MXPA99004049A - Device for cooling convex glass sheets - Google Patents

Abstract

The invention concerns a device for cooling glass sheets moving past on a roller conveyor, comprising blow boxes inserted between the rollers, and having one surface opposite the glass sheet at a distance less than 30 mm and preferably less than 10 mm, said surface being perforated with several holes for discharging air in the direction of the glass sheets.

Description

DEVICE FOR COOLING FOLDED GLASS SHEETS DESCRIPTION OF THE INVENTION The invention relates to a device for cooling folded glass sheets. More specifically, the invention relates to a device for cooling glass sheets during travel, ie when the glass sheets are advancing while being cooled. Although the invention is not limited to such devices, it will be described in a very particular way with reference to the techniques for bending and hardening the glass sheets that are running along a roller conveyor having a profile that is curved in the direction in which the glass sheets run. The aforementioned techniques are known, especially from French Patents FR-B-2, 242, 219 and FR-B-2, 549, 465, and consist of making hot glass sheets in a horizontal oven, which run between the two layers of the rollers - or other rotating elements - arranged in a curvilinear profile and passing through a terminal hardening zone. For the production of side windows, sun visors, or other windows especially cylindrical in shape, the layers consist, for example, of straight cylindrical rods arranged in a circular profile. The layers may also consist of elements that give the windows a second curvature, such as conical elements or of the type of diabo lo / bar ri 1. This technique makes it possible to achieve a very high production capacity since, on the one hand, the glass sheets do not have to be widely separated, it being possible for a sheet of glass to enter the forming zone without any problem while the treatment for the present sheet has not been completed and, on the other hand, if the length of the sheets has not been completed. As the rollers permit, two or three sheets of glass arranged transversely can be treated simultaneously. The travel speed of the glass sheets, or plates, is at least equal to 10 cm / s and is approximately 15 to 25 cm / s. The speed normally does not exceed 30 cm / s in order to allow a sufficient hardening time. Under relatively normal blowing conditions and for a 3.2 mm thick glass sheet, which has to comply with the requirements of European Standard No. 43 regarding the omologation of safety glass windows and window materials whose objective is to To conform to automotive vehicles and their trailers, the techniques described above are completely satisfactory. In accordance with the requirements of the aforementioned standard, the hardening efforts should be such that the window, if broken, would do so in a number of fragments that, in any square of 5 x 5 cm, were not less than 40 nor larger. of 350 (this number increases to 400 in the case of windows that have a thickness less than or equal to 2.5 mm). In addition, in accordance with these requirements, no fragment should be larger than 3.5 cm *, except that a 2 cm wide strip is possible on the periphery of the window and within a radius of 7.5 cm around the point of impact, without there is a long fragment with a length greater than 7.5 cm. When the thickness of the glass sheet decreases, and in order to meet the same hardening standards, the heat exchange coefficient must be greatly increased. With respect to normal hardening plants, ie plants having nozzles of a given diameter, the heat exchange coefficient improves by increasing the air flow rate, which leads to a greater velocity of the air around the sheets of air. glass. Such a construction first has the disadvantage of requiring more powerful reinforcers or novel plants in order to produce the required air flow rates, this being very expensive. In addition, this results in local problems and limited air that can not easily escape, especially on the upper face in the case of a sheet running on a concave ascending conveyor. Such a limitation results in a decrease in the heat exchange coefficient. Another solution is to decrease the diameter of the nozzles in order to increase the speed of the air at a constant flow rate. In such a case, the decrease in diameter of the nozzles means that the orifices have to be closer to the glass sheets in order to maintain the required speeds on the surface of such glass sheets. However, to obtain such a result, it is necessary to use very long nozzles which result in very large pressure drops unacceptable from an industrial point of view, especially due to costs. The object of the invention is therefore to provide a novel device for cooling bent glass sheets which is more flexible from the point of view of use than the current techniques and which makes it possible to increase the heat exchange coefficient while at the same time obviously disadvantages mentioned above and, in a very particular way, without requiring fundamentally different and expensive plants. This object is achieved according to the invention by means of a device for cooling glass sheets bent on a roller conveyor, the device comprises blow boxes inserted between the rollers and having a surface opposite to the glass sheet at a distance from the the latter being less than 30 mm and preferably less than 10 mm, the surface being perforated by various holes from which the air is urged towards the glass sheet. It should be understood that the rollers mean any type of asymmetric element which, due to its shape and / or its arrangement, can give curvature to the glass sheets. These are, for example, cylinders, di abo lo / bar ri 1 type devices, conical systems and arched systems, especially as those described in EP-B-0,263,030 and E PB-0, 474, 531. Such a device according to the invention it also allows an effective increase in the heat exchange coefficient while retaining the basic chiller plants and does not require reinforcers, especially for the purposes of obtaining higher blow air flow rates. Because the blowing air flow rates have not increased with respect to the usual operating conditions, the risk of local overpressure and thus air limitation are avoided. Likewise, the construction of the boxes having a perforated plate with holes considerably limits the pressure drops, especially with respect to the air flow in the tube forming a squeegee. According to a preferred embodiment of the invention, especially in the case of hardening of the folded glass sheets, the boxes are placed above and below the path of the glass sheets. Preferably, again, the diameters of the holes are between 2 and 8 mm and advantageously less than 5 mm; these are distributed with a space smaller than 20mm and preferably between 3 and 6m. This preferred embodiment not only allows the heat exchange coefficient to increase with respect to the usual cooling techniques, especially for a given air flow rate, but also allows the more homogeneous distribution of cooling on the surface of a glass sheet This is due, in comparison with the usual chiller plants, to the blowing orifices being closer to each other and result in a greater blow homogeneity on the surface of a glass sheet. The usual cooling plants consist of distributed nozzles with a separation generally greater than 30 m, which results in an acceptable cooling of the glass surface from a viewpoint in terms of results, however, the cooling is markedly less homogeneous than in the device proposed by the invention.

