JPH0351312Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a small heating device for stretching a long glass rod connected to a feed rod of different diameters, and particularly relates to a heating device for stretching a long glass rod connected to a feeding rod of different diameters, and in particular for a heating device for stretching a long glass rod connected to a feed rod of different diameter. This invention relates to a heating device for drawing a glass rod suitable for drawing.

[Conventional technology]

Conventionally, as a heating device for drawing a glass rod, for example, an optical fiber base material, one having the structure shown in FIGS. 2a to 2c has been used. An optical fiber base material 3 is placed inside the furnace body 20 at the center of the upper end wall of the furnace body 20.
The furnace body 20 has a cylindrical insertion opening 21 for inserting the 0, and a cylindrical extraction opening 22 for pulling out the stretched glass body 31 from the furnace body 20 at the center of the lower end wall of the furnace body 20. Further, in the insertion port 21 of the furnace body 20, there is a feed rod 32 for operating the optical fiber base material 30 that is fed to the heating element 23, and a feed rod 32 that maintains a gap between the seals and is airtightly placed on the upper end of the insertion port 21. A sealing lid 24 is provided.

In order to draw the optical fiber base material 30 with this type of conventional heating device for glass drawing, first place the blind cover 27 shown in FIG. The lower lid 29 shown in FIG. Create an active gas atmosphere.

Next, the temperature of the heating element 23 in the furnace body 20 is raised to a predetermined drawing temperature and maintained at that temperature. To insert the optical fiber preform 30 into the furnace body 20 for stretching, the gas outlet 28 is closed, the lower cover 29 is completely sealed, and the blind cover 27 of the insertion port 21 is removed. Insert the optical fiber base material 30 with the feed rod 32 and the pull-out rod 33 connected to both ends into the furnace body 20 through the opening, place the sealing lid 24 on the upper end of the insertion port 21, and remove the lower lid 29. The inert atmosphere inside the furnace body 20 is maintained. Next, when the lower end of the optical fiber base material 30 is heated and softened, the pull-out rod 33 is pulled down.
A glass stretched body 31 is formed. During this time and thereafter, while the heating element 23 is in a high temperature state, it is necessary to maintain the inside of the furnace body 20 in an inert gas atmosphere in order to prevent deterioration of the heating element 23 and contamination of the stretching atmosphere.

[Problem that the invention attempts to solve]

When trying to draw a long optical fiber preform using a conventional glass rod drawing heating device, the upper end of the optical fiber preform protrudes from the upper end wall of the furnace main body, so the upper end of the insertion opening is closed by a sealing lid. cannot be hermetically sealed. Therefore, the length of the cylindrical insertion opening of the heating furnace needs to be long enough to accommodate the optical fiber preform 30. Furthermore, the feed rod that supports the optical fiber preform needs to have a sufficient length to feed the optical fiber preform from the upper end of the insertion opening to the position of the heating element. As a result, the entire heating device becomes taller, which worsens the space factor of the heating device and requires the use of a long feed rod, which poses a problem in that workability is extremely degraded.

[Means for solving problems]

The present invention solves the conventional problems and provides a heating device for stretching a glass base material that can stretch a long glass base material without increasing the length of the furnace main unit or the feeding rod. At the top end wall 1
an insertion port 2 into which a glass rod to be drawn is inserted, in which a feed rod 8 having an outer diameter smaller than the outer diameter of the glass rod to be drawn is attached to the upper end of the glass rod to be drawn 30 in the center of a;
A furnace body 1 has a drawer opening 3 in the center of the lower end wall 1b for pulling out the glass rod 30 to be drawn, and a glass rod to be drawn arranged in a space surrounded by the upper end wall 1a, the lower end wall 1b, and the side wall 1c of the furnace main body 1. Between the heating element 6 that heats and softens the glass rod 30 and the outer circumferential wall of the feed rod 8 that is slidably engaged with the feed rod 8 that is airtightly placed on the insertion port 2 of the furnace body 1. A first seal disc 9 that maintains a gap between the seals and a first seal disc 9 that is airtightly installed above the insertion port 2 of the furnace body 1 and that is divided into at least two or more parts in the circumferential direction. The upper part of the chimney 10 has an inner diameter larger than the outer diameter of the first seal disk 9 and a larger inner diameter than the diameter of the glass rod to be drawn over the entire length, and a feed rod 8 formed integrally with the chimney 10. A chimney roof 10a having an airtight opening with an inner diameter larger than the outer diameter of Seal between the second
The structure is characterized by a sealing disc 16.

[Effect]

In the present invention, the glass rod to be drawn is fed into the furnace main body through the insertion port, the second sealing disk is placed on the top surface of the chimney, the chimney is closely placed on the top surface of the insertion port, and the second sealing disk is placed on the top surface of the chimney.
The glass rod is heated and stretched while maintaining airtightness inside the furnace body with the sealing disk and the feed rod, and after the stretching progresses and the first sealing disk is placed tightly on the top surface of the insertion port. Since it has a structure that maintains airtightness with the first seal disc and the feed rod,
There is no need to prepare a tall heating device for long glass rods, and long glass rods can be heated and drawn using a small heating device for short lengths. Examples will be described below based on the drawings.

〔Example〕

An embodiment in which the heating device for drawing a glass rod according to the present invention is applied to an optical fiber base material will be described with reference to the schematic diagrams shown in FIGS. 1a to 1c.

In FIG. 1, the center of the upper end wall 1a of the furnace body 1 has an insertion opening 2 into which the optical fiber base material 30 is inserted.
A stretched glass body 14 of the optical fiber base material 30 is provided in the center of the lower end wall 1b of the furnace body 1.
A drawer opening 3 is provided for drawing out. Furnace body 1
A heating element 6 that heats and softens the optical fiber base material 30 is arranged in a space surrounded by the upper end wall 1a, the lower end wall 1b, and the side wall 1c.

To draw the optical fiber base material 30, first, the inside of the furnace body 1 is made into an inert gas atmosphere and the temperature of the heating element 6 is raised. To raise the temperature of the heating element 6, the blind lid 7 shown in FIG. 5, an inert gas such as nitrogen gas or argon gas is fed into the furnace body 1, and the on-off valve 15 of the gas outlet 12 of the lower lid 11 is opened.
The atmosphere inside the furnace body 1 is replaced with an inert gas, and the inert gas continues to be blown away.

Next, in this state, the temperature of the heating element 6 is raised and maintained at a predetermined temperature thereafter. For stretching, first lower lid 11
Close the on-off valve 15 to ensure the atmosphere inside the furnace body 1 is an inert gas, remove the blind lid 7, and install the feed rod 8 and the pull-out rod 1 at both ends in advance.
Insert the optical fiber base material 30 to which 3 is connected from the insertion port 2 so as to be concentric with the furnace body 1 and the heating element 6, and place the optical fiber base material 30 at the height of the heating element 6.
Set it where the bottom edge of is located. At this time, in the heating device of the present invention, since the optical fiber preform 30 to be stretched is particularly long, the upper part of the optical fiber preform 30 protrudes from the insertion opening 2. Therefore, the first sealing disk 9, which is locked to the connection between the optical fiber base material 30 and the feed rod 8, is not in close contact with the upper surface of the insertion port 2, and the inside of the furnace body 1 is not airtight. Must not be. In this embodiment, airtightness during this period is maintained as follows. That is, the first seal disc 9 is placed on the insertion port 2.
For example, a half-split chimney 10 is installed in close contact with the upper surface of the insertion port 2 so as to encompass the optical fiber base material 30, and a second sealing disc 16 is placed on the chimney 1.
The furnace body 1 is placed in close contact with the chimney roof 10a on the upper surface of the furnace body 1, and a seal gap is maintained between the second seal disk 16 and the feed rod 8, thereby making the inside of the furnace body 1 airtight.

In this way, when the airtightness of the upper part of the furnace body 1 is ensured, the lower cover 11 is removed, and the lower end of the optical fiber base material 30 is heated, and when it becomes soft, the pull-out rod 1
3 is pulled down to form a stretched glass body 14. After the stretching progresses and the first seal disc 9 reaches the position placed on the top surface of the insertion slot 2,
The seal distance is maintained between the first seal disk 9 and the feed rod 8, and airtightness within the furnace body 1 is maintained. At this point in time, the chimney 10, which is divided into halves, is removed.

