DE2555551A1 - Refractory tube production - Google Patents

Abstract

In the mfr. of a refractory tube starting from a preformed tube of refractory material round which a concentrated heating zone is arranged by means of radiant energy of uniform intensity in such a way that a molten ring of uniform height is formed in, and is displaced along, the tube, the height being such that the surface tension forces and gravitational force hold the molten ring connected to the solid parts of the tube on each side thereof while the relative translatory motion between the refractory tube and the heating zone is regulated so as to displace the molten ring along the tube, (a) the radiant energy is formed by laser energy and the heating zone is formed by a series of laser beams of semicircular form uniformly distributed round the tube and each beam is focussed on the refractory tube to form the molten ring therein, and (b) the focussing is carried out in such a way that the energy density distribution of each beam is adjusted to give equal absorption of the laser energy round the whole surface of the tube within the molten ring. Enables the virtually full theoretical density to be achieved by eliminating any porosity introduced by e.g. impurities. Also permits, when appropriate, the production of a tube as a single crystal, so that limitations arising from the presence of grain boundaries, e.g. chain of atmosphere during treatment, are no longer of importance. The technique is particularly suitable for the production of Al2O3 envelopes for sodium halide-especially NaI- lamps, which operate at high pressure and temperature.

Description

MÜLLER-B ORJE · GROEWING · DEÜIEL · SCiiÖIi ■ HERTEL

FATENTAIfVÄLTE

DR. WOLFGANG MÜLUR-BOHE HANS W. GROENING. D1PL.-1NG. DR. PAUL DEUFEL. DiPL.-CHEM. DR. ALFRED SCHÖN, DIPL.-CHEM. WERNER HERTEL. DIPL.-PHYS.

Hl / V / e / th - L 1087

fa AT W3

Arthur D. Little, Inc., Cambridge, Hass. (UNITED STATES.)

Method and device for producing a heat-resistant

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The invention relates to a method of making tubes from refractory materials, and particularly relates on the manufacture of a heat-resistant tube in amorphous Form, in polycrystalline form or in the form of a single crystal.

The term "heat-resistant" or "refractory" is used hereinafter to refer to materials which are relatively have high melting points and which can be relatively highly corrosive. It should be amorphous and crystalline Materials may be included, including glass, including materials in polycrystalline form and in the form of a single crystal. Compounds such as aluminum oxide, silicon oxide, thorium oxide, Zirconium oxide, xtterium oxide, etc. are also included. Farther such materials include intermetallic compounds such as gallium arsenide and pseudo binary compounds such as AlAs-GaAs

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as well as elements like germanium and silicon. Any refractory or heat resistant materials suitable for the purpose of the invention must be able to exist in a molten state, either under ambient conditions or in a special atmosphere.

A number of refractory materials have been used in tubular form. by conventional methods using Powder manufactured and at present, aluminum oxide is the most prominent of these refractory materials, of which high temperature resistance and a high specific electrical resistance are required and which are chemically inert must be. Aluminum oxide can therefore be considered when considering the state of the art and the possible uses as Example can be used. Of course, one of the other heat-resistant materials, in particular the Oxides of yttrium, zirconium, and thorium, are brought into tubular form and they can be used in the same way as is the case with aluminum oxide.

Alumina tubes are currently used to make capsules for high pressure sodium halide lamps. The term "high pressure" is relative in this context, since the actual gas pressure in such Lamp is less than an atmosphere. It is desirable to use sodium halide (usually sodium odide) lamps operate at high pressures, as the light emitted is no longer yellow light, as occurs with sodium vapor lamps, but approaching white light. However, since the pressure in the light capsule is increased, the pressure also increases Operating temperature and the resulting higher heated gases become too corrosive for capsules made of silica glass. This has resulted from the use of capsules

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Out of aluminum oxide, which is produced by sintering the aluminum oxide in the desired shape. This process produces a polycrystalline form of the Alumina. Alumina in the form of a multicrystalline is usually not transparent, which means that the Capsule absorbs energy and thus heats up more than if it were transparent. This increased operating temperature such a capsule poses two problems. The first is due to being in a polycrystalline ceramic Material such as aluminum oxide, impurities separate themselves at the grain boundaries. These impurities are high Dimensions movable and they interact with the gases in the lamp capsule, serving as a getter for these gases. Since initially only a few milligrams of gas are present in the capsule, the effective elimination of one is reduced Milligrams reduce the quality of the light by reacting with the impurities. The second problem is based on the The fact that capsules made of aluminum oxide are closed with end caps and hermetically sealed on them have to. When the tube temperature rises, the thermally induced tensions increase, which makes it even more difficult it becomes more difficult to achieve a reliable hermetic seal.

These two problems can be eliminated or reduced to a minimum if the tube is out of one Single crystal could be formed with the source of impurities switched off at the grain boundaries and thus the gettering of the gas in the capsule would be eliminated. In addition, the lamp would be at a lower level Working temperature, as pure aluminum oxide is transparent in the form of a single crystal and does not absorb energy due to light scattering.

