JP4018247B2 - Method for connecting rod-shaped bodies and method for manufacturing optical fiber preform - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for connecting rod-like bodies with a connecting shaft pin and a method for manufacturing an optical fiber preform using the same.
[0002]
[Prior art]
In order to manufacture an optical fiber preform (a so-called transparent optical fiber preform after sintering), first, an optical fiber preform (so-called porous material before sintering) once formed of a porous glass fine particle laminate by the VAD method or the like. Quality soot preform), and it is necessary to make it transparent by sintering.
[0003]
For example, as shown in FIG. 6, this sintering is performed by using a sintering apparatus 10 including a heating furnace in which a heating unit 12 such as an electric heater is installed on the outer periphery of a furnace core tube 11 (muffle). A pre-sintered optical fiber preform (soot preform) 20 made of a body is inserted into the core tube 11 and heated in a heat zone.
[0004]
During this sintering, the dummy rod 30 connected to the optical fiber preform 20 is usually held by a chuck 15 attached to the tip of an arm 14 extending from a traverser 13 that is movable in the vertical direction of the sintering apparatus 10. On the other hand, the optical fiber preform 20 is inserted while being appropriately rotated by another rotating means (not shown) and heated.
[0005]
Therefore, for example, as shown in FIG. 7, a method of manufacturing an optical fiber preform in which a dummy rod 30 is suspended by interposing a hanging rod 40 between the sintering device 10 and the chuck 15 has been proposed. That is, while providing the cylindrical connection part 41 in the lower end part of the hanging rod 40 and letting the connection holes 42 and 42 penetrate through the connection part 41 in the horizontal direction, the upper end part of the dummy rod 30 also extends in the horizontal direction. In this method, the connecting hole 31 is penetrated, the connecting shaft pin 50 is inserted into each of the connecting holes 42, 42, 31 and the dummy rod 30 is suspended.
[0006]
According to this method, the length of the dummy rod 30 can be shortened by using the suspension rod 40 in combination, and the handleability is improved. Usually, the dummy rod 30 is made of high-purity quartz glass. Since the dummy rod 30 can be reused, there are advantages such as a reduction in the amount of wasted quartz glass used, and at the same time, the connecting shaft pin 50 can be easily and easily connected. There are also benefits.
[0007]
[Problems to be solved by the invention]
However, when the connecting hole 31 is drilled in the upper end portion of the dummy rod 30, it is difficult to drill with a high degree of horizontality. For example, as shown in FIG. The actual hole formation direction may be shifted.
If there is a deviation in the direction in which the connection hole 31 is formed in this way, the dummy rod 30 and the optical fiber preform suspended by the connection shaft pin 50 cannot be suspended vertically but are inclined.
[0008]
If the suspended dummy rod 30 and the optical fiber preform are inclined as described above, for example, when they are rotated in the above-described sintering, rotation blur occurs, and the optical fiber preform is heated by the sintering. Since it softens itself, it tends to sag downwards and bends easily. In this way, when the transparent optical fiber preform is bent, the eccentricity of the core portion becomes larger or smaller during subsequent spinning, so that the so-called eccentricity is deteriorated, etc. The transmission characteristics as a fiber are deteriorated.
[0009]
The present invention has been made in view of such circumstances, and firstly, while providing a method for connecting a rod-like body substantially vertically by a connecting shaft pin, this method is used for sintering an optical fiber preform. An optical fiber preform manufacturing method applied to spinning or the like is provided.
[0010]
[Means for Solving the Problems]
The present invention according to claim 1 is a method of connecting a rod-like body in which a connecting shaft pin is inserted into a connecting hole opened in a horizontal direction of the rod-like body and the rod-like body is suspended, and the contact of the connecting hole with the connecting shaft pin According to another aspect of the present invention, there is provided a method for connecting rod-shaped bodies, wherein a protruding portion is provided on a surface so that the rod-shaped bodies are suspended substantially vertically by making line or point contact with the connecting shaft pin.
[0011]
According to a second aspect of the present invention, there is provided a method of manufacturing an optical fiber preform in which a connecting shaft pin is inserted into a connecting hole opened in a horizontal direction of a dummy rod having an optical fiber preform connected to the lower end thereof, and the dummy rod is suspended. The light is characterized in that a projection is provided on a contact surface of the connection hole with the connection shaft pin so that the dummy rod is suspended substantially vertically by making a line or point contact with the connection shaft pin. A method for manufacturing a fiber preform.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an example of a connection system for carrying out the method of manufacturing an optical fiber preform according to the present invention. The connection system is basically the same as the connection system of FIG. Are denoted by the same reference numerals.
