Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/07—Controlling or regulating
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/01—Manufacture of glass fibres or filaments
  • C03B37/04—Manufacture of glass fibres or filaments by using centrifugal force, e.g. spinning through radial orifices; Construction of the spinner cups therefor
  • C03B37/045—Construction of the spinner cups

Definitions

• the invention relates to a process for forming glass fibers.
• the method according to the invention applies in particular to the industrial production of mineral wool intended to enter, for example, into the composition of thermal and/or acoustic insulation products.
• a device for forming glass fibers typically comprises a centrifuge, also called fiberizing dish, comprising an annular wall called the primary wall or “band” pierced with a plurality of orifices (here -after primary orifices).
• the fiber-drawing device also comprises a shaft intended to be driven in rotation by a motor and to which the centrifuge is fixed.
• the so-called “bottomless” centrifuge is open at its lower end.
• the shaft is hollow and connected at its upper end to the molten glass supply means.
• the shaft is connected to a basket located inside the centrifuge and intended to be driven in rotation with the centrifuge and the shaft.
• the basket comprises a secondary annular wall pierced with a plurality of secondary orifices.
• the invention also aims to improve the quality of the fibers obtained.
• the invention thus relates to a process for forming glass fibers by means of a rotary assembly comprising:
• centrifuge secured to the shaft and provided with a primary annular wall comprising a plurality of primary orifices
• the method comprising the following steps: a) the acquisition, using a camera, of at least one primary image of the centrifuge, b) the processing of said at least one primary image by an image processing system , and c) the evaluation of a parameter representative of the volume of the primary reserve by a system for processing data from the primary image.
• the invention proposes to evaluate in an automated way a parameter of the fiber formation process which has been established to have an influence on the quality of the fibers obtained and on the proper functioning of the centrifuge: this is the volume of the molten glass reserve formed against the annular wall of the centrifuge.
• the volume of glass contained in the primary reserve of the centrifuge is an important parameter in the operation of the fiber-drawing device. This volume defines the pressure applied to the molten glass. However, this pressure determines the exit speed of the glass through the primary orifices, which itself influences the quality of the filaments produced.
• the parameter evaluated is a parameter representative of the volume of the reserve.
• the actual volume is not necessarily calculated as part of the claimed method.
• the evaluated parameter can in particular be proportional to this volume. This is for example a (horizontal) thickness of the resist calculated geometrically from a glass height measured on the primary image and characteristics of the centrifuge and the camera.
• the method according to the invention applies to all types of fiber-drawing devices.
• the primary image acquired by the camera can be an image of at least part of the underside of the rotating assembly. This image reveals at least a lower part of the centrifuge.
• the centrifuge has an opening at its lower end, and in step a) the primary image is acquired through this opening.
• the centrifuge is said to be “bottomless”.
• the primary annular wall has free lower edges or the primary annular wall is extended, at its lower end, by a lower wall or reverse extending towards the inside of the centrifuge and forming an angle with the annular wall. , an opening being delimited by the free edge of the lapel.
• the camera used in step a) preferably has a direction of observation forming an angle with the axis of rotation. In this way, the camera can in particular directly visualize the free surface of the primary reserve oriented towards the axis of the centrifuge.
• the centrifuge has a (solid) bottom
• the acquired image is an image of at least part of the bottom of the centrifuge.
• the volume of the primary reserve can be evaluated from the color variation on the bottom of the centrifuge, in particular obtained either by optical camera in operation with visible light or by infrared camera: the bottom of the centrifuge has a higher temperature at the place where the net of glass falls vertically than at the right of the reserve (the glass having had time to cool a little during its projection in the direction of the primary annular wall).
• the limits of the reserve can be obtained by image processing (contrast, thresholding, etc.)
• the image can in certain cases be acquired from above the centrifuge.
• step b) the image processing includes the identification of at least one limit of the primary reserve on the primary image.
• the at least one limit comprises the edge of the opening of the centrifuge and the upper edge of the primary reserve.
• the identification of the at least one limit comprises the determination of at least one series of points by a digital edge detection method, in particular by thresholding, and the adjustment by ellipse of said series of dots.
• the image acquisition in step a) is carried out using an infrared camera.
