JPH027853Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention is based on the internal CVD process of optical fiber base material.
This invention relates to improvements in devices manufactured by the chemical vapor deposition method.

This type of manufacturing apparatus produces an optical fiber preform by passing an optical fiber raw material through one end of a rotating reaction tube, heating the reaction tube from the outside, and depositing the raw material on the inner surface of the reaction tube. When a base material is manufactured by this internal CVD method, unreacted raw materials and toxic by-product gases such as chlorine gas flow out from the other end of the reaction tube, worsening the working environment. For this reason, especially
In order to prevent this toxic by-product gas from flowing out into the working environment, an exhaust gas treatment means is connected to this reaction tube. In the prior art, for example, a suction type exhaust hood is connected to the other end of the reaction tube, or a gas collection chamber is connected to the other end of the reaction tube via a swivel connector. However, with a suction-type exhaust hood, if the air is not sucked in at a rate higher than the controlled air velocity, there is a risk that the exhaust gas will diffuse into the atmosphere, making it difficult to process the exhaust gas reliably and making it difficult to control the pressure inside the reaction tube. In addition, since exhaust gas is a corrosive gas, the method of collecting exhaust gas with a mechanical seal such as a swivel connector has a limited material and a complicated structure, which reduces operability. If the outer diameter is not uniform and the outer periphery is not smooth, the sealing performance will deteriorate, resulting in the need for an expensive reaction tube, which is uneconomical.

An object of the present invention is to provide an apparatus for manufacturing an optical fiber base material that is highly operable, has a high degree of sealing performance, and is capable of collecting by-product gases.

An embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an optical fiber base material manufacturing apparatus 10 according to the present invention, which is rotatable by bearings 13 on a machine frame 12. A reaction tube 14 that is part of a base material such as quartz supported by a rotary drive source (not shown) that rotationally drives this reaction tube 14 and a reaction tube 14
and a burner 16 that uniformly heats the entire length from the outside. The burner 16 uniformly heats the reaction tube 14 by rotating the reaction tube 14 and reciprocating the burner itself. The optical fiber material to be vapor-deposited is supplied from one end of the reaction tube 14 together with oxygen gas, and this material is vapor-deposited on the inner surface of the reaction tube 14 by heating with the burner 16 .

The manufacturing apparatus 10 of the present invention also includes an internal pressure regulating chamber 18 connected to the other end of the reaction tube 14 to collect by-product gas, and an exhaust gas treatment chamber 18 connected to the internal pressure regulating chamber 18 via a pressure regulator 20. means 22. Therefore, the exhaust gas generated in the reaction tube 14 and collected in the internal pressure adjustment chamber 18 is supplied to the exhaust gas treatment means 22 via the pressure regulator 20 and is treated. In order to prevent exhaust gas from leaking from the joint between the reaction tube 14 and the internal pressure adjustment chamber 18, high-pressure gas, which is provided outside the other end of the reaction tube 14 and whose pressure is higher than the pressure inside the internal pressure adjustment chamber 18, is introduced. A gas seal chamber 24 is provided for allowing a portion of the high-pressure gas to flow into the internal pressure adjustment chamber 18. Therefore, part of the high-pressure gas flows into the internal pressure adjustment chamber 18 and the other part is discharged to the atmosphere, but since this high-pressure gas is higher than the pressure inside the internal pressure adjustment chamber 18, the exhaust gas is discharged to the atmosphere. It can be seen that high sealing performance can be obtained. The pressure Pi in the internal pressure control chamber 18 is, for example, 20 mm.
H ₂ O, and therefore there is no pressure in the gas seal chamber 24.
Pg can be _25mmH2O . Nitrogen gas with an original pressure of 5 kg/cm ² can be used as the sealing gas. Although the flow rate of nitrogen gas varies depending on the gap between the reaction tube 14 and the gas seal chamber 24,
It is adjusted to a predetermined pressure. Measuring the concentration of chlorine gas in a specific example of the present invention
High sealing performance was confirmed at 0.1 ppm. In FIG. 2, reference numerals 26 and 28 are pressure gauges provided in the internal pressure adjustment chamber 18 and the gas seal chamber 24, respectively.

According to the present invention, as mentioned above, the toxic exhaust gas generated from the reaction tube is collected with high sealing performance, so it does not leak outside, improving the working environment, and the internal pressure between the reaction tube and the Since there is no contact with the control chamber, the internal pressure control chamber does not wear out and can be used for a long period of time, and the reaction tube can be attached and detached in a short time, which has the practical benefit of good operability. .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus for manufacturing an optical fiber base material according to the present invention, and FIG. 2 is an enlarged sectional view of the main part of the present invention. 10... Optical fiber base material manufacturing device, 14
... Reaction tube, 16 ... Burner, 18 ... Internal pressure adjustment chamber, 22 ... Exhaust gas treatment means, 24 ... Gas seal chamber.

Claims (1)

[Scope of utility model registration request] The apparatus for producing a base material for an optical fiber by an internal CVD method in which an optical fiber raw material is passed through one end of a rotating reaction tube and the raw material is vapor-deposited on the inner surface of the reaction tube while heating the reaction tube from the outside. In an apparatus for producing an optical fiber base material comprising an internal pressure regulating chamber for collecting harmful byproduct gas generated from the other end of the reaction tube and an exhaust gas treatment means connected to the internal pressure regulating chamber, the other end of the reaction tube for an optical fiber, characterized in that it is provided with a gas seal chamber provided outside of the inner pressure regulating chamber, into which high pressure gas higher than the internal pressure of the internal pressure regulating chamber is introduced, and a part of this high pressure gas flows into the internal pressure regulating chamber. Base material manufacturing equipment.