JPH08192232A - Method for forming projecting part of pipe and device therefor - Google Patents

Abstract

PURPOSE: To obtain a sharp corner part at the circumferential periphery without extremely increasing the internal pressure by forming by bulging a projecting part at a proper place of a tube, pressing the top face of the projecting part by a pressing die and forming a flat plane sharp in the corner part of the circumferential periphery. CONSTITUTION: When the hydraulic pressure is applied from one side (arrow mark direction) inside a pipe 3 after the pipe 3 is sealed hermetically inside a bulge die 1, the pipe 3 is apt to be bulged inside the die 1, but bulging is obstructed by the hermetically sealed die 1, so the mass of the pipe is centralized to a part of the die 1b and it is bulged, the projecting part 4 along the die part 1b is formed. Next, when the projecting part 4 is pressed by a pressing die by operating a hydraulic cylinder, the bulge forming hydraulic pressure is made as a reaction force receiver, the top face 4a is made in a flat projecting part 4, the corner part of circumferential periphery 4b is made sharp and the total top face 4a of the projecting part 4 can be made flat at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for forming a protruding portion on a pipe by bulging, and more particularly to a method and apparatus for forming a protruding portion of a pipe capable of sharply forming a corner portion of the protruding portion. .

[0002]

2. Description of the Related Art Conventionally, for example, as shown in FIG. 6, in order to form a protruding portion b on a pipe a, a pipe having a required length is put in a bulge mold having a concave mold portion for forming the protruding portion and hermetically sealed. After that, bulge processing is performed in which a part of the pipe is expanded along the mold part by introducing hydraulic pressure or the like into the pipe to pressurize the pipe to form a desired protruding part.

[0003]

However, in the above method, even if internal pressure is applied, it is difficult for the peripheral corners of the top surface of the protruding portion to be sharp, and as shown in FIG. In many cases, it does not reach the corner e (spot display portion) of the concave portion d of the mold c.

For this reason, when other parts are welded to the top surface of the projecting portion formed as shown in FIG. 7, the welding allowance increases, or the top surface of the projecting portion serves as a contact surface with other parts. In this case, problems such as insufficient contact surface occur.

As a method of solving these problems, theoretically, if the internal pressure is increased, the peripheral corners can be formed to some extent sharply. However, the pressure in this case is

[0006]

[Equation 1] Given in. For example, when the cross section of a pipe material with an inner diameter of 4.3 cm is formed into a triangular shape with one corner (1R) (R = 1 mm), the pipe t = 0.28 cm, δt = 3800
When kg / cm ² , k ₁ = 1.4, k ₂ = 1.1,

[0007]

[Equation 2] Becomes If such a high pressure is required, the probability of cracks and cracks in the pipe material increases, and a decrease in productivity cannot be avoided.

In view of the above, the present invention is directed to a method and apparatus for forming a protruding portion of a pipe in which a sharp peripheral edge portion can be obtained without excessively increasing the internal pressure by applying an embossing process to a bulge process. The purpose of the invention is to solve the drawbacks of the prior art.

[0009]

In order to achieve the above object, the present invention is to form a protrusion for a mounting seat or the like by bulging at an appropriate portion of a pipe material, and press the top surface of the protrusion. It is characterized in that the top surface of the bulge mold is pressed to form a flat surface having a peripheral edge corner portion as a shear shape. In claim 2 of the present invention, a through hole is provided in the protrusion molding die portion of the bulge mold. A pressing die for pressing the top surface of the protrusion formed by bulging is slidably fitted in this hole.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the drawings.

As shown in FIG. 1, a pipe projection forming apparatus according to the present invention comprises a bulge mold 1 (consisting of an upper mold and a lower mold) and a pressing mold 2. The pressing mold 2 is a desired portion of the bulge mold 1. Can be fitted into the through hole 1a provided in the. The rod end such as a hydraulic cylinder (not shown) is attached to the tip (upper end in FIG. 1) opposite to the pressing side, and the through hole 1a is extended by expanding and contracting the rod. The inside can be slid. The pipe material 3 side of the through hole 1a is a mold portion 1 for molding the protruding portion.
b.

