Optical radiation emitter and method and device for manufacturing same

Abstract

In known methods for manufacturing an optical radiation emitter comprising a glass cladding tube with a wall having a pinch point with a power feedthrough gas-tightly embedded therein, the pinch point is produced by heating and pinching a predefined length portion of the cladding-tube wall. In order to provide, on this basis, a simple and inexpensive method for manufacturing an optical radiation emitter and avoiding rejects, it is proposed according to the invention that a wall profile of the cladding-tube wall is optically scanned before heating, and that the energy input during heating is adjusted as a function of the scanned wall profile.

Description

[0001] DESCRIPTION

[0002] Optical radiator and method and device for producing the same

[0003] TECHNICAL FIELD

[0004] The present invention relates to a method for producing an optical radiator with a cladding tube made of glass, which has a wall with at least one pinch with a current feedthrough embedded therein in a gas-tight manner, wherein the pinch is produced by heating and squeezing a predetermined length section of the cladding tube wall.

[0005] Furthermore, the present invention relates to a device for producing an optical radiator with a cladding tube made of glass, which has a wall with at least one pinch in which a current feedthrough is embedded in a gas-tight manner, comprising:

[0006] • a holder for the sheath tube and a current feedthrough arranged therein,

[0007] • at least one burner for heating a predetermined length of the cladding tube wall, and

[0008] • two interacting squeezing jaws for squeezing the heated length section in the area of ​​the current feedthrough.

[0009] The method and device according to the invention relate to the production of an optical radiator; in particular, the method steps for closing the cladding tube ends by embedding a current feedthrough.

[0010] The invention also relates to such an optical radiator. PRIOR ART

[0011] The cladding tube of conventional optical emitters is often filled with a gas or gas mixture, for example, an inert gas or mercury vapor. This makes it necessary to seal the cladding tube of the optical emitter gas-tight during production. This is particularly true in the area of ​​a current feedthrough into the cladding tube. This is because conventional optical emitters have at least one component arranged within the cladding tube that requires an electrical connection, such as a filament or electrodes. In this case, it has proven effective to seal the cladding tube by pinching the cladding tube wall. This has several advantages: firstly, such a pinch is gas-tight, and secondly, it can be manufactured simply, quickly, and cost-effectively, using as few components as possible.

[0012] Crimping machines are typically used to produce the crimp seal. These typically comprise a crimping device with at least two interacting crimp jaws and a burner unit with one or more rotating or stationary burners. To produce the crimp seal, a length of the cladding tube is first heated. Once the length has softened sufficiently, the crimp jaws are moved past the burners toward the quartz glass tube, compressing it. A current feedthrough previously inserted into the length of the cladding tube is encased in a gas-tight manner by the crimp seal.

[0013] Such crimps have a certain length, which is also determined by the length of the inserted power feedthrough – usually a foil with electrically conductive pins connected on both sides. Typical crimp lengths are 18 to 40 mm.

[0014] From the document DE 102007 008696 B3, a method for producing an infrared radiator from a quartz glass body is known, in which the quartz glass body is softened at section ends by means of a burner and then squeezed with two squeeze jaws.

[0015] The cross-section and radial dimensions of the cladding tube—inner diameter, outer diameter, wall thickness—depend on the intended use. Cladding tubes with a figure-eight cross-section are also available, which are used for so-called twin-tube radiators. To produce the crimp, the crimping process parameters, such as the heating temperature, heating time, or crimping speed, are usually set manually at the beginning of the processing based on experience, and a test crimp is performed. The test crimp serves to ensure that a specified crimp quality is achieved with the set parameters. In the best case, the set parameters can remain unchanged during the processing of a complete cladding tube batch with the same nominal cross-section and radial dimensions.

[0016] In practice, however, readjustment of the squeezing process parameters is often necessary. In principle, any readjustment is time-consuming, labor-intensive, and costly. Readjustments are usually necessary after process interruptions or after a change in the raw material format, and especially when several consecutive squeezings of inadequate quality (rejects) have been obtained. In the latter case, however, the need for readjustment is usually only noticed after excessive scrap has already been produced. This is particularly cost-intensive.

[0017] TECHNICAL TASK

[0018] The present invention is therefore based on the object of providing a simple and cost-effective method for producing an optical radiator, which can be carried out quickly and reproducibly and in which, if possible, no rejects are produced.

[0019] Furthermore, the present invention is based on the object of providing a device for producing an optical radiator with which the generation of rejects can be counteracted.

[0020] Furthermore, it is an object of the invention to provide an optical emitter with reliably and reproducibly sealed pinch ends. SUMMARY OF THE INVENTION

[0021] With regard to the method for producing an optical radiator, the above-mentioned object is achieved according to the invention in that a wall profile of the cladding tube wall is detected before heating, and in that the energy input during heating is adjusted as a function of the detected wall profile.

