Vacuum degassing apparatus and glass manufacturing apparatus

Abstract

To fabricate a vacuum degassing tank having a hermetically sealed structure that does not react with molten glass.SOLUTION: A vacuum degassing apparatus 3 includes: a riser tube 5c for moving molten glass GM upward; a vacuum degassing tank 11a for degassing the molten glass GM; and a downcomer tube 6b for moving the molten glass GM degassed by the vacuum degassing tank 11a downward, where the vacuum degassing tank 11a is constituted of quartz glass.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vacuum degassing apparatus for degassing molten glass, and a glass manufacturing apparatus. [Background technology]

[0002] As is well known, in the glass manufacturing process, glass raw materials are melted in a melting furnace to produce molten glass, and then a degassing process (fining process) is carried out to remove bubbles generated in the molten glass.

[0003] For example, Patent Document 1 discloses a vacuum degassing apparatus used in a degassing step, which includes a vacuum housing, a vacuum degassing vessel, an uprising pipe as an introduction means for introducing molten glass before degassing treatment into the vacuum degassing vessel, and a downcomer pipe as an outlet means for discharging molten glass after degassing treatment from the vacuum degassing vessel (see claim 1 and paragraphs 0012 and 0013 of the same document).

[0004] The vacuum degassing vessel is a hollow tube made of a metal such as platinum or a platinum alloy, which has excellent heat resistance and corrosion resistance against molten glass (see paragraph 0014 of the same document). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2011 / 083736 Summary of the Invention [Problem to be solved by the invention]

[0006] For example, when producing molten glass made of a metal raw material, such as chalcogenide glass, if the vacuum degassing vessel is made of metal, the molten glass may react with the vacuum degassing vessel, which may result in a deterioration in the quality of the molten glass. Furthermore, the vacuum degassing vessel needs to have a structure that is easy to seal so that the degassing process can be reliably performed under reduced pressure.

[0007] The present invention has been made in view of the above circumstances, and has as its technical object to provide a vacuum degassing vessel with a sealed structure that does not react with molten glass. [Means for solving the problem]

[0008] (1) The present invention is intended to solve the above-mentioned problems, and provides a vacuum degassing apparatus comprising an uprising pipe for moving molten glass upward, a vacuum degassing vessel for degassing the molten glass, and a downcomer for moving downward the molten glass degassed in the vacuum degassing vessel, wherein the vacuum degassing vessel is made of quartz glass.

[0009] According to this configuration, by constructing the vacuum degassing vessel from quartz glass, it is possible to prevent the molten glass flowing into the vacuum degassing vessel from reacting with the vacuum degassing vessel. Because quartz glass can be easily joined by means of welding or the like, it is possible to make the vacuum degassing vessel have a sealed structure.

[0010] (2) In the vacuum degassing apparatus having the configuration described in (1) above, the uprising pipe and the downcomer pipe may be made of quartz glass.

[0011] According to this configuration, the uprising pipe and the downcomer pipe are made of quartz glass, and therefore, reaction with the molten glass can be prevented.

[0012] (3) In the vacuum degassing apparatus described in (1) or (2) above, the vacuum degassing vessel may have a cylindrical shape that is long in the vertical direction, the uprising pipe may be connected to the vacuum degassing vessel, and the downcomer pipe may be connected to the vacuum degassing vessel via a horizontal pipe.

[0013] According to this configuration, by connecting the downcomer pipe to the vacuum degassing vessel via the horizontal pipe, the downcomer pipe can be separated from the upcomer pipe, thereby enabling appropriate temperature control of the molten glass flowing in the upcomer pipe and the molten glass flowing in the downcomer pipe.

[0014] (4) The vacuum degassing apparatus according to any one of (1) to (3) above may further include a cushion tank connected to the vacuum degassing tank, and a decompression device connected to the cushion tank and decompressing the vacuum degassing tank.

[0015] According to this configuration, when an excess amount of molten glass is supplied to the vacuum degassing vessel, the molten glass can be accommodated in the cushion vessel.

[0016] (5) In the vacuum degassing apparatus described in any one of (1) to (4) above, the vacuum degassing tank may include a plurality of thermometers, and the plurality of thermometers may be arranged at intervals in the vertical direction.