• the method comprises, prior to step c), a step b′) of calibrating the data processing system by measuring an element of the rotating assembly on the primary image acquired and comparing the measured value with the known dimension of said element.
• the method further comprises, after at least one succession of steps a) to c), a step d) of determining a deviation of the volume of the primary reserve with respect to a nominal value and adjustment of the speed of rotation of the rotary assembly as a function of said deviation.
• step d) at least N successions of steps a) to c) are carried out, in particular N successions regularly spaced in time, for example by at least 30 seconds.
• step d when at the end of step d), the speed of rotation of the rotary assembly reaches a predetermined maximum value, an alert is emitted.
• the rotary assembly usually comprises a basket arranged below the shaft, secured to the shaft and provided with a secondary annular wall comprising a plurality of secondary orifices, and under the effect of the centrifugal force resulting from the rotation of the rotary assembly, a secondary reserve of glass is formed against the secondary annular wall.
• the method can also comprise the evaluation of a parameter representative of the volume of the secondary reserve by the system processing data from said at least one primary image of the centrifuge or from another so-called secondary image.
• the volume of the secondary reserve can be evaluated from the color variation on the bottom of the basket, in particular obtained either by optical camera in operation with visible light or by infrared camera: the bottom of the basket has a higher temperature at the point where the glass net falls vertically than at the secondary reserve.
• the limits of the reserve can be obtained by image processing (contrast, thresholding, etc.).
• the invention also relates to a device for forming glass fibers comprising a rotary assembly comprising:
• a centrifuge secured to the shaft and provided with a primary annular wall comprising a plurality of primary orifices, the rotary assembly being configured so that, under the effect of the centrifugal force resulting from its rotation, a primary reserve of glass is formed against the primary annular wall, and the device further comprising:
• a data processing system configured to evaluate a parameter representative of the volume of the primary reserve from the data from the primary image.
• the invention also relates to a computer program comprising instructions for the execution of at least steps b) and c) of the method defined above, when said program is executed on a computer.
• the computer program further comprises instructions for the execution of step d) mentioned above, when said program is executed on a computer.
• the invention also relates to a computer-readable medium on which such a computer program is recorded.
• the [Lig.1] represents a section, according to an axial plane, of a device for forming glass fibers according to the invention
• - [Fig.2] is a detail view of [Fig.1];
• FIG.3 is an example of an image acquired by the camera in [Fig.1] (in negative, for better visualization);
• FIG.4 illustrates the results of tests illustrating the impact of variations in the rotational speed of the rotating assembly on the volume of the secondary reserve
• FIG.5 is a schematic illustration of the basket as it would be seen by a camera oriented in the direction of the axis of rotation.
• FIG.1 shows a sectional view of a device 100 for forming glass fibers according to the invention.
• the device 100 for forming glass fibers comprises a rotary assembly 1 rotating around an axis A, under the effect of a drive motor 8.
• the rotating assembly 1 comprises a shaft 2, of axis A, intended to be driven in rotation by the motor 8.
• the device further comprises a centrifuge 3 comprising an annular side wall (hereinafter primary wall) 30 pierced with a plurality of orifices (hereinafter primary orifices) 31 and a veil 32 forming the top of the centrifuge 3
• the centrifuge 3 is fixed to the shaft 2 via a socket 4, which is in the extension of the veil 32.
• the axis A is vertical.
• the primary annular wall 30 is extended, at its lower end, by a lower wall or reverse 33 extending towards the inside of the centrifuge 3 and forming an angle with the primary annular wall 30
• the lapel 33 here extends almost horizontally in the fiber-drawing position.
• a central opening 34 (here of circular section) is delimited by the free edge of the reverse 33.
• the centrifuge 1 is said to be “bottomless”.
• shaft 2 is hollow. It comprises a central channel 20 connected, at its upper end, to means (not shown) for supplying molten glass. At its lower end, the shaft 2 is connected to a basket 5 comprising a secondary annular side wall 50 pierced with a plurality of orifices called secondary orifices 51, and a bottom 52.
• the basket 5 is located inside the centrifuge 3, as can be seen in [Fig.1],
• the glass fiber forming device 100 also comprises at least one annular burner 6 generating a high temperature gaseous drawing jet.
• the gaseous stretching jet is a high temperature gas stream (typically 1350°C at 1600° C.), which leaves the annular burner 6 via its outlet 60, such that the gaseous drawing jet is tangential to the annular wall 30 of the centrifuge 3.
• the outlet 60 of the annular burner 6 is located above the primary annular wall 30 of the centrifuge 3.
• the molten glass from said secondary reserve R2 passes through the plurality of secondary orifices 51 (with a diameter of between about 1.5 mm and 3 mm) of the basket 5 and, in the form of filaments vo- light V 1 (of the order of 2 mm in diameter), is projected onto the primary annular side wall 30, usually referred to as the "strip", of the centrifuge 3.
• a primary permanent reserve of molten glass R1 then forms in the centrifuge 3 , to supply the plurality of orifices 31 drilled in the annular wall primary area 30.
• Molten glass finally passes through the plurality of primary orifices 31 (diameter between approximately 0.5 mm and 1 mm) of the spinner 3 to form fore-fibers V2. Under the action of the gaseous drawing jet from burner 6, the fore-fibers V2 stretch, their terminal portion generating discontinuous fibers V3 then collected under the centrifuge 3.
• the device taken as an example comprises means intended to automatically evaluate the volume of the primary reserve R1 of the centrifuge.
• These means comprise: means for acquiring at least one primary image of the centrifuge 3, a system 72 for processing said at least one primary image, and a data processing system 74 configured to evaluate a parameter represented - sentiment of the volume of the primary reserve based on data from the image.
• the image acquisition means here comprise a camera 7, oriented towards the underside of the rotating assembly 1.
• a first reference point P1 is identified corresponding to the interior junction line between the side wall 30 of the centrifuge 3 (which generally extends substantially vertically) and the web 32 which is rounded, with a radius of curvature RC.
• a high point M of the reserve R1 is also identified, corresponding to the limit high of primary reserve R1.
• the high point M is typically a point on the veil 32, but can, in the event of zero reserve R1, be a point on the side wall 30.
• the representative parameter of the volume of the reserve R1, evaluated by the data processing system 72 is for example the thickness e of the reserve, which corresponds to the distance measured horizontally, between the reference point P1 and the high point Mr.
• the thickness e of the resist is determined by acquiring a primary image of the centrifuge 3, by the camera 7, and using said image.
• the camera 7 is oriented so as to acquire an image showing at least a portion of the upper limit of the edge 33a of the reverse 33 and a portion of the upper limit of the primary reserve R1.
• the direction of observation of the camera forms an angle f different from 0 or 90° with the horizontal, and therefore an axis 90- f with the axis of rotation A.
• the optical axis of the camera is oriented in the direction of the center O of the underside of the basket 5.
• Fa camera 7 can be a matrix camera or, particularly advantageously, an infrared camera.
• Fa camera is connected to a computer 70, comprising a computer program implementing the system 72 for processing the image(s) acquired by the camera, and the data processing system 74, communicating with the processing system. picture 72.
• the computer program includes instructions
• the image processing system 72 For each image acquired by the camera 7, the image processing system 72 detects the upper limit of the reserve R1 and the upper limit of the edge 33a of the reverse 33, for example by a method of the "edge detection” type. ". This type of detection, which is well known, consists in identifying the points of the image which correspond to a sudden change in the light intensity. Several methods exist, which include for example thresholding, or the determination of the contrast gradient of the image.
• the contour detection is very advantageously supplemented by a step of adjustment by ellipse of the contour thus determined.
• the ellipse E1 corresponds to the upper limit of the primary reserve R1.
• the ellipse E2 corresponds to the upper limit of the edge 33a of the reverse 33.
• the ellipse E3 corresponds to the outer contour of the bottom 52 of the basket 5.
• the data processing system 72 is able to calculate the thickness of the resist R1 from the known geometric characteristics of the centrifuge 3, the characteristics of the camera 7 used for acquire the image of the reserve R1, and of the height h measured, on the image, between the upper limit of the reserve and the top of the edge 33a of the reverse 33.
• the geometric characteristics of the centrifuge 3 that can be used in the calculation are:
• the characteristics of the camera 7 that can be used in the calculation are:
• the system can calculate the height hO, thanks to equation 1 below.
• the system can calculate e using equations 2 to 5 below, by placing itself in a frame (u, v) of origin P1, u being parallel to the line of sight of the camera:
• the data processing system 74 is configured to undergo calibration, before operation or on a regular basis.
• the contour of the basket 5 identified on the acquired image can be used to carry out this calibration from the real dimensions of the basket 5 which are known and the dimensions of the contour identified on the image.
• the steps of acquiring an image, processing this image to extract the edges of the resist, and processing the image data to determine the thickness of the resist are advantageously repeated several times, at regular time intervals, for example of the order of 30 seconds.
• the data processing system 74 determines a deviation of the volume of the primary reserve R1 with respect to a nominal value and sends to the drive motor 8 of shaft 2 an adjustment signal for the speed of rotation of the rotary assembly proportional to said deviation, typically via a P1D.
• the [Fig.4] illustrates the result of tests illustrating the impact of variations in the speed of rotation of the rotary assembly 1 on the volume of the primary reserve R1:
• the curve in solid line represents the speed of rotation of the centrifuge 3 (in revolutions per minute), and the dotted curve, the variation of the thickness e of the primary reserve R1, with e in pixels. It can be seen that there is a direct correlation between variation in the rotational speed and variation in the volume of the reserve.
• the data processing system 74 can be configured to transmit a signal to a warning device 9, which can be any device capable of indicating to an operator the need to adjust other parameters, in particular the temperature of the glass feeding the fiber manufacturing device.
• the image here in negative, reveals a dark central ring G (lighter in reality) and a lighter peripheral ring H (darker in reality).
• the luminous central crown G is the zone of the basket 5 coming into direct contact with the stream of molten glass falling vertically through the supply channel 20 and whose temperature T is very high.
• the darker peripheral ring H is the zone of the bottom of the basket 5 in contact with the molten glass of the secondary reserve R2, the temperature of which has already decreased and is lower than T.
• the camera 7 or an auxiliary camera could be configured to acquire an image different from the primary image and said secondary image of the basket 5, for example according to a direction of observation aligned with the axis of rotation A of the rotating assembly 1.
• Such a secondary image of the basket seen from below is illustrated schematically in [Fig.5].
• the image processing system 72 is suitable for detecting the limits of the peripheral ring H, by thresholding, and approximating these limits by ellipses or as in [Fig.5] by concentric circles H1 , H2 (the line of sight of the camera being in this case vertical).
• the data processing system 74 can then determine the thickness e′ of the ring H, in other words the distance between said contours H1, H2, which is representative of the volume of the secondary reserve R2.
• the evaluation of the secondary reserve thus described can be transposed identically for the evaluation of the volume of the primary reserve R1 in the case of a centrifuge of the “full” type.
• the image of the bottom of the centrifuge, acquired by the camera, will be identical in principle to the images of the bottom of the basket illustrated in figures 3 and 5: it will show a bright central ring, and a darker peripheral ring, the thickness of which will be representative of the volume of the primary reserve R1. The description is therefore not further detailed here.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Centrifugal Separators (AREA)
• Manufacture, Treatment Of Glass Fibers (AREA)
• Treatment Of Fiber Materials (AREA)
• Preliminary Treatment Of Fibers (AREA)

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• 2021
  • 2021-06-07 FR FR2105959A patent/FR3123647B1/fr active Active
• 2022
  • 2022-06-03 CA CA3220769A patent/CA3220769A1/fr active Pending
  • 2022-06-03 JP JP2023573281A patent/JP2024521835A/ja active Pending
  • 2022-06-03 WO PCT/FR2022/051062 patent/WO2022258918A1/fr not_active Ceased
  • 2022-06-03 AU AU2022291011A patent/AU2022291011A1/en active Pending
  • 2022-06-03 US US18/567,622 patent/US20240279105A1/en active Pending
  • 2022-06-03 CN CN202280040820.6A patent/CN117460702A/zh active Pending
  • 2022-06-03 EP EP22735206.9A patent/EP4352017A1/de active Pending

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