EP3697733A1

EP3697733A1 - Gravity-bending glass between a frame and a counter-frame

Info

Publication number: EP3697733A1
Application number: EP18812230.3A
Authority: EP
Inventors: Christophe Machura; Thierry Olivier; Philippe Frebourg; Jérôme PELLETIER
Original assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2017-10-19
Filing date: 2018-10-18
Publication date: 2020-08-26
Also published as: CN109937192B; US20200346965A1; WO2019077277A1; WO2019077278A1; CN109937192A; CN109952276B; CN109952276A; US20210188686A1; EP3697734A1

Abstract

The invention relates to a device and a method for gravity-bending a glass sheet or stack of glass sheets having a plurality of sides, referred to as the glass, comprising a frame for bearing the glass in the peripheral zone thereof by means of a contact track, said contact track having concave curvatures at each of the sides of said frame, and a counter-frame that can make contact with the glass in the central zone of at least one side of the peripheral zone of the upper main face of the glass. The invention is particularly useful for bending thin glass and for reducing the ripples that tend to form towards the middle of the sides.

Description

GLASS BOMBAGE BY GRAVITY

BETWEEN SKELETON AND COUNTER SKELET

The invention relates to gravity bending of glass on a skeleton. A counter-skeleton is placed above the glass to prevent the formation of corrugations at its edges.

The gravity bending of glass is well known and in particular documented in EP448447, EP0705798, EP885851. In US999558, the glass is forced to bulge by a support on the wafer.

Gravity bending of glass sheets greater than 2.1 mm thick can be performed by methods described in the prior art. The tendency is to reduce more and more the thickness of the glass sheets intended to be assembled within a laminated glazing. It tends to associate a thin sheet with a sheet of greater thickness. It was found that the gravity bending of a glass sheet less than or equal to 2.1 mm thick produced, on a conventional skeleton, ripple defects on the edges of the glass, more particularly in the area of the glass. middle of the different sides of the glass. The phenomenon responsible for the creation of folds at the periphery of the glazing during its support at the periphery is a phenomenon of instability similar to buckling (or buckling) of elastic plates. In the same way as in the case of thin elastic plates, the phenomenon of peripheral instability observed in the forming of glass sheets is all the more important that the thickness of the glass is low and the temperature at the periphery of the glass is high.

If one seeks to thwart the formation of these undulations by pressing the upper face of the glass during bending this tends to produce marks on this face and on the underside, and even to hinder the bending since the glass is found stuck between a lower tool and a superior tool as in a jaw, which slows down its collapse. The "marks" correspond to slight mechanical indentations created by the tools on the glass during its bending. They are particularly troublesome when they are on the lower surface of the glass during bending because they are then visible from outside the vehicle. The glazing is then put to rebus. The "marks" that are on the upper side of the glass during bending are generally more easily accepted because they are inside the vehicle once mounted on it and these imperfections are hidden from the view of an observer outside the vehicle. Moreover, these marks inside the vehicle are hidden only if they are on the periphery of the glazing and therefore in the gluing area of the inner glass on the bodywork. According to the invention, the bending of glass, in particular of thin glass, is correctly achieved by means of a gravity bending device of a glass sheet or a stack of glass sheets comprising a plurality of sides, said glass , comprising a skeleton for supporting the glass in its peripheral zone by a contact track, said contact track comprising concave curvatures at each of the sides of said skeleton, and a counter-skeleton able to come into contact with the glass in the area of the at least one side of the peripheral zone of the upper main face of the glass. Preferably, the backbone contacts the middle region of all sides, generally four sides, of the peripheral zone of the upper main face of the glass. The peripheral zone is the area between the edge of the glass and a distance from the edge of the glass of 50 mm, whether it is the upper face or the lower face of the glass. Preferably, the back-skeleton is removable (synonym: retractable).

The invention also relates to a method of gravity bending a glass sheet or a stack of glass sheets, said glass (which has a thickness e), comprising the bending of the glass by gravity on a skeleton comprising a contact track supporting the glass in the peripheral zone of its lower main face, a counter-skeleton comprising a metal bar being in contact with the glass during the bending in the peripheral zone of its upper face, at the places where undulations appear in the Absence of the back-skeleton. The method comprises bending the glass by gravity on a skeleton supporting the glass in its peripheral zone by a contact track, said contact track comprising concave curvatures in each of the sides of said skeleton, a counter-skeleton coming into contact with the glass in the middle zone of at least one side of the glass in the peripheral zone of its upper main face.

The glass placed on the skeleton may be an individual sheet of thickness less than or equal to 2.1 mm, or even less than or equal to 1.2 mm thick. Generally, the thickness of an individual sheet is greater than or equal to 0.4 mm. The glass placed on the skeleton can also be a stack of glass sheets, especially sheets whose thickness has just been given. The stack may also include sheets of different thickness. This stack may comprise 2, 3 or 4 sheets. In particular, the device according to the invention can be bombarded with the following two sheets in the superimposed state: a sheet whose thickness is in the range from 1.4 to 2.7 mm, generally in the range from 1 , 4 to 2.5 mm, with a sheet whose thickness is in the range of 0.4 to 1.6 mm, especially in the range of 0.4 to 1.2 mm, the most thick, preferably lying under the thinnest sheet during bending on the skeleton. The curved sheets together by the device according to the invention are not necessarily intended to be associated together in the same laminated glazing. For simplicity, the term "glass" is used to denote an individual sheet or a stack of sheets.

The skeleton supports the lower main face of the glass in its peripheral zone. The skeleton comprises a metal strip (which may also be called "vertical plate", even if its large faces may optionally be inclined) having one of its slices upwards to support the periphery of the glass. The skeleton also comprises coated on the upper edge of its metal strip, a refractory fibrous material well known to those skilled in the art, forming the contact track for the glass. The metal band is rigid while the fibrous material has some elasticity and compressibility. This material is generally of the felt or knit type or fabric of metal and / or ceramic refractory fibers, as is well known to those skilled in the art. These materials reduce the risk of glass marking by the skeleton. The metal strip in the backbone generally has a width in the range of 1 to 10 mm. The fibrous material generally has a thickness in the range of 0.3 to 1 mm. The skeleton provides the glass, via its refractory fibrous material, with a contact track of width generally in the range from 1.6 to 12 mm (which includes the thickness due to the refractory fibrous material), more generally in the range from 3 mm to 10 mm. The skeleton has concave curvatures in its contact face for the glass, for each of its sides and generally at least in the middle of each of its sides, generally four sides. The contact track of the skeleton has concave curvatures for at least 80% and generally at least 90% of its length, said concavity being considered parallel to its contours (inside or outside). The contact track of the skeleton has concave curvatures for at least 80% and generally at least 90% of the length of its longitudinal sides, said concavity being considered parallel to its contours (inside or outside). In particular, the contact track of the skeleton has concave curvatures for the middle zone of its longitudinal sides, in particular for at least up to 20 cm on each side of this medium. The contact track of the skeleton has concave curvatures for at least 80% and generally at least 90% of the length of its transverse sides, said concavity being considered parallel to its contours (inside or outside). In particular, the contact track of the skeleton has concave curvatures for the middle zone of its transverse sides, in particular for at least up to 20 cm on each side of this medium. The glass collapses under the effect of gravity on the skeleton during the bending and takes a concave shape seen from above (the concave face is the face superior) in its central zone and in each of its sides, in particular in the middle of its sides. The skeleton has a shape conferring this concavity, since at the end of bending, the glass touches the entire periphery of the contact track of the skeleton. At the end of bending, the glass being placed on the skeleton, the central zone of the upper face of the glass is concave in all directions. Seen from above, the skeleton has roughly the same outline as the glass it must receive while being smaller since the glass overflows all the outer circumference of the skeleton. The contact track of the skeleton therefore generally has a concave shape in each of its sides, especially in the middle of its sides. The skeleton has as many sides as the glass and therefore generally has four sides (also called "strips"). Before bending, the glass usually overflows all around the skeleton by a distance in the range of 2 to 45 mm. This overflow decreases during the bending. This decrease depends on the importance of the curvatures given to the principal faces of the glass during the bending. At the end of bending, this overflow is generally in the range of 1 to 25 mm. From the beginning to the end of the bending, the skeleton generally supports the glass entirely in its peripheral zone and without overflowing out of this zone, neither outwards nor inwards. Viewed from above, the skeleton has a continuous annular shape and without interruption. Indeed, if the skeleton was segmented, this segmentation could produce a mark on the underside of the glass, given that in the process according to the invention the glass collapses essentially under the sole effect of its weight and therefore follows quite easily the shape of its support and remains quite sensitive to the unevenness of the skeleton.

