JPS61190892A - Lighting tube - 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 Field of the Invention The present invention relates to lighting tubes, and more particularly to improvements in lighting tubes used to assist in starting discharge lamps such as high-pressure steam discharge lamps.

Conventional technology In general, lighting tubes are placed in an airtight container filled with an easily dischargeable electrical substance.
It has a pair of electrodes made of bimetal, which is a thermally responsive element, supported by welding or other means to an internal lead-in wire planted in the stem, and the heat generated by the discharge between the electrodes causes the electrodes to come into contact with each other and the discharge is cut off. When the bimetal separates because it is no longer heated by discharge, a high kick voltage of 1500V or more is generated due to a momentary interruption of the current, which starts the discharge of high-pressure steam discharge lamps such as metal halide lamps and high-pressure sodium lamps. It is something that makes you

In a conventional lighting tube, a tungsten contact is attached by welding to each tip of a thermally responsive element, which is supported by welding to two internal lead-in wires planted in a stem sealed at one end of an airtight container. was.

Problems to be Solved by the Invention In such a conventional configuration, the material of the bimetal contact is generally called doped tungsten.
Its shape is cylindrical, and when it is welded to the Pimetal ρ plate, it is heated and an oxide is formed on its surface, so when the above-mentioned large current is momentarily cut off, a high kick voltage is generated.
This voltage causes an arc discharge between the contacts, and due to the repeated operation of the lighting tube, the surface of the contact is scattered into the pool of kick voltage, forming small sharp protrusions on the surface, and finally due to the large current, the contact There was a drawback that they would weld together and no longer generate kick voltage, making it impossible to light a high-pressure steam discharge lamp.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and provides a lighting tube that is capable of stable repeated operation and that can reliably supply a predetermined high kick voltage to, for example, a high-pressure steam discharge lamp to light it. This is what we provide.

Means for Solving the Problem In order to solve this problem, the lighting tube of the present invention is equipped with a thermally responsive element that encapsulates an easily discharging electric body and at least one of the electrodes has a contact point at its tip. , the contact is made of tungsten containing 0.6% by weight or more of thorium oxide.

As described above, by using thoriated tungsten containing 0.6% or more of thorium oxide for the contacts, arc discharge between the contacts that occurs during repeated opening and closing operations of the thermally responsive element is reduced, and the contacts are deformed. , stable repeated operations are possible without causing welding, and a predetermined high kick voltage can be reliably supplied to, for example, a high-pressure steam discharge lamp.

The embodiment diagram is a partially cutaway front view of a lighting tube according to an embodiment of the present invention. The lighting tube 1 has a stem 3 sealed at one end of an airtight container 2 made of soft glass, and an internal lead-in wire 4 erected in the stem 3 .
The structure is such that electrodes 6 and 7 made of thermally responsive elements such as bimetals are planted at a predetermined distance from each other. After the air inside the airtight container 2 is exhausted from the exhaust pipe 8 of the stem 3, a helium-hydrogen-argon or helium-hydrogen mixture gas is filled from the same exhaust pipe, and the exhaust pipe 8 is tipped off. ing. The external lead wires 9.1o are electrically connected to the internal lead-in wires 4, 6, respectively. At the tips of each of the electrodes 6 and 7, contacts 11 and 12 made of thoriated tungsten rods are attached. The above-mentioned thoriated tungsten contains thorium oxide in 1.
It consists of tungsten containing 5% by weight.

As mentioned above, a total of 1.6 thorium oxide is applied to contacts 11 and 12.
By using tungsten containing % by weight, deformation and welding of the contacts did not occur, and stable repeated operation could be obtained.

Next, in order to achieve the object of the present invention, an experiment in which the content of thorium oxide in tungsten, which is a constituent material of the contact, was investigated will be described.

For a lighting tube with the structure shown in the figure, 5% of a gas mixture of 93% helium, 6% hydrogen, and 2% argon was placed in an airtight container.
Ten lighting tubes were manufactured by enclosing Q TOrr, using thoriated tungsten round rods as contacts, and varying the thorium oxide content of the contact material. In such a lighting tube, 400! Chiyoke ballast and 300
A current limiting resistor of 0 and a lighting tube were connected in series, an alternating current voltage of 200 Vi was applied, and after 5000 cycles of 20 seconds on and 6 minutes off, the required characteristics were measured.

The results are shown in the table below.

As is clear from the table above, in lighting tubes using tungsten containing 0.5% by weight or more of thorium oxide as the contact material, welding between the contacts does not occur even after 5000 flashes. No generation occurred, and good characteristics were obtained with a pulse voltage of 1500 V or more, which is necessary for starting a high-pressure steam discharge lamp.

On the other hand, in the case of a lighting tube using a contact with thorium oxide in the range of 0% by weight to 0.4% by weight, sample No. 1 uses a so-called doped tungsten contact that does not contain any thorium oxide. Pulse voltage 1500V required to turn on a high pressure steam discharge lamp after 5000 flashes
However, 8 out of 10 had welding between the contacts. In addition, samples A2 and &3 using contacts containing 0.3% and 0.4% by weight of thorium oxide
Also, in 5 out of 10 cases and 4 out of 10 cases, welding occurred between the contacts.

The pulse voltage tends to decrease as the thorium oxide content increases, but when the thorium oxide content is about 3
%, there is no practical problem because a pulse voltage of 1500 V or more required for startup can be obtained. The reason why the pulse voltage decreases as the content of thorium oxide increases is thought to be due to the form of minute arcs between the contacts that occur during opening and closing operations, but the details are unknown.

If the content of thorium oxide exceeds 3%, defects such as cutting will occur frequently during wire drawing during the wire manufacturing process, and workability will deteriorate significantly. The amount is considered to be limited to 3%.

In addition, in the above embodiment, as an easily dischargeable electric body in the lighting tube,
Although an example has been described in which a mixed gas of helium, hydrogen, and argon is filled, the desired effect can also be obtained with a mixed gas of other inert gases as an easily dischargeable electric body.

As described in detail, the present invention provides a thermoresponsive element having a pair of electrodes in an airtight container enclosing an easily discharging electric body, and at least one of the electrodes having a contact point at its tip. Since the contacts are made of tungsten containing 0.5% by weight or more of thorium oxide, there will be no welding due to arcing between the contacts in the lighting tube, and a stable high kick voltage can be generated.
In particular, it is possible to provide a lighting tube having excellent characteristics that can be used to light a high-pressure steam discharge lamp such as a metal halide lamp.

[Brief explanation of drawings]

The figure is a partially cutaway front view of a lighting tube according to an embodiment of the present invention. 1...Lighting tube, 2...Airtight container, 6,
7... Electrode, 11.12... Contact. Name of agent: Patent attorney Toshi Nakao Haga 1 person 1-
-IchiyuyT Suga 2- Tribe 254 Qin 3---Stehe 1-■ Grit

Claims (1)

[Claims] It has a pair of electrodes in an airtight container containing an easily dischargeable electric body,
1. A lighting tube comprising a thermally responsive element in which at least one of the electrodes has a contact at its tip, wherein the contact is made of tungsten containing 0.5% by weight or more of thorium oxide.