Method for controlling a fibre drawing facility

Abstract

The invention in question relates to a method for determining the specific points of a rotary fiberizing reel (10) used in a fiber drawing machine (1), which includes the following steps: - Taking temperature measurements of the fiberizing reel by means of a temperature measuring device (40) suitable for taking temperature measurements of the reel according to various angular positions of the measuring device, in order to provide data to at least one computational unit (30, 45) which forms a curve representing the temperature depending on the angular position of the measuring device; - Processing these measurements by calculating the second derivative of the temperature curve depending on the angular position by a computational unit (30); - Searching for at least one specific point where the second derivative satisfies a predefined condition.

Description

[0001] The present invention relates to the field of fiber optic devices. ART ANTÉRIEUR

[0002] Glass fibers used for insulation are commonly produced by internal centrifugation, which involves introducing a stream of molten glass into a centrifuge, also called a fiber-spunting plate, rotating at high speed and having a large number of perforations around its periphery. Under the action of centrifugal force, the glass is propelled through these perforations in the form of filaments. In addition to the centrifugal force, a high-temperature, high-speed gas stream, emitted tangentially to the perforated wall of the centrifuge's peripheral belt, may also be used for stretching. In these techniques, the centrifuge is subjected to very high stresses of mechanical origin (high rotational speed), thermal origin (glass at around 1000 °C), and chemical origin (corrosion by the molten glass).

[0003] These stresses exerted on the centrifuge cause it to deteriorate, i.e. wear which is manifested, for example, by a variation in the dimensions of its orifices.

[0004] However, the quality of the fibers produced depends very closely on the proper functioning of the centrifuge, that is to say on its good general condition and on compliance with the speed and temperature instructions.

[0005] Today, it is known that centrifuge wear can be reduced by controlling the temperature. Indeed, for improved longevity, temperature control at the top and bottom of the belt, as well as the profile along the belt, can be monitored.

[0006] A known control method from document EP 0 479 675 A2 consists of measuring the temperature of the fiber-forming plate at different points and then regulating it by changing the rotation speed of the plate and / or by changing the temperature of the molten glass.

[0007] These specific points are located by measuring the temperature of the plate via a temperature sensor.

[0008] This sensor is a pyrometer, at least part of which is pivotally mounted and sweeps an angle intercepting the vertical axis of symmetry of the fiber-laying device, thus covering the entire height of the peripheral strip with a continuous back-and-forth movement. With each sweep of the peripheral strip, the vertical coordinate of each measured point is determined, and the temperature profile is recorded in vertical coordinates along the strip's height. This profile includes three key points, A, B, and C, corresponding respectively to the highest point of the strip, the hottest point, and the lowest point of the strip. It should be noted that point A does not always correspond to an extremity of the curve, but its vertical coordinate can be determined from the position of point C, the distance between A and C corresponding exactly to the height of the peripheral strip.Points B and C are located by analyzing the curve derived from the temperature profile curve using vertical coordinates. The known control method determines the temperatures and coordinates of the key points in the strip (high and low points and the hottest point) by analyzing the curve derived from the temperature profile curve along the height of the peripheral strip. However, using these vertical coordinates has the drawback of introducing inaccuracies in temperature regulation over time. Indeed, the fiber layer wears over time, causing the vertical coordinate of each point to change. Therefore, the regulation is performed on points that are no longer the desired key points.

[0009] Furthermore, the fiber-laying plate can vibrate during operation. These vibrations mean, as with wear, that the points used for regulation are not the desired reference points. RÉSUMÉ DE L'INVENTION

[0010] The present invention therefore aims to resolve these drawbacks by providing a fiber-laying process that allows for more efficient regulation and better longevity.

[0011] For this purpose, the invention relates to a method according to claim 1.

[0012] The method for determining specific points on a fiber bed advantageously provides reliable points. Indeed, the method for determining specific points on a fiber bed according to the invention eliminates the effects of wear and / or vibrations on the fiber bed. To achieve this, the method according to the invention is based on analyzing the variation in the slope of the curve (temperature, position) and uses the second derivative of a curve representing the temperature as a function of the angular position of a temperature measuring device, rather than the vertical coordinates that change with said vibrations or wear.

[0013] According to the invention, the predefined condition consists of having the value of the second derivative equal to zero.

[0014] According to one example, this determination process includes an additional research step consisting of searching for the specific point characterized by the fact that the temperature is at its maximum there.

[0015] In one example, temperature measurements are taken at regular intervals and then averaged before the processing step.

