JPH0244041A - Glass fiber spinning device - Google Patents

Abstract

PURPOSE:To reduce the eccentricity of core glass due to the nonuniformity of clad glass and the variance in the outer diameters of the core glass and fiber by providing a means for forcedly agitating the molten glass in the pots both in a core pot part and in a clad pot part. CONSTITUTION:The molten core glass 4 in the core pot 2 and the molten clad glass 5 in the clad pot 3 are rotated and agitated by a common agitator 20. An impeller 22 to be dipped in the core glass 4 is provided to the rotating shaft 21 of the agitator 20, a cylindrical clad glass stirrer 30 is fixed to the upper part of the rotating shaft 21, and the impeller part 36 of the stirrer 30 is dipped in the molten clad glass layer 5. The core glass 4 is agitated by the impeller 22, and the impeller part 36 is circularly moved along the shape of the clad pot 3 to agitate the molten clad glass 5. The glass is homogenized simultaneously with the agitation, and the core and clad glass having uniform viscosity are obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a glass fiber spinning device, and particularly for forming a glass fiber such as an optical fiber, which has a core glass portion and one or more clad glass layers surrounding it. The present invention relates to a technology for highly accurately controlling the shape and dimensions of each glass portion within a fiber cross section and the outer diameter of the fiber.

[Conventional technology]

A pot method is known as a method for directly and continuously forming an optical fiber having a core glass and a cladding glass layer having a lower refractive index from a molten glass state.

In addition to optical fibers, for example, in the process of molding the glass fiber that is the base material of a gradient index Ronde lens, when the lens is constructed with a glass composition that does not have very good thermoformability, the outer periphery of the lens base glass is used. There is a method (Japanese Patent Application No. 62-231848) in which a clad glass layer made of glass with good thermoformability is provided and integrally formed by spinning, and then an ion exchange treatment is performed to create a refractive index distribution. The pot method is also used for implementation.

The basic structure of the spinning device used in the pot method is shown in FIG.

As shown in the figure, the spinning apparatus 1 consists of a core pot part 2 with a circular cross section arranged at the center, and a clad pot part 3 arranged in a concentric ring shape so as to surround the outer periphery of this core pot part 2. Both of these pot parts 2° Molten glass outflow nozzles 2A and 3A are provided at the bottom of the nozzle 3, respectively, and these nozzles 2A and 34 are also arranged concentrically.

And these pot part 2.3 and nozzle part 28.

3A is maintained at a high temperature by a heating device not shown. A core glass 4 is held in a molten state in the core pot part 2, and a clad glass 5, which is different from the core glass 4, is held in a molten state in the turret part 3.

The molten glass 4.5 in both pot parts 2, 3 is supplied to the nozzle 2A,
3A, merge at the confluence point 6, further flow down the inside of the nozzle, be gradually cooled, and be pulled out from the lower end opening to form a continuous glass fiber 10 with a constant outer diameter.

The obtained glass fiber 10 has a double structure consisting of a core glass part 10A and a thalassod glass layer 10B surrounding the outer periphery of the core glass part 10A, as shown in the cross-sectional view in FIG.

In the pot spinning apparatus as described above, generally, in order to improve the quality of the main core glass, a stirring device 7 made of rotating blades is provided to stir the molten glass in the core pot part z.

Although the figure shows a double pot in which only one layer of clad pot portions 3 is provided, the clad pot portions may be provided in a concentric ring shape in two or more layers as necessary, and the present invention does not apply to such a method. Although multiple pots are also included, for convenience, a double pot will be explained as an example.

[Problem that the invention seeks to solve]

As mentioned above, the advantage of providing a stirring device in the core pot part is that it can prevent non-uniformity that occurs during glass melting and make the core glass, which is the main body of optical signal transmission or image transmission, highly homogeneous. Conventionally, little consideration has been given to the clad glass portion that cannot be used.

However, according to the research and experiments conducted by the present inventors, it has been found that the eccentricity of the core glass within the cross section of the core-clad glass fiber and the variation in the outer diameter of the fiber are largely caused by the non-uniformity of the clad glass. Ta.

If the clad glass is heterogeneous in its molten state, the viscosity of the clad glass itself changes discontinuously when spinning fibers under constant temperature conditions, so it is difficult to maintain a constant spun wire diameter by controlling the spinning speed alone. As a result, the outer diameter of the formed fiber will vary greatly in the length direction, and even if it were possible to control the outer diameter, the diameter of the core glass, which determines the optical performance. I can't control it. As a result, the core glass becomes eccentric within the fiber cross section (the thickness of the cladding glass becomes non-uniform), and even if the fiber outer diameter is constant, the core diameter varies in the length direction.

The above-described non-uniformity in shape and size causes non-uniformity in the optical performance of the optical fiber or lens.

[Means for solving problems]

Both the core pot section and the cladding pot section are provided with means for forcibly stirring the molten glass in these pot sections.

This stirring means generally consists of stirring blades immersed in the molten glass and rotated by an external drive mechanism, and the stirring blades in the core section and the cladding section are common, as shown in the preferred embodiment below. They may be provided on the rotation shafts of the two and rotated at the same time, or they may be made as separate bodies and rotated independently.

