Bending tool for glass panes

Abstract

A bending tool for bending at least one glass pane by suction, includes a frame-like convex contact surface and a cover having a peripheral air guide plate that surrounds the contact surface at least in regions is described. The bending tool is suitable for generating a first, reduced pressure in a first pressure region between the air guide plate and the contact surface; a second reduced pressure in a second pressure region. The second pressure is less than the first pressure; and a third pressure in a third pressure region, wherein the third pressure is greater than the first pressure.

Claims

1. A bending tool for bending at least one glass pane by means of suction, the bending tool comprising: a frame-like, convex contact surface; and a cover having a peripheral air guide plate that surrounds the convex contact surface at least in regions, wherein the bending tool is configured to generate: a first, reduced pressure in a first pressure region between the peripheral air guide plate and the convex contact surface, a second, reduced pressure in a second pressure region, wherein the second pressure is less than the first pressure, and a third pressure in a third pressure region, wherein the third pressure is greater than the first pressure, wherein the bending tool is constructed and arranged to contact a peripheral portion of a main surface of the glass pane such that a majority of the main surface of the glass pane is without contact with the bending tool during bending of the glass pane by the bending tool, and wherein the convex contact surface contacts said peripheral portion during the bending.

2. The bending tool according to claim 1, wherein the bending tool is further configured to generate the first pressure region for suctioning an edge of the glass pane to be bent with a stream of air at least in sections, and for pressing the glass pane against the convex contact surface.

3. The bending tool according to claim 1, wherein the bending tool is further configured to generate the second pressure in at least one corner of the bending tool, and to bend at least one corner of the glass pane at a sharper angle than a remaining portion the glass pane.

4. The bending tool according to claim 1, wherein the bending tool is further configured to generate the third pressure region in a central region inside the convex contact surface, and to bend a central region of the glass pane at a shallower angle than an edge region of the glass pane.

5. The bending tool according to claim 1, further comprising a suction pipe connecting the first pressure region and the second pressure region.

6. The bending tool according to claim 1, further comprising at least one vent pipe connecting the third pressure region with air surrounding the bending tool.

7. The bending tool according to claim 6, wherein the at least one vent pipe comprises a valve for regulating air flow.

Description

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

(2) They depict:

(3) FIG. 1 a cross-section through a generic bending tool according to the prior art,

(4) FIG. 2 a plan view of an embodiment of the bending tool according to the invention,

(5) FIG. 3 a cross-section along A-A through the bending tool of FIG. 2,

(6) FIG. 4 a cross-section along B-B through the bending tool of FIG. 2,

(7) FIG. 5 a stepwise depiction of an embodiment of the method according to the invention, and

(8) FIG. 6 a flowchart of an embodiment of the method according to the invention.

(9) FIG. 1 depicts a tool for glass bending processes according to the prior art. The tool is an upper mold that is suitable for holding two glass panes I, II lying one atop the other against a frame-like, convex contact surface 2 by means of suction against the influence of gravity. The contact surface 2 is arranged on a so-called bending skeleton 13. For generating the suction, the tool includes a suction pipe 5, via which the air is extracted. The tool further has a cover 3, whose end is equipped with a peripheral air guide plate 4. The air guide plate 4 surrounds the contact surface 2 peripherally. By means of the bending skeleton 13 and the cover 3 with the air guide plate 4, the stream of air generated through the suction pipe is guided such that it sweeps the edges of the glass pane. Thus, the pair of glass panes I, II is securely held against the contact surface 2.

(10) The panes I, II are pre-bent, for example, by sag bending in a lower bending mold. The tool depicted can, for example, be used, to pick up the pair of glass panes I, II out of the lower mold and to transfer it to another mold. For example, the pair of glass panes I, II can be subjected to a press bending process, wherein it is deformed between the tool depicted and a counter mold under the effect of pressure and/or suction.

(11) The tool and bending method in which it can be used depicted, are known from WO 2006/072721 A1, WO 2012/080071 A1, and WO 2012/080072 A1.

(12) FIG. 2, FIG. 3, and FIG. 4 each depict a detail of an improved bending tool 1 according to the invention. The bending tool 1 is, like the tool in FIG. 1, an upper mold for a bending process. FIG. 2 depicts a plan view of the lower side of the tool bending 1 provided for contacting with the glass pane to be bent, whereas FIGS. 3 and 4 depict, in each case, a cross-section.

