JPH0584017U - Low pressure discharge lamp - Google Patents

Abstract

(57) [Abstract] [Objective] To provide a low-pressure discharge lamp having an electrode with an improved ability to start cold operation and further reducing blackening of a lamp bulb. The metal cylinders are closed at one end, and each metal cylinder and the electrode filament provided in the metal cylinder have only one common current lead. The lead portion is configured to support the electrode filament and the metal cylinder of the electrode filament.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention is a low-pressure discharge lamp consisting of a discharge vessel with an ionizable filling and two electrodes for producing a gas discharge, each electrode consisting of an electrode filament with an electron emitter. , A low-pressure discharge lamp in which the electrode filaments are arranged axially in a metal cylinder.

[0002]

[Prior Art]

 Lamps of this kind are known, for example, from FR-PS 1152572. This lamp is a fluorescent lamp with so-called cold startable electrodes. The electrodes of this lamp consist of an electrode filament with electron emitters, each wound in triplicate. Each of the electrode filaments is surrounded by an open-ended metal cylinder. In addition to the current leads, the electrode filament also has a feedback supply. This feedback supply enables activation of the electron emitter on the coil using the heater current flowing through the electrode filament.

Such an electrode system has the following drawbacks. That is, there is a drawback that the arc discharge does not start at a predetermined arc starting point. Therefore, fluorescent lamps with this type of electrode system tend to flicker. Arc discharges can occur in the electrode filament, but not in the feedback supply or current leads below the filament, for example. In addition, the open type metal cylinder cannot suppress the blackening of the lamp bulb to a desired degree.

The use of triple filaments instead of single filaments also has a negative effect. This is because triple filaments have a higher heat capacity than single filaments, and the transition from glow discharge to arc discharge, which is harmful to the electrodes, is delayed when triple filaments are used. is there.

US Pat. No. 3,883,764 discloses a low-pressure discharge lamp which operates as a UV irradiator. This low-pressure discharge lamp also has two electrodes that can be cold started. The two electrodes here consist of one electrode filament each with an electron emitter. The electrode filament is surrounded by an open metal cylinder. Besides the current leads for the energy supply, this electrode filament also has a return supply. This feedback supply allows activation of the electron emitter material on the filament using a heater current through the electrode filament. The return supply portion extends along the inner wall of the metal cylinder. Furthermore, the return supply is welded together with the electrode filament at the discharge side end of the axially arranged electrode filament. This welding point has a negative effect. This is because this weld point tends to form a starting point for the arc discharge instead of the electrode filament. This can lead to premature electrode loss.

In addition, apertured metal cylinders cannot avoid the desired blackening of lamp bulbs due to sputtered emitter material. The electrode system disclosed in US-PS 388 3764 is also not suitable for compacting low pressure discharge lamps because of its relatively large size.

A so-called cup-type electrode is known from the specification of CH-PS449117. This electrode consists of a cup-shaped electrode container. An electron emitter is arranged in this electrode container. This electrode does not have an electrode filament and cannot guarantee the desired start of a stable arc discharge in a low-pressure discharge lamp.

[0008]

[Challenges for devising]

 An object of the present invention is to provide a low-pressure discharge lamp having an electrode with an improved ability to start cold operation and further reducing blackening of the lamp bulb.

[0009]

[Means for Solving the Problems]

 According to the present invention, the above-mentioned problem is that the metal cylinders are closed at one end respectively, and each metal cylinder and the electrode filament provided in the metal cylinder have only one common current lead portion. Therefore, the current lead portion is constituted so as to support the electrode filament and the metal cylinder of the electrode filament, which is solved.

The electrodes of the low-pressure discharge lamp according to the invention consist of one electrode filament arranged axially in the metal cylinder. The metal cylinder is closed at one end. Therefore, this metal cylinder is better protected from blackening of the lamp bulb than the electrode shielding means in the cited prior art. Advantageously, the closed end of this metal cylinder can be collapsed. In this case, the current lead for the electrode filament is sandwiched in this crush. Thereby, the metal cylinder is supported.

Experiments have revealed the following. That is, it has been found that if the opening end of the metal cylinder is additionally provided with a cover having a central opening for the discharge current, the blackening of the bulb in the electrode region can be further reduced.

The electrode filament is preferably single-wound and has a low heat capacity. Therefore, the electrode filament heats up relatively quickly by the discharge current and thermally emits electrons. This shortens the transition from glow discharge, which is harmful to the electrodes, to arc discharge. In addition, the sputtering of filament material is significantly reduced. Furthermore, the electrode according to the invention ensures that the arc discharge is initiated preferentially in the heated electrode filament.

The electrode filament preferably consists of tantalum or niobium. In such electrode filaments the emitter material (barium peroxide, barium tantalate or other conventional fluorescent lamp emitters) deposits better than in tungsten filaments. The electron emitter is formed not by direct passage of current through the electrode filament but by induction heating of the filament, preferably by high frequency, so that there is only one common A metal cylinder surrounding the current lead and the electrode filament is sufficient. A separate feedback supply, which may influence the initiation of the arc discharge, as described in the cited prior art, is dispensed with.

[0014]

【Example】

 The invention will now be described in more detail below on the basis of two particularly advantageous embodiments.

