JPS60238038A - Bending method of pipe - Google Patents

Abstract

PURPOSE:To make the thickness of every part of a pipe with a bend working nearly equal by making the thickness of a straight pipe to be bend unequal in a specific peripheral direction and by performing a bend working with the arrangement of the thicker part and thinner part respectively on an outer and inner sides. CONSTITUTION:Since the center of the inner diameter of a straight pipe prior to its bend working is not co-axial to the lower part of a figure from the center of the outer diameter, the thickness of the pipe of the upper part of the figure is a thicker part of t5 thickness and the thickness of the pipe of the lower part of the figure is a thinner part 6 of t6 thickness. A bending work is executed by making the thicker part 5 of this pipe as the outside for bending and the thinner part 6 as the inside for bending. The thicker part 5 bent as the outside for bending is then elongated and thinned, and becomes a bent outside part 7 of t7 thickness and the thinner part 6 bent as the inside for bending is compressed and thicked and becomes a bent inside part of t8 thickness. Such bent pipe as being worked above can have nearly the same thickness in the t7 thickness of the bent outside part 7 and the t8 thickness of the bent inside part 8.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a method for bending a pipe, and more specifically, a method for bending a pipe so that the cross-sectional wall thickness of the bent pipe becomes equal. Regarding.

[Prior art] Methods for bending metal pipes such as steel pipes and copper pipes include:
There are two methods: heating the pipe and filling it with sand, etc., and bending it with a pipe bender at room temperature.

Conventionally, as shown in FIGS. 5 and 6, a pipe to be bent has the same wall thickness to at any location (1) before being bent. If this is bent using the method described above, no matter which method is used, the outer 2 portion of the bent tube will be stretched in the axial direction of the tube, as shown in FIGS. 7 and 8. Therefore, the wall thickness t2 is inevitably thin, and the inner side 3 of the bent tube is compressed in the axial direction of the tube, so the wall thickness t3 is inevitably thick.
becomes.

This also applies to pipes other than metal, such as plastic pipes.

[Problem] In this way, the bent pipe inevitably has a thin wall t2 at the outside part 2 of the bend, and a thick wall t2 at the inside part 3 of the bend.
It becomes 3. Therefore, the pressure resistance of the entire pipe system and the wall thickness in preparation for corrosion are determined by the thin wall thickness t2 at the bending outer side 2.
It will be limited by. That is, the above-mentioned design requirements for the tube, such as strength and durability, must be based on the thickness t2 of the thin wall portion 2.

In this case, all parts of the pipe system other than this thin wall portion 2 will have an extra pipe wall thickness, which is (2) extremely uneconomical.

[Purpose] Therefore, the purpose of this invention is to bend a pipe,
The purpose is to solve the above-mentioned problems by realizing a method of bending a tube so that all parts have the same wall thickness.

[Structure] In order to achieve this object, the present invention provides a straight pipe whose outer diameter center and inner diameter center are eccentric in a certain direction and whose wall thickness is unequal in the circumferential direction when bending the pipe. The pipe is characterized in that the pipe is bent with the thicker wall placed on the outside of the bend and the thinner wall placed on the inside of the bend.

[Function] Since the present invention is configured as described above, by bending the pipe, as described above, the wall thickness of the pipe is stretched and thinned on the outside of the bend, and becomes thicker on the inside of the bend. In this bending process, the pipe is bent with the thicker wall on the outside and the thinner wall on the inside, so most of the products resulting from the bending process are curves of equal thickness. You can get the tube.

[Example] The present invention will be described in detail below with reference to the illustrated embodiments.

1 and 2 show a straight pipe before bending, and FIGS. 3 and 4 show a bent pipe after bending by the method according to the invention.

In Figures 1 and 2, the center of the inner diameter of this tube is eccentric to the lower part of the figure than the center of the outer diameter, so the tube wall in the upper part of the figure becomes a thick part 5 with a thickness of t5, and as shown in the figure The inside of the lower tube becomes a thin wall portion 6 with a thickness t[l.

The bending process is carried out with the thick part j of this tube as the outside bending part and the thin part 6 as the inside part. Then, as shown in FIGS. 3 and 4, the thick part 5 bent as the outside of the bend stretches and becomes thinner, and the pipe wall thickness L? It becomes the bent outer part 7 of
The thin wall portion 6 bent as the inner side of the bend is compressed and becomes thicker, and becomes the inner side of the bend 8 having a tube wall thickness t8.

As shown in FIGS. 3 and 4, the bent pipe bent in this manner has a thickness t? of the bent outer portion 7 where the thick portion 5 is stretched and thinned. (4) The thickness t8 of the bent inner side portion 8, which has become thicker due to compression, can be made approximately the same thickness.

The thickness t5 of the thick part 5 and the thickness t6 of the thin part 6, which should be set in order to make the outer wall thickness t7 and the inner wall thickness t8 almost the same thickness, should be set depending on the curvature of the bending process. Bye. That is, in bending with a large radius of curvature, the difference in wall thickness must be small, and in bending with a small radius of curvature, the difference in wall thickness must be large.

In actual application, it is desirable that the wall thickness of the curved pipe portion be slightly thicker than that of the straight pipe portion in order to compensate for deterioration of the material due to processing.

[Effects of the Invention] As explained in detail above, according to the present invention, the wall thickness of the bent pipe after bending can be made almost equal in all parts, which is different from the conventional method. It is possible to prevent the occurrence of a thin wall portion on the outer side of the bend, which was caused by the bending method described above.

As a result, the problem of weak and small parts can be solved, and the pipe (5) system as a whole can be manufactured with no waste in terms of strength, durability, and other functions.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view of the tube before bending according to the present invention, FIG. 2 is a cross-sectional view of the tube shown in FIG. 1, and FIG. 3 is a partially cutaway side view of the tube after bending according to the present invention. Figure 4 is the third
5 is a partially cutaway side view of the tube before bending by the conventional method, FIG. 6 is a cross-sectional view of the tube in FIG. 5, and FIG. 7 is a conventional bending method. FIG. 8 is a partially cutaway side view of the tube after processing, and is a cross-sectional view taken along the line -■ in FIG. 7. In the figure, 5 is the thick part of the pipe before bending according to the present invention, t5 is the thickness of the thick part, 6 is the thin part of the pipe before bending according to the present invention, and t6 is the thickness of the thin part. , 7 is the bent outer part after bending according to the present invention, t7 is the thickness of the bent outer part, 8 is the bent inner part after bending according to the present invention,
t8 is the thickness of the inner side of the bend. Applicant Mitsubishi Heavy Industries, Ltd. Sub-Agent Patent Attorney Hara 1) Yukio (6) Figure 1 Figure 3 Figure 2 Figure 5 Figure 7 Figure 101 -- Figure 6 Figure 8

Claims (1)

[Claims] The outside diameter center and the inside diameter center of the pipe are eccentric in a certain direction, and the thickness of the straight pipe is made uneven in the circumferential direction. A method for bending a pipe, the method comprising bending a pipe.