WO2007051582A1

WO2007051582A1 - Method for testing glasses for inclusions

Info

Publication number: WO2007051582A1
Application number: PCT/EP2006/010418
Authority: WO
Inventors: Thomas Schuller
Original assignee: Glassiq Gmbh & Co. Kg
Priority date: 2005-11-04
Filing date: 2006-10-30
Publication date: 2007-05-10
Also published as: AT502411A4; AT502411B1

Abstract

The invention relates to a method for testing a glass object, especially a flat glass such as a float glass, for inclusions such as nickel sulfide particles or particles made of fireproof materials, the test being performed during the production of the object in which the object is produced from liquid glass in a first step and the object is allowed to cool, especially naturally, to the ambient temperature so as to solidify in a second step. In order to be able to detect particles such as nickel sulfide/s and/or particles made of fireproof material in a glass object in a simple manner without using an external light source, electromagnetic radiation emitted at least temporarily by the glass object during the second step is recorded in a locally resolving fashion, and the radiation that is recorded in said way is evaluated to determine inclusions.

Description

Method for testing glasses for inclusions

The invention relates to a method for testing an article made of glass, in particular a flat glass such as a float glass, on inclusions such as nickel sulfide or refractory particles, wherein the testing is carried out during manufacture of the article, wherein in a first step the object made of liquid glass is and this is allowed to cool in a second step under solidification to ambient temperature, of course, of course.

In a production of objects made of glass such as a production of glass sheets in the float glass process, a complete avoidance of particle inclusions or impurities in the glass is technically conceivable, but hardly possible with economically acceptable measures. It is therefore not surprising that, for example, in flat glass impurities are encountered as a companion of the glass and in the glass matrix inclusions are present. Under these

Inclusions include, in particular, nickel sulphide inclusions and inclusions of refractory materials, which usually make up the largest proportion of these impurities, and which can often be up to about 600 microns in size.

Inclusions or particles of nickel sulfide (s) and / or refractory materials in the sub-millimeter range are not perceived by the human eye throughout and therefore do not affect the aesthetic appearance of glass panes or the like products. However, the inclusions mentioned are foreign bodies, which have different material properties in comparison with glass and, under certain circumstances, especially after hardening, lead to spontaneous breakage of the material

Glass object can lead. Such spontaneous fractures, such as those observed with façade glazing, can result in considerable personal injury and property damage. It is therefore very hard to obtain suitable methods already before further use education on possible inclusions, for example, glass panes with a particularly high risk of breakage before a

To be able to eliminate tempering or hardening and a use for facade glazings.

With regard to detection of inclusions in flat glass, optical inspection methods have been proposed, which are based essentially on scattering of laser light in the amorphous glass and analysis of the scattered light. These Methods allow to detect inclusions without destroying the product. Examples of such methods can be found in US 4,697,082, WO 01/73408 A1 or WO 01/18532 A1

Although by scattering of laser light and analysis of the scattered radiation inclusions can be generally detected quite reliable and non-destructive with respect to the glass, it is extremely disadvantageous that these methods always laser light and consequently also a laser light source or a laser presuppose. This causes on the one hand large equipment and cost expenses. On the other hand is a usable cross section of a laser output or a

Laser beam diameter limited and usually many hundreds of times smaller than the object to be examined. This means that either many lasers have to be used simultaneously and / or the object has to be scanned in small steps.

This is where the invention is based and sets itself the goal of providing a method of the type mentioned, with which in a simple manner and without an external light source particles such as nickel sulfide (s) and / or particles of refractory material can be detected in a glass article.

This object is achieved by a method having the features according to claim 1. Advantageous embodiments of a method according to the invention are the subject matter of claims 2 to 5.

The invention is based on the finding that particles of a nickel sulfide or of refractory materials, as formed in the course of a glass production and finally included in the finished article of glass, at elevated temperatures each emit a characteristic electromagnetic radiation and that this radiation significantly more intense is, as a self-emission of the glass, so that the inclusions at a given temperature from the glass matrix quasi shine out.

