JPH0891861A - Glass rod drawing method - Google Patents

Abstract

(57) [Summary] [Purpose] A glass rod stretching method capable of maintaining the finished outer diameter of a glass rod after stretching with high accuracy in the longitudinal direction even if the outside diameter of the glass rod varies before stretching. provide. [Structure] While heating and melting from the tip side of a glass rod, the heated and melted portion is stretched to a desired outer diameter. Either or both of the glass rod supply speed and the take-up speed are controlled so that the gradient between the two adjacent points A and B of the neck-down portion 1b due to the stretching of the glass rod 1a becomes constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass rod stretching method for obtaining a glass rod having a constant outer diameter (for example, an optical fiber preform) by stretching the glass rod to a desired outer diameter.

[0002]

2. Description of the Related Art Conventionally, a glass rod is stretched by heating and melting it from the tip side of the glass rod by heating means such as an electric furnace or an oxyhydrogen burner, while applying tension to the heated and melted portion. To obtain a glass rod having a constant outer diameter.

In order to make the outer diameter of the glass rod constant,
A method of measuring an outer diameter near the end of a neck-down portion in a heated and melted portion of the glass rod, and adjusting a supply speed or a take-up speed of the glass rod based on a result of the measurement. Has been taken (JP-A-56
-9231, JP-A-57-195139).

Further, even when the outer diameter varies in the longitudinal direction of the glass rod, the outer diameter immediately after the start of the neck down portion and immediately before the end of the neck down portion are set in order to obtain a target outer diameter with a good finished outer diameter accuracy. Of the outer diameter of the neck down portion immediately before the end of the neck down portion is calculated in advance from the outer diameter of the neck down portion immediately after the start of the neck down portion. A method has been used in which the deviation between the two is calculated from the measured value of the diameter, and either one or both of the feed rate and the take-up rate of the glass rod is controlled (JP-A-5-147971).

[0005]

However, the former conventional technique has a problem that if the outer diameter varies in the longitudinal direction of the glass rod, it also appears in the finished rod diameter.

In the latter prior art, the accuracy of the finished outer diameter can be made higher than that of the former, but in measuring the outer diameter immediately after the start of the neck down portion and controlling the outer diameter immediately before the end of the neck down portion, There is a problem that the influence when the outer diameter changes immediately after the start of the neck down portion does not immediately affect the outer diameter immediately before the end of the neck down portion, resulting in a time delay. It is considered that the time delay changes depending on the length of the neck down portion. Therefore, there is a problem that the time delay changes as the outer diameter of the glass rod fluctuates, making it difficult to control the outer diameter of the glass rod.

The neck-down shape changes depending on the outer diameter of the glass rod. Therefore, even if the outer diameter of the neck-down portion is measured immediately after the start, the distance from the location where neck-down starts due to fluctuations in the outer diameter of the glass rod to the location where the outer diameter of the neck-down portion is measured immediately after the neck-down portion changes. Therefore, in the conventional control method of measuring the outer diameter immediately after the start of the neck-down portion and predicting the outer diameter immediately before the end, the prediction includes an error. Therefore, the accuracy of the finished outer diameter of the glass rod may be deteriorated. In fact, when the variation of the outer diameter of the glass rod occurs in a relatively short cycle, there is a problem that the accuracy of the finished outer diameter of the glass rod deteriorates.

An object of the present invention is to provide a glass rod drawing method capable of maintaining the finished outside diameter of a glass rod after drawing with high accuracy in the longitudinal direction even if the outside diameter of the glass rod varies before drawing. To provide.

[0009]

DISCLOSURE OF THE INVENTION The present invention is directed to an improvement in a glass rod drawing method in which a glass rod is heated and melted from its tip end while the heated and melted portion is drawn to a desired outer diameter.

In the glass rod drawing method of the present invention, the gradient Sab between the two adjacent points A and B of the neck-down portion due to the glass rod drawing is constant,
It is characterized in that either one or both of the feeding speed and the drawing speed of the glass rod is controlled.

In the glass rod drawing method of the present invention, the slope Sab between two points A and B adjacent to each other in the neck-down portion formed by the glass rod drawing and the average outer diameter Rab between the two points A and B are set. Is controlled so that Sab / Rab = constant, either one or both of the feed rate and the take-up rate of the glass rod is controlled.

