DEVICE AND METHOD FOR LENGTH CUTTING IN ULTRATHIN GLASSES

Abstract

A method for the production of glass ribbon portions is provided that includes: transporting a glass ribbon at a velocity v.sub.1, wherein the velocity v.sub.1 is dependent on the predetermined glass thickness (d.sub.1), with the application of a tensile stress parallel to the edges of the glass ribbon, in a plane E.sub.1, and cooling the glass ribbon at a cooling rate that is dependent on the predetermined glass thickness (d.sub.1), inserting a score on the surface of the glass ribbon in at least one edge area by scoring the glass surface with a scoring tool, wherein the score has an angle a to the transport direction of the glass ribbon, deflecting the glass ribbon in a plane E.sub.2 to generate a bending stress and separating a glass ribbon portion with the formation of edges by breaking the glass ribbon on the extension of the score running transversely to the glass ribbon.

Claims

1. A method for producing glass ribbon portions, comprising: hot forming a continuous glass ribbon with a ribbon thickness (d) in a range from 15 μm to 150 μm from a glass melt; cooling the glass ribbon at a cooling rate that is dependent on the ribbon thickness (d); transporting the glass ribbon along a first plane in a transport direction and at a first velocity (v.sub.1) so as to provide a tensile stress parallel to edges of the glass ribbon; generating a score in a surface the glass ribbon using a scoring tool at a scoring velocity (v.sub.score) and at an angle (β) to the transport direction; and diverting the glass ribbon from the first plane to a second plane so as to generate a bending stress with a main stress line with a glass ribbon portion breaking from the glass ribbon through spontaneous crack propagation at the score along the main stress line in a direction of the ribbon thickness (d) of the glass ribbon.

2. The method of claim 1, wherein the edges have an edge thickness that is greater than the ribbon thickness (d), and wherein the step of generating the score comprises generating the score on at least one of the edges.

3. The method of claim 1, further comprising transporting the glass ribbon in the second plane at a second velocity.

4. The method of claim 3, wherein the first velocity (v.sub.1) is different from the second velocity.

5. The method of claim 3, wherein the first velocity (v.sub.1) is less than the second velocity.

6. The method of claim 1, further comprising separating the glass ribbon portion from the glass ribbon by transporting the glass ribbon portion at a third velocity.

7. The method of claim 6, wherein the first velocity (v.sub.1) is less than the third velocity.

8. The method of claim 1, wherein the angle (β) is in a range from 80° to 100°.

9. The method of claim 1, wherein the angle (β) is adapted to the first velocity (v.sub.1) and to the scoring velocity (v.sub.score) so that:
β=arccos(v.sub.1/v.sub.score).

10. The method of claim 1, further comprising moving the scoring tool on an elastic tool carrier so that the scoring tool moves in the transport direction.

11. The method of claim 1, wherein the first and second planes are angled with respect to one another and/or have a height difference with respect to one another.

12. The method of claim 1, wherein the diverting step further comprises: contacting the glass ribbon with a guiding wheel, wherein a contact point between the glass ribbon and the guiding wheel is in the first plane; and driving the guiding wheel at a rotational speed that is greater than the first velocity (v.sub.1).

13. The method of claim 1, wherein the diverting step comprises allowing the glass ribbon to bending by its own weight.

14. The method of claim 1, wherein the cooling rate is equal to or greater than 10 K/s.

15. The method of claim 1, wherein the cooling rate is greater than 25 K/s.

16. The method of claim 1, wherein the cooling rate is dependent on the ribbon thickness (d) in a range from (1/d) 5 K/(min*μm) to 280 K/(min*μm).

17. The method of claim 1, further comprising removing border areas of the glass ribbon portion.

18. The method of claim 1, further comprising: repeating the generating and diverting so as to break a plurality of glass ribbon portions from the glass ribbon; and stacking the plurality of glass ribbon portions.

19. The method according to claim 1, wherein the glass ribbon portion has a length in a range from 100 to 2000 m.

20. The method according to claim 1, further comprising: repeating the generating and diverting so as to break a plurality of glass ribbon portions from the glass ribbon; sticking the plurality of glass ribbon portions to a paper tape; and coiling the plurality of glass ribbon portions together with the paper tape.

21. A device for producing glass ribbon portions, comprising: a first transport device configured to transport a glass ribbon in a transport direction, wherein the first transport devices is wider than a width of the glass ribbon and is driven by a first drive; a second transport device configured to transport the glass ribbon in the transport direction, wherein the second transport devices is wider than the width of the glass ribbon and is driven by a second drive, the first and second drives being independent of one another; and a scoring device in an area of the first transport device, the scoring device being configured to score a surface of the glass ribbon and being arranged so that the scoring takes place at an angle (a) in the range from 80 to 100° to the transport direction, wherein the first and the second transport devices are arranged with respect to one another so as to subject the glass ribbon to bending stress as the glass ribbon runs from the first transport device to the second transport device.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0060] The invention is explained in more detail below with reference to FIGS. 1 to 13.

[0061] FIG. 1 shows the schematic representation of an embodiment of the device according to the invention in a top view,

[0062] FIG. 2 is a schematic representation of the embodiment shown in FIG. 1 in side view,

[0063] FIG. 3 shows the schematic representation of the cross-sectional profile of the glass ribbon,

[0064] FIG. 4 shows a schematic representation of the position and scoring movement of the scoring tool,

[0065] FIG. 5 shows a schematic representation of a scoring tool with an elastic arm,

[0066] FIG. 6 shows a schematic representation of a further embodiment of the invention with an additional guide device in a plan view,

[0067] FIG. 7 shows a schematic representation of the further development shown in FIG. 6 in a side view,

[0068] FIG. 8 shows a schematic representation of a packaging station in a plan view,

[0069] FIG. 9 shows a schematic representation of a further embodiment of the invention including a device for trimming edgings and a packaging station for rolling up the glass ribbon portions in a side view,

[0070] FIG. 10 shows the relationship between the glass thickness and the drawing rate,

[0071] FIG. 11 shows the relationship between cooling rate and glass thickness,

[0072] FIGS. 12a-12c show schematic representations of various embodiments in side view which differ from one another with regard to the arrangement of the layers E.sub.1 and E.sub.2 and

[0073] FIG. 13 shows a schematic representation of a further embodiment of the invention with a hot forming station.

DETAILED DESCRIPTION

[0074] FIGS. 1 and 2 show a schematic representation of an embodiment of the device according to the invention in a plan view (FIG. 1) or in a side view (FIG. 2). The device of this embodiment comprises the three transport devices 1, 2 and 3, which are designed as belts and are guided over pulleys. The deflecting pulleys preferably have a diameter D.sub.1 in the range from 40 to 150 mm. The belt straps 1, 2 and 3 have a width b.sub.2 which is greater than the width b.sub.1 of the glass ribbon 4, so that the glass ribbon 4 is completely supported by the belt straps. The glass ribbon 4 has a thickness in the range from 15 to 150 μm, wherein the glass thickness in the area of the edgings is greater than in the center of the glass and thus is also greater than 150 μm.

[0075] The belt straps 1, 2 and 3 are driven independently of one another at the velocities v.sub.1, v.sub.2 and v.sub.3. Here, the first belt strap 1 and the second belt strap 2 run with the velocities v.sub.1 and v.sub.2. The velocity v.sub.1 of the first belt strap corresponds to the drawing rate of the drawing machine which pulls the glass ribbon out of the mold (not shown) and is thus largely determined by the desired glass thickness d.sub.1 of the glass ribbon 4. The drawing rate and thus also the velocity v.sub.1 of the first belt strap or the first transport device increases with decreasing glass thickness d.sub.1 of the glass ribbon 4. The velocity v.sub.3 of the third belt strap ensures that the glass ribbon portions 60, 61, 62 are separated and the breaking edges of the individual glass ribbon portion 60, 61, 62 don't strike against each other. Preferably, the velocity v.sub.3 is greater than the velocity v.sub.1 of the first belt strap 1. The length L.sub.3 of the third belt strap 3 is chosen so that there is sufficient space for packing stations (not shown).

[0076] At the end of the first transport device or the first belt tape 1, a scoring device 5 is positioned in a way that the glass ribbon 4 is scored in the area of the edgings. The score runs at right angles or at least approximately at right angles to the transport direction, which also represents the main drawing direction, and in particular has a length in the range from 2 to 6 mm.

