JPH0756355B2 - Thin multi-layer telescopic 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 structure of a thin-walled multi-layered expansion tube in which end tubes are welded and fixed to both ends of a bellows tube formed by laminating a large number of thin-walled metal tubes.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, a thin-walled multi-layered expansion tube is formed by deforming a number of laminated thin-walled metal pipes to form a laminated bellows tube (50). Dispose the metal fittings (51) inside and outside of the part, and weld the end faces together while pressing the straight pipe parts at both ends of the laminated bellows pipe (50) with the metal fittings (51) to integrate them. Bellows tube integrated with (51) (5
(0) is butt-welded to the end pipe (52), and the inner tube (53) whose end is formed in a bell mouth shape for smooth fluid flow is welded and fixed to the inner surface of the end pipe (52). Was there.

[0003]

However, in this conventional thin multi-layer expansion tube, the end tube (52) and the laminated bellows tube (50) were butt-welded together, so a back wave was formed at this welding point. In addition to the problem that this welding is troublesome, and because the inner cylinder (53) has to be formed into a bell mouth shape, its processing is troublesome, which causes a cost increase.

Further, since the laminated bellows pipe (50) is welded all around with the end pipe (52) butted against it, distortion is likely to occur at the welded portion due to the influence of welding, and a bellmouth-shaped inner cylinder is formed. There is a problem that internal stress remains in (53) and it is difficult to maintain high quality and accuracy of products.
Furthermore, when the inner tube (53) formed in a bell mouth shape is placed on the inner surface of the end tube (52), it is difficult to set it in the correct posture, and the axis of the inner tube (53) becomes the axis of the thin-walled multi-layer telescopic tube. There is also a problem in that the inner cylinder (53) and the laminated bellows pipe (50) become non-uniform in the pipes as they cross each other, and the flow of the fluid flowing inside is disturbed.

The present invention has been made in view of the above points, and an object thereof is to provide an inexpensive, high-quality thin-walled multi-layer tube.

[0006]

In order to achieve the above-mentioned object, the present invention forms an inner end portion of the outer peripheral surface of the end tube having a smaller diameter than the outer end portion thereof, and accords the small diameter portion. While being formed in the insertion fitting portion to the pipe, the inner end portion of the inner peripheral surface of the end pipe is formed to have a smaller diameter than the outer end portion, and the small diameter portion is formed in the fitting portion of the inner cylinder, The bellows pipe externally fitted to the insertion portion of the end pipe is welded and fixed to the end pipe, and the straight tubular inner cylinder internally fitted to the fitting portion of the end pipe is welded and fixed to the end pipe.

[0007]

According to the present invention, the small diameter portion on the outer peripheral surface of the end tube in which the inner end portion is formed to have a smaller diameter than the outer end portion allows the bellows tube to be externally fitted to the insert portion of the bellows tube and fixed by welding. Therefore, this small diameter portion serves as a backing metal, and welding distortion is less likely to occur. In addition, since a straight tubular inner cylinder is internally fitted and welded and fixed to the small diameter part on the inner peripheral surface of the end tube formed with the diameter near the inner end smaller than that near the outer end, internal stress is not applied to the inner cylinder. Is not left, and it becomes easy to arrange the inner cylinder so that its axis coincides with the axis of the bellows tube.

[0008]

1 and 2 show an embodiment of the present invention, FIG. 1 is an enlarged view of a main portion, and FIG. 2 is a vertical sectional front view. This multi-layered expandable tube includes an accordion tube (1), an end tube (2) connected and fixed to both ends of the accordion tube (1), and an end tube (2) in a state of protruding into the accordion tube (1). It is composed of an inner cylinder (3) fixed to 2).

The bellows pipe (1) is composed of a laminated pipe in which a large number of thin pipes made of metal such as stainless steel are laminated, and a ring-shaped pad ( 4) are arranged respectively, and the end face of the laminated pipe is covered
It is welded and integrated with (4).

The end tube (2) is formed by machining a metal cylindrical body, and the outer diameter of the portion near the outer end is smaller than the outer diameter of the portion near the inner end. At the same time, the inner diameter of the outer end portion is smaller than the inner diameter of the inner end portion.
(5) is formed in the fitting portion of the bellows tube (1), and the small diameter portion (6) on the inner peripheral surface is formed in the fitting portion of the inner cylinder (3). And
The large-diameter portion and the small-diameter portion on the inner peripheral surface are connected by an inclined surface of the inner recess.

