JP2003054972A - Method for manufacturing glass tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a glass tube at a low cost by which a glass tube of long-length and thick wall having a hole of high precision at a central part can be easily obtained. SOLUTION: An axle 2 of prescribed size is almost concentrically inserted and arranged in a cylindrical glass tube 1 and further a plurality of glass element wires 3 are charged in parallel between the cylindrical glass tube 1 and the axle 2. Then the cylindrical glass tube 1 is hermetically sealed in a state where the inside is evacuated to vacuum to produce a vacuum packed body 5. After the vacuum packed body 5 is pressurized while heating to integrally fuse the inside glass element wires 3 with the cylindrical glass tube 1, the axle 2 is pulled out to perform mold-releasing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a glass tube, and more particularly to a method for manufacturing a glass tube suitable for manufacturing a ferrule that supports an end portion of an optical fiber in a semiconductor laser module or the like.

[0002]

2. Description of the Related Art When an optical fiber is optically coupled with another optical component, the end of the optical fiber is usually protected by a ferrule in order to protect the end of the optical fiber and facilitate end face processing. It is inserted and fixed in a thin glass tube called. An example of such a ferrule is disclosed in Japanese Patent Laid-Open No. 10-96.
As disclosed in Japanese Patent No. 839, a semiconductor laser module or the like that couples emitted light from a semiconductor laser to an optical fiber using a lens is used as an example to support the end portion of the optical fiber. .

The ferrule usually has an outer diameter of 1.8 m.
m is a thin glass tube having an inner diameter of about 125 μm, which corresponds to the outer diameter of the optical fiber. For its manufacture, first, for example, an outer diameter of 50 mm or more, an inner diameter of 10 mm or less, and a length of 100 mm or more High precision glass tube (inner diameter 10 mm,
A method is used in which the length is 300 mm, the circularity and the cylindricity are both 30 μm or less), and then this is stretched in the axial direction.

By the way, in order to produce a large-diameter thick glass tube before drawing as described above, generally, a machining method and vacuum heating of a multiple glass tube disclosed in Japanese Patent Publication No. 60-33771 are disclosed. There is a fusion method. The machining method is a method of making holes using a tool such as a gun drill or a core drill in the center of a cylindrical glass, but the smaller the hole diameter and the longer the overall length, the more disadvantageous the rigidity and life of the tool becomes. It is difficult to process with high precision and low cost. Especially, inner diameter 5
It is very difficult to make a thin and long hole with a length of mm and a length of 100 mm or more with high precision.

On the other hand, the vacuum heating fusion method for a multiple glass tube disclosed in the above Japanese Patent Publication No. 60-33771 discloses a thin glass outer tube made of a thin raw glass tube having a mandrel inserted through the center thereof. The tube is externally inserted, and then, while the inside of the tube is evacuated, the glass tube and the glass tube are heated to near the softening temperature, and the glass tube and the glass tube are fused and integrated by atmospheric pressure. After that, by pulling out the central mandrel, a large-diameter thick-walled glass tube with a desired hole is obtained. A thick glass tube can be easily obtained.

[0006]

However, in the vacuum heating fusion bonding method for multiple glass tubes as described above, in the case of obtaining various kinds of thick glass tubes having different sizes by changing the inner and outer diameters of the glass outer tube. Has to prepare different types and numbers of raw glass tubes for each size.
The larger the diameter, the more complicated the management of the raw glass tube and the higher the procurement cost.

Further, since the size of the thick-walled glass tube is limited by the type of the raw glass tube, it is difficult to obtain a thick-walled glass tube of any size. Therefore, an object of the present invention is to solve the above problems, and to provide an inexpensive glass tube manufacturing method capable of easily obtaining a long thick glass tube having a highly accurate hole in the center. Is.

