JPS5838364B2 - Glass pipe manufacturing method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method of manufacturing a glass pipe.

In particular, the present invention relates to a method suitable for producing small quantities of glass pipes with high precision from glass pipes having a uniform wall thickness, especially from glass having a viscosity curve with a large temperature dependence.

Conventional. The industrial manufacturing method for glass pipes involves continuously drawing a stream of molten glass from a tank kiln for molten glass.
Shaping a coating of molten glass on a rotating mandrel fffL
The Danner method is known, in which a glass pipe is manufactured by continuously pulling the glass pipe in the axial direction of a mandrel.

In fact, West German Patent No. 579506 states. The molten glass is drawn from between the bottom outlet wall of the melting kiln and a Dorn provided in the bottom outlet at right angles to the bottom outlet opening and approximately parallel to the glass pipe to be formed. Due to the method of manufacturing glass pipes continuously, the non-uniformity of the wall thickness of the glass pipe caused by the change in the drawing direction can be corrected by moving the door eccentrically with respect to the exit axis. A method of averaging is disclosed.

1, West German Patent No. 604,579 K discloses that when manufacturing a glass pipe by flowing liquid glass around an annular or overflow in a tubular flow type, the inner surface of the tubular glass flow is A method for locally cooling the glass body using a cooling object that protrudes into the pipe but does not come into contact with the glass body is disclosed.

1, Japanese Patent Publication No. 40-325-8 and Japanese Patent Publication No. 45-14917 disclose air pressure supplied to the inside of the pipe in a glass pipe manufacturing apparatus equipped with a bell-shaped body at the L opening of the molten glass drawer. There is a method of automatically controlling the outer diameter of the tube by reducing the above factors, and a method of automatically controlling the inner diameter of the tube that measures the pressure inside and outside the tube, adjusts the air pressure supplied to the inside of the tube, and adjusts the tensioning speed of the tube. Are listed.

Furthermore, in % Publication No. 53-31166, below? Silicon dioxide as a raw material is supplied into a melting crucible equipped with a certain molding device in the belt, and the raw material is forcefully heated at a predetermined temperature 1 in the crucible, and a glass pipe is continuously molded through the entire molding device. A method is disclosed.

However, these methods are not suitable for industrially producing large quantities of glass pipes for fluorescent lights, ampules, syringes, etc., as seen in the '/'i Danner method. However, it does not provide a simple industrial method for manufacturing small quantities of glass pipes.

In recent years, as the technological development of fiber optics has progressed, various glass assemblies have been developed as coating glasses for optical fibers. There is a need for the development of a method for manufacturing with high precision.

In particular, there has been no known industrial manufacturing method suitable for industrially producing small quantities of high-precision glass pipes from so-called short glass, which has a viscosity curve that is highly temperature-dependent. Even today, when trying to produce glass pipes in small quantities, hand-blowing is still relied on.

The method of continuously industrially producing large quantities of glass pipes described in E has been devised to be suitable for large-scale production, so it is easy to industrially produce glass pipes with high F'i but high precision in small quantities. Therefore, a simple method suitable for small-scale production of glass pipes, which is the object of the present invention, has not been disclosed.

According to the research conducted by the present inventors, a method has been discovered that allows for industrially and easily manufacturing glass pipes having uniform wall thickness with high accuracy even in small quantities.

That is, the present invention provides a method for producing a glass pipe by drawing out all of the molten glass from a molten glass crucible having a nozzle with a core at the bottom through the nozzle, in which the length of the nozzle is set to 1.5 times its diameter. A supporting member is provided on the core to fix the core concentrically within the nozzle, and the tip of the core protrudes from the tip of the nozzle. At least three types of heaters are provided around the main body of the Luppo and the nozzle portion, each of which can control the temperature separately. This method of manufacturing a glass pipe is characterized in that the temperature of the molten glass is separately obtained by temperature control ML.

The method of the present invention will be explained in detail below with reference to the attached FIGS. 1 to 3.

FIG. 1 is a schematic cross-sectional view of an example of a glass pipe manufacturing apparatus used to carry out the method of the present invention, and FIG. 2 is a schematic perspective view of an example of a core. , FIG. 3 shows another embodiment of the glass pipe manufacturing apparatus used to carry out the method of the present invention, and is a schematic cross-sectional view.

In FIGS. 1 and 3, a molten glass crucible (hereinafter referred to as a molten crucible) 1 has a nozzle 2 at its bottom, and this nozzle 2 has a pipe-shaped hollow core in its center. It has 3.