The invention relates more particularly to the bending of glass for the production of glazing intended to equip vehicles (automobile, bus, truck, agricultural vehicle, etc.). It can be windshield, rear window, roof, side window sliding or fixed. The glass considered here comprises a plurality of sides, generally four sides (also called "strips"), one side joining another in a corner of the glass, this corner comprising a segment of curve comprising radii of curvature much smaller than those of curvatures of the sides. Consideration here is given to the radii of curvature of the perimeter of the main faces in vision perpendicular to the main faces and the edge of the glass. The middle of one side is approximately equal distance from two corners of this side. These glasses have a PS vertical plane of symmetry when they are mounted on the vehicle, the direction of movement of the vehicle (non-turned wheel) being included in this plane of symmetry. The intersecting sides of this plane of symmetry are said transverse sides, the other two sides being said longitudinal sides. The middle of the sides can be found in the following way: the curved glass (preferably in the form of low-deformable assembled glazing) is placed on a horizontal plane, concave side downwards. The glass touches the horizontal plane by 4 points of contact at its corners. The points of contact between them are connected by segments of the line. The intersection with the edge of the glass plane perpendicular to the segment and passing through the middle of this segment, is the middle side of the glass. The middle of the transverse sides is also at their intersection with the vertical plane of symmetry PS.

It has been observed that problems of glass rippling occur mainly in the middle of the sides and, to remedy this problem, the counter-skeleton comes into contact with the glass in the middle zone of at least one of its sides and generally in the middle zone on all sides. The back-skeleton may also come into contact with the glass in the peripheral zone out of the middle zone on one side and even above the corners of the glass, but this is not usually necessary. The counter-skeleton may therefore possibly be absent above corners of the glass, the glass being better formed in these places. This is particularly possible when the complexity of the glazing is not too high, typically when its main arrow is less than 100 mm. The middle area of one side is the area surrounding this medium in the peripheral area of the glass. In particular, the middle zone of one side is the peripheral zone in the vicinity and on either side of the middle, at least up to 5 cm on each side of the medium, and even at least up to 10 cm from each side of the middle, and even at least up to 20 cm on each side of the middle, parallel to the edge of the glass and in the peripheral area. This middle area of one side is fully concave at least up to 20 cm on each side of the middle. The counter-skeleton presses the glass in this area, but not necessarily throughout this area. The backbone supports enough to prevent the formation of undulations, but insufficiently to mark the glass. The counter-skeleton optionally supports continuously throughout the length of this zone parallel to the edge of the glass, but generally not throughout the width of this zone. If necessary, the contact with the glass may therefore be only partial, that is to say that along the periphery of the glass, the back-skeleton may touch the glass only in certain areas and not in others. The counter-skeleton is preferably vis-à-vis the skeleton on the other side of the glass during bending. However, it may be slightly offset inwards or outwards relative to the skeleton, but its contact with the glass is preferably only in the peripheral zone of the upper face.

The glazings referred to herein generally have four sides and are symmetrical with respect to their plane of symmetry passing through the middle of their transverse sides. The two transverse sides generally have a length in the range of 80 cm to 250 cm (length of segments between contact points, when the glazing is placed on a horizontal plane concave face facing downwards). Both longitudinal sides have typically a length in the range of 60 cm to 180 cm (length of segments between contact points, when the glazing is placed on a horizontal plane). The two longitudinal sides generally have the same length.

The counter-skeleton comprises a metal bar at least partially covering, viewed from above, the peripheral zone of the upper face of the glass. The counter-skeleton has a shape complementary to that to be given to the glass (final shape after bending at the periphery), where it touches the glass. Its shape can deviate from that of glass (and therefore the skeleton) where it does not touch the glass. The counter-skeleton has convex curvatures to face the concave curvatures of the upper face of the glass. Since the skeleton has the shape of glass, the backbone has curvatures parallel to those of the skeleton, at least where the skeleton touches the glass.

The counter-skeleton comes into contact with the glass with a refractory fibrous material. At the places where the counter-skeleton touches the glass, it preferably has a structure similar or identical to that of the skeleton, that is to say that its metal bar comprises a metal strip (or flat vertical) having one of its slices downwards, said lower portion possibly being covered with a refractory fibrous material already described for the backbone. All the materials and thicknesses given for the skeleton (metal band and refractory fibrous material) are then valid for the back-skeleton.

The refractory fibrous material is capable of compressing and compressing during bending under the effect of the gravitational force acting on the backbone. This property of the fibrous material can be used to distribute the pressure exerted by the back-skeleton on the glass. The beneficial effect on the reduction of undesired peripheral ripples is also associated with the mechanical effect of the two tools (skeleton and counter-skeleton) which physically prohibit any possibility of the glass being deformed in a vertical direction to the tooling right. The beneficial effect is related to the use of the refractory fibrous material coupled with the control of the gap between the skeleton and the back-skeleton; a slight local modulation of the distance between these two tools results in a slight compression of the fibrous material, which is insufficient to induce a mark on the glass. If necessary, a counterweight system connected to the backbone reduces the backstage pressure on the glass.

We can distinguish two variants:

V1: the counter-skeleton touches the glass and the fibrous material compresses under the effect of the gravitational force exerted on the back-skeleton, but its compression is limited because of the presence of a means of imposing a minimum distance given Dm between the metal strip in the skeleton and a metal bar in the back-skeleton.

V2: the counter-skeleton touches the glass and the fibrous material is compressed under the effect of the pressure exerted by the back-skeleton, but its compression is not blocked by means of imposing a given minimum spacing between the band metal in the skeleton and a metal bar in the counter-skeleton.

Variant V1 involves a means of imposing a given minimum distance Dm between the metal strip of the skeleton and the metal bar of the backskeleton. The skeleton and counter-skeleton can not move closer together so that the distance between the metal skeleton band and the metal bar of the back-skeleton falls below Dm. This means serves to prevent the back-skeleton exerting too much pressure on the glass. In addition to reducing the risk of marking the glass, it also allows the glass to slide on the skeleton during bending, without being held back because of a too strong pinch between skeleton and back-skeleton. This is favorable for obtaining a shorter bending cycle time.

The curvatures of glazing are characterized by the notions of arrow and double-bending. For the definitions of these characteristics, reference may be made to FIGS. 1a and 1b and to the description corresponding to them of WO2010 / 136702.

The invention is suitable for bending glass whose complexity of shape is moderate (arrow less than 100 mm and / or double bending less than 20 mm) or stronger (arrow greater than 100 mm and / or double bending greater than 20 mm ).

Variant V1 is preferably used when the geometrical instability (ripples) takes place well localized on the glazing such as for example in the middle of the high band of a windshield (upper horizontal edge when mounted on the vehicle). We then focus on fine-tuning the distance between the skeleton and the back-skeleton in this particular region. It is naturally possible to use this variant V1 over the entire periphery of the glass, especially when the propensity for geometric instabilities is distributed over the entire periphery of the glass.

Variant V2 is preferably used when the adjustment of the distance between the skeleton and the backskeleton is particularly difficult. This variant V2 works not by adjusting geometric dimensions, but in pressure thanks to the force of gravity exerted on the back-skeleton pressing on the glass. This type of tooling leads to a particularly reproducible bending process, less sensitive to small geometric variations of the tools, especially following the successive cycles of heating and cooling.

The function of the counter-skeleton is not to bend the glass (this is the role of gravity), but just to prevent the formation of edge ripples. A bending without the counter-skeleton would result in an identical bending in the central zone of the glass compared to a bending with counter-skeleton, all other conditions of realization being identical. In particular, the back-skeleton should not press too hard on the glass as this could result in a pinching of the glass hindering its sliding on the skeleton during bending and slowing or even preventing its bending. This is why the pressure exerted by the back-skeleton must be finely dosed. In the device according to the invention, preferably, the back-skeleton during bending a weight on the glass per linear meter of back-skeleton (parallel to the skeleton) less than 2 kg / m and preferably less than 1 kg / m. Preferably, the counter-skeleton exerts a weight on the glass per linear meter of back-skeleton (parallel to the skeleton) greater than 0.1 kg / m.

