EP2619554A2

EP2619554A2 - Device and method for detecting flaws in continuously produced float glass

Info

Publication number: EP2619554A2
Application number: EP11817464.8A
Authority: EP
Inventors: Wolfgang Zorn; Peter Krug; Winfried Baller; Florian Bader
Original assignee: Grenzebach Maschinenbau GmbH
Current assignee: Grenzebach Maschinenbau GmbH
Priority date: 2010-09-24
Filing date: 2011-09-21
Publication date: 2013-07-31
Also published as: DE102010046433A1; US20130176555A1; IL225327A0; UA104966C2; CN103154710A; WO2012041285A2; MX2013003334A; KR20130046443A; JP2013539026A; EA201390358A1; DE102010046433B4; WO2012041285A3; BR112013007477A2

Abstract

The invention relates to a method and device for detecting flaws in a continuously produced float glass band by checking a glass strip, which extends perpendicularly to the conveying direction and which is observed in transmitted light, characterized in that the device has the following characteristics: a) the flow of a float glass band is thoroughly monitored by means of a modularly constructed fastening bridge and scanning sensors fastened to said fastening bridge and two transmission lighting means arranged perpendicular to the glass band, b) each scanning sensor can be oriented by means of an adjusting apparatus according to the three spatial coordinates in the positive and negative directions and can be finely adjusted by means of a target apparatus that can be pivoted in, in the form of an artificial measurement plane, and c) the lighting means are cooled by means of a cooling apparatus.

Description

Apparatus and method for detecting defects in continuously generated float glass

The invention relates to an apparatus and a method for detecting

Defects in continuously generated float glass.

DE 19643 017 C1 discloses a method for determining optical defects, in particular the refractive power, in large-area panes of a transparent material such as glass, in which by means of projecting a defined pattern onto the glass and imaging this pattern onto a camera the observed image is evaluated. This occurs because a light-dark sequence of the raster pattern is imaged in each case on a number of adjacently arranged pixels of the camera and the number is an integer multiple of the light-dark sequence. The object of this invention is to specify a method with the optical error in at least one dimension of a disc without

Reference patterns can be determined locally. Defects in a continuous production process of float - glass can not be determined hereby.

DE 198 13 072 A1 describes a method and a device for determining the optical quality and for detecting defects of flat glass, in particular of float glass, or other optically transparent materials. Essentially, a video camera looks through the glass through it

Lighting device, wherein the focus is on the glass and the video camera generates signals depending on the quality of the glass and these are evaluated. With such a known method, the object to be achieved, to provide a method in which no dead zones are present and the strength of the deflection {refractive power) and the size of the glass defect can be determined. In addition, a measurement of the core of the defects in the glass should be possible.

This task should be solved by

in that a lighting device is used whose color and / or intensity changes from one outer edge to the other, further,

that the viewing spot of the video camera is in the fault-free state of the glass approximately in the middle of the lighting device, in that the illumination device is assigned two video signals ui _, u ₂ according to color and / or intensity, and

that a change in the intensity of the video signal ui, u _{2 is used} to assess the quality of the glass.

Defects in a continuous production process of float glass can also not be determined with this method.

The device according to the invention, or the corresponding method, is therefore based on the object of introducing a device and a method with which, during the ongoing process of producing a strip of liquid glass, a so-called float glass, the formation of imperfections, for example in the form of inclusions, blisters or similar undesirable phenomena, can be constantly detected and monitored.

This object is achieved with a device according to claim 1 and a method according to claim 8.

The device according to the invention will be described in more detail below,

In detail, they show:

Fig. 1: a perspective plan view of an inventive

Contraption,

2 shows a front view of the device according to Fig.1,

3 shows a view from above of the device according to Fig.1 _f

Figure 4; a side view of the device of FIG. 1

5 shows a perspective view of the lighting means;

6 shows a functional sketch of the adjustment of a scan sensor;

The basic idea of the present invention is on the one hand by means of so-called scan sensors, eg. in the form of line scan cameras, to constantly monitor the flow of the float glass ribbon and, on the other hand, to provide the ability to readjust or replace the individual scan sensors during a repair or partial failure during this continuous monitoring process. Fig. 1 shows a perspective top view of a device according to the invention. The bird's-eye view shows the bridge-like overall conception of the glass ribbon continuously flowing from the melting furnace

This is not drawn here, but only the rollers that carry the glass ribbon are sketched. On the left and the right side of the observation and maintenance bridge, stairs lead to an observation and maintenance bridge. Here, only a part of the entire protective covering is designated 1.

