CN1057865C - Composite discharge lamp - Google Patents

Abstract

The present invention relates to a composite glow discharge lamp comprising a long and thin glass tube. The first ends of the opposite ends of the long and thin glass tube are provided with an electrode assembly respectively. Each electrode assembly comprises a central electrode used for transmitting electrons and a glow electrode surrounding the central electrode, wherein the glow electrode is composed of a cap with an opening and an enclosed bottom. The glow electrode is arranged in this way, which makes the opening face the opposite end near the glass tube and the enclosed bottom face the middle part on the longitudinal direction of the glass tube. Consequently, the glass tube can be prevented from blackening, and the service life of the composite discharge lamp can be prolonged.

Description

Composite discharge lamp

The present invention relates to the composite discharge lamp such as hot cathode low-voltage fluorescence discharge lamp, this hot cathode low-voltage fluorescence discharge lamp has the glass tube that an introducing has some electrode assemblies, each electrode assemblie is made up of a central electrode and a glow discharge electrode that surrounds central electrode that is used for emitting electrons, and these electrode assemblies lay respectively near the position the elongated shape glass tube opposite end.

Similar with bulb, hot cathode low-voltage fluorescence discharge lamp is that so-called fluorescent lamp is widely used as the high efficiency light source.

Applied by one deck electronic emitting material (below will be referred to as " emitter ") on the heater winding cathode electrode in the fluorescent lamp, this electron emitter mainly is made up of barium, the gill and calcium, the sputter that this material reason ion bombardment on negative electrode causes and when opening discharge lamp itself evaporation and be depleted, make lamp can not be lighted or finish the useful life of lamp.

The someone proposes a kind of conventional fluorescent lamp, in this fluorescent lamp, in order to prolong the useful life of fluorescent lamp, anode is installed on the heater winding negative electrode to eliminate the bombardment of ion.But, the feasible optical flare that is sent of anode is installed, therefore do not re-use this fluorescent lamp in fact now.

The structure of the electrode assemblie in conventional cold cathode or the hot-cathode fluorescent lamp comprises filament (central electrode) and surrounds the glow discharge electrode of filament.Glow discharge electrode is a cover that has an opening and closed bottom.The opening of glow discharge electrode is facing to the middle part of the slender glass tube that electrode assemblie is housed, and the bottom of glow discharge electrode then faces toward the end near its glass tube.Can be referring to Japanese patent application " flat 4-22057 number ".This conventional fluorescent lamp has following shortcoming:

(1) lacks the useful life of lamp, promptly be generally 4000 to 5000 hours;

(2) in two relative ends of glass tube melanism appears;

(3) produce a large amount of heats in the later stage in useful life;

As mentioned above, in the conventional fluorescent lamp opening surface of glow discharge electrode to the middle part of glass tube, thereby the filament cathode that glow discharge electrode surrounded is exposed to ion or electronics.Although emitter in the glass tube of conventional fluorescent lamp or air pressure have been carried out various improvement,, can not prevent sufficiently that still be shortened because of ion bombardment the useful life of fluorescent lamp.

The present invention proposes in order to eliminate above-mentioned shortcoming, therefore, an object of the present invention is to provide a kind of composite discharge lamp that can eliminate above-mentioned shortcoming.

For this reason, according to the present invention, provide a kind of composite discharge lamp, it comprises: a slender glass tube (as shaft-like glass tube or ring-type glass tube), and it has the middle part of a length direction and the relative termination of length direction; Some electrode assemblies, each electrode assemblie is made up of a central electrode and a glow discharge electrode that surrounds central electrode that is used for emitting electrons, electrode assemblie lays respectively near the relative along its length two ends of glass tube, glow discharge electrode is a cover with an opening and a closed bottom, this opening towards in the glass tube length side in relative two ends a close with it end, this closed bottom is the middle part on the glass tube length direction then.

As mentioned above, because it is opposite that glow discharge electrode according to the present invention is arranged with conventional fluorescent lamp, it is the opening surface of a glow discharge electrode close with it end in the relative two ends on the glass tube length direction, also since the bottom of glow discharge electrode towards the middle part of glass tube length direction, therefore, the opening that hot electron at first passes (comprising the secondary electron that glow discharge causes) glow discharge electrode penetrates, then towards the end of glass tube.Utilize the bottom of the ion bombardment glow discharge electrode that electron discharge produces, the bombarding energy that obtains like this is as the secondary electron discharge energy that increases lamp current.In routine techniques,, therefore, it is believed that the ion pair discharge lamp is harmful to because ion has brought the problem of ion bombardment.But,, but can effectively utilize the effect of ion according to the present invention.