[0017] According to this configuration, the temperature of the molten glass flowing into the vacuum degassing vessel can be measured by the plurality of thermometers, which makes it possible to identify the position of the liquid surface of the molten glass in the vacuum degassing vessel and facilitates management of the molten glass in the vacuum degassing vessel.

[0018] (6) The present invention is intended to solve the above-mentioned problems, and provides a glass manufacturing apparatus including a melting tank for melting glass raw materials to produce molten glass, a vacuum degassing apparatus according to any one of (1) to (5) above for degassing the molten glass produced in the melting tank, and a forming apparatus for shaping the molten glass degassed in the vacuum degassing tank, wherein the forming apparatus includes a forming tank for temporarily storing the molten glass degassed in the vacuum degassing tank, and the melting tank and the forming tank may be made of quartz glass.

[0019] According to this configuration, by forming the melting tank and the forming tank from quartz glass, it is possible to give them a sealed structure that does not react with the molten glass.

[0020] (7) The glass manufacturing apparatus described in (6) above may further include an upstream connecting pipe connecting the melting tank and the uprising pipe, and a downstream connecting pipe connecting the downcomer pipe and the forming tank, wherein the upstream connecting pipe and the downstream connecting pipe are made of quartz glass, and the melting tank, the upstream connecting pipe, the vacuum degassing tank, the downstream connecting pipe, and the forming tank may be integrated by welding.

[0021] According to this configuration, the melting tank, the upstream connecting pipe, the vacuum degassing tank, the downstream connecting pipe, and the forming tank are integrated by welding, thereby making it possible to give the glass manufacturing apparatus a sealed structure.

[0022] (8) In the glass manufacturing apparatus described in (6) or (7) above, the melting tank may be configured to melt the glass raw materials under a reducing atmosphere, and the forming tank may be configured to store the degassed molten glass under a reducing atmosphere, thereby preventing oxidation of the molten glass.

[0023] (9) The glass manufacturing apparatus according to any one of (6) to (8) above may be used for manufacturing chalcogenide glass. [Effects of the Invention]

[0024] According to the present invention, the vacuum degassing vessel can have a sealed structure that does not react with the molten glass. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a side view of a glass manufacturing apparatus according to the present invention. [Figure 2] FIG. 2 is a side view of the vacuum degassing apparatus. [Figure 3] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figs. 1 to 3 show one embodiment of a glass manufacturing apparatus according to the present invention. The glass manufacturing apparatus according to this embodiment is used to manufacture chalcogenide glass, but is not limited to this application. An example of chalcogenide glass manufactured by the present invention is chalcogenide glass containing, in mole percent, 20 to 90% Te, 1 to 50% Ge, 0 to 40% Ag+Al+Bi+Cr+Cu+Ga+In+Mn+Sb+Si+Sn+Ti+Zn, and 0 to 40% F+Cl+Br+I.

[0027] 1, the glass manufacturing apparatus 1 includes a melting apparatus 2, a vacuum degassing apparatus 3, a forming apparatus 4, a first pipe 5 connecting the melting apparatus 2 and the vacuum degassing apparatus 3, and a second pipe 6 connecting the vacuum degassing apparatus 3 and the forming apparatus 4. Each of these components 2 to 6 is made of quartz glass.

[0028] The glass manufacturing apparatus 1 utilizes the Torricelli principle and the siphon principle to transport the molten glass GM produced in the melting apparatus 2 to the forming apparatus 4 via the first pipe 5, the vacuum degassing apparatus 3, and the second pipe 6.

[0029] The melting apparatus 2 includes a melting tank 7 in which glass raw materials are melted to produce molten glass GM. The melting tank 7 is a vertically long container with a bottom. The melting tank 7 is configured to melt the glass raw materials in a reducing atmosphere. A heater (not shown) is disposed around the melting tank 7. The melting tank 7 and the heater are covered with a refractory material (not shown).

[0030] The melting tank 7 has a raw material supply unit 8 on its side. The raw material supply unit 8 also functions as a gas supply unit that supplies reducing gas to the melting tank 7. An exhaust unit (not shown) that exhausts gas from inside the melting tank 7 is provided at the top of the melting tank 7.

