Note: Descriptions are shown in the official language in which they were submitted.
2~2
METHOD AND APPARATUS FOR PASSING OPTICAL FIBERS
THROUGH TUBULAR PRODUCTS
Background of the Invention
Field of -the Invention
This invention relates to a method and apparatus
for passing optical fibers through tubular products, and
more particularly to a method and apparatus for making
optical fiber core wires, optical fiber cords and/or
optical fiber cables comprising optical fibers passed
through protective tubes or sheaths.
For the purpose of this invention, optical fibers
are defined as element fibers comprising a core and a
cladding layer, such element fibers as are coated with
syntetic resins, metals and ceramics and their
variations comprising a single fiber, multiple fibers
and stranded fibers. Tubular products are such metal
tubes as those of steel and aluminum, and such nonmetal
tubes as those of plastic.
Description of the Prior Art
Recently optical fiber cables have come to be used
widely for communications services. And many of them
are metal-coated to make up for the limited strength of
optical fibers.
Optical fibers passed through metal and other tubes
have been made by a method that combines tape forming
and welding (such as that disclosed in Japanese
~6~22
Provisional Patent Publication No. ~6869 of 1985) and a method
that passes an optical fiber through a tube (such as that
dlsclosed in Japanese Provi~ional Patent Publication No. 25606 of
1983).
In the former method, an optical fiber is passed through
a metal tube while a metal tape is being formed into a tubular
shape and both edges of the tape are being welded together. But
there is a shortcoming that the optical fiber is liable to
degenerate under the influence of welding heat when it passes the
welding polnt. Also, an optical fiber is difficult to pass
through tubes whose diameter is as small as 2 mm or under.
In the latter method, an aluminum tube is made with a
steel wire passed therethrough. After the tube is subjected to a
diameter-reducing process, the steel wire inside the tube is
replaced with an optical fiber. This method requires intricate
processes. Besides, the force with which the steel wire is pulled
out for replacement should not exceed the strength of the optical
fiber in order to avoid the risk of fiber breaking. Accordingly,
optical fiber cable having a length of 200 m or more have been
difficult to make.
Summarv of the Invention
The invention provides a method of passing an optical
fiber through a tube which comprises the steps of: forming a coil
of the tube; causing the coil of the tube to vibrate in such a
manner that a given point thereof reciprocates along a helical
path; feeding the optical fiber into one end of the coil of tube
that is being thus vibrated, whereupon the optical fiber fed into
~;~6~
the tube moves forward under-the influence of the intermittent
conveying force exerted by the inner wall of the tube in the
direction of the circumference of the coll of tube, said ~eedlng
step lncluding positively feeding the optical fiber into the coil
of tube at substantially the same speed as the speed of forward
movement o~ the optical fiber through the coil of tube.
To facilitate passing~ ~he difference between the inside
diameter of the tube and the diameter of the optical fiber should
be not less than 0.1 mm and the diameter of the coil of tube
should be not smaller than lS0 mm or preferably 300 mm or more.
For the matter of vibration, the angle of vibration (i.e., the
lead angle of helix) should be not smaller than 1 degree, or
preferably between S and 30 degrees, the frequency of vibration
not les~ than 5 Hz, or preferably between 10 and 30 H~, and the
total amplitude of vibration in terms of vertical component not
less than 0.1 mm, or preferably between O.S and 2.0 mm.
~ rom another aspect the invention provides an apparatus
for passing an optical fiber through a tube which comprises: a
cylindrical body around which the tube to admit the optical fiber
is coiled; means to vibrate the cylindrical body in such a manner
that a given point of the tube reciprocates along a hellcal path;
and means to feed the optical fiber into the coil of tube belng
thus vibrated from one end thereof, whereupon the optical fiber
fed lnto the tube moves forward under the influence of the
intermittent conveying force exerted by the inner wall of the tube
in the dlrection of the circumference of the coil of tube, said
feeding means including means to positively feed the optical fiber
B
2~
at a speed substantially the same as the speed of forward movement
of the optical fiber through the coil of tube. The passlng
apparatus may also
3a
. .
6~
incorporate a sensor to detect the difference be-tween the passing
speed and feed speed of the optical fiber and a device to control
the feed speed oE the optical fiber feeding device on the basis of
the speed difference detected by the aforementioned sensor.
