JPH0556609B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for manufacturing an arc tube for a high-pressure sodium lamp, and in particular to a method for sealing an electrode support tube.

[Prior art and its problems] Conventionally, in high-pressure sodium lamps, due to the chemical reaction between Na added in the arc tube and the sealant frit, and the physical diffusion of Na into the sealant, There is a phenomenon in which Na, which contributes to light emission, disappears from within the arc tube. When this phenomenon occurs, the vapor pressure inside the arc tube changes as the composition of the Na-Hg amalgam accumulated in the coldest part of the arc tube changes, causing fluctuations in the electrical and optical characteristics of the lamp. For this reason, ordinary high-pressure sodium lamps reduce the amount of evaporation.
Since about 100 times as much Na is enclosed, the effect of Na loss is small. However, for example, there are so-called unsaturated high-pressure sodium lamps that are made to fit constant-power ballasts and contain Na that is equal to or slightly more than the amount of evaporation, or about 10 times the normal amount.
In high-color-rendering high-pressure sodium lamps with increased Na vapor pressure, significant changes in characteristics due to Na loss are seen, and sufficient measures must be taken to prevent Na loss.

Generally, Na loss tends to increase in proportion to the amount of frit exposed within the arc tube. Therefore,
Conventionally, in order to prevent the frit from being exposed inside the arc tube, sealing was carried out using the method shown in FIGS. 1 to 4. This uses the capillary phenomenon during sealing to connect the electrode support tubes 3a and 3b made of Nb and the closure body 4.
This is a method of filling the frit between the two. In more detail, the first method is shown in FIGS. 1 and 2. FIG. 1 shows the case where the arc tube is a so-called monolithic pipe type in which the translucent ceramic tube 1 and the closure body 4 are integrally formed, and FIG. Separate blocker 4
This shows a case of a so-called open pipe type formed by a and 4b. As shown in FIGS. 1 and 2, the frits 6a and 6b are connected to a disk.
When the frits 6a and 6b are melted by placing scissors between them and a member made of high melting point metal such as the Ta plate 5a and 5b plate (the Ta plate serves as a frit stopper), the frits 6a and 6b are melted. This is a method of sealing by moving the TA plates 5a, 5b in parallel toward the disk to adjust the electrode protrusion length to a set value.
However, in this method, the electrode support tube 3b may be sealed in an inclined state with respect to the ceramic tube 1, as shown in FIG. As a result, the sealing portion becomes extremely short in some parts, and the reliability of the seal becomes a problem. Further, there is a drawback that the electrode protrusion length also differs from the set value.

Another method is as shown in FIGS. 3 and 4.
There is also a method in which the frit 6a is placed on the disks 4, 4a on the upper side, and the Ta wire 9 is used as a frit stopper to support the frit 6b on the lower side and suck up the frit 6b. However, in this method, as shown in FIG.
However, the electrode support tube 3b and the translucent ceramic pipe 1
Instead of being sucked up into the gap between the frit and the Ta wire 9, it may harden like a lump around the Ta wire 9, which is the frit stopper, and cause a seal failure.

In addition, the conventional method uses a frit stopper and a stopper for adjusting the protrusion length of the electrode (arc tube stopper).
The structure is complicated because each was provided separately.

[Object of the Invention] In order to eliminate the above-mentioned drawbacks, the present invention has been developed by welding two Ta wires in the axial direction of the Nb tube on the lower side during sealing, bending it into an L shape, and increasing the protruding length of the electrode. Used as a stopper for alignment and a frit stopper, it is highly reliable (there are no short parts of the sealing part) and provides a reliable seal.It can also be used as a stopper for adjusting the electrode protrusion length, making it easier to process. The purpose is to simplify work and reduce costs.

[Summary of the Invention] The present invention provides an electrode support tube in which an electrode support tube is inserted into holes in both closed portions of a translucent ceramic tube, and the electrode support tube is sealed with a frit. In the sealing method, at least two L-shaped metal wires made of high-melting point metal are welded to the required positions of the lower electrode support tube, a frit is placed on the L-shaped part, and the frit is placed on the L-shaped part. This method of manufacturing an arc tube is characterized in that the electrode support tube and the closure are sealed after melting the frit.

The required position here means that when the electrode support tube is sealed to obtain the required electrode protrusion length,
This is the position where the required electrode protrusion length can be obtained.

[Embodiments of the Invention] FIGS. 5 and 6 are drawings showing embodiments of the present invention, in which 1 is a monolithic type translucent ceramic tube, 1' is an open type translucent ceramic tube,
2a, 2b are electrodes, 3a, 3b are Nb tubes, 4a,
4b is a disk, 5 Ta wires, and 6a and 6b are frits.

As shown in Figure 5, when sealing, the lower Nb pipe 3
Two L-shaped Ta wires 5 are welded to b and are used as a stopper for adjusting the protrusion length of the electrode and a frit stopper. Since it is configured like this,
During sealing, the electrode support tube 3b does not tilt, and the frit 6b does not harden into a lump shape by passing through the Ta wire 5, which is the frit stopper, so accidents such as those shown in Figures 7 and 8 do not occur. does not occur,
As shown in FIG. 9, reliable and reliable sealing can be achieved. In addition, compared to the conventional method, since the stopper for adjusting the length of the electrode protrusion (arousal tube stopper) and the frit stopper are used together, less materials are required, labor is saved, and costs can be reduced and work efficiency improved.

The specific specifications of the lamps used in this example are as follows.

Lamp used: normal 360W arc tube with inner diameter
8.0φ alumina pipe Nb tube...outer diameter 3.01φ Nb tube-disc distance...0.045mm (0.09mm when Nb tube contacts one side of the disk) Diameter and length of L-shaped metal wire...0.1~0.2φ , 4 to 5 mm [Effects of the Invention] As explained above, according to the method of the present invention, the reliability of sealing between the lower translucent ceramic tube and the closing body is higher than that of the conventional method. It can be done reliably, and costs and work efficiency can be improved.

[Brief explanation of the drawing]

Figures 1 to 4, and Figures 7 and 8.
The figure is a sectional view showing a conventional example, and FIGS. 5, 6, and 9 are sectional views showing embodiments. 1... Translucent ceramic tube, 2a, 2b... Electrode, 3a... Upper electrode support tube (Nb tube), 3b...
Lower electrode support tube (Nb tube), 4... Closure body, 4a,
4b...Closing body (disk cap), 5a, 5
b... Ta plate, 6a, 6b... Fritz, 7a,
7b... Fritz, 8a, 8b... Stoppa, 9
...Ta line.

Claims (1)

[Claims] 1. In a method for sealing an electrode support tube, the electrode support tube is inserted into holes in both closed parts of a translucent ceramic tube, and the electrode support tube is sealed with a frit. Weld at least two L-shaped metal wires made of high-melting point metal to the required positions of the electrode support tube, place a frit on the L-shaped part, and weld the placed frit, A method for manufacturing an arc tube, comprising sealing the electrode support tube and the closure body.