JPH11139834A - Reduced pressure defoaming device for molten glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the drastic reduction of a cost, the increase in the capacity of the device, the elevation of a reduced pressure defoaming temp., etc., while ensuring a sufficient durability by forming a reduced pressure defoaming vessel of a molten glass and a riser and downcomer communicating therewith of electorforming bricks and forming the extension pipes of the riser and the downcomer of platinum or platinum alloys. SOLUTION: The reduced pressure defoaming device 10 continuously executes the reduced pressure defoaming treatment of the molten glass G in a melting vessel 20 and supplies the glass to a molding stage. The reduced pressure defoaming vessel 14 disposed in a reduced pressure housing 12 and the riser 16 and downcomer 18 for introducing and leading out the molten glass G into and out of the reduced pressure defoaming vessel 14 are formed of the electroforming bricks in at least the parts thereof in direct contact with the molten glass. The extension pipes 26, 28 which are disposed in communication with the bottom ends of the riser 16 and the downcomer 18 and are immersed into the molten glass are formed of the platinum or platinum alloys. The top ends of the extension pipes 26, 28 are flanged and the flanges are held and fixed by inserting the flanges into the joints of the electroforming bricks forming the riser 16 and the downcomer 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a vacuum degassing apparatus for molten glass for removing air bubbles from a continuously supplied molten glass.

[0002]

2. Description of the Related Art Conventionally, in order to improve the quality of molded glass products, a vacuum degassing apparatus for removing air bubbles generated in a molten glass before molding the molten glass in a melting furnace by a molding apparatus. Is used. FIG. 3 shows such a conventional vacuum degassing apparatus. The vacuum degassing apparatus 100 shown in FIG. 3 is used for a process in which the molten glass G in the melting tank 112 is degassed under reduced pressure and is continuously supplied to the next processing tank. I have. A decompression degassing tank 104 is horizontally accommodated in a decompression housing 102, and an ascending pipe 106 and a descending pipe 108 vertically attached to both ends thereof are accommodated and arranged.

The rising pipe 106 communicates with the vacuum degassing tank 104, and the molten glass G before defoaming is lifted from the melting tank 112 and introduced into the vacuum degassing tank 104. The downcomer 108 is
The molten glass G after the defoaming process is communicated with the vacuum degassing tank 104.
Is lowered from the vacuum degassing tank 104 and led out to the next processing tank (not shown). Then, in the decompression housing 102, the decompression degassing tank 104, the rising pipe 106 and the downcomer 1
Around the area 08, a heat insulating material 110 such as a heat insulating brick that covers the heat insulating material is provided. The decompression housing 102 is made of metal, for example, stainless steel, and is vacuum-sucked from the outside by a vacuum pump (not shown) or the like to decompress the inside, and a predetermined decompression inside the decompression degassing tank 104 provided therein. For example, the pressure is maintained at 1/20 to 1/3 atm.

In the conventional vacuum degassing apparatus 100, the molten glass G at a high temperature, for example, at a temperature of 1200 to 1400 ° C.
Therefore, as disclosed in Japanese Unexamined Patent Application Publication No. 2-221129 filed by the present applicant, the vacuum degassing tank 104, the riser 106 and the downcomer 1
08, etc., the part which is in direct contact with the molten glass G,
Usually, it is formed of a circular pipe made of a noble metal such as platinum or a platinum alloy such as platinum rhodium. Here, these are made of a circular tube made of a noble metal such as a platinum alloy because not only the molten glass G has a high temperature, but also the noble metal has a low high-temperature reactivity with the molten glass, and is heterogeneous due to the reaction with the molten glass. This is because the formation at a high temperature can be ensured to a certain degree without causing the formation of a layer. In particular, in addition to the above-mentioned reason, the vacuum degassing tank 104 is composed of a precious metal circular tube. In addition to the above-mentioned reason, an electric current is applied to the precious metal circular tube itself to cause self-heating, and the molten glass G in the cylinder is uniformly heated and melted. This is for maintaining the temperature of the glass G at a predetermined temperature.

