DE2362964B2 - PROCESS AND DEVICE FOR THE THERMAL PRESETRESSING OF GLASS OBJECTS IN A LIQUID BATH - Google Patents

Description

above

with liquid to

Pretensioning are supplied, the memory through an overflow (14) of the container with Liquid is fed.

The invention relates to a method for the thermal toughening of glass objects in a liquid bath and to a device for carrying out the method. It is known that glass objects, in particular panes of flat glass, can be prestressed by immersing them in a cooling liquid after they have been heated to a temperature in the vicinity of their softening temperature. The liquids used can be molten salts, molten metals or organic liquids such as. B. Oils, Polyäthylsiloxane od. Like. Act.
Such a thermal prestressing in a liquid brings with it considerable advantages, one of which is to be seen in the fact that the cooling capacity of liquids is significantly greater than that of gases and that it is therefore possible during the prestressing process to have a greater temperature gradient between the To preserve the skin and core of the glass object; the latter in turn makes it possible to obtain a degree of prestressing in objects of small thickness, in particular glass panes, which is practically impossible to achieve when prestressing in a gaseous atmosphere.

The toughening of glass objects in a liquid unfortunately also leads to disadvantages and often in particular to a poor optical quality of the surfaces of the prestressed object; presumably this results from the different cooling conditions of the glass surface from one point to the others due to the presence of bubbles and / or rising convection currents in the bathroom occur the moment the hot object to be prestressed is introduced.

To avoid these disadvantages, attempts have already been made with the arrangement according to DT-PS 6 40 176 for stirring the bath with a stirrer

to ensure that the temperature conditions inside the bath are homogenized. The experience shows, however, that such a method does not lead to the desired result. You can also do certain Do not avoid irregularities in the pre-tensioning of the object to be pre-tensioned as a whole, in particular not between the part of the object which first comes into contact with the liquid bath comes, and the rest of the subject.

Fernftr it is known from US-PS 20 52 254, for thermal toughening of glass objects To use coolant bath, with a relative movement between the glass object on the one hand and the cooling liquid is provided on the other hand. To the Achieving this relative movement there is either the introduction of compressed air or the actuation of a Propeller provided for generating a flow in the liquid bath, which is essentially tangential flows along the panes of glass. In a modified embodiment of the method according to the US-PS 20 52 254 a back and forth movement of the glass pane is provided so that the intensified in this way Heat exchange brings about the desired thermal prestress Arrangement according to US-PS 20 52 254 on the fact that a uniform as possible exposure of the Glasgegensiandes should take place through the coolant. Apart from the fact that in such a process certain difficulties with regard to the homogeneous exposure of the entire surface of glass panes occur, it is hardly possible with such a method in different areas of one Targeted glass pane to produce different pre-stresses.

It is also known that there are liquids for thermal toughening with a low viscosity generally allow higher than that of the more viscous liquids because of their cooling capacity is to obtain an increased degree of bias; however, they have one in the previously known methods unfavorable influence on the optical quality of the pre-stressed surfaces.

The object of the invention is, while avoiding the disadvantages explained above, a method and a Specify device for carrying out the method, which make it possible to increase the degree of prestressing to achieve even with objects of small thickness and at the same time satisfactory optical properties maintain.

The solution according to the invention consists in developing a method for toughening glass objects, in particular to guide glass panes in a liquid bath so that inside the liquid bath Liquid jets are directed onto the object to be toughened glass.

In a further embodiment of the invention, the liquid introduced into the bath in the form of jets can to bias the glass objects either the same liquid as the liquid forming the bath or a liquid can be used for the liquid jets, which is mixed with the liquid of the bath is immiscible and which has a higher cooling capacity than the bath.

Furthermore, the inventive method can be carried out so that only a part! of the pretensioned Object is acted upon by the liquid jets.

It is particularly advantageous if the organs emitting the liquid jets are at a sufficient level Are immersed deep into the bath and overlaid by a substantially turbulence-free layer of liquid will.

The essentially turbulence-free liquid layer expediently consists of a liquid, which has a lower specific gravity than the liquid in the bath and which does not is miscible, whereby a liquid floating on the surface can be used, which is a larger Has cooling capacity than the liquid forming the bath.

In a further embodiment of the invention, the organs emitting the liquid jets are in one Movement driven with respect to the glass surface.

It is particularly advantageous if the liquid introduced in the form of jets is on another Temperature than the liquid forming the bath.

A device for the thermal toughening of glass objects, in particular glass panes, in one The liquid bath is expediently designed in such a way that organs in which the liquid is pretensioned Containers containing are provided, which for prestressing the glass sheet on both sides Radiate jets of liquid onto the surface of the glass pane.

