JPS5994357A - High pressure sodium lamp - Google Patents

Abstract

PURPOSE:To provide such function as to bring a lamp to disable state in short time when discharge has occurred between asymmetrical electrode and starting rare gas has flowed out from a light emission tube, by incorporating an interruptor for interrupting power supply to the light emission lamp and said electrode. CONSTITUTION:Normally it is high vacuum in a tube 1, thereby no discharge will occur between the electrodes 10, 11. But if crack has occurred in a light emission tube 4 or air-tightness at the sealing section has lowered during operation of lamp, and starting rare gas or xenon gas has flowed out from said tube 4, discharge will occur between the leading edges of electrodes 10 and 11. Because of structural difference between the electrodes, current flowing through both electrodes will increase in positive half cycle of electrode 11 to approximate to half-wave rectification. Consequently the core of ballast 13 will saturate to flow current more than two times of the shortcircuit current of the ballast 13. As a result, lead wire 7 or 8 will be blown off to disable the lamp.

Description

[Detailed description of the invention] Industrial applications The present invention relates to high pressure sodium lamps.

Conventional structure and problems High-pressure sodium vapor lamps have electrodes at both ends and a light-transmitting ceramic luminous tube that is filled with sodium, mercury, and a starting rare gas, and is housed in a vacuum outer tube. It was constructed as follows. However, in conventional high-pressure sodium lamps, cranks occur in the arc tube during lamp movement, and the airtightness of the electrode sealing part deteriorates.
If the starting rare gas inside the arc tube leaks into the outer bulb, the thermal insulation inside the outer bulb will deteriorate and the rung voltage will be lower than the rated value, causing the lamp to operate with a current higher than the rated value. As a result, the temperature of the ballast increases significantly, and the practical life of the ballast is significantly shortened.

Purpose of the Invention The present invention was made to solve such problems.If the starting rare gas leaks from the arc tube into the vacuum outer tube during operation, the lamp becomes inoperable in a short period of time. The present invention provides a high-pressure sodium lamp with built-in functions that lead to.

Structure of the Invention In order to achieve the above object, the high-pressure sodium lamp of the present invention includes an arc tube and a pair of asymmetrically structured electrodes connected in parallel with the arc tube in an evacuated outer bulb. When the starting rare gas flows out from inside the arc tube into the outer tube, a discharge is caused in the outer tube between the asymmetric structure electrodes, and the lamp is operated by the asymmetric abnormal current caused by this discharge. It has a built-in shutoff device that makes it inoperable.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In the figure, 1 is an outer tube, and the end of this outer tube 1 is sealed with a stem 2 and a base 3 is provided. Reference numeral 4 denotes an arc tube made of alumina ceramic or the like, and both ends thereof are electrically connected to support wires 5 and 6, respectively. The support wire 5 and the support wire 6 each pass through the stem 2 and are connected to a terminal of the base 3 via a lead wire 7 and a lead wire 8. The inside of the outer tube 1 is evacuated to a high vacuum, and the degree of vacuum is maintained by a getter 9 made of barium or the like. Further, inside the outer tube 1, a pair of asymmetrically structured electrodes 10 and 11 are electrically connected to the support wire 5 and the support wire 6, respectively.

Electrodes are sealed at both ends of the arc tube 4, and the interior thereof is filled with mercury, sodium, and xenon as a starting rare gas. In addition, the electrodes 10 and 1
Both electrodes 1 are made of a high-melting point metal material such as tungsten, similar to the electrodes used in the arc tube of ordinary high-pressure discharge lamps, but one electrode, electrode 10 in the figure, operates as a cathode. In this way, the heat capacity is made smaller than that of the other electrode 11, and an electron emitting material such as a metal oxide is applied or retained in the applied area.

The electrode 11 is not provided with an electron emitting material so that it acts only as an anode. Since both of these electrodes operate only when the lamp is abnormal, their dimensions and shapes are not critical, but as a rough guide:
Compared to the electrodes used in the arc tube 4, the electrode 1o may be made smaller, and the electrode 11 may be made larger.