[0008]

The above object of the present invention is to arrange a mandrel of a predetermined size substantially concentrically in a cylindrical glass tube, and to dispose a plurality of glass strands between the cylindrical glass tube and the mandrel. After filling in parallel, the inside of the cylindrical glass tube is sealed in a vacuumed state to form a vacuum packed body, and then the vacuum packed body is heated and pressed to integrally integrate the glass element wire and the cylindrical glass tube. It is achieved by a method for producing a glass tube, which comprises melting the core and then pulling out the mandrel.

According to the above method, since the shape accuracy of the mandrel is transferred to the inner diameter of the hole of the glass tube, a thick glass tube having a long and highly accurate hole of arbitrary diameter in the center portion which cannot be machined. Can be easily obtained. Further, when manufacturing thick glass tubes of different sizes by changing the inner diameter of the cylindrical glass tube and the outer diameter of the mandrel, the amount of glass strands to be filled between the cylindrical glass tube and the mandrel (number) Since it is only necessary to change the number, it is not necessary to prepare many kinds of raw glass tubes having different outer diameters as in the conventional case.

The heating and pressurizing are preferably performed while the vacuum pack body is rotated in a rotary container so as to hold the mandrel concentrically with the vacuum pack body. In this case, it is possible to prevent the core rod from being misaligned due to its own weight with respect to the glass element wire and the cylindrical glass tube which are softened by heating. Further, as the glass strand in the present invention, a solid or hollow glass wire can be used.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for manufacturing a glass tube according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 1 to 5 are explanatory views for explaining a method for manufacturing a thick glass tube according to an embodiment of the present invention, and FIG. 6 is a thickness manufactured by the method for manufacturing a glass tube according to an embodiment of the present invention. It is a longitudinal cross-sectional view of a meat glass tube.

The method of manufacturing a glass tube according to an embodiment of the present invention is roughly classified into a cylindrical glass tube 1 in which a mandrel 2 is inserted substantially concentrically, and the cylindrical glass tube 1 and the mandrel 2 are combined. Firstly, a plurality of glass strands 3 are filled in parallel with each other
Steps, a second step of sealing the inside of the cylindrical glass tube 1 in a vacuumed state to create a vacuum pack body 5, and pressurizing the vacuum pack body 5 while heating the glass wire 3 inside.
And a third step of integrally fusing the cylindrical glass tube 1 and a fourth step of pulling out the mandrel 2 from the fused and integrated thick glass tube 6 and releasing it.

As shown in FIG. 1, the materials required for the method of manufacturing a glass tube according to this embodiment are a cylindrical glass tube 1 having a relatively large diameter, a mandrel 2 having a predetermined size, and a large number of glass strands. Three
Is. One end of the cylindrical glass tube 1 has a vacuum suction port 21.
Is a funnel-shaped portion 22 in which is formed. The cylindrical glass tube 1, the mandrel 2 and the glass element wire 3 all have a linear expansion coefficient α as close as possible (for example, α in order to prevent cracks due to strain during heat treatment and cooling).
= 20 × 10 ⁻⁷ ) must be used.

The mandrel 2 has a predetermined size (for example, an outer diameter of 1 to 40) for transferring a hole of a predetermined size to the thick glass tube 6.
mm, length 100-1000 mm),
At this time, the shape and dimension are processed with high accuracy (diameter 10 mm or less, total length 300 mm or more, roundness 10 μm or less, cylindricity and coaxiality 30 μm or less). The mandrel 2 is preferably made of a material that has heat resistance and does not melt with glass (for example, tungsten, carbon, or amorphous carbon).

The glass element wire 3 has a length dimension shorter than that of the mandrel 2 and may be solid or hollow. However, in order to perform compression integration between the cylindrical glass tube 1 and the mandrel 2, the glass element wire 3 is formed. Since it is better that the filling rate of the wire 3 is higher, it is preferable to use the solid glass element wire 3. Further, the outer diameter of the glass strand 3 depends on the outer diameter of the thick glass tube 6, but a range of several mm is suitable in consideration of handling in work. Since the cylindrical glass tube 1 is fused and integrated with the glass element wire 3 to form the thick glass tube 6, it is preferable to use the same glass material as the glass element wire 3.