According to an advantageous embodiment of the invention, the device, combined with a blowdown pressure less than 3000mm of a water column, allows a heat exchange coefficient with the glass of at least 800 W / m2. and preferably of at least 1000 W / m2.K. Current techniques, although not associated with very expensive means, such as reinforcers, can not exceed a heat exchange coefficient of approximately 800 / m2.K. According to an alternative form of the invention, the device is used at the beginning of the cooling zone, the rest of the zone remains in a normal configuration. In this way, the glass sheets run along a conveyor and are cooled in two phases, with the highest heat exchange coefficient during the first phase. Such an embodiment is particularly advantageous in the case of glass curing; This is because it allows a high heat exchange coefficient at the beginning of the hardening and a lower one afterwards. The inventors make evident the fact that, to harden a given glass sheet, the modulated hardening consisting of a high heat exchange coefficient at the beginning, and then a smaller one, leads to results from a hardening point of view which are higher than those obtained with a constant heat exchange coefficient, for the same overall energy costs. According to other alternative forms of the invention, it is possible to provide differential cooling of a glass sheet between its two faces, in particular, in fact it is possible to equip the chiller unit with a device according to the invention opposite to only one face of the glass sheets, the other side being cooled by normal devices. In this way, it is possible to obtain a higher heat exchange coefficient for one of the two faces. Especially in the case of hardening, such a technique allows the curvature of the folded glass sheets to be modified. In order to achieve similar results, the invention also proposes to differentiate the heat exchange coefficient on the same surface at a given time. To do this, the invention advantageously causes the surface of the boxes that is opposite one face of the glass to have drilled holes that are not all of the same size. According to a preferred embodiment of the invention, the blow holes are holes of variable aperture; these can be obtained by means of movable elements that will partially or completely frame a hole. According to a preferred embodiment of the invention, the conveyor rollers are placed in a curved concave ascending profile. The device thus described according to the invention is advantageously directed to harden glass sheets bent over plants of the type described in French Patents FR-B-2, 242, 219 and FR-B-2, 549, 65. In the technique described in these documents, the rolls usually have diameters of between 20 and 30mm and are separated with a diameter of between 40 and 130mm. It was not obvious to insert into these plants devices such as those of the invention which, especially in the case of small diameter holes, should be very close to the surfaces of the glass sheets, for fear of the problem of extract the blown air. Tests have shown that, in spite of the proximity of the blow holes to the glass sheets, the air can be • extracted appropriately, resulting in heat exchange coefficients that are superior to those obtained with the enduron plants. Normal ace ecedor. The use of a device according to the invention in this type of plants makes it possible to bend and harden glass sheets that are thinner than those normally hardened in this type of plant. This is because the minimum thickness of the glass sheet that current plants usually allow to harden is 3.15mm, which corresponds to a heat exchange coefficient of approximately 600 / m2.K. Without any modification, the device according to the invention allows to harden glass sheets with a thickness of 2.85mm and even 2.5mm, corresponding this to a coefficient of heat exchange that can be as large as 1000 W / m2.K. The invention also makes it possible to improve, especially from a productivity point of view, the results usually obtained for hardening glass sheets having holes passing through their thickness. It is very frequent that these are holes of this type in the glass sheets designed to equip automotive vehicles and to fit in a sliding form, in order to allow its opening. The device according to the invention also makes it possible to improve the optical quality of the glass sheets, this device allowing a more homogeneous blow distribution than the usual techniques. This improvement in the optical quality of the glass sheets is even greater for the production of laminated glaze assemblies. This is because the combination of two sheets of glass, or more, usually two sheets of transparent materials, does not mean that their defects are added from an optical point of view, but that it increases them much more. The DIN 32 305 standard defines an "optical quality", for side windows intended for the automotive industry. The invention therefore makes it possible to produce laminated glaze assemblies comprising at least one glass sheet having surface shear stresses greater than 60 MPa, such laminated glaze assembly fulfilling DIN 32 305. In particular, The invention allows the production of a laminated glaze assembly comprising at least one sheet of hardened glass having surface shear stresses greater than 100 MPa and preferably around 130 MPa, with such a laminated glaze assembly fulfilling the standard DIN 32 305. A laminated glaze assembly of this type is especially advantageous for impact resistance functions. These laminated glaze assemblies may comprise one or more sheets of glass, whatever their thickness. However, the invention also makes it possible to produce such laminated glaze assemblies using glass sheets with a thickness of less than 3mm and preferably less than 2mm, it being possible for these laminated glaze assemblies to have the same thickness of the monolithic glaze assemblies currently. used in automotive vehicles. The additional details and advantages characteristic of the invention will emerge later on from the description of an illustrative embodiment, with reference to the figures that appear in Figure 1: a diagram of a production line adapted for the use of a device according to the invention, Figure 2: a diagram of a partial view of part of the line in Figure 1, into which a device according to the invention is inserted, Figure 3: a diagram of a view partial, in perspective, of a modality of a device according to the invention. Figures 1, 2, 3 are simply diagrams illustrating the invention and do not include all the details of the plants and are not shown to scale in order to simplify their understanding. Also, these Figures 1, 2 and 3 should not be construed as a limiting illustration of the invention. In Figure 1, only the ones have been shown. conveyor elements for clarity: Figure 1 describes the trajectory that the glass sheets follow in the plants operating according to the technique, such as those plants that are known especially from, of the Patent FR-B-2, 242 , 219. According to this technique, the glass sheet 1 passes through a heating zone 2 in which it is transported by a horizontal conveyor consisting of a series of driving rollers. After leaving the warming zone 2, its temperature is greater than or equal to its bending temperature, enters the first part of flexure zone 3 in which the rollers are mounted longitudinally with a cylindrical profile of radius R. The rollers thus form a configuing bed, preferably an ascending concave, and transport the sheets (from left to right in Figure 1) on this bed; "The glass sheets thus acquire a cylindrical curvature with a radius of curvature R obtained by the action of either gravity, or of possible superior elements, or their velocity, or else a combination of two or more of these factors. The first part of the flexure zone 3 is followed by a second part which is a cooling zone in which the rollers are also arranged in a circular profile of radius R. The cooling means consist of the blow boxes 4 arranged on each side of the rollers., thus acting on both sides of the window so that, when passing between these boxes 4 and depending on the blowing pressure, which is chosen as a function of its thickness, the folded glass sheet is either Hardened or simply fixed in the bent position The cooled glass sheets are finally removed by a flat conveyor 5 which passes through a secondary cooling zone, facilitating the arrangement tivo 6 molder that those leave the cooling zone 4. Optionally, the glass sheet can be given a secondary curvature of radius r perpendicular to the main curvature of radius R and parallel to the straight edges, with r being preferably greater than 5 meters, this limit depending on the technical considerations relative to the construction of the configured rollers. In this case, the rollers will preferably be equipped with arching devices, as indicated in Patent Application EP-A-413, 619, and the configurator bed will also have a second set of rollers acting on the upper face of the sheet of glass and that help to move the glass forward. These top elements are also used when the configurator bed follows a conical, non-cylindrical true section.

