JP2016210646A - Production method of glass tube, production apparatus and glass tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production apparatus and a production method of a glass tube capable of producing continuously a large quantity of the glass tube having a fine cross-sectional shape while securing high dimensional accuracy, and to provide glass tubes produced by such a production method.SOLUTION: In a production method of a glass tube G for forming the glass tube G by allowing heated and melted molten glass Ga to flow down from the outer peripheral edge of a core tube 30 so as to be solidified, a region of a part of the molten glass Ga flowing down from the core tube 30 is protected by a heat insulation tube 60 having a double structure.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a glass tube manufacturing method, a manufacturing apparatus, and a glass tube technology, and more specifically, manufacturing for continuously mass-producing glass tubes having a minute cross-sectional shape while ensuring high dimensional accuracy. The present invention relates to a method, a manufacturing apparatus, and a glass tube technology.

In recent years, the demand for glass tubes is increasing and mass production is desired. Further, for example, a glass tube used for an optical component has a minute cross-sectional shape and requires high dimensional accuracy with respect to the outer diameter and inner diameter.
Here, conventionally, a redraw molding method is known as one of glass tube molding methods (see, for example, “Patent Document 1”).
The redraw molding method is a method of forming a glass tube having a desired sectional shape by reducing the similarity of a glass tube (base material) having a large sectional shape.
Specifically, a standard tube made of a glass tube of a predetermined size or a material obtained by processing the standard tube is used as a base material, and one end of the base material is fixed by a base material holder, and the other is heated by a heater. A glass tube having a smaller cross-sectional shape with a desired dimension is formed by heating in order from the end of the substrate and stretching in the axial direction of the base material by a pair of tension rollers.
However, in such a redraw molding method, it is necessary to adjust the size of the base material to a predetermined size, or to perform the work of attaching the base material to the base material holder. It was difficult to continuously mass-produce the glass tubes having the problem, and the manufacturing cost increased.

Therefore, a down draw molding method is known as one of molding methods for continuously mass-producing glass tubes (see, for example, “Patent Document 2”).
In the down draw molding method, a glass tube having a desired cross-sectional shape is formed by directly pulling a molten glass material (molten glass) downward through an opening (outlet) provided at the bottom of the furnace. It is a method to do.

JP 2005-53754 A JP 2012-167004 A

  However, according to the above-described downdraw molding method, it is possible to continuously mass-produce glass tubes by continuously supplying molten glass, but it is possible to mold glass tubes having a minute cross-sectional shape. In such cases, it was difficult to ensure high dimensional accuracy.

  The present invention has been made in view of the present problems described above, and is capable of continuously mass-producing glass tubes having a minute cross-sectional shape while ensuring high dimensional accuracy. It is an object to provide a manufacturing method, a manufacturing apparatus, and a glass tube manufactured by such a manufacturing method.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, the method of manufacturing a glass tube according to the present invention is a method of manufacturing a glass tube that is molded into a glass tube by solidifying the molten glass that has been heated and melted while flowing down from the outer periphery of the core tube. A partial region of the molten glass flowing down from the core tube is protected by the heat insulating tube.

According to the manufacturing method which consists of such a structure, it is possible to mass-produce a glass tube continuously by supplying molten glass continuously.
In addition, according to the manufacturing method of the present invention, the temperature of the molten glass is rapidly increased by the influence of the outside air, for example, by protecting a part of the molten glass flowing down from the core tube with the heat insulating tube having a double structure. Dimensional accuracy can be improved even with a glass tube having a minute cross-sectional shape.

  Moreover, in the manufacturing method of the glass tube which concerns on this invention, a part area | region of the said molten glass protected by the said heat retention tube may be a softening point area | region where the temperature of the said molten glass becomes a temperature range of a softening point. More preferred.

With such a configuration, the dimensional accuracy of the glass tube can be improved.
Specifically, although the molten glass in the softening point region has already been formed into a tubular shape, it is still in a softened state. For example, when the glass is partially touched by the outside air, the temperature suddenly decreases, and the glass temperature becomes uneven. The dimension of the glass tube to be molded (for example, the outer diameter dimension, the inner diameter dimension, or the wall thickness dimension) can be easily and non-uniformly deformed.
Therefore, the molten glass in such a softening point region is protected by the double heat insulating tube, so that the dimensional accuracy of the glass tube can be improved.

