JPH06345468A - Production of glass rod - Google Patents

Abstract

PURPOSE:To efficiently produce a glass rod by improving the efficiency of deposition of silica fine powder to a target rod. CONSTITUTION:Four conductive target rods 1 are erected in the vertical direction and discharge electrode 2 as a point electrode is set at the central part. A high-voltage D.C. power supply 3 is connected between the target rods 1 and the discharge electrode 2 and a high voltage is applied. Each of the target rods 1 is allowed to rotate on its own central axis and the discharge electrode 2 is allowed to perform a reciprocating motion between both the ends of the target rod 1. A silica fine powder is sent to a space between the target rod 1 and the discharge electrode 2 so as to be charged negative with electricity and the charged fine powder is attracted through a coulomb force to the target rod 1, thus depositing the silica fine powder on the surface of the target rod 1.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to a method for producing glass rods by depositing fine silica powder.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a glass rod which is a base material of an optical fiber, a VAD method and an external attachment method have been known. In these methods, oxygen and hydrogen are sent to a burner and burned, a raw material gas of glass such as silicon tetrachloride is sent into the flame, and a silica (silicon dioxide) fine powder (glass fine particles) is generated by a hydrolysis reaction. Then, this is sprayed onto a target rod and deposited to form a columnar porous preform. If this porous preform is heated and sintered, it can be made into transparent glass and a transparent glass rod can be obtained.

[0003]

However, in the conventional method for producing a glass rod as described above, the deposition efficiency of fine silica powder on the target rod is as bad as about 40%, and more than half of the raw materials used are used. There is a problem that it is not used and is discarded.

In view of the above, it is an object of the present invention to provide a glass rod manufacturing method improved so that the deposition efficiency of fine silica powder on a target rod can be improved to efficiently manufacture a glass rod.

[0005]

In order to achieve the above object, in the method of manufacturing a glass rod according to the present invention, a positive high voltage is applied to the target rod and a negative high voltage is applied to the discharge electrode near the target rod. Is applied to feed the silica fine powder into this electric field, and the silica fine powder is collected and deposited on the target rod by utilizing the Coulomb force.

[0006]

When a positive high voltage is applied to the target rod and a negative high voltage is applied to the discharge electrode near the target rod, most of the space between the target rod and the discharge electrode becomes a negative charge space. When silica fine powder is sent into the space, it is negatively charged and is attracted to the positive target rod by Coulomb force. As a result, the silica fine powder is collected and deposited on the target rod, so that the deposition efficiency of the silica fine powder is improved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the drawings. 1 and 2 show an embodiment of the present invention. FIG. 1 is a schematic view seen from the lateral direction, and FIG. 2 is a schematic view seen from above. In this embodiment, four target rods 1 are erected vertically and a discharge electrode 2 is arranged in the center thereof. The target rod 1 needs to be electrically conductive, here a diameter of 5 mm and a length of 100
0 mm conductive FRP (reinforced plastic) is used. The discharge electrode 2 is a point electrode and constitutes a Pb-Ti alloy.

A direct current high voltage power source 3 is connected between the target rod 1 and the discharge electrode 2 to apply a high voltage of 30 kV between the target rod 1 and the discharge electrode 2. Then, near the surface of the discharge electrode 2, a strong electric field causes ionization / collision of gas molecules, and as a result, an ionization region 6 is generated near the discharge electrode 2.
Is formed. This area 6 is charged with a positive charge to form a positive charge space 4, while most of the other region is a space 5 occupied with a negative charge.

Therefore, when the silica fine powder is blown into the space surrounded by the four target rods 1, the silica fine powder has a negative charge due to the negative charge that occupies most of the space. As a result, the fine silica powder is attracted to the positive target rod 1 by the Coulomb force and gathers, and is deposited on the surface of the target rod 1. That is, this target rod 1 functions as a positive dust collecting electrode.

In practice, the target rod 1, the discharge electrode 2 and the DC high-voltage power source 3 are used to produce silica fine powder at a rate of 40 per minute.
When it was continuously fed at 5 g for 5 hours for deposition on the target rod 1, about 2000 g of silica fine powder could be deposited on each of the four target rods 1. This indicates that the deposition was performed with a high efficiency of 60% or more. Here, the target rod 1 is rotated at a rate of 10 revolutions per minute, and
The discharge electrode 2 was moved back and forth between both ends of the target rod 1 at a moving speed of 50 mm / min. The distance between the target rod 1 and the discharge electrode 2 was 300 mm.

The porous preform thus obtained by depositing silica fine powder is drawn out from the target rod 1, heated and sintered to form a transparent glass, and the hole formed by the extraction is collapsed. When a glass rod was formed by using it, it became a good base material for an optical fiber.

Although the description of the step of producing the fine silica powder is omitted in the above, it may be performed by a flame hydrolysis reaction using an ordinary burner. Also,
The silica fine powder that could not be attached to the target rod in the first stage deposition process may be collected and attached by the above method, but the deposition process is performed normally and cannot be attached in that process. The above method may be performed in the middle of the line for exhausting the silica fine powder.

[0013]

According to the glass rod manufacturing method of the present invention, the fine silica powder is collected and deposited on the target rod by utilizing Coulomb force, so that the deposition efficiency of the fine silica powder is significantly improved. The manufacturing efficiency is improved.

[Brief description of drawings]

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

FIG. 2 is a schematic view of the same embodiment seen from above.

[Explanation of symbols]

 1 Target rod 2 Discharge electrode 3 DC high voltage power source 4 Positive charge space 5 Negative charge space 6 Ionization area

Claims (1)

[Claims] 1. A positive high voltage is applied to a target rod and a negative high voltage is applied to a discharge electrode in the vicinity of the target rod, fine silica powder is fed into this electric field, and Coulomb force is used to produce the fine silica particles. A method for manufacturing a glass rod, comprising collecting and depositing powder on a target rod.