JP2003212608A - Coating applicator for optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel coating applicator for optical fibers by which a favorable coating is applied with few thickness deviation and outside diameter fluctuation, even when increasing the drawing speed. <P>SOLUTION: The coating applicator for optical fibers comprising a nipple 1 and a die 2 possesses an upstream parallel land portion 10 that extends in parallel toward a die inlet 9 in the upstream of a tapered portion 6 of the die 2. This prevents the accompanying amount of a coating resin to the tapered portion 6 from increasing while extending the contact time between the coating resin and a fiber element wire F. In consequence, a favorable coating with few thickness deviation and outside diameter fluctuation is achieved, even when increasing the drawing speed of the fiber element wire F. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber coating apparatus for continuously forming a protective coating layer of resin or the like on a glass optical fiber drawn at high speed.

[0002]

2. Description of the Related Art An optical fiber, which is indispensable for constructing an optical communication network and the like, generally has a coating layer made of resin or the like formed on the surface thereof so as to protect the fiber strand from an external impact or the like.

This coating layer is formed by heating and drawing a preform rod, which is a material, to form a fiber strand having a predetermined diameter, and passing it through an optical fiber coating device as shown in FIG. The coating is continuously formed around the circumference of the.

That is, this optical fiber coating apparatus is mainly composed of a nipple 1 for guiding the fiber strand F drawn to a predetermined diameter, and a die 2 positioned near the nipple 1 with a resin flow path 3 interposed therebetween. When passing the fiber strand F from the passage hole 4 of the nipple 1 toward the passage hole 5 of the die 2, the coating resin is pressurized and supplied into the resin flow path 3 to the fiber strand F side. The coating resin is supplied.

As shown in the drawing, the passage hole 5 on the die 2 side is formed in parallel with the taper portion 6 having a reduced diameter in the traveling direction of the fiber strand F and the die outlet 7 direction from the downstream side of the taper portion 6. The coating resin supplied from the resin flow path 3 is caused to accompany the taper portion 6 together with the fiber wire F, and the taper portion 6 and the parallel land portion 8 are allowed to pass therethrough. The coating layer J having a predetermined outer diameter is continuously formed around the wire F.

The optical fiber coated with the coating layer J by this optical fiber coating apparatus is fixed to the coating layer J as it is, and then continuously wound on a winding bobbin (not shown) for a predetermined inspection. And so on.

[0007]

By the way, in order to further improve the coating work efficiency, it is necessary to increase the drawing speed of the fiber strand F, and then the fiber strand F contacts the coating resin. Since the time is shortened, the coating resin does not sufficiently adhere to the fiber strand F, and the fiber strand F remains unstabilized and passes through the parallel land portion 8 and exits from the die exit 7. There is a problem that the fluctuation of the outer diameter becomes large.

Therefore, as the drawing speed increases, the length L2 of the taper portion 6 is extended from 1.5 times to 2.0 times that of the conventional case, so that the contact time between the fiber filament F and the coating resin is lengthened. By doing so, it is possible to reduce the variation in the outer diameter of the coating layer J.

However, if the length L2 of the taper portion 6 is made longer than in the conventional case, the diameter of the die inlet 9 inevitably becomes large and the amount of resin accompanying the taper portion 6 increases, and the diameter of the die outlet 7 increases. An imbalance occurs with the coating thickness determined by As a result, the self-centering function of the fiber wire F passing through the through hole 5 of the die is lost, and a circulation phenomenon occurs in the flow of the resin, which causes a new problem that the uneven thickness of the coating layer J increases. Occurs.

As a method of reducing the amount of resin entrained in the taper portion 6 and lengthening the contact time between the resin and the fiber strand F, the angle θ of the taper portion 6 is made smaller than before, for example, 2 It is possible to set it below °,
If this angle is too small, the stability of the coating outer diameter is likely to collapse, and as the drawing speed increases, the outer diameter variation of the coating layer J increases, and if the taper angle is eliminated, the coating variation will occur even in the low speed range. Since it becomes extremely large and it becomes impossible to continue the drawing work, it is necessary to secure at least 2 ° or more for the angle of the tapered portion.

Therefore, the present invention has been devised to effectively solve such a problem, and an object thereof is to provide a good coating with less uneven thickness and outer diameter variation even if the drawing speed is improved. The present invention provides a novel optical fiber coating device that can be used.

