EP0591777A2 - Process for manufacturing a low power, high pressure discharge lamp having a single pinch, and high pressure discharge lamps - Google Patents

Abstract

In the case of a method for manufacturing a discharge vessel whose discharge volume (3) is sealed by a single pinch (4), the discharge volume (3) is produced in its final shape (by means of blow moulding) at the same time that the open end (25) is sealed. An incline (17) is advantageously formed on the narrow sides (14) of the pinch in this case. <IMAGE>

Description

The invention relates both to a method for producing high-pressure discharge lamps of small wattage that are squeezed on one side, and to such lamps themselves. Typical wattages of these lamps are between 35 and 150 W. Frequently, the actual quartz glass discharge vessel is still surrounded by an outer bulb. The discharge vessel, in which two angled electrodes are arranged, encloses an ionizing filling, which usually contains ignition gas, metal vapors and metal halides. The area of application of these lamps is primarily interior and shop window lighting, because they are characterized by high luminous efficacy and good color rendering. These lamps are described for example in DE-OS 32 32 207 and 38 42 483.

The production of these single-sided lamps is much more difficult than with double-pinched lamps. During manufacture, a one-sided squeeze disturbs the symmetry of the discharge volume much more sustainably than a two-sided squeeze. In addition, the operating pressure of these lamps (up to approx. 50 bar) is generally higher due to the smaller electrode spacing and the more uniform heating of the discharge space and therefore the risk of bursting is greater than with comparable lamps pinched on both sides (up to approx. 28 bar). In addition, the heat losses in the case of extremely small-watt lamps (below about 100 W) must be considered particularly strongly, which is why two-sided squeezed discharge tubes are hardly used for this. The extremely small volumes required here (typically only 0.1 to 3.0 cm³), however, require special care in the manufacture in order to keep the spread in the volume size and thus in the lamp properties within an acceptable range.

The usual manufacture of such lamps takes place, as indicated in EP-A 369 370, in that a pump tube is formed on a quartz tube, then the tube is heated and the actual discharge volume is blown free without support by introducing an inert gas under excess pressure. As the next step, the end opposite the pump tube is squeezed under inert gas purging with two crimping jaws with prior heating. However, it has been shown that the size of the discharge volume fluctuates considerably from lamp to lamp in the case of free blowing and, in addition, the discharge volume is subsequently deformed when squeezed, which ultimately causes the undesirable scattering of the lamp properties and leads to inhomogeneities in the wall thickness distribution.

Accordingly, it is proposed in EP-A 369 370 to dispense with a pump tube and instead to seal a tube end on one side by means of a form roller, then to precisely define the final shape of the future lamp vessel by means of blow molding and then after rinsing and filling through the still open one second pipe end to seal this with a pinch.

This process has two disadvantages: the filling is already in the discharge volume during the preparatory heating and the actual crushing process and therefore has to be cooled in a complex manner; secondly, the precisely pre-shaped volume is deformed again during the squeezing process.

Furthermore, from DE-OS 39 39 193 a manufacturing process for small-watt metal halide lamps is known, in which the pinch is first formed and the discharge volume is preformed, and only then is the discharge volume blown into the desired shape, obviously via the still open pump stem. In this way, the desired discharge volume can be maintained almost exactly, but only at the expense of time-consuming and energy-intensive production, since the discharge vessel has to be heated again for the blow molding.

It is an object of the present invention to produce a discharge vessel for a high-output discharge lamp of small wattage that is squeezed on one side in a reproducible and cost-effective manner. Another task is to improve the operational safety of high-pressure discharge lamps squeezed on one side.

These tasks are solved by the characterizing steps of claim 1 and by the high-pressure discharge lamps of claims 9 and 10. Particularly advantageous configurations can be found in the dependent claims dependent thereon.

According to the invention, the sealing and the final shape of the discharge vessel are made in one Work step carried out. This is advantageously done by squeezing the tube piece equipped with a pump tube with four crimping jaws (two main and two side crimping jaws), wherein at the same time the shaping jaws which determine the shape of the discharge vessel comprise the tube section which is to form the future discharge volume. An inert gas (nitrogen or argon) with excess pressure is introduced into the future discharge volume via the pump tube. The four crimping jaws are each advantageously equipped with a shaping attachment (extension part), so that separate molding jaws can be dispensed with. The discharge volume can thus be reproduced particularly well. The volume fluctuations are reduced from around 7% to 4% now.

A very special advantage of this method is that the simultaneous creation of squeeze and discharge volume, the intermediate transition area can be designed in an ideal manner by the side squeeze jaws have obliquely projecting ramps that shape the transition area so that a defined slope between the Wall of the discharge volume and the narrow sides of the bruise, which is arranged substantially below the discharge volume. In this way, disruptive "pockets" are eliminated, which would form due to the lateral action of the side crushing jaws without this trick in the transition area between the discharge volume and the crushing during the crushing process.

These "pockets" increase the discharge volume in an unpredictable manner and reduce the one-sided Lamps particularly important resistance to possible bursting. The obliquely projecting ramps on the side jaws, however, divert the flow of quartz during the squeezing process in the direction of the pinch seal, so that these "pockets" cannot even arise. The burst pressure is increased by up to 20%.

A problem with "pockets" is also known for double-sided discharge vessels (EP-A 271 927). There, however, these "pockets" lead to an undesirable lowering of the "cold-spot" temperature in the zone behind the electrodes and they are also eliminated in a different manner, namely by the side crimping jaws pressing dents into the wall of the discharge volume with fingers protruding at right angles.

The bevels presented here are also to be clearly distinguished from the bevels described in DE-OS 38 42 483 for metal vapor lamps pinched on one side. These are positioned slightly below the electrodes next to the discharge volume and are also intended to increase the "cold spot" temperature behind the electrodes. They have no function during manufacture. They therefore do not serve to improve the burst protection by avoiding "pockets" below the discharge volume. Such "pockets" could not even occur in this prior art because the discharge vessel was obviously closed with only two pinch jaws, which can be concluded from the width of the pinch, which is significantly greater than the discharge volume.

The slope according to the invention is particularly advantageously inclined at approximately 20-30 ° against the narrow side, since the formation of the "pockets" is then most reliably avoided.

For optimal control of the quartz flow when squeezing, it is particularly favorable that the main crimping jaws have side bevels which interact with the obliquely projecting ramps of the side crimping jaws by increasing their inclination, in particular by 15-30%, so that the quartz flow from Discharge volume is directed away. This creates a double-T-shaped pinch on the discharge vessel, in which the outer edge of the bevel has a greater inclination, in particular by 15-30%, than the inner edge of the bevel.

The method according to the invention can be modified in such a way that, in order to increase the machine output, the tube piece is first roughly pre-shaped before closing and at the same time final forms. This is done by approximating a part or almost the entire pipe to the desired final shape.

For example, after moderate heating, the open end of the tube is deformed by compression molding so that it has an oval cross section. Various techniques are described in DE-OS 35 37 880, 35 37 879 and 35 37 878.

This in particular facilitates the insertion of the electrode system and thus prevents the foils or electrodes from accidentally sticking to the glass wall during insertion.

Another or additional possibility is to preform the area of the future discharge volume by heating this area and then - with the open tube end being closed - by blow molding to approximate the future shape. In particular, the area of the future discharge volume close to the pump tube, which is only insufficiently captured during final shaping, can be precisely shaped. In many cases, especially in the case of relatively large discharge volumes, preforming by means of shaping rolls in this area also meets the requirements.

The preforming of the future crushing area, in particular by compression molding, has the particular advantage in the present case that it facilitates the safe insertion of electrode systems whose straight electrode shafts are slightly (approx. 5 °) inclined outwards with respect to the optical axis. In principle, however, the use of such electrode systems is not restricted to this special production method.

A lamp with such inclined electrodes has the advantage, regardless of the manufacturing process, that the electrode spacing is increased. As a result, a higher operating voltage is achieved, so that the operating pressure can be reduced. Ultimately, this measure also improves the burst protection.

In particular, a further improvement in operational safety can be achieved by combination with the bevels on the narrow sides of the pinch.

