METHOD AND DEVICE FOR BENDING A GLASS DISC

Description

[0001] The present invention relates to a method and device for bending a sheet of glass, in particular of the type where the sheet of glass brought to a softening temperature passes by continuous movement between a bed of lower rollers and a bed of upper rollers which impose on the sheet of glass a curved path in the direction of movement of the sheet of glass to bend the sheet of glass which is then immediately cooled to be solidified in its curved shape.

[0002] This technique allows the production of glass sheets with a curvature in the direction of their movement between the two roller beds. It thus enables the production of curved glass sheets in cylindrical shapes, but also more complex non-cylindrical curved shapes, since it also allows the glass sheet to be curved in a direction perpendicular to its movement between the two roller beds, depending on the shape of the rollers in the two roller beds.

[0003] This technique is notably used for manufacturing automotive glazing, such as side windows, which generally have a toroidal surface. It is typically implemented at very high production rates, primarily due to the ability to feed sheets of glass spaced only a few centimeters apart between the upper and lower roller beds. This ensures excellent reproducibility of the curvature and optical quality of the final glazing.

[0004] This technique is described in particular in US 4,139,359, US 4,540,425, US 4,540,426, US 5,236,487, US 6,598,427, US 2007 / 0084245 A1 and US 2015 / 0259234 A1.

[0005] However, the shapes of these curved glass sheets are becoming increasingly complex. To avoid machining specific roller beds and changing the roller beds for each new batch of curved glass sheets—operations that are time-consuming and require precision—US 2006 / 0010916 A1 proposed a technology involving continuous air blowing on at least one face of the glass sheets as they pass between the roller beds. This continuous air blowing is designed to asymmetrically influence the final concavity of the curved glass sheets compared to the final curvature that would have occurred without the air blowing. This continuous air blowing is achieved using at least one fixed nozzle positioned between consecutive rollers at a location where the glass sheet is still softened.This air blowing thus makes it possible to modify the resulting curvature of the glass sheets in the direction perpendicular to their movement between the roller beds.

[0006] Today there is also a need to produce sheets of glass with an asymmetrical curvature in the direction of the glass sheet's movement between the roller beds.

[0007] This need exists particularly for the side windows of motor vehicles. For these, it is desirable that the upper part of the window, in its mounting position in the motor vehicle, be over-curved - that is to say, have a locally smaller radius of curvature - in order to accommodate the influence of the vehicle's aerodynamics when the side window is closed while driving at high speed.

[0008] Indeed, when driving at high speeds, the vehicle's sides experience a low-pressure zone that tends to pull the side window outwards. Under these conditions, when the window is open, it can happen that during the closing operation, the window deforms and slips out of the seal at the top of the door, resulting in noise and a lack of rain protection.

[0009] This phenomenon can be avoided by slightly overarching the upper part of the side window without altering the overall shape of the side window so as not to affect the style of the vehicle.

[0010] However, the previously described curving technique does not allow for such over-curving of the upper part of car side windows. This is because, as it passes between the roller beds, the upper edge of the glass extends transversely to the direction of its movement between the roller beds, while the roller beds impart a fixed radius of curvature to each section of the glass in the direction of its movement between them. Continuous air blowing through one or more fixed nozzles, in accordance with US 2006 / 0010916 A1, would only achieve over-curving of the glass around an axis extending in the direction of its movement between the roller beds.

[0011] One object of the present invention is to address the aforementioned need. It aims to provide a technology for creating an overcurve in the upper part of the side windows of motor vehicles. More generally, another object of the invention is to provide a technology for varying the curvature profile of glass sheets beyond the possibilities offered by the prior art.

[0012] To this end, the present invention proposes a method for curving a sheet of glass, comprising: the continuous displacement of a sheet of glass brought to a softening temperature in a forming device in which the sheet of glass is, as it passes through the forming device, curved and subjected to forced cooling to solidify the entire sheet of glass in the curved state, and the blowing of gas, preferably air, onto at least one face of the sheet of glass as it passes through the forming device, which blowing of gas is applied to at least one face of the sheet of glass upstream of the forced cooling with respect to the direction of movement of the sheet of glass in the forming device, in which said gas blowing: is carried out under conditions capable of causing a change in the shape of the curvature of the glass sheet obtained after its passage through the forming device compared to the shape of the curvature which would be obtained in the absence of said gas blowing, and comprises or consists of at least a local gas blowing impacting one face of the glass sheet only locally, the process further comprising the control of the local gas blowing as a function of the time elapsed from a detection of the arrival of the glass sheet in the forming device.

[0013] The glass sheet enters the forming device at its softening temperature, allowing it to undergo plastic deformation within the device, shaping it into a curved form. The forced cooling process that solidifies the entire glass sheet in its curved state generally involves a heat treatment that results in its mechanical strengthening through the generation of internal mechanical stresses. This is most frequently a thermal quenching or a partial thermal quenching, also known as thermal hardening.Forced cooling is not usually applied simultaneously to the entire glass sheet in the forming device, but as it passes through the forming device, which has the effect of solidifying it in the curved state as it passes through the forming device until the entire glass sheet is solidified.