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This in turn reduces the rate or extent of reaction of the entrapped gas as well the change in voltage at the hermetically sealed connections of the tube ends and the caps. In the end can be a capsule made of a single crystal for a given light output in terms of dimensions be smaller, as higher energy densities can be transmitted through the capsule walls.

Although the method and the device according to the invention are not based on "the formation of a heat-resistant As a tube in the form of a single crystal is limited, such a heat-resistant tube can be manufactured thereby so that the associated benefits are achieved.

The invention is essentially based on the object to provide a method for forming heat-resistant tubes, with which in particular such a tube in the ■ Shape of a single crystal. can be produced. Furthermore, the cross-sectional shape and the wall thickness of such a heat-resistant tube can be varied and it should be used widely in high-temperature materials including those normally referred to as corrodible. In the end is intended with the invention a device for forming heat-resistant Tubes, especially in the form of a single crystal. proposed for a variety of Materials can be used.

The invention accordingly encompasses various stages and the relationship of one or more such stages to one another as well as a device with structural features, connections of elements and the arrangement of parts, which serve to to carry out these procedural steps.

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The method according to the invention is essentially distinguished characterized in that a prefabricated Eöhrenrohling from a Heat-resistant material is designed as a feed tube that a concentrated heating zone around the tube blank is formed by means of a radiant energy of substantially uniform intensity, so that a a molten ring of substantially uniform height is produced all the way through the tube, that the height is chosen so that the forces of surface tension and the gravitational pull of the molten ring with massive sections on either side of the molten one Keep the ring of the tube in contact so that a relative translational movement continues in a controllable manner between the refractory tube and the heating zone, so that thereby the molten ring through the Tube is moved further, further characterized in that The radiation energy is laser energy that continues to contain an inverse number of laser bundles in the production of the heating zone one. Halbrxngkonfiguratxon are used, which are arranged equidistantly around the tube, that each of the laser beams is focused on the refractory tube with a half-length configuration to form the molten ring in the tube, that furthermore the focusing takes place in such a way that the energy-dense distribution of each bundle is formed in such a way is that essentially the absorption of the laser energy around the entire surface of the tube within the molten Ring is balanced.

The massive sections on either side of the melted The ring can be rotated in the same direction or in opposite directions and the tube can be used as a single crystal be formed by using appropriately shaped seed crystals. When each end of the tube is kept separate

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will and if separate movement devices one or "be assigned to both of the ends of the two fixed sections (one on each side of the molten ring) it is by adjusting the speed on the agitators or on a movement device possible, with a suitable one Setting the relative speed in relation to the other movement device or by setting the speed, with which the heating zone is moved to control the thickness of the final tube wall accordingly. There are too other process modifications are possible.

A device preferred for carrying out the method according to the invention is characterized in that the heating device a laser device having at least one Bundles of radiant energy is supplied by the optical device comprising means for expanding the bundle, that further means is provided for dividing the resulting expanded bundle into a plurality of bundles, which substantially equidistant from the surface of the tube are arranged that an energy distribution device is also provided to ensure the energy-density distribution of each bundle, which belongs to the plurality of bundles, to be designed essentially in such a way that the absorption of the radiant energy is leveled around the entire surface of the tube, within the molten ring, and that means provided to focus each of the plurality of bundles onto the surface of the tube within a heating zone, which surrounds the tube, a substantially uniform heating of the tube surface being achievable.

A radiation shielding device can preferably also be provided be, which surrounds the heating zone, and it can also be provided a device which serves to the massive

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Sections of the tube either in the same direction or in to rotate in opposite directions. Finally, a 'device can be used to be a controlled or controlled one Build atmosphere around the tube. Advantageously, a device can also be used to to control the movement of the receiving element in such a way that that the movement of the molten ring is triggered.

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The invention is hereinafter "for example based on the Drawing described; in this show:

Fig. 1 shows a tube during manufacture in a longitudinal section, the finished heat-resistant tube in has essentially the same wall thickness as the preformed one Output tube,

J ¹ Xg. 2 a tube during manufacture in a longitudinal section, the finished heat-resistant tube having a reduced wall thickness,

3 and 4 representations of typical cross-sectional shapes, wherein the cutting plane is perpendicular to the tube axis,

5 schematically shows the use in a perspective view a seed part in the form of a ring for training a tube made of a single crystal,

Figures 6 and 7 schematically illustrate the use of a seed member in the form of a flat plate to form a tube from a single crystal,

8 shows the use of a seed part in the form of a rod to form the tube from a single crystal,

9 "through 12 show the steps for beginning the formation of a A tube made of a single crystal according to a preferred embodiment of the invention, wherein a combination is used from a feed tube and a seed crystal,

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15 "to 17 other combinations of a supply pipe and a seed crystal,

18 shows a plan view of an optical system which can be used in conjunction with a laser to achieve the To form heating device, v / obei this optical system has a device which serves to focus the laser beam in such a way that four beams are formed with each controlled energy density,

19 shows a schematic representation of the effect of the focusing device of Fig. 1.8,

20 shows a side view of an embodiment of the radiation shielding device, which surrounds the hot zone, partially broken away and

21 shows a schematic cross section of a controlled fluid ■ feed which surrounds the tube during operation of the laser heating system of FIG.