The counter-skeleton acts positively (by reducing the undulations) on the glass by thermal effect, at the places it touches as in the places it does not touch but that it approaches, especially at less than 50 mm. This thermal effect depends essentially on three criteria: 1) the relatively moderate temperature of the counter-skeleton at the furnace inlet, preferably less than 250 ° C., 2) the propensity of the back-skeleton to remain colder than the periphery of the glass whereas the glass is between 300 and 650 ° C, and especially during bending, 3) the area of glass exposed to the backbone.

Criterion 1 is provided by sufficient cooling of the backbone after bending. Part of this cooling takes place in the bending furnace itself but also on the tool return chain when they go up empty from the furnace outlet to the furnace inlet. Additional cooling systems specifically dedicated to cooling the backbone can be installed, such as additional fans or air jets directed to this tool. It is also possible to provide a dedicated cooling circuit, directly attached to the backbone, and activated on its return path out of the oven. It may in particular be a tube capable of receiving a current of a cooling fluid, especially fresh air (that is to say generally at room temperature, generally between 0 and 50 ° C). Such a metal tube can be attached to the metal bar of the back-skeleton. It may also be a counter-skeleton whose metal bar comprises a metal tube with square or rectangular section in which fresh air is circulated. Criterion 2 is ensured, either by increasing the mass of metal embedded in the backbone, which has the consequence of increasing its thermal inertia and therefore the amount of heat required to heat it, or by limiting the heat input to back-skeleton by covering the latter with thermal insulation. Thus, the heating elements arranged in the vault of the oven can heat the glass without losing unnecessarily energy to directly heat the backbone. The periphery of the glass is then all the colder that it is on the one hand masked from the direct heating by the heating elements of the oven (generally vault) and on the other hand that it faces the counter-skeleton which is kept at reduced temperature. It should be noted that the cooling of a backbone coated with an insulating material is slower because the surface directly exposed to the open air on the tool return chain is reduced. Criterion 3 depends on the geometry of the backbone and the distance between the backbone and the glass.

The counter-skeleton can be segmented. It then includes as many bands (or "segments") that the glass has sides, usually four. At one side of the glass is associated a band of the back-skeleton. Each backbone band may cover the middle area on one side, and if necessary, not go to the corners of the glass.

According to the invention, the skeleton may comprise a metal strip whose slice is directed upwards, said slice being covered with a refractory fibrous material forming the contact track for the glass, the back-skeleton may comprise a metal bar, the device comprising means for imposing a given minimum distance Dm between the metal strip of the skeleton and the metal bar of the backbone. The means for imposing Dm may include a stop member, said abutment, secured to the skeleton and on which a counterbiased element, said abutment, integral with the backbone is able to rest. The stop is fixed directly or indirectly to the rigid metal band of the skeleton. It may be the upper surface of a plurality of candles or jack screws. The abutment is fixed directly or indirectly to the rigid metal bar of the back-skeleton. The device generally comprises a frame on which the skeleton is fixed. Any stop element can be fixed on the frame or on the skeleton, it always amounts to the fact that the abutment is integral directly or indirectly with the skeleton. Advantageously, the means of imposing Dm is adjustable so as to adjust the value of Dm. This allows in particular to adjust the degree of compression of the refractory fibrous material equipping the backbone and the skeleton and pressing the glass, and therefore the pressure on the upper face of the glass and the pressure on the underside of the glass. The adjustment means can be located at the abutment and / or abutment.

In practice, the distance between the two tools (skeleton and counter-skeleton) can be adjusted and controlled by toolmakers using shims. For the adjustment of the height dimension of the back-skeleton, the toolmaker can proceed by introducing a shim between the upper face of a previously convex glass and the refractory fibrous material of the back-skeleton by exerting a certain lateral force. During this adjustment, the fibrous material contracts slightly and decreases a little thick. The actual measurement made by the toolmaker is therefore the result of the distance between the glass and the back-skeleton, the thickness of the fibrous material that covers it, the compressibility of the fibrous material, the thickness of the wedge the thickness itself, and the lateral force exerted by the toolmaker during the control or when adjusting the distance between the two tools. By this way, the operator realizes whether a shim thickness passes easily or not between the glass and the back-skeleton and routine tests, he learns to finely adjust the device.

For the case of pronounced curvatures or complex shapes, in particular comprising pronounced curvatures in directions orthogonal to each other, it may be advantageous for the device according to the invention to comprise a system able to modify during bending the distance between the skeleton and the counter-skeleton. Indeed, the counter-skeleton has a shape closer to that of the upper face of the glass at the end of the bending, rather than at the beginning of the bending. When the glass is placed on the skeleton, the glass is flat or only slightly curved because of its natural flexibility. The counter-skeleton therefore has a shape more curved than the glass at the beginning of the bending and could touch it and, by elastic deformation, force it to adopt the peripheral shape of the skeleton. Such a situation may cause a breakage of the glass at the entrance of the oven. This is why, without excluding the fact that the back-skeleton can not touch the glass from the beginning of the bending (from the oven entrance), it may be preferable that the backbone is at first rather far from the skeleton and then bring it closer during the bending. This reduces the gap between the skeleton and the glass (and therefore between the skeleton and the skeleton) as the glass softens and follows the contours of the skeleton. The duration of the approach phase between the glass and the backbone can be adjusted between five tenths of a second to 30 seconds, or even up to one minute depending on the previous heat history and the complexity of the glazing itself.

If the forces applied to the glass in the oven inlet and during the bending are sufficiently moderate to avoid breakage of the glass, it is firstly possible that the back-skeleton is in partial contact with the glass, particularly at mid or close to the middle of the top and bottom sides of the glass (in position mounted on a motor vehicle) as soon as it is placed in the oven and on the other hand, it is possible to force the glass to bulge by the action of the counter-skeleton pressing on the glass. The counter-skeleton presses on the glass during its descent, which forces the peripheral bending. Such kinematics is advantageous because it facilitates the main bending of the glass and thus reduces the forming cycle time. Note that at the beginning of the process towards the entrance of the furnace, the glass is at low temperature and less sensitive to the marking and that is why, except for the case of breakage, the contact supported enough of the back-skeleton at this stage is not necessarily embarrassing, and may even be advantageous. The initiation of the approximation between glass and back-skeleton can be relatively brutal (simple trigger that is to say, passing from a single stroke of a remote configuration to a close configuration) or progressive. A trip system can be operated through the side walls of the oven or through the oven floor. A triggering system may in particular be similar to that described in US8156764. By way of example, the distance between the glass and the backbone in the middle zone of one side can be in the range from 0 to 10 mm at the beginning of the bending, and finally at 0 mm at the end of bending while concomitantly, the distance between the glass and the skeleton in the middle zone of one side can be in the range from 0 to 300 mm at the beginning of bending to finish at 0 mm at the end of bending. Thus the skeleton and the back-skeleton may eventually move closer during bending.

According to the embodiment V2, the back-skeleton touches the glass and no stop / abutment system stops the progression of the back-skeleton towards the glass (and therefore also to the skeleton) under the effect of gravity. It is the glass itself that plays the role of a stop. In this case, the back-skeleton rests on the glass, which causes a more or less significant compression of the fibrous material equipping it. If the counter-skeleton is relatively light, you can let it rest on the glass. If the back-skeleton is too heavy and exerts too much pressure on the glass despite the presence of the fibrous material equipping it, one can compensate part of the weight of the back-skeleton by a counterweight system. In this case, the weight of the back-skeleton is lightened by a counterweight acting at the end of a lever. This lever is connected to the frame supporting the skeleton by a pivot connection to the substantially horizontal axis, one end of the lever carrying the counterweight, the other end of the lever being connected to the back-skeleton and pulling it upwards under the effect of the counterweight at the other end of the lever.

