JP2001235067A - Method of manufacturing clad tube made of tube of glass or the like and metal tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of bubbles in a glass tube resulting from a gasified substance emitted during heating of the glass tube, in a clad tube where the glass tube is combined in a metal tube. SOLUTION: The glass tube 2 inserted in the metal tube 1 is stored in an airtight container 3, and the interior of the glass tube 2 is opened to the atmosphere. With a vacuum pump 10 evacuating the airtight container 3, a heater 8 is energized to heat the glass tube 2. A gasified substance emitted from the metal tube 1 or glass tube 2 in the heating is discharged by the vacuum pump 10, and the glass tube 2 softened in the heating is, at the same time, radially expanded due to the difference in the internal and external pressures and closely combined with the internal surface of the metal tube 1.

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 clad tube in which a tube of glass or the like is combined with the inner surface of a metal tube.

[0002]

2. Description of the Related Art The above-mentioned cladding tube is used for an ozone generating tube and the like. As a manufacturing method, a metal tube in which a tube such as glass is inserted coaxially is induction-heated by an induction coil, and radiant heat from the metal tube is used. A method is known in which a tube made of glass or the like is heated and softened, and the tube made of glass or the like is pressurized from the inside of the tube so as to expand radially and adhere to the inner surface of a metal tube (Japanese Patent Publication No. 3-35549). reference).

[0003]

In such a manufacturing method, when a tube such as a metal tube or glass is heated, impurities contained in the tube and dirt attached to the surface are gasified and released. In this case, this gasified substance acts on a softened glass tube or the like to form air bubbles on its surface or inside. As a result, for example, in an ozone generating tube, the function of the glass layer as a dielectric is reduced, and There was a problem of causing defects. An object of the present invention is to prevent the formation of air bubbles in a tube such as glass in a process of manufacturing a clad tube in which a tube such as glass is closely attached to the inner surface of a metal tube.
It is to improve the quality of the clad tube.

[0004]

In order to solve the above-mentioned problems, the present invention relates to a method in which a glass tube or the like is coaxially inserted into a metal tube and the outside of the glass tube or the like is depressurized. The tube is heated, and the tube of glass or the like is expanded in the radial direction so as to adhere to the inner surface of the metal tube (Claim 1). According to the method of the first aspect, by heating the outside of the tube such as a glass while reducing the pressure, the gas released from the tube such as the metal tube or the glass is quickly discharged, and the formation of bubbles is prevented. Can be. Further, the tube made of glass or the like expands in the radial direction due to the reduced pressure on the outside, and adheres to the inner surface of the metal tube without being hindered by the released gas.

In order to decompress the outside of a tube made of glass or the like,
This glass tube or the like is made longer than the metal tube, and both ends of the glass tube or the like inserted into the metal tube are made to protrude from the metal tube, and the metal tube and the glass tube are placed in an airtight container. By accommodating and drawing both ends of the glass or the like tube protruding from the metal tube to the outside of the airtight container via a sealing mechanism, the inside of the glass or the like tube is communicated with the atmosphere, and in this state, Preferably, the inside of the airtight container is evacuated (claim 2).

On the other hand, in order to heat the tube made of glass or the like,
A cylindrical heater is coaxially arranged inside the glass tube or the like and energized, and the glass or other tube is heated by radiant heat from the heater (Claim 3), or a cylindrical heater is placed outside the metal tube. It is preferable that the induction coil is coaxially arranged, a high-frequency current is passed through the induction coil, the metal tube is induction-heated, and the glass or other tube is heated by radiant heat from the metal tube. .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention in a clad tube used for an ozone generating tube will be described below with reference to FIGS. First, FIG. 1 is a schematic sectional view of a clad tube manufacturing apparatus showing an embodiment in the case of using a heater as a heating means. In FIG. 1, 1 is a metal tube made of stainless steel, 2 is a glass tube coaxially inserted into the metal tube 1, the glass tube 2 is longer than the metal tube 1, and both ends protrude from the metal tube 1. To illustrate the dimensions in this case, the outer diameter of the metal tube 1 is about 76 mm, the wall thickness is 2 mm, and the length is about 1200
mm, the outer diameter of the glass tube 2 is about 70 mm, the wall thickness is 1.5 mm, the length is about 1500 mm, and the distance between the metal tube 1 and the glass tube 2 is about 1 mm.
Is open.

A metal tube 1 and a glass tube 2 inserted therein
Is housed in an airtight container 3 as shown, and both ends of a glass tube 2 protruding from the metal tube 1 are airtightly led out via a seal mechanism 4. The airtight container 3 is a cylindrical body made of a stainless steel plate having an inner diameter of about 150 mm and a length of about 1400 mm. The inner surfaces of which are lined with a heat insulating material (not shown). A round hole is formed in the end plate 6 to penetrate the end of the glass tube 2, and an annular packing 7 is mounted as a seal mechanism 4 around the hole. In order to accommodate the metal tube 1 and the glass tube 2 in the airtight container 3, the body 5 from which the end plate 6 is removed
Then, the end plates 6 are fitted into both ends of the glass tube 2 protruding from the metal tube 1 and fastened to the body 5.

A heater 8 is arranged inside the glass tube 2. The heating part of the heater 8 has an outer diameter of about 30 mm and a length of about 1200 m
A heating tube (Nichrome wire) is enclosed in a stainless steel tube having a cylindrical shape with one end closed and an insulating material. The heater 8 is supported by a support member 9 outside the glass tube 2, and both ends of the glass tube 2 are closed by a heat insulating material 10 inserted between the glass tube 2 and the heater 8. Insulation material 10
For example, it is made of a porous material having air permeability such as asbestos, and the inside of the glass tube 2 communicates with the atmosphere through the air holes of the heat insulating material 10. The heat insulating material 10 prevents the heat from the heater 8 from escaping from the end of the glass tube 2 and heats the metal tube 1 and the glass tube 2 efficiently. On the other hand, a pipe flange 5b is provided on the body 5 of the airtight container 3, and this pipe flange 5b is provided.
Is connected to a vacuum pump 11 as a pressure reducing device.

In such an apparatus, when the metal tube 1 and the glass tube 2 are set in the hermetic container 3 as shown in the figure, the vacuum pump 11 is started to evacuate the hermetic container 3 to about 10 ^-3 Torr. Next, the heater 8 is energized, and the glass tube 2 is heated to 650 to 700 ° C. by the radiant heat. At that time, the metal tube 1 is also heated to 600 to 650 ° C. In the course of this temperature increase, dirt and impurities contained in the surfaces of the metal tube 1 and the glass tube 2 are gasified and released into the space between the metal tube 1 and the glass tube 2. The substance is immediately discharged by the vacuum pump 11. In parallel, the heated glass tube 2 is heated to a softening point (about 620).
(° C.), softening starts, and it expands in the radial direction due to the pressure difference between the inside and outside of the glass tube 2, approaches the inner surface of the metal tube 1, and comes into close contact with it. After the composite clad tube thus obtained is taken out of the airtight container 3, both ends protruding from the metal tube 1 are cut along the end surface of the metal tube 1 before use.

In the above-described manufacturing method, by heating the outside of the glass tube 2 while reducing the pressure, the gas released from the metal tube 1 or the glass tube 2 is quickly discharged, and defects such as bubbles are generated in the glass tube 2. Will not cause. At the same time, the glass tube 2 undergoes a radial expansion action due to the reduced pressure on the outside thereof, and adheres well to the inner surface of the metal tube without being hindered by the released gas. That is, the pressure reduction outside the glass tube 2 is caused by the discharge of the gasified substance and the expansion of the glass tube 2.
Plays two functions at the same time.

FIG. 2 shows an embodiment in which an induction coil is used as a heating means. The difference from the embodiment of FIG. 1 is that the induction coil is provided outside the metal tube 1 instead of the heater 8. 12 is that they are arranged coaxially. The induction coil 12 is supported in the airtight container 3 via a support member 13 made of a nonmagnetic material such as stainless steel, and is insulated from the metal tube 1 by a cylindrical heat insulating material 14. The lead wire 15 of the induction coil 12 is drawn out through a flange 5c sealed with an O-ring. In FIG. 2, when the pressure in the airtight container 3 is reduced,
A high-frequency current of about 3000 Hz flows. As a result, an induced current flows through the metal tube 1 inserted into the induction coil 12, and heat is generated due to the current loss. The metal tube 1 is heated to about 800 ° C., and the inner glass tube 2 is heated to 650 to 700 ° C. by radiant heat from the metal tube 1. Other configurations and actions are shown in Fig. 1.
The description is omitted because it is the same as that of the embodiment.

In the above embodiment, both ends of the glass tube 2 are made to project from the metal tube 1 and are led out of the airtight container 3 in order to open the inside of the glass tube 2 to the atmosphere. It is also possible to close both ends of a glass tube having substantially the same length as the tube and house the entirety in a hermetic container, and to communicate the inside with the outside of the hermetic container via a thin tube.
Further, the tube that is combined with the metal tube is not limited to a glass tube, and any other material that can be softened by heating can be used.

[0014]

As described above, according to the present invention, it is possible to improve the quality of the clad tube by preventing the formation of bubbles in the tube of glass or the like, and to increase the pressure for radially expanding the tube of glass or the like. By simultaneously using the means as a means for discharging a gasified substance, it is possible to manufacture a high-quality and inexpensive clad tube without complicating the manufacturing process and the manufacturing apparatus.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a clad tube manufacturing apparatus showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a clad tube manufacturing apparatus showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal tube 2 Glass tube 3 Airtight container 4 Sealing mechanism 7 Packing 8 Heater 9 Heat insulating material 11 Vacuum pump 12 Induction coil

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H111 AA01 BA01 BA10 CB03 DA26 DB27 EA12 EA13 EA14 3K059 AA08 AB16 AB23 AB27 AB28 AD05 AD34 AD35 AD40 CD63 CD66 4F100 AB01A AG00B BA02 DA11 EJ241 EJ421 GB90 JL02

Claims (4)

[Claims] 1. A glass tube or the like is coaxially inserted into a metal tube, and the glass or other tube is heated while decompressing the outside of the glass or the like tube to expand the glass or the like tube in the radial direction. A method of manufacturing a clad tube comprising a tube made of glass or the like and a metal tube, wherein the clad tube is brought into close contact with the inner surface of the metal tube. 2. The glass tube or the like is made longer than the metal tube, and both ends of the glass tube or the like inserted into the metal tube are projected from the metal tube. By accommodating the tube in an airtight container, and by guiding both ends of the glass or other tube protruding from the metal tube to the outside of the airtight container via a sealing mechanism, the inside of the glass or other tube is exposed to the atmosphere. 2. The method for producing a clad tube comprising a tube such as a glass and a metal tube according to claim 1, wherein the inside of the airtight container is evacuated in this state. 3. A tube made of glass or the like is coaxially arranged inside a tube made of glass or the like and energized, and the tube made of glass or the like is heated by radiant heat from the heater.
3. A method for producing a clad tube comprising the glass tube and the metal tube according to claim 1 or 2. 4. A cylindrical induction coil is coaxially arranged outside the metal tube, and a high-frequency current is passed through the induction coil to heat the metal tube by induction, and radiant heat from the metal tube causes the glass or the like to be heated. Heating said tube
3. A method for producing a clad tube comprising the glass tube and the metal tube according to claim 1 or 2.