Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
2000-07-07
2004-01-06
O'Shea, Sandra (Department: 2875)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
C445S027000
Reexamination Certificate
active
06672923
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing an arc tube to be used as a light source such as a headlamp for vehicles.
2. Description of the Related Art
In recent years, an arc tube has often been used as a light source such as a headlamp for vehicles because it can carry out high-intensity irradiation.
As shown in
FIG. 5
, an arc tube to be used as the headlamp for vehicles generally comprises an arc tube body
114
made of quartz glass in which pinch seal portions
114
b
1
and
114
b
2
are provided on both sides of a light emitting tube portion
114
a
forming a discharge space
112
, and a pair of electrode assemblies
116
A and
116
B pinch-sealed with the pinch seal portions
114
b
1
and
114
b
2
such that tip portions thereof are protruded toward the discharge space
112
.
The arc tube is manufactured by forming the light emitting tube portion
114
a
on a quartz glass tube and sequentially forming the pinch seal portions
114
b
1
and
114
b
2
on both sides thereof. At each pinch-sealing step, a portion to be pinch-sealed is pinch-sealed with a pincher immediately after it is heated with a burner. Consequently, the pinch seal portions
114
b
1
and
114
b
2
are formed.
As shown in
FIGS. 6A and 6B
, it is necessary to fill the discharge space
112
with a liquefied inert gas at a second pinch-sealing step (that is, a step of forming the second pinch seal portion
114
b
2
on a quartz glass tube
114
′ provided with the light emitting tube portion
114
a
and the first pinch seal portion
114
b
1
). Therefore, the light emitting tube portion
114
a
is cooled. As shown in
FIG. 6A
, the cooling operation has conventionally been carried out by jetting liquid nitrogen from a cooling nozzle
104
provided on the side of the light emitting tube portion
114
a
toward the light emitting tube portion
114
a
in a state in which a thermal insulating plate
102
is provided in a boundary position between the light emitting tube portion
114
a
and the portion
114
b
2
′ to be pinch-sealed in the outer peripheral space of the quartz glass tube
114
′ provided almost vertically with the first pinch seal portion
114
b
1
provided in a lower part.
In the conventional manufacturing method, however, the cooling nozzle
104
is provided laterally in the vicinity of the lower part of the thermal insulating plate
102
. Therefore, the liquid nitrogen is vaporized in the early stage through heat transfer from the thermal insulating plate
102
and a burner
106
. Consequently, the light emitting tube portion
114
a
is cooled insufficiently. Depending on the circumstances, the liquefied inert gas filled in the discharge space
112
is vaporized (expanded), and the light emitting tube portion
114
a
bursts immediately after the pinch-sealing operation using a pincher
108
so that the inert gas leaks as shown in FIG.
6
B.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above-mentioned circumstances and has an object to provide a method of manufacturing an arc tube which can increase the cooling efficiency of the light emitting tube portion through the jet of the liquid nitrogen, thereby preventing the light emitting tube portion from bursting at the second pinch-sealing step.
The object of the present invention is achieved by devising the arrangement of the cooling nozzle.
The present invention provides a method of manufacturing an arc tube including pinch seal portions on both sides of a light emitting tube portion in which a second pinch seal portion is formed on a quartz glass tube provided with the light emitting tube portion and a first pinch seal portion, the method comprising the steps of:
providing the quartz glass tube almost vertically with the first pinch seal portion positioned in a lower part and providing a thermal insulating plate in a boundary position between the light emitting tube portion and a portion to be pinch-sealed in an outer peripheral space of the quartz glass tube;
jetting liquid nitrogen from a cooling nozzle provided obliquely below the light emitting tube portion toward the light emitting tube portion, thereby cooling the light emitting tube portion in this state, and heating the portion to be pinch-sealed with a burner; and
pinch-sealing the portion to be pinch-sealed with a pincher immediately thereafter.
If the “cooling nozzle” is provided obliquely below the light emitting tube portion and serves to jet the liquid nitrogen toward the light emitting tube portion, a specific structure including the number of the cooling nozzles to be provided and a liquid nitrogen jet angle is not restricted particularly.
With the above-mentioned structure, in the method of manufacturing an arc tube according to the present invention, liquid nitrogen is jetted from the cooling nozzle provided obliquely below the light emitting tube portion toward the light emitting tube portion in order to cool the light emitting tube portion at the second pinch-sealing step. Therefore, the cooling nozzle is set somewhat apart from the thermal insulating plate. In that case, moreover, the thermal insulating plate as well as the light emitting tube portion can be cooled through the jet of the liquid nitrogen to be carried out obliquely upward. Consequently, the cooling nozzle is not easily influenced by heat transferred from the thermal insulating plate and the burner. For this reason, the liquid nitrogen jetted from the cooling nozzle is vaporized slowly so that the light emitting tube portion is fully cooled. Accordingly, the liquefied inert gas filled in the discharge space is not vaporized (expanded) for a while after the pinch-sealing operation. Consequently, the light emitting tube portion can be prevented from bursting to leak the inert gas.
According to the present invention, thus, the cooling efficiency of the light emitting tube portion which is obtained through the jet of the liquid nitrogen can be increased at the second pinch-sealing step. Consequently, it is possible to prevent the light emitting tube portion from bursting to leak the inert gas.
In the present invention, furthermore, the liquid nitrogen is jetted obliquely upward. Therefore, the thermal insulating plate as well as the light emitting tube portion can be cooled. Consequently, it is possible to prevent the thermal insulating plate itself from being deteriorated.
According to the present invention, moreover, the burner and the cooling nozzle are positioned sufficiently apart from each other. Therefore, it is possible to prevent the burner from being cooled through the cooling nozzle to reduce a thermal efficiency thereof.
With the above-mentioned structure, if a portion of the thermal insulating plate in the vicinity of the outer periphery of a quartz glass tube is formed like an upward taper, a cooling space formed around the light emitting tube portion can be reduced and the liquid nitrogen can be prevented from being scattered in such a direction as not to contribute to the cooling operation of the light emitting tube portion. Consequently, the cooling efficiency can be enhanced still more.
While the specific structure of the cooling nozzle is not particularly restricted as described above, it is preferable, for the following reasons, that the liquid nitrogen jet angle is set upwardby 10° to 60° with respect to a horizontal plane.
More specifically, the cooling nozzle is heated through heat transfer from the thermal insulating plate at an angle of less than 10° so that the light emitting tube portion is often cooled insufficiently. On the other hand, if the angle exceeds 60°, the liquid nitrogen is jetted upward from a clearance between the thermal insulating plate and the quartz glass tube. Consequently, the heating temperature of the lower end of the portion to be pinch-sealed is dropped so that insufficient melting operation is often carried out. The angle is not set to 10 to 60° but preferably 20° to 50°, and more preferably
30
to 45°.
With the above-mentioned structure, it
Irisawa Shinichi
Nagata Akihiro
Ohkawai Nobuo
Ohshima Yoshitaka
Dong Dalei
Koito Manufacturing Co. Ltd.
O'Shea Sandra
Sughrue & Mion, PLLC
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