JPH0680251U - Electrode holding structure for high pressure sodium lamp - Google Patents

Abstract

(57) [Summary] [Objective] The present invention provides a high-pressure sodium lamp that is not only easy to process as an electrode support tube for arc tubes and can be mass-produced, but also has good product yield and excellent lamp characteristics. The purpose is to do. [Structure] End caps are sealed at both ends of the translucent alumina tube, the electrode support tubes are inserted and fixed in the end caps, and the metal tube is placed so that the electrode mandrel is arranged on the tube axis inside the electrode support tube. The electrode mandrel is welded and fixed to the inner peripheral surface of the metal tube, and the metal tube is welded and fixed to the inner wall surface of the electrode support tube.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement of an arc tube for a high-pressure sodium lamp, and to an arc tube electrode support structure.

[0002]

[Prior art]

 As shown in FIGS. 5 and 6, an arc tube for a high-pressure sodium lamp has end caps 22 sealed at both ends of a translucent alumina tube 21, and an electrode support having an electrode 23 held at the tip at the center of the end cap. The tube 24 is inserted and fixed. Then, as shown in FIG. 5, the tip of the electrode support tube 24 is fixed by inserting the end of the electrode mandrel 25 made of tungsten into the tip of the niobium tube, caulking it, and then welding the caulking part. ing.

However, since the electrode support tube has to be caulked or the caulked portion has to be uniformly melted to fix the electrode mandrel, there is a disadvantage that not only the labor is required for machining but also the yield is poor. Further, when the electrode support tube is used as an exhaust tube of an arc tube, it is necessary to provide an exhaust hole at its tip end, which requires special processing.

[0004]

[Problems to be solved by the device]

 In this type of lamp, the protrusion length of the electrode mandrel from the tip of the electrode support tube is a fluctuation requirement of the lamp voltage, and the variation in the protrusion length affects the lamp characteristics. Therefore, it is necessary to specify it within a predetermined range. However, it is difficult to mass-produce the arc tube having the crimped portion with the electrode protruding length being constant. Moreover, when molybdenum, which is a metal having poor ductility, is used as the electrode supporting tube instead of the niobium tube, it is difficult to crimp and it is difficult to hold the electrode mandrel at the center of the arc tube axis.

The present invention has been made in view of the above, and as an electrode supporting tube for an arc tube for a high-pressure sodium lamp, it is not only easy to process and can be mass-produced, but also has a good yield and a lamp voltage. It is an object of the present invention to provide a high-pressure sodium lamp having excellent lamp characteristics that does not fluctuate.

[0006]

[Means for Solving the Problems]

 The present invention relates to a high-pressure sodium lamp in which end caps are sealed at both ends of a translucent alumina tube, and electrode support tubes are inserted and fixed in the end caps, and an electrode mandrel is provided on a tube shaft inside the electrode support tube. Is arranged so that the electrode mandrel is welded and fixed to the peripheral surface of the conductor, and the conductor is welded and fixed to the inner wall surface of the electrode support tube. The conductor is made of a metal tube, and the electrode mandrel is welded and fixed to the inner peripheral surface or the outer peripheral surface of the metal tube. Further, the conductor is made of a metal rod, and an electrode mandrel is welded and fixed to the outer peripheral surface of the metal rod.

[0007]

[Action]

 With the above structure, the electrode mandrel can be easily inserted and fixed in the central portion of the electrode support tube, and the protruding length of the electrode can be controlled very easily. Further, it is not necessary to separately form an exhaust hole in the electrode support tube, and the yield is improved.

[0008]

【Example】

 Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an example of an end cap of an arc tube for a high pressure sodium lamp according to the present invention, in which an electrode support tube 2 is inserted and fixed in the center of an end cap 1 made of niobium metal. An electrode 3 is arranged at the tip of the tube 2 inside the arc tube, and the other end is constructed by sealing the inside of the arc tube after exhausting. As shown in FIGS. 2 and 3, the tip end of the electrode support tube 2 has a plasma on the inner peripheral surface of the metal tube 5 which is a conductor so that the electrode mandrel 4 is arranged on the tube center axis of the electrode support tube 2. It is fixed by welding or the like, and the metal tube 5 is fixed to the inner wall surface of the electrode supporting tube 2 by plasma welding or the like.