[0022] The present invention is based on the finding that differences in the radial dimensions of the cladding tube pre-material are a frequent reason for the generation of rejects in the production of optical emitters.

[0023] Glass raw materials, such as those used in the manufacture of optical emitters, are not exactly identical and often exhibit dimensional deviations within specified tolerances. For cladding tube raw materials, this applies in particular to the wall thickness or the outer diameter. The phenomenon of "siding" is also frequently observed (see also Figure 1). This occurs when the longitudinal axes of the inner and outer cylinders of a hollow cylindrical cladding tube are not coaxial, but run next to each other or even at an oblique angle. This results in the inner and outer surfaces being shifted relative to one another, so that the cladding tube has different wall thicknesses, in particular a wall thickness profile that continuously changes both in the azimuthal direction and in the longitudinal axis direction.

[0024] The geometry of the cladding tube precursor material in a length directly impacts the glass volume of that length. This is because the geometry of the cladding tube precursor material determines the glass volume of a given length of the cladding tube precursor material. This means that, depending on the geometry of the cladding tube precursor material, the glass volume and thus also the amount of glass in the crush area can vary, not only from precursor material to precursor material in different batches, but also between precursor materials from the same batch.

[0025] Even small volume fluctuations in the cladding tube precursor material can have a detrimental impact on the final product quality. This is particularly evident in the crimping of optical emitters. When heating the length of the cladding tube precursor material with the same energy input, the glass volume of the cladding tube precursor material particularly affects the glass viscosity in the heated length of the cladding tube precursor material. The heating device for producing optical emitters is typically set up manually, usually by performing one or more test crimps and varying the crimping parameters as appropriate. However, this means that the heating device is 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 precursor material.If the glass volume of a length section is smaller than the volume for which the heating device is set up, and the energy input into the length section remains the same, the glass viscosity in that 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 initial setup can negatively impact the quality of the crimp and lead to rejects.

[0026] The present invention is therefore based on the idea of ​​continuously or discontinuously detecting the actual geometric shape of the cladding tube precursor material in the form of a wall profile during the manufacturing process of the optical emitter – and thus indirectly also the volume in the crush area – and controlling the manufacturing process according to the detected wall profile. The wall profile is detected using a method suitable for measuring the wall thickness of the cladding tube. Examples include methods for determining layer or wall thicknesses using inductive or capacitive sensors, as well as ultrasonic measuring methods. Preferably, the wall profile is detected using an optical method using one or more cameras for image capture or using one or more optical sensors.

[0027] Discontinuous recording of the geometric shape is possible because, for one and the same cladding tube, the parameters of outer diameter and wall thickness fluctuate only within narrow and generally tolerable limits. Typically, the fluctuations in outer diameter and wall thickness for one and the same cladding tube are less than 0.05 mm over 3,000 mm. Therefore, in the best case, one measurement is sufficient for each cladding tube pre-material. This reduces the measurement effort and saves time and money. Depending on the length of the cladding tube pre-material, it can be processed into multiple optical emitters. In this case, it may be sufficient to record the wall profile of the cladding tube wall only once for a cladding tube, regardless of how many emitters are to be manufactured from this cladding tube.

[0028] In particular, the method according to the invention provides for the measured wall profile to be used as the basis for controlling or regulating the manufacturing process. This allows the energy input during heating of the specified length section to be adapted to the geometric shape. This has the advantage of allowing a timely response to fluctuating properties of the precursor material, and the glass viscosity in the length section to be crimped can be kept approximately constant even when the wall profile of the cladding tube precursor material changes.

[0029] Both of these factors contribute to significantly reducing the amount of scrap. Furthermore, cladding tubes can also be used as starting material in the manufacture of optical emitters, which meet lower requirements and have a wider tolerance range. This contributes to a reduction in material costs.

[0030] Dynamic measurement of the precursor material has proven to be particularly advantageous in this case. This is because dynamic measurement of the precursor material volume during operation of the device according to the invention or during implementation of the method according to the invention has the advantage that temporal changes in the measurement data (trends) that occur during operation or implementation of the method can be recorded and evaluated, and readjustment is particularly simple and time- and cost-saving, even during operation. The precursor material is fed in discontinuously, i.e. as individual glass tubes one after the other. The dynamic measurement is therefore time-limited. In a preferred modification of the method according to the invention, the energy input is adjusted by adjusting the heating duration and / or the heating temperature.

[0031] The quality of the subsequent crush depends on the glass viscosity of the corresponding length at the time of the crushing process. The glass viscosity, in turn, depends on the glass temperature (T 0 ), and the glass temperature, in turn, depends on the glass volume (V pre-material) of the length to be crushed and the energy input during heating of the corresponding length.

[0032] The energy input into the length to be crimped can generally be adjusted by adjusting the heating temperature. However, the easiest way to change the energy input is by adjusting the heating time (theating). For a given heating temperature, the following applies:

[0033] Toias f (tHeizen, Vvormateriai)

[0034] The glass volume of the precursor material (Vpremateriai) fluctuates. The heating time, however, is an easily controllable process parameter. If the actual value of the glass volume is known, the energy input can be adjusted over the heating time so that the average glass temperature (Tias) is as constant as possible and thus a consistent glass viscosity can be maintained for the hot forming process.

[0035] Advantageously, the wall profile is recorded over a measuring section.

[0036] In the simplest case, the wall profile can be recorded with a measurement at a single point on the cladding tube precursor material. However, this entails inaccuracies, particularly if the measurement is not taken in the cross-sectional center of the cladding tube precursor material, but rather in an edge region, or if there is an irregularity in the glass at the measurement point that leads to a measurement artifact. If the wall profile is recorded over a measuring section, a larger area of ​​the cladding tube precursor material is recorded. This increases measurement accuracy. The measuring section can extend along or perpendicular to a longitudinal axis of the entire radiator precursor material. The measuring section can extend over the entire cladding tube precursor material or only over part of it. Preferably, the wall thickness profile is recorded perpendicular to the longitudinal axis of the cladding tube precursor material. In this way, a wall profile of the cladding tube precursor material can be created.The wall profile indicates a maximum value for the outer and inner diameter of the cladding tube stock at one point each. Measurement accuracy is highest at this point. The points for the maximum value of the outer diameter and the maximum value of the inner diameter can differ from each other, for example, due to siding. Consequently, an optimal measuring range can be determined from the wall profile, within which a reliable measurement is possible. Ideally, the wall thickness profile is recorded in a section of the cladding tube stock that will later be crimped. This enables a particularly reliable measurement of the cladding tube stock geometry.

[0037] With optical wall profile measurement, the glass volume to be heated is calculated based on optically measured data from the cladding tube wall. It is sufficient to measure the cladding tube's outer diameter and either the wall thickness or the inner diameter of the cladding tube. It has proven effective to use at least one confocal displacement sensor to measure the wall profile.

[0038] The wall profile can generally be measured from the inside, the end face, and / or the outside of the cladding tube precursor material. However, if the wall profile is to be measured automatically, and in particular if a corresponding measuring system is to be integrated into a device for producing an optical emitter, measuring the wall thickness profile from the inside or the end face of the cladding tube precursor material proves to be complex. A confocal displacement sensor enables the wall profile to be measured only from the outside of the cladding tube precursor material. For 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 a device for producing an optical emitter, a confocal displacement sensor can be easily integrated and connected to and / or integrated into a control system of the device.Preferably, the wall profile is measured in a process step in which the position of the cladding tube is fixed, such as for processing in a squeezing machine. Measured wall thickness differences in the cross-sectional direction of the cladding tube can thus directly enable adjustment of the process parameters (heating time and / or heating temperature).

[0039] In this context, it has proven advantageous if at least one displacement sensor at least partially surrounds the cladding tube wall while recording the wall thickness profile.

[0040] At least partially circling the cladding tube wall increases the accuracy of measuring the wall thickness profile. In particular, when circling the cladding tube wall by more than 180°, the opposing inner and outer diameters of the cladding tube can be determined with a single displacement sensor.

[0041] Alternatively, it has proven advantageous if the at least one displacement sensor is moved orthogonally to the longitudinal axis of the cladding tube during the detection of the wall thickness profile.

[0042] By orthogonally moving the at least one displacement sensor relative to the longitudinal axis of the cladding tube, the outer and inner diameters can be measured across the entire cross-section of the cladding tube or part of it - preferably using two opposing displacement sensors rotated by 180° to each other. Both the outer and inner diameters reach a maximum when the at least one displacement sensor has reached the center of the cladding tube. At these points, the measurement is particularly accurate. The advantage of orthogonally moving the displacement sensor is that the displacement sensor does not have to be aligned as precisely as possible to the cladding tube in order to obtain accurate measured values. Rather, an optimal measured value or a range of suitable measured values ​​with good measurement accuracy can be determined from the recorded measured values.

[0043] According to a further, equally preferred modification of the method according to the invention, it is provided that a heating device is used to heat the length section, and that the at least one distance measuring sensor is moved together with the heating device.

[0044] The wall profile must be recorded before heating in order to be able to adjust the energy input during heating in a targeted manner and adapted to the measured wall profile. For accurate recording of the wall profile, the cladding tube should be as slightly heated as possible at the time of recording. If at least one displacement sensor is moved together with the heating device, the displacement sensor and heating device are at a fixed distance from each other. This ensures, on the one hand, that the wall profile is recorded at a sufficient distance from the heating process. On the other hand, the cladding tube always has a roughly constant cladding tube temperature at the measuring point. This improves the measurement accuracy and the comparability of recorded wall profiles.