The invention also relates to a method of gravity bending of the glass, by the device according to the invention. The bending of the glass is carried out by gravity on a skeleton supporting the glass in its peripheral zone, a counter-skeleton coming into contact with the glass in the middle zone of at least one of the sides of the glass in the peripheral zone of its main face. higher. In particular, the glass is bulging by gravity at a temperature in the range of 570 to 650 ° C, more generally in the range of 610 to 650 ° C. To achieve this bending, we can convey the skeleton / counter-skeleton charged with glass through a tunnel kiln heated to the plastic deformation temperature of the glass. This oven can be traversed by such sets each loaded with glass and circulating behind each other in the oven, the skeleton and counter-skeleton forming an embedded assembly capable of being conveyed together horizontally but without relative horizontal displacement of one relative to the other. The oven can include different temperature zones to gradually heat up and gradually cool the glass.

The glass is in contact with the skeleton for more than 10 minutes and generally more than 15 minutes and more generally between 15 and 30 minutes in the oven while being conveyed into the oven. In the oven, the glass undergoes a rise in temperature, bending and after bending a controlled drop in temperature. Similarly, in the oven, the back-skeleton usually also affects the glass for more than 10 minutes and generally the same time that the glass touches the skeleton. The bending is done by gravity. In the absence of counter-skeleton, during the bending, the glass will touch the entire skeleton, then some areas (especially in the middle area of at least one side of the peripheral area) would recover to leave the contact with the skeleton. The counter-skeleton serves to prevent this raising of the glass and to guarantee a total contact of the glass with all the circumference of the skeleton at the end of the bending. The skeleton and the counter-skeleton form an embedded assembly capable of being conveyed into the furnace by a conveying means. The device according to the invention does not allow a relative horizontal movement of the skeleton and the back-skeleton relative to each other, even though the skeleton / counter-skeleton assembly is conveyed into the furnace. The device may include means for the skeleton and backbone to move toward or away from each other by relative vertical movement without relative horizontal displacement relative to each other, even though skeleton / counter-skeleton is conveyed into the oven. The term "relative" qualifying a movement means that it may be the effect of the single backbone or the skeleton alone or both. The absence of relative horizontal movement of the skeleton and the back-skeleton relative to each other means that these two elements remain vis-à-vis one another in view-over while moving horizontal skeleton / counter-skeleton assembly during bending in the oven. Thus, the device according to the invention generally comprises an oven and a conveying means able to move horizontally together the skeleton and the back-skeleton in the oven while they are facing each other, and means of vertical translation allowing the skeleton and the back-skeleton to move towards or away by a relative vertical movement during their horizontal movement and without relative horizontal displacement relative to one another. If necessary, the device may be such that it is possible to place a counter-skeleton on a glass before the entrance of the oven and to remove it after leaving the oven.

After bending, the glass is cooled. For this cooling and in order not to generate in the glass too large edge extension constraints, we move away advantageously the counter-skeleton of the glass. The removal of the back-skeleton is advantageously carried out during cooling of the glass and when the latter is at a temperature of between 620 and 500 ° C. This distance can be achieved by different systems. It can be a re-engagement system that performs the inverse function of the "trigger" described above. Alternatively, the backbone may be composed of retractable strips laterally, generally four in number. The strips of the back-skeleton deviate vertically and laterally at the time of retraction so as not to be above the upper face of the glass. The system controlling the retraction of the strips may be similar to one of those described in US 8156764, that is to say for example through the side walls of the furnace.

The backbone and the backbone are advantageously independent of each other, that is to say that the backbone can then be separated entirely without having any link with the backbone. The glass can then be loaded on the skeleton and then the back-skeleton is put in place.

The loading of the glass on the device according to the invention can be carried out manually. The back-skeleton being removed, operators put the glass on the skeleton. Then they place the counter-skeleton according to its intended position. The position of the backbone is advantageously given by positioning means fixed to the skeleton or to the frame. These positioning means guide the back-skeleton during its installation. This guidance is made possible for example by holes in guide tabs connected to the backbone and through which pass positioning columns.

The loading and unloading of the glass can also be automated, in particular using robots, one for loading, the other for unloading. The use of robots makes it possible to have precise and reproducible movements as well as a reliable and tolerant coupling system between the skeleton and its associated counter-skeleton. This system in which the back-skeleton is completely separable from the skeleton, allows 1) to have a minimum of embedded functions in the tool and thus to minimize the weight of the latter, which is an important factor of energy consumption , 2) to minimize the risk of mechanical seizure and 3) to minimize maintenance operations, usually expensive on forming tools.

Alternatively, the back-skeleton can be part of a system directly embedded on the skeleton itself and able to retract the back-skeleton. To do this, for example, the back-skeleton may be composed of four separate bands integral with the skeleton and which can move away or join each other by displacements having both a horizontal component and a component vertical allowing to move away from the glass, without sliding on it, while moving away laterally from the skeleton. Such a movement can be performed by a simple rotation whose axis is judiciously chosen, especially outside the skeleton. As these bands move away, the skeleton becomes accessible for unloading or loading glass.

If the back-skeleton is of too light constitution, it may be of low rigidity and its shape may change slightly during its use, due to thermal stresses during the heating and cooling cycles. In this case, it can be found that the gap between skeleton and back-skeleton (and therefore between the metal band of the skeleton and the metal band of the back-skeleton) is no longer uniform and as it had been initially adjusted . The glass may eventually get to some places too wedged between skeleton and back-skeleton, reducing the bending in these places by preventing the glass from slipping on the skeleton. Thus, depending on the bending case, a simple adjustment of deviation only at the corners of the device, in particular by four jack screws, may prove to be insufficient. That is why, advantageously, the back-skeleton comprises a structural element disposed above its metal bar, the structural element and the metal bar being interconnected by a plurality of adjustable spacers for locally adjusting the distance between the structural element and the metal bar. The structural element is rigid and indeformable despite the multiple heating and cooling thermal cycles experienced for bombarding glass sheets industrially. It can be used as a reference to adjust the shape of the metal bar. The structural element advantageously comprises a metal tube, in particular of the frame type. This tube may in particular have a square or rectangular section. It may include lateral extensions to come over the adjustment areas, the upper end of the struts being connected to the extensions. The upper end of the spacers can also be connected directly to the structural element. Thus, the back-skeleton may comprise a structural element arranged at a dimension higher than that of its metal bar, the structural element and the metal bar being connected by a plurality of adjustable spacers for locally adjusting the distance between the element structural and metallic bar, and locally distance back-skeleton / skeleton. The plurality of spacers is evenly distributed all around the counter-skeleton.

In order to minimize the risks of deformation of the back-skeleton due to thermal stresses, it is possible to give its metal band the structure of a chain, by decomposing the back-skeleton into a plurality of sectors interconnected by joints. . A sector is a piece of metal strip presenting one of its slices downwards, said slice being covered or not, as the case may be, with a refractory fibrous material. A sector comprises a length and a height, its thickness being that of the metal strip. Its length is substantially parallel to the edge of the glass and the skeleton. The downward slice of the sector is substantially parallel to the slice of the skeleton at the same location. The sectors are interconnected as a chain so that their downwardly directed slices are aligned and substantially parallel to the edge of the glass and the skeleton. A sector is connected to two other sectors by joints comprising a pivot connection to the substantially horizontal axis located at both ends of its length, except in the case of a sector at the end of the chain, in which case it is is connected to only one other sector by an articulation at one of its ends. A sector counter-skeleton may be composed of four strips (corresponding to the four sides of the glass and the skeleton) each, in use, with respect to one side of the skeleton and thus also to one side of the glass. Each of these strips has a plurality of sectors, for example from 2 to 10 sectors. Thus, according to the invention, the back-skeleton may comprise a metal bar of the vertical metal strip type, a slice of which is turned downwards, comprising a plurality of sectors connected to each other by hinges, each hinge comprising a pivot connection to the hinge. substantially horizontal axis connecting two sectors between them.

Thanks to the joints the counter-skeleton with sectors follows very well the deformations of the glass. Similarly, his own tendency to distort is thwarted by the play of the joints. Thus, the sector counter-skeleton takes off much less from the glass than if it were in one piece and without articulation. The marks on the glass depend essentially on the effective pressure exerted by the back-skeleton on the glass, and therefore on the following parameters: the weight of the different sectors of the back-skeleton, the contact surface of the fibrous material covering the back-skeleton and and finally, the texture of the fibrous material itself, which preferably has a smooth and flexible surface. We can use a counterweight system, already mentioned above, to reduce the pressure of the sectors on the glass. In this case, the end of the lever connected to the sector backbone is preferably connected to a joint joining two sectors.

