Optical emitter and method and device for producing the same

Abstract

In known methods for producing an optical radiator with a glass cladding tube having a wall with a pinch seal and a gas-tight electrical feedthrough embedded therein, the pinch seal is created by heating and squeezing a predetermined length of the cladding tube wall. In order to provide a simple and cost-effective method for producing an optical radiator that counteracts the generation of rejects, the invention proposes that a wall profile of the cladding tube wall be optically detected before heating, and that the energy input during heating be adjusted depending on the detected wall profile.

Description

TECHNICAL FIELDThe present invention relates to a method for producing an optical radiator having a cladding tube made of glass, which cladding tube has a wall with at least one pinch seal with a current lead-through embedded therein in a gas-tight manner, wherein the pinch seal is produced by heating and pinch-sealing a predetermined length section of the cladding tube wall.The present invention further relates to a device for producing an optical radiator having a cladding tube made of glass, which cladding tube has a wall with at least one pinch seal, in which a current lead-through is embedded in a gas-tight manner, having:• a receptacle for the cladding tube and a current lead-through arranged therein,• at least one burner for heating a predetermined length section of the cladding tube wall, and• two mutually cooperating squeezing jaws for squeezing the heated length section in the region of the current lead-through.The method according to the invention and the device according to the invention relate to the production of an optical radiator; in particular, the method steps for closing the cladding tube ends with embedding of a current feedthrough.The invention also relates to such an optical radiator.PRIOR ARTThe cladding tube of known optical emitters is often filled with a gas or gas mixture, for example with an inert gas or with mercury vapor. This makes it necessary to close the cladding tube of the optical radiator in a gas-tight manner during production. This applies in particular to the region of a current lead-through into the cladding tube. This is because known optical emitters have at least one component which is arranged within the cladding tube and requires an electrical connection, for example a filament or electrodes. Here, it has proven to be useful to close the cladding tube by means of a squeezing of the cladding tube wall. This has several advantages: on the one hand, such a pinch seal is gas-tight, on the other hand, it can be produced simply, quickly and cost-effectively, and indeed using as few components as possible.Crimping machines are usually used to produce the crimping. These usually have a squeezing device with at least two squeezing jaws interacting with one another and a burner unit with one or more rotating or stationary burners. During the production of the pinch seal, a length section of the cladding tube is first heated. As soon as the length section has softened sufficiently, the squeezing jaws are moved past the burners against the quartz glass tube, so that they compress it. In this case, a current lead-through previously inserted into the longitudinal section of the cladding tube is enclosed in a gas-tight manner by the pinch seal.Such squeezings have a certain longitudinal extent which is also predetermined by the length of the inserted current lead-in, usually a foil with connecting pins electrically conductively connected on both sides. Typical lengths of the nip are 18 to 40 mm.The publication DE 10 2007 008 696 B3 discloses a method for producing an infrared radiator from a quartz glass body, in which the quartz glass body is softened at section ends by means of a burner and is subsequently squeezed using two squeezing jaws.The cross section and the radial dimensions of the cladding tube--inner diameter, outer diameter, wall thickness--depend on the intended use. Cladding tubes with an eight-shaped cross section are also available, which are used for so-called twin tube radiators. To make the nip, the parameters of the nip process, for example, the heating temperature, heating time or speed of the nip, are usually set manually at the beginning of the processing process from experience values, and test nip is performed. The test pinch serves to ensure that a predetermined quality of pinch is achieved with the set parameters. In the most favorable case, the set parameters can remain unchanged during the processing of a complete cladding tube batch with nominally the same cross section and radial dimensions.In practice, however, readjustment of the parameters of the squeezing process is frequently necessary. In principle, any readjustment is time-consuming, labor-intensive and cost-intensive. Readjustments are usually necessary after process interruptions or after a change of the primary material format, and in particular when several squeezings with inadequate quality (rejects) have been obtained successively. In the latter case, however, the need for readjustment is generally not noticed until excessive waste has already been produced. This is particularly cost-intensive.JP 2003-100 263 A is concerned with a manufacturing method of a tubular bulb having high productivity by preventing the generation of cracks at the sealing part. For this purpose, a tubular bulb to be sealed is moved successively to a plurality of heating positions in order to heat, soften and seal them. In a prescribed heating position, the diameter of the bulb neck is detected by a CCD camera to determine a size relationship (large / small) between its diameter and a prescribed reference value. Depending on the decision result, the heating power of a burner provided for heating, softening and sealing the lamp neck is regulated in the heating position with diameter detection or subsequent heating positions.TECHNICAL TASKThe object of the present invention is therefore to specify a simple and cost-effective method for producing an optical radiator which can be carried out quickly and reproducibly and in which no waste is produced as far as possible.Furthermore, the object of the present invention is to specify a device for producing an optical radiator, with which the generation of waste can be counteracted.It is a further object of the invention to provide an optical emitter with reliably and reproducibly closed pinch ends.SUMMARY OF THE INVENTIONWith regard to the method for producing an optical radiator, the aforementioned object is achieved according to the invention in that a wall profile of the cladding tube wall is