(13) The bending tool 1 has, like the tool of FIG. 1, a suction pipe 5 for generating suction, as well as a cover 3 with an air guide plate 4 and a bending skeleton 13 with a frame-like contact surface 2. In contrast with the known tool, the suction in the bending tool is selectively divided, by which means an optimized pressure distribution is produced. This enables realizing more complex pane shapes. The glass panes can be provided by the bending tool 1 according to the invention, for example, with pre-bending, and can be brought, in a subsequent bending step, for instance, by press bending or sag bending, into their final shape. Pre-bending with the bending tool 1 according to the invention enables a more complex final pane shape.

(14) The bending tool has three different pressure regions B1, B2 and B3, in which different pressures that act on the glass panes I, II can be generated. The second pressure region B2 has four sections, with each section arranged in one corner of the bending tool 1. A corner of the bending tool 1 is, in this case, the region that is provided to act on one corner of the glass pane I, II to be bent. The first pressure region B1 likewise has four sections, with each section arranged along one side edge of the bending tool 1 between air guide plate 4 and contact surface 2 and running between two adjacent sections of the second pressure region B2. Here, a side edge of the bending tool 1 is the region that is provided to act on a side edge of the glass pane I, II to be painted. The third pressure region B3 is arranged in the central region of the bending tool 1 surrounding the contact surface 2.

(15) The bending tool 1 is suitable for generating, in the first pressure region B1 a first, reduced pressure p.sub.1. The pressure p.sub.1 results in an upwardly directed stream of air between air guide plate 4 and contact surface 2. When one or a plurality of glass panes I, II are in contact according to the invention with the bending tool 1, the side edges of the glass panes are swept by the stream of air. The stream of air is suitable for holding one or even a plurality of glass panes lying atop one another, against the influence of gravity, against the contact surface of the bending tool 1. The first pressure p.sub.1 in the first pressure region B1 thus fulfills the function of the stream of air in the tool according to the prior art of FIG. 1. A first pressure p.sub.1, which corresponds, based on the ambient pressure, to a vacuum of 3 mbar to 6 mbar, is suitable for holding a pair of glass panes I, II each having a typical pane thickness of roughly 2.1 mm.

(16) The bending tool 1 is further suitable for generating, in the second pressure region B2, a second, reduced pressure p.sub.2, which is lower than the first pressure p.sub.1. The suction in the second pressure region B2 is thus greater than in the first pressure region B1. Whereas the glass panes are merely to be held by the stream of air in the first pressure region B1, active deformation of the pane is to be obtained in the second pressure region B2 by means of the stream of air. The contact surface 2 in the second pressure region B2 is set back compared to that in the first pressure region B1 such that the glass panes are not in contact with the contact surface 2 before the bending operation. By means of the suction in the second pressure region B2, the softened glass panes I, II are bent and cling to the contact surface 2. The sections of the second pressure region B2 are arranged in the corners of the bending tool 1. By means of the strong suction in the second pressure region B2, the corners of the glass panes I, II can be provided with a curvature that is stronger than the curvature of the rest of the pane. Thus, very complex pane shapes can be realized. The shape of the pane corners affected by the bending operation, which is typically different for the lower corners and the upper corners, is determined by the contact surface 2. A second pressure p.sub.2, which is, based on the ambient pressure, a vacuum from 30 mbar to 60 mbar, is, for example, suitable for bending a pair of glass panes I, II with a typical pane thickness of roughly 2.1 mm each.

(17) The bending tool 1 is further suitable for generating, in the third pressure region B3, a third pressure p.sub.3, which is greater than the first pressure p.sub.1. The suction is, in the third pressure region B3, thus less than in the first pressure region B1 and in the second pressure region B2, The third pressure region B3 effectively prevents excessive bending in the central region of the glass panes I, II due to the strong curvature in the second pressure region B2. The expression excessive bending refers to the production of an undesirable counter curvature as a result of a strong curvature in an adjacent region. The third pressure region B3 effectively prevents excessive bending and other bending defects, for instance, unevenness in the central region of the glass panes I, II. A typical third pressure p.sub.3 is, for example, roughly the ambient pressure or is only slightly below it with a vacuum of, for example, 1 mbar.

(18) A vacuum in the suction pipe 5 that is suitable for being divided among the pressure regions as described above, is, for example, roughly 80 mbar.

(19) To generate the suction, the bending tool 1 has a suction pipe 5. The suction pipe 5 is arranged on the side of the bending tool 1 facing away from the contact surface 2, i.e., the top. The pressure regions B1, B2, and B3 are connected to the suction pipe, by which means a reduced pressure is generated. The cover 3 and the skeleton 13 bearing the contact surface 2 form a conduit between the first pressure region B1 and the suction pipe 5, as is known from the tool according to the prior art of FIG. 1. In the bending tool 1 according to the invention, additional conduits 6 are implemented, which connect the sections of the second pressure region B2 to the suction pipe 5. The different pressures p.sub.1 and p.sub.2 are realized by means of appropriately selected conduit cross-sections. The extracted air is indicated in the figures by arrows.