Moreover, in the manufacturing method of the glass tube which concerns on this invention, the viscosity of the said molten glass is 10 < ⁶ >. In the one part area | region of the said molten glass protected by the said heat retention tube. ⁵ Pa · s or more and 10 ⁹ . More preferably, it is ⁵ Pa · s or less.

By setting it as such a structure, the further improvement of the dimensional accuracy of a glass tube can be aimed at.
That is, 10 ⁶ . ⁵ Pa · s or more and 10 ⁹ . A molten glass having a viscosity within a range of ⁵ Pa · s or less is in a softened state. For example, when the glass is partially touched by the outside air, the temperature is suddenly lowered to cause unevenness in the glass temperature. A dimension (for example, an outer diameter dimension, an inner diameter dimension, or a wall thickness dimension) can be easily and non-uniformly deformed.
Therefore, the dimensional accuracy of the glass tube can be further improved by protecting the softened molten glass with the double heat insulating tube.

  Further, in the method for manufacturing a glass tube according to the present invention, the heat insulating tube is constituted by an outer cylindrical tube and an inner cylindrical tube disposed coaxially with the outer cylindrical tube inside the outer cylindrical tube, More preferably, the downstream end of the inner tube is located inside the outer tube.

  By adopting such a configuration, for example, an unexpected force is applied from the outside of the heat insulation tube, the inner tube is damaged, the contact between the inner tube and the glass, or between the glass and the inner tube. It is possible to prevent the space from fluctuating.

  Moreover, in the manufacturing method of the glass tube which concerns on this invention, the said manufacturing method is used for the direct melt method, and it is more preferable that the said glass tube is shape | molded with the said molten glass directly supplied from the melting furnace.

  By setting it as such a structure, it becomes possible to supply a molten glass continuously and a glass tube can be mass-produced continuously.

  The glass tube manufacturing apparatus according to the present invention is a glass tube manufacturing apparatus for forming a glass tube by solidifying the molten glass that has been heated and melted while flowing down from the outer peripheral edge of the core tube. A double-layered heat insulating tube is provided to protect a part of the molten glass that has flowed down.

According to the manufacturing apparatus having such a configuration, it is possible to continuously mass-produce glass tubes by continuously supplying molten glass.
Moreover, according to the manufacturing apparatus according to the present invention, the temperature of the molten glass is drastically lowered due to the influence of the outside air by protecting a part of the molten glass flowing down from the core tube with the heat insulating tube having a double structure. For example, even a glass tube having a minute cross-sectional shape can improve dimensional accuracy.

  Further, in the glass tube manufacturing apparatus according to the present invention, the heat insulating tube is constituted by an outer tube, and an inner tube arranged coaxially with the outer tube in the outer tube, More preferably, the downstream end of the inner tube is located inside the outer tube.

  By adopting such a configuration, for example, an unexpected force is applied from the outside of the heat insulation tube, the inner tube is damaged, the contact between the inner tube and the glass, or between the glass and the inner tube. It is possible to prevent the space from fluctuating.

  The glass tube manufacturing apparatus according to the present invention is more preferably formed by a direct melt method, and the glass tube is formed by the molten glass directly supplied from a melting furnace.

  By setting it as such a structure, it becomes possible to supply a molten glass continuously and a glass tube can be mass-produced continuously.

  Moreover, the glass tube which concerns on this invention was shape | molded by the manufacturing method of said glass tube, It is characterized by the above-mentioned.

  By manufacturing by the above method, glass tubes having high dimensional accuracy can be continuously mass-produced.

As effects of the present invention, the following effects can be obtained.
That is, according to the glass tube manufacturing method, manufacturing apparatus, and glass tube according to the present invention, glass tubes having a minute cross-sectional shape can be continuously mass-produced while ensuring high dimensional accuracy.

The cross-sectional front view which showed the whole structure of the manufacturing apparatus of the glass tube which concerns on one Example of this invention.