There are of course numerous publications on flow zone melting of solid bars made of different materials. For example, reference is made to the publication "Zone Melting" by William G-. Pfann, John Wiley & Sons, Inc., New York, New York, 158 and US Pat. No. J 121 619 are referred to. These However, technology has not yet been applied in any practical way to the manufacture of pipes, there are special problems that do not exist when processing solid or solid rods. In the British Patent specification 1 226 4-73 is basically mentioned that a laser beam be focused on a point on a pipe surface can, but no applicable method is described

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which makes it possible to overcome the problems which at Pipes occur or which occur in order to produce refractory pipes of the type in question here, as it was only through the invention becomes possible. One of the special problems encountered with pipes is maintenance and adjustment the wall thickness, the retention of the desired cross-section of the pipe, the homogenization of the refractory material, the preferably formation of a single crystal and the like problems. Pipes of molten material have also been drawn contained in a crucible as described in US Pat. No. 3,015,592. Both the However, physical and external conditions as well as the device of the ElieSzone process are opposite to the The procedure for a crucible is fundamentally different.

There are, of course, numerous publications in the field drawing of glass tubes using molds and spindles (see, for example, U.S. Patents 3,620,704- and 3,672,201). However, such methods are not applicable to the manufacture of refractory pipes, and in particular are not on the production of materials that have high melting points or not on the production of pipes with extreme high degree of purity and / or in the form of a single crystal.

Before various embodiments of the device and the method according to the invention are described, the method should first be described in general with reference to S ¹ Xg. 1, which shows a longitudinal section through the portion of the system forming the melt zone. While a solid, pre-formed as a tube blank 20 (which is generally produced by pressing heat-resistant powder and optionally by pre-sintering) 'is moved up through a heating zone 21, a ring of molten heat-resistant material is formed, which is continuously fed through the tube hikes down and a

\
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crystalline tube 23 made of refractory material results. the The height h of the heating zone must be adjusted or controlled and the fixed sections 20 and 23 of the tube must have such a Speed are moved so that they always remain connected by the molten ring 22 which the connection through the Maintains surface tension and gravity forces.

The preformed solid tube 20 that is fed has an inside radius r * , an outside radius rp, a wall thickness t, and a relative density? (The relative density is the ratio of the actual density to the theoretical density of the material used). In the same way, the solid crystalline tube 23 has an inner radius r, _ ,, an outer radius ^r -K_2 ', its wall thickness t-, and a relative density j ^1,. In order to obtain a stable system in which the molten ring 22 can progress continuously, the throughput of the mass flow in the cross section at the boundary line 24 between solid and liquid or between the tube section 20 and the molten ring 22 must correspond to the throughput of the mass flow in the cross section the boundary line 25 between liquid and solid body or between the molten ring 22 and the crystalline tube section 23 be the same. Since the speeds at which the fed tube section 20 and the crystalline tube section 23 are moved can be adjusted separately, one being lifted and the other being pulled, it is possible to adjust the wall thickness and, to a certain extent, also the outer diameter of the formed crystalline tube by moving the crystalline tube portion 23 at a higher or lower speed. The illustration in FIG. 2 shows how the wall thickness can be reduced by moving the section 23 faster than the section 20.

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Since the mass flow rate is equal to the product of relative Density, cross-sectional area and speed is achieved when the required stable system is achieved

where ν and v are the velocities at which the Move tube sections. Assuming that the relative Density of the fed tube is essentially 100%, then is

Since r-v _2 remains essentially the same as r ρ, it is possible to enlarge by v, t, decreased or by decreasing v, t. enlarged of course, as long as the basic condition is met that the two sections are continuous through the molten ring stay connected. In this way, it is possible to control the wall thickness of the finished heat-resistant tube.

The inside diameter and outside diameter of the final tube are, of course, functions of the zone height and dimensions of the fed tube or feed tube. If no weakening occurs during the formation of the final tube, the resulting tube generally has a slightly smaller diameter and a greater wall thickness. With a Attenuation or damping, it is possible to change the relationship between the outside diameter and the wall thickness. Of the However, the outside diameter of the growing tube is always less than or equal to the outside diameter of the feed tube.

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According to the invention, heat-resistant tubes can also be used Another cross-sectional shape can be formed, wherein the wall thickness can be uniform or uneven. As an example of a circular cross-section with a uniform wall thickness, a tube 28 is shown in FIG. 3 and as an example an elliptical cross-section with uneven wall thickness, a tube 29 is shown in FIG. The final Cross-sectional shape can be determined by the shape of the tubular blank and to a certain extent by the Design of the heating zone can be set or controlled.

Although it is possible, this allows the growth of the final tube to begin by introducing the feed tube into the melting zone in such a way that the melting process occurs at any time between Beginning at the ends of the feed tube, it is generally more desirable to have the melting process at one end of the Feed tube to begin. To do this, it is necessary to have one end of the feed tube, which is placed in the melting zone is to be brought into contact with a solid contact surface element, which is hereinafter referred to as a receptacle and which is attached to a load-bearing rod in such a way that it is in the! ig. 17 illustrates and is described in a corresponding manner. Upon melting the end of the feed tube and forming a melt In the contact surface it is possible to bring about a contact and a Y he welding of the tube with the receptacle. The receptacle can have any shape and can be a single crystal in some curls, which serves as a seed for the formation a single crystal tube. Various exemplary forms of receptacles are shown in FIGS. 5 to 17.