The inventive method has the advantage that light sources such as laser are no longer necessary to determine inclusions of nickel sulfide (s) or refractory particles. Rather, it is exploited that the enclosed particles themselves represent light sources at the high temperatures of a production process, from the emissions of which information about the inclusions can be obtained. In the planned spatially resolved recording of emissions can be so particular Statements about forehand, position and number of trapped particles are taken.

In addition to statements on the location and number of trapped particles can also make statements about a particle size, so that after evaluation of the recorded emissions accurate knowledge about nickel sulfide inclusions and / or inclusions of refractory materials in the glass are available. This knowledge can be used to decide on further processing or treatment of the object. Specifically, in the manufacture of glass in the float glass process, based on this knowledge, it can be decided whether or not to subject the produced glass article to cure: When fracture-critical inclusions have been found and breakage is likely after subsequent curing, hardening does not occur carried out. The glass produced is then used for applications in which it is little stressed. If, due to the knowledge, a break after curing is not to be expected, this is cured and can subsequently be used for applications in which high mechanical strength is required. Depending on their quality, glass panes can thus be selectively directed to various uses.

In the context of the invention, it may be favorable if the natural cooling of the article made of glass is delayed by the supply of heat. Thereby, the glass article is kept for a long time in a temperature range in which emissions can be observed. Furthermore, it is possible to take pictures with an increased exposure time and thus improved signal-to-noise ratio, which increases the reliability of a statement about present inclusions.

In order to be able to observe intense emissions and consequently obtain a high significance of the evaluation results, it is expedient if the temperature of the article made of glass, at which electromagnetic radiation is registered, is at least 250 ^° C., preferably at least 380 ^° C., in particular more than 500 ⁰ C, is.

Furthermore, it can be provided that the object made of glass is moved substantially uniformly in the second step and the reception of emitted radiation with one or more line or area detectors such as a CCD (charge coupled device) camera or CMOS (complementary metal oxide semiconductor). Camera performed is adjusted, wherein an exposure time of the area detector is adapted to a movement speed of the object.

Such a variant of the method is compatible with large-scale systems in which glass sheets can not be cooled in a stationary position for technical and / or economic reasons, but must be removed from the production area in the hot state, and has proved to be particularly suitable in this regard. Above all, this applies to a production of glass panes in the float glass process, where glass tapes are continuously removed from the liquid tin bath with a temperature of about 600 ⁰ C. By using line or area detectors, it is now possible to detect inclusions such as nickel sulfide over an entire width of the glass ribbon. At the same time, an exposure time of the area detector is adapted to a speed of movement of the glass ribbon to ensure that inclusions can be determined without gaps even over a whole band length. A movement of the glass ribbon relative to the detectors can be taken into account computationally with knowledge of the movement speed in the evaluation of the measurement signals in order to obtain as exact as possible information on the position of inclusions. Thus, a complete examination of a glass ribbon can be done without having to intervene in a conventional production process. It is very beneficial to perform photographs immediately after deduction of the glass ribbon from the metal bath, since the glass ribbon is at this point at a temperature of at least about 550 ⁰ C and emissions of nickel sulfide and / or refractory inclusions at these temperatures are intense. In addition, gas bubbles can also be observed in the glass, as they appear bright as emissive inclusions on the detector.

In order to eliminate extraneous light influences as much as possible and to avoid resulting distortions of evaluation results, the object made of glass for receiving emitted radiation can be introduced into a dark room or moved by it. Avoiding disturbing extraneous light makes it possible to obtain measurement results or evaluation results of the same quality with shorter exposure times.

A recording of electromagnetic radiation can take place in the wavelength range from 200 to 2000 nm. In this wavelength range are at elevated temperatures

Emissions of nickel sulphides and inclusions due to contact of glass with refractory Material are much more intense than emissions of a glass, so that in local resolution measurement inclusions of inclusion-free zones can be discriminated. It is expedient and simple to register radiation emitted at a wavelength of 350 to 1600 nm, since cheap, commercially available cameras or spectrometers can be used for this area and the emissions of the inclusions in these areas have maxima.

