Method for continuous manufacturing of fiber optic waveguide sensors mounted in drilled metallic hollow shapes

Abstract

To provide a method for continuous production of an optical fiber waveguide sensor mounted in a perforated metal hollow profile.SOLUTION: A method includes: a step of locating a protective tube which reaches a tip of a perforated point on a drawing side, in a welded metal hollow profile; a step (111) of feeding one or a plurality of fiber waveguides through one or a plurality of fiber unwinders, the one or more fiber waveguides being introduced downstream of the perforated point in a drawing direction, from a guide or the protective tube, into the perforated metal hollow profile; and a step (124) of receiving the perforated metal hollow profile with the one or more fiber waveguides mounted therein, in a receiving unit (25).SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to the manufacture of optical fiber waveguide sensors made of metal and having an outer shell perforated by drill holes, and in particular to the continuous manufacture of such fiber waveguide sensors having a metal casing. [Background technology]

[0002] Fiber waveguides for light signal transmission, also called optical waveguides or light guides, are housed in plastic and / or metal shells depending on the application and the requirements for mechanical stability and protection from environmental influences and hydrogen diffusion. Fibers in metal shells are used, for example, in the case of undersea cables and are also commonly laid as communication channels in the earth wires of high-voltage lines. Fiber waveguides surrounded by a metal shell are also called optical fiber covered with metal tube, or FIMT for short.

[0003] Glass fibers can also be used as sensors for various physical variables, such as for measuring pressure, temperature, vibration and other measurable variables in bridge structures, wind turbines or in oil and natural gas production systems. These fiber waveguide sensors are often housed in a metal shell, especially to protect them from mechanical damage, and especially from high grade steels for their chemical resistance. Holes can be introduced into the metal shell to allow better transmission of the measurable variables through the metal shell to the glass fiber.

[0004] One or more fibers may be inserted into one metal tube. To avoid tearing or breaking of the fibers due to changes in the length of the metal tube caused by temperature changes or mechanical tensile stresses, the fibers may be accommodated in the metal tube at a length longer than that of the metal tube.

[0005] In the case of a known continuous process for the production of metal tubes with fiber waveguides mounted therein, a fiber waveguide or a bundle of fiber waveguides is fed to a tube-forming process, in which a flat strip of metal, such as high-grade steel, is formed into a tube in which a longitudinal slot is formed to accommodate the fiber waveguide or the bundle of fiber waveguides. The flat strip formed into the tube is welded with a longitudinal seam along the slot. A process of this kind and an apparatus constructed therefor are shown, for example, in US Pat. No. 5,399,323.

[0006] Since when drilling holes in the metal shell the fiber waveguide guided therein can be damaged and even a single damage of the fiber waveguide during the drilling process can make the entire production length unusable, the holes are introduced in the metal shell before the fiber waveguide is introduced. Usually, holes are first introduced, for example by punching, in the metal strip which is then formed into the metallic hollow shape, as shown for example in (US Pat. No. 5,399,323).

[0007] If welding is performed by arc welding methods, e.g. tungsten inert gas welding (TIG), wall thicknesses below 0.15 mm cannot be reliably welded. Tubes welded with known arc methods may also have highly visible weld beads that protrude into the interior of the tube and expose the fiber waveguides mounted therein to the risk of mechanical damage. Furthermore, tubes with a diameter below φ4.0 mm cannot be produced by known methods. Thus, there is a lower limit to the dimensions of the metal tubes that house the fiber waveguides or bundles of fiber waveguides, which leads to larger minimum bending radii and heavier weights.

[0008] The laser welding method allows the continuous production of metal tubes with a diameter of at least 2 mm with waveguides inserted therein. To achieve much smaller diameters, the diameter reduction must be carried out after welding of the metal strips formed into a closed metallic hollow shape by drawing dies, rollers and other punching tools. All these methods for tube diameter reduction have the common problem that the compressive stress in the circumferential direction causes a plastic flow of the material, which has the effect of closing the previously introduced perforations. Even with a diameter reduction of more than 20%, the holes close completely. The change in the shape of the perforations during tube diameter reduction is shown diagrammatically in FIG. 1. In FIG. 1a) a segment of a tube R with a first diameter D1 and provided with a round hole L is shown. After diameter reduction by the drawing process, the tube segment becomes longer due to the plastic flow of the material and has a smaller diameter D2, but the previously round hole L has also been transformed into an elongated oval. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] European Patent Application Publication No. 0727679A1 [Patent Document 2] Japanese Patent Application Publication No. 05-157589 Summary of the Invention [Problem to be solved by the invention]

[0010] It is therefore an object of the present invention to propose an improved method and a corresponding device for the continuous production of fiber waveguide sensors mounted in drilled metallic hollow shapes. [Means for solving the problem]

[0011] This object is achieved by a method according to claim 1 and by a device according to claim 9. Further developments and embodiments are specified in the respective dependent claims.

[0012] In the method according to the invention for the continuous production of perforated hollow metal shapes, in which one or more waveguides are attached, a flat metal strip is first fed, for example from a coil. The width of the fed metal strip preferably already corresponds to the circumference of the hollow metal shape. If the fed metal strip is wider than required by the circumference of the hollow metal shape or if the edges of the metal strip are not sufficiently smooth, it can be trimmed to size on one or both sides in a continuous process during the feeding operation. In the present description, the expression "metal" is used for all types of metals and their alloys, including non-ferrous metals, in particular high-grade steels. The speed at which the metal strip is fed or the length fed per unit time can be continuously detected.

[0013] Metal strips available in suitable widths are successively formed into hollow metal shapes with the desired cross-section in a one-step or multi-step deformation process. The deformation process may for example comprise bending steps along the length of the strip, carried out in several successive steps on rollers and moulds of corresponding configuration, where the cross-section may be circular, elliptical, in particular vertical elliptical or any desired polygonal shape. A vertical elliptical cross-section may offer advantages during the closing of the hollow metal shape, allowing easy transformation into a circular hollow metal shape after closing.

[0014] During or after the deformation process, one or more individual fiber waveguides or one or more bundles of fiber waveguides are fed in to be mounted in the hollow shape. The one or more fiber waveguides can be surrounded by a non-metallic layer. If several fiber waveguides are fed in, guide means can be provided that prevent the fiber waveguides from twisting or entangling with each other. In order to prevent damage to the fiber waveguide or bundle of fiber waveguides as a result of the welding process by the means for radially closing the metallic hollow shape, the fiber waveguide or bundle of fiber waveguides is guided in a guide or protective tube, which advances from the feed side as seen in the drawing direction and projects into the metallic hollow shape beyond the welding point, only after which the one or more fiber waveguides are exposed.

[0015] In an embodiment of the method, the length of the fiber waveguide delivered per unit time can be determined continuously, for example by continuous measurement of the delivery speed. This can be particularly useful to determine the excess length of the fiber waveguide(s) introduced into the metallic hollow shape. The excess length of the fiber waveguide(s) can compensate for differences in linear expansion between the metallic hollow shape and the fiber waveguide(s) when there is a temperature change, so that no breakage or tearing of the fiber waveguide(s) occurs.

[0016] After deformation, the metallic hollow profile has a longitudinally extending region in which the edges of the metal strip butt flush against one another. The edges that butt flush against one another are welded to one another along the abutting edges and are thus radially closed. The welding can be performed, for example, by laser or arc welding.

[0017] In the following, the electromagnetic radiation emitted by the laser will be referred to as "light", but the wavelength of the electromagnetic radiation may be in the wavelength range invisible to humans.