[0031] The top of the melting tank is open and is closed by a lid 9. The lid 9 is detachably attached to the top of the melting tank .

[0032] A part of the first pipe 5 penetrates through a part of the bottom of the melting tank 7. The bottom of the melting tank 7 has a through-hole 10 through which the first pipe 5 is inserted.

[0033] A heater (not shown) is disposed around the first pipe 5. The first pipe 5 and the heater are covered with a refractory material (not shown). The first pipe 5 has a first portion 5a connected to the melting tank 7, a second portion 5b connected to the first portion 5a, and a third portion 5c connected to the second portion 5b. These portions 5a to 5c are integrated by welding.

[0034] The first section 5a of the first pipe 5 is a pipe arranged in the vertical direction. The upper part of the first section 5a is inserted into the interior of the melting tank 7 through a through-hole 10 in the bottom of the melting tank 7. In other words, the upper part of the first section 5a is a protrusion that protrudes upward from the bottom of the melting tank 7.

[0035] The tip of the first section 5a of the first pipe 5 is provided at a position spaced above the bottom surface of the melting tank 7. The tip of the first section 5a functions as a discharge section that discharges the molten glass GM stored in the melting tank 7 to the outside of the melting tank 7.

[0036] A middle portion of the first section 5a of the first pipe 5 is fixed to the through-hole 10 of the melting tank 7 by welding. The lower portion of the first section 5a is located outside the melting tank 7 and extends downward. The lower end of the first section 5a is connected to the second section 5b.

[0037] The second section 5b of the first pipe 5, together with the first section 5a, constitutes an upstream connecting pipe for connecting the third section 5c to the melting tank 7. The second section 5b is a pipe (horizontal pipe) configured horizontally between the first section 5a and the third section 5c. As a result, the third section 5c is separated from the first section 5a and the melting tank 7 by the length of the second section 5b. The second section 5b is located below the bottom of the melting tank 7. One end of the second section 5b is connected to the lower end of the first section 5a by welding.

[0038] The third section 5c of the first pipe 5 is provided along the vertical direction and functions as an uprising pipe for moving upward the molten glass GM discharged from the melting tank 7. The lower end of the third section 5c is located below the bottom of the melting tank 7 and is connected to the end of the second section 5b. The upper end of the third section 5c is connected to the vacuum degassing apparatus 3.

[0039] The vacuum degassing apparatus 3 is used to degas the molten glass GM produced in the melting tank 7. As shown in FIG. 1, the vacuum degassing apparatus 3 is disposed above the melting apparatus 2. The vacuum degassing apparatus 3 includes a vacuum degassing vessel 11 and a decompression device 12. A heater is disposed around the vacuum degassing vessel 11. The vacuum degassing vessel 11 and the heater are covered with a refractory material (not shown).

[0040] The vacuum degassing vessel 11 includes a first vacuum degassing vessel 11a, a second vacuum degassing vessel 11b, and a connecting pipe 11c connecting the first vacuum degassing vessel 11a and the second vacuum degassing vessel 11b.

[0041] The first vacuum degassing vessel 11a and the second vacuum degassing vessel 11b have a cylindrical shape that is long in the vertical direction. The bottom of the first vacuum degassing vessel 11a is connected to the upper end of the third section 5c of the first piping 5. The second piping 6 is connected to the lower side of the first vacuum degassing vessel 11a.

[0042] As shown in Fig. 2, the first vacuum degassing vessel 11a has a plurality of thermometers 13a to 13d on its side. The thermometers 13a to 13d are arranged at regular intervals in the vertical direction. Hereinafter, the thermometers 13a to 13d will be referred to as the first thermometer 13a, the second thermometer 13b, the third thermometer 13c, and the fourth thermometer 13d, respectively, from bottom to top.

[0043] The second vacuum degassing vessel 11b is in communication with the first vacuum degassing vessel 11a via a connecting pipe 11c. The second vacuum degassing vessel 11b is disposed to the side of the first vacuum degassing vessel 11a. A decompression device 12 is connected to the top of the second vacuum degassing vessel 11b. The second vacuum degassing vessel 11b functions as a cushion vessel capable of accommodating the molten glass GM leaking from the first vacuum degassing vessel 11a.