Further, in the glass rod drawing method of the present invention, of the three adjacent points A, B, C of the neck-down portion formed by the glass rod drawing, two adjacent points A, B are provided.
Ratio (Sab / Rab) between the slope Sab between the two points A and B and the average outer diameter Rab between the two points A and B, and the slope Sbc between the two adjacent points B and C and the average outer diameter between the two points B and C. Ratio with Rbc (Sb
c / Rbc) is controlled such that (Sab / Rab) / (Sbc / Rbc) = constant, either one or both of the feed rate and the take-up rate of the glass rod is controlled.

[0013]

When the gradient Sab between the two adjacent points A and B of the neck-down portion due to the stretching of the glass rod is controlled to be constant, the flow rate of the molten glass between these two points A and B is constant. In addition, the density of the molten glass at the neck-down part is practically constant, and since it is uncompressed, it will be stretched to a constant outer diameter in any other cross section, and therefore, in the longitudinal direction of the glass rod before stretching. Even if the outer diameter changes,
It is possible to perform stretching so that the finished outer diameter of the stretched glass rod can be maintained in the longitudinal direction with high accuracy.

Further, the slope Sab between two points A and B adjacent to each other in the neck-down portion due to the stretching of the glass rod and the average outer diameter Rab between the two points A and B are controlled so that Sab / Rab = constant. Then, in this stretching method, the average outer diameter Rab of the neck-down portion is also included in the control element, so that the slope is constant despite the change of the outer diameter of the neck-down portion. Avoid erroneous control in
It can be stretched so that the finished outer diameter of the glass rod can be maintained in the longitudinal direction with high accuracy.

Further, among the three adjacent points A, B and C of the neck-down portion due to the stretching of the glass rod, the gradient Sab between the two adjacent points A and B and the average outer diameter Ra between the two points A and B.
The ratio (Sab / Rab) to b and the ratio (Sbc / Rbc) between the slope Sbc between two adjacent points B and C and the average outer diameter Rbc between the two points B and C are (Sab / Rab) If control is performed so that / (Sbc / Rbc) = constant, even in this stretching method, the average outer diameter Rab between the two points A and B and the average outer diameter Rbc between the two points B and C of the neck-down portion are control elements. As a result, erroneous control is avoided in situations where the gradient is constant despite the change in the outer diameter of the neck-down portion, and the finished outer diameter of the glass rod is adjusted in the longitudinal direction. It can be stretched so as to maintain high precision.

In particular, in this drawing method, since the three points A, B, and C that are close to each other in the neck-down portion are to be detected, the outer diameter of the wider portion of the neck-down portion can be controlled to be constant and the glass can be controlled. The rod can be stretched so that the finished outer diameter of the rod can be maintained more accurately in the longitudinal direction.

When the neck-down portion is detected between two points A and B and then between two points B and C, control can be performed twice, and control and pulling on the sending side can be performed. There is an advantage that the take-up side can be effectively controlled, and the accuracy of the finished outer diameter of the glass rod can be improved more easily.

Further, in any of the above-mentioned stretching methods, the numerical values to be controlled are such that the gradient Sab between the two points A and B is constant, Sab / Rab = constant, (Sab / Rab) / (S
Since one numerical value that is constant is the control target, such as bc / Rbc) = constant, it is easy to avoid a situation in which it is difficult or impossible to implement with multiple numerical values as the control targets. Has the advantage that it can be industrially implemented.

[0019]

FIG. 1 shows a first embodiment of an apparatus for carrying out the glass rod drawing method according to the present invention.

The glass rod drawing apparatus of this embodiment is equipped with a heating furnace 2 for accommodating the glass rod 1a before drawing, and the glass rod 1a before drawing is heated from the lower side inside the heating furnace 2. A heater 3 for melting is provided. The upper glass rod 4 for gripping is connected in advance to the upper part of the glass rod 1a before stretching, and the lower glass rod 5 for gripping is also connected in advance to the lower part. Glass rod 1a before drawing
When a drawing force is applied to the heating and melting part by the heater 3, the glass rod 1c after drawing having a constant outer diameter is formed through the neck down part 1b. Therefore, the lower glass rod 5 for grasping is in a state of being connected to the glass rod 1c after being stretched.

The upper glass rod 4 for gripping is gripped by the upper chuck 6, whereby the glass rod 1a before stretching is driven up and down by the upper drive unit 7 via the upper chuck 6.

The lower glass rod 5 for gripping is gripped by the lower chuck 8, so that the glass rod 1c after stretching is driven to descend by the lower driving section 9 via the lower chuck 8.

Immediately before the end of the neck-down portion 1b, the heating furnace 2 corresponding to two points A and B adjacent to each other is provided with first and second measuring holes 10 and 11 penetrating in the horizontal direction. These measurement holes 10 and 11 are transparent bodies 10a and 11a such as glass.
Is closed.