[0018] In laser welding, the laser introduces light energy at a point in the weld zone, which is absorbed and converted into heat when it hits the surface of the weld material. In order to introduce a sufficient amount of energy into the weld material, the light must be focused intensively. Intensive focusing is therefore also necessary since welding is intended to take place only in the contact area of ​​the edges along the slot. Due to the high energy density at the point where the laser beam hits the workpiece, the material melts locally on both sides of the abutting edges, whereby the melt flows and fuses together. The material solidifies again when the laser beam no longer hits it, forming a weld seam. Due to heat conduction in the metal, the area directly adjacent to the point where the laser beam hits can be heated intensively and melted as well. Especially when the cross-sectional dimensions of the metallic hollow shapes to be produced are small, for example when the cross-sectional dimensions are less than 4 mm, therefore focusing of the laser beam is very important to avoid uncontrolled outflow of liquefied material or material detachment.

[0019] The metallic hollow shape, in which one or more fiber waveguides are received, is guided continuously past a static laser, so that a continuous weld seam is produced connecting the two edges. In order to prevent uncontrolled flow of the liquid material, which would occur in the case of practically small wall thicknesses, the power of the laser introduced and the speed at which the tube is moved past the laser must be coordinated with each other. With the proper coordination, a smooth weld seam is produced on the outside and inside, without the need for rework.

[0020] In contrast to known arc welding with tungsten inert gas (TIG) or metal inert gas (MIG), where an inert gas atmosphere prevents the melt from reacting with the surrounding air and thus achieves a high level of seam quality, the laser welding used in the present invention allows metals with a material thickness of less than 0.15 mm to be butt-welded to one another even without the use of shielding gas, whereby the energy input can be better controlled and no weld bead is formed on the inner surface of the tube. However, even in laser welding, an inert shielding gas, for example argon, can flow around or cover the weld point. The use of a shielding gas atmosphere can depend in particular on the weld material and its thickness. The shielding gas can be conveyed to the weld area on the inner surface of the metallic hollow shape, for example through an annular gap in a guide or protective tube.

[0021] The distribution of the energy input by the laser can be carried out either by focusing on a relatively large target area, so that the available energy acts on a larger or smaller area than required, or by moving a particularly finely focused laser beam back and forth accordingly. Focusing on a relatively large target area can also be achieved by a laser profile with a central focus of high intensity and an annular region of lower intensity surrounding the central focus. In this way, the weld area can be heated and cooled in a particular temperature profile, which results in a cleaner weld seam and can affect the structure in particular after solidification. Furthermore, the laser beam can be easily pulsed, the control of the energy input being carried out, for example, by pulse duration and pulse interval.

[0022] Welding with a laser, especially heat conduction welding with a power density that does not lead to evaporation of the weld material, produces smooth, rounded weld seams that do not require further rework. In the case of heat conduction welding, outside the area where the laser hits, the energy spreads in the workpiece only by heat conduction. In general, the width of the seam is greater than the depth of the seam. If the heat cannot be dissipated quickly enough, the processing temperature will be higher than the evaporation temperature, which will result in the formation of metal vapor and a sharp increase in the weld depth. The process therefore changes to deep penetration welding. Here, the weld seam quality will decrease, the process stability will be affected and the list of weld defects will be high. Even damage to the guide or protective tube through which the fiber is inserted into the tube can occur. This can be avoided by controlling the laser power accordingly.

[0023] The high quality of the weld seams on the outer surface and especially on the inner surface of the tubes produced according to the invention, which are free of noticeable material beads along the weld seam due to the fine control of the energy input to the weld point, makes it possible to produce metallic hollow shapes with thin wall thicknesses and small cross-sectional dimensions in a continuous process.

[0024] After welding, the metal hollow shape is pulled from the welding area by a feeding unit, e.g., by a pulling collet, pulling cleat, pulling capstan or pulling belt, and fed to a drilling device, which perforates the metal hollow shape to better transmit the measured variable to the fiber waveguide or waveguides.

[0025] The drilling is preferably performed by a laser. Various drilling methods can be used for this, such as single pulse or percussion drilling, trepanning drilling or helical drilling.

[0026] In single-pulse drilling, a short laser pulse with high power density delivers energy very quickly into the workpiece, causing the material to melt and vaporize. The higher the pulse energy, the more material is melted and vaporized. During vaporization, the volume of material in the drilled hole increases rapidly, creating high pressure. This vapor pressure expels the molten material from the drilled hole.

[0027] In the case of percussion drilling, ultrashort laser pulses in the nanosecond range or shorter are used, and the material evaporates directly from the solid state by sublimation, i.e. without melting of the material; the component is not heated or is only slightly heated in this case. Shorter pulse lengths in the picosecond or femtosecond range promote sublimation.

[0028] In helical drilling, the laser is moved in an elliptical or circular path over the material, which is removed by the laser pulses. Like a spiral staircase, the laser works downwards, and the focus can readjust itself so that it is always at its lowest point. Once the material is drilled, the edges can be smoothed to obtain an approximately cylindrical hole. In helical drilling, a relatively large amount of material is ejected upwards.

[0029] In the case of trepanning drilling, a drill hole can similarly be created with multiple laser pulses. An initial hole is first drilled by percussion drilling and then enlarged by moving the laser in multiple increasingly oval or circular paths over the workpiece. In the case of trepanning drilling, molten material can be driven downward from the drill hole.

[0030] The drilling methods may also be used in sequence, for example by first drilling a blind hole by helical drilling and then drilling through it by percussion drilling, etc. In this way, the molten material will hardly penetrate into the interior of the metal hollow shape.

[0031] In the case of the above-mentioned drilling methods in which multiple laser pulses are used, the laser can be conveyed by the moving workpiece, for example by a correspondingly configured scanner or by being conveyed by an optical system, in which case the pulse frequency of the laser and the feed speed of the workpiece are synchronized.

[0032] The shape of the drill holes can in this case be chosen with some freedom within the limits of the dimensions of the metallic hollow shape: thus, circular or elliptical holes can be drilled or transverse or longitudinal slots can be introduced into the metallic hollow shape.

[0033] In order to prevent the fiber waveguide(s) or their plastic casing from being damaged by the material used for drilling or the laser radiation penetrating the metallic hollow shape during the drilling process, according to the invention, a guide or protective tube is extended beyond the drilling point, so that the fiber waveguide(s) is / are located unconstrained only in the part of the metallic hollow shape beyond the drill hole.

[0034] With respect to the wavelength of the laser used for drilling, the material of the guide or protective tube preferably has a lower energy absorption rate or a higher reflectivity than the metallic hollow shape. For example, in the case of a metallic hollow shape made of high-grade steel, a laser with a wavelength longer than 600 nm can be used for drilling. Since light of these wavelengths is very well absorbed by high-grade steel, but is largely reflected, i.e. only slightly absorbed, by copper and other metals, copper and other metals can advantageously be used as material for the guide or protective tube. In this way, the protective tube can prevent one or more fiber waveguides guided therein from damage with respect to multiple drill holes until the guide or protective tube itself is drilled.

[0035] In order to further delay the occurrence of a change of the guide or protective tube during production, i.e. interruption of production, the guide or protective tube can be introduced into the metallic hollow shape at the beginning of the production run a specific first length beyond the drilling point and can be pulled back each time a specific second length after a specified number of drill holes. As a result, the laser beam does not always hit the same point of the guide or protective tube and the molten material of the metallic hollow shape, which can penetrate into the metallic hollow shape during the drilling process, cannot accumulate at one point and weld the metallic hollow shape to the guide or protective tube. In the case of a radially closed guide or protective tube, it can be rotated by a specified angle around its longitudinal axis before being pulled back a specific second length after a specified number of drill holes, so that a different point of the guide or protective tube is below the drill holes. A combination of rotation and pulling back is also envisaged. The second length is preferably significantly shorter than the first length and is at least as long as the diameter of the drilling holes.

[0036] Instead of being radially closed, the guide or protective tube can have the form of a channel, which covers one or more fiber waveguides towards the drilling side. This form can be used in particular whenever the drill holes are introduced from only one side of the metallic hollow shape. The form of the channel is placed on the inner wall of the metallic hollow shape of the guide or protective tube and has the effect of reducing the surface area that can be rubbed, thus making the introduction and withdrawal easier.

[0037] In an embodiment of the method, the cross-sectional dimension, i.e. for example the diameter, of the metallic hollow shape is reduced to the desired final size after welding and before drilling. For this purpose, the welded metallic hollow shape can be guided through a drawing die or a forming die by one or more separate feeding units. For example, in the case of materials such as high-grade steels, the reduction of the cross-sectional dimension can also be used, in particular, for strength enhancement by cold forming and therefore for increasing the resistance to mechanical environmental influences. Since the drilling is performed only after the main reduction step of the cross-sectional dimension, the drill hole is not deformed or is only slightly deformed.

[0038] In an embodiment of the method, the cross-sectional dimensions of the drilled metallic hollow shape may be slightly reduced again by the drawing process after drilling. For example, even if it is reduced by 5-10%, the deformation or reduction in size of the drilled hole is still acceptable. In this way, a larger gap may remain between the guide or protective tube, reducing or preventing rubbing or adhesion.

[0039] In order to avoid the heated material sticking to subsequent drawing and feeding devices after welding, the metallic hollow shape can be cooled by a cooling device downstream of the welding area, preferably before the next feeding unit. Furthermore, the welded structure can be particularly affected by the cooling.

[0040] A filler gel introduced into the hollow metal shape may be used to further reduce rubbing of the guide or protective tube against the inner surface of the hollow metal shape, but is primarily used in embodiments of the method for embedding one or more fiber waveguides into the hollow metal shape.

[0041] The filler gel can be introduced into the metallic hollow shape via a guide or protective tube, for example via an annular gap in the guide or protective tube, which is arranged away from the opening exposing the fiber and surrounds the fiber waveguide or waveguides. The filler gel can be less viscous at higher temperatures than at lower temperatures. Therefore, in order to make it particularly easy to introduce the filler gel, it can be warmed up before introduction, for example in a storage container. Fine adjustment of the gel temperature can be performed in a filling hose and / or in a filling head connecting the storage container to the guide or protective tube. During the introduction of the filler gel, the through flow rate per unit time is measured and set so that the filler gel does not flow back against the production direction.

[0042] The filler gel can be provided in the guide or protective tube up to the point of perforation or introduced directly before, for example at the point where the reduction in cross-sectional dimension occurs. In the latter case, the guide or protective tube guiding the fiber waveguide is guided in the gel to the part of the metallic hollow shape with reduced cross-sectional dimension up to the point where the metallic hollow shape is perforated, which can facilitate pulling back or rotating the guide or protective tube.

[0043] In order to be able to introduce one or more fiber waveguides into the hollow metal shape with a certain slack, in the configuration of the method, the perforated hollow metal shape can be stretched elastically. In this case, the one or more fiber waveguides are placed in the stretched hollow metal shape without tensile stress. Here, the fiber gel in which the one or more fiber waveguides are embedded is preferably introduced into the hollow metal shape. The expression "slack" is used in the present description as the ratio of the length of the fiber waveguide in the unstretched, respectively unstressed state to the length of the hollow metal shape surrounding it, which is by definition always greater than 1. The part of the fiber waveguide that is outside the hollow metal shape is here ignored.

[0044] The elastic stretching can be performed, for example, using a drawing capstan, which introduces a tensile force into the metallic hollow shape. The tensile force can be continuously monitored and controlled in a closed-loop manner by correspondingly controlling the capstan drive, thereby preventing it from being permanently lengthened. The fiber waveguide(s) embedded in the filler gel in the metallic hollow shape are not stretched by this tensile force. Rather, a correspondingly additional length of the fiber waveguide(s) must be delivered in order to ensure that the fiber waveguide(s) introduced into the metallic hollow shape are substantially free of tensile stress throughout the entire manufacturing process. Since the filler gel viscosity is still low due to the temperature, again during the elastic stretching, substantially no forces are transmitted between the inner surface of the elastically stretched metallic hollow shape and the fiber waveguide(s). A cooling device downstream of the welding area, in this case the metallic hollow shape, can be controlled in a closed-loop manner so that the temperature does not drop below a temperature at which the viscosity of the filler gel exceeds a predetermined value. The elastically stretched hollow metal shape can be brought in a stretched state around the drawing capstan several times, so that the hollow metal shape and the filler gel introduced therein can be further cooled, in particular to a temperature at which the viscosity of the filler gel increases significantly. Downstream of the drawing capstan there can be another feed unit, for example a drawing belt, which holds the hollow metal shape on the capstan. The other feed unit delivers the hollow metal shape from the drawing capstan to the winder in an unstretched and substantially free of tensile stress. Here, "substantially free of tensile stress" is understood to mean that the hollow metal shape is not subjected to any elastic stretching or is only subjected to a negligible degree. The length of the hollow metal shape delivered from the drawing capstan per unit time is continuously determined, for example by continuous detection of the speed.

[0045] The tensile stress downstream of the drawing capstan is eliminated, and the hollow metal shape contracts again elastically. The gel, introduced in a hotter and liquid state, is now harder as a result of the cooling that has taken place so far and acts as a kind of frictional force enhancer between the fiber waveguide and the inner surface of the hollow metal shape, which transfers the movement of the contracting hollow metal shape to the fiber waveguide or fibers. Since the cooled gel does not allow a completely free movement of the fiber in the hollow metal shape, and in particular does not allow a simple longitudinal displacement over a relatively long section, the fiber waveguide or fibers, which are always present in a substantially unstressed state in the metal tube during the manufacturing process, are too long for the shorter hollow metal shape in an unstressed, unstretched state, and are, so to speak, "compressed" on average over the entire length of the hollow metal shape. The fiber is not actually compressed in this case, but is displaced from its longitudinal axis so as to buckle inside the hollow metal shape.

[0046] During the manufacturing process, the length of the hollow metal profile delivered from the drawing capstan per unit of time and the length of the fiber waveguide(s) delivered per unit of time are continuously determined and averaged over a specified time to compensate for closed-loop control fluctuations of the drive control. A suitable time may be in the range of minutes, but a longer duration leads, on the one hand, to more accurate results, but on the other hand, to a correspondingly longer time until a closed-loop control intervention that may be required. From the averaged measurements, the excess length of the waveguide(s) in the hollow metal profile manufactured during that time is determined. In order to be able to dynamically correct deviations from the setpoints, in addition to detecting the length of the fiber waveguide(s) fed per unit time and the length of the hollow metal shape fed from the drawing capstan per unit time, at least one controllable variable in a non-exhaustive first list is continuously recorded, including the feed rate of the metal strip or the length of the metal strip fed per unit time, the power of the laser, the temperature of the filler gel, the flow rate of the filler gel per unit time, the drawing rate of the hollow metal shape from the welding area, the pulling force on the hollow metal shape and the temperature of the hollow metal shape upstream of the drawing capstan. From the at least one controllable variable, at least one operable variable is detected for the open-loop control of the power of the laser, for the closed-loop control of the heater, the filling head and / or the cooling device of the storage vessel and / or for the open-loop control of the drive of the one or more feed units and / or the drawing capstan.

