JP5538073B2 - Optical fiber preform stretching apparatus and stretching method - Google Patents

Description

  The present invention relates to a stretching apparatus and a stretching method for stretching an optical fiber preform.

As an optical fiber preform drawing method, for example, there is one disclosed in JP-A-10-338535.
In this method, as shown in FIG. 6, an optical fiber preform (hereinafter abbreviated as a preform) 1 made of rod-shaped quartz glass is inserted into a core portion 2a of a heating furnace 2 from above, and a mother portion is sent by a delivery portion 8. The material 1 is gradually sent downward. Thereby, the base material 1 is heated by the heater 3 of the heating furnace 2 from the lower part and softens. The softened base material 1 is drawn out by a take-up section 4 disposed below the heating furnace 2, and is made into a stretched base material 11 having a small diameter by increasing the take-up speed higher than the delivery speed. Is done.

The take-up portion 4 has a caterpillar structure, and a pair of endless belts 4a, 4a sandwiches and pulls a base material 11 having a small diameter, and sends it out downward.
The base material 11 drawn from the heating furnace 2 is cooled by the cooling device 5. The cooling device 5 is provided between the heating furnace 2 and the take-up unit 4, and has a double-pipe structure cooling cylinder 5a, a refrigerant supply unit 5b for supplying refrigerant to the cooling cylinder 5a, The refrigerant | coolant suction part 5c which attracts | sucks the refrigerant | coolant from the cylinder 5a, sends it to the refrigerant | coolant supply part 5b, and circulates is comprised.

Then, a low-temperature fluid is allowed to flow through the space between the double pipes of the cooling cylinder 5a, and the base material 11 drawn out into the hollow cavity of the cooling cylinder 5a is allowed to pass through so that it can be cooled. It has become.
In such a stretching method, since the base material 11 drawn out from the heating furnace 2 is cooled to about 300 ° C. or less by the cooling device 5, it is sandwiched between the endless belts 4 a and 4 a of the take-up part 4. The endless belts 4a, 4a made of synthetic resin or the like are not melted or damaged even if they contact the base material 11.

However, the following disadvantages remain in the stretching method of the prior invention.
That is, since the take-up unit 4 is directly under the outlet of the heating furnace 2, the take-up unit 4 is irradiated with radiant heat radiated downward from the heating furnace 2, and the take-up unit 4 is thereby heated. While the base material 1 is being stretched, the endless belts 4a, 4a of the take-up section 4 are constantly rotating, and the radiant heat is unlikely to concentrate on one endless belt 4a, 4a. Is unlikely to occur.

However, when the stretching of the base material 1 is completed and the movement of the endless belts 4a, 4a of the take-up section 4 is stopped to cool the stretched base material 11, the endless belts 4a, 4a face the heating furnace 2 side. The portion is locally overheated by the direct radiant heat from the heating furnace 2, and is melted and damaged.
For this reason, the endless belts 4a and 4a must be frequently exchanged, leading to a reduction in productivity of the stretched base material 11.

  As a method for solving this problem, a solution can be conceived in which a heat shield plate is provided between the take-up unit 4 and the heating furnace 2 to block radiant heat, but the heat shield plate is provided in close contact with the base material 11 after stretching. Then, since there is a risk of scratching the base material 11, a gap must be provided between the base material 11 and the heat shield plate. For this reason, it is impossible to completely block the radiant heat transmitted from the heating furnace 2, and the endless belts 4a and 4a of the take-up portion 4 cannot be prevented from being melted or damaged.

In addition, after the end of the stretching operation, the endless belts 4 a and 4 a are separated from the base material 11 to stop the operation of the take-up unit 4, and further, the entire take-up unit 4 is moved away from the heating furnace 2.
However, the base material 11 immediately after the drawing is finished and the take-up unit 4 is stopped is very hot. If the take-up unit 4 is separated from the base material 11 in this state, the base material 11 is connected to the upper part. Since it is supported only by the dummy rod 6, there is a problem that the high temperature base material 11 extends downward due to its own weight.

JP-A-10-338535

  Therefore, the problem in the present invention is that when the base material is stretched, the contact sending member made of rubber or synthetic resin that feeds the base material such as an endless belt of the take-up portion while receiving it concentrates the radiant heat from the heating furnace. This is to prevent melting and damage of the contact delivery member.

To solve this problem,
The invention according to claim 1 is a heating furnace that heats the optical fiber preform, a take-up portion that is disposed below the heating furnace and that draws and stretches the optical fiber preform, and holds the stretched optical fiber preform. With a gripping part,
The take-up unit has a contact delivery member that sends out the drawn optical fiber preform while making contact with the drawn optical fiber preform. After the grasped portion grasps the stretched optical fiber preform, the contact delivery member is lightened. An optical fiber preform drawing apparatus that performs an operation of retracting from a region immediately below a heating furnace while being separated from a fiber preform.

According to a second aspect of the present invention, there is provided a heating furnace for heating the optical fiber preform, a take-up portion disposed below the heating furnace for drawing and stretching the optical fiber preform, and gripping the stretched optical fiber preform. Using an optical fiber preform stretching device having a gripping portion and having a contact delivery member that feeds the take-up portion while contacting the stretched optical fiber preform,
After the optical fiber preform is gripped by the gripping portion, the optical fiber preform is retracted from the region immediately below the heating furnace after separating the contact delivery member of the take-up portion from the optical fiber preform. Is the method.

  According to the present invention, the gripping portion grips the stretched base material to prevent deformation due to the weight of the base material, and thereafter, the contact delivery member of the take-up portion is separated from the base material, and is further retracted from the region directly below the heating furnace. Therefore, the radiant heat from the heating furnace is not concentrated on the specific part of the contact delivery member, and the contact delivery member made of rubber or synthetic resin is not melted or damaged by the heat.

It is explanatory drawing which shows an example of the extending | stretching apparatus of the state in the extending | stretching in the extending | stretching method of this invention. It is explanatory drawing which shows the 1st example of the state after the completion | finish of extending | stretching in the extending | stretching method of this invention. It is explanatory drawing which shows the 2nd example of the state after the completion | finish of extending | stretching in the extending | stretching method of this invention. It is explanatory drawing which shows the 3rd example of the state after the completion | finish of extending | stretching in the extending | stretching method of this invention. It is explanatory drawing which shows the extending | stretching method of an Example. It is explanatory drawing which shows the conventional extending | stretching method.

FIG. 1 shows an example of a stretching apparatus in a stretching state in the stretching method of the present invention. The same components as those in FIG.
In this example, the take-up unit 4 is generally configured by a moving unit 41, a pair of rotating bodies 42, 42, and a pair of contact delivery members 43, 43.
The moving part 41 is supported by a support device (not shown) and can move freely in three axial directions. The moving unit 41 includes a driving unit that drives the pair of rotating bodies 42 and 42 to rotate and moves the rotating bodies 42 and 42 closer to or away from each other. The pair of rotating bodies 42, 42 are cylindrical members, and are rotated in opposite directions by the drive unit.

  The pair of contact delivery members 43 and 43 are ring-shaped members attached to the outer peripheries of the rotating bodies 42 and 42, respectively, and play a role of sending them downward while directly contacting and holding the stretched base material 11. It is made of rubber or synthetic resin that does not damage the surface of the stretched base material 11 and can be elastically adhered to the base material 11 and sent out.

  A gripping part 7 is provided. This gripping portion 7 has a function of gripping the base material 11 when the take-up portion 4 separates the base material 11, and a pair of grip pads 71, 71 for gripping the stretched base material 11, and these A drive unit (not shown) for moving the grip pads 71 and 71 closer to or away from each other is provided, and the grip pads 71 and 71 are always kept at a position below the cooling device 5 and away from the stretched base material 11. It is what. The grip pads 71, 71 are made of a material having good heat resistance, such as carbon.

  During the stretching operation, as shown in the figure, the gripping portion 7 is on standby while being separated from the stretched base material 11, and the take-up portion 4 is in contact with the stretched base material 11. While rotating in opposite directions, they are sent downward.

FIG. 2 shows a first example of the state after stretching. In this example, first, the gripping portion 7 starts operation, and the pair of gripping pads 71 and 71 are brought close to the base material 11 to grip the base material 11. When the holding member 7 holds the base material 11, the take-up part 4 separates the pair of contact delivery members 43, 43 from the base material 11, stops its rotation, and then moves the entire moving part 41 downward sufficiently. The distance is moved so that the radiant heat radiated from the heating furnace 2 is withdrawn to a position where it hardly reaches the contact delivery members 43 and 43.
In this retracted state, even if the contact delivery members 43 and 43 stop rotating, they are not melted or damaged by the radiant heat from the heating furnace 2. In this form, since the moving part 41 moves considerably downward, the entire stretching device is increased in size.

FIG. 3 shows a second example of the state after the end of stretching. In this example, after the gripping part 7 grips the stretched base material 11, the contact delivery members 43, 43 of the take-up part 4 move away from the base material 11, and the entire moving part 41 moves to the side of the base material 11. Then, it is retracted to a position outside the region irradiated with radiant heat from the heating furnace 2.
Even in this retracted state, even if the contact delivery members 43 and 43 stop rotating, they are not melted or damaged by the radiant heat from the heating furnace 2.

FIG. 4 shows a third example of the state after the end of stretching. In this example, after the gripping part 7 grips the stretched base material 11, the contact delivery members 43, 43 of the take-up part 4 are far away from the base material 11 to the side, and the radiation heat irradiation region from the heating furnace 2 Is retracted to the outside position.
Even in this retracted state, even if the contact delivery members 43 and 43 stop rotating, they are not melted or damaged by the radiant heat from the heating furnace 2.

As described above, in the embodiment shown in FIGS. 2 to 4, the gripping portion 7 grips the stretched base material 11, and the pair of contact delivery members 43, 43 of the take-up portion 4 are removed from the base material 11 when this gripping is performed. The contact delivery members 43 and 43 are retreated to a region where they do not receive radiant heat from the heating furnace 2.
As is clear from these embodiments, the “region immediately below the heating furnace” in the present invention is that the radiant heat from the heating furnace is applied to the contact delivery member of the take-up section, and the contact delivery member is thermally damaged. This is a possible area.
Therefore, by retracting the contact delivery member of the take-up portion from this region, the contact delivery member is not melted or damaged by the radiant heat from the heating furnace.

Regarding the gripping of the stretched base material 11 by the gripping part 7, a method of gripping after the rotation of the contact delivery members 43, 43 of the take-up part 4 stops after the stretching work is completed, There is a method in which the base material 11 is gripped while moving, and then the movement of the gripping portion 7 and the rotation of the contact delivery members 43 and 43 of the take-up portion 4 are stopped simultaneously.
The former can be performed with a simple apparatus, and the latter can separate the contact delivery members 43 and 43 from the base material 11 in a very short time after the take-off portion 4 stops, so that the contact delivery members 43 and 43 are melted. -The possibility of damage can be further reduced.
As a result, the replacement frequency of the contact delivery members 43 and 43 of the take-up section 4 is reduced, and the productivity of the optical fiber preform can be improved.

Specific examples are shown below.
(Example)
In this example, using a stretching apparatus having the structure shown in FIG. 5, the rod-shaped base material 1 made of quartz glass having an outer diameter of 100 mm is heated to 2000 ° C. or more and stretched, and the stretched base material 11 having an outer diameter of 30 mm A stretching operation was performed.
In this apparatus, the contact delivery member 43 of the take-up portion 4 has a caterpillar structure having a pair of rubber endless belts. The take-up unit 4 moves in the horizontal direction. In the apparatus shown in FIG. 5, the same components as those in the apparatus shown in FIG.
The grip part 7 has a pair of grip pads 71, 71 made of carbon, and these grip pads 71, 71 sandwich and grip the base material 11 by a chuck mechanism (not shown).

  After the end of stretching, the rotation of the endless belts 43, 43 of the take-up section 4 is stopped, and immediately, the stretched base material 11 is gripped by the gripping section 7, and then the endless belt is separated from the base material 11, and the entire moving section 41 is It was moved horizontally from the material 11 to the side of the base material 11, and retreated from a position directly below the heating furnace 2 to a position not on the extension line of the outlet of the heating furnace. This state was maintained for 3 hours, and the base material 11 was cooled. After cooling the base material, the rubber endless belt that was in contact with the base material was observed, and no melting or damage of the belt could be confirmed.

1 .... Optical fiber preform 2 .... Heating furnace 4 .... Take-up part 43 ... Contact delivery member 7 ... Holding part

Claims (2)

A heating furnace that heats the optical fiber preform, a take-up section that is disposed below the heating furnace and that draws and stretches the optical fiber preform, and a carbon gripping part that grips the stretched optical fiber preform. ,
The take-up portion has a contact delivery member made of rubber or synthetic resin that feeds the drawn optical fiber preform while making contact with the drawn optical fiber preform, and the grasping portion holds the drawn optical fiber preform. After that, the optical fiber preform stretching apparatus is configured to perform an operation of separating the contact delivery member from the optical fiber preform and retracting from the region immediately below the heating furnace. A heating furnace that heats the optical fiber preform, a take-up section that is disposed below the heating furnace and that draws and stretches the optical fiber preform, and a carbon gripping part that grips the stretched optical fiber preform. , Using an optical fiber preform stretching device having a contact delivery member made of rubber or synthetic resin, while the take-out portion is in contact with the stretched optical fiber preform and sends it out,
After the optical fiber preform is gripped by the gripping portion, the optical fiber preform is retracted from the region immediately below the heating furnace after separating the contact delivery member of the take-up portion from the optical fiber preform. Method.

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