JPH04331884A - Bellows pipe and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a bellows pipe and a manufacture thereof by increasing the mechanical strength of parts of a corrugated wall in the vicinity of the crests of the latter, and in particular by increasing the fatigue-resistant strength in those parts during use under compression so as to reduce and prevent cracking and damage for a long time. CONSTITUTION:A parts of a bellows pipe in the vicinity of the crests of the latter are roll-pressed diametrically by a retaining roll from the outside so as that a residual compression stress remains in the vicinity of each outside crest part 3' of corrugation 3 of the corrugated wall of the bellows pipe 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a bellows tube used as a flexible joint for a piping connection or as a flexible tube itself in automobiles or various machines and equipment, and a method for manufacturing the same.

0002

2. Description of the Related Art Conventionally, as shown in FIG. 3, a bellows pipe (11) of this type has been constructed by partially protruding a plurality of corrugated walls (13) on the circumferential surface of a metal pipe (12). It consisted of

0003

[Problems to be Solved by the Invention] However, in such a conventional technique, residual stress in the tensile direction due to elongation during the bulging process is generated near the top (13') of the corrugated wall (13). This causes deterioration in mechanical strength, and tends to cause cracks and breakage due to fatigue, mainly when used in a compressed state as a bellows tube.

The present invention has been made in view of these problems of the prior art, and increases mechanical strength by allowing compressive stress to remain in the vicinity of the top, so that even when used in a compressed state, there is no stress in the vicinity of the top. The object of the present invention is to propose a bellows tube and a method for manufacturing the same that can reduce and prevent the problems of cracks and breakage.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a bellows pipe having a corrugated wall along the circumferential surface of a metal tube, in which the outer top of each of the corrugated walls is A bellows pipe in which compressive stress remains in the vicinity, and a bellows pipe formed by partially bulging out a plurality of corrugated walls on the circumferential surface of a metal pipe material. On the other hand, the gist of each is a method of manufacturing a bellows tube, which is constructed by rolling and pressing from the outside in the radial direction using presser rolls arranged at approximately equal intervals.

[0006]

[Operation] After the conventional primary processing for forming a corrugated wall, the present invention rolls and presses the vicinity of the top of the corrugated wall from the outside in the radial direction with a plurality of presser rolls. It is possible to increase the mechanical strength by generating residual stress in the compressive direction due to pressing, and it is also possible to form a smooth curved surface near the top, and it is also possible to correct the collapse of corrugated walls and uneven pitches. As a result, it is possible to reduce and prevent cracks and breakage by increasing the fatigue strength near the top over a long period of time, especially when used in a compressed state, even if the connection is forced in the bending direction. Become.

[0007]

[Example] Hereinafter, embodiments of the present invention will be described based on the drawings. Fig. 1 is a partially cutaway plan view of the bellows pipe of the present invention, and Fig. 2 is a cross-sectional view showing a method of manufacturing the bellows pipe of the present invention. FIG. 3 is an explanatory diagram, and the present invention starts from a bellows tube that has been subjected to primary processing as shown in FIG. 3.

The next secondary processing is performed as shown in FIG. That is, a plurality of (three in the illustrated embodiment) presser rolls (4) are arranged at approximately equal intervals with respect to the central axis (C) of a metal tube (2) having a corrugated wall (3). The presser roll (4) is brought into contact with the vicinity of the outer apex (3') of the corrugated wall (3) from the outside in the radial direction, and the presser roll is rolled and pressed inward to remove the corrugated wall (3), especially the corrugated wall (3). The area near the outer top (3') is concentrated in a substantially U-shape, and the pressure generates residual compressive stress near the top, forming a smooth curved surface, and forming a corrugated wall (3).
It is also possible to correct tilting and uneven pitches.

Although the illustrated embodiment shows the formation of a wavy wall with a U-shaped cross section, a wavy wall with an Ω-shaped cross section can also be manufactured according to the present invention with the same effect.

0010

As explained above, according to the present invention, especially in the vicinity of the top (3') of the corrugated wall (3), a plurality of presser rolls roll and press the vicinity of the top from the outside in the radial direction. This creates a residual stress in the compressive direction near the top, thus increasing the mechanical strength, and the product has high durability near the top (3') even if it is forced to connect in the bending direction. It increases the fatigue strength, especially when used in a compressed state, and reduces and prevents cracks and breakage over a long period of time.It also has a smooth curved surface near the top.
Furthermore, it is an extremely useful bellows tube and its manufacturing method that can correct the collapse of corrugated walls and uneven pitches.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway plan view of a bellows tube showing an embodiment of the present invention.

FIG. 2 is a cross-sectional explanatory view showing the method for manufacturing a bellows tube of the present invention.

FIG. 3 is a partially cutaway plan view of a bellows tube showing a conventional example.

[Explanation of symbols]

2 Metal pipe material 3. Corrugated wall 3' Top 4 Presser roll

Claims (2)

[Claims] Claim 1. In a bellows tube having a corrugated wall along the circumferential surface of a metal pipe material, each of the corrugated walls (3)
A bellows tube characterized in that compressive stress remains near the outer top (3') of the bellows tube. 2. The vicinity of the top of the corrugated walls of a bellows tube formed by partially protruding a plurality of corrugated walls on the circumferential surface of a metal pipe material with respect to the central axis (C) of the bellows tube (2). 1. A method for manufacturing a bellows tube, comprising rolling and pressing from the outside in the radial direction using a plurality of press rolls arranged at approximately equal intervals.