[0016] According to one example, said measurement interval is between 2 and 5 seconds, preferably 3 seconds. The invention further relates to a method for controlling the manufacture of mineral fiber by a fiber-pulling process using a fiber-pulling device to manufacture mineral fibers, the fiber-pulling device comprising a perforated fiber-pulling plate to allow the generation of fibers by centrifugation and an annular burner generating an annular gas stream to draw the fibers, said method comprising the following steps: to perform temperature measurements of the fiber plate using a temperature measuring device, according to different angular positions of the temperature measuring device; to determine at least one specific point using the determination method according to one of the preceding claims; to compare the measured temperature to a predetermined value for this specific point; to generate at least one first control signal to regulate the temperature of the fiber device at said specific point using a first regulating element.

[0017] According to one example, a second specific point is determined and regulated.

[0018] According to one example, the fiber-laying device includes a first means of varying the temperature of the first specific point.

[0019] According to one example, the fiber-laying device includes a second means of varying the temperature of the second specific point.

[0020] According to one example, said fiber plate comprises an annular wall pierced with a plurality of orifices and extended laterally by an upper part and a lower part, and in which at least one specific point is determined among the point of the rounding which is at the junction between the perforated part of the peripheral strip and an upper part extending laterally from the peripheral strip, the hot spot corresponding to the point where the temperature is highest and the low point.

[0021] According to one example, temperature regulation is done on at least two of the specific points determined: a first specific point being the low point and a second specific point being the point of rounding.

[0022] The invention further relates to a computer program comprising instructions for executing the steps of a method for determining specific points or the steps of a method for regulating a fiber-laying plate when said program is executed by a computer.

[0023] The invention further relates to a computer-readable recording medium on which is recorded a computer program comprising instructions for executing the steps of a process for determining specific points or the steps of a process for regulating a fiber-laying plate. DESCRIPTION DES FIGURES

[0024] Other features and advantages will become clear from the description given below, which is indicative and in no way exhaustive, with reference to the attached drawings, in which: there fig. 1 is a schematic representation of a fiber-laying system according to the invention; the fig. 1' is a schematic representation of a centrifuge variant of the fiber-laying system; the fig. 2 is a schematic representation of a sensor module according to the invention; the fig. 3 is a schematic representation of a temperature diagram as a function of the fiber-laying plate position; the fig. 4 is a schematic representation of specific points on a fiber-laying plate; the fig. 5 is a schematic representation of a fiber system with a means for varying the temperature of the plate according to the invention; the fig. 6 is a schematic representation of a fiber system with two means of varying the temperature of the plate according to the invention; DESCRIPTION DETAILLÉE DE L'INVENTION

[0025] To the figure 1 Figure 1 represents a fiber-forming system. Such a fiber-forming system comprises a centrifuge, also called a fiber-forming plate, 10, fixed to a shaft 12, rotating at high speed and having a very large number of orifices around its periphery. Under the action of centrifugal force, the glass is projected through these orifices in the form of filaments. Of course, the centrifuge can be of any type: with a bottom as seen in the figure 1' or without a background as visible to the figure 1 .

[0026] The fiber-laying plate 10 is an internal centrifugation device for mineral fibers of micrometer diameter. A fiber-laying plate 10 comprises an annular wall 10a perforated with a plurality of orifices, extended laterally by an upper and a lower part. In a first configuration, at the figure 1 The upper part is a sheet 10b connecting the plate to the drive shaft, and the lower part is an inner lip 10c folded towards the drive shaft. In a second configuration, called the fully retracted plate, shown in the figure 1' , the upper part is an inner lip 10c' folded towards the drive shaft and the lower part is a veil 10b' forming the bottom of the plate 10'.

[0027] This fiber drawing plate is heated by a heating module 20. The heating module 20 includes at least one burner 22 for drawing the fiber. This internal combustion burner has a combustion chamber supplied with fuel and oxidizer, the chamber having a casing (having a first closed end and a second opposite open exhaust end through which the combustion gases escape), the casing having at least two opposite walls connecting the two ends. The burner includes, within the chamber and at the first closed end, at least one combustion device supplied with oxidizer and fuel.

[0028] By means of the burner, the filaments projected under the effect of centrifugal force are then subjected to the action of an annular gaseous drawing current at high temperature and speed along the wall of the centrifuge which thins them and transforms them into fibers.

[0029] This heating module 20 is controlled by a computing unit 30. Such a computing unit 30 consists, for example, of a computer equipped with an interface allowing the operator to adjust the fiber-laying system. The computing unit 30 is therefore connected to the heating module 20 in order to send it commands.

[0030] The fiber system 1 further includes a sensor module 40, as shown in the figure 2 . Such a sensor module 40 includes a temperature sensor 41 and is connected to the computing unit 30.

[0031] The temperature sensor used is a pyrometric type. Such a pyrometric sensor uses infrared radiation. Indeed, an IR thermometer / pyrometer measures temperature by quantifying the radiative energy emitted in the infrared spectrum, based on the fact that any object above absolute zero (0 K) emits this radiation. By knowing the amount of energy emitted by an object, and its emissivity, its temperature can therefore be determined. In simplified terms, the principle consists of measuring the light energy in the infrared range with a detector, which converts it into an electrical signal. A lens focuses the IR radiation onto the detector. This method is advantageous for measuring temperature remotely.

[0032] The IR temperature sensor is associated with a visible mirror system at the figure 2 Such a mirror system makes it possible to direct infrared radiation from any point towards the detector. The mirror system 42 includes a mirror 43 pivotally mounted on a support 44. This pivoting mounting of the mirror 43 allows it to direct the IR radiation from different points on the fiber-laying plate as seen at the figure 2 primarily in a vertical plane of the plate extending in a direction parallel to the plate's axis of rotation and in a direction orthogonal to it. However, the temperature sensor can be used alone and is itself mounted for swiveling.

[0033] The ability of the assembly, including the pyrometer and mirror, to measure temperature at different points allows for a temperature reading of the fiber-laying plate. This temperature reading is used by the computing unit 30 to regulate the temperature.

[0034] To obtain this reading, a first step in the process of controlling the manufacture of mineral fiber according to the invention consists of using the pyrometer (measuring range 500-2000°C) and the oscillating mirror. The mirror 43 is set into oscillation at a certain frequency to scan the fiber-laying plate 10 and obtain temperature measurements as a function of the angular position α of the mirror. These measurements can be processed by an internal computing unit 45 of the sensor module 40 to directly provide a temperature curve as a function of the angular position of the mirror, or they can be sent to the computing unit 30 to which the sensor module 40 is connected for processing and to obtain a temperature curve as a function of the angular position α of the mirror.

[0035] We then obtain the curve of the figure 3 representative of a plate according to the figure 1 .

[0036] These temperature measurements are taken continuously. To smooth the curve and eliminate noise, it is possible to smooth the temperature curve based on angular position. To do this, measurements taken at a predefined regular interval are averaged; this interval is between 2 and 5 seconds, preferably 3 seconds. It is therefore understood that the measurements are stored in memory for a period of time and then averaged.

[0037] In a second step of the control process, this curve is processed by the calculation unit 30 in order to extract at least one specific point according to the specific point determination method according to the invention.

[0038] The determination method includes a first step consisting of obtaining temperature measurements of the fiber plate obtained by means of a temperature measuring device 40.

[0039] A second step in the determination method involves processing the data using the computing unit 30 to calculate and obtain the second derivative of the temperature curve as a function of the angular position of mirror 43. This second derivative is used to search for characteristic / specific points. Indeed, the second derivative allows us to obtain the variation of the slope.

[0040] In a third step of the determination method, the second derivative of the temperature curve as a function of the angular position of mirror 43 is analyzed by the computing unit 30 to identify specific points. These specific points are those for which the second derivative fulfills a predefined condition. According to the invention, this condition is that the value of the second derivative is equal to zero. This condition is characteristic of the high and low points of a fiber-reinforced plate, which correspond to extreme points of the curve.

[0041] It is then possible to define what the specific / characteristic point corresponds to. It will be understood that the points representing the bottom of the plate band and the rounding of the plate are on either side of said hot spot, at the local extrema of the curve.

[0042] In the present case of the invention, two specific / characteristic points (which correspond to zones 1 and 3 of the figure 4 ) are being sought. A first specific point corresponds to the bottom band temperature of the plate (zone 1) and a second specific point corresponds to the plate's curvature (zone 3) as visible at the figure 4 .

[0043] Furthermore, an optional fourth step in the determination method can be performed. This optional fourth step consists of finding the hot spot of the fiber bed. To do this, the calculation unit 30 searches for the absolute maximum of the curve that corresponds to this hot spot. This hot spot is the specific / characteristic central point (zone 2), located between the points corresponding to the bottom band temperature of the bed (zone 1) and the bed's curvature (zone 3).