The first measuring hole 10 has a first outside on one end side.
Is provided with a light emitting portion 12a of a first laser measuring device 12 as a neck-down portion outer diameter measuring device of the first measuring hole 10
A light receiving portion 12b of the first laser measuring device 12 is provided outside the other end side of the.

The second measuring hole 11 has a second outside on one end side.
Is provided with a light emitting portion 13a of a second laser measuring device 13 as a neck down portion outer diameter measuring device of the second measuring hole 11
A light receiving portion 13b of the second laser measuring instrument 13 is provided outside the other end side of the.

The output of the light receiving section 12b of the first laser measuring instrument 12 and the output of the light receiving section 13b of the second laser measuring instrument 13 are given to the arithmetic processing unit 14, and the arithmetic processing unit 14 controls the neck down section 1b. The slope Sab between two adjacent points A and B is measured, and a control signal that makes the measured slope Sab constant is obtained.

These control signals are given to the speed control section 15 to control the speeds of the upper drive section 7 and the lower drive section 9.

The upper part of the heating furnace 2 is sealed by an upper sealing lid 16, and the lower part of the heating furnace 2 is sealed by a lower sealing lid 17.

A light emitting portion 18a of a laser measuring device 18 as a stretched glass rod outer diameter measuring device for measuring the outer diameter of the stretched glass rod 1c is provided on one side below the heating furnace 2 and the other end. A light receiving portion 18b of the laser measuring device 18 is provided on the side.

Next, a method of drawing a glass rod by using such a glass rod drawing apparatus will be described.

The upper drive unit 7 basically has the glass rod 1a before being stretched so that the neck-down portion 1b of the glass rod 1a before being stretched is always present at the position shown in the figure.
Is driven so as to be lowered as it is stretched.

The lower drive unit 9 basically drives the glass rod 1c after drawing as it grows as the glass rod 1c after drawing grows.

In this state, the outer diameters at two points A and B which are close to each other immediately before the end of the neck-down portion 1b are measured by the first laser measuring instrument 12 and the second laser measuring instrument 13, respectively. The measured output is given to the arithmetic processing unit 14, respectively. Based on these measured outputs, the arithmetic processing unit 14 calculates a slope Sab between two points A and B which are close to each other in the neck-down section 1b.
Is obtained, and a control signal that makes the obtained gradient Sab constant is given to the speed control unit 15. In the speed control unit 15,
The speed of the upper drive unit 7 and the lower drive unit 9 is controlled so that either the feed speed or the take-up speed of the glass rod is adjusted so that the slope Sab between the two adjacent points A and B of the neck-down unit 1b becomes constant. Control either or both.

When the gradient Sab between the two adjacent points A and B of the neck-down portion 1b due to the stretching of the glass rod is controlled to be constant, the flow rate of the molten glass between these two points A and B is controlled. It becomes constant and the neck down part 1
In b, the density of the molten glass is practically constant, and since the flow is incompressible, it is stretched to have a constant outer diameter in any other cross section. Therefore, the outer diameter varies in the longitudinal direction of the glass rod 1a before stretching. Even if there is, it can be drawn so that the finished outer diameter of the glass rod 1c after drawing can be maintained in the longitudinal direction with high accuracy.

However, the reason why this is true is that
Since it is based on the assumption that the viscosity of the glass rod does not change in the measurement section, it is preferable to measure the outer diameters at the points of two adjacent points A and B immediately before the end of the neck-down portion 1b. This is because the temperature of the glass rod is lower immediately before the end of the neck-down portion 1b and the outer diameter of the glass rod is stable even when the supply speed or the take-up speed of the glass rod is changed.

Comparative Experimental Example For a glass rod of 85 mmφ ± 4 mm, the final drawing diameter was 40 mm.
Φ was drawn in the heating furnace 2 having a heater temperature of 1900 ° C.

In the prior art, the variation of the final diameter of the glass rod was ± 0.2 mm. This is a short section with an average diameter of 85
This is because the diameter variation is ± 4 mm with respect to mmφ, and the pitch varies from 10 to 20 mm. If such a rapid change in diameter occurs, the change in the final diameter will increase in the prior art. This is because the places where the diameters are measured are far apart.

However, according to the stretching method of the present invention, the fluctuation of the final diameter of the glass rod was ± 0.09 mm.

Therefore, according to the present invention, it was found that the finished diameter after stretching becomes highly accurate in the longitudinal direction even if the diameter of the glass rod varies in the longitudinal direction.