Next, an embodiment of the invention will be described with reference to FIG.
In the following description, for convenience, the vertical direction in FIG. 1 is described as the vertical direction of the glass tube G manufacturing apparatus 1 (hereinafter simply referred to as “manufacturing apparatus 1”).
Moreover, the direction of the arrow A in FIG. 1 is described as the conveying direction of the molten glass Ga.

[Overview]
First, an overview of a method for manufacturing a glass tube according to the present invention will be described.
The glass tube manufacturing method embodied by this embodiment is a method for continuously mass-producing, for example, a glass tube G having a minute cross-sectional shape while ensuring high dimensional accuracy.

Here, as a method for continuously mass-producing glass tubes G, a downdraw molding method is generally known.
The down draw molding method enables continuous mass production of glass tubes G by drawing molten glass Ga heated and melted from the outer periphery of the core tube into a tubular shape and solidifying by slow cooling. .
On the other hand, however, it has been difficult to ensure high dimensional accuracy for the glass tube G having a minute cross-sectional shape by the downdraw molding method.

  Accordingly, the inventors pay attention to a “softening point region (region X shown in FIG. 1)” in which the temperature of the molten glass Ga is a temperature region of the softening point, and the molten glass Ga in this “softening point region X”. On the other hand, an attempt was made to improve the dimensional accuracy of the glass tube G by providing "protection means" for making it less susceptible to external influences.

Specifically, the molten glass Ga in the “softening point region X” is formed into a tubular shape but is still in a softened state. For example, the temperature is rapidly lowered by partially touching the outside air, and the glass temperature is increased. Unevenness occurs, and the dimension (for example, the outer diameter dimension, the inner diameter dimension, or the wall thickness dimension) of the glass tube G to be molded can be easily and non-uniformly deformed.
Therefore, in view of such points, the present inventors as an example of “protection means” for protecting the molten glass Ga in the “softening point region X”, a heat insulating tube made of a cylindrical heat insulating material or the like. (For example, equivalent to the outer tube 61 in the present embodiment) is provided separately, and the tubular molten glass Ga is passed through the inside of the heat retaining tube, thereby suppressing the influence of the molten glass Ga from the outside air, and the molded glass. An attempt was made to improve the dimensional accuracy of the tube G.

  As described above, when the molten glass Ga in the “softening point region X” is protected by the heat insulating tube, the temperature of the molten glass Ga can be suppressed to some extent due to the influence of outside air, and the molded glass tube The dimensional accuracy of G could be improved.

  However, even if such a heat insulating tube is provided, a space portion surrounding the molten glass Ga exists inside the heat insulating tube, and the heat of the molten glass Ga is transferred to the outside of the heat insulating tube through the space portion. When the heat is dissipated, there is a possibility that the glass temperature may be uneven due to the influence of the airflow in the space portion, etc., so it cannot be said that the heat retaining effect is sufficient, and the dimensional accuracy of the glass tube G to be molded is adversely affected. There was a possibility of affecting.

  Therefore, as a result of intensive research, the inventors have constructed a manufacturing apparatus 1 to be described later, thereby continuously producing a glass tube G having a minute cross-sectional shape while ensuring high dimensional accuracy. And the present invention has been realized.

[Manufacturing equipment 1]
Next, the structure of the manufacturing apparatus 1 in this embodiment is demonstrated.
The manufacturing apparatus 1 mainly includes a molten glass supply unit 10, a molten glass lead-out unit 20, a core tube 30, a gas supply unit 40, a muffle furnace 50, a heat insulating tube 60, a tube drawing machine 70, a cutting machine 80, a conveyance facility 90, and the like. Consists of.

The molten glass supply unit 10 heats and melts a glass material to generate molten glass Ga, and continuously supplies the molten glass Ga to the molten glass lead-out unit 20.
The molten glass supply unit 10 includes a melting furnace 11 that heats and melts a glass material, a first flow path 12 that communicates the melting furnace 11 and the molten glass outlet 20, and the like.