However, since the upper opening of the clad pot part is annular and the gap is narrow, the former structure is used instead of immersing the blades in a specific location within the thalasso pot part. It is preferable that the stirring blade rotates because a higher homogenization effect can be obtained.

[Function] By using the spinning device with the above structure, not only the core glass but also the cladding glass can be made sufficiently homogeneous, and therefore the viscosity of the molten glass becomes uniform in both the core and the cladding glass, so that the viscosity of the molten glass becomes uniform in both the core and the cladding glass. Core glass eccentricity in the fiber, core glass diameter variation, and fiber outer diameter variation are significantly reduced compared to conventional methods.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments shown in the drawings.

FIG. 1 is a cross-sectional view of the spinning device according to the present invention, which has a structure in which the molten core glass 4 in the core pot section 2 and the molten clad glass 5 in the clad bot 3 are rotationally stirred by a common stirring device 20. ing.

The stirring device 20 includes stirring blades 22 immersed in the core glass 4 on a rotating shaft 21 that is rotationally driven by a drive device (not shown), and a cylindrical stirring blade 22 fixed to the rotating shaft 21 above this. clad glass cooler 3
It is configured with 0. A plan view, a side view, and a perspective view of the clad glass cooler 30 are shown in FIGS. 2 and 3, respectively.
It is shown in Fig. 4.

The clad glass cooler 30 has a substantially cylindrical shape with an open bottom, and the rotating shaft 21 is passed through the center hole of the upper wall 31, and is integrally fixed to the rotating shaft 21 with radially extending ribs 32. A gas vent opening 33 is provided on the upper wall surface to release gas generated from the molten glass.

Further, the lower end of the cylindrical side wall 34 has notches 3 at regular intervals.
5, narrow protruding stirring blade portions 36 are formed at equal intervals between adjacent notches. In order to further increase the stirring effect, the stirring blade part 36 is made thicker than the other side wall parts, and is wedge-shaped so that the front end in the rotation direction is thinner than the rear end in plan view. In other words, when the Stark-30 rotates in the direction of arrow 37, the wedge-shaped stirring blade portion 36 pushes the molten glass toward the outer periphery, increasing the stirring and mixing effect in the radial direction of the pot. The portion 36 also has a wedge shape when viewed from the side, so as to increase the effect of stirring and mixing the molten glass in the depth direction.

The stirring blade part 36 of the Stark-30 having the above structure is immersed in the molten clad glass 5 in the clad pot 3.

Note that the core glass stirring blade 22 may be the same as the conventional one, and in the illustrated example, a multistage group of blades is provided in the length direction of the rotating shaft 21, and the blades are arranged so that the slopes of the blades are opposite to each other between adjacent stages. A slope is provided.

In the above device, when the rotating shaft 21 is rotated by an external drive device, the stirring blade 22 stirs the core glass 4, and at the same time, the stirring blade part 36 of the clad glass cooler 30 moves the molten glass inside the annular TARAD POSOTO 3. The molten clad glass 5 is stirred by circular motion along the shape of the pot.

In addition, at the same time as stirring, non-uniformity, so-called surface skin, caused by volatilization of specific components in the glass, which occurs when the glass is left at high temperatures, is also removed.

According to the experimental results, when glass fibers with a diameter of 1 mm were formed using the conventional spinning device shown in Fig. 5, the variation in the outer diameter of the fibers was ±15 μm, and the variation in the thickness of the cladding glass was ±20 μm. When glass fibers with the same wire diameter as above were spun using the rad glass cooler 30 as shown in Figures 1 to 4, the variation in the outer diameter of the fibers and the cladding thickness was as large as ±5 μm. Improved.

〔Effect of the invention〕

According to the present invention, when forming a glass fiber consisting of a core and a cladding layer, not only the core glass but also the cladding glass is stirred in the molten glass holding pot, so that non-uniformities in the glass are removed even in the cladding glass. This results in a core and clad glass of uniform viscosity, and therefore, the eccentricity and diameter variations of the core glass and the variations in the outer diameter of the fibers, which conventionally occur due to the non-uniformity of the clad glass, are significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing one embodiment of the present invention, FIG. 2 is a plan view showing the Tallad glass stirrer portion of the apparatus shown in FIG. 1, FIG. 3 is a side view of the same, and FIG. FIG. 5 is a longitudinal sectional view showing a conventional pot method spinning device, and FIG. 6 is a sectional view showing the structure of the glass fiber to be formed. 2...Core pot part, 3...Clad pot part, 2
A. 3A... Nozzle, 4... Molten core glass, 5...
Fused clad glass, 10...Glass fiber 2
0... Stirring device, 21... Rotating shaft, 22... Core glass stirring blade, 30... Cland glass stirrer, 32... Rib, 33... Gas vent opening, 34...
- Side wall, 35... Notch, 36... Clad glass stirring blade, 37... Rotation direction. Figure Figure

Claims (1)

[Claims] A core pot section that holds a first molten glass, and at least one clad pot section that is provided in a concentric ring shape around the outer periphery of the core pot section and that holds a molten glass that is different from the glass, and is provided at the bottom bottom of both pots. In a spinning device that forms a glass fiber having a core glass and at least one layer of cladding glass surrounding the core glass by continuously drawing out molten glass from a nozzle portion,
A glass fiber spinning apparatus characterized in that both the core pot section and the clad pot section are provided with molten glass stirring means.