JPH0433638Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Purpose of invention] (Industrial application field) The present invention relates to a high pressure sodium lamp.

(Prior art) In high-pressure sodium lamps that use light-transmitting ceramic arc tube bulbs made of high-density polycrystals or single crystals with excellent heat resistance and corrosion resistance, such as transparent alumina and sapphire, quartz glass is used. Since it is difficult to heat and soften the opening end of the arc tube bulb and seal it by crushing it, it is difficult to seal it by heating and softening the opening end, so a metal cap made of a metal such as niobium or tantalum, which has a coefficient of thermal expansion similar to that of the arc tube bulb mentioned above, or the same type of cap is used. The opening end portion is sealed with a separate sealing member such as a disk made of ceramics. Further, a metal tube which also serves as an exhaust pipe, for example, passes through the sealing member in an airtight manner, and an electrode is fixedly supported at one end of the metal tube.

The characteristics of such lamps are particularly influenced by the vapor pressure of the enclosed sodium, which is determined by the temperature of the coldest part of the arc tube. of mercury and sodium are sealed, and the vapor pressure is controlled by leaving the excess mercury and sodium in an unevaporated condensed state in the coldest part during lighting, that is, in the metal tube. We make it easy to do.

With this configuration, the electrodes reach a high temperature when the lamp is started, and the mercury and sodium (usually present as sodium amalgam) remaining in the metal tube are also heated and evaporated, causing the pressure inside the arc tube to rise. Due to the difference in pressure, the air blows out from the exhaust hole provided in the metal tube into the arc tube bulb and collides with the inner surface of the bulb.

At this time, there is no particular problem if the temperature of the arc tube bulb is close to the temperature of the blown out sodium amalgam vapor, but immediately after starting, the two temperatures do not necessarily rise in the same way. In other words, the inner surface of the end of the bulb of the arc tube, which is close to the extremely high-temperature electrode, rapidly becomes hot, but the temperature of the sodium amalgam vapor that collides with this portion is much lower, resulting in a strong thermal shock. Cracks sometimes occurred in ceramic valves.

(Problem that the invention aims to solve) As mentioned above, in high-pressure sodium lamps, the sodium amalgam remaining in the metal tube vaporizes and blows out from the exhaust hole, especially when starting, and this vapor becomes much hotter. It collided with the arc tube bulb made of ceramics, causing a crack in that part of the bulb.

Therefore, the present invention aims to eliminate these conventional drawbacks and prevent the occurrence of cracks in the bulb by alleviating the direct and strong impact of sodium amalgam vapor on the bulb. shall be.

[Structure of the idea]

(Means for solving the problem) In the high-pressure sodium lamp of the present invention, both ends of an arc tube bulb made of translucent ceramic are sealed with metal caps that support electrodes, and at least one electrode is sealed with metal caps that support electrodes. is supported by one end of a metal tube passing through the arc tube airtightly, and is lit vertically or inclined so that one electrode side is located lower than the other electrode side, and the end of the arc tube bulb and the metal A shield is installed between the hole provided in the pipe and the metal cap, and the shield is attached to the metal pipe such that there is a gap between the outer peripheral surface and the metal cap. be done.

(Function) According to the configuration of the present invention, since a shield is provided between the hole in the metal tube through which sodium amalgam vapor blows out especially when the lamp is started, and the end of the arc tube bulb, the vapor is blown out from the hole. The sodium amalgam vapor once collides with the shield and is blocked, and the vapor whose force has been relaxed enters the arc tube bulb through the space between the shield and the metal cap, so it is not allowed to flow into the arc tube bulb. The thermal shock is significantly weakened compared to the conventional method, and cracks in the arc tube bulb are therefore prevented. The attachment of the shield is weak in terms of strength, and when attached by welding, it is possible to avoid the metal cap part where the crystals tend to become coarse and cause arc tube leaks. There is also a manufacturing advantage in that the attachment of the shield does not require much care, since it is fixed to the metal tube, which will not cause any damage.

(Example) Hereinafter, the present invention will be explained in detail based on the example shown in the drawings. Figure 2 shows an average lamp voltage of 200V,
Figure 1 shows the overall configuration of a large-capacity high-pressure sodium photochemical lamp with a lamp current of 19.5A and a rating of 3.5KW, and a vertical cross-sectional view of one end of the arc tube, which is the main part.

In the figure, reference numeral 1 denotes an outer tube made of hard glass, and a pair of bipost-shaped metal terminals 3, 3 are hermetically sealed to the opening at one end of the tube through a sealing glass 2. A pair of supports 4A and 4B, which also serve as conductive wires, are provided at one end to the equal metal terminals 3, 3. One support 4A extends to the top of the outer tube 1, and its tip is bent into a U-shape, and is locked to the inner surface of the outer tube 1 by locking tools 5, 5.