The organs radiating the liquid jets for prestressing are expediently composed of Tubes with slots along a generatrix parallel to the pane of glass, the slots provided Pipes from a storage tank are supplied with liquid via a pump, while the storage tank is fed with liquid through an overflow of the container.

In a further embodiment of the invention is a large number of organs provided in the form of tubes equipped with slots graduated over the height of the container, so that the ejected liquid can be applied to the entire surface of the disk.

In another embodiment of the device according to the invention, the organs which emit the liquid jets for pretensioning consist of vertical boxes, which are provided with openings on their surface opposite the glass pane are.

A flow control slide can expediently be used in the supply of the organs for radiation of the Liquid jets can be provided.

In a further embodiment of the invention, the container containing the liquid for prestressing has a layer of liquid above the organs emitting the liquid jets, so that the in the liquid contained in the layer is essentially free of turbulence.

The containers of the device according to the invention are expediently closed and kept under nitrogen.
With the method according to the invention, the possibility is advantageously created, in the case of glass objects and in particular in the case of glass panes, of achieving a pre-tensioning in the respective glass objects which can be adjusted both in terms of its intensity and in its scope or in its areas, without

f> 5 that the optical properties of the glass objects be affected. The exposure of an object to be prestressed with gas jets or also with finely divided liquid in gaseous form

The atmosphere is known, but the cooling conditions in a liquid bath are different due to their nature and duration of those in a gaseous atmosphere, in particular the ratio lies between the compressive stresses reached on the surface and the tensile stresses achieved in the core for one and the other same glass thickness when toughening in a liquid bath is considerably higher. Also occurs at the fast Cooling of the glass skin at the moment of contact with the liquid bath a solidification of the molecular state of the glass, which differs from that which occurs during tempering in a gaseous atmosphere differs.

In addition, it follows from the fact that the glass object to be toughened is not over at the same time the entire surface is brought into contact with the cooling liquid, the occurrence of permanent or temporary stresses that are very different from what one would get when biasing in gaseous form Atmosphere observed both in terms of its distribution and its intensity.

The invention is intended in the following with the aid of exemplary embodiments and with the aid of the drawings are explained in more detail. The drawings show in

F i g. 1 shows a first embodiment of the device according to the invention to carry out the method according to the invention, in which the treatment of the lower Part of the glass pane is carried out by liquid jets;

F i g. 2 another embodiment according to the invention, in which the jets of liquid are directed onto the entire surface of the glass pane;

F i g. 3 shows a further, different from the embodiment according to FIG. 2 modified embodiment for implementation of the method according to the invention.

In Fi g. 1 shows a container 6, its tank the pre-stressing liquid bath 7 contains which is of a conventional manner used for pre-stressing There is liquid, e.g. B. heavy and viscous oil. Such oils are in particular in DT-PS 8 9!) 402 described.

The glass sheet 8 to be prestressed is inserted vertically into the bath 7 and in this in a manner known per se Way held by self-clamping pliers 5.

In the arrangement according to the Ausführungsbetspiel one arranges in the bathroom on both sides of the lower Part of the glass sheet 8 horizontal tubes 10 and 10 ', which along their generatrices with the glass sheet oppositely arranged slots 9 and 9 'are in communication. The tubes 10 and 10 'are with a Oil-containing reservoir 11 connected via a pump 12 and lines 13, 13a and 13b, wherein a Slide 16 is provided in line 13.

The memory 11 contains suitable devices, not shown, to the oil on the desired Keep temperature. An overflow 14 makes it possible to dispose of the oil in excess in the container 6 continuously to be sent back to the memory 11.

In Fig. 2 is an example embodiment for Manufactured a device for pretensioning in a liquid bath, which allows the entire Whether ?: surface of the glass pane due to the jets of liquid to be coated for pre-tensioning.

In Fig. 2 you can see that the one containing the bath Container 6 with three pairs of pipes 10-10 'for supplying oil similar to those in FIG. 1 reproduced Pipes is equipped, which are provided with longitudinal slots 15-15 '. These feed pipes are with the oil-containing reservoir 11 via the pump 12 and lines 13 connected, the lines supplying the feed pipes in the left part of the figure For reasons of clarity in the drawing are omitted. As in the embodiment according to F i g. 1, an overflow 14 enables the liquid overflowing from the container 6 into the reservoir 11 send back.

In particular, one recognizes in FIG. 2 that the container 6 is of sufficient height that a noticeable layer of liquid h is above the upper pair of slots. In this way it is possible to maintain a considerable layer of liquid, which is essentially free of turbulence, above the area of the bath for biasing in which the jets of liquid emerge. This arrangement is advantageous insofar as tests have shown that it is desirable if the glass pane introduced into the bath experiences a start of cooling in still oil for a certain period of time as it passes through the liquid layer thickness Λ.

F i g. 3 shows a variant embodiment compared to the device according to FIG. 2. In this embodiment the pairs of oil spouting pipes 10-10 'are replaced by two vertical boxes 18-18' which fed with oil from the memory 11 and with openings 17 are provided on the side that is opposite to the glass sheet 8 to be toughened is arranged. In order to avoid the oxidation of the oil, the container 6 and the reservoir 11 are apart from the slot 3, they are closed and pressurized with nitrogen via a pipe 4

In the embodiments of the device according to FIG. 2 and 3, it can be advantageous to use the one with slots provided pipes 10-10 'or the perforated boxes 18-18' oscillating movements in a vertical To give level in order to compare the effect of the liquid radiation on the glass surface. This measure is particularly important when it comes to a thin pane of glass acts, d. H. if the pane of glass is on the order of a few millimeters or even less The further the thickness of the glass is reduced and the more you attach the slots or boxes to the Glass surface must approach in order to intensify the heat exchange, the greater the effect of the liquid jets then localized if they are held stationary.

Generally, the oil introduced into the bath is from of the same kind as the bath-forming oil contained in the container 6. However, it can in certain If you want to achieve special pretensioning effects, it may be advantageous to introduce one To use liquid that has a greater cooling capacity than that of the bath for biasing To be able to easily separate the two liquids, it is useful in this case to use immiscible liquids to choose.

In particular, when making this choice in the bath a liquid with a lower density or a lower specific weight than that the liquid of the bath, so that this introduced oil on the surface of the bath floating layer of immobile oil forms, which is circulated through the overflow 14 and its Layer thickness, moreover, to any desired value between a few centimeters and the height Λ can be adjusted.

If the liquid distributors are fed via individual slides, for example via the slides 16 in the embodiment according to FIG. 2, it is possible to adjust the throughput of the oil jets on the different Adjust parts of the glass pane to different values. Often times it is particularly beneficial to have a direct a larger amount of liquid on the lower part of the glass than on the upper part of the Washer to eliminate the pretensioning errors that occur without this precaution due to the fact ι ο may occur that the lower part of the glass pane necessarily first enters the bath for toughening immersed.

The jets of liquid can be introduced continuously into the bath, into which the glass panes to be tempered are immersed one after the other; but one can proceed to immerse the glass panes in a completely quiet bath and the liquid jets according to the foregoing Ausführun _b sbeispielen only trigger when the glass sheet reaches the final position in the bath and in special cases.

In principle, it is in the form of rays introduced liquid at the same temperature as the bath for biasing, so that one is continuous can work. As already mentioned, the heating elements for this liquid are advantageously in Memory ί 1; the container 6 contains the actual pre-tensioning bath and is not necessarily itself equipped with heating elements.

When producing very special glass objects, one can switch to a liquid in the form of Introducing rays into the tempering bath, which is at a different temperature, in particular a lower temperature than the bath itself has. This can easily be done under the Realize the condition that the bath is set to the desired level between the individual pre-tensioning operations Temperature is returned, for example with the aid of heating elements located in the container 6.

The method described above is explained in more detail below using an exemplary embodiment will:

A device is used as shown in FIG is shown in which the perforated plates of the boxes have dimensions of 160 mm χ 130 mm and 6 mm. These plates are each provided with 70 holes of 1 mm diameter. In the holes are 10 mm apart in the horizontal direction and 30 mm in the vertical direction. The holes a row are arranged in a checkerboard manner with respect to those of the upper and lower rows.

The level of the oil in the liquid bath is brought to a level of 130 mm above the top row of Holes set. The outer surfaces of the perforated plates are at a distance of 40 mm from the surfaces of the glass pane.

The bath consists of a commercially available oil, whose viscosity is about 25.3 centipoises at 10O ⁰ C. The same oil is contained in storage II for introduction into the boxes. The oil of the bath and of the memory 11 is maintained at 120 ⁰ C, and the pump 12 is adjusted such that the pressure loss in the openings 15 at 0.1 bar.

The glass objects to be toughened are glass panes with a thickness of 2 mm and with dimensions of 150 mm χ 100 mm. They are heated in an electric furnace for a sufficient period of time so that the surface temperature at the time of immersion in the oil is at about 68O ⁰ C. As shown in FIG. 3, the panes of glass are hung on self-locking pliers. Your immersion speed in the oil bath is 75 cm / sec. Each pane remains in the bathroom for 30 seconds; the oil is continuously introduced through the openings in the boxes.

