Device and method for press bending glass panes

Abstract

A device for bending glass panes, includes a lower press-bending mould with a frame-shaped contact surface, an upper press-bending mould arranged opposite the contact surface, wherein the lower press-bending mould and the upper press-bending mould are suitable for reshaping a glass pane situated therebetween by pressing, wherein the side edge of the glass pane rests on the contact surface along a contact line, wherein during pressing, the contact line migrates from a first contact line all the way to a pressing line, and wherein the contact surface between the first contact line and the pressing line is convexly curved.

Claims

1. Device for bending glass panes, comprising a lower press-bending mould with a frame-shaped contact surface, an upper press-bending mould arranged opposite the contact surface, wherein the lower press-bending mould and the upper press-bending mould are suitable for reshaping a glass pane situated therebetween by pressing, wherein a side edge of the glass pane rests on the contact surface along a contact line, wherein during pressing, the contact line migrates from a first contact line all the way to a pressing line, wherein the contact surface between the first contact line and the pressing line is convexly curved, and wherein a curvature of the contact surface between the first contact line and the pressing line is selected to prevent direct contact between the contact surface and a lower surface of the glass pane during said pressing when the contact line migrates from the first contact line all the way to the pressing line.

2. The device according to claim 1, wherein a clearance angle between the contact surface and the glass pane at the pressing line is at least 3°.

3. The device according to claim 2, wherein the clearance angle is at least 5°.

4. The device according to claim 1, wherein a radius of curvature of the curved contact surface is at most 750 mm.

5. The device according to claim 4, wherein the radius of curvature of the curved contact surface is at most 500 mm.

6. The device according to claim 1, wherein a radius of curvature of the curved contact surface increases, at least in sections, in a direction from the first contact line to the pressing line.

7. The device according to claim 1, wherein the contact surface of the lower press-bending mould and a contact surface of the upper press-bending mould are not covered with a fabric.

8. The device according to claim 1, wherein a distance between the first contact line and the pressing line is from 2 cm to 50 cm.

9. The device according to claim 8, wherein the distance between the first contact line and the pressing line is from 5 cm to 30 cm.

10. The device according to claim 1, wherein the upper press-bending mould has a full-surface active surface.

11. The device according to claim 1, comprising a gravity bending mould with a frame-shaped support surface and which is suitable for transferring the glass pane from the gravity bending mould to the lower press-bending mould by vertical displacement of the gravity bending mould and the lower press-bending mould relative to one another.

12. The device according to claim 11, wherein the support surface of the gravity bending mould has a planar and horizontal outer region, an inclined, planar, or curved central region, and a convexly curved inner region, wherein the inner region is more strongly curved than the central region.

13. Method for bending glass panes, comprising: (a) arranging a glass pane heated to at least its softening temperature between a lower press-bending mould with a frame-shaped contact surface and an upper press-bending mould and establishing contact between a side edge of the glass pane and the contact surface along a first contact line, (b) press bending the glass pane between the lower press-bending mould and the upper press-bending mould, wherein the side edge of the glass pane rests on the contact surface along a contact line, which migrates during pressing from the first contact line all the way to a pressing line, wherein the contact surface is convexly curved between the first contact line and the pressing line, and wherein a curvature of the contact surface between the first contact line and the pressing line is selected to prevent direct contact between the contact surface and a lower surface of the glass pane during said pressing when the contact line migrates from the first contact line all the way to the pressing line.

14. The method according to claim 13, wherein a clearance angle between the contact surface and the glass pane at the pressing line is at least 3°.

15. The method according to claim 14, wherein the clearance angle is at least 5°.

16. The method according to claim 13, wherein the glass pane is pre-bent before step (a).

17. The method according to claim 16, wherein the glass pane is pre-bent on a gravity bending mould and subsequently transferred to the lower press-bending mould by a vertical displacement of the gravity bending mould and the lower press-bending mould relative to each other.

18. The method according to claim 13, wherein the glass pane is thermally prestressed after step (b).

19. A method comprising utilizing a device according to claim 1 for bending glass panes for means of transportation for travel on land, in the air, or on water.

20. The method according to claim 19, wherein the glass panes are window panes of rail vehicles or motor vehicles.

Description

(1) In the following, the invention is explained in detail with reference to drawings and exemplary embodiments. The drawings are schematic representations and are not to scale. The drawings in no way restrict the invention.

(2) They depict;

(3) FIG. 1 a cross-section through a generic device during press bending of a glass pane,

(4) FIG. 2 a cross-section through a section of a prior art device during press bending,

(5) FIG. 3 a plan view of the contact surface of the lower press-bending mould of a generic device,

(6) FIG. 4 a cross-section through a section of a device according to the invention during press bending,

(7) FIG. 5 a cross-section through a section of a lower press-bending mould according to the invention with a final bent glass pane,

(8) FIG. 6 a cross-section of a tool, in which the lower press-bending mould is combined with a gravity bending mould, and

(9) FIG. 7 a flowchart of an embodiment of the method according to the invention.