Further advantages and effects of the invention will become apparent from the context of the description and the embodiments.

In the following, the invention is further illustrated by way of examples.

Show it:

Figure 1: intensity of emissions of different inclusions at different

temperatures;

Figure 2a: Scheme of a range detection of emissions of inclusions in a glass sheet;

FIG. 2b shows the emission intensity corresponding to the areas shown in FIG. 2a; FIG. 3: Use of a method according to the invention in a production of

Glass panes in the float glass process.

With reference to Figure 1, the inventive concept is explained in more detail. Figure 1 shows results obtained in emission measurements on various glass sheets and at different temperatures. To measure the glass sheets with a temperature of 320 ⁰ C (measurement A1) 400 ⁰ C (measurement A2) 380 ⁰ C (measurement B1) and 600 ° C (measurement B2) were charged into a sealable darkroom. Emissions were registered via a CCD camera mounted on and projecting into a top surface of the darkroom in the range of 350 to 800 nm and evaluated by means of a computer connected to the CCD camera. The glass sheets were not moved during the test.

Measurement A1 in FIG. 1 shows the intensity of emission of a region with a refractory material particle (dotted column) in comparison with the intensity of emission of an inclusion-free region of the glass matrix (white column). As can be seen, an emission in the region of inclusion exceeds that of an inclusion-free region by one Many times, so that a quantitative analysis of the existence of the inclusion can be determined beyond doubt. If a temperature of an examined glass pane is increased (measurement A2), an emission intensity of refractory inclusions relative to the emission intensity of the glass matrix can be increased, so that a reliability or significance of the test results is improved. Similarly, even with nickel sulfide inclusions, which emit slightly more light at temperatures of 380 ^° C. than a glass matrix (hatched or white column of measurement B1), a higher discrimination results in a clearer discrimination of inclusion-free and inclusion-afflicted areas (measurement B2). ,

With reference to FIGS. 2 a and 2 b, a region-wise or spatially resolved detection of inclusions in a glass pane G is explained. In a plane above the glass pane G, a CCD (charged coupled device) camera is mounted whose pixels emissions of the glass pane G dissolved over the lines 1, 2, 3 ... 9, 10 over its entire width B and over part of the Length L takes up area by area. If a foreign inclusion is present, an intense emission is registered by the assigned pixel or with a corresponding size of an inclusion, if appropriate by a plurality of pixels, whereas only a comparatively small emission is detected by the remaining pixels. This situation is shown schematically for a row R in which two inclusions, namely a refractory inclusion in row 3 and an inclusion of a nickel sulfide in row 9, are shown in figures 2a, 2b. As can be seen, large emission intensities are registered by the respectively corresponding pixels, whereas with the other pixels only low-intensity matrix emissions are detected. A spatial resolution depends on the pixel size and can be selected 20 μm or better. The analog signals of the individual pixels can be converted into digital data for further evaluation and, for example, further processed with a computer.

When recording the emissions, the glass pane G shown in FIG. 2a is expediently located in a darkroom, in order to avoid disturbing influences of extraneous light. The CCD camera can then be attached to the ceiling of the darkroom. However, it is preferred if the camera is mounted on the outside of the top surface of the darkroom, so that emissions of the glass pane G can fall on an entrance slit of the camera. For this purpose, the darkroom may be provided with a small gap in the plane of which the entrance slit of the mounted CCD camera or a CMOS camera comes to rest. It can also be provided in particular when measuring on virtually endless glass bands or glass panes with a large aspect ratio, that a multiplicity of similar cameras arranged one behind the other is used. This allows large areas to be checked for inclusions in a short time.

When using a CCD camera or a CMOS camera, an exposure time is usually in the range of 1 to 50 milliseconds. In principle, it is favorable to choose the longest possible exposure time in order to obtain a measurement result which is averaged over as long a time as possible and has a high signal-to-noise ratio. If a test is carried out on uniformly moving glass bands or glass panes, then an exposure time is adapted to a speed of movement of the glass band or the glass panes, so that a complete inspection is possible.

