Apparatus and method for manufacturing glass articles

Abstract

To suppress surely wear of a transfer pipe due to oxidation evaporation of a platinum component.SOLUTION: A manufacturing apparatus of a glass article includes a tubular part 10 of a transfer pipe made of platinum or a platinum alloy, for transferring molten glass Gm, and a casing 12 surrounding the tubular part 10. The tubular part 10 has an end 10a including a projection 10ax projecting to the outside of the casing 12. A spray deposit 19 is formed only on the outer peripheral surface of the end 10a including the projection 10ax in the outer peripheral surface of the tubular part 10.SELECTED DRAWING: Figure 2

Description

【Technical Field】 【0001】 The present invention relates to an apparatus and a method for manufacturing glass articles such as sheet glass. 【Background Art】 【0002】 A glass article manufacturing apparatus includes a transfer pipe made of platinum or a platinum alloy to supply molten glass generated in a melting furnace to a forming apparatus. The periphery of the transfer pipe is surrounded by a metal casing. Inside the casing, a refractory is disposed between the inner surface of the casing and the outer peripheral surface of the transfer pipe, and the transfer pipe is held by this refractory. In this state, the end of the transfer pipe has a protruding portion that protrudes outside the casing, and the protruding portion is connected to other members (such as other transfer pipes) outside the casing (see, for example, Patent Document 1). 【0003】 Here, in a transfer pipe made of platinum or a platinum alloy, the platinum component may be oxidized and evaporated due to contact with oxygen, resulting in wear. Therefore, in order to prevent this, Patent Document 2 discloses forming a sprayed film on the outer peripheral surface of at least the middle portion of the transfer pipe located inside the casing among the outer peripheral surfaces of the transfer pipe. Hereinafter, the phenomenon in which the platinum component is oxidized and evaporated is referred to as "oxidative evaporation", but this phenomenon is also called "oxidative volatilization". 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2019-108258 【Patent Document 2】 WO2019 / 045099 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 As a result of diligent research, the inventors of this application have found that forming a thermal spray coating on the outer surface of the intermediate portion of the transfer pipe located inside the casing results in the following problems. 【0006】 Cracks can occur in the thermal spray coating due to thermal expansion of the transfer tube, among other factors. In this case, the transfer tube remains protected by the thermal spray coating in areas other than the cracked portion. Therefore, oxidative pitting corrosion concentrates in the cracked portion of the thermal spray coating, leading to oxidation and evaporation of the transfer tube. However, the condition of the thermal spray coating formed on the outer surface of the intermediate portion of the transfer tube located inside the casing cannot be seen from the outside because the casing obstructs the view. In other words, even if a crack occurs in the thermal spray coating, it cannot be detected early. As a result, oxidative pitting corrosion progresses in the cracked portion of the thermal spray coating, which can actually lead to localized wear of the transfer tube. 【0007】 The present invention aims to reliably suppress wear and tear on transfer pipes due to the oxidative evaporation of platinum components. [Means for solving the problem] 【0008】 (1) The present invention, devised to solve the above problems, is a glass article manufacturing apparatus comprising a transfer tube made of platinum or a platinum alloy for transferring molten glass, and a casing surrounding the transfer tube, wherein the transfer tube has an end portion including a protrusion that extends to the outside of the casing, characterized in that a thermal spray coating is formed only on the outer surface of the end portion including the protrusion among the outer surfaces of the transfer tube. 