Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B23/00—Re-forming shaped glass
  • C03B23/02—Re-forming glass sheets
  • C03B23/023—Re-forming glass sheets by bending
  • C03B23/025—Re-forming glass sheets by bending by gravity
  • C03B23/0252—Re-forming glass sheets by bending by gravity by gravity only, e.g. sagging
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
  • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
  • B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
  • B32B17/10807—Making laminated safety glass or glazing; Apparatus therefor
  • B32B17/10889—Making laminated safety glass or glazing; Apparatus therefor shaping the sheets, e.g. by using a mould
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B23/00—Re-forming shaped glass
  • C03B23/02—Re-forming glass sheets
  • C03B23/023—Re-forming glass sheets by bending
  • C03B23/03—Re-forming glass sheets by bending by press-bending between shaping moulds
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B25/00—Annealing glass products
  • C03B25/04—Annealing glass products in a continuous way
  • C03B25/06—Annealing glass products in a continuous way with horizontal displacement of the glass products
  • C03B25/08—Annealing glass products in a continuous way with horizontal displacement of the glass products of glass sheets
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P40/00—Technologies relating to the processing of minerals
  • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
  • Y02P40/57—Improving the yield, e-g- reduction of reject rates

Definitions

• the invention relates to the bending of automotive glazing.
• Glazing for cars must meet many requirements. In particular, their optical and mechanical characteristics must meet rigorous standards. The many techniques developed for the bending of the glass sheets that compose them strive to meet these requirements while keeping production costs as low as possible.
• the first is called gravity bending.
• the or flat glass sheets are brought to softening temperature of the glass. Under their own weight the leaves come to rest on a support.
• the support is either a frame that holds the sheets at their periphery, or conveyor rolls progressively presenting a more curved profile.
• the second mode of bending which is often combined with the first, imposes a local or global pressure on the glass sheets to make them marry the shape of the press.
• the advantage of the contact with the pressing mold is to achieve a better compliance of the sheet with the model fixed in the central part of the glazing. In return the contact of the sheet with the surface of the mold can alter the optical quality of the glazing. Improvements of all sorts have been proposed to try to combine the advantages of these two modes.
• the invention aims to meet these various needs.
• it aims to propose means that retain the essential qualities of products, optical qualities and mechanical qualities, by increasing production rates, in other words by reducing the cycle time.
• each step of the forming process is involved in the determination of the cycle time.
• the main previous efforts have focused on the steps that relate to formatting.
• later treatments have been little considered. Nevertheless, these are decisive steps for certain properties, especially mechanical properties.
• the cooling is necessarily rapid. It is a function of this rapidity that the stresses are developed in the glass by the formation of a temperature gradient between the surface and the inside of the sheet.
• the presence of surface stresses in the central part of the glazing must be avoided.
• the presence of these constraints makes the windshield very fragile to impacts such as gravel. If slowing the cooling seems necessary to avoid the formation of constraints, the rigorous maintenance of the shape obtained, also imposes that the time which separates the shaping of that where the sheet reaches the range of glass transition temperature, is sufficiently short, in order to avoid possible post-bending deformation.
• non-quenched are products such as glass sheets used in the composition of laminated windshields, products which, with regard to their mechanical properties, must have high resistance, in particular to gravel impacts.
• the method according to the invention aims to maintain a high speed of cooling of the glass sheets until they can no longer be deformed. In this cooling time, to avoid as much as possible the formation of surface stresses, the temperature is maintained substantially uniform over the entire surface of the sheets. To achieve this result the leaves are subjected to cooling by means of an intense gas stream, temperature controlled. The circulation of this flow leads it to the contact of the two faces of the exposed leaves. Increasing the speed of the convection atmosphere on the faces establishes a good balance of thermal exchanges avoiding temperature differences generating constraints that we strive to minimize.
• the temperature of the atmosphere in contact with the leaves determines the intensity of the exchanges.
• the operation is done continuously or step by step.
• the sheets pass continuously in a single chamber and the temperature of the atmosphere is adjusted essentially so that at the outlet the temperature is lower than that of the glass transition.
• the atmosphere In contact with the glass, the atmosphere necessarily warms up, which can lead to an initial ambient temperature higher than that which prevails, still in the atmosphere, towards the exit of the enclosure.
• the set temperatures take into account these glass / atmosphere exchanges.
• successive sections may have different temperature conditions.
• the temperature of the final cooling step remains in all cases lower than that of glass transition. But for the preceding steps, the choice of the set temperature for the atmosphere is preferably decreasing in steps corresponding to each of these steps. In this case, each temperature is chosen so as to guarantee the desired decay rate.
• the final temperature in both continuous and step modes is preferably between 360 and 480 ° C and preferably between 400 and 460 ° C.
• the glass transition temperature for the most usual silico-soda-lime glasses is of the order of 550 ° C.
• the intensity of the convection is kept sufficient to maintain the desired cooling rate.
• the cooling is performed in an enclosure in which the gas flows advantageously circulate in a loop. This circulation is ensured by means of powerful fans or turbines. These means ensure a rapid renewal of the contact of the atmosphere with the glass sheets. This renewal ensures the uniformity of the temperature of the leaves.
