EP2122666B1 - Infrared emitter comprising an opaque reflector and production thereof - Google Patents

Description

The invention relates to a method for producing an infrared radiator from an endlessly shaped quartz body, wherein on the surface of the body of quartz glass at least partially a reflector layer is applied, and a thus produced infrared radiator.

Quartz glass components are used in a variety of applications, such as in lamp manufacturing for cladding, piston cover plates or reflector supports for lamps and radiators in the ultraviolet, infrared and visible spectral range. In this case, the quartz glass is doped with other substances to produce special properties.

Quartz glass is characterized by a low coefficient of expansion, by optical transparency over a wider wavelength range and by high chemical and thermal resistance.

In the manufacture of lamps, the temporal constancy, the spatial orientation and the efficiency of the emitted working radiation play an important role. In order to minimize radiation losses or to direct the radiation in a targeted manner, optical radiators are provided with a reflector. In this case, the reflector is either firmly connected to the radiator or it is a reflector component arranged separately from the radiator.

The US 2,980,820 describes a short-wave infrared radiator.

In the DE 198 22 829 A1 an infrared radiator is disclosed in which the lamp tube is designed in the form of a so-called twin tube. Here, a quartz glass tube is divided by a longitudinal ridge into two mutually parallel subspaces, wherein in one or both subspaces a heating coil runs. The main radiation direction of the infrared radiation opposite side of the twin tube is covered with a gold layer, which serves as a reflector. This gold layer has a reflectivity of> 95% over the entire infrared in the new state and persists permanently a maximum temperature of 600 ° C, at higher temperatures cause loss of adhesion and evaporation of the gold after a short time to a loss of reflective property. In the DE 102 11 249 A1 is a glossy gold preparation described that permanently up to a maximum temperature of 750 ° C and short-term far beyond can be operated, without causing the effects described above. Due to the composition, however, this gold has a poor reflection of less than 70%, so that the effectiveness of this reflector does not meet the requirements placed on it.

Reflective layers of gold with high reflectivity of over 90% generally have the disadvantage that they are only limited temperature resistance, or of low reflection rate.

The DE 10 2004 051 846 A1 describes a quartz glass component with a reflector layer. The reflector layer consists of at least partially opaque quartz glass. In order to produce such a component with a reflector layer, it is necessary to apply the reflector to the empty radiator tube, since process temperatures of 1250 ° and more are needed for the manufacturing process in order to achieve the sintering of the layer. At temperatures above 1100 ° C, quartz glass softens noticeably. In particular, then an excess pressure in a quartz container leads to an inflation of the container. IR emitters are usually filled with argon at a pressure of 800 mbar to 1 bar, so that finished emitters would be destroyed safely in the application of the reflector layer.

In the hitherto known methods for producing radiators with a reflector layer, it is not possible to coat the quartz body or the quartz tube first and then perform the pinch. The reflector can only be applied to the empty radiator tube, since the process temperatures exceed 1250 ° C. Due to the process, the reflector therefore has to be applied to the emitter tube before the spotlight production begins, to the size required later. He must not reach into the area of bruising. This is necessary because the radiator tubes are evenly heated when squeezed with rotating burners. Due to the different amounts of quartz on the front and back of tubes with the reflector layer described either the coated side would not warmed enough to deform them, or the uncoated portion of the tube is heated too much, so that the quartz tube is too viscous and ruptures.

Typical incandescent bulbs consist of two opposed gas burners rotating around the quartz tube to be squeezed. If the quartz tube is sufficiently hot for the pinch, the two burners stop in their rest position, so that the two crimping jaws can move past the burners to the quartz tube and compress the quartz glass around the molybdenum foil. The technique of pinching and molybdenum foil is in the DE 29 47 230 A1 shown.

Both burners are fed together from one supply line and thus have essentially the same burner output. The contusion can only be triggered when the entire tube is thoroughly warmed up. In this case, however, the part not covered with reflector material has already converged strongly, so that although the radiator can usually be closed, the shape of the pinch is random and insufficient. In addition, leaks of pinch are very often observed, which are due to uneven temperature of the glass or heavily deformed tube cross-sections directly before crushing. It could not be produced for a sufficient amount of emitters. Furthermore, the rejection rate is very high, which also increases production costs.

