JP7497678B2 - Method for manufacturing glass articles - Google Patents

Description

The present invention relates to a method for manufacturing glass articles.

Patent Document 1 discloses a glass manufacturing apparatus that manufactures tubular glass using the Danner process. The glass manufacturing apparatus includes a melting pot that stores molten glass, a muffle furnace to which molten glass is supplied from the melting pot, and a sleeve disposed in the muffle furnace. In the glass manufacturing apparatus, molten glass is supplied onto the sleeve in the muffle furnace, and the molten glass that wraps around the sleeve is drawn out while air is pumped in from the tip of the sleeve, forming tubular glass.

JP 2015-137207 A

As a method for supplying molten glass into the muffle furnace of the above-mentioned glass manufacturing apparatus, a hole-shaped supply port is provided in the upper wall constituting the ceiling of the muffle furnace, a supply nozzle for discharging the molten glass in the melting pot is inserted into the supply port, and the molten glass is allowed to flow down from the supply nozzle inserted into the supply port. In this case, a gap must be provided between the upper wall of the muffle furnace and the supply nozzle to allow expansion of the supply nozzle due to an increase in temperature, but this gap may cause a deterioration in the quality of the tube glass produced.

In more detail, when there is a gap between the upper wall of the muffle furnace and the supply nozzle, an ascending air current is generated in the muffle furnace, which is in a high-temperature state, in which gas containing volatile components of the molten glass flows toward the gap in the upper wall of the forming chamber. When this ascending air current reaches the gap and passes through the gap to flow out of the furnace, the volatile components condense and adhere to the inner surface of the supply port and the upper wall around the supply port because the temperature of the supply port and its surroundings is low. As the volatile component condenses and adheres to the inner surface of the supply port and the upper wall around the supply port, the condensed volatile components fall onto the molten glass wrapped around the sleeve, and the condensed volatile components adhering to the molten glass cause product defects.

In addition, the agglomerates that adhere to the upper wall around the supply port react with the refractory that constitutes the upper wall, eroding the refractory. This causes the supply port to expand, making it easier for upward air currents to occur inside the muffle furnace, promoting the adhesion of the agglomerates to the upper wall and promoting the falling of the agglomerates onto the molten glass wrapped around the sleeve and the reaction products between the agglomerates and the refractory, resulting in an increase in product defects.

The present invention was made in consideration of these circumstances, and its purpose is to suppress deterioration in the quality of glass articles caused by gaps between the upper wall of the forming chamber and the supply nozzle that supplies molten glass to the forming chamber in a method for manufacturing glass articles using the Danner process.

A method for manufacturing a glass article that solves the above problem is a method for manufacturing a glass article that uses a Danner-type glass manufacturing device equipped with a cylindrical sleeve for forming molten glass into tubular glass or rod-shaped glass and a forming chamber that houses the sleeve, and includes a forming step in which molten glass flowing down from a supply nozzle inserted into a supply port provided in the upper wall of the forming chamber is wound around the rotating sleeve and pulled out from the tip of the sleeve to form tubular glass or rod-shaped glass, and includes a sealing step prior to the forming step in which an outflow path for gas passing between the supply port and the supply nozzle and flowing out of the forming chamber is sealed based on the expansion of at least one of the supply nozzle and the upper wall due to a temperature rise in the forming chamber.

According to the above configuration, the outflow path of the gas passing between the supply port and the supply nozzle and flowing out of the forming chamber is sealed, thereby suppressing the generation of an updraft flowing toward the gap in the upper wall within the forming chamber. This reduces adhesion of agglomerates of volatile components to the inner surface of the supply port or the upper wall around the supply port. As a result, it is possible to suppress deterioration in the quality of the glass article caused by agglomerates or their reaction products adhering to the inner surface of the supply port or the upper wall around the supply port falling onto the molten glass wrapped around the sleeve.