[0013]
In the present invention, for example, an unsintered optical fiber preform (soot preform) is connected to the lower end of the connecting portion 41 of the rod 40 for suspension (which can be a bifurcated shape such as an inverted U shape). The upper end portion of the dummy rod 30 (corresponding to a rod-like body) is fitted, and the connecting holes 31, 42, 42 are aligned and communicated. In this state, the connecting shaft pin 50 is inserted and connected.
[0014]
Here, both the hanging rod 40 and the dummy rod 30 are made of quartz glass or the like, and in particular, when forming the connecting hole 31 of the dummy rod 30, as a taber-like (conical shape) hole from the left and right in the horizontal direction. A projecting portion 32 made of a ridge line which is drilled and is raised in a conical shape just at the center of the hole is provided. The projecting shape of the projecting portion 32 is not limited to this raised ridge line, and may be formed by a simple projection consisting of a portion left uncut in the hole, or a separate fulcrum inside the hole. You may form by mounting | wearing a protrusion piece.
[0015]
Further, the connecting shaft pin 50 has a handle portion (operation portion) 52 at one end of the shaft portion 51, and a mark M indicating the insertion depth position is provided near the handle portion of the shaft portion 51. Good.
[0016]
In any case, due to the formation of the protruding portion 32 in the connecting hole 31 of the dummy rod 30, the connecting shaft pin 50 is exactly aligned with the protruding portion 32 on the contact surface side (upper surface side in the figure) of the protruding portion 32. Therefore, even if there is a slight error in the formation accuracy of the connecting hole 31, the dummy rod 30 is suspended substantially vertically.
[0017]
For example, as shown in FIG. 2, when forming a taber-shaped connecting hole 31 having a 10 ° inclined surface (dashed line in the figure) of the dummy rod 30 from the left and right in the horizontal direction, a 9 ° inclined surface ( Even if a solid line in the figure is formed (formation error = 1 °), the deflection of the lower end portion of the dummy rod 30 can be suppressed to be considerably small in the case of the connecting hole 31 having the protruding portion 32. For example, if the dummy rod 30 has a total length of 2000 mm, an outer diameter of 30 mm, and a simple connection hole without a protrusion, when the hole formation error is about 1 °, the deflection of the lower end of the dummy rod 30 is about 30 mm. However, the connecting hole 31 having the protrusion 32 in FIG. 2 can be suppressed to about 3.40 mm, and the width of deflection can be reduced to about 1/9.
[0018]
That is, in the case of a simple connecting hole 31 without a projecting portion, as shown in FIG. 8 above, when the actual hole forming direction is deviated from the horizontal line H by an angle θ and the value is small, 3, the connecting shaft pin 50 is supported at two points on the upper surface side (between points A and B) of the connecting hole 31, and the deflection of the lower end portion of the dummy rod 30 at this time is the dummy rod 30. When the total length of L is L, it is approximately represented by L sin θ.
[0019]
However, when the deviation angle θ ′ is large, the dummy rod 30 is supported by only one point (point A) on the upper surface side of the connection hole 31 with respect to the connection shaft pin 50 as shown in FIG. At this time, assuming that the center of gravity 30a of the dummy rod 30 is at the midpoint on the central axis, that is, the position of L / 2, and the outer diameter of the dummy rod 30 is D, the center of gravity 30a is shifted by D / 2 and the supporting point. Come under (point A). For this reason, the deflection at the lower end portion of the dummy rod 30 is twice that of D. The critical value of θ ′ at which this deflection becomes D is represented by θ′th = sin ⁻¹ D / L.
[0020]
Therefore, as described above, when the total length of the dummy rod 30 is 2000 mm and the outer diameter is 30 mm, θ′th = 0.86 °. Therefore, when the hole deviation (formation error) is about 1 °, One point is supported at the point A of the hole 31, and the deflection of the lower end portion of the dummy rod 30 is about D = 30 mm.
[0021]
On the other hand, in the case of FIG. 2 described above, even if the hole shift (formation error) is about 1 °, the position of the protruding portion 32 inside the hole is shifted only about 1.70 mm from the central axis. Therefore, the deflection of the lower end portion of the dummy rod 30 is only about 3.40 mm, which is twice that, and as described above, it is 3.40 / 30 compared to the case of the simple connecting hole 31 without the protruding portion. It can be seen that this is reduced to about 1/9.
[0022]
FIG. 2 shows another example of a connection system for carrying out the method of manufacturing an optical fiber preform according to the present invention, which is basically the same as the connection system of FIG. In this example, while providing the protrusion part 43 in the connection hole 42 of the lower end side of the rod 40 for suspension (what is corresponded to a 1st rod-shaped body), it is the dummy rod 30 (what is corresponded to a 2nd rod-shaped body). A connecting portion 33 having a cylindrical shape (a bifurcated shape such as an inverted U shape is also possible) is provided on the side, and connecting holes 31 and 31 are provided in the connecting portion 33 and are connected by a connecting shaft pin 50. Also in this case, substantially the same operation and effect as in the case of FIG. 1 can be obtained.
