JPH0152085B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a branch pipe directly from a main pipe.

[Conventional technology]

Several proposals have been made and put into practice as a method for manufacturing branched pipes directly from steel pipes, and the most common method is to provide a circular hole in the main pipe and pull out a die from inside the main pipe. There are two methods, such as a method of forming a branch pipe or a bulging method, and an example of the former method is the method described in Japanese Patent Publication No. 30-8916.

[Problem that the invention seeks to solve]

However, although such conventional methods can produce a branch pipe with a branch pipe integrated into the main pipe, the wall thickness of the branch pipe is considerably reduced compared to that of the main pipe. There were flaws.

This is because when the epigonal hole provided in the main tube is expanded while being curved outward to the diameter of the branch tube to be formed, the peripheral part of the epigonal hole is pulled in the circumferential direction of the hole. It is believed that there is.

Therefore, when a branch pipe is formed using the conventional method, there is a problem in that a high quality branch pipe cannot be manufactured unless the diameter of the branch pipe is made considerably smaller than that of the main pipe.

In order to solve this problem, it may be possible to use a thicker main pipe, but this is not preferable because other problems such as an increase in the overall weight arise.

By the way, the wall thickness decreases until the branch pipe is formed, as mentioned above, mainly in the peripheral part of the oval hole provided in the main pipe, so the peripheral part is made to protrude outside of the main pipe. If it is possible to make the wall thickness of the peripheral part thicker than that of the main pipe in advance, the wall thickness of the branch pipe formed in this way will be the same as that of the main pipe surrounding the oval hole. Naturally, the wall thickness will be thicker than that of a branch pipe of the same diameter as above that is formed directly from the pipe.

Therefore, if we compare the reduction rate of the wall thickness of these two branch pipes with respect to the wall thickness of the main pipe, the former will naturally be smaller, but in the conventional method of manufacturing branch pipes, There is no manufacturing method in which the thickness of the peripheral part of the oblong hole is made thicker than the thickness of the main pipe before forming it to protrude outside the main pipe.

[Means for solving problems]

The present invention has been made for the purpose of providing a method for manufacturing a branch pipe that can solve the problems of the prior art as described above, and its structure is as follows:
At the location where a branch pipe of the main pipe is to be installed, an elongated hole whose long axis is shorter than the inner diameter of the branch pipe is pre-drilled so that its long axis faces in the axial direction of the main pipe, and the area around the elongated hole is made. is heated, and an inverted cone-shaped die having a narrow end diameter shorter than the short axis of the elongated hole is heated so as to expand the elongated hole and curve the peripheral part of the hole toward the inner surface of the mother pipe. Then, the slope of the die is brought into contact with the pipe wall of the circular hole, and the die is press-fitted from the narrow end side into the circular hole, and then the outer diameter of the large end is formed in the branch pipe. A conical molding die having approximately the same diameter as the inner diameter of the outer end, and having an inclined surface that is approximately perpendicular to the curved pipe wall of the hole and in contact with the pipe wall of the hole is placed on the inner surface of the hole. By pulling vertically from the side toward the outer surface of the main pipe, the curved peripheral part of the hole is pulled out by the force acting through the slope of the molding die that is in contact with the pipe wall part. It is pulled up toward the outer surface of the main pipe while being compressed and deformed in the direction of the surrounding pipe wall surface, and then the peripheral part of the hole thus pulled up and the nearby pipe wall part continuous with the part are curved and protruded toward the outer surface of the main pipe. It is characterized by forming a branch pipe.

[Effect]

The method of the present invention having the above configuration first involves forming an elliptical hole whose major axis is shorter than the inner diameter of the branch pipe formed in the main pipe.
The peripheral part is heated to soften it, and an inverted conical die is press-fitted into the circular hole so as to expand the circular hole and curve the peripheral part toward the inner surface of the main tube. By pulling out from the main pipe a forming die having a slope that abuts at a right angle to the pipe wall around the curved oblong hole, the surrounding part is compressed in the direction along the wall surface. raise the
The process consists of forming a branch pipe by protruding this part and the nearby wall of the main pipe to the outside of the main pipe. The wall thickness of the main pipe can be made thicker than that of the main pipe, and since the branch pipe is formed from this thickened part, the thinning rate of the branch pipe based on the wall thickness of the main pipe is the same as the wall thickness of the main pipe. It is smaller than when forming a branch pipe directly from the pipe.

