JPH08326992A - Flexible heat insulating double tube - Google Patents

Abstract

PURPOSE: To stabilize the welding between an inner tube and an outer tube and connecting tubes in a flexible heat insulating double tube composed by welding the ends of the outer tube covered on the flexible inner tube through connecting tubes and forming a heat insulating layer between the inner tube and the outer tubes. CONSTITUTION: At the welding parts of an inner tube 1 and an outer tube 2, with connecting tubes 3, one or several steps of step smashing parts 7 and 5 are provided, and the step smashing parts 7 and 5, and the ends of the connecting tubes 3 are welded.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a conventionally known flexible heat-insulating double pipe, both ends of an outer pipe in which a thin corrugated pipe is used to form an inner pipe and an outer pipe, and the inner pipe is covered with a required gap. There is one in which the inner pipe is welded as it is, and a vacuum is drawn from the exhaust port attached by brazing to the corrugated step of the outer pipe.

Further, 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 welded inner pipe and outer pipe made of corrugated pipes are both thin in order to impart flexibility, and these are used as the welding base metal. There is a problem that it is too thin to be melted. A method of brazing can be considered instead of welding, but brazing is unstable and the accuracy of maintaining the vacuum is poor.

Also, when the exhaust port is brazed to the outer tube, the vacuum maintaining accuracy at the brazed portion is also poor.

On the other hand, in the case where the thick connecting pipe is welded to the end portion of the outer pipe as described above, since the thickness of the outer pipe is smaller than the thickness of the connecting pipe, the difference in heat capacity between the two at the welded portion is growing. As a result, welding becomes unstable and workability is poor.

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

[0008]

In order to achieve the above-mentioned object, the present invention covers the outer circumference of an inner tube made of a flexible corrugated tube with an outer tube made of the same corrugated tube through a heat insulating layer, Flexible heat insulation obtained 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 to several stages of the corrugate at the end of the outer pipe and one to several stages of the corrugate at the welded portion of the inner pipe are respectively axially compressed to form a step crushed portion, and the outer pipe and The inner pipe and the connecting pipe are welded to each other at the step crushed portions.

A structure in which an outward flange is formed at an end portion of the above connecting tube which is welded to the outer tube, and the outer end surface of the flange and the end surface of the stepped portion of the outer tube are joined together and welded at the joining portion. Can be taken.

Further, the connection pipe may be provided with an exhaust port for vacuuming.

[0011]

In the flexible heat-insulating double pipe having the above-described structure, the crushed portions of the inner pipe and the outer pipe have a wall thickness approximately equal to the weld end portion of the connecting pipe, so that stable welding can be performed.

[0012]

The embodiment shown in FIG. 1 is a flexible vacuum double tube, and an outer tube made of a similar corrugated tube with a required space around an inner tube 1 made of a flexible corrugated tube. Tube 2
Is covered. The connecting pipes 3 are welded between both ends of the outer pipe 2 and the outer diameter surface of the inner pipe 1.

The outer tube 2 has a wall thickness of about 0.25 mm in order to have flexibility, and both ends thereof are step-crushed by axially compressing and adhering three step portions 4 of the corrugate. The part 5 is formed. The inner tube 1 also has a wall thickness of about 0.3 mm in order to have flexibility, and the welded portion also has a step crushed portion 7 in which the corrugated step portions 6 of three steps are similarly compressed and adhered in the axial direction. Has been formed.

The number of step portions 4 and 6 forming each of the step crushed portions 5 and 7 is 1 to several in accordance with the wall thickness of the connecting pipe 3 so that the heat capacity is almost equal to that of the welded portion of the connecting pipe 3. It is selected within the range of steps.

The connecting pipe 3 has a large diameter portion 8 having a diameter equivalent to the diameter of the valley portion of the step portion 4 of the outer pipe 2, and a small diameter portion 10 formed at one end of the large diameter portion 8 via a step 9. To be done. An outward flange 11 is formed on the outer end of the large diameter portion 8.