[0044] The connecting pipe 11c is a horizontal pipe made of quartz glass and arranged between the first vacuum degassing vessel 11a and the second vacuum degassing vessel 11b. One end of the connecting pipe 11c is connected to the side of the first vacuum degassing vessel 11a, and the other end of the connecting pipe 11c is connected to the side of the second vacuum degassing vessel 11b.

[0045] The decompression device 12 is configured by, for example, a vacuum pump, and is capable of decompressing the first vacuum degassing vessel 11a via the second vacuum degassing vessel 11b.

[0046] A heater is disposed around the second pipe 6. The second pipe 6 and the heater are covered with a refractory material (not shown). The second pipe 6 has a first portion 6a, a second portion 6b, a third portion 6c, a fourth portion 6d, and a fifth portion 6e. These portions 6a to 6e are integrated by welding. The heater that heats the second pipe 6 can individually adjust the heating temperature of each of the portions 6a to 6e of the second pipe 6.

[0047] The first section 6a of the second piping 6 serves to separate the second section 6b from the first piping 5. The first section 6a is a horizontal pipe connected to the first vacuum degassing vessel 11a of the vacuum degassing apparatus 3. One end of the first section 6a is connected to the lower part of the side of the first vacuum degassing vessel 11a. The other end of the first section 6a is connected to the second section 6b.

[0048] The second portion 6b of the second piping 6 is disposed along the vertical direction and functions as a downcomer pipe for moving downward the molten glass GM degassed by the vacuum degassing apparatus 3. The upper end of the second portion 6b is connected to the first portion 6a. That is, the second portion 6b is connected to the vacuum degassing vessel 11 via the first portion 6a, which serves as a horizontal pipe. The lower end of the second portion 6b is connected to the third portion 6c. The lower end of the second portion 6b is located below the bottom of the melting tank 7 in the melting apparatus 2.

[0049] The third section 6c, fourth section 6d, and fifth section 6e of the second piping 6 are provided downstream of the second section 6b as a downcomer pipe. That is, these sections 6c to 6e constitute downstream connecting pipes that connect the second section 6b to the molding device 4.

[0050] The third section 6c of the second piping 6 is a connecting pipe for separating the second section 6b and the fourth section 6d. The third section 6c is a pipe (horizontal pipe) installed in the horizontal direction. The third section 6c is located below the melting tank 7 and the molding device 4. One end of the third section 6c is connected to the lower end of the second section 6b. The other end of the third section 6c is connected to the fourth section 6d.

[0051] The fourth section 6d of the second piping 6 is a pipe that connects the third section 6c and the fifth section 6e. The fourth section 6d is provided along the vertical direction. The lower end of the fourth section 6d is connected to the third section 6c. The upper end of the fourth section 6d is connected to the fifth section 6e.

[0052] The fifth section 6e of the second piping 6 has a first end 6e1 connected to the upper end of the fourth section 6d and a second end 6e2 connected to the molding device 4. The fifth section 6e is an inclined connecting pipe that is inclined with respect to the horizontal direction. That is, the fifth section 6e is inclined so that the second end 6e2 is higher than the first end 6e1. The inclination angle θ of the fifth section 6e with respect to the horizontal direction is preferably 3° or more and 30° or less.

[0053] The molding device 4 is used to mold the molten glass GM that has been degassed by the vacuum degassing device 3 into a glass article having a predetermined shape. As shown in FIG. 1, the molding device 4 includes an injection device 14 and a molding die 15.

[0054] The injection device 14 includes a forming tank (cylinder) 16 that temporarily stores the molten glass GM that has passed through the vacuum degassing device 3, and a plunger 17 that can reciprocate up and down within the forming tank 16.

[0055] 1 and 3, the forming tank 16 has a cylindrical shape that is long in the vertical direction. The forming tank 16 has a storage section 16a that stores the degassed molten glass GM. A second end 6e2 of the fifth section 6e of the second piping 6 is connected to a side of the storage section 16a. The storage section 16a has a discharge port 16b at its bottom that discharges the molten glass GM downward. The discharge port 16b is configured as a circular hole, but is not limited to this shape.