Two sectors interconnected by a joint can be juxtaposed locally at the joint. The juxtaposition zones of the two sectors are then juxtaposed in a direction perpendicular to the axis of the joint, said axis passing through the zones of juxtaposition of the two sectors. The zone of juxtaposition of at least one of the two sectors may be, in top view, offset with respect to its slice facing downwards, so as to provide a space capable of being occupied by the juxtaposition zone of the other associated sector in the articulation. This local offset can be achieved by local embossing. This local offset can also be achieved by cutting the juxtaposition zone so as to form a tongue that is can shift by deformation of the metal relative to the plane of the sector in plan view. In this way, even if locally at the level of the juxtaposed zones of the joint, the set of two articulated sectors is twice as thick as a single sector, the slices facing downwards of two sectors connected to each other by an articulation can be aligned in top view. Thus, the slices facing downwards from two sectors interconnected by a hinge, can be aligned in plan view, the juxtaposition zone of at least one of the two sectors being, in top view, offset with respect to its slice turned down, so as to spare a space occupied by the juxtaposition zone of the other sector. A sector backbone can operate according to the modes V1 or V2 mentioned above and the advantage resulting from the existence of the joints is exerted in both cases. Indeed, the sector counter-skeleton does not deform as much as if it were in one piece. Its lower edge follows better the surface of the glass during the bending despite the thermal stresses. In this way, the pressure exerted by the back-skeleton on the glass is more uniform and better distributed over its entire contact zone.

According to the V1 mode, a sector backbone can touch the glass via a fibrous material whose compression is limited due to the presence of a means of imposing a given minimum spacing Dm between the metal strip in the skeleton and the metal band in the back-skeleton. To do this, the skeleton may comprise a metal strip having a slice directed upwards and a plurality of stops connected to the metal strip. These stops are advantageously placed vis-à-vis joints of the back-skeleton. Counterbutts are then connected to the counter-skeleton and placed opposite the abutments, in particular to the stems forming axes of the articulations, so that they can come to bear on the abutments, so that a minimum distance Dm between the metal band the skeleton and the metal bar of the back-skeleton can be imposed at each sector when the abutments rest on the stops, and therefore when the back-skeleton is placed above glass. The joints ensure that despite the thermal stresses, each sector is based on its associated stop. According to this construction, the sectors at the ends of each segment are slightly shorter so as not to hinder their movement around their horizontal axis.

A specific cut at the joint of the sectors located at the ends of each strip limits their downward vertical movement and thus does not interfere with the movement of the back-skeleton during the loading and unloading of the glass. Indeed, the sectors can be grouped into as many bands that the glass has sides, each band corresponding to one side of the glass and being substantially parallel, the ends of the strips not being connected to their neighboring strips.

The figures below are not to scale.

Figure 1 shows in section a device according to the invention comprising a skeleton 320 and a backbone 321. A stop 327 is fixed to the metal strip 322 of the skeleton. The edge of this upwardly-turned metal strip is covered with a refractory fibrous material 323. The counter-skeleton comprises as a metal bar a metal strip 324 whose downward-facing slice is covered with a refractory fabric 325 for contact with the glass 328. A counterbutter 326 is connected to the metal bar 324 and can rest on the stop 327, blocking the descent of the back-skeleton to the skeleton. With a vacuum (in a)), the gap E between skeleton and back-skeleton is less than the thickness e of the glass 328. When the glass 328 is placed between these two tools (in b)), the fibrous refractory materials 325 and 323 compress under the weight of the back-skeleton until abutment 326 rests on abutment 327. The gap between backbone bar 324 and backbone metal band 322 is the minimum distance Dm. Stop 327 and abutment 326 are a means of imposing a minimum distance between 324 and 322. In this way the pressure force on the glass exerted by the skeleton and the back-skeleton is limited.

Figure 2 shows a windshield-type automotive glazing seen from above, and placed on a horizontal plane, concave face facing downwards. It comprises four sides, two transverse sides 350 and 351 and two longitudinal sides 352 and 353. One side joins another side by a corner having radii of curvature R (in vision perpendicular to the surface of the glass and in each corner) on the surface weak relative to the radii of curvature at the surface towards the middle of the sides. This glazing is symmetrical with respect to the vertical plane of symmetry PS. This PS plane passes through the mediums 354 and 355 of the transverse sides. This glazing rests on four points 356, 357, 358, 359 located in the corners. Dotted lines 360, 361, 362 and 363 connecting these four points. These are the segments closest to the edges. At an edge is associated a segment. Each of these segments has a medium 364, 365, 366, 367. For each segment, there is a plane perpendicular (368, 369, 370, 371) to the segment and passing through its middle. Each of these planes intersects the edge of the nearest lens at a point 372, 355, 373, 354 which is their center. The glazing is concave (in this figure, the concave face is facing downwards) at least at the midpoints 372, 355, 373, 354 and in all the hatched areas on either side of these midpoints, said concavity being considered parallel to the outer edge of the glazing. It is the same for the skeleton having supported this glass and for the zones of the skeleton corresponding to the zones of the middle of the sides of the glass, said concavity being considered parallel to the contours (inside or outside) of the skeleton and top view in a bending situation. The dotted line 376 is 50 mm from the edge of the glass and forms the boundary of the peripheral zone, which is between the edge of the glass and this line. The middle zone of the side 353 of the peripheral zone of the upper main face of the glass is the hatched area on the left. This zone surrounds the middle point 373. The hatched area is included in the peripheral zone between points 374 and 375 on the edge. These points 374 and 375 are each at a distance from point 373 of at least 5 cm, or even at least 10 cm or even at least 20 cm. The counter-skeleton presses the glass at least in this zone and, where appropriate, continuously throughout the entire length of this zone parallel to the edge of the glass, that is to say without discontinuity between the points 374 and 375, but not necessarily in the full width of this area.

FIG. 3 represents a device according to the invention at the moment when a backbone 8 (grayed in the figure) is being placed in position above the glass, the latter not being represented in the figure by concern for clarity. There is a frame 1 on which is fixed the skeleton 2 via lugs 3 and 4. The glass (not shown) is placed on the skeleton 2. Operators hold the back-skeleton 8 by handles 6. These handles are fixed on a frame 7 on which is also fixed the backbone 8 by means of lugs 9 and 10. The exact positioning of the back-skeleton is ensured by guidance with four positioning columns (1 1 and 12 in the first plan), one at each corner. These columns are integral with the frame 1. Tabs 13 and 14 fixed to the frame 7 of the backbone each comprising an orifice are threaded onto the columns 1 1 and 12 through their orifices. Candles 15 and 16 are part of the means of imposing a given minimum distance Dm between the skeleton and the backskeleton. They are each provided with bearing surfaces 17 and 18 adjustable in height by means of screws 19 and 20. The frame 7 of the back-skeleton comprises tabs 21 and 22 which rest on the support surfaces 17 and 18. when the operators have finished depositing the counter-skeleton. The weight of the backbone therefore rests on the support surfaces 17 and 18, the height thereof being adjusted so that the spacing between the backbone and the skeleton is the chosen one. The bearing surfaces 17 and 18 form abutments integral with the skeleton and the pastes 21 and 22 are abutments integral with the back-skeleton. The skeleton and the counter-skeleton form here an embedded assembly able to be moved horizontally in an oven. The four positioning columns (1 1 and 12 in the foreground) are part of vertical translation means allowing the skeleton and the back-skeleton to move towards or away by a relative vertical movement without relative horizontal displacement of the one compared to each other. In this way, the skeleton and the back-skeleton remain opposite each other. on the other side (on both sides of the glass) during the horizontal movement of the skeleton / counter-skeleton assembly in the oven.