[0047] In one or more embodiments of the method, the width of the metal strip being fed is measured and the cutting width is adjusted in a manner dependent on the measurement and on a standard value, the width approximately corresponding to the circumference along the neutral element of the metal hollow shape surrounding the waveguide or bundle of waveguides, where the standard value can be different and the deformation device can be controlled accordingly in a manner dependent on the changing width of the metal strip, for example to adjust the amount of material required for a clean weld seam.

[0048] In one or more embodiments of the method, a transverse temperature profile is measured with respect to the weld seam. The measured temperature profile can be used to control the energy input to the weld point. The measured temperature profile can be compared, for example, to a standard profile, and the control of the energy input can include changing the diameter of the focal spot, the path described by the focal spot on the weld material, and / or the pulse duration and / or the pulse interval of the laser beam. This is likewise envisaged for the feed speed of the metal strip, which is controlled in a closed-loop manner depending on the measured temperature profile. The measured temperature profile can also be stored for quality control and documentation purposes.

[0049] In one or more embodiments of the method, for this purpose the length of the metal strip fed per unit of time is continuously measured. From the ratio of the length of the welded, reduced metal hollow shape fed per unit of time to the length of the metal strip fed in unit of time, substantial deviations of the metal strip, for example different yield strengths, can be detected, which can be taken into account directly in the closed-loop control of the production process.

[0050] In one or more embodiments of the method, the weld seam is inspected by ultrasonic, x-ray, eddy current measurement or other non-destructive measurement methods. The results of the inspection can be used, for example, to control the input and / or delivery rate of energy to the weld point.

[0051] The device according to the invention for the continuous production of perforated hollow metal shapes, in which at least one fiber waveguide is mounted, comprises a feed unit configured to feed a flat strip of metal. The feed unit may, for example, comprise a mount for a flat metal strip wound on a reel or coil. The metal strip is unwound from the reel or coil and fed to a deformation tool, which deforms the flat metal strip into a hollow metal shape such that the opposite edges of the flat metal strip butt against each other in the same plane in a butt joint manner. The deformation device may, for example, comprise a plurality of rollers and dies, for example drawing dies, which deform the metal strip passing through it in the length direction to form the desired hollow metal shape. The deformation device may further comprise two or more guide means, which are spaced apart from each other in the length direction of the deformed metal strip or hollow metal shape, between which the edges are held so that they butt against each other in the same plane at least at the points where they are to be welded. If desired, the strip may be guided laterally at one or more points upstream of and within the tool to minimize lateral movement of the strip.

[0052] The apparatus further includes a welding device for welding together the edges that are in a mutually flush butt position between the guide means. The welding device may, for example, include a laser that emits a light of energy that locally melts the metal on either side of the edges. However, the welding device may also include an arc welding device.

[0053] As a result of the continuous drawing of the deformed and welded hollow metal shape, areas leave the welded area and the molten material solidifies again. The energy input to the material for its heating is adjusted to the material, its thickness and the speed at which the hollow metal shape is led through the weld so that the material melts in the area directly at the edges where they butt flush with each other, but no liquid material flows into the interior of the hollow metal shape. During laser welding, the distance between the optical system of the laser and the edges of the hollow metal shape to be welded can be kept constant by guide means. In order to keep the position of the edges abutting each other constant with respect to the optical system of the laser, upstream of the guide means closing the longitudinal slot, a guide blade can be arranged in the longitudinal slot between the edges to prevent the hollow metal shape from twisting in the axial direction.

[0054] The device further comprises a feeding unit configured to feed at least one fiber waveguide. The fiber waveguide or waveguides, which may be surrounded by a non-metallic layer, are for example unwound from one or more fiber unwinders and introduced into the welded metallic hollow shape via a guide or protective tube starting from the entry side of the metallic hollow shape and ending beyond the welding point. If several fiber waveguides are fed, the feeding unit may have fiber guides that guide the fiber waveguides separately, preventing the fibers from twisting or twisting together. Alternatively or additionally, the feeding unit may have one or more so-called fiber binders, which combine several fibers to form a bundle and wind a thread around it. The feeding unit further comprises a measuring unit for continuously, preferably contactlessly, measuring the length of the fiber waveguide or waveguides fed per unit time.

[0055] The apparatus further includes one or more feed units, which draw the welded hollow metal shape from the welding area and deliver it to a drilling device, whereby the hollow metal shape is drilled.

[0056] The drilling device may in particular include a laser, which may be configured for single pulse, percussion, trepanning or helical drilling and / or other drilling methods depending on the drilling method used, the size of the hole and the wall thickness of the metal hollow shape. The drilling device may be movably arranged to be moved at the feed rate of the metal hollow shape or may have a movable optical system or scanner for deflecting the laser beam to move at the feed rate of the metal hollow shape if the drill holes are not produced by a single pulse drilling method.

[0057] In the device according to the invention, the guide or protective tube through which the fiber waveguide or waveguides are introduced into the hollow metal shape is arranged in the drawing direction of the hollow metal shape up to the drilling device, so that the fiber waveguide or waveguides are free in the hollow metal shape only after the introduction of the hole, thereby preventing damage to the waveguide or waveguides or their plastic casing by the material penetrating into the hollow metal shape during the drilling process or by the laser radiation used for the drilling process.

[0058] With respect to the wavelength of the laser used for drilling, the material of the protective tube preferably has a lower energy absorption rate, i.e. a higher reflectivity, than the material of the metallic hollow shape. For example, in the case of a metallic hollow shape made of high-grade steel, a laser with a wavelength longer than 600 nm can be used for drilling. Since light of these wavelengths is very well absorbed by high-grade steel, but is largely reflected, i.e. only slightly absorbed, by copper and other metals, copper and other metals can advantageously be used as material for the guide or protective tube. In this way, the protective tube can prevent one or more fiber waveguides guided therein from damage with respect to multiple drill holes until the guide or protective tube itself is drilled.

[0059] In order to further delay the change of the guide or protective tube during production, i.e. the interruption of production, an embodiment of the device according to the invention can be configured to introduce the guide or protective tube into the metallic hollow shape by a first length beyond the drilling point at the beginning of the production run and to withdraw it by a specific second length each time after a specified number of drill holes. As a result, the laser beam does not always hit the same point of the guide or protective tube and it does not occur that the molten material of the metallic hollow shape, which may penetrate into the metallic hollow shape during the drilling process, accumulates at one point and welds the metallic hollow shape to the protective tube. In the case of radially closed guides or protective tubes, the device according to the invention can also be configured to rotate the guide or protective tube by a specified angle around its longitudinal axis before withdrawing it by a specific second length after a specified number of drill holes, so that a different point of the guide or protective tube is below the drill holes. A combination of rotation and withdrawal is also envisaged.

[0060] In an embodiment, the device may be configured to introduce a channel-shaped guide or protective tube into the metallic hollow shape beyond the drilling point.