The molten glass lead-out unit 20 is for leading the molten glass Ga supplied from the molten glass supply unit 10 downward while being transmitted to the core tube 30.
The molten glass lead-out portion 20 is made of, for example, a cylindrical platinum member, and is disposed in a posture extending in the vertical direction.

A tapered portion 20 </ b> A that gradually decreases in diameter toward the lower side is formed at the lower end portion of the molten glass lead-out portion 20.
Moreover, the lower end surface of the molten glass derivation | leading-out part 20 is opened, and the outflow port 20B is formed.

The core tube 30 is for forming the molten glass Ga derived from the molten glass outlet 20 into a tubular shape.
On the other hand, the core tube 30 constitutes a gas supply unit 40 described later.

The core tube 30 is made of, for example, a tubular platinum member, and the length dimension thereof is set to be longer than the length dimension of the molten glass outlet portion 20.
Further, the core tube 30 is arranged inside the molten glass lead-out portion 20 so as to be coaxial with the molten glass lead-out portion 20 and its both upper and lower end portions project from the molten glass lead-out portion 20 toward both the upper and lower sides. The

The gas supply part 40 is for improving the dimensional accuracy of the glass tube G to be molded by ejecting gas into the tubular molten glass Ga.
The gas supply unit 40 includes a blower 41 that supplies gas, a core tube 30 that ejects the gas supplied from the blower 41 into the tubular molten glass Ga, and a second flow path that communicates the blower 41 and the core tube 30. 43 or the like.

Here, various gases other than general air can be used as the gas supplied by the blower 41.
For example, when a chemical reaction with molten glass Ga is concerned, an inert gas such as argon (Ar) and nitrogen (N ₂ ) can be used, and when it is desired to oxidize and reduce molten glass Ga, Hydrogen (H ₂ ) gas and oxygen (O ₂ ) gas can be used.
In addition, you may comprise so that the gas heated previously may be supplied in the core pipe 30. FIG.

Further, the pressure of the gas supplied by the blower 41 is appropriately set according to the desired dimensions of the glass tube G to be molded, various conditions such as a pipe for supplying the gas, and a regulating valve.
Specifically, it is desirable to supply gas by the blower 41 with a pressure of 1 [KPa] to 5 [MPa].

The muffle furnace 50 is for controlling the temperature of the molten glass Ga to a predetermined temperature according to the manufacturing conditions.
The muffle furnace 50 is configured in a cylindrical shape extending in the vertical direction, and a molten glass lead-out portion 20 is coaxially provided at the upper end surface thereof.
As a result, the muffle furnace 50 is disposed so as to cover at least the lower half of the molten glass outlet 20 and further extend downward of the molten glass outlet 20.

  Moreover, the lower end surface of the muffle furnace 50 is provided with a carry-out port 50A that opens coaxially with the molten glass lead-out portion 20, and the molten glass Ga formed into a tubular shape is fed into the muffle furnace 50 through the carry-out port 50A. To the outside.

A plurality of heating wires 51, 51,... Are provided on the inner wall surface of the muffle furnace 50.
Moreover, these several heating wires 51 * 51 ... are arrange | positioned with a fixed space | interval along the axial center direction of the molten glass derivation | leading-out part 20. As shown in FIG.

The heat insulating tube 60 is a member that embodies the present invention, and is formed by protecting the molten glass Ga in the “softening point region X” formed into a tubular shape against the outside air outside the muffle furnace 50. This is to improve the dimensional accuracy of the glass tube G.
The heat insulation tube 60 is constituted by an outer tube 61 and an inner tube 62.

The outer tube 61 has a larger inner diameter than the inner diameter of the carry-out port 50 </ b> A of the muffle furnace 50.
The outer tube 61 is disposed on the lower end surface, which is the downstream side in the conveying direction of the molten glass Ga, in the muffle furnace 50 so as to extend coaxially with the carry-out port 50A and downward.

The inner tube 62 has a smaller outer diameter than the outer tube 61 and a slightly larger inner diameter than the molten glass Ga formed into a cylindrical shape. The
Further, the length dimension of the inner tube 62 is set to be longer than the range dimension of the “softening point region X” in the molten glass Ga formed into a tubular shape.

  The inner cylindrical tube 62 is coaxial with the outer cylindrical tube 61, that is, the molten glass Ga formed into a tubular shape, and covers the entire “softening point region X” of the molten glass Ga inside the outer cylindrical tube 61. Placed in position.

As a result, for example, the inner tube 62 in the present embodiment has its upper end 62a (that is, the end on the upstream side in the flow direction of the molten glass Ga) inserted into the muffle furnace 50 while its lower end 62b (that is, The end of the molten glass Ga in the downstream direction of the molten glass Ga) is disposed above the lower end of the outer tube 61.
In other words, the “softening point region X” of the molten glass Ga formed into a tubular shape is caused by the “protection means” having a double structure of the muffle furnace 50 or the outer cylindrical tube 61 and the inner cylindrical tube 62. This is a configuration in which a part of the region (that is, “softening point region X” in the present embodiment) is protected from the outside air.

  In addition, about the member which comprises the outer cylinder pipe 61 and the inner cylinder pipe 62, if it is a heat-resistant member which can endure the temperature of about 600 [degreeC], for example, it will not specifically limit, If it is stainless steel (SUS), oxidation etc. This is more preferable because the surface does not get dirty.

By providing such a "protection means" having a double structure, the heat of the molten glass Ga is less radiated to the outside of the heat insulating tube 60, and the dimensional accuracy of the glass tube G to be formed is reduced. Improvements can be made.
Specifically, even if the heat of the molten glass Ga is radiated to the outside of the inner cylindrical tube 62, it is suppressed from being released to the outside of the heat insulating tube 60 by the outer cylindrical tube 61 or the muffle furnace 50. Therefore, it is possible to improve the dimensional accuracy of the glass tube G to be formed.

  Further, the gap between the inner cylindrical tube 62 and the molten glass Ga is set to be sufficiently smaller than the gap between the inner cylindrical tube 62 and the inner cylindrical tube 62. Even if an air flow generated outside the air enters the outer cylindrical tube 61, it is rare that the air flow penetrates into the inner cylindrical tube 62 and causes unevenness in the glass temperature of the molten glass Ga. Dimensional accuracy can be improved with respect to the glass tube G to be molded.

Further, as described above, the lower end portion 62 b of the inner cylindrical tube 62 is located above the lower end portion of the outer cylindrical tube 61, and the inner cylindrical tube 62 protrudes downward from the outer cylindrical tube 61. In other words, it is in a state of being completely contained in the outer tube 61.
Therefore, for example, an unexpected force is applied from the outside of the heat insulating tube 60, the inner tube 62 is damaged, the contact between the inner tube and the glass, or the space between the glass and the inner tube is changed. Can be prevented.

  In the present embodiment, the “softening point region X” of the molten glass Ga is protected by the “protecting means” having a double structure of the muffle furnace 50 or the outer cylindrical tube 61 and the inner cylindrical tube 62. However, it is not limited to this, For example, it is good also as a structure which protects the other area | region of molten glass Ga.

However, in the molten glass Ga in the region below the “softening point region X”, since the annealing is further advanced and the temperature is low, the effect seen when the molten glass Ga is protected by the “protecting means” is small.
Therefore, it is more preferable to protect “softening point region X” of molten glass Ga by “protection means”.
In addition, in the region above the “softening point region X”, the entire glass glass Ga is protected by the muffle furnace 50, so that the molten glass Ga is hardly affected by outside air.

The tube drawing machine 70 is for deriving molten glass Ga from the molten glass deriving unit 20.
The tube drawing machine 70 includes a pair of rollers 71 and 71 that are rotationally driven by a motor (not shown), and is disposed on the lower side of the heat insulating tube 60 (downstream in the conveying direction of the molten glass Ga).

  And a pair of roller 71 * 71 is comprised so that it may pay | feed out toward the downward direction (a conveyance direction downstream direction of molten glass Ga), clamping the molten glass Ga shape | molded by the tubular shape.

  The cutting machine 80 is used for forming the glass tube G by cutting the molten glass Ga, which is led out downward by the pipe drawing machine 70, into a predetermined length.