When leaving the bath, the glass panes are cooled and checked for their fracture pattern: it is found that the glass splinters into very small pieces under the impact of a sharp object, the number of fragments being around 20 / cm ² , ie that one has received a · * prestressing, as it is usual for so-called single-pane safety glass.

If the prestressing is carried out at the same temperature with the same oil, but without oil To introduce according to the embodiments described above, the glass panes only reach a much lower preload; this is shown in the fracture pattern by larger fragments.

Incidentally, it can be seen that the optical quality of the surface of the glass toughened under the conditions of the above embodiments is excellent. In particular, it is much better than that which would have been obtained for panes of the same glass in unstirred oil, which are brought to a high degree of tension of about 20 pieces per square centimeter, which requires the choice of a substantially less viscous oil than the oil used above would have done beispieis as an oil whose viscosity is only 4 cps at 100 ⁰ C.

In the above example, an attempt was made to apply a uniform prestress in the toughened glass sheets to obtain.

It can be seen that in many instances, particularly automotive windshields, it is desirable is. Manufacture panes of glass with different bias. For example one tries in certain Cases to make windshields from toughened glass, their toughening wheel in the circumferential area is much higher than in the central area (compare FR-PS 12 59 550).

The procedure described above also makes it possible to obtain such results by using the The impingement of the oil jets is limited to special, specific zones of the disc to be prestressed, such as B. in the case of the arrangement according to FIG. 1, where oil jets only hit the lower edge of the glass. Around To obtain a windshield that has a higher degree of pretensioning around the circumference than in the middle Has area, you can therefore design a device of the type explained above so that its the spray oil dispensing slots or openings act only on the circumferential area of the disk.

For this purpose 3 sheets of drawings

Claims (17)

Patent claims: 1. A method for the thermal toughening of glass objects, in particular glass panes, in a liquid bath, characterized in that inside the liquid bath Liquid jets are directed onto the object to be toughened glass. 2. The method according to claim 1, characterized in that the in the form of rays in the bath The liquid introduced to bias the glass objects is the same as that of the bath forming liquid is 3. The method according to claim 1, characterized in that the in the form of rays in the bath introduced liquid is immiscible with the liquid in the bath and has a higher cooling capacity than the bathroom has. 4. The method according to any one of claims 1-3, characterized in that only part of the to be prestressed object is acted upon by the liquid jets. 5. The method according to any one of claims 1-4, characterized in that the organs emitting the liquid jets at a sufficient Are immersed deep into the bath and by a substantially turbulence-free layer of liquid are superimposed. 6. The method according to claim 5, characterized in that the substantially turbulence-free Liquid layer consists of a liquid that has a lower specific gravity than the liquid of the bath and which cannot be mixed with it. 7. The method according to claim 6, characterized in that one on the surface »floating Liquid is used that has a greater cooling capacity than the liquid that builds up the bath owns. 8. The method according to any one of claims 1-7, characterized in that the organs emitting the liquid jets in one movement are driven with respect to the glass surface. 9. The method according to any one of claims 1-8, characterized in that the in the form of The liquid introduced by rays is at a different temperature than that of the bath forming liquid. 10. Device for thermal bracing of Glass objects, in particular panes of glass, in a liquid bath, characterized in that Organs (10-10 ', 18-18') provided in the container ((i) containing the biasing liquid are, which to bias the glass pane (8) on both sides of the liquid jets Sandblast the surface of the glass pane (8). 11. The device according to claim 10, characterized in that the liquid jets for Bias radiating organs made of tubes (10-10 ') with slots (9-9') along a generatrix exist parallel to the glass pane. 12. Apparatus according to claim 10 or 11, characterized in that the with slots provided pipes (10-10 ') from a storage (11) b i 13. Device according to one of claims 10-12. characterized in that a Large number of organs in the form of tubes equipped with slits, graduated over the height of the: Container (6) is provided so that the entire surface of the glass pane with the blasted Liquid can be acted upon. 14. The device according to claim 10, characterized in that the liquid jets for Tension-releasing organs consist of vertical boxes (18-18 ') with openings (17) are provided on their surface opposite the glass sheet (8). 15. Device according to one of claims 10-14, characterized by a throughput control slide (16) in the supply of the organs for radiation of the fluid jets. 16. Device according to one of claims 10-15, characterized in that the Containers (6) containing liquid for pre-tensioning, above those dispensing the jets of liquid Organs has a liquid layer thickness, so that the liquid contained in the layer in the is essentially free of turbulence. 17. Device according to one of claims 10-16. characterized in that the container are closed and kept under nitrogen.