JPS5930655B2 - Continuous manufacturing equipment for rod-shaped or tubular opaque vitreous bodies - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a manufacturing apparatus for continuously manufacturing rod-shaped or tubular opaque vitreous bodies.

Conventionally, to manufacture this type of opaque glassy material, raw material powder with many air bubbles, such as silica powder, is fed into a cylindrical crucible with a nozzle at the bottom, and then heated and melted using an electric heater from the surrounding area. A continuous manufacturing device is used in which a rod-shaped or tubular glass body is drawn from the nozzle portion using a drawing roller.

However, in the above device, since the molten glass in the crucible is simply pulled out from the nozzle, air bubbles in the surface layer of the pulled vitreous body burst, which not only significantly impairs the appearance but also causes dimensional stability. The drawback was that it was not possible to obtain products with excellent properties.

For this reason, it is conceivable to lower the temperature of the molten glass near the nozzle part and reduce the viscosity of the surface of the rod-shaped or tubular glass material pulled out from the nozzle part to prevent the bubbles from bursting. If the viscosity is lowered in this manner, the drawing speed will be lowered, which will not only reduce productivity, but also cause crystallization after a long period of time in the temperature range where molten glass becomes cristobalite, which may lead to a decrease in strength.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and provides a manufacturing apparatus for efficiently producing rod-shaped or tubular opaque glassy bodies with excellent dimensional stability and good surface appearance, and in which air bubbles are uniformly dispersed. The purpose is to provide.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In the figure, 1 is a cylindrical water-cooled reactor shell having a cooling water circulation chamber 2 inside, an upper water-cooled lid 4a having a peephole 3 at the upper and lower ends of the reactor shell 1, and a pulled-out rod-shaped or tubular glass body. A lower water-cooling lid 4b having an opening 5 through which the water-cooling lid 4b is inserted is hermetically fixed.

A protruding chamber 6 is formed in the center of the upper water-cooled lid 4a, and a raw material input section 7 for supplying raw material powder and a protective gas introduction pipe 8 for supplying protective gas are provided in the protruding chamber 6.

Further, in the center of the furnace shell 1, there is a long tube made of molybdenum, which communicates with the protrusion chamber 6 via an intermediate cylinder 9 protruding from the lower surface of the upper water-cooling lid 4a, and has a nozzle part 10 made of molybdenum at the bottom. A cylindrical crucible 11 is provided.

A shielding cylinder 12 made of molybun, which is supported by a lower heat-insulating cylinder to be described later, is suspended from the lower surface of the nozzle portion 10 of the crucible 11.

Further, between the furnace shell 1, the intermediate cylinder 9, the crucible 11, and the shielding cylinder 12, an upper heat-insulating cylinder 13, a central heat-insulating cylinder 14, and a lower heat-insulating cylinder 1 made of zircon insulation bricks, etc.
5 are arranged, and the inner peripheral surface of the furnace shell 1 and each heat insulation cylinder 13, 1
4.15, and an inner cavity 17 is formed between the outer circumferential surface of the crucible 11, the upper outer circumferential surface of the shielding cylinder 12, and the central heat-retaining cylinder 14.

A desired number of exhaust holes 18 communicating with the inner cavity chamber 17 are opened at the upper part of the long cylindrical crucible 11, and an L-shaped mandrel 19 is disposed inside the crucible 11. .

One end of this mandrel 19 is fixed through the furnace shell 1, the central heat-insulating cylinder 14, and the side wall of the crucible 11, and the other end of the mandrel main body 20 is inserted through the nozzle part 11 and shields the lower part thereof. It extends into the cylinder 12.

Further, a heating element 21 for melting the raw material, which is a meandering round rod made of, for example, molybdenum, is loaded in the inner cavity 17 so as to surround the crucible 11 from the center to the lower part of the outer periphery.

This heating element 21 is connected to a pair of power supply parts 22a and 22b protruding from the furnace shell 1 and the central heat-insulating cylinder 14.

