JPS5927445A - Electrode structure for high pressure sodium lamp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high pressure sodium (vapour) lamp with an improved electrode structure.

BACKGROUND OF THE INVENTION The electrode structure commonly used in high-pressure sodium vapor lamps consists of a tungsten shank wound with a tungsten coil, which is usually a tubular translucent ceramic tube containing an ionizable substance. All ends are sealed. Lamps of this common type are disclosed in U.S. Pat.

The reramic arc tube is supported within an elongated glass outer envelope or jacket, which is typically provided with a conventional threaded cap at one end thereof. High-pressure sodium lamps are typically kept in a vacuum to retain heat and increase efficiency.

The high costs and rotational effects of manufacturing conventional all-tungsten electrode structures for high pressure puttrium lamps suggest replacing this refractory metal with a suitable metal to the extent that the harsh lamp operating conditions permit. Tungsten wire, which is commonly used in the manufacture of coil parts for electrode structures, is prone to surface and internal defects, which can lead to wire breakage and machine wear during electrode fabrication, as well as various problems during lamp operation. This causes some difficulties. Tungsten, on the other hand, has been found to withstand the extremely high electrode operating temperatures and corrosive environments encountered within the arc tubes of sodium lamps. Although all tungsten electrode structures experience some sputtering during lamp operation, these electrodes maintain acceptable lumens for significant periods of time.

SUMMARY OF THE INVENTION Surprisingly, when a molybdenum electrode coil wound around a tungsten shank is used as an electrode structure in a high-pressure lithium lamp, it exhibits the expected abnormal deterioration. I found out that there is no. Quite surprisingly, such an improved electrode structure exhibits increased initial lumen and acceptable lumen maintenance compared to an all tungsten electrode structure under the same lamp operating conditions.

The invention therefore makes it possible to improve the operation of this type of lamp without significantly changing the lamp manufacturing process or increasing costs. In a preferred embodiment of the improved thermionic electrode structure of the present invention, a molybdenum metal wire coil is wound around the tip of a tungsten shank and consists of a helical outer layer and an inner layer of overlapping molybdenum wire coils. , spacing each turn of the inner helical layer from each other. The preferred embodiment further includes dispersing the mixed oxide luminescent material into spaced turns of the helical inner coil of one electrode structure.

In another variation of the preferred embodiment, each molybdenum wire coil is wound around the tip of the tungsten shank, with the pitch of the inner helical coil being opposite to the pitch of the outer helical coil. By winding the superimposed helical coils in opposite directions, mutual interlocking between the coils, which could lead to electrode deterioration and thus loss of lumen maintenance, can be avoided. A typical high-pressure sodium lamp incorporating the improvements described above and operating at a given horn input of about 400 watts and a given lamp voltage drop of about 100 pols has (a) sealed thermionic electrodes at both ends; (b) a tubular translucent alumina ceramic arc tube in which an excess of sodium-mercury amalgam filler material than would evaporate during normal operation is enclosed along with a reservoir of xenon gas to facilitate starting; an evacuated light-transmitting glass sub-length outer envelope having a stem press seal at the bottom thereof, and a pair of lead-in conductors electrically connected to the thermionic electrodes passing through the stem press seal; (0) Each of the electrodes is comprised of a pair of refractory metal helical coils wrapped around the tip of a tungsten shank and wound in opposite winding pitch directions, with each turn of the inner helical coil being spaced apart from each other. a mixed oxide luminescent material is dispersed in spaced turns of one helical inner side of said electrode; Increase lumens. In this improved lamp structure, the luminescent material is preferably calcium nivalium tungstate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a high pressure notrium vapor lamp incorporating the improved electrode structure of the present invention. This high pressure 1~
1 vapor lamp corresponds to a size of 400 watts,
It comprises a glass outer envelope 2, a standard large screw cap 3 attached to one end thereof, and a recessed stem press seal 4. The stem press seal 4 is penetrated in a conventional manner by a pair of relatively heavy lead-in conductors 5 and 6, the outer ends of which are connected respectively to the threaded shelf and eyelets 1-8 of the base. An inner envelope or arc tube 9 is centered within the outer envelope 2 and is comprised of a length of translucent laminate tubing, preferably made of translucent polycrystalline alumina ceramic. Although preferred, colorless and transparent single crystal alumina can also be used. The upper end of the arc tube 9 is closed with an alumina ceramic plug, and a niobium in-lead 11 is passed through the plug in an airtight manner. The in-lead 11 carries the upper electrode, and the two-part electrode is generally similar to the lower electrode, which will be specifically described in connection with FIG. 2 below. The outer portion of the inlead 11 passes through the loop 12 of the lateral support wire A713 attached to the side rod 14. With this configuration, the arc tube will heat up during operation of the lamp when the bottom seal is fixed in place. The elastic metal ribbon 15 can be stretched to ensure that a good electrical connection is maintained. The side rod 14 is welded to the lead-in conductor 6 and is clamped at its upper end by a spring clamp 16 which engages an inverted nipple 17 in the domed end of the glass outer envelope 2. A metal reflective band 18 is preferably placed around the top of the arc tube 9 to maintain the desired temperature at the top seal, especially for small lamps such as those below 250 watts. The lower end closure and electrode support assembly includes a shouldered alumina ceramic plug 20 with a central hole penetrated by a thin-walled niobium tube 21 that serves as an exhaust pipe and an in-lead. 2
1 protrudes only a small distance through the ceramic plug 20 and is hermetically sealed to the hole in the ceramic plug by a sealing material shown in bold line 22 in FIG. Ceramic stopper 2
The neck of 0 is inserted into the ceramic envelope 9, and the envelope 9 is inserted into the ceramic envelope 9.
the end thereof abuts against the shoulder of the stopper 20. From this 9-10-, the space between both members is also airtightly sealed using sealing materials shown at 23 and 24 in FIG.

