JPH0359015B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold used for molding glass into a plate shape.

[Conventional technology]

Conventionally, there is a roll method as a method for forming plate glass. This method involves continuously pouring molten glass from a tank and passing it between two rolls to form a plate. Ford) law. In this method, glass flows out from the tip (lip) of the floor hearth in a width of several _feet , is formed into a plate of a certain thickness by a pair of large and small rolls, and is then passed through a long slow-cooling kiln. Sent (Naruse ``Glass Engineering'' p161-162 Kyoritsu Publishing, 1962).

[Problem that the invention seeks to solve]

The above-mentioned Ford method is a manufacturing method suitable for cases where internal quality is not a major concern and the amount of pulling up per unit time is large, such as for automobile window glass.

On the other hand, in the production of optical grade plate glass that requires high optical internal homogeneity, a tank made of platinum or a platinum alloy, or a tank lined with these, is generally used as the melting tank.
The structure of the melting furnace is significantly different from that of window glass melting furnaces, etc., and has a working tank at the end of the furnace equipped with a stirring mechanism to ultimately homogenize the molten glass. The molten glass is flowed out from a platinum pipe attached to the bottom of the working tank, which is the final tank, but the amount of glass flowing out, or the amount of glass pulled up, is extremely small in optical glass melting furnaces, and is usually several hundred kilograms. Several tons/day. Conventionally, no technology has been established for efficiently forming molten glass flowing out from such a small-diameter outflow pipe with a small pulling amount into a plate glass of any desired thickness. In addition, as a method for forming optical glass into plate glass, an attempt was made to gradually widen the tip of a platinum outflow pipe led from a working tank into a flattened shape, and then let it flow out in the form of a plate through a nozzle with a slit-shaped tip. However, due to the head difference and viscosity in the pipe, the flow rate in the center of the slit increased, and it did not work.

[Means for solving problems]

In the present invention, molten glass supplied from a supply source is once received in a mold having a special shape, and a plate-shaped glass is taken out from there. That is, the mold of the present invention is configured such that the glass inlet part constitutes the deepest glass reservoir, and the glass inlet part gradually becomes shallower and wider.
The guide slope has an upwardly sloped bottom surface and an outflow lip section having a downwardly sloped surface connected to the top of the guiding slope.

[Effect]

The molten glass that has flowed into the glass inflow portion does not immediately flow out of the mold, but sequentially moves along the guiding slope toward the outflow lip portion, forming a laminar flow and flowing while widening its width. Thereby, the molten glass flowing into the mold maintains its original high internal homogeneity. Then, at the top of the outflow lip,
The glass overflows while maintaining a constant width and flows down the outflow lip, resulting in sheet glass without defects such as folds.

〔Example〕

1 and 2 are schematic configuration diagrams showing one embodiment of the present invention, with FIG. 2 being a plan view and FIG. 1 being a sectional view taken at the center thereof.

The mold 1 is installed directly below the platinum outflow pipe 2 and consists of a protective refractory tank 3 and a platinum receiving tank 4 formed inside the protective refractory tank 3. Although the platinum receiving tank 4 was molded to match the protective refractory tank 3 and installed so as to be in contact with the inner surface thereof, a mold in which the inner surface of the protective refractory tank 3 is lined with platinum may also be used.
Furthermore, instead of platinum, a platinum alloy such as platinum-rhodium may be used.

The bottom surface of the platinum receiving tank 4 is flat at the part where the molten glass 5 first flows into the receiving tank from the pipe 2 (glass inflow part), but there is an upward slope guiding slope part 6 following this part, and then At the top, there is an outflow lip 7 which has a continuous downward slope. Therefore, the molten glass 5 flowing from the outflow pipe 2 is
The water does not immediately flow out of the receiving tank 4, but is stored up to the top of the guiding slope 6 and then continuously flows out from the tip of the outflow lip 7. At this time, since the guiding inclined portion 6 has a structure in which the width gradually increases toward the top thereof, the molten glass 5
It will have a corresponding width. The glass that overflowed from the top of the guiding slope 6 was
It flows down along the downwardly sloped surface of the outflow lip portion 7 while maintaining its width.

The slope of the guiding slope part 6 is preferably gentle so that the molten glass 5 in the receiving tank 4 continuously flows out in a laminar flow without becoming partially stagnant.
The angle is preferably around 10°, but may be selected as appropriate depending on the desired quality of the plate glass.

The same applies to the slope of the outflow lip portion 7, and the preferred angle is about 45°, but it may be selected as appropriate. especially,
This slope is made larger when a relatively thin plate glass is to be obtained, and is made smaller when a relatively thick plate glass is to be obtained.

The glass that has left the tip of the outflow lip portion 7 immediately passes between rolls 8 and 9, becomes a plate glass 10 of a constant thickness, and is sent to a lehr (not shown). The thickness of the glass can be controlled to any desired thickness by adjusting the rotational speed and gap of the rolls 8 and 9, but furthermore, the glass plate is continuous with the plate glass portion that was previously fed into the lehr. Therefore, it receives a tensile force due to its movement. Since the portion immediately after passing through the rolls 8 and 9 has not yet solidified, the thickness of the sheet glass is affected by this tensile force, that is, the rare speed, and the higher the rare speed, the thinner the glass sheet becomes.