FIG. 4 shows a sectional part of the device according to the invention in which there is a stack 30 of two glass sheets comprising a thin sheet (for example of thickness 1.1 mm thick) in the upper position and a sheet thicker (for example 2.1 mm thick) in the lower position. The gap between the glass and the back-skeleton (and therefore also between the skeleton and the back-skeleton) is being adjusted thanks to the wedge 40. This operation is done on a previously already curved glass. The glass rests with its lower main face 31 on the skeleton 32, which consists of a metal strip 33 and a fibrous refractory material 34 covering the contact surface for the glass. The counter-skeleton 35 has the same structure. Skeleton and counter-skeleton are exactly opposite each other on both sides of the glass. There is a gap 36 between the back-skeleton 35 and the upper face of the glass 37, filled by the adjustment wedge 40. Skeleton and counter-skeleton act entirely inside the peripheral zone 38 of the glass between the edge of the glass. glass and 50 mm from the edge of the glass.

FIG. 5 is a top view of a back-skeleton comprising a rigid structural element 50 above a part 51 of the back-skeleton comprising a vertical plate (non-visible) coming on the glass. The visible part 51 is a horizontal plate 57 coming above the vertical plate and to which it is connected. This structural element is a metal tube of square section and has the shape of a rectangular frame in plan view. It comprises a plurality of extensions 52 connected to its inner or outer vertical faces, said extensions coming, in top view, above zones 53 of local adjustment of the position of the lower portion of the back-skeleton. These adjustments are made by jack screws 54 passing through the rigid structural element 50 here.

Figure 6 shows the counter-skeleton of Figure 5 according to section AA 'in a) and the side view in the direction B in b). The metal square of the rigid structural element 50 is found, an extension 52 being welded to an outer vertical face of said square. This extension is also in square metal. The vertical plate 55 is indirectly connected to the rigid structural element 50 so that it is integral. The lower edge 56 of this vertical plate 55 comes on the glass and its distance to the skeleton can be finely adjusted by the screw jack 54 by screwing or unscrewing the nuts 58 and 59. The vertical plate 55 is welded by its edge greater than one. horizontal plate 57, in order to stabilize the position of the plate 55. The horizontal plate 57 is connected to the lower end of the jack screw 54 by means of a pivot connection 60 whose pivoting is adjustable and biocable at a given position thanks to the nuts 61 and 62. The adjustment of this pivoting makes it possible to adjust the inclination of the edge 56 so that it is well parallel to the skeleton and that the distance between the skeleton and the back-skeleton is quite constant for the entire periphery of the glass.

FIG. 7 represents a back-skeleton according to the invention seen entirely in a), a portion being enlarged in b). This back-skeleton comprises a structural element 75 made from pieces of metal squares welded together. Viewed from above, this structural element has a shape similar to that of the skeleton and therefore the glass to be bomber. Lateral extensions 76 have been welded to inner vertical faces of the structural member. Adjusting cylinder screws traverse these extensions vertically. The adjustment of a jackscrew makes it possible to locally adjust the dimension of the lower edge 77 of a vertical plate 78. This vertical plate is secured to a horizontal plate 79 by a system of brackets 80 and screws and nuts. A pivot connection 81 above the horizontal plate 79 makes it possible to adjust the local inclination of the horizontal plate 79 in the context of the adjustment of the height dimension of the edge 77. There are also some handles 82 enabling operators to manipulate this against skeleton and lay it over the glass. The correct lateral positioning of the back-skeleton is ensured by a centering means of the type already described for FIG. 3 and not represented here for the sake of simplification.

FIG. 8 shows in side view and schematically the assembly of a skeleton 90 and its counter-skeleton 91. It can be seen that the contact track of the skeleton is concave along the entire length of the visible side in the figure, parallel to its inner and outer contours, this concavity being in the plane of the figure. The backbone 91 is composed of a plurality of sectors (S1, S2, S3, S4, S5, S6) interconnected by articulations. A sector has an elongated dimension parallel to the edge of the glass which is called length L (substantially horizontal in FIG. 8a), and a height (substantially vertical in FIG. 8a). Two sectors connected by a joint present a juxtaposition locally in the area of the joint. Figure 8b) shows a side view, a zoom of the pivot joint 92 between sectors S2 and S3 (of Figure 8a) and the abutment system and associated abutment. Figure 8c) represents the identical of Figure 8b) but seen in the direction of the length of the sectors, the eye being on the sector S2 side and looking towards the sector S3. In order to simplify the figures, the hidden edges in FIGS. 8a) to 8d) have not been shown and the fibrous material covering the tools has not been shown either. The back-skeleton comprises a rigid structural member 96 whose height dimension relative to the skeleton 90 is preliminarily and approximately adjusted by jack screws 97 located at the four corners of the back-skeleton. The plurality of sectors S1 to S6 connected to each other by chain-like joints (92, 93) form an articulated vertical plate. A sector S3 is connected at each of its ends to two neighboring sectors S2 and S4 by pivot links 92 and 93 to the axes substantially horizontal. These articulations leave the possibility for the sectors to move relative to each other under the sole effect of their own weight. Each sector is provided with a rod 94 acting as abutment and pressing against a stop 95 integral with the skeleton 90. When the height adjustable abutment 94 presses on the stop 95, the gap skeleton / against backbone desired is obtained. A lock-nut 99 makes it possible to block the screw 94 and thus freeze the skeleton / back-skeleton gap. The pivot connection 92 shown in Figure 8c is composed of a horizontal axis 102 connecting two sectors S2 and S3 which is connected to a bridge 103 which spans the two sectors S2 and S3. The sectors S2 and S3 can therefore move in free rotation relative to the bridge 103 and around the axis 102. A rod 98 is connected to each axis of articulation via a bridge identical to the bridge 103 and can have a free vertical movement relative to the rigid structural element 96. As shown in detail in Figure 8d), a slide 104 is interposed between the rigid structure 96 and the vertical rod 98. A mechanical clearance between 0.3 and 0.5 mm between the inner bore of the slider 104 and the vertical rod 98 provides a good mechanical compromise between the possible vertical translation of the rod 98 and the accuracy of its vertical guidance. This rod 98 is surmounted by a head 100 so that the rod can not pass through the rigid structural element 96. When the back-skeleton is removed, each head comes to rest on the rigid structural element 96, which simply keeps cohesion across sectors. Similarly, an abutment 101 is also disposed on the rod 98 but this time under the rigid structure 96 to limit the movement of the sectors upward, especially when handling the backbone. A flyweight 105 (shown in FIG. 8c) has been disposed at each articulation but on the side opposite to the adjustable abutment 94. Such a counterweight makes it possible to counterbalance the weight exerted by the abutment 94 and thus to promote the sliding of each rod. 98 when its backbone is in position as in FIG. 8a), then the heads 100 do not rest on the rigid structural element 96, so that it is the position of the abutments and abutments which determine the position of the sectors. The rigid structural element 96 then plays no role of reference. During a thermal cycle, the sectors can move relative to each other by the play of the joints so that the abutments always rest on the abutments, which guarantees the conservation of the gap skeleton / counter-skeleton wished during the thermal cycle .

FIG. 9 shows in side view and schematically the assembly of a skeleton 1 10 and its back-skeleton 1 1 1 composed of a plurality of sectors (S1, S2, S3, S4, S5, S6 ) interconnected by pivot joints to substantially horizontal axes. Unlike the case of Figure 8 (where the minimum gap skeleton / counter-skeleton is fixed using a combination of stops and abutments arranged at level of each articulation), the tooling is here used in direct pressure, without system of abutments and abutments. FIG. 9 schematizes a counterweight system that can be installed at the ends of the rods 1 18 in order to lighten the effective weight of each sector, and therefore the contact pressure that the back-skeleton exerts on the current lens 1 14 bending. The counter-skeleton comprises a rigid structural element 1 16 whose height dimension relative to the skeleton 1 10 is adjusted in a preliminary and approximate manner by jack screws 1 17 located at the four corners of the back-skeleton. The plurality of sectors S1 to S6 connected to each other by chain-like joints (1 12, 1 13) form an articulated vertical plate. A sector S3 is connected at each of its ends to two neighboring sectors S2 and S4 by pivot links January 12 and January 13 to the substantially horizontal axes. These articulations leave the possibility for the sectors to move relative to each other under the sole effect of their own weight. The hinge January 12 is connected by a bridge January 19 which spans the ends of the two sectors S2 and S3. The sectors S2 and S3 can therefore move in free rotation relative to the bridge 1 19 and following the articulation 1 12. A rod 1 18 is connected to the hinge 1 12 via a bridge 1 19 and can have a free vertical movement relative to the rigid structural element 1 16. This rod 1 18 is surmounted by a hinge 120. The counterweight system is composed of a vertical bar 121 provided with a hinge 124 at its upper end, a rod 122 rotating at a point between its ends, freely around the hinge 124 and a mass 123 attached to the end of the rod 122. The bar 121 is integral with the rigid structure 1 16 and located near the the stem 1 18. The second end of the rod 122 is connected to the hinge 120 connected to the rod 1 18.