Next, each step in the glass tube manufacturing method according to this embodiment will be described in order. First, in the first step, as shown in FIG. 2, the mandrel 2 is inserted into the cylindrical glass tube 1 and arranged substantially concentrically. In this state, the cylindrical glass tube 1 is inserted.
A large number of glass strands 3 are densely packed in parallel in the space between the rod 2 and the mandrel 2. The outer diameters of the glass strands 3 are all the same in the present embodiment, but the cylindrical glass tube 1
If it is possible to fill the gap between the core rod 2 and the mandrel 2, glass strands 3 having different outer diameters may be filled.

As a method of arranging the mandrel 2 in the cylindrical glass tube 1 substantially concentrically so as to correspond to the coaxiality of the thick glass tube 6, for example, a jig 10 as shown in FIG. 2 is used. You can The jig 10 is a disk-shaped nut having a relatively large thickness, and its diameter is made slightly smaller than the inner diameter of the cylindrical glass tube 1. At the center of the jig 10, a supporting hole (female screw) 12 through which the mandrel 2 is fixed is formed.
It is formed substantially concentric with the outer circumference of 0. Therefore, the support hole 1
When the jig 10 having the mandrel 2 fitted in 2 is inserted into the cylindrical glass tube 1, the mandrel 2 is arranged substantially concentrically in the cylindrical glass tube 1.

Even after the glass element wire 3 is filled, a jig 11 having a shape substantially similar to that of the jig 10 is inserted into the end portion on the opposite side of the end portion of the mandrel 2 into which the jig 10 is inserted. good. This allows
It is possible to prevent the filled glass element wire 3 from moving in the axial direction within the cylindrical glass tube 1 in the subsequent steps.

Next, in the second step, as shown in FIG. 3, the cylindrical glass tube 1 filled with the glass element wire 3 is used.
The open end for insertion is heated and fused with a burner or the like to form an airtight bowl-shaped sealing end 20. Then, the inside of the cylindrical glass tube 1 is evacuated from the vacuum suction port 21 using a vacuum pump (not shown) in a heating furnace (not shown). The cylindrical glass tube 1
After the inside reaches a predetermined degree of vacuum (0.02 Torr or less), if the surrounding area of the vacuum suction port 21 is locally heated to a temperature higher than the Tg point (glass transition point), the vacuum suction port 21 is heated.
Since this portion is softened and sealed by the atmospheric pressure, a vacuum pack body 5 in which a mandrel 2 and a large number of glass element wires 3 are closely packed in a high vacuum cylindrical glass tube 1 is manufactured.

Next, in the third step, as shown in FIG.
The vacuum packed body 5 taken out of the heating furnace is newly housed in the high-pressure heating furnace 30, and then pressurized while being heated by the external heater 31 in the non-oxidizing atmosphere filled with nitrogen gas or the like or in the atmosphere. . Further, the vacuum pack body 5 is rotated at a constant speed in a rotary container (not shown) in the high-pressure heating furnace 30. Therefore, the cylindrical glass tube 1 and the glass element wire 3 are integrally fused so as to have a constant thickness, and are formed by copying along the outer periphery of the mandrel 2.

At this time, the vacuum pack body 5 is heated and softened by being heated and pressurized while being rotated in a rotary container so as to hold the mandrel 2 concentrically with the vacuum pack body 5. With respect to the glass element wire 3 and the cylindrical glass tube 1, the core rod 2 can be prevented from being misaligned due to its own weight.

Next, in the fourth step, after gradually cooling the glass material used for the cylindrical glass tube 1 and the glass element wire 3 based on the gradually cooling conditions, a vacuum pack which is a work after molding is performed from the high pressure heating furnace 30. The body 5 is taken out, unnecessary parts at both ends are removed, and the mandrel 2 is pulled out and released. Then, as shown in FIG.
As shown in FIG. 6, a highly accurate thick-walled glass tube 6 having a hole 7 in the center and having an outer diameter of 50 mm or more and an outer diameter / inner diameter ratio of 10 or more.
Can also be obtained.