(20) The suction pipe 5 and the conduits 6 are actually not discernible in the plan view of FIG. 2; however, their position is indicated by dotted lines.

(21) The third pressure region B3 has a connection (not shown in the figures) to the suction pipe 5, by means of which a reduced pressure p.sub.3 is also generated in the third pressure region B3. The bending tool 1 has vent pipes 7 for increasing the third pressure p.sub.3. The vent pipes 7 run between the bending skeleton 13 and the cover 3 and connect the third pressure region B3 to the surroundings on the side of the bending tool facing away from the contact surfaces 2. The third pressure p.sub.3 results from the suction of the suction pipes 5 and the air entrained through the vent pipes 7. The vent pipes 7 are provided with valves 12 for active regulation of the third pressure p.sub.3. The entrained air is indicated in the figures by arrows.

(22) The bending skeleton 13 is provided with a deflector plate 8, which has a central opening. The deflector plate 8 deflects the air entrained through the vent pipes 7 such that it flows roughly centrally into the third pressure region B3. By this means, a homogeneous dispersion is achieved, which is advantageous for the surface of the glass pane. A centrally mounted central vent pipe is not possible in the embodiment depicted since the space needed for it is occupied by the central suction pipe 5.

(23) FIG. 5 depicts steps of an exemplary embodiment of the method according to the invention. First, two glass panes I, II lying one atop the other, which are flat in the initial state, are positioned on a lower bending mold 9 (Part a). The panes on the bending mold 9 are heated to bending temperature, for example, 600 C., and cling as a result of gravity to the shape of the lower bending mold 9 (Part b). The glass panes I, II are thus pre-bent by sag bending. After the sag bending, the glass panes I, II are taken over by the bending tool 1 according to the invention. To that end, the bending tool 1 is brought into proximity with the glass panes I, II on the lower bending mold 9 from above and brought into contact with the contact surface 2 (Part c). Then, suction is generated via the suction pipe 5. Due to the first pressure p.sub.1, the glass panes I, II are held against the bending tool 1 and can be moved upward by it and thus removed from the lower bending mold 9 (Part d). The second pressure p.sub.2 effects the further bending of the corners of the pane, whereas the third pressure p.sub.3 prevents bending defects in the center of the pane. By means of the bending tool 1, a further pre-bending into a more complex shape is achieved (Part e). Then, a lower suction bending mold 10 is brought into proximity with the glass panes I, II from below. The glass panes I, II are bent between the bending tool 1 according to the invention and the lower suction bending mold 10 by press bending into their final shape (Part f). The lower suction bending mold 10 is subsequently lowered again (Part g) and the glass panes I, II are placed by means of the bending tool 1 on a lower holding mold 11 and transferred to this holding mold 11 by turning off the suction (Part h). The bending tool 1 is then moved upward (Part i) and is ready for the bending process of the next pair of panes. On the lower holding mold 11, the glass panes I, II cool to the ambient temperature. The same mold or a mold designed the same as the first lower bending mold 9 (sag bending mold) can be used as the lower holding mold 11.

(24) By means of the method according to the invention, due to the pre-bending with the bending tool 1 according to the invention, clearly more complex pane shapes can be obtained than with prior art methods. That is the major advantage of the present invention.

(25) The upstream and downstream process steps of the bending with the bending tool 1 presented must be understood merely as examples and in no way restrict the invention. Thus, for example, the final pane shape can be achieved by sag bending instead of press bending. It is also conceivable that the final pane shape is achieved merely with the bending tool 1 according to the invention without a further bending step.

(26) FIG. 6 depicts the exemplary embodiment of FIG. 5 using a flowchart.

LIST OF REFERENCE CHARACTERS

(27) (1) bending tool (2) frame-like contact surface (3) cover (4) air guide plate (5) suction pipe (6) conduit between B2 and 5 (7) vent pipe (8) deflector plate (9) lower sag bending mold (10) lower suction bending mold (11) holding mold (12) valve of 7 (13) bending skeleton (B1) first pressure region (B2) second pressure region (B3) third pressure region (p.sub.1) first, reduced pressure (p.sub.2) second, reduced pressure (p.sub.3) third pressure (I) glass pane (II) glass pane