JPH074629B2 - Bulge forming method for long pipes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention forms a bulging portion in a long and relatively thin pipe material in order to form a branched tubular connection portion uniformly. The present invention relates to a bulge forming method for long pipes.

(Prior Art) As a means for forming a branch-tube-shaped connecting portion on a side surface of a pipe material in order to connect another pipe material or a joint member to the pipe material, conventionally, the side surface of the pipe material is bulged by bulging. Then, a means for forming a connection portion by cutting or punching the tip of the bulging portion is adopted.

By the way, in the conventional bulge forming method, a pipe material to be processed is placed in a bulge forming die, a pressure liquid (for example, water) is press-fitted from an end portion of the pipe material, and a part of the pipe material is inserted into a forming die portion of the die. Is bulged, and after molding, the tip of the bulged portion is opened to form a connection portion.

In the above-mentioned bulge forming, as illustrated in FIG. 8, in order to assist the formation of the bulging portion 1A formed in the pipe material 1, both ends of the pipe material 1 in the forming die 2 are pushed by the pushing rods 3, 3 is pressed in the direction of the arrow to give a flesh pulling force, and the pressure liquid for bulging is passed through the pipes 1 through the flow paths 3A, 3A in the pushing rods 3, 3.
The bulging portion 1A is press-fitted into the inside, and the bulging portion 1A is easily and uniformly formed by the pressure P of the pressure liquid and the press-fitting force of the pushing rods 3,3.

(Problems to be Solved by the Invention) However, in the above bulge forming method, when the pipe material 1 to be processed is long (for example, 1000 mm) and has a relatively small diameter (for example, about 20φ), the pushing rods 3 and 3 are used. Even if the end of the pipe material 1 is pressed, the pressing force by the pressing rods 3,3 (the thickness reduction) is increased because the distances a and b between the tips of the pressing rods 3,3 and the bulging molding portion 1B of the bulging portion 1A are long. Force) causes the meat of the pipe material 1 not to reach the bulging molding site 1B due to so-called biting due to the strong frictional force caused by the pressure bonding between the outer peripheral surface of the pipe material 1 and the inner surface of the molding die 2 Not only a large molding liquid pressure is required, but also a bulge
There were various problems such as it was difficult to form 1A in a uniform thickness with other parts.

In view of this, the present invention is a long pipe that can reliably bring the bulging portion to the bulging-molded portion even with a long pipe material and can form a uniform bulging portion with a small molding liquid pressure. It was made for the purpose of providing a bulge forming method for a material.

[Structure of Invention]

(Means for Solving the Problems) In order to solve the problems of the above-described conventional technology, the present invention provides a ridge in the circumferential direction of the inner peripheral surface at a position near at least one side of the bulging-molded portion of the pipe material to be molded. Is preformed, the pipe material is placed in a bulge forming mold, and the tip pressing surface of the pressing shaft portion of the insertion rod that is inserted as closely as possible from the end portion of the pipe material abuts the side surface of the ridge, It is characterized in that the pushing rod is pressed to provide a bulging force to the bulging-molded portion of the pipe material through the ridge, and a pressure liquid is pressed into the pipe material to perform bulging molding.

(Operation) With the above configuration, the pressing force of the pushing rod is applied to the ridge formed on the inner circumference of the pipe material in the vicinity of the bulging molding site, and the bulge of the pipe material and the ridge bulge through the ridge. Since the flesh in a short range with the forming part is brought closer to the bulging forming part side, the fleshing is performed without being affected by galling due to the strong frictional force between the pipe material and the bulge forming die. The uniform bulging portion can be molded by a smaller molding liquid pressure.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
The same parts as those in the figure will be described using the same reference numerals.

In the bulge forming method according to the present invention, as shown in FIG. 1 as an example, first of all, a bead 4, 4 is formed on the inner periphery of the pipe material 1 to be processed near the bulging and forming portion 1B by a circumferential ridge 5, Preform 5.

The push rods 3, 3 are a push shaft portion 6 which can be inserted into the inner circumference from the end portion of the pipe member 1 as closely as possible, and a push shaft portion 6 which is continuously provided at the tip end of the push shaft portion 6 and is inserted into the protrusion 5. A small diameter shaft portion 7 and a guide shaft 8 that is connected to the base portion of the pressing shaft portion 6 and that can be inserted into the molding die 2 as closely as possible, and supplies a pressure liquid into each of the shaft portions. A flow path 3A for forming is formed. The length of the pressing shaft portion 6 is such that when the pressing surface 6A at the tip of the pressing shaft portion 6 comes into contact with the side surface of the ridge 5 of the pipe material 1, the end surface 8A of the guide shaft 8 becomes the end surface 1C of the pipe material 1. The dimensions are not met.

A seal ring 9 is fitted to the outer peripheral portion of the pressing shaft portion 6 near the pressing surface 6A so that the pressure liquid does not leak at the time of expansion molding.