〔Example〕

In the method of the present invention, the main pipe P shown in FIG. An oblong hole 1 shorter than the inner diameter is provided in advance, and while the periphery of the oblong hole 1 is heated, an inverted conical shape is formed in the hole 1, the narrow end of which is smaller than the short axis of the hole 1. The first step is to press-fit the die 2 and apply pressure in the direction of the pipe wall surface of the main pipe P to compress the periphery of the oblong hole 1 of the main pipe P in the direction of the pipe wall surface and to curve the periphery inward.
Process. After the first step, as shown in FIG. 2, a molding die 3 having a conical shape and a large end corresponding to the inner diameter of the branch pipe to be formed is inserted from inside the circular hole of the main pipe P. The second step is to pull it out to the outside of the main pipe P through the oval hole 1.

During the second step of drawing the die, the side surface of the conical forming die 3, that is, the tapered surface,
The tube wall around the oblong hole 1, which is curved toward the inner surface of the main tube P, is deformed outward while increasing the thickness by pressing in the direction along the wall surface, and further, the outer surface of the main tube P is Since the pulled out part is curved and extended to form a branch pipe that protrudes to the outside of the main pipe P, a branch pipe BP whose wall thickness does not decrease much compared to the main pipe P is formed and a branch pipe is manufactured. It is something that can be done.

Here, when pre-processing the periphery of the circular hole 1 of the main pipe P as the first step, the inverted conical die 2 is used in the above, but the present invention is not limited to this, and other Appropriate means may be adopted.

In addition, when heating the periphery of a circular hole and press-fitting a conical die into the circular hole from the narrow end side, it is possible not only to simply push the die, but also to press-fit it while rotating, or to press-fit it while rotating. It also includes press-fitting by reciprocating while rotating together with the die to increase the thickness of the pipe wall.

Furthermore, in the above example, the inverted conical die 2 and the molding die 3 were separated, but in order to efficiently manufacture branched pipes, the two dies 2 and 3 are integrated to perform the work. It can also be done.

Figures 3 and 4 show an example of a state in which the dies 2 and 3 are used together for work, and the inverted conical die 2 is placed outside the circular hole 1 of the main pipe P. Place dice 3 on the inside as well,
They are connected by a connecting rod 4 with their narrow ends facing each other, and while or after heating the periphery of the oblong hole 1, the connecting rod 4 is operated to connect both the dies 2 and 3 to the motherboard. The periphery of the circular hole 1 of the main pipe P is compressed in the direction of the pipe wall surface by reciprocating the pipe P in the inner and outer directions, or by rotating it and reciprocating in the same manner as described above. By pulling out the die 3 from inside the main pipe P through the circular hole 1, the branch pipe BP is removed.
The branch pipes are manufactured by forming a branch pipe.

As described above, the method of the present invention is based on the branch pipe BP of the main pipe P.
A circular hole 1 whose major axis is shorter than the inner diameter of the branch pipe BP is provided at the location where the branch pipe BP is to be provided, and a die 2 is press-fitted into the circular hole mainly around the short axis side of the circular hole 1. By compressing it in advance in the direction of the pipe wall surface and bending it toward the inner surface of the main pipe, and in this state, by pulling out the branch pipe forming die 3 from the inside of the main pipe P through the circular hole 1, the flesh of the branch pipe BP is Thickness is main pipe P
This makes it possible to reduce the reduction in branch pipe BP with a relatively large diameter.

Here, the size of the circular hole 1 should be determined taking into consideration the diameter, length, and required thickness of the branch pipe to be formed, so that the thickened part necessary for deformation can be formed. This makes it possible to obtain a branch pipe with an appropriate shape, and when heating the area around the oblong hole 1,
For example, as shown in Fig. 5, by taking into consideration the heating temperature of the short axis of the oval hole 1 to be higher than the heating temperature of the long axis, it is possible to reduce By promoting the deformation of the shaft,
It is possible to obtain good effects.

