Glass plate manufacturing method and manufacturing device

Abstract

The present invention comprises: a cutting step for cutting a glass ribbon G, which is moving downward in a vertical orientation, along the width direction of the glass ribbon G at a standard cut length L0 so as to obtain a glass plate g; and a determination step for determining the presence / absence of damage to a determination target which is a part including at least one of the glass ribbon G and the glass plate g after the cutting in the cutting step. If it is determined in the determination step that there is damage to the determination target, the glass ribbon G will be, in the next cutting step, cut at an extended cut length L1 which is longer than the standard cut length L0.

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for manufacturing a glass sheet, in which a glass ribbon moving downward in a vertical position is cut along its width direction to a standard cutting length to obtain a glass sheet. [Background technology]

[0002] As is well known, in the field of glass sheet manufacturing, glass sheets are cut out from a glass ribbon that has been formed by a downdraw method and is moving downward. A specific example of a method and apparatus for manufacturing glass sheets in this manner is disclosed in Patent Document 1.

[0003] The apparatus disclosed in the publication includes a scribing means for forming a scribe line on a glass ribbon that moves downward in a vertical position, a breaking bar (called a fulcrum bar in the publication) that is pressed against a region of the glass ribbon where the scribe line is formed, and a support means (called a breaking arm in the publication) that supports the glass ribbon below the scribe line. The method disclosed in the publication for cutting out a glass sheet using this apparatus involves first forming a scribe line along the width direction of the glass ribbon with the scribing means, and then pressing the breaking bar against the region of the glass ribbon where the scribe line is formed. Next, the support means, which is supporting the glass ribbon, is operated to bend the region of the scribe line using the breaking bar as a fulcrum. This bends and breaks the glass ribbon along the scribe line, and a glass sheet is cut out from the glass ribbon. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-90446 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if a cutting defect occurs in the cutting process as described above, damage such as cracks or chips may occur in the lower end of the glass ribbon remaining after the glass sheet is cut and separated. If the glass ribbon is cut again at the same standard cutting length as when no damage occurs in a state in which such damage has occurred, there is a risk of vertical cracks occurring in the glass ribbon during the cutting process, in which the damage propagates upward. If such vertical cracks propagate upward beyond the cutting position of the glass ribbon (e.g., the scribe line), there is a risk that it will be impossible to cut out a normal, undamaged glass sheet for a long period of time. Furthermore, in the worst case scenario, there is a risk that the vertical cracks will lead to damage to the entire glass ribbon over time, ultimately making it completely impossible to cut out a glass sheet from the glass ribbon.

[0006] An object of the present invention is to reliably prevent vertical cracks from occurring in a glass ribbon when a glass sheet is cut out from the glass ribbon. [Means for solving the problem]

[0007] (1) The present invention, which was invented to solve the above-mentioned problems, is a method for manufacturing a glass plate, which includes a cutting step in which a glass ribbon moving downward in a vertical position is cut along its width direction at a standard cutting length to obtain a glass plate, and further includes a determination step in which a portion including at least one of the lower end of the glass ribbon and the upper end of the glass plate after cutting in the cutting step is used as the determination object and whether or not the determination object is damaged, and if it is determined in the determination step that the determination object is damaged, in the next cutting step, the glass ribbon is cut at an extended cutting length longer than the standard cutting length.

[0008] When breakage occurs in the lower end of the glass ribbon after cutting in the cutting step, breakage often also occurs in the upper end of the glass sheet cut and separated from the glass ribbon at a position corresponding to the breakage in the glass ribbon. Therefore, in the above configuration, in order to determine whether or not the lower end of the glass ribbon after cutting in the cutting step is broken, in the determination step, at least one of the lower end of the glass ribbon and the upper end of the glass sheet after cutting in the cutting step is used as the determination target, and the presence or absence of breakage in the determination target is determined. Then, if it is determined in the determination step that breakage exists in the determination target, the glass ribbon is cut at an extended cutting length longer than the standard cutting length in the next cutting step, so that the lower end where breakage occurs is sufficiently separated downward from the cutting position of the glass ribbon in the next cutting step. Therefore, it is possible to reliably prevent a vertical crack from occurring in the glass ribbon beyond the cutting position of the glass ribbon.

[0009] (2) In the above-described configuration (1), it is preferable that the determination step measures the object to be determined by a sensor and determines whether or not the object to be determined is damaged based on the measurement results.

[0010] In this way, it is possible to automatically determine whether or not the object to be determined is damaged.

[0011] (3) In the above configuration (2), it is preferable that the sensor measures the widthwise end of the object to be determined.

[0012] The widthwise ends of the glass ribbon generally include ears that are thicker than the widthwise center portion. If the glass ribbon is cut (particularly broken by bending) without any ears near the cutting position, a vertical crack extending beyond the cutting position is likely to occur in the glass ribbon. Therefore, as in the above configuration, it is preferable that the sensor measures the widthwise end of the glass ribbon to be determined in order to determine whether or not the widthwise end of the glass ribbon is damaged.

[0013] (4) In the configuration of (2) or (3) above, it is preferable that the sensor measures the widthwise end portion and widthwise center portion of the object to be determined.

[0014] Even when cutting (particularly bending and splitting) the glass ribbon while there is damage in the widthwise center near the cutting position, a vertical crack may occur in the glass ribbon that extends beyond the cutting position. Therefore, as in the above configuration, it is preferable that the sensor measures the widthwise end portions and the widthwise center portion of the object to be determined in order to determine whether or not there is damage in the widthwise center portion in addition to the widthwise end portions of the object to be determined.

[0015] (5) In any one of the above configurations (1) to (4), it is preferable that the value obtained by subtracting the standard cut length from the extended cut length is 0.05 m or more and 4.0 m or less.

[0016] If the value obtained by subtracting the standard cutting length from the extended cutting length, i.e., (extended cutting length - standard cutting length) is set to 0.05 m or more, the portion where the breakage has occurred can be sufficiently separated downward from the cutting position of the glass ribbon. On the other hand, if (extended cutting length - standard cutting length) is set to 4.0 m or less, it is possible to prevent the cutting length from becoming unduly long, making it easier to ensure space during cutting.

[0017] (6) In any one of the above configurations (1) to (4), the extended cut length is preferably 1.02 to 4.1 times the standard cut length.

[0018] If the extended cutting length is 1.02 times or more the standard cutting length, the portion where the breakage has occurred can be sufficiently separated downward from the cutting position of the glass ribbon. On the other hand, if the extended cutting length is 4.1 times or less the standard cutting length, the cutting length can be prevented from being unduly long, making it easier to ensure space during cutting.

[0019] (7) In any one of the above configurations (1) to (6), in the cutting step, the extended cutting length may be adjusted depending on the type of damage to be determined.

[0020] In this way, the length of the glass sheet cut to the extended cutting length can be set to an optimum length depending on the type of breakage, and therefore, even if the glass sheet cut to the extended cutting length is discarded, waste of glass can be minimized.

[0021] (8) In the configuration of (7) above, in the cutting step, the extended cutting length may be adjusted depending on at least one of the position and the size of the damage to be determined.

[0022] When the size of the breakage is considered as the type of breakage, for example, the extended cutting length can be increased if the size of the breakage is large, and can be decreased if the size of the breakage is small. Furthermore, when the location of the breakage is considered as the type of breakage, for example, the extended cutting length can be increased if the location of the breakage is likely to have an adverse effect, and can be decreased if the location of the breakage is unlikely to have an adverse effect. In other words, the length of the glass sheet cut to the extended cutting length can be set to an optimal length depending on the location and size of the breakage. Therefore, even if the glass sheet cut to the extended cutting length is discarded, waste of glass can be minimized.

[0023] (9) In any one of the above configurations (1) to (8), the cutting process includes a scribing process for forming a scribe line on the glass ribbon along its width direction, and a bending and splitting process for cutting out a glass sheet by bending and splitting the glass ribbon along the scribe line while supporting the glass ribbon below the scribe line with a support means, and it is preferable that in the bending and splitting process, a bending and splitting bar is pressed against the scribe line formation area of ​​the glass ribbon (hereinafter referred to as the scribe line formation area).

[0024] In this way, the glass ribbon can be easily cut along the width direction. In the cutting step, the glass ribbon can also be cut by laser cleaving, laser fusing, or the like, but the setting of cutting conditions, etc. tends to be more complicated than in the above configuration.

[0025] (10) In the configuration of (9) above, the bending and splitting process is a process of bending and splitting the glass ribbon by operating the support means while pressing the bending bar against the scribe line formation area, and bending the scribe line formation area vertically using the bending bar as a fulcrum, and when cutting the glass ribbon at the extended cutting length, it is preferable to slow down the operating speed of the support means for bending the scribe line formation area compared to when cutting the glass ribbon at the standard cutting length.

[0026] When the glass ribbon is cut to the extended cutting length, the glass ribbon contains breakage. Therefore, also from the viewpoint of suppressing vertical cracks in the glass ribbon, it is preferable to cut the glass ribbon safely by slowing the operating speed of the support means down compared to normal, as in the above configuration.

[0027] (11) In the configuration of (9) above, the bending and splitting process is a process of bending and splitting the glass ribbon by operating the support means to bend the scribe line formation area in the vertical direction and pressing a bending bar against the scribe line formation area, and when cutting the glass ribbon at the extended cutting length, it is preferable to slow down at least one of the operating speed of the support means for bending the scribe line formation area and the operating speed of the bending bar pressed against the scribe line formation area compared to when cutting the glass ribbon at the standard cutting length.

[0028] When the glass ribbon is cut to the extended cutting length, the glass ribbon contains breakage. Therefore, also from the viewpoint of suppressing vertical cracks in the glass ribbon, it is preferable to cut the glass ribbon safely by slowing down at least one of the operating speed of the support means and the operating speed of the breaking bar as in the above configuration.

[0029] (12) In any one of the configurations (9) to (11) above, in the cutting step, it is preferable to set the extended cutting length so that, if there is any break in the glass ribbon, the broken portion is positioned below the contact position of the support means with the glass ribbon.

[0030] This can reliably prevent the support means from coming into contact with a broken portion of the glass ribbon, causing vertical cracks in the glass ribbon.

[0031] (13) The present invention, which was invented to solve the above-mentioned problems, is a glass plate manufacturing apparatus equipped with a cutting device that cuts a glass ribbon moving downward in a vertical position along its width direction at a standard cutting length to obtain a glass plate, and is equipped with: a determination unit that determines whether or not the object to be determined is damaged, using a portion including at least one of the lower end of the glass ribbon and the upper end of the glass plate after cutting by the cutting device; and a control unit that adjusts the cutting length of the glass ribbon based on the determination result of the determination unit, characterized in that when the determination unit determines that the object to be determined is damaged, the control unit sets the cutting length of the glass ribbon by the cutting device for the next time to an extended cutting length that is longer than the standard cutting length.

[0032] In this way, the same effects as those of the corresponding configurations already described can be obtained. [Effects of the Invention]

[0033] According to the present invention, it is possible to reliably prevent vertical cracks from occurring in the glass ribbon when cutting out a glass sheet from the glass ribbon. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a schematic side view showing the overall configuration of a glass sheet manufacturing apparatus according to a first embodiment of the present invention. [Figure 2] 1 is a schematic front view (viewed from direction A in FIG. 1) illustrating a state in which a method for producing a glass plate according to a first embodiment of the present invention is carried out. [Figure 3] 1 is a schematic front view (viewed from direction A in FIG. 1) illustrating a state in which a method for producing a glass plate according to a first embodiment of the present invention is carried out. [Figure 4] 1 is a schematic front view (viewed from direction A in FIG. 1) illustrating a state in which a method for producing a glass plate according to a first embodiment of the present invention is carried out. [Figure 5]1 is a schematic front view (viewed from direction A in FIG. 1) illustrating a state in which a method for producing a glass plate according to a first embodiment of the present invention is carried out. [Figure 6] 1 is a schematic front view (viewed from direction A in FIG. 1) illustrating a state in which a method for producing a glass plate according to a first embodiment of the present invention is carried out. [Figure 7] 1 is a schematic front view (viewed from direction A in FIG. 1) illustrating a state in which a method for producing a glass plate according to a first embodiment of the present invention is carried out. [Figure 8] 1 is a schematic front view (viewed from direction A in FIG. 1) illustrating a state in which a method for producing a glass plate according to a first embodiment of the present invention is carried out. [Figure 9] 1 is a schematic front view (viewed from direction A in FIG. 1) illustrating a state in which a method for producing a glass plate according to a first embodiment of the present invention is carried out. [Figure 10] 10 is a schematic front view (as viewed from the direction A in FIG. 1) showing a main part of an apparatus for producing a glass plate according to a third embodiment of the present invention. [Figure 11] 10 is a schematic front view (viewed from the direction A in FIG. 1) showing a main part of an apparatus for producing a glass plate according to a fourth embodiment of the present invention. [Figure 12] 10 is a schematic front view (viewed from the direction A in FIG. 1) showing a main part of an apparatus for producing a glass plate according to a fifth embodiment of the present invention. [Figure 13] FIG. 10 is a schematic front view (viewed from the direction A in FIG. 1) illustrating a state in which a method for producing a glass plate according to a fifth embodiment of the present invention is carried out. [Figure 14] FIG. 10 is a schematic front view (viewed from the direction A in FIG. 1) illustrating a state in which a method for producing a glass plate according to a fifth embodiment of the present invention is carried out. [Figure 15] FIG. 10 is a schematic front view (viewed from the direction A in FIG. 1) illustrating a state in which a method for producing a glass plate according to a fifth embodiment of the present invention is carried out. [Figure 16] FIG. 10 is a schematic front view (viewed from the direction A in FIG. 1) illustrating a state in which a method for producing a glass plate according to a fifth embodiment of the present invention is carried out. [Figure 17] 10 is a schematic front view (viewed from the direction A in FIG. 1) showing a main part of a modified example of the apparatus for producing a glass sheet according to the fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, a glass sheet manufacturing method and manufacturing apparatus according to an embodiment of the present invention will be described with reference to the drawings. In each embodiment, corresponding components are designated by the same reference numerals, and redundant description may be omitted. When only a portion of the configuration is described in each embodiment, the configuration of another embodiment previously described can be applied to the remaining portions of the configuration. Furthermore, in addition to the combination of configurations explicitly stated in the description of each embodiment, configurations of multiple embodiments can be partially combined together even if not explicitly stated, as long as there is no particular problem with the combination.

[0036] (First embodiment) 1, the glass sheet manufacturing apparatus according to the first embodiment of the present invention includes a processing device 1 for a glass ribbon G, a cutting device 2, and a determination device 3. In this embodiment, the glass ribbon G is configured to move downward in a vertical position (preferably a vertical position) from the processing device 1 to the cutting device 2.

[0037] The processing device 1 includes a forming zone 11 for continuously forming a glass ribbon G, a heat treatment zone 12 for heat treating (slowly cooling) the glass ribbon G, a cooling zone 13 for cooling the glass ribbon G to near room temperature, and a conveying device 14 consisting of roller pairs R arranged in multiple vertical stages in each of the forming zone 11, the heat treatment zone 12, and the cooling zone 13.

[0038] The forming zone 11 and the heat treatment zone 12 are constituted by furnaces in which the transport path of the glass ribbon G is surrounded by walls, and heating devices such as heaters that adjust the temperature of the glass ribbon G are disposed at appropriate locations within the furnaces. On the other hand, the cooling zone 13 is open to the external atmosphere at room temperature without the transport path of the glass ribbon G being surrounded by walls, and no heating device such as a heater is disposed therein.

[0039] A forming body 15 is disposed in the internal space of the forming zone 11, and forms a glass ribbon G from molten glass Gm by the overflow downdraw method. The molten glass Gm supplied to the forming body 15 overflows from a groove (not shown) formed in the top 15a of the forming body 15. The overflowing molten glass Gm flows down both side surfaces 15b, which have a wedge-shaped cross section, of the forming body 15 and joins at the lower end. In this way, a plate-shaped glass ribbon G is continuously formed.

[0040] The internal space of the heat treatment zone 12 has a predetermined temperature gradient downward. The glass ribbon G in the vertical position is heat-treated (slowly cooled) so that its temperature decreases as it moves downward through the internal space of the heat treatment zone 12. This heat treatment reduces internal strain in the glass ribbon G. The temperature gradient in the internal space of the heat treatment zone 12 is adjusted, for example, by a heating device provided on the inner wall surface of the heat treatment zone 12.

[0041] The plurality of roller pairs R constituting the conveying device 14 clamp both widthwise ends of the glass ribbon G in a vertical position from both the front and back sides. The uppermost roller pair R arranged in the forming zone 11 is a cooling roller, and may also be referred to as an edge roller. Note that, in the internal space of the heat treatment zone 12, the plurality of roller pairs R may include rollers that do not clamp the side ends of the glass ribbon G. In other words, the distance between the opposing roller pairs R may be made larger than the thickness of both widthwise ends of the glass ribbon G, and the glass ribbon G may pass between the roller pairs R.

[0042] In this embodiment, both widthwise end portions of the glass ribbon G produced by the processing device 1 have portions (hereinafter referred to as ear portions) that are thicker than the widthwise central portion due to the influence of shrinkage during the forming process and the like.

[0043] The cutting device 2 is configured to cut the glass ribbon G in a vertical position below the processing device 1 in the width direction at predetermined lengths (standard cutting length L0), thereby sequentially cutting out glass sheets g from the glass ribbon G. Here, the width direction is a direction perpendicular to the longitudinal direction (conveyance direction) of the glass ribbon G, and in this embodiment, substantially coincides with the horizontal direction.

[0044] The cutting device 2 includes a scribing device 21 and a breaking device 22. The scribing device 21 and the breaking device 22 are configured to perform cutting-related operations while moving downward at the same speed as the glass ribbon G.

[0045] The scribing device 21 includes a wheel cutter 23 that forms a scribe line S on the first main surface of the glass ribbon G moving downward at the scribing position P1 while traveling along the width direction (in Figure 1, the direction perpendicular to the paper surface), and a support rod 24 that is long in the width direction and supports the portion of the glass ribbon G along which the wheel cutter 23 travels from the second main surface side.

[0046] The wheel cutter 23 has a blade (edge) on the periphery that rotates during travel, and is formed in a disk shape.

[0047] The support rod 24 has a contact surface that contacts the portion along which the wheel cutter 23 travels. The contact surface of the support rod 24 protrudes from both ends of the glass ribbon G in the width direction. The wheel cutter 23 and the support rod 24 are configured to move downward together with the glass ribbon G and form a scribe line S over the entire width direction or a portion of the glass ribbon G. In this embodiment, the scribe line S is also formed on the ear portion.

[0048] The slicing device 22 is a device that slicing the downwardly moving glass ribbon G along a scribe line S at a slicing position P2 provided below the scribing position P1, and cuts out the portion of the glass ribbon G below the scribe line S (the lower region of the glass ribbon G) as a glass sheet g. In this embodiment, the slicing device 22 includes a slicing bar 25 that abuts against the scribe line formation region Sx from the second main surface side, and a support means 26 that supports the glass ribbon G below the slicing position P2. Note that in this embodiment, because cutting-related operations are performed while the glass ribbon G is moved downward, strictly speaking, the scribing position P1 and the slicing position P2 are regions that have widths in the vertical direction.

[0049] The cleaving bar 25 has a contact surface having a convex vertical cross section (e.g., semicircular or curved) that contacts the second main surface side of the scribe line formation region Sx. The contact surface of the cleaving bar 25 protrudes from both widthwise ends of the glass ribbon G. Here, the scribe line formation region Sx is a region that includes the scribe line S, and is, for example, a region between portions of the glass ribbon G that are 80 to 120 mm above and below the scribe line S.

[0050] The support means 26 includes a plurality of chucks 27 that grip both widthwise ends of the glass ribbon G, and an arm 28 that holds the plurality of chucks 27 (see FIG. 2).

[0051] The support means 26 is configured to change its posture from a basic posture indicated by a dotted line in FIG. 1 to an inclined posture indicated by a solid line in the same figure while supporting the glass ribbon G. This change in posture of the support means 26 is achieved by a rotational movement (movement in the direction B in FIG. 1 ) of the support means 26 about the position of the breaking bar 25 (the position indicated by the solid line in FIG. 1 ). Furthermore, the change in posture of the support means 26 is achieved while the support means 26 moves downward at the same speed as the glass ribbon G. Then, by the above-mentioned rotational movement, the support means 26 curves the scribe line formation region Sx in the vertical direction so that the first main surface side is convex. This rotational movement of the support means 26, in cooperation with the movement of pressing the breaking bar 25 against the scribe line formation region Sx, serves to break the glass ribbon G along the scribe line S.

[0052] The wheel cutter 23, support rod 24, breaking bar 25, and support means 26 are configured to perform their respective functions while moving downward at the same speed as the glass ribbon G. The wheel cutter 23, support rod 24, and breaking bar 25 are configured to move along the thickness direction of the glass ribbon G between an operating position where they perform their respective functions and a retracted position where they are retracted away from the glass ribbon G. The movement of each of these components along the thickness direction is performed while they move downward at the same speed as the glass ribbon G. The position of the breaking bar 25 shown by the solid line in FIG. 1 is the operating position, and the position shown by the chain line in the same figure is the retracted position. Meanwhile, the position of the wheel cutter 23 and the support rod 24 shown by the chain line in FIG. 1 is the operating position, and the position shown by the solid line in the same figure is the retracted position.

[0053] As shown in FIGS. 4, 5, 8, and 9, the determination device 3 is a device for determining the presence or absence of breakage occurring in the determination objects Gt, gt, by using the lower end Gt of the glass ribbon G and the upper end gt of the glass sheet g (standard glass sheet gx or extended glass sheet gy) after being cut by the cutting device 2 as determination objects. Note that the determination object may be only one of the lower end Gt of the glass ribbon G and the upper end gt of the glass sheet g. The reason why only the upper end gt of the glass sheet g may be the determination object is that, as shown in FIG. 5, when breakage D1 occurs in the lower end Gt of the glass ribbon G, breakage D2 often occurs at a position corresponding to the upper end gt of the glass sheet g, and the presence or absence of breakage D1 in the lower end Gt of the glass ribbon G can be predicted from the presence or absence of breakage D2 in the upper end gt of the glass sheet g. The determination object may further include a portion of the glass ribbon G above the lower end Gt and / or a portion of the glass sheet g below the upper end gt.

[0054] In this embodiment, the determination device 3 includes a sensor 31 , a determination unit 32 , and a control unit 33 .

[0055] The sensor 31 is composed of a thermograph that measures the temperature distribution of the test objects Gt, gt, and is disposed below the height of the wheel cutter 23 and above the lower end of the support means 26. The sensor 31 of this embodiment is disposed below the height of the breaking bar 25 and above the lower end of the support means 26, and measures the temperature distribution across the entire width of the test objects Gt, gt. The sensor 31 is disposed at the center of the test objects Gt, gt in the width direction, on one main surface side of the test objects Gt, gt (the first main surface side of the glass ribbon G) and spaced apart from the main surface. The distance between the sensor 31 and the test objects Gt, gt can be set arbitrarily within a range that allows non-contact measurement of the temperature distribution of the test objects Gt, gt (for example, in the range of 800 to 3000 mm). The sensor 31 may also be disposed on the other main surface side of the test objects Gt, gt.

[0056] The determination unit 32 performs image analysis on the thermal image showing the temperature distribution captured by the sensor 31, and determines whether or not damage has occurred to the objects Gt, gt based on the results of the image analysis. Since the temperature differs between areas where glass is present and areas where no glass is present due to damage or the like, using a thermograph as the sensor 31 makes it possible to determine whether or not damage has occurred based on the temperature distribution. The determination unit 32 is configured with an information processing device such as a personal computer.

[0057] Here, when the glass ribbon G is cut by breaking, not only does the glass ribbon G vibrate after cutting, but the glass sheet g may also vibrate due to vibration or vibration of the support means 26. Furthermore, when the glass ribbon G is thin or when warping occurs in the glass ribbon G, the vibration of the glass ribbon G and the glass sheet g after cutting may become significant. However, the determination unit 32 determines whether or not breakage has occurred in the determination objects Gt, gt from the temperature distribution measured by the sensor 31, and is therefore less susceptible to adverse effects caused by the vibration of the glass ribbon G and the glass sheet g.

[0058] The control unit 33 adjusts the cut length of the glass ribbon based on the determination result of the determination unit 32. In detail, when the determination unit 32 determines that there is no breakage in the determination targets Gt, gt, the control unit 33 sets the cut length of the glass ribbon G to be cut by the cutting device 2 next to the standard cut length L0, as shown in FIGS. 2 to 4. On the other hand, when the determination unit 32 determines that there is breakage in the determination targets Gt, gt, the control unit 33 sets the cut length of the glass ribbon G to be cut by the cutting device 2 next to the extended cut length L1, which is longer than the standard cut length L0, as shown in FIGS. 6 to 8. In order to perform cutting at the standard cut length L0 or the extended cut length L1, the control unit 33 issues control signals to the wheel cutter 23, the support rod 24, the breaking bar 25, the support means 26, etc., according to the respective cut lengths L0, L1. The cut lengths L0, L1 are managed by the downward movement distance and / or movement time of the glass ribbon G.

[0059] Next, a method for manufacturing a glass sheet using the manufacturing apparatus configured as above will be described.

[0060] 1, the method for manufacturing a glass plate according to this embodiment includes a forming step, a transporting step, and an evaluation step. The transporting step includes a heat treatment step, a cooling step, and a cutting step.

[0061] The forming step is a step of forming a glass ribbon G by an overflow downdraw method in the forming zone 11. In the forming step, the glass ribbon G may be formed by other downdraw methods such as a redraw method or a slot downdraw method.

[0062] Here, the glass ribbon G and the glass plate g have a widthwise length of 1000 to 3500 mm and a thickness of 100 to 2000 μm. The standard cutting length L0 of the glass ribbon G is 800 to 3000 mm. The extended cutting length L1 is longer than the standard cutting length L0, and the difference (L1-L0) is preferably 0.05 m or more and 4.0 m or less, and more preferably 0.5 m or more and 1.5 m or less. Furthermore, the ratio (L1 / L0) of the extended cutting length L1 to the standard cutting length L0 is preferably 1.02 or more and 4.1 or less, and more preferably 1.05 or more and 2.0 or less. Here, as shown in FIGS. 2 and 6, the standard cutting length L0 and the extended cutting length L1 each refer to the length from the position (upper end) of the scribe line S formed in the current (nth) cutting step to the position (lower end) of the scribe line S formed in the previous (n-1th) cutting step. Therefore, if the glass ribbon G is damaged, the position of the scribe line S, which is the reference for the cutting length, may be an imaginary position where no glass is present.

[0063] The conveying step is a step of conveying the formed glass ribbon G downward by a pair of rollers R (conveying device).

[0064] The heat treatment step is a step of subjecting the glass ribbon G that has been subjected to the forming step to heat treatment (slow cooling) while transporting the glass ribbon G in the heat treatment zone 12.

[0065] The cooling step is a step in which the glass ribbon G that has been subjected to the heat treatment step is cooled while being transported in the cooling zone 13.

[0066] The cutting step is a step in which the glass ribbon G that has been subjected to the cooling step is conveyed and cut into glass sheets g by cutting the glass ribbon G in the width direction using a cutting device 2.

[0067] The cutting process includes a scribing process in which a scribe line S is formed on the glass ribbon G along its width direction, and a bending and breaking process in which the glass ribbon G is supported below the scribe line S by the chuck 27 of the support means 26, and the glass ribbon G is bent and broken along the scribe line S to cut out a glass plate g (standard glass plate gx or extended glass plate gy).

[0068] In the scribing step, first, the wheel cutter 23 and the support rod 24 are moved from the retracted position to the operating position while the glass ribbon G is supported by the multiple chucks 27 of the support means 26. Next, as shown in Fig. 2 or 6 , the wheel cutter 23 that has been moved to the operating position is caused to run along the width direction on the first main surface of the glass ribbon G to form a scribe line S.

[0069] After the scribing step is completed, the wheel cutter 23 and the support rod 24 are moved from the operating position to the retracted position. In this case, the support of the glass ribbon G by the chuck 27 of the support means 26 continues even after the scribing step is completed. Here, at the time when the scribing step is completed, the wheel cutter 23 and the support rod 24 are at the same height as the scribe line S. Thereafter, as the glass ribbon G moves further downward, the breaking bar 25 is held at the same height as the scribe line S instead of the wheel cutter 23 and the support rod 24, as shown in FIG. 3 or 7 .

[0070] In the bending and splitting step, as shown in Fig. 1, the bending and splitting bar 25 is moved from the retracted position to the working position, and the support means 26 is rotated as shown by arrow B. That is, in the bending and splitting step, the bending and splitting bar 25 is pressed against the first main surface of the scribe line formation region Sx, and the support means 26 is rotated to curve the scribe line formation region Sx in the vertical direction, with the bending and splitting bar 25 as a fulcrum, so that the first main surface side is convex. As a result, as shown in Fig. 4 or 8, the glass ribbon G is bent and split along the scribe line S, and a glass sheet g is cut out.

[0071] The determination step is a step of performing image analysis on a thermal image showing the temperature distribution captured by the sensor 31, and determining whether or not damage has occurred in the objects Gt, gt based on the results of the image analysis. In this embodiment, if it is determined in the determination step that damage has occurred in the objects Gt, gt, detailed information such as the location, shape, and size of the damage is also determined from the thermal image. In this embodiment, the determination step is automatically performed by the determination unit 32.

[0072] One method for determining the extent of damage is to determine the area of ​​high-temperature regions in the image obtained by thermography, where the temperature is equal to or higher than a predetermined value. In this case, for example, if the area of ​​the high-temperature regions falls below a predetermined threshold, it can be determined that there is significant damage to the glass. This is because the area where glass is present becomes hot, and the area where there is no glass due to the damage becomes cold.

[0073] If the determination unit 32 determines in the determination step that there is no damage to the determination objects Gt, gt, the control unit 33 sets the cutting length of the glass ribbon G in the next cutting step to the standard cutting length L0 and issues a control signal corresponding to the standard cutting length L0 to the wheel cutter 23, the support rod 24, the breaking bar 25, the support means 26, etc. As a result, as shown in FIGS. 2 to 4 , in the next cutting step, the glass ribbon G is bent and broken in the width direction at the standard cutting length L0, and a standard glass sheet gx cut at the standard cutting length L0 is obtained as the glass sheet g. In detail, as shown in FIG. 2 , at a scribing position P1, a scribe line S is formed in the width direction on the first main surface of the glass ribbon G by the wheel cutter 23 and the support rod 24 at a position corresponding to the standard cutting length L0. Thereafter, as shown in FIGS. 3 and 4 , at a breaking position P2, the glass ribbon G is bent and broken in the width direction at the standard cutting length L0 by the breaking bar 25 and the support means 26, and a standard glass sheet gx is cut out. The cut-out standard glass plate gx becomes a glass substrate (mother glass plate) from which one or more product glass plates are obtained. In other words, if the cut-out standard glass plate gx is not broken, it is transported to subsequent processes, including a process for cutting off the edge portions, a cleaning process, a testing process, and a packaging process.

[0074] On the other hand, as shown in FIG. 5 , if the determination unit 32 determines in the determination step that the determination objects Gt, gt have breaks D1, D2, the control unit 33 sets the cutting length of the glass ribbon G in the next cutting step to the extended cutting length L1 and issues control signals corresponding to the extended cutting length L1 to the wheel cutter 23, the support rod 24, the breaking bar 25, the support means 26, etc. As a result, as shown in FIGS. 6 to 8 , in the next cutting step, the glass ribbon G is bent and broken in the width direction at the extended cutting length L1, and an extended glass sheet gy cut at the extended cutting length L1 is obtained as the glass sheet g. In detail, as shown in FIG. 6 , at the scribing position P1, a scribe line S is formed in the width direction on the first main surface of the glass ribbon G by the wheel cutter 23 and the support rod 24 at a position corresponding to the extended cutting length L1. Thereafter, as shown in FIGS. 7 and 8 , at the breaking position P2, the glass ribbon G is bent and broken in the width direction at the extended cutting length L1 by the breaking bar 25 and the support means 26, and an extended glass sheet gy is cut out. The cut-out extended glass plate gy is discarded because it is a defective product. If the determination unit 32 determines that the determination objects Gt, gt have breaks D1, D2, the glass plate g including the determination object gt is also discarded. In other words, if the determination unit 32 determines that the determination objects Gt, gt have breaks D1, D2, at least two glass plates g are discarded consecutively. The glass plates g are discarded, for example, by releasing the support by the chuck 27 of the support means 26 and dropping the glass plates g into a recovery chamber located below the cutting chamber.

[0075] 9 , if it is determined in the determination step again that there are breaks D3 and D4 in the determination targets Gt, gt after the glass ribbon G has been cut at the extended cutting length L1, the glass ribbon G is also cut at the extended cutting length L1 in the next cutting step. On the other hand, if it is determined in the determination step that there is no break in the determination targets Gt, gt after the glass ribbon G has been cut at the extended cutting length L1, the glass ribbon G is cut at the standard cutting length L0 in the next cutting step. Thereafter, the same operation is repeated while adjusting the cutting length of the glass ribbon G to either the standard cutting length L0 or the extended cutting length L1 depending on the result of the determination step.

[0076] According to the above configuration, if there is breakage in the determination objects Gt, gt, the glass ribbon G is cut at an extended cutting length L1 that is longer than the standard cutting length L0. Therefore, the portion of the glass ribbon G where there is breakage can be sufficiently separated downward from the cutting position (scribe line formation region Sx) of the glass ribbon G. Therefore, it is possible to reliably prevent a situation in which a vertical crack occurs in the glass ribbon G beyond the cutting position of the glass ribbon G.

[0077] The extended cutting length L1 is preferably set so that the portion of the glass ribbon G where the break D1 exists is located below the position where the glass ribbon G comes into contact with the lowest chuck 27 of the support means 26. This reliably prevents the glass ribbon G from being cracked vertically due to contact between the portion of the glass ribbon G where the break D1 exists and the chuck 27.

[0078] In this embodiment, the extended cutting length L1 is a predetermined fixed value, but it may be a variable value that changes depending on the size of the breaks D1 and D2 of the objects Gt and gt (such as the vertical length or area on the thermal image). That is, if the size of the breaks D1 and D2 determined by the determination unit 32 is large, the extended cutting length L1 may be increased, and if the size of the breaks D1 and D2 is small, the extended cutting length L1 may be decreased. In this way, the length of the extended glass plate gy can be optimized depending on the size of the break, thereby reducing glass waste.

[0079] In the scribing step, it is preferable to set the travel speed V1 of the wheel cutter 23 when cutting the glass ribbon G at the extended cutting length L1 as shown in Fig. 6 to be slower than the travel speed V0 of the wheel cutter 23 when cutting the glass ribbon G at the standard cutting length L0 as shown in Fig. 2. Furthermore, in the bending and splitting step, it is preferable to set the operating speed W1 (operating speed in the direction B in Fig. 1) of the support means 26 that curves the scribe line formation region Sx when cutting the glass ribbon G at the extended cutting length L1 as shown in Fig. 8 to be slower than the operating speed W0 of the support means 26 that curves the scribe line formation region Sx when cutting the glass ribbon G at the standard cutting length L0 as shown in Fig. 4. This allows the glass ribbon G having breaks to be cut more safely at the extended cutting length L1, thereby more reliably suppressing vertical cracks in the glass ribbon G.

[0080] Second Embodiment The glass sheet manufacturing apparatus and glass sheet manufacturing method according to the second embodiment of the present invention differ from the first embodiment in the bending and breaking step of bending and breaking the glass ribbon G. In the bending and breaking step in the first embodiment, the glass ribbon is bent and broken by rotating the support means 26 while the bending and breaking bar 25 is pressed against the scribe line formation region Sx, and bending the scribe line formation region Sx in the vertical direction with the bending and breaking bar 25 as a fulcrum. In contrast, in the bending and breaking step in the second embodiment, the glass ribbon is bent and broken by pressing the bending bar 25 against the scribe line formation region Sx while operating the support means 26 to bend the scribe line formation region Sx in the vertical direction. In other words, the timing of pressing the bending bar 25 and the timing of rotating the support means 26 differ from the first embodiment.

[0081] In this type of bending and splitting process, even if the glass ribbon G moving downward in a vertical position has warpage along the longitudinal direction (vertical direction) or the width direction perpendicular thereto, the glass ribbon G can be properly bent and split without being adversely affected by the warpage. In other words, breakage due to cutting is less likely to occur at the lower end or the like of the glass ribbon G. In detail, in this method, in the bending and splitting process after the scribing process, the scribe line formation region Sx of the glass ribbon G is first bent in the vertical direction, and the warpage naturally disappears due to the bending deformation that is forcibly generated in the region Sx at this time. Next, by pressing the bending bar 25 against the scribe line formation region Sx that has been bent in a state where the warpage has disappeared, the bending bar 25 makes uniform contact with the region Sx without locally contacting it. Then, the glass ribbon G is bent and split while maintaining uniform contact with the bending bar 25, making it less likely that cutting errors will occur. Furthermore, since there is less need to consider cutting errors when folding and splitting, it becomes possible to operate the support means 26 at high speed, thereby shortening the tact time.

[0082] In this case, in the breaking step, when cutting the glass ribbon G at the extended cutting length L1, it is preferable to slow down at least one of the operating speed of the support means 26 that curves the scribe line formation region Sx and the operating speed of the breaking bar 25 that presses against the scribe line formation region Sx (the moving speed of the breaking bar 25 from the retracted position to the operating position in FIG. 1 ) compared to when cutting the glass ribbon G at the standard cutting length L0. This allows the glass ribbon G having damage to be cut more safely at the extended cutting length L1, thereby more reliably suppressing vertical cracks in the glass ribbon G.

[0083] If the operating speed of the supporting means 26 when cutting at the extended cutting length L1 is X1 and the operating speed of the supporting means 26 when cutting at the standard cutting length L0 is X0, then X1 / X0 is preferably 10% to 90%. Also, if the operating speed of the cutting bar 25 when cutting at the extended cutting length L1 is Y1 and the operating speed of the cutting bar 25 when cutting at the standard cutting length L0 is Y0, then Y1 / Y0 is preferably 10% to 90%.

[0084] (Third embodiment) As shown in Fig. 10, the glass sheet manufacturing apparatus and glass sheet manufacturing method according to the third embodiment differ from the above-described embodiments in that a plurality of sensors (thermographs) 31 (three in the illustrated example) are installed along the width direction. In this manner, the entire width of the objects Gt, gt can be measured more precisely than when a single sensor 31 is used to measure the entire width of the objects Gt, gt. Therefore, in the determination step, the determination unit 32 can more precisely determine whether or not the objects Gt, gt are damaged in the width direction. When a plurality of sensors 31 are installed, it is preferable to install a dedicated sensor 31 in at least three regions of the objects Gt, gt: one end in the width direction, a center in the width direction, and the other end in the width direction.

[0085] (Fourth embodiment) As shown in Figure 11, the glass plate manufacturing apparatus and glass plate manufacturing method according to the fourth embodiment of the present invention differ from the above-mentioned embodiments in that in the determination process, the sensor 31 measures only the widthwise edge (ear portion) of the object to be determined (the lower end portion of the glass ribbon G) Gt.

[0086] In the present embodiment, the sensors 31 are respectively installed on both arms 28 of the support means 26. In the illustrated example, one sensor 31 is installed on each arm 28 between the lowest chuck 27 and the second-lowest chuck 27. The determination unit 32 measures the presence or absence of both widthwise end edges of the object to be determined Gt, which moves downward while passing between the chucks 27 of the support means 26, while the chucks 27 are in an open state. The control unit 33 issues control signals to the wheel cutter 23, the support rod 24, the breaking bar 25, the support means 26, etc., so as to start cutting-related operations a predetermined time after the determination unit 32 determines that both widthwise end edges of the object to be determined Gt are present. In other words, when there is damage to the widthwise end edge of the object to be determined Gt, the cut length of the glass ribbon G (the length from the position (upper end) of the scribe line S formed in the n-th cutting step to the position (lower end) of the scribe line S formed in the n-1-th cutting step) is longer than when there is no damage. Therefore, even with this configuration, if it is determined in the determination process that the object Gt to be determined is damaged, in the next cutting process, the glass ribbon G will be cut to an extended cutting length longer than the standard cutting length.

[0087] In the above configuration, even if there is breakage in the widthwise central portion of the glass ribbon G, if there is no breakage at both widthwise end edges of the glass ribbon G, it is not determined that there is breakage in the glass ribbon G. However, vertical cracks in the glass ribbon G are particularly likely to occur when the glass ribbon G is cut in the vicinity of the cutting position of the glass ribbon G without both widthwise end edges. Therefore, simply determining whether or not there is breakage at both widthwise end edges of the glass ribbon G has the effect of suppressing vertical cracks in the glass ribbon G. In addition, from the viewpoint of further suppressing vertical cracks, it is preferable to add a sensor for determining whether or not there is a widthwise central portion of the glass ribbon G in the above configuration.

[0088] Fifth Embodiment As shown in FIG. 12 , the glass plate manufacturing apparatus and the glass plate manufacturing method according to the fifth embodiment of the present invention differ from the above-described embodiments in that a plurality of sensors 31 are arranged in the vertical direction, and in the determination step, the upper sensor 31 a and the lower sensor 31 b determine different objects to be determined.

[0089] For example, as shown in Figures 13 and 14, the judgment area (area surrounded by dotted lines) Ja of the upper sensor 31a includes the entire width of the upper end gt of the glass plate g as the judgment target, and the judgment area (area surrounded by dotted lines) Jb of the lower sensor 31b includes the entire width of the central portion gu of the glass plate g below the upper end gt as the judgment target.

[0090] With this configuration, as shown in FIGS. 13 and 14 , when large breaks D5 and D6 extending from the upper end gt to the central portion gu of the glass sheet g occur, the glass breakage is detected not only by the upper sensor 31a but also by the lower sensor 31b. When glass breakage is detected by the lower sensor 31b in this manner, the extended cutting length L1 is set to the first length. On the other hand, as shown in FIG. 15 , instead of large breaks extending from the upper end gt to the central portion gu of the glass sheet g, breakage D7 may occur only at the upper end gt of the glass sheet g. In this case, glass breakage is detected only by the upper sensor 31a. When glass breakage is detected only by the upper sensor 31a in this manner, the extended cutting length L1 is set to a second length shorter than the first length. Note that, as shown in FIG. 16 , breakage D8 may occur only at the central portion gu of the glass sheet g (in the illustrated example, at the widthwise end of the central portion gu). In this case, glass breakage is detected only by the lower sensor 31b. Even if glass breakage is detected only by the lower sensor 31b in this way, there may be small scratches on the upper end gt of the glass plate g, and it is preferable to set the extended cutting length L1 to the first length (>second length).

[0091] For example, it is preferable that the vertical ranges of the determination area Ja of the upper sensor 31a and the determination area Jb of the lower sensor 31b are equal, or that the vertical range of the determination area Ja of the upper sensor 31a is wider than the vertical range of the determination area Jb of the lower sensor 31b. The vertical ranges of the determination area Ja of the upper sensor 31a and the determination area Jb of the lower sensor 31b are each preferably 0.5 to 10% of the standard cutting length L0 of the glass ribbon G, and more preferably 1 to 7%.

[0092] 17 , the determination area (area surrounded by a dotted line) Jb of the lower sensor 31b may include the entire width direction of the lower end Gt of the glass ribbon G as the determination target, and the determination area (area surrounded by a dotted line) Ja of the upper sensor 31a may include the entire width direction of the central portion Gu of the glass ribbon G above the lower end Gt as the determination target. In this case, as in the above, it is possible to distinguish between the following cases: (1) there is significant damage extending from the lower end Gt to the central portion Gu of the glass ribbon G, (2) there is damage only in the lower end Gt of the glass ribbon G, and (3) there is damage only in the central portion Gu of the glass ribbon G, and to adjust the extended cutting length L1. For example, in the cases where there is significant damage extending from the lower end Gt to the central portion Gu of the glass ribbon G and where there is damage only in the central portion Gu of the glass ribbon G, the extended cutting length L1 may be set to a relatively long first length, and in the case where there is damage only in the lower end Gt of the glass ribbon G, the extended cutting length L1 may be set to a relatively short second length.

[0093] In this embodiment, the extended cut length L1 is adjusted according to the type of damage, specifically, the vertical position of the damage. However, the extended cut length L1 may also be adjusted according to the widthwise position of the damage (or the vertical and widthwise positions). For example, if the location of the damage includes the widthwise end portions, the extended cut length L1 may be set relatively long, and if the location of the damage is limited to the widthwise center portion, the extended cut length L1 may be set relatively short. Furthermore, the type of damage may include not only the location of the damage but also the size of the damage, and the extended cut length L1 may be adjusted taking the size of the damage into consideration. For example, if the size of the damage is large, the extended cut length L1 may be set relatively long, and if the size of the damage is small, the extended cut length L1 may be set relatively short. Furthermore, the type of damage may include, for example, the shape of the damaged portion, and the extended cut length L1 may be set according to the shape of the damaged portion.

[0094] The above describes a glass sheet manufacturing apparatus and a glass sheet manufacturing method according to an embodiment of the present invention, but the embodiment of the present invention is not limited to this, and various modifications can be made within the scope of the gist of the present invention.