The core 3 is fixed concentrically within the core 3 by supports 4 and 5.

FIG. 2 shows one example of the core 3 as described above.

Usually, the nozzle 2 and the core 3 provided therein are arranged in the same manner.

According to the research of the present inventor, in order to achieve the object of the present invention, the length of the nozzle, that is, the length from the bottom of the crucible to the nozzle tip 1, must be 1.5 times the diameter (inner diameter) of the nozzle. More L
It's been a long time since I've been in the middle of a long time since I've been in the middle of a long time since I've been in the middle of a long time since I've been in the middle of a long time since I've been in the middle of a long time. If the nozzle length is less than 1.5 times the nozzle diameter, it becomes extremely difficult to control the temperature, that is, the viscosity, of the glass flowing through the nozzle, making it impossible to manufacture a pipe with high precision.

It has become clear that the tip of the core needs to protrude from the tip of the nozzle, as shown in FIGS. 1 and 3.

The length of the tip of the core protruding from the nozzle is preferably 0.2 to 5 times the distance between the inner diameter of the nozzle and the outer diameter of the core.

If the core does not protrude from the tip of the nozzle, it is difficult to determine the external shape of the pipe at the nozzle exit, so a pipe with a poor external shape and poor wall thickness is manufactured.

The material of the nozzle 2 and the core 3 may be any material as long as it is resistant to heat and the glass assembly used.
A noble metal, quartz, or the like is used, and preferably, for tL<, a noble metal such as platinum, which has good heat conductivity, is used.

The melting crucible 1 and the nozzle 2ii each have separate heaters.

Figures 1 and 3 K are. Three types of heaters 6, 7 and 8 are shown which can be controlled separately.

In other words, these three types of heaters 6, 7 buttons and 8 are
The temperature K=J is sensed through thermocouples 9, 10 and 11, respectively, and the temperature of the molten glass in each part is heated to the desired set temperature.

The number of heaters (3 types in Figures 1 and 3) that are individually controlled determines the temperature of the molten glass in the crucible body, the molten glass in the nozzle part, and the molten glass drawn out from the nozzle part. It is necessary to use at least three types so that all can be individually controlled.

The glass introduced into the crucible 1 is generally kept at a constant temperature for a certain period of time in order to degas and equalize the temperature.

While this holding is continued, the molten glass in the crucible 1 is maintained in the crucible 1 by a water cooler 13 that matches the nozzle 2 and the tip of the core 3, as shown in FIG.

The holding temperature of the molten glass at this time differs depending on the glass assembly, but it is heated by heaters 6, 7, and 8 at a temperature necessary for defoaming the glass, and in particular, the temperature inside the nozzle 2 is kept at a temperature necessary for defoaming the glass. The glass has a temperature distribution in the downward direction as if it were rapidly cooled by the water cooler 13. It is said to be the temperature at which devitrification does not occur.

When degassing and temperature uniformization of the molten glass 12 are completed in the molten glass 1, the water cooler 13 is removed and glass pipe production begins.

The molten glass maintained in the melting crucible 1 at a temperature approximately suitable for pipe production is further adjusted to the temperature required for pipe production within the nozzle 2 in the trench where it is discharged through the nozzle 2.

The apparatus suitable for carrying out the method of the invention illustrated in FIGS. 1 and 2 is a batch-type apparatus using a single melting crucible. The height of the crow's base surface decreases.

The method of the present invention is not only applicable to such a batch method, but also to, for example, J:. The device described above can be installed in a tank kiln, but in the case of a batch type as shown in L, K is a system that compensates for the decrease in the flow rate of molten glass due to the decrease in the height of the base surface by adjusting the temperature of the molten glass in the melting crucible 1. This can be compensated for by making the temperature of the molten glass in the nozzle 2 approximately equal or by making the latter temperature higher than the former temperature.

Such temperature control is performed by the heater 6 and the heater 7, or further by the heater 8K depending on the case.

According to the method of the present invention. By controlling the temperature of the nozzle E part as shown in L, the influence of the height of the base surface due to the batch method as shown in Okaki is offset, and the influence of the decrease in the height of the base surface is minimized to create a glass pipe with high precision. There are many advantages to manufacturing.

In the apparatus of FIGS. 1 and 2, the heater 8 is generally used to temperature control the cooling rate of the glass in a mold section of the glass pipe immediately after leaving the nozzle 2 from the bottom of the nozzle 2.

