JPH02280921A - Method for bending pipe - Google Patents

Abstract

PURPOSE:To bend a pipe without generating wrinkles and flattening the pipe and while keeping a given section by rolling down nearly the whole outside peripheral surface of the pipe nearly uniformly in the peripheral direction, plasticizing the whole periphery and exerting pressing means from one side. CONSTITUTION:A pipe slightly larger in diameter than a product is used as stock, an upper and a lower roll 1, 4 are rotated in the direction opposite to each other, the pipe P is forced into and rolled by a caliber roll 7 and delivered to the outlet side. Since the pipe is pressed by a binding roll 8 from one outer side, a part plasticized inside the caliber roll 7 undergoes bending deformation and the pipe P is bent and delivered out of the caliber roll 7. The bend of the pipe P is adjusted by changing the distance 9a) between the central axis X-X of the caliber roll 7 an the rotary center of the binding roll 8 by a position adjusting means 11. Or, when the binding roll 8 is moved in the direction parallel with the central axis X-X to change the distance (b), the bend of the pipe can be adjusted, too.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a method for bending a pipe by plastic working, more specifically, a method for bending a straight pipe by a plastic working means consisting of a combination of rolling and pressing. The present invention relates to a method for straightening canals that are present in the body.

(Prior Art) Techniques for bending pipes, particularly circular metal pipes, using rolls, rams and anvils, dies, etc. are well known. In addition, it is widely known that if the tube is particularly thin or has a large curvature, wrinkles are likely to occur inward due to buckling, or the cross-sectional shape may become flat and localized immersion may occur. It is a fact that

As a countermeasure against these problems, it is known to put granular materials such as sand, low melting point metals such as lead, flexible mandrels such as coil springs, and other fillers into the tube, and these are quite effective against the occurrence of wrinkles. However, it has almost no effect on flattening.

On the other hand, in some cases, a curved mandrel or an eccentric plug having a diameter larger than the inner diameter of the pipe is forced through the pipe. This bending technique can almost completely prevent flattening, but although it is possible to bend the entire length of the tube to a -like curvature, it is not possible to bend only a portion of a straight tube.

Applicable only to pipes for specific purposes.

(Problems to be Solved by the Invention) The present invention solves the problems that occur when bending a pipe, which are unavoidable with conventional processing techniques, such as wrinkles tending to occur, the cross-sectional shape becoming flat, and the possibility of bending only a part of the pipe. This was done to solve a technical problem, and its purpose is to create a bending process for pipes that does not cause wrinkles, maintains a predetermined cross-sectional shape, and can even partially bend to any desired curvature. The purpose is to provide a method.

(Means for Solving the Problems) The present invention involves rolling a tube by rolling it almost uniformly in the circumferential direction from almost the entire outer circumferential surface, and pressing the rolled tube from the outside on one side, so that the tube is brought into a plastic state by rolling. A means for solving the above technical problem is to bend and deform the placed portion.

In other words, 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 makes use of this property by applying a reduction blade to a pipe, for example. By using a rolling roll for rolling and a restraining roll placed on the exit side of the roll for applying an external force to the pipe from one side and bending it, the rolling means using the rolling roll and the pressing means using the restraining roll are used in combination. It is something that bends pipes,
It is possible to bend and deform without wrinkles and maintain a predetermined cross-sectional shape.

Flattening that occurs when a tube is bent is a result of the tensile and compressive stresses generated by the bending causing the outer portion of the bend to move inward and the inner portion of the bend to move outward. According to the method of the present invention, rolling is performed by applying rolling edges approximately uniform in the circumferential direction from almost the entire outer circumferential surface and placing it in a plastic break, so that the external force required for bending is small even when bending in any direction. The generation of compressive stress can be extremely reduced, and as a result, flattening can be effectively prevented. Furthermore, bending deformation occurs in the tube at the portion where the rolling blade is applied, and almost the entire outer peripheral surface is pressed down there, which is another reason why flattening can be prevented.

