WO2000052736A1

WO2000052736A1 - Gas discharge lamp

Info

Publication number: WO2000052736A1
Application number: PCT/GB2000/000716
Authority: WO
Inventors: Rocco Borgese
Original assignee: Rocco Borgese
Priority date: 1999-03-01
Filing date: 2000-03-01
Publication date: 2000-09-08
Also published as: GB2347554A; GB9904686D0; AU5647000A

Abstract

A gas discharge lamp is manufactured by providing a gas discharge lamp and filling the lamp with inert filler gas and then adding a predetermined amount of vaporised plastic material, such as polystyrene, to the filler gas. A predetermined amount of mercury vapour may also be added to the filler gas in the lamp.

Description

"GAS DISCHARGE LAMP"

THIS INVENTION relates to a gas discharge lamp and method for manufacturing the same and more particularly to a gas discharge lamp having a variable gas discharge path. The invention also relates to a product incorporating the discharge lamp.

Conventional gas discharge lamps are filled with argon or neon gases and evacuated to produce an enclosed volume, typically elongate, provided at either end with excitation electrodes. When the electrodes are excited to an excitation voltage of approximately 9 kN, an ionisation path is established between the electrodes and the excited gas provides an illumination source. The ionisation path between the electrodes is stable so as to provide a constant light strip. It is a known practice to introduce a small amount of mercury vapour into an argon filled tube to improve the brightness of the resultant light source.

It is an object of the present invention to seek to provide a gas discharge lamp and method of manufacturing the same with a variable gas discharge path. Accordingly, one aspect of the present invention provides a method of manufacturing a gas discharge lamp comprising the steps of: providing a gas discharge lamp; filling the lamp with an inert filler gas; and adding a predetermined amount of vaporised plastics material to the filler gas.

In this Specification the term "plastics" material is used to mean a polymer material. The polymer maybe a thermoplastic polymer.

Advantageously, the method comprises the further step of adding a predetermined amount of mercury vapour to the filler gas in the lamp .

Conveniently, the mercury is added to the lamp as vaporised mercury.

Advantageously, the vaporised plastics material is added to the lamp by vaporising solid plastics material located in a reservoir of plastics material and exhausting the vaporised plastics material from the reservoir into the lamp.

Preferably, the reservoir of plastics material is connected to the lamp via a conduit with a restricted portion.

Conveniently, the lamp is evacuated prior to being filled with the inert filler gas, the lamp being evacuated slowly so as to prevent solid plastics material being drawn from the reservoir.

Advantageously, the lamp is filled with the filler gas to a pressure of between 10 to 15 ton-. Preferably, the lamp is filled with filler gas to a pressure which is approximately 30% more than the pressure which would be used in a conventional lamp of the same structure.

Conveniently, the resultant lamp is aged, after striking up, by being operated at a voltage greater than the normal operating voltage for a predetermined amount of time.

Preferably, the predetermined amount of time is in the region of one hour.

Advantageously, the plastics material is a polystyrene.

Another aspect of the present invention provides a gas discharge lamp comprising a gas discharge volume having two electrodes and a gas discharge path between the electrodes, the gas discharge volume being filled with a filler gas and a pre-determined amount of vaporised plastics material.

Preferably, the plastics material is a polystyrene.

Advantageously, the gas discharge volume also contains a predetermined amount of mercury.

Conveniently, the filler gas is neon.

Alternatively, the filler gas is argon.

Preferably, the cross-section of the lamp varies along the length of the lamp. A further aspect of the present invention provides a gas discharge tube for a gas discharge lamp having a stemming formed thereon, the stemming having an opening onto the tube, a reservoir to hold material and a constricted portion between the reservoir and the opening to prevent material from passing through the opening into the tube.

The invention also relates to a method of manufacturing a gas discharge lamp comprising the steps of: providing a gas discharge lamp; filling the lamp with an inert filler gas; and adding a pre-deteπnined amount of vaporised plastics material to the filler gas.

In order that the present invention may be more readily understood embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which:

FIGURE 1 is a cross-sectional side view of one end of a gas discharge lamp for use in the manufacture of an embodiment of the present invention,

FIGURE 2 is a cross-sectional side-view of a gas discharge lamp embodying the present invention, and

FIGURE 3 is a partly cut-away view of a product incorporating a gas discharge lamp.

Referring to the drawings, a gas discharge lamp embodying the present invention is manufactured by the following steps. Initially one or more sections of glass tube 1 are joined together and manipulated into a desired shape so as to form a single conduit having two open ends 2 of, for example, one metre in length. A respective electrode 3 is inserted at each end of the resultant tube 1 and the ends are sealed. The electrodes 3 are conventional gas discharge electrodes.

Adjacent each end of the tube 1 a stemming 4 is formed. Each stemming 4 comprises an opening 5 in the side of the tube 1 adjacent the tube end 2. The stemming 4 protrudes from the opening 5 into a narrow constriction 6 which subsequently opens out along a passage 7 of approximately 2 inches (50 mm) in length into a reservoir or bell 8. A feed tube 9 extends from the bell 8 to an open end 10.