A feature of the invention is the electrode structure itself, which is shown in detail in FIG. 2 for the lower electrode structure and electrode support assembly. Specifically, this electrode structure consists of two molybdenum wire layers 25 and 26 wrapped around the tip of a tungsten shank 27 and placed within a ceramic inner envelope 9. By deforming the tube 21 at a position outside the ceramic inner envelope 9 such that the shank 27 extends downwardly and fully penetrates the tube, i.e. the inlead 21, and thus pinches the shank over a considerable length,
The shank can be securely held in place. Preferably, the deformation is carried out at an intermediate point of the tube 21, leaving one section beyond the intermediate deformation section to serve as a reservoir for excess amalgam. The crimping shown in the diagram has this kind of character, and is a butterfly crimp.
), this crimping crimps the shank 27 along a significant flat portion, or wing 28. At the same time, narrow channels (not shown) are left on each side of the shank 27 to communicate with the outer portion of the exhaust tube up to the tip 30. Under normal operating conditions, when the lamp is inverted, such a connection will prevent the passage of the lium-mercury amalgam in the vapor state, but prevent the movement of the same amalgam in the liquid state. . In the improved electrode construction described herein, two layers of molybdenum wire coils 25 and 26 are wound around shank 27 in overlapping helical layers in one operation. inner layer 25
The outer layer 2 is loosely wound around the shank 27, crimp welded to the shank, and then reversely wound in a close-wound relationship to form the outer layer 2.
6 on the inner layer 25. In the case of reverse winding, the shank is rotated in the same direction, the pitch of the winding rotation is reversed, and the direction of rolling is reversed, and the inner layer is fixed with the outer winding. The entire winding process (including the step of immersing the reversely wound coil in a suitable suspension of luminescent material) can be performed mechanically. The only remaining operation in the fabrication of such an electrode is to insert the shank of the coated electrode into position in the niobium tube for caulking. The spiral inner layer 25 is provided with turns H spaced apart, and the luminescent material is dispersed between the two turns. Try to get it. A preferred luminescent material is calcium nivalium tungstate. The remaining structural components of the lower electrode support assembly are illustrated in FIG. The arc tube 9 itself is supported within the outer envelope 2 by a connecting part 31 which extends from the tubular in-lead 21 to the support rod 32 connected to the lead-in conductor 5. Welded.

The lamp operating characteristics of the lamp embodiments described above including the improved multiple electrode writing of the present invention were measured. Specifically, 40
Lamp operation tests were conducted on a 0 watt sized lamp to compare the performance of a conventional all tungsten electrode and an electrode of the same geometry using a molybdenum coil in place of the tungsten coil. The results of this comparative lamp test are summarized in Table 1 below, and are graphically displayed in Figure 3.

11- Table 1■ Number of lamps Type of coil Lumens/
Watt Operating bolt No. 1 15 Tungsten (100 hours) 119.1 95.8 No.
2 15 Molybdenum (100 hours) 121
．． 2 95. ONo, 3 25 Tungsten (100 hours) 120.3 107.0 Tungsten (100 hours) 119.8 97.1
As evident from the above test results, molybdenum coil electrodes were found to be uniformly superior to tungsten coil electrodes in obtaining relatively higher lumen/watt values during the first 100 hours of lamp operation. It was done.

The unique lumen maintenance characteristics achieved in a 400 watt size lamp according to the present invention are illustrated in FIG.

As shown in the graph, when comparing the molybdenum coil electrode and the all-tungsten electrode, the initial lumen drop was greater in the case of the molybdenum coil electrode -13-.

12- Regardless, it can be seen that the final lumen decrease is significantly small. The exact mechanism leading to this unexpected result is currently unknown, but is likely due to differences in the behavior of these refractory metals during lamp electrode fabrication as well as during subsequent lamp operation. The greater ductility of the molybdenum electrode 17 compared to tungsten wire allows it to form a tighter, tighter outer coil profile during electrode fabrication as described above, better retains the oxide luminescent material, and improves the initial 100 hour lamp life. Higher lumen output can be obtained during operation. Approximately 4,000 after that
During lamp operation up to an hour, molybdenum coils degrade at a faster rate than tungsten coils in the particular lamp operating environment. However, it is clear that during more prolonged lamp operation, the molybdenum electrode will degrade at a much slower rate, and perhaps with less loss of luminescent material, so the final lumen maintenance shown is lower than that of tungsten. better than seen in the case of electrodes.

, 1,1-14--As is clear from the above description, the improved electrode structure for high-pressure mono-lithium vapor lamps provided by the present invention is generally useful. Therefore, it is common practice in the lamp industry to use modified 4M construction in place of the usual all-tungsten electrodes in this type of lamp, but to use the remaining components of the lamp as is, except as noted above. This will be obvious to those with ordinary knowledge. For example, seal structures for the other end of ceramic arc tubes other than those specifically described are known, and the electrode improvements of the present invention may be utilized here as well. It is the intention, therefore, to be limited only by the scope of the claims that follow.

[Brief explanation of drawings]

Figure 1 is an elevational view of a high-pressure sodium lamp incorporating the improved electrode structure of the present invention, Figure 2 is an enlarged view of an example of the electrode used in the lamp of Figure 1, and Figure 3 is a molybdenum and It is a graph showing the lumen maintenance rate of a tungsten electrode. 1... High pressure sodium lamp, 2...
External envelope, 3... Cap, 4... Stem breath seal, 5.6... Leading conductor, 9... Inner/outer filler (arc tube), 20・
... Ceramic stopper, 21 ... Niobchicope (Inlead), 25
...Inner layer coil, 26...Outer layer coil, 27...Tungsten steel 11 link, 28...
... Caulking wing part, 31 ... Connection part shrine, 32 ... Support rod. Patent Applicant General ■Ref 1 ~ Rick Company Agent (7
630) Raw Swamp Cannon Ni Keyaki San N4 Mei-t

Claims (1)

[Claims] 1. Thermionic electrodes are sealed at both ends of a tubular translucent ceramic envelope, an ionized substance is sealed in the ceramic envelope, and the electrodes are wrapped around a tungsten shank using a refractory metal. A high-pressure sodium lamp constructed by winding a wire coil, characterized in that the initial lumen is increased at a lumen maintenance rate that is acceptable for the refractory metal wire coil as a molybdenum compound. 2. The lamp according to claim 1, wherein the molybdenum wire coil has a spiral shape. 3. The lamp of claim 1, wherein the molybdenum wire coil comprises a superimposed helical outer layer and an inner helical layer, and each turn of the helical inner layer is spaced apart from each other. 4. The lamp of claim 1, wherein spaced spans of said inner helical layer of one of said electrodes include a mixed oxide luminescent material. 5. The lamp according to claim 4, wherein the luminescent material is calcium nivalium tungstate. 6. The molybdenum wire coils are each wound around a tip of a tungsten shank, and the winding pitch of the helical inner layer coil is in a direction opposite to the winding pitch of the helical outer layer coil. The lamp mentioned. 7. (a> Tubular translucent alumina with thermionic electrodes sealed at both ends and a lithium-mercury amalgam filling material in excess of what evaporates during normal operation, along with xenon gas to facilitate starting. a ceramic arc tube; and (b) an evacuated discharge tube surrounding the arc tube and having a stem press seal at one end and having a pair of lead wires extending through the stem press seal electrically connected to the thermionic electrode. (C) each of said electrodes comprises a pair of refractory metal helical coils superimposed around the tip of a tungsten shank in τ and opposite winding pitch directions; In a high pressure sodium lamp comprising a spiral inner coil, each turn being spaced apart from each other, a mixed oxide luminescent material being dispersed in the spaced turns of the inner helical coil of one of the electrodes,
A high-pressure lumen lamp characterized in that the helical coil is made of molybdenum and the initial lumen is increased at a lumen maintenance rate that is too high. 8. The lamp according to claim 7, wherein the luminescent material is calcium nivalium tungstate.