JPH05266861A - High pressure sodium lamp - Google Patents

Abstract

(57) [Summary] [Objective] To provide a safe high-pressure sodium lamp that shuts off an overcurrent generated when sodium amalgam leaks to the high-pressure sodium lamp. [Arrangement] An amalgam forming metal 5 is arranged in series with an electrode of the arc tube 3 in an airtight glass container 2 which houses the arc tube 3.
To provide. [Effect] When sodium amalgam leaks, the amalgam forming metal is melted and the overcurrent is cut off. Therefore, a safe high-pressure sodium lamp without burnout of the ballast due to the overcurrent can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-pressure sodium lamp, more specifically, a glass container in which at least a translucent ceramic tube is sealed with a pair of electrodes and an arc tube in which sodium, mercury and a rare gas are sealed. High-pressure sodium lamp enclosed in.

[0002]

2. Description of the Related Art A high pressure sodium lamp is installed in an arc tube.
At least sodium and mercury are enclosed, the arc tube is made of a transparent ceramic, and the atmospheric pressure in the arc tube at the time of lighting is set to several atmospheres. Regarding the high-pressure sodium lamp, the Journal of Illuminating Engineering Society, published in 1982, 1
It is described on page 231 to page 240.

[0003]

When using a high pressure sodium lamp, it is necessary to prevent an excessive current from flowing.
A ballast consisting of a choke coil is provided between the power supply and the high pressure sodium lamp. The ballast has an extremely long life compared to the high-pressure sodium lamp, and is not installed as a power supply facility in a building or the like and frequently replaced.
When a high-pressure sodium lamp is lit for a long time or a defective arc tube is lit, the sodium amalgam enclosed in a translucent ceramic tube
It leaks into the airtight glass container through the ceramic tube or the boundary between the ceramic tube and the electrode. As a result, the vapor pressure of the amalgam in the translucent ceramics tube decreases, so the lamp voltage decreases and the lamp current increases.

When the lamp current increases remarkably, the temperature of the ballast rises and the ballast may be burnt, which causes a problem such as a fire. For such problems, it has been considered to provide an overcurrent prevention fuse in the ballast, but it is difficult to realize a ballast that can be automatically reset. Becomes complicated. It is an object of the present invention to provide a high pressure sodium lamp which does not use a special ballast and shuts off the current immediately when an overcurrent occurs during use of the high pressure sodium lamp.

[0005]

To achieve the above object, the high-pressure sodium lamp of the present invention supplies a current to the arc tube in an airtight glass container that seals the arc tube outside the arc tube. The amalgam forming metal is provided in series with a part of the line. As the amalgam forming metal, an alloy containing one or more metals selected from gold, silver, indium, lead, platinum and zinc as the main component is effective.

[0006]

When the sodium amalgam in the arc tube leaks into the airtight glass container, the temperature of the airtight glass container in which the translucent ceramics tube is enclosed is usually about 200 ° C. Therefore, mercury in the amalgam is airtight. It exists as vapor in the glass container. Therefore, the mercury in the airtight glass container adheres to the amalgam-forming metal that is electrically connected to the arc tube in series and forms an amalgam. When the amalgam forming metal becomes an amalgam, the electric resistance increases and the melting point decreases.

That is, the leakage of sodium amalgam increases the electrical resistance of the amalgam forming metal and also increases the lamp current, so that the heat generation in the amalgam forming metal increases and its temperature rises. In addition, since the melting point of the amalgam-forming metal is lowered, the amalgam-forming metal is fused. Since the amalgam forming metal is installed in series with the arc tube electrically, the lamp current is cut off by the melting of the amalgam forming metal, overcurrent is prevented from flowing, and the choke coil of the ballast is damaged. Is prevented.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view of an embodiment of a high pressure sodium lamp according to the present invention. An arc tube 1 and supporting wires 3 and 4 for supplying electric power to the arc tube 1 and supporting the arc tube 1 are provided in an airtight glass container 2. The amalgam forming metal 5 is electrically connected in series to a part of the line between the support line 3 and the electrode terminal of the arc tube 1. A zinc ribbon was used as the amalgam forming metal 5 in this example.