When the vacuum degassing tank 104 is made of a noble metal, it is preferable to use a circular tube from the viewpoint of high-temperature strength. However, since a noble metal such as platinum is expensive, its thickness cannot be increased, so that cost and strength are reduced. From both points, the diameter of the circular pipe is limited and cannot be so large,
There is also a limit on the flow rate of the molten glass G that can be defoamed by
There was a problem that a vacuum degassing apparatus with a large flow rate could not be constructed. Of course, it is conceivable to increase the total length of the cylindrical vacuum degassing tank 104 to increase the flow rate, thereby increasing the amount of degassing treatment. There is also a problem that the device becomes longer than in the case of the above. For this reason, there is also a problem that the degassing processing amount (flow rate) of the molten glass G in the vacuum degassing apparatus 100 cannot be increased.

Since the molten glass G is obtained by melting and reacting the powdery raw material, it is preferable that the temperature of the melting tank 112 be higher in terms of melting, and that the molten glass G be reduced in terms of degassing under reduced pressure. It is preferred that the viscosity be low and therefore the temperature be high. However, while it is necessary to use a noble metal alloy in the vacuum degassing tank 104 and the like from the viewpoint of high temperature strength,
Since the noble metal is expensive and the thickness of the circular tube cannot be increased so much from the viewpoint of cost, if a noble metal such as platinum is used, the temperature of the molten glass G at the inlet of the vacuum degassing apparatus 100 becomes the above-mentioned predetermined temperature. (1200-1400 ° C.).

[0007]

In order to solve such a problem, the vacuum degassing tank 104, the riser tube 106 and the downcomer tube 108 are made of refractory bricks which are less expensive than noble metal alloys. Similarly, if the molten glass can be continuously degassed under reduced pressure, compared to the case of using a noble metal alloy such as platinum, the amount used can be limited from the viewpoint of cost, and the size can be reduced from the viewpoint of reduced strength. The need for restriction is eliminated, and the degree of freedom in equipment design is dramatically improved, so that it is possible to construct a vacuum degassing apparatus with a large flow rate and also to perform vacuum degassing processing at higher temperatures. It is considered something.

However, if all components of the vacuum degassing apparatus 100 are to be made of refractory bricks, there are the following problems. In other words, at the tubular open end such as the lower end portion of the riser pipe 106 or the downcomer pipe 108, there is no support for the lower end, so that a heavy refractory brick is supported only by the adhesive force of the joint material. As a result, sufficient strength cannot be obtained, and instead, the cost becomes extremely high even if an attempt is made to produce a long cylindrical refractory brick. For this reason, there is a problem that it is practically difficult to make the lower end portions of the riser pipe 106 and the descender pipe 108 from refractory bricks.

Even if the lower ends of the riser pipes 106 and the downcomer pipes 108 are made of refractory bricks in this way, damage and deterioration are apt to occur at joints. At a position near the interface between the molten glass G and the atmosphere in the tank 112, since the temperature is high and the atmosphere is present, there is a problem that the refractory is rich in reactivity and easily deteriorates selectively. When the joints and the interface deteriorate as described above, the lower ends of the riser 106 and the downcomer 108 have an uneven shape in the height direction, causing breakage such as cracks, and in the worst case, the riser 106 and downcomer 10
There is a possibility that a part of the lower end portion of 8 may be broken and fall, and there is a problem that sufficient durability cannot be obtained. Further, if the broken refractory is mixed into the molten glass G, there is a problem that the uniformity of the glass composition may not be maintained.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art. In a vacuum degassing apparatus for molten glass, which removes air bubbles from a continuously supplied molten glass, a high-temperature molten glass is used. To provide a vacuum degassing apparatus for molten glass that can significantly reduce costs while ensuring sufficient durability, and can increase the capacity of the apparatus and increase the temperature of the vacuum degassing process. It is in.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a decompression housing for vacuum suction, and a decompression tank for defoaming molten glass provided in the decompression housing. A rising pipe that is provided in communication with the vacuum degassing tank, raises the molten glass before the vacuum degassing and introduces the molten glass into the vacuum degassing tank, and is provided in communication with the vacuum degassing tank. The molten glass after the decompression and degassing has a downcomer pipe that descends from the decompression degassing tank and is extended therefrom, and an extension pipe provided in communication with lower ends of the riser pipe and the downcomer pipe, respectively. At least a portion of the vacuum degassing tank and the downcomer which is in direct contact with the molten glass is formed of electroformed brick, and the extension tube is formed of platinum or a platinum alloy. Provide a foaming device.

Further, the extension pipe has a flange formed at an upper end thereof, and the flange is inserted into a joint of the electroformed brick forming the riser pipe or the downcomer pipe so as to be clamped, thereby forming the riser pipe. Alternatively, it is preferably fixed to the downcomer tube.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a vacuum degassing apparatus for molten glass of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 is a schematic sectional view of a vacuum degassing apparatus for molten glass according to the present invention. As shown in FIG. 1, the vacuum degassing apparatus 10 performs a degassing process on the molten glass G in the melting tank 20 under reduced pressure, and a next processing tank not shown, for example, a plate-shaped forming processing tank such as a float bath, It is used for the process of continuously supplying to a molding work tank such as a bottle. Basically,
It has a decompression housing 12, a decompression degassing tank 14, an ascending pipe 16, a descending pipe 18, and extension pipes 26 and 28. The decompression housing 12 is for ensuring the airtightness of the decompression degassing tank 14, and is formed in a substantially portal shape. The material and structure of the decompression housing 12 are not particularly limited as long as it has the airtightness and strength required for the decompression and degassing tank 14. Is preferred. Such a decompression housing 12 is vacuum-sucked from the outside by a vacuum pump (not shown) or the like,
The inside is depressurized, and the inside of the decompression degassing tank 14 provided therein is maintained at a predetermined reduced pressure, for example, a reduced pressure of 1/20 to 1/3 atm.

A vacuum degassing tank 14 is provided in the upper part of the pressure reducing housing 12. A rising pipe 16 communicates with the left end of the vacuum degassing tank 14, and a downcomer pipe 18 communicates with the right end of the vacuum degassing tank 14. The riser pipe 16 and the lowering pipe 18 are respectively connected to the legs 12a, 1
2b (hereinafter, referred to as housing legs 12a and 12b, respectively).

In the vacuum degassing apparatus 10 of the present invention, the vacuum degassing tank 14, the riser pipe 16 and the downcomer pipe 18 are all formed of electroformed bricks 30. In other words, by forming the main part of the vacuum degassing apparatus 10 which is in direct contact with the molten glass G with the electroformed brick 30, the cost is significantly reduced as compared with a conventionally used platinum alloy, and accordingly, Since it is possible to design a free shape and a free thickness, it is possible to increase the capacity of the vacuum degassing apparatus 10 and to perform vacuum degassing at a higher temperature. In addition, electroformed bricks have higher durability at high temperatures than ordinary bricks and can minimize elution of components, so that the uniformity of molten glass can be maintained.

Accordingly, the shapes of the vacuum degassing tank 14, the riser pipe 16 and the descender pipe 18 are not particularly limited as long as they are at least cylindrical. For example, the cross-sectional shape may be not only circular but also angular. . Vacuum degassing tank 1 using electroformed brick 30
The method of constructing the riser pipe 16 and the descender pipe 18 is not particularly limited, and for example, a small rectangular electroformed brick 3
Pile up 0, fill the joint part between them with joint material,
A cylindrical tube of a predetermined length may be formed, or cylindrical electroformed bricks 30 cast and formed into a cylindrical or square tube shape are stacked in a line, and the joint portion therebetween is filled with a joint material. May be formed.

The electroformed brick 30 is made of a refractory raw material.
After electro-melting, the brick is cast into a predetermined shape
It is not particularly limited as long as there are various conventionally known electroformed bricks.
Just use it. Above all, corrosion resistance is high,
Alumina-based electrocast refractories, zirconia-based
Electroformed refractories, AZS (Al_TwoO_Three-ZrO_Two-Si
O _Two) -Based electroformed refractories and the like are preferably exemplified.
Marsnite (MB-G), ZB-X950, Zircona
(ZB) (all manufactured by Asahi Glass Co., Ltd.) and the like.
You.

Around the vacuum degassing tank 14, a brick 32 for heat insulation (hereinafter referred to as an insulating brick 32) for covering the vacuum degassing tank 14 is provided. A heat insulating brick 32 for covering each of them is also provided. Various known bricks may be used as the heat insulating bricks 32, and there is no particular limitation. The heat insulating brick 32 arranged in this manner is accommodated in the decompression housing 12 by covering the outside thereof with the decompression housing 12.

Insulation bricks 32 may be provided around the vacuum degassing tank 14, the riser pipe 16 and the descender pipe 18 if necessary.
In addition, a configuration may be adopted in which a heater can be provided to enable heating, or a configuration in which cooling water is allowed to pass and cooling is possible.

Here, the lower end of the riser 16 must be fitted into the open end of the upstream pit 22 and immersed in the molten glass G in the upstream pit 22. Similarly, the lower end of the downcomer pipe 18 needs to be fitted into the open end of the downstream pit 24 and immersed in the molten glass G in the downstream pit 24. By the way, as described above, the main part of the vacuum degassing apparatus 10 of the present invention is constituted by the electroformed brick 28.

However, as described above, the riser 1
It is practically difficult from the viewpoint of strength and cost to make the lower end of 6 and the portion that is fitted into the upstream pit 22 and immersed in the molten glass G with the electroformed brick 30. Even if it is made of cast brick 30, joint portions and interface portions are liable to be deteriorated, and there is a possibility that damage such as cracks may occur, and there is a problem that sufficient durability cannot be obtained. The same problem as described above also occurs when the lower end of the downcomer 18 is made of the electroformed brick 30 so as to be fitted into the open end of the downstream pit 24 and immersed in the molten glass G.

On the other hand, according to the present invention, as shown in FIG. 1, extension pipes 26 and 28 made of platinum or a platinum alloy are provided at the lower ends of the riser pipe 16 and the descender pipe 18, and
6 and 28 to upstream pit 20 and downstream pit 2 respectively
4, and is immersed in the molten glass G inside. With such a configuration, the riser tube 16 and the descender tube 18 made of electroformed brick are directly connected to the molten glass G.
Therefore, it is not necessary to immerse the molten glass G in the upstream pit 20 and the downstream pit 24, so that the durability against the molten glass G can be greatly improved, and the above problem can be solved.

More specifically, as shown in FIG. 2, an extension pipe 26 made of platinum or a platinum alloy is provided at the lower end of the riser pipe 16 so as to communicate therewith. The extension pipe 26 on the riser pipe 16 side
Since the extension pipe 28 on the downcomer 18 side is configured identically, only the extension pipe 26 on the ascending pipe 16 will be described, and the description of the extension pipe 28 on the downcomer 18 will be omitted.

The extension pipe 26 has a cylindrical body 26a,
Fixing flange 26 formed at one end of this cylindrical body 26a
b and a sealing flange 26c formed at a predetermined distance from the fixing flange 26b, and is made of platinum or a platinum alloy. The inner diameter of the cylindrical body 26a is such that the riser tube 1 is smoothly communicated with the riser tube 16.
6 may be configured to be approximately the same size as the inner diameter.

The fixing flange 26b is formed so that the upper end thereof can be fixed to the riser tube 16 by being inserted between the electroformed bricks 30 constituting the riser tube 16, that is, the joint. The fixing of the extension pipe 26 to the riser pipe 16 is not limited to the fixing flange 26b, and may be performed by various methods. However, it is preferable that the extension pipe 26 be fixed using the fixing flange 26b. That is, the cylindrical body 26a
Is not provided with a fixing flange 26b at the upper end of the molten glass G between the outside of the cylindrical body 26a and the electroformed brick 30.
Penetrates, the heat insulating brick 32 and the heat insulating material 38 are eroded, the thermal conductivity near the bottom surface of the housing leg 12a increases, the temperature of the housing outer wall surface increases, and the housing may be deformed. By forming the fixing flange 26b at the upper end, such a problem is also solved. This increases the temperature of the housing leg 12a,
And the accompanying downward distortion is prevented, and the molten glass G leaks due to displacement or looseness of the joint between the electroformed brick 30 and the insulating brick 32 in the housing leg 12a, and furthermore, the excessive temperature of the housing leg 12a. Ascent can be prevented. Accordingly, it is possible to prevent thermal stress deformation of the entire apparatus due to such a partial temperature rise and accelerated temperature rise due to an increase in leakage of the molten glass G.

On the other hand, when the extension pipe 26 is provided at the lower end of the downcomer pipe 18, the sealing flange 26c closes the lower end of the housing leg 12a from the outside together with a sealing member 34 described later, and The purpose is to ensure the airtightness. In addition, this sealing flange 2
6c as an electrode, an extension tube 26 made of platinum or a platinum alloy
May be configured to generate heat by itself and maintain an appropriate temperature. A mechanism for ensuring airtightness at the lower end of the housing leg 12a includes a sealing flange 26.
Not limited to the method using c, various mechanisms can be used. It is preferable that the extension pipe 26 is fixed to the riser pipe 16 by the fixing flange 26b as described above.
The sealing flange 26c also serves to carry the vacuum seal and the weight of the extension tube 26, and the fixing flange 26b prevents the outer surface of the extension tube from separating from the inner surface of the brick in the passage surrounded by the electroformed brick 30a. It may be limited to the role, and in this case, the fixing flange 26b plays a role of preventing the horizontal eccentricity of the extension pipe 26 from being slightly eccentric.
It also serves to prevent molten glass G from entering between the outer surface of the extension tube and the inner surface of the brick.

The composition of the platinum or platinum alloy used for the extension tubes 26 and 28 is not particularly limited, but contains platinum in an amount of 70 wt% to 98 wt%.
A platinum alloy containing 2 wt% or more of Rh is preferable because the high-temperature strength is particularly excellent.

In the extension pipe 26 thus configured, the fixing flange 26b is inserted into the joint between the electroformed bricks 30 near the lower end of the riser pipe 16, and is clamped.
A sealing member 34 is disposed between the sealing flange 26c and the decompression housing 12, and the housing leg 12a
Airtightness at the lower end is ensured. In addition, the sealing member 3
4 is not particularly limited as long as it has airtightness and heat resistance.
Since the pressure may be reduced to the atmospheric pressure, a heat-resistant material may be selected from ordinary vacuum sealing materials used for a vacuum device.

By the way, as described above, the fixing flange 26b of the extension tube 26 is sandwiched between the joints of the electroformed bricks 30, and the clamping force at this time is secured by the own weight of the electroformed bricks 30. . Therefore, when the number of the electroformed bricks 30 loaded on the fixing flange 26b is small, the joint is opened due to the expansion and contraction by the molten glass G, and the holding force is reduced, and the fixing flange 26b is sufficiently held. And the molten glass G may leak out. For this reason, as shown in FIG. 2, a reinforcing member 36 may be provided above the extension pipe 26 to reinforce the clamping force of the fixing flange 26b by the electroformed brick 30.
The reinforcing member 36 may be any material that can press the electroformed brick 30 above the fixing flange 26b downward, and the material and structure thereof are not particularly limited. For example, when the electroformed brick 30 is stacked high on the fixing flange 26b, the reinforcing member 3
6 does not have the fixing flange 26b due to its own weight.
Can be firmly held.

As shown in FIG. 2, an electroformed brick 30a provided at the lowermost end in the housing leg 12a.
Is formed by cutting out an inner portion facing the extension tube 26 and a lower corner portion facing the bottom surface of the housing leg 12a along a circumference, and a heat insulating material 38 is provided in the cutout portion. Preferably. That is, since the vicinity of the extension tube 26 on the bottom surface of the housing leg portion 12a is most easily heated, the temperature rises excessively, causing distortion and deformation,
Leakage of the molten glass G from the joint to the insulating brick layer 32 may be induced. Therefore, by disposing the heat insulating material 38 near the extension pipe 26, an excessive rise in temperature of the bottom surface of the housing leg 12a can be prevented, and the durability in this portion can be further improved. Further, since the heat insulating material 38 is provided only on the lower portion of the electroformed brick 30a, it is possible to secure sufficient strength in the upper portion of the electroformed brick 30a and firmly clamp the fixing flange 26b. it can. The heat insulating material 38 is not particularly limited as long as the material has higher heat insulating properties than the electroformed brick 30.

In this way, the lower end of the riser pipe 16 and the portion immersed in the molten glass G in the upstream pit 22 and the lower end of the downcomer pipe 18 immersed in the molten glass G in the downstream pit 24 The lower portion of the riser 16 and the lowerer 18 are formed by forming the portion to be made of platinum or a platinum alloy.
The lower end of the glass can be prevented from being deteriorated or damaged, and sufficient durability can be ensured for the molten glass G.

Incidentally, it is preferable that a buffer mechanism 40 is provided on the housing leg portion 12a so as to be able to expand and contract according to the thermal expansion and contraction of the electroformed brick 30 and the heat insulating brick 32 in the vertical direction. By doing so, the riser 16
Bricks 30 and the surrounding insulating bricks 3
When the thermal expansion of the bricks 2 occurs, the buffer mechanism 40 can absorb the thermal expansion of the riser tube 16. On the other hand, when these bricks contract, the housing legs 12a are contracted so as to follow the contraction. This can prevent the joint from opening due to shrinkage and effectively prevent the molten glass G from leaking. Therefore, damage to the decompression housing 12 and a decrease in the degree of decompression caused by the damage can be prevented, and the durability and safety of the device can be improved.

Specifically, as shown in FIG. 2, the buffer mechanism 40 has a cylindrical bellows 42 and push-up means 44. The tubular bellows 42 has the housing legs 12a cut and separated in the horizontal direction, and the upper portion of the once separated housing legs 12a (hereinafter referred to as the upper portion 13a).
And a lower portion (hereinafter, referred to as a lower portion 13b) in a gas-tight and expandable manner. The material of the cylindrical bellows 42 is not particularly limited, but is preferably made of metal, particularly stainless steel, as in the case of the decompression housing 12.

The push-up means 44 is connected to the housing leg 12.
The mechanism is not particularly limited as long as it can urge the lower portion 13b upward, and various mechanisms can be adopted. For example, as shown in FIG. 2, two connecting members 46 and 48 fixed to the upper part 13a and the lower part 13b in pairs with each other.
And a bar 50 whose lower end is fixed to the lower connecting member 48 and is provided so as to pass through the through hole of the upper connecting member 46.
And an urging member 52 that connects the two connecting members 46 and 48 and urges the lower portion 13b upward. The urging member 52 is not particularly limited, but is preferably a coil spring. With this configuration, the thermal expansion of the electroformed brick 30 and the insulating brick 32 can be released downward against the urging force of the urging member 52,
Distortion and damage of the device caused by thermal expansion can be prevented, and the safety of the device can be enhanced. Further, even if the electroformed brick 30 or the heat insulating brick 32 shrinks, the opening of the joint can be prevented by following the lower portion 13b. It is preferable that a plurality of such push-up means 44 be provided for one tubular bellows 42. Further, the lower end of the housing leg 12a may be reinforced with a rib or the like.

