Method for manufacturing glass article

Abstract

Provided is a method for manufacturing a glass article, whereby an exhaust step can be efficiently performed. A method for manufacturing a glass article includes a temperature raising step (S1), a starting step (S2), and a molding step (S4). The forming furnace (2) is provided with a top wall (2b) positioned above the formed body (6). The temperature of the top wall (2b) of the forming furnace (2) in the start step (S2) is lower than the temperature of the top wall (2b) of the forming furnace (2) in the forming step (S4).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a glass article. Background Art

[0002] The overflow downdraw method is sometimes used to manufacture glass products such as glass sheets. This method uses a forming apparatus with a generally wedge-shaped forming body. Molten glass supplied to the forming body overflows in two directions from a groove formed at the top of the forming body, then flows along the two outer side surfaces of the forming body and merges at the lower end.

[0003] This method continuously forms a ribbon-shaped glass ribbon from molten glass. According to this method, the front and back surfaces of the formed glass ribbon do not come into contact with the forming body during the forming process, thereby having the advantage of being able to form a smooth glass ribbon without scratches on the front and back surfaces.

[0004] Patent Document 1 discloses a method for producing glass articles that includes a step of venting a forming body (isopress) before forming a glass ribbon from molten glass. In this method, the venting step involves bringing the molten glass into contact with the forming body, whereupon the molten glass is transferred to the molten glass, thereby removing gases contained within and on the surface of the forming body (see paragraph 0023 of the document).

[0005] Furthermore, in the exhaust step, the forming body is tilted at a predetermined tilt angle θ from its normal posture at which the molten glass can be formed in order to promote contact of the molten glass with the forming body (see claim 5 and paragraph 0012 of the document).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-120845 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] In the conventional method for producing a glass article as described above, a large-scale operation of tilting the formed body is performed in the exhaust step, and thus there is a problem in that the production efficiency of the glass article is reduced.

[0011] The present invention has been made in view of the above circumstances, and a technical object of the present invention is to efficiently perform the exhaust process.

[0012] Solutions to Problems

[0013] (1) The present invention is a method for manufacturing a glass article for solving the above-mentioned problems, comprising: a heating step of heating a forming body accommodated in a forming furnace; a starting step of starting to supply molten glass to the forming body that has passed the heating step; and a forming step of forming a glass ribbon from the molten glass by an overflow method using the forming body that has passed the starting step. The method for manufacturing the glass article is characterized in that the forming furnace has a top wall located above the forming body, and the temperature of the top wall of the forming furnace in the starting step is lower than the temperature of the top wall of the forming furnace in the forming step.

[0014] This structure allows the top wall of the forming furnace to be at a lower temperature during the initial process than during the forming process. This reduces the velocity of the molten glass flowing over the forming body. This allows the molten glass to flow evenly over a wider area of ​​the forming body. This eliminates the need to tilt the forming body as previously required, allowing for efficient exhaust after the initial process.

[0015] (2) In the method for manufacturing a glass article having the structure of (1) above, the method may include a degassing step of degassing the formed body by continuously supplying the molten glass to the formed body between the starting step and the forming step.

[0016] According to this configuration, in the exhaust step, molten glass is continuously supplied to the forming body, and the forming body can be reliably exhausted.

[0017] (3) In the method for manufacturing a glass article described in (2) above, the forming body may include: a groove portion to which the molten glass is supplied; an upper portion for the molten glass overflowing from both directions of the groove portion to flow down respectively; and a lower portion for merging the molten glasses flowing down respectively at the upper portion to form the glass ribbon, the forming furnace may include a heater for heating the lower portion of the forming body, and the temperature of the heater in the exhaust process may be higher than the temperature of the heater in the forming process.

[0018] According to this structure, the temperature of the heater that heats the lower portion of the forming body in the exhaust step is set higher than the temperature of the heater in the forming step, thereby preventing the block of molten glass falling from the lower portion of the forming body from becoming larger. This makes it easier to handle the molten glass falling from the forming body and prevents damage to the equipment.

[0019] (4) In the method for manufacturing a glass article described in (2) or (3) above, the forming furnace may include a pressing member for pressing the formed body, and the pressing force applied to the formed body by the pressing member in the exhaust step is smaller than the pressing force applied to the formed body by the pressing member in the forming step.

