JP2002324516A - Discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp which is capable of preventing cracks in an arc tube due to temperature rise after turning on, and also obtaining excellent productivity. SOLUTION: This discharge lamp comprises an arc tube, and a pair of rod- like electrodes disposed face-to-face with each other in the arc tube, and metal leafs and lead wires connecting the respective rod-like electrodes to an external power source. Further, the edge and its peripheral portion of each electrode, the metal leaf connected to the electrode and a part of the lead wire are sealed by pressing each edge and its peripheral portion of the arc tube, and each coil wound helically with a metal wire is fixed around the sealed portion of the electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp used as a light source for various illuminations.

[0002]

2. Description of the Related Art Discharge lamps are used as light sources for general lighting, stage lighting, movie / TV shooting lighting, studio shooting lighting, architectural lighting, store lighting and the like. The discharge lamp is
This is a lamp that utilizes light emission due to discharge in a gas containing metal vapor. As a discharge lamp, a mercury lamp, a sodium lamp, a xenon lamp, a metal halide lamp and the like are known.

[0003] The discharge lamp is composed of an arc tube filled with metal vapor and a rare gas, a pair of rod-shaped electrodes provided at opposing positions of the arc tube, and a metal foil and a lead wire for connecting each rod-shaped electrode to an external power supply. Consists of Then, one end of the rod-shaped electrode, a metal foil connected to the one end, and a part of the lead wire are sealed by pressure welding between both ends of the arc tube and respective peripheral portions.

When such a discharge lamp is turned on, a crack may be formed in the arc tube from around the sealed portion of the rod-shaped electrode. Generally, the arc tube is made of quartz glass, and the rod-shaped electrode is made of a metal represented by tungsten or the like. When the discharge lamp is turned on, the temperature of the arc tube and rod electrode rises,
The quartz glass sealing the metal rod-shaped electrode and its surroundings expands. Quartz glass is known as a material having a small coefficient of thermal expansion, and has a large difference in coefficient of thermal expansion from metals used for rod-shaped electrodes. Accordingly, when the quartz glass sealing the rod-shaped electrode and the periphery thereof expands due to a rise in temperature, internal stress is generated in the sealed portion, and cracks occur in the quartz glass.
For this reason, conventionally, a metal foil (for example, molybdenum or the like) whose coefficient of thermal expansion is close to the coefficient of thermal expansion of the metal used for the rod-shaped electrode
Was wound around the sealing portion of the rod-shaped electrode to relieve the generated internal stress and prevent the occurrence of cracks.

[0005]

The winding of the metal foil around the rod-shaped electrode is performed manually, and therefore, the workability is poor, and this is one of the causes that the productivity of the discharge lamp cannot be improved. Further, it is difficult to uniformly wind the metal foil by hand, and depending on the degree of winding, the arc tube may be cracked. An object of the present invention is to provide a discharge lamp which prevents the arc tube from being cracked due to a rise in temperature after the discharge lamp is turned on, and is excellent in productivity.

[0006]

SUMMARY OF THE INVENTION The present inventor has proposed that, instead of using metal foil, a cylindrical coil in which a metal wire is spirally wound is mounted around the sealing portion of a rod-shaped electrode, so that the arc tube cracks. And improved the productivity of the discharge lamp. The present invention comprises an arc tube, a pair of rod-shaped electrodes provided at opposing positions inside the arc tube, and a metal foil and a lead wire for connecting each rod-shaped electrode to an external power supply, and one of the electrodes. A discharge lamp in which ends and peripheral portions thereof, a metal foil connected thereto, and a part of a lead wire are sealed by press-welding both side ends of an arc tube and peripheral portions thereof, and The discharge lamp is provided with a cylindrical coil around which a metal wire is spirally wound around a sealed portion of the discharge lamp. In the discharge lamp of the present invention, it is preferable that the cylindrical coil is flexible.

