METHOD FOR CONTROLLING A FIBERIZING DEVICE

Abstract

A method for forming glass fibers by a rotary assembly including a shaft rotated about an axis of rotation, a centrifuge secured to the shaft and provided with a primary annular wall including a plurality of primary orifices, and a supply system configured to supply the centrifuge with molten glass, and wherein, under the effect of a centrifugal force resulting from a rotation of the rotary assembly, a primary reserve of glass is formed against the primary annular wall of the centrifuge, the method including a) acquiring, using a camera, of at least one primary image of the centrifuge, b) processing the at least one primary image by an image processing system, and c) evaluating a parameter representative of a volume of the primary reserve by a system for processing the data from the primary image.

Claims

1. A method for forming glass fibers by a rotary assembly including: a shaft rotated about an axis of rotation, a centrifuge secured to the shaft and provided with a primary annular wall comprising a plurality of primary orifices, and a supply system configured to supply the centrifuge with molten glass, and wherein, under the effect of a centrifugal force resulting from a rotation of the rotary assembly, a primary reserve of glass is formed against the primary annular wall of the centrifuge, the method comprising the following steps: a) acquiring, using a camera, of at least one primary image of the centrifuge, b) processing said at least one primary image by an image processing system, and c) evaluating a parameter representative of a volume of the primary reserve by a system for processing the data from the primary image.

2. The method according to claim 1, wherein the centrifuge includes an opening at its lower end, and in step a) the primary image is acquired through said opening.

3. The method according to claim 1, wherein in step b) the image processing comprises an identification of at least one boundary of the primary reserve on the primary image.

4. The method according to claim 2, wherein in step b) the image processing comprises an identification of at least one boundary of the primary reserve on the primary image, and wherein the at least one boundary comprises an edge of the opening of the centrifuge and an upper edge of the primary reserve.

5. The method according to claim 3, wherein the identification of the at least one boundary comprises a determination of at least one series of points by a digital method for detecting contours, and an ellipse adjustment of said series of points.

6. The method according to claim 1, wherein the camera used in step a) has an observation direction forming an angle with the axis of rotation.

7. The method according to claim 1, wherein the image acquisition in step a) is carried out using an infrared camera.

8. The method according to claim 1, comprising, prior to step c), a step b) of calibrating the data processing system by measuring an element of the rotary assembly on the acquired primary image and comparing the measured value with a known dimension of said element.

9. The method according to claim 1, further comprising, at the end of at least one succession of steps a) to c), a step d) of determining a deviation of the volume of the primary reserve relative to a nominal value and of adjusting a rotational speed of rotation of the rotary assembly as a function of said deviation.

10. The method according to claim 9, wherein prior to step d), at least N successions of steps a) to c) are carried out.

11. The method according to claim 9, wherein, when the rotational speed of the rotary assembly reaches a predetermined maximum value at the end of step d), an alert is emitted.

12. The method according to claim 1, wherein the rotary assembly further includes 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 glass reserve is formed against the secondary annular wall and the method further comprises evaluating a parameter representative of a volume of the secondary reserve by the data processing system from said at least one primary image of the centrifuge or another image.

13. A device for forming glass fibers comprising: a rotary assembly including: a shaft rotated about an axis of rotation, a centrifuge secured to the shaft and provided with a primary annular wall comprising a plurality of primary orifices, the rotary assembly being configured such that, under the effect of the centrifugal force resulting from its rotation, a primary reserve of glass is formed against the primary annular wall, an image acquisition system configured to acquire at least one primary image of the centrifuge, a system for processing said at least one primary image, and a data processing system configured to evaluate a parameter representative of a volume of the primary reserve from the data from the primary image.

14. (canceled)

15. (canceled)

16. A non-transitory computer-readable medium comprising instructions for executing at least steps b) and c) of the method for forming glass fibers according to claim 1, when said instructions are executed on a computer.

17. The method according to claim 5, wherein the determination of at least one series of points for detecting contours is done by thresholding.

18. The method according to claim 10, wherein said N successions are N successions regularly spaced over time.

19. The method according to claim 18, wherein said N successions are N successions regularly spaced every at least 30 seconds.