[0023]
In each of the above embodiments, the first rod-shaped body is the hanging rod 40 and the second rod-shaped body is the dummy rod 20, but the present invention is not limited to this, and the second rod-shaped body is Of course, the present invention can be applied to other general uses that hang vertically. In addition, when the protruding shapes of the protruding portions 32 and 43 are configured other than the conical raised ridge line, the connecting shaft pin 50 can be brought into point contact with the protruding portion 32.
[0024]
【The invention's effect】
As is clear from the above description, according to the connecting method of the rod-shaped body and the manufacturing method of the optical fiber preform according to the present invention, the following excellent effects can be obtained.
[0025]
(1) First, in the first or second aspect, when connecting the rod-shaped body or the dummy rod to which the optical fiber preform is connected by the connecting shaft pin, there is some molding error in the connecting hole at the upper end, Even if the body or the dummy rod itself is slightly bent, it can be connected substantially vertically by the line or point contact between the protruding portion of the connecting hole and the connecting shaft pin, and can be suspended.
[0026]
(2) Next, in Claims 3 to 4, the dummy rod in which the optical fiber preform is connected to the lower end of the first rod-shaped body and the upper end of the second rod-shaped body and the lower end of the suspension rod Are connected by the connecting shaft pin, there is some molding error in the connecting hole in the lower end of the first rod-like body and the lower end of the hanging rod, or the second rod-like body and the dummy rod itself are slightly bent. Even if there exists etc., it can connect substantially vertically and can hang down by the line or point contact of the protrusion part of a connection hole, and a connection shaft pin.
[0027]
(3) Moreover, in any one of Claims 1-4, it can be connected and cancel | released easily and rapidly by insertion and extraction of a connecting shaft pin, and favorable workability | operativity is obtained.
[0028]
(4) In any one of claims 1 to 4, since a certain amount of formation error is allowed in forming the connecting hole, the connecting hole can be easily formed.
[0029]
(5) Particularly in the second and fourth aspects, since the dummy rod to which the optical fiber preform is connected can be connected substantially vertically and suspended, the rotational blurring of the optical fiber preform can be minimized. be able to. As a result, since the bending of the transparent optical fiber preform is effectively suppressed, an optical fiber having good transmission characteristics can be obtained with little deterioration of the eccentricity during subsequent spinning.
[Brief description of the drawings]
FIG. 1 is a partially enlarged longitudinal sectional view showing a connecting portion between a hanging rod and a dummy rod as an example of a method for manufacturing an optical fiber preform according to the present invention.
2 is a partially enlarged schematic explanatory view showing a formation state of a connecting hole of a dummy rod in FIG. 1. FIG.
FIG. 3 is a schematic explanatory view showing a formation state of a connection hole of a normal dummy rod and a deflection of the dummy rod.
FIG. 4 is a schematic explanatory view showing another formation state of a connection hole of a normal dummy rod and the deflection of the dummy rod.
FIG. 5 is a partially enlarged longitudinal sectional view showing a connecting portion between a hanging rod and a dummy rod, which is another example of the method for manufacturing an optical fiber preform according to the present invention.
FIG. 6 is a schematic explanatory view showing a sintering apparatus system for an optical fiber preform.
7 is a partial longitudinal sectional view showing a connecting portion between a hanging rod and a dummy rod in the optical fiber preform sintering apparatus system of FIG. 6;
8 is a partially enlarged longitudinal sectional view showing a connection hole formed in the dummy rod of FIG.
[Explanation of symbols]
30 dummy rod (second rod)
31 connecting hole 32 projecting portion 33 connecting portion 40 hanging rod (first rod-like body)
41 connecting portion 42 connecting hole 43 protruding portion 50 connecting shaft pin

Claims (2)

In the connecting method of the rod-shaped body in which the connecting shaft pin is inserted into the connecting hole opened in the horizontal direction of the rod-shaped body and the rod-shaped body is suspended, a protrusion is provided on the contact surface of the connecting hole with the connecting shaft pin, A method for connecting rod-like bodies, wherein the rod-like bodies are suspended substantially vertically by making line or point contact with a connecting shaft pin. In the manufacturing method of an optical fiber preform in which a connecting shaft pin is inserted into a connecting hole opened in a horizontal direction of a dummy rod having an optical fiber preform connected to the lower end and the dummy rod is suspended, the connecting shaft pin of the connecting hole and A manufacturing method of an optical fiber preform characterized in that a protrusion is provided on the contact surface of the optical fiber so that the dummy rod is suspended substantially vertically by making a line or point contact with the connecting shaft pin.

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