In FIG. 5, the receptacle 30 has the shape of a circular ring on (or has another suitable cross-section) and has

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any length, with the inclusion with a melted Ring 31 is brought into contact, at one end of the supply tube 20 is made while the end of the tube is in the heating zone and by means of a device is heated, which is shown schematically by arrows 32. Figures 6 and 7 illustrate the use of a Recording in the form of a flat plate 3 ^, which in similar Way like the annulus 30 with a fused ring 31 in the heating zone is brought into contact. After the molten tubular ring 31 is brought into contact with the receptacle, the tube manufacturing process continues as described above. If the flat plate 3 ^ as a seed crystal is used, a connection 35 can be established, such as it is shown in Fig. 7, which will be removed later.

In FIG. 8, the receptacle is a rod 36 , the end 37 of which is melted and brought into communication with the melted end of the feed tube 20. In some instances it has been found advantageous that the rod be a preferred form of surface contact element because such an element can be used to form a tighter weld to the feed tube than is the case with thin ring 30 or flat plate 34 - Figs. 5 and 6 is possible.

Figures 9 "through 17 illustrate the use of various Embodiments of a receptacle in the form of a tube. This form of recording has proven itself in the production of a single crystal tube proven beneficial. Figures 9-12 illustrate the use of a tubular receptacle to begin the manufacture of a tube according to the invention. One preferred delivery tube 38? whose upper edge 39 transversely and just cut, is held in a holder or chuck 40, and a receiving tube 4-1, which is a truncated cone has shaped contact end 42 is in a

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Holder or a putter 43 held. These brackets 4-0 and 43 are attached so that they are respectively support rods 44 and 45 ■ burden. A separate device, not shown, is provided to give the load-bearing rods 44 and 45 a translational one and to give a rotational movement and thus also the sections of the tube. Since every last recording is from his own has its own individual movement device, the translational and the rotational movement of the feed rod of the receptacle can be controlled separately. Devices, which can serve as an example, such load bearing rods with a desired axial speed and a desired angular speed are described in TTS Patent 3,552. Since the load would decrease as it was in the device U.S. Patent 3,552,931 can be used by separate Devices are moved, it is possible to adjust the wall thickness and the pipe diameter-by-different translational motion rates as well as uniformity in pipe size and homogeneity of material "through a To achieve rotary motion.

As shown in FIG. 10, a feed tube 38 is inserted into the heating zone 21 introduced in order to produce an initially melted Hing 46, the ■ cross-section of which is caused by the forces of surface tension Has a tendency to approach a circle. Once this initially melted ring 46 around the top of the feed tube 3S is formed around, the receiving seed tube 41 is lowered to make physical contact with the initially molten Manufacture ring 46, as shown in the! Ig. 11 is illustrated. This leads to a welding of the receiving germination tube to the initially melted ring 47 (see Fig. 12), which then is advanced along the length of the feed tube, ura the make final tube according to the invention.

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It is also part of the invention, the pickup tube (or the Rod) in communication with the delivery tube prior to heating, d. H. formed in front of the molten ring will. It is also part of the invention to move either only the receptacle and the delivery tube to make contact or to move both elements.

The relative sizes and configurations of the supply tube and the receiving tube must be chosen such that: when the initially melted ring 4-6 on the end of the feed tube is designed, the pickup tube is able to make physical contact therewith, so that a molten ring is formed between these two elements and extends all the way through the tube extends through and around the tube.

In a preferred embodiment of the method according to the invention, as illustrated in FIG the feed tube 38 and the take-up tube together with the subsequently manufactured tube, which is attached to it, rotated in opposite directions while the melted Ring 4-7 is moved through the tube. This counter-rotating of the two solid sections on either side of the molten one Ringes homogenizes the material in the manufactured tube and brings about changes in the heating intensity within the heating zone 21 to a minimum.

The relative size / configuration combination of the guide tube and the pickup tube can be implemented in a number of different embodiments, examples of which 9 and 13 to 17 are illustrated. For example becomes in Figs. 9i 13 and 14 such a uniform

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and ensuring complete contact of the pickup tube with the initially molten hang on the end of the feeder tube by using a pickup tube having an outside diameter OD greater than the inside diameter ID »of the feeder tube, the wall thickness of the pickup tube being substantially the same or slightly less than that of the feed tube. In the 5 ¹ Ig. Both the feed tube 38 and the take-up tube 41 have just cut contact ends 39 and 48, while in Figure 14- the feed tube 38 has a contact end 49 in which the tube wall is cut so that it has an inwardly sloping configuration These figures illustrate the contact of the pickup and delivery tubes prior to the manufacture of the molten ring.

In the embodiment of the Pig. 15 have the feed and the pick-up tube has substantially the same cross-sectional dimensions and the mating ends of the feed tube and the pick-up tube are cut off so that they have complementary frustoconical surfaces 49 and 42, respectively. It is of course within the scope of the invention to use the tube sections opposite to that in FIG.

In the embodiment of Figure 16, the pick-up tube is sized to fit into the delivery tube. This is possible so long as the increase in the molten volume, which by the molten ring 46 at its Production arises, it is sufficient to ensure the desired contact with the end of the receiving tube 41. According to FIG. 17, it is finally also possible to use a receiving tube which is larger in cross section than that Feed tube. Fig. 17 also shows the use of a

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Feed tube with a frustoconical Contact end 50.

Although in the I ¹ Xg. 9-17 the feed tube is shown serving as the lower tube and the take-up tube is illustrated as the upper tube, the reverse arrangement can also be used since surface tension can be used to keep the initially molten ring 4 -6 to keep on the end of the feed tube. The optimal selection of the receiving tube configuration and its arrangement is easy for any refractory material and a corresponding tube size.

The use of a laser has decisive advantages for equipping the Eeizzone according to the invention. When glowing or extraordinarily hot heating system makes up a large part of its radiation emit in a wavelength range in which many refractory materials are permeable in their molten state the laser can be used to avoid such troubles. Glowing or extraordinary Hot systems can also have heat transfer problems onto the tube, but the laser energy can be directed to overcome such problems will. The laser energy has no characteristic temperature and so there are no upper temperature limits. The usage the laser also brings few restrictions on that Atmosphere in which the tube is manufactured, and the use of a laser offers the possibility of a To use a number of different atmospheres, including a vacuum, with different pressures also applied and reducing and oxidizing states are also possible. Using a laser enables one too

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is-

visual observation of the process.

Figure 18 illustrates a "preferred embodiment the heating device of the device according to the invention. to The features of this device include a device which serves to shape the laser beam into the shape of a ring to bring, furthermore a device which serves to divide the bundle into two rings, furthermore a device, which serves to subdivide both rings into half rings, and a device which serves to divide the rings into the way to focus that they bundle in line bzxir. Line configurations form, which have energy-dense distributions, which are particularly useful for heating a section of a pipe surface are suitable.

In the device of FIG. 18, the radiation beam is 150 first passed by the laser 100 through a beam expansion device 151, which has a spherical mirror 152 and has a spherical mirror 153. By suitable selection of the focal length of the two spherical mirrors, it is possible expand the laser beam by a factor of 2, 4 or more. A sotierendes Dove prism 15 ^ is used to expand the Form bundle 155 into a bundle 156, which is a has an annular configuration. Dove prisms are known and described in the literature. (See, for example, Modem Optical Engineering "by Warren J. Smith, McGraw-Hill Book Co., New York, New Xork, 1966, p. 87.) By focusing the expanded Bundle 155 through the. Dove prism 154- above or below the optical axis of the prism and by rotating the prism around its own axis with the help of a suitable one Means like a motor 157 it is possible to use the laser beam reshape into an annular configuration.

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The annular bundle 156 is then passed through a bundle divider 158 which typically includes a water cooled, "coated GaAs S ¹ window 159 and a front surface mirror 160. The coating thicknesses on the surfaces of the window 159 are designed to be 50 % of the bundle reflect from the front of the window to form an annular beam 161 so that no reflection loss occurs from the rear surfaces These two ring-shaped bundles are then each divided in such a way that they form two half-ring bundles, and the resulting four half-ring bundles can be grounded as a line bundle on that section of the pipe surface which is arranged within the heating zone 21.

First, the annular bundle 161 is turned into a semicircular Mirror 165 directed, which is positioned so that it allows one half of the annular Bundle in the form of a half-ring bundle 166 impinges on a plane mirror 167 in order to reach a cylindrical mirror 168 with variable focal length, which the bundle as Line (bundle of lines 169) focused on the tube around the molten ring 22 to produce. The optical elements of Fig. 18 are mounted on or suspended from a support base, as is customary in optics, the elements being spatially arranged in such a way that these optical paths are possible will. In FIG. 18, the bundle of lines 169 is shown as a dashed line to show that it extends from the half-ring bundle 166 differs. It can be seen, however, that these two bundles are attached in two different planes are and not next to each other. Similarly, that will

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Half-ring bundle 72 through the cylindrical mirror 173 which returns a line bundle 174 that aimed at the tube to remove the melted Hing 22 to manufacture. Similarly, the bundle of rings 162 is divided into two half-ring bundles 175 and 176 by the semicircular mirror 177 · The bundle 175 is through the plane mirror 178 is focused on the cylindrical mirror 179 to be converted into a line bundle 180. Finally, the half-ring bundle 176 is focused into the line bundle 182 by the cylinder mirror 181.

A toroidal radiation shield 185 comprising four Has openings 186 to allow the passage of the bundles of lines 169, 174-, 180 and 182, is provided to power radiate, which is reflected by the molten pipe surface, back to the surface to the Concentrate and conserve the energy expended in melting the tube. This radiation shielding is shown in Connection with the discussion of FIG. 20 explained in more detail.

