GRAVITY BENDING ON A DOUBLE SUPPORT

Abstract

A device for the gravity-bending of a glass sheet, includes a longitudinal roughing mold including two longitudinal roughing supports, and a finishing frame including two lateral finishing supports and two longitudinal finishing supports, the supports forming shaping rails. The distance between middles of the longitudinal finishing supports is shorter than that between middles of the lateral finishing supports. The roughing mold and finishing frame are movable vertically relative to each other during bending to switch from a rough-bending to a final-bending configuration. In the rough-bending configuration, the shaping rails of the longitudinal roughing supports are higher up than those of the longitudinal finishing support. In the final-bending configuration, the shaping rails of the longitudinal finishing supports are higher up than those of the longitudinal roughing supports. The shaping rails of the lateral finishing supports are the only ones under lateral edges of the glass in the roughing and final-bending configurations.

Claims

1. A device for the gravity-bending of a sheet of glass, comprising a longitudinal roughing mold comprising two longitudinal roughing supports, and a finishing frame comprising two lateral finishing supports and two longitudinal finishing supports, said supports forming shaping rails, a distance between middles of the longitudinal finishing supports being shorter than a distance between middles of the lateral finishing supports, the roughing mold or the finishing frame being able to be moved vertically one relative to the other during bending in order to switch from a rough-bending configuration to a final-bending configuration, wherein, in the rough-bending configuration, the shaping rails of the longitudinal roughing supports are higher up than the shaping rails of the longitudinal finishing supports, and wherein, in the final-bending configuration, the shaping rails of the longitudinal finishing supports are higher up than the shaping rails of the longitudinal rough-molding supports, and wherein the shaping rails of the lateral finishing supports are the only shaping rails under lateral edges of the glass in the rough-bending configuration and in the final-bending configuration.

2. The device as claimed in claim 1, wherein the roughing mold is circumscribed by the finishing frame when viewed from above.

3. A method for the gravity-bending of a sheet of glass at a deformation temperature using the device of claim 1, the sheet of glass comprising two lateral edges and two longitudinal edges, a distance between the middles of the longitudinal edges of the sheet being shorter than a distance between the middles of the lateral edges of the sheet, the method comprising supporting the sheet by the device in the rough-bending configuration and, in order to undergo rough-bending, the longitudinal edges of the sheet being bent by contact with the shaping rails of the longitudinal roughing supports, and switching the device to the final-bending configuration in order to make the sheet undergo a final bending, the sheet then being bent in contact with the shaping rails of the longitudinal finishing supports and in contact with the shaping rails of the lateral finishing supports.

4. The method as claimed in claim 3, wherein during the rough bending, the longitudinal edges of the sheet fully follow the shaping rails of the longitudinal roughing supports.

5. The method as claimed in claim 3, wherein during the rough bending, the lateral edges of the sheet come at least partially into contact with the shaping rails of the lateral finishing supports.

6. The method as claimed in claim 3, wherein during the rough bending, the middles of the lateral edges of the sheet do not come into contact with the shaping rails of the lateral finishing supports.

7. The method as claimed in claim 3, wherein, at the end of the bending, the edges of the sheet fully follow the shaping rails of the longitudinal finishing supports and the shaping rails of the lateral finishing supports.

8. The method as claimed in claim 3, wherein 4 to 10 mm of glass at the periphery of the sheet are not supported on the finishing frame at the end of bending.

9. The method as claimed in claim 3, wherein a temperature at the middle of each of the lateral edges of the sheet of glass remains below 615 C.

10. The method as claimed in claim 3, wherein at the end of bending, a depth of lateral bending is between 5 and 20 mm.

11. The method as claimed in claim 3, wherein at the end of bending, a depth of longitudinal bending is between 40 and 150 mm.

12. The method as claimed in claim 3, wherein a ratio between a developed distance between the middles of the lateral edges of the sheet to a developed distance between the middles of the longitudinal edges of the sheet ranges from 1.3 to 2.

13. The method as claimed in claim 3, wherein a plurality of superposed sheets of glass are bent simultaneously.

14. (canceled)

15. (canceled)

16. (canceled)

17. The method as claimed in claim 9, wherein the temperature at the middle of each of the lateral edges of the sheet of glass remains below 610 C.

18. The method as claimed in claim 10, wherein at the end of bending, the depth of lateral bending is between 8 and 17 mm.

19. The method as claimed in claim 13, wherein the plurality of superposed sheets of glass is two.

20. (canceled)

Description

[0027] FIG. 1 depicts a motor vehicle windshield 1 made of laminated glass. It has been bent using the method according to the invention. This glazing comprises a top longitudinal edge 2, a bottom longitudinal edge 3, and two lateral edges 4 and 5. A peripheral layer of black enamel darkens the border of the glazing. The width of this layer of enamel is reduced (under 15 mm) along the lateral edges and notably at the middles 6 and 7 of these lateral edges 4 and 5. The width of the layer of enamel is greater (more than 15 mm) along the longitudinal edges 2 and 3.

[0028] FIG. 2 depicts a bending device 20 according to the invention. This device comprises a roughing mold consisting of two longitudinal roughing supports 21 and 22 and a finishing frame comprising two longitudinal finishing supports 23 and 24 and two lateral finishing supports 25 and 26. This device is shown at the start of bending, with the roughing mold in the raised position relative to the finishing frame. The tabs 27 and 28 fixed to the ends of the longitudinal roughing supports 21 and 22 orthogonally with respect to the latter are intended to give the latter rigidity and do not serve to support the glass. Two other equivalent tabs exist at the non-visible other two ends of the longitudinal roughing supports 21 and 22. In the configuration shown in FIG. 2, if a sheet of glass is being bent on the device, after being heated to its deformation temperature the glass comes into contact with the pair of longitudinal roughing supports 21 and 22 and, if appropriate, with the two lateral finishing supports 25 and 26. In general, the roughing mold is retracted downward before the glass touches the entirety of the lateral finishing supports.

[0029] FIG. 3 depicts the same support 20 of FIG. 2, except that it is in the configuration for the end of bending. The roughing mold has thus been retracted downward and the glass is therefore resting on the lateral finishing supports and the longitudinal finishing supports 23 and 24.

[0030] FIG. 4 depicts what is meant by the depth of lateral bending and depth of longitudinal bending on a glazing 40 having two lateral edges 41 and 42 and two longitudinal edges 43 and 44. The lateral bending depth Pl is the greatest length of segment between the lateral edge of the glazing and the straight line 46 connecting the two ends 47 and 48 of the lateral edge in question, said segment being orthogonal to said straight line 46. In FIG. 4, it is the point 45 that is furthest from the straight line 46. The depth of longitudinal bending PL is the greatest length of segment between the longitudinal edge and the straight line 50 connecting the two ends 47 and 49 of the longitudinal edge in question, said segment being orthogonal to said straight line 50. In FIG. 4, it is the point 51 that is furthest from the straight line 50. The longitudinal bending corresponds to the formation of curvatures between the lateral edge 41 and the lateral edge 42, as is the case with the curvature 52. The lateral bending corresponds to the formation of curvatures between the longitudinal edge 43 and the longitudinal edge 44 as is the case with the curvature 53.

[0031] FIG. 5 depicts two superposed sheets of glass 51 and 52 on the device according to the invention in the final-bending position and in a view from the side, which means to say that the plane of the figure passes through the middle of the longitudinal supports. These two sheets are intended to be assembled into a laminated glazing. The bottom sheet of glass is in contact with the shaping rail of the longitudinal finishing support 53. The longitudinal roughing support 54 has been retracted downward so that its shaping rail 55 is no longer touching the glass. The sheet protrudes beyond the finishing frame by the distance 56 corresponding to the 4 to 10 mm of glass at the periphery of the sheet not supported on the finishing frame at the end of bending. The distance 58 is the distance that can have the layer of enamel in the final glazing in order to cover all of the peripheral zone that has been in contact with the supports 53 and 54, which are separated from one another by a clearance 57.

[0032] FIG. 6 depicts two superposed sheets of glass 61 and 62 on the device according to the invention in a longitudinal view which means to say that the plane of the figure passes through the middle of the lateral supports. At a), the sheets are at the end of rough-bending and, in the instance depicted, the glass has not yet touched the shaping rail in the middle of the lateral support 64. At b) the sheets are at the end of final bending and the glass has conformed to the shaping rail 63 of the lateral support 64. In a) as in b) there is no other support shaping rail closer to the glass than that 63 of the lateral finishing support 64. It may therefore be stated that the shaping rails of the lateral finishing supports are the shaping rails highest up under the middles of the lateral edges of the glass in the rough-bending configuration and in the final-bending configuration. Because of the use of just one lateral finishing support 64, the layer of enamel can encroach over a distance 65 from the lateral edge of the final glazing that is shorter than the distance of enamel from the longitudinal edge of the final glazing (denoted 58 in FIG. 5).