JPH0318967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method of manufacturing an elbow from a tubular material.

(Prior art) Elbows have conventionally been manufactured by welding both end faces of a metal plate punched into a predetermined shape, which is a complicated process and has the disadvantage of poor surface smoothness and dimensional accuracy. Metal parts that are difficult to weld, such as those made of metal, have a problem in that the manufacturing process is particularly complicated and the manufacturing cost is high.

On the other hand, as a manufacturing method for elbows that does not involve welding, as shown in International Patent Classification IPC B21D9/01 to 9/03, a flexible mandrel is inserted inside the tubular material, and then the tubular material is In the former method, a mandrel in which balls are connected in a curved shape is known. It is also known to use However, as shown in Figure 8, when a sphere is used as a mandrel, when the bending radius of the pipe material is decreased from R ₁ to R ₂ , the point of contact between the spheres shifts from A ₁ to A ₂ , and the curvature increases. The distance between the spheres on the center line will also increase from S ₁ to S ₂ , but if the spheres are connected in a straight line, there will be a limit to the expansion of the distance between the spheres, resulting in bending of the pipe material. It has the disadvantage that it is difficult to reduce the radius, making it unsuitable for manufacturing articles that require a small curvature, such as elbows. Furthermore, since the yuzu-shaped mandrel is inserted into the inside of the tubular material in advance and then applied bending stress to the tubular material from the outside to bend it, the inner surface of the tubular material has a perfect circular shape on the tangent to the sphere. was maintained, but the part that did not touch the sphere had the disadvantage of being easily distorted. This distortion can be partly repaired by press-fitting a rectangular mandrel into the inside of the curved tubular material, but as will be described later using Figure 8, a sphere with a fixed central axis will Since it can only rotate around, P and Q ₁ are shown in Figure 8.
The problem is that the sliding friction resistance of the part indicated by is large and a large force is required to press-fit the mandrel, the effect of modifying the inner shape is insufficient, and two processes are required: a bending process and an internal shape correction process. It was hot too.

(Problems to be Solved by the Invention) The present invention solves these problems by punching out an elbow with a smooth surface and excellent dimensional accuracy, and by curve welding.
It can be manufactured without the need for complicated processes such as post-processing, it can also manufacture metal elbows that are difficult to weld, and it solves the problems of the method using a straight-shaped mandrel. This method was developed with the aim of creating an elbow manufacturing method that can easily produce an elbow with a small bending radius and a perfectly rounded inner surface over the entire surface.

(Means for Solving the Problems) The present invention involves inserting a tubular material from the end of a curved hole for elbow forming provided in a mold, and inserting an independent sphere with a diameter slightly smaller than the inner diameter into the tubular material. The tubular material is press-fitted into the curved hole together with the sphere using a press die having a large diameter part that presses the upper end of the tubular material and a small diameter part that presses the sphere. By repeatedly press-fitting the tubular material using a pressing mold having a diameter portion, the tubular material is plastically deformed by progressing along the curved hole while holding the inner surface with a plurality of independent spheres. This will be described in detail below with reference to process diagrams and examples.

In the figure, 1 is a split-type mold, 2 is a curved hole for elbow molding provided on the split surface of the mold 1, and the curved hole 2 is formed from a lower curved part 2a and an upper straight part 2b. It's summery. After applying lubricating oil to the inner surface of the mold 1, an annular stopper fitting 3 is set at the lower end of the curved hole 2 and firmly fixed by a suitable mold clamping mechanism such as a hydraulic cylinder. Then, a tubular material 20 cut into a predetermined size and shape in advance is inserted from the end of the curved hole 2 on the straight section 2b side using the gripping tool 4 as shown in FIG. The tubular material 20 can be made of not only iron but also any metal material that is difficult to weld, such as titanium alloy.The tip and rear ends of the tubular material 20 are cut diagonally in advance so that both end surfaces of the bent tubular material 20 align with the central axis. Keep it vertical. Next, as shown in FIG. 2, the rear end of the tubular material 20 is press-fitted into the curved hole 2 by the first press die 5, and the tip of the tubular material 20 reaches the upper part of the curved part 2a of the curved hole 2. .
The first mold 5 consists of a large diameter part 5a whose outer diameter is approximately equal to the inner diameter of the curved hole 2 and a small diameter part 5b whose outer diameter is approximately equal to the inner diameter of the tubular material 20.
The rear end of the tubular material 20 is pressed by the stepped portion 5c at the lower end. Next, remove the first mold 5,
An independent sphere 6 made of steel with a diameter slightly smaller than the inner diameter is inserted into the interior of the tubular material 20 from the rear end of the tubular material 20.
Apply lubricating oil as necessary and supply one piece. Since the tip of the tubular material 20 has started plastic deformation at the top of the curved section 2a, the sphere 6 engages with the inner peripheral surface of the tip of the tubular material 20 located at the top of the curved section 2a and stops. As shown in Figure 3, the first
The rear end of the tubular material 20 and the sphere 6 are press-fitted into the curved hole 2 by a second press die 7 having a large diameter portion 7a longer than the press die 5. In addition, when the tubular material 20 is a titanium alloy pipe with an outer diameter of 48.6 mm, a wall thickness of 3 mm, and a total length of 125 mm, the total load applied to the mold 7 is approximately 25 tons, and the tubular material 20 is attached to the second mold 7. The rear end is pressed by the stepped part 7c at the lower end of the large diameter part 7a, and the sphere 6 is further plastically deformed along the curved hole 2, but the sphere 6 is also pushed downward by the lower end of the small diameter part 7b of the second pressing die 7. Since the inner surface of the portion of the tubular material 20 that undergoes plastic deformation due to the curved portion 2a is held by the sphere 6, the plastic deformation progresses. Next, as shown in FIG. 4, an independent sphere 8 having the same diameter as the sphere 6 is additionally supplied inside the tubular material 20, and a second mold having a large diameter part 9a longer than the second mold 7 is added as described above. When the tubular material 20 and the sphere 8 are press-fitted into the curved hole 2 by the pressing die 9 of 3, the tubular material 20 advances along the shape of the curved portion 2a while its inner surface is held by the spheres 6 and 8. plastically deformed. Next, as shown in FIG.
In addition to supplying one more piece into the tubular material 20, a large diameter portion 11 that is longer than the third mold 9 is added.
When the tubular material 20 and the sphere 10 are press-fitted by the fourth mold 11 having a shape, the tubular material 20 is press-fitted into the curved hole 2 until its tip abuts against the stopper fitting 3, and a plurality of independent spheres 6, It is plastically deformed along the curved hole 2 to the final shape while the inner surface is held by the holes 8 and 10. After that, the fourth mold 11
is pulled out and a sphere 12 with a slightly smaller diameter is supplied inside the tubular material 20, and when the sphere 12 is press-fitted by the fourth press die 11, the sphere 6 is ejected to the outside from the opening of the stopper fitting 3, and the spheres are 8,10
After discharging the mold 1, the mold 1 is opened and the manufactured elbow is taken out. In this way, in the present invention, the tubular material 20 is sequentially plastically deformed while its inner surface is always held by the independent spheres 6, 8, and 10, each having an outer diameter approximately equal to its inner diameter. Not only is it molded, but the inner surface shape is also spherical 6,
8 and 10, it is molded with good dimensional accuracy so that the cross section becomes a perfect circle and the surface is smooth, and deformation such as unevenness that tends to occur on the inner surface during plastic deformation can be completely prevented.

(Effects of the Invention) As is clear from the above description, the present invention manufactures an elbow by press-fitting a tubular material into a curved hole for forming an elbow. In addition, it is possible to manufacture elbows using only press-fitting with a mold that has a large diameter part that presses the upper end of the tubular material and a small diameter part that presses the sphere. There is no need for complicated processes such as punching, welding, and post-processing. Furthermore, the inner surface of the tubular material is held by a plurality of independent spheres with a diameter slightly smaller than the inner diameter, and the material is gradually press-fitted into the curved hole by a mold having a larger diameter portion that gradually becomes longer, so that it conforms to the shape of the curved hole. Since the molded elbow is plastically deformed, not only the outer surface but also the inner surface of the resulting elbow are molded with good dimensional accuracy and a smooth surface, resulting in an excellent quality elbow with low flow resistance.