[0007]

DETAILED DESCRIPTION OF THE INVENTION A discharge lamp according to the present invention is a mercury lamp,
Any of a sodium lamp, a xenon lamp, a metal halide lamp and the like may be used, but a typical one is a metal halide lamp. Therefore, in the following description, a metal halide lamp will be described as a typical example of the discharge lamp of the present invention.

FIG. 1 is a plan view schematically showing the structure of an example of the discharge lamp of the present invention. FIG. 2 is a sectional view of the discharge lamp of the present invention shown in FIG. 1 and 2, a discharge lamp 1 includes an arc tube 2, a pair of bar electrodes 3 and 4 provided at opposing positions inside the arc tube, and an external power supply (not shown). ) To be connected to the metal foils 5 and 6 and the lead wires 7 and 8, and the metal wire attached to the rod-shaped electrodes 3 and 4, which is a spirally wound cylindrical coil 9.
And 10.

Generally, the arc tube 2 is made of quartz glass. After the inside of the arc tube 2 is evacuated from the exhaust tube 13 to a high vacuum, mercury as a buffer gas and a rare gas (eg, argon) as a starting auxiliary gas are used. ) And the metal halide, the exhaust pipe 13 is sealed off. Examples of metal halides include Na, Tl, Th, In, Sn,
Examples include compounds of a metal such as Si, Sc, Dy, Ho, and Tm with a halogen such as iodine or bromine.

As a material for the rod-shaped electrodes 3 and 4, tungsten is preferably used. Metal wires 11 and 12 are doubly wound and fixed on opposing sides of the rod-shaped electrodes 3 and 4 (in FIG. 2, cylindrical coils 9 and 1 are formed).
0, and the metal wires 11 and 12 are shown uncut). The metal wires 11 and 12 function as electrodes and also function to prevent the cylindrical coils 9 and 10 mounted on the rod-shaped electrodes from shifting from predetermined positions. One end of the rod-shaped electrodes 3 and 4 on which the cylindrical coils 9 and 10 are mounted and their peripheral parts, the metal foils 5 and 6 connected thereto, and part of the lead wires 7 and 8 are located on both sides of the arc tube. Sealing is performed by pressure welding between the end portion and each peripheral portion.

FIG. 3 is a perspective view of a rod-shaped electrode provided with a cylindrical coil. FIG. 3 illustrates the rod-shaped electrode 4 on which the cylindrical coil is mounted, but the rod-shaped electrode 3 has the same configuration. The rod-shaped electrode 4 is generally made of tungsten. A metal wire 12 is doubly wound around and fixed to one end of the rod-shaped electrode 4. A metal foil 6 and a lead wire 8 are welded to the other end of the rod-shaped electrode 4. As the metal foil 6, an aluminum foil, a molybdenum foil, or the like can be used, and a molybdenum foil is preferably used. The metal foil 6 may be made of two foils, and may have a form in which high silicate glass or quartz glass is sandwiched between the foils. Around the bar-shaped electrode 4 on the side of the metal foil 6 (at the sealing portion), a cylindrical coil 10 in which a metal wire is spirally wound is mounted.

Conventionally, around the sealing portion of the rod-shaped electrode 4,
The metal foil was wound by hand. This metal foil alleviated the internal stress generated in the sealed portion of the rod-shaped electrode 4 and prevented the occurrence of cracks. Manually winding a metal foil around the rod-shaped electrode 4 is very troublesome, and has been one of the reasons why productivity of the discharge lamp cannot be improved. Further, it is difficult to uniformly wind the metal foil by hand, and depending on the degree of winding, the arc tube may be cracked.

By using a cylindrical coil 10 as shown in FIG. 3 instead of the metal foil, the operation becomes extremely simple, and the generation of cracks at the sealing portion of the rod-shaped electrode 4 can be prevented. Productivity can be improved. Further, unlike the manual winding of the metal foil, the mounting state of the tubular coil 10 is less likely to vary. Therefore, it is possible to manufacture a discharge lamp of a stable quality in which the effect of preventing cracks is uniform. If the coil is easily deformed when handling the cylindrical coil 10, it takes time to mount the coil on the rod-shaped electrode 4. Then, at the time of sealing, it is preferable that the cylindrical coil 10 and the rod-shaped electrode 4 are brought into close contact with each other. Therefore, it is preferable that the tubular coil 10 is flexible. Further, in order to alleviate the internal stress generated in the sealing portion of the rod-shaped electrode 4, the value of the coefficient of thermal expansion of the metal used for the cylindrical coil 10 should be close to the value of the coefficient of thermal expansion of the metal used for the rod-shaped electrode. preferable. Examples of metals that can be preferably used for the tubular coil 10 include tungsten and molybdenum. It is also preferable to use a metal having a coefficient of thermal expansion between the coefficient of thermal expansion of the arc tube and the coefficient of thermal expansion of the rod-shaped electrode 4 for the cylindrical coil 10.

In the discharge lamp of the present invention, a known ultraviolet absorbing film or a film containing a known fluorescent substance may be provided on the inner or outer surface of the arc tube. Further, the arc tube may be formed of ultraviolet absorbing quartz glass.

Further, the discharge lamp may be sealed in an outer tube made of quartz glass or the like for the purpose of protecting and keeping the temperature of the discharge lamp, preventing oxidation of metal parts and blocking ultraviolet rays. When enclosed in an outer tube, the discharge lamp lead wire may be wired to one position of the outer tube to form a single-ended lamp with one base, or each of the discharge lamp lead wires may be connected to the outer tube. A double-end lamp may be provided at each of the positions opposite to each other and provided with bases. A lamp may be provided by providing a bulb cap at one position of the outer tube and enclosing a discharge lamp.
A known ultraviolet absorbing film or a film containing a known fluorescent substance may be provided on the inner surface or outer surface of the outer tube. Further, the outer tube may be formed of quartz glass that absorbs ultraviolet light. A gas such as a nitrogen gas or an argon gas can be sealed inside the outer tube.

[0016]

According to the discharge lamp of the present invention, a cylindrical coil in which a metal wire is spirally wound around a sealing portion of a rod-shaped electrode is mounted. This tubular coil reduces internal stress generated in the sealed portion when the discharge lamp is turned on and the temperature rises, thereby preventing the arc tube from cracking. Also, compared to the conventional method of wrapping metal foil around the sealing part,
The workability of mounting is good, and the productivity of the discharge lamp can be improved. Further, the discharge lamp of the present invention has stable quality without variation in the effect of preventing cracks.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing a configuration of an example of a discharge lamp of the present invention.

FIG. 2 is a cross-sectional view schematically showing a configuration of an example of the discharge lamp of the present invention.

FIG. 3 is a perspective view showing a state in which a cylindrical coil is mounted on a rod-shaped electrode used in the discharge lamp of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge lamp 2 Arc tube 3, 4 Rod electrode 5, 6 Metal foil 7, 8 Lead wire 9, 10 Cylindrical coil 11, 12 Metal wire 13 Exhaust tube

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koji Machida 1279-2 Owada, Miwa-machi, Sarushima-gun, Ibaraki F-term (reference) in Koto Electric Co., Ltd. 5C043 AA14 CC01 DD11 EA09

Claims (2)

[Claims] An arc tube, a pair of rod-shaped electrodes provided at opposed positions inside the arc tube, and a metal foil and a lead wire for connecting each rod-shaped electrode to an external power supply;
A discharge lamp in which one end of the electrode and its periphery, a metal foil connected to it, and a part of the lead wire are sealed by pressure welding of both sides of the arc tube and their respective peripheral portions. A discharge lamp, wherein a cylindrical coil in which a metal wire is spirally wound is mounted around a sealed portion of the electrode. 2. The method according to claim 1, wherein said tubular coil is flexible.
The discharge lamp according to item 1.