JPH07291633A - Production of glass - Google Patents

Abstract

PURPOSE:To improve a defoaming efficiency by controlling the crosssectional area of a flow way of fused glass flowing into a reduced-pressure defoaming- tank and controlling the flow of the fused glass. CONSTITUTION:Fused glass, e.g. soda lime silica glass of about 10<2>-10<4> poise in viscosity is continuously introduced into a reducedpressure defoaming-tank 11 whose pressure is adjusted to about 0.05-0.3 atm, from a fusing tank 10 through an inlet tube 15 and a valve 21 placed at its end and the fused glass is defoamed there. The valve 21 lined with platinum and placed at a flow controlling part is composed of a rod 13 having a conical tip and a funnel-shaped member 3 where the tip is inserted. The flow of the fused glass is controlled by changing the cross-sectional area of the flow way through the adjustment of the gap 16 between the tip of the rod 13 and the funnel-shaped member 3. Subsequently, the defoamed fused glass is delivered through a discharging tube 17 provided with a screw 14 into a working tank 12 whose level of the fused glass is controlled to the same as that of the reduced pressure tank 11. The fused glass is formed by e.g. press molding after the temperature is adjusted to a specified value and a glass article having little void is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing glass.

[0002]

2. Description of the Related Art A method for producing glass has been proposed in which molten glass is introduced into a vacuum degassing tank for defoaming, and then discharged from the vacuum degassing tank to be molded into a predetermined shape.

In such a manufacturing method, since the pressure in the vacuum degassing tank is set to 1/20 to 1/3 atmospheric pressure, the vacuum degassing is performed with respect to the bath surface level of the molten glass in the melting tank for melting the raw material to obtain molten glass. The bath surface level of molten glass in the foam tank is about 3.5 m
Get higher This has various difficulties in terms of equipment and work.

In order to solve these difficulties, a screw is provided in each of an introduction pipe for introducing molten glass from the melting tank to the vacuum degassing tank and a discharge pipe for discharging molten glass from the vacuum degassing tank, and the screw is rotated. Has proposed a method of controlling the flow rate of the molten glass flowing through the introduction pipe and the discharge pipe. According to this method, the difference between the bath surface levels of the molten glass in the melting tank and the vacuum degassing tank can be reduced.

However, in such a method, since the bubbles contained in the molten glass are subdivided by the screw provided in the introduction pipe, there is a problem that the degassing under reduced pressure cannot sufficiently remove the bubbles.

[0006]

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a method for producing glass in which bubbles contained in molten glass are not subdivided in an introduction pipe and can be sufficiently defoamed in a vacuum degassing tank. To do.

[0007]

According to the present invention, molten glass is introduced into a vacuum degassing tank while controlling the flow rate, and degassed under reduced pressure.
Then, controlling the flow rate of the degassed molten glass from the vacuum degassing tank while controlling the flow rate, and controlling the cross-sectional area of the flow path of the molten glass to be introduced into the vacuum degassing tank in the glass manufacturing method of forming into a predetermined shape. The method for producing glass is characterized in that the flow rate of the molten glass is controlled by.

A description will be given below with reference to the drawings. FIG. 1 is a schematic view of an apparatus for carrying out the manufacturing method of the present invention.

Molten glass melted under atmospheric pressure is continuously introduced from the melting tank 10 into the vacuum degassing tank 11 via the introducing pipe 15. A valve 21 is provided at the end of the introduction pipe 15 to control the flow rate of the molten glass by changing the cross-sectional area of the flow path. This valve 21 is composed of a rod 13 having a truncated cone shape with a tapered tip, and a funnel 3 into which the diameter of the rod is expanded and the tip of the rod is inserted. By moving the rod 13 up and down, The gap 16 between the tip portion of the rod 13 and the funnel portion 3, that is, the cross-sectional area of the flow path of the molten glass can be changed.

If the gap 16 is too large, it becomes difficult to control the flow rate of the molten glass, which is not preferable. On the other hand, if it is too small, it is difficult to make the dimensions highly accurate in use, and as a result it becomes difficult to control the flow rate, which is not preferable. In controlling the flow rate, it is desirable that the gap be within the range of 1 to 20 mm.

The rod 13 and the funnel portion 3 are made of a heat-resistant material such as refractory or heat-resistant metal other than platinum,
Platinum lining the surface in contact with the molten glass is preferable in order to prevent erosion by the molten glass.

The valve 21 acts so as to prevent the molten glass from flowing into the vacuum degassing tank 11 due to the pressure difference between the melting tank 10 and the vacuum degassing tank 11, and The bath surface level and the bath surface level of the molten glass in the vacuum degassing tank 11 are substantially the same.

Although not shown in the drawing, the vacuum degassing tank 11 is provided.
Is equipped with a bath surface level meter for detecting the bath surface level of molten glass. Rod 1 based on the output of this bath level meter
3 moves up and down, and thereby the flow rate of the molten glass introduced into the vacuum degassing tank 11 is controlled.
Keep the bath surface level of. The molten glass passing through the valve has a viscosity of about 10 ² to 10 ⁴ poise.

Molten glass is passed through a valve 21 to a vacuum degassing tank 1
1, and degassed under reduced pressure. This vacuum degassing tank 1
1 is usually 0.05 to 0.3 atm.

Next, the molten glass is discharged from the vacuum degassing tank 11 through the discharge pipe 17 to the working tank 12 under atmospheric pressure.

The discharge pipe 17 is provided with a screw 14. The screw 14 operates so as to forcibly flow the molten glass from the vacuum degassing tank 11 to the working tank 12, and the screw 14 of the vacuum degassing tank 11 is operated. The bath surface level of the molten glass and the bath surface level of the molten glass in the working tank 12 are made substantially the same.

It is preferable that the discharge pipe 17 and the screw 14 are also made of a refractory material or a heat-resistant material such as a heat-resistant metal other than platinum, and that the portion in contact with the molten glass is lined with platinum in order to prevent erosion by the molten glass.

The molten glass introduced into the work tank 12 is adjusted to a predetermined temperature and then formed into a glass having a predetermined shape by a molding method such as press molding, float molding, roll-out molding.

As the molten glass, a wide range of glasses such as soda-lime-silica glass and optical glass can be used.

[0020]

EXAMPLES Using the apparatus shown in FIG. 1, molten glass was melted from a melting tank 10 through an introducing pipe 15 and a valve 21 under reduced pressure degassing tank 11.
And degassed. Next, this molten glass was discharged into the working tank 12 through a discharge pipe 17 provided with a screw 14. At this time, the valve 21 and the screw 14 were controlled so that the molten glass 10, the vacuum degassing tank 11, and the working tank 12 had the same molten glass bath surface level. The vacuum degassing tank 11 was adjusted to about 0.18 atm, the viscosity of the molten glass therein was about 10 ³ poise, and the residence time was about 30 minutes. Further, the molten glass was soda-lime-silica glass used for ordinary window glass.

In the molten glass, 1 to 2 m in the melting tank 10
Bubbles of mφ were contained at 500 cells / kg, and the diameter and number of the bubbles were the same after passing through the valve 21. In the molten glass in the work tank 12, bubbles of about 1 mmφ were reduced to 0.1 cells / kg.

As a comparative example, the introduction pipe 15 is used instead of the valve 21.
A screw is provided in the melting tank 1, and the flow rate of the molten glass is controlled by suppressing the molten glass introduced into the vacuum degassing tank 11.
The same test as in Example 1 was conducted by setting the molten glass bath surface levels of 0, the vacuum degassing tank 11 and the working tank 12 to be the same.

As a result, about 500 cells / kg of 1 to 2 mmφ bubbles were contained in the molten glass 10 in the molten glass, and after passing through the screw provided in the introduction pipe 15, 0.2 to 0.
60000 cells / kg of 5 mmφ bubbles were contained, and the bubbles were fragmented by the screw. And working tank 12
The molten glass of No. 1 contained 10 cells / kg of bubbles of about 1 mmφ.

[0024]

EFFECTS OF THE INVENTION According to the present invention, the molten glass in the melting tank and the vacuum degassing tank have substantially the same bath surface level, which is excellent in workability, and the bubbles of the molten glass introduced into the vacuum degassing tank are excellent. Since it is not subdivided, glass with good defoaming efficiency and less bubbles can be obtained. Further, if the amount of remaining bubbles is the same, the viscosity of the molten glass in the vacuum degassing tank can be increased, so that the temperature of the molten glass can be lowered, which is extremely advantageous in terms of the operation of the apparatus.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus for carrying out the present invention.

[Explanation of symbols]

 10: Melting tank 11: Vacuum degassing tank 13: Rod 14: Screw 21: Valve

Claims (2)

[Claims] 1. A molten glass is introduced into a vacuum degassing tank while controlling the flow rate, degassed under reduced pressure, and then the degassed molten glass is discharged from the vacuum degassing tank while controlling the flow rate to a predetermined shape. In the method for producing glass to be molded, the flow rate of the molten glass is controlled by controlling the cross-sectional area of the flow path of the molten glass introduced into the vacuum degassing tank. 2. The method for producing glass according to claim 1, wherein the portion for controlling the flow rate of the molten glass is platinum lined with a heat resistant material.