JPH04342435A - Apparatus for drawing optical fiber - Google Patents

Abstract

PURPOSE:To automatically open and close a shutter by automatically sensing approach of a melt tip of a preform of optical fiber to the shutter on the undersurface of a heating furnace and its passage through the shutter. CONSTITUTION:An openable and closable shutter 7 is installed on the undersurface of a heating furnace 1 for a preform 2 of optical fiber and the first photosensor 6 capable of sensing the presence of a melt tip (2a) of the preform 2 of the optical fiber and opening the shutter 7 is installed near the upper part of the aforementioned shutter 7. The second photosensor 12 for sensing the presence of the melt tip (2a) passing through the shutter 7 and closing the shutter 7 is simultaneously provided near the lower part of the shutter 7.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an optical fiber drawing device, and more particularly, to an optical fiber drawing device that automatically detects the position of the molten tip of an optical fiber preform and automatically opens and closes a shutter on the lower surface of a heating furnace. The present invention relates to a fiber drawing device.

0002

2. Description of the Related Art FIG. 3 shows a general example of an optical fiber spinning line. Heated by the heater 21 in the heating furnace 20 (
(Heating radiant heat is increased by the furnace core tube 20b) The molten tip of the optical fiber preform 22 is heated to the outlet 20 of the heating furnace 20 due to its own weight.
It descends to a. The molten tip is pulled out from the outlet 20a and passed through a resin coating device 23 such as an ultraviolet curable resin and a resin curing device 24 containing an ultraviolet lamp and the like to pass the resin-coated optical fiber strand (hereinafter referred to as optical fiber strand) 2.
5 is made. Next, the optical fiber strand 25 drawn to a predetermined diameter is passed through the pulling device 26 and passed through the dancer 27 while keeping the speed and tension constant (relative to the optical fiber 25 stretched between the pair of rolls 27a). roll 27a
(by changing the spacing between the two) on the winding device 28.

By the way, the size of the molten tip of the optical fiber preform 22 that is heated and falls under its own weight in the heating furnace 1 is not constant (the diameter varies within a range of about 5 to 20 mm). Therefore, even if the melting tip is large, the outlet 20 of the heating furnace 20
It is conceivable to increase the diameter of the outlet 20a so that the outlet 20a is not blocked, but since the inside of the heating furnace 20 is at a high temperature of about 2000°C, if outside air enters the heating furnace 20, the heating furnace 2
0 carbon parts (e.g., furnace core tube 20b, heater 2
1, etc.) may be oxidized and its functionality may deteriorate, so it is preferable that the diameter of the outlet 20a be as small as possible.

Therefore, as shown in FIGS. 4(A) and 4(B), conventionally a shutter 29 divided into two parts that can be opened and closed is provided on the lower surface of the heating furnace 20, and a small half formed opposite to the center of the joint surface of the shutter 29 is provided. The circular concave portion 30a forms a small circular hole 30 when the shutter 29 is closed to prevent outside air from entering as much as possible, and when the shutter 29 starts drawing, the shutter 29 is opened wide to the left and right so that the molten tip of the optical fiber preform 22 is large. But I am allowing it to pass.

[0005]

[Problems to be Solved by the Invention] In the conventional method, in order to avoid missing the timing for opening the shutter 29, it is necessary for the operator to make sure that the molten tip of the optical fiber preform 22 comes down close to the shutter 29. It is necessary to look through the small circular hole 30 of the shutter 29 for monitoring, which is preferable in terms of work efficiency.

In view of this, the present invention automatically detects that the molten tip of the optical fiber preform approaches the shutter on the lower surface of the heating furnace and passes through the shutter, and automatically opens and closes the shutter. An object of the present invention is to provide an optical fiber drawing device as described above.

[0007]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the optical fiber drawing apparatus of the present invention is provided with a shutter that can be opened and closed on the lower surface of the heating furnace for the optical fiber preform, and near the upper part of the shutter. A first photosensor is installed near the bottom of the shutter to detect the presence of the molten tip of the optical fiber base material and open the shutter, and close the shutter by detecting the presence of the molten tip that has passed through the shutter. This is due to the installation of a second photosensor.

[0008]

[Operation] The first photosensor detects that the molten tip of the optical fiber preform has fallen near the shutter on the lower surface of the heating furnace, and the shutter is opened wide left and right to allow even the large molten tip to pass through. A second photosensor detects the molten tip that has passed through the shutter, closes the shutter again, and shortens the shutter open time.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical fiber drawing apparatus according to the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, 1 is a heating furnace for heating an optical fiber preform 2, and has a heater 3 and a furnace tube 4 made of carbon material, and a first annular support 5 is provided at the lower end. A first light emitting element 6a and a first light receiving element 6b forming a first photosensor 6 are disposed facing each other on the inner circumferential wall of the support base 5.

Reference numeral 7 designates a funnel-shaped shutter divided into two parts, which opens and closes the lower surface of the heating furnace 1 from side to side, and slides on the lower surface of the first support base 5, and when the shutter is closed, the shutter opens approximately 10 mm from the center of the lower end surface.
A small circular hole 7a with a diameter of mm is formed to prevent outside air from entering the heating furnace 1 as much as possible. Each of the two divided shutters 7 is driven by an air cylinder 8 via a rod 9, and the air cylinder 8 is attached to the inner peripheral wall of a cylindrical second support 10 provided on the first support 5. . In addition,
The lower end surface of the second support base 10 is longer than the lower end surface of the shutter 7.

Reference numeral 11 designates an annular third support base provided at the lower end of the second support base 10, on the inner peripheral wall of which a second light emitting element 12a and a light receiving element 12b forming a second photosensor 12 are attached. They are placed opposite each other.

[0012]The first and second light emitting elements 6a
, 12a are connected to the power supply device 13, the outputs of the first and second light receiving elements 6b, 12b are inputted to the cylinder drive control device 14, and the air passage switching valve device 15 is actuated by the output of the control device 14. Then, air is supplied and exhausted to each air cylinder 8, and the shutter 7 is opened and closed.

[0013] Therefore, when drawing an optical fiber,
The shutter 7 is closed by the air passage switching valve device 15 (
(The small circular hole 7a with a diameter of about 10 mm prevents the intrusion of outside air as much as possible), and the heater 3 is energized to heat the optical fiber preform 2. When the molten tip 2a of the optical fiber preform 2 falls near the shutter 7 due to its own weight, it is detected by the first photosensor 6, and the melted tip 2a of the optical fiber preform 2 is detected by the first photosensor 6, The shutter 7 opens widely to the left and right, allowing the melting tip 2a to pass (
Even if the melting tip 2a is large, it can pass through). The melted tip 2a that has passed through the shutter 7 is then transferred to the second photosensor 1.
2, the shutter 7 is closed again via the cylinder drive control device 14, the air passage switching valve device 15, and the air cylinder 8, and the opening time of the shutter 7 is shortened.
Prevent outside air from entering.

[0014]

[Effects of the Invention] The optical fiber drawing apparatus of the present invention is provided with a shutter that opens and closes from side to side on the lower surface of the heating furnace, and
Photo sensors were installed near the top and bottom of the shutter. It is no longer necessary to visually monitor the descent of the melting tip, which improves the work efficiency of the worker, and the small circular hole in the shutter is not blocked by the large melting tip, causing stagnation of wire drawing work. . (b) The shutter closes again when it detects that the molten tip of the optical fiber preform has passed through the open shutter, so the shutter opening time can be minimized and outside air can be prevented from entering the heating furnace. This can be prevented as much as possible, and oxidation of carbon parts such as heaters and furnace tubes in the heating furnace can be suppressed, and durability can be improved.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the invention.

FIG. 2 is a plan view of the shutter.

FIG. 3 is a diagram showing a general example of an optical fiber spinning line.

FIG. 4 shows a conventional optical fiber drawing device, and FIG.
A) is a longitudinal sectional view, and FIG. 4(B) is a plan view of the shutter.

[Explanation of symbols]

1 Heating furnace 2 Optical fiber base material 2a Melting tip 3 Heater 6 First photosensor 7 Shutter 8 Air cylinder 12 Second photosensor

Claims (1)

[Claims] 1. A shutter that can be opened and closed is provided on the lower surface of the heating furnace for the optical fiber preform, and a first photosensor that detects the presence of the melted tip of the optical fiber preform and opens the shutter near the top of the shutter. An optical fiber drawing apparatus characterized in that a second photosensor is installed near the bottom of the shutter to detect the presence of a molten tip that has passed through the shutter and close the shutter.