[0045] Advantageously, the creation of the pinch and the recording of the wall profile are carried out in one operation.

[0046] The wall thickness profile of a length and the heating of this length of the cladding tube are measured sequentially. For this purpose, the burners are regularly switched off or the burner power is reduced while the wall thickness profile is being recorded. However, if multiple cladding tubes for multiple optical emitters are manufactured from a single cladding tube raw material, it is advantageous to simultaneously crimp a first length and detect the wall profile of a second length that is different from the first length. This increases productivity and saves time and money, since immediately after the first length is crimped, the wall profile of the second length to be crimped is already detected, thus preparing the second length for a crimping process.

[0047] It has therefore proven particularly useful to measure the wall profile of a second length of the cladding tube wall at the same time as heating a first length of the cladding tube wall.

[0048] 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 depending on the detected wall profile.

[0049] The present invention is based on the finding that differences in the geometry of the cladding tube pre-material are a frequent reason for the generation of rejects in the production of optical emitters.

[0050] The geometry of the cladding tube precursor material in a length directly impacts the glass volume of that length. If the glass volume of a length is smaller than the volume for which the device is designed, and the energy input into the length remains the same, the glass viscosity in that length decreases. Conversely, a larger glass volume with the same energy input is associated with an increased glass viscosity. Even small volume fluctuations in the cladding tube precursor material can have a detrimental effect on the subsequent product quality. This is particularly evident in the area of ​​pinching optical emitters.

[0051] The present invention is therefore based on the idea

[0052] 1 . a measuring device shall be provided with which the actual geometric shape of the cladding tube material can be recorded, and

[0053] 2. provide an adjustment unit with which the energy input of the burner can be adjusted depending on the detected geometric shape.

[0054] To capture the geometric shape, it is sufficient to capture a wall profile. In the simplest case, this would be two – preferably opposite – wall thicknesses of a cross-section through the duct.

[0055] The wall profile is recorded using a device suitable for measuring the wall thickness of the cladding tube. Examples include devices for determining layer or wall thickness using inductive or capacitive sensors, as well as ultrasonic measuring devices. Preferably, the wall profile is recorded using an optical method using cameras for image capture or optical sensors. It has proven effective to calculate an average wall thickness from the wall thickness profile. Such an average is easy to calculate; it correlates with the glass volume, usually for a given length of the longitudinal section.

[0056] Alternatively, the glass volume can also be calculated, ideally by a control or regulating unit. Therefore, the recorded geometric shape is preferably transmitted to a control or regulating unit, which then uses it to control or regulate the energy input. This allows the glass viscosity in the length to be squeezed to be kept approximately constant, even with a variable shape of the cladding tube pre-material, and reduces the production of scrap.

[0057] 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 setting unit as a function of the detected wall profile.

[0058] The energy input into the length to be squeezed can generally be adjusted by adjusting the heating temperature. However, the easiest way to change the energy input is by adjusting the heating time (theating). The heating time is an easily adjustable process parameter. If the actual glass volume is known, the energy input can be adjusted via the heating time to maintain a glass temperature as constant as possible for the hot forming process.

[0059] In a further embodiment of the device according to the invention, the measuring device can be moved in the direction of a longitudinal axis of the holder and perpendicular to the longitudinal axis of the holder.

[0060] In the simplest case, the wall profile can be measured at a single point on the cladding tube material. However, this involves inaccuracies. If the wall profile is measured over a measuring section, a larger area of ​​the cladding tube or cladding tube material is measured. If the measuring section extends along and / or perpendicular to the longitudinal axis of the recording, the glass volume can be determined particularly precisely in a specific length. The measuring device advantageously comprises a confocal displacement sensor with two measuring heads rotated 180° relative to each other.

[0061] A confocal displacement sensor enables automated measurement of the wall profile only from the outside of the cladding tube precursor material. For 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. The confocal displacement sensor is preferably mounted stationary in the device for producing an optical emitter. A displacement sensor with two measuring heads rotated 180° relative to each other can compensate for deviations in the concentricity of the inner and outer diameters of the cladding tube precursor material. This enables the most accurate determination of the average wall thickness and the most accurate calculation of the glass volume.

[0062] It has proven advantageous if the measuring device and at least one burner are mounted on a common burner carriage.

[0063] The wall profile must be recorded before heating in order to be able to adjust the energy input during heating. For accurate recording of the wall profile, the cladding tube should be as slightly heated as possible at the time of recording. If the measuring device and at least one burner are mounted on a common burner carriage, they can be moved together, with the measuring device and burner being kept at a fixed distance from each other. This ensures, on the one hand, that the wall profile is always recorded at a sufficient distance from the heating process. On the other hand, the cladding tube always has a roughly constant cladding tube temperature at the measuring point. This improves the measurement accuracy and the comparability of recorded wall profiles.

