JPH09156932A - Vacuum degassing and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum degassing apparatus for molten glass capable of coping with a variation of a plate-making condition such as producing amount of glass product without changing clarifying conditions such as pressure, temperature and basis depth and also copping with a case required so as to vary the clarifying condition in relating to a problem of a product quality. SOLUTION: This vacuum degassing apparatus produces a glass product by introducing molten glass to a storing tank 1, a raising tube 2, a vacuum degassing tank 3, a lowering tube 4 and the storing tank 1, in turn, and a vertical lever of the vacuum degassing device can freely be changed by an elevating device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a glass product by removing bubbles contained in molten glass and then introducing the glass into a forming step through a homogenizing step of the molten glass.

[0002]

2. Description of the Related Art Conventionally, as a method for producing glass products from molten glass, there is a method of holding the molten glass at a high temperature for a long time to float and remove bubbles generated in the glass, and then molding the glass into a predetermined shape. Are known. However, according to, for example, Japanese Patent Laid-Open No. 2-188430, although bubbles are highly removed by such a method, there is a drawback that a molten glass becomes inhomogeneous in the process of removing bubbles to obtain a product with reduced homogeneity. Therefore, for this reason, the molten glass is defoamed under reduced pressure, the defoamed molten glass is stirred, and the homogenized molten glass is guided to a molding step to be molded into a desired shape.

As a technique for defoaming under reduced pressure in this way, Japanese Unexamined Patent Publication No. 2-221129 and Japanese Unexamined Patent Publication No. 3-33 have been used thereafter.
No. 020 and JP-A-5-58646 are proposed. Among them, the device described in JP-A-3-33020 is
A flexible seal member that takes a form that leads to the molding process through a dissolving tank, an ascending pipe, a vacuum defoaming tank, a descending pipe, and a storage tank in order, and covers them in a steady expansion state of the ascending pipe and descending pipe It is characterized in that it suppresses the amount of change in bending of the molten glass, but this device basically uses the siphon principle to degas the molten glass from the melting tank in the vacuum degassing tank. To obtain a glass product with high homogeneity.

FIG. 3 is a schematic view showing an example of a glass product manufacturing apparatus to which the siphon type vacuum degassing apparatus as described above is applied. In FIG. 3, 1 is a storage tank, 2 is an ascending pipe, 3 is a vacuum degassing tank, 4 is a descending pipe, and 5 is a storage tank. Of these, the ascending pipe 2, the vacuum degassing tank 3, and the descending pipe 4 are housed in a casing 6, and heat insulation is prevented by a heat insulating material 7 packed therein, and is insulated from the outside air. The ascending pipe 2, the vacuum degassing tank 3 and the descending pipe 4 are heated by electric heating (not shown) or other appropriate heating means, and are maintained at a predetermined temperature, for example, about 1200 to 1450 ° C. by a temperature control system. The arrow (→) in the figure indicates the flow direction of the molten glass, and 8 is the molten glass bypass pipe.

In the glass manufacturing apparatus constructed as described above, the flow of the molten glass to the ascending pipe 2, the decompression degassing tank 3 and the descending pipe 4 is based on the principle of Sanphon, and therefore, in the storage tank 5. The liquid surface of the molten glass is lower than the liquid surface of the molten glass in the storage tank 1, and the depressurized degassing tank 3 is in a depressurized state by the pressure difference of the head. At this time, the height of the vacuum degassing tank 3 is set according to the preset flow rate of the molten glass (= mainly corresponding to the preset production amount of the glass product), the fining conditions, etc. Maintaining a predetermined height, a space S for breaking bubbles is formed on the surface.

The molten glass containing bubbles generated during melting is guided to the lower end of the rising pipe 3 and rises in the rising pipe 2,
It is introduced into the vacuum degassing tank 3. For example, the inside of the vacuum degassing tank 3 is 1
Since it is set to a reduced pressure state of about / 20 to 1/3 atmospheric pressure, the molten glass that has been raised in the rising pipe 2 and guided to the reduced pressure defoaming tank 3 is under reduced pressure in the reduced pressure defoaming tank 3. Defoaming is carried out, and the bubbles contained in the molten glass are removed here.

As described above, the stored gas is removed by keeping the pressure in the vacuum degassing tank 3 at a predetermined level. Next, the clarified molten glass descends from the vacuum degassing tank 3 in this state through the downcomer pipe 4 and is guided to the storage tank 5, where it is homogenized by a normal stirring operation. In this case, the molten glass degassed in the vacuum degassing tank 3 contains no bubbles, the dissolved gas temperature is lowered, and the molten glass is sent to the molding step in a homogenized state, Various glass products are formed into desired shapes.

However, in the vacuum degassing apparatus which uses the siphon principle for the vacuum degassing as described above, when the flow amount or temperature of the molten glass flowing varies, the degassing tank 3 in the vacuum degassing tank 3 is changed. The degree of decompression and the surface of the molten glass (depth of the base material) change. For this reason, it is necessary to compensate for this change each time it occurs and to return to a normal state, and it is difficult to cope with changes in plate making conditions such as the amount of flat glass products produced.

[0009]

DISCLOSURE OF THE INVENTION The present invention utilizes the principle of the Sanfon, and the molten glass is sequentially introduced into a forming step through a storage tank, an ascending pipe, a vacuum degassing tank, a descending pipe and a storage tank. The defoaming device eliminates the above-mentioned drawbacks and problems of the decompression defoaming device, and can immediately respond to fluctuations in pressure, temperature, substrate depth, etc. in the decompression defoaming device. Another object of the present invention is to provide a vacuum degassing method and apparatus capable of coping with changes in the flow rate of molten glass due to changes in plate making conditions such as plate glass product production.

[0010]

[Means for Solving the Problems] That is, the present invention provides a method for defoaming molten glass by sequentially guiding molten glass through a storage tank, an ascending pipe, a decompression defoaming tank, a descending pipe and a storage tank to a molding step. Providing a vacuum defoaming method characterized in that the bubble breaking condition of the molten glass in the vacuum degassing tank is kept constant by changing the height of the vacuum degassing tank, and the molten glass is sequentially stored in a tank, In an apparatus for defoaming molten glass by introducing it into a molding process through an ascending pipe, a vacuum defoaming tank, a descending pipe and a storage tank, the vacuum defoaming tank can be freely moved up and down by an elevating device. The present invention provides a vacuum degassing apparatus characterized by the following.

[0011]

According to the present invention, when it is desired to change the pressure in the vacuum degassing tank to 100 mmHg for the molten glass having the same composition, it can be performed by taking a vertical movement allowance of about 500 mm. The vertical movement allowance can be determined by determining the pressure reduction treatment condition for each composition of the target glass in the basic test (Lab. Test) and selecting the length of the vertical movement allowance. In addition, the lifting device, for example, the lifting pipe, the vacuum degassing tank, and the descending pipe move up and down by the jack operation. The gap at the bottom of the tube is filled by setting a heat insulating material or a heating source according to the length.

The vacuum degassing apparatus according to the present invention will be described below with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to these embodiments. FIG. 1 is a schematic diagram for explaining an embodiment of the vacuum degassing apparatus according to the present invention, and FIG. 2 is a view showing an embodiment in which a jack is attached as an example of a lifting device in the vacuum degassing apparatus of FIG. 3 in FIGS.
The same reference numerals are used for the same or similar members, and the meanings of arrows (→) and the like are also the same.

As in the case of FIG. 3, the flow of the molten glass to the ascending pipe 2, the vacuum degassing tank 3 and the descending pipe 4 is based on the principle of Sanphon. Therefore, the liquid level of the molten glass in the storage tank 5 is Is lower than the liquid level of the molten glass in the storage tank 1. Further, since the position of the vacuum degassing tank 3 is set higher than that of the storage tank 1 and the storage tank 5 as shown in the figure, the inside of the vacuum degassing tank 3 is maintained in a predetermined reduced pressure state due to the head pressure difference.

