JP2000226217A - Heating furnace for dehydrative sintering of porous glass preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating furnace for the dehydrative sintering of a porous glass preform capable of preventing the buckling deformation of a furnace core tube with own weight in the heating at a high temperature. SOLUTION: A furnace core tube 3 for holding a porous glass preform 2 in the tube is passed through the center of a furnace body 1. The furnace core tube in the furnace body 1 is surrounded by a heater 4 for heating the porous glass preform 2 in the furnace core tube 3. A furnace core tube supporting means 13 for supporting the own weight of the furnace core tube 3 in a state divided in the longitudinal direction is placed on the outer circumference of the furnace core tube 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating furnace for dehydrating and sintering a porous glass base material for dehydrating a porous glass base material and sintering the glass base material into a transparent glass.

[0002]

2. Description of the Related Art FIGS. 4 and 5 show two types of conventional heating furnaces for dehydrating and sintering a porous glass base material of this kind.

[0003] These heating furnaces for dehydrating and sintering a porous glass preform are provided with a furnace tube 3 made of quartz glass or the like which penetrates a central portion of a furnace body 1 and accommodates a porous glass preform 2 therein.
Is disposed around the furnace tube 3 in the furnace body 1 and
A heating element 4 such as an electric heater for heating the porous glass preform 2 therein; a muffle tube 5 disposed between the furnace tube 3 and the heating element 4 so as to surround the outer periphery of the furnace tube 3; A heat insulating material 6 disposed outside the tube 5 along the inner wall of the furnace body 1 is mainly constituted. In the heating furnace for dehydration sintering shown in FIG. 4, an example in which one heating element 4 is provided is shown, and FIG.
In the heating furnace for dehydration sintering shown in FIG. 1, there is shown an example in which the number of heating elements 4 is plural (five in this example). The furnace tube 3 has a quartz annular flange 7 integrally projecting from the upper periphery thereof mounted on the upper surface 1a of the furnace body 1 and a quartz annular flange integrally projecting from the lower periphery thereof. Is supported on the furnace body 1 by being placed on the bottom surface 1b of the furnace body 1. The upper end of the furnace tube 3 is closed by an upper lid 8, and the upper lid 8 is provided with a hole 9 through which the starting base material 2 a of the porous glass base material 2 penetrates. A processing gas inlet 10 is provided at the lower end of the furnace tube 3, and He gas or C
l ₂ gas or the like is supplied. An exhaust port 11 for discharging exhaust gas in the core tube 3 is provided at an upper portion of the core tube 3.
Is provided. An inert gas such as an Ar gas or a N ₂ gas is supplied into the furnace body 1.

[0004] When the porous glass base material 2 is dehydrated and sintered by using such a heating furnace for dehydration and sintering, when the heating element 4 shown in FIG. 1 or by moving the porous glass base material 2 in the vertical direction with respect to the fixed heating element 4. In the case where there are a plurality of heating elements 4 shown in FIG. This is performed by switching the power supply to the heating elements 4 and moving the heating zones created by the respective heating elements 4 in the vertical direction.

[0005]

In recent years, as the demand for optical fibers has increased, the size and length of the porous glass preform 2 for optical fibers has been increasing. Large heating furnaces are becoming necessary. However, when the large and long porous glass base material 2 is dehydrated and sintered, the quartz core tube 3 is heated to 1500 ° C. or more over a wide range, so that the quartz softens and the core tube 3 is heated. However, there is a problem that buckling deformation occurs due to its own weight.

An object of the present invention is to provide a heating furnace for dehydrating and sintering a porous glass base material, which can prevent the core tube from buckling under its own weight during high-temperature heating.

Another object of the present invention is to provide a heating furnace for dehydrating and sintering a porous glass base material, which can prevent the core tube from being buckled and deformed by its own weight during high-temperature heating by using a muffle tube. is there.