Fig. 2 shows a front view of the device according to Fig.1. In addition to the stairs known from FIG. 1, the maintenance bridge 10 can be seen here in section, which is supported on the base frame 6. A web of flat glass 7 is sketched here on a conveyor roller 8, which is mounted on a cross member 9 and is driven by a drive 5. As upper end of the base frame 6 is above the

Guard rail of the maintenance bridge 10 to recognize the mounting bridge 3 for the scan sensors 2 in section. With 11 here is the track for a lighting device 17 and 12 shown the positional support for this lighting device. On the left side of the entire device is a lifting device 13 of

Mounting bridge 3 for the scan sensors 2 referred to. A corresponding lifting device 13 is also located on the right side of the mounting bridge. 3

With this lifting device 13, it is possible for repairing one or more scanning sensors 2 and / or the associated adjusting device 14 to lift the entire mounting bridge 3 and to adjust the respective scanning sensor 2 without the reference surface of an otherwise necessary flat glass 7 by means of the respective swiveling target device 16. This requires a short-term

Interruption of the detection of defects, however, the process of

Adjusting a scan sensor by means of the pivotable target device 16 are shortened so much compared to the prior art that a continued running of the glass ribbon can be economical. Because it can, from an economic point of view, the temporary failure of the possibility of detection of defects compared to the previously required elaborate breaking and melting of the

Glass ribbon as wearable appear. An additional illumination device 4 is shown in section on the right side of the maintenance bridge 10, analogous to a corresponding one

Facility 4 on the left. This device spans the entire width of the web of flat glass, but its middle part is not visible in this illustration. The function of this device will be described later in the explanation of Fig.6.

FIG. 3 shows a view from above of the device according to FIG. In addition to the known maintenance bridge 10 and an already described conveyor roller 8, the spatial allocation of the support 12 for the lighting device 17 can be seen better here. From this position, the adjusting devices 14 (8 pieces are shown here) are clearly visible for the scanning sensors 2.

These adjusting devices 14 can be raised and lowered not only by means of the lifting device 13 as a whole with the scanning sensors 2, but additionally each have the possibility of being in all three

Space coordinates to move independently.

Thus, on the one hand, it is necessary for the scanning sensors 2 to be able to move both in the positive and in the negative X direction in the direction of the longitudinal extension of the mounting bridge 3, here referred to as the X direction, in order to ensure a gapless combination of the images of all involved Scan sensors 2 over the entire width of the glass sheet to be checked. That is, in this way it can be ensured by control technology that an image of a scan sensor 2 stops where the image of the adjacent scan sensor 2 begins.

Furthermore, it is necessary for the correct alignment of each individual scanning sensor 2 that its center point exactly on the dividing line between the

line-shaped light source 20 (oscillating) and the lighting means 23 {constant lighting) is aligned. (Figure 5). For this, a movement possibility in both the positive and in the negative Y - direction is necessary, wherein the Y - direction forms a horizontal plane with the X - direction and encloses a right angle with the X - direction.

Furthermore, an adjustment of a single Scansenors 2 in the vertical direction, ie the Z - axis is additionally necessary for the case that a single Scan sensor 2 must be fine tuned by means of the target device 16 described later.