detected before the heating, and in that the energy input during the heating is adjusted as a function of the detected wall profile, wherein a thickness of the cladding tube wall is detected for detecting the wall profile.The present invention is based on the finding that differences in the radial dimensions of the cladding tube primary material are a common reason for the generation of waste in the production of optical radiators.Glass precursors, as are used in particular in the production of optical emitters, are not exactly identical and frequently exhibit dimensional deviations within predefined tolerances. For cladding tube primary material, this applies in particular to the wall thickness or the outer diameter. The phenomenon of "sideding" is also frequently observed (see also FIG. 1 ). This occurs when, in the case of a hollow cylindrical cladding tube, the longitudinal axes of the inner cylinder and the outer cylinder do not run coaxially, but rather side by side or even obliquely. This has the consequence that the inner surface and the outer surface are displaced relative to one another, so that the cladding tube has different wall thicknesses, in particular a wall thickness profile which continuously changes both in the azimuthal direction and in the longitudinal axis direction.The geometry of the cladding tube primary material in a length section has a direct effect on the glass volume of this length section. This is because the geometry of the cladding tube precursor defines the glass volume of a predetermined length section of the cladding tube precursor. This has the result that, depending on the geometry of the cladding tube precursor material, the glass volume and thus also the glass quantity in the nip region can vary, specifically not only from precursor material to precursor material of different batches, but also in the case of precursor materials of the same batch.Even small volume fluctuations of the cladding tube precursor material can have a disadvantageous effect on the later product quality. This is shown in particular in the region of squeezing optical emitters.This is because, when heating the longitudinal section with the same energy input, the glass volume of the cladding tube primary material has an effect in particular on the glass viscosity in the heated longitudinal section of the cladding tube primary material. The heating device for producing optical emitters is usually set up manually, usually by carrying out one or more test squeezing operations and in the process suitably varying the squeezing parameters. However, the heating device is thus only set up for a specific glass volume which does not necessarily have to be the average glass volume according to the specification of the cladding tube primary material. If the glass volume of a length section is now smaller than the volume on which the heating device is set up and the energy input into the length section remains the same, the glass viscosity in the length section decreases. Conversely, a larger glass volume with the same energy input is associated with an increased glass viscosity. Consequently, deviations from the glass volume of the first device can have a negative effect on the quality of the squeezing and lead to rejects.The present invention is therefore based on the concept of detecting the actual geometric shape of the cladding tube primary material in the form of a wall profile continuously or discontinuously during the production process of the optical radiator-and thus indirectly also the volume in the squeezing region-and controlling the production process in accordance with the detected wall profile. The wall profile is detected using a method which is suitable for measuring the wall thickness of the cladding tube. Examples of these are methods for determining layer or wall thicknesses on the basis of inductive or capacitive sensors and ultrasonic measurement methods. The wall profile is preferably detected on the basis of an optical method using one or more cameras for image detection or on the basis of one or more optical sensors.Discontinuous determination of the geometric shape is possible, since in the case of one and the same cladding tube, the parameters outer diameter and wall thickness only fluctuate within narrow and generally tolerable limits. In most cases, the variations in the outer diameter and the wall thickness for one and the same cladding tube are less than 0.05 mm to 3,000 mm. In the best case, therefore, a measurement for each cladding tube primary material is sufficient. This reduces the measurement effort and saves time and costs. Depending on the length of the cladding tube primary material, it can be processed to form a plurality of optical emitters. Here, it may be sufficient that the wall profile of the cladding tube wall for a cladding tube is detected only once, regardless of how many emitters are to be produced from this cladding tube.In particular, in the method according to the invention, it is provided that the detected wall profile is used as the basis for a control or regulation of the production method. Thus, the energy input during heating of the predetermined length section can be adapted to the geometric shape. This has the advantage that it is possible to react promptly to fluctuating properties of the primary material and the glass viscosity in the longitudinal section to be squeezed can be kept approximately constant even in the event of changes in the wall profile of the cladding tube primary material.Both help to substantially reduce the generation of waste. Furthermore, cladding tubes can also be used as a primary material in the production of optical radiators, which satisfy lower requirements and have a greater tolerance range. This contributes to a reduction in material cost.In this case, a dynamic measurement of the primary material has proven to be particularly advantageous. This is because a dynamic measurement of the primary material volume during operation of the device according to the invention or during the execution of the method according to the invention has the advantage that temporal changes in the measurement data (trends) that occur even during operation or the execution of the method can be detected and evaluated and readjustment is possible particularly easily, in a time-saving and cost-saving manner even during operation. The feeding of the precursor material takes place discontinuously, i.e. as individual glass tubes one after the other. The dynamic measurement is therefore limited in time.In a preferred modification of the method according to the invention, it is provided that the energy input is adjusted by adjusting the heating duration