• the volume of the atmosphere circulating in contact with the leaves is relatively large and its warming can not usually result from the mere thermal input of the leaves themselves. Heating means in contact with the gas flow ensure temperature maintenance.
• the circulation of the cooling atmosphere is such that, outside the immediate edges of the sheets, the temperature differences do not exceed 20 ° C., and preferably not 10 ° C.
• the atmosphere of the chamber is circulated preferably such that a volume at least equal to that of the chamber is stirred every 8 seconds.
• this stirring is obtained in 5 seconds or less.
• the conditions of the convection atmosphere, circulating volume, circulation speed near the faces of the sheet, and the maintained temperature of this atmosphere are adjusted so that the temperature of the sheet decreases by at least 1 C. per second and preferably at least 1.5 ° C. per second.
• the cooling time to a temperature below and close to the glass transition is advantageously at most about 120s and preferably at most 90s. It is preferably as short as allowed to maintain a uniform temperature throughout the entire sheet with the exception of the edges in contact with the support of the sheet.
• the invention also proposes to ensure that the appearance of these constraints is followed by a step that allows them to be minimized, or even practically to eliminate them.
• the sheet at first is cooled to a temperature substantially lower than that of glass transition to freeze its shape.
• cooling may be more intense, for example by using the atmosphere at a lower temperature, and result in faster cooling.
• this cooling is followed in a second time of a warming of the sheet to a temperature and for a time leading to the relaxation of the surface stresses in question.
• the sheet is then in a third time brought to lower temperature as before.
• the temperature for stress relaxation is preferably not more than 20 and preferably 10 ° C higher than the temperature of the glass transition range.
• This domain is not likely to be precisely defined as its name indicates a "domain" transition between two states. The transition takes place gradually and can extend over twenty degrees.
• the values indicated for the relaxation temperatures are values determined from the median values of these domains.
• the treatment involves the temperature but also the time during which this temperature is maintained so that this treatment does not touch only the surface. The higher the imposed temperature, the shorter the time can be. A temperature as low as possible is preferred not to recreate during the subsequent cooling constraints that are strived to remove. A compromise is necessary so that the treatment time is not too long either. In practice, the conditions are set so that the level of temperature is not more than 30 seconds and preferably not more than 20 seconds.
• FIGS. 1a, 1b and 1c are schematic views illustrating various embodiments of bending installations according to the invention.
• FIG. 2 is a sectional view of a cooling chamber according to the invention.
• FIG. 3 represents a temperature curve of sheets subjected to stress relaxation.
• the installation shown schematically in Figure la comprises an oven 1.
• the oven is heated by a set of electrical resistors 2.
• a conveyor 3 carries frames 4 which support the glass sheets 5 in their progression in the oven.
• the frame carries one or two sheets of glass. In the second case the superimposed sheets are curved simultaneously. The two sheets are intended to be subsequently assembled in a laminated glazing unit.
• the glass sheets 5 are flat. As they progress they warm up to softening. As shown in 6 the softened leaves curl under their own weight to match the profile of the frame that supports them.
• the frames carrying the sheets, still on the conveyor then pass into the cooling zone, usually a simple tunnel without heating or substantial thermal insulation, whose walls are intended only to avoid expose glass to too random cooling conditions. After sufficient cooling the frames and the glass sheets in continuing their progress, they cool in the open air until the temperature is close to the ambient temperature. The end of cooling can be done on the storage area. The frames are then returned to the oven entrance for further processing.
• the cooling zone usually a simple tunnel without heating or substantial thermal insulation, whose walls are intended only to avoid expose glass to too random cooling conditions.
• the sheets are subjected to forced convection by means of fans 10.
• the convection gas streams are maintained at the appropriate temperatures by circulating the convection gases on heating means, for example electrical resistors 11.
• Gaseous convection currents are associated with ducts in the walls, which direct them so that all the leaves, with the possible exception of their edges, are treated as uniformly as possible.
• the glass sheets are arranged on the same frame in all their progression.
• Figure lb shows a variant of the.
• the glass sheets are subjected to a bending by gravity. This bending is not complete.
• the leaves are taken up by a pressing technique.
• the sheets are for example conducted on a male form 7 under the traditional conditions.
• the pressing is for example carried out by a movement bringing the frame 4 and the press 7 closer together. Additional suction means can also complete the contacting of the glass sheet with the surface of the press 7.
• the pressing is presented as performed in the oven itself 1.
• Various alternatives are also possible that drive the pressing outside the oven. This solution facilitates the implementation of the pressing means.
• the temperature conditions in the pressing stage differ slightly to account for this lack of heat input at this stage.
• the figure shows schematically another form of implementation in which the glass sheets are systematically treated individually.
• the conveyor drives the softened and preformed sheets by a suitable arrangement of the curved rollers up to a press 7.
• the glass sheet is applied to the press, for example by means of a frame which lifts it from the conveyor .
• Various means are known for placing the sheet on the frame, including for example a vacuum gripping system.
• the glass sheet After bending the glass sheet is preferably arranged on a support 8.
• the support is constituted by a frame which supports the sheet at its periphery.
• Other modes are also possible in which the sheet is for example deposited directly on a profile conveyor adapted or not to the curved shape of the sheet.
• the advantage of using the frame with respect to the other possibilities is that it limits the contact of the glass to the sole periphery of the sheet. In this way, any further deterioration in the quality of the viewing areas is avoided.
• the only marks, if any, are in a part of the sheet in which these marks do not cause any discomfort.
• the glass sheets brought back under the conditions indicated previously up to the glass transition temperature can then continue cooling to room temperature outside the chamber in the step referenced 12. If the various steps preceding the final cooling must be carried out as quickly as possible, the quality of the glazing obtained is not linked to the duration of the last stage. The sheets can therefore cool without any particular arrangement simply in contact with the ambient atmosphere.
• FIG. 2 shows in section an embodiment of the enclosure 9 for the implementation of the invention.
• the suction by the fans 10 returns the gas in the double side walls of the enclosure.
• the heating means of the gas stream 11 are arranged in these double walls. The representation puts these means in the vertical walls. It goes without saying that the heating means can be located differently and in particular for all or part of the upper wall of the enclosure.
• tests are performed on glass sheets entering the windshield composition.
• the glass sheets are clear soda-lime glass.
• the thickness of each of these sheets is 2.1mm.
• the two sheets which are then assembled, are produced individually as indicated with reference to FIG.
• the press is disposed at the exit of the oven enclosure. At the exit of the press the sheet is placed on a frame to proceed with the cooling.
• the temperature of the sheet at the exit of the press is not uniform. Deviations can reach 30 ° C enter the edge temperature and that in the center of the sheet. The goal is to achieve as little difference as possible while cooling the sheet, and this in the shortest possible time.
• the conditions are for an enclosure whose volume is 3m 3 , an air circulation of 1000m 3 / h.
• the gain obtained is also a function of the temperature of the convection gas.
• three gas temperatures are tested at 575, 520 and 450 ° C.
• the time gain to reach the temperature difference of not more than 10 ° C is all the more significant as the intensity of the convection is greater and the temperature of the convection gas is higher.
• the cooling and uniformization time of the sheet temperature is reduced by 30%.
• a second series of tests is carried out in which still in the arrangement comprising a bending by gravity followed by pressing, the invention is applied to glass sheets treated in pairs intended to enter into the constitution of a windshield. .
• the leaves are respectively 2.1 and 1.6 mm thick, the outer leaf being the thickest.
• the induced edge stresses in the process are measured in relation to the same quantities without using convection. Temperatures in the convection zone are 300, 360 and 450 ° C. The cooling of the glass sheets is fast.
• the compressive stress of the edge is important, it is even more important to minimize the stress in tension which immediately follows it when one deviates from the edge.
• the minimum is obtained with convection at 450 ° C is thus established on average at 2, lMPa and does not exceed 3,4MPa, while without convection the stress exceeds 3, lMPa and at most is of the order of 4.3MPa .
• the fragility is related to the formation of surface stresses during cooling in which the edges of the sheet and its central portion are not at a sufficiently uniform temperature.
• the presence in particular of a voltage stress value is a certain cause of fragility.
• the inventors propose, if necessary, to carry out a stress relaxation step before the final cooling.
• Figure 3 shows an example of a temperature curve associated with subsequent operations.
• the temperature at the outlet of the bending furnace is about 640 ° C.
• the process is completed by a warming of the formed sheet at a temperature and for a time that relaxes the constraints without the shape being altered.
• the heating is conducted for example in a first chamber similar to that used previously for the standardization of the temperature during cooling. Warming is the opportunity to obtain a uniform temperature and, for this purpose, is conducted with intense convection.
• the atmosphere is brought to about 650 ° C.
• the stress relaxation temperature is at about 550 ° C. It is reached after about 90 seconds. The temperature is maintained above 550 ° C for about twenty seconds.
• Subsequent processing again includes decreasing the temperature of the sheet as before. This decrease is made from a substantially lower temperature than at the output of the forming. For this reason, the stresses produced, if the other conditions are preserved, are appreciably lower. This is a substantial advantage with respect to the surface tension stresses that control the resistance especially to gravelling.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)
• Joining Of Glass To Other Materials (AREA)
• Laminated Bodies (AREA)

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• 2012
  • 2012-09-21 BE BE2012/0627A patent/BE1024010B1/fr active IP Right Grant
• 2013
  • 2013-09-02 WO PCT/EP2013/068058 patent/WO2014044516A1/fr active Application Filing
  • 2013-09-02 BR BR112015006259-8A patent/BR112015006259B1/pt active IP Right Grant
  • 2013-09-02 EP EP13759470.1A patent/EP2897916A1/de active Pending
  • 2013-09-02 JP JP2015532360A patent/JP6412870B2/ja active Active
  • 2013-09-02 CN CN201380048717.7A patent/CN104661971B/zh active Active
  • 2013-09-02 EA EA201590263A patent/EA029529B1/ru not_active IP Right Cessation
  • 2013-09-02 US US14/429,915 patent/US10486999B2/en active Active

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