JPH06256034A - Apparatus for drawing glass preform for optical fiber - Google Patents

Abstract

PURPOSE:To enable the miniaturization of an apparatus, use of inexpensive supporting rods made of quartz and reduction in production cost for optical fiber by providing a structure in which an extensible bellows-shaped cylinder is installed in the upper part of a heating furnace and the upper flange of the cylinder is connected with an upper chuck and a wire. CONSTITUTION:This apparatus has a bellow-shaped cylinder 10 having airtightness, flexibility and heat resistance at a position surrounding a part for inserting a glass preform 4 for optical fiber in the upper part of a heating furnace 5 in an apparatus for drawing a glass preform 4 to a prescribed diameter by controlling the moving speed in the vertical direction of mobile type upper and lower chucks 1 and 7 in holding supporting rods 2 and 8, made of quartz and attached to both ends of the glass preform 4 in the vertical direction with the upper and lower chucks 1 and 7 on the outside of the heating furnace 5, inserting the part of the glass preform into the heating furnace and heating the glass preform. The apparatus especially preferably has a mechanism for interlocking the bellows-shaped cylinder 10 while keeping a prescribed distance from the upper chuck 1 so as to enable the expansion and contraction of the bellows-shaped cylinder 10 following the movement of the upper chuck 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for drawing a glass preform for optical fibers.

[0002]

2. Description of the Related Art An apparatus for stretching a glass preform for optical fibers is, for example, a glass in which both ends of the glass preform for optical fiber are horizontally held by chucks and heated while being rotated to apply tension in the horizontal direction. Lathes are known. Examples of the heating means include a combustion burner that supplies combustion gas to a burner and heats it with a flame generated by ignition, and a heating furnace. There is also known a device that holds a glass preform for optical fibers in a vertical direction, inserts it into a heating furnace, and applies tension in the vertical direction to draw the glass. In this case, (a) and (b) of FIG.
As shown in FIG. 2, a metal cylinder (3) surrounding the glass base material (4) for optical fiber is provided on the upper part of the heating furnace (5). In FIG. 2, (1) is the upper chuck,
(2) and (8) are quartz support rods, (6) is a heater, (7) is a lower chuck, and (9) is a glass base material stretched body for optical fiber.

[0003]

In a conventional apparatus having a heating furnace having a metal cylinder attached to the upper portion thereof, in order to insert and completely store the glass preform for optical fiber, the entire length of the glass preform for optical fiber is used. Therefore, a metal cylinder having a length corresponding to the above is required, and there is a problem that the heating furnace main body and the glass fiber preform for an optical fiber are enlarged in size. Furthermore, it is also necessary to connect a quartz support rod having a total length corresponding to the length of the metal cylinder to the upper part of the glass preform for optical fibers. Further, in order to secure the atmosphere in the heating furnace and suppress the oxidative consumption of the heat insulating material, it is effective to maintain the airtightness of the heating furnace main body and prevent oxygen from entering the heating furnace. During the stretching process, the quartz support rod penetration part in the upper part of the metal cylinder narrows the clearance between the through hole and the quartz support rod outline to ensure airtightness, but in order to obtain high airtightness, the quartz support High outer diameter uniformity over the entire length of the rod is required. Since an expensive quartz support rod having a full length corresponding to the length of the glass base material for an optical fiber and high outer diameter uniformity is required, this conventional device is disadvantageous to the production cost of the optical fiber itself. It was The present invention has been made to solve the above problems, and intends to provide a novel glass base material drawing apparatus for an optical fiber.

[0004]

As a means for solving the above-mentioned problems, the present invention is to use quartz support rods attached to both ends of a glass preform for optical fibers in a vertical direction by a movable upper and lower chucks outside a heating furnace. By controlling the vertical movement speed of the movable upper and lower chucks when gripping and inserting the glass preform for optical fiber into the heating furnace and heating the same, the vertical direction to the heating portion of the glass preform for optical fiber is controlled. In a device for applying a tension and stretching to a constant diameter, it is characterized by having a bellows-shaped cylinder having airtightness, flexibility and heat resistance at a position surrounding a glass base material insertion portion for an optical fiber in an upper part of a heating furnace. An apparatus for stretching a glass preform for an optical fiber is provided. As a particularly preferred embodiment of the present invention, by having a mechanism for interlocking the bellows-shaped cylinder while keeping a constant distance from the top chuck, the bellows-shaped cylinder is configured to expand and contract as the top chuck moves. The above-mentioned stretching device can be mentioned, and the above-mentioned interlocking mechanism has a configuration in which a wire drawn from a wire winding section attached to an upper chuck is connected to an upper flange of the bellows-shaped cylinder, and the tension of the wire is An example of the bellows-shaped cylinder can be expanded and contracted by controlling. Further, in the present invention, it is particularly preferable that the wire is configured to always secure a tension of a certain value or more, and the wire is automatically fed out when a tension of a predetermined value or more is applied, and a bellows shape. It is desirable that the wire winding section has a mechanism for limiting the tension applied to the cylinder.