FIG. 10 is a diagrammatic view from above of all the sectors that make up the counter-skeleton according to the invention and described in FIG. 8. The sectors are grouped in as many bands as the glass has sides (four bands B1, B2 , B3 and B4), each band corresponding to one side of the glass, the ends of the strips not being connected to their neighboring band. For reasons of simplification, only the different sectors (S1, S2, S3, S4, S5, etc.), their axes of rotation (A1, A2, A3, A4, etc.) and the outer periphery of the glass 130 have been represented. The sectors positioned at the ends of each band (as for example the sectors S1, S4 and S5) are not connected to the neighboring sector belonging to an immediately adjacent band. They are slightly shorter in order to allow free movement around their horizontal axis without interference with neighboring sectors belonging to an adjacent band. A means described in Figures 1 1 to 13, but not shown here, limits the downward movement of the sectors at the ends of the strips. Thus, the sectors at the ends do not interfere with the glass during the loading and unloading of the back-skeleton. FIG. 11 shows different representations of the ends of two adjacent sectors of a sector backbone such as the sectors S3 and S4 of FIG. 8 intended to be connected by a hinge. Figure 11 (a) shows the end of a sector, such as sector S3 of Figure 8a) in front view, from above and from the side. Figure 11 (b) is similar to Figure 11 (a) but represents the adjacent sector, such as sector S4 of Figure 8a). FIG. 11 (c) represents the set of two ends of sectors arranged as articulated, such as the sectors S3 and S4 of FIGS. 8a) and 8b) in front view, from above as well as three vertical sections, two of which are located in the vertical plane passing through the axis of articulation between sectors S3 and S4. To form the articulation, a rod (not shown) is passed through the hole 140, the axis of said rod corresponding to the axis 141. FIG. 11 shows that a suitable cutout combined with a local embossing of the sectors in the zone of their articulation makes it possible to obtain a face turned downwards of constant width all along the strip, without doubling the thickness at level of the joints, which would take place if the sectors, kept entirely flat, were simply juxtaposed. Indeed, the contact tracks with the glass of the two sectors are aligned in top view. Each sector S3 and S4 is composed of a sheet. Their cutting is symmetrical and is shown in front view in Figures 1 1 a) and 1 1 b). A hole 140 of axis 141 is provided at their end to pass the axis of the joint. The end 142 of the sector S3 is cut into the shape of a half-ring around the hole 140. Moreover, an embossing in the form of a disk of diameter greater than the half-ring 142 and of axis 141 makes it possible to form a boss. half a thickness of component sheet S3 or S4. The deformations 143 by embossing the sheets are visible in the views from above and from the side and are shown schematically in fine lines 144 in the front views. By this boss, the zone of juxtaposition of a sector is, in top view, offset with respect to its slice facing downwards. This boss provides a space 150 in which the area of the joint of a neighboring sector can be placed to form the joint. Thus the bosses of two sectors intended to be connected together by a joint are complementary and allow the local juxtaposition of the two sectors of the joint without thickening of the slice facing down the set of two sectors. The set of two assembled sectors is only thicker locally at the juxtaposition zones of the sectors to form the joint. These juxtaposition zones are juxtaposed in a direction perpendicular to the axis of the joint, which passes through the juxtaposition zones of the two sectors. The slices facing downwards from the two sectors connected to each other by a hinge are aligned in plan view. Two notches 145 and 146 are cut in the sheet so as not to cause edge effects that could disturb the rotational movement of the two sectors S3 and S4 relative to each other. Finally, a notch 147 is made in the lower part of each sector in order to form a housing for maintaining a fibrous material coating the lower edge of the sectors. Two projections 148 and 149, one (148) in the upper part of each sector and the other (149) in the lower part of each sector are cut along a line which passes through the axis of rotation 141 and which forms a angle Θ with the vertical. This angle is present both to allow and limit the rotation of the two sectors relative to each other. In particular, the projecting portions 149 opposite the two adjacent sectors can form abutments while meeting, which makes it possible to limit the downward movement of the sectors situated at the ends of the strips, especially when the back-skeleton is removed from the device.

FIG. 12 shows in front view two adjacent sectors of a sector backbone of identical shape to sectors S3 and S4 of FIG. These two sectors are centered along a common axis. Figure 12a shows the two sectors S3 and S4, each moving upwards while the axis of their joint joint remained in a lower position. In contrast, Figure 12b shows the two sectors S3 and S4, each moving downward while the axis of their joint joint remained in a higher position. The objective of FIG. 12 is to show that the appropriate cutting of the ends of sectors S3 and S4 makes it possible to limit the relative angular displacement of S3 and S4. The maximum angle that can form the sectors between them is limited by the parts 188 and 189 which act as stops. This angle is twice the angle Θ of Figure 1 1. The notches 187 allow to fix a fibrous material covering the lower edge of the sectors. In fact, FIG. 12b shows the two sectors in the closed position at the bottom and it can be seen that the space 190 between the notches 187 remains sufficient to let the fibrous material pass. The projecting portions 189 facing the sectors S3 and S4 may form abutments when they meet (FIG. 12b), which makes it possible to limit the downward movement of the sectors situated at the ends of the strips, especially when the backskeleton is removed from the device.

Fig. 13 shows a simple alternative to making sector ends of backbone sectors. Figure 12a shows the end of a sector, such as sector S3 of Figure 8a, in front view, from above and from side. Figure 12b shows the adjacent sector, such as sector S4 of Figure 8a, to be hingedly connected with the sector of Figure 13a. There is a half-ring 162 surrounding a hole 160 of axis 161 for these two sectors, the axis 161 being that of the joint. The end of the sectors consists roughly of 3 tabs 171, 172 and 173. The upper tab 171 consists of a projecting portion 168 which limits the closure of the two sectors S3 and S4 as already explained for the sectors of the This projecting portion 168 forms an angle Θ with the vertical. The tabs 171 and 172 on the one hand and 172 and 173 on the other hand are respectively separated by two reentrant cuts 175 and 176 which essentially allow to perform a simple folding of the central tongue 172 rather than a circular embossing such as that presented on Figure 1 1. Such folding is easier to achieve than embossing. The deformations of the central tongue 172 are visible in the views from above and are shown schematically in fine lines 164 in the front views. The tongue 172 includes the juxtaposition zone of the joint. The offset of the tab 172 induced by the deformations 164 provides a space 180 useful for the placement of the juxtaposition zone of the neighboring sector to form the axis articulation 161. The low tab 173 consists of a projecting portion 169 which allows to limit the closure of the two sectors S3 and S4 by abutting. This projecting portion 169 forms an angle Θ with the vertical. Finally, a notch 167 in the lower part of each sector provides space for the passage of the fibrous material coating the lower edge of the sectors.

Figure 14 shows in section a schematic view of a backbone 205 comprising laterally retractable strips. For simplicity, only one side 205 of the back-skeleton has been shown, and this seen in the direction of its length. The glass rests with its lower main surface 201 on the skeleton 202, which comprises a metal strip 203, a slice of which is directed upwards. The counter-skeleton comprises as a metallic bar a vertical plate 214 and a horizontal plate 215. Both skeleton and counter-skeleton are provided with a refractory fibrous material (not shown) for contacting the glass. The backbone 205 is secured to a U-shaped structure returned 208. The latter is connected to a foot 206 itself secured to the structure 207 of the skeleton 202 via a substantially horizontal axis pivot connection 209. During the bending, the counter-skeleton touches the upper main surface of the glass 210. The pivot connection makes it possible to retract the entire 'counter-skeleton +'"U" structure once the bending of the glass is done, which allows to easily clear the curved glass. The assembly 'back-skeleton + structure' U 'is shown in the retracted position in dashed line 212. The position of the axis of rotation 209 of the structure of the back-skeleton, both high enough and away from the edge glass 21 1, which allows the back-skeleton to deviate from the glass by a rotational movement (arrow 213) causing it both upwards but also laterally. The retraction system is made by a trigger system not described here but may for example pass through the side walls of the oven or the oven floor. The retraction performed during cooling makes it possible to obtain good glass edge stresses. Moreover, the retraction also makes it possible to remove the skeleton glass by a conventional harrow system pushing it from below, and to easily load it in the oven inlet, using a robot for example. The counter-skeleton is set up again by a reverse rotary motion once the next glass is loaded onto the skeleton.

