Method for producing glass and device for shaping glass

Abstract

It is an object of the present invention to provide a method for producing glass in which the temperature distribution between around a central portion and around a side wall of a shaping mold (temperature distribution between around a central portion and around a side wall of molten glass in the shaping mold) is regulated within a range of ±150° C. to produce large-size glass, and to provide a device for shaping glass used in the method for producing glass. The object may be attained by carrying out a step of flowing the molten glass in a melting furnace, through a pipe to which a heat-insulating member is fixed to prevent the heat dissipation of the molten glass, into the shaping mold covered with a low heat-conductive member, and a step of maintaining the distance between the lower portion of the heat-insulating member and the liquid surface of the molten glass.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross section of a device for shaping glass according to the present invention.

FIG. 2 shows a perspective view in the vicinity of a shaping mold of a device for shaping glass according to the present invention.

FIG. 3 shows a overhead view in the vicinity of a shaping mold of a device for shaping glass according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The method for producing glass according to the present invention is characterized by including a step of flowing molten glass within a melting furnace from a flow-out portion equipped with a heat-insulating member into a shaping mold covered with a low heat-conductive member, and a step of maintaining the distance between the lower portion of the heat-insulating member and the liquid surface of the molten glass flowed into the shaping mold.

The device for shaping glass according to the present invention is characterized by including a melting furnace to melt glass, a shaping mold to shape molten glass that is flowed therein from the melting furnace, in which the inside of the shaping mold is covered with a low heat-conductive member, a heat-insulating member to prevent the heat dissipation of the molten glass that is flowed into the shaping mold, and a flow-out portion to flow the molten glass from the melting furnace into the shaping mold.

The method for producing glass and the inventive device for shaping glass of the present invention are explained in detail in regards to embodiments thereof, but to which the present invention should not be construed as to be limited, and various modifications may be appropriately conducted within the purpose of the present invention. In addition, in cases where explanations are repeated, sometimes portions of the explanations are omitted, which should not be construed as to limit the scope of the invention.

Device for Shaping Glass

FIG. 1 shows a cross section of device for shaping glass of the present invention; FIG. 2 shows a perspective view that shows the vicinity of shaping mold 5; and FIG. 3 shows a top portion view at the periphery of shaping mold 5. The device for shaping glass 1 is provided with a melting furnace 2 to melt glass materials, and to produce and store a molten glass 3, and a flow-out portion 4 that is connected to the lower portion of the melting furnace 2 and flows the molten glass 3 into the shaping mold 5 to shape the molten glass 3. A cooler 8 is also provided at the lower portion of the shaping mold 5 to cool the molten glass flowed into the shaping mold 5.

The melting furnace 2 may be one that has a heating element (not shown) to generate heat upon energizing, and to supply the heat to the melting furnace 2 and a stirring device (not shown) to stir the molten glass 3 within the melting furnace 2. The melting furnace 2 is preferably a fire-resistant crucible suited to pour, dissolve, clarify and stir the glass raw materials. The fire-resistant crucible is preferably of gold, platinum, platinum alloys, alloys or complex materials thereof, quartz crucible, or electroforming brick, for example.

The flow-out portion 4 is connected to the lower portion of the melting furnace 2 to flow the molten glass 3 within the melting furnace 2 into the shaping mold 5. The connecting site between the melting furnace 2 and flow-out portion 4 is not limited specifically, and, for example, the flow-out portion 4 may be connected to the bottom face, side wall, or the like of the melting furnace 2. The flow-out portion 4 is not required to be a linear shape, and may be appropriately tapered as necessary. The flow-out portion 4 may be directly heated by flowing an electric current through the flow-out portion 4 itself, indirectly heated by an external heating device, or the both may be employed to control the temperature inside the flow-out portion 4.

In cases where the flow-out portion 4 is heated directly, the flow-out portion 4 is constructed from platinum or platinum alloys, etc. so that the flow-out portion 4 is heated by direct energization, and the viscosity of the molten glass flowing within the flow-out portion 4 is adjusted at a pre-determined level by controlling the temperature. The flow-out portion 4 shown in FIG. 1 is constructed as an elongated structure, which is not limited, and alternatively may be a gutter-like shape of which the upper portion is open along the direction to which the molten glass flows, for example.

The flow-out portion 4 is equipped with a heat-insulating member 7 that prevents heat dissipating from the molten glass 3 in the shaping mold 5 and stores heat. The heat-insulating member 7 can decrease the temperature distribution range between around the central portion and around the side wall of the molten glass 3 within the shaping mold 5. The area of the heat-insulating member 7 is approximately the same with the opening area of the shaping mold 5, as shown in FIG. 3. The heat dissipation of the molten glass 3 within the shaping mold 5 can be suppressed by making the area of the heat-insulating member 7 approximately the same with the opening area of the shaping mold 5. The site to fix the heat-insulating member 7 may be appropriately changed depending on the shaping mold 5 and size of the flow-out portion 4, etc. The heat-insulating member 7 may be fixed to the flow-out portion 4 or movable together with the flow-out portion 4.

The heat conductivity at room temperature of the heat-insulating member 7 is preferably no higher than 2.0 W/m·K. When the heat conductivity at room temperature is higher than 2.0 W/m·K, it is difficult to sufficiently suppress the heat dissipation from the liquid surface of the molten glass 3 within the shaping mold 5, and thus it is difficult to decrease the temperature difference between the molten glass 3 around the liquid surface of the shaping mold 5 and the molten glass around the central portion of the shaping mold 5. That is, the temperature distribution range cannot be regulated within ±150° C. between around the central portion and around the side wall of the molten glass within the shaping mold, in the course of cooling until vitrification. The material of the heat-insulating member 7 is not specifically limited as long as the heat conductivity at room temperature is no higher than 2.0 W/m·K, and, for example, the material is preferably aluminum oxide or complexes of aluminum oxide. The heat-insulating member 7 may be formed of one material or combinations of materials.

In cases where the heat-insulating member 7 is fixed to the flow-out portion 4, the molten glass 3 flowed into the shaping mold 5 from the flow-out portion 4 is flowed between the lower portion of the heat-insulating member 7 and the bottom face of the shaping mold 5.

The shape of the shaping mold 5, which is not specifically limited, may be box-like such as a cube and rectangular solid, as shown in FIGS. 1 and 2. The inner wall face of the shaping mold 5 and the bottom face inside the shaping mold 5 are covered with a low heat-conductive member 6. The molten glass 3 around the side wall of the shaping mold 5 can be easily suppressed from dissipating heat to outside the shaping mold 5 by covering the inner wall face of the shaping mold 5 and the inner bottom face of the shaping mold 5 (hereinafter referred to as “entire inner side of the shaping mold 5”). Breakage, etc. of the shaping mold 5 can also be easily prevented by way of the heat stored in the molten glass 3. Furthermore, the life of the shaping mold 5 can be extended and a thickness thereof decreased by using the low heat-conductive member 6, which also makes it possible to decrease the cost.

The heat conductivity at room temperature of the low heat-conductive member 6 is preferably no higher than 2.0 W/m·K. When the heat conductivity at room temperature is higher than 2.0 W/m·K, it is difficult to suppress the heat dissipation from the molten glass 3 around the side wall of the shaping mold 5 to outside the shaping mold 5, and thus it is difficult to decrease the temperature difference between the molten glass around the central portion of the shaping mold 5 and the molten glass around the side wall of the shaping mold 5. That is, the temperature distribution range cannot be regulated within ±150° C. between around the central portion and around the side wall of the molten glass 3 in the shaping mold, in the course of cooling until vitrification. The material of the low heat-conductive member 6 is not limited specifically as long as the heat conductivity at room temperature is no higher than 2.0 W/m·K, and, for example, the material is preferably aluminum oxide or complexes of aluminum oxide. The low heat-conductive member may be formed of one material or combinations of materials.

The thickness of the low heat-conductive member 6 is preferably below 5 mm, and more preferably below 3 mm. When the thickness of the low heat-conductive member 6 is no less than 5 mm, the molten glass 3 may devitrify during its shaping within the shaping mold 5.