According to below in conjunction with the description of the drawings, other features and advantages of the present invention will be very clear.In the accompanying drawings:

Fig. 1 is the schematic diagram of an electrode assemblie structure of general description fluorescent lamp;

Fig. 2 is the schematic diagram of explanation according to an electrode assemblie structure in the composite discharge lamp of the present invention;

Fig. 3 is the schematic cross sectional views of the configuration of the part of composite discharge lamp in the explanation first embodiment of the invention, and said composite discharge lamp is equipped with electrode assemblie shown in Figure 2;

Fig. 4 is the schematic cross sectional views of composite discharge lamp structure in the expression second embodiment of the invention;

Fig. 5 is the electric winding diagram of composite discharge lamp among expression control first embodiment;

Fig. 6 is the schematic diagram of the part of composite discharge lamp in the explanation second embodiment of the invention, and wherein the part is broken away;

Fig. 7 is the schematic diagram of composite discharge lamp in the explanation third embodiment of the invention, and the part is broken away among the figure.

Fig. 8 is the electric winding diagram of composite discharge lamp in the expression control third embodiment of the invention;

Fig. 9 is another electric winding diagram of composite discharge lamp in the explanation control third embodiment of the invention;

Figure 10 is the perspective view of position relation between expression one glow discharge electrode and the heater winding electrode;

Figure 11 is the profile of position relation between explanation one glow discharge electrode and the arc electrodes;

Figure 12 is the cutaway view of explanation electrode assemblie configuration shown in Figure 4, and wherein part is broken away;

Figure 13 is the curve chart of the endurance life characteristic of indication lamp, and be to measure at the middle part of glass tube this useful life, for relatively, shows the endurance life characteristic of conventional fluorescent lamp and composite discharge lamp of the present invention among the figure respectively;

Figure 14 is the cutaway view of a kind of modification of explanation composite discharge lamp shown in Figure 6;

Figure 15 is the perspective view of a kind of modification of explanation composite discharge lamp shown in Figure 2;

Figure 16 is the perspective view of electrode assemblie shown in expression one illustration 4;

Figure 17 is the perspective view of a kind of modification of explanation electrode assemblie shown in Figure 16.

Referring to Fig. 1, the electrode assemblie in its expression fluorescent lamp, this electrode assemblie is made up of heater winding electrode 5 that is coated with electronic emitting material above it and lead 2,3, and electric current is added on the heater winding electrode 5 by lead 2,3. Lead 2,3 is connected on the stem stem 1 of a steam vent 4.Referring to Fig. 2, it also represents to have a glow discharge electrode 6 except that expression electrode 5 shown in Figure 1.Glow discharge electrode 6 is made up of aluminium, nickel, main sintering metal or the materials similar of being made up of electronic emission material, and it is a cylindricality, has an opening 25 and a closed bottom 26.Lead 2 is by spot welding or be riveted on the glow discharge electrode 6, and opening 25 is set to towards stem stem 1.

Manufacturing has the fluorescent lamp of electrode assemblie shown in Figure 2 and has the fluorescent lamp of electrode assemblie shown in Figure 1 and compare its luminous situation mutually.Interchange igniter circuitry with 100 volts of 50HZ is made power supply.

Having current value is that 215mA, magnitude of voltage are that the fluorescent lamp with electrode assemblie shown in Figure 1 sends 9 under the situation of 10.1W power of 47V, the brightness of 000nt (middle part at lamp is measured); And be that the voltage of 225mA, lamp is that 45V, power are under the situation of 10.1W at electric current, the fluorescent lamp with electrode assemblie shown in Figure 2 presents 9, the brightness of 500nt (middle part at lamp is measured).

Referring to Fig. 3, an end parts of composite discharge lamp in its expression first embodiment of the invention, electrode assemblie shown in Figure 2 wherein is housed, heater winding central electrode 5 is made up of two heater windings, glow discharge electrode 6 external diameters are 8mm, length is that 10mm, wall thickness are 0.15mm, and it is made by the aluminium of purity about 95%.

