JPH0334833Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Technical Field of the Invention] The present invention relates to a metal vapor discharge lamp in which the electrode support portion of a translucent insulator arc tube made of translucent ceramics or the like is improved. [Prior art and its problems] Conventionally, high-pressure sodium discharge lamps whose arc tube bulbs are made of translucent insulators, such as translucent ceramics,
When supporting the electrode, it is not possible to crush and seal the ends like a quartz arc tube bulb and fix it, so a metal tube is attached to a closing body made of ceramics or niobium metal that seals both ends of the arc tube bulb. It is fixed by means such as welding, brazing, or crimping. For example, in Japanese Patent Publication No. 49-36593, as shown in FIG.
In the electrode 4 provided with the outer coil 3, the length of the inner coil 2 is made longer than the length of the outer coil 3,
The exposed part of the inner coil is mechanically supported by inserting it into an exhaust pipe 5 made of a heat-resistant metal with a notch at the end, and then fixed by metal brazing, and then attached to the end of the exhaust pipe. An electrode support structure is shown in which a portion of the cut formed forms an exhaust hole 6. However, such a structure is extremely prone to breakage near the brazing points. Moreover, especially in recent years,
In small lamps of 100W or less, it is necessary to reduce the shape of the electrodes in order to obtain reliable starting characteristics, and the amount of electron emitting material filled in the electrode coils to maintain discharge is inevitably reduced. However, it has the disadvantage that it fades out during its life, resulting in a short life. Also, in Utility Model Publication No. 48-14950, the second
As shown in the figure, an electrode support structure is shown in which the electrode mandrel 1 is crimped and fixed to one end of the metal tube 5 via a refractory metal component 7 formed into a coil shape. Similarly, especially in small electrodes for small lamps, the filling amount of electron emitting material is small, resulting in a short lifespan. Furthermore, since this device utilizes the gap created in the space between the coiled refractory metal parts, it is difficult to exhaust the air if the refractory metal parts are tightly wound. Therefore, it is not possible to use a tightly wound coil shape, and as a result, in order to securely hold the electrode, the length of the part that is crushed from the outside must be increased, and the temperature of the coldest part must be increased. This caused a decrease in the amount of water. [Purpose of the invention] The present invention was made to address the above-mentioned drawbacks.
By improving the electrode support structure of metal vapor discharge lamps whose arc tube bulbs are made of translucent insulators such as translucent ceramics, electrode fixation can be ensured without lowering the temperature of the coldest part. At the same time, the objective is to provide a long-life discharge lamp. [Key points of the invention] The features of the invention are that both ends of an arc tube bulb made of a translucent insulator are sealed with a closing body fitted with an exhaust pipe, and when supporting an electrode on the exhaust pipe, the electrode is placed inside. a coil and an outer coil attached to the electrode mandrel, the outer coil extending beyond the inner coil to the proximal end of the electrode mandrel with a gap formed between the end of the inner coil, and at least The gap between the inner coil and the outer coil is filled with an electron emitting substance, and the proximal end of the electrode mandrel is fixed by caulking to form a fold in the exhaust pipe via the outer coil extending to the proximal end. The point is that I supported it. [Embodiment of the invention] An embodiment of the invention will be described below with reference to the drawings. Figure 3 shows the arc tube of a 75W high-pressure sodium lamp, and reference numeral 8 indicates an arc tube made of a translucent insulator, such as translucent ceramic, with an inner diameter of 4.5 mm and a length of 45 mm, which is filled with sodium, mercury, and a rare gas. A bulb 9 is a closure made of a heat-resistant metal or a heat-resistant insulator, such as ceramics, for sealing the open end of the arc tube bulb 8, and 5 is installed by passing through the center of the closure 9 in an airtight manner. This is an exhaust pipe made of heat-resistant metal such as niobium, and also serves to enclose substances such as metal amalgam and rare gas. 4 is an electrode with a diameter of 0.6 mm and a length as shown enlarged in Figure 4.
11mm tungsten electrode core 11 with a diameter of 0.25mm
Inner coil 1 is formed by winding a tungsten wire with a diameter of 0.1 mm around the outer circumference of the tungsten wire to form a double coil.
2 is wound around the outer periphery of the inner coil 12.
A 0.45 mm outer coil 13 is wound, and one end of the outer coil 13 extends beyond the inner coil 12 to the proximal end 11a of the electrode mandrel 11. The base end 11a of the electrode is inserted into the end of the exhaust pipe 5,
As shown in FIG. 5, if several parts of the exhaust pipe end are pressed inward to form folds, the electrode base end 1
1a is firmly fixed to the exhaust pipe 5 via the inner coil 13. Further, an electron emitting material 14 made of, for example, an oxide of an alkaline earth metal, a tungstate, etc. is filled between the inner coil and the outer coil, but according to the above structure, the outer coil extends beyond the inner coil. Therefore, a gap 15 is formed at the lower ends of both coils, and this gap can be filled with more electron emitting material 14. As a result of measuring the amount of electron emitting material filled in the electrode of the present invention formed in this way and the electrode of the conventional lamp shown in Fig. 2 formed to the same dimensions, the results are shown in the table below. It can be seen that according to the present invention, the filling amount can be increased by more than 40%.

[Effect of idea]

As explained above, it is possible to securely fix the electrode without reducing the temperature of the coldest part, increase the amount of electron emitting material filled, and have a long life without fading during the life. metal vapor discharge lamp.

[Brief explanation of the drawing]

Figures 1 and 2 are sectional views of the electrode mounting and fixing part of a conventional lamp, Figure 3 is a sectional view of an arc tube according to an embodiment of the present invention, Figure 4 is a sectional view of the electrodes, and Figure 5 is the same. FIG. 6 is a front view of the electrode mounting and fixing part of another embodiment. 1, 11... Electrode mandrel, 2, 12... Inner coil, 3, 13... Outer coil, 5... Exhaust pipe, 1
1a... Proximal end of electrode mandrel, 14... Electron emitting material.

Claims (1)

[Scope of utility model registration request] The electrode is formed by sealing both ends of an arc tube bulb made of a translucent insulator with a closure body equipped with an exhaust pipe, and wrapping an inner coil around the electrode core and an outer coil around the outer periphery of the inner coil. In a metal vapor discharge lamp held in the exhaust pipe via a mandrel,
The outer coil is formed to extend to the base end of the electrode mandrel with a gap between it and the end of the inner coil, and at least the gap between the inner coil and the outer coil is filled with an electron emitting substance, A metal vapor discharge lamp characterized in that the proximal end of the electrode mandrel is caulked and fixed to the exhaust pipe via an outer coil extending to the proximal end so as to form a fold.