[0014] Generally, bending is done before forced cooling, but bending and forced cooling can also be done on the sheets almost simultaneously.

[0015] By controlling the localized gas blowing onto the glass sheet face based on the detection of the glass sheet's arrival in the forming device, greater latitude is gained in influencing the final shape of the glass sheet's curvature. The temperature and pressure conditions of the gas blowing are preferably selected by a person skilled in the art to create a thermal gradient in the area(s) of impact of the localized gas blowing on the glass sheet. This gradient, after the glass sheet has cooled and solidified, will result in a modification of the glass sheet's curvature in the corresponding area. The localized gas blowing can be applied before the bending process or between the bending process and forced cooling.

[0016] In preferred embodiments, the process of the invention comprises one or more of the following features: The control of the local gas blowing includes one or more or all three of the following actions: the displacement of the impact zone of the local gas blowing on the face of the glass sheet transversely to the direction of movement of the glass sheet in the forming device as a function of the time elapsed since the detection of the arrival of the glass sheet in the forming device; the activation and deactivation of the local gas blowing as a function of the time elapsed since the detection of the arrival of the glass sheet in the forming device; and the modification of the pressure of the local blowing gas as a function of the time elapsed since the detection of the arrival of the glass sheet in the forming device;the process includes the use of at least one nozzle to perform local gas blowing, and the movement of the nozzle transversely to the direction of movement of the glass sheet as a function of the time elapsed from the detection of the arrival of the glass sheet to achieve the movement of the impact zone of the local gas blowing on the face of the glass sheet transversely to the direction of movement of the glass sheet in the forming device; the forced cooling of the glass sheet includes or consists of the thermal quenching or thermal hardening of the glass sheet;the process includes the application of local gas blowing within a partial area of ​​one face of the glass sheet, the partial area having an elongated shape extending transversely to the direction of movement of the glass sheet in the forming device, the impact area of ​​the local gas blowing on the face of the glass sheet being displaced according to the time elapsed from a detection of the arrival of the glass sheet in the forming device so as to be displaced within said partial area during the movement of the glass sheet in the forming device;The process includes carrying out gas blowing under conditions causing a local increase in the concavity of the curvature of the glass sheet obtained after its passage through the forming device, compared to the concavity of the curvature that would be obtained in the absence of gas blowing, said local increase in curvature being located along an edge of the glass sheet extending transversely to the direction of travel of the glass sheet; the glass sheet is a side window of a motor vehicle and the process includes controlling the gas blowing so as to cause a local increase in the curvature located along an upper edge of the side window of a motor vehicle compared to its intended mounting in a motor vehicle;The forming device comprises a lower roller bed and an upper roller bed, and the process comprises the continuous movement of the glass sheet, brought to a softening temperature, between the lower roller bed and the upper roller bed, which are arranged to impose a curved path on the glass sheet in the direction of movement of the glass sheet so as to curve the glass sheet.

[0017] The method of the invention applies to individual sheets of glass having a thickness preferably in the range of 0.49 to 6.1 mm inclusive, and more preferably in the range of 0.9 to 5.1 mm inclusive. They may or may not be coated with one or more thin layers, such as one or more IR-blocking layers, for example silver, or one or more so-called Low-E : these layers are not taken into account in the aforementioned thickness ranges.

[0018] According to another aspect, the invention proposes a device for curving a sheet of glass, comprising: a forming device for curving a sheet of glass previously brought to a softening temperature, by continuous movement through the forming device, the forming device being arranged to, as the sheet of glass passes through the forming device, curvature it and subject it to forced cooling so as to solidify the entire sheet of glass in the curved state, a local gas blowing system for blowing gas, preferably air, locally onto one face of the sheet of glass as it passes through the forming device, the local gas blowing system being arranged to blow gas locally onto the face of the sheet of glass upstream of the forced cooling relative to the direction of movement of the sheet of glass in the forming device,a detector to detect an edge of the glass sheet as it passes through the forming device upstream of the local gas blowing system, relative to the direction of movement of the glass sheet in the forming device, and a control system provided to control the local gas blowing system according to the time elapsed from a detection signal of the edge of the glass sheet provided by the detector.

[0019] This device for curving a sheet of glass is capable of being used to implement the process of the invention described above.