The me-thod and apparatus of this invention permits pass-
ing an optical fiber through a tube of small diameter (such as one
having an outside diameter of 2 mm or under) and long length (such
as one having a length of 1 km or over) without deteriorating or
damaging the optical fiber. Their simplicity is conducive to
cutting down the production cost of optical fibers covered with
protective tubes. With the feed speed of an optical Eiber con-
trolled by the feeding device of this passing apparatus, the
optical fiber can be fed into a tube in the most favourable condi-
tion, without applying excessive tension on the optical fiber and
exerting any backward force to prevent the admission thereof into
the tube.
Brief Description of the Drawings
. .
Fig. 1 is a side elevation showing a preferred embodi-
ment of an optical fiber passing apparatus according to this
invention;
Fig. 2 is a plan view of a vibrating table of the same
apparatus;
Fig. 3 is a front view showing an example oE a bobbin
mounted on the vibrating table;
Figs. 4a and 4b show cross-sectional profiles of
grooves cut in the bobbin;
Fig. 5 is a cross-sectional view of an example of an
22
anti-vibrating guide provided in the apparatus;
Fig. 6 is a cross-sectional view of an example of a
protective guide provided in the apparatus;
Fig. 7 illustrates a principle on which an optical fiber
is carried forward in a tube;
Figs. 8a and ~3b diagramatically show vibrating condi-
tions of a coil of tube;
Figs. 9a and 9b show front views of other examples of
bobbins;
Fig. 10 is a front view showing an example of means to
fasten a coil of tube to a bobbin;
Fig. 11 is a perspective view showing an example of an
elastic belt used as the fastening means;
Fig.12 is a front view showing another example of the
means to fasten a coil of tube;
Fig. 13 is a perspective view of a bobbin used with the
fastening means shown in Fig. 12;
Fig. 14 is a front view of an elastic belt used with the
fastening means shown in Fig. 12;
Fig. 15 is a partially cross-sectional front view show-
ing still another example of the means to fasten a coil of tube;
Fig. 16 is a cross-sectional view showing another
example of the anti-vibrating guide; and
Fig. 17 is a cross-sectional view showing another
example of the protective guide provided at the inlet end of a
tube.
-- 5
~2~2~
Description of the Preferred Embodiments
Now preferred embodiments o~ this invention will be
described by reference to the accompanying drawings. ~ig. 1 is an
overall view of a passing apparatus according to this invention,
and Fig. 2 is a plan view of a vibrating table.
A base 11 is firmly -fastened to a floor surface 9 so as
not to vibrate. Coil springs 18 to support a vibrating table are
mounted at the four corners of the top surface of the base 11.
A square panel-like vibrating table 14 is p:laced on the
base 11, with the support springs 18 interposed therebetween.
support frame 15 extends downward from the bottom surface of the
vibrating table 14.
The support frame 15 under the vibrating table 14
carries a pair of vibrating motors 21, 22. The vibrating motor 22
is placed diametrically opposite motor 21 relative to central axis
C of table 14. The rotating sha~ts of the vibrating motors 21, 22
are respectively parallel to a vertical plane containing the
central axis C and oppositely tilted with respect to the surface
of the vibrating table at an angle of 75 degrees. Unbalanced
weights 24 are fastened to both ends of the rotating shafts of the
vibrating motors 21, 22. The centrifugal force resulting from the
rotation of the unbalanced weights 24 applies a vibrating force to
the vibrating table 14 that works aslant to the surface thereof.
The paired vibrating motors 21, 22 are driven in such a manner
that vibrations they cause have equal frequency and amplitude, and
vibrating forces they exert are displaced 180 degrees from each
other. Accordingly, when the vibrations caused by the paired
-- 6 --
~6~
vibrating motors 21, 22 are combined, the vibrating table 14
vibrates in such a manner as to move along a helical path whose
central axis coincides with the central axis C of the vibrating
table 14. The vibration of the vibrating table 14 is not
transmitted to the base 11 because the support springs 18 are
interposed therebetween.
In place of the vibrating motors 21, 22, such vibrating
means as those employing cranks, cams or electromagnets may be
used~ Also, vibrating motors 21, 22 may be fastened to the
vibrating table 14 in other ways than shown in Fig. 1.
A bobbin 27 is fastened on the vibrating table 14 in
such a manner that the axis of the bobbin 27 coincides with the
central axis C of the vibrating table 14. A tube 1 through which
an optical fiber 7 is to be passed is coiled around the bobbin 27,
forming a coil of tube 5. The optical fiber 7 is fed into the
tube 1 from the lower end of the coil of tube 5. To avoid the
~ ~6~1~2~
development of excessive bending stress in the optical
fiber, the diameter of the coil of tube should
preferably be not smaller than 150 mm. The optical
fiber 7 used in this embodiment consists of an element
optical fiber precoated with resin. The tube 1 is a
steel tube. The outer periphery of the bottom flange 29
of the bobbin 27 is fastened to the vibrating table 14
with fastening jigs 31 so that the vibration of the
vibrating motors 21, 22 is surely received. As is shown
in Fig. 3, a groove 30 is cut around the circumference
of the barrel 28 of the bobbin 27 using a shaper so that
ridges and recesses pointing to the axis of the bobbin
are successively formed. The groove 30 is shaped so
that the tube 1 comes in contact therewi-th closely. In
cross-sectional profile, the groove 30 may be either a
triangular groove 30a as shown at (a) of ~ig. 4 or an
arc-shaped groove 30b as shown at (b) of the same
figure. Any other cross-sectional profile is allowable
so long as the tube 1, which is shown by a broken line,
is firmly retained on the bobbin 27.
The optical fiber 7 is passed through gradually
while the bobbin 27 is being vibrated. If the directly
vibrated bobbin 27 and the tube 1 wound therearound are
not kept in close contact with each other, precise
transmission of the vibration to the tube 1 and,
therefore, smooth passing of the optical fiber 7 will
not be achieved. The tube 1 wound around the barrel 28
6~2~
,
of the bobbin 27 easily clings to the barrel 28 in the
direction of the diameter of the bobbin 27, but not in
the direction of the axis thereof. Then, it becomes
difficult to uniformly vibrate the entirety of the tube
1 vertically. But if the tube 1 is held tightly in the
groove 30 around the barrel of the bobbin 27, the
vibration of the bobbin 27 will be precisely
transmitted to the tube 1, thereby ensuring smooth and
efficient vibration and passing of the optical fiber 7.
A feed spool 34 that constitutes an optical fiber
feeder 33 is placed beside the bobbin 27. The feed
spool 34 is rotatably supported on a bearing stand 35.
The feed spool 34 pays off the optical fiber 7 wound
therearound into the coil of tube 1. The point at which
the feed spool 34 pays off the optical fiber 7 is
substantially at the same level as the point at which
the optical fiber 7 is fed into the tube 1.
A drive motor 38 is positioned next to the feed
spool 34. The feed spool 34 and drive motor 38 are
~;~v Co~ct~
intcPlocl~cd by a belt transmission 40. Rotated by the
drive motor 38, the feed spool 34 pays off the optical
fiber 7 into the tube 1 wound around the bobbin 27.
A support guide 43 is provided near the optical
fiber pay-off point of the feed spool 34. Consisting of
a short tubular guide proper 44 and a stand 45 that
horizontally supports the guide proper~ the support
guide 43 supports the optical fiber 7 paid off from the
feed spool 34.
An optical fiber feed condition sensor 47 is
installed downstream of the support guide 43. The
optical fiber feed condition sensor 47 is made up of a
support column 48 and an optical fiber level sensor 49
attached thereto. The optical fiber level sensor 49
consists of an image sensor and an oppositely disposed
light source. Installed in the pass line of the optical
fiber 7, the optical fiber level sensor 49 senses the
sagging condition thereof. A CCD line sensor is used as
the image sensor.
To the optical fiber feed condition sensor 47 is
connected a rotation speed controller 52 that controls
the voltage of power supply 39 to said drive motor 38 on
the basis of signals sent from -the optical fiber feed
condition sensor 47. That is, thé rotation speed of the
drive motor 38 or, in other words, the pay-off speed of
the optical fiber 7 is controlled depending on the level
at which the optical fiber 7 interferes with the travel
of light from the light source in the optical fiber
level sensor 49.
The speed with which the optical fiber 7 is passed
through the tube 1 is not always constant but may vary
when a resonance occurs or depending on the condition of
the inner surface of the tube 1 and the surface of the
optical fiber 7. A change in the running speed of the
optical fiber 7 in the tube 1 affects the feeding
~ ~2~ 2~
condition of the optical fiber 7 on the outside. If the
feed speed does not follow the passing speed, the
optical fiber 7 may either sags e~cessively or break as
a result of overtight stretching. Either way 7 smooth
feeding of the optical fiber 7 will be hindered. But
the optical fiber 7 can always be fed at a feed speed
within the desired range if the feed spool 34 is rotated
so that the rotation thereof is varied or stopped
depending on the travelling condition of the optical
fiber 7 in the tube 1. Namely, the optical fiber 7 is
then kept in the optimum condition (in which the optical
fiber 7 sags slightly as shown in Fig. 1), without
oversagging or getting overstretched. As a consequence,
the optical fiber 7 is passed through the tube without a
hitch, with no load placed thereon or no resistance
built up against the passing thereof. Incidentally, an
optical fiber 0.4 mm in diameter will not enter a steel
tube having an inside diameter of 0.5 mm if a force of
20 gf or greater directed to the feeder side works on
the optical fiber.
The optical fiber feed condition sensor 47 is not
limited to the illustrated image sensor, but may consist
of a pair of photoelectric tubes that are vertically
spaced iu~ to detect the upper and lower limits of the
sagging of the optical fiber 7. In this case, -the drive
motor 38 is on-off controlled. Instead of sensing the
position and form of the optical fiber 7, just the feed
~i9~2
speed of the optical fiber 7 may be sensed to control
the motor speed in accordance with signals based on the
sensed results.
An anti-vibrating guide 54 is installed between the
optical fiber feed condition sensor 47 and the inlet end
2 of the tube. The anti-vibrating guide 54 consists of
a cylindrical guide proper 55 and a stand 58 that
horizontally supports the guide proper. As shown in
Fig. 5, both ends of the guide proper 55 of the anti-
vibrating guide 54 expand outward to form tapered
(funnel-shaped) portions 57. The boundary between each
tapered portion 57 and a cylindrical portion 56 should
preferably be shaped into a smooth curved surface. The
length of the anti-vibrating guide 54 may be chosen
appropriately depending on the distance between the inlet
end 2 of the ~ube and the feed spool ~4. When the
distance is long, the anti-vibrating guide 54 should
naturally be long. The anti-vibrating guide 54 must be
made of such material~s as glass and plastic that have
such a low coefficient of friction that the transfer of
the optical fiber by vibration is not impeded.
A lubricant feeder 59 filled with a lubricant is
attached to the cylindrical portion 56 of the anti-
vibrating guide 54. The lubricant is a solid lubricant
comprising a powder of carbon, talc, molybdenum
disulfide and so on. The lubricant S that falls from
the lubricant feeder 59 into the cylindrical portion 56
. ~ ~
~Z~ 2~
-
adheres to the surface of the optical fiber when passing
therethrough.
When the coi]. of tube 5 into which the optical
fiber 7 has been inserted is vibrated, the optical fiber
7 immediately ahead of the tube 1 may swing wildly. The
swinging optical fiber 7 may impede smooth vibration and
passing thereof and, at the same time, may damage the
surface thereof on coming in contact with the edge of
the inlet end 2 of the tube 2. When the swing is very
wild, even cracks may occur inside the optical fiber.
But the anti-vibrating guide 54 keeps down the swing
outside the end of the tube 1, thereby allowing the
optical fiber 7 to be conveyed in good condition,
without damaging the optical fiber 7 and offering no
resistance to the vibration and passing thereof.
A separately prepared protective guide 61 is
fastened to the inlet end of the tube 1, as shown in
Fig. 6. The protective guide 61 is made of such
material as plastic that has a low coefficient of
friction and provided with a tapered guide 62 having an
outwardly diverged surface.
The optical fiber 7 passed through the coiled tube 1
by the vibration of the tube 1 may move forward while
bumping against the inlet end 2 of the tube 2 because
the optical fiber 7 is also vibrating. Then, the edge
B of the inlet end 2 of the tube may produce ~
longitudinal scratches on the optical fiber 7~Y~ may
~2~
cause the cracking of the optical fiber 7 and the deterioration of
a final product. But the pro-tective guide 61 of the above-de-
scribed structure enables the optical fiber 7 to be readily
inserted into the tube 1 and smoothly carried forward therein,
without causing any surface defect or damage aE-ter insertion.
Next, a method of passing an optical fiber 7 through a
tube 1 using the above-described apparatus will be described.
In advance, a coil 5 is formed by winding a tube 1
around a bobbin 27, while an optical fiber 7, which consists of a
precoated element fiber, is wound around the feed spool 34. The
tube 1 need not always be wound around the bobbin 27 in a single
ring, but can be wound in mul-tiple rings. In a coil of multiple
rings, the first ring fits closely in a groove 30 cut around the
barrel 28 of the bobbin 27, but the second and subsequen-t rings
will fit in the recessed portion formed between turns of the tube
1 of the preceding ring. Then, the bobbin 27 carrying the wound
tube 1 is fastened on the vibrating table 14 in such a manner that
the axis of the coil coincides with the central axis C of the
vibrating table 14. The leading end of the optical fiber 7 pulled
out of the feed spool 34 is inserted through the protective guide
61 into the inlet end of the tube, after passing through the
support guide 43, optical fiber feed condition sensor 47 and
anti-vibrating guide 54. With the inlet end 2 of the tube being
positioned at the lowermost end of the the coil 5, the op-tical
fiber 7 is passed through the tube 1 substantially along the
tangent of the coil or tube 5.
In the beginning, after a length of the optical fiber 7
- 14 -
6g~
of 5 to 150 m is manually pushed into the coil of tube. After
this, the inner surface of the vibrating tube exerts adequa-te
conveying force to cause the op-tical fiber to steadily move for-
ward through the tube. The length of the pushed-in optical fiber
(i.e., the length of initial insertion) depends on the inside
diameter of the tube, outside diameter of the optical fiber, and
coefficient of friction between the optical fiber and the inner
wall surface of the tube. The insertion is readily achieved if
the optical fiber is inserted while vibrating the tube. To ensure
the smooth entry of the optical fiber into the tube, a certain
amount of clearance must be left between the optical fiber and
tube. The clearance should preferably be not less than 0.1 mm.
When the vibrating motors 21, 22 are started, the vib-
rating table 14 is subjected to a torque working around the
central axis C thereof and a force working therealong because of
the position and posture in which the vibrating motors 21, 22 are
placed as described previously. Consequently, a given point on
the vibrating motors 21, 22 vibrates in such a manner as to
- 15 -
LZ~
move along a helical H shown in Fig. 1. The vibration
is transmitted from the vibrating table 14 through the
fas-tening jigs31, bobbin 27 and coil of tube 5 to the
optical fiber 7.
The motion of the optical fiber varies with the
type of the vibration, properties of the optical fiber,
inside diameter of the tube and other parameters. The
optical fiber is considered to move forward through the
tube in the following manner.
As is shown in Fig. 7, the bo-ttom surface of the
inner wall of the tube is moving with a vibration V
centered on 0. While the angle of the vibration is 9,
the maximum acceleration is n times (n sin a > 1) the
acceleration g of gravity. The optical fiber is
assumed to contact the bottom surface of the inner wall
~U~ pitches L since it is hardly conceivable that the
optical fiber is in contact therewith throughout. A
point of contact is defined as a. The optical fiber is
released when the vertical downward acceleration of the
bottom surface of the inner wall becomes equal to g,
namely at a point of release Pl on a line of release Ql
The released optical fiber begins to jump at a speed vl
and an angle of projection 3. Meanwhile, a non-contact
point b moves differently from the point of contact a
since the optical fiber is not a rigid substance. The
vibration V does not produce as much lifting force as at
the point of contact a. After being released on the
16
~2~
line of release Ql' therefore, the op-tical fiber is
subjected to a depressing force resulting from the
motion of the point of contact a. Consequently, the
optical fiber falls onto a line of contact Q2 at another
point of contact bl that is different from the first
point of contact a. If the vibration V of the bottom
surface of the inner wall is in the rising direction,
the optical fiber continues to move upward until it is
released on the line of release Ql If the vibration V
is in the descending direction, the optical fiber first
drops to the lowermost point and then moves upward until
it is similarly released on the line of release Ql
Such a surging motion is repeated in each cycle or
several cycles of the vibration, whereby the optical
fiber is caused to move forward through the tube. The
most efficient way is such that the optical fiber begins
to jump upward the moment it touches the bottom surface
of the inner wall when the line of contact Ql agrees
with the line of release Q2.
Strictly speaking, friction, repulsion and other
phenomena occuring between the optical fiber and the
bottom surface of the inner wall of the tube must be
considered. If the jumping optical fiber comes ln
contact with the top surface of the inner wall of the
tube, the advancing motion thereof will naturally be
different.
When n sin ~ _ 1, the optical fiber will not jump,
17
but may slide forward depending on the condition of
friction between the optical fiber and -the bottom
surface of the inner wall of the tube.
As is obvious from the above, the optical fiber 7
is driven forward through the tube 1 by a component of a
force exerted by the inner wall of the tube 1 in the
circumferential direction of the coil of tube. Because
the axis of the coil of tube is in agreement with the
central axis C of the vibrating table 14, the optical
fiber 7 in the tube makes a circular motion about the
central axis C (a circular motion in the
counterclockwise direction P in the embodiment shown in
Fig. 2).
Reference is now made to Fig. 1 again.
When the helical vibration is transmit-ted through
the vibrating table 14 to the coil of tube 5, the
optical fiber 7 fed from the inlet end 2 of the tube
below the coil of tube 5 continuously moves forward
through the tube 1 under the influence of the Gonveying
force resulting from -the vibration. That is, the
B vibration of the coil of tube 5 moves 1~vaæ~ the
~ Po~
optical fiber 7 paid off from the feed spool 34~through
the support guide 43, optical fiber feed condition
sensor 47, anti-vibrating guide 54, protective guide 61,
inlet end 2 of the tube, coil-formed tube 1 and outlet
end 3 of the tube. Thus, the optical fiber 7 is passed
through the entire length of the coil of tube 5 in a
18
given time.
Any variation in the passing speed of the optical
fiber 7 affects the feed condition thereof at the
optical fiber level sensor 49, with the resulting change
in the feed condition being instantly detected by the
optical fiber level sensor 49. If the optical fiber
level sensor 49 senses that the optical fiber 7 is over-
stretched, a corresponding signal will be sent to the
drive motor 38 to increase the rotation speed of the
feed spool 34, thereby increasing the feed speed of the
optical fiber 7. If the excessive sagging of the
optical fiber 7 is sensed, the drive motor 38 will be
accordingly controlled to slow down the feed speed of
the optical fiber 7. In this way, any abnormal
condition in the forward travel of the optical fiber is
instantly sensed, corrected and returned to the normal
condition.
(Example)
To confirm the effect of this invention, optical
fibers were passed through steel tubes under the
following conditions (Table 1) using the apparatus shown
in Fig. 1. The result of passing are shown in Table 1.
(1) Specimens
Coils of steel tubes:
Seven types of steel tube coils prepared
by winding seven different steel tubes
ranging between o.8 mm and 2.0 mm in
19
2~
outside diameter and between 0.5 mm and
1.6 mm in inside diameter and having a
length of lO km regularly (in 10 to 20
rings) around steel bobbins having a
barrel diameter of 1200 mm.
Optical fibers:
Optical fibers, 0.4 mm in diameter, o~
silica glass (125 ~m in diameter) coated
with silicone resin.
(2) Vibrating conditions:
Because the numbers of rings were 10
(Coils Nos. 1 to ~ in Table 1) and 20
(Coil No. 7) on the steel tube coils
tested, vibrating conditions were
substantially the same at any point of
the tube.
Angle of vibration with respect to the
horizontal plane of the coil: 15 degrees
Frequency of vibration: 20 Hz
Vertical component of total amplitude:
1.25 to 1.55 mm
~ ~ ~ o o o o o o o
~1 .~ ~ . O ~ ~ O o
In 0 ~ ~ O ~ CO ~7 CO In u,
Ul 0 ~ 1
u~ ~r
~ ~ -
~ ~ -- - ----
o ~-
u~ ~
.
0 E~ ~ r
-~
-
ul ~
~ o o
o ~ r~
.,l rc ~ ~ - o o o o o o o
~ ~-rl ~ ~ u~ ~ o co t`
.,1 ~ ~ a.~ -- ~ ~ ,~
~-r
U ~ 1 H H
t~ ~ Q~
,~
u~
O 0-~1
~1 ~ ~E'.-I ~
.q ~, ~ Q,_ r~l ~ ~1 ~1 ~1 ~( ~1
.,1 ~ 0~ ~ .
~U 0
V~
~1 O
O ~ _~ ~ ~ ~r ~ er ~r
. -~
.~ ~.,R ~ o o o O O O O
E~ a o ~
._
s O O O O O O O
~ ~ O O O~O O O O
~ ~ O O O O O O O
a) o o o o o o o
..... __ . _ _
~ ~a ~
.,~ ~ U~ ~D 1` CO a~ ~ ~D
~ 0
~ ~ _ O O O O O
$ H a
_ u~ u)
.,, _ O O O o O O O
~ E~
. _ _ _
a~
.,1 ,_ c~ a~ o ~ D O
J~ ~ ~ O O
. o '~ ~
_ .
O ,~ ~ ~ ~ In ~ r~
Z
21
d~
. ~ .~` ,
The obtained results are shown in Table 1.
Figs. 8a and 8b show the vibrations of the bobbin in
Example No. 4 shown in Table 1. While the diagram of Fig. 8a
shows a condition in which the optlcal fiber is still not inserted
in the tube, another diagram of Eig. 8b shows a condition in which
1000 m of the optical fiber has been inserted in the tube. In
these diagrams, Av and AH respectively designate the vertical
and horizontal components of amplitude. As is obvious Erom Fig. 8
(b), a high-frequency component appeared in the vibration of the
coil when the optical fiber has been inserted in the tube. The
amplitudes were measured by an accelerometer attached to the
bobbin flange.
The test proved that optical fibers can be quite
smoothly passed through the entire length of steel tubes in the
desired periods of time. As is obvious from Table 1, optical
fibers can be satisfactorily inserted into tubes having such a
small diameter as 2 mm or under and such a large length as about
10 km. Even in such cases, the optical fibers passed through do
not deteriorate or get otherwise damaged.
Now other variations of the component parts of the em-
bodiment just described will be described in the following.
Similar parts are designated by similar reference characters, with
the description thereof omitted.
In this invention, a number o~ circular grooves 67
parallel to the flange 66 of a bobbin 64 may be provided as shown
in Fig. ga. Such grooves 67 need no-t be provided throughout the
whole circumference of the barrel 65. Ins-tead, grooves 67 and a
- 22 -
~L2~
smooth portion 68 may be provided in different portions thereof as
shown in Fig. 9b.
Smooth passing of an optical Eiber through a tube is
impracticable unLess the tube is kept in close contact with the
bobbin because precise transmission of vibration is not achieved
then. The tube readily clings to the barrel in the direction of
the barrel diameter, but not so in the direction of the barrel
axis. This is likely to entail a disturbance in vertical
vibra-tion.
In Fig. 10, the tube 1 coiled around the barrel of the
bobbin 27 is wrapped by a wide elastic belt 71 shown in Fig. 11.
The elastic belt 71 consists of a flat rubber belt 72 and flanges
73 integrally fastened to both ends thereof. The tube l is tight-
ly pressed in the direction of the diameter of the bobbin 27 by
fastening the bolts 75 passed through the bolt holes 74 provided
in the opposite flanges 73 with nuts 76 after the coil of tube 5
has been wrapped by the rubber belt 72. The tightening force of
the belt 72 can bç adjusted by turning the nuts 76.
