JP2599512B2 - Optical fiber soot synthesizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber soot synthesizing apparatus for synthesizing an optical fiber soot on the outer periphery of a seed rod.

[0002]

2. Description of the Related Art In the structure of an optical fiber, a core is provided at the center and a clad surrounds the core.
In the production of such an optical fiber, first, a core portion is made by a VAD method, this is transparently vitrified into a seed rod, and an optical fiber soot is obtained by synthesizing a clad portion around the seed rod. The optical fiber soot is transparently vitrified to obtain an optical fiber preform, and the optical fiber preform is drawn.

Conventionally, an optical fiber soot has been manufactured as shown in FIG.
Alternatively, this was performed by the optical fiber soot synthesis apparatus shown in FIG.

The optical fiber soot synthesizing apparatus shown in FIG. 10 comprises seed rod supporting mechanisms 4a and 4b for rotating both ends of a seed rod 1 while horizontally supporting them on chucks 2a and 2b on rotating shafts 3a and 3b, respectively. A soot synthesizing burner 6 which is arranged opposite to a part of the peripheral surface of the rod 1 and synthesizes an optical fiber soot 5 on the outer periphery of the seed rod 1; and the burner 6 while rotating the seed rod 1 around its axis. And a soot synthesizing rotation / reciprocation drive mechanism 7 which reciprocates relatively with respect to.

[0005] The seed rod support mechanisms 4a and 4b are provided with a common bed 8, a rail 9 installed on the bed 8 in a direction parallel to the seed rod 1, and a bearing 10 for each of the rotating shafts 3a and 3b.
The brackets 11a, 11b, which are rotatably supported via the rails 9a and 10b, are guided by the rail 9, and simultaneously reciprocate in the same direction.
11b.

The soot synthesizing rotary / reciprocating drive mechanism 7 includes base members 12a, 12b of the brackets 11a, 11b.
Nut members 13a, 13b provided integrally with the nuts, a screw shaft 14 provided in parallel with each of the rotating shafts 3a, 3b and screwed to each of the nut members 13a, 13b, and rotating the screw shaft 14 The brackets 11a, 1
A seed rod reciprocating motor 15 for reciprocating the seed rod 1 with respect to the soot synthesizing burner 6 via the rotary shafts 3a, 3b and the like as described above, and a screw shaft 16 provided in parallel with the screw shaft 14. And the rotational force of the screw shaft 16 is
a, 3b for transmitting torque to the members a, 3b;
It comprises a seed rod rotating motor 18 which rotates the seed rod 1 around its axis by rotating the screw shaft 16 via each of the rotating shafts 3a, 3b and the like.

That is, this optical fiber soot synthesizing apparatus
With the soot synthesizing burner 6 fixed, the seed rod 1 is reciprocated at a position facing the soot synthesizing burner 6 while being rotated around the axis thereof by the soot synthesizing rotation / reciprocation drive mechanism 7. The optical fiber soot 5 is synthesized around the seed rod 1 by the soot synthesizing burner 6.

In the optical fiber soot synthesizing apparatus shown in FIG. 11, the parts corresponding to those in the apparatus shown in FIG. The optical fiber soot 5 is synthesized on the outer periphery of the seed rod 1 while rotating the soot synthesizing burner 6 reciprocally along the longitudinal direction of the seed rod 1 while rotating around the heart.

The factors that affect the quality of an optical fiber include the fact that the ratio between the core diameter and the clad diameter is constant in the longitudinal direction and the concentricity between the core and the clad is high. The quality of these is determined at the time of combining the optical fiber soot 5 . That is, unless the clad weight with respect to the core weight and the position of the center of gravity are managed, a high-quality optical fiber cannot be produced. At present, the weight is controlled by a signal of a mass flow controller (MFC) of a source gas supply system and a synthesis time.

Since the method of managing the weight or the position of the center of gravity of the optical fiber soot 5 is not very accurate, the weight of the optical fiber soot 5 after completion of the synthesis is measured with a platform scale.

[0011]

However, in such a conventional method, the rate at which a product satisfying the target accuracy can be obtained is about 80%. If less than the target weight,
Returning to the device again, the shortage is additionally synthesized, and when the weight is larger than the target weight, the excess is removed by a glass lathe, so the correction work is troublesome and the optical fiber soot 5 is damaged during the correction work In many cases, productivity was poor.

Therefore, it has been proposed to measure the weight of the optical fiber soot 5 online during its synthesis (Japanese Patent Laid-Open No. 63-144139). However, the weight of the entire main part of such a device can be hundreds of kilograms, so a highly rated weight detector must be used, and unless a very accurate measuring device is used, an accuracy of 100 g can be obtained. However, it is difficult to obtain the same, and a major remodeling of the device is required, which is not practical.

An object of the present invention is to provide an optical fiber soot synthesizing apparatus capable of measuring the weight or the position of the center of gravity of an optical fiber soot with high accuracy during synthesis.

[0014]

In order to achieve the above object, the present invention will be described. The present invention relates to a seed rod for rotating both ends of a seed rod horizontally while being supported by a rotary shaft via chucks. A support mechanism, a soot synthesizing burner that is disposed opposite to a part of the peripheral surface of the seed rod and synthesizes an optical fiber soot on the outer periphery of the seed rod, and the soot while rotating the seed rod around its axis. A soot synthesis rotation / reciprocation drive mechanism for reciprocating either the soot synthesis burner or the seed rod so as to change the longitudinal positional relationship of the seed rod facing the burner; and An optical fiber soot synthesizing apparatus for synthesizing the optical fiber soot with the burner on the outer periphery of the seed rod while changing the positional relationship in the longitudinal direction of the seed rod facing the burner while rotating around the axis. The rotating shaft is divided into a driving shaft portion and a driven shaft portion, and the driving shaft portion and the driven shaft portion are mutually separated by rotation transmitting means for absorbing the displacement of the shaft of the driven shaft portion at each of the divided portions. A soot weight detection sensor is provided at a position where the weight of the optical fiber soot is connected to each of the driven shafts.

[0015]

In this manner, the rotary shafts on both sides are divided into a drive shaft portion and a driven shaft portion, and the divided portions are mutually connected by a rotation transmitting means for absorbing the displacement of the shaft of the driven shaft portion, for example, a universal joint. If soot weight detection sensors are provided at locations where the weight of the optical fiber soot is connected on each driven shaft side, the total weight of these soot weight detection sensors can be reduced as compared with the conventional one, The soot weight can be accurately detected. As a result, it is practically possible to measure the weight of the optical fiber soot online during the synthesis thereof, and the weight accuracy of the optical fiber soot can be greatly increased.

Further, the position of the center of gravity of the optical fiber soot can be calculated from the ratio of the weight distributed to the left and right of the seed rod and the amplitude of the load variation. Is detected and the blowout amount of the soot synthesizing burner is controlled to return the center of gravity to the center of the optical fiber soot.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. Parts corresponding to those in FIGS. 10 and 11 are denoted by the same reference numerals.

FIGS. 1 and 2 show a first embodiment of the optical fiber soot synthesizing apparatus according to the present invention. In the optical fiber soot synthesizing apparatus of this embodiment, each of the rotating shafts 3a,
3b is a drive shaft portion 3ak, 3bk and a driven shaft portion 3a, respectively.
j, 3bj. These drive shaft portions 3a
k, 3bk and the driven shaft portions 3aj, 3bj are provided with a universal joint 19 as a rotation transmitting means for absorbing the displacement of the shafts of the driven shaft portions 3aj, 3bj at the divided portions.
a and 19b. Accordingly, the brackets 11a and 11b of the seed rod support mechanisms 4a and 4b are divided into driving-side brackets 11ak and 11bk and driven-side brackets 11aj and 11bj. The drive shaft portions 3ak and 3bk and the driven shaft portions 3aj and 3bj are respectively connected to the drive side bearing portions 1ak and 11bk and the driven side bracket portions 11aj and 11bj.
It is rotatably supported via 0ak, 10bk and driven side bearings 10aj, 10bj. Each drive shaft 3a
k and 3bk are configured to transmit torque from the torque transmitting members 17a and 17b. The drive side bracket portions 11ak and 11bk are installed on the base members 12a and 12b. Driven bracket portions 11aj, 11
bj is the base member 12 via the soot weight detection sensors 20a and 20b, each of which is composed of, for example, a 50 kg rated load cell.
a, 12b. The driven-side bracket portions 11aj and 11bj are supported by the driven-side bracket portion vertical movement permitting mechanisms 21a and 21b composed of linear guides so as to be able to move up and down. Each of the driven side bracket portion vertical movement allowing mechanisms 21a, 21b is provided with a guide rail 22a, 22.
b, which are guided by the guide rails 22a, 22b so as to be able to move up and down, so that the driven side brackets 11aj, 11
bj supporting lifting members 23a and 23b. At the end of the drive shaft 3ak, the drive shaft 3a
A rotary encoder 24 for detecting the rotation angle of k is provided.

FIGS. 3A and 3B show an example of the universal joints 19a and 19b.

When the synthesis of the optical fiber soot 5 is performed using such an optical fiber soot synthesis apparatus, as the synthesis progresses and the weight of the optical fiber soot 5 increases, the deformation of the soot weight detection sensors 20a and 20b formed of load cells. As a result, the driven side bracket portions 11aj and 11bj are slightly displaced in the vertical direction. At that time, the drive shaft portions 3ak, 3b
The center between k and the driven shaft portions 3aj and 3bj is shifted by several tens of μm. However, the drive shafts 3ak and 3bk and the driven shaft 3a
j, 3bj are universal joints 19a, 19
Since they are connected by b, the displacement does not hinder rotation, and the drive shafts 3ak and 3bk do not bear a part of the load to be applied to the soot weight detection sensors 20a and 20b. Therefore, accurate weight measurement can be performed while synthesizing the optical fiber soot 5. In addition, a force other than gravity is applied to the driven side bracket portion 11a.
Even when it is applied to j and 11bj, it is supported by the driven-side bracket portion vertical movement allowing mechanisms 21a and 21b so as not to move except in the vertical direction, so that the driven-side bracket portions 11aj and 11bj are subjected to forces other than gravity. There is no displacement.

A method for calculating the weight or the position of the center of gravity with this device will be described with reference to FIGS. 4 (a) to 4 (d). When the seed rod 1 is mounted between the chucks 2a and 2b and operated at a rotation speed N, the two soot weight detection sensors 20
a, 20b, load signals Wa (θ), Wb (θ) that repeatedly increase and decrease in synchronization with the rotation speed N of the drive shafts 3ak, 3bk.
Is detected. Here θ, the drive shaft portion 3AK, Ru rotation angle der of 3Bk. For example, the direction directly under the seed rod 1 to <br/> Direction of theta = 0. The causes of the fluctuations of the load signals Wa (θ) and Wb (θ) are the bending of the drive shafts 3ak and 3bk and the displacement between the centers of the drive shafts 3ak and 3bk and the driven shafts 3aj and 3bj. It can be reduced to some extent, but not completely.

Hereinafter, a method of removing an error caused by the mechanical accuracy will be described. The load signals Wa (θ), Wb
The change in (θ) is independent of the change in weight of the optical fiber soot 5 and remains unchanged unless the seed rod 1 is replaced or the device is readjusted. Therefore, load signals Wa (θ) and Wb, which are outputs of the two soot weight detection sensors 20a and 20b, respectively.
(Θ) Sum value Wnt (θ) = Wa (θ) + Wb (θ)
That is, the error due to the mechanical accuracy is measured before synthesizing the optical fiber soot 5, and the relationship between θ and Wnt (θ) is shown in FIG.
Record as shown in (a).

Thereafter, when the synthesis of the optical fiber suit 5 is started, during the synthesis of the optical fiber suit 5, a sum value Wrt (θ) different from that before the synthesis is obtained as shown in FIG. Can be Now determine the difference between Wnt (theta) and Wrt (theta), the true fluctuating load signal to remove errors coming from the mechanical accuracy ^{W * (θ) = W rt} (θ) -W nt (θ) It can be obtained as shown in FIG.

The thus obtained variable load signal W ^* (θ)
Is the sum of the weight of the optical fiber soot 5 and the vertically downward component of the whirling centrifugal force due to the eccentricity of the center of gravity. this

[0025]

^* (Θ) = ^* + ^* cos (θ−α)

By approximation by the following equation, the variable load signal W
^* The center value of the fluctuation of (θ) is 1 outside the weight, and the amplitude is 2 outside the centrifugal force.

[0027]

[Outside 1]

[0028]

[Outside 2]

Further, the phase angle α of the eccentricity of the optical fiber soot 5 can be obtained.

The amount of eccentricity R of the center of gravity G is represented by the relationship of centrifugal force = (mass) × (radius) × (angular velocity) ² , that is,

[0031]

^* = ( ^* / G) · R · (2πN) ² g: gravity acceleration

From

[0033]

R = ( ^* · g) / [ ^* · (2πN) ² ]

Can be obtained as

The two soot weight detecting sensors 20
If the ratio of the temporal average value of the load shared by the a and 20b is taken, the ratio of the average value is taken as shown in FIG. 4D as follows: L: M = (measured value of the right sensor 20a) From the left sensor 20b to the center of gravity G from L + M = (interval between two sensors 20a and 20b) (2) And the distance L of
The distance M from the right sensor 20a to the center of gravity G is known,
The position of the center of gravity G can be obtained.

The above data processing is performed at a high speed by a computer. When the optical fiber soot 5 is manufactured, the members on the bed 8 traverse left and right, but since the speed is slow, even when the direction is changed, this measurement is hardly affected. When this device was used, the total number was within ± 50 g of the target weight. The position of the center of gravity was controlled within 2 mm in the radial direction and within 5 mm in the longitudinal direction from the center.

FIG. 5 shows the driven side bracket portions 11aj, 1
This shows another example of the driven-side bracket portion vertical movement allowing mechanisms 21a and 21b that allow the vertical movement of 1bj. In this case, the driven side bracket portion vertical movement allowing mechanism 21a, 2
Reference numeral 1b denotes frames 25a, 25b erected on the base members 12a, 12b, and one end of each of the frames 25a, 25b rotatably supported by the shafts 27a, 27b, and the driven side brackets 11aj, 11bj at the other end. The supporting rotary arms 26a and 26b are formed in a hinge shape.

According to the hinge type driven side bracket portion vertical movement permitting mechanisms 21a and 21b, the height of the apparatus can be reduced.

FIG. 6 shows the driven side bracket portions 11aj, 1
This shows still another example of the driven-side bracket portion vertical movement allowing mechanisms 21a and 21b that allow the vertical movement of 1bj. In this case, the driven side bracket portion vertical movement allowing mechanism 21
a and 21b are frames 25a and 25b erected on the base members 12a and 12b, and the frames 25a and 25b.
b, the center side is rotatably supported by shafts 27a and 27b, one end supports the driven side bracket portions 11aj and 11bj, and the other end supports the balance weights 28a and 28b. It is configured.

According to the driven side bracket portion vertical movement allowing mechanisms 21a and 21b, the balance weight 28
a, 28b, soot weight detection sensor 20a,
The resolution and accuracy of the measurement can be improved by reducing the rating of 20b. In this case, the balance weights 28a, 28a,
Distance to the center of gravity of 28b is 250mm, balance weight 2
8a and 28b weighed 25 kg. As a result, the rating of the soot weight detection sensors 20a and 20b is reduced to 10
kg, and the measurement accuracy has been improved to ± 10 g with respect to the target weight.

FIG. 7 shows the driven side bracket portions 11aj, 1
This shows still another example of the driven-side bracket portion vertical movement allowing mechanisms 21a and 21b that allow the vertical movement of 1bj. In this case, the driven side bracket portion vertical movement allowing mechanism 21
a and 21b are guide rails 22a and 22b provided on side surfaces of frames 25a and 25b erected on the base members 12a and 12b, and the guide rails 22a and 2b.
Elevating member 23 which is guided by 2b so as to be able to move up and down and supports driven side bracket portions 11aj and 11bj.
a, 23b, adjusting screws 36a, 36b threaded through horizontal brackets 35a, 35b at the upper ends of the frames 25a, 25b, and a driven side bracket 11a.
j, 11bj, spring receiving arms 37a,
37b, adjusting screws 36a, 36b and spring receiving arm 3
7a, 37b, tension springs 38a,
38b and an adjusting nut 39 screwed to the adjusting screws 36a and 36b to adjust the tension of the tension springs 38a and 38b.
a and 39b.

Even with the driven side bracket portion vertical movement allowing mechanisms 21a and 21b, the tension springs 38a and 38b
, The rating of the soot weight detection sensors 20a and 20b can be reduced, and the resolution and accuracy of measurement can be improved.

In this case, the tension springs 38a and 38b have a total length of 150 mm and a spring constant of 5000 N / m, and the tension can be adjusted by adjusting screws 36a and 36b.
The total weight of the driven shaft portions 3aj and 3bj and the driven side bracket portions 11aj and 11bj was 38 kg.

Using this apparatus, 3 kgf is applied to the soot weight detection sensors 20a and 20b before the seed rod 1 is attached.
After adjusting the tension of the tension springs 38a and 38b so as to apply the load, the soot weight at the time of combining the optical fiber soot 5 is adjusted and the tension of the tension springs 38a and 38b is adjusted. The soot weight at the time of synthesis of No. 5 was measured. In this case, since the tension springs 38a and 38b bear a part of the soot weight, the true weight was calculated by multiplying the output of the soot weight detection sensors 20a and 20b by a coefficient obtained by calibration. The value at the end of soot synthesis is
When compared with the value measured by another precision balance, the difference was a maximum of 7 g.

The soot weight detection sensors 20a, 20a
As a method for canceling the weight on b, other than the above, it is also possible to apply electromagnetic force, buoyancy, and the like.

FIG. 8 shows a second embodiment of the optical fiber soot synthesizing apparatus according to the present invention. The optical fiber soot synthesizing apparatus of the present embodiment applies the present invention to an apparatus of a type in which the optical fiber soot 5 rotates around its axis and the soot synthesizing burner 6 reciprocates in the longitudinal direction of the seed rod 1. FIG.

With such a structure, the overall length of the device can be shortened.

FIG. 9 shows an example of the universal joint 19a used in the apparatus of the second embodiment of the optical fiber soot combining apparatus according to the present invention shown in FIG. The universal joint 19a is
ak and the driven shaft portion 3aj are provided with a center member 29
ak, 29aj and the outer surrounding members 30ak, 30aj, respectively.
The grooves 31ak and 31a are provided at one location in the circumferential direction of k and 29aj.
j, and the center member 2 at the position of each groove 31ak, 31aj.
The spheres 32ak, 32aj are respectively interposed between 9ak, 29aj and the outer surrounding members 30ak, 30aj, and both center members 29ak, 29aj and the outer surrounding members 30ak, 3 are sandwiched between the spheres 32ak, 32aj.
Both ends of a common torque transmitting arc piece 33 are inserted into a space between the two members, and the outer periphery of each member is surrounded by a common cover 34. The other universal joint 19b has a similar structure.

As the rotation transmitting means for absorbing the displacement of the shaft of the driven shaft, a universal joint, a magnetic coupling, a fluid coupling or the like other than those shown in the above embodiment can be used.

[0050]

As described above, according to the optical fiber soot synthesizing apparatus of the present invention, the following effects can be obtained.

(A) The rotating shafts on both sides of the seed rod are divided into a driving shaft portion and a driven shaft portion, and the divided portions are connected to each other by rotation transmitting means for absorbing the displacement of the shaft of the driven shaft portion. Since a soot weight detection sensor is provided at a position where the weight of the optical fiber soot is applied on each driven shaft side,
The total weight applied to these soot weight detection sensors can be reduced as compared with the conventional one, so that the weight of the optical fiber soot can be detected with high accuracy. As a result, it is practically possible to measure the weight of the optical fiber soot online during the synthesis thereof, and the weight accuracy of the optical fiber soot can be greatly increased.

(B) The position of the center of gravity of the optical fiber soot can be calculated from the ratio of the weight distributed to the left and right of the seed rod and the amplitude of the load variation. Therefore, when an optical fiber soot whose center of gravity is not centered is manufactured, By detecting this and controlling the blowing amount of the soot synthesizing burner, the center of gravity can be returned to the center of the optical fiber soot.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of an optical fiber soot synthesis apparatus according to the present invention.
It is a longitudinal section showing an example.

FIG. 2 is a sectional view taken along line AA of FIG.

FIGS. 3A and 3B are a side view and a plan view of a universal joint used in this embodiment.

FIGS. 4A to 4D are explanatory diagrams showing an example of a method of obtaining a weight and a position of a center of gravity in the optical fiber soot synthesizing apparatus of the present invention.

FIG. 5 is a longitudinal sectional view showing another example of the driven side bracket portion vertical movement allowing mechanism used in the present embodiment.

FIG. 6 is a longitudinal sectional view showing another example of the driven side bracket portion vertical movement allowing mechanism used in the present embodiment.

FIG. 7 is a longitudinal sectional view showing another example of the driven-side bracket vertical movement allowing mechanism used in the present embodiment.

FIG. 8 shows a second embodiment of the optical fiber soot synthesis apparatus according to the present invention.
It is a longitudinal section showing an example.

FIG. 9 is a longitudinal sectional view showing an example of a universal joint used in the second embodiment.

FIG. 10 is a longitudinal sectional view showing an example of a conventional optical fiber soot synthesis apparatus.

FIG. 11 is a longitudinal sectional view showing another example of the conventional optical fiber soot synthesis apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Seed bar, 2a, 2b ... Chuck, 3a, 3b ... Rotary axis, 3ak, 3bk ... Drive shaft part, 3aj, 3bj ... Followed shaft part, 4a, 4b ... Seed rod support mechanism, 5 ... Optical fiber suit, 6 ... burner for soot synthesis, 7 ... rotation for soot synthesis
Reciprocating drive mechanism, 8: bed, 9: rail, 10a, 10
b: bearing, 10ak, 10bk: driving side bearing portion, 10a
j, 10bj: driven side bearing portion, 11a, 11b: bracket, 11ak, 11bk: driving side bracket portion, 11
aj, 11bj... driven side bracket portion, 12a, 12b
... Base member, 13a, 13b ... Nut member, 14 ... Screw shaft, 15 ... Single rod reciprocating motor, 16 ... Screw shaft, 17
a, 17b: rotational force transmitting member, 18: seed rod rotating motor, 19a, 19b: universal joint (rotation transmitting means for absorbing displacement of the shaft of the driven shaft), 20a, 20
b: soot weight detection sensor, 21a, 21b: vertical movement permitting mechanism of driven side bracket portion, 22a, 22b: guide rail, 23a, 23b: elevating member, 24: rotary encoder, 25a, 25b: frame, 26a, 26b ...
Rotating arm, 27a, 27b ... shaft, 28a, 28b ... balance weight, 29ak, 29aj ... central member, 30
ak, 30aj ... external surrounding members, 31ak, 31aj ...
Grooves, 32ak, 32aj: spherical body, 33: rotational force transmitting arc piece, 34: cover, 35a, 35b: horizontal bracket,
36a, 36b: adjusting screw, 37a, 37b: spring receiving arm, 38a, 38b: tension spring, 39a, 39
b ... Adjustment nut.

Claims (1)

(57) [Claims] A seed rod support mechanism for rotating both ends of the seed rod while horizontally supporting the both ends of the seed rod via a chuck with a rotating shaft;
A soot synthesizing burner that is arranged to face a part of the peripheral surface of the seed rod and synthesizes an optical fiber soot on the outer periphery of the seed rod, and faces the burner while rotating the seed rod around its axis. A soot synthesis rotation / reciprocation drive mechanism for reciprocating either the soot synthesis burner or the seed rod so as to change the longitudinal positional relationship of the seed rod, and An optical fiber soot synthesizing apparatus for synthesizing the optical fiber soot with the burner on the outer periphery of the seed rod while changing the longitudinal positional relationship of the seed rod facing the burner while rotating around the burner; Is divided into a drive shaft portion and a driven shaft portion, respectively, and the drive shaft portion and the driven shaft portion are connected to each other by rotation transmission means for absorbing the displacement of the shaft of the driven shaft portion at each of the divided portions, each Optical fiber soot synthesis apparatus characterized by soot weight detection sensors are provided respectively at positions weight of the optical fiber soot is applied at the shaft portion side.