JPS6065747A - Cooling of optical fiber - Google Patents

Abstract

PURPOSE:To carry out the quenching of an optical fiber obtained by the thermal elongation and spinning of a preform rod, and to keep the spun optical fiber in a stable state free from meandering and fluctuation, by quenching the fiber with a gyrating cooling medium. CONSTITUTION:The preform rod 7 is inserted slowly into the spinning furnace 1, and the lower end of the heated and softened rod 7 is drawn at a high speed to produce an optical fiber 8, which is quenched with a quenching means 2. A gyrating flow of a cooling medium is applied to the outer circumference of the optical fiber 8 passing through the cylinder 4 of the quenching means 2 by the following manner. When a cooling medium is introduced into the cylinder 4 through the plural injection nozzles 51-54 opened at the outer circumference of the cylinder 4 at the part 4a having large diameter, the cooling medium descends under gyration along the inner surface of the part 4a having large diameter to form a gyrating flow S. The flow is accelerated at the tapered part 4b, and further accelerated with the rotating blades 6 at the part 4c having small diameter. The optical fiber 8 passing through the cylinder 4 maintained to the above state is quenched, aligned at the center of the gyrating flow, and held at a definite position.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cooling optical fiber after spinning.

As is known, an optical fiber is manufactured by spinning a preform rod (an optical fiber base material) using a heated drawing means, and a primary coat is formed on the outer periphery of the optical fiber after the spinning.

When performing high-speed production of optical fibers using the above-mentioned spinning method, the optical fibers immediately after spinning are rapidly cooled by cooling means such as jetting clean air, but if the cooling at this time is insufficient, the subsequent The next coating (organic coating) cannot be performed well.

A commonly used method for cooling optical fibers is to actively blow clean air toward the optical fiber from a direction perpendicular to the direction in which the optical fiber runs. The collision force of the injected air causes the optical fiber to shake, causing the original fiber to meander.

Even if we increase the number of air injection lines and arrange them in a well-balanced manner, in reality, considerable optical fiber deflection occurs, and it is impossible to technically solve the above problem. If such oscillation and meandering occur, uneven thickness of the first coat will occur during the subsequent first coating performed via a die coater, and if the thickness is extreme, the optical fiber will come into contact with the coating die and cause this. This causes an optical fiber disconnection accident.

In order to solve the above problems, the present invention attempts to efficiently and stably cool an optical fiber after spinning through a cooling medium in a vortex state. The specific method will be explained below with reference to the first embodiment shown in the drawings.

In FIG. 1, 1 is a spinning furnace consisting of a known electric heating furnace, 2 is a cooling means arranged as close as possible to the lower part of the spinning furnace 1, and 3 is a lower part of the cooling means 2. A means for coating the arranged dice coater.

As clearly shown in FIGS. 2 and 3, the cooling means 2 described above includes a cylinder 4 having an upper large-diameter portion 4a, an intermediate inclined portion 4b, and a lower small-diameter portion 4C, and the large-diameter portion 4a of the cylinder 4. A plurality of refrigerant injection pipes 6□, 6□, 53, 5 connected to the outer periphery with openings
．． and a rotary blade body 6 rotatably installed at the axial center position within the small diameter portion 4c. - 64 are in a state in which they are inclined downward along the tangential direction of the large diameter portion 4a, while the rotor body 6 in the small diameter portion 4c has its axial center as shown in the figure. In the present invention, as illustrated in FIG. 1, the preform rod 7 is inserted into the spinning furnace 1 at a low speed and heated there. An optical fiber 8 is created by drawing the softened lower end of the rod 7 at high speed, and the optical fiber 8 immediately after spinning is cooled by a cooling means 21 and sent to the next coating means 3, where it is coated. In means 3, a primary coat is formed on the outer periphery of the optical fiber 8 to form a primary coated optical fiber 9.
However, the cooling means 2 cools the optical fiber 8 passing through the cylinder 4 by generating a vortex flow around the outer periphery of the optical fiber 8 due to the cooling medium.

To explain this in detail below, each refrigerant injection pipe 6□~64
When a cooling medium is blown into the cylinder 4 through the cylinder 4, the cooling medium swirls downward along the inner surface of the large-diameter portion 4a and generates a vortex S. While gradually increasing the flow velocity,
On the other hand, in the small diameter portion 4c, the speed of the vortex S is further increased by the rotary blade body 61 which is rotated via the motor M.

The optical fiber 8 passing through the cylinder 4 in which a vortex is generated due to the cooling medium G is rapidly cooled by the high-speed vortex, that is, the cooling medium, which contacts the outer periphery of the optical fiber 8.
The optical fiber 8 is instantly captured at the center of the vortex, and the optical fiber 8 that has entered the center of the vortex is held at a fixed position (the center of the vortex) by hydrodynamic action without escaping from the center, meandering and moving laterally. It exhibits a state of no shake.

Therefore, when the cooling medium is made into a vortex state as described above, and the optical fiber 8 is held at the center of the vortex S to cool the optical fiber 8, not only can this be rapidly cooled, but also the running state of the optical fiber (8) can be cooled. As a result, when the optical fiber 8 after quenching is coated by the coating means 31, even at a high linear speed of 200 m/yritn or more, the optical fiber 8 is stable, which eliminates the problem of uneven coating thickness. Phyno (8 damage, disconnection accidents, etc. will almost never occur) Note that the cooling medium used in the above is of course preferably a fluid, specifically one that cools air purified by filling, LN2, LHe, etc. Vaporized liquefied gases and other liquids with high volatilization are used.

In addition, when generating the vortex S of the cooling medium through the cylinder 4 described above, if the cylinder 4 is supported by an adjustment device 'IN+ for adjusting the movement in the front and rear directions and the left and right directions,
The optical fiber 8 can be more accurately centered on the coating means 3 and the like.

Furthermore, when using a liquid with low volatility as a cooling medium,
It is sufficient to arrange a receiver under the small diameter portion 4c of the cylinder 4, and connect the receiver and each of the refrigerant injection pipes 61 to 64 with piping equipped with a pump, a filter, etc. to configure a circulation system. The number of refrigerant injection pipes 61 to 64 may be increased than in the illustrated example, or
It may be less.

As explained above, in the method of the present invention, in the method of cooling an optical fiber spun by heating and drawing a preform rod, a vortex is generated by a cooling medium around the outer circumference of the optical fiber after spinning, and the cooling medium is Yo#)
Since it is characterized by cooling the original fiber and holding the optical fiber at the center of the vortex, not only can the optical fiber be rapidly cooled by the cooling medium in the vortex state, but also the optical fiber during cooling can be cooled by the vortex. It can be maintained in a stable state with little meandering or wobbling, and since the cooling means also serves as a holding means for the optical fiber, this can be done economically.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing one embodiment of the method of the present invention, and FIG.
Fig. 3 is a vertical cross-sectional view and a plan view of the cooling means in method 1 of the above. ...Cylindrical large diameter portion 4b...Cylindrical inclined portion 4c...Cylindrical small diameter portions 51 to 64...Refrigerant injection pipe 6...Rotor blade body 7 -...Fliform rod 8...Optical fiber S...Eddy current No./E Fig. 2 Fig. 3

Claims (2)

[Claims] (1) Using a method of cooling spun optical fiber by heating and drawing a 7-ohm rond, a vortex is generated by a cooling medium around the outer circumference of the optical fiber after spinning, and the optical fiber is cooled by the cooling medium. At the same time, there is an optical fiber cooling method that maintains the vortex in the center of the optical fiber. (2) The method for cooling an optical fiber according to claim 1, wherein the cooling medium is a gas. (31) The optical fiber cooling method according to claim 1, wherein the cooling medium is a highly volatile liquid.