As shown in Figure 3, known by above-mentioned contrast experiment that even glow discharge electrode 6 is covered on the heater winding central electrode 5, luminous intensity can not reduce yet, it increases about 5% on the contrary.

Using electrode assemblie shown in Figure 1, utilize ion bombardment heater winding central electrode 5, is the emitter sputter so that the energy of ion bombardment makes electronic emitting material, causes fluorescent lamp shortening in useful life, and, produce a large amount of heats in the later stage in useful life.On the contrary, according to the present invention, use Fig. 2 and electrode assemblie shown in Figure 3, the bottom and the sidewall of 12 bombardments of ion glow discharge electrode, the energy of ion bombardment is absorbed so that launch a large amount of secondary electron 11 on glow discharge electrode 6 whole broad outside wall surface, thereby the electric current of lamp is increased.

Referring to Fig. 3, if as shown in the figure electrode assemblie is arranged at negative (-) end, then the hot electron 10 that is produced by heater winding central electrode 5 passes the opening 25 of glow discharge electrode 6, pass the space between the inner peripheral surface of the outer peripheral face of glow discharge electrode 6 and glass tube 13 then, attracted by electrode assemblie at unshowned just (+) end, thus the motion of the right side in Fig. 3.Because mercuryvapour or steam atom are recharged in glass tube, therefore, hot electron 10 encourages mercury atom to send ultraviolet radiation in its path, and this ultraviolet radiation encourages the fluorescent substance film 9 that is coated on glass tube 13 internal faces again, thereby emits beam 7.Because hot electron passes reflection after the opening 25 of glow discharge electrode 6 with being reversed, therefore, can't see shade as the glow discharge electrode 6 of cover through glass tube, that is to say that fluorescent lamp is lighted with uniform brightness.

Referring to Fig. 4, it represents second embodiment of the invention, and it is equipped with a domeshape glow discharge electrode 32 shown in Figure 12, and Figure 12 is a cutaway view.Glow discharge electrode 32 diameter D are 8mm, and height H is 4mm, in adorn a 10w heater winding central electrode 5 of making by wire, the about 4mm of its width C, its traverse is in glass tube 14.

Referring to Fig. 4, glass tube 14 diameters are about 25.5mm, length is 33cm, in be filled with the argon gas of 5 torrs and the mercuryvapour of 0.006 millimetres of mercury.In addition, the inner surface of glass tube 14 is coated with fluorescent material film 9.Glass tube 14 has 4 lamp bases 27,28,29,30, and starter 15 is connected between the lamp base 27,28, and AC power 16 and a ballast 31 then are connected between the lamp base 29,30.

If the fluorescent lamp left side is negative (-), then pass the opening 25 of glow discharge electrode 26 by the hot electron 10 of heater winding central electrode 5 emissions, pass the space between the outside wall surface of the internal face of glass tube 14 and glow discharge electrode 32 again, final just (+) electrode assemblie that arrives a relative end after the middle part on passing glass tube 14 length directions.Simultaneously, comprise the periphery wall of the glow discharge electrode 32 of bottom 26 with ion 12 bombardment, so that produce secondary electron 11, these secondary electrons 11 also are attracted to the anode electrode assemblie.That is to say that the electric current of lamp is to flow through middle part on glass tube 14 length under a kind of like this condition that hot electron 10 and secondary electron 11 obtain mixing at the middle part.Basically the glow discharge electrode 32 of the electric current of all these lamps arrival positive electrode assembly comprises the periphery wall of bottom surface, but does not arrive the heater winding central electrode 5 in the positive electrode assembly.Therefore, small amount of current flows near the opening of positive glow discharge electrode 32, thereby not luminous in its vicinity.

But because power supply 16 is an AC power, therefore negative terminal and anode replace mutually in every half cycle of a-c cycle ripple, and the result sends light from the opposite end part of glass tube 14.In order to eliminate near the dash area the glow discharge electrode as much as possible, Fig. 4 and domeshape glow discharge electrode 32 shown in Figure 12 use better, and need not cylindricality glow discharge electrode 6 shown in Figure 3.In addition, do not contact with glow discharge electrode and to exceed, the diameter of glow discharge electrode is reduced to minimum value want more favourable with the heater winding central electrode.