[0020] During the forming process, a pressing force is applied to the formed body by a pressing member to prevent creep deformation. During the heating and exhausting processes, the formed body is heated, causing it to expand. Therefore, applying the same pressing force from the pressing member as during the forming process could cause the formed body to crack due to expansion. In this method, the pressing force during the exhausting process is reduced compared to the pressing force during the forming process, thereby promoting expansion of the formed body during the exhausting process and preventing cracking of the formed body.

[0021] (5) In the method for manufacturing a glass article described in any one of (2) to (4) above, the temperature of the top wall of the forming furnace in the exhaust step may be higher than the temperature of the top wall of the forming furnace in the start step.

[0022] According to this structure, the temperature of the top wall of the forming furnace during the exhaust process is higher than the temperature at the start of the process, thereby promoting the exhaust treatment of the formed body. In addition, the temperature of the top wall during the exhaust process is close to the temperature of the top wall during the forming process, so that the forming process after the exhaust process can be started smoothly.

[0023] (6) In the method for manufacturing a glass article described in any one of (1) to (5) above, the forming body may include: a groove portion to which the molten glass is supplied; an upper portion for the molten glass overflowing from both directions of the groove portion to flow down respectively; and a lower portion for merging the molten glasses flowing down respectively from the upper portion to form the glass ribbon, and the forming furnace may include a heater for heating the lower portion of the forming body, and the temperature of the heater in the starting process may be higher than the temperature of the heater in the forming process.

[0024] With this configuration, the molten glass supplied to the forming body during the initial step does not form a glass ribbon, but rather forms lumps that fall from the forming body. In this method, the temperature of the heater used to heat the lower portion of the forming body during the initial step is set higher than the temperature of the heater used during the forming step. This prevents the lumps of molten glass that fall from the lower portion of the forming body from becoming larger. This facilitates handling of the molten glass that falls from the forming body and prevents damage to the equipment.

[0025] Effects of the Invention

[0026] According to the present invention, the exhaust step can be performed efficiently. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a side view showing a manufacturing apparatus for a glass article.

[0028] Figure 2 This is a front view showing a glass article manufacturing apparatus.

[0029] Figure 3 It is a side view of the forming furnace.

[0030] Figure 4 This is the front view of the forming furnace.

[0031] Figure 5 is a flowchart illustrating a method for manufacturing a glass article.

[0032] Figure 6 This is a side view of the forming furnace during the heating process.

[0033] Figure 7 This is a front view of the forming furnace during the heating process.

[0034] Figure 8 This is a side view of the forming furnace in the initial process.

[0035] Description of Reference Numerals

[0036] 2 Forming furnace

[0037] 2b Top wall of forming furnace

[0038] 6 formed body

[0039] 6a Upper part of the formed body

[0040] 6b Lower part of the molded body

[0041] 7a First pressing member

[0042] 7b Second pressing member

[0043] 15. Second external heater

[0044] Gm molten glass

[0045] S1 Heating process

[0046] S2 Start process

[0047] S3 exhaust process

[0048] S4 forming process. DETAILED DESCRIPTION

[0049] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Figures 1 to 8An embodiment of a method for manufacturing a glass article according to the present invention is shown. It should be noted that in the orthogonal coordinate system consisting of X, Y, and Z shown in the figure, the X and Y directions are horizontal directions, and the Z direction is the vertical direction. Furthermore, the direction corresponding to the width of the formed glass ribbon is referred to as the width direction X, and the direction corresponding to the thickness of the formed glass ribbon is referred to as the thickness direction Y.

[0050] Figure 1 as well as Figure 2 A glass article manufacturing apparatus for implementing the present method is shown. The manufacturing apparatus 1 includes a forming furnace 2; an annealing furnace 3 located below the forming furnace 2; a cooling chamber 4 located below the annealing furnace 3; and a cutting chamber 5 located below the cooling chamber 4. The forming furnace 2 and annealing furnace 3, the annealing furnace 3 and cooling chamber 4, and the cooling chamber 4 and cutting chamber 5 are separated by partition members (e.g., building floors) F1, F2, and F3, respectively, each having an opening (e.g., a slit) through which the glass ribbon Gr passes.