FIG. 2 shows a second embodiment of the apparatus for carrying out the glass rod drawing method according to the present invention. The parts corresponding to those in the first embodiment described above are designated by the same reference numerals.

In the glass rod stretching apparatus of this embodiment,
In the heating furnace 2 corresponding to the two points A and B which are close to each other immediately before the end of the neck-down portion 1b, a measurement hole 19 made of one long hole having a vertical width slightly larger than the interval between the two points A and B is provided. It is provided penetrating in the horizontal direction. The measurement hole 19 is closed by a light-transmitting body 19a such as glass.

A light emitting portion 20 of a laser measuring device 20 as a neck-down portion outer diameter measuring device is provided outside one end of the measuring hole 19.
a is provided, and the light receiving portion 20b of the laser measuring device 20 is provided outside the other end of the measurement hole 19.

The light emitting portion 20a and the light receiving portion 20b are
Immediately before the end of the neck-down portion 1b, elevating mechanisms 21 and 22 are provided for elevating and lowering at intervals between two points A and B which are close to each other. These lifting mechanisms 21 and 22 include holders 21a and 22a for the light emitting unit 20a and the light receiving unit 20b, and a guide shaft 2 for guiding the holders 21a and 22a so as to move up and down.
1b, 22b, screw screws 21c, 22c penetrating the holders 21a, 22a by screw coupling and moving the holders 21a, 22a up and down, and a motor 21 for rotating these screw screws 21c, 22c.
d and 22d. These motors 21d,
A control signal is supplied from the speed control unit 15 to 22d.

Next, a stretching method using such a stretching device will be described. In the present embodiment, the light emitting unit 20a and the light receiving unit 20b are synchronized with each other and are moved up and down between the two points A and B by the lifting mechanisms 21 and 22. As a result, the neck-down part 1b
It is possible to measure the outer diameter at two points A and B which are close to each other immediately before the end of the above, by one set of the laser measuring device 20. In this embodiment, the measurement point B is the position where the neck down portion 1b is the final diameter, and the measurement point A is 10 mm above the measurement point B.

In this state, the outer diameters at the two points A and B which are close to each other immediately before the end of the neck-down portion 1b are measured by the common laser measuring device 20, and the measurement output is calculated.
Give to 4 respectively. In the arithmetic processing unit 14, based on these measured outputs, two points A, which are close to each other, of the neck-down unit 1b,
The gradient Sab between B is obtained, and a control signal that makes the obtained gradient Sab constant is given to the speed control unit 15. The speed control unit 15 controls the speeds of the upper drive unit 7 and the lower drive unit 9, and supplies the glass rod so that the slope Sab between the two points A and B adjacent to each other in the neck-down unit 1b becomes constant. Either or both of the speed and the take-up speed are controlled.

When the gradient Sab between the two adjacent points A and B of the neck-down portion 1b due to the stretching of the glass rod is controlled to be constant in this way, the flow rate of the molten glass between these two points A and B is increased. It becomes constant and the neck down part 1
In b, the density of the molten glass is practically constant, and since the flow is incompressible, it is stretched to have a constant outer diameter in any other cross section. Therefore, the outer diameter varies in the longitudinal direction of the glass rod 1a before stretching. Even if there is, it can be drawn so that the finished outer diameter of the glass rod 1c after drawing can be maintained in the longitudinal direction with high accuracy.

When the same glass rod as in Example 1 was drawn, the variation in the final diameter was ± 0.1 mm.

FIG. 3 shows another embodiment of the glass rod drawing method according to the present invention. In the case of this embodiment,
Since the structure of the apparatus is almost the same as that of FIG. 1 described above, it will be described with reference to FIGS. 1 and 3.

Also in this case, the upper drive unit 7 basically moves the glass rod 1a before stretching so that the neck-down portion 1b of the glass rod 1a before stretching is always present at the position shown in the figure. It is driven so as to be lowered as it is stretched.

The lower drive unit 9 basically drives the glass rod 1c after drawing, so as to draw the glass rod 1c after drawing, as the glass rod 1c after drawing grows.

In such a state, the outer diameters at two points A and B which are close to each other immediately before the end of the neck-down portion 1b are measured by the first laser measuring instrument 12 and the second laser measuring instrument 13, respectively. The measured output is given to the arithmetic processing unit 14, respectively. Based on these measured outputs, the arithmetic processing unit 14 calculates a slope Sab between two points A and B which are close to each other in the neck-down section 1b.
And the average outer diameter Rab between the two points A and B and the gradient S
The ratio of the ab to the average outer diameter Rab (Sab / Rab) is determined.