  The conveying device 90 is made of, for example, a known belt conveyor, and is for conveying the glass tube G cut by the cutting machine 80 to a predetermined next process.

With the manufacturing apparatus 1 configured as described above, glass tubes G having a minute cross-sectional shape are continuously mass-produced while ensuring high dimensional accuracy.
Specifically, in the molten glass supply unit 10, the glass material is heated and melted by the melting furnace 11 to generate molten glass Ga, and the generated molten glass Ga passes through the first flow path 12 to the molten glass outlet 20. Supplied directly.

Thus, the manufacturing apparatus 1 in the present embodiment is configured by the direct melt method, and the glass tube G is formed by the molten glass Ga directly supplied from the melting furnace 11.
Therefore, it is possible to continuously supply the molten glass Ga, and the glass tube G can be continuously mass-produced.

  The molten glass Ga supplied to the molten glass lead-out portion 20 flows downward (downstream in the conveying direction of the molten glass Ga), and after the pressure is gradually increased by passing through the tapered portion 20A, the outlet It is led out of the molten glass lead-out part 20 via 20B.

  And the molten glass Ga derived | led-out from the molten glass derivation | leading-out part 20 flows down (the conveyance direction downstream direction of molten glass Ga) flowing along the outer periphery of the core tube 30, and is detach | leave from the core tube 30 after that. .

Here, the molten glass Ga is gradually formed into a tubular shape while flowing down from the outer peripheral edge of the core tube 30.
The temperature of the molten glass Ga immediately after being derived from the molten glass outlet 20 is about 1000 [° C.], and the viscosity of the molten glass Ga at this time is 10 ⁴ . ⁶ [Pa · s] to 10 ⁵ . ⁰ [Pa · s].

  The molten glass Ga detached from the core tube 30 is formed into a tubular shape having a predetermined size, and is then guided downward (downstream in the conveying direction of the molten glass Ga) to the inside of the inner tube 62 of the heat retaining tube 60. It is inserted.

  The tubular molten glass Ga inserted into the inner cylindrical tube 62 is guided further downward (downstream in the conveying direction of the molten glass Ga), and sequentially passes through the inner cylindrical tube 62 and the outer cylindrical tube 61 to keep the heat insulating tube. 60 to the outside.

  Here, in the inside of the muffle furnace 50., the molten glass Ga led out from the molten glass lead-out unit 20 moves downward (downward in the conveying direction of the molten glass Ga), and moves to a plurality of heating wires 51, 51,.・ ・ The temperature is gradually controlled by gradually cooling.

When the temperature reaches the inside of the inner tube 62, the temperature of the molten glass Ga is gradually cooled to the softening point, and as described above, the molten glass Ga inside the inner tube 62 has " A softening point region X "is formed.
In other words, in the present embodiment, a partial region of the molten glass Ga that is protected by the “protecting means” having a double structure of the muffle furnace 50 or the outer tube 61 and the inner tube 62 is the molten glass. The temperature of Ga is a “softening point region X” that is a temperature region of the softening point.

The temperature of the molten glass Ga in the “softening point region X” is about 500 [° C.] to 900 [° C.], and the viscosity of the molten glass Ga at this time is 10 ⁶ . ⁵ [Pa · s] to 10 ⁹ . ⁵ [Pa · s].
In other words, in a partial region of the molten glass Ga that is protected by the “protecting means” having a double structure of the muffle furnace 50 or the outer cylindrical tube 61 and the inner cylindrical tube 62 in the present embodiment, the molten glass Ga Has a viscosity of 10 ⁶ . ⁵ [Pa · s] or more and 10 ⁹ . ⁵ [Pa · s] or less.

The tubular molten glass Ga carried out to the outside of the heat insulating tube 60 is sandwiched by the pair of rollers 71 and 71 of the tube drawing machine 70 and fed downward.
As a result, the molten glass Ga in the molten glass outlet 20 is guided downward by the tube drawing machine 70.

Thereafter, the tubular molten glass Ga is cut into a predetermined length by a cutting machine 80, formed into a glass tube G, and conveyed to the next process by the conveying device 90.
The glass tube G is continuously mass-produced by the manufacturing apparatus 1 according to the above procedure.