Generally, the temperature controlled by the heater 8 and the roll 1
The dimensions of the glass pipe are determined by the drawing speed of the glass pipe according to No. 4.

When pulling a glass pipe, air may be blown into the pipe through the core.

As described above, according to the method of the present invention, a melting crucible equipped with a nozzle having a length of at least 1.5 times the diameter and a core with a protruding tip at the center of the nozzle is used. By providing a heater that separately heats the crucible body and the nozzle part, it is possible to easily shape the molten glass discharged from the nozzle tip and control the temperature. Glass pipes with good thickness accuracy can be easily manufactured.

Hereinafter, the method of the present invention will be explained in more detail with reference to Examples.

In the example, the apparatus shown in FIGS. 1 and 3 equipped with the core shown in FIG. 2 was used.

The glass used was S i02 2 0. 5% (
Weight circulation (same below). B20336.0%, Na20
8.0%, K20 2. 5% and Ba033.0
It is a so-called short glass with a rising viscosity curve.

The material of the crucible and core is] o%Rh-pt alloy.

1, crucible diameter (inner diameter) 270 mrnφ, nozzle diameter (inner diameter) 90 m'rltφ, nozzle length 200 plates.
A melting crucible having a nozzle with a core at the bottom having a diameter (outer diameter) of 55 mm at the tip of the core and a length of 1Q mm protruding from the tip surface of the nozzle was used.

1. A silicon carbide heating element was used for the heater (heater 6) that heated the crucible body, and Kanthal wire windings were used for the heaters (heater 7 and heater 8) that heated the nozzle.

In order to manufacture pipes using the melting crucible described above, first, the lower part of the nozzle is cooled with a copper water cooler and sealed off L, , f
:The glass used in the preparation was introduced when the base surface of the molten glass reached the specified height.

Next, the temperature of the molten glass was raised to 1050°C with a viscosity of about 10 poise using heaters 6 and 7.
The glass was held for more than 6 hours to defoam the glass and equalize the temperature.

At this time, heater 8 was not operated. During this period, no occurrence of devitrification of the molten glass i'il:tj was observed.

Next, heater 6, heater 7, and heater 8 are
The viscosity of the molten glass was set at 720°C, which indicates a viscosity of about 05°2 poise, 735°C, which indicates a viscosity of about 10 poise, and 685°C, which indicates a viscosity of about 10 poise, respectively.
．． The temperature of the molten glass in each section was brought to these temperatures by holding for 5 hours.

Next, the water cooler at the bottom is removed and the heater 8 is removed.
By controlling the temperature by the temperature detected by a thermocouple 11K, glass pipe production was started.

A glass pipe 15 having an outer diameter of 25 mm and a wall thickness of IWL7IL was manufactured at a speed of 0.5 mm/min.

The glass pipe manufactured in this way has a variation in outer diameter of 1 m in length and a difference between the major and minor diameters of the outer diameter within ±1, and a variation in wall thickness of 1 m within ±1. It was 0.5 mtn.

On the other hand, an attempt was made to manually manufacture a glass pipe with dimensions E from glass with E assembly, but since the glass was short, it was extremely difficult to manufacture, and it was impossible to manufacture glass pipes with high precision. There wasn't.

In other words, the variation in the outer diameter per meter of length and the difference between the major axis and the minor axis of the outer diameter are both ±5 degrees. The variation in wall thickness was 0.4 wLm.

[Brief explanation of the drawing]

Figures 1 and 3 show schematic cross-sectional views of an example of a glass pipe manufacturing apparatus used to carry out the method of the present invention. shows the state during pipe manufacturing. FIG. 2 shows a schematic perspective view of one example of the core.

Claims (1)

[Claims] 1. In a method for manufacturing a glass pipe by drawing molten glass through a nozzle from a molten glass crucible having a nozzle with a core at the bottom, the length of the nozzle is at least 1.5 times the diameter of the crucible. , a support is provided on the core to fix the core concentrically within the nozzle, the tip of the core protrudes from the tip of the nozzle, and a support is provided on the main body of the Lupo and around the nozzle portion At least three types of heaters are provided to independently control the temperature of the molten glass in the receptacle body, the molten glass in the nozzle section, and the molten glass drawn out from the nozzle section. A method for manufacturing a glass pipe characterized by obtaining controlled ML.