JPH0526732B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and apparatus for producing a porous glass base material for optical systems such as optical fibers and rod lenses by the VAD method.

``Prior art'' When manufacturing a porous glass base material for optical systems using the VAD method, it is necessary to stabilize the airflow in the reaction vessel that forms the manufacturing atmosphere, and it is necessary to stabilize the airflow in the reaction vessel that forms the manufacturing atmosphere. , the variation in the outer diameter of the porous glass base material and the variation in the refractive index distribution become large.

For this reason, appropriate measures have been taken, such as controlling the exhaust pressure of the reaction vessel, and flowing flow-controlled and pressure-controlled gas into the interior of the reaction vessel from the upper part of the reaction vessel. -69234 publication, JP 57-135738
The invention of the publication is provided.

In FIGS. 3A and 3B, which illustrate the invention disclosed in Japanese Patent Application Laid-Open No. 57-135738 as a conventional method, 1 is a reaction vessel having an exhaust port 2, and 3 is a passage pipe inserted into the inside of the reaction vessel 1 from the upper part thereof. , 4 is a burner for producing glass fine particles whose tip is attached to the inside of the reaction vessel 1 from the lower part thereof, 5 is a target, and 6 is a porous glass rod.

In the method shown in FIG. 3, when forming the porous glass rod 6, a predetermined gas is caused to flow from inside the passage tube 3 downward. However, as shown in FIG. The clearance is large,
As the porous glass rod 6 grows, this becomes the passage tube 3.
When the liquid penetrates into the interior, the above-mentioned clearance becomes smaller.

Therefore, as the porous glass rod 6 grows, the fluidity through the passage pipe 3 changes, and along with this, the directivity of the burner flame (the direction of injection of glass particles) inside the reaction vessel 1 also changes. .

A similar phenomenon occurs in the invention disclosed in Japanese Patent Application Laid-Open No. 56-69234, the explanation of which is omitted.

"Problems to be Solved by the Invention" As mentioned above, in the case of the conventional method, the directivity of the burner flame changes, so when manufacturing the porous glass rod 6 of a desired length, the It is not possible to reliably prevent variations in the outer diameter or the refractive index distribution, and it is also difficult to control the flow rate in the passage pipe 3 and the pressure in the reaction vessel 1 to compensate for this.

On the other hand, if the inner diameter of the passage tube 3 is increased to make the change in fluidity so small as to be negligible, the outer diameter of the porous glass rod 6 becomes stable, but in this case, the flow energy is not absorbed from the upper part of the reaction vessel. As a result, the glass particles from the burner 4 dance wildly within the container 1, and the stability of the refractive index distribution of the porous glass rod 6 is impaired.

In view of the above-mentioned problems, the present invention aims to provide a method and apparatus for stabilizing fluidity within a reaction vessel and thereby obtaining a porous glass rod with a stable outer diameter and refractive index distribution in the longitudinal direction. It is.

"Means for solving problems" *In the case of the method of the present invention.

The present invention provides a reaction vessel having an exhaust port on the side of the container, a vertical passage extending from the upper part of the container to the inside thereof, and a burner for producing glass particles whose tip is installed from the lower part of the container into the inside thereof; A target is inserted into a reaction vessel so as to be freely movable and rotatable, and glass fine particles generated via a burner are injected and deposited on the lower end of the target rotating at a predetermined position within the reaction vessel. In the method for producing a porous glass rod, a porous glass rod is formed and a target is pulled up according to the growth rate of the porous glass rod, a downward air current is generated in the reaction vessel along the outer periphery of the passage. It is characterized by

*In the case of the device of the present invention.

The present invention provides a reaction vessel having an exhaust port on the side of the container, a vertical passage extending from the upper part of the container to the inside thereof, and a burner for producing glass particles whose tip is installed from the lower part of the container into the inside thereof; In an apparatus for producing a porous glass rod, the target is vertically movable and rotatably inserted into a reaction vessel, and an airtight cylinder is connected above the passage. A gas flow path for forming a downward airflow is formed between the periphery and the outer periphery of the passage portion, and a gas inflow portion is formed at the upper end of the gas flow path.