Next, when using rolling rolls as a tube rolling means,
A plurality of rolling rolls with grooves are arranged so as to cover almost the entire outer peripheral surface of the tube. Generally, two rolling rolls are used, but it may be difficult to push the tube into the groove formed by the grooves, and when bending on a plane parallel to the spindle of the rolling roll, the groove Since the curvature radius cannot be made small because the side surfaces of the curvature block the bending, it is better to use three or four rolling rolls if you want to bend the curvature in various directions with a large curvature.

In addition, a pressing means such as a restraining roll that presses the tube in a plastic state from one side outside is placed close to the rolling means and on the exit side thereof, but the pressing means is perpendicular or parallel to the central axis of the groove of the rolling means. Preferably, the position can be adjusted in the direction or diagonally, and the curvature can be changed arbitrarily. Furthermore, by installing a plurality of pressing means around the central axis of the hole so that their positions can be adjusted individually, it is also possible to form curved portions in different bending directions in a tube, for example, to process it into a wave-shaped curved tube. can.

The present invention is mainly used to bend straight pipes, but since it gives a relative bend to the pipe, it can also be used to straighten bent pipes to make them straight. .

(for production) The material used is a pipe with a diameter slightly larger than that of the product.

It is pushed into the hole of the rolling means and pressed from one side outward by the pressing means on the exit side thereof. The part of the tube that has been rolled to the required diameter is in a plastic state, and the stress caused by rolling and the stress caused by pressing are combined and the tube is bent toward the opposite side of the pressing means. The cross-sectional shape of the product depends only on the shape of the groove of the rolling means, and the non-uniformity of the wall thickness distribution in the circumferential direction depends on the curvature, but since the wall thickness increases with rolling, even on the outside of the bend, the wall thickness is greater than the initial wall thickness. It is possible to make it thicker.

(Example) Fig. 1.2 schematically shows an example of an apparatus for carrying out the present invention, in which two grooved rolling rolls 1.4 are arranged with the support shafts 3 and 6 horizontally. 2.5 grooves placed above and below
A hole 7 with a required diameter is formed by the above method, and on the outlet side of this hole 7, an hourglass-shaped restraining roll 8 with a vertical support shaft 9 supported by a bearing member 10 is installed, and the bearing member 10 is connected to a hydraulic cylinder. It is configured such that it is attached to the position adjustment means 11 such as the above. Incidentally, rolls 22 and 23 are arranged on the entrance side of the hole mold 7 to prevent the pipe P from shifting.

The upper and lower rolling rolls 1 and 4 are rotated in opposite directions at the same circumferential speed, and the pipe P is pushed into the hole 7 from the entry side and rolled while being sent out to the exit side by the rotation of the rolling rolls 1.4.

Next, by pressing with a restraining roll 8 from the outside on the negative side, the part that is in a plastic state inside the hole mold 7 is bent and deformed, and the pipe P becomes a curved state and is sent out from the hole mold 7 one after another. It will be done.

The distance a between the center axis XX of the groove 7 and the rotation center of the restraining roll 8, the distance between the rotation center of the rolling roll 1.4 and the rotation center of the restraining roll 8, determines the curvature 1/ρ of the pipe P. Therefore, by changing the distance a using the 1-position adjustment means 11, it is possible to adjust the bending of the pipe P, and furthermore, it is possible to create a pipe in which straight portions and bent portions coexist. Alternatively, the bending of the pipe P may be adjusted by moving the restraining roll 8 in a direction parallel to the central axis XX and changing the distance. Furthermore, another restraining roll 12 may be installed at a position facing the restraining roll 8 with the pipe P interposed therebetween so that its position can be adjusted, so that it can be bent in the opposite direction as well.

In addition, almost the entire outer peripheral surface of the pipe P is in contact with the surface of the groove 2.5 in the groove 7, and when bent in a plane parallel to the support shafts 3 and 6 of the rolling roll 1.4, those side surfaces If the curvature is large, three rolling rolls 13, 14, and 15 are arranged radially as shown in Fig. 3 to form the groove 1.
6 or by arranging four rolling rolls 17, 18, 19, 20 at right angles to each other as shown in FIG.
It is best to use one that has been formed.