[0061] In an embodiment of the device, devices for reducing the cross-sectional dimensions of the metallic hollow shapes to the desired final size, such as rollers, drawing dies and / or moulds, may be provided between the welding device and the punching device. The metallic hollow shapes may be fed to the device for reducing the cross-sectional dimensions by one or more feeding units, for example by one or more drawing collets, drawing cleats or drawing belts of known configuration. Different feeding units may be combined. Upstream of the feeding units, in an embodiment of the device, the metallic hollow shapes heated by welding are cooled to a temperature at which subsequent adhesion to the tool is effectively avoided and the tool does not leave an indentation in the metallic hollow shapes. Furthermore, the welded structure may be particularly influenced by the cooling.

[0062] In an embodiment of the apparatus, a device for reducing the cross-sectional dimension of the drilled metallic hollow shape may be provided downstream of the drilling point in the drawing direction, the reduction being small in this case such that the drilled hole is not deformed or reduced in size more than is acceptable for the intended application.

[0063] The device may further comprise a gel filling unit for introducing a filler gel into the metallic hollow shape in which the fiber waveguide or fibers are mounted. The filler gel may increase in viscosity with increasing temperature and may likewise be introduced into the metallic hollow shape via a guide or protective tube or via a tube coaxially surrounding it. In one embodiment, an annular gap for introducing the filler gel is formed between the guide or protective tube and the tube guiding the filler gel, downstream of the welding point, e.g. beyond the point where the cross-sectional dimension of the metallic hollow shape is reduced to the desired final size or beyond the drilling point. The guide and protective tube for the fiber waveguide or fibers may in this case be coaxially movable within an outer tube surrounding the protective tube and through which the filler gel is introduced. The gel filling unit may have a storage container and be configured to introduce the filler gel into the metallic hollow shape at a temperature at which the viscosity of the filler gel does not exceed a predetermined value. For this purpose, the storage container, the filling hose connected thereto and / or the filling head connected thereto may be heated in a manner that is controlled, in particular by a closed-loop temperature control unit. The gel filling unit is further configured to continuously detect a volume of the filler gel introduced into the metallic hollow shape per unit time.

[0064] In an embodiment, the device may be configured to introduce the fiber waveguide with a slack in the metallic hollow shape. For this purpose, the device may include a drawing capstan arranged downstream of the drilling device, through which a pulling force is applied to the metallic hollow shape, stretching it elastically. The elastically stretched metallic hollow shape may then be guided around the drawing capstan multiple times. The pulling force provided by the drawing capstan may be continuously monitored by a force measuring device and adjusted to a set point by a closed-loop control. Alternatively, the drawing capstan may be driven at a constant speed slightly higher than the speed of the preceding drive, thus resulting in an elastic stretching of the perforated metallic hollow shape. The perforated metallic hollow shape is guided substantially stress-free from the drawing capstan, thereby terminating the elastic stretching. The fiber waveguide or fibers are then introduced unstretched into the metallic hollow shape.

[0065] The apparatus may further comprise a measuring unit, which is arranged downstream of the drawing capstan and serves to measure, preferably without contact, the length of the metallic hollow shapes drawn from the drawing capstan and fed to the winder per unit time.

[0066] After the drawing capstan, a further feeding unit may be arranged, which holds the hollow metal shapes on the drawing capstan such that the hollow metal shapes are not substantially elastically stretched. A measuring unit for determining the length of the hollow metal shapes drawn from the drawing capstan and fed to the winder per unit time may be arranged between the drawing capstan and the further feeding unit or downstream of the feeding unit.

[0067] In one or more embodiments of the device, a measuring device is provided upstream of the deformation device for ascertaining the tensile force, which is fed as an actual value to the closed-loop control means and can be used together with a set value for the closed-loop control of the drive of the device, for example for the closed-loop control of the feed speed of the metal strip.

[0068] In one or more embodiments, the apparatus further comprises a cutting unit, which is arranged upstream of the deformation unit, whereby one or both edges of the fed flat metal strip are trimmed, the width of the trimmed metal strip approximately corresponding to the circumference along the neutral line of the hollow metal shape. In these embodiments, the fed metal strip is cut to the required width and another tool of the apparatus is adapted thereto, making it possible to produce hollow metal shapes of different circumferences without great expense.

[0069] In one or more embodiments of the device comprising a cutting unit, a measuring unit is provided downstream of the cutting unit for measuring the width of the cut-to-length metal strip. Based on the measured value, the cutting unit can be controlled such that the desired width of the metal strip is maintained over time. The cutting unit can be provided with corresponding standard values ​​with which the measured width of the metal strip is compared to generate control signals for the settings of the cutting unit.

[0070] The cut-off portions at one or both edges of the strip may, in one or more embodiments, be fed into an apparatus provided to receive the cut-off portions.

[0071] In one or more embodiments, the apparatus further includes a measurement unit for determining a transverse and / or longitudinal temperature profile with respect to the weld seam. The measured temperature profile can be sent to the welding apparatus for closed-loop control of the output energy, to the feed unit, for open-loop control of the feed rate and / or to the supply unit for open-loop control of the temperature of the filler gel.

[0072] In one or more embodiments, the device is further configured to cover the inner and / or outer weld point with shielding gas. Inner, the shielding gas can be introduced, for example, through a tube surrounding the guide or protective tube and forming therewith an annular gap at the weld point or into another protective tube. Outer, the shielding gas can be supplied at or near the weld point. To achieve a longer coverage with shielding gas, the welded hollow metallic shape can be guided through a tube section through which the shielding gas flows.

[0073] In one or more embodiments, the apparatus further comprises a measuring unit for measuring at least one dimension of the metallic hollow shape after welding and / or after reduction of the cross-sectional dimension. This measuring unit may be used for integrated quality control in one or more embodiments, similar to the measuring units provided for inspecting the weld seam and / or material defects or material inhomogeneities. The dimensions may preferably be measured contact-free, for example by laser.

[0074] The above-mentioned method and device allow the production of perforated metallic hollow shapes, with or without excess lengths down to a diameter or cross-sectional diameter of less than 1 mm, in a simple manner and at a high quality level, into which one or more fiber waveguides can be introduced in the same work step, without costly reworking. Besides high-grade steel, other metals or metal alloys can of course also be used for the metallic hollow shapes. Perforated metallic hollow shapes deviating from a circular or elliptical cross-section can also be produced by the method according to the invention.

[0075] The smaller cross-sectional dimensions of the perforated metallic hollow shapes in which the fiber waveguides are embedded than those known from the prior art can contribute to saving metal and thus preserving valuable resources. As the dimensions as well as the weight of the product are reduced, the lengths that can be wound on the same type of reel are longer, facilitating transportation and installation or laying.

[0076] The continuous measurement of the slack makes it possible to dynamically adjust process parameters, such as, for example, the temperature and amount of filler gel introduced per unit time, the tensile force acting on the metallic hollow profile and thus the elastic stretching, the fiber feed rate as well as the feed rate of the metal strip being transformed into the metallic hollow profile, already during the ongoing manufacturing process in order to distribute the slack of the fiber waveguide uniformly. Here, it is also possible to detect material-related deviations of the metal strip, for example the elastic yield strength, so that during the elastic stretching or during the drawing for the purpose of diameter reduction of the welded metallic hollow profile, a corresponding adjustment of the tensile force can be made during the ongoing process.

