JPH0332426A - Bending method for tube - Google Patents

Abstract

PURPOSE:To execute bending to a prescribed curvature without causing fold and flattening by forming a caliber made by opposed grooves of a rotary die and a pressure die so as to become smaller than a cross section of a stock tube, bringing the whole outside peripheral surface of the stock tube to rolling reduction equally and bending it, while setting it to a plastic state. CONSTITUTION:A pressure die 6 is separated from a rotary die 1, a clamping means 5 is positioned in front of an admission path of a stock tube P and the tip of the stock tube P inserted through between the rotary die 1 and the pressure die 6 is fixed to the clamping means 5. Subsequently, the pressure die 6 is brought close to the outside peripheral surface 2 and a prescribed caliber 10 is formed by two grooves 3, 7, and the stock tube P is fitted into this caliber 10. Next, when the rotary die 1 is rotated in a state that the pressure die 6 is brought into contact with the outside peripheral surface 2, the stock tube P is drawn into the caliber 10, rolled by receiving roughly equal rolling down force from almost the whole outside peripheral surface in its inside, set to a plastic state, and also, pressed against the outside peripheral surface 2 of the rotary die 1 by the clamping means 5, and bent along the outside peripheral surface 2 of the rotary die 1 by a stress by rolling and a stress by pressure.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method of bending a pipe by plastic working, more specifically, a method of bending a pipe to a predetermined curvature using draw bending, which is known as one of the bending methods. It is related to.

(Prior Art) Pipes, especially bent metal circular pipes, are widely used for various types of fluid piping, and are increasingly being used in a wide range of fields such as building construction members.

These bend-formed products are made by processing the primary product, a straight material tube, using methods such as roll bending, press bending, tension bending, pressing bending, and draw bending. When forcibly bending a raw material pipe using a mold or mold, especially if the pipe is thin or has a large curvature, wrinkles are likely to occur on the inside of the bend due to buckling, or the cross-sectional shape may become flattened, causing further localized wrinkles. It is a widely known fact that they are susceptible to collapse.

As a countermeasure against buckling, processing using a full-area tensile stress field is said to be effective, but it has the disadvantage of being prone to cracking.

In addition, as a measure against flattening, it has been considered to restrain the tube with a mold or apply an axial force in the compression direction, but this is not sufficiently effective for thin-walled tubes. Another measure against flattening is to force a curved mandrel or plug through the material tube, and although this method is effective, it cannot be applied to long material tubes.

Furthermore, apart from these problems, due to the strength of the rolls and molds as well as the overall strength of the equipment that supports them, it is not possible to increase the processing force that bends and deforms the material tube, so heating means must be used or comparison There is a restriction that a pipe made of soft material must be used.

(Problems to be Solved by the Invention) In the present invention, when bending a pipe, the pipe is simply forcibly bent using rolls, molds, or the like. The conventional processing technology has a tendency to buckle.

There are restrictions on the material of the tube, which tends to flatten. This was done to solve technical problems such as, and the purpose is to create bent pipes of a predetermined curvature that do not generate wrinkles and maintain a predetermined cross-sectional shape by using drawing and bending technology. An object of the present invention is to provide a method for bending pipes that can be produced without being limited by materials.

(Means for Solving the Problems) The present invention uses a rotary mold having a groove on the outer circumferential surface and a holding mold having a groove opposite to the groove, and fixes a material tube to the rotary mold and The hole shape formed by the two grooves is created by using a drawing and bending method in which the tube is sandwiched between the two grooves and the rotary die is rotated to pull the material tube along the outer circumferential surface to bend and deform it. In order to solve the above-mentioned technical problem, the material pipe is formed smaller than the cross section of the material pipe, and the material pipe is compressed almost uniformly in the circumferential direction from almost the entire outer circumferential surface in this hole mold, and is bent and deformed while being made into a plastic state. It was used as a means.

That is, metal materials have the property of being easily deformed by applying a slight external force when they are in a plastic state, and the present invention applies this property to drawing and bending to bend pipes. Therefore, it is possible to easily bend and deform even a hard tube without causing wrinkles and maintaining a predetermined cross-sectional shape.

Flattening that occurs when a pipe is bent is a result of the tensile and compressive stress generated by one bend, which causes the outer part of the bend to move inward and the inner part of the bend to move outward, and is caused by wrinkles. The cause of buckling is a plastic instability phenomenon due to compressive stress existing in the inner part of the bend.

According to the present invention, the material tube is sandwiched between two grooves each having a hole shape smaller than its cross section, and rolling blades are applied almost evenly in the circumferential direction from almost the entire outer circumferential surface to keep it in a plastic state. Even when bending, the force required for bending can be small, and the generated tensile and compressive stresses can be extremely small, making it possible to effectively prevent flattening and buckling. In addition, since the force required for bending is small, there is no need for the mold itself and the entire device supporting the mold to have high strength, which is advantageous in terms of equipment, or it is possible to use highly rigid materials that were conventionally considered impossible to bend. It becomes possible to bend the tube. Furthermore.

Bending deformation of the material tube occurs in the part where the reduction edge is applied by the hole shape formed by the groove, and the fact that almost the entire outer circumferential surface is pressed down there also helps to prevent flattening. .

Here, we confirmed by measuring the cross-sectional shape that flattening is prevented when the material tube is rolled with a reduction blade that is applied from almost the entire outer circumferential surface and the part made into a plastic state is bent. The explanation will be based on the test results.

The test was carried out using two rolling rolls 11.13 having grooves 12.14 on their outer peripheral surfaces and these grooves 12.13 as shown in FIG.
A restraint roll 1 installed on the exit side of the hole mold 15 formed by the
Using a device equipped with 6, the material pipe P is pushed into the groove 15 and sent out by the rotation of the rolling rolls 11 and 13 while being rolled. This was done by bending and deforming one roll 11.

The material tube P used was an extruded aluminum circular tube (A6063-F) with an outer diameter of 30 mm, a wall thickness of 1.5 mm, and 2.
There are three types: 0mm, 3, and 0am. Further, the rolling roll 11.13 has a diameter of 150 mm, the groove 12.14 is formed into an arc with a radius of 14.5 mm, and the corners at both ends have a radius of 1.
It has a roundness of mm. Note that the center of the arc of the groove 12.14 is located 1 mm outward from the outer circumferential surface of the rolling roll 11.13, so that the arc is slightly shorter than a semicircle (see FIG. 6). Two such rolling rolls 11.
By changing the rolling height U corresponding to the acid amount distance of grooves 12 and 13 and the radius of curvature ρ on the outside of bending, the three types of circular pipes P are
was bent. When U = 29.0 mm, the two grooves 12.14 form a hole shape 15 consisting of a perfectly circular arc (see FIG. 7).

First, let the curvature 1/ρ be 3×10−3mad−”,
FIG. 8 shows the results of measurements of the outer diameter at various angular positions, with the angle φ from the radial direction of bending set at the outside position of the bend (point V in FIG. 7) as φ=0. In this figure, the horizontal axis is the angle φ, and the vertical axis is the outer diameter of the circular pipe before processing.

The solid line in Figure 1 represents the rolling height, U = 29.00 am, U 2 = 2.
These are the calculated values of the hole size when U3=27.20 ma+ and 8.45 mm, and the actual measured values are in good agreement with these calculated values.

In addition, in conjunction with this test, a circular tube with a wall thickness of 1.5 mm was rolled at a constant rolling height of 27.20 mm, and the curvature l/ρ (X 10
As a result of measuring the cross-sectional shape when changing ``-''m+e-1), as shown in Figure 9, the calculated value of the solid line and the case without bending (1/ρ = 0) agree well. It was confirmed that there is.

Note that φ=90 corresponds to the gap between opposing rolling rolls, and it can be seen that no abnormal bulge deformation occurs despite not being constrained by the rolling rolls. Moreover, from these results, it was found that the shape of the bent tube is determined only by the shape of the hole, not by conditions such as wall thickness or curvature.

Second, we bent a circular tube with a wall thickness of 3.0 m4 and measured the wall thickness at various angular positions with φ = 0 at the same position as the measurement of the cross-sectional shape. The results are shown in Figure 10. The horizontal axis is the angle φ, and the vertical axis is the wall thickness S before processing. and the wall thickness S after processing is the ratio S/So.

A constant curvature of 1/ρ = 3 x 10-3 mm-1 was used, and the rolling height was the same as in the test shown in Fig. 8, U, U2. Bending was performed as U3. The non-uniformity of the wall thickness in the circumferential direction is caused by bending, but in the case of the present invention, the wall thickness increases by rolling with a groove, so depending on the conditions even outside the bend, the wall thickness becomes thicker than the initial thickness. I understand that.

From these results, the rolling height can be determined according to the outer diameter and target curvature of the material tube to be processed.

It was found that by determining the constraint position, it was possible to create a tube bent to an accurate target curvature, and no wrinkles were observed in the bent tube through these tests.

In the present invention, it is clear that the one-rotation die corresponds to one of the rolling rolls, the holding die corresponds to the other rolling roll, and the means for tightening the material tube to the rotating die corresponds to the restraining roll. Therefore, the material tube is bent according to the shape of the outer peripheral surface of the rotary mold.

(Function) A tube with a slightly larger diameter than the product is used as a material, and this material tube is fixed to the outer circumferential surface of the rotary mold, and the presser die is brought into almost contact with the outer circumferential surface of the rotary mold behind it. The material tube is sandwiched between the two grooves and the rotary mold is rotated. The hole shape created by the two grooves is smaller than the cross section of the material tube, and the material tube is rolled by receiving the reduction blade from almost the entire outer circumferential surface, and is placed in a plastic state inside the hole shape, and is restrained at a fixed point and rotated. Pressed onto the outer circumferential surface of the mold. Therefore, as the rotary die rotates, the material tube that is drawn through the groove is bent along the outer circumferential surface of the rotary die under the combined effect of the stress caused by rolling and the stress caused by pressing at the groove portion.

(Example) The present invention will be described in detail with reference to the drawings.

FIG. 1 schematically shows an example of an apparatus for carrying out the present invention, in which a rotary mold 1 consisting of a roll has a groove 3 having a semicircular cross section on the outer peripheral surface 2 over the entire circumference. It is fixed to a central support shaft 4 and rotated reciprocally by a suitable prime mover such as an electric motor. The presser die 6, which is also made of a roll, has a groove 7 with a semicircular cross section over the entire outer circumference, and the presser die 6 is rotatably supported by a spindle 6a attached to a support frame 8. , the support frame 8 is attached to pressing means 9 such as a hydraulic cylinder. Furthermore, a tightening means 5 such as a clamp for fixing and restraining the material tube is provided on the outer circumferential surface 2 of the rotary mold 1.

The two grooves 3.7 face each other and form a hole type lO similar to that in FIG.

In order to bend a raw material pipe using a device having such a configuration, first, the presser die 6 is separated from the rotary die l, and the tightening means 5 is positioned in front of the approach path of the raw material tube P, and the rotary die 1 and the presser die 6 are The tip of the material tube P passed through the gap is fixed to the tightening means 5 (FIG. 2). Next, the presser mold 6 is brought close to the outer circumferential surface 2 to form a predetermined hole 10 with the two grooves 3.7, and the material tube P is fitted into this hole 10 (FIG. 3). Then, when the rotary mold 1 is rotated with the presser mold 6 almost in contact with the outer circumferential surface 2, the material pipe P is pulled into the hole mold 10, and inside it, a substantially uniform reduction blade is applied from almost the entire outer circumferential surface. The material is rolled and placed in a plastic state, and is then pressed against the outer peripheral surface 2 of the rotary mold 1 by the means 5, and is bent along the outer peripheral surface 2 of the rotary mold 1 by the stress caused by rolling and the stress caused by pressing. At this time, it is preferable to install a guide 6A made of rolls in front of the entrance of the hole mold 10 so that the material pipe P is pulled into the hole mold 10 through a predetermined approach path, and to apply bending pressure. Figure 4).

Furthermore, when making a product that has a straight part and a curved part,
Although the curved portion has been slightly reduced, it has no wrinkles and is not flattened, so it can reduce loss when used in piping that handles fluids, and it does not damage the appearance when used as a building construction member.

(Effects of the Invention) As described above, according to the present invention, a slight change is made to the bending technique by drawing and bending in that the hole shape formed by the facing grooves of the rotary die and the presser die is made slightly smaller than the cross section of the material pipe. It is very easy to bend to a specified curvature just by applying pressure, and since it compresses almost the entire outer circumferential surface of the material pipe almost uniformly in the circumferential direction and bends it in a plastic state, even hard pipes can be bent with small force. It can be bent reliably and maintains a predetermined cross-sectional shape without wrinkling or flattening. Therefore, it is possible to easily manufacture bent pipes used in a wide range of fields such as various fluid piping and building construction members.

[Brief explanation of drawings]

FIG. 1 is a schematic front view showing an example of a device implementing the present invention;
Figures 2, 3, and 4 are explanatory diagrams showing the operation, and Figure 5
6 is an enlarged partial view of the rolling roll in FIG. 5, FIG. 7 is an explanatory diagram of the groove shape in FIG. 5, and FIGS. 8, 9, and 10 The figure shows the test results. 1...Rotating type, 2...Outer peripheral surface, 3...Groove, 5...
... Tightening means, 6... Holding mold, 7... Groove, 10.
...hole type, P...material pipe,

Claims (1)

[Claims] Using a rotary mold having a groove on the outer circumferential surface and a holding mold having a groove opposite to the groove, a material tube is fixed to the rotary mold and held between the two grooves behind it, and the rotary mold is rotated. When bending and deforming the material tube by pulling it along the outer circumferential surface, the hole shape formed by the two grooves is formed smaller than the cross section of the material tube, and the material tube is bent almost entirely outside within this hole shape. A method for bending a pipe, which is characterized by bending and deforming the pipe by compressing it almost uniformly in the circumferential direction from the circumferential surface to a plastic state.