19 is intended to illustrate the advantages that come with the optical system of Fig. 18 can be achieved. When a halter laser bundle assembly, for example, as represented by the bundle 166, is focused in a line, so it can be shown that such a bundle of lines has an energy-dense curve at which at the end or in the region of the end of the line bundle peaks occur. When a beam of radiation hits a circular surface, as in the Tube is present, the energy absorbed by the surface decreases when the angle Θ, which is between a line, which is arranged perpendicular to the pipe surface, and the bundle direction is formed, becomes greater than zero. Consequently

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obvious that when a bundle of lines, which along its longitudinal extent has a constant energy density, meets a circular surface, the sections of the Surface that pick up radiation from the ends of the bundle will absorb less energy. However, by using a half-beam laser beam is focused into a line bundle, it is possible to form a bundle which is larger towards its ends Has energy densities, precisely where such additional energy is needed to make the difference in Balance energy absorption as described above. This is shown in FIG. Thus, the device delivers 18 shows a possibility of heating the tube in the melting zone more uniformly around its entire tube circumference, because each of the four bundles of lines has this unique energy-density distribution. It should be noted that the expression "Line bundle" is used to denote a bundle which actually has a certain height, the Height is controlled by focusing the cylindrical mirror.

FIG. 20 illustrates, as an example, a radiation shield, which is designed so that it has a toroidal shape Surface 190 defines which surrounds the heating zone 21, and is so curved that radiation is reflected back which is from reflected or emitted from the molten ring, back to the molten ring. Usually corresponds to the radius of curvature R is twice the focal length of the mirror defining the surface 190. This mirror is in the Coated way that it produces a surface that reflects extremely strongly in the infrared range, being as Material for example bright or bare gold can be used. The toroidal, its inner surface as a mirror 190 is designed so that there is an upper half 192 and

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has a correspondingly adapted lower half 193. Each of these toroidal halves is furthermore designed in such a way that they has an integral connection and a support device, 'which has the form of a shorter bracket portion 194-, the one on the upper half 195 "and on the lower half 196 each is formed, with a longer section

197 is present, the one on the upper half 198 and on the lower half 199 is formed so that means is formed which serves to cool the toroidal halves and align. The carrier device must be dimensioned such that it exposes the openings 186 in the toroid. A Clamping, or stapling, is done with a series of screws 200 and nuts 201, and the alignment of the toroidal halves and the carrier halves is determined by a series of Dowel pins and corresponding (not shown) pin holes brought about and maintained, namely in the longer sections 198 and 199 of the holder device. the all radiation shielding means 185 is preferred Made of copper and is cooled by a cooling liquid like water through the longer shark section halves

198 and 199 goes through. The cooling liquid is fed through an inlet conduit 202 into one or more passages such as introduced and discharged through passages 204- which are outside the holding section half 195 open out, specifically as an annular outlet line 205, which the inlet line 202 concentrically surrounds. Appropriate sealing rings such as O-rings 206 and 207 provide an adequate seal between the mated ones Passages in section halves 198 and 199.

The radiation shielding device is supported by a base bracket held by the coolant conduit 205, and thus the upper portion of the shield remains fixed with respect to the other optical components. It is therefore a simple matter to remove and replace the lower section, while maintaining alignment.

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It should be noted that that illustrated in FIG Construction as described above, only as an example of a possible configuration and a corresponding arrangement the radiation shielding device is used. It is thus within the scope of the invention to include any suitably designed Use radiation shielding (e.g. a spherically shaped device) which is appropriate is assembled.

Since it is usually advantageous to use a single type of laser to make tubes of different materials, the use of radiation shielding is particularly valuable when working with materials that reflect a significant proportion of the laser radiation.

Figure 21 illustrates a controlled atmosphere arrangement around the tube during its Manufacturing. The housing 63 can be evacuated or filled with a gas having desired properties, for example with a reducing, an oxidizing or a carrying gas. It becomes that shown in FIG Laser optics are used, the same reference numerals being used to denote the optical shown for illustration To designate elements. The housing 63 has a plurality of windows such as 210 and 211, each window for one Laser energy bundle is present, which is applied to the pipe surface hits. For example, a device that can be used to create a controlled atmosphere is a pressure and temperature controlled oven as described in U.S. Patent 3,639,718.

FIG. 21 illustrates a device which serves to give the fixed sections 20 and 23 of the tube a translational effect

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Movement and possibly also a rotational movement granted. The fixed section 20 is held in a holder 40 ″, which in turn would take rod 44 from a load pickup is held. In a similar way, the fixed section 23 is held in a holder 43, which in turn is held by a. Xastaufnähmestab 45 is held. With such equipment designs, which have a device which serves to establish a controlled atmosphere around the tube Seals 68 and 69 for the La st recording rods 45 and 44 are provided. Any suitable device "can be used to translate the load-bearing rods 44 and 45 and to impart a rotational movement, including the device described in US Pat. No. 3,552,931 as Example can serve. It is also within the scope of the invention to move the heater with respect to the tube when this seems appropriate.