[0056] In addition to the above configuration, the molding tank 16 has a gas supply unit 18 for supplying a reducing gas into the interior thereof. The gas supply unit 18 is provided on the side of the molding tank 16. The molding tank 16 is also provided with an exhaust unit (not shown) for discharging gas from the interior thereof.

[0057] The plunger 17 is a rod-shaped member made of quartz glass. The plunger 17 has, at its lower end, a closing portion 17a that can close the discharge port 16b of the forming tank 16. The closing portion 17a is formed in a spherical shape with a diameter larger than the diameter of the discharge port 16b, but is not limited to this shape.

[0058] As shown in Fig. 3, the plunger 17 is configured to reciprocate up and down at a predetermined stroke. Specifically, the plunger 17 is configured to be positionally changeable between a blocking position (shown by a solid line in Fig. 3) where the blocking portion 17a blocks the discharge port 16b of the molding tank 16 and a retracted position (shown by a two-dot chain line in Fig. 3) above the blocking position.

[0059] The forming mold 15 is disposed below the injection device 14. The forming mold 15 has a recess for forming the molten glass GM discharged from the discharge port 16b of the forming tank 16.

[0060] As described above, the melting tank 7 of the melting device 2, the vacuum degassing tank 11 of the vacuum degassing device 3, the forming tank 16 of the forming device 4, the first pipe 5, and the second pipe 6 are all made of quartz glass. These components are integrated by welding to form a sealed structure.

[0061] A method for manufacturing a glass article using the glass manufacturing apparatus 1 having the above configuration will be described below. In this embodiment, a case will be described in which an ingot (preform) made of chalcogenide glass is manufactured using the molding apparatus 4. The type and shape of the glass article manufactured by this method are not limited to those in this embodiment.

[0062] This method includes a melting step, a degassing step, and a forming step. In this method, a glass manufacturing apparatus 1 is heated entirely by a heater. The glass manufacturing apparatus 1 has a plurality of zones that are individually heated by a plurality of heaters. As a result, a temperature gradient (temperature distribution) is set in the glass manufacturing apparatus 1 so that the temperature of the molten glass GM gradually decreases from the melting device 2 on the upstream side toward the forming device 4 on the downstream side due to heating by the heaters.

[0063] In the melting step, glass raw materials are supplied from the raw material supply unit 8 of the melting device 2 to the melting tank 7. The melting tank 7 is heated by a heater, whereby the glass raw materials are melted and molten glass GM is produced.

[0064] The melting step is carried out under a reducing atmosphere. That is, a reducing gas such as hydrogen gas is supplied to the melting tank 7 from the raw material supply unit 8. In the melting step, the temperature of the molten glass GM produced in the melting tank 7 is, for example, 700°C or higher and 950°C or lower.

[0065] The molten glass GM produced in the melting tank 7 is transferred to the vacuum degassing apparatus 3 through the first pipe 5 (first transfer step). Specifically, the molten glass GM flows into the first portion 5a of the first pipe 5 from the tip of the first portion 5a and moves downward inside the first portion 5a. Thereafter, the molten glass GM moves from the first portion 5a to the second portion 5b and moves horizontally inside the second portion 5b. Thereafter, the molten glass GM moves from the second portion 5b to the third portion 5c and moves upward inside the third portion 5c.

[0066] Thereafter, the molten glass GM flows into the first vacuum degassing vessel 11a of the vacuum degassing apparatus 3 from the upper end of the third portion 5c.

[0067] A heater disposed around the first pipe 5 heats the first pipe 5 so that the temperature of the molten glass GM flowing in the first pipe 5 is lower than the temperature of the molten glass GM in the melting tank 7. The temperature of the molten glass GM flowing in the first pipe 5 is, for example, 400°C or higher and 700°C or lower.

[0068] The degassing step is performed on the molten glass GM that has flowed into the first vacuum degassing vessel 11a of the vacuum degassing apparatus 3. The molten glass GM is maintained at a temperature of, for example, 400°C or higher and 700°C or lower by a heater that heats the first vacuum degassing vessel 11a. By heating the molten glass GM at a temperature lower than the temperature in the melting tank 7, bubbles made of hydrogen gas and the like are more likely to be generated.

[0069] In the degassing step, the position of the liquid surface GM1 of the molten glass GM in the first vacuum degassing vessel 11a can be identified by the multiple thermometers 13a to 13d. That is, as shown in Fig. 2, when the liquid surface GM1 of the molten glass GM is located between the second thermometer 13b and the third thermometer 13c, the temperature measured by the second thermometer 13b will be higher than the temperature measured by the third thermometer 13c. By detecting this temperature difference, it is possible to identify the position of the liquid surface GM1 of the molten glass GM.

[0070] The insides of the first vacuum degassing vessel 11a and the second vacuum degassing vessel 11b are depressurized by the decompression device 12, and the molten glass GM is degassed in a reduced pressure atmosphere. Bubbles contained in the molten glass GM are removed from the liquid surface GM1 of the molten glass GM in the first vacuum degassing vessel 11a. The molten glass GM that has been degassed is discharged from the first vacuum degassing vessel 11a through the second piping 6.

[0071] For example, immediately after the start of this method, the pressure in the first vacuum degassing vessel 11a may fluctuate, causing the liquid level GM1 of the molten glass GM to rise suddenly in the first vacuum degassing vessel 11a. When the liquid level GM1 of the molten glass GM rises significantly, the molten glass GM flows into the second vacuum degassing vessel 11b through the connecting pipe 11c. In this way, by collecting the molten glass GM overflowing from the first vacuum degassing vessel 11a in the second vacuum degassing vessel (cushion vessel) 11b, the molten glass GM is prevented from being sucked into the decompression device 12, and the degassing process in the first vacuum degassing vessel 11a can be continued.

[0072] The molten glass GM discharged from the first vacuum degassing vessel 11a is transferred to the forming device 4 by the second piping 6 (second transfer step). Specifically, the molten glass GM moves horizontally through the first portion 6a of the second piping 6, and then descends through the second portion 6b. Thereafter, the molten glass GM moves horizontally through the third portion 6c of the second piping 6, and then moves upward through the fourth portion 6d. Thereafter, the molten glass GM flows into the forming tank 16 of the forming device 4 through the fifth portion 6e of the second piping 6. The molten glass GM transferred by the second piping 6 is maintained at a temperature of, for example, 400°C or higher and 700°C or lower by a heater that heats the second piping 6.

[0073] 3, in the forming step, the plunger 17 is in the closing position, and the closing portion 17a closes the discharge port 16b of the forming tank 16. In this state, the molten glass GM flows from the second end 6e2 of the fifth portion 6e of the second piping 6 into the reservoir 16a of the forming tank 16. The molten glass GM stored in the reservoir 16a is maintained at a temperature of, for example, 300°C or higher and 600°C or lower by a heater that heats the forming tank 16.

[0074] When a predetermined amount of molten glass GM is stored in reservoir 16a, plunger 17 rises and moves to the retracted position. This unblocks discharge port 16b by blocking portion 17a of plunger 17. The molten glass GM is discharged downward from discharge port 16b and supplied to forming mold 15 located below.

[0075] When a predetermined amount of molten glass GM has been supplied to forming mold 15, plunger 17 descends and moves to the closing position. This causes closing portion 17a of plunger 17 to close discharge port 16b, thereby terminating the supply of molten glass GM to forming mold 15. The molten glass GM supplied to forming mold 15 is cooled for a predetermined time and then formed into a predetermined shape (cooling process).

[0076] According to the glass manufacturing apparatus 1 and the method for manufacturing a glass article according to the present embodiment described above, by constructing the vacuum degassing apparatus 3 from quartz glass, it is possible to prevent the molten glass GM that has flowed into the vacuum degassing apparatus 3 from reacting with the vacuum degassing apparatus 3. Quartz glass can be easily joined by means such as welding, making it possible to realize a sealed structure for the vacuum degassing apparatus 3. By constructing the components other than the vacuum degassing apparatus 3, i.e., the melting apparatus 2, the forming apparatus 4, the first piping 5, and the second piping 6, from quartz glass as well, it is possible to easily configure a sealed structure that does not react with the molten glass GM.

[0077] 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.

[0078] In the above embodiment, the first piping 5 is configured from the first section 5a to the third section 5c, but the present invention is not limited to this configuration. For example, a horizontal connecting pipe may be provided at the upper end of the third section 5c, and the third section 5c serving as an uprising pipe may be connected to the side of the first vacuum degassing vessel 11a via this connecting pipe.

[0079] In the above embodiment, the second pipe 6 is configured by the first section 6a to the fifth section 6e, but the present invention is not limited to this configuration. For example, the first section 6a may be omitted, and the upper end of the second section 6b, which serves as a downcomer, may be directly connected to the bottom of the first vacuum degassing vessel 11a.

[0080] Furthermore, the third portion 6c and the fourth portion 6d of the second pipe 6 may be omitted, and the second portion 6b and the fifth portion 6e may be directly connected.

[0081] The second portion 5b of the first pipe 5 and the first portion 6a and third portion 6c of the second pipe 6 are not limited to being horizontal, but may be configured to be inclined. Moreover, the fifth portion 6e of the second pipe 6 is not limited to being inclined, but may be configured to be horizontal. [Explanation of symbols]

[0082] 1. Glass manufacturing equipment 3. Vacuum degassing device 4 Molding equipment 5a First section of first piping (upstream connecting pipe) 5b Second section of first piping (upstream connecting pipe) 5c Third section of first piping (riser pipe) 6a First section of second piping (horizontal pipe) 6b Second section of second piping (downcomer) 6e Fifth section of second piping (downstream connecting pipe) 7 Melting tank 11. Vacuum degassing tank 11a First vacuum degassing tank 11b Second vacuum degassing tank (cushion tank) 12 Pressure reducing device 16 Forming tank GM Molten Glass

Claims

1. A vacuum degassing apparatus comprising: an uprising pipe for moving molten glass upward; a vacuum degassing vessel for performing a degassing treatment on the molten glass; and a downcomer for moving downward the molten glass degassed in the vacuum degassing vessel, The vacuum degassing tank is made of quartz glass. A vacuum degassing apparatus characterized by:

2. The riser pipe and the downcomer pipe are made of quartz glass.

2. The vacuum degassing apparatus according to claim 1.

3. The vacuum degassing tank has a vertically elongated cylindrical shape, the riser pipe is connected to the vacuum degassing vessel, the downcomer pipe is connected to the vacuum degassing tank via a horizontal pipe; 2. The vacuum degassing apparatus according to claim 1.

4. a cushion tank connected to the vacuum degassing tank; and a decompression device connected to the cushion tank and decompressing the vacuum degassing tank.

4. The vacuum degassing apparatus according to claim 3.

5. the vacuum degassing tank is equipped with a plurality of thermometers, The plurality of thermometers are arranged at intervals in the vertical direction.

4. The vacuum degassing apparatus according to claim 3.

6. A glass manufacturing apparatus comprising: a melting tank for melting glass raw materials to produce molten glass; a vacuum degassing apparatus according to any one of claims 1 to 5, which performs a degassing treatment on the molten glass produced in the melting tank; and a forming device for forming the molten glass degassed in the vacuum degassing tank, the forming apparatus includes a forming tank that temporarily stores the molten glass that has been degassed in the reduced pressure degassing tank, The melting tank and the forming tank are made of quartz glass. A glass manufacturing apparatus characterized by:

7. an upstream connecting pipe connecting the melting tank and the uprising pipe, and a downstream connecting pipe connecting the downcomer pipe and the forming tank; the upstream connecting pipe and the downstream connecting pipe are made of quartz glass, the melting tank, the upstream connecting pipe, the vacuum degassing tank, the downstream connecting pipe, and the molding tank are integrated by welding; 7. The glass manufacturing apparatus according to claim 6.

8. The melting tank is configured to melt the glass raw material under a reducing atmosphere, The forming tank is configured to store the degassed molten glass under a reducing atmosphere.

8. The glass manufacturing apparatus according to claim 7.

9. For the production of chalcogenide glasses, 9. The glass manufacturing apparatus according to claim 8.

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