Since the degree of decompression of the decompression degassing tank 3 in this decompressed state is proportional to the height of the molten glass in the storage tank 1 and the storage tank 5 from the liquid surface, the height is conventionally about that of molten glass. It is set corresponding to a preset flow rate (this flow rate corresponds to the production amount of glass products). However, if there is a change in the temperature of the molten glass flowing, the production amount of glass products, etc., the depth of the base material in the vacuum degassing tank 3 will change, so it was necessary to compensate for this and restore the normal state each time. . In the present invention, these fluctuations are absorbed by the elevating device of the vacuum degassing tank 3 to restore the normal state.

2 (a) and 2 (b) are views showing a mode in which a jack is used as an example of the lifting device, of which FIG. 2 (a) is a front view and FIG. 2 (b) is a side view. is there. As shown in the figure, with respect to the casing 6 of the vacuum degassing tank 3, two jacks 9 are provided on each of the left and right sides in the longitudinal direction, for a total of four jacks 9.
Is installed. In FIG. 2, 10 is a fixing portion of the jack 9 to the casing 6, and 11 is a leg portion of the jack 9, which is placed and fixed on an appropriate pedestal. Although FIG. 2 shows a screw jack, it goes without saying that any one of a hydraulic jack, a rack drive jack and the like can be used.

In the glass manufacturing apparatus as shown in FIGS. 1 and 2, for example, when the flow rate of the molten glass decreases from the steady state, the molten glass surface in the vacuum degassing tank 3 rises (that is, the depth of the substrate is deep). Nari), and along with this, the space S for breaking bubbles
Becomes relatively small. Then, the defoaming degree in the decompression defoaming tank 3 changes and the quality of the molten glass changes. Therefore, in order to avoid this, it is necessary to correct the depth of the substrate and the space S to be constant. . Therefore, at this time, when the vacuum degassing tank 3 is raised by manipulating the jack, the molten glass surface in the vacuum degassing tank 3 is relatively lowered by the action of gravity, and the space S for breaking bubbles is correspondingly lowered. Is relatively large and can be returned to the normal state.

Further, when the vacuum degassing tank 3 is raised by such a jacking operation, the lower end of the casing 6 covering the ascending pipe 2 and the descending pipe 5 rises from its lower limit, and a gap is formed there. A heat insulating material or a heating source is set in the gap depending on the gap length. Reference numeral 12 in FIG. 1 indicates the heat insulating material or the heat source.

[0018]

EFFECTS OF THE INVENTION According to the present invention, in a device for producing a glass product by sequentially introducing molten glass to a forming process through a storage tank, an ascending pipe, a decompression defoaming tank, a descending pipe and a storage tank, By changing the upper and lower levels of the defoaming tank by using the lifting device, it is possible to change the plate making conditions without changing the fining conditions such as pressure, temperature and substrate depth in the vacuum degassing device. You can On the contrary, when it is desired to change the refining conditions in the vacuum degassing apparatus due to problems such as quality, it can be dealt with by moving the vacuum degassing apparatus up and down.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining an embodiment of a vacuum degassing apparatus according to the present invention.

FIG. 2 is a diagram showing a mode in which a jack is attached as an example of an elevating device in the vacuum degassing apparatus in FIG.

FIG. 3 is a schematic view showing an example of a glass product manufacturing apparatus to which a conventional siphon type vacuum degassing apparatus is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Storage tank 2 Ascending pipe 3 Vacuum degassing tank 4 Downcomer pipe 5 Storage tank 6 Casing 7 Insulating material 8 Bypass pipe 9 Jack L Liquid surface of molten glass in vacuum degassing tank 3 Space for foam generation 10 Casing 6 Fixing part of the jack 9 to the arm 11 Leg part of the jack 9 12 Insulating material or heating source

Claims (2)

[Claims] 1. A method for defoaming molten glass by successively guiding molten glass through a storage tank, an ascending pipe, a vacuum degassing tank, a descending pipe and a storage tank to defoam the molten glass. A vacuum degassing method, characterized in that the conditions for breaking the molten glass in the vacuum degassing tank are kept constant by changing the conditions. 2. An apparatus for defoaming molten glass by successively guiding molten glass through a storage tank, an ascending pipe, a vacuum degassing tank, a descending pipe and a storage tank to the degassing degassing tank. A vacuum degassing device characterized in that the vertical level can be freely changed by an elevating device.