and / or the heating temperature.The quality of the subsequent squeezing is dependent on the glass viscosity of the associated length section at the time of the squeezing process. The glass viscosity in turn depends on the glass temperature (T Glas), and the glass temperature in turn depends on the glass volume (V Vormaterial) of the length section to be squeezed and the energy input during heating of the associated length section.The energy input into the length section to be squeezed can in principle be adjusted by adjusting the heating temperature. Most easily, however, the energy input can be changed by adapting the heating duration (t Heizen). At a predetermined heating temperature, the following applies:The glass volume of the precursor (V Vormaterial) varies. The heating duration, on the other hand, is a process parameter that can be easily regulated. If the actual value of the glass volume is known, the energy input can be adapted over the heating period such that the average glass temperature (T Glas) which is as equal as possible and thus a constant glass viscosity for the hot forming process can be maintained.Advantageously, the wall profile is detected via a measurement path.In the simplest case, the wall profile can be detected by a measurement at a single point of the cladding tube primary material. However, this involves inaccuracies, in particular if the measurement does not take place in the cross-sectional central region of the cladding tube primary material, but in an edge region, or there is accidentally an irregularity in the glass at the measurement point, which leads to a measurement artifact. If the wall profile is detected over a measurement path, a larger region of the cladding tube precursor material is detected. This increases the measurement accuracy. The measurement path can extend along or transversely to a longitudinal axis of the entire radiator front material. In this case, the measurement path can extend over the entire cladding tube precursor material or only over a part thereof. Preferably, the capturing of the wall thickness profile takes place perpendicular to the longitudinal axis of the cladding tube primary material. In this way, a wall profile of the cladding tube primary material can be produced. The wall profile has a maximum value for the outer diameter or for the inner diameter of the cladding tube primary material in one point in each case. At this point, the measurement accuracy is the highest. The points for the maximum value of the outer diameter and for the maximum value of the inner diameter may differ from one another, for example, due to a sideding. Consequently, an optimum measurement range can also be determined from the wall profile, in which range a reliable measurement is possible. Ideally, the wall thickness profile is detected in a section of the cladding tube primary material which is to be squeezed later. This enables a particularly reliable measurement of the geometry of the cladding tube precursor material.In the optical detection of the wall profile, the glass volume to be heated is calculated on the basis of optically measured data of the cladding tube wall. It is sufficient if the outer diameter of the cladding tube and either the wall thickness or the inner diameter of the cladding tube are measured. It has proven to be useful if at least one confocal displacement sensor is used for detecting the wall profile.The capturing of the wall profile can basically take place from the inside, the end face and / or the outside of the cladding tube primary material. However, if the wall profile is to be recorded in an automated manner and, in particular, a corresponding measuring system is to be integrated into a device for producing an optical radiator, the recording of the wall thickness profile from the inner side or the end face of the cladding tube primary material has proven to be complicated. A confocal displacement sensor enables a measurement of the wall profile only from the outside of the cladding tube primary material. In the case of a transparent cladding tube precursor material made of glass, a confocal displacement sensor detects two reflection peaks, one for the outer tube wall and one for the inner tube wall. In an apparatus for producing an optical radiator, a confocal displacement measurement sensor can be easily integrated and connected to a controller of the apparatus and / or integrated therein. The wall profile is preferably detected in a method step in which the position of the cladding tube is fixed, for example for the purpose of machining in the squeezing machine. Measured wall thickness differences in the cross-sectional direction of the cladding tube can thus directly enable an adaptation of the process parameters (heating duration and / or heating temperature).In this context, it has proven to be favorable if the at least one displacement sensor at least partially surrounds the cladding tube wall during the detection of the wall thickness profile.At least partially surrounding the cladding tube wall increases the accuracy of the determination of the wall thickness profile. In particular, when surrounding by more than 180°, inner and outer diameters of the cladding tube opposite the cladding tube wall can be determined with only one displacement sensor.Alternatively, it has proven advantageous if the at least one displacement sensor is moved orthogonally to the cladding tube longitudinal axis during the detection of the wall thickness profile.By orthogonally moving the at least one displacement sensor relative to the cladding tube longitudinal axis, the outer and inner diameters can be detected over the entire cross section of the cladding tube or a part thereof, preferably by means of two opposing displacement sensors rotated through 180° with respect to one another. Both the outer and inner diameters each assume a maximum when the at least one displacement sensor has reached the cladding tube center. At these points, the measurement has a particularly high accuracy. The advantage of moving the displacement sensor orthogonally is that the displacement sensor does not have to be aligned as exactly as possible with respect to the cladding tube in order to obtain accurate measurement values. Instead, an optimum measured value or a range of suitable measured values can be determined from the recorded measured values, which have good measurement accuracy.According to a further, likewise preferred modification of the method according to the invention, it is provided that a heating device is used for heating the length section, and that the at least one displacement sensor is moved together with the heating device.The capturing of