In the above-mentioned method for manufacturing a glass article, the supply nozzle of the glass manufacturing apparatus preferably comprises a nozzle body having a double cylindrical shape with an outer tube portion and an inner tube portion, and a shape retaining portion provided inside the nozzle body for suppressing deformation of the inner tube portion, and a buffer structure is preferably provided between the shape retaining portion and the outer tube portion to allow deformation of the outer tube portion radially inward.

According to the above configuration, when the outer tube expands, the outer tube comes into contact with the upper wall, sealing the outflow path. In addition, because a buffer structure is provided, when the outer tube comes into contact with the upper wall, the inner tube hardly deforms, and the flow pattern of the molten glass flowing inside the inner tube does not change significantly. Therefore, clogging of the supply nozzle caused by contact between the outer tube and the upper wall can be suppressed.

In the above-mentioned method for manufacturing a glass article, it is preferable that the glass manufacturing apparatus is provided with an annular sealing member that is elastically deformable in the axial direction, and the sealing member is disposed so as to surround the outer periphery of the supply nozzle between a flange provided on the outer periphery of the supply nozzle and the upper surface of the upper wall of the forming chamber.

According to the above configuration, when the upper wall expands, the seal member is compressed between the flange and the upper wall. This allows the seal member to come into close contact with the flange and the upper wall, sealing the outflow path.

In the above method for manufacturing a glass article, it is preferable that the sealing member is made of platinum or a platinum alloy, and the upper surface of the upper wall is provided with a coating layer made of platinum or a platinum alloy. With the above configuration, it is easy to improve the sealing performance between the sealing member and the upper wall by welding the sealing member and the upper surface of the upper wall.

In the above-mentioned method for manufacturing a glass article, it is preferable that a coating layer made of platinum or a platinum alloy is provided on the inner peripheral surface of the supply port of the upper wall. This configuration makes it possible to prevent aggregates of volatile components from reacting with the refractory constituting the upper wall and eroding the refractory.

The present invention can suppress deterioration in the quality of glass articles caused by gaps between the upper wall of the forming chamber and the supply nozzle that supplies molten glass to the forming chamber.

1 is a cross-sectional view of a glass manufacturing apparatus. FIG. 4 is an enlarged cross-sectional view of the vicinity of the supply nozzle at room temperature. FIG. 4 is an enlarged cross-sectional view of the supply nozzle and its surroundings during expansion. 13A to 13E are cross-sectional views of a sealing member according to a modified example.

Hereinafter, one embodiment of the present invention will be described.
As an example of a method for producing a glass tube, a method for producing a glass tube will be described below. First, a Danner type glass manufacturing apparatus used in the method for producing a glass tube will be described.

As shown in FIG. 1, the glass manufacturing apparatus 10 includes a melting pot 11 for storing molten glass, a sleeve 12 for forming the molten glass supplied from the melting pot 11 into tubular glass, and a muffle furnace 13 for housing the sleeve 12. In FIG. 1, the melting pot 11 is not shown in cross section, but the sleeve 12 and the muffle furnace 13 are shown in cross section.

The melting pot 11 is a device for storing molten glass, and is equipped with a supply nozzle 11a for supplying the molten glass to the muffle furnace 13. The supply nozzle 11a is a cylindrical member that extends downward, and has an opening at its lower end that allows the molten glass to flow down. The supply nozzle 11a is fixed integrally to the main body of the melting pot 11.

The sleeve 12 is a cylindrical member made of refractory material, and its tip is tapered so that the diameter decreases toward the tip. A drive unit (not shown) that rotates the sleeve 12 around its axis is connected to the base end of the sleeve 12.

The muffle furnace 13 is a box-shaped furnace located downstream of the melting pot 11, and includes a first upper wall 20 forming the ceiling, a lower wall 21 forming the bottom, and a side wall 22 surrounding the sleeve 12 housed in the muffle furnace 13. The side wall 22 facing the base end of the sleeve 12 is provided with a sleeve opening 22a through which a shaft (not shown) that connects the base end of the sleeve 12 to a drive unit is inserted. The side wall 22 facing the tip of the sleeve 12 is provided with an outlet (not shown) for drawing the molten glass wrapped around the sleeve out of the muffle furnace 13.

A partition wall 23 is provided inside the muffle furnace 13, dividing the interior of the furnace into a molding chamber A1 that houses the sleeve 12 and a combustion chamber A2 that surrounds the molding chamber A1. The combustion chamber A2 is an enclosed space for heating the molding chamber A1 via the partition wall 23, and a heating unit 24 such as a burner or electric heater is disposed inside the combustion chamber A2. The partition wall 23 is a wall with a generally U-shaped cross section that extends in the axial direction of the sleeve 12, with its upper end connected to the first upper wall 20 and both axial ends of the sleeve 12 connected to the side walls 22.

A hole-shaped first supply port 20a is provided in the first upper wall 20 of the muffle furnace 13 at a portion located above the sleeve 12 housed in the molding chamber A1. The supply nozzle 11a of the melting pot 11 is inserted into this first supply port 20a from above. A second upper wall 25 is disposed above the first upper wall 20.

The second upper wall 25 is a member that covers the gap S around the supply nozzle 11a in the first supply port 20a from above, and is made of a block material separate from the first upper wall 20. The second upper wall 25 has a second supply port 25a through which the supply nozzle 11a is inserted. The gap S between the outer peripheral surface of the supply nozzle 11a and the inner peripheral surface of the second supply port 25a is narrower than the gap S between the outer peripheral surface of the supply nozzle 11a and the first supply port 20a.

In this embodiment, the first upper wall 20 and the second upper wall 25 form the upper wall of the molding chamber A1, and the first supply port 20a and the second supply port 25a form the supply port of the upper wall. As shown in FIG. 2, the upper surface of the second upper wall 25 and the inner surface of the second supply port 25a are provided with a coating layer 25b made of platinum or a platinum alloy that coats the upper surface and the inner surface.

The first upper wall 20, the lower wall 21, the side wall 22, the partition wall 23, and the second upper wall 25 that constitute the muffle furnace 13 are made of refractory materials. Examples of the refractory materials include oxide-based refractories such as alumina zircon refractories, mullite refractories, and alumina refractories, and non-oxide-based refractories such as silicon carbide refractories, aluminum nitride refractories, and silicon nitride refractories.

As shown in FIG. 2, the supply nozzle 11a includes a nozzle body 30 having a double cylindrical structure made of platinum or a platinum alloy. The nozzle body 30 includes an inner cylinder portion 31, an outer cylinder portion 32 arranged on the outer periphery of the inner cylinder portion 31 with a radial gap therebetween, and an end wall portion 33 that closes the tip of the inner cylinder portion 31 and the outer cylinder portion 32.

The inner peripheral surface of the inner cylinder 31 is the portion that forms the flow path of the molten glass, and is formed into a shape suitable for supplying the molten glass from the melting pot 11 to the muffle furnace 13. The outer cylinder 32 is the portion that forms the outer periphery of the supply nozzle 11a. The outer diameter of the outer cylinder 32 is set to be smaller than the inner diameter of the first supply port 20a of the first upper wall 20 and the second supply port 25a of the second upper wall 25.

The distance between the outer peripheral surface of the outer cylinder 32 and the inner peripheral surface of the second supply port 25a is smaller than the distance between the outer peripheral surface of the outer cylinder 32 and the inner peripheral surface of the first supply port 20a, and is, for example, 1 to 10 mm.
A cylindrical partition member 34 is inserted into the nozzle body 30 to divide the inside of the nozzle body 30 into an inner side and an outer side in the radial direction. The partition member 34 is made of a refractory tube such as alumina. A shape retaining portion 35 made of a refractory material for retaining the shape of the inner cylindrical portion 31 is provided in the radially inner portion of the nozzle body 30, i.e., between the partition member 34 and the inner cylindrical portion 31. Inside the nozzle body 30, the shape retaining portion 35 is disposed so as to be in contact with the entire outer circumferential surface of the inner cylindrical portion 31. In this embodiment, the shape retaining portion 35 is a hardened cement, and the shape retaining portion 35 is formed by hardening the cement filled between the partition member 34 and the inner cylindrical portion 31.

A buffer structure is provided in the radially outer portion of the nozzle body 30, i.e., between the outer tube 32 and the partition member 34, to allow the outer tube 32 to deform radially inward. In this embodiment, the buffer structure is formed by disposing a buffer material 36 having cushioning properties between the outer tube 32 and the partition member 34. Examples of the buffer material 36 include cotton and nonwoven fabric made of glass or ceramics. The size of the buffer structure, i.e., the radial distance between the outer tube 32 and the partition member 34, is, for example, 2 to 10 mm. The space in the nozzle body 30 in which the buffer material 36 is accommodated is a closed, sealed space. The buffer structure is provided in a portion located inside the portion of the outer tube 32 that faces the inner circumferential surfaces of the first supply port 20a and the second supply port 25a.

In the nozzle body 30, the outer tube portion 32 exposed from the second upper wall 25 of the molding chamber A1 is provided with an annular flange 37 that protrudes radially outward from the outer peripheral surface of the outer tube portion 32. Between the lower surface of the flange 37 and the upper surface of the upper wall, i.e., the upper surface of the second upper wall 25, an annular seal member 40 that surrounds the outer periphery of the nozzle body 30 of the supply nozzle 11a is arranged. The seal member 40 is made of platinum or a platinum alloy. The seal member 40 is also configured to be elastically deformable in the up and down direction, which is the axial direction. In this embodiment, a coned disc spring that has a bent portion in the center of the axial direction and has a cross section that is convex inward and is generally V-shaped and oriented sideways is used as the seal member 40.

As shown in Figures 1 and 2, a heat insulating material 38 is disposed on the upper part of the second upper wall 25 so as to surround the flange 37 of the supply nozzle 11a and the periphery of the second upper wall 25. The heat insulating material 38 is a block-shaped member made of a refractory material. The refractory material constituting the heat insulating material 38 may be the same as the refractory material constituting the wall portion of the muffle furnace 13.

Next, a method for manufacturing tubular glass by the Danner method using the glass manufacturing apparatus 10 will be described along with the operation of this embodiment. In the following, the term "upper wall" may be used as a higher-level concept including the first upper wall 20 and the second upper wall 25, and the term "supply port" may be used as a higher-level concept including the first supply port 20a and the second supply port 25a.

The method for manufacturing a glass tube includes a forming step of forming a glass tube, and a sealing step which is carried out before the forming step.
In the forming process, the molten glass melted in the melting pot 11 is allowed to flow down from the supply nozzle 11a to supply the molten glass to the base end of the sleeve 12 in the muffle furnace 13. The supplied molten glass is wound around the sleeve 12, which is rotated by a drive device, and formed into a cylindrical shape. At this time, the molten glass is formed into a continuous cylindrical glass tube by blowing air from a hole provided at the tip of the sleeve 12. Thereafter, the tip of the formed glass tube is drawn from the tip of the sleeve 12 to the outside of the furnace through an outlet of the muffle furnace 13, and is continuously drawn into a tube, and the drawn glass tube is cut into predetermined lengths.

As shown in Figures 1 and 2, in the case of a glass manufacturing apparatus 10 in which molten glass is supplied into the forming chamber A1 through a supply nozzle 11a inserted into a supply port provided in the upper wall of the forming chamber A1, a gap S is provided between the supply port provided in the upper wall and the supply nozzle 11a. If this gap S is configured to be open to the outside air, an outflow path R is formed through the gap S to allow the gas in the forming chamber A1 to flow out. In the case of a glass manufacturing apparatus 10 in which an outflow path R is formed, an updraft AF is generated in the forming chamber A1, which is in a high-temperature state during the forming process, through which gas containing volatile components of the molten glass flows toward the gap S in the upper wall of the forming chamber A1.

When this rising air current AF reaches the gap S and flows out of the furnace through the gap S, the temperature of the supply port and its surroundings is lower than that of the inside of the molding chamber A1, so the volatile components condense and adhere to the inner surface of the supply port and the upper wall around the supply port. As the amount of volatile component condenses and adheres to the inner surface of the supply port and the upper wall around the supply port increases, they fall onto the molten glass wrapped around the sleeve 12, and the condensates adhering to the molten glass cause product defects.

In addition, the agglomerates that adhere to the upper wall around the supply port react with the refractory that constitutes the upper wall and erode the refractory. This causes the supply port to expand, making it easier for an updraft AF to occur inside the muffle furnace 13, promoting adhesion of the agglomerates to the upper wall and promoting the generation of agglomerates on the molten glass wrapped around the sleeve 12 and reaction products between the agglomerates and the refractory, resulting in an increase in product defects.

In the manufacturing method of this embodiment, before the molding process, a sealing process is performed in which the outflow path R, which allows the gas in the molding chamber A1 to flow out through the gap S, is sealed based on the expansion of the supply nozzle 11a and the upper wall caused by the temperature rise in the molding chamber A1.

In more detail, in the sealing process, the molten glass flowing down from the supply nozzle 11a is wrapped around the rotating sleeve 12 and pulled out from the tip of the sleeve 12 to form the tubular glass, and an operation is performed to raise the temperature in the forming chamber A1 prior to the forming process.

As shown in FIG. 3, when the temperature of the supply nozzle 11a rises in accordance with the temperature rise in the molding chamber A1, the outer tube portion 32 of the nozzle body 30 of the supply nozzle 11a, the first upper wall 20, and the second upper wall 25 expand. Note that FIG. 2 illustrates the room temperature state before the temperature rise in the molding chamber A1. Around the supply port, the outer tube portion 32 expands radially outward of the supply nozzle 11a, and the first upper wall 20 and the second upper wall 25 expand radially inward of the supply nozzle 11a.

As a result, the outer tube portion 32 of the nozzle body 30 and the first upper wall 20 approach each other, and the outer tube portion 32 of the nozzle body 30 and the second upper wall 25 come into contact with each other. After the contact, the outer tube portion 32, which is relatively soft compared to the second upper wall 25, is deformed so as to be pushed radially inward by the second upper wall 25. FIG. 3 illustrates the state in which the outer tube portion 32 and the second upper wall 25 come into contact with each other. The contact between the outer tube portion 32 of the nozzle body 30 and the second upper wall 25 closes the gap S between the outer peripheral surface of the supply nozzle 11a and the inner peripheral surface of the second supply port 25a, sealing the outflow path R.

Here, the nozzle body 30 of the supply nozzle 11a has a double cylindrical structure including an inner cylinder portion 31 and an outer cylinder portion 32, which are portions that constitute a flow path of the molten glass. Inside the nozzle body 30 of the double cylindrical structure, a shape retaining portion 35 that suppresses the deformation of the inner cylinder portion 31 and a cushioning material 36 having cushioning properties as a cushioning structure that allows the outer cylinder portion 32 to deform radially inward are provided. Therefore, when the outer peripheral surface of the outer cylinder portion 32 contacts the second upper wall 25 due to expansion, the outer cylinder portion 32 is partially deformed, but the stress due to the deformation of the outer cylinder portion 32 is alleviated by the cushioning material 36, so that the inner cylinder portion 31 is hardly deformed. Therefore, even when the outer cylinder portion 32 contacts the second upper wall 25, the flow state of the molten glass flowing inside the inner cylinder portion 31 does not change significantly, and clogging of the supply nozzle 11a due to contact with the second upper wall 25 can be suppressed.

In addition, when the temperature of the first upper wall 20 and the second upper wall 25 rises with the temperature rise in the molding chamber A1, the first upper wall 20 and the second upper wall 25 expand upward, and the upper surface of the second upper wall 25 moves upward. This narrows the gap between the flange 37 of the supply nozzle 11a and the second upper wall 25, and the seal member 40 arranged between the flange 37 and the second upper wall 25 is compressed. As a result, the seal member 40 adheres to the flange 37 and the second upper wall 25, sealing the outflow path R. In addition, due to the temperature rise in the molding chamber A1, the seal member 40, which is made of platinum or a platinum alloy, the flange 37, and the coating layer 25b provided on the second upper wall 25 adhere to each other at the contact portion. This further enhances the sealing ability of the seal member 40 to seal the outflow path R.

In this embodiment, the members (sealing parts) that seal the outflow path R, which allows the gas in the molding chamber A1 to flow out through the gap S, based on the expansion of the supply nozzle 11a and the upper wall due to the temperature rise in the molding chamber A1, are the second upper wall 25, the supply nozzle 11a, and the sealing member 40. The second upper wall 25 and the supply nozzle 11a use the radial expansion of the supply nozzle 11a and the upper wall to block the airflow flowing along the axial direction of the supply nozzle 11a. The sealing member 40 uses the upward expansion of the upper wall to block the airflow flowing radially outward from the supply nozzle 11a.

As described above, by sealing the outflow passage R that communicates between the forming chamber A1 and the outside air through the gap S, the flow rate of the ascending air current AF passing through the gap S is reduced, and adhesion of volatile component aggregates to the inner surface of the supply port and the upper wall around it is reduced. In addition, by sealing the outflow passage R, the temperature drop around the supply nozzle 11a is suppressed, and aggregation of volatile components is suppressed. As a result, deterioration in the quality of the glass article caused by aggregates and their reaction products adhering to the inner surface of the supply port and the upper wall around it falling onto the molten glass wrapped around the sleeve 12 can be suppressed.

Next, the effects of this embodiment will be described.
(1) A method for manufacturing a glass article using a Danner type glass manufacturing apparatus 10 includes a forming step in which molten glass flowing down from a supply nozzle 11a inserted into a supply port provided in the upper wall of a forming chamber A1 is wound around a rotating sleeve 12 and drawn out from the tip of the sleeve 12 to form a tubular glass or a rod-shaped glass. The glass manufacturing method further includes a sealing step, prior to the forming step, in which an outflow path R for gas passing between the supply port and the supply nozzle 11a and flowing out to the outside of the forming chamber A1 is sealed based on the expansion of the supply nozzle 11a and the upper wall accompanying a temperature rise in the forming chamber A1.

According to the above configuration, the outflow path R of the gas passing between the supply port and the supply nozzle 11a and flowing out to the outside of the forming chamber A1 is sealed, thereby reducing adhesion of aggregates of volatile components to the inner surface of the supply port and the upper wall around the supply port. This makes it possible to suppress deterioration in the quality of the glass article caused by aggregates and their reaction products adhering to the inner surface of the supply port and the upper wall around the supply port falling onto the molten glass wrapped around the sleeve 12.

(2) The supply nozzle 11a includes a nozzle body 30 having a double cylindrical shape with an outer cylinder portion 32 and an inner cylinder portion 31, and a shape retaining portion 35 provided inside the nozzle body 30 to suppress deformation of the inner cylinder portion 31. A buffer structure is provided between the shape retaining portion 35 and the outer cylinder portion 32 to allow deformation of the outer cylinder portion 32 radially inward.

According to the above configuration, when the outer tube portion 32 expands, the outer tube portion 32 comes into contact with the upper wall, thereby sealing the outflow path R. In addition, since a buffer structure is provided, when the outer tube portion 32 comes into contact with the upper wall, the inner tube portion 31 hardly deforms, and the flow pattern of the molten glass flowing inside the inner tube portion 31 does not change significantly. Therefore, clogging of the supply nozzle 11a caused by contact between the outer tube portion 32 and the upper wall can be suppressed.

In addition, with regard to the size of the gap S between the outer peripheral surface of the outer tube portion 32 and the upper wall during assembly, in the prior art it was necessary to make it large enough to absorb the expansion so that the outer peripheral surface of the outer tube portion 32 and the upper wall would not come into contact even during expansion. In contrast, with the above configuration, the outer peripheral surface of the outer tube portion 32 and the upper wall can come into contact during expansion, so the gap S between the outer peripheral surface of the outer tube portion 32 and the upper wall during assembly can be made narrower than in the prior art. Therefore, the outflow path R itself can be made a narrower passage.

(3) The buffer material 36 is disposed inside the outer cylinder portion 32 of the nozzle body 30 as a buffer structure.
According to the above configuration, when the outer tube portion 32 comes into contact with the upper wall, stress caused by deformation of the outer tube portion 32 is absorbed by the buffer material 36. Therefore, deformation of the inner tube portion 31 caused by contact between the outer tube portion 32 and the upper wall can be more effectively suppressed.

(4) The glass manufacturing apparatus 10 is provided with an annular sealing member 40 that is elastically deformable in the axial direction. The sealing member 40 is disposed between a flange 37 provided on the outer peripheral surface of the supply nozzle 11a and the upper surface of the upper wall of the forming chamber A1 so as to surround the outer periphery of the supply nozzle 11a.

According to the above configuration, when the upper wall expands, the seal member 40 is compressed between the flange 37 and the upper wall. This allows the seal member 40 to come into close contact with the flange 37 and the upper wall, sealing the outflow path R.

(5) The coating layer 25b made of platinum or a platinum alloy is provided on the upper surface of the second upper wall 25.
According to the above-described configuration, it is easy to improve the sealing performance between the seal member 40 and the second upper wall 25 by welding the seal member 40 and the second upper wall 25 together.

(6) The coating layer 25b made of platinum or a platinum alloy is provided on the inner circumferential surface of the second supply port 25a of the second upper wall 25.
According to the above-described configuration, it is possible to suppress the agglomerates of the volatile components from reacting with the refractory constituting the second upper wall 25 and eroding the refractory.

(7) The molding process is carried out in a state in which the heat-insulating material 38 is disposed around the sealing member 40.
According to the above-described configuration, by disposing the heat insulating material 38 around the sealing member 40, a decrease in temperature around the first supply port 20a is suppressed, and aggregation of the volatile components is further suppressed.

This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.
The supply nozzle 11a may be provided integrally with the main body of the melting pot 11 or may be provided separately.

A coating layer similar to the coating layer 25b may be provided on the inner circumferential surface of the first supply port 20a of the first upper wall 20.
One or both of the coating layer 25b provided on the upper surface of the second upper wall 25 and the coating layer 25b provided on the inner circumferential surface of the second supply port 25a may be omitted.

The second upper wall 25 may be omitted. In this case, a seal member 40 is disposed between the upper surface of the first upper wall 20 and the flange 37, and a gap S is formed so that the inner circumferential surface of the first supply port 20a of the first upper wall 20 comes into contact with the outer tube portion 32 during expansion.

Instead of arranging a cushioning material 36 inside the outer tube portion 32 of the supply nozzle 11a, the supply nozzle 11a may have a hollow structure with a space inside the outer tube portion 32, thereby providing a cushioning structure that allows deformation of the outer tube portion 32 radially inward.

The position of the buffer structure in the axial direction of the supply nozzle 11a is not limited to the configuration of the above embodiment, but may be located inside the portion where the gap S between the outer peripheral surface of the outer tube portion 32 and the upper wall is narrowest.

The sealing member 40 may be welded to one or both of the flange 37 and the upper surface of the upper wall due to the temperature rise in the molding chamber A1, or may not be welded. The sealing member 40 may also be formed integrally with the lower surface of the flange 37.

The sealing member 40 is not limited to the configuration of the above embodiment, but may be an elastically deformable annular member that, when compressed in the vertical direction, increases its adhesion to the flange 37 of the supply nozzle 11a and the upper surface of the upper wall all around the entire circumference of the supply nozzle 11a.

For example, the seal member 40 may be as shown in FIG. 4. The seal member 40 shown in FIG. 4(a) is a ring-shaped member having a bent portion in the center of the axial direction and a cross section that is convex outwardly and is substantially V-shaped. The seal member 40 shown in FIG. 4(b) is a ring-shaped member having a substantially C-shaped cross section that is convex inwardly. The seal member 40 shown in FIG. 4(c) is a bellows-shaped ring-shaped member having a bent portion in the center of the axial direction. The seal member 40 shown in FIG. 4(d) is a hollow tubular ring-shaped member. The seal member 40 shown in FIG. 4(e) is a ring-shaped member having a substantially C-shaped cross section that is convex outwardly. In the case of a shape having a bent portion as shown in FIG. 2, FIG. 4(a), and FIG. 4(c), the corners of the bent portion may be sharp or rounded. In addition, a plurality of seal members 40 may be used by stacking them vertically.

- The portion that functions as a seal that seals the outflow path R that allows the gas in the molding chamber A1 to flow out through the gap S may be only one of the supply nozzle 11a and the seal member 40. In other words, the supply nozzle 11a may be changed to a normal supply nozzle that does not function as a seal, or the seal member 40 may be omitted. Note that if the seal member 40 is omitted, there is no need to provide a flange 37 for the supply nozzle 11a.

The heat insulating material 38 may be omitted.
The glass article produced by the production method of the present invention may be a rod-shaped glass. A rod-shaped glass can be formed by omitting the process of blowing air from the hole at the tip of the sleeve 12 in the forming step.

A1: molding chamber; 11a: supply nozzle; 12: sleeve; 20: upper wall; 20a: supply port; 30: nozzle body; 31: inner cylinder portion; 32: outer cylinder portion; 35: shape retaining portion; 36: cushioning material; 37: flange; 40: sealing member;

Claims (5)

A method for manufacturing a glass article, comprising a forming step of forming a tube glass or a rod-shaped glass by using a Danner type glass manufacturing apparatus having a cylindrical sleeve for forming molten glass into a tube glass or a rod-shaped glass and a forming chamber for accommodating the sleeve, and winding molten glass flowing down from a supply nozzle inserted into a supply port provided in an upper wall of the forming chamber around the rotating sleeve and drawing the molten glass out from a tip end of the sleeve,
a sealing step, prior to the molding step, of sealing an outflow path of gas passing between the supply port and the supply nozzle to the outside of the molding chamber based on expansion of at least one of the supply nozzle and the upper wall due to a temperature rise in the molding chamber. The supply nozzle is
A nozzle body having a double cylindrical shape including an outer cylinder portion and an inner cylinder portion;
a shape retaining portion provided inside the nozzle body and suppressing deformation of the inner cylinder portion;
The method for manufacturing a glass article according to claim 1 , wherein a buffer structure is provided between the shape-retaining portion and the outer tubular portion to allow the outer tubular portion to deform radially inward. The glass manufacturing apparatus includes an annular seal member that is elastically deformable in an axial direction,
3. The method for manufacturing a glass article according to claim 1, wherein the sealing member is disposed between a flange provided on an outer peripheral surface of the supply nozzle and an upper surface of the upper wall so as to surround an outer periphery of the supply nozzle. The sealing member is made of platinum or a platinum alloy,
The method for manufacturing a glass article according to claim 3, wherein an upper surface of the upper wall is provided with a coating layer made of platinum or a platinum alloy. The method for manufacturing a glass article according to any one of claims 1 to 4, wherein a coating layer made of platinum or a platinum alloy is provided on the inner peripheral surface of the supply port of the upper wall.