[0020] According to preferred embodiments, the glass sheet bending device according to the invention comprises one or more of the following features: The control system is capable of controlling the local gas blowing system so as to: move the impact zone of the local gas blowing on the face of the glass sheet transversely to the direction of movement of the glass sheet in the forming device as a function of the time elapsed since the detection of the arrival of the glass sheet in the forming device; and / or activate and deactivate the local gas blowing as a function of the time elapsed since the detection signal of the edge of the glass sheet provided by the detector; and / or modify the pressure of the local gas blowing as a function of the time elapsed since the detection signal of the edge of the glass sheet provided by the detector; the local gas blowing system includes at least one nozzle;The local gas blowing system includes a nozzle displacement device for moving the nozzle transversely to the direction of movement of the glass sheet in the forming device, the control system being capable of controlling the nozzle displacement system according to the time elapsed from the detection signal of the edge of the glass sheet provided by the detector; the forming device includes a bed of lower rollers and a bed of upper rollers arranged to pass the glass sheet between them and to impose on the glass sheet passing between them a curved path in the direction of movement of the glass sheet so as to curve the glass sheet; the nozzle is disposed between two successive rollers of one of the roller beds, the nozzle displacement device being provided to move the nozzle between these two successive rollers;The forming device is intended to subject the glass sheet to thermal tempering or thermal hardening by means of said forced cooling of the glass sheet; the device further comprises an assembly of gas blowing nozzles for subjecting the glass sheet to said forced cooling, the nozzles of said assembly being distributed transversely to the direction of travel of the glass sheet and arranged between successive rollers (21; 22) of at least one of the roller beds, preferably of both roller beds.

[0021] In the context of this invention, the term "roller of the lower roller bed and the upper roller bed" refers to any type of element of revolution which, by its shape and / or arrangement, can impart a curvature to the glass sheets. Examples include cylinders, barrel-shaped devices, conical systems, counter-bent systems, rods with a curved longitudinal profile equipped with a sheath that can rotate around the rod, etc. In particular, it may, for example, refer to rollers such as those described in US 4,139,359, US 5,069,705, US 5,094,679, US 5,236,487, or US 2015 / 0259234 A1.

[0022] In the context of this invention, thermal tempering of a glass sheet is understood as imparting to the glass sheet a surface stress greater than 90 MPa, generally between 90 and 200 MPa. Semi-thermal tempering—also called thermal hardening—is understood as imparting to the glass sheet a surface stress in the range of 15 to 90 MPa, more generally in the range of 20 to 60 MPa. The aforementioned stress values ​​are absolute values. Surface stress is measurable by an instrument operating on the principle of polariscopy, such as the Scalp-04 polariscope marketed by GlasStress Ltd.Its value is determined as the arithmetic mean of five measurements taken on a main surface of the glass sheet. One measurement is taken at the center of the glass sheet—which can be chosen as its center of mass—and the other four measurements are taken at equal intervals along an imaginary line drawn around the main surface of the glass sheet at a distance from the edge of the glass sheet equal to ten times the thickness of the sheet. However, in the specific case of four-cornered glass sheets, it is preferable for each of these four measurements to be taken on this imaginary line at a respective corner of the glass sheet.

[0023] Other aspects, features and advantages of the invention will become apparent from the following description of a preferred embodiment of the invention, given by way of example and with reference to the accompanying drawings. [ Fig 1 [ ] is a schematic side view representation of a bending installation according to an embodiment of the invention. ] Fig 2 ] is a partial schematic side-view representation of the shaping device of the installation of the figure 1 . [ Fig 3 ] is an isolated and simplified schematic representation of the lower roller bed of the forming device alone. figure 2 Top view, as well as the mobile nozzle for local air blowing and the detector designed to detect an edge of the glass sheet. Fig 4 ] illustrates a side window of a motor vehicle exhibiting an over-bulge along its upper edge which is likely to be produced with the installation of the figure 1 . [ Fig 5 ] is a graph of the displacement of the glass pane figure 4 depending on the time in the shaping device of the installation of the figure 1 . [ Fig 6 ] is a graph of the transverse displacement of the local air blowing nozzle of the shaping device of the installation of the figure 1 depending on the time required to achieve the desired over-bulge along the upper edge of the glass figure 4 . [ Fig 7 ] is a graph representing the curve of the air blowing location on the window of the figure 4 obtained by combining the displacement of the glass in the shaping device according to the graph of the figure 5 and the movement of the local air blowing nozzle in accordance with the figure 6 . [ Fig 8 ] represents the curve of the figure 7 on the window of the figure 4 .

[0024] With reference to the figures, we will now describe an embodiment of the invention. Figure 1 This schematically represents a bending installation in which sheets of glass 10 pass continuously to be bent. This installation comprises successively a heating zone 1, a forming device 2 in which the glass sheets are bent and fixed in the bent shape by cooling, and a secondary cooling zone 4 where the glass sheets undergo final cooling.

[0025] For a given sheet of glass 10, the bending process takes place as follows.

[0026] The flat glass sheet 10 first passes through the heating zone 1 to be brought to a softening temperature which then allows it to be curved by the forming device 2. The softening temperature is generally 600 to 700°C.

