Abstract
A device and a process for the gravity bending of a glass sheet or a stack of glass sheets, referred to as the glass, includes the gravity bending of the glass on a skeleton including a contact rail supporting the glass in the peripheral zone of the lower main face thereof, the contact rail including concave curvatures in each of the sides of the skeleton, a counter-skeleton including a metal bar being present during the bending at a distance d from the edge face or from the peripheral zone of the upper main face of the glass, the peripheral zone of a main face being the zone between the edge of the glass and a distance from the edge of the glass of 50 mm of the main face, d being within the range from 0.1 to 50 mm.
Claims
1. A process for the gravity bending of a glass sheet or a stack of glass sheets, the process comprising the gravity bending of the glass on a skeleton comprising a contact rail supporting the glass in the peripheral zone of the lower main face thereof, said contact rail comprising concave curvatures in each of the sides of said skeleton, a counter-skeleton comprising a metal bar being present during the bending at a distance d from an edge face or from the peripheral zone of the upper main face of the glass, the peripheral zone of a main face being the zone between the edge of the glass and a distance from the edge of the glass of 50 mm of said main face, d being within the range from 0.1 to 50 mm.
2. The process as claimed in claim 1, wherein the process gives the glass concave shapes seen from above in its central zone and in each of its sides, the metal bar being at the distance d at least at the end of bending.
3. The process as claimed in claim 1, wherein the condition regarding the distance d is satisfied in at least one vertical plane perpendicular to the edge of the glass passing through the zone of the middle of at least one side of the glass, said zone of the middle being within the peripheral zone up to 20 cm on either side of the middle of the side.
4. The process as claimed in claim 3, wherein the condition regarding the distance d is satisfied in at least one vertical plane perpendicular to the edge of the glass passing through the zone of the middle of at least one side of the glass, said zone of the middle being within the peripheral zone up to 10 cm on either side of the middle of the side.
5. The process as claimed in claim 1, wherein the condition regarding the distance d is satisfied for any vertical plane passing through the zone of the middle of at least one side of the glass.
6. The process as claimed in claim 1, wherein the glass comprises four sides.
7. The process as claimed in claim 1, wherein d is within the range from 1 mm to 50 mm.
8. The process as claimed in claim 1, wherein the counter-skeleton touches neither the upper main face of the glass nor the edge face thereof at least at the end of bending.
9. The process as claimed in claim 1, wherein the counter-skeleton is covered with thermal insulation on at least one of the faces thereof opposite the glass.
10. The process as claimed in claim 1, wherein the counter-skeleton shields the glass from thermal radiation coming directly from heating elements.
11. The process as claimed in claim 1, wherein the counter-skeleton slows down the temperature rise of the periphery of the glass during the temperature rise phase in preparation for the bending.
12. The process as claimed in claim 1, wherein the glass is a stack of glass sheets.
13. The process as claimed in claim 1, wherein the glass is bent by gravity at a temperature within the range from 570 to 650° C.
14. The process as claimed in claim 1, wherein the counter-skeleton is colder than the periphery of the glass during the bending.
15. The process as claimed in claim 1, wherein the bending is carried out in a furnace, the counter-skeleton being at a temperature below 250° C. on entering the bending furnace.
16. The process as claimed in claim 1, wherein the skeleton and the counter-skeleton are conveyed together into a furnace, the glass being in contact with the skeleton for more than 10 minutes in the furnace.
17. The process as claimed in claim 1, wherein the counter-skeleton does not touch the glass when the glass comes into contact with the entire perimeter of the skeleton.
18. The process as claimed in claim 1, wherein when the glass comes into contact with the entire perimeter of the skeleton, the upper face of the glass is only in contact with the ambient air.
19. A device for the gravity bending of a glass sheet or a stack of glass sheets, the device comprising a skeleton comprising a contact rail for supporting the peripheral zone of the lower main face of the glass, said contact rail comprising concave curvatures in each of the sides of said skeleton, and a counter-skeleton comprising a metal bar, said counter-skeleton being configured so that its metal bar is present at a positive distance d from the peripheral zone of the upper main face of the glass or from the edge face thereof.