【0009】 The oxygen content tends to be higher outside the casing than inside. Therefore, the ends of the transfer tube, including the protruding portion, have more opportunities to come into contact with oxygen than the middle portion of the transfer tube located inside the casing, making them more susceptible to wear due to oxidative evaporation of the platinum component. Furthermore, if a thermal spray coating is formed on the outer surface of the middle portion of the transfer tube located inside the casing, localized wear of the middle portion due to oxidative pitting corrosion becomes more likely, as described above. Therefore, in the present invention, the area in which the thermal spray coating is formed is limited to the outer surface of the end portion of the transfer tube, including the protruding portion. Since the end portion, including the protruding portion, is easily visible from the outside without being affected by the casing, cracks in the thermal spray coating formed on the end portion can be detected early. In other words, the transfer tube can be protected by the thermal spray coating while suppressing localized wear of the transfer tube due to oxidative pitting corrosion. 【0010】 (2) In the configuration of (1) above, it is preferable that the thermal spray coating is formed over the entire circumference of the outer surface of the end portion including the protruding portion. 【0011】 This method more effectively suppresses wear and tear on the transfer pipes caused by the oxidation and evaporation of platinum components. 【0012】 (3) In the configuration of (1) or (2) above, it is preferable that the thermal spray coating is a zirconia thermal spray coating. 【0013】 Zirconia thermal spray coatings have higher gas barrier properties compared to alumina thermal spray coatings and other materials. Therefore, using zirconia thermal spray coatings can more reliably suppress wear on transfer pipes due to the oxidative evaporation of platinum components. 【0014】 (4) In any of the configurations (1) to (3) above, it is preferable that the thickness of the thermal spray coating is 50 to 500 μm. 【0015】 This approach ensures sufficient gas barrier properties in the thermal spray coating, more effectively suppressing wear on the transfer pipe due to oxidative evaporation of the platinum component. 【0016】 (5) In any of the configurations (1) to (4) above, it is preferable that the protruding portion is covered with a removable heat-insulating member. 【0017】 In this way, the insulating material can suppress localized temperature drops at the protruding parts. Localized temperature drops at the protruding parts can cause defects (such as foreign matter defects) in the manufactured glass articles, but the provision of insulating material can suppress the occurrence of such defects. Furthermore, by covering the protruding parts with insulating material, the amount of contact the protruding parts with oxygen can be reduced, so the synergistic effect of the insulating material and the thermal spray coating can more reliably suppress the oxidation and evaporation of platinum components at the protruding parts. Moreover, since the insulating material is removable, the condition of the thermal spray coating can be easily observed with the insulating material removed. Therefore, even if cracks occur in the thermal spray coating, the ability to detect those cracks early is maintained. 【0018】 (6) The present invention, devised to solve the above problems, is a method for manufacturing a glass article comprising a preheating step of thermally expanding a transfer tube made of platinum or a platinum alloy surrounded by a casing, and a production step after the preheating step of transferring molten glass through the thermally expanded transfer tube to manufacture a glass article, wherein the method further comprises a thermal spray coating forming step before the preheating step of forming a thermal spray coating only on the outer surface of the end of the transfer tube among the outer surfaces of the transfer tube, and in the preheating step, the thermal expansion of the transfer tube causes at least a part of the end of the transfer tube on which the thermal spray coating has been formed to protrude outside the casing. 【0019】 In this way, by utilizing the thermal spray coating formation process and preheating process performed before the preheating process, it is easy to create a state in which a thermal spray coating is formed only on the outer circumferential surface of the end portion, including the protruding part of the transfer pipe. [Effects of the Invention] 【0020】 According to the present invention, wear and tear on the transfer pipe due to the oxidation and evaporation of platinum components can be reliably suppressed. [Brief explanation of the drawing] 【0021】 [Figure 1]It is a side view showing a manufacturing apparatus for a glass article according to a first embodiment of the present invention. [Figure 2] It is a cross-sectional view showing a fining tank included in the manufacturing apparatus shown in FIG. 1. [Figure 3] It is a cross-sectional view taken along the line A-A of FIG. 2. [Figure 4] It is a cross-sectional view taken along the line B-B of FIG. 2. [Figure 5] It is a flowchart showing a manufacturing method for a glass article according to the first embodiment. [Figure 6] It is a diagram for explaining a thermal spraying film formation step included in the manufacturing method shown in FIG. 5. [Figure 7] It is a diagram for explaining a preheating step included in the manufacturing method shown in FIG. 5. [Figure 8] It is a diagram for explaining a preheating step included in the manufacturing method shown in FIG. 5. [Figure 9] It is a cross-sectional view showing a fining tank included in a manufacturing apparatus for a glass article according to a second embodiment of the present invention. 