The gradient Sab between the two points A and B is obtained from the difference Sab = Ra-Rb between the outer diameter Ra of the neck-down portion 1b at the point A and the outer diameter Rb of the neck-down portion 1b at the point B.

The average outer diameter Rab between the two points A and B is calculated by Rab = (Ra + Rb) / 2.

Further, the gradient Sab and the average outer diameter Rab
The ratio (Sab / Rab) is calculated from the values of and.

In the present embodiment, the speed controller 15 is provided with a control signal such that the ratio (Sab / Rab) between the obtained gradient Sab and the average outer diameter Rab is Sab / Rab = constant. The speed control unit 15 controls the speeds of the upper drive unit 7 and the lower drive unit 9, and determines the ratio (Sab / Ra) of the slope Sab between two points A and B adjacent to each other in the neck-down unit 1b and the average outer diameter Rab.
Either or both of the feed rate and the take-up rate of the glass rod are controlled so that b) becomes constant.

By controlling in this way, in the stretching method of this embodiment, the average outer diameter Rab of the neck-down portion 1b is also included in the control element, so that the outer diameter of the neck-down portion 1b also changes. Regardless, it is possible to avoid erroneous control in the situation where the gradient Sab is constant and to extend the finished outer diameter of the glass rod in the longitudinal direction with high accuracy.

The device for measuring the outer diameters of the two points A and B adjacent to each other in the neck-down portion 1b is not limited to the device shown in FIG. 1 described above, and the device shown in FIG. 2 described above is also used. can do.

FIGS. 4 and 5 show a third embodiment of the apparatus for carrying out the glass rod stretching method according to the present invention.

The glass rod drawing apparatus of this embodiment has three points A, B and C which are close to each other immediately before the end of the neck-down portion 1b.
The heating furnace 2 corresponding to the first, second, and third measurement holes 1
0, 11, and 19 are provided so as to penetrate in the horizontal direction.
These measurement holes 10, 11, and 19 are closed by a light transmitting body 20 such as a common glass.

The first measuring hole 10 has a first outside on one end side.
Is provided with a light emitting portion 12a of a first laser measuring device 12 as a neck-down portion outer diameter measuring device of the first measuring hole 10
A light receiving portion 12b of the first laser measuring device 12 is provided outside the other end side of the.

The second measuring hole 11 has a second outside on one end side.
Is provided with a light emitting portion 13a of a second laser measuring device 13 as a neck down portion outer diameter measuring device of the second measuring hole 11
A light receiving portion 13b of the second laser measuring instrument 13 is provided outside the other end side of the.

The third measuring hole 19 has a third outside on one end side.
Is provided with a light emitting portion 21a of a second laser measuring device 21 as a neck down portion outer diameter measuring device of the third measuring hole 19
A light receiving portion 21b of the third laser measuring instrument 21 is provided outside the other end side of the.

The output of the light receiving section 12b of the first laser measuring instrument 12, the output of the light receiving section 13b of the second laser measuring instrument 13, and the output of the light receiving section 21b of the third laser measuring instrument 21 are sent to the arithmetic processing unit 14. Given. In the arithmetic processor 14, a slope Sab between two points A and B adjacent to each other in the neck-down section 1b,
The average outer diameter Rab between the two points A and B and the gradient Sab
And the average outer diameter Rab (Sab / Rab), the slope Sbc between two adjacent points B and C, the average outer diameter Rbc between the two points B and C, and the gradient Sbc and the average outer diameter Rbc. Ratio (Sbc / Rbc) and these ratios (Sab / Rab)
Ratio of (Sbc / Rbc) {(Sab / Rab) /
(Sbc / Rbc)}.

The gradient Sab between the two points A and B is obtained from the difference Sab = Ra-Rb between the outer diameter Ra of the neck-down portion 1b at the point A and the outer diameter Rb of the neck-down portion 1b at the point B.

The average outer diameter Rab between the two points A and B is calculated by Rab = (Ra + Rb) / 2.

Further, the gradient Sab and the average outer diameter Rab
The ratio (Sab / Rab) is calculated from the values of and.

The gradient Sbc between the two points B and C is obtained from the difference Sbc = Rb-Rc between the outer diameter Rb of the neck-down portion 1b at the point B and the outer diameter Rc of the neck-down portion 1b at the point C.

The average outer diameter Rbc between the two points B and C is calculated by Rbc = (Rb + Rc) / 2.

Also, the gradient Sbc and the average outer diameter Rbc
The ratio (Sbc / Rbc) is calculated from the values of and.