[0077] The invention is explained in more detail below on the basis of embodiments and with reference to the accompanying drawings, by way of example, which are all purely schematic and not to scale. [Brief description of the drawings]

[0078] [Figure 1] 1 shows a schematic diagram of the change in shape of a round hole introduced into a tube before diameter reduction by the drawing process. [Diagram 2] 1 shows an example of a method according to the invention, provided as an example, for the continuous production of optical fiber waveguides mounted in drilled metallic hollow shapes. [Diagram 3] 1 shows an example of an apparatus according to the invention, provided by way of example, for the continuous production of optical fiber waveguide sensors mounted in drilled metallic hollow shapes. [Figure 4] 1 shows various arrangements, given by way of example, of guide and protective tubes in the application of the method according to the invention or in the device according to the invention. [Diagram 5] FIG. 1 shows a simplified schematic of the mounting of a fiber waveguide in a filler gel inside a metallic hollow shape that is elastically stretched and not subjected to longitudinal stress. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0079] In the drawings, the same or similar elements are indicated with the same or similar reference numbers.

[0080] FIG. 1 has already been described in detail with respect to the prior art and will not be described again here.

[0081] 2 illustrates steps of an exemplary method 100 for manufacturing a perforated hollow metallic shape having a fiber waveguide attached therein, according to one embodiment of the present invention. In method step 102, a flat metal strip is fed at a first feed rate to a deformation device, e.g., unwound from a coil. In the deformation device, the fed flat metal strip is deformed in step 108 into a configuration corresponding to the desired hollow metallic shape. Deformation may be performed, for example, by a roll forming tool.

[0082] An optional step 106 can be performed in the cutting unit, in which the edges of one or both sides of the metal strip are trimmed or otherwise adjusted before deformation. In this way, even if the edges of the metal strip are of poor quality, the width of the strip can be set uniformly and accurately, and the edges can be adjusted, if necessary, for a subsequent welding process. The cutting unit can be supplied with measurements from a measuring device that detects the width of the metal strip after the trimming process. The cut-off portion can be received in a corresponding receiving device.

[0083] During deformation, the edges of the metal strip are guided by guide elements to prevent twisting before welding, and edges that are in the same plane butting against each other are guided to a defined position and at a defined distance through the welding device. The guide elements can, for example, comprise one or more fin-type washers or guide blades and one or more guide bushings that are adapted to the geometry of the metallic hollow profile and thus to the geometry of the hollow part to be produced. Closing of the geometry can, for example, be performed by drawing dies, closing rings or side roller stages.

[0084] After deformation, the two edges of the flat strip butt against each other in the same plane in the contact area. In step 110, the edges butting against each other in the same plane in the contact area are continuously welded to each other. The welding is performed by a laser or any other welding device adapted to the material. If necessary, the weld seam can be covered on one or both sides by a shielding gas adapted to the required weld seam quality.

[0085] After welding, the metal hollow shape is extracted from the welding area by a feed unit and perforated in step 112, for example by a laser which drills holes in the wall of the metal hollow shape.

[0086] Prior to this, in step 111, the metal hollow shape may be sent to an apparatus for reducing the cross-sectional dimension to the desired final size.

[0087] Prior to the welding in step 110, in step 109, one or more fiber waveguides are introduced from one or more fiber winders into the metallic hollow shape. According to the invention, the one or more fiber waveguides are guided by a protective or guide tube under the welding area and under a drilling point downstream of the welding area in the drawing direction, where the welded metallic hollow shape is drilled, so that the fiber waveguides only exit from the protective or guide tube in the already welded and drilled metallic hollow shape.

[0088] Along with the fiber waveguide(s), a filler gel may be introduced into the hollow metal tube in which the fiber waveguide(s) are embedded, step 109. The filler gel may be introduced into the hollow metal shape through a guide or protective tube, for example through an annular gap of the guide or protective tube, spaced from the opening exposing the fiber and surrounding the fiber waveguide(s). The filler gel may have a lower viscosity at higher temperatures than at lower temperatures.

[0089] The length of the fiber waveguide or fibers delivered per unit time and possibly the amount of filler gel introduced can likewise be determined continuously in step 109. The filler gel and the metallic hollow shape can be temperature-controlled in step 116 after welding so that the viscosity of the filler gel does not exceed a predetermined value. Before that, the temperature can be measured in step 114. If the embedding of the fiber is to be performed with a predetermined extra length, in step 120 the metallic hollow shape can be elastically stretched, for example by a force applied to the metallic hollow shape by a drawing capstan. The tensile force can in this case be monitored in step 121. The elastically stretched metallic hollow shape is therefore cooled in step 122 so that the viscosity of the filler gel in the stretched state becomes high, whereby it is then sent in step 124 to a receiving device where it is received after the elastic stretching has subsided or been reduced. As another measurement value for the determination of the extra length in step 126, the received length of the metallic hollow shape can be determined continuously in step 123. Recordings 128 of the controlled variables at various times in the method and corresponding determinations 130 of the manipulated variables for the drives and actuators of the apparatus 200 are indicated in the figure by dashed arrows. In particular, the detection of the fiber waveguide and the feed length of the metal strip and the length of the finished product sent to the receiving device for receipt can be used to ascertain the current excess length and adjust it by controlling process parameters such as, for example, the feed speed of the strip, the power of the welding device, the temperature and throughflow rate of the filler gel, the feed rate after welding, the pulling force for elastic stretching, etc.

[0090] To monitor the quality of the weld seam, an optional step 110a may determine a transverse and / or longitudinal temperature profile for the weld seam. The ascertained temperature profile may also be sent to the controller of the laser apparatus and other elements of the apparatus performing the method, in particular to one or more drives providing closed-loop control of the feed rate of the metal strip or the rate at which the welded hollow metal shape is withdrawn from the weld area.

[0091] The method optionally also includes verifying the tensile force applied to the strip before deformation in step 104. The verified tensile force may likewise be sent to one or more drives as a measured variable for closed-loop control.

[0092] The method may further include an optional step 110b, in which one or more dimensions of the welded metallic hollow shape are identified. The ascertained dimensions may be provided as input variables for closed-loop control of the deformation process and the cutting process, in particular for setting the width of the strip.

[0093] The method may also include an optional step 118 after welding, in which the quality of the weld seam and / or the weld material is inspected non-destructively for material defects, for example by eddy current inspection, ultrasound or X-ray.

[0094] In FIG. 2 the subsequent process of cutting the hollow metal shape into pieces or enclosing the hollow metal shape with an insulating or protective layer is not shown.