``Operation'' In the present invention, glass fine particles injected from the tip of a burner in a reaction vessel are deposited on the lower end of a rotating target to form a porous glass rod, and the target is pulled up according to the growth rate of the porous glass rod. Although this is the same as the conventional example, when a porous glass rod is formed in this way, a downward air current is generated in the reaction vessel along the outer periphery of the passage.

When manufacturing a porous glass rod as described above, the porous glass rod passes along with the target inside the passage, and the downward airflow flows along the outer periphery of the passage to the exhaust port.

Therefore, even if the clearance inside the passage changes as the target passes through it first and then the grown porous glass rod passes through it, the airflow descending along the outer periphery of the passage will have the above-mentioned change in clearance. It does not have any influence from other people and always exhibits stable fluidity.

As a result, the outer diameter of the porous glass base material is almost constant due to the stable downdraft, the directivity of the burner flame is constant with respect to the deposition surface, and the downdraft prevents the glass particles from dancing, all of which are synergistic. As a result, the refractive index distribution over the longitudinal direction of the porous glass base material is also made constant, and thus a porous glass base material with good quality and properties can be obtained.

``Example'' Hereinafter, specific examples of the method and apparatus of the present invention will be described.
This will be explained with reference to the drawings.

In FIGS. 1 and 2, 11 is a reaction vessel having an exhaust port 12, 13 is a passage provided from the top of the reaction vessel 11 to the inside thereof, and 14 is a tip extending from the bottom of the reaction vessel 11 to the inside thereof. The burner 15 for producing glass particles equipped with a burner 15 is a known target that is rotatable and movable up and down.

In the above, an airtight cylindrical body 16 is connected to the upper surface of the passage section 13, and a gas flow path 17 is provided between the upper inner periphery of the reaction vessel 11 and the outer periphery of the passage section 13 for generating a downward airflow. A gas introduction section 18 is formed at the upper end of the gas flow path 17.
is formed.

In addition, in the case of FIG. 1, the gas introduction part 18 is formed by a plurality of circular through holes bored at equal intervals on the upper surface of the reaction vessel 11, and in the case of FIG. A gas inlet 18 is formed through a member having a gas discharge port 20, and a piping system 22 having a flow rate regulator 21 is connected to the gas inlet 19.

In the figure, 23 indicates a porous glass rod.

The porous glass rod 23 is formed by the illustrated apparatus described above.
When manufacturing the target 15, the lower end thereof is inserted into the reaction vessel 11 to a predetermined position and rotated, and the product of the flame hydrolysis reaction via the burner 14, that is, the glass fine particles, is transferred to the target 1.
It is injected and deposited towards the lower end of 5.

Due to the deposition of such glass particles, a porous glass rod 23 is formed at the lower end of the target 15.
Depending on the growth rate of the porous glass rod 23, the target 15 is pulled upward within the passage 13 and the cylindrical body 16, but at this time, the inside of the reaction vessel 11 is exhausted from the exhaust port 12, and the exhaust gas A predetermined gas is introduced from the gas introduction part 18 into the gas flow path 1 by natural introduction or forced introduction from the piping system 22.
7, thereby creating a downward airflow along the outer periphery of the passage section 13.

As described above, the downward airflow flowing along the outer periphery of the passage section 13 toward the exhaust port 12 flows through the passage section 13.
It exhibits stable fluidity unaffected by changes in the internal clearance, has effects such as constant directivity of the burner flame to the deposition surface, and prevention of scattering of glass particles. The diameter and refractive index distribution are constant.

In addition, when manufacturing the porous glass rod 23 in the above, it is preferable to perform pressure control and flow rate control to keep the exhaust pressure inside the reaction vessel 11 constant, the flow rate of the descending air, etc., and these controls are performed at the exhaust port. This adjustment is performed using a displacement regulator (not shown) of the piping system connected to the gas inlet 12, a flow regulator 21 of the piping system 22 connected to the gas inlet 19, and the like.

"Effects of the Invention" As explained above, when using the method of the present invention,
When manufacturing porous glass rods by the VAD method,
Since a downward airflow is generated along the outer periphery of the passage in the reaction vessel, this stable downward airflow is unaffected by changes in the clearance within the passage, and as a result, a porous glass base material with a constant outer diameter and refractive index distribution in the longitudinal direction is formed. can get.

On the other hand, the apparatus of the present invention is not only equipped with an exhaust port and passage of the reaction vessel, a burner for generating glass particles, a target, etc., but also has a gas flow between the inner periphery of the upper part of the reaction vessel and the outer periphery of the passage. A passage is formed, a gas inflow part is formed at the upper end of the gas flow passage, and an airtight cylinder is connected above the passage part, so that a predetermined downward airflow can be easily generated. The operation of pulling up the porous glass rod can also be carried out using the cylindrical body above the passage without damaging the atmosphere inside the reaction vessel.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram schematically showing one embodiment of the method and apparatus of the present invention, Fig. 2 is an explanatory diagram schematically showing another embodiment of the same, and Fig. 3 A and B are explanatory diagrams of a conventional example. . 11... Reaction container, 12... Exhaust port, 13...
Passage section, 14... burner, 15... target,
16... Cylindrical body, 17... Gas flow path, 18... Gas inlet, 19... Gas inlet, 20... Gas discharge port, 21... Flow rate regulator, 22... Piping system, 23
...Porous glass rod.

Claims (1)

[Scope of Claims] 1. A reaction vessel having an exhaust port on the side of the vessel, a vertical passage extending from the top of the vessel to the inside thereof, and a burner for producing glass particles whose tip is installed inside the vessel from the bottom of the vessel; Using a target that is vertically movable and rotatably inserted into the reaction vessel from the passage section, glass fine particles generated via a burner are placed at the lower end of the target rotating at a predetermined position within the reaction vessel. In the method for producing a porous glass rod, in which a porous glass rod is formed by injecting and depositing a porous glass rod, and a target is pulled up according to the growth rate of the porous glass rod, a A method for producing a porous glass rod characterized by generating a downward air current. 2. The method for manufacturing a porous glass rod according to claim 1, wherein the flow rate of the airflow is adjusted so that the downward airflow along the outer periphery of the passage portion is constant. 3. The method for manufacturing a porous glass rod according to claim 1, wherein the flow rate of the descending air flow along the outer periphery of the passage section is adjusted so that the exhaust pressure in the reaction vessel is constant. 4. A reaction vessel having an exhaust port on the side of the container, a vertical passage extending from the top of the container to the inside thereof, and a burner for generating glass particles whose tip is installed inside the vessel from the bottom of the vessel, and a passage from the passage to the inside of the reaction vessel. In an apparatus for manufacturing a porous glass rod, the target is vertically movable and rotatably inserted into the target, and an airtight cylinder is connected above the passage, and the upper inner periphery of the reaction vessel and the passage are connected to each other. 1. An apparatus for manufacturing a porous glass rod, characterized in that a gas flow path for forming a downward airflow is formed between the rod and the outer periphery of the rod, and a gas inflow portion is formed at the upper end of the gas flow path. 5. The apparatus for manufacturing a porous glass rod according to claim 4, wherein the gas inflow portion comprises a plurality of through holes drilled in the upper surface of the reaction vessel. 6. The apparatus for manufacturing a porous glass rod according to claim 4, wherein the gas inflow portion is formed through a member having a gas inlet and a ring-shaped gas discharge port. 7. The porous glass rod manufacturing apparatus according to claim 6, wherein a piping system having a flow rate regulator is connected to the gas inlet.