Here, the electrode mandrel 4 projecting from the tip of the electrode support tube 2 will be described with reference to FIG. When the metal tube 5 and the electrode mandrel 4 are fixed by welding, an electrode mandrel of a predetermined size is brought into contact with the inner peripheral surface of the metal tube and at least one of the contact portions is plasma-welded. At this time, if the length l ₁ of the metal tube 5 is kept constant and welding is performed so that the end portion of the electrode mandrel 4 and the end portion of the metal tube 5 always match, the protruding length l ₂ of the electrode mandrel 4 becomes It will always be constant. In this way, it becomes easy to make the electrode protrusion length constant for each type of lamp, and variations in lamp characteristics are eliminated.

It is necessary to select the diameter of the metal tube 5 so that the electrode mandrel 4 is always arranged on the tube axis of the electrode support tube 2. The tip of the electrode support tube is constructed as shown in FIGS. 2, 3 and 4 (a), and the diameter of the metal tube is made small as shown in FIG. The electrode mandrel 4 may be brought into contact with and fixed by welding. Further, as shown in FIG. 4 (c), a metal rod 7 having a predetermined size and having an electrode mandrel fixed to the outer peripheral surface thereof by welding is brought into contact with the inner wall surface of the electrode support tube 2 and at least one of the contact portions is plasma-welded. However, the electrode mandrel 4 can be arranged at the tube center of the electrode support tube 2, that is, on the tube axis of the arc tube.

According to the above configuration, when manufacturing the lamp, the metal tube and the electrode mandrel shown in FIG. 3 are welded by setting the metal tube in a welding machine and contacting the metal tube with a jig holding the electrode mandrel. Welding is possible by holding the electrode core. Similarly, the electrode can be held on the central axis of the arc tube by welding the parts shown in FIG. 3 to the electrode support tube. Further, in any of the structures shown in FIG. 4, since the tip of the electrode support tube is not caulked or welded as in the conventional case, the tip opening can be used for exhausting the inside of the arc tube. There is no need to provide an exhaust hole. Further, as the electrode support tube or the metal tube material, not only niobium metal which is rich in ductility but also molybdenum metal which is poor in ductility can be used, which is advantageous in that it is inexpensive.

[0012]

[Effect of device]

 As is clear from the above description, the electrode holding structure of the high-pressure sodium lamp according to the present invention can regulate the protruding length of the electrode within a certain range, so that a lamp having various stable characteristics can be obtained. Further, there are advantages that not only the arc tube is easily manufactured and mass-produced, but also the yield is high and the cost is low.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of an end cap according to the present invention.

FIG. 2 is a perspective view of an essential part of the electrode support tube.

FIG. 3 is a side view of a metal tube similarly used for the electrode supporting tube.

4 (a), (b) and (c) are side views showing an embodiment of an electrode support tube.

FIG. 5 is an explanatory view showing an end portion of a conventional electrode support tube.

FIG. 6 is a perspective view showing an arc tube of a general high-pressure sodium lamp.

[Explanation of symbols]

 1 End cap 2 Electrode support tube 3 Electrode 4 Electrode mandrel 5 Metal tube 6 Metal tube 7 Metal bar

Claims (3)

[Scope of utility model registration request] 1. A high-pressure sodium lamp in which end caps are sealed at both ends of a translucent alumina tube, and electrode support tubes are inserted and fixed in the end caps. An electrode holding structure for a high-pressure sodium lamp, in which an electrode mandrel is welded and fixed to a peripheral surface of a conductor so that the electrode mandrel is arranged, and the conductor is welded and fixed to an inner wall surface of an electrode support tube. 2. The electrode holding structure for a high pressure sodium lamp according to claim 1, wherein the conductor is made of a metal tube, and an electrode mandrel is welded and fixed to an inner peripheral surface or an outer peripheral surface of the metal tube. 3. The electrode holding structure for a high pressure sodium lamp according to claim 1, wherein the conductor is made of a metal rod, and an electrode mandrel is welded and fixed to an outer peripheral surface of the metal rod.