Within the scope of the invention it is also possible to distinguish between different types of emitting inclusions by additionally analyzing radiation emitted by inclusions, for example by spectral analysis of the emission bands. In particular, in refractory inclusions, which do not emit in crystalline form per se or only very weak, such as aluminum, zirconium or chromium oxide or crystalline phases of silica, and where emissions due to defects in the crystal lattice and / or the incorporation of emitting foreign ions in the crystal lattice are often characteristic emissions, which allow a perfect allocation to certain types of inclusion.

Finally, FIG. 3 shows the use of a method according to the invention in the production of glass panes in the float glass process. Starting material 11 made of glass is supplied via a storage container 12 to a storage chamber 13, via which the starting material 11 is transported by means of a conveying means, not shown, into a melting chamber 14. In the melting chamber 14, for example, flat heating elements 15 are arranged to melt the starting material 11 and a

To keep molten glass 16 in the liquid state. From the melting chamber 14, the glass melt 16 is transferred into a rest chamber 17, in which the glass melt 16 is calmed. Subsequently, the about 1400 ⁰ C hot molten glass 16 is transferred to a tin bath 18, where the molten glass 16 spreads on the surface of a tin melt 19 and withdrawn at one end by means of a transport 21 as a glass ribbon and transferred to a heat chamber 20. In the heat chamber 20, the semi-solid Glass ribbon cooled slowly or delayed to avoid strains in the glass ribbon. Finally, a natural cooling in the downstream region 22, before the glass ribbon with a cutting and breaking device 23 into individual glass sheets

24 is shared.

According to the invention, a CCD or CMOS camera 25 is attached to the top surface of the heat chamber 20, with which emissions of the glass ribbon are recorded in a spatially resolved manner. In order to largely protect the camera 25 from the effects of temperature, this is expediently mounted on the outside of the heat chamber 20 and the heat chamber 20 has an opening through which emitted radiation impinges on the camera 25. In this regard, it may also be very convenient to position the camera 25 in the gap between the tin bath 18 and the heat chamber 20. The camera 25 is connected via a line 26 to a computer 27 in connection with which the camera

25 recorded signals are processed or evaluated. The computer 27 is in turn connected to a removal device 28 for glass panes 24 and controls them. If an evaluation of the emission values supplied by the camera 25 shows that there are inclusions in a glass pane 24, which lead to a considerable risk of breakage upon hardening thereof, then the glass pane 24 is removed from the removal device 28 by the transport means 21. The removed glass 24 is then placed on another transport and transported. Thus, the glass sheets 24 are separated in terms of quality depending on the inclusions and can be treated according to their quality targeted or used.

To remove individual glass panes 24, the removal device 28 may be equipped with a preferably pneumatic or hydraulic lifting device 29. Alternatively, instead of the lifting device 29, a device for marking the glass panes 24 may be provided. In this case, the individual glass panes are provided with a mark which gives information about their quality.

Claims

claims

A method of testing an article of glass, in particular a flat glass such as a float glass, on inclusions such as nickel sulfide particles or particles of refractory materials, wherein the testing is carried out during manufacture of the article, wherein in a first step the object is made of liquid glass and this is allowed to cool naturally in a second step, while solidifying to ambient temperature, of course, characterized in that during the second step at least temporarily emitted from the object of glass electromagnetic radiation is recorded spatially resolving and the radiation thus recorded is evaluated to determine inclusions.

2. The method according to claim 1, characterized in that the natural cooling of the article is delays from glass by the supply of heat.

3. The method according to claim 1 or 2, characterized in that the temperature of the article of glass, in which electromagnetic radiation is registered, at least 250 ⁰ C, preferably at least 380 ⁰ C, in particular more than 500 ^C C, is.

4. The method according to any one of claims 1 to 3, characterized in that the object of glass in the second step is moved substantially uniformly and carried the recording of emitted radiation with one or more line or area detectors such as a CCD camera or CMOS camera is adjusted, wherein an exposure time of the area detector is adapted to a movement speed of the object.

5. The method according to any one of claims 1 to 4, characterized in that the object is introduced from glass for receiving emitted radiation in a dark room or is moved by such.