The shaping mold 5 has such a configuration that it moves up and down in a substantially vertical direction when the molten glass 3 is flowed into the shaping mold 5, as shown in FIG. 1. Therefore, the distance between the heat-insulating member 7 and the liquid surface of the molten glass 3 within the shaping mold 5 can always be maintained constant. The heat dissipation and the heat stored by the molten glass 3 can be balanced by maintaining constant the distance between the heat-insulating member 7 and the liquid surface of the molten glass 3 within the shaping mold 5, and thus the temperature distribution range can be regulated within ±150° C. between around the central portion and around the side wall of the molten glass 3 in the shaping mold, in the course of cooling until vitrification, and mold striae can be reduced. The process to move up and down the shaping mold 5 in a substantially vertical direction may be appropriately modified depending on the size of the molded glass, etc.; for example, the up and down motion of the shaping mold 5 may be controlled such that the shaping mold 5 comes down at a constant speed by means of measuring the flow-out amount of the molten glass 3 introduced. The control may be carried out by projecting a laser to the molten glass 3.

The distance between the heat-insulating member 7 and the liquid surface of the molten glass 3 within the shaping mold 5 may be properly changed depending on the size of the molded glass, etc., the distance being preferably no more than 50 cm. When the distance between the heat-insulating member 7 and the liquid surface of the molten glass 3 within the shaping mold 5 is more than 50 cm, it is difficult to suppress the heat dissipation from the liquid surface of the molten glass 3 within the shaping mold 5, sometimes resulting in cracking of the glass in the steps of heat treatment or processing.

A cooler 8 is provided at the outer bottom of the shaping mold 5. The molten glass 3 around the bottom face of the shaping mold 5 dissipates no substantial heat and easily stores heat compared to upper portions. Therefore, the temperature distribution range of the molten glass 3 can be decreased between the molten glass 3 around the central bottom face of the shaping mold 5, the molten glass 3 around the side wall of the shaping mold 5, and the molten glass 3 around the central portion, by way of cooling the bottom portion of the shaping mold 5. That is, the temperature distribution range can be regulated within ±150° C. The cooler 8 may be provided at the side wall of the shaping mold 5 as required.

The temperature distribution range is preferably within ±150° C. between around the central portion and around the side wall of the molten glass 3 within the shaping mold 5, more preferably within ±100° C., and still more preferably within ±50° C.

Method for Producing Glass

The method for producing glass of the present invention may be carried out using the glass molding device of the present invention described above.

Initially, the molten glass 3 within the melting furnace 2 is flowed into the shaping mold 5, which is covered with the low heat-conductive member 6, under the heat-insulating member 7 through inside the flow-out portion 4 to which the heat-insulating member 7 is fixed to prevent heat dissipating from the molten glass 3.

The flow-out portion 4 is connected to the lower portion of the melting furnace 2 to flow the molten glass 3 within the melting furnace 2 into the shaping mold 5. The velocity of flow of the molten glass 3 into the melting furnace 2 may be properly adjusted depending on the species, etc. of the glass to be produced, with the velocity preferably being less than 50 kg/min. When the velocity of flow of the molten glass 3 is higher than 50 kg/min, the mold striae is likely to be large, sometimes resulting in cracking problems in the steps of heat treatment or processing.

The heat conductivity at room temperature of the heat-insulating member 7 is preferably no higher than 2.0 W/m·K. When the heat conductivity at room temperature is higher than 2.0 W/m·K, it is difficult to sufficiently suppress the heat dissipated from the liquid surface of the molten glass 3 within the shaping mold 5, and thus it is difficult to decrease the temperature difference between the molten glass 3 around the liquid surface of the shaping mold 5 and the molten glass around the central portion of the shaping mold 5. That is, the temperature distribution range cannot be regulated within ±150° C. between around the central portion and around the side wall of the molten glass in the shaping mold, in the course of cooling until vitrification. The material of the heat-insulating member 7 is not specifically limited as long as the heat conductivity at room temperature is no higher than 2.0 W/m-K, the material being, for example, preferably aluminum oxide or complexes of aluminum oxide.

The molten glass flowed into the shaping mold 5 from the flow-out portion 4 is directed to flow between the lower portion of the heat-insulating member 7 and the bottom face of the shaping mold 5, since the heat-insulating member 7 is fixed to the flow-out portion 4.

