JPH07101745A - Glass forming method and device therefor - Google Patents

Abstract

PURPOSE:To improve the raw material yield in OVD(outer vapor deposition) and to reduce the production cost. CONSTITUTION:A fine particle current from a burner 10 is switched into the horizontal and flat current in the axial direction of a target rod 20 and the vertical and flat current orthogonal to the axial direction, and the moving base 16 of the burner 10 is moved upward along a rail 17 when a columnar fine glass particle deposit 30 is grown as the deposition proceeds and the diameter is increased to direct the particle current in the direction in contact with the upper surface of the deposit 30, and an exhaust pipe moving base 42 is moved downward along a rail 43 to lower an exhaust pipe 40 and to direct it upward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass forming method by a gas phase reaction process suitable for producing a glass preform for an optical fiber and an apparatus therefor.

[0002]

2. Description of the Related Art A glass base material for optical fibers is usually VA.
A part of the core and the clad are manufactured by the D (vapor phase axial attachment) method, and the clad part, which is a low refractive region occupying most of the cross-sectional area around the core and the clad, is formed by the OVD (external vapor phase attachment) method. It

Clad formation by this OVD method is shown in FIG.
It is performed as shown in. First, glass raw material gas such as silicon tetrachloride is fed into the oxyhydrogen flame formed by the burner 10 to cause a hydrolysis reaction in the flame to generate glass (silicon dioxide) fine particles. The glass particle flow 50 is sprayed onto the rotating target rod 20 to deposit glass particles around the target rod 20 to form the glass particle deposit body 30 in a cylindrical shape. The target rod 20 is made of a part of a core and a clad which are previously manufactured by the VAD method, and the like, and the target rod 20 is held horizontally and rotated about its axis as a rotation center axis. The target rod 20 is arranged on the central axis of the burner 10 so as to be orthogonal thereto, and the exhaust pipe 40 is arranged on the side opposite to the burner 10. The burner 10, the target rod 20 (and the glass particle deposit 30), and the exhaust pipe 40 are placed side by side on one axis on the same horizontal plane. Exhaust pipe 40
Is for collecting and exhausting undeposited glass fine particles and the like and sending the collected dust and exhaust to a processing device (not shown).

[0004]

However, the glass forming method by the OVD method has a problem that the raw material yield is as low as about 50% at the maximum. This problem has hitherto been regarded as a key point for reducing the manufacturing cost of optical fibers.

To explain this problem in a little more detail, the OV
In the glass forming method by the D method, the size of the glass fine particles generated in the flame is about 0.2 μm, and these are deposited on the peripheral surface of the target rod and the like, and the mechanism is governed by thermophoresis. ing. At the initial stage of deposition, the glass particle deposit 30 formed around the target rod 20 is still small as shown in FIG. 7A. Therefore, the cross-sectional area that effectively contributes to the deposition of the glass particulate stream 50 is larger than the projected area of the target rod 20 and the glass particulate deposit 30 as shown in B of FIG. 7, and corresponds to the difference between them. Since the glass particles in the region flow into the exhaust pipe 40 as they are without being involved in deposition, the yield is poor at this stage.

As the deposition progresses and the glass particulate deposit 30 grows to some extent as shown in FIG.
Since the effective cross-sectional area of the glass fine particle stream 50 is almost the same as the projected area of the glass fine particle deposit 30, as shown in B, almost all of the glass fine particles are involved in the deposition and the yield is improved.

As the deposition proceeds further, the glass particulate deposit 3
When the diameter of 0 increases as shown in A of FIG. 9, the projected area of the glass particle deposit body 30 becomes larger than the effective cross-sectional area of the glass particle flow 50 as shown in B of FIG. Since the area of the deposition surface (the surface of the glass particulate deposit body 30) close to 90 ° increases, turbulence easily occurs near the deposition surface. In addition, the velocity of the glass particle flow 50 increases near the upper and lower ends of the side surface of the deposit 30, and the position where the particle flow 50 separates from the side surface of the deposit 30 does not change, so the effective deposition area decreases. To do. These causes the deposition efficiency to decrease.

In view of the above, the present invention improves the yield,
An object of the present invention is to provide a glass forming method and an apparatus therefor capable of reducing the manufacturing cost.

[0009]

In order to achieve the above object, according to the present invention, the burner for producing fine glass particles, the horizontally placed target rod and the exhaust pipe are arranged on a horizontal plane to cause the flame of the burner. In the glass forming method of depositing the glass particles generated in the columnar shape around the target rod, in accordance with the growth of the cylindrical glass particle deposits formed around the target rod, the glass particle flow is changed to the target rod. The horizontal flat shape along the axial direction and the vertical flat shape orthogonal to the axial direction, and
At the stage where the deposition progressed and the columnar glass fine particle deposit grew and its diameter became large, the glass fine particle flow was directed in the direction of contacting the upper surface of the cylindrical glass fine particle deposit and the position of the exhaust pipe was lowered. The feature is that the direction is changed upward while lowering.

Further, in the glass forming apparatus according to the present invention for achieving the above object, a glass fine particle generating means capable of switching the glass fine particle flow between a horizontal flat surface and a vertical flat surface. The target rod holding means for holding the target rod horizontally while rotating it, the exhaust means for sucking and exhausting the glass fine particle flow, the glass fine particle generating means, and the glass fine particle flow generated from it are on the same horizontal plane as the target rod. In the above, there is provided a means for holding the target rod so as to be orthogonal to the central axis of the target rod and a means for vertically moving the position of the glass particulate generation means, and a means for rotationally moving the exhaust means with the central axis of the target rod as the central axis of rotation. It is characterized by being.

[0011]

The flow of glass fine particles generated from the burner is controlled to be a horizontal flat shape along the axial direction of the target rod when the diameter of the cylindrical glass fine particle deposit is small in the initial stage of deposition. As a result, it is possible to reduce the portion of the glass fine particle flow that passes through the target rod and its surrounding deposits without hitting them. Therefore, the yield in the initial stage of deposition can be improved. Further, as the deposition progresses and the diameter of the columnar glass particulate deposit increases, the glass particulate stream is formed into a vertical flat shape that is orthogonal to the axial direction of the target rod. It is possible to reduce the portion that hits the columnar glass particulate deposit at an angle close to a right angle, prevent turbulent flow from occurring, and improve the yield. At the stage where the diameter of the cylindrical glass fine particle deposit increases as the deposition proceeds further, the glass fine particle flow is made horizontal and flat along the axial direction of the target rod, and then the cylindrical glass fine particle deposit is formed. Since it is directed in a direction in contact with the upper surface of the glass particle, the portion of the glass particle flow that hits the cylindrical glass particle deposit at an angle close to a right angle is reduced. Further, at this time, since the position of the exhaust pipe is lowered downward and the direction thereof is changed to the upward direction, the flow distance of the glass fine particle stream along the upper side surface of the cylindrical glass fine particle deposit body becomes long, and the effective The deposition area is increased. Therefore, the yield can be improved even at the stage near the end of the deposition.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the drawings. In FIG. 1, a burner 10 is a burner for producing fine glass particles, and hydrogen,
A gas such as oxygen is fed to generate an oxyhydrogen flame, and a glass raw material gas such as silicon tetrachloride is fed into the flame to generate glass fine particles by a flame hydrolysis reaction. The burner 10 is attached to a moving base 16, and the moving base 16 can be moved along a rail 17 extending in the vertical direction.

The target rod 20 is held by a holding device (not shown) so as to be orthogonal to the central axis of the burner 10. Further, the holding device allows the target rod 20 to rotate about the central axis thereof.

The exhaust tube 40 has a flexible tube 41.
The exhaust gas and the like collected and exhausted by the exhaust pipe 40 are sent to an exhaust treatment device (not shown) via the flexible tube 41. The exhaust pipe 40 is attached to the moving table 42. Moving table 42
Are movable along the arc-shaped rail 43.

The burner 10, the target rod 20, and the exhaust pipe 40 are generally arranged on the same horizontal plane. That is, when the horizontal central axis 60 orthogonal to the target rod 20 is used as a reference, the burner 10 and the exhaust pipe 40 are opposed to each other with the target rod 20 interposed therebetween on the reference central axis 60. They are arranged so that they can be lined up on one straight line.

Since the burner 10 is attached to the moving base 16 which moves on the rail 17, its position can be moved up and down with respect to the central axis 60 while maintaining its horizontal orientation. On the other hand, the rail 43 on which the movable table 42 to which the exhaust pipe 40 is attached is placed is provided along a vertical plane including the central axis 60,
The center of the arc of the rail 43 is set to be the central axis of the target rod 20. Therefore, the exhaust pipe 40 rotates with the center axis of the target rod 20 as the rotation center axis while always facing the direction of the target rod 20 as the moving table 42 moves on the rail 43. In this case, the rail 43 is set so that the exhaust pipe 40 can rotate about 45 ° with respect to the central axis 60.

As shown in FIG. 2, the burner 10 has four raw material nozzles 11 to 14 at its tip. Gas that forms an oxyhydrogen flame is ejected from a portion other than these, and the glass raw material gas ejected from these material nozzles 11 to 14 is introduced into this flame. 4 raw material nozzles 11
Nos. 14 to 14 are arranged in the vertical direction and the horizontal direction to form a cross shape. Then, the switching device 1 of the burner 10
5 (see FIG. 1), the nozzles for feeding the raw material gas can be switched between the raw material nozzles 11 and 13 arranged in the vertical direction and the raw material nozzles 12 and 14 arranged in the horizontal direction. When the raw material nozzles 11 and 13 arranged in the vertical direction eject the raw material nozzles, the glass fine particle flow has an elliptical cross section with the long axis oriented in the vertical direction, and the raw material nozzles 12 and 14 arranged in the horizontal direction When ejected from a nozzle, the glass particle flow has an elliptical cross section with its major axis oriented in the horizontal direction. In this way, the changer 15 can switch the flow of the glass fine particles to the flat one in the vertical direction and the one flat in the horizontal direction.

Therefore, first, the burner moving base 16 and the exhaust pipe moving base 42 are moved to position the burner 10 and the exhaust pipe 40 so as to be aligned on the central axis 60 as shown in FIG. In this state, glass particles are generated from the burner 10 and the glass particles are deposited around the target rod 20 to form a columnar deposit 30. In the initial stage of this deposition, the deposit 30 is not formed, or even if it is formed, its diameter is small. Therefore, at this stage, the switching device 1 is so arranged that the raw material gas is ejected from the raw material nozzles 12 and 14 arranged in the horizontal direction.
Switch 5 beforehand. In this way, the glass particle flow 50 is made flat in the horizontal direction so that as much of the glass particle flow 50 as possible hits the target rod 20 or the deposit 30 having a small diameter, and the glass particle flow 50 flows in the direction of the exhaust pipe 40 without hitting it. It is possible to reduce the glass particles that go away. By the above operation, the yield at the early stage of this deposition can be improved by about 20 to 40%.

Next, when the diameter of the cylindrical glass fine particle deposit 30 becomes large as shown in FIG. 4 due to the progress of the deposition, the switch 15 is switched to change the glass fine particle flow 5
Make 0 flat in the vertical direction. Then,
When the glass particle flow 50 hits the side surface of the cylindrical glass particle deposit body 30, the central portion of the side surface of the cylinder (the central axis 6
Not only in the vicinity where 0 passes) but also in the tangential direction above and below. Therefore, the number of collision angles near the right angle decreases, and the number of oblique collisions increases. When the glass particles collide with the deposit 30 at a right angle, a turbulent flow occurs and the deposition efficiency deteriorates, but when the glass particles collide obliquely, no turbulent flow occurs and the glass particles adhere more.
As a result, it is possible to contribute to a yield improvement of about 5 to 10% at this stage.

At the stage where the diameter of the columnar glass particulate deposit 30 has become larger due to the further deposition, as shown in FIG. 5, the glass particulate flow 50 is switched to a horizontal flat one again. To be Then, the burner moving table 16 is moved upward along the rail 17, whereby the burner 10 is pulled up above the central axis 60, and the exhaust pipe moving table 42 is moved downward along the rail 43. As a result, the exhaust pipe 40 is positioned downward and is directed upward.

At a stage near the end of this deposition, the burner 10 moves upward as described above, and the glass particle flow 50 is increased.
Is flat in the horizontal direction, the glass particle flow 50 mainly hits the upper side of the cylindrical side surface of the glass particle deposit body 30. That is, the glass particle flow 50
Among them, there are few that collide with the side surface of the deposit 30 at a right angle and many that collide obliquely. Therefore, it is possible to further suppress the occurrence of turbulence. Further, the exhaust pipe 40
As described above, the glass fine particle flow 50 is located at the lower side and faces slightly upward, so that the glass fine particle flow 50 is sucked into the exhaust pipe 40 along the upper side surface of the columnar deposit 30, and along the side surface. The flow distance becomes longer and the effective deposition area increases. Therefore, this glass particle flow 50
The amount of glass particles adhering to the side surface of the deposit 30 increases in the process of flowing along the side surface of the cylindrical deposit 30. For these reasons, the raw material yield is improved by about 30 to 50% near the end of the deposition.

When moving the burner 10 upward,
It is preferable to gradually move the burner moving table 16 so that the angle between the central axis of the burner 10 and the side surface (the normal line) of the columnar glass particle deposit body 30 is always 10 ° or more.

[0023]

As described in the above embodiments, according to the present invention, the glass particle flow is adjusted according to each of the characteristics at each stage of the glass particle deposition process by the OVD method. The raw material yield in the stage can be improved, the efficiency can be improved as a whole, and the glass molding can be performed at low cost.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of the present invention.

FIG. 2 is a schematic diagram of a burner according to the same embodiment.

FIG. 3 is a schematic diagram at an early stage of deposition.

FIG. 4 is a schematic diagram at an intermediate stage of deposition.

FIG. 5 is a schematic diagram at the final stage of deposition.

FIG. 6 is a schematic diagram for explaining the OVD method in principle.

FIG. 7 is a schematic diagram for explaining a problem at the initial stage of deposition in the related art.

FIG. 8 is a schematic diagram for explaining a problem at an intermediate stage of conventional deposition.

FIG. 9 is a schematic diagram for explaining a problem in the last stage of deposition in the related art.

[Explanation of symbols]

 10 Glass Fine Particle Generation Burner 11-14 Raw Material Nozzle 15 Switching Device 16 Burner Moving Stand 17 Burner Rail 20 Target Rod 30 Glass Fine Particle Deposit 40 Exhaust Pipe 41 Flexible Tube 42 Exhaust Pipe Moving Stand 43 Exhaust Pipe Rail 50 Glass Fine Particle Flow 60 Central axis

Claims (2)

[Claims] 1. A burner for producing glass particles, a horizontally placed target rod and an exhaust pipe are arranged on a horizontal plane to deposit glass fine particles produced in the flame of the burner in a columnar shape around the target rod. In the glass molding method,
According to the growth of the cylindrical glass particle deposit formed around the target rod, the glass particle flow is divided into a horizontal flat shape along the axial direction of the target rod and a vertical flat shape perpendicular to the axial direction. When the deposition progresses and the columnar glass fine particle deposit grows and its diameter becomes large, the glass fine particle stream is directed to the direction in contact with the upper surface of the columnar glass fine particle deposit. At the same time, the glass molding method is characterized in that the direction of the exhaust pipe is changed downward while the position of the exhaust pipe is lowered downward. 2. A glass fine particle generating means capable of switching the glass fine particle flow between a horizontally flat one and a vertically flat one, and a target rod holding means for holding the target rod horizontally while rotating the target rod. The glass fine particles are held by the exhaust means for sucking and exhausting the glass fine particle stream and the glass fine particle producing means so that the glass fine particle stream generated from the means is orthogonal to the central axis of the target rod on the same horizontal plane as the target rod. A glass forming apparatus comprising: a means for moving the position of the generating means in the vertical direction; and a means for rotating the exhaust means with the center axis of the target rod as a rotation center axis.