[0064] Ideally, two burners and two measuring devices are provided. Two measuring devices increase the accuracy of the wall profile measurement, and two burners enable the most even heating of the length section possible. Preferably, the two burners and the two measuring devices are arranged so that they occupy a fixed position relative to each other, in particular, the two burners are rotated by an angle of 180° relative to each other, and the two measuring devices are rotated by an angle of 180° relative to each other.

[0065] DEFINITIONS

[0066] Individual process steps and terms from the above description are defined in more detail below. These definitions are part of the description of the invention. In the event of a factual contradiction between one of the following definitions and the rest of the description, the statement in the description shall prevail.

[0067] Optical emitter

[0068] A radiation source that emits electromagnetic radiation with a wavelength in the range of 100 nm to 1 mm. The term "optical radiator" includes not only infrared radiators but also lamps with an emission spectrum in the visible range and UV radiators.

[0069] cladding tube

[0070] The lamp vessel of the optical radiator, for example, the lamp bulb, as well as the precursor material used in the manufacture of the optical radiator. A cladding tube precursor material in this sense is, for example, a cylindrical glass body from which the lamp vessel of the optical radiator can be manufactured.

[0071] Wall profile

[0072] Includes the outer diameter and either the inner diameter and / or the wall thickness of the radiator cladding tube at several measuring points distributed along the cladding tube wall, preferably at opposite measuring points on the cladding tube wall. Based on the wall profile, the volume within a length of the cladding tube can be determined. For this purpose, if the outer diameter is known or measured at measuring points in this length, knowledge of the wall thickness or the inner diameter at these measuring points is sufficient. Measuring device

[0073] It is used to measure the wall profile of the cladding tube wall. It comprises one or more sensors for detecting electrical, magnetic, or optical signals and / or one or more cameras for image acquisition and image processing. Sensors include inductive, capacitive, and optical sensors, as well as sound sensors, particularly for ultrasound. The measuring device can be movable parallel to the cladding tube's longitudinal axis and perpendicular to it.

[0074] Measuring section

[0075] Along the measuring section, measurement data for the wall profile are recorded using a measuring device. This device comprises several measuring points distributed perpendicular to the longitudinal axis of the cladding tube. The measuring section can extend over the entire cladding tube or only over part of it. In a preferred embodiment, the measuring device comprises one or more confocal displacement sensors.

[0076] Confocal displacement sensor

[0077] It enables optical measurement of the cladding tube wall profile from the outside of the cladding tube material. The measuring principle of the confocal displacement sensor is based on directing a beam of multicolored light onto the cladding tube. Depending on the distance between the measuring head and the cladding tube, a specific wavelength is in focus on the outer wall of the measuring object. The focused light is reflected back into the measuring head with particular intensity, where it is detected by a spectral unit. From there, depending on the wavelength, it is reflected by a spectrometer onto a CMOS sensor, where it forms a first reflection peak. The distance between the measuring head and the cladding tube is determined from the position of the first reflection peak on the CMOS sensor; this distance is a measure of the cladding tube's outer diameter.In a transparent glass cladding tube, a second focused light beam at a different wavelength is reflected back into the measuring head on the inner wall, resulting in a second reflection peak at the other wavelength on the CMOS sensor, from which the inner diameter of the cladding tube and thus its wall thickness can be determined. Such confocal displacement sensors are commercially available, for example, from Keyence Deutschland GmbH.

[0078] When using two confocal displacement sensors opposite each other on the cladding tube, two measurement profiles are produced, each with two reflection peaks, from which the outer diameters and inner diameters (wall thicknesses) can be read in the respective measuring range.

[0079] Setting unit

[0080] It is used to adjust the energy input into a given length of the cladding tube using a heating device, depending on the wall profile detected or determined there. The duration and temperature of the heating device can be adjusted using the adjustment unit.

[0081] Heating system

[0082] It comprises at least one heating burner for heating the cladding tube length, preferably at least two heating burners located opposite each other on the cladding tube. The heating device can be movable parallel to the cladding tube's longitudinal axis and perpendicular to it. It advantageously forms a common movement unit with the measuring device, for example, a common burner carriage. If necessary, the heating device and measuring device can be "movable" together.

[0083] squeezing machine

[0084] It is used to perform a crimping process in which crimps are created at one or both ends of a radiator cladding tube. The crimps serve to seal the cladding tube gas-tight. The crimping machine comprises the heating device and a crimping unit with at least two crimping jaws positioned opposite each other on the cladding tube.

[0085] By using two measuring devices and two heating devices spaced apart by the distance between the cladding tube crimps, both crimps of an extended cladding tube can be performed simultaneously. EXAMPLE EMBODIMENT

[0086] The method and device according to the invention are explained in more detail below with reference to the drawings. The following schematic representation shows:

[0087] Figure 1 shows a cladding tube with an axial siding in cross section,

[0088] Figure 2 shows an example of the effects of fluctuations in the

[0089] Cladding tube pre-material volume on the glass viscosity in the pinch area,

[0090] Figure 3 shows a device according to the invention for producing an optical radiator, in which the wall profile of a cladding tube can be detected with a measuring device and the energy input during heating of the cladding tube can be adjusted with an adjustment unit depending on the wall profile,

[0091] Figure 4 shows a measuring device for optically detecting a wall profile of a cladding tube wall,

[0092] Figure 5 shows a measurement signal-time diagram for a single cladding tube with a nominal cladding tube diameter of 19 mm, and

[0093] Figure 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 single tubes, connected with a 3 mm web.

[0094] Figure 1 shows a schematic cross-section through a typical cladding tube 1 with siding. The cladding tube 1 is made of quartz glass and has a cladding tube wall 2, which is surrounded on the one hand by the inner wall 3 and on the other hand by the

[0095] Outer wall 4 of the cladding tube 1 is limited.

[0096] 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.

[0097] Such hollow-cylindrical cladding tubes are well-known raw materials for the production of optical radiators. However, conventional cladding tubes often exhibit deviations from their nominal values, particularly in their nominal wall thickness or their nominal outer diameter. These deviations are associated with a variable glass volume relative to a length section of the cladding tube. Furthermore, it can happen that in a cladding tube - as shown in Figure 1 - the longitudinal axes 5, 6 of the inner cylinder describing the inner wall 3 of the cladding tube 1 and the outer cylinder describing the outer wall 4 of the cladding tube 1 are non-coaxial. Consequently, the inner wall 3 and outer wall 4 of the cladding tube 1 are shifted relative to one another. This phenomenon is referred to as "siding." In some cases, the longitudinal axes 5, 6 of the inner cylinder and outer cylinder run parallel but non-coaxially. This results in a wall thickness profile with different wall thicknesses in the cross-section.The cladding tube 1 from Figure 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.

[0098] Table 1 shows that even fluctuations in the outer diameter and wall thickness within a specified tolerance of ± 0.38 mm have a significant impact on the volume of the cladding tube stock in a length section of 35 mm. A length section of 35 mm corresponds approximately to the typical length of the cladding tube stock required for a conventional crimp.

[0099] Table 1

[0100] Table 2 shows the measurement results of a single measurement of quartz glass tubes with a nominal outer diameter of 19 mm and a length of 3,000 mm using a confocal sensor. Table 2

[0101] Finally, deviations in the average wall thickness can also have a detrimental effect on the squeezing process. Figure 2 shows an example of the effects of fluctuations in the cladding tube pre-material volume on the glass viscosity in the squeezing area. This shows how even small changes in the volume of the pre-material can change the glass viscosity, with otherwise identical burner parameters (heating time: 30 s, volume flow of the combustion gases: O2: 40 Nl / min, H2: 70 Nl / min).

[0102] Table 3

[0103] However, by reducing the heating time from 30 s to 15 s, a stable crimping process could also be achieved for cladding tubes of the precursor material type B. As a result of this adjustment of the heating time, an optical emitter with reliably and reproducibly sealed crimp ends could be produced.

[0104] Figure 3 schematically shows the structure of an apparatus according to the invention for producing an optical radiator, which is assigned the reference numeral 30 overall. The apparatus 30 comprises a receptacle (not shown) for a cladding tube 31 with a current feedthrough arranged therein (also not shown), a measuring device 33, a burner unit 32, and a crimping device 34. The measuring device 33, the burner unit 32, and the crimping device 34 are arranged one after the other in the direction of the cladding tube's longitudinal axis 35. The apparatus can therefore be divided into a measuring section I, a softening section II, and a crimping section III.

[0105] In measuring section I, two confocal displacement sensors 36a, 36b are arranged, for example those from the CL-3000 model series from Keyence Deutschland GmbH. The two confocal displacement sensors 36a, 36b are arranged relative to one another such that they are rotated 180° to one another and located at a distance c on a measuring axis 37 running perpendicular to the cladding tube's longitudinal axis 35. Due to the transparency of the quartz glass cladding tube 31, the displacement sensors 36a, 36b detect maxima at two wavelengths. Therefore, the displacement sensors 36a, 36b can be used to determine both the distances ai, bi of the displacement sensor 36a, 36b to the outer surface of the cladding tube 31 and the distances a2, b2 of the displacement sensor 36a, 36b to the inner surface of the cladding tube 31. The average wall thickness W m is as follows:

[0106] (c-ai-bi)-(c-ct2-b2) ci -ai+b -bi W m = - = -

[0107] 2 2

[0108] Measurement variant 1

[0109] To increase measurement accuracy, the displacement sensors 36a, 36b encircle the cladding tube 31 while measuring the wall thickness profile. From the values ​​determined in this way, an average value of the average wall thickness is calculated. Measurement variant 2

[0110] The displacement sensors 36a, 36b are moved orthogonally to the longitudinal axis of the cladding tube. The values ​​thus determined are used to determine the outer diameter, the inner diameter, and the average wall thickness W m determined.

[0111] The determined average wall thickness Wm and the outer diameter are transmitted to the setting unit 40. This unit then determines the target heating time tsoii and target temperature Tsoii to be set for the respective cladding tube 31 on the heating unit of the squeezing machine and transmits these values ​​to the burner unit 32.

[0112] In the downstream softening section II, a section of the cladding tube is softened by heating. Located therein is the burner unit 32 with two rotationally fixed burners 38a, 38b, which are mounted on a burner axis 39 extending perpendicular to the cladding tube's longitudinal axis 35 and offset by 180°. The burners 38a, 38b are part of the heating unit of the squeezing machine, which is not shown in Figure 3 for simplification reasons. The burners heat the cladding tube with the heating duration tsoii and heating temperature Tsoii previously determined in measuring section I. They are mounted on a burner carriage (not shown), to which the displacement sensors are also attached.

[0113] In the crimping section III, two interacting crimping jaws 34a, 34b are arranged. Here, the previously heated and softened cladding tube 31 is crimped by moving the crimping jaws 34a, 34b toward each other. The current feedthrough (not shown) is embedded in the crimp, and one side of the cladding tube 31 is sealed gas-tight.

[0114] The method according to the invention is explained in more detail below using the device 30:

[0115] A cladding tube and a current feedthrough arranged therein are provided. The cladding tube is measured using the measuring device, whereby a wall profile of the cladding tube wall is optically recorded. From this, an average value for the outer diameter and for the wall thickness is calculated, and from this the glass volume in the crush zone is calculated. In principle, optimal values ​​for the burner process parameters, for example for the heating time and / or the heating temperature, can be determined for any glass volume, in practice for specific glass volume ranges. Optimized burner process parameters can therefore be assigned to the determined glass volume in the crush zone, from which the energy input when heating the cladding tube is adjusted. After heating a length of the cladding tube according to the previously determined parameters, this length is crushed.

[0116] In this way, pinch seals of particularly high quality can be produced, and thus, optical emitters with reliably and reproducibly sealed pinch seals can be produced.

[0117] In order to accelerate the process, a second length section of the cladding tube wall can be measured by the measuring device 33 during the heating of a first length section of the cladding tube wall and / or during the squeezing.

[0118] Figure 4 shows a measuring device designed for optically detecting the wall profile of a cladding tube wall. The measuring device as a whole is assigned the reference number 100. The measuring device 100 comprises a U-shaped mounting bracket 102, to which two displacement sensors 103a, 103b of the CL-3000 model series from Keyence Deutschland GmbH are attached so that their measuring heads face each other. The mounting bracket 102 and, with it, the displacement sensors 103a, 103b can be moved in the x-direction (indicated by arrow 106) via a linear actuator 104 and in the y-direction (indicated by arrows 107) via the displacement unit 105. This enables movement of the mounting bracket 102 and thus of the displacement sensors 103a, 103b in the xy-plane. By moving the displacement sensors 103a, 103b in the xy plane, they can be guided over and along a cladding tube 101, which is measured in the process.The measuring device 100 is suitable for measuring a wide variety of geometries, such as round tubes or twin tubes. No adjustment of the measuring device is required.

[0119] If the displacement sensors 103a, 103b are moved in the x-direction along the distance defined by the points NP-0 across the cladding tube from the known, stationary point N via the point P to the known, stationary point O, and if the outer diameter of the cladding tube is recorded in the process, the recorded outer diameter reaches a maximum at point P. The measurement also has the highest accuracy at this point. Therefore, the measured values ​​recorded by the measuring device at point P are preferably used to calculate the cladding tube volume in the longitudinal section. Point P shifts between the fixed starting point N and the likewise fixed starting point 0 due to tolerances in the positioning of the cladding tube and as a result of tolerances in the geometry of the cladding tube itself. Therefore, point P is usually not known in advance, but is always recorded during the measurement.This is because the wall profile recorded during the measurement always shows a rising flank from the point up to the maximum point P, and from there a falling flank. By recording the measured values ​​for diameter and wall thickness along the entire distance NP-0 and a measuring system-integrated output of the maximum diameter value and minimum value of the average wall thickness, an exact measured value for the outer diameter and the average wall thickness can be generated regardless of the exact position of point P on the measuring distance NP-0.