Reference numeral 6 denotes an arc tube, and both ends 7a and 7b of the arc tube bulb are made of translucent ceramics, such as alumina ceramics, and filled with a starting rare gas such as xenon gas and sodium amalgam. They are hermetically sealed with metal caps 9A and 9B made of a heat-resistant and sodium-resistant metal, such as niobium, via glass solder 8, which is the main component. Metal tubes 10A and 10B made of niobium, for example, penetrate airtightly through the center of each metal cap 9A and 9B, and electrodes 11A and 11 are provided at one end thereof.
B is supported, and the other end is hermetically sealed.
Note that when the lamp is lit in a vertical position as shown in the figure, the lower metal tube 10A is formed longer than the upper metal tube 10B, so that the luminous tube is connected to the sealed end 10Aa of the lower metal tube 10A. The coldest part of the area is formed. Such setting of the coldest part can be made more reliable by surrounding the upper end of the arc tube with a heat insulator 12 as shown in the figure. A hole (not shown) provided in the upper metal tube 10B is
The hole 13 of the lower metal tube 10A serves as an exhaust hole in the manufacture of the arc tube, and the hole 13 serves as a supply hole for the filling material into the arc tube bulb 7. 14
1 is a disk-shaped shield made of a heat-resistant and alkali-resistant material such as tantalum, and as shown in an enlarged view in FIG. attached to the outer circumferential portion of the metal tube 10A so as to be located in the middle of the
A gap 15 is created between the outer peripheral surface of the shield 14 and the metal cap 9A. Note that 16 is sodium amalgam that accumulates at the end of the metal tube 10A.

Further, the arc tube 6 is connected to a power supply body 17A, which also serves as an arc tube support, which is bridged to the U-shaped bent portion of one support 4A, and an insulator 18 is bridged between both supports 4A and 4B. and the other metal tube 10 and a power supply body 17B which also serves as the other arc tube support.
It is supported by being electrically conductively fixed to A and 10B.

With such a configuration, the electrodes 11A and 11B reach a high temperature when the lamp is started, and as a result, the temperature of the excess sodium amalgam 16 accumulated in the metal tube 10A also rises, and a part of it vaporizes, causing the metal tube to evaporate. 1
Even if steam is blown out from the hole 13 of 0A with a strong force, it is temporarily blocked by the shield 14 located between the hole 13 and the end 7a of the arc tube bulb 7, and its force weakens. Then, it passes through 15 between the outer peripheral surface of the shield 14 and the metal cap 9A and comes into contact with the inner surface of the arc tube bulb end 7a, which is at a high temperature, so that the heat on the inner surface of the arc tube bulb end 7a due to the sodium amalgam vapor is absorbed. The shock is alleviated,
Therefore, it is possible to prevent cracks from occurring in the end portion 7a of the arc tube bulb 7 made of translucent ceramics.

Moreover, the attachment point of the shield 14 is weak in strength,
Moreover, the welding method avoids the 9A part of the metal cap where the crystals tend to become coarse and cause arc tube leaks, and the metal tube has great strength, and even if a crack occurs at the attachment part, it will not cause any serious damage. 1
Since it is fixed at 0A, there is also the manufacturing advantage that attachment of the shield 14 does not require much care.

In addition, in the above embodiment, the hole provided in the metal tube located above is used as the exhaust hole during the manufacture of the arc tube,
Although the hole in the lower metal tube is used as the filler supply hole, the hole may be provided only in the lower metal tube and used for both supply and exhaust, and furthermore, the arc tube is limited to a vertical position. The present invention is also effective when used at an angle.

[Effect of idea]

As described above, according to the structure of the present invention, the thermal shock caused by the sodium amalgam vapor to the inner surface of the end of the arc tube bulb during lamp startup is alleviated, so that the occurrence of cracks at the end of the arc tube bulb can be prevented.

Moreover, the shield is strong and is attached to the metal tube, which will not cause arc tube leaks even if a crack occurs at the attachment point, so this attachment process requires great care. It also has the advantage of being easy to manufacture.

[Brief explanation of drawings]

FIG. 1 is an enlarged longitudinal cross-sectional view of a main part of an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the entire structure of the lamp. 6... Arc tube, 7... Arc tube bulb, 7a...
Arc tube bulb end, 9A...Metal cap, 1
0A...metal tube, 11A...electrode, 13...hole, 14...shielding body, 15...between, 16...sodium amalgam.

Claims (1)

[Scope of utility model registration request] Both ends of an arc tube bulb made of translucent ceramics containing excess mercury and sodium along with a starting rare gas are sealed with metal caps that support electrodes, and at least one electrode is hermetically sealed from the metal cap. In a high-pressure sodium lamp that is supported by one end of a metal tube that penetrates the arc tube and is lit vertically or inclined so that the one electrode side is located below the other electrode side, the end of the arc tube bulb and A shield is installed between the hole provided in the metal tube, and the shield is attached to the metal tube such that there is a gap between its outer circumferential surface and the metal cap. A high-pressure sodium lamp featuring