Note that, in order to accurately control the temperature of the receiving tank 4, it is desirable that the receiving tank 4 has a structure that can be appropriately heated. FIG. 3 shows a structure in which a power supply flange is attached for this purpose.

Generally, the temperature of the molten glass 5 is higher at the center in the outflow direction than at the side edges, and therefore the outflow velocity at the center tends to be higher than at the side edges. For this reason, immediately after the start of molding, the power supply flange 1 is used to selectively heat the relatively central portion of the receiving tank 4.
After the glass begins to steadily flow from the outflow lip portion 7 by applying electricity and heating between the power supply flanges 11 and 12 and between the power supply flanges 13 and 14,
Electricity is applied between them to mainly heat the sides of the receiving tank 4.
The amount of heating heat required for this receiving tank 4 is closely related to the forming speed of the plate glass and its plate thickness, and needs to be adjusted appropriately. In particular, when the amount of glass flowing into the receiving tank 4 per unit time is large, it is necessary to cool the bottom of the receiving tank 4, so a cooling means such as water cooling or air cooling may be provided as appropriate. By providing such a heating and cooling means, it is possible to freely adjust the temperature of the molten glass to the optimum molding temperature.

Next, a specific example of the molding method will be explained.

Borosilicate crown glass BSC7 (HOYA product name), which is the most commonly used optical glass, is melted and clarified in a melting furnace, and then passed through a working tank to produce a fully homogenized optical grade without bubbles or striae. With quality glass. This molten glass is continuously supplied to a receiving tank 4 from an outflow pipe 2. At this time, the temperature of the glass flowing out from the outflow pipe 2 is
The temperature of the molten glass 5 near the center of the induction slope portion 6 after being supplied to the receiving tank 4 was 1120°C and 1080°C. The mold 1 was entirely housed in a heat-retaining furnace equipped with heating means (not shown), and the ambient temperature therein was 850°C. In addition, the glass temperature near the center of the outflow lip part 7 is 970℃,
The glass temperature near the left and right ends was 920°C.

The molten glass 5 is supplied to the rolls 8 and 9 through the guiding slope part 6 and the outflow lip part 7, and the rolls 8 and 9 have a plate width of 250 mm.
A glass plate 10 having a thickness of 3.5 mm was formed and supplied to a lehr. Note that the plate width was determined according to the width of the outflow lip portion 7, and at this time, the width was 300 mm. In addition, as mentioned above, the plate thickness is mainly determined by the roll 8,
9, but it also changes depending on the rare speed. By setting this to 10m/hr, the above plate glass will finally have a width of 250mm and a thickness of 3.0mm.
It became mm.

In this way, a highly homogeneous optical grade plate glass free of striae, bubbles, foreign matter, etc. was obtained.
In addition, the amount of molten glass flowing out from the outflow pipe 2,
The temperature of the glass, the temperature of the molten glass 5 in the receiving tank 4, the gap between the rolls 8 and 9, the lair speed, and the width of the outflow lip 7 are all correlated to the width and thickness of the glass plate to be obtained. Therefore, it is necessary to select it appropriately.

In addition, although an example has been described in which the glass that has left the outflow lip section 7 is sent to the cooling furnace through between the rolls 8 and 9, the present invention is not limited to this, and the glass that has left the outflow lip section 7 is sent to the cooling furnace. isn't it.

In the above, the protective refractory is platinum (or platinum alloy)
The explanation was given using an example of a molding die consisting of a combination of
The mold of the present invention is not limited to this, and may be made of carbon or other heat-resistant refractories such as electroformed bricks and fired bricks into a desired shape.

〔Effect of the invention〕

According to the present invention, a molding comprising a glass inflow portion, a guiding slope portion having an upwardly sloped bottom surface configured to gradually become shallower and wider, and an outlet lip portion consisting of a downwardly sloped surface continuous to the top of the guiding slope portion. By supplying molten glass to the glass inlet using a mold, it is possible to manufacture plate glass having any desired width and thickness, regardless of the amount of glass flowing out from the outflow pipe. In particular, the molten glass that has flowed into the glass inflow section sequentially moves through the guiding slope toward the outflow lip section, becoming a laminar flow and flowing while widening its width. Optical-grade sheet glass without any defects is obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
This figure is also a plan view, and FIG. 3 is a plan view showing an example of the configuration of a molding die with a power supply flange. DESCRIPTION OF SYMBOLS 1... Molding mold, 2... Outflow pipe, 3... Protective refractory tank, 4... Platinum receiver tank, 5... Molten glass, 6... Guiding slope part, 7... Outflow lip part, 10... Plate glass,
11-14...Power supply flange.

Claims (1)

[Scope of Claims] 1. A glass inflow section constituting the deepest glass reservoir, a guiding slope section having an upwardly sloped bottom surface and configured to gradually become shallower and wider following the glass inflow section, and the guide. A mold for forming plate glass, characterized in that it is provided with an outflow lip section consisting of a downwardly sloped surface connected to the top of the slope section. 2. The method according to claim 1, characterized in that the protective refractory tank is constructed by inscribing a receiving tank made of platinum or a platinum alloy, or by lining the inner surface of the protective refractory tank with platinum or a platinum alloy. A mold for forming plate glass. 3. A mold for forming plate glass according to claim 1 or 2, characterized in that it is provided with a power supply flange.