JPS604977Y2 - Raw material supply equipment for manufacturing optical fiber base material - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an automatic supply device for silicon tetrachloride, which is the main raw material of the base material, in the production of optical fiber base materials by the VAD method.

Conventionally, this type of equipment fills silicon tetrachloride, which is the raw material for glass, and doping substances, such as germanium tetrachloride, phosphorus oxychloride, boron tribromide, etc., into each raw material container, and controls the flow rate. The apparatus was configured to bubble a carrier gas such as argon gas into the liquid glass raw material in each container to obtain the desired vapor of each of the raw materials.

FIG. 1 is a schematic diagram showing the configuration of a specific example of such an apparatus, in which 1 is a container for glass raw materials, 2 is a bubbler, 3 is an outlet for vaporized frit, and 4 is a supply for liquid glass raw material. 5 is a liquid glass raw material, 6 is a chamber, 7 is a hot air heater, 8 is a liquid raw material storage tank, and 9 is a valve.

In the container 1, the carrier gas is blown out from the bubbler 2 with its flow rate controlled and bubbles the liquid glass raw material 5 to obtain a vaporous glass raw material.

Since the liquid glass raw material decreases with the passage of time, the liquid glass raw material must be supplied into the container according to the amount of decrease.

Conventionally, the method for supplying liquid glass raw materials is to connect the liquid glass raw material storage tank 8 and the supply port 4 with a corrosion-resistant pipe, apply pressure with an inert gas such as argon gas, etc.
When the liquid level of the liquid frit 5 is at a predetermined position, for example 1 or
A method is used in which the valve 9 is opened when lrIIL decreases and liquid glass raw material is supplied.

However, in this supply method, the raw material is supplied under pressure, so the pressure inside the raw material container 1 increases at the moment the valve 9 is opened, and the amount of vaporous frit obtained from the outlet 3 of the vaporous frit depends on the pressure. It increases and decreases according to changes, and these fluctuations continue until the supply of glass raw materials ends.

As a result, it is not possible to stably supply the vaporized glass raw material, and the refractive index of the optical fiber base material produced by this causes slight fluctuations, which adversely affects the optical properties of the optical fiber. It turns out.

The present invention was devised to solve these drawbacks, and its purpose is to prevent pressure fluctuations in the frit container that occur when liquid frit is supplied, and to stably supply vaporized frit. An object of the present invention is to provide a raw material supply device for manufacturing an optical fiber base material.

To summarize the present invention, the raw material supply device for producing an optical fiber base material of the present invention supplies liquid glass raw material from a storage tank to a container, bubbles carrier gas into it,
In a raw material supply device for producing an optical fiber preform, which supplies a mixture of a vaporous glass raw material and a carrier gas, a raw material container for pressure adjustment is provided in a liquid glass raw material supply pipe 4 provided in a glass raw material container. .

In the raw material supply system equipped with the pressure-adjusting raw material container according to the present invention, pressure fluctuations in the glass raw material container caused by supplying liquid glass raw material to the glass raw material container are prevented, and the vaporized glass is always maintained at a constant pressure. raw materials are obtained,
Refractive index (Δn) of the optical fiber base material manufactured by this method
fluctuations can also be significantly reduced.

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a schematic diagram showing the configuration of a specific example of a raw material supply system for manufacturing optical fiber preforms, in which 1 and 13 are raw material containers, 2
is a bubbler, 4 is a raw material supply port, 5 and 14 are silicon tetrachloride, 6 is a chamber, 7 is a hot air device, 8 is a silicon tetrachloride storage tank, 9. 10, 11 and 12 are valves, 15
16 is a vaporized glass raw material, 17 is a pressure adjustment tube, and 18 is a liquid level detector.

The silicon tetrachloride storage tank 8 and the raw material container 13 for pressure adjustment were connected with a Teflon pipe, and a valve 11 was provided in the pipe line.

An exhaust pipe was attached to the upper part of the raw material container 13 for pressure adjustment, and a valve 12 was provided in the pipe line.

The upper part of the raw material container 13 for pressure adjustment and the upper part of the raw material container 1 were connected to each other by a Teflon pipe, and a valve 10 was provided in the pipe line.

The lower part of the pressure regulating raw material container 13 and the raw material container were connected by a raw material supply pipe 4, and a valve 9 was provided in the pipe.