[0051] like Figure 1 as well as Figure 2 As shown, the forming furnace 2 is an area for forming a glass ribbon Gr from molten glass Gm by an overflow downdraw method. The forming furnace 2 includes a forming body 6 for forming the glass ribbon Gr from the molten glass Gm, pressing members 7a and 7b for pressing the forming body 6, and first conveying rollers 8 for cooling both ends of the glass ribbon Gr formed by the forming body 6 in the width direction X. The forming furnace 2 also has side walls 2a located to the sides of the forming body 6 and a top wall 2b located above the forming body 6.

[0052] The forming body 6 is formed of a refractory material that is elongated along the width direction X. Examples of the refractory material include zircon, zirconia, alumina, magnesia, and xenotime. The forming body 6 includes an upper portion 6a to which the molten glass Gm is supplied and a lower portion 6b for shaping the molten glass supplied to the upper portion 6a.

[0053] The molded body 6 has a groove portion (overflow groove) 8 formed in its upper portion 6a along the width direction X. A supply pipe 10 is connected to one end 9a of the groove portion 9 in the width direction X. Hereinafter, the end 9a of the groove portion 9 to which the supply pipe 10 is connected is referred to as the first end, and the end 9b located opposite the first end 9a in the width direction X is referred to as the second end.

[0054] The molten glass Gm is supplied into the groove portion 9 through the supply pipe 10. The method of supplying the molten glass Gm is not limited thereto. For example, the molten glass Gm may be supplied from both sides of the first end portion 9a and the second end portion 9b of the groove portion 9, or from above the groove portion 9.

[0055] The formed body 6 has a symmetrical shape in the thickness direction Y. The two outer side surfaces 11 of the formed body 6 in the thickness direction Y respectively include a vertical surface 12 in the form of a plane along the vertical direction and an inclined surface 13 connected to the bottom of the vertical surface 12 and in the form of a plane inclined relative to the vertical direction. The vertical surface 12 is located in the upper part 6a of the formed body 6, and the inclined surface 13 is located in the lower part 6b of the formed body 6. The vertical surface 12 is a plane parallel to each other. The inclined surface 13 is a plane that is inclined so as to approach each other in the thickness direction Y as it goes downward. That is, the formed body 6 has a wedge shape that becomes thinner at the front end as it goes downward when viewed from the width direction X by forming the inclined surface 13, and the corner where the inclined surface 13 intersects forms the lower end 6b1 of the formed body 6. It should be noted that the vertical surface 12 can also be changed in shape to an inclined surface, a curved surface, etc., or can be omitted.

[0056] The pressing members 7a and 7b are used to suppress creep deformation of the formed body 6 and to press the lower portion 6b of the formed body 6. The pressing members 7a and 7b are formed, for example, of refractory bricks. The pressing members 7a and 7b include a first pressing member 7a that presses one end of the formed body 6 in the width direction X, and a second pressing member 7b that presses the other end of the formed body 6. The first pressing member 7a and the second pressing member 7b are arranged so as to oppose each other in the width direction X. By sandwiching the lower portion 6b of the formed body 6, they can apply a force (pressing force) to the formed body 6 that presses the lower portion 6b of the formed body 6 in the width direction X.

[0057] like Figures 1 to 4 As shown, the first conveying rollers 8 are configured as a pair of rollers that sandwich the ends of the glass ribbon Gr in the width direction X in the thickness direction Y immediately below the forming body 6. The first conveying rollers 8 are cantilever-type rollers with internal cooling mechanisms. The first conveying rollers 8 are also referred to as cooling rollers or edge rollers.

[0058] like Figure 4 As shown, in a state in which the glass ribbon Gr can be formed, the first conveying roller 8 of the forming furnace 2 is inserted from outside the forming furnace 2 into the furnace through an opening 2c provided in the side wall 2a of the forming furnace 2. The gap between the opening 2c and the shaft 8a of the first conveying roller 8 is sealed by a first sealing member 2d made of, for example, refractory fiber. One end of the shaft 8a is held by a bearing (not shown) disposed outside the forming furnace 2.

[0059] like Figure 3 as well as Figure 4 As shown, a first external furnace heater 14 for heating the upper portion 6a of the formed body 6 and a second external furnace heater 15 for heating the lower portion 6b of the formed body 6 are provided on the side wall 2a of the forming furnace 2. A third external furnace heater 16 for heating the upper portion 6a of the formed body 6 is provided on the top wall 2b of the forming furnace 2.