In fact, STPG38, 6B×S/
40 (outer diameter 165.2 mm, wall thickness 7.48 mm) main pipe, short shaft 36
By creating a circular hole with a long axis of 72 mm and simply pulling out a conical die from inside this circular hole.
4B x S/40 (outer diameter 114.3mm, wall thickness 6mm), height 15
An attempt was made to form a branch pipe of STPG38 mm, but the average wall thickness of the branch pipe actually formed was 5.43 mm, and the wall thickness reduction rate was 27.4%.
A round hole with a short axis of 26 mm and a long axis of 62 mm is made in a 6B x S/40 (outside diameter 165.2 mm, wall thickness 7.24 mm) main pipe, and an inverted cone-shaped die is press-fitted into the round hole. After deforming the pipe inwardly while thickening it, the conical forming die is pulled out from the inside of the deformed circular hole to increase the thickness, and then the branch pipe is deformed outwardly to form the same branch pipe as above. When attempting to form a branch pipe, the average wall thickness of the branch pipe actually formed was 6.01 mm, and the wall reduction rate was 17%.
The thinning rate was reduced by approximately 10% compared to the conventional method.

Incidentally, in the conventional method, the formula for calculating the wall thickness reduction rate is: 7.48 (main pipe wall thickness) - 5.43 (branch pipe wall thickness) / 7.48 (main pipe wall thickness) × 100 = 27.4 (%) In the present invention method is 7.24 (main pipe wall thickness) - 6.01 (branch pipe wall thickness) / 7.24 (main pipe wall thickness) × 100 = 17 (%), and the difference is 27.4 - 17 = 10.4.

This difference in thickness reduction rate is due to the difference in the size of the lateral holes originally provided for both methods when forming branch pipes of the same diameter and height, and it is also possible to reduce the size of the lateral holes. It can be seen that this contributes to a reduction in the thickness reduction rate in the method of the present invention.

〔Effect of the invention〕

The present invention is as described above, and according to the method of the present invention, the thinning rate of branch pipes can be reduced compared to the conventional method. The cylindrical hole is compressed in the direction of the tube wall surface by press-fitting an inverted cone-shaped die, and the tube is curved and deformed toward the inner surface of the tube. After that, the forming die is pulled out to undergo a thickening process, and then the branching portion is pulled out and deformed. This is because branch pipes are formed by using the method described in Japanese Patent Publication No. 30-8916, which is cited as an example of the conventional method, as well as short pipes, as well as long pipes. In addition, there is no need to compress or bend the main pipe in the axial direction, so equipment for this is not required and equipment costs are reduced.

In addition, when trying to obtain a long pipe with branch pipes at an appropriate pitch, conventionally commercially available cheese is welded, but according to the method of the present invention, branches can be directly attached to the long pipe at the desired pitch. Since a tube can be formed, a product with high pitch accuracy can be obtained at low cost, and furthermore, it is also possible to manufacture a branch tube having branch tubes having a relatively larger diameter than the main tube as a whole.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view showing a thickening step in one example of the method of the present invention, FIG. 2 is a longitudinal sectional front view showing a branch pipe forming step, FIG. 3 is a longitudinal sectional front view of another example of the method of the invention, The figure is also a vertical side view, and FIG. 5 is a plan view showing the temperature distribution during heating. P...Main pipe, 1...Hydraulic hole, 2...Inverted conical die, 3...Forming die, BP...Branch pipe.

Claims (1)

[Scope of Claims] 1. At the location where a branch pipe of the main pipe is to be provided, a circular hole is drilled in advance so that its long axis is shorter than the inner diameter of the branch pipe so that its long axis faces in the axial direction of the main pipe. The periphery of the circular hole is heated by heating the periphery of the circular hole, and an inverted cone-shaped die having a narrow end diameter shorter than the short axis of the circular hole is heated, and while expanding the circular hole, the peripheral portion of the hole is inserted into the main tube. so that it curves towards the inner side of the
After the slope of the die is brought into contact with the tube wall of the circular hole and the die is press-fitted from the narrow end side into the circular hole, the outer end of the branch pipe where the outer diameter of the thick end is formed. A conical molding die having approximately the same diameter as the inner diameter of the hole, and having an inclined surface that is approximately orthogonal to the curved tube wall of the hole and in contact with the tube wall of the hole is inserted from the inner surface of the hole. By pulling the tube vertically toward the outer surface of the main tube, the curved peripheral portion of the hole is pulled out by the force acting through the slope of the molding die that is in contact with the tube wall. The pipe is compressed and deformed in the direction of the pipe wall surface while being pulled up toward the outer surface of the main pipe, and then the peripheral part of the hole thus pulled up and the pipe wall part in the vicinity continuous with this part are curved and protruded toward the outer surface of the main pipe. A method for producing a branched pipe, the method comprising forming a branched pipe.