JPH0426418Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a high-frequency induction heating type glass melting device equipped with a stirring device.

[Conventional technology]

There are various heating means for melting glass, and high frequency induction heating means is known as one of them. FIG. 2 shows a glass melting apparatus using this high frequency induction heating means. A crucible 22 made of platinum or a platinum alloy housed in a protective refractory 23 is provided in a melting furnace 21 made of a refractory. This crucible 22 is heated by a high frequency induction coil 24. The molten glass 26 in the crucible 22 is stirred by a stirring device 25, and this stirring device includes a drive unit (not shown) and a shaft 25a.
and a blade 25b.

When melting glass using this melting device, first, the lid 27 is opened, and the prepared glass raw materials are introduced into the crucible 22 through the upper opening. The charged glass raw material receives heat from the crucible 22 generated by the high-frequency induction coil 24 and is melted. After the crucible 22 is filled with the molten glass 26, the molten glass 26 is left standing to be defoamed, and stirred by the stirring device 25 to produce homogeneous glass.

[Problem that the invention attempts to solve]

In the case of the conventional high-frequency induction heating type glass melting apparatus having the above structure, the upper part of the crucible 22 is open for inputting glass raw materials, so the molten glass 26
Heat radiation from the surface is relatively large.

Further, the side wall of the crucible 22 generates heat and the glass is melted by the heat, so the high temperature molten glass 26 near the side wall rises along the side wall of the crucible 22 and radiates heat on the surface of the molten glass 26. . The molten glass 26, whose temperature has slightly decreased due to heat radiation, descends from the center of the surface of the crucible 22, which is away from the side wall. Therefore, in high-frequency induction heating, a convection phenomenon occurs in the molten glass 26, and the temperature of the central portion of the molten glass 26 becomes lower than that of the other portions.

Further, the heat of the molten glass 26 escapes through the shaft 25a of the stirring device 25 installed in the center of the crucible 22 by conductive heat transfer.

Therefore, the temperature of the molten glass 26 in the crucible 22 is lowest near the center of the surface due to heat radiation at the surface and conductive heat transfer by the shaft 25a.

For the above reasons, if the temperature near the shaft 25a in the surface layer of the molten glass 26 drops below the liquidus temperature of the glass, crystals will precipitate near the shaft 25a, and these crystals will mix into the inside of the glass, causing the product to deteriorate. resulting in quality defects.

Furthermore, if the crystals spread over the entire surface, the stirring device 25 will be damaged due to the resistance caused by the solidified crystals during stirring.

As a measure to prevent crystal precipitation, a method is known in which the entire molten glass 26 is heated more than necessary in order to raise the temperature near the shaft 25a, where the temperature drops the lowest, to above the liquidus temperature of the glass 26.
In this case, 1) Energy loss will increase, 2) Since a large amount of energy is supplied, the life of the melting equipment, especially parts made of platinum or platinum alloys, will be shortened, and 3) Optimal glass temperature conditions for forming cannot be obtained, so molten glass The viscosity of the molten glass cannot be adjusted appropriately, and as a result, the quality of products molded with this molten glass becomes unstable.This is not the best solution.

The present invention was made to solve the above problems, and its purpose is to create a uniform temperature distribution without creating localized low-temperature regions in the molten glass in the crucible when melting glass by high-frequency induction heating. An object of the present invention is to provide a melting device capable of melting glass in a state in which glass is melted.

[Means to achieve the purpose]

To achieve this objective, the present invention provides a high-frequency induction heating type glass melting apparatus equipped with a stirring device for stirring the melt in the crucible, in which the shaft of the stirring device is provided with a reflector so as to face the surface of the melt. It is characterized by the provision of a plate.

[Effect]

During glass melting, the reflecting plate prevents heat radiation from the surface of the molten glass and reflects axial heat from the surface layer of the molten glass, so that the surface of the molten glass can be heated.

〔Example〕

Next, a high frequency induction heating type glass melting apparatus according to an embodiment of the present invention will be described in detail with reference to FIG.

In FIG. 1, 1 is a melting furnace made of refractory material, in which a crucible 2 made of platinum or platinum alloy is housed, and this crucible 2 is housed in a protective refractory material 3. There is. A high frequency induction coil 4 for generating heat in the crucible 2 is arranged around the protective refractory 3.

5 is a stirring device for stirring and homogenizing the molten glass 6 in the crucible 2;
a, a blade 5b, and a drive section (not shown) disposed at the top of the shaft.

Reference numeral 7 denotes a reflecting plate made of platinum or platinum alloy attached to the shaft 5a of the stirring device 5, and its lower surface is perpendicular to the longitudinal direction of the shaft 5a. This reflecting plate 7 is disk-shaped, its edges are bent upward, and it is filled with a heat insulating material 8 made of heat-resistant fibers (ceramic wool, for example).

A thermocouple 9 is welded to the outer wall of the crucible 2 and is arranged to control the temperature of the molten glass 6. Note that this thermocouple 9 is connected to a temperature display device and a temperature control device (not shown) via a conductive wire. 10 is a lid provided on the top of the melting furnace 1.

The dimensions of the crucible 2 are, for example, an outer diameter of 90 mm and a height of 130 mm, and the outer diameter of the reflecting plate 7 is 80 mm and the height of the bent portion is 40 mm. The reflecting plate 7 is the crucible 2
They are placed 50 mm above the liquid level of the molten glass 6 inside and facing each other.

Next, a glass melting operation using the high frequency induction heating type glass melting apparatus having the above structure will be explained.
The melting temperature of the glass is controlled by a temperature control device so as to reach a set temperature based on the temperature detected by a thermocouple 9 welded to the outer wall of the crucible 2.

First, the lid 10 is opened and the stirring device 5 is taken out of the furnace. Next, the glass raw material is charged into the crucible 2 through an input port (not shown) provided in the upper part or side wall of the melting furnace 1, and the side wall of the crucible 2 is heated by the high frequency induction coil 4, and the glass raw material is melted. do. After the crucible 2 is filled with the molten glass 6 to a depth of 30 mm below the top of the crucible 2, the stirring device 5 is placed in the furnace again, and the distance between the liquid level of the molten glass 6 and the bottom surface of the reflector plate 7 is set to 50 mm. . Next, defoaming by standing still and stirring by the stirring device 5 are performed to make the molten glass homogeneous.The crucible 2 together with the protective refractory 3 is taken out of the melting furnace 1, and the molten glass 6 is cast into a mold to form the desired shape. Form into shape.

Note that if an outflow pipe made of platinum or platinum alloy is attached to the bottom or side of the crucible 2, the molten glass 6 can be taken out of the melting furnace 1 without taking the crucible 2 out of the melting furnace 1. .

During glass melting, the reflecting plate 7 prevents heat radiation from the surface of the molten glass 6 and reflects radiant heat from the surface layer of the molten glass, so that the surface of the molten glass 6 can be heated. Therefore, since the temperature distribution of the molten glass 6 becomes uniform, the shaft 5a
Since the glass does not crystallize in the surrounding area, it is possible to prevent product quality defects and decrease in yield. Furthermore, it is no longer necessary to raise the melting temperature of the entire glass more than necessary to prevent glass crystallization, so energy loss is small, the life of the melting equipment is extended, and the viscosity of the glass is optimally adjusted for molding. , product quality is stable.

The temperature at the center of the surface of the molten glass 6 was compared when the reflective plate 7 according to the present invention was used and when it was not used. This temperature measurement was carried out by bringing a separately prepared thermocouple into contact with the surface glass near the shaft 5a of the stirring device 5, during which time the stirring was temporarily stopped.

At a set temperature of 1000°C, the molten glass temperature near the shaft 5a is 990°C when the reflector 7 of the present invention is used, and the molten glass temperature at the same position when the reflector 7 is not used is 930°C. It was hot.

Further, at a set temperature of 1300°C, the temperature of the molten glass near the shaft 5a when the reflector 7 of the present invention is used is 1285°C, and the temperature of the glass at the same position when the reflector 7 is not used is 1225°C. It was warm at ℃.

At any set temperature, when the reflective plate 7 of the present invention is used, the shaft 5a in the center of the crucible 2
The temperature of the nearby surface glass is close to the set temperature, and it can be seen that the effect of the reflector plate 7 of the present invention is significant.

Note that the present invention is not limited to the above-mentioned embodiments, and the lower surface of the reflecting plate may be shaped like a concave reflecting mirror. Thereby, the radiant heat reflected by the reflection plate 7 can be concentrated on the central surface of the molten glass 6 where the temperature is lowest.

Furthermore, if the liquidus temperature of the glass to be melted is low, the problem of crystallization of the glass will not occur even if the temperature of the center surface of the molten glass falls slightly below the set temperature, so the reflector plate 6 should be placed flat without bending. It is not necessary to use a circular disk and place the heat insulating material on the top of the disk. This simplifies the shape of the reflector, making it easier to manufacture the reflector. In this case, the reflector only performs the function of reflection and does not function to prevent heat radiation.

Furthermore, the dimensions of each part of the melting device are not limited to the dimensions shown in the embodiments, but can be determined according to the temperature, type, amount, etc. of the glass to be melted.

[Effect of idea]

As described above, according to the present invention, since the reflector is attached to the shaft of the stirring device, the reflector prevents heat radiation from the surface of the molten glass and reflects radiant heat from the surface layer of the molten glass during glass melting. Therefore, the surface of the molten glass can be heated. Therefore, since the temperature distribution of the molten glass becomes uniform, the glass does not crystallize around the shaft, and it is possible to prevent product quality defects and decrease in yield.

Furthermore, it is no longer necessary to raise the melting temperature of the entire glass more than necessary to prevent glass crystallization, so energy loss is small, the life of the melting equipment is extended, and the viscosity of the glass is optimally adjusted for molding. , product quality is stable.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a high frequency induction heating type glass melting apparatus according to the present invention, and FIG. 2 is a longitudinal sectional view of a conventional high frequency induction heating type glass melting apparatus. 1... Melting furnace, 2... Crucible, 3... Protective refractory, 4... High frequency induction coil, 5... Stirring device,
5a... Shaft, 5b... Blade, 6... Molten glass, 7... Reflector, 8... Heat insulating material, 9... Thermocouple, 10... Lid.

Claims (1)

[Scope of Claim for Utility Model Registration] In a high-frequency induction heating type glass melting device equipped with a stirring device for stirring the molten material in the crucible, a reflecting plate is provided on the shaft of the stirring device so as to face the surface of the molten material. A high frequency induction heating type glass melting device characterized by: