JPH07196327A - Glass molding unit - Google Patents

Abstract

PURPOSE:To provide a glass molding unit designed to improve the system so as to address emergencies by assuredly detecting, even in densification, the development of such an abnormality that a glass fine particle stack is about to crack during its production process by VAD method. CONSTITUTION:In such a process that a target rod 12 is pulled up under revolution by a revolving pull device 13 and glass fine particles produced from burners 21 to 23 are stacked on the lower end of the rod to form a glass fine particle stack 11, a distance detector 43 is provided to detect the lower end position of the stack 11 irrespective of its location for the purpose of controlling the revolving pull device 13, independent of a TY camera 41 to detect said lower end position, and the signals from the distance detector 43 are inputted into a computer 42. Thereby such an abnormality that the stack 11 is about to crack and fall is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass forming apparatus by a VAD (vapor phase axising) method utilizing a vapor phase reaction process, which is suitable for producing a glass preform for an optical fiber.

[0002]

2. Description of the Related Art In the VAD method, glass particles generated by a burner are deposited on the lower end of a rotating target rod,
The columnar soot preform is formed by pulling up the target rod in accordance with the growth of the glass particulate deposit (porous soot preform). Specifically, the lower end position of the soot preform (that is, the growth position of the core part of the soot preform formed by the burner for the core) is monitored by a TV camera or the like and pulled up so that the growth position is always constant. Control the speed.

The porous soot preform thus manufactured has a cylindrical shape as a whole, but is gradually tapered at both ends thereof to have a conical shape. In other words, in the part that is formed at the start of deposition (this is called seeding) (seeding part) and the part that is formed at the end of deposition (called baking) (baking part), at steady time (excluding both ends) Unlike the case of forming the portion), the amount of glass fine particles generated from the burner is reduced so that both end portions have a conical shape.

[0004]

However, there is a problem that the soot preform is cracked in the manufacturing process of the soot preform. In particular, if a broken soot preform falls, it may damage the burner, which is a serious problem. In particular, the possibility of damaging the burner due to the fall of the cracked preform is greater when the soot preform grows and is tightened.

As described above, in the glass forming apparatus using the VAD method, generally, the growth position of the soot preform is monitored, and the soot preform is pulled up according to the position. Therefore, the growth position (lower end position) of the soot preform can be monitored at the time of seeding or in a steady state, and it is possible to detect that the lower end position is abnormally lowered and there is a risk of falling. However, at the time of baking, the amount of glass particles produced is reduced and the glass is pulled up at a specified constant speed, so the lower end position of the soot preform is out of the field of view of the TV camera, etc. It is impossible to detect an abnormality such as a drop with a camera or the like. Since the soot preform is in a sufficiently grown state at the time of baking and fastening, if the soot preform cracks and drops, large damage will occur, and there is a great problem that an abnormality cannot be detected at the time of baking and fastening.

[0006] In view of the above, the present invention enables reliable detection of the occurrence of an abnormality that causes the soot preform to crack during the manufacturing process of the soot preform by the VAD method even during baking and tightening, so that countermeasures can be taken. It is an object of the present invention to provide an improved glass forming apparatus.

[0007]

In order to achieve the above object, according to the present invention, a target rod is pulled up while rotating and glass particles are deposited on the lower end of the target rod to form a glass particle deposit. In the glass forming apparatus, the position of the lower end position of the glass particle deposit is determined separately from the means for detecting the growth point position of the glass particle deposit that obtains a detection signal for controlling the pulling amount during seeding and in a steady state. However, it is characterized by including position detecting means for detecting the lower end position thereof.

[0008]

The pulling amount is controlled so that the growth point position of the glass fine particle deposit body becomes a predetermined value at the time of seeding and in the steady state, but since the growth point position is constant, The detecting means for detecting the position of the growing point also detects the position only within the certain range. Therefore, if the lower end position of the glass fine particle deposit rises during baking, it becomes impossible for the detecting means to detect the lower end position of the glass fine particle deposit. However, separately from this detecting means, there is provided position detecting means for detecting the lower end position of the glass fine particle deposit body regardless of the position of the lower end position of the glass fine particle deposit body. The lower end position of the body can be detected. as a result,
Even at the time of baking up, it is possible to reliably detect an abnormality in which the glass particulate deposit is likely to break and fall, and it is possible to stop the manufacturing process or issue an alarm.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the drawings. In FIG. 1, glass fine particles are generated near the lower end of the target rod 12 3
Two burners 21, 22, 23 are arranged. An oxyhydrogen flame is generated from these burners 21, 22 and 23, and a raw material gas of glass such as silicon tetrachloride is fed into the flame,
Glass particles (fine particles of silicon dioxide) are generated by the hydrolysis reaction, deposited on the lower end of the target rod 12, and the target rod 12 is pulled up by the rotary pulling device 13 while being rotated, so that a cylindrical glass fine particle deposit ( Soot preform 11 is formed.

The burner 21 is a core burner for forming a central core portion, the burner 22 is a clad burner for forming a clad portion occupying the outer periphery of the core portion, and the burner 23 is this clad. It is a burner for clad for forming a clad part further on the outer periphery of the part. Here, the clad portion is formed by two deposited layers. In addition to the silicon tetrachloride gas which is the glass raw material gas, germanium tetrachloride gas which is the raw material gas of the dopant for controlling the refractive index is fed into the burner 21 for the core.

Soot preform 11 and target rod 1
2 is disposed in the chamber 14, and the burners 21 to 23 are attached to the side wall of the chamber 14 or the like so that the deposition process of the glass particles is performed in the chamber 14. To obtain an image near the tip (lower end) position of the core portion accumulated by the core burner 21, T
A monitoring device such as a V camera 41 is attached to the chamber 14.

The image signal from the TV camera 41 is taken into the computer 42, and the growth position of the core portion is detected. A pulling speed control signal is sent to the rotary pulling device 13 in accordance with the detected growth position, and the pulling speed corresponding to the growing speed is set. A pull rate monitor signal representing the actual pull rate is returned to computer 42. The computer 42 controls the mass flow controller 31 that controls the flow rate of the gas supplied to each of the burners 21 to 23 according to the pulling speed monitor signal.
~ 33 to send a gas flow rate control signal. With such a control system, the soot preform 11 is controlled to have a predetermined size (diameter, length).

Further, a distance detector 43 such as a laser displacement meter is attached to the lower end of the chamber 14 so that the lower end position of the soot preform 11 (distance from the distance detector 43) can be detected. There is. This distance detection signal is sent to the computer 42. Therefore, the lower end position of the soot preform 11 is constantly monitored by the distance detector 43 and the computer 42.

In the glass forming apparatus having such a structure, the pulling speed and the gas flow rate are controlled so that the lower end position of the soot preform 11 captured by the TV camera 41 becomes a predetermined position at the time of seeding and at a steady state. , Glass fine particles are deposited. Therefore, during this normal deposition, as shown in FIG. 2, the detection distance is constant regardless of the amount of pulling up of the soot preform 11. When this normal deposition is completed and the tightening process is started, a control signal is sent from the computer 42 to the rotary pull-up device 13 so as to keep the pull-up speed constant regardless of the lower end position of the soot preform 11 captured by the TV camera 41. At the same time, the gas supply amount to the core burner 21 is gradually reduced and finally becomes zero. In addition, the gas flow rates to the other burners 22 and 23 are likewise gradually reduced.

Therefore, during this baking, the lower end position of the soot preform 11 gradually rises. Therefore, the lower end portion of the soot preform 11 is removed from the field of view of the TV camera 41, and the TV camera 4
Depending on 1, the lower end position cannot be captured.
However, since the distance detector 43 is arranged just below the soot preform 11 and detects the distance from the soot preform 11 to the lower end of the soot preform 11, as shown in FIG. In addition, it can be seen that the detection distance is increasing.

Therefore, when the soot preform 11 is about to break and fall during this baking, the detection signal from the distance detector 43 shows a rapid change,
You can catch the anomaly. It is needless to say that the abnormality can be similarly detected at the time other than the baking and fastening, that is, at the time of seeding and at the steady state. When an abnormality is detected in this way, the computer 4
It is possible to give a signal to the mass flow controllers 31 to 33 from No. 2 to the mass flow controllers 31 to 33, give a pulling stop signal to the rotary pulling-up device 13, and generate an alarm that an abnormality has occurred to alert the worker.

The above is one example, and the number of burners is not limited to the above. Further, the TV camera 41 is used to detect the lower end position of the soot preform 11, but a detector using another laser beam or the like may be used. Similarly, as the distance detector 43, various ones other than the displacement meter using the laser beam can be used. Various control systems for controlling the gas flow rate and the pulling rate can be considered. In addition, various modifications can be made without departing from the scope of the present invention.

[0018]

As described above with reference to the embodiments, according to the glass forming apparatus of the present invention, when an abnormality occurs such that the glass particle deposit is broken and tends to drop in the step of depositing glass particles by the VAD method. This makes it possible to reliably detect the abnormality, especially at the time of baking, which causes great damage due to a fall accident. Therefore, it is possible to reduce the burden of the monitoring work by the worker who is manufacturing the soot preform. In addition, since the risk of cracking or falling of the soot preform can be detected quickly, it has become possible to take appropriate measures to avoid damage to the device due to dropping.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the detection distance at the lower end of the soot preform and the pulling amount.

[Explanation of symbols]

11 Glass Fine Particle Deposit (Soot Preform) 12 Target Rod 13 Rotation Lifting Device 21, 22, 23 Burner 31, 32, 33 Mass Flow Controller 41 TV Camera 42 Computer 43 Distance Detector

Claims (1)

[Claims] 1. A pulling means for pulling while rotating a target rod, a glass fine particle producing means for producing glass fine particles and depositing the glass fine particles on the lower end of the target rod, and detecting a growth point position of the glass fine particle deposit. Means and the above-mentioned pulling-up amount is controlled so that the above-mentioned detected growth point position is set to be a predetermined value at the time of seeding and in a steady state, and regardless of the detected growth point position during baking. A glass forming apparatus comprising: a control unit that controls a predetermined amount of pulling up and a position detection unit that detects the lower end position of the glass fine particle deposit body at any position.