[0077] The first belt strap 1 and the second belt strap 2 show an offset in height, i.e., in the z-direction, so that in area 5, i.e., between the first belt strap 1 and the second belt strap 2, a step with the height difference h.sub.1 is formed. Due to the difference in height Δh in the area 7 between the first strap 1 and the second strap 2, the glass ribbon 4 is subjected to a bending stress, which causes the glass ribbon 4 to break along the score, forming a glass edge, so that the endless glass ribbon 4 is divided into glass ribbon portions 60, 61, 62. The length of the glass ribbon portions 60, 61, 62 is determined by the time interval between two scoring processes. Here, the minimum length of the glass ribbon portions 60, 61, 62 is limited by the shortest possible time interval between two scoring processes. This time interval includes, for example, the times for the outward and return journeys of the scoring tool, the duration of the cutting process and, if applicable, the duration of a synchronous movement. Since in the method according to the invention the score is only 2 to 6 mm long, the time interval between two scoring processes can be kept very short. Hence, even very thin glass ribbons 4 can be divided into relatively short glass ribbon portions 60, 61, 62. Particularly in the case of embodiments in which synchronization of the tool can be dispensed with, the minimum panel length is no longer dependent on the minimum distance between two scores. It rather depends on the length of the glass ribbon 4, which still breaks independently when it is transferred over the radius to the plane E.sub.2. Said corresponding glass ribbon length is in turn dependent on the relative position of the planes E.sub.1 and E.sub.2, in the exemplary embodiment shown thus on the height difference between the planes E.sub.1 and E.sub.2. Depending on this, the lower limit for the length of the glass ribbon portions or glass plates lies in the range from 150 to 250 mm.

[0078] The bending of the glass ribbon 4 takes place under its own weight. In the exemplary embodiment shown in FIGS. 1 and 2, the bending radius and thus also the bending stress are set by the height difference Δh between the first belt strap 1 and the second belt strap 2. Furthermore, the bending radius and thus the bending stress can be fine-tuned by the ratio of the velocities v.sub.1 and v.sub.2 of the belt straps 1, 2. If the first belt strap 1 runs at a higher velocity than the second belt strap 2, a relatively small bending radius is created and vice versa.

[0079] FIG. 3 shows a schematic cross section through the glass ribbon 4. The glass ribbon 4 here has edgings 41 with an increased glass thickness d.sub.2 at both edge regions, while the glass thickness d.sub.1 in the central region 40 of the glass ribbon is significantly less. Preferably the glass is an aluminosilicate glass.

[0080] The maximum glass thickness in the are of the edgings can be up to 5 times thicker than the glass thickness d.sub.1 in the central area of the glass ribbon. The edgings 41 have an asymmetrical cross-sectional profile in which the glass thickness increases gently from the glass center 40 towards the edges of the glass ribbon. According to an advantageous embodiment of the method, the scoring tool 5 is therefore guided from the inside to the outside, i.e., towards the edge of the glass ribbon 4, in order to produce the scoring 8 in the edging 41. This is shown in FIG. 4. The arrow 9 here symbolizes the direction of movement of the scoring tool 5 during the scoring process.

[0081] FIG. 5 schematically shows a further embodiment of the scoring device 50 in side view. The scoring device 50 comprises a rotating disk 11 on which an elastic tool carrier 12 is arranged. The tool carrier 12 is designed as an elastic arm. At the other end of the tool carrier 12, the cutting or scoring tool 13 is arranged in the form of one or more hard material elements, for example a diamond or diamond dust, or diamond grains. By rotating the disk 11 (symbolized by the arrow 90), the cutting tool 13 generates the score 8. The cutting movement is symbolized by the arrow 91. Due to the elastic tool arm of the tool carrier 12, it can simultaneously execute the transport movement of the glass ribbon 4, so that the score 8 shows over its entire length an angle α of 90° to the transport direction of the glass ribbon 4. This eliminates the need for synchronous travel when using the scoring device 50. Further, an additional angle adjustment of the scoring tool adapted to the belt speed can take place. By eliminating the synchronization runs, the minimum time between two scoring processes can be further shortened and thus glass sheets with short minimum lengths can be obtained even with very thin glasses.

[0082] In FIG. 6, a further embodiment of the device according to the invention is shown schematically in a top view and side view. The device has additionally guiding wheels 14 in the area of the glass edgings for setting the bending radius. The guide wheels 14 are arranged behind the step 7 in the x-direction and are mounted on the common shaft 15. The shaft 15 is driven by its own drive. The guiding wheels 14 here have a higher circumferential velocity than the belt strap 1, so that there is no stop pulse when the glass ribbon 4 is touched. FIG. 7 shows a side view of the device. The shaft 15 of the guiding wheels can be adjusted in terms of their height and their distance from the step, i.e., in the x- and z-directions. Thus, the distances x.sub.1, x.sub.2 and the height h.sub.2 can be adjusted by the position of the guiding wheels 14 or the shaft 15. The point A denotes the point of contact of the glass edge with the guiding wheel 14. The guiding wheel 14 mechanically forces the glass ribbon 4 to bend. Thus, the device shown in FIGS. 6 and 7 is particularly suitable for relatively thick glass ribbons with a thickness in the range from 80 to 150 μm. Due to the high stiffness of the glass, said glass ribbons does not bend, or at least not in time, without applying additional mechanical action.

[0083] Further, in the device shown in FIGS. 6 and 7, it is possible to influence the bending radius and the bending stress by using various parameters. The bending stress is influenced by the diameter D.sub.1 of the deflection pulleys of the first belt strap 1. The smaller the diameter D.sub.1, the greater the bending stress. The diameter D.sub.1 is preferably in the range from 25 to 150 mm.

[0084] Furthermore, the bending stress can also be controlled by the velocity of the second belt strap 2. The slower the feeding rate v.sub.2, the better the glass can lie against the diameter D.sub.1 of the deflecting pulley and the more precisely the bending radius can be set via the diameter D.sub.1 of the deflecting pulleys. In this case, however, v.sub.2 must be large enough that the individual glass ribbon portions still can be separated from each other.

[0085] Furthermore, through the height h.sub.1 of the step, i.e., the distance between the two belt straps 1 and 2 in the z-direction, the above-described minimum speed of the second belt strap 2 and thus indirectly the bending tension can be set. The higher h.sub.1, the better the glass rests against the pulley with the diameter D.sub.1 and the greater the time lag and thus the distance to the preceding sheet. This in turn enables the velocity v.sub.2 to be reduced, so that the glass can lie even better against the diameter D.sub.1 of the deflection pulleys.

[0086] The distance and height of the shaft 15 must be in a certain ratio to the edge of the glass ribbon. The height h.sub.2 denotes the distance between the two shafts of the belt strap 1 and the guiding wheels. If this height h.sub.2 corresponds to the half of the sum of the two diameters D.sub.1 and D.sub.2, i.e., if h.sub.2=0.5*(D.sub.1+D.sub.2), then a tangent at the lowest point of the guiding wheels is just as high as the glass ribbon 4 on the belt strap 1, i.e., just as high as the belt strap surface of the first belt strap 1. The highest possible contact point A for the guiding wheel 14 is then given. The optimum maximum contact point is achieved when additionally applies to the position of the contact point A: 0.5*(D.sub.1+D.sub.2)+x.sub.1. The displacement x.sub.1 in the horizontal direction is dependent on the glass thickness d.sub.1 of the glass ribbon 4, since a thin glass can be contacted earlier than a thick glass and the glass thickness is included in the bending stress as a square. For example, for x.sub.1:

TABLE-US-00001 TABLE 1 Dependence of the distance x.sub.1 on the glass thickness Glass thickness d.sub.1 [μm] x.sub.1 [mm] 150 245 100 75 75 75 50 45 30th 30th 20th 25th

[0087] If the guiding wheels 14 or the shaft 15 are lowered further, then x.sub.2, ie the distance from the center point of the pulley to the shaft 15, must be increased at the same time in the horizontal direction so that x.sub.1 remains the same. The setting of the distances x.sub.2 and h.sub.2 follows the following equation:

[00001]$x_2=\frac{D_1}{2}+x_1+\sqrt{\frac{D_2^2}{4}-{\left(h_2-\frac{D_1}{2}\right)}^2}$

[0088] FIG. 8 shows a section of an embodiment of the device in which two packaging stations 160, 161 are arranged in the region of the third transport device 3. Each packaging station 160, 161 contains a first robot 17 and a second robot 20, a stacking platform 18 and a paper feed system 20. The first robot 17 stacks a glass sheet or a portion of glass ribbon 60 from the third transport device 3 onto the stacking platform 18. Then the second robot 20 places a sheet of paper, which it has removed from the paper feed system 19, onto the glass sheet 60 on the destacking platform 18. The stacking platform moves down by the amount of the glass sheet and paper thickness after each stacking process. This creates stacks of glass and paper of 100 to 500 pieces which can then be fed to the final packaging. Due to the high feeding rate v.sub.3 of the third transport device, two packaging stations are arranged in the area of the third transport device 3 in the embodiment shown in FIG. 8. At the end of the third transport device 3 there is a cullet funnel 21 through which rejected sheets are fed to a collecting container. The collecting container is located on a building level below the production level. Since there is a higher air pressure in the production level than in the level of the collecting container, it is ensured that no glass dust can get from the collecting container into the production level.