FIG. 2 is a characteristic diagram for explaining the operating characteristics of the high pressure sodium lamp according to the present invention. In the figure,
The horizontal axis represents the lighting time of the lamp, and the vertical axis represents the lamp current. The solid line a indicates normal operation, the dotted line b indicates normal operation, and the arc tube 1
When the sodium amalgam inside leaks into the glass container 2, the dotted line c shows the characteristics when the ceramic tube 9 is damaged from the beginning.

When the sodium lamp operates normally,
While the power is turned on and the light is turned on (about 2 minutes), the temperature inside the arc tube 1 is low, the pressure in the tube is low, and a relatively high current flows. After lighting, the inside of the arc tube 1 is warmed and the pressure increases,
Lamp current is low and stable. At this time, since there is no sodium amalgam in the glass container 2, the amalgam forming metal 5 operates as a normal power supply line.

When the sodium amalgam inside the arc tube 1 leaks into the glass container 2 after normal operation after lighting, the lamp current increases because the pressure inside the arc tube 1 becomes low, and the inside of the arc tube 1 and the light emission. The temperature inside the tube 1 becomes high. Amalgam forming metal 5 due to sodium amalgam leak
Of the amalgam forming metal 5 increases its electrical resistance and also increases the lamp current. In addition, since the melting point of the amalgam forming metal is lowered, the amalgam forming metal 5 is fused. Therefore, a large lamp current is maintained and the ballast provided on the power supply side is prevented from being burnt out.

If the product is defective, such as the ceramic tube 9 being damaged from the beginning, a large lamp current is not generated and the heat generated in the amalgam forming metal 5 increases, and after normal operation after lighting. Similarly to the case where the sodium amalgam inside the arc tube 1 leaks into the glass container 2, the amalgam forming metal melts and cuts.

FIG. 3 is a side sectional view showing the construction of the arc tube 1 in the above embodiment. The arc tube 1 is a translucent amina tube 9 having an inner diameter of 8 mm, and a pair of electrodes 7 and 8 having a distance between electrodes of 80 m.
It is configured by enclosing with m. The alumina disks 10 and 11 hold the electrodes 7 and 8, respectively, and have a function of sealing the gas in the amina tube 9. As an inclusion in the amina tube 9, 45 mg of xenon gas of 100 kPa and sodium amalgam containing 15% by weight of sodium were enclosed.

When a sodium amalgam leak occurred in a sodium lamp, mercury adhered to the amalgam forming metal 5 made of a zinc ribbon to form an amalgam, and the amalgam forming metal 5 melted and the lamp current was cut off. Therefore, burnout of the ballast due to overcurrent was prevented.

In the above embodiment, a zinc ribbon was used as the amalgam forming metal 5, but the amalgam forming metal 5
As the main component, one or more metals selected from gold, silver, indium, lead, platinum and zinc may be used as the main component.

[0016]

According to the present invention, there is no need to change the ballast. Moreover, it is possible to obtain a safe high-pressure sodium lamp that can be blown only when overcurrent due to leakage of sodium amalgam does not occur when there is no high-current lamp current when the high-pressure sodium lamp is turned on. it can.

[Brief description of drawings]

FIG. 1 is a side view of an embodiment of a sodium lamp according to the present invention.

FIG. 2 is a characteristic diagram illustrating the operation of the high-pressure sodium lamp according to the present invention.

FIG. 3 is a vertical cross-sectional view of an arc tube used in an embodiment of a sodium lamp according to the present invention.

[Explanation of symbols]

 1 arc tube, 2 airtight glass container, 3 alumina tube, 5 amalgam forming metal, 7 electrode, 8 electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaiji Arai 888 Fujibashi, Ome, Tokyo Metropolitan area, Ome factory, Hitachi, Ltd. (72) Kenji Miyata 888 Fujibashi, Ome city, Tokyo Ome factory, Hitachi, Ltd.

Claims (2)

[Claims] 1. A high-pressure sodium lamp in which a pair of electrodes and an arc tube in which sodium, mercury, and a rare gas are encapsulated in a translucent ceramic tube is enclosed in a glass container, wherein the electrode of the arc tube is contained in the glass container. A high pressure sodium lamp characterized in that an amalgam forming metal is provided electrically in series with the amalgam forming metal. 2. The amalgam forming metal is composed of an alloy containing one or more metals selected from gold, silver, indium, lead, platinum and zinc as a main component. The high-pressure sodium lamp according to 1.