As a special embodiment it is provided that in the case of readjustment of a single scan sensor 2 during operation of the float glass production a complete test operation is maintained by each scanned sensor 2 with its associated adjusting device 14 at the next possible distance in the direction of the glass flow has an associated 2nd version of himself. This 2nd version is used during the adjustment or the complete replacement of the corresponding 1st version to replace them functionally. For this purpose, it may be necessary, depending on the spatial conditions, in a particular embodiment, to provide in the second version, the additional possibility of a slight tilting tendency to cover the same area on the dividing line between the two bulbs 20 and 23. This is due to the horizontal displacement of the respective I .Version and the second version of a scan sensor 2 and its associated adjusting device 14th

FIG. 4 shows a side view of the device according to FIG. 1.

Starting from the top, here is a scan sensor 2 with its associated

Adjusting device 14 shown in section. 16 denotes a pivotable target device 16 whose function is explained in more detail in the description of FIG. 6. Below, the lighting device 17 with the associated fenders 15, of which only the left is designated to recognize.

The cross member 19 which is connected to the base frame 6, carries the main carrier 18 of the lighting device. In addition, the running rail 11, which can be seen in the Figure 2 in longitudinal view, shown in cross section. The running rail 1 serves the purpose of pulling out the lighting device 17 during operation

To allow repair purposes and to ensure a quick insertion after repair. A cooling device 21 provides for the cooling of the lighting device 17 and thus for the maintenance of the correct operating temperature of the lighting device 17, the bulbs 20,23.

FIG. 5 is a perspective view of the lighting means 20, 23 in FIG

shown in enlarged form. The bulbs are appropriately according to the width of the glass ribbon to be illuminated in terms of their longitudinal extent assembled in a modular manner. Together they form, as it were, two parallel light bands, one of which has a line-shaped light source which oscillates in its light intensity and which has another light-emitting means 23 arranged in a line-shaped manner and constant in its light intensity.

The frequency of the oscillating light intensity is in this case preferably equal to the line frequency of the line scan camera, or the frequency of driving a scan sensor 2. It is also preferred that these frequencies are in an integer multiple to each other.

The center of view of each scan sensor, for example a video camera, lies in the region of the demarcation line in the case of a defect-free lens

Bulb 20 and the bulb 23. When a glass defect occurs, this center of view shifts due to refraction of light from this center point position. This results in the location of the detected glass defect different influences on the output signal in the region of the relevant scanning sensor 2. From the change of two consecutive signals of a scan sensor 2 and the additional information of the fault location, or the location in the region of the relevant scan sensor 2, can be in a new way gain a resulting error signal from the comparison of the measured values of two, related, optical channels and supply a circuit arrangement for error detection and for further signal processing.

For a more detailed explanation, the two surface pieces A1 and A2 are shown in FIG. Here, the larger area A1, the dividing line of the two

Luminous means 20 and 23 overlapping, assigned to two bulbs, while the area A2 only the area of the luminous means 23 with the constant

Light intensity is assigned. Both surfaces A1 and A2 provide different measured values in the region of a pixel-like detection of these optical channels, which, in the range of certain threshold values, allow safe conclusions to be drawn regarding the type and extent of a detected defect.

The cooling device 21 acts on the underside of the two light bands. A

Cover 22, which also acts as a light diffuser, forms the end of the light bands opposite the underside of the glass strip to be tested.

As a particular embodiment of the device according to the invention, a second version of the above-described bulbs 20 and 23 may be provided, which from the position forth (parallel to the 1st version) with the above-described 2nd version of Adjusting device 14, and the respective associated scan sensor 2, correspond. This additional arrangement ensures in the case of repair or the entire replacement of a lighting unit, or parts thereof, by means of an automatic switching operation on this 2.Version the undisturbed operation of the entire device according to the invention. The above-mentioned additional tilting device on each adjusting device 14 for the respective scanning sensor 2 is not necessary in this case, since the second version of an adjusting device 14 is arranged directly above the center line of the second version of the lighting means 20 bzw.23. The respective second version, be it the adjusting device 14 or the lighting means 20 or 23, are arranged upstream of the first version in order to detect approaching fault points in advance and to supply them to a further evaluation. It goes without saying that these second versions must also have corresponding additional pivotable target devices 16.

FIG. 6 shows a functional sketch of the adjustment of a scan sensor.