Further, the raw material supply pipe 4 was made long so as to be located below the liquid level of the silicon tetrachloride 5 filled in the raw material container 1.

Next, the operation of the present invention will be explained.

The temperature inside the chamber 6 was raised to 40° C. by the hot air heater 7.

Next, open valves 9, 10, 11 and 12, and add 9/C71! to 0.15 with argon gas to the silicon tetrachloride storage tank 8! The raw material container 1 was filled with silicon tetrachloride by applying a pressure of .

After the raw material container 1 was filled with silicon tetrachloride, the valve 9 was closed, the pressure-adjusting raw material container 13 was filled with silicon tetrachloride, and the valves 11 and 12 were closed.

In such a state, argon carrier gas 15 controlled at 100 cc/min is flowed through bubbler 2 to bubble silicon tetrachloride 5 to form vaporized silicon tetrachloride 16.
I got it.

After 1 hour had passed, the liquid level of silicon tetrachloride 5 was lowered by 1 - from the initial state.

Here, the valve 9 was opened, and the silicon tetrachloride 14 in the pressure adjustment raw material container 13 was filled into the raw material container 1, and when the liquid level of the silicon tetrachloride 5 returned to the initial state, the valve 9 was closed. .

During these operations, the pressure fluctuation on the outlet 3 side of the vaporous raw material is as follows:
was hardly recognized.

This result shows that when opening the valve 9 and filling silicon tetrachloride into the raw material container 1, the pressure in the space above the silicon tetrachloride liquid level in the raw material container 1 increases, but this pressure increase is It can be concluded that the liquid was absorbed into the pressure regulating raw material container 13 via the pipe line 17.

The present inventors used this raw material supply system to obtain a vaporized glass raw material, and as a result of producing an optical fiber base material using this raw material, the change in refractive index (Δn) in the longitudinal direction of the base material was 0.01.
% or less.

For comparison, the raw material container 13 for pressure adjustment was not provided.
An experiment was conducted by connecting the raw material supply port 4 and the valve 11, but in this case, the pressure fluctuation when supplying the raw material was large, and the refractive index (Δn) of the obtained optical fiber base material in the longitudinal direction was )
The change was as large as 0.2%, and the dimensional accuracy of the base material also deteriorated.

Furthermore, the present invention can automate the opening and closing of four valves by interlocking them using a simple relay circuit.
A considerable amount of constant vaporized glass raw material can be obtained automatically and easily.

Furthermore, according to the present invention, the liquid level detector 18 is connected to the raw material container 1.
By connecting the liquid level detector 18 and the valve 9, it is possible to arbitrarily set the drop in the liquid level, and when the liquid level falls to the set value, the raw material can be automatically supplied. .

As explained above, according to the present invention, by providing the raw material container for pressure adjustment, the influence of pressure changes in the raw material container caused by supplying raw materials is improved, and the vaporized glass raw material is kept at a constant pressure. can be supplied over a long period of time, and fluctuations in the refractive index (Δn) in the longitudinal direction of the optical fiber base material manufactured from this raw material can also be suppressed to a minimum.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the configuration of a conventional raw material supply device;
The figure is a schematic diagram showing the configuration of a raw material supply device according to the present invention. 1.13... Container for raw material, 2... Bubbler, 3... Outlet for vaporized glass raw material, 4...
...Liquid glass raw material supply port, 5, 14...
Liquid glass raw material, 6...chamber, 7...
・・Hot air heater, curved raw material storage tank, 9.1G
, 11, 12...Bent valve, 15...Carrier gas, 16...Vaporous glass raw material, 17...
...Pressure adjustment pipe, 18...Liquid level detector.

Claims (1)

[Scope of utility model registration request] In the raw material supply device for producing an optical fiber preform, the liquid glass raw material storage tank is filled with liquid glass raw material into a glass raw material container under pressure from the liquid glass raw material storage tank, and the vaporized glass raw material is supplied by bubbling carrier gas into the glass raw material container. A raw material container for temporarily storing the liquid glass raw material is provided in a raw material supply pipe connecting the glass raw material container and the glass raw material container, and the upper space of the raw glass raw material container is connected to the upper space of the glass raw material container. A raw material supply device for manufacturing an optical fiber base material, characterized in that: