JPH0650514Y2 - Optical fiber base material molding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical fiber preform molding apparatus, and more particularly to a preform molding apparatus for the VAD method.

[Conventional technology]

FIG. 2 shows a typical apparatus for carrying out the conventional VAD method. A hollow cylindrical heating cylinder 101 is provided on the lower chamber 2 and the central axis position of the heating cylinder 101 is shown. A dummy rod 102 is arranged in the.

The upper end of the dummy rod 102 is gripped and rotated by a chuck 106 directly connected to a rotary motor provided at one end of the arm 105, and the other end of the arm 105 is screwed onto an appropriate feed screw shaft 103 such as a ball screw. Threaded body sent 1
It is fixed to 04.

In the VAD method, in the above-mentioned device, Si is attached to the lower end of the dummy rod 102.
A glass material gas such as Cl ₄ or GeCl ₄ is blown from the burners 3 together with the oxyhydrogen flame, and SiO _{2 is} generated by the hydrolysis reaction.
It becomes glass soot such as GeO ₂ and deposits on it.

However, when the dummy rod 102 is moved upward with the progress of this chemical reaction, the deposition of glass soot extends in a columnar shape on the outer periphery of the dummy rod 102 and is generated in the heating cylinder 101 as the optical fiber preform 1 as shown in the figure. Is done.

In this apparatus, the heating cylinder 101 serves the purpose of maintaining a high temperature for the glass soot formation reaction and, if necessary, also serves as a heating furnace for vitrifying the optical fiber preform 1 in the next step. Therefore, the inside is shut off from the outside air.

[Means for solving the problem]

As can be seen from FIG. 2, the length of the optical fiber preform 1 produced by the conventional apparatus is almost commensurate with the axial length L ₀ of the heating cylinder 101, so that a long preform is produced. If so, a long heating cylinder is naturally required, and therefore the dummy rod 102 is unavoidably long, and therefore, there is a disadvantage that the runout of the dummy rod easily occurs.

Further, if the heating cylinder 101 becomes longer, the length of the preform 1 plus the length of the heating cylinder 101 is required as the stroke of the feed screw 103 in order to draw out the generated optical fiber preform from the inside of the heating cylinder. It has the drawback of becoming longer.

[Means for Solving the Problems]

The present invention has been made in order to solve the above problems, and a preform forming apparatus for an optical fiber preform having a heating cylinder in which a dummy rod on which glass soot is deposited moves in the longitudinal direction while rotating inside. The heating cylinder comprises a hollow cylindrical fixed cylinder, at least one slide cylinder coaxially slidable with respect to the fixed cylinder, and a device for moving the slide cylinder in its axial direction. An optical fiber preform molding apparatus characterized by the above.

[Action]

The slide cylinder slides coaxially with respect to the fixed cylinder to form a heating cylinder having a maximum length of the two.

When starting the production of the optical fiber preform or drawing it out after the preform is produced, the axial length can be shortened by pushing the slide tube fully into the fixed tube.

〔Example〕

 An embodiment of the present invention will be described with reference to FIG.

Since the chamber 2 at the lower part of the apparatus and the oxyhydrogen flame burners 3 for blowing glass material provided inside the chamber 2 are the same as the conventional ones, the description thereof will be omitted.

A fixed cylinder 4, which is a hollow cylindrical quartz tube, is fixed immediately above the chamber 2, and a similar hollow cylinder-shaped slide cylinder 5 is slidably provided coaxially with the fixed cylinder 4.

The fixed cylinder 4 and the slide cylinder 5 are hermetically connected by an appropriate seal member 41 so that the heat inside does not escape to the outside.

The dummy rod 8 is arranged at the central axis line position of the fixed cylinder 4, and its upper end is gripped by the chuck portion 73 directly connected to the spindle of the motor. The chuck portion 73 is attached to an arm 72 fixed to a female screw body 71 that is slidably engaged with an appropriate feed screw shaft 7 such as a ball screw, and this structure allows the dummy rod 8 to rotate around its axis. It is also rotated and sent in the axial direction.

An arm 62 is attached to the upper end of the slide cylinder 5, and this arm 62 is connected to a female screw body 61 that is screwed onto the feed screw shaft 6 and slides. Therefore, by rotating the feed screw shaft 6, the slide cylinder 5 can be moved in the axial direction.

If the length of the fixed cylinder 4 in the axial direction is L ₁ and that of the slide cylinder 5 is L ₂ , then when the slide cylinder 5 is fully pulled out from the fixed cylinder 4, the heating cylinder as a whole (L ₁ + L ₂ ) However, if the slide cylinder 5 is pushed all the way into the fixed cylinder 4, the length of the entire heating cylinder becomes the same as the length L ₁ of the fixed cylinder 4. .

Therefore, the length of the dummy rod 8 may be set so as to correspond to the shortest length L ₁ of the heating cylinder, and as the optical fiber preform 1 is produced by the deposition of the glass soot on the heating cylinder, the slide cylinder 8 is moved. 5 may be sequentially pulled out upward and the axial length of the heating cylinder may be sequentially increased in accordance with the generation of the base material.

Further, when the optical fiber preform 1 is drawn out from the heating cylinder after the production is completed, the slide cylinder 5 may be pushed fully into the fixed cylinder 4 to shorten the length of the heating cylinder. It can be seen that the length of 7 is (length of fixed cylinder L ₁ + length of base material).

As another modified embodiment, although not shown, two or more slide cylinders may be provided so that the slide drawer can be pulled out in two or more stages with respect to the fixed cylinder.

[Effect of device]

According to this invention, the slide cylinder slides coaxially with respect to the fixed cylinder, and a heating cylinder having a maximum length of the two can be formed. There is an effect that a long optical fiber preform can be manufactured.

In addition, the length of the dummy rod can be shortened because the axial length can be shortened by fully pushing the slide tube against the fixed tube when starting the production of the optical fiber preform or pulling it out after the preform is produced. There is an advantage that the runout of the dummy rod can be made compact and the runout of the dummy rod can be eliminated without reducing the runout and increasing the feed screw shaft of the dummy rod.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention, and FIG. 2 is a side sectional view showing an example of a conventional technique. DESCRIPTION OF SYMBOLS 1 ... Optical fiber base material, 4 ... Fixed cylinder, 5 ... Slide cylinder, 6 ... Feed screw shaft, 61 ... Female screw body, 62 ... Arm, 8 ... Dummy rod.

Claims (1)

[Scope of utility model registration request] 1. A preform forming apparatus for an optical fiber preform having a heating cylinder in which a dummy rod for depositing glass soot moves in a longitudinal direction while rotating inside, wherein the heating cylinder is a hollow cylindrical fixed cylinder ( 4), at least one slide cylinder (5) provided so as to be coaxially slidable with respect to the fixed cylinder, and a device (6, 61, 62) for moving the slide cylinder in the axial direction thereof. An optical fiber preform molding device characterized by the above.