JPS58153735A - Method for cooling wire-drawing oven - Google Patents

Abstract

PURPOSE:To accelerate a cooling speed in a wire-drawing oven for shortening a time necessary for the exchange of a heating body, by compressing cooled inert gas by a compressor, introducing it into the wire-drawing oven, recooling heated inert gas discharged from the oven and then introducing it into the oven again. CONSTITUTION:When the heating body 14 of an oven for drawing optical fibers is to be exchanged, a power source is cut, a circulatory system is packed with inert gas from an accumulator 34, water is supplied to a heat exchanger 32, and a compressor 33 is driven. The pressure of the inert gas cooled by the heat exchanger 32 is raised above 2kg/cm<2> by the compressor 33, and said inert gas is introduced from the inlet hole 27 of an upper cover 9 into a manifold 25 through piping 35. The inert gas is dispersed therein, sprayed through draft holes 26, 26', 26'' into the oven, and let flow through the periphery of a heat shield 19 and a draft hole 31 to cool the heat shield 19. The heated inert gas is circulated by letting it flow from the draft holes 29, 29', 29'' of a lower cover 6 through an outlet hole 30 into the heat exchanger 32 again.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cooling a drawing furnace of an optical fiber drawing apparatus using a carbon heating element.

Optical fibers are manufactured by heating and melting one end of an optical fiber base material (rod-shaped) while drawing it. Carbon is generally used as a heating element in the drawing furnace that performs the heating, and an electric current is passed through the carbon to generate heat. A so-called carbon resistance furnace is a common device. Conventionally used heating furnaces have structures shown in the sectional view in FIG. 1, the AA sectional view in FIG. 2, and the 13-B sectional view in FIG. 3. That is, the optical fiber 1eJ, +4' 1 is held by the Nayanoku 2, which is a device that feeds the base material vertically downward, and is sent vertically downward into the furnace at a constant speed, and the optical fiber 40 is drawn out from below the drawing furnace 3. . To explain the structure of the drawing furnace 3,
The cylindrical housing 4 has five water-cooled jackets inside the wall and is cooled by water supply from an external water supply device (not shown).
On the lower side, an F lid 6 that covers a water cooling jacket 7 is tightly fixed with bolts 8, and on 1-41!11, a 1-lid 9 with a water-cooling jacket 10 is attached to -1
1, it is closely fixed to the housing 4.

The lower lid 6 and the lower lid 7 have attached cylinders 12° and 13, respectively.
is being made. There is a power supply piece 15 on the upper bottom in the center of the furnace.
, 15' is provided. A power supply rod 16.16' that supplies power to the heating element 14 is attached to a power supply piece 15.15' with carbon bolts 17, l7'.
It is fixedly joined by. The feed rod 16.16' is held in the cylindrical housing 4 in an electrically insulated manner by an insulator 18.18'. The heating element 14 and the cylindrical housing 4 and ]-
A heat shield 19 is arranged between the lower lids 6 and 9. The heat shield 19 is generally made of graphite and prevents heat conduction from the heating element 14 to reduce energy loss. At the center of the furnace is a core cylinder 2o that keeps the inside of the furnace airtight and shields the base material and the heating element airtight. The upper cover 9 is provided with an inert gas inlet hole communicating with the reactor core, and the casing 4 is provided with an inert gas inlet hole 22 and an inert gas outlet hole 2; 3 communicating with the inside of the reactor body.

To use this furnace, first, cooling water is supplied from a water supply device (not shown) and inert (IJ-gas) is supplied from an inert gas supply device to cool the lower covers 6 and 9 to the cylindrical casing 4. and in the furnace,
0. Filling the reactor core with inert gas. The inert gas prevents the heating element 14, heat shield 19, and core cylinder 20 from deteriorating due to oxidation reactions. Next, when power is supplied from a power supply device (not shown) to the heating element 14 through the power supply rods 16, 16', the heating element 14 is heated to approximately 2000° C. by Joule heat due to the resistance of the heating element 14. With this, the matrix 1
The end of □゛1 is heated and the optical fiber is pulled out.

However, carbon or graphite, which is the heating element 14 of the furnace, gradually deteriorates at high temperatures and eventually breaks, and its lifespan is correlated with the temperature of the heating element, and the higher the temperature, the shorter the lifespan. - With the increase in the drawing speed of horn optical fibers, the temperature of the heating element needs to be raised by 1r, which shortens the life of the heating element and requires frequent replacement of the heating element 14. The heating element is replaced after the temperature of the heating element has decreased, but in conventional furnaces, the heat shield 19 has the largest heat capacity and is surrounded by the cylindrical casing 4 and the lower lids 6 and 9. Because of this, it takes a lot of time to cool down the inside of the furnace after the power is turned off, which has the disadvantage of lowering the operating rate of the equipment.

In order to eliminate the drawbacks of conventional furnaces, the present invention has the following features: - J2 In order to eliminate the drawbacks of conventional furnaces, a large amount of cooled inert gas is flowed into the cooling end furnace, thereby increasing the cooling rate of the furnace internal parts and the heat shield, thereby increasing the furnace operation rate. The purpose is to increase the

The present invention will be explained below with reference to the drawings.

The heating furnace of the present invention has a structure shown in FIGS. 4 and 5. The basic structure is the same as that of the conventional furnace, but in the furnace of the present invention, in addition to the water-cooled jacket 10 in the upper cover 9, there are many small ventilation holes 26, 26', 26'', etc.
Manifold 2 for distributing inert gas with
5 has been made. Providing a large number of small ventilation holes has the advantage of widening the range of high temperatures. Also, the inner wall of the top cover, which is exposed to high temperature gas, is cooled by the water cooling jacket. This is to make the flow of active gas uniform. Similarly, the lower cover 6 is also provided with a 1-l nifold 28 having a large number of ventilation holes 29, 29', 29'', etc. into the furnace.Furthermore, the upper cover is provided with an inert gas manifold 25. There are an inlet hole 27 and a similar outlet hole 30 in the lower lid.

On the other hand, in order to increase the cooling effect, the heat shield 19 is provided with a plurality of ventilation holes 31 to increase the contact area with the inert gas. Furthermore, an inert gas heat exchanger 32, a compressor 33, and an inert gas accumulator 34 are provided outside the furnace.
2, compressor 33, 1-lid 9 person ``1 hole is each pipe 3
7, 36, and 35 to form an inert gas circulation system. Accumulator-34i (
J, piping; connected to the circulation system by 38, heat exchanger 3
2 are connected to cooling water pipes 39 and 40.

In the heating furnace of the present invention, when the carbon heating element 14 deteriorates and needs to be replaced, the power supply is turned off and the circulation system is filled with inert gas from the accumulator; to drive. Then, the inert gas cooled by the heat exchanger 32 is pressurized by the compressor 33 and passes through the pipe 35 to the inlet hole 27 of the lid 9.
to the manifold 25, distributed, and ventilated through the ventilation holes 26.
．． 26', 26"... into the furnace, passes through the outer periphery of the heat shield 19 and the ventilation hole 31, and cools the heat shield 19. Excess inert gas is always kept in the accumulator 34. When the amount of circulating inert gas decreases and store power becomes low, inert gas is supplied to compensate.

According to experiments conducted by the inventors, when working in a conventional heating furnace while maintaining the temperature of the heating element at 2200°C and then stopping the power supply, it took approximately 60 minutes for the heating element and heat shield to reach 100°C. . - In the heating furnace invented by Rikiki, the nitrogen gas is cooled to 20"C and is
When compressed at atmospheric pressure and flushed for approximately 5 rr + 7 minutes, the temperature of the heating element and heat shield is approximately 3
The temperature dropped to 100°C in 0 minutes.

-1=Heating furnace Q- of the present invention as described in detail,
Since inert gas is circulated through the furnace body to accelerate cooling, the cooling time for the heating element and heat shield can be shortened to +1J. Therefore, when the heating element is worn out, the time to replace it is shortened, and the heating element can be replaced easily. It is possible to improve the operating rate of people [1].

[Brief explanation of drawings]

Figure 1 is a C-Cr sectional view of a conventional drawing furnace, and Figure 2 is the same A.
-A' sectional view, and FIG. 3 is a B-H' sectional view. FIG. 4 is a cross-sectional view of E El 1-11 of the present invention's drawing force. FIG. 5 is a cross-sectional view of the same. l: matrix, 2: chunk, 4: cylindrical 1f body, 5.7,
10: Water cooling jacket, 6: T-lid, 9: 1-lid, 8.1
1: Bolt, 12, 13: Attached cylinder, 14; Heating element, 1
5: Power supply piece, 16: Power supply rod, J7: Carbon bolt, 1
8: Insulating support, 19: Heat shield, 20: Core cylinder, 21, 22, 23: Inert gas inlet/outlet, 25
．． 28: Manifold, 26.26'..., 29.
29'...: Ventilation hole, 27: Artificial hole, 30:
lJt port hole, 31: Ventilation hole, 32: Heat exchanger, 33:
Compressor, 34 Niaccumulator, 35.36,37
．． 38...: Piping, 39° 40: Cooling water piping. Agent Patent Attorney 1) Rio Naka

Claims (1)

[Claims] (1) In a drawing furnace using a carbon resistance heating element, a compressor, a heat exchanger, and an inert gas accumulator are provided outside the furnace, and the furnace and these devices are connected by piping. The inert gas cooled during furnace cooling is boosted in pressure by a compressor and sent into the furnace, and the heated inert gas discharged from the furnace is cooled again and pumped into the furnace. A method for cooling a drawing furnace characterized by feeding the wire into a drawing furnace. 2. In a drawing furnace that uses a carbon resistance heating element, the upper and lower lids are equipped with manifolds for distributing inert gas that have numerous ventilation holes into the furnace, and the heat shield is equipped with multiple ventilation holes for cooling. A patent claim characterized in that air holes are provided so that inert gas pressurized during furnace cooling enters the furnace through the manifold and ventilation holes, and cools the heat shield by passing through the outer periphery of the heat shield and the ventilation holes. A method for cooling a drawing furnace according to item 1. 3. The wire according to claim 1 or 2, characterized in that the drawing furnace is an L fiber drawing furnace using a carbon resistance heating element and a graphite heat shield for heat shielding. Method for cooling a drawing furnace 0 4 A method for cooling a drawing furnace according to any one of claims 1 to 3, characterized in that an inert gas is circulated at a pressure of 2 or more.