Subsequently, the feed rod 8 is further lowered and the pull-out rod 13 is pulled out to extend the chimney 10.
Since the feed rod 8 can be lowered further down by the removed length, the feed rod 8 can be shortened by this amount, and the elevating mechanism for the feed rod 8 can be made more compact, which greatly reduces equipment costs. can be reduced to
In addition, work efficiency is significantly improved, and the consumption of the feed rod 8 can be suppressed, thereby reducing the manufacturing cost and realizing an economically efficient heating device.

In addition, in FIG. 1a, the furnace main body 1 of this embodiment
A furnace core tube 17 is provided in the center of the furnace body 1 at a position surrounding the optical fiber base material 30 as shown by the dotted line, and an inert gas inlet 18 and an inert gas inlet are provided on the side wall 1c of the furnace body 1 as shown by the dotted line. By providing the outlet 19, the life of the heating element 6 can be extended, which is effective and is included in the aspect of the present invention.

[Effect of idea]

As described above, according to the present invention, when drawing a long glass rod, the airtightness inside the furnace body is improved by using the first sealing disk, the second sealing disk, and the chimney. It can be held in two separate processes, and long glass rods can be heated and stretched using a small heating device for short lengths, without the need for tall equipment for long glass rods. .

In addition, the heating device for drawing glass rods of the present invention requires only a short feeding rod for feeding the glass rods, which significantly improves operability and reduces the overall price of the heating device and the cost of supplementary materials. This is remarkable, and it is extremely advantageous to reduce the price of products obtained by applying the heating device for glass rod drawing of the present invention.

[Brief explanation of drawings]

FIGS. 1a to 1c are schematic cross-sectional structural views of an embodiment of the heating device for drawing a glass rod according to the present invention, and FIGS. 2 a to c are schematic cross-sectional structural views of a conventional heating device for drawing a glass rod. 1, 20...furnace body, 1a...upper end wall, 1b...
...lower end wall, 1c...side wall, 2, 21...insertion port,
3,22...Drawer opening, 4,5...Inert gas supply port, 6,23...Heating element, 7,27...Blind lid, 8,32...Feeding rod, 9...First Seal disc, 10...Chimney, 10a...Chimney roof, 11,
29...Lower lid, 12, 28...Gas exhaust port, 1
3, 33... Pull-out rod, 14, 31... Glass elongated body, 15... On-off valve, 16... Second seal disc, 17... Furnace tube, 18... Inert gas inlet, 19... ...Inert gas outlet, 25, 26...
Inert gas supply port, 30... Optical fiber base material.

Claims (1)

[Claims for Utility Model Registration] The glass rod to be drawn is inserted into the center of the upper end wall 1a, the glass rod to be drawn having a feed rod 8 attached to the upper end thereof having an outer diameter smaller than the outer diameter of the glass rod to be drawn. a furnace body 1 having a drawer opening 3 in the center of the lower end wall 1b for pulling out the glass rod to be drawn; a heating element 6 disposed in the space for heating and softening the glass rod to be drawn, and slidably engaged with the feed rod 8 airtightly placed on the insertion opening 2 of the furnace body 1; and a first seal disc 9 that maintains a seal gap between the feed rod 8 and the outer circumferential wall of the feed rod 8;
It is divided into at least two parts in the circumferential direction, and the upper part of the first sealing disc 9 has an inner diameter larger than the outer diameter of the first sealing disc 9, and the upper part of the first sealing disc 9 has an inner diameter larger than the outer diameter of the first sealing disc 9. a chimney 10 having an inner diameter larger than the chimney diameter; and the feed rod 8 integrally formed with the chimney 10.
a chimney roof 10a having an airtight opening with an inner diameter larger than the outer diameter of the chimney roof 10a; and a chimney roof 10a that is airtightly placed on the chimney roof 10a, is slidably engaged with the feed rod 8, and has an outer periphery of the feed rod 8. A heating device for drawing a glass rod, comprising a second seal disk 16 for maintaining a seal gap between the glass rod and the wall.