20. The non-transitory computer-readable medium according to claim 16, wherein said instructions include instructions for executing a step d) of determining a deviation of the volume of the primary reserve relative to a nominal value and of adjusting a rotational speed of rotation of the rotary assembly as a function of said deviation

Description

[0058] FIG. 1 shows a section, along an axial plane, of a device for forming glass fibers according to the invention;

[0059] FIG. 2 is a detailed view of FIG. 1;

[0060] FIG. 3 is an example of an image acquired by the camera of FIG. 1 (in negative, for better viewing);

[0061] FIG. 4 shows the test result showing the impact of variations in the speed of rotation of the rotary assembly on the volume of the secondary reserve;

[0062] 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.

[0063] FIG. 1 represents a cross-sectional view of a glass fiber forming device 100 according to the invention.

[0064] 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.

[0065] The rotary assembly 1 comprises a shaft 2, of axis A, intended to be rotated by the motor 8.

[0066] The device further includes a centrifuge 3 comprising an annular side wall (hereinafter the primary wall) 30 pierced by a plurality of orifices (hereinafter primary orifices) 31 and a web 32 forming the top of the centrifuge 3. In the example, the centrifuge 3 is fastened to the shaft 2 via a tulip 4, which is in the extension of the web 32. When the glass fiber forming device 100 is in the fiberizing position, the axis A is vertical.

[0067] In the remainder of this document, up, down, above and under and upper and lower parts are defined relative to a vertical axis when the centrifuge 1 is in the centrifuging position, that is to say when the axis of rotation A of the centrifuge is on a vertical axis, as in [FIG. 1].

[0068] In the particular example shown, the primary annular wall 30 is extended, at its lower end, by a lower wall or cuff 33 extending towards the inside of the centrifuge 3 and forming an angle with the primary annular wall 30. Here, the cuff 33 extends almost horizontally in the fiberizing position. A central opening 34 (here of circular cross-section) is delimited by the free edge of the cuff 33. It is said that the centrifuge 1 is bottomless.

[0069] As shown in [FIG. 1], the 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 by 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].

[0070] The device for forming glass fibers 100 also comprises at least one annular burner 6 generating a high-temperature gaseous drawing jet. The gas drawing jet is a high-temperature gas stream (typically 1350? C. to 1600? C.), which leaves the annular burner 6 through its outlet 60, such that the gas drawing jet is tangential to the annular wall 30 of the centrifuge 3. In the fiberizing position, the outlet 60 of the annular burner 6 is situated above the primary annular wall 30 of the centrifuge 3.

[0071] When the device for forming glass fibers 100 is in operation, the centrifuge 3, the shaft 2 and the basket 5 are rotated about the axis A. Molten glass flows into the shaft 2 from the molten glass supply means, to the basket 5. Under the effect of the rotation, the molten glass is sprayed onto the secondary annular wall 50 of the basket 5 forming a permanent reserve R2 (hereinafter secondary reserve) against said annular wall 50. The molten glass coming from said secondary reserve R2 passes through the plurality of secondary orifices 51 (with a diameter comprised between about 1.5 mm and 3 mm) of the basket 5 and, in the form of bulky filaments V1 (of the order of 2 mm in diameter), is sprayed onto the primary annular side wall 30, usually called the strip, of the centrifuge 3. A primary permanent reserve of molten glass R1 is then formed in the centrifuge 3, in order to feed the plurality of orifices 31 pierced in the primary annular wall 30. Molten glass finally passes through the plurality of primary orifices 31 (with a diameter comprised between about 0.5 mm and 1 mm) of the centrifuge 3 to form pre-fibers V2. Under the action of the gaseous drawing jet from the burner 6, the pre-fibers V2 are stretched, their terminal portion generating discontinuous fibers V3 that are then collected under the centrifuge 3.

[0072] In accordance with the invention, the device taken as an example comprises means intended to evaluate in an automated manner the volume of the primary reserve R1 of the centrifuge.

[0073] These means comprise: [0074] means for acquiring at least one primary image of the centrifuge 3, [0075] a system 72 for processing said at least one primary image, and [0076] a data processing system 74 configured to evaluate a parameter representative of the volume of the primary reserve from the data from the image.

[0077] The image acquisition means herein comprise a camera 7, oriented toward the bottom of the rotary assembly 1.

[0078] The parameter representative of the volume of the primary reserve R1 is explained in connection with [FIG. 2], which is a detail view of [FIG. 1].

[0079] On this view of the rotary assembly 1 in section in an axial plane (that is, including the axis A), a first reference point P1 is identified corresponding to the inner junction line between the side wall 30 of the centrifuge 3 (which extends generally substantially vertically) and the web 32 that is rounded, having radius of curvature RC.

[0080] A high point M of the reserve R1 is also identified, corresponding to the upper boundary of the primary reserve R1. The high point M is typically a point of the web 32, but may, in the case of zero reserve R1, be a point of the side wall 30.

[0081] Finally, a second reference point P2 corresponding to the upper boundary of the edge 33a of the cuff 33 is identified.

[0082] The parameter representative 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 M.

[0083] In accordance with the invention, the thickness e of the reserve is determined by acquisition of a primary image of the centrifuge 3, by the camera 7, and use of said image.

[0084] In the example, the camera 7 is oriented so as to acquire an image showing at least a portion of the upper boundary of the edge 33a of the cuff 33 and a portion of the upper boundary of the primary reserve R1. The direction of observation of the camera forms an angle ? different from 0 or 90? with the horizontal, and therefore an axis 90-? with the axis of rotation A. In practice, as shown in [FIG. 1], the optical axis of the camera is oriented in the direction of the center O of the lower face of the basket 5.

[0085] An example of an image acquired in this way by a matrix camera (in negative) is shown in [FIG. 3] and will be described in more detail below.

[0086] The camera 7 can be a matrix camera or, particularly advantageously, an infrared camera.

[0087] The camera is connected to a computer 70, comprising a computer program implementing the processing system 72 of the image(s) acquired by the camera, and the data processing system 74, communicating with the image processing system 72.

[0088] In practice, the computer program comprises instructions [0089] acquisition of an image, here the primary reserve R1, [0090] processing of the images by the image processing system 72, [0091] processing the data from the image processing, by the data processing system 74, [0092] when executed on a computer.

[0093] For each image acquired by the camera 7, the image processing system 72 detects the upper boundary of the reserve R1 and the upper boundary of the edge 33a of the cuff 33, for example by a method of the contour detection type. This type of detection, which is well known, consists of identifying the points of the image that correspond to an abrupt change in light intensity. Several methods exist, which include for example thresholding, or determining the contrast gradient of the image.

[0094] Contour detection is very advantageously completed by an ellipse adjustment step of the contour thus determined.

[0095] In [FIG. 3], the ellipse E1 corresponds to the upper boundary of the primary reserve R1. The ellipse E2 corresponds to the upper boundary of the edge 33a of the cuff 33. The ellipse E3 corresponds to the outer contour of the bottom 52 of the basket 5.

[0096] Once the contours of the reserve R1 have been identified, the data processing system 72 is able to calculate the thickness of the reserve R1 from the known geometric characteristics of the centrifuge 3, characteristics of the camera 7 used to acquire the image of the reserve R1, and of the height h measured, on the image, between the upper boundary of the reserve and the top of the edge 33a of the cuff 33.

[0097] The geometric features of the centrifuge 3 that can be used in the calculation are: [0098] the coordinates x1, y1 of the reference point P1, in a reference frame x, y whose origin is the center of the lower face of the basket 5; [0099] the coordinates x2, y2 of the reference point P2 in the frame x, y; [0100] the radius of curvature RC of the inner face of the web 32; [0101] the distance DC measured horizontally between the center of curvature C of the web E2 and the axis A of the centrifuge 3.

[0102] The features of the camera 7 that can be used in the calculation are: [0103] the distance D between the camera 7 and the basket 5; [0104] the angle q between the line of sight and the horizontal; [0105] the focal length f; [0106] the size of each pixel.

[0107] From all these parameters, the system can calculate the height h0, thanks to equation 1 below.