[0012]

In order to solve the above-mentioned problems, according to the present invention, as shown in claim 1, after coating resin is applied onto the fiber strand that has passed through the nipple, the fiber strand is coated. In a coating device for an optical fiber, which is configured to pass through a through hole of a die together with a resin to form a coating layer having a constant thickness around the fiber element wire, the through hole of the die is located downstream of the running direction of the fiber element wire. A tapered portion having a tapered diameter toward the side, and a downstream parallel land portion extending from the downstream end of the tapered portion in parallel to the die exit side,
An upstream side parallel land portion extending in parallel to the die inlet side is coaxially arranged from the upstream end portion of the taper portion.

That is, an upstream parallel land portion extending in parallel to the die inlet side is further provided on the upstream side of the die side taper portion, thereby suppressing an increase in the amount of the coating resin entrained on the taper portion. The contact time between the coating resin and the fiber strand can be made significantly longer than before. As a result, even if the drawing speed of the fiber strand, that is, the coating speed is improved as compared with the conventional case, it is possible to achieve excellent coating with less uneven thickness and outer diameter variation.

More specifically, as described in claim 2, the angle of the tapered portion is ensured to be 2 ° or more, and the length of the upstream side parallel land portion is set as described in claims 3 and 4. If the diameter of the upstream parallel land portion is 2.5 times or less than the diameter of the downstream parallel land portion, the object of the present invention can be reliably achieved. You can

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment for carrying out the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an essential part of an optical fiber coating apparatus according to the present invention. In the figure, 1 is a nipple for guiding a fiber strand F after drawing, and 2 is an outlet of a passage hole 4 of the nipple 1. The die 3 fixed to the 11 side is a resin flow path formed between the die 2 and the nipple 1.

As shown in the drawing, the die 2 is provided with a through hole 5 having a circular cross section so as to be positioned coaxially with the through hole 4 of the nipple 1, and the through hole 4 of the nipple 1 is provided.
The fiber strands F sent from the above are allowed to pass straight without being brought into contact with the die 2 side.

The passage hole 5 formed in the die 2 is gradually reduced in diameter in the traveling direction (passing direction) with the passage position of the fiber strand F as an axis, that is, from the die inlet 9 side toward the die outlet 7 side. The tapered portion 6, the downstream parallel land portion 8 extending in parallel from the downstream end portion of the tapered portion 6 to the die exit 7 side, and the upstream parallel land extending from the upstream end portion of the tapered portion 6 in parallel to the die inlet 9 side. The land portion 10 and the land portion 10 are coaxially arranged.

The length L2 of the taper portion 6 and the length L3 of the downstream parallel land portion 8 are the same as those in the conventional case, and the width LA of the resin flow path 3 and the resin supply pressure thereof are also the same as those in the conventional case. It is similar.

In the optical fiber coating apparatus of the present invention having such a configuration, first, the fiber element wire F is run from the nipple 1 to the die 2 side to enter into the resin passage 3, and this is preliminarily obtained. The coating resin pressurized and supplied to the portion flows into the passage hole 5 side of the die 2 while being accompanied by the fiber strand F, and the diameter D2 of the die inlet 9 of the passage hole 5 is set.
Since the upstream side parallel land portion 10 has the same diameter as the conventional one, the resin does not circulate near the die inlet 9 and uniformly flows together. Next, the coating resin flowing along with the fiber strand F in this manner flows through the upstream parallel land portion 10 in the same direction as the traveling direction of the fiber strand F, and passes through the taper portion 6, thereby By adhering to the strand F and being stable, and then passing through the downstream parallel land portion 8 having a predetermined length L3, the coating outer diameter is adjusted, and a good coating layer J free from uneven thickness and outer diameter variation is obtained. The coating is continuously formed.

Further, since the length of the passage hole 5 formed in the die 2 is increased by the length of the upstream parallel land portion 10 formed on the upstream side of the taper portion 6, the passage hole 5 is passed through. The contact time between the fiber strand F and the coating resin can be made longer than before.

Therefore, the drawing speed of the fiber strand F,
That is, the coating speed can be improved as compared with the conventional one,
Good coating operations can be achieved efficiently.

Here, the length L of the upstream parallel land portion 10
As for No. 1, it is important to secure at least ¼ or more of the length L2 of the tapered portion 6.
That is, as will be understood from Examples described later, if the length L1 is ¼ or less of the length L2 of the tapered portion 6,
This is because the effect of suppressing the fluctuation of the outer diameter cannot be sufficiently obtained.