[0089] In FIG. 9 a section of a further variant of the device is shown schematically in side view. Here the device in the area of the second transport device 2 has a device for continuously separating the edgings on both edge areas of the glass ribbon portion 60. The device 22 is preferably designed as a laser separation. The severed edgings 41 are directed downwards by the transport device 25, while the now border-free glass ribbon portion 40 is transported further from the second transport device 2 to the third transport device 3. A roller device 24 for rolling up the glass ribbon portion 40 is placed in the area of the third transport device 3. Here, the glass ribbon portion 40 is rolled up together with an intermediate paper 26 which is provided by the paper feed 23. The variant shown in FIG. 9 is particularly suitable for rolling up glass ribbon portions with a length in the range from 100 to 1000 m.

[0090] FIG. 10 illustrates the relationship between the desired glass thickness d.sub.1 and the needed drawing rate v.sub.z necessary. The drawing rate v.sub.z corresponds to the feeding rate v.sub.1 of the first transport device. It becomes clear that drawing rate v.sub.z increases significantly with decreasing glass thickness. As a result, very thin glasses have to be drawn at very high drawing drawing rates v.sub.z. Because of the velocity v.sub.z and thus also v.sub.1, short process times in the cutting process are decisive for the production of short glass sheets.

[0091] According to a variant of the method according to the invention the glass ribbon passes through a cooling furnace after the shaping process and before it is transported and scored on the first transport device. Since the drawing speed v.sub.z has to be be maintained in the cooling furnace as well, the cooling times for thinner glasses are correspondingly shorter than for thick glasses. One embodiment of the invention therefore provides that the cooling rate increases as the thickness d.sub.1 of the glass ribbon decreases. The relationship between glass thickness d.sub.1 and cooling rate is shown in FIG. 11.

[0092] In FIGS. 12a to 12c, various embodiments of the device are shown schematically in side view, which differ from one another with regard to the arrangement of the planes E.sub.1 and E.sub.2. In FIG. 12a, a device is shown in which the two planes E.sub.1 and E.sub.2 show a height difference without having an angle difference to each other. In contrast, the planes E.sub.1 and E.sub.2 in the embodiment shown in FIG. 12b have an angular offset. In the embodiment shown in FIG. 12c, the height difference and the angular offset of the layers E.sub.1 and E.sub.2 are combined with one another.

[0093] FIG. 13 schematically shows an embodiment of the device with a device for hot forming 6. Here, the glass ribbon 4 is first drawn with the hot forming device 6 in the vertical direction. The transport takes place in the vertical direction by the drawing device 9. After the glass ribbon 4 has been deflected into the horizontal plane, the glass ribbon is transported with the aid of the first transport device 1. In the area of the first transport device 1 there is the scoring device 5 for making a scoring in at least one edge area of the glass ribbon. The glass ribbon 4 is then guided onto the second transport device 2 in a manner analogous to the embodiment described in FIG. 2.

LIST OF REFERENCE SYMBOLS

[0094] 1, 2, 3 Transport device [0095] 4 Glass ribbon [0096] 5 Scoring device [0097] 6 Hot forming device [0098] 7 Range between 1 and 2 [0099] 8 Score [0100] 9 Drawing device [0101] 10 Device for the production of glass ribbon portions [0102] 11 disc [0103] 12th Tool carrier [0104] 13 Scribing tool [0105] 14 Guiding wheel [0106] 15 Shaft [0107] 17, 20 Robot [0108] 18 Stacking platform [0109] 21 Crock funnel [0110] 22 Device for trimming the edgings [0111] 23 Paper feeder [0112] 24 Roller device [0113] 25 Transport device [0114] 26 Intermediate paper [0115] 40 Middle area [0116] 41 edging area [0117] 50 Scoring device [0118] 60, 61, 62 Glass ribbon portion [0119] 160, 161 Packing station