[00001]$\begin{array}{cc}h0=\left(\left(\sin ?\right)?{\left({\left(y2-y1\right)}^2+{\left(x2-x1\right)}^2\right)}^{\frac{1}{2}}\right)?\left(\frac{f}{s}\right)?\left(\frac{1}{D}\right)& \left[\mathrm{Math}1\right]\end{array}$

[0108] Then the system can calculate e using equations 2 to 5 below, being placed in a reference frame (u, v) of origin P1, u being parallel to the line of sight of the camera:

[0109] The ordinate vm of point M in the reference frame u, v is obtained by equation 2 below:

[00002]$\begin{array}{cc}{v}_M=\left(h-h_0\right)?D?\frac{s}{f}& \left[\mathrm{Math}2\right]\end{array}$

[0110] Next:

[00003]$\begin{array}{cc}?=?+\mathrm{arc}\tan \left[\frac{\left(DC-y1\right)}{\mathrm{RC}}\right]& \left[\mathrm{Math}3\right]\end{array}$

[0111] The abscissa um of point M in the reference frame u, v is obtained by means of equation 4:

[00004]$\begin{array}{cc}{u}_M=-\mathrm{RC}?\sin ?+\sqrt{{\mathrm{RC}}^2-{\left(v_m-\mathrm{RC}?\cos ?\right)}^2}& \left[\mathrm{Math}4\right]\end{array}$

[0112] Then, e is obtained using equation 5:

[00005]$\begin{array}{cc}e=\frac{u_M}{\cos ?}+\left(v_M-u_M^{*}?\tan ?\right)?\sin ?& \left[\mathrm{Math}5\right]\end{array}$

[0113] Advantageously, the data processing system 74 is configured to undergo calibration, before operation or in a regular manner. The contour of the basket 5 identified on the acquired image can be used to perform this calibration from the actual dimensions of the basket 5, which are known, and the dimensions of the contour identified in the image.

[0114] The steps of acquiring an image, processing this image in order to extract therefrom the edges of the reserve, and processing the data of the image to determine the thickness of the reserve are advantageously repeated several times, at regular time intervals, for example on the order of 30 seconds.

[0115] At the end of one oradvantageouslymore successions of these steps, the data processing system 74 determines a deviation of the volume of the primary reserve R1 relative to a nominal value and sends to the drive motor 8 of the shaft 2 a signal to adjust the rotational speed of the rotary assembly proportional to said deviation, typically via a PID.

[0116] FIG. 4 shows the test result showing the impact of variations in the rotational speed of the rotary assembly 1 on the volume of the primary reserve R1: The solid curve represents the rotation speed 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 being in pixels. It is noted that there is a direct correlation between the variation of the speed of rotation and variation of the volume of the reserve.

[0117] When the volume of the primary reserve R1 is too great, it is possible to increase the speed of rotation of the rotary assembly up to a maximum operating value of the device (typically 2000 rpm or even 3000 rpm). Beyond this maximum speed value, the data processing system 74 can be configured to transmit a signal to an alert device 9, which may be any device able to indicate to an operator the need to adjust other parameters, in particular the temperature of the glass supplying the fiber manufacturing device.

[0118] It may also be interesting, in addition to, to evaluate the volume of the secondary reserve inside the basket 5.

[0119] On the image reproduced in [FIG. 3] acquired by the camera, the lower face 52 of the basket 5 is visible.

[0120] The image, here negative, reveals a dark center ring G (lighter in reality) and a lighter peripheral ring H (darker in reality).

[0121] The central light ring G is the area of the basket 5 that comes into direct contact with the molten stream of glass falling vertically through the supply channel 20 and whose temperature T is very high.

[0122] 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 dropped and is less than T.

[0123] In one variant embodiment, 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 in an observation direction aligned with the axis of rotation A of the rotary assembly 1. Such a secondary image of the basket seen from the bottom is schematically shown in [FIG. 5].

[0124] Advantageously, the image processing system 72 is adapted to detect boundaries of the peripheral ring H, by thresholding, and approximate these boundaries by ellipses or as in [FIG. 5] by concentric circles H1, H2 (the line of sight of the camera being vertical in this case).

[0125] 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.

[0126] The evaluation of the secondary reserve described in this way can be transposed identically to the evaluation of the volume of the primary reserve R1 in the case of a centrifuge of the with bottom type. The image of the bottom of the centrifuge, acquired by the camera, will be identical in principle to the images of the basket bottom shown in FIGS. 3 and 5: it will show a central light 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 detailed further here.