the wall profile must take place before the heating in order to be able to set the energy input during the heating in a targeted manner and in a manner adapted to the measured wall profile. For accurate detection of the wall profile, the cladding tube should still have been heated as little as possible at the time of detection. If the at least one displacement sensor is moved together with the heating device, the displacement sensor and the heating device have a fixed distance from one another. This ensures, on the one hand, that the capturing of the wall profile takes place at a sufficient distance from the heating process. On the other hand, the cladding tube always has an approximately constant cladding tube temperature at the measurement point. This improves the measurement accuracy and the comparison of detected wall profiles.Advantageously, the production of the pinch and the gripping of the wall profile take place in one working step.The measurement of the wall thickness profile of a longitudinal section and the heating of this longitudinal section of the cladding tube take place successively. For this purpose, the burners are usually switched off or the burner output is reduced when the wall thickness profile is detected. However, if a plurality of cladding tubes for a plurality of optical emitters are produced from a single cladding tube precursor material, it has proven to be advantageous if the squeezing of a first longitudinal section and the capturing of the wall profile of a second longitudinal section different from the first longitudinal section take place simultaneously. This increases productivity and saves time and costs since the wall profile of the second length section to be subsequently squeezed is already captured immediately after the squeezing of the first length section and the second length section is thus prepared for a squeezing process.It has therefore proved particularly advantageous if the wall profile of a second longitudinal section of the cladding tube wall is detected simultaneously with the heating of a first longitudinal section of the cladding tube wall.With regard to the device for producing an optical radiator, the above-mentioned object is achieved according to the invention in that it has a measuring device for detecting a wall profile of the cladding tube wall, and comprises an adjustment unit with which the energy input of the at least one burner during heating of the length section can be adjusted as a function of the detected wall profile.The present invention is based on the finding that differences in the geometry of the cladding tube primary material are a common reason for the generation of waste in the production of optical emitters.The geometry of the cladding tube primary material in a length section has a direct effect on the glass volume of this length section. If the glass volume of a length section is less than the volume to which the device is set up and the energy input into the length section remains the same, the glass viscosity in the length section decreases. Conversely, a larger glass volume with the same energy input is associated with an increased glass viscosity. Even small volume fluctuations of the cladding tube precursor material can have a disadvantageous effect on the later product quality. This is shown in particular in the region of squeezing optical emitters.The present invention is therefore based on the concept of 1. providing a measuring device with which the actual geometric shape of the cladding tube primary material can be detected, and 2. providing an adjusting unit with which the energy input of the burner can be adjusted as a function of the detected geometric shape.To detect the geometric shape, it is sufficient to detect a wall profile. In the simplest case, therefore, two-preferably opposite-wall thicknesses of a cross section through the cladding tube.The wall profile is detected on the basis of a device which is suitable for measuring the wall thickness of the cladding tube. Examples of these are devices for determining layer or wall thicknesses on the basis of inductive or capacitive sensors and ultrasonic measurement devices. Preferably, the wall profile is detected using an optical method using cameras for image detection or using optical sensors.It has proven to be useful if an average value of the wall thickness is calculated from the wall thickness profile. Such an average value is simple to calculate; it correlates with the glass volume for a normally predefined length of the length section.Alternatively, the glass volume can also be calculated, ideally by a control or regulating unit. The detected geometric shape is therefore preferably transmitted to a control or regulating unit and is used as a basis for controlling or regulating the energy input. Thus, the glass viscosity in the length section to be squeezed can be kept approximately constant even with a variable shape of the cladding tube primary material and the production of waste can be reduced.In a preferred embodiment of the device according to the invention, it is provided that the heating duration and / or the heating temperature can be adjusted with the adjusting unit as a function of the detected wall profile.The energy input into the length section to be squeezed can in principle be adjusted by adjusting the heating temperature. Most easily, however, the energy input can be changed by adapting the heating duration (t Heizen). The heating duration is a process parameter that can be easily regulated. If the actual value of the glass volume is known, the energy input can be adapted over the heating period such that a glass temperature that is as constant as possible can be maintained for the hot forming process.In a further embodiment of the device according to the invention, the measuring device is movable in the direction of a longitudinal axis of the receptacle and perpendicular to the longitudinal axis of the receptacle.In the simplest case, the wall profile can be detected by a measurement at a single point of the cladding tube primary material. However, this involves inaccuracies. If the wall profile is detected over a measurement path, a larger region of the cladding tube or of the cladding tube primary material is detected. If the measurement path extends along and / or perpendicular to the longitudinal axis of the receptacle, the glass volume can be determined particularly accurately in a longitudinal section.The measuring device advantageously comprises a confocal displacement measuring sensor with two measuring heads rotated by 180° with respect to one another.A confocal displacement sensor enables an automated measurement of the wall profile only from the outside of the cladding tube primary material. In the case of a transparent cladding tube precursor material made of glass, a confocal displacement sensor detects two reflection peaks, one for the outer tube wall and one for the inner tube wall. Preferably, the confocal displacement sensor is arranged stationary in the apparatus for producing an optical radiator. By means of a displacement measuring sensor with two measuring heads rotated through 180° with respect to one another, deviations in the concentricity of the inner and outer diameters of the cladding tube primary material can be compensated. This enables the most accurate possible determination of the average wall thickness and the most accurate possible calculation of the glass volume.It has proven to be advantageous if the measuring device and the at least one burner are fastened on a common burner carriage.The capturing of the wall profile must take place before the heating in order to be able to set the energy input during the heating. For accurate detection of the wall profile, the cladding tube should still have been heated as little as possible at the time of detection. If the measuring device and the at least one burner are fastened on a common burner carriage, they can be moved together, wherein the measuring device and the burner have a fixed distance from one another. This ensures, on the one hand, that the capturing of the wall profile always takes place at a sufficient distance from the heating process. On the other hand, the cladding tube always has an approximately constant cladding tube temperature at the measurement point. This improves the measurement accuracy and the comparison of detected wall profiles.Ideally, two burners and two measuring devices are present. Two measuring devices increase the accuracy of the detection of the wall profile and two burners make possible the most uniform possible heating of the longitudinal section. Preferably, the two burners and the two measuring devices are arranged such that they assume a fixed position with respect to one another, in particular that the two burners are rotated by an angle of 180° with respect to one another, and the two measuring devices are rotated by an angle of 180° with respect to one another.DEFINITIONSIndividual method steps and terms of the above description are defined in addition below. The definitions form part of the description of the invention. In the case of a relevant contradiction between one of the following definitions and the remaining description, what has been stated in the description is decisive.Optical RadiatorA radiation source emitting electromagnetic radiation having a wavelength in the range of 100 nm to 1 mm. In addition to infrared emitters, the term "optical emitter" covers, for example, lamps with an emission spectrum in the visible range or UV emitters.Cladding tube AThe lamp vessel of the optical radiator, for example the lamp bulb, and the primary material in the production of the optical radiator. A cladding tube primary material in this sense is, for example, a cylindrical glass body from which the lamp vessel of the optical radiator can be produced.Wall profileIf the outer diameter and either the inner diameter and / or the wall thickness of the radiator cladding tube comprise at a plurality of measurement points distributed over the cladding tube wall, advantageously at mutually opposite measurement points of the cladding tube wall. On the basis of the wall profile, the volume in the region of a length section of the cladding tube can be determined. For this purpose, with a known or measured outer diameter at measurement points in this length section, it is sufficient to know the wall thickness or the inner diameter at these measurement points.Measuring DeviceIt serves to grasp the wall profile of the cladding tube wall. It comprises one or more sensors for the detection of electrical, magnetic or optical signals and / or one or more cameras for image detection and image processing. Sensors include inductive, capacitive and optical sensors as well as sound sensors; in particular for ultrasound. The measuring device can be movable parallel to the longitudinal axis of the cladding tube and perpendicular thereto.Measurement pathAlong the measurement path, measurement data for the wall profile are recorded by means of a measurement device. It comprises a plurality of measurement points which are distributed perpendicular to the longitudinal axis of the cladding tube. In this case, the measurement path can extend over the entire cladding tube or only over a part thereof. In a preferred embodiment, the measuring device comprises one or more confocal displacement measuring sensors.Confocal displacement sensorIt enables an optical measurement of the cladding tube wall profile from the outside of the cladding tube primary material. The measuring principle of the confocal displacement sensor is based on a light beam of multi-coloured light being directed onto the cladding tube. Depending on the distance between the measuring head and the cladding tube, a specific wavelength is located in focus on the outer wall of the measurement object. The focused light is reflected particularly intensively back into the measuring head, captured there by means of a spectral unit, and from there reflected by means of spectrometers depending on the wavelength onto a CMOS sensor, where it forms a first reflection peak. From the position of the first reflection peak on the CMOS sensor, the distance between the measuring head and the cladding tube is determined, which is a measure of the cladding tube outer diameter. In the case of a transparent cladding tube made of glass, a second focused light beam at a different wavelength is reflected back into the measuring head at the inner wall, which second focused light beam leads on the CMOS sensor to a second reflection peak at the other wavelength, from which peak the inner diameter of the cladding tube and thus also the wall thickness thereof can be determined. Confocal displacement sensors of this type are commercially available, for example from Keyence Germany GmbH.When two confocal displacement measuring sensors lying opposite one another on the cladding tube are used, two measurement profiles are obtained each with two reflection peaks, at which the outer diameters and inner diameters (wall thicknesses) in the respective measurement range can be read.Adjusting UnitIt serves for setting the energy input into a predetermined length section of the cladding tube as a function of the wall profile detected or determined there by means of a heating device. The duration and temperature of the heating device can be adjusted by means of the adjustment unit.Heating deviceIt comprises at least one heating burner for heating the cladding tube length section, preferably at least two heating burners which are opposite one another on the cladding tube. The heating device can be movable parallel to the longitudinal axis of the cladding tube and perpendicular thereto. In this case, it advantageously forms, together with the measuring device, a common movement unit, for example a common burner carriage. If necessary, the heating device and the measuring device are jointly "movable".Squeezing machineIt serves for carrying out a squeezing process in which squeezing is produced at one end of a radiator cladding tube or at both ends of the cladding tube. The pinch joints serve for the gas-tight sealing of the cladding tube. The squeezing machine comprises the heating device and a squeezing unit with at least two squeezing jaws, which are opposite each other on the cladding tube.By using two measuring devices and two heating devices spaced apart from one another at the distance of the tube squeezings, both squeezings of an elongated tube can also be carried out simultaneously.EMBODIMENTThe method and the device according to the invention are explained in more detail below with reference to drawings. In this case, the following is shown in schematic representation: FIG. 1 shows a cladding tube with an axial "sideding" in cross section, FIG. 2 shows an example of the effects of fluctuations in the cladding tube precursor material volume on the glass viscosity in the pinch region, FIG. 3 shows an apparatus according to the invention for producing an optical radiator, in which the wall profile of a cladding tube can be detected by means of a measuring device and the energy input during heating of the cladding tube can be adjusted as a function of the wall profile by means of an adjusting unit, FIG. 4 shows a measuring device for optically detecting a wall profile of a cladding tube wall, FIG. 5 shows a measurement signal-time diagram for a single cladding tube with a nominal cladding tube diameter of 19 mm, and FIG. 6 shows a measurement signal-time diagram for a twin tube with a nominal cladding tube total diameter of 33 mm, corresponding to 2 x 15 mm individual tube, connected to 3 mm web.FIG. 1 schematically shows a cross section through a typical cladding tube 1 with "sizing". The cladding tube 1 is made of quartz glass and has a cladding tube wall 2 which is bounded on the one hand by the inner wall 3 and on the other hand by the outer wall 4 of the cladding tube 1.The cladding tube 1 has a nominal outer diameter of 19 mm, a nominal inner diameter of 16 mm, and a nominal wall thickness of 1.5 mm.Such hollow cylindrical cladding tubes are known primary materials for the production of optical emitters. However, conventional cladding tubes frequently exhibit deviations from their nominal values, in particular from their nominal wall thickness or their nominal outer diameter. These are associated with a variable glass volume with respect to a length section of the cladding tube. In addition, it can occur that in the case of a cladding tube-as shown in FIG. 1-the longitudinal axes 5, 6 of the inner cylinder describing the inner wall 3 of the cladding tube 1 and of the outer cylinder describing the outer wall 4 of the cladding tube 1 run non-coaxially. Consequently, the inner wall 3 and the outer wall 4 of the cladding tube 1 are displaced relative to one another. This phenomenon is referred to as "sizing". If appropriate, the longitudinal axes 5, 6 of inner cylinder and outer cylinder run parallel, but non-coaxial. This results in a wall thickness profile with different wall thicknesses in the cross section. The cladding tube 1 from FIG. 1 therefore has a maximum wall thickness 8 of 1.65 mm, a minimum wall thickness 7 of 1.35 mm with an average wall thickness of 1.5 mm.Table 1 shows that even variations in the outer diameter and the wall thickness within a predetermined tolerance of ±0.38 mm have a strong effect on the volume of the cladding tube precursor material in a length section of 35 mm. A length section of 35 mm corresponds approximately to the typical length of the cladding tube primary material as is required for conventional squeezing. Table 1 Table 1Upper limit measure19,381,883.61868Lower limit measure18,621,122.155Table 2 shows, by way of example, the measurement results of an individual measurement of quartz glass tubes having a nominal outer diameter of 19 mm and a length of 3,000 mm using a confocal sensor. Table 2 Table 2Mean ValueMin.Max.Mean ValueMin.Max.h=35 mm1,661,601,700,090,080,103.1601,541,491,580,080,070,092.9561,411,381,460,050,040,052.724Finally, deviations in the average wall thickness can also have a disadvantageous effect on the squeezing process. FIG. 2 shows an example of the effects of variations in cladding tube precursor volume on glass viscosity in the nip region. It can be seen from this how even small volume changes of the primary material change the glass viscosity with otherwise identical parameters of the burner (heating duration: 30 s, volume flow of the combustion gases: O 2: 40 NI / min, H 2: 70 NI / min). Table 3 Table 3A. A1,663.16016%B. B1,412.724However, by reducing the heating time from 30 s to 15 s, a stable squeezing process could also be achieved for cladding tubes of the primary material type B.As a result of this adaptation of the heating duration, it was thus possible to produce an optical radiator with pinch ends which are reliably and reproducibly closed.FIG. 3 schematically shows the structure of an apparatus according to the invention for producing an optical radiator, to which the reference numeral 30 is assigned overall. The device 30 comprises a receptacle (not shown) for a cladding tube 31 with a current lead-through (likewise not shown) arranged therein, a measuring device 33, a burner unit 32 and a squeezing device 34. The apparatus can therefore be divided into a measuring section I, a softening section II and a squeezing section III.Two confocal displacement measuring sensors 36 a, 36 bare arranged in the measuring section I, for example those of the model series CL-3000 from Keyence Germany GmbH. The two confocal displacement sensors 36 a, 36 bare arranged relative to one another such that they are arranged at a distance c, rotated by 180° with respect to one another, on a measurement axis 37 running perpendicular to the cladding tube longitudinal axis 35. Due to the transparency of the quartz glass cladding tube 31, the displacement sensors 36 a, 36 bdetect maxima at two wavelengths. Therefore, the distances a 1, b 1 of the distance measuring sensor 36 a, 36 bto the outer surface of the cladding tube 31 and the distances a 2, b 2 of the distance measuring sensor 36 a, 36 bto the inner surface of the cladding tube 31 can be determined with the distance measuring sensors 36 a, 36 b. The average wall thickness W m is as follows:Measurement Variant 1To increase the measurement accuracy, the displacement sensors 36 a, 36 bround the cladding tube 31 during the detection of the wall thickness profile.Measurement Variant 2The displacement measuring sensors 36 a, 36 bare moved orthogonally to the cladding tube longitudinal axis. From the values determined in this case, the outer diameter, the inner diameter and the average wall thickness W m are determined.The determined average wall thickness W m and the outer diameter are transmitted to the adjusting unit 40. From this, this determines the setpoint heating duration t soll and setpoint temperature T soll to be set for the respective cladding tube 31 on the heating unit of the squeezing machine and transmits these to the burner unit 32.In the downstream softening section II, a section of the cladding tube is softened by heating. The burner unit 32 is located therein with two burners 38 a, 38 barranged fixed in rotation and offset from one another by 180° on a burner axis 39 running perpendicular to the longitudinal axis 35 of the cladding tube. The burners 38a, 38b are part of the heating unit of the squeezing machine, which for reasons of simplicity is not shown in FIG. 3. The burners heat the cladding tube with the heating duration t soll and heating temperature T soll. previously determined in the measuring section I. They are held on a burner carriage (not shown), to which the position measuring sensors are also fastened.In the squeezing section III, two mutually cooperating squeezing jaws 34 a, 34 bare arranged. Here, the previously heated and softened cladding tube 31 is squeezed by moving the squeezing jaws 34a, 34b towards each other. In this case, the current lead-through (not shown) is embedded in the pinch seal and one side of the cladding tube 31 is sealed in a gas-tight manner.The method according to the invention is explained in more detail below with reference to the device 30.A cladding tube and a current lead-through arranged therein are provided. The cladding tube is measured with the measuring device, wherein a wall profile of the cladding tube wall is optically detected. From this, an average value for the outer diameter and for the wall thickness and from this the glass volume in the pinch region is calculated. In principle, optimum values for the burner process parameters can be determined for each glass volume, in practice for specific glass volume ranges, for example for the heating duration and / or the heating temperature. Optimized burner process parameters can therefore be assigned to the determined glass volume in the pinch region, from which parameters the energy input is adjusted during heating of the cladding tube. After heating a length section of the cladding tube, taking into account the previously determined parameters, this length section is squeezed.In this way, squeezings with a particularly high quality and associated optical emitters with reliably and reproducibly closed squeezing ends can be produced.In order to speed up the process, a second longitudinal section of the cladding tube wall can already be measured by the measuring device 33 during the heating of a first longitudinal section of the cladding tube wall and / or during the squeezing.FIG. 4 shows a measuring device which is designed for optically detecting a wall profile of a cladding tube wall. The reference numeral 100 is assigned to the measuring device as a whole. The measuring device 100 comprises a U-shaped holding bracket 102 to which two displacement measuring sensors 103 a, 103 bof the model series CL-3000 from Keyence Germany GmbH are fastened in such a way that their measuring heads point towards one another. The holding bracket 102 and with it the travel measurement sensors 103 a, 103 bare movable in the x direction (indicated by arrow 106) via a linear actuator 104 and in the y direction via the displacement unit 105 (indicated by arrows 107). This allows a movement of the holding bracket 102 and thus of the travel measurement sensors 103 a, 103 bin the x-y plane. By the movement of the distance measuring sensors 103 a, 103 bin the x-y plane, these can be guided over and along a cladding tube 101, wherein this is measured in the process. The measuring device 100 is suitable for measuring a wide variety of geometries, for example round tubes or twin tubes. An adaptation of the measuring device is not necessary in this case.If the displacement measuring sensors 103 a, 103 bare moved in the x direction along the distance defined by the points N-P-O across the cladding tube from the known, fixed point N across the point P to the known, fixed point O and the outer diameter of the cladding tube is thereby detected, the detected outer diameter reaches a maximum at the point P. In this point, the measurement also has the highest accuracy. The measured values recorded at point P by the measuring device are therefore preferably used as the basis for the calculation of the cladding tube volume in the longitudinal section. The point P is displaced between the stationary starting point N and the likewise stationary starting point O due to tolerances in the positioning of the cladding tube and due to tolerances in the geometry of the cladding tube itself. This is because the wall profile detected during the measurement always exhibits a rising edge starting from the point up to the point P at the maximum, and from there a falling edge. By acquiring the measured values for diameter and wall thickness along the entire section N-P-O and an output of the maximum value of diameter and minimum value of the averaged wall thickness integrated with the measuring system, an exact measured value for the outer diameter and the average wall thickness can be generated independently of the exact position of point P on the measuring section N-P-O.This is an advantage of the method according to the invention, because stable measured values are obtained even without previous exact alignment of the measuring heads to a specific position. The additional measurement step is therefore not associated with an increase in the process time for the hot forming process.FIG. 5 shows a measurement signal-time diagram for a hollow cylindrical cladding tube 101 with a round nominal cladding tube diameter of 19 mm. Therein, the measurement signal of the measuring head 103 ais illustrated as a function of the time for the one side of the cladding tube in which the measuring