[0095] FIG. 3 shows an example of an apparatus 200 according to the invention, provided by way of example, for the continuous production of perforated hollow metal shapes, in which one or more fiber waveguides are attached. From a reel or unwinder 2, a thin metal strip 1 is unwound, for example made of high-grade steel. The metal strip 1 is fed to a roll-forming tool 3,7, whereby it is brought into the form of the desired hollow metal shape, for example formed into a round tube with a longitudinal slot. Between the reel or unwinder 2 and the roll-forming tool 3,7 a cutting device 4 can be provided, which cuts the metal strip 1 to the required width or cuts off the edges of the metal strip 1 on one or both sides to obtain clean and smooth edges. A receiving device can be provided for receiving the cut-off part of the metal strip 1. The width of the cut-to-length metal strip 1 can be checked with a strip width measuring device. The measurement results can be sent to the cutting unit 4 for closed-loop control. Furthermore, between the reel or unwinder 2 and the roll forming tool 3, 7 a measuring device can be arranged to check the tension, the measured values ​​of which can be used, for example, for closed-loop control of the drive of the device 200. A measuring device 5 can also be provided for monitoring the stripping speed and / or the length of the fed metal strip. Before closing the metal hollow shape, one or more fiber waveguides are fed by a feeding device 9, and a filler gel is provided by a gel filling unit 13, into which the one or more fiber waveguides received in the metal hollow shape are attached. The fiber waveguides can be guided in a fiber guide 10, which prevents entanglement of the fibers. The filler gel can be supplied to the filling head 15 via a filling hose 14, which is connected to a guide or protective tube 12, through which one or more fiber waveguides are also introduced into the metal hollow shape. The length of the fiber waveguide fed per unit time can be monitored with a first measuring unit 11. The gel filling unit may be configured to detect the amount of filler gel dispensed per unit time, for example by a through-flow meter.The edges of the strips which butt against each other after the formation of the metallic hollow shape can be guided by one or more guide elements 6 in front of the laser welding device 8, which prevents the metallic hollow shape from twisting before welding and maintains a space for its passage under the light system of the laser welding device 8. The guide elements 6 can include one or more fin-type washers or guide blades and one or more guide bushings adapted to the metallic hollow shape forming an outer conductor. The geometry of the metallic hollow shape to be welded is closed by drawing dies, closing rings, side roller stages or guide bushings 7, whereby the edges of the metal strip 1 to be transformed into the metallic hollow shape butt against each other in the area of ​​the laser welding device 8. The welding area can be covered with a shielding gas, for example argon, for example by a shielding gas device not shown, which prevents a reaction of the welding material with the atmosphere. The supply of the welded metallic hollow shapes is carried out by a supply unit 16. The feed unit 16 may include, for example, one or more pulling collets, pulling cleats, or pulling belts, or combinations thereof.

[0096] The metallic hollow shape being pulled out of the welding area can be cooled by the cooling device 17 to a temperature at which the viscosity of the filler gel does not exceed a predetermined value and / or the risk of the metallic hollow shape sticking after the guiding, feeding and / or unit is reduced.

[0097] Another feed unit 18 and drawing die mount 19 reduce the size of the hollow metal shape to the desired final size, and then the walls of the hollow metal shape are drilled by a laser drilling device 27 .

[0098] In the case of the device 200 according to the invention, the guide or protective tube 12, through which the fiber waveguide or waveguides are introduced into the hollow metal shape, is provided in the drawing direction of the hollow metal shape up to the drilling device 27, so that the fiber waveguide or waveguides are free in the hollow metal shape only from the introduction of the perforation onwards. As a result, damage to the waveguide or waveguides or their plastic casing by the material penetrating into the hollow metal shape during drilling or by the laser radiation used for drilling can be prevented. The drilling device 27 or the optical system of the drilling device can be arranged on a moving guide 26, so that the drilling device or its optical unit can follow the movement of the hollow metal shape passing through it and can compensate for the relative movement.

[0099] A tensile force causing elastic stretching can be applied to the perforated metal hollow shape by the drawing capstan 20. The elastically stretched metal hollow shape can be brought around the drawing capstan 20 several times, towards the drawing side the temperature further decreases and the viscosity of the filler gel increases. Before the introduction of the tensile force, the temperature of the metal hollow shape can be checked contactlessly by a temperature measuring device and sent to the cooling device 17 as a controlled variable. Further temperature measurements can be arranged in the production direction downstream of the welding area, downstream of the cooling device 17, downstream of the drawing dies 19 and 23 and / or downstream of a further feeding unit 22 which holds the metal hollow shape on the drawing capstan. From the drawing capstan 20, the metal hollow shape is sent to the winder 25 practically without tensile stress. In this case, the length of the product received per unit time is measured contactlessly by a second measuring device 24. The elastic stretching is terminated by removing the tensile stress, and the fiber waveguide(s) are buckled and compressed by the filler gel due to its higher viscosity during the contraction of the metallic hollow shape, whereby a longer fiber waveguide(s) is received in relation to the length of the metallic hollow shape received by the winder. A control unit, not shown, continuously ascertains the current excess length of the fiber waveguide from the difference in the length measurements of the first and second measuring devices 11 and 24. Furthermore, the current process parameters or reference variables, such as the feed speed of the metal strip, the laser power, the gel temperature, the gel throughflow, the feed speed, the pulling force and the temperature outside the tube, are recorded, and these operating values ​​for the laser power, the gel temperature, the feed speed, the cooling power and / or the pulling force are determined for an automatic closed-loop control of the excess length.

[0100] FIG. 4 shows various exemplary arrangements of guides and protective tubes in the application of the method according to the invention or in the device according to the invention.

[0101] In Fig. 4a), the fiber waveguide F is introduced into the metallic hollow shape H in a guide or protective tube 12. The guide or protective tube 12 in this case extends below the laser welding device 8 up to the end of the hole drilling device 27 into the metallic hollow shape drilled by the hole drilling device. A reduction in the outer diameter of the metallic hollow shape H occurs between the laser welding device 8 and the hole drilling device 27. The arrow on the right side of the figure indicates the drawing direction of the metallic hollow shape.

[0102] Figure 4b) shows a similar arrangement to figure 4a), except that in addition now a filler gel has been introduced into the metallic hollow shape H. The filler gel can for example be guided past the punching device 27 via another tube 12' surrounding the guide or protective tube 12 before entering the metallic hollow shape H.

[0103] Figure 4c) shows a variant of the arrangement of figure 4b), in which the filler gel is already present in the metallic hollow shape H after the reduction of its outer diameter and before the punching device 27. The further tube 12' surrounding the guide or protective tube 12 also ends here correspondingly earlier.

[0104] In all the arrangements shown in FIG. 4, the guide or protective tube 12 and possibly also the further tube 12' surrounding it can be gradually pulled back from the metallic hollow shape H in the direction opposite to the drawing direction until the fiber waveguide lies free under the drilling device 27 and production has to be stopped.

[0105] Figure 5 shows a highly simplified representation of an elastically stretched metallic hollow shape 500 and the attachment of a fiber waveguide 502 within a filler gel 504 within the interior of the metallic hollow shape 500 that is not subject to longitudinal stress. The representation in Figure 5 is not to scale.

[0106] In FIG. 5a), a tensile stress is applied to the hollow metal shape 500, which stretches it elastically, as indicated by the arrows pointing away from each other at both ends of the illustrated section. It is assumed that the hollow metal shape 500 is stretched only in length, and no change in diameter occurs. The hollow metal shape 500 is still not completely filled with the filler gel 504, leaving a clearance 506 on the upper side. The fiber waveguide 502 is embedded in the filler gel in an unstressed state. Before removing the tensile stress, the temperature of the arrangement is reduced, which increases the viscosity of the filler gel 504. The increased viscosity increases the friction between the inner surface of the hollow metal shape 500 and the filler gel 504, and between the filler gel 504 and the fiber waveguide 502.

