JP2000011948A - Annular fluorescent lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce scattering due to the sputtering of a tungsten in case of abnormal lead heat of a filament at the end of service life, so as to prevent current-carrying between a pair of internal lead wires by forming a part of the filament provided on a pair of internal lead wires inside a light emitting tube of a tungsten alloy having a specified fusing point. SOLUTION: A pair of internal lead wires are made to pass airtightly through the sealed end part of a light emitting tube, and the end parts of the paried internal lead wires inside the light emitting tube are provided with a filament 4 made by a tungsten wire 4a. An alloy part 5 made of nickel and tungsten is provided on a part of the tungsten wire 4a, the fusing point of which is adjusted to 1,500-2,000 deg.C by the alloy proportion of nickel and tungsten, and provided at a suitable position, and electron emitting material such as barium oxide or the like is applied to the filament 4. Thus, even if the filament 4 is heated red abnormally at the end of its service life, the alloy part 5 is fused earlier and then the filament 4 is broken.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent lamp which prevents thermal damage to stem glass caused by the evaporation and scattering of tungsten as a filament material at the end of life.

[0002]

2. Description of the Related Art When a fluorescent lamp is turned on for a long time, an electron emitting material (BaO or the like) applied to a filament is used.
Is consumed and scattered, and at the end of life, only filaments are present. At this time, in high-frequency lighting, the supply of thermoelectrons is not performed, so that the cathode loss increases, the filament heats up abnormally, tungsten as a filament material is sputtered, and tungsten scatters around the filament. This scattered matter attaches and accumulates in a large amount on the surface of the flare stem close to the filament. Since the deposit is a conductive substance, a conductive path is formed between a pair of internal leads insulated by the glass of the flare stem.

In such a case, after the filament breaks,
Because a conductive path is formed on the surface of the flare stem,
An electric current may flow between the pair of internal leads to generate heat, which may cause thermal damage to the flare stem. Therefore, a technique described in Japanese Patent Application Laid-Open No. 6-338289 has been provided to make it difficult for flying substances to adhere and deposit.

The technique described in Japanese Patent Application Laid-Open No. 6-338289 discloses a method of forming a recess at the base of at least one of a pair of internal leads or between a pair of internal leads, or forming a pair of internal leads. At least one of the internal leads is provided with an insulator surrounding the sealing portion or an overhanging member using an insulator in the middle of the internal lead to prevent scattered substances from adhering to the sealing member. Technology that provides

[0005]

However, the technique described in the above-mentioned Japanese Patent Application Laid-Open No. 6-338289 discloses that when the filament at the end of life abnormally glows abnormally, the heat rarely causes the internal lead wire to reach a high temperature and the overhang member However, there is a disadvantage that the material is melted or deformed to lose its shielding effect and is thermally damaged.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a fluorescent lamp which can reduce the above-mentioned scattered filaments and can secure insulation between internal lead wires. It is the purpose.

[0007]

In order to achieve the above object, according to the present invention, there is provided a fluorescent lamp having a pair of internal leads penetrating through a sealed end of an arc tube, and a filament provided at an inner end of the internal leads. In the lamp, a part of the filament between the pair of internal lead wires is changed from 1500 ° C. to 2000 ° C.
Characterized by being formed of a tungsten alloy having a melting point of

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the embodiments shown in FIGS. 1, 2 and 3. FIG. FIG. 1 is a sectional view of an end portion of a fluorescent lamp, FIG. 2 is a perspective view showing the entire fluorescent lamp, and FIG. 3A is an enlarged view of a double coil filament.
(B) is a partially enlarged view in which a tungsten alloy is formed on a part of the tungsten 4a according to the present invention.

In FIG. 1, reference numeral 1 denotes an arc tube made of a glass tube having a phosphor coating on the inner surface. The end of the arc tube 1 is closed by a flare stem 2. The flare stem 2 has a pair of internal lead wires 3 made of nickel, iron, or the like.
a, 3b are hermetically penetrated, and a filament 4 made of tungsten 4a is provided at the end of these internal lead wires 3a, 3b.

The filament 4 is provided with an alloy portion 5 made of nickel and tungsten at a part of the tungsten wire 4a. The alloy portion 5 made of nickel and tungsten is adjusted to a melting point of 1500 to 2000 ° C. according to the alloy ratio, and is provided at an appropriate position between the pair of internal lead wires 3a and 3b. The filament 4 is coated with an electron emitting material made of barium oxide or the like (the electron emitting material is not shown).

In the arc tube configured as described above, when the filament 4 abnormally glows at the end of its life, the temperature of the filament 4 reaches 2,000 and several hundred degrees, but the tungsten 4a
Before the spatter became severe, the alloy portion 5 melted and the filament 4 was broken, and almost no tungsten was deposited and deposited on the surface of the flare stem.

Thus, the pair of internal lead wires 3a, 3
Almost no tungsten scattered substance adheres and accumulates between the b, and conduction between the pair of internal lead wires 3a and 3b can be prevented.

In the process of manufacturing the fluorescent lamp, the temperature of the filament 4 is controlled to 1200 to 140 by the electron emitting substance.
To activate at 0 ° C., the melting point of the alloy part 5 should be at least 15
A temperature of at least 00 ° C is required. In this embodiment, nickel is used for forming an alloy with tungsten. However, any metal other than nickel may be used as long as it has a melting point of 2000 ° C. or less. There may be several places where the alloy part 5 is provided, and the size of the alloy part 5 is preferably 1 mm or more in order to surely cut the filament. The filament 4 used a double coil in this embodiment,
Similar results can be obtained with multiple coils.

[0014]

As described above, according to the present invention, when the alloy portion 5 is provided on a part of the tungsten 4a of the filament 4, the filament 4 is blown out early when the filament is abnormally heated at the end of the life, so that the tungsten sputtering is performed. Scattered, and there is almost no adhesion or deposition of scattered matter on the surface of the flare stem, so that it is difficult to form a conductive path, and it is possible to prevent conduction between a pair of internal lead wires.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an end portion of a fluorescent lamp according to one embodiment of the present invention.

FIG. 2 is a perspective view showing the entire fluorescent lamp of one embodiment of the present invention.

FIG. 3 is an enlarged view of a double coil filament according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Arc tube, 2 ... Flare stem, 3 ... Internal lead wire, 4
... filament, 5 ... alloy part.

Claims (1)

[Claims] 1. A fluorescent lamp in which a pair of internal leads are hermetically penetrated through a sealed end of an arc tube and a filament is provided at ends of the pair of internal leads inside the arc tube. A fluorescent lamp, wherein a part of the filament between the internal lead wires is formed of a tungsten alloy having a melting point of 1500 to 2000 ° C.