JP3083429B2 - High pressure sodium lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-pressure sodium lamp.

[0002]

2. Description of the Related Art Among high-pressure sodium lamps, lamps with improved color rendering and color temperature have been widely used as light sources for indoor lighting such as store lighting. Such a lamp achieves good color rendering by increasing the sodium vapor pressure in the arc tube during operation to spread the emission spectrum over the entire visible range. In order to increase the sodium vapor pressure, it is necessary to increase the temperature of the end of the arc tube. For this reason, a metal foil such as tantalum is usually wound around the arc tube end.

[0003]

However, such a conventional high-pressure sodium lamp has the following problems. This will be described with reference to FIG.

In FIG. 5, when the operating temperature of the end portion of the arc tube 1 is high, the ceramic frit 4 exposed along the boundary between the end surface of the arc tube 1 and the conductor 3 formed of a niobium tube.
Therefore, some of the components gradually evaporate during the long-term lamp operation, and locally adhere to the inner surface of the outer tube (not shown). When the size of the outer tube is extremely small as in the case of a compact lamp, there is a problem that a part of the outer tube is blackened due to adhesion of the evaporated ceramic frit 4 to the inner surface of the outer tube, causing a decrease in light output. there were.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a high-pressure sodium lamp in which evaporation from a ceramic frit is prevented from adhering to the inner surface of an outer tube and light output is prevented from being reduced. With the goal.

[0006]

According to the high pressure sodium lamp of the present invention, a conductor having electrodes at its ends at both ends is sealed with a ceramic frit, and sodium is contained inside.
In a high-pressure sodium lamp having an arc tube filled with mercury and a rare gas inside an outer tube, a shield is movably fitted to the conductor led out from the arc tube and exposed to the end surface of the arc tube. The ceramic frit is covered with the shield.

Further, at both ends, a conductor having electrodes at the tips is sealed with a ceramic frit, and an arc tube in which sodium, mercury and a rare gas are sealed is supported in the outer tube by a stem support wire. A cylindrical shield having a flange at an end is fixed to the stem support line by a support, and the shield is movably fitted to the conductor led out from the arc tube. And the flange portion covers the ceramic frit exposed from the end face of the arc tube.

[0008]

According to the present invention, since the ceramic frit is prevented from reaching the inner surface of the outer tube by the shield even if the ceramic frit tries to evaporate during the operation of the lamp, local blackening of the inner surface of the outer tube is achieved. Can be prevented.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, the high-pressure sodium lamp according to the embodiment of the present invention comprises a light-emitting tube 1 made of a translucent alumina tube, and a conductive tube made of a niobium tube having an electrode 2 at its tip. The body 3 is sealed with a ceramic frit 4. Sodium, mercury, and xenon are sealed inside the arc tube 1. A tantalum foil 5 is wound around the outer peripheral surfaces of both ends of the arc tube 1. As a shield, a disc-shaped shield plate 6 made of a heat-resistant material such as ceramic and having a hole in the center is movably inserted into the conductor 3 led out of the arc tube 1 to the outside. The ceramic frit 4 exposed on the end face of the arc tube 1 is covered with the shielding plate 6. The shielding plate 6 is for preventing the evaporated matter from the ceramic frit 4 from scattering to the inner surface of the outer tube 10, and does not need to be in close contact with the end surface of the arc tube 1. The shielding plate 6 is fixed to the support wire 9 b of the stem 8 by a fixing metal wire 7. The arc tube 1 is fixed to the supporting wires 9a and 9b of the stem 8, and the outer tube 1 evacuated to a high vacuum.
0 is provided. A base 11 is provided at one end of the outer tube 10.
Is provided.

As described above, in the high-pressure sodium lamp according to the embodiment of the present invention, the shielding plate 6 is movably inserted into the conductor 3 extending to the outside from the end face of the arc tube 1 so that the end face of the arc tube 1 is moved. Ceramic frit 4 which is gradually evaporated during long-term lamp operation because it is covered with shielding plate 6
Evaporated matter adheres to one surface of the shielding plate 6, thereby preventing blackening of the inner surface of the outer tube 10 and preventing a decrease in light output.