device 100 from FIG. 4 is moved in the x-direction 50 over the cladding tube 101. With the opposite measuring head 103 b, a similar (substantially mirrored) measurement signal of a 4 is simultaneously moved over the cladding tube 101 in the x direction 50 for the other, opposite side of the cladding tube. Since the cladding tube 101 is transparent, two measurement curves are obtained: a first measurement curve s 1 for the outer boundary surface of the cladding tube 101 and a second measurement curve s 2 for the inner boundary surface of the cladding tube 101. Measurement inaccuracies and irregularities occur in the two edge regions of the cladding tube 101 (not shown here for reasons of simplification). The measured values obtained there cannot be evaluated and are therefore shown as 0 mm in FIG. 5. In the central region of the cladding tube 101, stable and evaluable measured values are obtained. The measured values in this range assume a maximum when the measuring axis 120 of the displacement measuring sensors 103 a, 103 bruns through the center of the cladding tube 101. The difference between the measurement curves s 1, s 2 yields the wall thickness d. This is likewise entered in the diagram of FIG. 5.FIG. 6 shows a further measurement signal-time diagram for a twin tube with a nominal cladding tube total diameter of 33 mm. The measurement signal is shown therein as a function of the time in which the measuring device 100 from FIG. 4 is moved in the x-direction 50 over the twin tube. Since the twin tube is transparent, two measurement curves are obtained: a first measurement curve s 1 for the outer boundary surface of the twin tube and a second measurement curve s 2 for the inner boundary surface of the twin tube. Measurement inaccuracies and irregularities occur in the edge regions of the twin tube and in the region of the web. The measured values obtained there cannot be evaluated. In the central region of each of the two tubes of the twin tube, stable and evaluable measured values are obtained. The measured values in these ranges assume a maximum when the measuring axis 120 of the displacement sensors 103 a, 103 bruns through the center of one of the individual tubes of the twin tube. The difference between the measurement curves s 1, s 2 yields the wall thickness d. This is likewise entered in the diagram.

Claims

Method for producing an optical radiator with a cladding tube (1; 31; 101) made of glass, which has a wall with at least one pinch seal with a current lead-through embedded therein in a gas-tight manner, wherein the pinch seal is produced by heating and pinch-sealing a predetermined length section of the cladding tube wall (2), characterized in that a wall profile of the cladding tube wall (2) is detected before the heating, and in that the energy input during the heating is set as a function of the detected wall profile, wherein a thickness of the cladding tube wall (2) is detected for detecting the wall profile.Method according to claim 1, characterised in that the wall profile of the cladding tube wall (2) is optically detected.Method according to Claim 1 or 2, characterized in that the energy input is adjusted by adjusting the heating duration and / or the heating temperature.Method according to one of Claims 1 to 3, characterized in that the wall profile is detected via a measurement path.Method according to one of the preceding claims, characterized in that at least one confocal displacement sensor (36a; 36b; 103a; 103b) is used for detecting the wall profile.Method according to Claim 5, characterized in that the at least one distance measuring sensor (36a; 36b; 103a; 103b) surrounds the cladding tube wall (2) at least partially during the detection of the wall thickness profile.Method according to Claim 5, characterized in that the at least one distance measurement sensor (36a; 36b; 103a; 103b) is moved orthogonally with respect to the cladding tube longitudinal axis (35) during the detection of the wall thickness profile.Method according to one of the preceding claims 5, 6 or 7, characterized in that a heating device is used for heating the length section, and in that the at least one displacement sensor (36a; 36b; 103a; 103b) is moved together with the heating device.Method according to one of the preceding claims, characterized in that the wall profile of a second length section of the cladding tube wall (2) is recorded simultaneously with heating a first length section of the cladding tube wall (2).Device (30) for producing an optical radiator with a cladding tube (1; 31; 101) made of glass, which has a wall with at least one pinch seal, in which a current lead-through is embedded in a gas-tight manner, having: • a receptacle for the cladding tube (1; 31; 101) and a current lead-through arranged therein, • at least one burner (38a; 38b) for heating a predetermined length section of the cladding tube wall (2), and • two mutually interacting pinch jaws (34a; 34b) for pinching the heated length section in the region of the current lead-through, characterized in that the device (30) has a measuring device (33; 100) for detecting a wall profile of the cladding tube wall (2), and comprises an adjustment unit (40), with which the energy input of the at least one burner (38a; 38b) can be adjusted during heating of the length section depending on the detected wall profile, wherein the adjustment unit (40) is configured to detect a thickness of the cladding tube wall (2) for detecting the wall profile.Device (30) according to claim 10, characterised in that the measuring device (33; 100) is designed for optically detecting the wall profile of the cladding tube wall (2).Device (30) according to claim 10 or 11, characterised in that the heating duration and / or the heating temperature can be adjusted with the adjusting unit (40) as a function of the detected wall profile.Device (30) according to one of the preceding claims 10 to 12, characterised in that the measuring device (33; 100) can be moved in the direction of a longitudinal axis of the receptacle and perpendicular to the longitudinal axis of the receptacle.Device (30) according to one of the preceding claims 10 to 13, characterized in that the measuring device (33; 100) comprises at least one confocal displacement measurement sensor (36a; 36b) with two measuring heads rotated through 180° with respect to one another.Device (30) according to one of the preceding claims 10 to 14, characterized in that the measuring device (33; 100) and the at least one burner (38a; 38b) are fastened on a common burner carriage.An optical radiator manufactured according to one or more of claims 1 to 9.

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