Figur 1

eine Metallhalogenidentladungslampe, die gemäß der vorliegenden Erfindung hergestellt wurde, in Seitenansicht (Figur 1a) sowie einen Querschnitt durch die Quetschung dieser Lampe (Figur 1b)

Figur 2

die Herstellung des zukünftigen Entladungsgefäßes in mehreren Schritten (Figuren 2a bis 2f)

Figur 3

die bei der Herstellung verwendete Vorrichtung in Seitenansicht (Figur 3a) sowie in Draufsicht (Figur 3b).

The invention is explained below using several exemplary embodiments. Show it:

Figure 1

a metal halide discharge lamp, which was produced according to the present invention, in side view (Figure 1a) and a cross section through the pinch of this lamp (Figure 1b)

Figure 2

the production of the future discharge vessel in several steps (Figures 2a to 2f)

Figure 3

the device used in the manufacture in side view (Figure 3a) and in plan view (Figure 3b).

The 35 W high-pressure discharge lamp 1 shown in FIG. 1 consists of a discharge vessel 2 made of quartz glass, squeezed on one side, with an ellipsoidal (or also spherical or barrel-shaped) discharge volume 3, which is arranged in particular in an outer bulb (not shown). On the side of the volume 3 opposite the pinch 4, a pump connection 5 is arranged. The electrodes consist of straight shafts 6, to which tips 7 bent approximately at right angles are attached, the shafts 6 being inclined outward about 5 ° with respect to the optical axis A and the tip 7 being able to be coiled or spherical. They are melted into the pinch 4 by means of molybdenum foils 8. A holding wire 9 for a getter, which acts in the outer bulb, is also melted into the pinch 4. The power supply lines 10 connected to the foils 8 Molybdenum also serve as a holder for the discharge vessel 2 in the outer bulb. The discharge vessel 2 has an internal volume 3 of 0.11 cm 3. The filling is composed, for example, of NaJ, SnJ₂, TlJ and Hg, and argon is used as the ignition gas. The ellipsoidal discharge volume 3, which is surrounded by a 1.3 mm thick wall 11, is in a very good approximation (due to the blow molding) due to a large semi-axis of approximately 9.0 mm overall length and two perpendicular to the connecting line of the electrode tips 7 small semiaxes with a total length of 4.8 mm each are characterized. The operating pressure is around 35 - 40 bar. This low pressure (approx. 80% of the usual value) results from the relatively large electrode spacing of 5.2 mm (previously approximately 4.5 mm), which is achieved in that the straight electrode shafts 6 (diameter 0.3 mm) face each other the optical axis A are inclined outwards by approximately 5 °. The current flowing through the shafts 6 is approximately 0.5 A. Since there is a risk of an arc discharge between the shafts 6 at the point at which they emerge from the wall 11 in such an arrangement during ignition, it is expedient to use the shafts 6 with a sleeve 12 made of insulating material (eg ceramic or quartz glass).

The cross section of the pinch seal 4 which seals the discharge volume 3 has the double T shape which is known per se (ie, two “T” abut one another at the base). With a length of 35 mm, it has a width of approximately 11 mm on the broad sides 13 of the pinch, which corresponds approximately to the maximum width of the discharge vessel 2. On the narrow sides 14, the width, including that which determines the double T shape, is Bead 15 about 5 mm. The narrow sides 14 are each connected to their starting point 16 on the wall of the discharge volume via a bevel 17. The outer surface (or, in a side view, the outer edge) 18 of the bevel is inclined by approximately 26 ° to the optical axis A, whereas the inner edge 19 of the bevel, which is produced by the bead 15, is only inclined by approximately 20 ° to the axis A, so that the bead 15 tapers towards the starting point 16. For an optimal effect preventing the formation of “pockets”, it is essential that the bevels 17 start at approximately the level of the lower edge of the discharge volume 3 facing the pinch 4.

In other exemplary embodiments, lamps of similar design have a power of 150 W or 70 W. The inside diameter of the discharge volume is 0.82 cm³ or 0.28 cm³ at an operating pressure of 25-30 bar or 35-40 bar. The ellipsoid forming the discharge volume has a large semiaxis of 15.0 and 10.8 mm and small semiaxes of 10.2 and 7.0 mm, respectively. The lamp current is 1.8 A or 0.9 A with a diameter of the electrode shaft of 0.5 mm or 0.4 mm.

One possibility for producing the discharge vessel is described with reference to FIG. 2.