If identically shaped radiators are to be produced in large numbers, it may be bearable with regard to the production costs to individually coat the already cut pipe sections with the reflector and to process them only subsequently to radiators. The transition from the coated to the uncoated area then remains almost independent of the application process of inferior quality appearance, since it can not be made cost-effective straight and clear - beads, splashes, cracks, threads, etc. affect the visual impression.

In contrast, in a production of visually satisfactory spotlights, or in the production of small numbers identically sized radiator, the method described is complex, due to the often required rework very slowly and expensive due to the large number of tools and small batches.

The object of the invention is to provide a method by which infrared radiators with opaque reflector in any length and in small series can be produced.

This object is already achieved with the features of the independent claim.

Advantageous developments are shown in the respective subclaims.

The inventive method for producing an infrared radiator from an endless quartz body wherein at least partially a reflector layer is applied to the surface of the body of quartz glass, provides that the quartz body is divided into individual sections after application of the reflector layer. This method enables infrared radiators of any length to be manufactured. The infrared radiator thereby has a continuous coating.

Advantageously, a SiO ₂ layer is applied as the reflector layer. SiO ₂ is characterized by excellent chemical and thermal resistance and mechanical strength. Furthermore, SiO _{2 has} a high thermal shock resistance. In addition, it has proven to be cost effective to apply a reflector layer of SiO ₂ . The production of SiO ₂ reflector layers of quartz glass is for example in the DE 10 2004 051 846 A1 described, which is hereby fully comprehended.

It is also advantageous if the reflector layer is an opaque, diffusely scattering reflector layer.

The inventive method provides that the individual sections of the quartz body are squeezed at their ends by means of at least one burner. In this case, the individual sections of the quartz body are heated vertically or horizontally lying with two opposite preferred in the plane perpendicular to the radiator axis and the connection axis between the burners moving burners.

It is advantageous if the ends of the sections are crushed by means of two rotating burners.

It has been shown that it is advantageous if the two burners have a different gas flow. This gas flow should be sufficient so that at the same time the entire area of the sections to be crimped is thoroughly heated without heating a part. At the same time the internal cavity pressure can be adjusted by means of suitable control of the inert gas flowing through the tube so that the quartz body is not in the deformable region is inflated. In this case, it is advantageous if the flow speed of the lower flame in the case of horizontal pinching is selected so that the deformable region of the quartz body is experiencing a force counteracting the force of gravity.

The invention further provides an infrared radiator, which has been produced by the above-mentioned method. Such a radiator can be made as required, even after the application of the coating and thus the reflector in a desired length. Thus, such a radiator in any length is conceivable.

• Figur 1 zeigt eine bevorzugte Ausführung mit exzentrisch rotierenden Brennern;
• Figur 2 zeigt eine bevorzugte Ausführung mit zwei gegenüberliegenden rotierenden Brennern und einzeln geregeltem Gasfluss;
• Figur 3 zeigt eine bevorzugte Ausführung mit vier feststehenden Brennern, von denen jeweils zwei zusammen geregelt werden.

The invention will be explained in more detail below with reference to preferred figures and embodiments:

• FIG. 1 shows a preferred embodiment with eccentrically rotating burners;
• FIG. 2 shows a preferred embodiment with two opposed rotary burners and individually controlled gas flow;
• FIG. 3 shows a preferred embodiment with four fixed burners, two of which are controlled together.

Embodiment 1

The system with eccentrically rotating burners is in FIG. 1 shown.

Deviating from the prior art, the emitter tube (10) with its half-side applied coating (11) for squeezing is not centric on the axis (20) about which the burners (21, 22) rotate, but with its axis of symmetry (12) added that the coated side is located much closer to the rotating burners, as the uncoated side. The strength of the eccentricity to be selected depends on the ratio of the applied layer to the radiator tube thickness, as well as the properties of the flame, in particular the average temperature field.

For a flame with strong entrainment, less eccentricity is sufficient because the temperature of the flame drops faster than in a laminar, long-range stable flame.