As shown in FIG. 1, the pipe material 1 preliminarily processed as described above is housed in a molding die 2 composed of upper and lower dies 2A and 2B, and pushing rods 3 are inserted from both ends of the molding die 2. As shown in the first illustration, the pressing surfaces 6A, 6A at the tips of the pressing shafts 6, 6 are formed on the ridges of the pipe material 1.
Contact the side of 5,5. After this, if the pressure liquid is pressed in through the flow paths 3A, 3A and the pushing rods 3,3 are pressed in as indicated by the arrows, the forming die 2 is formed by the pressure wall in the bulging molding portion 1B of the pipe material 1 by hydraulic pressure. The bulging portion 1A is molded in accordance with
At the same time, a pressing force (clamping force) is applied by the pushing rods 3,3, and this force is generated between the pipe material 1 and the molding die 2 because the ridges 5,5 are located near the bulging molding portion 1B. The flesh of the pipe material 1 is brought closer to the bulging-molded portion 1B without being affected by the galling during the bulging, and the bulging portion 1A is smoothly molded.

In addition, in order to smooth the beads 4 and 4, if necessary, the pressure liquid is released after the bulging portion 1A is molded and only the pushing rods 3 and 3 are pushed in, and the pushing shaft portions 6 and 6 are projected. It is press-fitted to the inner circumference of 5 to expand it, and the beads 4 and 4 disappear, and as shown in FIGS. 5 and 6, the ridges 5 and 5 disappear and become a form similar to a normal pipe. be able to. If the beads 4 and 4 are allowed to remain, the press-fitting step of the pushing rods 3 and 3 may be omitted. Further, when the ridges 5, 5 are formed on the inner circumference of the pipe material 1 by the wall-thickening process as shown in FIG. 7, the above steps are not necessary.

When the molding position of the bulging portion 1A is near the end of the pipe material 1, as shown in FIG. 4, the bead 4 is formed only on the pipe material 1 on the long side with respect to the bulging molding portion 1B. On the other side, the pushing rod 3 may directly press the end face.

After completion of the molding, the pipe material 1 is taken out from the molding die 2 and the tip of the bulging portion 1A is cut as shown in FIG. 5 or is perforated as shown in FIG. A tubular connection 11 is formed.

〔The invention's effect〕

As described above, the bulge forming method according to the present invention is
Preliminarily form a ridge in the circumferential direction of the inner peripheral surface at least near one side of the bulging part of the pipe material to be molded, put this pipe material in the bulging mold, and move it from the end of the pipe material as much as possible. The tip pressing surface of the pressing shaft portion of the pushing rod to be inserted in close contact is brought into contact with the side surface of the ridge, and the pushing rod is pressed to give a relieving force to the bulging molding portion of the pipe material through the ridge. At the same time, the pressure liquid was press-fitted into the pipe material to perform expansion molding,
The pressing force by the pushing rod is applied to the ridge formed on the inner circumference of the pipe material in the vicinity of the bulging molding site, and through this ridge, a short range between the ridge and the bulging molding site of the pipe material is applied. The meat can be brought closer to the bulging molding site side, which allows the meat to be gathered without being affected by galling between the pipe material and the molding die, and the molding pressure of the bulging portion can be reduced. At the same time, there is an excellent effect that the thickness of the bulging portion can be made uniform.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing the embodiment of the method of the present invention at the stage of completion of molding of a bulging portion, and FIG. 2 is a partial cross-section showing a long pipe material before the molding. Front view, FIG. 3 is an enlarged cross-sectional view of the main part,
FIG. 4 is a view corresponding to FIG. 1 showing the other embodiment, FIGS. 5 and 6 are sectional views of a pipe material showing a bulging portion after completion of molding, and FIG. 7 is another embodiment of a ridge. FIG. 8 is a sectional view showing an example, and FIG. 8 is a sectional view showing a conventional technique. DESCRIPTION OF SYMBOLS 1 ... Pipe material, 1A ... Bulging part, 1B ... Bulging molding site, 1C ... End surface, 2 ... Mold, 3 ... Push rod, 4 ... Bead, 5 ... Ridge,
6 ... Pressing shaft portion, 6A ... Pressing surface, 7 ... Small diameter shaft portion, 8 ... Guide shaft, 9 ... Seal ring, 10 ... Opening, 11 ... Connecting portion.

Claims (1)

[Claims] 1. A ridge is preformed in a circumferential direction of an inner peripheral surface of a pipe material to be molded at least at a position near one side of a bulging molding site, and the pipe material is housed in a bulge molding die. The tip pressing surface of the pressing shaft portion of the pushing rod that is inserted as close as possible from the end is brought into contact with the side surface of the ridge, and the pushing rod is pushed to the bulging-molded portion of the pipe material through the ridge. A bulge forming method for a long pipe material, which is characterized in that a pressure liquid is press-fitted into the pipe material and bulging is performed while giving a gravitational force.