A tube section 20 made of quartz glass is inserted into a rotating receptacle (arrow B) and heated in the center by means of a gas burner 21 (FIG. 2a) until it can be pulled apart (arrows C1, C2), so that two tube sections 20a, 20b are formed between which a central portion 22 of smaller diameter is arranged over tapered portions 23, the central section 22 later forming the two pump tubes (FIG. 2b). After the two pipe sections 20a, 20b have been separated, the area of the taper 23 between a pipe section, for example 20a, and the associated pump tube 22 'is heated with a gas burner 21' and shaped like a dome by means of a rotating shaping roller 24, the part being desired at this point Radius of the future discharge volume is adjusted. The parameters determining this radius are the width of the heating zone and the shape of the shaping roller 24 (FIG. 2c).

Subsequently, the open end region 25 of the pipe section 20a is moderately heated and deformed by mold jaws 26 so that it has an oval cross section (FIG. 2d). The mold jaws 26 are advantageously so wide (26a) that part of the future discharge volume 3 'is roughly preformed.

Next (FIG. 2e), an interchangeable receptacle 27, the two electrode systems 28, consisting of power supply lines 10, sealing foils 8 and electrodes 6, 7, the shafts 6 of which are inclined outwards by 5 °, is inserted through the open deformed end 25 of the tube piece 20a (Arrow). About the pump tube 22 'N₂ or another inert gas for purging and cleaning the discharge vessel is supplied. The interchangeable receptacle 27 is provided on its outer surface with resilient element 27a known to the person skilled in the art (preferably three elements; only one is visible in FIG. 2e). These are quasi supported on the inner wall of the tube piece 20a and thereby hold the interchangeable holder 27 by themselves. The defined position of the electrode systems 28 within the future lamp vessel is achieved by lowering a punch 27b, which is connected to the exchangeable receptacle via an arm 27c, to a stop (schematically shown) for inserting the exchangeable receptacle 27 into the tube piece 20a. This process is also known to the person skilled in the art and is therefore not shown separately (FIG. 2e).

Finally (FIG. 2f), the entire pipe section 20a, with the exception of the pump pipe 22 'and the immediately adjacent region of the dome-like taper 23, is brought to processing temperatures by gas burners 21' '.

A crimping machine 29 (FIG. 3) with two main crimping jaws 30 (one is partially removed in FIG. 3a) and two side crimping jaws 31 now seals the open pipe end by means of a double-T-shaped crimp. The crimping jaws 30, 31 advantageously have extension pieces 33a, 33b attached to the actual crimping surfaces 32a, 32b. These have concave troughs 34a, 34b (indicated by dashed lines) on their broad sides facing the pipe section, which in the closed, ie, squeezing, state of the squeezing machine 29 almost fit together and define the shape of the discharge volume. Within a very short time after the crimping jaws 30, 31 have been moved together (a few 100 ms), the pumping tube 22 'N 2 or another inert gas is introduced into the future discharge volume under slight overpressure and the discharge volume 3 is thus formed in the region of the extension pieces 33a, 33b.

At the same time, ramps 35, which form the transition area between the squeeze surfaces 32b and the extension pieces 33b, produce the bevels 17 on the narrow sides of the squeeze (FIG. 1) on the two side squeeze jaws 31 (FIG. 3), with bevels 36 on the two main squeeze jaws 30 interaction. The bevels 36 taper the width of the squeeze surfaces 32a of the main jaws to the width of the associated extension pieces 33a. They produce the inner edge 19 of the bevels in the finished discharge vessel (FIG. 1).

As FIG. 3 shows, the four crimping jaws 30, 31 do not abut one another in the closed, that is to say crimping state, but rather leave some leeway, so that in the region of the crimping surfaces 32a, 32b the bead 15 of the crimp, which is double-T-shaped in cross section can train. The squeezing surfaces 32a of the main jaws 30 also have the known centering knobs 37 and centering recesses 38 for the power supply lines and for the holding wire 9 arranged in the center. It should also be noted that the main crimping jaws 30 have a cutout 39 in the area of the zenith, that is to say at the point where the pump tube 22 'starts. In order not to endanger the stability of this area, it is neither heated nor shaped. The discharge vessel 3 thus shaped is then filled through the pump tube 22 '. Then the pump tube attachment is heated and the pump tube is pulled off, so that the pump nozzle 5 remains.