Next, another embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 3 and 4, a high-pressure sodium lamp according to another embodiment of the present invention has an arc tube 1 supported by a stem 8 in an outer tube 10 evacuated to a high vacuum.
A light emitting tube 1 made of a translucent alumina tube has a conductor 3 made of a niobium tube and a ceramic frit 4 at both ends of which an electrode rod 14 having an electrode 2 at its tip is brazed.
And sealed therein with sodium, mercury and xenon. A tantalum foil 5 is wound around both ends of the arc tube 1. The conductor 3 is inserted into a hole of a shield 12 made of a heat-resistant insulator such as ceramic and having a flat flange portion 12a and a cylindrical support portion 12b, and is supported movably in the axial direction. . Shield 12
One end of a metal support plate 13 is wound around the support portion 12b, and the other end of the metal support plate 13 is welded to the support wire 9b of the stem 8 so that the arc tube 1 is fixed within the outer tube 10 at a predetermined position. Supported in position. The ceramic frit 4 exposed from the end face of the arc tube 1 is covered by the flange 12 a of the shield 12. The current supply to the electrode rod 14 is performed by leads 15 and 16, and one of the leads 15
For example, a flexible material such as a Monel wire is used to cope with the thermal expansion of the arc tube 1 in the axial direction that occurs during the operation of the lamp. Reference numeral 17 denotes a getter for maintaining a high vacuum in the outer tube, and reference numeral 18 denotes a base.

By properly selecting the material and dimensions of the lead wire 15, a current considerably larger than the short-circuit current of the ballast may be generated in the lamp due to failure of the ballast or breakage of one electrode of the arc tube. In the case of a flow, the lead wire 15 may be melted quickly to have a role of a fuse for preventing damage to the arc tube and burning of the ballast.

With this configuration, most of the components of the ceramic frit 4 that gradually evaporate from the ceramic frit 4 during the long-term operation of the lamp adhere to the surface of the flange 12 a of the shield 12. , Outer tube 10
Blackening of the inner surface can be prevented, and therefore, a decrease in light output can be prevented. Further, when a large current flows through the lamp, the lamp is quickly blown, and damage to the arc tube and burning of the ballast are prevented, so that safety can be improved.

[0015]

As described above, the high-pressure sodium lamp of the present invention can prevent the evaporation of the ceramic frit from adhering to the inner surface of the outer tube, thereby preventing the outer tube from being blackened. The output can be prevented from lowering.

[Brief description of the drawings]

FIG. 1 is a front view of a high-pressure sodium lamp according to an embodiment of the present invention.

FIG. 2 is a cutaway enlarged front view of a main part of the arc tube.

FIG. 3 is a front view of a high-pressure sodium lamp according to another embodiment of the present invention.

FIG. 4 is an enlarged front view of a cutout of a main part of the arc tube.

FIG. 5 is an enlarged front view of a cutout of a main part of an arc tube of a conventional high pressure sodium lamp.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Arc tube 2 Electrode 3 Conductor 4 Ceramic frit 6 Shield plate 7 Metal wire 10 for fixing 10 Outer tube 12 Shield 12a Flange portion 12b Tube portion 13 Metal support plate 15, 16 Lead wire

Continuation of the front page (56) References JP-A-5-151937 (JP, A) JP-A-2-256154 (JP, A) JP-A-50-101165 (JP, U) (58) Fields investigated (Int) .Cl. ⁷ , DB name) H01J 61/36 H01J 61/34

Claims (3)

(57) [Claims] 1. A high-pressure sodium lamp in which a conductor having electrodes at both ends is sealed with a ceramic frit and an arc tube in which sodium, mercury and a rare gas are sealed is provided in an outer tube. A high-pressure sodium lamp, wherein a shield is movably inserted into the conductor led out of the arc tube to cover the ceramic frit exposed on the end face of the arc tube with the shield. 2. An arc tube in which conductors each having an electrode at a tip portion at both ends are sealed with a ceramic frit, and an arc tube in which sodium, mercury and a rare gas are sealed is supported in an outer tube by a stem support wire. A cylindrical shield having a flange at an end is fixed to the stem support line by a support, and the shield is movably fitted to the conductor led out from the arc tube. Wherein the flange portion covers the ceramic frit exposed from the end face of the arc tube. 3. The high-pressure sodium lamp according to claim 2, wherein the shield is made of an insulator, and the conductor and the stem support wire are connected via a lead wire having a current fuse function.