[0095] In the above embodiment, a case has been described in which a thermograph is used as the sensor 31 for measuring the object to be determined, but the sensor 31 is not limited to this. For example, the sensor 31 may be another temperature sensor such as a radiation thermometer, or a laser sensor that irradiates laser light and detects transmitted light or reflected light from the object to be determined Gt, gt.

[0096] Furthermore, in the above embodiment, the breaking bar 25 is pressed against the glass ribbon G (scribe line formation region Gx) at a height position that is the same as or approximately the same as the scribe line S. However, the breaking bar 25 may be pressed against a portion of the glass ribbon G above the scribe line S. Here, the portion above the scribe line S refers to a portion of the glass ribbon G that is not curved in the vertical direction and is spaced a predetermined distance above the scribe line S. This predetermined distance is 5 mm or more and less than 70 mm. Furthermore, considering that the glass ribbon G has an effective region (a region that will become the product glass sheet after breaking), this predetermined distance may be 5 mm or more and less than the distance from the scribe line S to the lower end of the effective region. In this case, the predetermined distance is 5 mm or more and less than 20 mm, taking into account the effective region of the glass ribbon G in this embodiment.

[0097] In the above embodiment, the support means 4 rotates along a circular orbit centered on the position of the dividing bar 25 (the position indicated by the solid line in FIG. 1), but it may also rotate along a curved orbit other than a circular orbit. Furthermore, the operation of the support means 4 may be an operation other than a rotation operation as long as it is an operation that can curve the scribe line formation region Gx.

[0098] In the above embodiment, the supporting means 4 is configured to support the glass ribbon G by clamping it with the chucks 27, but the supporting manner of the supporting means 4 is not limited to this. For example, the supporting means 4 may be configured to support the first main surface or the second main surface of the glass ribbon G by suction with a suction pad or the like.

[0099] In the above embodiment, the glass ribbon G is cut by bending along the scribe lines S, but the glass ribbon G may be cut by other methods such as laser cleaving or laser melting. [Explanation of symbols]

[0100] 1 Processing equipment 2 Cutting device 3 Judgment device 4 Support means 11 Forming Zone 12 Heat Treatment Zone 13 Cooling Zone 14 Conveyor equipment 15 Molded body 21 Scribe device 22 Folding device 23 Wheel cutter 24 Support rod 25 Breaking bar 26 Support means 27 Zipper 31 Sensors 32 Judgment section 33 Control Unit D1~D8 Damaged G Glass ribbon g Glass plate Gt Judgment target (bottom end of glass ribbon) gt Object to be judged (top edge of glass plate) Gx Scribe line formation area gx standard glass plate gy extension glass plate L0 Standard cutting length L1 extended cutting length S scribe line Sx Scribe line formation area

Claims

1. A method for manufacturing a glass sheet, comprising a cutting step of cutting a glass ribbon moving downward in a vertical position along its width direction to a standard cutting length to obtain a glass sheet, A determination step of determining whether or not a portion including at least one of a lower end of the glass ribbon and an upper end of the glass sheet after cutting in the cutting step is broken as a determination object, a cutting step for cutting the glass ribbon to an extended cutting length longer than the standard cutting length in the next cutting step when it is determined in the determination step that there is breakage of the object to be determined.

2. The method for manufacturing a glass plate according to claim 1 , wherein the determining step includes measuring the object to be determined by a sensor and determining whether or not the object to be determined is broken based on the measurement result.

3. The method for manufacturing a glass plate according to claim 2 , wherein the sensor measures the widthwise end portions of the object to be determined.

4. The method for manufacturing a glass plate according to claim 2 or 3, wherein the sensor measures the end portions and the central portion in the width direction of the object to be determined.

5. The method for manufacturing a glass plate according to any one of claims 1 to 4, wherein a value obtained by subtracting the standard cutting length from the extended cutting length is 0.05 m or more and 4.0 m or less.

6. The method for manufacturing a glass plate according to any one of claims 1 to 4, wherein the extended cutting length is 1.02 to 4.1 times the standard cutting length.

7. The method for manufacturing a glass plate according to any one of claims 1 to 6, wherein in the cutting step, the extended cutting length is adjusted depending on the type of breakage of the object to be determined.

8. The method for manufacturing a glass plate according to claim 7 , wherein in the cutting step, the extended cutting length is adjusted depending on at least one of a position and a size of the breakage to be determined.

9. the cutting step includes a scribing step of forming a scribe line in the glass ribbon along its width direction, and a bending and breaking step of bending and breaking the glass ribbon along the scribe line in a state in which the glass ribbon is supported by a support means below the scribe line, to cut out the glass sheet, The method for manufacturing a glass plate according to any one of claims 1 to 8, wherein in the bending and breaking step, a bending bar is pressed against a region of the glass ribbon where the scribe line is to be formed.

10. the bending and breaking step is a step of bending and breaking the glass ribbon by operating the support means in a state in which the bending and breaking bar is pressed against the scribe line formation region, and bending the scribe line formation region in a vertical direction with the bending and breaking bar as a fulcrum, 10. The method for manufacturing a glass plate according to claim 9, wherein, when cutting the glass ribbon to the extended cutting length, the operating speed of the supporting means for curving the region where the scribe line is formed is slower than when cutting the glass ribbon to the standard cutting length.

11. the bending and breaking step is a step of bending and breaking the glass ribbon by pressing the bending and breaking bar against the scribe line formation region in a state in which the support means is operated to bend the scribe line formation region in a vertical direction, 10. The method for manufacturing a glass plate according to claim 9, wherein, when cutting the glass ribbon at the extended cutting length, at least one of the operating speed of the support means that curves the scribe line formation region and the operating speed of the breaking bar that is pressed against the scribe line formation region is made slower than when cutting the glass ribbon at the standard cutting length.

12. The method for manufacturing a glass plate according to any one of claims 9 to 11, wherein, in the cutting step, the extended cutting length is set so that, if the glass ribbon is broken, the broken portion is positioned below a contact position of the support means with the glass ribbon.

13. A glass sheet manufacturing apparatus including a cutting device for cutting a glass ribbon moving downward in a vertical position along its width direction to a standard cutting length to obtain a glass sheet, a determination unit that determines whether or not a portion including at least one of a lower end of the glass ribbon and an upper end of the glass sheet after cutting by the cutting device is broken; a control unit that adjusts the cutting length of the glass ribbon based on the determination result of the determination unit, The control unit sets the next cutting length of the glass ribbon by the cutting device to an extended cutting length that is longer than the standard cutting length when the determination unit determines that the object to be determined has been damaged.

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