Further, the angle θ of the taper portion 6 needs to be at least 2 ° or more as described above, but if it is too large, the diameter of the upstream side parallel land portion 10 will increase accordingly and the resin Since the amount of entrainment increases and the flow resistance of the resin increases, it is desirable that the maximum is 5 ° or less.

Further, the diameter D2 of the upstream parallel land portion 10
Is preferably 2.5 times or less of the diameter D3 of the downstream side parallel land portion 8 as will be seen from an example which will be described later. Above this, the outer diameter variation is small but the uneven thickness amount is large. This is because it will end up.

It is desirable that the central axes of the passage hole 4 of the nipple 1 and the passage hole 5 of the die 2 are completely coincident with each other, but if the error is within 5 μm, there will be no practical problem. . Further, the fiber strand F fed into the apparatus may have a primary coating further provided upstream thereof.

[0027]

EXAMPLE In a coating apparatus having a structure as shown in FIG. 1, a nipple outlet diameter D1, a die inlet diameter D2, a taper angle θ, a die outlet diameter D3, a width (height) L of a resin passage 3
A, the length L1 of the upstream parallel land portion 10, the taper portion 6
L2 and the length L3 of the downstream parallel land portion 8 are set as shown in the respective columns of Table 1 below, and the outer diameter of the glass optical fiber strand 5 having an outer diameter of 125 μm is about 19
An attempt was made to form a primary coating layer having a thickness of 5 μm, and the thickness deviation and outer diameter variation of the obtained optical fiber were evaluated.

As the coating resin, urethane acrylate, which is commonly used, is used, and the drawing speed is 1
The speed was gradually increased from a low speed of 000 m / min or less, and the maximum speed was 1500 m / min.

[0029]

[Table 1]

As a result, in Nos. 1 to 3 of Table 1, the uneven thickness of the coating layer was 5 μm or less at a drawing speed of 1500 m / min, and the coating outer diameter was constant. It was possible to do it.

On the other hand, in the case of No4 in which the die inlet diameter D2 is 2.5 times or more larger than the die outlet diameter D3,
Even if the drawing speed was increased, the variation in the outer diameter of the coating was small, but the uneven thickness amount was as large as 7 μm. Further, the length L1 of the upstream parallel land portion 10 is the taper portion 6
In the case of No5, which is 1/4 or less of the length L2 of
When the drawing speed exceeded 1200 m / min, the variation of the coating outer diameter began to increase, and at 1500 m / min, the variation of the coating outer diameter became ± 4 μm or more, and high-speed coating was impossible.

[0032]

In summary, according to the present invention, since the upstream parallel land extending parallel to the upstream end portion of the taper portion is formed, the flow inside the die is stable even during high-speed drawing, and the coating layer is biased. Meat and coating outer diameter fluctuations are avoided,
It is possible to efficiently obtain a high quality optical fiber.
Further, among the members constituting the present device, the objective effect of the present invention can be easily obtained by improving only the die,
The existing device can be used as it is, and the manufacturing cost of the device can be reduced.

[Brief description of drawings]

FIG. 1 is an enlarged view of an essential part showing an embodiment of an optical fiber manufacturing apparatus according to the present invention.

FIG. 2 is an enlarged view of a main part showing an embodiment of a conventional optical fiber manufacturing apparatus.

[Explanation of symbols]

1 nipple Two dies 3 resin flow paths 4 Nipple side passage hole 5 Die side passage hole 6 taper part 7 die exit 8 Downstream parallel land 9 die entrance 10 Upstream parallel land 12 Nipple outlet

Claims (4)

[Claims] 1. A coating resin is supplied onto a fiber strand that has passed through a nipple, and the fiber strand is passed together with the coating resin through a passage hole of a die to form a coating layer having a constant thickness around the fiber strand. In the optical fiber coating device that is formed, the through hole of the die has a taper portion that is tapered toward the downstream side in the running direction of the fiber element wire, and the die exit side from the downstream end of the taper portion. And a downstream parallel land portion extending in parallel with the upstream side parallel land portion extending in parallel to the die inlet side from the upstream end of the taper portion are coaxially arranged. . 2. The optical fiber coating apparatus according to claim 1, wherein the taper portion has an angle of 2 ° or more. 3. The optical fiber coating apparatus according to claim 1, wherein the length of the upstream parallel land portion is ¼ or more of the length of the taper portion. 4. The optical fiber according to claim 1, wherein the diameter of the upstream-side parallel land portion is 2.5 times or less the diameter of the downstream-side parallel land portion. Coating equipment.