[0008]

According to the present invention, there is provided a furnace tube penetrating a central portion of a furnace body and accommodating a porous glass base material therein, and the furnace tube disposed around the furnace tube in the furnace body. An object of the present invention is to improve a heating furnace for dehydrating and sintering a porous glass base material, comprising a heating element for heating a porous glass base material in a tube.

The heating furnace for dehydrating and sintering a porous glass base material according to the first aspect of the present invention is characterized in that the outer periphery of the furnace tube is provided with a furnace tube self-weight dividing means for dividing the own weight of the furnace tube itself in the longitudinal direction. It is characterized by being provided.

As described above, when the core tube own weight dividing / loading means is provided on the outer periphery of the core tube so as to divide the own weight of the core tube itself in the longitudinal direction thereof, the own weight of the core tube itself becomes plural in the longitudinal direction of the core tube. Since the parts are divided and burdened, it is possible to prevent the core tube from being buckled and deformed by its own weight during high-temperature heating.

According to a second aspect of the present invention, in the heating furnace for dehydrating and sintering a porous glass base material, the self-weight split bearing means for the core tube protrudes from the outer periphery of the core tube at predetermined intervals in the longitudinal direction thereof. And a plurality of flange portions provided, and core tube own weight receiving means for supporting each flange portion on the outer periphery of the core tube.

A plurality of flanges protruding from the outer periphery of the core tube at predetermined intervals in the longitudinal direction and the core tube own weight receiving means supporting each flange at the outer periphery of the core tube as described above. By configuring the means, the own weight of the core tube itself can be easily divided and loaded at a plurality of locations in the longitudinal direction.

According to a third aspect of the present invention, in the heating furnace for dehydrating and sintering a porous glass base material, the self-weight receiving means for the core tube may be provided on the outer periphery of the core tube between the vertically adjacent flanges. It is characterized by being constituted by a muffle tube which bears the own weight of the furnace tube which is interposed and acts on the upper flange portion.

When the core tube self-weight receiving means is constituted as described above, the core tube self-weight receiving means can be constituted using a plurality of short muffle tubes.

According to a fourth aspect of the present invention, in the heating furnace for dehydrating and sintering a porous glass base material, the muffle tube is arranged such that the core tube own weight receiving means is arranged along the outer periphery of the core tube.
The muffle tube is provided corresponding to each flange portion of the furnace tube, and is constituted by a plurality of support portions that support each flange portion.

When the core tube self-weight receiving means is constituted as described above, the core tube self-weight receiving means can be constituted using a muffle tube provided with supporting portions at predetermined intervals in the longitudinal direction.

[0017]

1A and 1B show a first example of an embodiment of a heating furnace for dehydrating and sintering a porous glass base material according to the present invention. FIG. 1) is a longitudinal sectional view of the heating furnace for dehydration and sintering, and FIG. 1 (B) is a perspective view showing the structure of a core tube self-weight split burden means used in the heating furnace for dehydration and sintering. In this example, the plurality of heating elements 4 shown in FIG.
5 shows an example in which the present invention is applied to a heating furnace for dehydration sintering of the type having the following. In FIG. 5, portions corresponding to those in FIG.

In the heating furnace for dehydrating and sintering the porous glass base material of the present embodiment, the furnace tube 3
A core tube own weight dividing / loading means 13 is provided, which divides its own weight in the longitudinal direction. The core tube own weight dividing / loading means 13 includes a plurality of quartz flanges 7 integrally and annularly projecting at predetermined intervals in the longitudinal direction on the outer periphery of an intermediate portion of the furnace tube 3, and the outer periphery of the furnace tube 3. It comprises a core tube own weight receiving means 14 for supporting each flange 7. In this example, the core tube self-weight receiving means 14 is a short length which is interposed between the upper and lower adjacent flange portions 7 on the outer periphery of the core tube 3 and acts on the upper flange portion 7 to bear its own weight. Of the muffle tube 5. These short muffle tubes 5 are set to the length between the flanges 7 vertically adjacent to each other, and have a split structure in which a split portion 5a is provided along the longitudinal direction to facilitate the installation. ing. These muffle tubes 5
It is made of carbon fiber reinforced carbon or the like.