[0005]

EXAMPLES AND OPERATION FIG. 1 shows an example of the stretching apparatus of the present invention to explain the present invention in detail, but the present invention is not limited to this. As shown in FIG. 1 (a), the glass base material for optical fiber (4) is connected with quartz support rods (4), (8) at both upper and lower ends, and each quartz support rod (4), (8) 8)
Is reliably gripped by the upper chuck (1) and the lower chuck (7). At the start of the drawing process, the tension of the plurality of wires (13) provided by the wire winding section (12) is controlled to raise the upper flange (11). Along with this, the bellows-shaped cylinder (10) expands, and the glass preform for optical fiber (6)
Is completely stowed. The glass (5) for optical fiber is heated by the heater (6) inside the heating furnace (5), and the moving speed of the upper chuck (1) and the lower chuck (7) is controlled at this time to control the glass for optical fiber. Tension is applied to the base material (4) to stretch it to a constant outer diameter. In this process as well, the tension of the wires (13) is controlled, the horizontal balance of the upper flange (11) is maintained, and the bellows type cylinder (10) is smoothly folded (see (b) of Fig. 1). ].

In the present invention, instead of a conventional metal cylinder, an expandable and contractible bellows-like cylinder (10) having airtightness, flexibility and heat resistance is adopted, so that it can be contracted (when folded).
The length of the heating furnace can be kept small, the size of the heating furnace main body can be prevented from increasing, and the required length of the quartz support rod can be made shorter than before. That is, by lowering the position of the upper chuck at the start of the stretching process, it is possible to downsize the device for moving the upper chuck and the lower chuck up and down. Furthermore, during the stretching process, since it is possible to lower the glass base material for optical fiber and to lower it together without changing the relative position of the penetrating portion of the quartz support rod that maintains the airtightness by motivation, The clearance does not change, high uniformity of the outer diameter over the entire length of the quartz support rod is unnecessary, and it is not necessary to use a highly accurate and expensive quartz support rod having a uniform outer diameter. Further, by attaching a metal flange to the uppermost part of the bellows-shaped cylinder, and connecting this metal flange to a plurality of wires provided from the wire winding section attached to the upper chuck,
A structure for synchronizing the lowering of the glass preform for optical fiber and the lowering of the metal flange can be obtained. Further, by controlling the tension of the plurality of wires by the wire winding portion, it is possible to maintain the horizontal balance of the metal flange and also maintain the clearance between the quartz support rod and the penetrating portion of the upper flange. Since the airtightness of the heating furnace is also high, the rate of oxidation and consumption of the heat insulating material in the heating furnace can be suppressed, and the frequency of maintenance can be reduced. As a concrete material of the bellows-shaped cylinder used in the present invention, a composite material in which a material having flexibility and airtightness and a heat resistant material that can withstand high temperature are combined is preferable, and for example, carbon fiber coated with Al is provided inside. A composite material in which a silicone resin for adhering airtightness is bonded to the outside can be used, but any material can be used as long as it has flexibility, airtightness and heat resistance.

As described above, the present invention employs an expandable and contractible bellows-shaped cylinder as a cylinder to be attached to the upper part of the heating furnace, and has a structure in which the upper flange of the bellows-shaped cylinder is connected to the upper chuck with a wire. Can be downsized, an inexpensive quartz support rod can be used, and the lifting device for the upper and lower chucks can be downsized, which is very effective in reducing the production cost of optical fibers.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of an embodiment of the apparatus of the present invention.

FIG. 2 is a schematic explanatory view of a conventional device.

[Explanation of symbols]

1 upper chuck, 2 quartz support rod, 3 metal cylinder, 4 glass base material for optical fiber, 5 heating furnace,
6 heater, 7 lower chuck, 8 quartz support rod, 9 optical fiber glass stretched body, 10 bellows-shaped cylinder, 11 upper flange, 12 wire winding section,
13 wires.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taku Yamazaki 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Yoshio Yokoyama 1 Taya-cho, Sakae-ku, Yokohama, Kanagawa Sumitomo Electric Ki Industry Co., Ltd. Yokohama Works

Claims (5)

[Claims] 1. A quartz support rod attached to both ends of an optical fiber glass preform is vertically held by a movable upper and lower chucks outside the heating furnace, and the glass preform for optical fiber is inserted into the heating furnace. In the device that applies vertical tension to the heating part of the glass preform for optical fiber to stretch it to a constant diameter by controlling the vertical moving speed of the movable upper and lower chucks when heating by An apparatus for stretching a glass preform for an optical fiber, comprising a bellows-shaped cylinder having airtightness, flexibility and heat resistance at a position surrounding a glass preform for fiber insertion. 2. The bellows-shaped cylinder can be expanded and contracted according to the movement of the upper chuck by having a mechanism for interlocking the bellows-shaped cylinder while keeping a constant distance from the upper chuck. An apparatus for drawing a glass preform for an optical fiber as described. 3. The interlocking mechanism has a structure in which a wire pulled out from a wire winding section attached to an upper chuck is connected to an upper flange of the bellows-shaped cylinder, and the tension of the wire is controlled. The apparatus for drawing a glass preform for an optical fiber according to claim 2, wherein the bellows-shaped cylinder is capable of expanding and contracting. 4. The apparatus for drawing a glass preform for an optical fiber according to claim 3, wherein the wire is configured to always maintain a tension of a certain value or more. 5. The wire winding section has a mechanism for automatically sending out the wire when a tension of a predetermined value or more is applied, and for limiting a tension applied to the bellows-shaped cylinder. The apparatus for drawing a glass preform for an optical fiber according to claim 4.