JPS624333B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber drawing method that prevents the oxidative consumption of carbon in the constituent materials of the furnace used and cleans the atmosphere inside the furnace.

In the method of drawing fibers from silica-based fiber materials, the drawing furnaces used in the past are made of carbon-based materials, which prevent oxidation at the high temperatures of 2000°C or higher required for drawing silica-based fibers. An inert gas such as argon or nitrogen is injected for this purpose. In a furnace having a core tube inside the heating element, argon gas is usually introduced in consideration of reaction products between nitrogen gas and quartz. When argon gas is allowed to flow into the core tube, continuous drawing over a long period of time will not prevent the oxidation and consumption of carbon and the generation of dust due to the reaction between quartz and carbon. The amount increases. As a result, the generated dust contaminates the surface of the fiber, forming scratches that reduce the breaking strength of the fiber, resulting in the disadvantage that a long, high-strength fiber cannot be obtained.

In order to eliminate these drawbacks, the present invention is characterized in that argon gas mixed with helium gas is flowed into the furnace core tube and drawing is performed in that atmosphere, thereby cleaning the atmosphere inside the drawing furnace for a long period of time. The present invention relates to an optical fiber drawing method for the purpose of obtaining a long, high-strength fiber by maintaining the same temperature, and will be explained in detail below with reference to the drawings.

FIG. 1 is a sectional view illustrating the configuration of a drawing furnace according to an embodiment of the present invention, in which 1 is a furnace body, 2 is an upper protrusion chamber, 3 is an upper opening on the upper surface of the upper protrusion chamber, and 4 is a lower protrusion. Chamber, 5 is a lower opening on the lower surface of the lower protruding chamber, 6
7 is a base material, 7 is a fiber, 8 is a cylindrical furnace tube made of carbon, 9 is the inside of the furnace tube, 10 is a furnace body 1
11 is a heater, 12 is a helium gas cylinder, 13 is an argon gas cylinder, 14 is a mixer, 15 is a gas inlet, and 16 is a gas outlet.

As can be seen from the figure, the furnace body 1 is provided with an upper protrusion chamber 2 at the upper center, and an upper opening 3 is provided on the upper surface of the upper protrusion chamber 2 so that a base material 6 can be suspended from outside the furnace. A lower protruding chamber 4 is provided at the lower center, and a lower opening 5 is provided on the lower surface of the lower protruding chamber 4 so that the drawn fiber 7 can be pulled out of the furnace. In addition, a cylindrical furnace core tube 8 is located at the center of the furnace body 1 and connects the upper projecting chamber 2 and the lower projecting chamber 4, and the inside 9 of the furnace tube 8 is airtight to the outside 10 of the furnace tube. It is set up like this. A heater 11 made of a cylindrical heating element is provided around the core tube 8 at the outside of the core tube 10 . A gas inlet 15 is provided on the side surface of the lower projecting chamber 4 , and a helium gas cylinder 12 and an argon gas cylinder 13 are connected to the gas inlet 15 via a mixer 14 . A gas outlet 16 is provided on the side surface of the upper projecting chamber 2, and although not shown, the gas outlet 16 is provided with an exhaust gas processing device.

Since the wire drawing furnace is configured as described above, the base material 6 is suspended from outside the furnace, and the base material 6 is drawn in a high temperature state in the core tube outside 10 in the furnace body 1 and the core tube interior 9 which is kept airtight. The drawn fiber 7 is pulled out of the furnace from the lower opening 5 of the lower protrusion chamber 4, and the helium gas from the helium gas cylinder 12 and the argon gas from the argon gas cylinder 13 are mixed at a predetermined flow rate ratio by the mixer 14, and the gas is inlet. The gas can be made to flow in from 15 and used as a clean atmosphere inside the furnace tube 9, and can be made to flow out from the gas outlet 16.

The outer diameter of the base material was 25 mm, and the relationship between the amount of dust generated for 3 hours after the start of drawing in the inner diameter of the core tube 3 with an inner diameter of 40 mm and the flow rate ratio of helium to argon was investigated.

The cleanliness of the atmosphere inside the furnace sampled from the gas outlet 16 is class 5000 or higher when the helium flow rate ratio is 0.
10,000, but when helium is mixed, the cleanliness starts to improve from a flow rate ratio of 0.05.
It remained almost constant at 0.3 and decreased to classes 100-300. If the helium flow rate is increased, the wire diameter will fluctuate, so the limit on the flow rate is 0.6.

A synthetic quartz glass rod with an outer diameter of 25 mm as a base material was drawn at a helium flow rate ratio of 0.3, and a fiber with an outer diameter of 125 ± 1 μm, a silicon coated outer diameter of 400 μm, and a single length of 10.7 km was coated with silicon using a known coating method. As a result of a tensile test with a length of 100 m and a tensile speed of 10%/min, the minimum value was 5.3Kg, the maximum value was 6.6Kg, and the average
It weighed 6.2Kg.

As explained in detail above, by carrying out the present invention in which argon gas mixed with helium gas is flowed into the inside of the reactor core tube, the inside of the reactor core tube where fibers are drawn from the base material can be kept clean in a high temperature state. Therefore, there is an effect that a long high-strength fiber can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view illustrating one embodiment of the present invention. 1: Furnace body, 2: Upper protrusion chamber, 4: Lower protrusion chamber,
6: Base metal, 7: Fiber, 8: Furnace tube, 11:
Heater, 12: Helium gas cylinder, 13: Argon gas cylinder, 14: Mixer, 15: Gas inlet, 16: Gas outlet.

Claims (1)

[Claims] 1. In the method of heating and stretching a rod-shaped fiber base material mainly composed of quartz glass and drawing it into a fiber, the furnace used has a cylindrical furnace core tube made of carbon inside a cylindrical heating element, This core tube maintains airtightness between the inside of the core tube and the outside of the core tube inside the furnace body, and the atmospheric gas that is introduced into the core tube to control the furnace atmosphere is mainly composed of argon. A method for drawing an optical fiber, characterized by using helium at a flow rate ratio of 0.05 to 0.6.