An enveloping piston squeezing machine with two rotating opposed burners (21, 22) with a torch spacing of 65 mm was rebuilt to crush coated round tubes 13.7 * 1.5 mm with a 1.0 mm reflector layer. The burners have five parallel rows of nozzles on an area of 10 * 30 mm ^ 2, from which lean H2 / O2 premix flames flow. The thus forming flame fronts (23) are quite stable, so that even an eccentricity of 5 mm here is sufficient to produce a visually excellent and tight bruise.

The tube is squeezed by means of the two crimping jaws (30,31), which on reaching the appropriate quartz glass temperature and when the burners (21, 22) do not stand in the way to drive each other directly. Then fold the two auxiliary jaws (32, 33) towards each other, so that an H-shaped pinch occurs.

Embodiment 2:

A section of a plant with rotating burners is in the FIG. 2 shown.

In a squeezing machine for rotating burners, the gas feed was optimized so that both burners are controlled independently of each other and position-dependent. The burner output is increased in the region of the additionally applied reflector layer such that the increase corresponds approximately to the additional mass located there.

Here, the rotary burner table (50) was provided with two separate gas supply grooves (51) and (52), from each of which feed lines (53) and (54) to the two burners (55) and (56) go out. The table is driven by a (not shown) motor, which drives the toothed wheels in the circular burner table milled gear (57). On both sides of the gas supply grooves (51, 52) there are further grooves (58) in which O-ring seals (59) are located.

The table is mounted in a receptacle (60) which, in addition to the drive mechanism (not shown), also provides the two gas supplies (61) and (62). Through both gas supplies, other gas mixtures or gas quantities can be added independently. The amounts of gas or gas mixtures are via an example in FIG. 3 shown controlled gas control function of the position of the burner table.

The tube (10) to be squeezed with the applied reflector layer (11) is arranged so that the Mo film (12) to be squeezed is at the level of the burners. The components of the radiator are thereby e.g. fixed on the tube mounted holder (13) in which the outer molybdenum rod (14) is hooked, while the coil (15) holds inside the radiator on their spring force all components in position.

During squeezing, argon is blown through the tube to protect the internal components from oxidation.

Specifically, a circular tube with a diameter of 19 mm and 1.6 mm wall thickness and a coating of 0.8 mm thickness and a density of> 95% of the lamp tube material, was applied over 180 ° of the pipe circumference squeezed. To do this, the burners rotate with 1 revolution per 2 s. In the range 30 ° before the burner aims at the reflector, the burner output is increased by 50% and switched back 30 ° before reaching the end of the reflector layer.

To this end, the ratio of oxygen to hydrogen is switched from a lean premix flame to a premix flame near the stoichiometric mixture fraction. The mixing point of the two gas streams is placed directly in front of the entrance of the gases in the rotating burner head, so that the shortest possible paths are realized. Nevertheless, a fairly high inertia of the flames is observed, so that a substantially sinusoidal course of the flame power is observed over the circumference.

Due to the wide-fanning flame and heat conduction, it is possible to heat the tube uniformly and quickly, so that after a usual time, and without a convergence of the tube is observed, the crushing can be performed. The emitters produced in this way have a negligible reject rate with a visually and mechanically cleanly executed pinch.

Embodiment 3

Plant with rotating burners, as in Example 3:

In a squeezing machine for rotating burners, the gas feed was optimized so that both burners are controlled independently of each other and position-dependent. The burner output is then increased in the angular range of the additionally applied reflector layer such that the increase corresponds approximately to the additional mass located there.

Specifically, a circular tube with a diameter of 19 mm with a wall thickness of 1.6 mm and a coating of 0.8 mm thickness and a density of> 95% of the lamp tube was squeezed over 200 ° of the tube circumference. To do this, the burners rotate with 1 revolution per 2 s.

To regulate the burner performance, the stoichiometry of the flame is left unaffected, but the power of the combustion gases is varied via the exit velocity. The fuel gas supply is increased 10 ° before reaching the reflector for both burners by 30% and 10 ° before reaching the end of the reflector again withdrawn. This procedure shows a higher reaction rate, since not only the stoichiometric change must flow into the burners, but only the pressure wave has to migrate from the controllers to the burner.

