JP3093957B2 - Flexible insulated double tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible insulated double pipe, and is used, for example, in a pipe for transferring a high or low temperature fluid.

[0002]

2. Description of the Related Art As a conventionally known flexible insulated double pipe, an inner pipe and an outer pipe are formed by a thin corrugated pipe, and both ends of the outer pipe are covered with a required gap on the inner pipe. Is welded to the inner pipe as it is, and vacuum is evacuated from the exhaust port attached to the corrugated step of the outer pipe by brazing.

In addition, one end of a thicker connecting pipe is welded to the outer pipe, and the other end of the connecting pipe is welded to the inner pipe.
There is also one that evacuates from an exhaust port provided in the connection pipe.

[0004]

As described above, the corrugated inner and outer pipes which are welded as they are are both thin in order to impart flexibility, and these are used as a welding base metal. There is a problem that it is too thin to melt. A method of brazing is conceivable regardless of welding, but brazing is unstable and the accuracy of vacuum maintenance is poor.

[0005] Also, when an exhaust port is brazed to the outer tube, the vacuum maintaining accuracy at the brazed portion is similarly poor.

On the other hand, in the case where the thick connection pipe is welded to the end of the outer pipe as described above, the difference in heat capacity between the two at the welded portion is small because the thickness of the outer pipe is smaller than the thickness of the connection pipe. growing. For this reason, welding becomes unstable and workability is poor.

Therefore, an object of the present invention is to provide a flexible insulated double pipe which solves these problems.

[0008]

In order to achieve the above-mentioned object, the present invention covers an outer tube made of a similar corrugated tube through a heat insulating layer around the outer periphery of an inner tube made of a flexible corrugated tube. Flexible insulation formed by welding one end of a connecting pipe thicker than the inner pipe and the outer pipe to at least one end of the outer pipe, and welding the other end of the connecting pipe to the outer peripheral surface of the inner pipe. In the double pipe, one or several steps of the corrugate at the end of the outer pipe and one or several steps of the corrugate at the welded portion of the inner pipe are each compressed in the axial direction to form a step collapse part, and the outer pipe and the The inner pipe and the connecting pipe are welded at the above-mentioned step crushing portions.

An outwardly facing collar is formed at the welded end of the connection pipe with the outer pipe, and the outer end face of the collar and the end face of the stepped portion of the outer pipe are joined and welded at the joint. Can be taken.

Further, a structure in which an exhaust port for evacuation is provided in the connection pipe may be employed.

[0011]

In the flexible insulated double pipe having the above-described structure, the stepped portions of the inner pipe and the outer pipe have substantially the same thickness as the welded end of the connection pipe, so that stable welding can be performed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiment shown in FIG. 1 is a flexible vacuum double tube, in which a similar corrugated tube is provided at a required interval around an inner tube 1 composed of a flexible corrugated tube. Tube 2
Is covered. Connection pipes 3 are welded between both ends of the outer pipe 2 and the outer diameter surface of the inner pipe 1 respectively.

The outer tube 2 has a thickness of about 0.25 mm in order to have flexibility, and the both ends of the outer tube 2 are three-stage corrugated step portions 4 which are compressed and adhered in the axial direction. The part 5 is formed. The inner tube 1 also has a thickness of about 0.3 mm in order to have flexibility, and also has a step crushing portion 7 in which three steps 6 of the corrugate are similarly compressed and adhered in the axial direction at the welded portion. Is formed.

The number of the step portions 4 and 6 forming the above-mentioned step crushing portions 5 and 7 is one or several in accordance with the thickness of the connection pipe 3 so that the heat capacity is substantially equal to that of the welded part of the connection pipe 3. It is selected within the range of steps.

The connecting pipe 3 has a large diameter portion 8 having a diameter equal to the diameter of the valley portion of the step portion 4 of the outer tube 2 and a small diameter portion 10 formed at one end of the large diameter portion 8 via a step 9. Is done. An outward flange 11 is formed at an outer end of the large diameter portion 8.

The tip tube 13 is welded to the exhaust port 12 provided in the large diameter portion 8 (see a two-dot chain line in FIG. 1). Due to the necessity of performing this welding, the connection pipe 3 is formed to have a certain thickness or more (0.8 mm in the case of the embodiment).

The connecting pipe 3 has a flange 1 of a large diameter portion 8.
1 is aligned with the end face of the step crushing part 5 of the outer pipe 2, and welding (TIG welding) is performed between the outer diameter surface and the step crushing part 7 to form a welded part 14 (see FIG. 2A). . Further, the small diameter portion 10 is put on the outer diameter of the step crushing portion 7 of the inner pipe 1, and the portion is similarly welded to form a welded portion 15 (see (b)).