Further, from the obtained ratio (Sab / Rab) and ratio (Sbc / Rbc) values, the ratio (Sab / Rab) is calculated.
b) / (Sbc / Rbc) is calculated.

In this example, the obtained ratio (Sab / Ra
b) and the ratio (Sbc / Rbc), the ratio (Sa
A control signal is given to the speed control unit 15 such that b / Rab) / (Sbc / Rbc) becomes (Sab / Rab) / (Sbc / Rbc) = constant. The speed control unit 15 controls the speeds of the upper drive unit 7 and the lower drive unit 9, and the ratio (Sab / Ra) between the slope Sab between two points A and B adjacent to each other in the neck-down unit 1b and the average outer diameter Rab (Sab / Ra).
b) and the ratio (Sbc / Rbc) of the gradient Sbc between two adjacent points B and C and the average outer diameter Rbc {(Sab / R
Either or both of the feed rate and the take-up rate of the glass rod are controlled so that ab) / (Sbc / Rbc)} becomes constant.

With this control, the average outer diameter Rab between the two adjacent points A and B of the neck-down portion 1b and the average outer diameter Rbc between the two adjacent points B and C of the neck-down portion 1b enter the control element. Therefore, erroneous control in the situation where the gradient is constant despite the change in the outer diameter of the neck-down portion 1b is avoided, and the finished outer diameter of the glass rod is set in the longitudinal direction. It can be stretched so as to maintain high precision.

In particular, in this stretching method, since the three points A, B and C that are close to each other in the neck-down portion 1b are to be detected, the outer diameter of the wider portion of the neck-down portion 1b can be controlled to be constant. The glass rod can be stretched so that the finished outer diameter of the glass rod can be maintained more accurately in the longitudinal direction.

If the neck-down portion 1b is detected between two adjacent points A and B and then detected between the two adjacent points B and C, control can be performed twice.
The control on the delivery side and the control on the take-up side can be effectively performed, and there is an advantage that the accuracy of the finished outer diameter of the glass rod can be improved more easily.

Further, in any of the stretching methods described above, the numerical values to be controlled are: the slope Sab between the two points A and B is constant, Sab / Rab = constant, (Sab / Rab) / (S
Since one numerical value that is constant is the control target, such as bc / Rbc) = constant, it is easy to avoid the situation where it is difficult or impossible to implement with multiple numerical values as the control targets. It has the feature that it can be industrially implemented.

The device for measuring the outer diameters of the three adjacent points A, B, C of the neck-down portion 1b is not limited to the device shown in FIG. 4, but the type shown in FIG. The device of can also be used. However, in this case, the laser measuring device 20 as the neck down portion outer diameter measuring device is configured to reciprocate between the two points A and C.

A summary of the preferred embodiments of the invention disclosed herein is as follows.

(1) In the glass rod drawing method in which the heated and melted portion is drawn to a desired outer diameter while being heated and melted from the tip end side of the glass rod, two points close to the neck-down portion due to the drawing of the glass rod. A method for stretching a glass rod, characterized in that either one or both of the feeding speed and the drawing speed of the glass rod are controlled so that the gradient Sab between A and B becomes constant.

(2) The gradient Sab between the two points A and B adjacent to each other in the neck-down portion due to the stretching of the glass rod is measured by measuring the outer diameter of the neck-down portion at each position of the two points A and B. Is performed by the neck down portion outer diameter measuring instruments respectively arranged at respective positions, and each measured value from these neck down portion outer diameter measuring instruments is processed by an arithmetic processing unit. Method for stretching glass rods.

(3) The slope Sab between the two points A and B adjacent to each other in the neck-down portion due to the stretching of the glass rod is measured by measuring the outer diameter of the neck-down portion at each position of the two points A and B. Is performed by a common neck-down portion outer diameter measuring device that reciprocates between each position, and each measured value from the neck-down portion outer diameter measuring device is processed by an arithmetic processing unit. The method for stretching a glass rod according to 1.

(4) The method for stretching a glass rod according to any one of items 1 to 3, wherein the gradient measurement at the neck down portion is performed near the end of the neck down portion. .

(5) In the glass rod drawing method of drawing the heated and melted portion to a desired outer diameter while heating and melting from the tip side of the glass rod, two points close to the neck-down portion due to the drawing of the glass rod. Either or both of the feed rate and the take-up rate of the glass rod are controlled so that the gradient Sab between A and B and the average outer diameter Rab between the two points A and B are Sab / Rab = constant. A method for stretching a glass rod, comprising:

(6) The gradient Sab between the two adjacent points A and B of the neck-down portion due to the stretching of the glass rod.
And the average outer diameter Rab is measured by a neck down portion outer diameter measuring device disposed at each position for measuring the outer diameter of the neck down portion at each of the two points A and B. The method for stretching a glass rod according to the fifth item, which is performed by processing each measurement value from the outer diameter measuring device with an arithmetic processing device.

(7) The slope Sab between two points A and B adjacent to each other in the neck-down portion due to the stretching of the glass rod and the average outer diameter Rab are measured by measuring the neck at each position of the two points A and B. The outer diameter of the down part is measured by a common neck down part outer diameter measuring device that reciprocates between each position, and each measurement value from the neck down part outer diameter measuring device is processed by an arithmetic processing unit. The method for stretching a glass rod according to the fifth aspect, which is characterized in that.

(8) The measurement of the gradient Sab and the average outer diameter Rab at the neck-down portion is performed near the end of the neck-down portion. The method for stretching a glass rod according to one.

(9) In the glass rod drawing method for drawing the heated and melted portion to a desired outer diameter while heating and melting from the tip side of the glass rod, three points close to the neck-down portion due to the drawing of the glass rod. Of A, B and C, the slope Sab between two adjacent points A and B and the two points A and
A ratio (Sab / Rab) between B and the average outer diameter Rab, and a ratio (Sbc / Rbc) between the slope Sbc between two adjacent points B and C and the average outer diameter Rbc between the two points B and C. A glass rod drawing method, characterized in that either one or both of the feed rate and the take-up rate of the glass rod is controlled so that (Sab / Rab) / (Sbc / Rbc) = constant.

(10) Of the three adjacent points A, B, C of the neck-down portion due to the stretching of the glass rod, the slope Sab between two adjacent points A, B and the average outside of the two points A, B Ratio with diameter Rab (Sab / Rab), slope Sbc between two adjacent points B and C, and average outer diameter Rb between the two points B and C
The ratio (Sbc / Rbc) to c is measured at the three points A,
The outer diameter of the neck-down portion at each position of B and C is measured by the neck-down portion outer diameter measuring device arranged at each position, and each measured value from the neck-down portion outer diameter measuring device is processed by a processor. The method for stretching a glass rod according to item 9, characterized in that the glass rod is stretched.

(11) Of the three adjacent points A, B, C of the neck-down portion due to the stretching of the glass rod, the slope Sab between two adjacent points A, B and the average outside of the two points A, B Ratio with diameter Rab (Sab / Rab), slope Sbc between two adjacent points B and C, and average outer diameter Rb between the two points B and C
The ratio (Sbc / Rbc) to c is measured at the three points A,
The outer diameter of the neck-down portion at each position B and C is measured by a common neck-down portion outer diameter measuring device that reciprocates between the two points A and C. The glass rod drawing method according to item 9, which is performed by processing the measured value with an arithmetic processor.

(12) The ratio (Sab / Rab) between the slope Sab between the two adjacent points A and B in the neck down portion and the average outer diameter Rab between the two points A and B, and the two adjacent points The slope Sbc between B and C and the average outer diameter Rb between the two points B and C
The method for stretching a glass rod according to any one of items 9 to 11, characterized in that the ratio (Sbc / Rbc) to c is measured near the end of the neck-down portion.

[0090]

As described above, in the glass rod stretching method according to the present invention, the two rods are controlled so that the gradient between the two adjacent points of the neck-down portion due to the stretching of the glass rod becomes constant. The flow rate of the molten glass between the two is constant, and the density of the molten glass is practically constant at the neck-down part, and since the flow is uncompressed, it will be stretched to a constant outer diameter in any other cross section. Therefore, even if the outside diameter of the glass rod varies in the longitudinal direction before stretching, it can be stretched so that the finished outside diameter of the glass rod after stretching can be maintained in the longitudinal direction with high accuracy.

Further, in the glass rod drawing method according to the present invention, the slope Sab between the two adjacent points A and B of the neck-down portion due to the glass rod drawing and the average outer diameter Rab between the two points A and B are set. Is controlled so that Sab / Rab = constant, so in this stretching method, the average outer diameter Rab of the neck-down portion is also included in the control element.
The finished outer diameter of the glass rod is maintained in the longitudinal direction with high accuracy by avoiding erroneous control when the gradient is constant despite the outer diameter of the neck-down portion changing. It can be stretched as needed.

