Electric lamp and discharge devices – With luminescent solid or liquid material – With gaseous discharge medium
Reexamination Certificate
2000-04-20
2003-07-22
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
With gaseous discharge medium
C313S493000, C313S634000, C313S565000
Reexamination Certificate
active
06597105
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a fluorescent lamp capable of adjusting a mercury vapor pressure in a discharge tube by using an amalgam.
BACKGROUND OF THE INVENTION
A fluorescent lamp uses fluorescence, which is obtained by exciting a fluorescent substance layer formed on an inner wall of a glass tube with an ultraviolet ray, as a light source. As the ultraviolet ray, a resonance line of mercury is widely used. In general, pure mercury is filled in a glass tube of a fluorescent lamp. In such a fluorescent lamp, when the temperature of the coolest portion of the lamp is about 40° C. and the ambient temperature around the lamp is about 25° C., the mercury vapor pressure in the glass tube becomes suitable, and the maximum luminous efficiency can be attained. However, in a compact fluorescent lamp produced, for example, by using a bent glass tube such as a U-shaped glass tube, etc. or, by connecting a plurality of glass tubes, the ambient temperature around the lamp is easily increased. Consequently, the lamp temperature tends to be increased.
Therefore, there have been proposed methods for placing a mercury amalgam pellet at a portion corresponding to the coolest portion in a fluorescent lamp so that the mercury vapor pressure in the glass tube is adjusted to fall within the appropriate range even if the temperature of the fluorescent lamp is increased. The mercury amalgam pellet is generally placed in the slender glass tube that is provided so as to be in communication with the glass tube that is a discharge tube. In this case, a slender glass tube is provided with a means for adjusting the location of the amalgam pellet and for preventing the mercury amalgam pellet from moving toward the inside of the discharge tube. Examples of the structure of the fluorescent lamp having such a means include, for example, a structure shown in
FIG. 7
(disclosed in, for example, JP 2-16513 Y), a structure including a member for preventing the mercury amalgam pellet from moving toward the inside of the glass tube (which will also be referred to as “a moving prevention member” hereinafter) in a slender glass tube, or the like. The structure of the fluorescent lamp shown in
FIG. 7
includes a glass tube
10
having a fluorescent substance layer
11
on the inner surface, a sealed portion
12
provided at the end of the glass tube
10
, and a slender glass tube
14
penetrating through the sealed portion
12
, and the slender glass tube
14
has a narrow portion
15
on the portion protruding outward from the sealed portion
12
. In the fluorescent lamp shown in
FIG. 7
, between the end of the slender glass tube
14
and the narrow portion
15
, a mercury amalgam pellet
13
is held.
Recently, in a compact fluorescent lamp such as a compact self-ballasted fluorescent lamp, as further miniaturization increasingly has been demanded, a more slender glass tube has been used as a discharge tube. As to a slender glass tube containing a mercury amalgam pellet, a further slender and shorter tube tends to be used. When such a slender and short slender glass tube is used, in a structure shown in
FIG. 7
, the part of the slender glass tube
14
protruding outward from the sealed portion
12
is shortened. Therefore, it is difficult to form a narrow portion
15
while securing a sufficient portion containing mercury amalgam pellet
13
. Furthermore, there is a risk that a slender glass tube
14
may be pressed and collapsed when the narrow portion
15
is formed. Furthermore, in the structure in which the moving prevention member is inserted into the slender glass tube, when the slender glass tube is used as an evacuation tube in manufacturing the fluorescent lamp, the moving prevention member may inhibit a smooth evacuation, which may lead to a defective evacuation in the fluorescent lamp.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the problems of the prior art. That is, the object of the present invention is to provide a fluorescent lamp capable of reliably preventing a mercury amalgam pellet from moving toward the inside of a glass tube while fully securing a portion for containing the mercury amalgam pellet.
In order to achieve the above-mentioned objects, according to a first aspect of the present invention, a fluorescent lamp includes a glass tube having a fluorescent substance layer on the inner surface, a sealed portion formed at the end of the glass tube, a container having an inner space that is in communication with the inside of the glass tube and is not in communication with the outside of the glass tube, and a mercury amalgam pellet contained in the container. In the fluorescent lamp of this configuration, the sealed portion is provided with a through hole for allowing communication between the glass tube and the container, and at least a part of the through hole in the sealed portion has an inner diameter smaller than the diameter of the mercury amalgam pellet.
With the fluorescent lamp having such a configuration, since the portion for preventing the moving of the mercury amalgam pellet is formed in the sealed portion, it is possible to prevent the moving of the mercury amalgam pellet while fully securing the volume of the container, regardless of the length of the portion of the container protruding outward from the sealed portion. Furthermore, since there is no member corresponding to the moving prevention member in the through hole and the container, it is possible to attain sufficient evacuation efficiency even when the container and the through hole are used as an evacuation tube.
It is preferable in the above-mentioned fluorescent lamp that at least a part of the container is placed in the sealed portion. According to such a preferred configuration, even when the length of a portion of the container protruding outward from the sealed portion is short, it is possible to fully secure the sufficient volume of the container.
According to another aspect of the present invention, a fluorescent lamp includes a glass tube having a fluorescent substance layer on the inner surface, a sealed portion formed at the end of the glass tube, a slender glass tube having an inner space that is in communication with the inside of the glass tube and is not in communication with the outside of the glass tube, and a mercury amalgam pellet contained in the slender glass tube. In the fluorescent lamp of this embodiment, the slender glass tube having a small-diameter part with an inner diameter smaller than the diameter of the mercury amalgam pellet and a large-diameter part with an inner diameter larger than the diameter of the mercury amalgam pellet, is welded to the glass tube so that the small-diameter part is placed in the sealed portion and the large-diameter part is placed further away from the glass tube than the smaller-diameter part.
Also in the fluorescent lamp having such a configuration, since the portion for preventing the moving of the mercury amalgam pellet is formed in the sealed portion, it is possible to prevent the amalgam pellet from moving while fully securing the volume of the portion for containing the mercury amalgam pellet. Furthermore, since there is no member corresponding to the moving prevention member in the slender glass tube, even when the glass tube is used as an evacuation tube, it is possible to attain sufficient evacuation efficiency.
It is preferable in the above-mentioned fluorescent lamp that at least a part of the large-diameter part is placed in the sealed portion. With such a preferred configuration, even in a case where the part of the slender glass tube protruding outward from the sealed portion is short, it is easy to secure the sufficient volume of the portion containing the mercury amalgam pellet.
According to a further aspect of the present invention, a method for manufacturing a fluorescent lamp includes: inserting a molding stick having a large-diameter part and a small-diameter part, which have different diameters, into a slender glass tube; forming a fluorescent substance layer on the inner surface o
Oga Toshiyoshi
Tsubakihara Nobuyuki
Uchida Noriyuki
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
Patel Nimeshkumar D.
Santiago Mariceli
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