Furthermore, a coil-shaped drawing heating element 23 is provided in the inner cavity 17 near the nozzle portion 10, that is, in the crucible 11.
It is loaded so as to surround the outer periphery of the shielding cylinder 12 from the outer periphery of the bottom part to the outer periphery of the upper part of the shielding cylinder 12.

This drawing heating element 23 is connected to the furnace shell 1 and the central heat-insulating cylindrical body 14.
, and a pair of extraction power supply parts 23a and 24b protruding from the furnace shell 1 and the lower heat-insulating cylinder 15.

On the other hand, a cooling gas introduction pipe 25 is inserted into the shielding tube 12 so as to penetrate through the furnace shell 1, the lower water cooling lid 15, and the shielding tube 12 so as to surround the pulled out rod-shaped or tubular molten glass body. ing.

Further, a drawing roller 26 is provided below the lower water-cooled lid 4b for drawing out the molten glass in the long cylindrical crucible 11 into rods and tubes.

In the figure, reference numeral 27 denotes a communication hole that passes through the central heat-insulating cylinder 14 and allows the gas in the inner cavity 17 to flow out into the outer cavity 16.

Further, in the figure, 28 is a gas inflow pipe inserted into the outer cavity chamber 16 through the upper water-cooling lid 4a, and 29 is a gas exhaust pipe inserted into the outer cavity chamber 16 through the lower water-cooling lid 4b. It's a tube.

Next, the operation of the continuous manufacturing apparatus having the above-described structure will be explained.

A protective gas consisting of a mixture of hydrogen and an inert gas or an inert gas alone is supplied in advance to the long cylindrical crucible 11 in the water-cooled furnace shell 1 from the protective gas inlet 8 via the intermediate cylinder 9. The inside of the crucible 11 is made into a non-oxidizing atmosphere.

After continuously charging raw material powder, for example, silica powder into the crucible 11 from the raw material input section 7, the power supply section 22a
, 22b to heat the raw material melting heating element 21 disposed around the outer periphery of the crucible 11 to 1400 to 2200°C.

When this heating element 21 generates heat, the silica powder in the crucible 11 is heated and melted to produce fused silica glass.

In this heating and melting process, if a mixed gas of hydrogen and inert gas (preferably a mixture ratio of H2:inert gas of 1:0.5 to 1) is supplied as a protective gas, defoaming from the fused silica glass can be suppressed. Then, when the silica powder in the crucible 11 is heated and melted so as to form an unmelted layer on top of the molten layer, the temperature of the upper surface of the fused silica glass decreases, suppressing defoaming, and thereby the bubbles are uniformly dispersed. fused silica glass can be effectively produced.

In this case, the protective gas in the crucible 11 flows from the exhaust hole 18 into the inner cavity chamber 17 loaded with the heating elements 21.23, prevents erosion and melting of the heating elements 21.23, and The gas flows into the outer cavity chamber 16 through the communication holes 27 of 14, and is discharged outside the furnace via the gas exhaust pipe 29 provided in the lower water-cooling lid 4b.

In addition, by introducing protective gas from the gas introduction pipe 28 into the outer cavity 16 between the furnace shell 1 and the central heat-insulating cylinder 14, air is prevented from entering the inside of the furnace shell 1 from the outside.
Oxidative deterioration of the heating elements 21 and 23 and the crucible 11 can be prevented.

Moreover, by introducing a protective gas into the cavity 16, a heat insulating effect can be exhibited together with the water-cooled furnace shell 1.

Next, when power is supplied to the power supply parts 24a and 24b for drawing to generate heat in the heating element 23 for drawing disposed on the outer periphery near the nozzle part 10 at the bottom of the long cylindrical crucible 11, the molten silica glass near the nozzle part 10 is further heated. The viscosity is reduced by heating, flows out from between the nozzle part 10 and the mandrel body 20 inserted into the nozzle part 10, and is rapidly pulled out by the drawing roller 26 to obtain a tubular opaque quartz glass body P. .

In this drawing process, the tubular fused silica glass body with low viscosity immediately after being drawn out from the nozzle part 10
The quartz glass body is rapidly cooled by the cooling gas (inert gas) from the cooling gas inlet pipe 25 provided near the bottom of the quartz glass body, and the viscosity of the surface of the quartz glass body becomes high. , a tubular opaque quartz glass body of predetermined dimensions without deformation is obtained.

In addition, by shortening the passage time of the heating element 23 for drawing and locally heating, the molten silica glass passes through the temperature range where it becomes cristobalite in a short time, thereby preventing devitrification (crystallization) of the quartz glass body. be done.

Therefore, according to the present invention, a heat generating part for drawing is provided on the outer periphery of the bottom of the long cylindrical crucible near the nozzle part, and a cooling gas for rapidly cooling the tubular fused silica glass body immediately after being drawn is provided near the bottom of the nozzle part. By providing an inlet pipe, ■ it is possible to improve the drawing speed, increase productivity, and reduce costs, ■ it is possible to prevent devitrification (crystallization) and improve strength, and ■ it is possible to improve the strength immediately after drawing. To obtain a tubular opaque quartz glass body with good appearance by preventing the bursting of bubbles in the tubular fused silica glass body, and also to obtain a tubular opaque quartz glass body with excellent dimensional stability by eliminating deformation. I can do it.

In particular, during the heating and melting process, a mixed gas of hydrogen and inert gas is used as a protective gas, and an unmelted layer of quartz glass powder is formed on top of the fused silica glass to suppress defoaming and eliminate air bubbles. It is possible to obtain a homogeneously opaque tubular quartz glass body that can be uniformly dispersed.

The vitreous raw material powder used in the present invention is not limited to quartz glass powder as in the above embodiments, but may be any vitreous powder such as high silicate glass powder or vitreous powder mixed with a coloring agent such as Cu, Ag, or Co. .

Further, the shape of each heating element in the present invention is not limited to the above embodiments, and it is possible to use the same cylindrical body or the like.

Furthermore, the position of the cooling gas introduction pipe and the gas flow rate for rapidly cooling the molten glass material immediately after being pulled out from the nozzle part may be appropriately selected depending on the type of the vitreous raw material powder used, the temperature near the nozzle part, etc. good.

Furthermore, in the present invention, when manufacturing a rod-shaped opaque vitreous body instead of manufacturing a tubular opaque vitreous body as in the above embodiment, a mandrel is not inserted into the nozzle portion at the bottom of the long cylindrical crucible. All you have to do is go to .

As described in detail above, according to the present invention, rod-shaped or tubular opaque vitreous bodies of good quality and excellent dimensional stability can be produced continuously and efficiently without causing poor appearance or devitrification and reducing yield. It has remarkable effects such as being easy to manufacture at low cost.

[Brief explanation of the drawing]

The figure is a cross-sectional view of an apparatus for continuously manufacturing an opaque vitreous quartz body, showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Water-cooled furnace shell, 7... Raw material input section, 8... Protective gas introduction pipe, 10... Nozzle section, 11... ...Long cylindrical crucible, 21...
... Heating element for melting raw material, 23 ... Heating element for drawing, 25 ... Cooling gas introduction pipe, 26 ...
- Pulling roller.

Claims (1)

[Claims] 1. A cylindrical water-cooled furnace shell provided with a raw material input part and a protective gas introduction part on the upper part, a heat insulation cylinder disposed inside this furnace shell, and a heat insulation cylinder formed between the furnace shell and the heat insulation cylinder. a hollow chamber through which a protective gas flows; an elongated cylindrical crucible located at the center of the furnace shell and having a nozzle portion at the bottom; a heating element for melting the raw material disposed around the outer periphery of the crucible; A drawing heating element disposed on the outer periphery near the nozzle portion, and a cooling gas introduction pipe provided near the bottom of the nozzle portion for cooling the rod-shaped or tubular molten glass body immediately after being drawn. A continuous production device for rod-shaped or tubular opaque vitreous bodies, characterized by: