Electric lamp and discharge devices – With gas or vapor – Envelope with particular structure
Reexamination Certificate
2001-03-09
2003-06-24
O'Shea, Sandra (Department: 2875)
Electric lamp and discharge devices
With gas or vapor
Envelope with particular structure
C313S623000, C313S570000
Reexamination Certificate
active
06583565
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high pressure discharge lamp. More specifically, the present invention relates to a high pressure discharge lamp which does not have problems such as a blowout of the bulb made of quartz glass or a leaking of a contained gas from the quartz glass bulb.
2. Description of Related Art
In general, a high pressure discharge lamp has a structure as shown in FIG.
3
. In the high pressure discharge lamp shown in
FIG. 3
, each electrode of a pair of electrodes (i.e., an anode
3
and a cathode
4
) is disposed so as to be opposite the other in a quartz glass bulb
2
, which includes an expanded portion for luminescence
21
and sealing portions
22
. The quartz glass bulb
2
is formed by welding the sealing portions
22
. The anode
3
and the cathode
4
are joined by, for instance, welding with molybdenum foils
5
and
5
′. Also, the sealing portions
22
of the quartz glass bulb
2
are airtightly sealed by, for example, welding with molybdenum foils
5
and
5
′. A gas for assisting an electric discharge is contained in the expanded portion for luminescence
21
of the quartz glass bulb
2
which has been airtightly sealed.
The temperature inside such a high pressure discharge lamp
1
tends to be increased when the luminous efficacy of the lamp
1
is enhanced by increasing the pressure of a light emitting material or a gas contained in the lamp
1
.
However, since each of the sealing portions is airtightly sealed by welding the two portions of the quartz glass, problems such as leaking, cracking, or even breaking at the welding portions may be caused when the internal pressure of the bulb
2
is increased.
Accordingly, one of the objectives of the present invention is to provide a high pressure discharge lamp which is capable of maintaining the airtightness even if the pressure of a light emitting material or a gas contained in the lamp is increased and to prevent such problems as leaking or a blowout of the quartz glass bulb.
The inventors of the present invention, after pursuing diligent studies to achieve the above-mentioned objectives, made observations of the angle between the quartz glass bulb and the direction along the length of an electrode in the vicinity of the sealing portion and have discovered that the internal pressure of the high pressure discharge lamp acts strongly in the direction of detachment of the welded portion of the quartz glass bulb when this angle is small, and that the internal pressure of the lamp, which acts in the direction detaching the welded portion of the quartz glass, becomes smaller as the angle increases. Accordingly, the airtightness of the high pressure discharge lamp may be maintained when the angle formed by the quartz glass bulb and the direction along the length of an electrode in the vicinity of the sealing portion is large and, hence, problems such as a leaking of the contained gas or a blowout of the bulb may be prevented.
SUMMARY OF THE INVENTION
The present invention provides a high pressure discharge lamp including: a quartz glass bulb having an expanded portion and sealing portions; conductive elements, which are airtightly sealed at the sealing portions of the quartz glass bulb; and a pair of electrodes, each electrode of the pair of electrodes being disposed so as to be opposite the other and each electrode being connected to one of the conductive elements, wherein an angle &thgr;
1
between a tangent along the inner surface of the expanded portion at a position 0.5 mm away from an origin of one of the sealing portions along the length of each electrode and the direction along the length of each electrode is at least about 40° (wherein the origin of one of the sealing portions is defined as a boundary point between the end of one of the sealing portions and an inner surface of the expanded portion; and the tangent along the inner surface of the expanded portion at a position 0.5 mm away from the origin is defined as a tangent which passes through a point of intersection defined by a straight line perpendicular to the direction along the length of each electrode, which passes through a point 0.5 mm away from the origin of one of the sealing portions toward the expanded portion along the length of each electrode, and the inner surface of the expanded portion and makes contact with the inner surface of the expanded portion).
In accordance with another aspect of the invention, the conductive elements are molybdenum foils.
In yet another aspect of the invention, an angle &thgr;
2
between a tangent along the inner surface of the expanded portion at an optional point between more than 0.5 mm and 1.5 mm from the origin of one of the sealing portions along the length of each electrode and the direction along the length of each electrode is at least about 45° (wherein the tangent along the inner surface of the expanded portion at an optional point between more than 0.5 mm and 1.5 mm from the origin is defined as a tangent which passes through a point of intersection defined by a straight line perpendicular to the direction along the length of each electrode, which passes through an optional point between more than 0.5 mm and 1.5 mm from the origin of one of the sealing portions toward the expanded portion along the length of each electrode, and the inner surface of the expanded portion and makes contact with the inner surface of the expanded portion).
In yet another aspect of the invention, an angle &thgr;
3
between a tangent along the inner surface of the expanded portion at an optional point between more than 1.5 mm and 3 mm from the origin of one of the sealing portions along the length of each electrode and the direction along the length of each electrode is at least about 50° (wherein the tangent along the inner surface of the expanded portion at an optional point between more than 1.5 mm and 3 mm from the origin is defined as a tangent which passes through a point of intersection defined by a straight line perpendicular to the direction along the length of each electrode, which passes through an optional point between more than 1.5 mm and 3 mm from the origin of one of the sealing portions toward the expanded portion along the length of each electrode, and the inner surface of the expanded portion and makes contact with the inner surface of the expanded portion).
In yet another aspect of the invention, the relationship among &thgr;
1
, &thgr;
2
and &thgr;
3
is &thgr;
1
<&thgr;
2
<&thgr;
3
.
In yet another aspect of the invention, &thgr;
1
is at least about 45°.
In yet another aspect of the invention, &thgr;
2
is at least about 60°.
In yet another aspect of the invention, &thgr;
3
is at least about 70°.
In yet another aspect of the invention, mercury vapor is contained in the high pressure discharge lamp in an amount between about 0.12 and 0.3 mg/mm
3
.
In yet another aspect of the invention, a halogen gas is contained in the high pressure discharge lamp in an amount between about 10
−8
and 10
−2
&mgr;mol/mm
3
.
In yet another aspect of the invention, an inert gas is contained in the high pressure discharge lamp at a pressure of about 6 kPa or greater.
In yet another aspect of the invention, the bulb wall loading in the high pressure discharge lamp is about 0.8 W/mm
2
or greater.
In yet another aspect of the invention, the pair of electrodes comprise tungsten containing potassium oxide.
In yet another aspect of the invention, the relationship between an internal pressure P (atm) of the high pressure discharge lamp and the angle &thgr;
1
is:
&thgr;
1
≧0.25
P+
5(wherein
P≧
140).
According to the present invention, it becomes possible to provide a high pressure discharge lamp which is capable of maintaining the airtightness even if the pressure of a light emitting material or a gas contained in the lamp is increased and to prevent such problems as a leaking or a blowout of the quartz glass bulb.
REFERENCES:
patent: 6181064 (2001-01-01), Narita
patent: 2000 637 (1978-07-01), None
patent: 5
Akiyama Yasuhiro
Nishida Kazuhisa
Macchiarolo Pete
McGinn & Gibb PLLC
NEC Microwave Tube, Ltd.
O'Shea Sandra
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