[0027] The heating zone 1 comprises a furnace 11, preferably of the tunnel type, through which the glass sheet 21 is transported on a conveyor 13. The conveyor 13 is preferably horizontal and driven by a series of straight drive rollers 14 aligned in a plane. The glass sheet 10 is thus transported along a horizontal, straight path. After leaving the furnace 11, the glass sheet 10, heated to its softening temperature, enters the forming device 2 where it will be curved. The forming device 2 is therefore located outside the furnace 11, or more generally, outside the heating zone 1.

[0028] The forming device 2 may, in a known manner, comprise a lower roller bed 29 and an upper roller bed 27 arranged to pass the glass sheet 10 between them. In the illustrated example, the roller beds 27, 29 are designed to impose an upward curved path on the glass sheet 21 in the direction of movement of the glass sheet 10, thus curving the glass sheet. In other words, the glass sheet 10 acquires, within the forming device 2, a curvature imposed by the rollers of the roller beds 27, 29 as it moves through the forming device 2. Alternatively, the path imposed by the roller beds 27, 29 may be downward. The curved path imposed on the glass sheet 10 by the roller beds 27, 29 is preferably tangent to the straight path of the glass sheet 10 before passing between the roller beds 27, 29.

[0029] The curvature imposed by the roller beds 27, 29 in the direction of movement of the glass sheet 10 can classically be at least 0.8 meters to infinity.

[0030] The rollers of the roller beds 27, 29 are rotating elements. At least some of them, and preferably all of them, are driven in rotation to advance the glass sheet 10 between them. As already mentioned, they can be any type of element of revolution whose shape and / or arrangement allows them to impart a curvature to the glass sheets as they pass between the roller beds 27, 29.

[0031] In particular, the roller beds 27, 29 can be provided to classically give the glass sheet 10 a curvature from 5 meters to infinity in the direction perpendicular to the direction of movement of the glass sheet 10.

[0032] In this embodiment, the curvature of the glass sheet 10 is carried out in a first zone 25 of the forming device 2, which is therefore a shaping zone. A local air blowing system 5 is provided in the shaping zone 25, which will be described in more detail later.

[0033] The shaping zone 25 is followed by a second zone of the forming device 2 which defines a zone 28 for tempering or cooling the glass sheet 10. This zone 28 therefore allows the glass sheet 10 to be subjected to thermal tempering or thermal hardening, also called semi-tempering, or more generally to forced cooling reducing the temperature of the glass sheet 10 sufficiently so that the glass sheet 10 retains its curved shape when it leaves the forming device 2. As a result of this forced cooling, the temperature of the glass sheet 10 is lowered to a temperature preferably between 400 and 500°C, the glass sheet 10 leaving the forming device 2 at this temperature.

[0034] The tempering or cooling elements can be constituted in a known manner by a set of air blow nozzles arranged, in particular, transversely to the direction of movement of the glass sheet 10 and preferably on either side of the rollers of the roller beds 27, 29. They are arranged to blow air onto the glass sheet 10 between consecutive rollers of the roller beds 27, 29. They are preferably arranged in a fixed manner. They can, in particular, be assembled into blow boxes 30 or into transverse bars arranged on either side of the rollers 27 and 29.The blow nozzles thus act on both sides of the glass sheet 10 so that, by passing between the boxes 30 and according to the blowing pressure chosen, the glass sheet 10 is either tempered, or simply hardened, or at least cooled in its curved conformation to retain this conformation after leaving the forming device 2.

[0035] The glass sheet 10 can leave the roller beds 27, 29 of the forming device 2 by tipping onto a conveyor 3 which transports the glass sheet 10 to a flat conveyor 41 which passes through a secondary cooling zone 4 to further lower the temperature of the glass sheet 10.

[0036] The former 2 former is illustrated in more detail in the figure 2 . The rollers 22 of the upper roller bed 27 and the rollers 21 of the lower roller bed 29 are visible, as well as the air blow nozzles 31 of the zone 28 for soaking or cooling the glass sheet 10 after bending in the shaping zone 25.

[0037] Also visible is the local air blowing system 5 located in the shaping zone 25, upstream of the air blowing nozzles 31 for tempering or cooling the glass sheet 10. This system includes an air blowing nozzle 51 arranged between two consecutive rollers – referenced 21a and 21b – of the lower roller bed 29. The nozzle 51 is positioned and sized to locally blow air onto the glass sheet 10 as it passes in front of the nozzle 51. In other words, the air blown by the nozzle 51 only impacts the glass sheet 10 locally over an impact area that is limited in size compared to the surface area of ​​the glass sheet 10.