As described above, the core tube 3 is provided around the outer periphery of the core tube 3.
When the core tube own weight dividing / loading means 13 which divides its own weight in the longitudinal direction is provided, the own weight of the core tube 3 itself is divided and loaded at a plurality of locations in the longitudinal direction of the core tube 3, so that the core is not heated during high temperature heating. The tube 3 can be prevented from being buckled and deformed by its own weight.

Further, the core tube own weight dividing / loading means 13 supports a plurality of flanges 7 protruding from the outer periphery of the core tube 3 at predetermined intervals in the longitudinal direction thereof, and supports the respective flange portions 7 on the outer periphery of the core tube 3. With the core tube own weight receiving means 14, the own weight of the core tube 3 itself can be easily divided and loaded at a plurality of locations in the longitudinal direction.

In particular, the core tube own weight receiving means 1 as in this embodiment
4 is constituted by the muffle tube 5 which is interposed between the upper and lower adjacent flange portions 7 on the outer periphery of the core tube 3 and bears the weight of the core tube 3 acting on the upper flange portion 7,
The core tube own weight receiving means 14 can be constituted by using a plurality of short muffle tubes 5.

FIGS. 2A and 2B show a second embodiment of a heating furnace for dehydrating and sintering a porous glass base material according to the present invention.
FIG. 2 (A) is a longitudinal sectional view of the heating furnace for dehydration and sintering, and FIG. 2 (B) is a configuration of a furnace tube self-weight split burden means used in the heating furnace for dehydration and sintering. FIG. This example also shows an example in which the present invention is applied to a heating furnace for dehydration sintering of the type having a plurality of heating elements 4 shown in FIG. Note that parts corresponding to those in FIGS. 1A and 1B are denoted by the same reference numerals.

In the heating furnace for dehydrating and sintering the porous glass base material of the present embodiment, the furnace tube 3
There is provided a core tube own weight dividing / loading means 13 for dividing the own weight in the longitudinal direction thereof, and the furnace tube own weight dividing / loading means 13 is integrally provided on the outer periphery of an intermediate portion of the furnace tube 3 at predetermined intervals in the longitudinal direction. A plurality of flanges 7 made of quartz protruding in a ring shape
It is the same as the first example in that it is constituted by core tube own weight receiving means 14 for supporting each flange portion 7 on the outer periphery of the core tube 3.

In particular, in the heating furnace for dehydration and sintering of the present embodiment, the furnace core tube own weight receiving means 14 includes the muffle tube 5 arranged along the outer periphery of the furnace tube 3 and the flanges 7 of the furnace tube 3. Correspondingly, it is constituted by a plurality of support portions 15 provided on the muffle tube 5 and supporting the respective flange portions 7. This muffle tube 5 is also made of carbon fiber reinforced carbon or the like. In order to provide the support portions 15 at predetermined intervals in the longitudinal direction on the inner circumference of the muffle tubes 5 of a required length, the short muffle tubes 5 are alternately connected via the support portions 15 in this example.

When the core tube self-weight receiving means 14 is configured in this manner, the core tube self-weight receiving means 14 can be configured using the muffle tube 5 provided with the support portions 15 at predetermined intervals in the longitudinal direction.

FIG. 3 is a longitudinal sectional end view showing a third embodiment of the heating furnace for dehydrating and sintering a porous glass base material according to the present invention. The present embodiment shows an example in which the present invention is applied to a heating furnace for dehydration sintering of the type having one heating element 4 shown in FIG. Note that FIG.
Parts corresponding to (A) and (B) are denoted by the same reference numerals.

In the heating furnace for dehydrating and sintering the porous glass base material of the present embodiment, the first example shown in FIGS. 1A and 1B is a type having a plurality of heating elements 4, The example is different in that it is of a type having one heating element 4, and the other configuration, particularly the configuration of the core tube own weight split burden means 13, is shown in FIG.
(A) Similar to the first example shown in (B).

Therefore, the effect of the core tube self-weight division burden means 13 is the same as that of the first example shown in FIGS. 1 (A) and 1 (B).

[0029]

In the heating furnace for dehydrating and sintering a porous glass base material according to the present invention, a means for dividing the weight of the core tube itself in the longitudinal direction is provided on the outer periphery of the core tube. Since the furnace tube is provided, the own weight of the furnace tube itself is divided and loaded at a plurality of portions in the longitudinal direction of the furnace tube, so that the furnace tube can be prevented from being buckled and deformed by its own weight at the time of high-temperature heating.

[Brief description of the drawings]

FIGS. 1A and 1B show a first example of an embodiment of a heating furnace for dehydrating and sintering a porous glass base material according to the present invention, and FIG. Longitudinal end view of the heating furnace,
(B) is a perspective view showing a configuration of a furnace core tube own weight division burden means used in the heating furnace for dehydration sintering.

FIGS. 2A and 2B show a second example of an embodiment of a heating furnace for dehydration and sintering of a porous glass base material according to the present invention, and FIG. Longitudinal end view of the heating furnace,
(B) is a perspective view showing a configuration of a furnace core tube own weight division burden means used in the heating furnace for dehydration sintering.

FIG. 3 is a longitudinal sectional view showing a third example of the embodiment of the heating furnace for dehydrating and sintering the porous glass base material according to the present invention.

FIG. 4 is a longitudinal sectional view showing the structure of a conventional heating furnace for dehydration and sintering of a porous glass base material in the case of one heating element.

FIG. 5 is a longitudinal sectional view showing the structure of a conventional heating furnace for dehydration and sintering of a porous glass base material when a plurality of heating elements are provided.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace body 1a Top surface 1b Bottom surface 2 Porous glass base material 2a Starting base material 3 Furnace tube 4 Heating element 5 Muffle tube 5a Split part 6 Heat insulating material 7 Flange part 8 Top lid 9 Hole 10 Processing gas inlet 11 Exhaust port 13 Furnace tube Own-weight division bearing means 14 Reactor core tube own-weight receiving means 15 Support

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masayuki Sakamoto 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. F-term (reference) 4G014 AH21 4G021 CA12

Claims (4)

[Claims] 1. A furnace tube penetrating a central portion of a furnace body and accommodating a porous glass base material therein, and the porous glass disposed in the furnace body around the furnace tube and inside the furnace tube. A heating furnace for dehydrating and sintering a porous glass base material, comprising: a heating element for heating the base material; a core tube having its own weight divided along its longitudinal direction on the outer periphery of the furnace tube. A heating furnace for dehydrating and sintering a porous glass base material, wherein a heating means is provided. 2. The core tube's own weight dividing and bearing means includes a plurality of flanges protruding from an outer periphery of the core tube at predetermined intervals in a longitudinal direction thereof, and a core supporting the flanges on the outer periphery of the core tube. 2. The heating furnace for dehydrating and sintering a porous glass base material according to claim 1, wherein the heating furnace comprises a tube own weight receiving means. 3. The core tube's own weight receiving means bears the own weight of the core tube acting on the upper flange portion between the respective vertically adjacent flange portions on the outer periphery of the core tube. The heating furnace for dehydrating and sintering a porous glass base material according to claim 2, wherein the heating furnace is constituted by a muffle tube. 4. The core tube self-weight receiving means is provided on the muffle tube corresponding to each of the muffle tubes arranged along the outer periphery of the core tube and the flanges of the core tube, respectively. 3. The heating furnace for dehydrating and sintering a porous glass base material according to claim 2, wherein the heating furnace is constituted by a plurality of support portions for supporting a flange portion.