[0060] like Figure 3 as well as Figure 4 As shown, the first external furnace heater 14 is disposed at a position corresponding to the upper portion of the side wall 2a of the forming furnace 2 to heat the upper portion 6a of the formed body 6. The second external furnace heater 15 is disposed at a position corresponding to the lower portion of the side wall 2a of the forming furnace 2 to heat the lower portion 6b of the formed body 6. The third external furnace heater 16 is disposed at a position corresponding to the top wall 2b of the forming furnace 2 to heat the upper portion 6a of the formed body 6, particularly the upper surface and the groove portion 9.

[0061] Furthermore, a first external-furnace thermometer 17 is provided on the side wall 2a for measuring the temperature of the side wall 2a at a position corresponding to the first external-furnace heater 14, and a second external-furnace thermometer 18 is provided for measuring the temperature of the side wall 2a at a position corresponding to the second external-furnace heater 15. A third external-furnace thermometer 19 is provided on the top wall 2b for measuring the temperature of the top wall 2b at a position corresponding to the third external-furnace heater 16. It should be noted that the external-furnace heaters 14-16 may be divided into a plurality of sections in the width direction X, each comprising a plurality of zone heaters. In this case, an external-furnace thermometer 17-19 may be provided for each zone heater.

[0062] like Figure 1 as well as Figure 2 As shown, the annealing furnace 3 is an area for reducing warpage and internal strain in the glass ribbon Gr. Second conveying rollers 20 are arranged inside the annealing furnace 3. The second conveying rollers 20 are also called annealing rollers. The second conveying rollers 20 are configured as a pair of rollers that clamp each end of the glass ribbon Gr in the width direction X in the thickness direction Y. The second conveying rollers 20 can also be rollers of the end support type arranged so as to span the entire width direction X of the glass ribbon Gr, but in this embodiment, they are cantilever rollers. The second conveying rollers 20 are arranged in multiple stages in the vertical direction Z.

[0063] like Figure 1 as well as Figure 2 As shown, the cooling chamber 4 is an area for cooling the glass ribbon Gr to near room temperature. Third conveyor rollers 21 are arranged within the cooling chamber 4. The third conveyor rollers 21 are configured as a pair of rollers that clamp each end of the glass ribbon Gr in the width direction X in the thickness direction Y. The third conveyor rollers 21 may also be rollers of the double-ended type arranged across the entire width direction X of the glass ribbon Gr, but in this embodiment, they are cantilever rollers. The third conveyor rollers 21 are arranged in multiple stages in the vertical direction Z.

[0064] In the present embodiment, both end portions in the width direction X of the glass ribbon Gr obtained by the production apparatus 1 include ear portions having a thickness greater than that of the central portion in the width direction X due to the influence of shrinkage during the forming process.

[0065] like Figure 1 as well as Figure 2 As shown, the cutting chamber 5 is an area for cutting the glass ribbon Gr into predetermined sizes to obtain glass sheets G as glass products. A cutting device (not shown) is disposed within the cutting chamber 5 to cut the glass ribbon Gr. In this embodiment, the cutting device cuts the glass ribbon Gr by forming score lines on the glass ribbon Gr and then breaking the glass ribbon Gr along the score lines. However, this is not limited to this method. The cutting device may also use laser cutting, laser melting, or other cutting methods, for example.

[0066] Glass sheet G is a raw glass sheet (mother glass sheet) from which one or more finished glass sheets are extracted. The finished glass sheet has a thickness of, for example, 0.2 mm to 10 mm, and dimensions of, for example, 700 mm x 700 mm to 3500 mm x 3500 mm. These finished glass sheets are used, for example, as substrates or cover glass for displays.

[0067] Hereinafter, a method for manufacturing a glass ribbon Gr and a glass plate G as glass articles using the manufacturing apparatus 1 having the above-mentioned structure will be described. Figure 5 As shown, the method includes a heating step S1, a starting step S2, and an exhaust step S3 as preparation steps, and a forming step S4, an annealing step S5, a cooling step S6, and a cutting step S7 as production steps.

[0068] The heating step S1 is a step of heating the formed body 6 accommodated in the forming furnace 2 before the forming step S4. Figure 6 as well as Figure 7 As shown, in the temperature raising step S1 , a furnace heater 22 for heating the lower portion 6 b (lower end portion 6 b 1 ) of the formed body 6 and a furnace thermometer 23 for measuring the temperature of the lower portion 6 b (lower end portion 6 b 1 ) of the formed body 6 are arranged inside the forming furnace 2 .

[0069] The furnace heaters 22 are arranged in pairs so as to sandwich the passage portion of the glass ribbon Gr below the lower end portion 6b1 of the forming body 6 from both sides in the thickness direction Y. In this embodiment, the furnace heaters 22 are composed of a pair of rod-shaped heaters (e.g., sheathed heaters) extending in the width direction X and facing each other in the thickness direction Y.

[0070] The furnace heaters 22 extend across the interior of the forming furnace 2 in the width direction X. Both ends of the furnace heaters 22 pass through the side walls 2a of the forming furnace 2 and are held outside the forming furnace 2. Note that a plurality of paired furnace heaters 22 may be arranged vertically.

[0071] In the temperature raising step S1, the first conveying rollers 8 are not provided in the forming furnace 2. Instead, a furnace heater 22 is provided. Specifically, the furnace heater 22 is provided from outside the forming furnace 2 through an opening 2c in the side wall 2a of the forming furnace 2. The gap between the opening 2c and the furnace heater 22 is sealed by a second sealing member 2e made of, for example, refractory fiber. One end of the furnace heater 22 and the furnace thermometer 23 are held by a member provided outside the forming furnace 2.

[0072] like Figure 6 As shown, in a side view, the furnace heater 22 is preferably positioned within a circle C centered on the lower end portion 6b1 of the formed body 6. The diameter D of the circle C is preferably, for example, 50 mm to 300 mm, and more preferably 100 mm to 200 mm. This allows the lower portion 6b of the formed body 6, including the lower end portion 6b1, to be efficiently heated.

[0073] like Figure 7 As shown, the width dimension W1 of the furnace heater 22 in the forming furnace 2 is larger than the width dimension W2 of the lower end portion 6b1 of the formed body 6. Thus, the lower end portion 6b1 of the formed body 6 is heated by the furnace heater 22 over its entire width.

[0074] A furnace thermometer 23 (e.g., a thermocouple) is disposed immediately below the lower end portion 6b1 of the forming body 6, i.e., the portion through which the glass ribbon Gr passes. The location of the furnace thermometer 23 is not particularly limited, as long as it can measure the temperature of the lower portion 6b of the forming body 6. For example, the furnace thermometer 23 may be disposed in contact with the lower portion 6b of the forming body 6, or multiple furnace thermometers 23 may be disposed.

[0075] like Figure 6 as well as Figure 7 As shown, in the temperature raising step S1, the lower portion 6b of the formed body 6 is heated by the furnace heater 22 disposed in the forming furnace 2. Thus, even when an upward airflow is generated in the forming furnace 2, the temperature of the lower portion 6b of the formed body 6 can be stabilized by the furnace heater 22 disposed near the lower portion 6b of the formed body 6, thereby reducing damage to the formed body 6 such as cracks due to thermal shock.

[0076] In the temperature raising step S1 of the present embodiment, the formed body 6 is also heated by the external heaters 14 to 16 disposed outside the forming furnace 2. This allows the temperature distribution in the forming furnace 2 to be appropriately adjusted.

[0077] The heating temperature of the in-furnace heater 22 and / or the external heaters 14 to 16 is adjusted based on the temperature measured by the in-furnace thermometer 23 and / or the external thermometers 17 to 19. For example, the heating temperature of the second external heater 15 and the in-furnace heater 22 is preferably set higher than the heating temperature of the first external heater 14 and the third external heater 16. The temperature distribution within the forming furnace 2 is not limited to that of the present embodiment.

[0078] The pressing force applied by the pressing members 7a and 7b to the formed body 6 in the heating step S1 is desirably set to be smaller than the pressing force applied by the pressing members 7a and 7b to the formed body 6 in the forming step S4. In the heating step S1, the formed body 6 expands due to being heated. Setting the pressing force smaller in the heating step S1 can appropriately promote the expansion of the formed body 6. The ratio (FP1 / FP4) of the pressing force FP1 (N) in the heating step S1 to the pressing force FP4 (N) in the forming step S4 can be, for example, 0.01 to 0.40, preferably 0.05 to 0.20.

