Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
1999-06-21
2002-03-12
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
C445S043000
Reexamination Certificate
active
06354900
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an arc tube used as a light source etc. of a discharge lamp and a manufacturing method thereof.
2. Description of the Related Art
A discharge lamp is able to irradiate light with high luminance, so that the discharge lamps have been used in many cases as head lights for vehicles, illuminating lights for stores or the like as well as field illuminating lights and road illuminating lights. Arc tube shown in
FIG. 1
is knows as a light source of such a discharge lamp.
The arc tube
2
is configured by a quartz glass tube
4
having a spherical portion
4
a
formed at the center portion thereof and a pair of electrode assemblies
6
provided at both sides of the spherical portion
4
a
within the quartz glass tube
4
. Each of the electrode assemblies
6
is formed in a manner that an electrode rod
8
protruding within the inner space (discharge room) of the spherical portion
4
a
is coupled to a lead wire
10
protruding from the end portion of the quartz glass tube
4
through a rectangular molybdenum foil
12
. Further, each of the electrode assemblies
6
is pinch-sealed by the quartz glass tube
4
at the molybdenum foil
12
portion.
The expression “pinch-seal” in the present specification means such a sealing method that a heated quartz glass tube is squeezed thereby to bury within the quartz glass tube insertion material (molybdenum foil etc.) placed within the quartz glass tube in a state that the insertion material is adhered to the material of the quartz glass tube.
Although the pair of the molybdenum foils
12
are sequentially pinch-sealed one by one, conventionally the pinch-seal process for the first one of the molybdenum foils has been performed in the following manner.
That is, as shown in
FIG. 7
, the electrode assembly
6
is inserted from the one end portion of the quartz glass tube
4
thereby to place the molybdenum foil
12
in the vicinity of the spherical portion
4
a
within the quartz glass tube
4
((
a
) of FIG.
7
). In this state, inactive gas such as argon gas, nitrogen gas or the like is flown into the quartz glass tube
4
thereby to exhaust the atmosphere within the quartz glass tube
4
, and simultaneously a portion of the quartz glass tube
4
surrounding the molybdenum foil
12
is heated by a burner
20
((
b
) of FIG.
7
). Then, the quartz glass tube
4
is squeezed by a pincher
22
((
c
) of
FIG. 7
) thereby to perform the pinch-sealing. As a result, the intermediate product of an arc tube shown in (
d
) of
FIG. 7
can be obtained.
The aforesaid conventional pinch-seal method is arranged in a manner that, in order to prevent the reduction of tensile strength of the molybdenum foil (breakage of the foil) due to the oxidation of the molybdenum foil, the inactive gas is flowed into the quartz glass tube
4
thereby to exhaust the air causing the oxidation. However, the inner pressure within the quartz glass tube
4
at the time of the pinch-sealing is kept almost at the atmospheric pressure. Thus, as shown in
FIG. 8
, interfaces
12
a
between the pinch-sealed molybdenum foil
12
and the quartz glass tube
4
are kept in a planer shape which is relatively smooth and similar to the surface shape of the molybdenum foil
12
before the pinch-sealing.
However, the thermal expansion coefficient largely differs between the molybdenum foil
12
and the quartz glass tube
4
. Thus, in the case where the interface
12
a
is a smooth planer shape, if the arc tube
2
is lightened or turned on, the exfoliation may likely occur between the molybdenum foil
12
and the quartz glass tube
4
due to the shearing stress &tgr; caused by the difference of the thermal expansion coefficients therebetween. If such an exfoliation occurs, there arises a problem that the leakage may occurs at the arc tube
2
and hence the life time of the arc tube becomes quite short.
SUMMARY OF THE INVENTION
The present invention has been performed in view of the aforesaid circumstance and an object of the present invention is to provide an arc tube and fabricating method thereof which can effectively prevent the occurrence of exfoliation between a molybdenum foil and a quartz glass tube which causes leakage.
In order to attain the aforesaid object, in the present invention, the pinch-sealing for the first one of the pair of molybdenum foils is not performed by flowing inactive gas within a quartz glass tube like the prior art but performed in a manner that the one end portion of the quartz glass tube is sealed, then the pinch-sealing is performed while air within the quartz glass tube is exhausted from the other end portion thereof so that pressure within the quartz glass tube becomes in a negative pressure state of a predetermined pressure and a pinch seal estimation portion of the quartz glass tube is heated, whereby fine concave and convex portions are formed on the interfaces between the molybdenum foils and the quartz glass tube thus having been pinch-sealed thereby to place the molybdenum foils and the quartz glass tube in an engage state to each other.
That is, in this invention, the arc tube according to the present invention is characterized in that, in the arc tube wherein a pair of molybdenum foils are pinch-sealed at both ends of a spherical portion of a quartz glass tube, the surface roughness of the molybdenum foils at the interfaces between the molybdenum foils and the quartz glass tube is set to be 1 &mgr;m (reference length of 0.08 mm) or more at ten-point average roughness.
In order to obtain such an arc tube, in this invention, the arc tube fabricating method according to the present invention is characterized in that, in a method for fabricating the arc tube, in which a pair of molybdenum foils are pinch-sealed at both ends of a spherical portion of a quartz glass tube, by sequentially pinch-sealing the pair of molybdenum foils, first one of the pair of molybdenum foils is pinch-sealed in a manner that the first one of the pair of molybdenum foils is inserted into the quartz glass tube thereby to seal one end portion of the quartz glass tube, and then a pinch seal estimation portion of the quartz glass tube is squeezed by a pincher while air within the quartz glass tube is exhausted from the other end thereof so that pressure within the quartz glass tube is in a negative pressure state of 100 torr or less and while heating the pinch seal estimation portion.
In this invention, “the interfaces between the molybdenum foils and the quartz glass tube” means both main and rear surfaces of each of the molybdenum foils and the surface roughness of the end portions of each of the molybdenum foils is not particularly limited.
In this invention, the concrete method for “sealing the one end portion of the quartz glass tube” is not particularly limited. For example, a method for heating and squeezing the one end portion of the quartz glass tube and heat-sealing by shrink-seal or the like, a method for choking the one end portion of the quartz glass tube by other member, or the like may be employed.
Since the arc tube according to the present invention is arranged in a manner that the surface roughness of the molybdenum foils at the interfaces between the molybdenum foils and the quartz glass tube is set to be 1 &mgr;m (reference length of 0.08 mm) or more at ten-point average roughness, the coupling intensity between the quartz glass tube and the respective molybdenum foils can be made sufficiently high. Thus, since the molybdenum foils and the quartz glass tube engage to each other by means of the fine concave and convex portions formed on the interfaces and the contact area between the molybdenum foils and the quartz glass tube is increased, at the time of turning-on of the arc tube, the exfoliation between the molybdenum foils and the quartz glass tube due to the difference of the thermal expansion coefficients therebetween can be prevented from being occurred in. Thus, the leakage of the arc tube can be prevented and the life time thereof can be made longer.
In the arc tube
Fukuyo Takeshi
Irisawa Shinichi
Ohkawai Nobuo
Ohshima Yoshitaka
Koito Manufacturing Co. Ltd.
Ramsey Kenneth J.
Sughrue & Mion, PLLC
LandOfFree
Arc tube and fabricating method thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Arc tube and fabricating method thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Arc tube and fabricating method thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2878431