[0038] The nozzle 51 is preferably mounted to move laterally in the X direction, which is perpendicular to the Y direction of movement of the glass sheet 10 through the forming device 2. The local air blowing system 5 may then advantageously include a displacement device 52 to move the nozzle 51 in the X direction between the two consecutive rollers 21a and 21b. This allows the lateral position of the nozzle 51, and therefore the lateral position of the air impact zone on the glass sheet 10 as it passes through the forming device 2, to be varied. To achieve this, the nozzle 51 is supplied with compressed air via a flexible supply hose. It is advantageous that the speed of movement of the nozzle 51 in the X direction can be varied and controlled.Thus, the nozzle 51 can follow a desired curve which extends transversely over the glass sheet 10 relative to its direction of travel in the forming device 2, for example along a transverse edge of the glass sheet 10 as will be described with reference to the . figure 8 .

[0039] Furthermore, a detector 6 is installed – preferably in a fixed position – between two other consecutive rollers – referenced 21c and 21d – of the lower roller bed 29 upstream of the nozzle 51. This detector 6 is designed to detect the edge of the glass sheet 10 and serves to control the local air blowing operated by the nozzle 51 in synchronization with the movement of the glass sheet 10 in the forming device 2. As we will see in more detail later, the control of the local air blowing can advantageously be achieved in three ways, or at least in one or two ways, namely, controlling the movement of the nozzle 51 by means of the movement device 52, activating and deactivating the air blowing by the nozzle 51, and controlling the pressure level of the air blown by the nozzle 51.

[0040] There figure 3 symbolically illustrates a position of the nozzle 51 between the two rollers 21a and 21b of the lower roller bed 29 and the position of the detector 6 between the rollers 21c and 21d.

[0041] The local air blowing system 5 serves to cause a change in the shape of the curvature of the glass sheet 10 obtained after its passage through the forming device 2 compared to the shape of the curvature which would be obtained in the absence of the local air blowing by the local air blowing system 5. This is achieved in particular by an appropriate choice of the temperature and pressure conditions of the air blowing by the nozzle 51.

[0042] In particular, the temperature of the air blown by the nozzle 51 onto the glass sheet 10 is chosen to be different from that of the glass sheet 10 so that the area of ​​the face of the glass sheet 10 subjected to its blowing has a thermal gradient resulting after cooling of the glass sheet in the tempering zone 28 or cooling by a modification of the curvature of the glass sheet 10 in the corresponding area.

[0043] The air blown by the nozzle 51 is preferably colder than the temperature of the glass sheet 10. It can advantageously be air at ambient temperature, which avoids heating or cooling the blowing air.

[0044] In the case of an air blowing system designed to lower the temperature of the face of the glass sheet 10 receiving the air from the nozzle 51, if this blowing is applied to the convex face of the glass sheet 10, as in the illustrated example, it will locally increase—that is, at the points where the air has been blown—the concavity of the glass sheet 10 compared to the concavity obtained without said air blowing. Conversely, if the air blown from the nozzle 51 is applied to the concave face of the glass sheet 10, it will locally decrease the concavity of the glass sheet 10 compared to the concavity obtained without said air blowing. The effect is reversed if the air blown by the nozzle 51 is hotter than the glass sheet 10.

[0045] The concavity is increased or decreased as appropriate in all directions, i.e. both in the Y direction of the glass sheet 10 and in the lateral X direction, it being specified that the overall modification of the concavity will depend on the definition of the area of ​​the glass sheet 10 subjected to the air blowing by the nozzle 51.

[0046] From the point of view of pressure, the blowing of air by the nozzle 51 is preferentially carried out at a pressure of 10 x 10 3< to 1000 x 10 3< Pa, and even more preferentially of 50 x 10 3< to 600 x 10 3< Pa.

[0047] Thanks to the displacement device 52, it is possible to move the impact zone of the local air blowing by the nozzle 51 onto the face of the glass sheet 10 in the lateral direction X. It is thus possible to blow air locally with the nozzle 51 onto an area of ​​the face of the glass sheet 10 extending transversely to the direction of movement of the glass sheet 10. The extent of the lateral displacement of the nozzle 51 permitted by the displacement device 52 is preferably greater than or equal to the maximum lateral extension of the glass sheets 10 treated by the forming device 2.

[0048] The lateral movement of the nozzle 51 by means of the movement device 52 is carried out in synchronization with the movement of the glass sheet 10 through the forming device 2. This synchronization is operated by a control system not represented preferably by control of the movement of the nozzle 51 as a function of the time elapsed from a detection signal of the edge of the glass sheet 10 which the control system receives from the detector 6, it being recalled that the glass sheet 10 is moved continuously and preferably at constant speed in the forming device 2.

[0049] The control system is preferably a computer or a programmable logic controller so as to be able to customize the movement of the nozzle 51 to different models of glass sheets and / or to different conformations of the glass sheets to be obtained through the local blowing of air from the nozzle 51.