[Verification experiment]
Next, a verification experiment conducted by the present inventors in order to determine the effectiveness of the glass tube manufacturing method according to the present invention will be described.

  First, as a heat insulating tube, an outer tube having an outer diameter of 100 [mm] and an inner diameter of 95 [mm], an inner diameter of 42 [mm] and an inner diameter of 40 [mm] A tube tube was prepared for each.

  Next, a plurality of glass tubes having an outer diameter dimension of 2.8 [mm] and an inner diameter dimension of 1.8 [mm] are formed by a manufacturing apparatus equipped with both of these outer tube and inner tube. The variation in outer diameter and inner diameter was measured.

  Further, as a comparative example, a plurality of glass tubes having an outer diameter of 2.8 [mm] and an inner diameter of 1.8 [mm] are formed by a manufacturing apparatus having only an outer tube, and the outer diameter is And the variation of inner diameter dimension was measured.

The glass tube formed by the manufacturing apparatus provided with both the outer tube and the inner tube was able to keep the variation range of the measured value of the outer diameter dimension within about 0.1 [mm].
Moreover, the variation range of the measured value of the inner diameter dimension was also able to be within about 0.1 [mm].

On the other hand, the variation range of the measured value of the outer diameter dimension of the glass tube formed by the manufacturing apparatus having only the outer tube as a comparative example was about 0.2 [mm].
Further, the variation range of the measured value of the inner diameter dimension was about 0.3 [mm].

  Based on the above results, the dimensional accuracy of the formed glass tube can be improved in the double-structured heat insulating tube made of the outer tube and the inner tube compared to the heat insulating tube made of only the outer tube. Was confirmed.

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 11 Melting furnace 30 Core tube 60 Thermal insulation tube 61 Outer cylinder tube 62 Inner cylinder tube 62b Lower end part G Glass tube Ga Molten glass X Softening point area | region

Claims (9)

A method of manufacturing a glass tube that is molded into a glass tube by solidifying the molten glass that is heated and melted while flowing down from the outer peripheral edge of the core tube,
Protecting a partial region of the molten glass that has flowed down from the core tube with a double-structured heat insulating tube;
A method of manufacturing a glass tube. The partial region of the molten glass protected by the heat insulating tube is
The temperature of the molten glass is a softening point region that becomes a temperature region of the softening point,
The manufacturing method of the glass tube of Claim 1 characterized by the above-mentioned. In some areas of the molten glass protected by the heat retaining tube,
The viscosity of the molten glass is 10 ⁶ . ⁵ Pa · s or more and 10 ⁹ . ⁵ Pa · s or less,
The manufacturing method of the glass tube of Claim 1 or Claim 2 characterized by the above-mentioned. The insulation tube is
An outer tube,
An inner tube disposed coaxially with the outer tube in the outer tube;
Composed of
The downstream end of the inner tube is located in the outer tube,
The manufacturing method of the glass tube as described in any one of Claims 1-3 characterized by the above-mentioned. The manufacturing method is used for the direct melt method,
The glass tube is formed by the molten glass supplied directly from the melting furnace.
The manufacturing method of the glass tube as described in any one of Claims 1-4 characterized by the above-mentioned. A glass tube manufacturing apparatus for forming a glass tube by solidifying the molten glass that has been heated and melted while flowing down from the outer periphery of the core tube,
Protecting a partial region of the molten glass flowing down from the core tube, comprising a double-structured heat insulating tube,
An apparatus for manufacturing a glass tube. The insulation tube is
An outer tube,
An inner tube disposed coaxially with the outer tube in the outer tube;
Composed of
The downstream end of the inner tube is located in the outer tube,
The glass tube manufacturing apparatus according to claim 6, wherein: The manufacturing apparatus is constituted by a direct melt method,
The glass tube is formed by the molten glass supplied directly from the melting furnace.
The glass tube manufacturing apparatus according to claim 6, wherein the glass tube manufacturing apparatus according to claim 6. It was shape | molded by the manufacturing method of the glass tube as described in any one of Claims 1-5.
A glass tube characterized by that.

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