Further, in the glass rod drawing method according to the present invention, of the three adjacent points A, B, C of the neck-down portion formed by the glass rod drawing, the gradient Sab between two adjacent points A, B and Ratio (Sab / Rab) to the average outer diameter Rab between the two points A and B, and the slope S between the two adjacent points B and C
bc and the average outer diameter Rbc between the two points B and C (Sbc
/ Rbc) is controlled so that (Sab / Rab) / (Sbc / Rbc) = constant, so even in this stretching method, the average outer diameter Rab between the two points A and B of the neck-down portion and the two points B, C
Since the average outer diameter Rbc between them is included in the control element, erroneous control is avoided in a situation where the gradient is constant despite the outer diameter of the neck-down portion changing. The glass rod can be stretched so that the finished outer diameter of the glass rod can be maintained in the longitudinal direction with high accuracy.

In particular, in this stretching method, since three points A, B, and C that are close to each other in the neck-down portion are to be detected, the outer diameter of a wider portion of the neck-down portion can be controlled to be constant, and the glass can be controlled. The rod can be stretched so that the finished outer diameter of the rod can be maintained more accurately in the longitudinal direction.

If the neck-down portion is detected between the two points A and B and then detected between the two points B and C, the control can be performed twice, and the control and the pulling on the sending side can be performed. There is an advantage that the take-up side can be effectively controlled, and the accuracy of the finished outer diameter of the glass rod can be improved more easily.

Further, in any of the above-described stretching methods, the numerical values to be controlled are: the slope Sab between the two points A and B is constant, Sab / Rab = constant, (Sab / Rab) / (S
Since one numerical value that is constant is the control target, such as bc / Rbc) = constant, it is easy to avoid the situation where it is difficult or impossible to implement with multiple numerical values as the control targets. It has the feature that it can be industrially implemented.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a first embodiment of a drawing apparatus for carrying out a glass rod drawing method according to the present invention.

FIG. 2 is a vertical cross-sectional view showing a schematic configuration of a second embodiment of a stretching device for carrying out the glass rod stretching method according to the present invention.

FIG. 3 shows measurement points A and B and outer diameters Ra and R of the neck-down portion in another example of the glass rod drawing method according to the present invention.
It is explanatory drawing which shows the relationship with b.

FIG. 4 is a vertical cross-sectional view showing a schematic configuration of a third embodiment of a stretching device for carrying out the glass rod stretching method according to the present invention.

FIG. 5 is an explanatory view showing the relationship between the measurement points A, B and C and the outer diameters Ra, Rb and Rc of the neck-down part in the glass rod drawing method according to the present invention using the drawing device of the third embodiment. Is.

[Explanation of symbols]

1a Glass rod before stretching 1b Neck down part 1c Glass rod after stretching 2 Heating furnace 3 Heater 4 Upper glass rod for gripping 5 Lower glass rod for gripping 6 Upper chuck 7 Upper driving part 8 Lower chuck 9 Lower driving part 10, 11 1st, 2nd measurement hole 10a, 11a Translucent body 12 1st laser measuring device (1st neck-down part outer diameter measuring device) 12a Light emitting part 12b Light receiving part 13 2nd laser measuring device (2nd Neck down part outer diameter measuring device) 13a light emitting part 13b light receiving part 14 arithmetic processing unit 15 speed control part 16 upper sealing lid 17 lower sealing lid 18 laser measuring device (glass rod outer diameter measuring device after stretching) 18a light emitting part 18b light receiving part 19 3rd measurement hole 20 Translucent body 21 3rd laser measuring device 21a Light emitting part 21b Light receiving part

Claims (3)

[Claims] 1. A method of stretching a glass rod, wherein the heated and melted portion is stretched to a desired outer diameter while being heated and melted from the tip side of the glass rod. , B is controlled such that either or both of the feed rate and the take-up rate of the glass rod are controlled so that the gradient Sab between B and B becomes constant. 2. A glass rod drawing method for drawing a heated and melted portion to a desired outer diameter while heating and melting the glass rod from the tip side thereof. , B is controlled so that the slope Sab between the two points A and B and the average outer diameter Rab between the two points A and B are constant Sab / Rab = Sab / Rab. A method for stretching a glass rod, comprising: 3. A glass rod drawing method for drawing a heated and melted portion to a desired outer diameter while heating and melting the glass rod from the tip side thereof. , B, C, the ratio of the slope Sab between two adjacent points A, B and the average outer diameter Rab between the two points A, B (Sa
b / Rab) and the ratio of the gradient Sbc between two adjacent points B and C and the average outer diameter Rbc between the two points B and C (Sbc / Rb
(c) and (Sab / Rab) / (Sbc / Rbc) = constant so that either or both of the feed rate and the take-up rate of the glass rod are controlled, Method.