[0050] The control system can also control a solenoid valve or other suitable component to selectively activate and deactivate the air blowing of the nozzle 51 based on the time elapsed since the detection signal of the edge of the glass sheet 10 received from the detector 6. This makes it possible, for example, to stop the air blowing of the nozzle 51 between two successive glass sheets 10 and / or to geographically and temporally confine the air blowing during the passage of the glass sheet 10 in front of the nozzle 51. In particular, by maintaining the nozzle 51 in a fixed position in the X direction during the air blowing, it makes it possible to blow gas onto the glass sheet 10 along one or more fictitious segments extending exclusively along the Y axis and having a limited length between the upstream and downstream edges of the glass sheet.The detector 6 is preferably located sufficiently upstream of the nozzle 51 to take into account the reaction time of the solenoid valve relative to its command, this making it possible to effectively blow air through the nozzle 51 in any position between the front edge and the rear edge of the glass sheet 10 with reference to its direction of movement Y in the forming device 2.

[0051] The control system can also be designed to control the pressure level of the air blown by the nozzle 51, thus allowing the pressure to be adapted for different glass sheet models and / or for different glass sheet conformations obtained through local air blowing by the nozzle 51. The control system can also be designed to control the pressure level of the blown air based on the point of impact of the local gas blowing on the face of the glass sheet 10. This functionality can also be achieved by controlling the pressure level of the blown air based on the time elapsed since the detection signal of the edge of the glass sheet 10 received from the detector 6 by the control system. Such control of the pressure of the air blown by the nozzle 51 can, for example, be implemented by means of a flow-regulating solenoid valve connected to a compressed air reservoir at a maximum pressure, for example, 10 6 < Pa.More specifically, the control of the pressure of the air blown by the nozzle 51 is then obtained by controlling the opening of the solenoid valve as a function of the time elapsed from the detection signal of the edge of the glass sheet 10, knowing that for this type of solenoid valve, the air flow that it allows to pass through is a function of its degree of opening according to a predefined curve and that the flow is proportional to the pressure difference between the inlet and outlet of the solenoid valve.

[0052] The air blowing can be controlled according to one or a combination of the three aspects just described. Alternatively, the air blowing nozzle 51 is fixedly arranged, with the air blowing from the nozzle 51 and / or the pressure of the blown air then advantageously being selectively controlled by the control system.

[0053] In the following, we will describe the use of the forming device 2 to curve a sheet of glass constituting a side window 10' of a motor vehicle, which is shown in top view at the figure 4 This is also represented on the figure 3 on the lower roller bed 29 before crowning.

[0054] In its final state, the glass pane 10' is asymmetrically curved, with a more pronounced curve in zone 13 along the upper edge 10a of the glass. This increased curve is achieved by locally blowing air into zone 13 using nozzle 51. Conversely, the majority of the glass pane 10', corresponding to zone 11 adjacent to the lower edge 10b of the glass, exhibits a lesser curve, essentially the same as that obtained by roller beds 27, 29, i.e., without air being blown into zone 11 by nozzle 51. For convenience, the demarcation between zone 11 and zone 13 has been drawn by a dummy line 12, although in reality the transition between the two zones 11 and 13 is gradual.

[0055] Given that such a 10' window enters the former 2-conforming device as illustrated in the figure 3 With its upper edge 10a extending transversely to the direction of movement of the glass, a local air blow in a fixed position, as in US 2006 / 0010916 A1, does not accentuate the curvature along its upper edge. In contrast, the shaping device 2 allows this thanks to the local air blowing system 5. To achieve this, the control system is programmed to move the nozzle 51 in front of the area 13 as the glass moves within the shaping device 2 and blows air into it in such a way as to induce the desired curvature in that area.

[0056] There figure 8 shows the glass pane 10' before curvature, on which is represented the fictitious curve C corresponding to the location described by the local blowing of the nozzle 51 – more precisely, it is the location of the center of the blowing impact zone – on the convex face of the glass pane 10'. This curve C results from the combination of the continuous displacement at constant speed of the glass pane 10' in the Y direction of the glass pane's movement through the forming device 2, which is illustrated by the graph of the figure 5 and the lateral displacement of nozzle 51 in the X direction illustrated by the graph of the figure 6 Curve C is the result of combining the curves of figures 5 et 6 as also shown by the figure 7 The airflow through nozzle 51 along curve C is preferably continuous. Furthermore, the control system is programmed to activate the airflow at the first end of curve C and deactivate it at the second end of curve C.

[0057] After processing a sheet of glass 10' by the local air blowing system 5 following the curve C, the nozzle 51 of the latter - which is then preferentially deactivated - is brought back towards the opposite lateral side to an initial waiting position for the processing of a next pane of glass 10'.

[0058] The use of a local air blowing system 5 with a movable nozzle 51 has the advantage of allowing local air blowing treatment of one face of the glass sheets 10 not only along a transverse oblique curve, but also with precise positioning and limited extension in the Y direction of movement of the glass sheets 10. This would be difficult, or even impossible, to achieve with local air blowing nozzles arranged fixedly adjacently in the transverse direction X, if only because of the reaction time of the solenoid valves for activating and deactivating the local air blowing by each nozzle.

[0059] The movement device 52 for the nozzle 51 can be implemented using any suitable technology that provides adequate control of the movement speed and sufficient movement accuracy. Since the travel speed of the glass sheets 10 in the Y direction can reach up to 150 mm / s, the nozzle 51 can travel up to 1 meter in 0.5 seconds. From this perspective, a linear motor is particularly suitable because this technology allows for both rapid and precise movements.

[0060] The detector 6 can be implemented using any suitable technology to detect the edge of the glass sheet 10. Preferably, this is a detector based on non-contact technology. In particular, it could be an optical detector such as a sensor coupled to an optical fiber that "sees" the glass sheet passing in front of it because the glass sheet emits light due to its high temperature. As another example, the optical detector could be a light barrier based, for example, on a laser beam that the glass sheet interrupts. It could also be an ultrasonic detector in which the glass sheet interrupts an ultrasonic transmission.

[0061] Numerous variations of the described local air blowing system 5 are possible. According to one variation, several local air blowing systems 5 can be provided, each with its nozzle 51 arranged between a pair of successive rollers 21 in the shaping zone 25. This variation offers even more possibilities for influencing the final curvature of the glass sheet 10. For example, each local air blowing system 5 can treat the same glass sheet 10 in adjacent areas or even in separate, distant areas, or possibly reprocess the same area to enhance the desired curvature-modifying effect. Alternatively, the local air blowing systems 5 can operate successively for each respective glass sheet 10 as the glass sheets 10 pass through the forming device 2.According to another variant, several local air blowing systems 5 can be provided, the nozzle 51 of each being arranged between the same pair of successive rollers 21 in the shaping zone 25. This allows several areas to be treated side by side with their own conditions.

[0062] According to another variant, alternatively or in addition to the one or more systems on the side of the lower roller bed 29, one or more local air blowing systems of the same type may be provided on the side of the upper roller bed 27, the nozzle 51 of each then being arranged between a respective pair of consecutive rollers 22 to blow on the concave face of the glass sheet 10.

[0063] In the case where several local air blowing systems 5 are used, they may share the same control system or have their own control system. Similarly, a single detector 6 may be used for the purpose of synchronizing the control of the local air blowing of the nozzle 51 of each with the movement of the glass sheet through the forming device 2, but alternatively each may use its own detector 6.

[0064] The use of one or more local air blowing systems 5 can make it possible to produce curved glass sheets with dimensional variations ranging from 0.1 mm to 5 mm compared to a curve without such local air blowing.

[0065] The local air blowing system(s) 5 can also be combined with other systems designed to influence the final curvature of the glass sheet, for example with fixed blowing nozzles blowing continuously at constant pressure as described in US 2006 / 0010916 A1. Such a fixed nozzle has been shown on the figure 2 under reference 60 on the side of the upper roller bed 27. There is also nothing to prevent the use of a gas other than air with the nozzle 51, although air is preferred because of its economical nature and ease of implementation.

Claims

1. A method for curving a glass sheet (10, 10') comprising: - moving the glass sheet at a softening temperature continuously through a forming device (2) in which the glass sheet is curved and subjected to forced cooling as the glass sheet passes through the forming device to solidify the entire glass sheet in the curved state, and - blowing gas, preferably air, onto at least one face of the glass sheet as the glass sheet passes through the forming device (2), said gas being blown on to at least one face of the glass sheet upstream of the forced cooling in relation to the direction of movement of the glass sheet through the forming device, in which said gas blowing: - is carried out under conditions liable to cause a modification in the form of the curvature of the glass sheet obtained after the glass sheet has passed through the forming device (2) compared to the form of the curvature that would be obtained without said gas blowing, and - is or includes at least one local gas blowing affecting one face of the glass sheet locally only, the method also including control of the local gas blowing as a function of the time elapsed since detection of the arrival of the glass sheet in the forming device.

2. The method as claimed in claim 1, in which control of the local gas blowing includes one or more or all of the three following actions: - moving the impact zone of the local gas blowing on the face of the glass sheet transversely to the direction of movement (Y) of the glass sheet in the forming device as a function of the time elapsed since detection of the arrival of the glass sheet in the forming device, - activating and deactivating the local gas blowing as a function of the time elapsed since detection of the arrival of the glass sheet in the forming device, and - modifying the pressure of the local blowing gas as a function of the time elapsed since detection of the arrival of the glass sheet in the forming device.

3. The method as claimed in claim 1 or 2, including: - the use of at least one nozzle (51) for the local gas blowing, and - moving the nozzle (51) transversely to the direction of movement (Y) of the glass sheet as a function of the time elapsed since detection of the arrival of the glass sheet to move the impact zone of the local gas blowing on the face of the glass sheet transversely to the direction of movement (Y) of the glass sheet in the forming device.