About the lighting device 17 described above, the glass tape to be tested runs on the sketched roles. If the readjustment or readjustment of a scan sensor 2 becomes necessary, the adjusting device 14 of FIG

corresponding scan sensor 2 is raised a bit and at the same time becomes a target

- Device 16 in the beam path of the illumination device 17th

pivoted.

This target device 16 has fixed markings in the form of simple lines and / or crossed lines of specific thickness and / or color, by means of which the respective sensor 2 can automatically align itself in a desired nominal position according to a defined program.

The corresponding scan sensor 2 is in this case raised as far as corresponds to the distance of the target device 16 from the glass ribbon. The adjusting device 14 subsequently adjusts the relevant scanning sensor 2 in accordance with the optical specifications of the target device in its horizontal orientation. After adjustment of the scan sensor, the carrier device 16 pivots back again and the scan sensor descends again to its predetermined working height above the glass plate 7.

The additional illumination device 4 has additional illumination means such as LED, UV emitters, quartz lamps, xenon emitters or helium. Spotlights that offer additional possibilities for the detection of undesired glass properties. These depend on the type of glass and the special requirements of the glass mixture produced and thus the respective glass parameters or glass defects to be detected.

In a particular embodiment, an additional device for measuring the glass thickness, for example by means of laser or ultrasound, each

Scanning sensor 2 positionally assigned to be provided. With such a device, the thickness of the produced glass ribbon, dissolved in the transverse direction and longitudinal direction, additionally detected during the manufacturing process and

to be recorded. These readings may be used to monitor the

Production process of the float - serve glass ribbon.

In a particular embodiment of the invention, it may additionally be provided that a device for measuring and monitoring stresses in the glass band is provided simultaneously with the detection of defects in the float glass.

For this purpose, a method is proposed in which polarized light is sent into the glass ribbon, wherein occurring stresses cause a birefringence, and the emerging light beam is analyzed to determine the changes caused by the birefringence and thus the occurring stresses. The determination of these stresses is carried out by continuously sweeping the width of the glass ribbon, the registration of said changes in the type of birefringence and the simultaneous measurement of the temperature at the respective, respectively swept, location. From the measured changes of

Birefringence and the associated measured temperature at the respective measuring point, the permanent voltage at the relevant measuring point and in total thus the total width of the glass ribbon can be determined. The

Continuous measurements of these stress gradients in the width of the glass ribbon provide important information on longitudinal stresses in the float glass ribbon, which represent a high risk potential for the entire production.

The area exposed to the incident polarized light beam preferably has a diameter of less than 20 mm. The

Temperature measurement can be done for example with an optical pyrometer. The control of the complex motion processes and the signal processing of the sensors used requires a special control program. LIST OF REFERENCES

paneling

Scan sensors (line scan cameras)

Mounting bridge for the scan sensors

Additional lighting device

Drive of the conveyor rollers

base frame

flat glass

conveyor roller

Cross member for the conveyor device

maintenance bridge

Running track for the lighting device

Support of the lighting device

Lifting device of the mounting bridge for the scan sensors

Adjustment device of the scan sensors

Mudguard of the illuminated shaft of the lighting device swiveling target device

lighting device

Main support of the lighting device

crossbeam

Light source (oscillating)

cooling device

Light diffuser and cover

Light source {constant)

Patch A 1

Patch A 2

Claims

claims

Claim 1:

Device for detecting defects in a continuously produced float glass strip by means of the examination of a transversely to the conveying direction, observed in the transmitted light glass strip, characterized in that it comprises the following features: a) a modular mounting bridge {3) for scanning sensors ( 2) which is designed according to the width of the float glass strip to be tested, wherein the scan sensors (2) completely cover this width with regard to their detection range and the float glass strip by means of a line - shaped luminous means (23) with constant luminous flux and

adjacent line-shaped illuminant (20) is continuously illuminated with oscillating luminous flux,

b) an adjustment device (14) which is assigned to each scan sensor (2) and which permits a change in the position of each scan sensor (2) along the three spatial coordinates in the positive and negative directions, c) a pivotable target device (16) assigned to each scan sensor (2) in the form of an artificial measuring plane for the exact alignment of a scanning sensor (2) on the surface of the float glass ribbon,

d) a cooling device (21) for cooling the lighting means (20,23).