Except that hot electron, the electronics that produces at negative terminal also comprises the secondary electron that the caused glow discharge of potential difference (about 11 to 12 volts) because of 32 of heater winding central electrode 5 and glow discharge electrodes produces.This electronics passes opening 25 and moves to the positive electrode assembly.As mentioned above, because the energy of emitter on the heater winding central electrode 5 in the glow discharge electrode 32 and ion bombardment is isolated, therefore, can eliminate its sputter.

Although the emitter on the heater winding central electrode 5 is owing to the evaporation of itself consumes,, the steam of emitter scatters, and is attached to then on the internal face of glow discharge electrode 32.The emitter steam that adheres to so also can emitting electrons, and therefore, this increases discharging current.Perhaps, they further spread, and then are attached on heater winding central electrode 5 or other part, thus on those positions emitting electrons.

Like this, heater winding central electrode 5 is isolated to eliminate sputter with ion bombardment, in addition, by the evaporation of itself diffusion of the emitter steam that causes back and forth between glow discharge electrode internal face and heater winding central electrode so that can keep the emission of electronics continuously, thereby reduce the loss of electrode greatly.As a result, prolonged the useful life of fluorescent lamp greatly.

Figure 13 is the figure that compared the useful life of the useful life of composite discharge lamp in this embodiment of the invention shown in Figure 4 and normally used conventional fluorescent lamp.Curve M and the comparison of useful life between the curve L of conventional fluorescent lamp in useful life by this embodiment of the invention, can see that prolonged the useful life according to composite discharge lamp of the present invention, even working 50, it also can be lighted after 000 hour, therefore, reach 8 times the height that is approximately conventional fluorescent lamp its useful life really.

Generally speaking, in the later stage in its useful life, fluorescent lamp has reduced its electron emissivity, and therefore, it is big that the pressure drop of negative electrode becomes.Like this, the diffusion of vapor of emitter is many more, and consumption is just many more, therefore, has just quickened the termination in fluorescent lamp useful life.Simultaneously, the energy of ion bombardment causes the generation of a large amount of heat.For example, be identified, the temperature of the outer wall of the every end parts of glass tube can rise to about 150 to 200 ℃ temperature.As a result, just may destroy the device that is connected and fixed of fluorescent lamp, and, using under the electronic notice board that illuminates colored screen on its relative two sides or analog are presented at image situation on the screen, just the problem that colored screen fades may appear.

According to the present invention, even under the situation that the later stage ion bombardment in composite discharge lamp of the present invention useful life becomes excessive, the radiation of secondary electron also can be more and more stronger, thereby can further increase the discharging current that causes light radiation.Because glow discharge electrode designs to such an extent that have very big thermal capacity, therefore, excessive bright spot can not occur, that is to say, can obtain stable discharge and not have flicker, with regard to its thermal capacity, the wall thickness of glow discharge electrode preferably is set to a value in 0.15 to the 0.2mm scope.

Fig. 6 has only represented the schematic cross sectional views in composite discharge lamp left side in the third embodiment of the invention.Electrode assemblie shown in Figure 6 is that central electrode is formed by the metal cup-shaped glow discharge electrode such as aluminium 22 with the cup-shaped starting the arc electrode 21 that is positioned within the glow discharge electrode 22, and this central electrode is made by the sintering metal of mainly being made up of electronic emitting material.Lead 19 aligns with the central axis of these electrodes, and it is connected near the tungsten filament 20 of electrode.In this embodiment, lead 19 is made by Dumet wire.Glow discharge electrode 22, starting the arc electrode 21 and tungsten filament 20 riveted joints and be fixed together and form the end of composition more than one 24.

In the composite discharge lamp that picture is formed as shown in Figure 6, a converter 18 is connected between the lead 19,19.When DC power supply 17 was connected to converter 18, composite discharge lamp was energized.Configuration shown in Figure 5 is applicable to the small-sized light wall pipe lamp that is approximately 3mm such as diameter, and it is used for the backside-illumination of LCDs.

For Fig. 5 and embodiment illustrated in fig. 6, be a particular design example below:

Frequency of oscillation: 50Hz, oscillating voltage: 700V (effective value), the body of inflating: the mercury of the argon gas of 50 torrs and 5 millimetress of mercury, glass tube external diameter: 6.5mm (wall thickness: 0.5mm), glass pipe range: 250mm, fluorescent material: three ripple fluorescent materials.

The size of electrode assemblie:

Glow discharge electrode:

Overall diameter: 4.5mm; Wall thickness: 0.15mm; Tube length: 5mm;

Starting the arc electrode (central electrode):

Overall diameter: 3.0mm; Wall thickness: 0.5mm; Tube length: 2mm;

Electrode multicomponent end:

Overall diameter: maximum 2mm

Lead:

Diameter: 0.5mm

Experimental result by this design example can confirm, the brightness that discharging current discharges during for 16mA is 30,000nt, and be 35,000 hours its useful life.

Fig. 5 and glow discharge electrode 22 shown in Figure 6 are so placed, and make its opening 25 towards the close with it end of glass tube, and its bottom is the middle part on glass tube length then.Therefore, starting the arc electrode is that central electrode 21 has been avoided ion bombardment fully.So, sputter can not occur, and the energy of ion 12 bombardments is absorbed to realize the emission of secondary electron by periphery wall.

Fig. 7 is the schematic diagram that the left part of composite discharge lamp in the fourth embodiment of the invention only is described, this figure partly is broken away.Different with composite discharge lamp shown in Figure 6, it makes starting the arc electrode with heater winding central electrode 23, and has used two leads 19 that Dumet wire is made.Fig. 8 represents to encourage the circuit of composite discharge lamp shown in Figure 7.This circuit is the high voltagehigh frequency start-up system of a use one converter.Another circuit shown in Figure 9 comprises that a high-frequency generator 33 and an oscillation transformer 34 are to constitute a quick starter and a system start-up circuit.By between Fig. 6 and the electrode assemblie shown in Figure 7 relatively, electrode assemblie shown in Figure 6 is its longer service life fortunately; On the other hand, its brightness is higher fortunately for electrode assemblie shown in Figure 7.

People are verified, are preferably in the gap X that is set with several millimeters magnitudes between the opening of glow discharge electrode and the central electrode.Referring to Figure 10, gap X is between the end of the opening 26 of glow discharge electrode 6 and filament adjacent hub of a spool electrode 5.Simultaneously, referring to Figure 11, gap X is set between the opening of the opening 25 of glow discharge electrode 22 and starting the arc electrode 21.Under the situation of small-sized light wall pipe composite discharge lamp, this gap X is more preferably greater than 2mm, and under the situation of 10w composite discharge lamp, this gap is more preferably greater than 4mm.

Because emitter can increase the emission of electronics, therefore, the inner surface of the most handy its coating glow discharge electrode.Although being described in the above-described embodiments, glow discharge electrode use the metal such as aluminium to make,, also can use transparent conducting glass to make.This transparent conducting glass can provide optical efficiency higher electrode.Glow discharge electrode can be arbitrary shape, as cylindricality, cup-shaped, infundibulate, domeshape, ship shape etc.But, point out that at this at the various metal materials that are used for glow discharge electrode, minimum a kind of of sputter is aluminium, if its purity is higher than 95% then better.

In order to make the glow discharge electrode of making by transparent conducting glass, for example, can use sputtered film to form technology, the indium oxide that mixes up with tin oxide in this technology forms conductive film on the glow discharge electrode all surface.Perhaps, also can use the vacuum evaporation of rafifinal.Can not fix with riveted joint owing to make the multicomponent end of glow discharge electrode by transparent conducting glass, therefore, adopt electrically conducting adhesive to fix.

Referring to Figure 14, its expression a kind of modification embodiment illustrated in fig. 6, cup-shaped glow-discharge electrode 22a is fixed in the far-end of lead 25a, and provides a pole shape central electrode 21a who is made by sintered metal materials to surround this lead 25a far-end.Pole shape central electrode 21a is impregnated with electronic emitting material.In addition, can be fixed in the end of central electrode 21a on the cup-shaped glow-discharge electrode 22a.

In addition, as shown in figure 14, owing on the glass tube outer peripheral face, can't see the shade of domeshape glow-discharge electrode basically, thereby domeshape electrode 22a can give gratifying aesthetic appearance of composite discharge lamp, so, preferably use the arch glow-discharge electrode 22a that makes by transparency conductive electrode, replace Fig. 2, Fig. 6, Fig. 7, Figure 10 or cylindricality glow discharge electrode shown in Figure 11.