The distance between the tips of the electrodes 10 and 11 is 5 to 10n,
The distance between conductors at opposite potentials within the outer tube 1 is set to be the smallest.

At least one of the lead wires 7 and 8 is configured to play the role of a hinny's wire, and is configured to handle the maximum current that flows during normal lamp operation, i.e., a short circuit of the ballast immediately after starting the lamp. Nickel is sized so that it will not be cut off at a current close to the current, but will melt in a few minutes due to self-heating and oxidation vaporization if an abnormal current of more than twice the short-circuit current of the ballast continues to flow, for example. , made of heat-resistant metal wire such as Monel.

A high-pressure sodium rung with such a configuration has ballast 1.
When connected to the power supply via 3, it operates just like a conventional high pressure sodium lamp.

In this case, no discharge occurs between the electrodes 10 and 11 because the inside of the outer tube 1 is in a high vacuum. However, if a crack occurs in the arc tube 4 during the operation of the lamp or the airtightness of the sealing part deteriorates, and xenon chips as a starting rare gas leak out from the arc tube 4, the electrode 10 and the electrode 1
Discharge begins between the tips of 1 and 1. In this case, the current flowing between the two electrodes becomes larger in the positive half cycle of the electrode 11 due to the difference in the structure of each electrode, resulting in a current close to half-wave rectification. Therefore, if the iron core of the ballast 13 is not magnetically saturated, a large current exceeding twice the short circuit current of the ballast 1.3 will flow through the circuit. As a result, the lead wire 7 or 8 is fused and the lamp becomes inoperable.

Next, a specific example of the present invention will be explained. sodium,
In a 150W high-pressure sodium lamp, a light-transmitting alumina ceramic arc tube containing mercury and xenon at a pressure of 300 torr is housed in a vacuum outer tube.
Inside the outer tube, a pair of electrodes coated with an electron-emitting substance on one side are installed with a distance of 5 m between the tips.
A nickel wire with a diameter of 0.45311+ was used as the lead wire inside the cap. This lamp has a rated current of 2A.

It works normally with a 150W high pressure sodium lamp ballast with a short circuit current of 2.6A.

Next, immediately after the rung started discharging, the impedance of the ballast was suddenly reduced, causing a large current to flow through the arc tube, causing the arc tube to crack, causing xenon gas to flow into the outer bulb. After cooling the lamp prepared in this way, when it is connected to the power supply again via the ballast, a discharge occurs between the asymmetric electrodes in the outer bulb, and an asymmetric current exceeding 1 OA in effective value flows through the lead wires in the base. It melted in 2 to 3 minutes.

In the above embodiments, xenon gas was used as the starting rare gas, but similar effects can be obtained even when other rare gases are used. Furthermore, although the above-mentioned embodiment relates to a high-pressure sodium lamp equipped with a starter in the ballast, the present invention can also be implemented in a high-pressure sodium lamp with a built-in starter. In addition, in the above embodiment, the wire connected to the base has the role of a heater, but this may be replaced with another interrupting device that performs the same function, such as a thermal protector.

As described in detail, according to the present invention, when starting gas flows from the arc tube into the outer tube during lamp movement, an abnormally large current with an asymmetrical waveform that does not flow during normal operation is intentionally generated. To provide a high-pressure sodium lamp capable of interrupting the energizing circuit of the lamp by generating a high-pressure sodium lamp and preventing the lamp from continuing to operate at a low lamp voltage and shortening the life of a ballast. It is something that can be done.

[Brief explanation of the drawing]

The figure is a front view of a high-pressure sodium lamp which is an embodiment of the present invention. 1... Outer tube, 4... Arc tube, 5, 6...
... Support line, 7.8 ... Lead wire, 10.1
1. Old... Electrode.

Claims (1)

[Claims] In an evacuated outer tube, an arc tube is provided with electrodes at both ends and mercury, sodium, and a starting rare gas are sealed inside, and a pair of asymmetrically structured electrodes are connected in parallel with the arc tube, and A high-pressure sodium lamp comprising a built-in cutoff device that cuts off electricity to the arc tube and the asymmetric structure electrodes when discharge occurs between the asymmetric structure electrodes.