Further, since the present invention uses independent spheres, the following advantages are produced compared to the conventional method using spheres connected in a cylindrical shape as a mandrel. First, as explained using FIG. 7, as the bending radius of the tubular material is reduced, the distance S between the spheres increases, so for a mandrel in which spheres are connected, the bending radius must be made smaller than a certain limit. However, in the present invention, since the spheres are mutually independent, the bending radius can be freely reduced, making it suitable for manufacturing elbows with a small radius of curvature. Second, in the present invention, since the contact point A between the spheres explained in FIG. 7 moves smoothly, the pressing force is transmitted between the spheres through the contact point A regardless of the bending radius of the tubular material. can be carried out smoothly. Thirdly, in the present invention, each sphere can roll three-dimensionally in any direction without having its central axis fixed, so the entire inner peripheral surface of the tubular material can be made perfectly circular and smooth with a relatively small force. can be finished. To explain this point in detail using Figure 8, if we microscopically observe the state in which the sphere is pushed into the tubular material, the frictional resistance between the sphere and the tubular material is large and uniform over the entire surface. Instead, if there is a small protrusion at point P and the sliding resistance is large, a force will act on the sphere to rotate it around point P, and point Q ₁ on the opposite side will move toward point Q ₂ and point P. is rolled by the surface of the sphere, creating a movement that modifies the small protrusions on the surface. By repeating such microscopic movements, the resistance between the sphere and the tubular material becomes smaller than in the case of mere sliding motion, and the sphere moves smoothly through the tubular material. When each sphere is independent and has a three-dimensional degree of freedom as in the present invention, even if there is a small protrusion in any part of the cross section of the tubular material, the sphere can rotate around that part. Therefore, all parts can be finished into perfect circles.
However, when the spheres are connected in a zigzag shape, the degree of freedom of the rotational movement of each sphere is greatly restricted, and the frictional resistance becomes large because the spheres simply slide.Moreover, due to the rotational direction of the spheres, In the portions shown as P and _Q1 in FIG. 8, the effect of correcting the inner surface shape as described above is insufficient. The mandrel in which the spheres are connected in a rainbow shape is suitable for use by inserting the spheres into the tubular material in advance, whereas the present invention uses independent spheres to bend the tubular material and the inner surface of the tubular material. This method is suitable for simultaneously finishing the entire piece into a perfect circle.

As explained in detail above, the present invention has significant operational advantages over the method using a straight-shaped mandrel, and has solved the problems of the conventional elbow manufacturing method. The contribution it makes to the development of the industry is extremely large.

[Brief explanation of the drawing]

Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, and Fig. 6 are all process explanatory diagrams of the embodiment of the present invention, and Fig. 7 and Fig. 8 are microscopic views of the sphere. FIG. 1: Mold, 2: Curved hole, 5: First press mold, 6:
Sphere, 7: second mold, 8: sphere, 9: third mold, 10: sphere, 11: fourth mold, 20: tubular material.

Claims (1)

[Claims] 1 A large-diameter tube material is inserted from the end of a curved hole for elbow forming provided in a mold, and an independent sphere with a diameter slightly smaller than the inner diameter is supplied into the tube material to press the upper end of the tubular material. The tubular material is press-fitted into the curved hole together with the sphere by a mold having a small diameter part that presses the sphere, and the tubular material is press-fitted by a mold having a large diameter part that gradually becomes longer and further supplies additional spheres. A method for manufacturing an elbow, characterized in that by repeating the process, a tubular material is plastically deformed by advancing along a curved hole while holding the inner surface by a plurality of independent spheres.