By the way, as shown in FIG. 5, a male screw 40 capable of screwing the jig 10 is formed on the end portion of the mandrel 2 in this embodiment. Since the melted cylindrical glass tube 1 and the glass element wire 3 are fused to the jigs 10 and 11, when the mandrel 2 is pulled out in the fourth step, the jig 1
By fixing 0 and rotating the mandrel 2 by an appropriate rotating means, the mandrel 2 can be easily pulled out.

Further, as another means for assisting the pulling-out of the mandrel 2, several tens of μs are provided on the outer circumference of the mandrel 2 with respect to the length.
A taper of about m (if the taper is about this amount, the change in the hole diameter of the final product can be ignored) is used to facilitate pulling to the larger diameter, or the surface of the mandrel 2 has a DLC (Diamond
A like carbon coating may be applied to prevent glass from welding to the mandrel 2, but these means may be used alone or in combination.

That is, according to the method for manufacturing a glass tube of this embodiment, the shape accuracy of the mandrel 2 processed with high accuracy is transferred to the inner diameter of the hole of the thick glass tube 6, which is impossible by machining. It is possible to easily obtain a thick glass tube 6 having a long and highly precise hole 7 having an arbitrary diameter at the center. Further, when manufacturing thick glass tubes 6 of different sizes by changing the inner diameter of the cylindrical glass tube 1 and the outer diameter of the mandrel 2, the glass strands to be filled between the cylindrical glass tube 1 and the mandrel 2. Since it suffices to change the amount (number) of 3, it is not necessary to prepare many kinds of raw glass tubes having different outer diameters as in the conventional case. As a result, the thick-walled glass tube 6 having an arbitrary outer diameter can be obtained easily and at low cost.

[0026]

As is apparent from the above description, according to the method for manufacturing a glass tube of the present invention, the shape accuracy of the mandrel is transferred to the inner diameter of the hole of the glass tube. In addition, it is possible to easily obtain a thick-walled glass tube having a highly accurate hole having an arbitrary diameter in the center. Further, when manufacturing thick glass tubes of different sizes by changing the inner diameter of the cylindrical glass tube and the outer diameter of the mandrel, the amount of glass strands to be filled between the cylindrical glass tube and the mandrel (number) Since it is only necessary to change the number, it is not necessary to prepare many kinds of raw glass tubes having different outer diameters as in the conventional case. Therefore, it is possible to provide an inexpensive glass tube manufacturing method capable of easily obtaining a long thick glass tube having a highly accurate hole in the center.

[Brief description of drawings]

FIG. 1 is a perspective view showing materials necessary for a method for manufacturing a thick glass tube according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining a first step in the method for manufacturing a thick glass tube according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram for explaining a second step in the method for manufacturing a thick glass tube according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram for explaining a third step in the method for manufacturing a thick glass tube according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram for explaining a fourth step in the method for manufacturing a thick glass tube according to the embodiment of the present invention.

FIG. 6 is a vertical cross-sectional view of a thick glass tube manufactured by a method for manufacturing a glass tube according to an embodiment of the present invention.

[Explanation of symbols]

1 cylindrical glass tube 2 mandrel 3 glass strands 5 vacuum packed body 6 thick glass tubes

Claims (2)

[Claims] 1. A cylindrical glass tube is provided with a mandrel of a predetermined size inserted substantially concentrically, a plurality of glass strands are filled in parallel between the cylindrical glass tube and the mandrel, and then the inside of the cylindrical glass tube is filled. The vacuum packed body is sealed in a vacuumed state to form a vacuum packed body, and then the vacuum packed body is pressurized while being heated to fuse the internal glass element wire and the cylindrical glass tube together, and then the mandrel is pulled out. A method of manufacturing a glass tube, characterized in that 2. The heating and pressurizing are performed while the vacuum pack body is rotated in a rotary container so as to hold the mandrel concentrically with the vacuum pack body. The method for producing a glass tube according to.