[0107] In FIG. 5b), the tensile stress is no longer applied to the hollow metal shape 500. Due to the increase in viscosity of the filler gel 504 due to cooling, a part of the contraction movement in the length direction of the hollow metal shape 500 is transferred to the fiber waveguide 502, which causes a force acting in the length direction of the fiber waveguide 502 that would compress the fiber waveguide. The forces are indicated in the figure by arrows pointing towards each other. The fiber waveguide 502 cannot absorb this force and deflects laterally, resulting in buckling compression. The buckling compression causes a longer fiber waveguide 502 to be attached in the hollow metal shape 500 per section of its length than corresponds to the unstressed length of the hollow metal shape 500. The filler gel 504 therefore completely fills the hollow metal shape 500, due to the reduced volume. Here, the fiber waveguide 502 is not stressed other than by the relatively small bending moment and can stretch again if the metallic hollow profile 500 expands, for example due to warming up. [Explanation of symbols]

[0108] R Pipe Segment L Circular hole / Oval hole D1,D2 diameter F Fiber waveguide H Hollow shaped object 1 metal strip 2 Coil / winding machine 3. Molding tools 4 Cutting unit 5. Measuring Equipment 6 Guide Elements 7 Closing die / bushing 8 Laser welding equipment 9 Fiber winding machine 10 Fiber Guide 11 First measuring unit 12,12' Guide / Protection Tube 13 Gel filling unit 14 Filling hose 15 Filling Head 16 Supply Unit 17 Tube cooling means 18 Supply Unit 19 Drawing die mount 20 Drawing capstan 21 Force measuring unit 22 Supply Unit 23 Drawing die mount 24 Second Measuring Unit 25 Winding machine 26 Mobile Guide 27 Hole punching device 100 ways 102 Feeds metal strip 104 Identifying Tensile Forces 106 Trimming edges 108 Forming hollow objects 109 Fiber Waveguide / Filler Gel Delivery 110 Welding 110a Identify the temperature profile 110b Specify dimensions 111 Reduce dimensions 112 Drilling holes in hollow objects 114 Identifying Temperature 116 Setting the temperature 118 Identifying Quality 120 Elastic stretch 121 Monitoring the tensile force 122 Cooling 123 Measure the received length 124 Reception Unit 126 Identifying the extra length 128 Recording Controlled Variables 130 Identify the manipulated variables 200 equipment

Claims

1. A method (100) for continuous manufacturing of thin-walled, perforated metallic hollow shapes having one or more optical fiber waveguides attached therein, comprising: - feeding (102) a flat metal strip (1) at a first feeding speed into a deformation device (3, 7), - a step (108) of continuously transforming the fed flat metal strip (1) into a hollow metal shape having a longitudinally extending slot, in which two opposite edges of the metal strip (1) transformed into the hollow metal shape butt flush with each other in a contact area extending in the longitudinal direction of the hollow metal shape and are continuously welded to each other in a welding device (8) (110), - extracting the welded metallic hollow shape from the welded area. In a method comprising: - piercing (112) the welded metallic hollow profile using a drilling device (27) arranged at the withdrawal side at a piercing point beyond the welding device (8); positioning a guide or protective tube which runs through underneath the welded area and reaches into the welded metal hollow shape beyond the point of drilling on the withdrawal side; - a step (109) of feeding one or more optical fiber waveguides from one or more fiber unwinders (9) through said guide or protective tube (12), whereby said one or more optical fiber waveguides are protected by said guide or protective tube (12) to a extent downstream of said drilling point in the drawing direction; receiving (124) said perforated metallic hollow shape, in which said one or more fiber waveguides are mounted, in a receiving unit (25); The method further comprising:

2. - Reducing (111) the cross-sectional dimensions of the welded metallic hollow shapes to the desired final size before the drilling step (112). The method of claim 1 , further comprising:

3. 3. The method (100) according to claim 1 or 2, wherein the guide or protective tube (12) protrudes into the metallic hollow shape beyond the drilling point by a specific first length and is withdrawn from the metallic hollow shape by a specific second length and / or is axially rotated by a specified angle after a specified number of drill holes.

4. The method (100) of any one of claims 1 to 3, wherein the drilling step (112) comprises drilling holes in the wall of the metallic hollow shape by means of a laser.

5. - introducing a filler gel to embed said fiber waveguide(s) in said filler gel within said metallic hollow shape; The method (100) of any one of claims 1 to 4, further comprising:

6. The one or more optical fiber waveguides are introduced with a slack in the perforated metallic hollow shape, and a filler gel is optionally introduced together with the one or more optical fiber waveguides, the method comprising: - elastically stretching (120) said perforated metallic hollow shape by introducing a tensile force into said perforated metallic hollow shape; - introducing (109) said optical fiber waveguide(s) and optionally said filler gel into said elongated metallic hollow shape; - terminating said elastic stretching after said introduction (109) of said optical fiber waveguide or waveguides and before reception (124) in said receiving unit (25); The method (100) of any one of claims 1 to 4, further comprising:

7. - continuously determining the length of said optical fiber waveguide(s) delivered in an unstretched state and of the metallic hollow shape removed after terminating said elastic stretching, in which said optical fiber waveguide(s) are introduced; - identifying (128, 130) control or controlled variables for controlling one or more process parameters from a non-exhaustive list including the feed rate of the strip, the power of the welding device, the temperature and the flow rate per unit time of the filler gel, the feed rate after the welding and the tension force for the elastic stretching in order to set the slack length of the optical fiber waveguide received in the metallic hollow shape; The method of claim 6, further comprising:

8. The method (100) of any one of claims 1 to 7, wherein the welding step (110) is performed by a laser welding device.

9. 1. An apparatus (200) for the continuous manufacture of thin-walled, perforated metallic hollow shapes having one or more optical fiber waveguides attached therein, comprising: a feeding unit (2) adapted to feed a flat metal strip (1), a deformation unit (3, 7) for deforming the flat metal strip (1) into the metallic hollow shape and around the fed fiber waveguide, so that opposite edges of the flat metal strip abut flush against one another in the manner of a butt joint; - guide means (6) between which said edges are held flush against one another, a welding device (8) for welding together said edges which butt flush with one another between said guide means (6); In an apparatus (200) comprising: a drilling device (27) arranged beyond the welding device (8) on the withdrawal side for drilling the welded metallic hollow shapes; a delivery device with one or more fiber winders (9), from which the optical fiber waveguide is wound and introduced into the welded metal hollow shape through a guide or protective tube (12) that passes under the welding device (8) and the drilling device (27), the guide or protective tube running through under the welded area and reaching beyond the drilling point in the welded metal hollow shape; a receiving unit (25) for receiving said perforated metallic hollow shape, in which said optical fiber waveguide or waveguides are embedded; The apparatus (200), further comprising:

10. - a device (19) for reducing the cross-sectional size of the welded metallic hollow profile, located between the welding device (8) and the drilling device (27); The apparatus (200) of claim 9, further comprising:

11. 11. The device (200) according to claim 9 or 10, wherein the guide or protective tube is mounted in an axially movable and / or rotatable manner and can be rotated a specific angle and / or pulled out a specific distance from the metallic hollow shape by a drive after a specified number of drill holes.

12. The apparatus (200) according to any one of claims 9 to 11, wherein at the wavelength of the laser of the drilling device used for drilling the holes, the material of the guide or protective tube has a lower energy absorption rate or a higher reflectivity than the material of the metallic hollow shape.

13. a gel filling unit (13) from which a filler gel can be introduced into said welded metallic hollow shape through an annular gap set at a distance from the exit opening for said fiber waveguide or waveguides; The apparatus (200) of any one of claims 9 to 12, further comprising:

14. 14. Apparatus (200) according to claim 13, wherein the gel filling unit comprises a heatable storage vessel, a heatable filling hose (14) and / or a heatable filling head (15).

15. - a device for elastically stretching the perforated metallic hollow shapes; The device (200) according to any one of claims 9 to 14, further comprising: the one or more fiber waveguides are introduced into the stretched metallic hollow shape in an unstretched state, and the elastic stretching is terminated before the metallic hollow shape is sent to the receiving unit (25).

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