JP2005262308A - Method for forming bellows pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a bellows pipe, which shows high productivity at a low cost. <P>SOLUTION: A metallic pipe 10 is axially compressed with a mandrel 20 arranged therein in order to produce the undulations thereon caused by buckling. Preferably, the metallic pipe is axially compressed at a speed higher than 999 mm/s. In addition, preferably, the metallic pipe is axially compressed after forming angular beads 11 serving as origins of the buckling, on the surface of the metallic pipe. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention has a bellows-like structure suitable for use in a part of a piping path in order to absorb stress generated by expansion or contraction due to heat or mechanical vibration, which is used for a liquid or gas transport pipe. With respect to the manufacture of the so-called bellows tube, the present invention provides a method for forming a bellows tube that keeps processing costs low and exhibits high productivity. The use of such bellows tubes covers a wide range of fields such as transportation facilities such as automobiles, ships and aircraft, air conditioning equipment, industrial plant equipment, scientific experimental equipment such as vacuum equipment.

  Various methods are known for manufacturing a so-called bellows tube having a bellows-like structure and a function of absorbing stress and vibration (see Non-Patent Document 1). The optimum processing method is selected according to the size of the bellows tube that is the product. The material of the bellows tube is austenitic and ferritic stainless steel from the viewpoint of corrosion resistance, and various special steels are selected depending on the application from the viewpoint of mechanical properties such as spring characteristics. Due to its strength, it is difficult to form compared to a metal tube made of mild steel.

  In particular, it is not easy to form a product having a relatively small diameter (φ20 to φ100 mm) and a short length (30 to 300 mm). Conventionally, for forming a bellows tube of the size, (1) a method of forming a predetermined number of folds in a single process by hydraulic forming using a ring-shaped movable mold (see Patent Document 1), Alternatively, (2) there is a method (see Patent Documents 2 and 3) in which folds are formed one by one by bulge molding using a liquid or an elastic body.

Japanese Patent Laid-Open No. 10-175028 JP-A-11-10242 JP-A-11-169958 Published by Japan Society for Technology of Plasticity “Plasticity and Processing” Vol. 32, No. 366, pp. 818-824

  However, although the former method (1) can complete a predetermined shape with a small number of steps, it is low in productivity because of hydraulic forming. In addition, if the ring-shaped movable mold has a complicated structure and is intended to be molded with different product shapes, there is a problem that the mold cannot be shared and the mold cost is high.

  On the other hand, the latter method (2) has an advantage that a relatively simple mold can be used and the number of creases can be freely created by sequential processing, but the productivity is still low.

  An object of the present invention is to provide a method for forming a bellows tube that exhibits high productivity and is low in cost.

  The present invention solves the above problem by arranging a mandrel inside and then compressing the metal tube in the axial direction to generate irregularities due to buckling on the surface.

  Further, when the metal tube is compressed in the axial direction, it is compressed at a speed of 999 mm / second or more.

  Further, when the metal tube is compressed in the axial direction, the metal tube surface is compressed in the axial direction after being bent on the surface of the metal tube.

  According to the present invention, it is possible to provide a low-cost bellows pipe forming method that exhibits high productivity.

  FIG. 1 shows an example of a method for forming a bellows tube according to the present invention. 10 is a metal tube as a material of the product, 20 is a mandrel inserted inside the metal tube 10, 22 is a lower ram, 24 is an upper ram, and 26 is a guide for the upper and lower rams 22, 24. .

  As shown on the left side of FIG. 1, a metal tube 10 and a lower ram 22, an upper ram 24, and a guide 26, which are tools, are arranged, and then a load is applied to the upper ram 24 to compress the metal tube 10 in the axial direction. Here, the holding portion A of the lower ram 22 and the upper ram 24 secures a straight pipe portion of the product. The mandrel 20 and the guide 26 keep the deformation inside and outside the metal tube 10 within a certain range, respectively. The load during the molding may be a static load, but it is preferable to mold by applying a relatively high speed so-called striking force because a uniform deformation can be obtained in the circumferential direction. The high-speed hitting force can be applied by, for example, dropping a weight onto the upper ram 24.

  Further, in order to improve the uniformity of axial deformation (please pitch and height) of the metal tube 10, prior to the above-described axial compression molding step, as shown in FIG. The bent bead 11 to be formed is preformed on the metal tube 10 so that the buckling position is controlled at a predetermined position where the bent bead is present, and the buckling is generated at a position other than the predetermined position. And the bellows tube having a more uniform and good shape can be formed.

  The preforming method in this case is not particularly limited. As shown in FIG. 3, a guide 30 having an inner surface formed in a mountain shape is arranged outside the metal tube 10, and a segment 32 is arranged inside. A method called segment tube expansion, in which an inner mold having an outer surface called a chevron shape, with the crest and trough positions of the guide 30 and the segment 32 facing each other and the segment 32 expanded outward, or hydraulic forming Etc. are available. In any case, since the amount of deformation of the folded bead 11 during the preforming may be small, it can be handled with a small apparatus output and does not require a complicated mechanism for operating the mold in conjunction with the conventional method. High productivity can be exhibited and costs such as equipment costs and mold costs can be kept low.

  A bellows pipe having a pleated shape (10 mm pitch, 7 mm height) shown in FIG. 4 was formed from the material metal pipe of SUS304 having a plate thickness of 0.6 mm and φ65 mm under the molding conditions A to D shown in Table 1. Table 1 also shows the number of creases that could be formed at that time.

  It can be seen that the bellows tube can be formed by following the method of the present invention. It can also be seen that the number of creases that can be formed increases by pre-forming the folded beads and increasing the forming speed. This is because buckling is prevented from occurring at a predetermined location by using the bent bead as a starting point to prevent buckling at a location other than the predetermined location.

Sectional drawing which shows one of embodiment of this invention Sectional drawing which shows another embodiment of this invention Sectional view showing the method of preforming folded beads Sectional drawing which shows the dimension of each part of the bellows pipe which is going to shape | mold in the Example of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Metal pipe 11 ... Folding bead 20 ... Mandrel 22 ... Lower ram 24 ... Upper ram 26, 30 ... Guide 32 ... Segment

Claims (3)

  A method for forming a bellows tube, wherein a mandrel is disposed inside, a metal tube is compressed in an axial direction, and unevenness due to buckling is generated on the surface.   The method for forming a bellows pipe according to claim 1, wherein the metal pipe is compressed at a speed of 999 mm / sec or more when compressed in the axial direction.   The bellows pipe according to claim 1 or 2, wherein when the metal pipe is compressed in the axial direction, the metal pipe surface is compressed in the axial direction after being bent on the surface of the metal pipe. Molding method.

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