Fig. 12 shows another means for fastening the coil of
tube 5 of the bobbin. A bobbin 79 has a slot 81 and
- 23 -
a plurality of stopper grooves 82 provided in each
flange 80 thereof as shown in Fig. 13. The elastic belt
consists of a rubber belt 84 having stopper rods 85, 86
fastened to both ends thereof. After the tube 1 has
been wound around the bobbin 79, the top and bottom ends
of one stopper rod 85 on the belt 84 are inserted in the
slots 81 in the top and bottom flanges. After the belt
84 has been wound around the tube 1, for example,
clockwise in such a manner that both ends thereof
overlap each other to some extent, the belt 84 is
fastened by inserting the top and bottom ends of the
other stopper rod 86 in an appropriate stopper groove
82. The elastic belt 84 thus keeps the tube 1 in close
contact with the barrel 83 of the bobbin 27, with the
tightening force thereof being adjusted by choosing a
stopper groove 82 in an appropriate position.
Fig. 15 shows still another means for fastening the
coil of tube to the bobbin 27. After the tube 1 has
been wound around the barrel of the bobbin 27 ~ in a
single or more rings), the tube 1 is fastended in
position by a adhesive tape 88 that is wrapped
therearound as illustrated. To ensure secure fastening,
the adhesive tape 88 is wrapped in a partially or fully
overlapped manner. Any kind of adhesive tape serves the
purpose so long as it has enough adhesive force to
tightly press the tube 1 wound around the barrel of the
bobbin 27 thereagainst and keep the tube 1 in such
24
~Z65~2;2
tightly pressed condition for a certain period of time.
B But the adhesive tape 88 should preferabl~ be of such
type as can be easily peeled off by hand when -the tube 1
is detached from the bobbin 27 after the optical fiber 7
has been passed therethrough. For example 7 gummed tape
is one of the most suitable adhesive tapes of such kind.
Any of the above-described fastening means keeps
the tube 1 in close contact with the barrel of the
bobbins 27, 79, thereby ensuring precise transmission of
the vibration of the bobbin 27, 79 to the tube 1 while
keeping to a minimum the freedom and wild vibration of
the tube 1. With the undesirable motion of the tube in
the direction of the bobbin axis and diameter thus
effectively held down, the optical fiber can be smoothly
and efficiently passed through the coil of tube. There
is yet another embodiment in which the tube is wound
around a bobbin that is circularly divided into two or
more segments. Then, the bobbin is expanded outward
from inside, using a hydraulic jack, link mechanism or
the like, thereby bringing the coil of tube into close
contact with the bobbin.
Fig. 16 shows another embodiment of the anti-
vibrating guide. The guide cylinder proper 91 of an
anti-vibrating guide 90 has a heavier wall thickness.
The guide ends 92 are rounded off to leave no angular
corners thereat. The anti-vibrating guide is of course
not limited to the illustrated embodiments, but may be
8~:
of any shape and structurè so long as no damage is
caused to the optical fiber at the inlet end 2 of the
tube.
Fig. 17 shows another embodiment of the protective
guide. Instead of attaching a separate protective
guide, the inlet end 2 of the tube itself may be
expanded to form a larger-diameter portion 94 as shown
in Fig. 17. This embodiment ~ill also produce similar
results.
A pair of rollers covered with sponge or other
cushioning material or a piece of cushioning material
that may hold the optical fiber in such manner as not
to impede the smooth travel thereof may be provided near
the inlet end of the tube as the protective guide.
The number of optical fiber to be passed through a
tube is not limited to one. A plurality of optical
fibers may be passed through if the relationship between
the inside diameter of the tube and the diameter of the
optical fiber 7 allows.
This invention is of course not limited to a
combination of the optical fiber consisting of a
precoated element fiber and the steel tube used in the
embodiments described hereinbefore. Many other
variations are possible, such as those in which an
optical fiber or cable is passed through tubes if
aluminum, synthetic resin or other materials. The
optical fiber passed through the tube may be subjected
26
6~2~
to a processing that reduces the cross-sectional area
thereof. Other appropriate modifications may be
introduced as required. The optical fiber may be fed
from the top of the coil of tube. The central axis of
the coil of tube should preferably agree with the
B central axis of the heli~, though such agreement is
not an absolute requisite. The central axis of the coil
of tube should preferably be vertical, but need not
always be so. For initial insertion o~ the optical
fiber, pinch rollers or other mechanical means may be
used instead of ~
27