The bell 8 of each stemming 4 is filled with a plurality of polystyrene balls (not shown), preferably a minimum of four 4 mm diameter balls. Additionally, the bell 8 of one (or optionally both) of the stemmings 4 is also provided with a 3 to 4 mm ball of mercury .

One of the open ends 10 of one of the feed tubes 9 is then sealed by heating the open end 10 to melting point with a blow lamp, for example, care being taken not to heat the balls within the bell 8 during the melting of the open end 10. Preferably, the feed tube 9 is at least 50 mm (2 inches) in length so that the sealing process does not cause any melting or vaporisation of the balls in the bell 8.

The open end 10 of the unsealed stemming 4 is then connected to an evacuation pump via a manifold (not shown). The tube 1 is evacuated through the stemming whilst the electrodes 3 are excited by a supply voltage of approximately 80 kN at 500 lnAs. The excited electrodes 3 heat up the surface of the tube during evacuation which is carried out until the tube reaches a pressure of approximately 1/100th atmospheric pressure and a temperature in the region of 280°C which can be easily identified as being the point at which a piece of paper in contact with the tube surface ignites. At this point, the electrodes 3 are switched off and evacuation continues. It should be noted that the conduit 7 through which evacuation is being effect between the bell 8 and the tube 1 is sufficiently long, of the order of 50 mm (2 inches), such that during the evacuation process the balls inside the bell 8 do not heat up or vaporise. Care should be taken that the tube 1 is evacuated slowly to prevent the polystyrene balls (and the mercury) being drawn from the bells 8. Evacuation is then stopped.

The tube 1 is then allowed to cool to ambient temperature. A source of filler gas injects a filler gas through the manifold into the tube 1. Preferably, the manifold allows for fluid comiection to both the evacuation pump and the source of filler gas. In the present example, the filler gas is neon and the tube is filled with neon to a pressure of between 10 to 25 torr and preferably in the region of 20 torr. Advantageously, the tube 1 is filled to a pressure which is approximately 30% to 50% more than the pressure to which a conventional lamp of the same structure would be filled.

The open end 10 of the stemming 4 through which gas has been injected is sealed whilst still attached to the manifold and the tube 1 is then removed from the manifold.

The tube 1 is then mechanically manipulated such that the balls within one bell 8 fall down the conduit 7 until they encounter the constriction 6 formed at the entry into the tube. Since the balls have a diameter of approximately 4 mm, the constiiction 6 should be fonned to be of the order of

2 to 3 mm in diameter.

Once the balls are in position adjacent the constriction 6, the balls are heated to vaporise the polystyrene. A preferred method of heating the balls 4 is to begin heating at the sealed end of the stemming 4 and progressively move the heat source down the stemming 4 such that the vaporisation products from the polystyrene balls (and the mercury if this is present in the stemming 4) are forced from the stemming 4 into the tube 1. The stemming 4 is then sealed at the narrow constriction 6 into a nipple 1 1 and the stemming itself is removed as shown in Figure 2 such that any vapours produced by the vaporised polystyrene (and mercuiy if present) are contained in the tube 1.

This process is then repeated on the other stemming 4 in the same fashion so that the polystyrene balls (and any mercuiy present) are vaporised and exhausted into the tube, the stemming 4 being sealed into a nipple 11 at the other end of the tube 1.

The resultant tube 1 is connected to an appropriate power supply and the electrodes 3 excited to approximately 10 kV at 50 mA for a period of between

3 to 20 minutes before the tube will strike up. After striking up, the tube is "aged" for approximately one hour under the same operating conditions. The ageing process serves to fix the characteristics of the resultant gas discharge lamp. If the ageing process is not carried out, then the lamp will not function optimally although some of the benefits of the present invention may still be achieved. Subsequent to the ageing process, the tube may be connected to a conventional neon power supply such as a transformer providing an up voltage in the region of 9 kN at a running current in the region of 20 to 25 mA.

In normal operation, a gas discharge path is established between the two electrodes 3 at the ends of the tube 1 embodying the present invention. However, unlike conventional gas discharge lamps, the gas discharge path in gas discharge lamps embodying the present invention varies with time in an aesthetically pleasing manner. For example, the gas discharge path may be seen to swirl and gyrate along the length of the tube 1. Another effect is that the gas discharge path appeals to break-up or segment in various regions causing a "jelly bean" effect. A further effect which may be produced in the neon filled tube is that the colour of the discharge in the tube at one electrode which may, for example, be blue, transforms gradually or in segments to a pink colour at the other end of the tube. Areas of the blue gas discharge path may also include some pink areas and vice versa.

The behaviour of these effects varies with different parameters such as the ambient room temperature. Also, during the manufacture of the tube, the characteristics of the effects can be changed by altering the pressure at which the tube is filled with the filler gas and vaiying the diameter of the tube. At higher gas pressures, greater activity is noted. Additionally, the frequency of movement of the gas discharge path within the tube varies with the applied operating voltage.

Various effects may also be achieved by putting mercuiy in both of the stemmings rather than just in a single stemming as described above. It is also possible to achieve effects by placing polystyrene in only one stemming and not in another, in which case the mercuiy can be added in either stemming. In the case where polystyrene is included in both stemmings and also a certain amount of mercury is included in both stemmings, the neon tube can produce three colours, blue/pink/red, which occur in three substantially separate bands along the tube length. Some effects are also obtained if no mercuiy is added to either stemming, although the use of mercuiy is preferred since it tends to lend brightness and clarity to the effects.

Whilst the above described examples use neon as the filler gas, argon may also be used as the filler gas. Whilst the argon tube can only create a single colour blue, movement of the gas discharge path within the tube and jelly-beaning effects are still achieved.

Other plastics materials have also been found to cause some or all of the above effects, but polystyrene achieved the best results.

By way of illustration, the following table sets out some exemplifying filling pressures for conventional glass tubes of various diameters filled with argon or neon, and the corresponding filling pressures required by a gas discharge lamp embodying the present invention. In this example, the filling pressures are approximately 30% greater than conventional pressures.

Figure 3 shows a product 20 incorporating a discharge lamp as described above. The product comprises a picture 21, which may, for example, be a painting or a print. Mounted to extend generally parallel with the surface of the picture are two discharge lamps 22, 23 of the type described above. A first sheet 24 of transparent material, such as glass or a transparent plastic, is located in front of the discharge lamp 22 by means of four elongate screws 25 which pass through the sheet 24 and thiough spacer tubes to engage the picture. A second sheet 26 of transparent material (part of which is shown cut away) extends over the second discharge tube, and is mounted by screws 27 which are associated with spacer tubes. The transparent sheets may be "frosted" in selected areas.

The discharge lamp, when provided with electric power to provide a discharge, may provide an appealing effect in the context of the picture.

In the present specification "comprise" means "includes or consists of and "comprising" means "including or consisting of .

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS:

1. A method of manufacturing a gas discharge lamp comprising the steps of: providing a gas discharge lamp; filling the lamp with an inert filler gas; and adding a pre-determined amount of vaporised plastics material to the filler gas.

2. A method according to Claim 1 comprising the further step of adding a pre-determined amount of mercuiy vapour to the filler gas in the lamp.

3. A method according to Claim 2, wherein the mercuiy is added to the tube as vaporised mercuiy.

4. A method according to any preceding claim, wherein the vaporised plastics material is added to the lamp by vaporising solid plastics material located in a reservoir of plastics material and transferring the vaporised plastics material from the reservoir into the lamp.

5. A method according to Claim 4, wherein the reservoir of plastics material is connected to the lamp via a conduit with a restricted portion.

6. A method according to Claim 4 or 5, wherein the lamp is evacuated prior to being filled with the inert filler gas, the lamp being evacuated slowly so as to prevent solid plastics material being drawn from the reservoir.

7. A method according to any preceding claim, wherein the lamp is filled with the filler gas to a pressure of between 10 to 25 torr.

8. A method according to any preceding claim, wherein the lamp is filled with filler gas to a pressure which is approximately 30% to 50% more than the pressure which would be used in a conventional lamp of the same structure.

9. A method according to any preceding claim, wherein the resultant lamp is aged, after striking up, by being operated at a voltage greater than the normal operating voltage for a predetermined amount of time.

10. A method according to Claim 9, wherein the predetermined amount of time is in the region of one hour.

11. A method according to any preceding claim, wherein the plastics material is a polystyrene.

12. A gas discharge lamp mode by a method of any one of the preceding Claims.

13. A gas discharge lamp comprising a gas discharge volume having two electrodes and a gas discharge path between the electrodes, the gas discharge volume being filled with a filler gas and a pre-determined amount of vaporised plastics material.

14. A gas discharge lamp according to Claim 13, wherein the plastics material is a polystyrene.

15. A gas discharge lamp according to any one of Claims 13 or 14, wherein the gas discharge volume also contains a predetermined amount of mercury.

16. A gas discharge lamp according to any one of Claims 13 to 15, wherein the filler gas is neon.

17. A gas discharge lamp according to any one of Claims 13 to 15, wherein the filler gas is argon.

18. A gas discharge lamp according to any one of Claims 13 to 17, wherein the cross-section of the lamp varies along the length of the lamp.

19. A gas discharge tube for a gas discharge lamp having a stemming formed thereon, the stemming having an opening onto the tube, a reservoir to hold material and a constricted portion between the reservoir and the opening to prevent material from passing thiough the opening into the tube.

20. A product comprising a picture, the picture having a discharge lamp according to any one of Claims 12 to 19 mounted thereon.

21. A product according to Claim 20 wherein the discharge lamp extends substantially parallel to the surface of the picture and a sheet of transparent material is mounted in front of the discharge lamp.

22. A product according to Claim 21 wherein at least regions of the transparent sheet are "frosted".