There are, of course, a number of different arrangements for causing relative movement of such a heater and the fixed sections of the tube possible. In addition, any embodiments of the device, such as as illustrated or discussed above, to be placed in a chamber in which the fluid environments during the Manufacture of the tube are controllable.

The method and the device of the invention can do this be used to manufacture refractory tubes from any refractory material that is capable of a assume liquid state, and which can be formed into a pipe blank. In addition to aluminum oxide, these include refractory materials, but without restricting the invention thereto, oxides such as zirconium oxide, titanium oxide, thoroxide, ytterium oxide and similar, furthermore carbides such as titanium carbide,

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Borides such as titanium boride, intermetallic compounds such as Gallium arsenide, ternary compounds such as HgCdTe, pneumatic binary compounds such as AlAs-G-aAs and elements such as boron and silicon. Both crystalline and amorphous materials can be used. For optical applications it is generally required to use materials with an extremely high degree of purity. It may be desirable for other applications be to use doping agents, for example titanium or other additives, which are present in smaller quantities.

The one used to manufacture the tube in poly crystalline form or Tube blank used as a single crystal can be manufactured by any suitable method, for example by centrifugal casting or by pressing the refractory material in powder form (with or without a heat removable Binder) under sufficient pressure so that a self-supporting structure results. This by applying pressure The structure formed can optionally be partially sintered in order to increase its strength. Tube blanks made from presintered materials such as AIpO ^ are commercial available. (See also, for example, "Introduction to Ceramics" by W. D. Kingery, John Wiley & Sons, Inc., New York, 1960, in particular chapter 3 for "molding process", which in detail describes such molding processes as powder molding, extrusion, centrifugal casting and sintering.) In terms of the far Advanced technology in the manufacture of ceramic materials or refractories lies in the selection of such Parameters such as particle size, binder and density of the material from which the delivery tube is made are at discretion of the specialist. Furthermore, the selection of the method by which the delivery tube is made is also a matter of discretion of the specialist.

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If a single crystal tube is to be made by using a Seed crystal is used, the quality of the seed crystal must correspond to the desired quality of the finished tube. It is also necessary to have a suitable pretreatment of the seed crystal is carried out in order to remove any work damage caused by the shaping and / or may have occurred when the seed crystal was cut. The production of suitable seed crystals is known per se.

The temperature reached in the heating zone must of course be such that it is sufficient to melt the tube. Though something higher temperatures are tolerable, the temperature should be kept slightly below the level of vaporization or would cause the molten material to settle under the respective ambient conditions. Thus the temperature range depends which can easily be determined from existing physical data, from the refractory or heat-resistant Material from which the tube is made.

The height of the migrating molten ring is controlled by known physical factors; H. the existing temperature gradients, which is a function of the thermal conductivity of the pipe material and the surroundings of the pipe. As above this environment can be the normal atmosphere or an inert, pressurized gas, whatever can be surrounded by a liquid, or a special atmosphere can be built up with the help of a gas, for example a reducing or an oxidizing atmosphere. Another factor affecting the environment is the · use of a radiation shield to keep reflected Reflect radiation back into the molten zone. the

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The growth rate of the completed tube is of course equal to the withdrawal rate ^v >> ·

Since the method of the invention uses the melting of the tube, it enables any suitable one to be selected Atmosphere to obtain such results as purification of the heat-resistant material and adjustment of the equilibrium to the state of To achieve additives. For example, if the process is carried out in an oxidizing atmosphere, it is possible a titanium dopant to a higher level of yalency

+4

bring or stop there, d. H. Ti. Other types of surroundings can of course be used to create other desired ones To achieve results.

The method according to the invention can furthermore be based on the following Example are explained, which serves only to illustrate and not to limit the invention.

A single crystal aluminum oxide tube was made according to the I? Ig. 9 to 12 illustrated method produced. A tube made of 99% pure alumina which was made by cold pressing to have a fractional density of 97 % and an outside diameter of 9 » 15® with a wall thickness of ^: 1.01 mm was used as the feed tube. A single crystal tube made of aluminum oxide with an outside diameter of 7> 1 mm, a wall thickness of 0.5 mm and a frustoconical contact end served in a double function at the same time as a receiving tube and as a seed crystal. A COp laser consuming 415-430 watts was used to create the heating zone. The arrangement according to FIGS. 25 and 27 was essentially used as optics, with the exception that the radiation shield was spherically shaped.

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Once the melted ring is in the touch feed and "When the pick-up tubes were trained, the tube became with a speed of about 8.7 cm. (3.4-3 inches) per hour moving upwards, and the massive ear section that attaches to the When the pickup tube was attached, it was being pulled at a rate of about 15} 3 cm (6.06 inches) per hour. Simultaneously the feed tube was used for these translatory movements rotated in one direction at 490 rpm, and the massive section the tube attached to the pickup tube was moving in the opposite direction at one speed rotated from 385 rpm.

The finished single crystal tube had an outer diameter of 7 µm and a wall thickness of 0.7 mm. It was transparent or translucent or transparent and free of cracks or cracks.

According to the invention, a method and an apparatus are thus provided created for the production of improved refractory or heat-resistant tubes, which may be in the Can be formed in the form of a single crystal, v / obei then operational advantages are achieved if the resulting crystalline tube used as a bulb for high pressure lamps.

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- patent claims -

Claims (1)

Claims Process for the manufacture of a heat-resistant tube, characterized in that a prefabricated Tube blank made from a heat-resistant material is designed as a feed tube that around the tube blank around a concentrated heating zone by means of radiant energy of substantially uniform intensity is formed so that a molten ring of substantially uniform height is produced in the tube is, and completely through the tube, that the height is chosen such that the forces of surface tension and the gravitational pull of the molten ring with massive sections on either side of the molten one Keep the ring of the tube in contact so that a relative translational movement continues in a controllable manner between the refractory tube and the heating zone, so that thereby the molten ring through the Tube is moved further, further characterized in that the radiant energy is laser energy that further a large number of laser beams with a half-ring configuration are used in the production of the heating zone, which are arranged equidistantly around the tube, that each of the laser beams with a half-ring configuration on the Refractory tube is focused to form the molten ring in the tube that continues to focus takes place in such a way that the energy-density distribution of each bundle is designed such that essentially the absorption of laser energy around the entire surface around the tube is balanced within the molten ring. ORIGINAL INSPECTED 7098UM079 2. The method according to claim 1, characterized in that the formation of a large number of laser beams with one Half-ring configuration takes place in such a way that a laser beam is expanded, that the expanded beam one annular configuration is given that the annular Bundle is divided into at least two ring bundles and that the ring-shaped bundles are then divided in such a way that that the half-ring bundles arise. J. The method according to claim 1, characterized in that the Focusing of the laser beam with a half-ring configuration includes focusing these bundles in line bundles. 4. Vex'fahren according to claim 1, characterized in that the reflected and emitted from the melted Hing 'Radiation is reflected back to the molten ring. 5. The method according to claim 1, characterized in that at least a rotary motion is given to one of the massive sections. 6. The method according to claim 1, characterized in that both a rotary motion is given to massive sections. 7. Method according to claim 6, characterized in that the rotational movement of the one solid section is opposite for the sighting of the other massive section. 3. The method according to claim 1, characterized in that the molten ring initially at one end of the prefabricated Tube is generated. 7098U / 1079 9. Method according to Claim S, characterized in that the receiving element is a single crystal, which acts as a seed ν or · ", / ends. 10. The method according to claim 1, characterized in that kept the tube within a controlled fluid environment will. 11. The method according to claim 1Q, characterized in that the controlled fluid environment has a gaseous atmosphere. 12. An apparatus for producing a heat-resistant Eöhre, wherein a holding device is present, which is designed such that on the one hit holds ζ ebeständigen Eöhre separate massive portions that continue a heater is present, in order to form a molten ring in the heat-resistant Eöhre, wherein furthermore the inlet has a substantially uniform height throughout the tube which is selected such that the forces of surface tension and gravity keep the molten inlet in communication with the solid portions, and with means for providing a controlled relative translational Causing movement between the holding means and the heating means whereby the molten input migrates through the tube, thereby. characterized in that the heating device comprises a laser device which supplies at least one bundle of radiant energy, in that the optical device comprises a device for expanding the bundle, that furthermore a device is provided for dividing the resulting expanded bundle into a plurality of bundles, which im ', ve s borrowed equidistantly around the surface of the duct 709814/1079 are arranged that further a Energieverteilimgseinrichtung is provided in order to reduce the energy density distribution of each bundle belonging to the plurality of bundles, essentially designed so that the absorption of the radiant energy around the entire surface of the tube is balanced around, within the molten Hing, and that means is provided to each of the plurality of bundles onto the surface. the Focusing the tube within a heating zone surrounding the tube with a substantially uniform heating the tube surface can be reached. 13 device according to claim 12, characterized in that the energy distribution means includes means for circulating the expanded bundle into a bundle of annular configuration converting, whereby the bundles have an annular configuration subsequent to splitting, and that there is a means of dividing the bundles with an annular configuration into twice as many bundles with a half-ring configuration, thereby forming the plurality of bundles. 14 ·. Device according to claim 12, characterized in that the means for focusing each of the plurality of bundles on the surface is cylinder mirror means to focus the bundles with a half-ring configuration as a bundle of lines on the surface. 15 · Device according to claim 13, characterized in that the means serving to focus the expanded bundle into a bundle with an annular configuration, has a rotatable Dove prism and a device for rotating this prism. 709814/1079 16. Device according to. Claim 13, characterized in that that the means for converting bundles with an annular configuration into bundles with a half-ring configuration having spaced apart mirrors. 17. The device according to claim 12, characterized in that a radiation shielding device surrounds the heating zone and is adapted to emit and reflect radiant energy, plural marriage, from the molten ring is reflected back onto the molten ring. 18. Apparatus according to claim 12, characterized in that means are provided to provide a controlled atmosphere around at least the molten ring produce. 19 device according to claim 12, characterized in that a device is provided to one or both of the give massive sections a rotary motion in the same direction or in opposite directions. 7098U / 1079