JPS62297243A - Resin coating method for optical fiber and apparatus therefor - Google Patents

Abstract

PURPOSE:To obtain an excellent resin-coated optical fiber free from disturbance of coating caused by the entrainment of air bubbles even at a high drawing speed, by drawing an optical fiber from a heating furnace, passing the fiber through a die of a specific resin-coating apparatus and coating the fiber with a resin while forcibly extruding the resin through the die. CONSTITUTION:The objective resin-coating apparatus 24 of an optical fiber has a coating die 2 having an inner diameter of 50mm and a diameter of 0.34mm at the outlet nozzle 9. A resin suction port 8 attached to the bottom part of the die 2 is connected with a resin outlet port 5 positioned along two opposite directions interposing a resin reservoir 6 between the suction port and the outlet port. The resin poured through a resin pouring pipe 10 is made to be forcibly extrudable under a specific pressure via an evacuated desiccator. An optical fiber 23 drawn from a preform 21 heated and melted in a heating furnace 22 is introduced into said resin-coating apparatus 24, passed through the above die 2 while forcibly extruding the resin 4 along the same direction as the running direction of the optical fiber 23 to effect the coating of the fiber with the resin 4, sent to a curing furnace 25 to cure the resin liquid 4 and wound to a reel 28 via a capstan 27.

Description

Detailed Description of the Invention 6. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an optical fiber in which a resin is coated on the outer periphery of an optical fiber that has been drawn by heating and melting a preform in a heating furnace. The present invention relates to a resin coating method and a coating device therefor.

[Conventional technology]

Figure 3 shows an overview of the series of steps for manufacturing the optical fiber. The optical fiber 23 drawn from the preform 21 heated and melted in the heating furnace 22 is immediately inserted into the resin coating device 24.
After applying the resin liquid to the outer periphery, the resin liquid is cured through a curing furnace 25, and wound onto a reel 28 through a capstan 27.

The reason for coating the outer periphery of the drawn optical fiber 23 with resin is to prevent accidents such as breakage, bending, bending, etc. during the secondary coating process of resin, nylon, polyethylene, etc. to prevent damage to the surface of the optical fiber. This is done to prevent this and further increase the mechanical strength of the optical fiber during cable production.

A conventional resin coating device 24 of this type uses, for example, an open die having a structure as shown in FIG. 2, a schematic cross-sectional view of which is shown. The drawn optical fiber 11 is introduced into a die storing resin 14, and the resin 14 is applied to the outer periphery of the optical fiber 11.
is applied to form a covering layer 17.

[Problem that the invention seeks to solve]

In the resin coating method using the conventional resin coating apparatus, as shown in FIG. 2, since the resin 14 is drawn out from the exit of the die 12 only by the adhesive force with the optical fiber 11, when the drawing speed of the optical fiber 11 increases, There is a problem in that slippage occurs between the resin 14 and the optical fiber 11, and as a result, a sufficient amount of resin is not applied for the coating, making it impossible to obtain a good coating.

Furthermore, in the open die structure shown in FIG. 2, the air bubbles drawn from the meniscus 19 at the insertion part of the optical fiber 11 into the resin 14 follow the resin streamlines 18 in the die 12 of the resin 14. This causes a problem in that the air bubbles circulate in the die 12 and remain in the resin 14, and the air bubbles discontinuously adhere to the optical fiber, making it impossible to obtain a good coating.

[Means for solving problems]

In order to solve the conventional problems, the present invention provides a resin coating method according to a first aspect of the present invention, which includes a resin coating device in which a resin is stored in a die on an optical fiber that is drawn by heating and melting the tip of a preform in a heating furnace. A resin coating method for an optical fiber in which the resin coating is applied by inserting a resin coating through the resin coating device is characterized in that the resin accumulated in the die is forcibly flowed out in the same direction as the passing direction of the optical fiber inserted through the resin coating device, The second invention is a resin coating device that is directly used to carry out the method for resin coating an optical fiber according to the first invention. It is characterized by having a resin outflow structure consisting of a resin suction port, a resin reservoir, and a resin outlet that forcefully flows out the resin in the direction.

[Effect]

In the present invention, by forcing the resin applied to the optical fiber to flow out in the same direction as the optical fiber passes through the die, the relative speed between the optical fiber and the resin is reduced, and a faster drawing speed is achieved. Also, the residence time of the resin in the die is short, preventing the occurrence of circulation flow that would cause air bubbles to accumulate inside the resin, and preventing the coating from being disturbed by air bubbles. Can be removed. Examples will be described below based on the drawings.