The glow-discharge electrode of low sputter can be made by sintering metal, and this class sintering metal also can be by the zirconium as main component except can being made up of aluminium, and tungsten and nickel composition.In addition,, and then heat-treat, then can simplify its manufacturing process if electrode 21a and 22a the time are made of one mutually in casting.

The glow discharge electrode (referring to Fig. 2 and Figure 12) that is about 10mm for bottom lock, diameter, form in the centre of glow discharge electrode bottom that a diameter is about 0.5 to 2mm, best about aperture of 0.5 to 1mm 40 (referring to Figure 15), measure the experiment that it lights situation then.Even such aperture also can obtain long useful life and high brightness, and not have ion bombardment and sputter.After doing like this, the starting resistor step-down (having lowered 3～5%), shortened start-up time.Do not have under the situation of aperture in the glow discharge electrode bottom, hot electron will pass the opening of glow discharge electrode and the gap between glow discharge electrode outside wall surface and the glass tube internal face, thereby impedance discharge has increased.On the contrary, under the glow discharge electrode bottom centre foraminate situation in position, shorten start-up time to improve starting resistor, that is to say that this aperture helps main discharge thereby hot electron passes this aperture.

If it is big that the diameter of this aperture becomes again, then ion bombardment can take place, thereby can cause the sputter of heater winding central electrode and produce a large amount of heats in the later stage in its useful life.On the other hand, littler if the diameter of this aperture becomes, then starting resistor is elongated with step-down thereby start-up time, that is to say, above-mentioned booster action is with meaningless.Experiment confirm is the glow discharge electrode face speech of 10mm to diameter, and the diameter of this aperture is preferably in 0.5 to 2mm the scope, and wherein, 0.5 to 1mm is best.

According to the present invention, can prolong the useful life (till the time when lamp can not be lighted) of composite discharge lamp greatly, and blackening phenomena can not occur in the opposite end of glass tube.In addition, can not produce a large amount of heats in the latter half in life-span.Can make the shade of glow discharge electrode not in sight in addition.

Referring to Figure 16, it represents the electrode assemblie shown in the illustration 4, except the lead 2,3 of the opposite end that stretches to heater winding type arc discharge electrode from stem stem 1, conducting bracket 26b stretches to domeshape glow-discharge electrode 26 from stem stem 1, and it comprises the lower end and the upper end that is welded to glow-discharge electrode 26 opening outer rims that embed in the stem stem.Support 26b supports glow-discharge electrode 26, and it is electrically connected so that encourage glow-discharge electrode 26 with lead 2 by conductor 26c.

Referring to Figure 17, it represents a kind of modification of electrode assemblie shown in Figure 16, lead 2,3 is made by the strip-shaped conductive material, and glow-discharge electrode 26 has a periphery from the brightness sparking electrode 26 openings tenon shape sheet 26a that extends out, and it curves inwardly so that spot weld on the lead 2.Therefore, in this modification, lead 2,3 is as the structural member that supports glow-discharge electrode 26.

In addition, because the discharging current of glow-discharge electrode opening part is excessive, therefore, the sputter or the taking off that cause because of electronics or ion bombardment may take place at the opening part of glow-discharge electrode, in order to prevent the appearance of this sputter or taking off, the most handy insulator 26d such as pottery or mica, the periphery by opening extends to interior perimeter surface from the outer surface of glow-discharge electrode, applies the periphery of glow-discharge electrode 26 openings.

Should be pointed out that with regard to production in enormous quantities Figure 16 or electrode group body shown in Figure 17 are better.

Claims (5)

1. composite discharge lamp, it comprises:

One slender glass tube, it has the middle part of relative two ends and on vertically;

Electrode assemblie is arranged in each end of described glass tube opposite end;

Described electrode assemblie comprises central electrode that is used for emitting electrons and the glow-discharge electrode of surrounding this central electrode, described glow-discharge electrode is made for the cover of an opening and closed bottom, it is characterized in that described being covered with is set to described opening towards a described glass tube end close with described cover, the middle part of described closed bottom on described glass tube is vertical.

2. the described composite discharge lamp of claim 1 is characterized in that forming an aperture in described closed bottom.

3. the described composite discharge lamp of claim 1 is characterized in that described cover made by transparent conducting glass.

4. the described composite discharge lamp of claim 1 is characterized in that described cover is coated with insulator along described opening.

5. the described composite discharge lamp of claim 4 is characterized in that described insulator is pottery or mica.

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