20. The device as claimed in claim 19, wherein the device is configured to give the glass concave shapes seen from above in its central zone and in each of its sides, the distance d being complied with at least at the end of bending.
21. The device as claimed in claim 19, wherein the condition regarding the distance d is satisfied in at least one vertical plane perpendicular to the edge of the glass passing through the zone of the middle of at least one side of the glass, said zone of the middle being within the peripheral zone up to 20 cm on either side of the middle of the side.
22. The device as claimed in claim 21, wherein the condition regarding the distance d is satisfied in at least one vertical plane perpendicular to the edge of the glass passing through the zone of the middle of at least one side of the glass, said zone of the middle being within the peripheral zone up to 10 cm on either side of the middle of the side.
23. The device as claimed in claim 19, wherein the condition regarding the distance d is satisfied for any vertical plane passing through the zone of the middle of at least one side of the glass.
24. The device as claimed in claim 19, wherein the glass comprises four sides.
25. The device as claimed in claim 19, wherein the distance d is within the range from 0.1 to 50 mm.
26. The device as claimed in claim 19, wherein the metal bar of the counter-skeleton is at least partially above the skeleton and/or opposite the outer face of the skeleton.
27. The device as claimed in claim 19, wherein the metal bar of the counter-skeleton is at least partially above the level of the centre of the contact rail for the glass of the skeleton.
28. The device as claimed in claim 19, wherein the skeleton comprises a metal strip, one edge face of which is oriented upward, said edge face being covered with a refractory fibrous material forming the contact rail for the glass.
29. The device as claimed in claim 19, wherein the counter-skeleton is removable.
30. The device as claimed in claim 29, wherein the counter-skeleton comprises laterally retractable strips.
31. The device as claimed in claim 19, further comprising a means for imposing the distance d comprising a stop attached to the skeleton and a counter-stop attached to the counter-skeleton, the counter-stop being able to rest on the stop.
32. The device as claimed in claim 19, further comprising a means for adjusting the distance d.
33. The device as claimed in claim 19, wherein the counter-skeleton is covered with thermal insulation on one of the faces thereof opposite the skeleton.
34. The device as claimed in claim 19, wherein the counter-skeleton comprises a tube able to receive a stream of a coolant.
35. The device as claimed in claim 19, further comprising a rigid structural element positioned above the metal bar of the counter-skeleton, the structural element and the metal bar being connected together by a plurality of spacers preferably that can be adjusted in terms of their length.
36. The device as claimed in claim 19, further comprising a furnace and a conveyor able to horizontally move the skeleton and the counter-skeleton together through the furnace and with no relative horizontal movement of one with respect to the other.
37. The device as claimed in claim 36, further comprising a plurality of skeleton/counter-skeleton assemblies each loaded with glass and circulating one behind the other through the furnace.
Description
[0044] The figures described below are not to scale.
[0045] FIG. 1 represents, in cross section and in a vertical plane perpendicular to the edge of the glass and of the skeleton, a device according to the invention comprising a skeleton 300 and a counter-skeleton 301. A stack of two glass sheets 310 rests via its periphery on the skeleton. The two tools each have an annular shape, the central zone of which is located to the left of their representation in the figure. The skeleton 300 comprises a metal strip 302 of width 303, the upper edge face 304 of which is covered with a refractory fibrous material 305 forming a contact rail of width 306 for the glass 310. The counter-skeleton comprises a metal bar 301 placed above the glass and having no contact therewith. The distance d between the metal bar of the counter-skeleton and the glass is within the range from 0.1 to 50 mm. This distance is that between the closest points of the counter-skeleton and of the glass. The metal bar of the counter-skeleton is above the level (horizontal line H in the figure) of the center 307 (at mid-width) of the glass-contacting rail of the skeleton.