4. The method as claimed in any one of claims 1 to 3, in which the forced cooling of the glass sheet includes or comprises: - the thermal tempering or thermal toughening of the glass sheet.

5. The method as claimed in any one of claims 1 to 4, including the application of the local gas blowing in a partial zone of one face of the glass sheet, the partial zone having an elongate form extending transversely to the direction of movement (Y) of the glass sheet in the forming device, the impact zone of the local gas blowing on the face of the glass sheet being moved as a function of the time elapsed since detection of the arrival of the glass sheet in the forming device such as to be moved into said partial zone during the movement of the glass sheet in the forming device.

6. The method as claimed in any one of claims 1 to 5, including blowing gas under conditions causing a local increase of a concavity of the curvature of the glass sheet obtained after the glass sheet has passed through the forming device (2) in relation to the concavity of the curvature that would be obtained without said gas blowing, said local increase in the curvature being located along an edge (10a) of the glass sheet (10') extending transversely to the direction of movement (Y) of the glass sheet.

7. The method as claimed in any one of claims 1 to 6, in which the glass sheet is a motor-vehicle side window (10'), the method including controlling the gas blowing such as to cause a local increase in the curvature along an upper edge (10a) of the motor-vehicle side window in relation to the assembly thereof in a motor vehicle.

8. The method as claimed in any one of claims 1 to 7, in which the forming device includes a bed of lower rollers (29) and a bed of upper rollers (27), the method including moving the glass sheet (10, 10') at a softening temperature continuously between the bed of lower rollers and the bed of upper rollers, which are arranged to force the glass sheet to follow a curved route in the direction of movement (Y) of the glass sheet such as to curve the glass sheet.

9. A device for curving a glass sheet that is designed to implement the method as claimed in any one of claims 1 to 8, including: - a forming device (2) designed to curve a glass sheet (10, 10'), previously brought to a softening temperature, by continuous movement through a forming device, the forming device being designed to curve the glass sheet and to subject the glass sheet to forced cooling as the glass sheet passes through the forming device to solidify the entire glass sheet in the curved state, - a local gas blowing system (5) for blowing the gas, preferably air, locally onto a face of the glass sheet as the glass sheet passes through the forming device, the local gas blowing system (5) being designed to blow the gas locally onto the face of the glass sheet upstream of the forced cooling in relation to the direction of movement of the glass sheet through the forming device, - a detector (6) for detecting an edge of the glass sheet during movement thereof through the forming device upstream of the local gas blowing system (5) in relation to the direction of movement of the glass sheet through the forming device, and - a control system designed to control the local gas blowing system as a function of the time elapsed since a detection signal of the edge of the glass sheet provided by the detector (6).

10. The device as claimed in claim 9, in which the control system is designed to control the local gas blowing system such as to: - move the impact zone of the local gas blowing on the face of the glass sheet transversely to the direction of movement (Y) of the glass sheet in the forming device as a function of the time elapsed since detection of the arrival of the glass sheet in the forming device, and / or - activate and deactivate the local gas blowing as a function of the time elapsed since the detection signal of the edge of the glass sheet provided by the detector (6), and / or - modify the pressure of the local blowing gas as a function of the time elapsed since the detection signal of the edge of the glass sheet provided by the detector (6).

11. The curving device as claimed in claim 9 or 10, in which the local gas blowing system (5) has at least one nozzle (51).

12. The curving device as claimed in claim 11, in which the local gas blowing system (5) includes a movement device of the nozzle (51) designed to move the nozzle (51) transversely to the direction of movement (Y) of the glass sheet in the forming device, the control system being designed to control the movement system of the nozzle (51) as a function of the time elapsed since the detection signal of the edge of the glass sheet provided by the detector (6).

13. The curving device as claimed in any one of claims 9 to 12, in which the forming device (2) includes a bed of lower rollers (29) and a bed of upper rollers (27) that are arranged to enable the glass sheet to pass therebetween and to force the glass sheet passing therebetween to follow a curved route in the direction of movement (Y) of the glass sheet in order to curve the glass sheet.

14. The device as claimed in claim 13 where dependent on claim 12, in which the nozzle (51) is arranged between two successive rollers (21a, 21b) of one of the beds of rollers (27, 29), the movement device of the nozzle (51) being designed to move the nozzle between these two successive rollers (21a, 21b).

15. The device as claimed in any one of claims 9 to 14, in which the forming device is designed to subject the glass sheet to thermal tempering or thermal toughening by means of said forced cooling of the glass sheet.

16. The device as claimed in any one of claims 9 to 15, also including a set of gas blowing nozzles (31) to subject the glass sheet to said forced cooling, the nozzles (31) of said set being distributed transversely to the direction of movement (Y) of the glass sheet and arranged between successive rollers (21; 22) of at least one of the beds of rollers (27, 29).