[0079] When the formed body 6 is heated to a predetermined temperature in the heating step S1, the process proceeds from the heating step S1 to the starting step S2. During the transition from the heating step S1 to the starting step S2, heating of the formed body 6 by the in-furnace heater 22 and the external heaters 14 to 16 is continued, and the in-furnace thermometer 23 is removed from the furnace.

[0080] The starting step S2 is a step for starting to supply molten glass Gm to the forming body 6 that has passed through the heating step S1. In the starting step S2, the flow path of the molten glass Gm that was closed by a plunger, a gate, etc. is opened, and the molten glass Gm is supplied to the groove portion 9 through the supply pipe 10. The molten glass Gm supplied to the groove portion 9 overflows from the groove portion 9 in two directions and flows downward along the pair of outer side surfaces 11. Thereafter, the molten glass Gm is as follows. Figure 8 As shown, it falls downward from the lower end portion 6b1 of the formed body 6.

[0081] The flow rate of the molten glass Gm supplied to the forming body 6 is less at the beginning of the starting step S2 than during the implementation of the forming step S4. However, the flow rate gradually increases as the starting step S2 progresses and reaches a predetermined flow rate. In this case, the molten glass Gm does not flow out of the groove 9 uniformly, and its flow is unstable. In particular, the molten glass Gm tends to overflow from the second end 9b side of the groove 9. Therefore, in the starting step S2, a process is implemented to uniformly flow the molten glass Gm over the entire lengthwise direction of the groove 9.

[0082] Specifically, the temperature of the top wall 2b of the forming furnace 2 in the starting step S2 is preferably set lower than the temperature of the top wall 2b of the forming furnace 2 in the forming step S4. That is, in the starting step S2, the heating temperature of the third external heater 16 is adjusted to be lower than the temperature during the execution of the forming step S4. The difference between the heating temperature of the third external heater 16 in the forming step S4 and the heating temperature of the third external heater 16 in the starting step S2 can be set, for example, to 10°C to 80°C, and preferably to 15°C to 60°C.

[0083] Thus, the temperature at which the groove portion 9 of the upper portion 6a of the forming body 6 is heated can be lowered compared to when the forming step S4 is performed. That is, by reducing the flow rate of the molten glass Gm flowing out of the groove portion 9 compared to when the forming step S4 is performed, it is possible to adjust the flow rate so that the molten glass Gm flows uniformly from the entire range of the groove portion 9. The molten glass Gm that flows out of the groove portion 9 and flows down the upper portion 6a and lower portion 6b of the forming body 6 in the starting step S2 does not form a glass ribbon, but forms a lump and falls from the lower end portion 6b1 of the forming body 6.

[0084] In the starting step S2, the heating temperature of the second external heater 15 and / or the internal heater 22 is preferably set higher than the heating temperature of the second external heater 15 in the forming step S4. Specifically, in the starting step S2, the temperature of the molten glass Gm flowing down the lower portion 6b of the forming body 6 is preferably adjusted to be higher than the temperature of the molten glass Gm flowing down the lower portion 6b of the forming body 6 in the forming step S4. This prevents the amount of molten glass Gm falling from the lower end portion 6b1 of the forming body 6 in the starting step S2 from increasing in size. The difference between the heating temperature of the second external heater 15 and / or the internal heater 22 in the starting step S2 and the heating temperature of the second external heater 15 in the forming step S4 can be set, for example, to 20°C to 200°C, and preferably to 40°C to 150°C.

[0085] Under the temperature management as described above, the molten glass Gm supplied to the groove portion 9 of the forming body 6 overflows evenly from the first end portion 9a to the second end portion 9b of the groove portion 9, covers the outer side surface 11 of the forming body 6 with a constant width, and falls from the lower end portion 6b1 of the forming body 6.

[0086] It should be noted that, similar to the temperature rising step S1, in the starting step S2, the pressing force applied to the formed body 6 by the pressing members 7a and 7b is also desirably set to be smaller than the pressing force applied to the formed body 6 in the forming step S4. The ratio (FP2 / FP4) of the pressing force FP2 (N) in the starting step S2 to the pressing force FP4 (N) in the forming step S4 can be set to, for example, 0.01 to 0.40, and preferably 0.05 to 0.20.

[0087] When the flow rate of molten glass Gm supplied to the forming body 6 in the start step S2 gradually increases to a predetermined flow rate and the molten glass Gm flows stably and uniformly, the heating of the forming body 6 by the external heaters 14 to 16 is continued, and the internal heater 22 is retracted from the position where it is heating the lower portion 6b of the forming body 6. In this embodiment, the internal heater 22 is removed from the furnace through the opening 2c of the forming furnace 2. Thereafter, the exhaust step S3 is performed.

[0088] The exhaust step S3 is a step of continuously supplying molten glass Gm at a predetermined flow rate to the forming body 6 that has passed the start step S2 to exhaust the forming body 6. The gas contained in the interior and surface of the forming body 6 is removed by the molten glass Gm in contact with the forming body 6.

[0089] In the exhaust step S3, the heating temperature of the second external heater 15 is preferably set higher than the heating temperature of the second external heater 15 in the forming step S4. Specifically, in the exhaust step S3, the temperature of the molten glass Gm flowing down the lower portion 6b of the forming body 6 is preferably adjusted to be higher than the temperature of the molten glass Gm flowing down the lower portion 6b of the forming body 6 in the forming step S4. This prevents the amount of molten glass Gm falling from the lower end portion 6b1 of the forming body 6 in the exhaust step S3 from increasing. The difference between the heating temperature of the second external heater 15 in the exhaust step S3 and the heating temperature of the second external heater 15 in the forming step S4 can be set, for example, to 20°C to 200°C, and preferably to 40°C to 150°C.

[0090] The temperature of the top wall 2b of the forming furnace 2 in the exhaust process S3 can be set lower than the temperature of the top wall 2b of the forming furnace 2 in the forming process S4, or can be set higher than the temperature of the top wall 2b of the forming furnace 2 in the forming process S4, or can be set to the same level as the temperature of the top wall 2b of the forming furnace 2 in the forming process S4.

[0091] It should be noted that, similar to the temperature rising step S1 and the starting step S2, in the exhaust step S3, the pressing force applied by the pressing members 7a and 7b to the formed body 6 is preferably set to be smaller than the pressing force applied to the formed body 6 in the forming step S4. The ratio (FP3 / FP4) of the pressing force FP3 (N) in the exhaust step S3 to the pressing force FP4 (N) in the forming step S4 can be set to, for example, 0.01 to 0.40, and preferably 0.05 to 0.20.

[0092] The average temperature of the molten glass Gm in the exhaust step S3 may be the same as, higher than, or lower than the average temperature in the forming step S4. The average temperature of the molten glass Gm here is the average of the temperature of the top wall 2b of the forming furnace 2 (the temperature measured by the third external-furnace thermometer 19) and the temperature of the lower portion of the side wall 2a (the temperature measured by the second external-furnace thermometer 18).

[0093] The ratio QS3 / QS4 of the flow rate QS3 of the molten glass Gm in the exhaust step S3 to the flow rate QS4 of the molten glass in the forming step S4 is preferably greater than 0.8 and 1.2, more preferably 0.85 to 1.15, and even more preferably 0.9 to 1.1.

[0094] The forming step S4 is a step for forming a glass ribbon Gr from the molten glass Gm using the forming body 6 that has undergone the exhaust step S3. The forming step S4 begins at a stage where predetermined preparations for producing the glass sheet G to be the product have been completed, such as positioning the first conveying roller 8 at a predetermined position within the forming furnace 2 through the opening 2c. In the forming step S4, the pressing force of the pressing members 7a and 7b on the forming body 6 is increased compared to the exhaust step S3.

[0095] In the forming step S4, the temperature distribution in the forming furnace 2 is also managed by the external heaters 14 to 16. In the forming step S4, the heating temperature of the second external heater 15 is preferably set lower than the heating temperature of the third external heater 16. Furthermore, the heating temperature of the second external heater 15 is preferably set lower than the heating temperature of the first external heater 14.