FIG. 1 schematically shows a cross section of an electrode according to the invention for a rod-shaped fluorescent lamp with an output of 18 W. This electrode comprises a niobium cylinder 1 having an open end 1a and a closed end 1b. In the area of the open end 1a, the niobium cylinder 1 has a substantially cylindrical shape with a diameter of approximately 3.3 mm. The wall thickness of the niobium cylinder 1 is about 0.1 mm and its depth is about 3 mm. In the niobium cylinder 1, a single winding of an electrode filament 2 made of tantalum is arranged in axial symmetry. The electrode filament 2 is supplied with electric energy from the current lead portion 3. The closed end 1b of the niobium cylinder 1 is formed by crushing the side wall of the niobium cylinder. At that time, the current lead portion 3 is sandwiched between the walls of the niobium cylinder 1. As a result, the current lead portion 3 is also used as a support pin for the niobium cylinder 1. Due to the crushing process, the cylindrical shape of the niobium cylinder 1 is no longer maintained in the region of the closed end 1b.

The electrode filament 2 and its current lead 3 are preferably constructed in one piece. Barium peroxide is used as the electron emitter 4 for the electrode filament 2. The electron emitter 4 is formed by inductively heating the electrode filament 2 with a high frequency. The sealing of the electrodes in the lamp bulb (prior to the formation of the emitter 4) takes place in a known manner. Therefore, detailed description is omitted here.

FIG. 2 schematically shows a cross section of an electrode according to a second embodiment of the present invention. The electrode of the second embodiment is almost the same as that of the first embodiment. However, this electrode additionally has a cover 5 made of a thin iron plate. The cover 5 covers the opening end 1 a of the niobium cylinder 1.

The cover 5 has a central opening 6. The arc discharge generated in the electrode filament 2 can be passed through the central opening 6. The two embodiments are all in agreement in different details.

However, the invention is not limited to the two illustrated embodiments. Thus, for example, the electrode filament may also consist of niobium, tungsten or molybdenum. The electron emitter may also be barium carbonate, barium tantalum, barium niobium, or any other conventional emitter. The formation of the emitter material can also be carried out by heating the electrode filament, for example with a laser, or by a discharge current. Alternatively, the electrode container can be made of molybdenum or other metal. The dimensions of the metal cylinder are not critical. For example, the metal cylinder could also have a depth of about 5 mm and a wall thickness of about 0.3 mm.

Furthermore, the current leads and the unwound electrode filament ends do not necessarily have to be crushed to the bottom of the associated metal cylinder as described in the preferred embodiment. The current lead with the electrode filament can also be joined to the closed end of the metal cylinder, for example using a welding point. In addition, since it is not necessary to integrally configure the current lead portion and the electrode filament, the current lead portion and the electrode filament can be similarly joined to each other by a welding point.

[0021]

[Effect of the device]

 The electrodes of the low-pressure discharge lamp according to the invention consist of an electrode filament arranged axially in a metal cylinder, which is closed at one end, so that It can protect the lamp bulb from blackening better than the shielding means. Advantageously, the closed end of this metal cylinder can be collapsed. In this case, the current lead for the electrode filament can be pinched in this collapsing part, so that the metal cylinder can be supported.

If the open end of the metal cylinder is additionally provided with a cover with a central opening for the discharge current, the blackening of the bulb in the electrode area can be further reduced.

Since the electrode filament of the present invention is preferably wound in a single piece and has a small heat capacity, the electrode filament is heated relatively quickly by the discharge current and emits thermoelectrons. be able to. As a result, the transition process from glow discharge, which is harmful to the electrodes, to arc discharge is shortened. In addition, the sputtering of filament material is significantly reduced. Furthermore, the electrode according to the invention ensures that the arc discharge is preferentially initiated in the heated electrode filament.

Advantageously, the formation of the electron emitter is not effected by direct passage of current through the electrode filament, but by induction heating of the filament by means of high frequencies, so that there is only one Only one common current lead and the metal cylinder surrounding the electrode filament are sufficient. This eliminates the need for a separate feedback supply, which would otherwise affect the initiation of arc discharge.

[Brief description of drawings]

FIG. 1 is a schematic view of electrodes of a low pressure discharge lamp according to a first embodiment of the present invention.

FIG. 2 is a schematic view of electrodes of a low pressure discharge lamp according to a second embodiment of the present invention.

[Explanation of symbols]

 1 Metal Cylinder 1a Open End 1b Closed End 2 Electrode Filament 3 Current Lead 4 Electron Emitter 5 Cover 6 Open

Claims (1)

[Scope of utility model registration request] 1. A low-pressure discharge lamp consisting of a discharge vessel with an ionizable filling and two electrodes for producing a gas discharge, each electrode consisting of a respective electrode filament with an electron emitter. In the low-pressure discharge lamp in which the electrode filaments are axially arranged in the metal cylinder, the metal cylinder (1) has one end (1).
closed in b), each metal cylinder (1) and the electrode filament (2) provided in the metal cylinder have only one common current lead (3), The low-pressure discharge lamp, wherein the lead portion (3) supports the electrode filament (2) and the metal cylinder (1) of the electrode filament (2).