【Embodiments for Carrying Out the Invention】 【0022】 Hereinafter, a manufacturing method for a glass article according to an embodiment of the present invention will be described with reference to the drawings. In each embodiment, corresponding components may be given the same reference numerals, and redundant explanations may be omitted. When only a part of the configuration is described in each embodiment, for the other parts of the configuration, the configurations of other embodiments described previously can be applied. Also, not only the combinations of configurations explicitly shown in the description of each embodiment, but also the configurations of a plurality of embodiments can be partially combined with each other as long as there is no problem with the combination. 【0023】 (First Embodiment) As shown in Figure 1, the glass article manufacturing apparatus according to the first embodiment comprises a melting tank 1, a clarification tank 2, a homogenization tank (stirring tank) 3, a pot 4, a molded body 5, and glass supply passages 6, 7, 8, and 9 connecting these components 1 to 5. In addition, the manufacturing apparatus comprises an annealing furnace (not shown) for slowly cooling the glass ribbon Gr formed by the molded body 5, and a cutting device (not shown) for cutting the glass ribbon Gr after annealing. 【0024】 In this embodiment, the clarification tank 2, homogenization tank 3, pot 4, and glass supply passages 6, 7, 8, and 9 correspond to transfer pipes for transporting molten glass Gm. These transfer pipes are equipped with tubular sections made of platinum (including reinforced platinum) or platinum alloy (including reinforced platinum alloy). 【0025】 The dissolution tank 1 is a container for performing a dissolution process in which the introduced glass raw material is dissolved to obtain molten glass Gm. The dissolution tank 1 is connected to the clarification tank 2 by a glass supply passage 6. 【0026】 The clarification tank 2 is a container for performing a clarification process in which molten glass Gm is transported while being degassed by the action of a clarifying agent. The clarification tank 2 is connected to the homogenization tank 3 by a glass supply passage 7. 【0027】 The homogenization tank 3 is a container for performing a homogenization process in which the clarified molten glass Gm is stirred and made uniform. The homogenization tank 3 is equipped with a stirrer 3a having stirring blades. The homogenization tank 3 is connected to the pot 4 by a glass supply passage 8. 【0028】 Pot 4 is a container for performing a conditioning process to adjust the molten glass Gm to a state suitable for molding. Pot 4 is exemplified as a volume control section for adjusting the viscosity and flow rate of the molten glass Gm. Pot 4 is connected to the molded body 5 by a glass supply passage 9. 【0029】 The molded body 5 is a molding apparatus for performing a molding process to shape molten glass Gm into a desired shape (e.g., a plate). In this embodiment, the molded body 5 shapes molten glass Gm into a plate by the overflow downdraw method. Specifically, the molded body 5 has a roughly wedge-shaped cross-section (cross-sectional shape perpendicular to the plane of the paper in Figure 1), and an overflow groove (not shown) is formed on the upper part of the molded body 5. 【0030】 The molded body 5 allows the molten glass Gm to overflow from the overflow groove and flow down along the side walls on both sides of the molded body 5 (the sides located on both the front and back sides of the paper). The molded body 5 then merges the flowing molten glass Gm at the lower end of the side walls. This forms a glass ribbon Gr having a molded confluence surface in the center in the thickness direction where the molten glass Gm merges. The molded body 5 may also be formed using other down-draw methods such as the slot down-draw method or the redraw method, or the float method. However, from the viewpoint of smoothing the surface of the glass ribbon Gr, it is preferable to use the overflow down-draw method. 【0031】 By cutting the glass ribbon Gr obtained in this way, a sheet of glass (glass article) is cut out. The glass sheet has a thickness of, for example, 0.01 to 2 mm and is used as a substrate or protective cover for displays such as liquid crystal displays and organic EL displays, organic EL lighting, and solar cells. When the glass ribbon Gr is formed using the overflow downdraw method, the cut glass sheet can be used with the surface left unpolished (fired surface). 【0032】 Examples of materials used for flat glass include alkali aluminosilicate glass and alkali-free glass. Using alkali-free glass allows for the production of flat glass suitable for display substrates. Using alkali aluminosilicate glass allows for the production of glass sheets suitable for chemical strengthening. Note that molten glass (Gm) has the same material composition as flat glass. 【0033】 Next, we will explain the detailed structure of the transfer pipe using clarification tank 2 as an example. 【0034】 As shown in Figures 2 to 4, the clarification tank 2 comprises a long tubular section 10 for transporting molten glass Gm, and flange sections 11 provided at both ends of the tubular section 10 in the longitudinal direction. 【0035】 The tubular section 10 is surrounded by a casing 12. The casing 12 is supported by a frame (not shown) or the like within a building such as a factory where glass manufacturing equipment is located, allowing its position to be changed. Inside the casing 12, a refractory material 13 is placed between the inner surface of the casing 12 and the outer surface of the tubular section 10. The tubular section 10 is held in place by this refractory material 13. Note that in Figure 1, the flange portion of the transfer pipe such as the clarification tank 2, the refractory material placed around the transfer pipe, the casing, etc., are not shown. 【0036】 The tubular portion 10 is constructed in a tubular shape (for example, a circular tube) from platinum or a platinum alloy. The tubular portion 10 is longer than the refractory material 13 and the casing 12. Therefore, both ends 10a of the tubular portion 10 have protrusions 10ax that project longitudinally from the ends of the refractory material 13 and the casing 12, respectively. The middle portion 10b of the tubular portion 10, excluding both ends 10a, is located inside the casing 12. 【0037】 The flange portion 11 is configured in a plate shape (for example, an annular shape). An electrode portion (not shown) is integrally provided on each flange portion 11. By passing an electric current through these electrode portions to the tubular portion 10 and heating it, the molten glass Gm being transported inside the tubular portion 10 is heated. Note that each flange portion 11 and each electrode portion of the clarification tank 2 may be equipped with a cooling section (not shown), such as water cooling, to suppress wear due to oxidation, etc. Furthermore, any transport pipe other than the clarification tank 2 may be heated by applying electric current in a similar manner to heat the molten glass Gm being transported inside the transport pipe. 【0038】 The flange portion 11 on the upstream side of the clarification tank 2 is connected in a butt-joint manner to the flange portion 15 provided at the downstream end of the tubular portion 14 of the glass supply passage 6. The flange portion 11 on the downstream side of the clarification tank 2 is connected in a butt-joint manner to the flange portion 17 provided at the upstream end of the tubular portion 16 of the glass supply passage 7. 【0039】 The refractory material 13 is arranged to surround the entire circumference of the tubular portion 10. In this embodiment, the cross-sectional shape of the refractory material 13 is circular on the inner surface and rectangular on the outer surface. The cross-sectional shape of the refractory material 13 is divided into, for example, two parts, upper and lower, to improve assembly to the tubular portion 10. The cross-sectional shape of the casing 12 that fixes the refractory material 13 is rectangular on both the inner and outer surfaces. The shapes of the refractory material 13 and the casing 12 are not limited to these. 【0040】 The refractory material 13 is made of refractory bricks with thermal insulation properties (for example, high-zirconia refractory bricks), but its material is not particularly limited. The casing 12 is made of steel or other metal, but its material is not particularly limited. 【0041】 A bonding layer 18 is interposed between the tubular portion 10 and the refractory material 13 to join the tubular portion 10 and the refractory material 13. For example, the bonding layer 18 can be a diffusion bonding body containing alumina powder and silica powder, glass powder, or alumina cement. The bonding layer 18 may also include a refractory fiber layer and a cement layer. Here, a diffusion bonding body is a bonding body constructed by filling the space between the tubular portion 10 and the refractory material 13 with the raw material powders and then diffusing-bonding them by heating. Diffusion bonding is a method of bonding by bringing powders into contact and utilizing the diffusion of atoms that occurs between the contact surfaces. 【0042】 A thermal spray coating 19 is formed on the outer circumferential surface of each end 10a of the tubular portion 10, including the protruding portion 10ax. The thermal spray coating 19 is formed only on the outer circumferential surface of the end 10a, including the protruding portion 10ax, of the outer circumferential surface of the tubular portion 10. In other words, the thermal spray coating 19 is not formed on the outer circumferential surface of the intermediate portion 10b of the tubular portion 10. 【0043】 The clarification tank 2 is not limited to being composed of a single tubular section (transfer pipe) 10, but may be composed of multiple tubular sections (transfer pipes) 10 connected in the longitudinal direction. In detail, when multiple tubular sections 10 are connected, each tubular section 10 is connected by butting its flange sections 17 together. In this case, each tubular section 10 is individually provided with a refractory material 13 and a casing 12 on its outside, and each tubular section 10 is provided with protruding sections 10ax that extend outside the casing 12 at both ends 10a. A thermal spray coating 19 is formed on the outer circumferential surface of each end 10a including each protruding section 10ax. 【0044】 Since the inside of the casing 12 is a nearly closed space, the amount of oxygen tends to be lower than outside the casing 12. In other words, the intermediate portion 10b located inside the casing 12 is less susceptible to oxidative evaporation of platinum components compared to the protruding portion 10ax located outside the casing 12. Therefore, as described above, the thermal spray coating 19 is formed only on the outer circumferential surface of the end portion 10a including the protruding portion 10ax. As a result, the end portion 10a including the protruding portion 10ax, which is prone to contact with oxygen, is protected by the thermal spray coating 19, thereby suppressing wear of the end portion 10a including the protruding portion 10ax due to oxidative evaporation of platinum components. Furthermore, since the end portion 10a including the protruding portion 10ax is easily visible from the outside without being affected by the casing 12, cracks in the thermal spray coating 19 can be detected early. In other words, it is possible to reliably suppress the situation in which the end portion 10a including the protruding portion 10ax is locally worn down due to oxidative pitting corrosion that occurs in the cracked portion of the thermal spray coating 19. 【0045】 The thermal spray coating 19 is a ceramic thermal spray coating, preferably an alumina thermal spray coating or a zirconia thermal spray coating. In particular, the zirconia thermal spray coating is suitable for the thermal spray coating 19 because it has higher gas barrier properties compared to the alumina thermal spray coating. 【0046】 Preferably, the thermal spray coating 19 is formed over the entire circumference of the outer surface of the end portion 10a, including the protruding portion 10ax. 【0047】 The thickness of the thermal spray coating 19 is preferably 50 to 500 μm, more preferably 100 to 400 μm, and even more preferably 200 to 300 μm. 【0048】 The end portion 10a, including the protrusion 10ax, may also include a small portion of the tubular portion 10 located inside the casing 12, in addition to the protrusion 10ax. In other words, it is permissible for the thermal spray coating 19 formed on the outer circumferential surface of the end portion 10a to include a small portion of the portion located inside the casing 12. However, it is preferable that the thermal spray coating 19 substantially does not include the portion located inside the casing 12. The depth to which the thermal spray coating 19 penetrates into the casing 12 is preferably 500 mm or less, more preferably 300 mm or less, and even more preferably 0 mm to 100 mm, along the longitudinal direction of the tubular portion 10 from the end face of the casing 12. 