[0096] like Figure 1 as well as Figure 2 As shown, in the forming step S4, molten glass Gm is supplied to the groove portion 9 of the upper portion 6a of the forming body 6 in the forming furnace 2. The molten glass Gm overflowing from the groove portion 9 in both directions flows down along the vertical surface portions 12 and the inclined surface portions 13 and rejoins at the lower end portion 6b1. Thus, a band-shaped glass ribbon Gr is continuously formed from the molten glass Gm. The first conveying rollers 8 convey the glass ribbon Gr downward while gripping the ends of the glass ribbon GR in the width direction X so as to maintain a constant width.

[0097] Next, in the annealing step S5, the glass ribbon Gr is annealed while being conveyed in the annealing furnace 3 using the second conveying rollers 20. In the subsequent cooling step S6, the glass ribbon Gr is cooled to near room temperature while being conveyed in the cooling chamber 4 using the third conveying rollers 21. Subsequently, in the cutting step S7, the glass ribbon Gr is cut in the cutting chamber 5 to obtain a glass sheet G. The cutting step S7 includes a first cutting step of cutting the glass ribbon Gr along the width direction X to obtain a glass sheet G at predetermined lengths, and a second cutting step of cutting and removing the ears at both ends of the glass sheet G in the width direction X. It should be noted that the post-processes of the forming step S4 are not particularly limited. For example, the present method may also include a cleaning step, an inspection step, a packaging step, etc.

[0098] According to the method for manufacturing a glass article of the present embodiment described above, in the starting step S2, the temperature of the top wall 2b of the forming furnace 2 is lower than the temperature of the top wall 2b of the forming furnace 2 in the forming step S4, so that the molten glass Gm can flow out uniformly from the entire range of the groove portion 9 of the forming body 6. As a result, the exhaust step S3 after the starting step S2 can be performed efficiently without the need for tilting the forming body 6 as in the conventional method.

[0099] It should be noted that the present invention is not limited to the configuration of the above-described embodiment, nor is it limited to the above-described effects. The present invention can be modified in various ways without departing from the spirit of the present invention.

[0100] In the heating step S1, an example is shown in which the forming furnace 2 is provided with an in-furnace heater 22 for heating the lower end portion 6b1 of the formed body 6. However, the present invention is not limited to this configuration. Alternatively, in the heating step S1, the in-furnace heater 22 may not be provided, and only the second external heater 15 may be used to heat the lower portion 6b (lower end portion 6b1) of the formed body 6.

Claims

1. A method for manufacturing a glass article, comprising: A heating step of heating the formed body contained in the forming furnace; a starting step of starting to supply molten glass to the forming body that has undergone the temperature raising step; as well as A forming step of forming a glass ribbon from the molten glass by an overflow method using the forming body that has passed the starting step, The method for manufacturing the glass article is characterized in that: The forming furnace includes a top wall located above the formed body. The temperature of the top wall of the forming furnace in the starting step is lower than the temperature of the top wall of the forming furnace in the forming step.

2. The method for manufacturing a glass article according to claim 1, wherein: The method for manufacturing a glass article includes, between the starting step and the forming step, a degassing step of continuously supplying the molten glass to the forming body to degas the forming body.

3. The method for manufacturing a glass article according to claim 2, wherein: The forming body comprises: a groove portion to which the molten glass is supplied; an upper portion for the molten glass overflowing from both directions of the groove portion to flow down; and a lower portion for merging the molten glasses flowing down the upper portion to form the glass ribbon. The forming furnace includes a heater for heating the lower portion of the formed body. The temperature of the heater in the exhaust step is higher than the temperature of the heater in the forming step.

4. The method for manufacturing a glass article according to claim 2 or 3, wherein: The forming furnace includes a pressing member for pressing the formed body. The pressing force applied by the pressing member to the formed body in the exhaust step is smaller than the pressing force applied by the pressing member to the formed body in the forming step.

5. The method for manufacturing a glass article according to claim 2 or 3, wherein: The temperature of the top wall of the forming furnace in the exhaust step is higher than the temperature of the top wall of the forming furnace in the start step.

6. The method for manufacturing a glass article according to claim 1 or 2, wherein: The forming body comprises: a groove portion to which the molten glass is supplied; an upper portion for the molten glass overflowing from both directions of the groove portion to flow down; and a lower portion for merging the molten glasses flowing down the upper portion to form the glass ribbon. The forming furnace includes a heater for heating the lower portion of the formed body. The temperature of the heater in the starting step is higher than the temperature of the heater in the forming step.

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