The end portion of the bellows tube (1) is externally fitted to the insertion portion (5) formed near the inner end of the outer peripheral surface of the end tube (2) to form the bellows tube (1).
Weld the end of the to the end tube (2). At this time, the end tube (2)
Since the insertion portion (5) formed in the above acts as a backing metal at the time of welding the bellows tube, welding distortion does not occur in the bellows tube (1).

Then, the inner cylinder (3) is welded and fixed to the fitting portion (6) formed in the inner peripheral surface of the end tube (1) near the inner end. At this time, since the inner peripheral surface of the end pipe (1) is formed with the inclined surface of the inner confinement serving as a fluid guide surface, the inner cylinder (3) may be a straight pipe and the inner cylinder (3) may be a straight pipe. The process for forming the bell-mouth shape is unnecessary, the manufacturing cost can be reduced, and no internal stress is left in the inner cylinder (3). Also, the inner cylinder
Since the outer peripheral surface of (3) comes into contact with the inner peripheral surface of the fitting portion (6) over a certain length, the shaft core of the inner cylinder (3) is connected to the end pipe (2).
The inner cylinder (3) and the bellows tube (1) can be aligned with the axis of the
The gap between and can be kept uniform.

[0013]

According to the present invention, the bellows tube is externally fitted to the insertion portion of the bellows tube, and the small diameter portion on the outer peripheral surface of the end tube, in which the inner end portion is formed to have a smaller diameter than the outer end portion, is welded and fixed. Since this is done, this small diameter portion becomes a backing metal, welding distortion does not occur, and the quality and accuracy of the product can be maintained at a high level. Furthermore, since the end tube is fitted inside the bellows tube, and the end tube at the fitting portion has a small diameter portion formed inside to increase the wall thickness, welding of the bellows tube and the end tube is performed. It is possible to provide a strong thin-walled multi-layered expansion tube without applying an unreasonable force to the joint portion.

Further, according to the present invention, a linear tubular inner cylinder is fitted in and welded to a small diameter portion on the inner peripheral surface of the end tube in which the inner end portion is formed to have a smaller diameter than the outer end portion. Therefore, the processing of the inner cylinder can be omitted, and the manufacturing cost can be reduced.

Since the inner cylinder is composed of a straight pipe, no internal stress remains in the inner cylinder, the strength of the inner cylinder can be maintained high, and the inner cylinder is fixed over a predetermined length. By contacting the fitting portion, it becomes easy to arrange the axis of the inner cylinder in line with the axis of the bellows tube, and easily form a constant gap between the inner tube and the bellows tube. You can As a result, the flow of the fluid flowing inside is not disturbed.

Since the connecting surface between the large-diameter portion and the small-diameter portion of the inner peripheral surface of the end pipe is formed as the inclined surface, the inclined surface corresponding to the fluid can be easily formed.

[Brief description of drawings]

FIG. 1 is an extracted view of a main part.

FIG. 2 is a sectional view of an embodiment to which the present invention is applied.

FIG. 3 is a cross-sectional view of a conventional expandable tube.

[Explanation of symbols]

1 ... Bellows tube, 2 ... End tube, 3 ... Inner cylinder, 5 ... Insertion part, 6 ... Fitting part.

Claims (1)

[Claims] 1. A thin-walled multi-layer expansion and contraction pipe in which a bellows tube (1) is formed of laminated thin metal bodies, and end tubes (2) are welded to both ends of the bellows tube (1). The outer diameter of the outer peripheral surface of the bellows tube is formed to be smaller than that of the outer end, and the small diameter portion is inserted into the bellows tube (1).
(5), the inner peripheral part of the inner peripheral surface of the end pipe (2) is formed to have a smaller diameter than the outer peripheral part, and the small diameter part is fitted to the fitting part (3) of the inner cylinder (3). 6) and insert part of the end tube (2)
The bellows pipe (1) externally fitted to (5) is welded and fixed to the end pipe (2), and the straight tubular inner cylinder (6) internally fitted to the fitting part (6) of the end pipe (2) is fitted to the end pipe.
Thin multi-layer expansion tube welded and fixed to (2).