[0044] This use of the second derivative offers the advantage of being independent of fluctuations in the plate's dimensions. Indeed, the plate's dimensions can vary with wear and / or vibrations. However, despite this variation in the plate's dimensions, its overall shape remains the same. Consequently, the specific / characteristic points persist. This ensures that these specific points can always be accurately identified. Thus, the resulting regulation is always performed on precise and truly representative points of the plate. It is clear that this second derivative calculation and the use of a temperature curve as a function of the mirror's angular position are interdependent.Indeed, using a temperature curve as a function of the mirror's angular position allows us to obtain a temperature profile that eliminates the effects of dimensional variations in the mirror plate caused by wear or deformation during operation due to thermal stress. Using the second derivative on this temperature profile ensures that the specific points of interest are always located. This then enables automatic regulation, meaning that an operator cannot perform additional calculations to obtain the desired result.

[0045] In a later phase of the control process, the temperature values ​​of specific points are used for regulation of the fiber bed 10.

[0046] Indeed, the temperature of the three specific points on the fiber bed—that is, the lowest point of the bed's band, the hot spot, and the point where the bed's curve is rounded—must be within a predefined range. In the case of the example of the figure 1 The preset temperatures are for guidance only. For the bottom of the band (zone 1): 905-930 °C For the rounding (zone 3): 960-990 °C For the hot spot (zone 2): 960-980 °C These predefined temperatures constitute threshold values ​​used to be compared with measured temperatures.

[0047] In the first control loop, the first specific point, or bottom point of the band on plate 10, is controlled. To achieve this, the first control loop acts on a first means of temperature variation 50, as seen in the figure 5 In this case, the first temperature variation means 50 is a means allowing variation of the temperature of the fiber-laying plate and comprises an induction coil 51 connected to a frequency generator 52 visible at the figure 5 which serves as the primary means of temperature variation. This frequency generator 52 generates a signal SI sent to the induction coil 51. This signal modulates the induction power of the induction coil 52 and thus allows the heating temperature to be varied. As a reminder, when the induction coil 51 carries the signal SI, which is a frequency-modulated electrical current, it generates a magnetic field that, in turn, induces electrical currents in the nearby metal. The eddy current and hysteresis losses produced in this metal generate thermal energy (heat) by the Joule effect. This induction coil 51 is positioned in the lower part of the fiber bed, and more specifically, beneath the fiber bed. This induction coil is positioned opposite the fiber mesh created by the bed in order to locally heat this lower area of ​​the bed.

[0048] An example of a control loop involves comparing the temperature measured at the bottom of the plate band (zone 1) to a setpoint temperature. An initial control signal is generated by the processing unit. This control signal determines the power supplied to the coil, which is dependent on the current and frequency. In this case, the desired increment is 1°C.

[0049] In a second loop, for example, the temperature of the second specific point or rounding point is regulated. For this, a second temperature variation method 60 is used, as can be seen in the figure 6In a non-limiting example, this second means for varying the temperature 60 is an air circulation means comprising a suction portion and a blowing portion. More precisely, the air circulation means according to the invention is a means used to control the evacuation of fumes generated by the burner. Indeed, it has been observed that the flow rate of these fumes significantly influences the plate rounding temperature. Consequently, the air circulation means according to the present invention is a means for decreasing or increasing the fume evacuation in order to modify the temperature of the rounding of a fiberglass plate.

[0050] This air circulation system includes a flow variation mechanism, which can be one or two turbines or a pair of air injection nozzles. In both cases, the goal is to generate an airflow that will be added to the flue gas exhaust flow. This additional flow will be either positive or negative; that is, if positive, it increases the exhaust flow, and if negative, it slows it down. The blowing section thus generates a negative additional flow, while the suction section generates a positive additional flow.

[0051] This second loop compares the measured temperature to a rounded value and then to a setpoint temperature. A second control signal is generated by the processing unit 30. In addition to adjusting the temperature of the incoming or outgoing air, the temperature can also be adjusted by varying the airflow rate. One solution is to control the opening of valves using the second signal generated by the processing unit. Each part of the air circulation system includes a solenoid valve. This solenoid valve can open more or less depending on the current applied to it. Consequently, it becomes possible to modify the airflow rate by changing the opening of these valves. This allows for precise temperature control.

[0052] Of course, it is conceivable that the two control loops could operate in parallel or sequentially. Furthermore, it is conceivable that the fiber-laying device according to the invention could comprise only one of the two loops.

[0053] Having both loops, meaning being able to control both the upper and lower parts of the fiber-laying plate 10, allows us to decouple the plate temperature and its profile along the band from the combustion gas temperature. This preserves the quality of the fibers produced, as the external burner is not affected.

[0054] The method for determining specific points and the method for regulating each take the form of a computer program containing instructions for executing the steps of said processes when executed by a computer.

[0055] The programs for determining specific points and for the regulation process are stored on a computer-readable storage medium. This medium can be a CD, DVD, flash memory, or any other possible medium such as the cloud.

[0056] To achieve the smoothest possible temperature control, it is advantageous to operate the various valves of the air circulation system in a staggered manner, avoiding simultaneous activation. A control system where the supply and intake valves are opened simultaneously would be unstable, resulting in fluctuating temperatures that would negatively impact fiber quality. Conversely, a sequential control system allows for less temperature fluctuation. Specifically, this type of control means that the valve currently in use is closed before the valve for the other circuit is opened. The control system therefore comprises several sequences. For example, if the air circulation system is in intake mode (i.e., the temperature is being raised), the temperature is lowered by closing the intake valve.If the closing of this valve is sufficient, then the supply air valve remains closed. Conversely, if the temperature has not dropped sufficiently after closing the suction valve, then the supply air valve is gradually opened. Thus, the flue gas flow modification step includes a sequence of injecting an additional flow that adds to the existing exhaust flow and / or a sequence of injecting an additional flow that opposes the existing exhaust flow.

[0057] This allows for a lower regulation frequency, resulting in a smoother regulation curve to optimize fiber quality.

Claims

1. Method of determination of specific points of a rotary fibre forming spinner wheel (10) used in a fibre forming device (1), said method comprising the following steps: - obtaining measurements of temperatures of the fibre forming spinner wheel obtained by means of a temperature measuring device (40) adapted to take measurements of temperatures of the spinner wheel at a plurality of angular positions of said measuring device in order to supply data to at least one calculation unit (30, 45) that constructs a curve representing the temperature as a function of the angular position of a temperature measuring device; - processing said measurements by effecting a calculation of the second derivative of the curve of the temperature as a function of the angular position by means of a calculation unit (30); - searching for at least one specific point for which the second derivative satisfies a predefined condition, the predefined conditions consisting in having the value of the second derivative equal to zero.

2. Determination method according to the preceding claim, comprising an additional searching step consisting in searching for the specific point characterized by the fact that the temperature there is at its maximum.

3. Determination method according to any one of the preceding claims, wherein the measurements of temperatures are taken during a regular interval and then averaged before the processing step.

4. Determination method according to the preceding claim, wherein said measurement taking interval is between 2 and 5 seconds inclusive, preferably 3 seconds.

5. Method of controlling the fabrication of mineral fibre by a fibre forming method using a fibre forming device (1) to fabricate mineral fibres, the fibre forming device comprising a fibre forming spinner wheel (10) pierced to enable centrifugal generation of fibres and an annular burner (22) generating an annular gas flow to stretch the fibres, said method comprising the following steps: - effecting measurements of temperatures of the fibre forming spinner wheel by means of a temperature measuring device (40) at different annular positions of the temperature measuring device; - determining at least one first specific point using the determination method according to any one of the preceding claims; - comparing the measured temperature to a predetermined value for said at least one first specific point; - generating at least one first control signal for regulating the temperature of said fibre forming spinner wheel at said at least one first specific point by means of a temperature variation means.

6. Control method according to the preceding claim wherein a second specific point is determined and regulated.

7. Control method according to Claim 5 or 6, wherein the fibre forming device comprises a first means (50) for variation of the temperature of the first specific point.

8. Control method according to Claim 6, wherein the fibre forming device comprises a second means (60) for variation of the temperature of the second specific point.

9. Control method according to the preceding claim, wherein the fibre forming spinner wheel (10, 10') comprises an annular wall (10a, 10a') pierced by a series of orifices and extended laterally by an upper part (10b, 10c') and a lower part (10c, 10b') and in which at least one specific point is determined from the point of the round-off that is found at the junction between the perforated part of the peripheral strip and an upper part extending the peripheral strip laterally, the hot spot corresponding to the point at which the temperature is the highest and the bottom point.

10. Control method according to the preceding claim, wherein the temperature is regulated at two at least of the specific points that have been determined: the first specific point being the bottom point and the second specific point being the point of the round-off.

11. Computer program including instructions for the execution of the steps of a method according to any one of Claims 1 to 4 when said program is executed by a computer.

12. Computer program including instructions for the execution of the steps of a method according to any one of Claims 5 to 10 when said program is executed by a computer.

13. Computer-readable storage medium on which is stored a computer program including instructions for the execution of the steps of a method according to any one of Claims 1 to 4 when said program is executed by a computer.

14. Computer-readable storage medium on which is stored a computer program including instructions for the execution of the steps of a method according to any one of Claims 5 to 10 when said program is executed by a computer.