The tip pipe 13 is welded to the exhaust port 12 provided in the large diameter portion 8 (see the chain double-dashed line in FIG. 1). In order to perform this welding, the connecting pipe 3 is formed so as to have a wall thickness of a certain degree or more (0.8 mm in the embodiment).

The connecting pipe 3 has a collar 1 of a large diameter portion 8 thereof.
1 is aligned with the end face of the step-crushed portion 5 of the outer tube 2, and welding (TIG welding) is performed between the outer diameter surface and the step-crushed portion 7 to form a welded portion 14 (see FIG. 2 (a)). . Further, the small-diameter portion 10 is covered on the outer diameter of the step-crushed portion 7 of the inner pipe 1, and the welded portion 15 is similarly welded at that portion (see the same (b)).

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

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

FIG. 3 shows another embodiment of the welded portion between the connecting 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-crushed part 5 of the outer tube 2, and the step-crushed part 5 is covered with the end of the connection pipe 3 and welded, The welded portion 14 'is formed. Other configurations are the same as those in the above case.

As a means for evacuating the inner tube 1 and the outer tube 2, in the above embodiment, the tip tube 13 is set up at the evacuation port 12, the tip tube 13 is evacuated and the tip tube 13 is in the middle. Although a so-called tip tube system in which the pressure is cut by pressure is shown, vacuuming is performed in a vacuum furnace, and the exhaust port 12 is covered with the cap 20 as shown in FIG.
The method of sealing by 1 may be a so-called vacuum furnace method.

It should be noted that 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 welded to the inner pipe of FIG.
As shown in FIG. 5A, welding is performed with an annular spacer 22 interposed, or as shown in FIG. 5B, the small diameter portion 23 at the end of the outer pipe 2 is directly welded to the inner pipe 1. You can

[0023]

As described above, according to the present invention, the inner pipe and the outer pipe, which are formed thin to give flexibility, and the connection pipe, which is formed thick to maintain the required strength. When welding and, a stepped portion was formed in each welded portion of the inner pipe and the outer pipe, and the thickened portion due to the stepped portion and the connecting pipe were welded. As a result, the heat capacities of the two welded portions become equal, stable welding can be performed, and the defective rate of welding can be reduced.

By providing the connecting pipes at two places and evacuating from the exhaust ports provided at each connecting pipe, the resistance at the time of evacuating is halved as compared with the case of evacuating from one place.
The exhaust time can be shortened.

[Brief description of drawings]

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

FIG. 2A is a partially enlarged cross-sectional view of the above, and FIG. 2B is a partially enlarged cross-sectional view of another portion of the above.

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

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

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

[Explanation of symbols]

 1 inner pipe 2 outer pipe 3 connecting pipe 4 step portion 5 step crushing portion 6 step portion 7 step crushing portion 8 large diameter portion 9 step 10 small diameter portion 11 flange 12 exhaust port 13 tip pipe 14, 14 'weld portion 15 weld portion 16 Nut 17 Step crushed part 18 Getter 19 Heat insulating material 20 Cap 21 Low material 22 Spacer 23 Small diameter part

Claims (3)

[Claims] 1. An outer tube made of a similar corrugated tube is covered on the outer circumference of an inner tube made of a flexible corrugated tube through a heat insulating layer, and at least one end of the outer tube is provided with the inner tube and the outer tube. In a flexible heat-insulating double pipe obtained by welding one end of a thicker connecting pipe and welding the other end of the connecting pipe to the outer peripheral surface of the inner pipe, one to one of corrugates at the end of the outer pipe is provided. Several steps and one to several steps of the corrugated portion of the welded portion of the inner pipe are respectively compressed in the axial direction to form a step crushed portion, and the outer tube and the inner tube and the connecting pipe are welded at each step crushed portion. A flexible heat-insulating double pipe characterized by the above. 2. An outward flange is formed on a weld side end of the connecting tube with the outer tube, and the outer end surface of the flange and the end surface of the step-crushed portion of the outer tube are joined together, and welding is performed at the joining portion. The flexible adiabatic double pipe according to claim 1, characterized in that. 3. The flexible heat-insulating double pipe according to claim 1, wherein the connecting pipe is provided with an exhaust port for vacuuming.