〔Example〕

FIGS. 1 and 1b are a schematic diagram of the cross-sectional structure of a specific embodiment of the optical fiber resin coating device of the present invention and a schematic diagram of the cross-sectional structure taken along the line AA'. 1 is an optical fiber, 2 is a die,
4 is a resin, 5 is a resin outlet, 6 is a resin reservoir, 7 is a coating layer,
8 is a resin suction port, 9 is a die outlet, and 10 is a resin injection pipe. The resin 4 is forcibly sucked out from the lower resin suction port 8, and the resin flows from the top to the bottom in the same direction as the passage direction of the optical fiber 1.

In this embodiment, the diameter of the die exit hole 9 is α34mmφ, and the inner diameter of the die 2 is 50mφ at the center. The die 2 has a circumferential resin outlet 8 at its lower bottom, and the resin outlet 8 is connected via a resin reservoir 6 to resin outlets 5 located in two opposing directions.

The resin outlet 5 is connected to a desiccator whose pressure is reduced using a conduit pump (not shown), and the degree of pressure reduction is adjusted by the degree of opening of the two-way tap connected to the desiccator while measuring the pressure with a manometer connected to the desiccator. I made it possible.

In order to evaluate the effect of sucking out the resin downward using the resin coating device of this example, an optical fiber was coated at a drawing speed of 40 m/min and the coating state was evaluated. However, if the resin is not sucked out downward, air bubbles will be mixed into the coating, and unevenness will occur every few meters, which is not good. When this was done, a good coating with no irregularities was obtained.

Furthermore, using the resin coating device of this example, an optical fiber was coated at a drawing speed of 100 m/min, and the effect of sucking out the resin downward was compared. The resin could only be coated on the surface. On the other hand, when drawing was performed, an optical fiber having a good coating was obtained as in the case where the drawing speed was 40 m/min.

Furthermore, by connecting the resin coating device according to the present invention with the resin suction device and the supply device, and adding a mechanism for re-supplying the sucked-out resin after defoaming, the resin is not wasted and is even more effective. If a particularly powerful suction device is used, it is possible to remove the air bubbles contained in the suctioned resin, and the resin can be reused without the need for a separate degassing process. is.

〔Effect of the invention〕

As described above, according to one aspect of the present invention, the resin is sucked in the same direction as the optical fiber passing direction, and the resin not coated on the optical fiber is sucked out to the outside of the die, thereby reducing the relative speed between the optical fiber and the resin. This makes it possible to coat at a higher drawing speed compared to conventional resin coating using an open die. Furthermore, since air bubbles are not accumulated in the die, it is possible to prevent the coating layer from being distorted due to entrainment of air bubbles.

[Brief explanation of the drawing]

Figures 1a and b are cross-sectional structural diagrams of the optical fiber resin coating apparatus of the present invention, Figure 2 is a cross-sectional structural diagram of a conventional optical fiber resin coating apparatus, and Figure 3 is a schematic diagram of the process of manufacturing the optical fiber. be. 1... Optical fiber, 2... Die, 4...
Resin, 5...Resin outlet, 6...Resin reservoir,
7... Coating layer, 8... Resin suction port, 9... Die exit hole, 10-... Resin injection tube, 11... Optical fiber, 12... Die, 14... Resin, 17--Coating layer, 18--Resin streamline, 19--Meniscus, 21
..."j') 7 oh A, 22...Heating furnace, 23
...Optical fiber, 24-...Resin coating device, 25
...hardening furnace, 27...capstan, 28...reel

Claims (2)

[Claims] (1) A resin coating method for an optical fiber in which a resin coating is applied to an optical fiber whose tip of a preform is heated and melted in a heating furnace and drawn, by inserting a resin coating device in which resin is stored in a die. A method for coating an optical fiber with resin, comprising: forcing the resin stored in the die to flow out in the same direction as the optical fiber passing through the device. (2) In an optical fiber resin coating device consisting of a die that stores resin through which an optical fiber obtained by heating and melting a preform in a heating furnace is inserted and coated with resin, a die exit hole from which the optical fiber of the die is drawn out. a resin suction port that forcibly flows out the resin in the direction of passage of the optical fiber running from the bottom side of the die, and a resin reservoir that temporarily stores the resin sucked out from the resin suction port, at the bottom of the die adjacent to the resin suction port; A resin coating device for an optical fiber, comprising: a resin outlet for forcibly flowing out the resin through a resin reservoir.