The shape of the shaping mold 5, which is not specifically limited, may be box-like such as a cube and rectangular solid, as shown in FIGS. 1 and 2. The inner wall face of the shaping mold 5 and the bottom face inside the shaping mold 5 are covered with a low heat-conductive member 6. The molten glass 3 around the side wall of the shaping mold 5 can easily be suppressed from dissipating heat to outside the shaping mold 5 by covering the inner wall face of the shaping mold 5 and the inner bottom face of the shaping mold 5 (hereinafter referred to as “entire inner side of the shaping mold 5”) with the low heat-conductive member 6. Breakage, etc. of the shaping mold 5 can also be easily prevented by way of the heat storage of the molten glass 3. Furthermore, the life of the shaping mold 5 can be extended and the thickness thereof decreased by using the low heat-conductive member 6, which also makes it possible to decrease the cost.

The heat conductivity at room temperature of the low heat-conductive member 6 is preferably no higher than 2.0 W/m·K. When the heat conductivity at room temperature is higher than 2.0 W/m·K, it is difficult to suppress the heat dissipation from the molten glass 3 around the side wall of the shaping mold 5 to outside the shaping mold 5, and thus it is difficult to uniformly decrease the temperature distribution range between the molten glass 3 around the central portion of the shaping mold 5 and the molten glass around the side wall of the shaping mold 5. That is, it is difficult to regulate the temperature distribution to within ±150° C. between around the central portion and around the side wall of the molten glass 3 in the shaping mold, in the course of cooling until vitrification. The material of the low heat-conductive member 6 is not limited specifically as long as the heat conductivity at room temperature is no higher than 2.0 W/m·K, and for example, the material is preferably aluminum oxide or complexes of aluminum oxide.

The thickness of the low heat-conductive member 6 is preferably less than 5 mm, more preferably no more than 3 mm. When the thickness of the low heat-conductive member 6 is no less than 5 mm, the molten glass 3 may devitrify during its shaping within the shaping mold 5.

A cooler 8 is provided at the outer bottom of the shaping mold 5. The molten glass 3 around the bottom portion of the shaping mold 5 dissipates no substantial heat and easily stores heat compared to upper portions. Therefore, the temperature distribution range can be decreased between the molten glass 3 around the bottom face of the shaping mold 5, the molten glass 3 around the side wall of the shaping mold 5, and the molten glass 3 around the central portion, by way of cooling the bottom portion of the shaping mold 5. The cooler 8 may be provided at the side wall of the shaping mold 5 as required.

The cooling process by the cooler 8 may be properly changed depending on the size, etc. of the glass to be produced and, for example, various conventional cooling processes such as mist-cooling, air-cooling, and water-cooling may be employed. These cooling processes may be used alone or in combination of two or more.

The shaping mold 5 is then lowered downward such that the distance is maintained between the lower portion of the heat-insulating member 7 and the liquid surface of the molten glass 3 flowed into the shaping mold 5.

The shaping mold 5 has such a configuration that it moves up and down in a substantially vertical direction when the molten glass 3 is flowed into the shaping mold 5, as shown in FIG. 1. Therefore, the distance between the heat-insulating member 7 and the liquid surface of the molten glass 3 within the shaping mold 5 can always be maintained constant. The heat dissipation and the heat storage of the molten glass 3 can be easily balanced by maintaining constant the distance between the heat-insulating member 7 and the liquid surface of the molten glass 3 within the shaping mold 5, and thus the temperature distribution range can be regulated within ±150° C. between around the central portion and around the side wall of the molten glass 3 in the shaping mold in the course of cooling until vitrification, and mold striae can be reduced. The process to move the shaping mold 5 up and down in a substantially vertical direction may be appropriately modified depending on the size of the molded glass, etc.; the up and down motion of the shaping mold 5 may be controlled such that shaping mold 5 comes down at a constant speed by measuring the flow-out amount of the introduced molten glass 3. The control may be carried out by projecting a laser to the molten glass 3.

The distance between the heat-insulating member 7 and the liquid surface of the molten glass 3 within the shaping mold 5 may be properly selected depending on the size of the glass to be molded, etc., and the distance is preferably no more than 50 cm. When the distance between the heat-insulating member 7 and the liquid surface of the molten glass 3 within the shaping mold 5 is more than 50 cm, it is difficult to suppress the heat dissipated from the liquid surface of the molten glass 3 within the shaping mold 5, and it is difficult to balance the heat dissipated and the heat stored. Furthermore, the mold striae is likely to be large, sometimes resulting in cracking of glass during the steps of heat treatment or processing.

An intended amount of the molten glass 3 is flowed into the shaping mold 5 while lowering the shaping mold 5 downward such that the distance is maintained constant between the lower portion of the heat-insulating member 7 and the liquid surface of the molten glass 3 flowed into the shaping mold 5, then the lowering of the shaping mold 5 is stopped, and the molten glass 3 is shaped.

Claims

1. A method for producing glass, comprising steps of: flowing a molten glass within a melting furnace into a shaping mold through a flow-out portion, andshaping the molten glass within the shaping mold,wherein the temperature distribution of the molten glass is regulated within ±150° C., in the course of cooling until vitrification.

2. The method for producing glass according to claim 1, further comprising the steps of: flowing the molten glass through the flow-out portion, between the shaping mold having a shaping face covered with a low heat-conductive member and the lower portion of a heat-insulating member which is movably interlocking with said flow-out portion or fixed to said flow-out portion; andmaintaining a fixed distance between said lower portion of the heat-insulating member and the liquid surface of said molten glass flowed into said shaping mold.

3. The method for producing glass according to claim 1, wherein the shaping mold is moved up and down in a vertical direction to maintain constant the distance thereof from the liquid surface of the molten glass.

4. The method for producing glass according to claim 1, wherein the molten glass is flowed into the shaping mold while cooling the lower portion of the shaping mold.

5. The method for producing glass according to claim 2, wherein the distance between the lower portion of the heat-insulating member and the liquid surface of the molten glass flowed into the shaping mold is no more than 50 cm.

6. The method for producing glass according to claim 2, wherein the thickness of the low heat-conductive member is less than 5 mm.

7. The method for producing glass according to claim 2, wherein the heat conductivity at room temperature of the low heat-conductive member is no higher than 2.0 W/m·K.

8. The method for producing glass according to claim 2, wherein the low heat-conductive member is of one selected from the group consisting of aluminum oxide and a complex of aluminum oxide.

9. The method for producing glass according to claim 2, wherein the heat conductivity at room temperature of the heat-insulating member is no higher than 2.0 W/m·K.

10. The method for producing glass according to claim 2, wherein the heat-insulating member is of one selected from the group consisting of aluminum oxide and a complex of aluminum oxide.

11. A device for shaping glass, comprising: a melting furnace to melt glass;a shaping mold to shape molten glass that is flowed therein from the melting furnace, wherein the inside of the shaping mold is covered with a low heat-conductive member;a heat-insulating member to prevent the heat dissipation of the molten glass that is flowed into the shaping mold; anda flow-out portion to flow the molten glass from the melting furnace into the shaping mold.

12. The device for shaping glass according to claim 11, further comprising a cooler at the lower portion of the shaping mold.

13. The device for shaping glass according to claim 11, wherein the shaping mold is moved up and down in a substantially vertical direction so as to make the distance between the lower portion of the heat-insulating member and the liquid surface of the molten glass flowed into the shaping mold constant.

14. The device for shaping glass according to claim 11, wherein the heat-insulating member is fixed to the flow-out portion.

15. The device for shaping glass according to claim 11, wherein the distance between the lower portion of the heat-insulating member and the liquid surface of the molten glass flowed into the shaping mold is no more than 50 cm.

16. The device for shaping glass according to claim 11, wherein the thickness of the low heat-conductive member is less than 5 mm.

17. The device for shaping glass according to claim 11, wherein the heat conductivity at room temperature of the low heat-conductive member is no higher than 2.0 W/m·K.

18. The device for shaping glass according to claim 11, wherein the low heat-conductive member is of one selected from the group consisting of aluminum oxide and a complex of aluminum oxide.

19. The device for shaping glass according to claim 11, wherein the heat conductivity at room temperature of the heat-insulating member is no higher than 2.0 W/m·K.

20. The device for shaping glass according to claim 11, wherein the heat-insulating member is of one selected from the group consisting of aluminum oxide and a complex of aluminum oxide.