【0049】 An inert gas (e.g., nitrogen) or water vapor may be supplied into the casing 12, filling it with the inert gas or water vapor. The inert gas or water vapor acts on the tubular portion 10 (mainly the intermediate portion 10b) located inside the casing 12, such as by penetrating the refractory material 13. This action of the inert gas or water vapor can more reliably suppress the oxidation and evaporation of the platinum component in the tubular portion 10 located inside the casing 12. Note that supplying an inert gas or water vapor into the casing 12 is not essential and can be omitted as appropriate. 【0050】 For other transfer pipes, if the end of the tubular portion of the transfer pipe has a protrusion that extends outside the casing, a thermal spray coating may be formed on the outer circumferential surface of the end including the protrusion. In this embodiment, thermal spray coatings 20 and 21 are formed on the outer circumferential surface of the end of the tubular portion 14 of the glass supply passage 6 connected to the upstream side of the clarification tank 2, and on the outer circumferential surface of the end of the tubular portion 16 of the glass supply passage 7 connected to the downstream side of the clarification tank 2, respectively. In addition, a thermal spray coating may be formed on the outer circumferential surface of the end including the protrusion in the glass supply passage 8 connecting the homogenization tank 3 and the pot 4. 【0051】 Next, a method for manufacturing glass articles (flat glass) using the manufacturing apparatus with the above configuration will be described. 【0052】 As shown in Figure 5, this method comprises a thermal spray coating process S1, a preheating process S2, an assembly process S3, a melting process S4, a molten glass supply process S5, a molding process S6, a slow cooling process S7, and a cutting process S8. Of these, the melting process S4, the molten glass supply process S5, the molding process S6, the slow cooling process S7, and the cutting process S8 are included in the production process of the glass article. In other words, the thermal spray coating process S1, the preheating process S2, and the assembly process S3 are pre-production processes. In the following description, the clarification tank 2 is sometimes used as an example of a transfer pipe in the pre-production processes, but the same process can be applied to other transfer pipes as well. 【0053】 As shown in Figure 6, in the thermal spray film formation process S1, the thermal spray film 19 is formed only on the outer circumferential surface of the end portion 10a, including the protruding portion 10ax, of the outer circumferential surface of the tubular portion 10 of the clarification tank 2. The thermal spray film 19 is formed, for example, by spraying thermal spray material onto the outer circumferential surface of the end portion 10a of the tubular portion 10. The thermal spray film formation process S1 is performed before the refractory material 13 and casing 12 are placed outside the tubular portion 10 of the clarification tank 2. In other words, the refractory material 13 and casing 12 do not interfere with the film formation work such as spraying thermal spray material, and the thermal spray film 19 can be easily formed. If part or all of the flange portion 11 is made of platinum or a platinum alloy, the thermal spray film may be formed on the end face of the flange portion 11 on the tubular portion 10 side, the abutting surface of the flange portion 11, or the outer circumferential surface of the flange portion 11. 【0054】 In the preheating process S2, each component 1 to 9 of the manufacturing apparatus is heated individually while separated. However, some components (for example, the pot 4 and the glass supply passage 9) may be heated while connected. In the preheating process S2, as shown in Figures 7 and 8, the refractory material 13 and the casing 12 are placed on the outside of the tubular section 10 of the clarification tank 2, and the space between the tubular section 10 and the refractory material 13 is filled with powder P. The powder P becomes a bonding layer 18 that fixes the tubular section 10 to the refractory material 13 through diffusion bonding. 【0055】 To raise the temperature of the tubular section 10 of the clarification tank 2, an electric current is passed through the tubular section 10 via the flange section 11. Due to this electric heating, as shown in Figure 8, the tubular section 10 of the clarification tank 2 expands longitudinally from the state shown by the dashed line in the figure. The tubular section 10 of the clarification tank 2 also expands radially. At this time, the powder P filled between the tubular section 10 and the refractory material 13 remains in a powder state and is fluid (movable) in the space between the tubular section 10 and the refractory material 13. This powder P acts as a lubricant, allowing the tubular section 10 to expand smoothly. 【0056】 In the preheating step S2, before the tubular portion 10 undergoes thermal expansion in the longitudinal direction, most of the end portion 10a of the tubular portion 10 on which the thermal spray coating 19 is formed is located inside the casing 12 (see Figure 7). On the other hand, in the preheating step S2, after the tubular portion 10 has undergone thermal expansion in the longitudinal direction, the end portion 10a of the tubular portion 10 on which the thermal spray coating 19 is formed includes a protruding portion 10ax that significantly extends outside the casing 12 (see Figure 8). In other words, as the tubular portion 10 undergoes thermal expansion in the longitudinal direction during the preheating step S2, the thermal spray coating 19 that was located inside the casing 12 also moves outside the casing 12. Therefore, by using such a thermal spray coating formation step S1 and preheating step S2, it is easy to create a state in which the thermal spray coating 19 is formed only on the outer circumferential surface of the end portion 10a of the tubular portion 10, including the protruding portion 10ax. 【0057】 When the tubular section 10 reaches a predetermined temperature (for example, 1200 to 1400°C), the preheating process S2 is completed and the assembly process S3 is executed. In the assembly process S3, the manufacturing apparatus is assembled by connecting the components 1 to 9 of the manufacturing apparatus after they have undergone thermal expansion. 【0058】 In the melting process S4, the glass raw material supplied into the melting tank 1 is heated, and molten glass Gm is produced. 【0059】 In the molten glass supply process S5, the molten glass Gm from the melting tank 1 is sequentially transferred through the glass supply channels 6, 7, 8, and 9 to the clarification tank 2, the homogenization tank 3, the pot 4, and finally to the molded body 5. In other words, the molten glass supply process S5 includes a clarification process, a homogenization process, and a conditioning process. In the clarification process, gas (bubbles) is generated from the molten glass Gm in the clarification tank 2 due to the action of the clarifying agent blended into the glass raw material. This gas is discharged to the outside from the clarification tank 2. In the homogenization process, the molten glass Gm is stirred and homogenized in the homogenization tank 3. In the conditioning process, the state of the molten glass Gm (e.g., viscosity and flow rate) is adjusted in the pot 4 and the glass supply channel 9. 【0060】 In the molten glass supply process S5, when the temperature of the powder P interposed between the refractory material 13 and the tubular portion 10 becomes high, the diffusion bonding of the powder P is activated, and ultimately, a bonding layer 18 that fixes the tubular portion 10 to the refractory material 13 is formed. The heating temperature of the powder P should be above the temperature at which the diffusion bonding of the powder P is activated (for example, 1400°C to 1650°C). 【0061】 In the molding process S6, the molten glass Gm that has passed through the molten glass supply process S5 is supplied to the molded body 5. The molded body 5 allows the molten glass Gm to overflow from the overflow groove and flow down along its side wall surface. The molded body 5 forms a glass ribbon Gr by converging the flowing molten glass Gm at its lower end. 【0062】 Subsequently, the glass ribbon Gr undergoes an annealing process S7 in an annealing furnace and a cutting process S8 in a cutting device to cut out glass sheets of predetermined dimensions. This completes the production of glass sheets as glass articles. 【0063】 (Second embodiment) As shown in Figure 9, the second embodiment illustrates a modified example of the clarification tank 2 as a transfer pipe. In the clarification tank 2 according to this embodiment, the outer surface of the protruding portion 10ax of the tubular portion 10 is covered with a removable heat-insulating member 22. More specifically, the heat-insulating member 22 is provided on the outside of the thermal spray coating 19 formed on the outer surface of the protruding portion 10ax. Preferably, the heat-insulating member 22 is provided around the entire circumference of the outer surface of the thermal spray coating 19. 【0064】 In this way, the heat-insulating member 22 keeps the protruding portion 10ax warm, suppressing localized temperature drops in the protruding portion 10ax. Localized temperature drops in the protruding portion 10ax can cause defects (such as foreign matter defects) in the manufactured glass plate (glass article), but by providing the heat-insulating member 22, the occurrence of such defects can be suppressed. 【0065】 Furthermore, by covering the protrusion 10ax with the heat-insulating member 22, the proportion of contact between the protrusion 10ax and oxygen can be reduced. Therefore, the synergistic effect of the heat-insulating member 22 and the thermal spray film 19 makes it possible to more reliably suppress the oxidation and evaporation of the platinum component in the protrusion 10ax. 【0066】 Furthermore, since the heat-insulating member 22 is detachable, the condition of the thermal spray coating 19 can be easily observed with the heat-insulating member 22 removed (for example, as shown by the dashed line in Figure 9). Therefore, even if a crack occurs in the thermal spray coating 19, the ability to detect the crack early is maintained. 【0067】 As the heat-insulating member 22, for example, a blanket, firebrick, or metal member can be used. As the blanket, for example, a blanket made of fire-resistant fiber material can be used. Specifically, a blanket that has heat resistance capable of withstanding temperatures of 1000°C or higher (preferably 1300°C or higher) and is also stretchable can be used. For example, a blanket made of alumina fibers, silica fibers, zirconia fibers, or blends thereof can be used. 【0068】 Although a method for manufacturing a glass article according to an embodiment of the present invention has been described above, the embodiments of the present invention are not limited thereto, and various modifications can be made without departing from the spirit of the present invention. 【0069】 In the embodiments described above, the case where the glass article is a sheet of glass was explained, but it is not limited to this. The glass article may be, for example, a glass roll. When manufacturing a glass roll, for example, after removing both ends in the width direction of a glass ribbon in a cutting process, the glass ribbon is wound into a roll shape to obtain a glass roll (winding process). [Explanation of symbols] 【0070】 1 Dissolution tank 2. Clarification tank 3. Homogenization tank 3a Starla 4 pots 5 Molded body 6-9 Glass supply channels 10 Tubular part 10a end 10ax protrusion 10b middle part 11 Flange section 12 Casing 13. Refractory materials (holding members) 18 Bonding layer 19 Thermal spray coating 22 Insulation material Gm molten glass Gr Glass Ribbon P powder S1 Thermal spray coating formation process S2 Preheating process S3 Assembly Process S4 Melting process S5 Molten glass supply process S6 Molding process S7 Slow cooling process S8 cutting process

Claims

[Claim 1] A glass article manufacturing apparatus comprising a transfer tube made of platinum or a platinum alloy for transferring molten glass, and a casing surrounding the transfer tube, wherein the transfer tube has an end portion including a protrusion that extends to the outside of the casing, A glass article manufacturing apparatus characterized in that a thermal spray coating is formed only on the outer circumferential surface of the transfer pipe, specifically on the outer circumferential surface of the end portion including the protruding portion. [Claim 2] The apparatus for manufacturing glass articles according to claim 1, wherein the thermal spray coating is formed over the entire circumference of the outer surface of the end portion including the protruding portion. [Claim 3] The apparatus for manufacturing glass articles according to claim 1 or 2, wherein the thermal spray coating is a zirconia thermal spray coating. [Claim 4] The apparatus for manufacturing glass articles according to claim 1 or 2, wherein the thickness of the thermal spray coating is 50 to 500 μm. [Claim 5] The apparatus for manufacturing glass articles according to claim 1 or 2, wherein the protruding portion is covered with a removable heat-insulating member. [Claim 6] A method for manufacturing a glass article, comprising: a preheating step of thermally expanding a transfer tube made of platinum or a platinum alloy surrounded by a casing; and a production step after the preheating step of transferring molten glass through the thermally expanded transfer tube to manufacture a glass article, Prior to the preheating step, the process further includes a thermal spray coating forming step in which a thermal spray coating is formed only on the outer surface of the end of the transfer pipe among the outer surfaces of the transfer pipe, A method for manufacturing a glass article, characterized in that, in the preheating step, the thermal expansion of the transfer pipe causes at least a portion of the end of the transfer pipe on which the thermal spray film is formed to protrude outside the casing.

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