drawbacks in their characteristics. Therefore, a glass containing a large amount of lead oxide is still used at present. When the glass containing a large amount of lead oxide is heated at a high temperature during the production steps for a lamp, toxic lead oxide is scattered and evaporated into the air. This fact may cause a large adverse effect on the workers or the environment. Therefore, a large financial investment is required to counter these problems so that the adverse effect on the workers or the environment can be reduced.
As described above, the lamp base and the lead glass in the conventional fluorescent lamp cause environmental problems. More specifically, the lamp base is buried in the earth after the lamp is disposed of The lead glass releases toxic lead oxide, which requires a large financial investment to prevent this problem. In addition, the lead glass is hardly recycled. Furthermore, the use of soda-lime glass for a fluorescent lamp prevents a reduction of the amount of mercury to be sealed up in the fluorescent lamp.
SUMMARY OF THE INVENTION
Therefore, with the foregoing in mind, it is the object of the present invention to provide a fluorescent lamp that can reduce an adverse effect on the environment (i.e., facilitate recycling and reduce environmental contaminants) by forming a glass bulb with a material that allows a reduction of the amount of mercury contained and by not using a lamp base or lead glass.
A fluorescent lamp of the present invention includes a glass bulb whose inner surface is coated with a fluorescent substance, a glass bead attached to an end of the glass bulb so as to seal the glass bulb, an exhaust tube provided in the glass bead and sealed, a filament coil arranged in an internal portion of the glass bulb, and an electrode terminal member, e.g., an electrode terminal pin, electrically connected to the filament coil. The glass bead controls a position of the electrode terminal member. According to the fluorescent lamp of the present invention, the glass bead regulates the position of the electrode terminal member. Therefore, there is no need to provide a lamp base for regulating the position of the electrode terminal member. Thus, there is also no need to use a cement for attaching the lamp base to the glass bulb. In addition, this can eliminate the steps of connecting the lead wire to the lamp base member and attaching the lamp base to the glass bulb. Thus, the present invention provides a fluorescent lamp having advantages with respect to the environment and the cost during production of the fluorescent lamp.
In one embodiment of the fluorescent lamp of the present invention, the glass bulb and the glass bead preferably have substantially the same composition. This is preferable because the sealing property of the fluorescent lamp can be improved.
In another embodiment of the fluorescent lamp of the present invention, the glass bulb, the glass bead and the exhaust tube preferably have substantially the same composition. In this preferred embodiment, since the glass bulb, the glass bead and the exhaust tube have substantially the same composition, it is not necessary to sort glass by type in a recycling treatment. This facilitates recycling.
In still another embodiment of the fluorescent lamp of the present invention, the glass bulb, the glass bead and the exhaust tube preferably contain silica as a main component, and have a composition substantially free of lead.
In yet another embodiment of the fluorescent lamp of the present invention, the glass bulb preferably has a composition comprising:
65 to 73 wt % of SiO
2
;
1 to 5 wt % of Al
2
O
3
;
0.5 to 2 wt % of Li
2
O;
5 to 10 wt % of Na
2
O;
3 to 7 wt % of K
2
O;
0.5 to 2 wt % of MgO;
1 to 3 wt % of CaO;
1 to 10 wt % of SrO; and
1 to 15 wt % of BaO.
The composition according to this embodiment contains less sodium oxide than a glass composition for a conventional glass bulb. Therefore, it is possible to reduce the consumption of mercury in the glass bulb, thus leading to a reduction of the amount of mercury to be sealed in the fluorescent lamp.
In still another embodiment of the fluorescent lamp of the present invention, the glass bulb, the glass bead and the exhaust tube preferably have the above composition.
According to
Kondoh Toshifumi
Koyamada Yutaka
Uchiyama Hisatoshi
Matsushita Electronics Corporation
Merchant & Gould P.C.
Patel Nimeshkumar D.
Williams Joseph
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