(10) FIG. 1 depicts a cross-section through a generic device for press bending of glass panes. The device comprises a lower press-bending mould 1 with a frame-like contact surface 2 and an upper press-bending mould 3 with a full-surface active surface, which are arranged opposite one another and are vertically movable relative to one another. The glass pane I to be bent is arranged between the press-bending moulds 1, 3. The press-bending moulds 1, 3 are brought closer to one another such that the glass pane I is pressed therebetween and reshaped thereby. Only the side edge S of the glass pane I rests on the contact surface 2 of the lower press-bending mould 1. The glass pane I and the contact surface 2 thus touch one another only along a circumferential line that is referred to as a contact line 4. The entire upper pane surface O is in contact with the active surface of the upper press-bending mould 3. The shape of the active surface of the upper press-bending mould 3 corresponds to the desired bent shape of the glass pane I.

(11) FIG. 2 depicts a cross-section through a section of a device whose lower press-bending mould 1 is implemented conventionally. The contact surface 2 is planar and inclined inward. First, the glass pane I is brought into contact with the lower press-bending mould 1 and the upper press-bending mould 3 (FIG. 2a). That contact line 4, along which the glass pane I initially comes into contact with the contact surface 2, is referred to as the first contact line 4A. The glass pane I is, for the sake of simplicity, shown planar here in the initial state; however, it can also be pre-bent. For press-bending, the press-bending moulds 1, 3 are brought closer to one another such that the glass pane I is reshaped. The contact line 4 migrates inward, starting from the first contact line 4A (FIG. 2b). The dashed arrows indicate the movement of the upper press-bending mould 3 and the contact line 4 during press bending. At the end of the press bending, the press-bending moulds 1, 3 have reached their final position and the glass pane I is bent into its final shape (FIG. 2c). The contact line 4 reaches its most inward position, which is referred to as the pressing line 4B.

(12) The figure illustrates the disadvantage of conventional lower press-bending moulds with a planar contact surface 2. In particular, in the production of glass panes I with strong curvatures in the edge region, there is a risk of the lower pane surface U making contact with the contact surface 2 in the region between the pressing line 4B and the inner edge, possibly with resultant negative impact on optical quality. The contact could, in principle, be prevented by orienting the contact surface 2 more steeply. In order for the contact line 4 to nevertheless cover the same horizontal distance, it would then be necessary to significantly lengthen the contact surface 2, with the result that the lower bending mould would have to be very extensive, in particular, unmanageably tall, and could be integrated into existing plants only with difficulty.

(13) FIG. 3 depicts a plan view of a lower press-bending mould 1. Discernible is the frame-shaped contact surface 2, which is delimited by an inner edge 6 facing the center and an outer edge 7 facing outward. The contact of the contact surface 2 with the side edge S of the glass pane I is made within a region between the frame-shaped first contact line 4A and the pressing line 4B, both of which are arranged circumferentially on the contact surface 2.

(14) FIG. 4 depicts, for comparison with FIG. 2, a cross-section through a section of a device with a lower press-bending mould 1 according to the invention. The contact surface 2 is convexly curved, in particular in the region between the first contact line 4A and the pressing line 4B. The curvature of the contact surface 2 is direction opposite the curvature of the pane. The bending increases the distance of the lower region of the contact surface 2 from the glass pane I, as a result of which making contact with the lower pane surface U can be avoided, even in the case of glass panes with strong curvatures in the edge region.

(15) FIG. 5 depicts a cross-section of another lower press-bending mould 1. The design according to the invention of the contact surface 2 (delimited by the inner edge 6 and the outer edge 7) ensures that the lower pane surface does not come into contact with the contact surface 2. The lower pane surface and the contact surface 2 thus always enclose an angle greater than 0°, which is referred to as a clearance angle α. Depending on the curvatures of the glass pane I and the contact surface 2, the clearance angle α can change during press bending, but always remains greater than 0°. The clearance angle at the pressing line 4B should advantageously be greater than 3°, for example, 7°.

(16) The clearance angle between the curved surfaces can be determined exactly by using the tangential planes at the respective contact line 4.

(17) FIG. 6 schematically depicts a lower press-bending mould 1 and a gravity bending mould 5 that are combined in a common tool. The gravity bending mould 5 has a frame-shaped support surface that is framed by the contact surface 2 of the lower press-bending mould 1. The press-bending mould 1 and the gravity bending mould 5 are vertically displaceable relative to one another such that it is possible to adjust whether the support surface of the gravity bending mould 5 or the contact surface 2 of the press-bending mould 1 is arranged higher and, consequently, can support the glass pane I. First, the glass pane I is pre-bent on the gravity bending mould 5 that is arranged higher (FIG. 6a). The bending moulds 1, 5 are subsequently displaced relative to one another, with the glass pane I being transferred from the gravity bending mould 5 to the lower press-bending mould 1 (FIG. 6b). The transfer can be done by moving the gravity bending mould 5 downward, by moving the press-bending mould 1 upward, or by a combination of both.

(18) FIG. 7 depicts an exemplary embodiment of the method according to the invention with reference to a flowchart.

LIST OF REFERENCE CHARACTERS

(19) (1) lower press-bending mould (2) contact surface of the lower bending mould 1 (3) upper press-bending mould (4) contact line between the glass pane I and the contact surface 2 (4A) first contact line (4B) pressing line (5) gravity bending mould (6) inner edge of the contact surface 2 (7) outer edge of the contact surface 2 α clearance angle between the contact surface 2 and the glass pane I (I) glass pane (0) upper pane surface of the glass pane I (U) lower pane surface of the glass pane I (S) side edge of the glass pane I