The manufacturing process presented here as an example can be modified in various ways. In particular, preforming can be dispensed with, for example, if electrode shafts are used which are arranged parallel to the optical axis.

Furthermore, the pump tube can be attached by attaching a separate cannula to the tapered tube end, so that there is no need to pull the pump tube out of the end of the tube section.

Finally, the pipe section 20a in particular can be heated to the pinch temperature before the electrode system 28 is inserted. The cleaning rinsing can also be carried out at any time before the squeezing process.

Claims (10)

Method for producing a discharge vessel for a low-power high-pressure discharge lamp, in which a discharge volume (3) is sealed by means of a single pinch (4), the pinch (4) introducing an electrode system (28) which is at least two electrically separate from one another. Has insulated power supply lines (10) and electrodes (6, 7) connected to them and arranged within the discharge volume (3), characterized by the following working steps: a) Manufacture of a tube section (20a) made of quartz glass, the first end (25) of which is open and at the second end of which a pump tube (22 ') is attached in the center via a dome-like taper (23) b) Perform the following three steps in any order: - Introducing an interchangeable holder (27) holding the electrode system (28) through the open first end (25) of the pipe section at a predetermined location - Cleaning rinsing of the discharge vessel - Heating the pipe section (20a) to just below the pump tube (22 ') including the open end (25) c) Sealing the open end (25) by a squeezing process, at the same time the discharge volume (3) is brought into its final shape by blow molding, by introducing an inert gas under excess pressure through the pump tube (22 ') into the pipe section (20a) d) Introducing the metered amounts of the filling substances and the ignition gas e) closing the discharge vessel by pulling off the pump tube (22 '). Method for producing a discharge vessel according to claim 1, characterized in that in step (c) the squeezing process is carried out by a four-jaw squeezing machine (29) with two main and two side squeezing jaws (30, 31), so that the squeezing (4) has a double Receives a T-shaped cross section and has a bead (15) with an inner (19) and an outer edge (18), at least the side crushing jaws (31) having obliquely projecting ramps (35) which have a bevel (17) between the wall (11 ) form the discharge volume and the narrow sides (14) of the pinch, which is arranged substantially below the discharge volume (3). A method according to claim 2, characterized in that the outer edge (18) of the bevel (17) is inclined approximately 20-30 ° against the optical axis (A) of the discharge vessel. Method according to claim 2 or 3, characterized in that the inclination of the inner edge (19) is approximately 15-30% weaker than the inclination of the outer edge (18). Method according to claim 1, characterized in that in method step (a) the radius of the dome-like taper (23) in the vicinity of the pump tube (22 ') is preformed in a defined manner by heating and pressing on a shaping roller (24). Method according to claim 1, characterized in that in step (c) the pinching takes place by means of pinching jaws (30, 31) which have an extension part (33) with a concave trough (34) for blow molding the discharge volume. Process according to Claim 1, characterized in that an additional process step (x) is inserted as part of process step (b): - Heating and deforming at least part of the pipe section (20a). Method according to Claim 7, characterized in that method step (x) is inserted directly after method step (a) and in that in method step (b) electrode shafts (6) are used as part of the electrode system which are slightly inclined outwards so that the electrode gap is extended. High-pressure discharge lamp of low power with a discharge vessel (2) made of quartz glass, in which a discharge volume (3) is sealed by means of a single pinch (4), two electrodes (6, 7) being passed through the pinch (4) and the pinch ( 4) has two broad sides (13) and two narrow sides (14) and has the shape of a double "T" in cross section, characterized in that each narrow side (14) is connected to the wall (11) of the discharge volume via a slope (17) is, wherein the slope (17) is arranged substantially below the discharge volume (3), whereby the discharge volume (3) no longer has any troublesome "pockets". High-pressure discharge lamp of low power with a discharge vessel (2) made of quartz glass, in which a discharge volume (3) is sealed by means of a single pinch (4), two electrodes (6, 7) being passed through the pinch (4) and consisting of straight electrode shafts (6) exist, at which approximately right-angled electrode tips (7) are attached, characterized in that the electrode shafts (6) are inclined relative to one another in such a way that the electrode spacing is extended.

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