An example of a process in which the molten glass G is degassed by the vacuum degassing apparatus 10 of the present invention and is continuously supplied to the next processing furnace will be described below. First, the inside of the vacuum housing 12 and the vacuum degassing tank 14 are maintained in a vacuum suction state by a vacuum pump (not shown). In this state, the glass G melted in the melting tank 20 rises through the upstream pit 22 through the extension pipe 26 and the riser pipe 16 and is guided into the vacuum degassing tank 14, where the molten glass G is degassed under reduced pressure. A defoaming treatment is performed in the tank 14 under reduced pressure conditions. Then, the defoamed molten glass G is guided to the downstream pit 24 via the downcomer pipe 18 and the extension pipe 28.

Although the vacuum degassing apparatus for molten glass of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the spirit of the present invention. Of course, you may.

[0038]

As described in detail above, according to the present invention, in a vacuum degassing apparatus for molten glass for removing bubbles from a continuously supplied molten glass, a high-temperature molten glass can be used. While ensuring sufficient durability, the cost can be significantly reduced, and the capacity of the apparatus can be increased, and the temperature of the vacuum degassing process can be increased. Therefore, it is very suitable for applications in which high-efficiency degassing treatment of molten glass with a large flow rate is performed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a vacuum degassing apparatus of the present invention.

FIG. 2 is a schematic sectional view showing a connecting portion between a riser tube and an extension tube in the vacuum degassing apparatus shown in FIG.

FIG. 3 is a schematic sectional view showing an example of a conventional vacuum degassing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Vacuum degassing apparatus (of molten glass) 12 Vacuum decompression housing 14 Vacuum degassing tank 16 Ascending pipe 18 Downcoming pipe 20 Melting tank 22 Upstream pit 24 Downstream hit 26, 28 Extension pipe 26a Cylindrical body 26b Fixing flange 26c Sealing flange 30 Electroformed brick 32 Insulated brick 34 Sealing member 36 Reinforcing member 38 Insulating material 40 Buffering mechanism 42 Cylindrical bellows 44 Pushing-up means 46, 48 Connecting means 50 Bar 52 Energizing member

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shoji Imamaki 1-1-1, Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Inside Keihin Plant of Asahi Glass Co., Ltd. (72) Inventor Masataka Matsuwaki 1 Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa 1-chome Inside the Keihin Plant of Asahi Glass Co., Ltd.

Claims (2)

[Claims] A vacuum housing for vacuum suction; a vacuum degassing tank provided in the vacuum housing for vacuum degassing of the molten glass; and a vacuum degassing tank provided in communication with the vacuum degassing tank. An ascending pipe that raises the molten glass before foaming and introduces the molten glass into the vacuum degassing tank, is provided in communication with the vacuum degassing tank, and lowers the molten glass after the vacuum degassing from the vacuum degassing tank. And an extension pipe provided in communication with lower ends of the riser and the downcomer, respectively, wherein the riser, the vacuum degassing tank and the downcomer are at least directly connected to the molten glass. A degassing apparatus for depressurizing molten glass, wherein a portion to be contacted is formed of electroformed brick, and said extension tube is formed of platinum or a platinum alloy. 2. The extension pipe has a flange formed at an upper end thereof, and the flange is inserted into a joint of the electroformed brick forming the riser pipe or the downcomer pipe to be clamped, thereby forming the riser pipe. The vacuum degassing apparatus for molten glass according to claim 1 or 2, wherein the apparatus is fixed to the downcomer.