The air between the inner tube 1 and the outer tube 2 is removed from each of the tip tubes 13 and the inside of the tube is evacuated.
The tip tube 13 is crimped in the middle and unnecessary portions are cut and removed. The shape after the removal is shown by a solid line in FIG. In addition,
A step crushing portion 17 for rotatably engaging a nut 16 is formed at an end of the inner tube 1.

A getter 18 for maintaining a vacuum between the inner tube 1 and the outer tube 2 is welded to the inner peripheral surface of the connecting tube 3. Also,
A heat insulating material 19 such as glass wool is interposed between the inner tube 1 and the outer tube 2 as needed to prevent contact between the two.

FIG. 3 shows another embodiment of a welded portion between the connection pipe 3 and the outer pipe 2. In this case, the inner diameter of the large diameter portion 8 of the connecting pipe 3 is formed to be equal to the outer diameter of the step crushing section 5 of the outer pipe 2, and the step crushing section 5 is covered with the end of the connecting pipe 3 and welded. This is one in which a welded portion 14 'is formed. Other configurations are the same as those described above.

In the above-described embodiment, as a means for evacuating the inner tube 1 and the outer tube 2, the tip tube 13 is set at the exhaust port 12, and the inside of the tip tube 13 is evacuated and evacuated from the tip tube 13. In this case, a chip tube method is shown, in which a vacuum is applied in a vacuum furnace to cover the exhaust port 12 with a cap 20 as shown in FIG.
1, a so-called vacuum furnace method may be used.

One end of the outer pipe 2 is welded to the inner pipe 1 via the connecting pipe 3 as described above, and the other end is connected to the inner pipe 1 shown in FIG.
As shown in FIG. 5A, welding is performed with an annular spacer 22 interposed therebetween, or as shown in FIG. 5B, the small diameter portion 23 at the end of the outer tube 2 is directly welded to the inner tube 1. Or you can.

[0023]

As described above, according to the present invention, the inner pipe and the outer pipe which are formed to be thin in order to provide flexibility, and the connecting pipe which is formed to be thick in order to maintain required strength. When welding the inner pipe and the outer pipe, a step crushing portion was formed at each welding portion of the inner pipe and the outer pipe, and the connection pipe was welded to a portion thickened by the step crushing. Thereby, the heat capacity of both welding parts becomes equal, stable welding can be performed, and the defective rate of welding can be reduced.

By providing the connecting pipes at two locations and evacuating from the exhaust ports provided in each connecting pipe, the resistance at the time of exhaustion is reduced by half compared to the case of evacuating from one location.
The evacuation time can be reduced.

[Brief description of the drawings]

FIG. 1 is a partially omitted cross-sectional view of an embodiment.

FIG. 2A is a partially enlarged sectional view of the same as the above. FIG.

FIG. 3 is a partially enlarged sectional view of another embodiment.

FIG. 4 is a partially enlarged cross-sectional view of another embodiment.

FIG. 5A is a partially omitted sectional view of another embodiment. FIG. 5B is a partially omitted sectional view of another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner pipe 2 Outer pipe 3 Connection pipe 4 Step part 5 Step crush part 6 Step part 7 Step crush part 8 Large diameter part 9 Step 10 Small diameter part 11 Collar 12 Exhaust port 13 Chip pipe 14, 14 'Weld part 15 Weld part 16 Nut 17 Step crushing part 18 Getter 19 Insulation material 20 Cap 21 Row material 22 Spacer 23 Small diameter part

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16L 59/153 F16L 9/18

Claims (3)

(57) [Claims] 1. An outer pipe made of a similar corrugated pipe is put on the outer periphery of an inner pipe made of a flexible corrugated pipe via a heat insulating layer, and the inner pipe and the outer pipe are placed on at least one end of the outer pipe. In a flexible insulated double pipe in which one end of a thicker connecting pipe is welded and the other end of the connecting pipe is welded to the outer peripheral surface of the inner pipe, one or more of the corrugates at the end of the outer pipe are provided. One or several stages of the corrugated portion of the welded portion of the several stages and the inner tube are each compressed in the axial direction to form a step crushed portion, and the outer tube, the inner tube, and the connection pipe are welded at the respective step crushed portions. Flexible insulated double tube characterized by the following. 2. An outer flange is formed at a welding end of the connecting pipe with the outer pipe, and an outer end face of the brim is joined to an end face of a stepped portion of the outer pipe, and welding is performed at the joint. The flexible insulated double pipe according to claim 1, wherein 3. The flexible insulated double pipe according to claim 1, wherein an exhaust port for evacuation is provided in the connection pipe.