Claims

A device for gravity bending a glass sheet or a stack of glass sheets comprising a plurality of sides said glass, comprising a skeleton for supporting the glass in its peripheral area by a contact track, said contact track comprising concave curvatures in each of the sides of said skeleton, and a counter-skeleton able to come into contact with the glass in the middle zone of at least one side of the peripheral zone of the upper main face of the glass.

Device according to the preceding claim, characterized in that it gives the glass concave shapes seen from above in its central zone and in each of its sides, in particular in the middle of its sides.

Device according to one of the preceding claims, characterized in that the back-skeleton comes into contact in the middle zone of all sides, generally four sides, of the peripheral zone of the upper main face of the glass.

Device according to one of the preceding claims, characterized in that the middle zone of at least one side comprises 5 cm on either side of the middle, or even 10 cm on either side of the middle, or the 20 cm on either side of the middle, parallel to the edge of the glass and in the peripheral zone.

Device according to one of the preceding claims, characterized in that the counter-skeleton comes into contact with the glass with a refractory fibrous material. Device according to the preceding claim, characterized in that the fibrous material is able to compress under the effect of the force of gravity acting on the back-skeleton.

Device according to the preceding claim, characterized in that a counterweight system connected to the back-skeleton reduces the pressure force of the back-skeleton on the glass.

Device according to one of the preceding claims, characterized in that the skeleton comprises a metal strip whose slice is directed upwards, said slice being covered with a refractory fibrous material forming the contact track for the glass, the counter skeleton comprises a metal bar, the device comprising means for imposing a given minimum distance Dm between the metal strip of the skeleton and the metal bar of the back-skeleton.

Device according to the preceding claim, characterized in that the means of imposing Dm comprises an abutment member, said abutment, integral with the metal strip of the skeleton and on which a counterstay integral with the metal bar of the back-skeleton is able to rest .

10. Device according to one of the two preceding claims, characterized in that the means of imposing Dm is adjustable.

1 1. Device according to one of the preceding claims, characterized in that the counter-skeleton comprises a metal strip of the metal strip type, a slice of which is turned downwards, comprising a plurality of sectors connected together by articulations, each hinge comprising a pivot connection to the substantially horizontal axis connecting two sectors together.

12. Device according to the preceding claim, characterized in that the ends of two sectors are interconnected by a joint, these ends each comprising a juxtaposition zone, these juxtaposition zones being juxtaposed in a direction perpendicular to the axis of the articulation, said axis passing through the zones of juxtaposition of the two sectors.

13. Device according to the preceding claim, characterized in that the downwardly slices of two sectors interconnected by a hinge, are aligned in plan view, the juxtaposition zone of at least one of the two sectors being, in top view, offset from its slice facing downwards, so as to provide a space occupied by the juxtaposition zone of the other sector.

14. Device according to one of claims 1 1 to 13, characterized in that the sectors are grouped in as many bands that the glass has sides, each band corresponding to one side of the glass, the ends of the strips not being connected to their neighboring bands.

15. Device according to one of claims 1 1 to 14, characterized in that the skeleton comprises a metal strip having a slice is directed upwards and a plurality of abutments connected to the metal strip and placed vis-à-vis counter-skeletal joints, counterbutts being connected to the counter-skeleton with respect to the stops, in particular to the rods forming axes of the articulations, to come to bear on the abutments, so that a minimum distance Dm between the metal strip the skeleton and the metal bar of the back-skeleton can be imposed at each sector when the abutments rest on the stops.

16. Device according to one of the preceding claims, characterized in that it comprises a progressive system adapted to change progressively during bending the distance between the skeleton and the backbone.

17. Device according to one of the preceding claims, characterized in that the back-skeleton comprises a metal bar and a structural element disposed above the metal bar, the structural element and the metal bar being interconnected by a plurality of adjustable spacers for locally adjusting the distance between the structural member and the metal bar.

18. Device according to one of the preceding claims, characterized in that the back-skeleton is removable.

19. Device according to one of the preceding claims, characterized in that the back-skeleton comprises laterally retractable strips.

20. Device according to one of the preceding claims, characterized in that it comprises means allowing the skeleton and the back-skeleton to move towards or away by a relative vertical movement without relative horizontal displacement of the one by report to the other.

21. Device according to one of the preceding claims, characterized in that it comprises an oven and a conveying means capable of moving horizontally together the skeleton and the back-skeleton in the oven while they are opposite the one of the other, and means of vertical translation allowing the skeleton and the back-skeleton to move towards or away from each other by relative vertical movement during their horizontal displacement and without relative horizontal displacement of the relative to the other.

22. Device according to one of the preceding claims, characterized in that the back-skeleton is capable of exerting a weight on the glass per linear meter of back-skeleton less than 2 kg / m and preferably less than 1 kg / m and preferably greater than 0.1 kg / m.

23. A method of bending a glass sheet or a stack of glass sheets comprising a plurality of sides, said glass, where appropriate by the device of one of the preceding claims, comprising bending the glass by gravity on a skeleton supporting the glass in its peripheral zone by a contact track, said contact track comprising concave curvatures in each of the sides of said skeleton, a counter-skeleton coming into contact with the glass in the middle zone of at least one of the sides of the glass in the peripheral zone of its upper main face.

24. Method according to the preceding claim, characterized in that the glass takes a concave shape seen from above in its central zone and in each of its sides, especially in the middle of its sides.

25. Method according to one of the preceding method claims, characterized in that the back-skeleton comes into contact with the middle zone of all sides of the glass, generally four sides, of the peripheral zone of the upper main face of the glass. glass.

26. Method according to one of the preceding process claims, characterized in that the back-skeleton comes into contact with the glass by a refractory fibrous material.

27. Method according to the preceding claim, characterized in that the refractory fibrous material compresses during the bending under the effect of the gravitational force acting on the backbone.

28. Method according to one of the preceding process claims, characterized in that the skeleton comprises a metal strip having a slice is directed upwards, said slice being covered with a refractory fibrous material forming the contact track for the glass said refractory fibrous material compressing during bending under the effect of the pressure exerted by the underside of the glass.

29. Method according to the preceding claim, the back-skeleton comprising a metal bar whose lower face is coated with refractory fibrous material, the compression of the refractory fibrous material equipping the skeleton and the back-skeleton being limited by a means able to impose a minimum distance Dm between the metal band of the skeleton and the metal bar of the back-skeleton.

30. Method according to one of the preceding method claims, characterized in that the skeleton and the back-skeleton are gradually approaching during the bending.

31. Method according to one of the preceding method claims, characterized in that the peripheral zone is the area between the edge of the glass and a distance from the edge of the glass of 50 mm.

32. Method according to one of the preceding process claims, characterized in that the glass is a stack of glass sheets, in particular a stack comprising a sheet of thickness in the range of 1, 4 to 2.7 mm generally in the range of 1.4 to 2.5 mm and a thickness sheet in the range of 0.4 to 1.6 mm.

33. Method according to one of the preceding process claims, characterized in that the glass is curved at a temperature in the range of 570 to 650 ° C.

34. Method according to one of the preceding process claims, characterized in that the counter-skeleton during bending a weight on the glass per linear meter of back-skeleton less than 2 kg / m and preferably less than 1 kg / m, and preferably greater than 0.1 kg / m.

35. Method according to one of the preceding method claims, characterized in that the skeleton and the back-skeleton are conveyed together in an oven while they are facing each other on the other hand. other glass, the glass being Skeleton contact for more than 10 minutes in the oven and counter-skeleton touching the glass for more than 10 minutes in the oven.