Here, when the protrusion 4 is formed on a part of the outer periphery of the pipe material 3 by bulging, the pipe material 3 is sealed in the bulge mold 1 and then from one side (in the arrow direction) of the pipe material 3. When the hydraulic pressure is applied, the pipe material 3 tries to expand in the mold 1, but the expansion is blocked by the closed mold 1, so that the bulging of the pipe material 3 concentrates in the mold portion 1b and expands.
The protrusion 4 is formed along the mold 1b. As shown in FIG. 1, its shape is convex because the top surface 4a is in an inflatable state, and is not flat. In the above-mentioned molding, the pressing die 2 is fitted in the through hole 1a and is held in an inoperative state against the pressure from the pipe material 3 side.

Next, when the pressing die 2 is actuated by a hydraulic cylinder (not shown) to press the projecting portion 4 with the pressing die 2, the bulge forming hydraulic pressure acts as a reaction force by this pressing and the top surface 4a.
Becomes a flat protrusion 4, and as shown in FIG.
It is possible to make b sharp and make the entire top surface 4a of the protrusion 4 flat.

The molding pressure P in this case can be obtained from P = 2tσ / di, where di is the inner diameter (pipe material) t is the pipe wall thickness σ is the tensile stress, and sharper molding can be achieved with significantly smaller pressure than in the past. It is possible and can be molded without cracks or cracks.

Further, in the case of FIG. 2, the top surface 4a is flat without any unevenness, but the shape of the pressing die 2 is, for example, as shown in FIG.
When an annular convex portion is provided as in Fig. 3, the top surface of the protruding portion 4'has an annular groove 5 as shown in 4a 'of Figs. For example, when a convex circular step is formed as shown in FIG.
As described above, the top surface of the protrusion 4 ″ has the recess 6 like 4a ″, and various protrusions can be selected to form a desired protrusion.

In the above embodiment, the pipe member 3 has a round shape. However, according to the present invention, as shown in FIG. Can also be molded. Although not shown in FIG.
It is needless to say that in each of (c), FIG. 4 (c) and FIG. 5, the peripheral corner portion is as sharp as in FIG.

[0017]

As described above, according to the present invention, it becomes possible to sharply form a peripheral corner portion, which was difficult to be sharply formed by the conventional bulge processing, and therefore, welding of other parts and other parts are performed. Not only is it easy to secure the contact surface in the case of contact with, but the shape of the protrusion can be changed to various shapes by changing the shape of the pressing die.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a pipe protrusion forming apparatus according to the present invention.

2 is a cross-sectional view showing the shape of a protrusion formed by the apparatus of FIG.

FIG. 3A is a sectional view of another embodiment of the die according to the present invention,
(B) is a plan view of the protrusion formed by this, (c)
Is a sectional view of (b).

FIG. 4A is a sectional view of another embodiment of the die according to the present invention,
(B) is a plan view of the protrusion formed by this, (c)
Is a sectional view of (b).

FIG. 5 is a perspective view of a protrusion according to another embodiment of the present invention.

FIG. 6 is a perspective view showing a protruding portion of a pipe formed by conventional bulging.

7 is a cross-sectional view of the protrusion of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bulge type 1a Through hole 1b Mold part 2 Stamping mold 3 Pipe material 4, 4 ', 4 "Projection part 4a, 4a', 4a" Top surface 4b Periphery corner part 7 Pipe material 8 Projection part

Claims (2)

[Claims] 1. A flat surface in which a protrusion for a mounting seat or the like is formed by bulging at an appropriate portion of a pipe material, and the top face of the protrusion is pressed by a pressing die to make the top face a peripheral edge corner sharp. 1. A method for forming a protruding portion of a pipe, which comprises: 2. A through hole is provided in a protrusion forming mold of a bulge mold, and a pressing die for pressing the top surface of the protrusion formed by bulge processing is slidably fitted into the through hole. Equipment for forming protruding parts of pipes.