[0120] This is an advantage of the method according to the invention, because stable measurement values ​​are obtained even without prior precise alignment of the measuring heads to a specific position. The additional measurement step therefore does not increase the process time for the hot forming process.

[0121] Figure 5 shows a measurement signal-time diagram for a hollow cylindrical cladding tube 101 with a round nominal cladding tube diameter of 19 mm. It shows the measurement signal of the measuring head 103a as a function of time for one side of the cladding tube, in which the measuring device 100 from Figure 4 is moved in the x-direction 50 over the cladding tube 101. At the same time, the opposite measuring head 103b generates a similar (essentially mirrored) measurement signal for the other, opposite side of the cladding tube, in which the measuring device 100 from Figure 4 is moved in the x-direction 50 over the cladding tube 101. Since the cladding tube 101 is transparent, two measurement curves are obtained: a first measurement curve si for the outer boundary surface of the cladding tube 101 and a second measurement curve S2 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 simplification reasons).The measured values ​​obtained there cannot be evaluated and are therefore shown as 0 mm in Figure 5. Stable and evaluable measured values ​​are obtained in the central region of the cladding tube 101. The measured values ​​in this region reach a maximum when the measuring axis 120 of the displacement sensors 103a, 103b passes through the center of the cladding tube 101. The difference between the measurement curves s1, s2 yields the wall thickness d. This is also plotted in the diagram in Figure 5.

[0122] Figure 6 shows another measurement signal-time diagram for a twin tube with a nominal cladding tube total diameter of 33 mm. It shows the measurement signal as a function of the time in which the measuring device 100 from Figure 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 si for the outer boundary surface of the twin tube and a second measurement curve S2 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. Stable and evaluated measured values ​​are obtained in the center region of each of the two tubes of the twin tube. The measured values ​​in these regions reach a maximum when the measuring axis 120 of the displacement sensors 103a, 103b passes through the center point of one of the individual tubes of the twin tube.The difference between the measurement curves si and S2 yields the wall thickness d. This is also shown in the diagram.

Claims

CLAIMS 1 . A method for producing an optical radiator with a cladding tube made of glass, which has a wall with at least one pinch with a current feedthrough embedded therein in a gas-tight manner, wherein the pinch is produced by heating and squeezing 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 heating, and that the energy input during heating is adjusted depending on the detected wall profile.

2. Method according to claim 1, characterized in that the wall profile of the cladding tube wall (2) is optically detected.

3. Method according to claim 1 or 2, characterized in that the energy input is adjusted by adjusting the heating time and / or the heating temperature.

4. Method according to one of claims 1 to 3, characterized in that the wall profile is detected over a measuring section.

5. Method according to one of the preceding claims, characterized in that at least one confocal displacement sensor (36a; 36b; 103a; 103b) is used to detect the wall profile.

6. The method according to claim 5, characterized in that the at least one displacement sensor (36a; 36b; 103a; 103b) at least partially surrounds the cladding tube wall (2) during the detection of the wall thickness profile.

7. The method according to claim 5, characterized in that the at least one displacement sensor (36a; 36b) is moved orthogonally to the cladding tube longitudinal axis (35) during the detection of the wall thickness profile.

8. Method according to one of the preceding claims 5, 6 or 7, characterized in that a heating device is used to heat the length section, and that the at least one displacement sensor (36a; 36b; 103a; 103b) is moved together with the heating device.

9. Method according to one of the preceding claims, characterized in that at the same time as heating a first longitudinal section of the cladding tube wall (2), the wall profile of a second longitudinal section of the cladding tube wall (2) is detected.

10. Device (30) for producing an optical radiator with a cladding tube made of glass, which has a wall with at least one pinch in which a current feedthrough is embedded in a gas-tight manner, comprising: • a receptacle for the cladding tube (1; 31; 101) and a current feedthrough arranged therein, • at least one burner (38a; 38b) for heating a predetermined length section of the cladding tube wall (2), and • two cooperating squeezing jaws (34a; 34b) for squeezing the heated length section in the area of ​​the current feedthrough, 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) when heating the length section can be adjusted depending on the detected wall profile.

11. Device (30) according to claim 10, characterized in that the measuring device (33; 100) is designed for optically detecting the wall profile of the cladding tube wall.

12. Device according to claim 10 or 11, characterized in that the heating time and / or the heating temperature can be adjusted with the setting unit (40) as a function of the detected wall profile.

13. Device (30) according to one of the preceding claims 10 to 12, characterized in that the measuring device (33; 100) is movable in the direction of a longitudinal axis of the holder and perpendicular to the holder's longitudinal axis.

14. 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 measuring sensor (36a; 36b) with two measuring heads rotated by 180° to each other.

15. 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 mounted on a common burner carriage.

16. Optical radiator, manufacturable or manufactured according to one or more of claims 1 to 9.

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