General plants of this type combine blow nozzles with boxes 4. As mentioned above, apparently although the blowing pressure can be increased effectively, these plants are against the limits in the hardening of the glass sheets, especially with respect to its thickness, due to the limited heat exchange coefficients. According to the invention, the boxes 4, illustrated in Figures 2 and 3, are combined with other boxes 7 inserted between the rollers 8 of the conveyor in the second part of the flexure zone 3. Figure 2 illustrates in more detail the lower part of the flexure zone 3 consisting essentially of the rollers 8 along which the glass sheets run in the direction F. According to this embodiment, the first three or four rollers 8 are sufficient to achieve the actual bending of the glass sheets. In the second part of the bending zone, the glass sheets are cooled, for example, to harden them. What is thus inserted are the boxes 7 according to the invention having a surface 9 with the perforated holes 10 for driving the blowing air over the glass sheets running along the rollers 8. In the case shown in Figure 2, the devices according to the invention, in a previously mentioned embodiment, are only present at the beginning of the cooling zone According to this embodiment, the end of the cooling zone is adjusted with the nozzles 11 According to this embodiment, it is possible to improve the hardening of the glass sheets with an energy cost that is consistent With other embodiments, the device according to the invention fits the entire cooling zone. Figure 3 describes in more detail the way in which the device according to the invention is inserted between the two rollers 8. In this Figure 3, the supply box 4 is that which is normally it is used, to which the blow nozzles are connected. This is an obvious economic advantage of the invention, which in fact allows existing plants to be conserved and that the device according to the invention simply conforms to them. This adjustment is achieved by means of a mounting flange 12 which can simply be fixed quickly; this makes it possible to change the cooling device and quickly change the conventional blowing nozzles with a device according to the invention. The air is directed from the boxes 4 to the boxes 7 through the profiled tubes 13 having a sufficient cross section to avoid pressure drops. The boxes 7 are closed at the other end by the plates 9 with the blowing holes 10 from which the air is urged to the surface of the glass sheets 1 running along the rollers 8 of the conveyor. Figure 3 shows that two boxes 7 are inserted between the two rollers 8. This embodiment should not be interpreted in a limiting manner, it being possible to perform a modality such as only one or with more than two boxes 7 between two rollers 8, the space provided being dependent on the rollers 8. 'The tests were carried out in a plant of the type shown in the figures. The device had the following characteristics: the plates 9 that close the boxes 7 have a width of 15 mm and two rows of holes 10 of 2.5 mm in diameter, the distance separating two holes is 4 mm, so that the "adhesion "Two jets of blown air do not occur. The distance between the two boxes 7 was less than 20 mm. The distance separating the plates 9 from the glass sheets was 7mm, with a tolerance of 4mm. The device presented and especially the number of rows of the holes can not be interpreted in a limiting manner, it being possible for the plates 9 to have one row or more than two rows of holes 10 to be used. The device thus described, combined with a blowing pressure of 3000mm of water column, made it possible to harden, in accordance with the requirements of European Standard No. 43 concerning safety glass windows, the • bent glass sheets with a thickness of 2.55mm . The minimum thickness of glass sheets hardened using normal techniques is 3.15mm. The device according to the invention thus makes it possible to harden thinner glass sheets obtaining a higher heat transfer coefficient. If a glass sheet with a thickness of at least 3.15 m is hardened using the device according to the invention, it is also conceivable to increase the speed of the path of the glass sheets, so that it is greater than about 25 cm. / s, hardening takes place more quickly. It is also possible, if the speed does not increase, to supply the system to overturn the glass sheets when leaving the hardening zone, since, as these sheets of glass are obtained more quickly, the distance that the latter travel to allow them to be reduced can be reduced. that hardening occurs. Thus it is possible to collect sheets of glass without a system of integrated use.

Claims (11)

• Í CLAIMS

1. A device for cooling folded glass sheets running along a roller conveyor, characterized in that it comprises blow boxes inserted between the rollers, in which it has a surface opposite the glass sheet at a distance from the last minor to 30mm and preferably less than 10mm, and in which the surface has several holes drilled from which the air is driven towards the glass sheet.

2. The device according to claim 1, characterized in that the rollers are asymmetric elements, such as cylinders, devices of a type of di abo lo / barr i 1, conical systems, arcing systems, etc.

3. The device according to claim 1 or 2, for hardening glass sheets, characterized in that the boxes are placed above and below the path of the glass sheets.

$. The device according to one of claims 1 to 3, characterized in that the diameters of the holes are between 2 and 8 mm and are distributed with a design of between 3 and 6 mm.

5. The device according to one of the preceding claims, characterized in that, combined with a blowdown pressure of less than 3000mm AC, it allows a heat exchange coefficient with the glass of at least 800 W / m2.K and advantageously by at least 1000 / m2.K.

6. The device according to one of claims 1 to 5, characterized in that the device is used at the beginning of the cooling zone.

7. The device according to one of claims 1 to 6, characterized in that said device is used opposite only one side of the glass sheets and / or in a differential manner with respect to that same face of the glass sheets.

8. The device according to one of claims 1 to 7, characterized in that the rollers are placed in a curved concave profile as cendent e.

9. The use of a device of one of claims 1 to 8 for hardening glass sheets having a thickness of less than 3mm and preferably less than 2.8mm.

10. The laminated glaze assembly consisting of at least one bent glass sheet having surface shear stresses greater than 60 MPa, such a glaze assembly complies with DIN 32 305.

11. The laminated glaze assembly consisting of at least one bent glass sheet having surface shear stresses greater than 100 MPa, the glazing assembly complies with DIN 32 305.