Claim 2:

Device according to claim 1,

characterized,

that the determination of defects by means of the scanning sensors (2) takes place via the comparison of the pixel measured values of two optical channels, wherein the one channel relates to a surface area A1 of the

Luminous means (20) and (23) comprises, while the other channel relates to an associated surface area A2 which comprises only the lighting means {23), and the comparison and the evaluation of these measured values takes place taking into account specific threshold values.

Claim 3:

Device according to one of claims 1 or 2,

characterized,

that, taking into account a short piece unchecked

Glasbandes, the entire mounting bridge (3) of a

Lifting device (13) can be raised for repair and lowered again

Claim 4:

Device according to one of claims 1 to 3,

characterized,

in that the adjusting devices (14) and the associated scanning sensors (2) and / or the light sources (20, 23) are each assigned an identical second version upstream of the float glass band, which can replace them if the first version fails.

Device according to one of the preceding claims, characterized

an additional illumination device 4 is provided which contains special illumination means for determining further glass parameters or glass defects.

Claim 6:

Device according to one of the preceding claims, characterized

that each scanning sensor (2) is spatially associated with an additional device for measuring the glass thickness in its detection range. Claim 7:

Device according to one of the preceding claims, characterized

that by means of a further, simultaneously operated, device monitoring of the stresses in the glass ribbon by means of a sliding, the width of the glass ribbon sweeping, local supply of polarized light and a simultaneous temperature measurement at the respective measuring point of the glass ribbon.

Claim 8.

Method for detecting defects in a continuously produced float glass ribbon by means of testing a transverse to the

Direction extending, observed in the transmitted light glass - strip, characterized in that it comprises the following features: a) by means of a module-like mounting bridge {3) and scanners attached thereto {2) and two arranged transversely to the glass ribbon fluoroscopy means (20, 23) the flow of a float glass band is monitored without interruption,

b) each scanning sensor (2) can be aligned in the positive and negative directions by means of an adjusting device (14) according to FIG. 3 and finely adjusted by means of a pivotable target device (16) in the form of an artificial measuring plane, c) the lighting means (20, FIG. 23) are cooled by means of a cooling device (21).

Claim 9:

Method according to claim 8,

characterized,

that the detection of defects by means of the scanning sensors {2) takes place via the comparison of the pixel measured values of two optical channels, wherein the one channel relates to a surface area A1 of the

Illuminant (20) and {23) comprises, while the other channel comprises an associated surface area A2 which comprises only the lighting means {23), and the comparison and the evaluation of these measured values taking into account certain threshold values.

Claim 10:

Method according to one of claims 8 or 9,

characterized,

that, taking into account a short piece unchecked

Glasbandes, the entire mounting bridge (3) of a

Lifting device {13) can be raised for repair purposes and lowered again

Claim 11:

Method according to one of claims 8 to 10,

characterized,

that the adjusting devices (14) and / or the lighting means (20, 23) upstream of the float glass band are each assigned an identical second version which can replace them in the event of a failure of the first version.

Claim 12.

Method according to one of claims 8 to 11,

characterized,

an additional illumination device 4 is provided which contains special illumination means for determining weathering glass parameters.

Claim 13:

Method according to one of claims 8 to 12,

characterized,

that each scanning sensor (2) is spatially associated with an additional device for measuring the glass thickness in its detection range. Claim 14:

Method according to one of claims 8 to 13,

characterized,

that by means of a further, simultaneously operated device, a monitoring of the stresses in the glass ribbon by means of a sliding, the width of the glass ribbon sweeping, local supply of polarized light and a simultaneous temperature measurement at the respective measuring point of the glass ribbon.

Claim 15:

Computer program with a program code for carrying out the method steps according to one of Claims 8 to 14, when the program is executed in a computer.

Claim 16:

A machine-readable medium having the program code of a computer program for carrying out the method according to one of claims 8 to 14, when the program is executed in a computer.