[0046] FIG. 2 represents, in cross section and in a vertical plane perpendicular to the edge of the glass and of the skeleton, a device according to the invention comprising a skeleton 333, one edge face 335 of which is oriented upward, and a counter-skeleton 331. The counter-skeleton is located relatively inwardly with respect to the glass, but it is at a distance d of less than 50 mm from the peripheral zone 332 of the upper face of the glass 334.
[0047] FIG. 3 represents, in cross section and in a vertical plane perpendicular to the edge of the glass and of the skeleton, a device according to the invention comprising a skeleton 320 and a counter-skeleton 321. A stop 327 is fastened to the metal strip 322 of the skeleton. The edge face of this metal strip oriented upward is covered with a refractory fibrous material 323. The counter-skeleton comprises a metal bar 324 not coated with fibrous material, and that does not come into contact with the glass. A counter-stop 326 is connected to the metal bar 324 and may rest on the stop 327, blocking the progression of the counter-skeleton toward the skeleton and preventing contact of the counter-skeleton with the glass.
[0048] FIG. 4 represents various possible configurations of a device according to the invention comprising a skeleton 401 and a radiative counter-skeleton 402, i.e. that has no contact with the glass 400 (here a stack of two glass sheets), but that stabilizes the periphery of the glass during the bending. This view is taken in a vertical plane perpendicular to the edge of the glass and of the skeleton. The following variants are distinguished: [0049] a) The counter-skeleton is a T-shaped metal bar, the vertical plate of the T is aligned with the strip of the skeleton. The horizontal bar helps to form a shield between the resistors of the furnace and the periphery of the glass. [0050] b) The T-shaped counter-skeleton 402 from a) is covered on the upper portion thereof with an insulating material 403 which slows down the warming of the metal bar of the counter-skeleton. [0051] c) The counter-skeleton 402 comprises a bar 404 of horizontal strip type forming a shield between the heating resistors and the glass, said bar being covered with an insulating material 403. [0052] d) The counter-skeleton is L-shaped and is opposite the edge face 411 of the glass and opposite the outer face 410 of the skeleton. The counter-skeleton 402 is neither above the skeleton nor above the glass. However, most of the metal bar 412 of the counter-skeleton is above the level H of the central line of the contact rail of the skeleton. Owing to this shape and arrangement, the counter-skeleton forms an effective shield for the glass against the radiation of the furnace resistors coming from lateral directions. An insulating material 413 covers the faces of the counter-skeleton on the opposite side to the glass. This arrangement of the counter-skeleton frees up the space above the glass, which is advantageous for the loading and unloading of the glass. [0053] e) The counter-skeleton comprises a T-shaped metal bar 405, the upper portion of which is covered with an insulating material 403. Metal tubes 406 through which a coolant travels make it possible to cool the counter-skeleton. [0054] f) The counter-skeleton comprises a metal bar 407 of tube type with a rectangular cross section. This bar is hollow, and a coolant may travel through the interior 409 thereof in order to cool it. Its upper portion is covered with an insulating material 408.
[0055] FIG. 5 represents a device according to the invention at the moment when a counter-skeleton 8 (shaded in the figure) is in the process of being positioned above the glass, the latter not being represented in the figure for the sake of clarity. A frame 1 is seen to which the skeleton 2 is fastened by means of lugs 3 and 4. The glass (not represented) is placed on the skeleton 2. Operators hold the counter-skeleton 8 by handles 6. These handles are fastened to a frame 7 to which the counter-skeleton 8 is fastened by means of lugs 9 and 10. The exact positioning of the counter-skeleton is ensured by guiding by means of four positioning columns (11 and 12 in the foreground), one at each corner. These columns are attached to the frame 1. Lugs 13 and 14 fastened to the frame 7 of the counter-skeleton that each comprise an orifice are slipped onto the columns 11 and 12 via their orifices. Jack stands 15 and 16 are part of the means for imposing a non-zero distance d between the glass and the counter-skeleton. They are each provided with bearing surfaces 17 and 18 that are height-adjustable by means of screws 19 and 20. The frame 7 connected to the counter-skeleton comprises lugs 21 and 22 that will rest on the bearing surfaces 17 and 18 when the operators have finished depositing the counter-skeleton. The weight of the counter-skeleton therefore rests on the bearing surfaces 17 and 18, the height of these being adjusted so that the spacing between the counter-skeleton and the glass is the chosen spacing. The bearing surfaces 17 and 18 form stops attached to the skeleton and the lugs 21 and 22 are counter-stops attached to the counter-skeleton. In this example, the counter-skeleton is present without interruption opposite the whole of the peripheral zone of the glass. It is made of a single part and, once positioned, does not touch the glass anywhere at least at the end of bending. The skeleton and the counter-skeleton here form an integrated assembly able to be moved horizontally through a furnace. The four positioning columns (11 and 12 in the foreground) are part of the means for vertical translation enabling the skeleton and the counter-skeleton to move closer together or further apart via a relative vertical movement and with no relative horizontal movement of one with respect to the other. In this way, the skeleton and the counter-skeleton remain opposite one another (on either side of the glass) during the horizontal movement of the skeleton/counter-skeleton assembly through the furnace.
[0056] FIG. 6 represents, in top view, a rigid structural element 50 above a portion 51 of the counter-skeleton comprising a vertical plate (not visible) that is just above the glass and that acts as a metal bar. The visible portion 51 is a horizontal plate 57 that is just above the vertical plate and to which it is connected. The structural element 50 is made of a metal square and has the shape of a rectangular frame in top view. It comprises a plurality of extensions 52 connected to its inner or outer vertical faces, said extensions being, in top view, above zones 53 for adjusting the distance d with the glass. These adjustments are carried out by jack screws 54 here passing through the rigid structural element 50.
[0057] FIG. 7 shows the counter-skeleton from FIG. 6 along the cross section AA′ in a) and the side view along the direction B in b). The metal square of the rigid structural element 50 is seen again, an extension 52 being welded to an outer vertical face of said square. This extension is also made of a metal square. The vertical plate 55 (metal bar) is indirectly connected to the rigid structural element 50 so that it is attached thereto. The lower edge 56 of this vertical plate 55 is just above the glass and it is its distance d from the glass that should be adjusted. This adjustment is carried out by the jack screw 54 by screwing or unscrewing nuts 58 and 59. The vertical plate 55 is welded via its upper edge to a 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, the pivoting of which is adjustable and can be locked in a given position by means of the nuts 61 and 62. The adjustment of this pivoting makes it possible to adjust the local inclination of the edge 56 so that this is indeed parallel to the skeleton and so that the distance between the counter-skeleton and the glass is indeed constant for the entire periphery of the glass.
[0058] FIG. 8 represents a counter-skeleton according to the invention seen entirely in a), one portion being enlarged in b). A structural element 75 is produced from segments of metal squares welded together. Seen from above, this structural element has a shape similar to that of the skeleton and therefore of the glass to be bent. Lateral extensions 76 have been welded to inner vertical faces of the structural element. Jack screws for adjusting the gap pass vertically through these extensions. The adjustment of a jack screw makes it possible to locally adjust the height level of the lower edge 77 of a vertical plate 78 acting as metal bar. This vertical plate is attached to a horizontal plate 79 by a system of angle 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 for the purpose of adjusting the height level of the edge 77. Handles 82 are also seen enabling operators to handle this counter-skeleton and to place it above the glass. The correct lateral positioning of the counter-skeleton is ensured owing to focusing means which are not represented and which may be of the type of the jack stands 11 from FIG. 5.
[0059] FIG. 9 represents, in cross section, a schematic view of a counter-skeleton 205 comprising laterally retractable strips. For simplification, a single side of the counter-skeleton has been represented, seen in the direction of its length. The glass rests via its lower main face 201 on the skeleton 202, which comprises a metal strip 203, one edge face of which is oriented upward. The counter-skeleton comprises as metal bar a vertical plate 214 and a horizontal plate 215. The skeleton and counter-skeleton are both provided with a refractory fibrous material (not represented) in order to come into contact with the glass. The counter-skeleton 205 is attached to an inverted U-shaped structure 208. The latter is connected to a base 206 itself attached to the structure 207 of the skeleton 202 via a pivot connection having a substantially horizontal axis 209. During the bending, the counter-skeleton is kept above the upper main surface of the glass 210, without touching it at least at the end of bending. The pivot connection makes it possible to retract the “counter-skeleton+U-shaped structure” assembly once the bending of the glass has been carried out, which makes it possible to easily remove the bent glass. The “counter-skeleton+U-shaped structure” assembly is represented in the retracted position by dotted lines 212. The position of the axis of rotation 209 of the structure of the counter-skeleton, is both quite high and far away from the edge of the glass 211, which enables the counter-skeleton to move away from the glass via a rotational movement (arrow 213) driving it both upward and also laterally. The retraction system is achieved by an initiation system, not described here but that may for example pass through the lateral walls of the furnace or else the hearth of the furnace. The retraction carried out during cooling makes it possible to obtain good edge stresses of the glass. Furthermore, the retraction also makes it possible to remove the glass from the skeleton by a conventional batten system pushing from underneath, and to easily load it at the furnace entry, with the aid of a robot for example. The counter-skeleton is again put in place by a reverse rotational movement once the next glass is loaded on the skeleton. It is seen that the contact rail of the skeleton is indeed concave over the entire length of the side visible in the figure, parallel to its inner and outer contours, this concavity being in the plane of the figure.
[0060] FIG. 10 represents a motor vehicle glazing 450, in top view, over its concave main face, surmounted by retractable strips (451, 452, 453, 454) of the counter-skeleton as explained for FIG. 9. These retractable strips are above the border of the glass and may be retracted laterally outward from the glass (according to the arrows) as explained for FIG. 9, so as to no longer be above the upper face of the glass.
[0061] FIG. 11 represents a motor vehicle glazing of the windshield type, seen from above, and laid on a horizontal plane, concave face turned downward. It comprises four sides, two transverse sides 350 and 351 and two longitudinal sides 352 and 353. One side joins another side via a corner, the edge of which has radii of curvature R (viewed perpendicular to the surface of the glass and in each corner) that are very low relative to the radii of curvature of the edges toward the middles of the sides. This glazing is symmetrical with respect to the vertical plane of symmetry PS. This plane PS passes through the middles 354 and 355 of the transverse sides. This glazing rests on four points 356, 357, 358, 359 that are in the corners. The segments 360, 361, 362 and 363 connecting these four points have been drawn as dotted lines. These are the segments closest to the edges. One segment is associated with one edge. Each of these segments has a middle 364, 365, 366, 367. For each segment, there is a plane (368, 369, 370, 371) perpendicular to the segment and passing through the middle thereof. Each of these planes intersects with its associated edge at a point 372, 355, 373, 354 which is the middle thereof. The glazing is concave (in this figure, the concave face is turned downward) at least at the middle points of the edges 372, 355, 373, 354 and in all the hatched zones on either side of these middle points, said concavity being considered parallel to the outer edge of the glazing. The same is true for the skeleton that has supported this glass and for the zones of the skeleton corresponding to the zones of the middles of the sides of the glass, said concavity being considered parallel to the (inner or outer) contours of the skeleton and seen from above during bending. The dotted line 376 is 50 mm from the edge of the glass and forms the limit of the peripheral zone, which is between the edge of the glass and this line. The zone of the middle of the side 353 of the peripheral zone of the upper main face of the glass is the hatched zone on the left. This zone surrounds the middle point 373. The hatched zone is within the peripheral zone between the points 374 and 375 on the edge. Between these points 374 and 375, there is a vertical plane 377 perpendicular to the edge of the glass in which the condition regarding the distance d is satisfied. The points 374 and 375 are each 20 cm, or even 10 cm, or even 5 cm away from the point 373. The counter-skeleton is opposite this zone (above the glass or facing the edge face thereof) at least in this zone and if necessary continuously above the entire length of this zone parallel to the edge of the glass, i.e. with no discontinuity between the points 374 and 375, but not necessarily over the entire width of this zone.
