Coating apparatus – Immersion or work-confined pool type – Running length work – longitudinally traveling
Reexamination Certificate
1999-11-24
2003-06-10
Lamb, Brenda A. (Department: 1762)
Coating apparatus
Immersion or work-confined pool type
Running length work, longitudinally traveling
C118S125000, C118S411000
Reexamination Certificate
active
06576058
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber coating method and coating apparatus; and, in particular, to those adapted to stably apply a coating resin in a higher linear velocity region.
2. Related Background Art
In the making of optical fibers, there has conventionally been employed a method comprising the steps of drawing an optical fiber by pulling an optical fiber preform while heating and melting it; applying two different types of resins to the surface thereof by use of a die adapted to apply two layers at the same time; curing the resins by use of a curing apparatus; and taking up the optical fiber with a take-up apparatus by way of a capstan, a pulley, and the like. An apparatus which applies two different types of resins by use of a die adapted to apply two layers at the same time is disclosed in Japanese Utility Model Application Laid-Open No. HEI 2-38437, Japanese Patent Application Laid-Open No. HEI 9-86971, or the like.
FIG. 16
is a sectional view of the conventional optical fiber coating apparatus disclosed in Japanese Patent Application Laid-Open No. HEI 9-86971. An optical fiber
1
comes into contact with a first coating resin A when passed through a die hole
30
of a first coating die
3
from a nipple hole
20
. The optical fiber
1
covered with the first coating resin A further comes into contact with a second coating resin B when passed through a die hole
40
of a second coating die
4
from the die hole
30
, and then is drawn out of the die hole
40
, whereby the optical fiber
1
with a double coating is fabricated.
From a first coating resin introduction hole
71
provided in the upper part of an outer sleeve
7
, the first coating resin A is successively supplied to an outer peripheral groove
65
of an inner upper sleeve
6
a
, a hole thereof, a first reservoir
11
disposed at the outer periphery of the nipple
2
, a first draw portion
9
, a first coating resin orthogonal flow path
10
formed by the tip surface of the nipple
2
and the upper face of the first coating die
3
, and a portion between the outlet of the nipple hole
20
and the inlet of the die hole
30
. From a second coating resin introduction hole
72
provided in the lower part of the outer sleeve
7
, the second coating resin B is successively supplied to an outer peripheral groove
66
of an inner lower sleeve
6
b
, a hole thereof, a second reservoir
12
disposed at the outer periphery of the second coating die
4
, a second draw portion
13
, a second coating resin orthogonal flow path
14
formed by the lower face of the first coating die
3
and the upper face of the second coating die
4
, and a portion between the outlet of the die hole
30
and the inlet of the die hole
40
.
It is described that the first coating resin
11
is thus once stored in the first reservoir
11
and then is sufficiently narrowed by the first draw portion
9
, thereby being regulated so as to form a uniform flow throughout the periphery, by which the optical fiber
1
is provided with a coating having a uniform thickness. On the other hand, the first coating resin orthogonal path
10
is formed between the outlet end face of the nipple hole
20
and the inlet end face of the die hole
30
and intersects the optical fiber
1
at right angles. It is also described that the first coating resin A consequently flows orthogonal to the optical fiber
1
, and thus can stably be applied to the latter while suppressing the recirculation thereof.
SUMMARY OF THE INVENTION
However, such a conventional coating apparatus has a drawback in that the outside diameter of the coating fluctuates as the drawing speed increases.
The inventors studied causes of the outside diameter fluctuation in detail by simulations and experiments. As a result, it has been found that, if the outlet portion of the die hole
30
at the lower face of the first coating die
3
is flat, then an unstable annular lower-pressure region is formed near this outlet, whereby the first coating resin A applied to the outer periphery of the optical fiber
1
is pulled by the annular lower-pressure region, so as to irregularly expand to the outside, thus forming the outside diameter fluctuation in the coating.
For eliminating the outside diameter fluctuation of the coating, the inventors have found it effective to provide a protrusion for regulating flows near the outlet. The present invention is based on this finding.
Here, the results of CFD (Computational Fluid Dynamics) simulations will be explained in brief.
Flow analysis program CFX 4.1 (Flow Solver) manufactured by AEA Technology PLC was used for the simulations, and influences of the form of the outlet portion were mainly studied. The analysis condition is shown in the following Table.
Taper angle of 1
st
layer die
3 degrees
1
st
layer die hole diameter
0.25 mm
Distance between 1
st
and 2
nd
layer
1.0 mm (parallel part)
dies
2
nd
layer die hole diameter
0.38 mm
Resin viscosity
1000 cps in both 1
st
and 2
nd
layers
Resin feed pressure
2.5 kg/mm
2
in both 1
st
and 2
nd
layers
Fiber linear velocity
1000 m/min
Under this analysis condition, two kinds of cases, i.e., case
1
in which the first layer die hole outlet is flat (corresponding to the conventional coating apparatus) and case
2
in which the first layer die hole outlet is provided with a beak-shaped protrusion having a height of 0.1 mm and a skirt width of 0.1 mm (corresponding to the coating apparatus of the present invention), were analyzed.
FIGS. 1 and 3
show the respective pressure distributions near the first layer die hole outlet of the two cases, whereas
FIGS. 2 and 4
show the respective stream line vector distributions near the first layer die hole of the two cases.
In case
1
corresponding to the conventional coating apparatus, as shown in
FIG. 1
, it can be seen that an annular lower-pressure region widely spreads near the first layer die hole outlet. Consequently, the resin coming out of the first layer die hole is outwardly pulled in the vicinity of the outlet as shown in FIG.
2
. As a result, a bulge occurs in the outside diameter of the coating.
In case
2
corresponding to the coating apparatus of the present invention, on the other hand, as shown in
FIG. 3
, it can be seen that the annular lower-pressure region becomes smaller. Consequently, resin flows substantially align in parallel with the optical fiber drawing direction as shown in
FIG. 4
, whereby the outside diameter of the coating becomes more stable than that in case
1
.
The inventors also studied influences of the form of the protrusion provided near the outlet by CFD simulations.
FIGS. 5A
to
5
D show their results, and are views schematically showing lower-pressure regions generated near the outlet of the first die hole
30
and their resulting outside diameter fluctuations. In the case shown in
FIG. 5A
provided with no protruded member, a lower-pressure region
15
of second coating resin B near the optical fiber
1
spreads over a wide area, whereby a bulge
11
of first coating resin A becomes remarkable. In the case with a protrusion shaped like a circular truncated cone as shown in
FIG. 5B
, on the other hand, it has been found that the lower-pressure region
15
near the optical fiber
1
is suppressed, so as to substantially eliminate the bulge
11
of first coating resin A. It has also been found that, in the case where the protruded member is substantially conical or shaped like a flat circular truncated cone with a large head or bottom portion as shown in
FIG. 5C
or
5
D, the effect on reducing the dimensions of the lower-pressure region
15
tends to be smaller.
Also, the inventors compared these CFD simulation results with experimental results, and have confirmed the effect on suppressing the outside diameter fluctuation obtained when the protrusion is shaped like a circular truncated cone with a small head portion.
The present invention is based on these findings, and it is an object of the present invention to provide an optical fiber coating method and c
Oishi Kazumasa
Okuno Kaoru
Takagi Masahiro
Tsuchiya Ichiro
Lamb Brenda A.
McDermott & Will & Emery
Sumitomo Electric Industries Ltd.
LandOfFree
Optical fiber coating method and coating apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical fiber coating method and coating apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical fiber coating method and coating apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3143464