Due to the wide fanning flame and heat conduction, it is possible to heat the tube uniformly and quickly, so that after a normal time, and without a convergence of the tube is observed, the crushing can be performed. Again, no failures occur.

Embodiment 4 Plant with rotating burners:

In a squeezing machine for rotating burners, the gas supply is optimized so that both burners are controlled independently of each other and position-dependent. The burner output is then increased in the region of the additionally applied reflector layer such that the increase corresponds approximately to the additional mass located there.

Specifically, a twin tube measuring 33 × 14 mm and having a mean wall thickness of 1.8 mm and a coating of 0.9 mm thickness and a density of> 95% of the lamp tube over 180 ° of the tube circumference was squeezed. To do this, the burners rotate with 1 revolution per 2 s.

To regulate the power, the stoichiometry of the flame is left unaffected, but the output speed of the combustion gases varies the power. The fuel gas supply is 10 ° before Reached the reflector for both burners increased by 40% and 10 ° before reaching the end of the reflector again withdrawn. In addition, in the area of the bridge, ie when the flame strikes the flat side of the twin tube, the performance is briefly increased by a further 30% on both sides.

Due to the wide fanning flame and heat conduction, it is possible to heat the tube uniformly and quickly, so that after a normal time, and without a convergence of the tube is observed, the crushing can be performed. So it is possible to produce bruises with only a small constriction. The default rates are less than 3%.

Embodiment 5:

The plant with standing burners is in FIG. 3 shown:

In a squeezing machine for four firmly positioned burners (20, 21, 22, 23), the gas feed was optimized so that two burners on each side were controlled together. The burner output is then increased in the region of the reflector layer (11) additionally applied to the tube (10) such that the increase corresponds approximately to the additional mass located there.

Here, fuel gas, here hydrogen and oxygen taken from pressure bottles. However, the invention is not limited to the exact selection of the fuel gas, nor to the exact form of gas storage or supply.

The gas stream is then distributed to the two burner groups via suitable pipelines and adjusted to the desired flow rates and stoichiometries shortly before the mixing points by means of controllers, in this case mass flow controllers (MFC). However, the invention is not limited to the use of MFC, it can just as well also variable area flow regulator or any other suitable form of control of gas quantities are used.

For each burner group, one regulator each is used for oxygen (40, 41) and hydrogen (42, 43). In principle, of course, each burner can be controlled individually.

Specifically, a circular tube with a diameter of 19 mm with a wall thickness of 1.6 mm and a coating of 0.8 mm thickness and a density of> 95% of the lamp tube was squeezed over 200 ° of the tube circumference.

In order to achieve an approximately constant back pressure on the tube, the stoichiometry of the flames is chosen differently. Reflector side, the flames are operated near the stoichiometric ratio. On the opposite side, a meager flame of the same momentum is selected, but at 30% less power.

If the quartz glass reaches its temperature suitable for the squeezing operation, then the two crimping jaws (30, 31) rapidly approach each other and form the pinch. For mechanical reinforcement of the pinch, grooves (32) are milled into the jaws, which create protuberances on the pinch.

Claims (4)

1. Method for producing an infrared emitter from a continuous quartz glass body, whereby a reflector layer is applied to part of the surface of the body made of quartz glass, characterised in that the quartz glass body is divided into individual emitter tube sections after the application of the reflector layer, and in that the ends of the emitter tube sections are crimped by means of two burners which rotate about a rotation axis, whereby either the emitter tube sections have their symmetry axis appropriately offset with respect to the rotation axis such that their side coated with the reflector layer is arranged more closely to the rotating burners than their uncoated side, or in that the two rotating burners comprise a gas feed by means of which the burners are controlled independent of each other and independent of position.
2. Method according to claim 1, characterised in that a reflector layer made of SiO₂ is being applied.
3. Method according to any one or more of the preceding claims, characterised in that an opaque, diffusely scattering reflector layer is being applied.
4. Infrared emitter, produced according to a method according to claims 1 to 3.

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