Next, we will discuss the results of testing the relationship between the cross-sectional shape, wall thickness distribution, rolling height and curvature, restraining force, rolling blade, etc. when a tube is bent using two rolling rolls.

The tube used was an extruded aluminum circular tube with an outer diameter of 30 mm (
A6063-F), wall thickness 1.5mm, 2.
0mm.

There are three types: 2 and 5 mm. Also, the rolling roll has a diameter of 1
50+u+, the groove is made into a circular arc with a radius of 14.5 mm, and the corners at both ends are rounded with a radius of ll1ffl. Note that the center of the arc of the groove is located 1flI11 outward from the outer surface of the rolling roll, and therefore the arc is slightly shorter than a semicircle (see FIG. 5).

When two such rolling rolls are arranged one above the other, a rolling height U corresponding to the distance between the groove bottoms and a radius of curvature p on the outside of the bending are obtained.
By changing H1ρ7, the three types of circular tubes having the above-mentioned wall thickness were subjected to horizontal bending BH in a plane parallel to the spindle of the rolling roll and vertical bending Bv in a plane perpendicular to the rolling roll. U = 29.0I1
When m, the opposing grooves form a hole shape consisting of a perfectly circular arc (see FIG. 6).

First, we investigated the cross-sectional shapes of circular tubes bent under various conditions. Outer curvature 1/ρ for horizontal and vertical bends
□, l/ρ7 are both 3X 10-3m+a-"1
The angle φ from the bending radial direction is the bending outer position φ = 0
(In Figure 6, point H for horizontal bending and point V for vertical bending.
Figures 7A and 7B show the results of measuring the outer diameter at various angular positions. A in Figure 7 is horizontal bending.

B is the result of vertical bending, where the horizontal axis is the angle φ, and the vertical axis is the ratio D/D0 of the outer diameter Do of the circular pipe before processing to the outer diameter after processing, and the outer diameter after processing. did. The solid lines in the figure indicate the rolling heights U□ (= 29.30 mm) and U 2 (= 29.30 mm).
00mm), U3 (=28.451!LIB), U4
(=27.20 mm), and the actual measured values are in good agreement with these calculated values.

In addition to this test, a circular tube with a wall thickness of 1.5 mm was rolled with a constant rolling height of U4 = 27.20 mm and a curvature of 1/ρ (X
Figures 7C and D show the results of measuring the cross-sectional shape when the diameter was changed (10-3 mm-1). C in FIG. 7 is the result of horizontal bending, and D is the result of vertical bending.

The calculated value shown by the solid line and the case without bending (1/
pH = 1/ρv; 0).

It can be seen that φ=0 in the case of horizontal bending and φ=90 in the case of vertical bending corresponds to the gap between opposing rolling rolls, and no abnormal bulge deformation occurs even though they are not constrained by the rolling rolls. . Moreover, from this result, it was found that the cross-sectional shape of a bent tube is determined only by the shape of the hole through which the tube passes, without depending on the wall thickness, bending direction, or curvature.

Second, FIG. 8 shows the results of bending a circular tube with a wall thickness of 3.0 mm and measuring the wall thickness at various angular positions with φ=0 at the same position where the cross-sectional shape was measured.

In Fig. 8, A is the result of horizontal bending, B is the result of vertical bending,
The horizontal axis is the angle φ, and the wall thickness S of the circular pipe before processing. The vertical axis is the ratio S/So of the thickness S and the thickness S after processing. For horizontal bending, the rolling height is set to a constant value U4 = 27°20mm, and the curvature is 1/ρ(X
10-3 mm-”), and the vertical bend has a constant curvature 1
/ρ+/ = 3 Xl0-3+nm-1 and the rolling height is U2 = 29.00 mm, U3 = 28.45
mm, U4=27.20 mm. Non-uniformity in wall thickness in the circumferential direction is caused by bending, and its degree depends on the curvature. However, according to the method of the present invention, the wall thickness increases due to rolling, so even outside the bend, the initial wall thickness may vary depending on the conditions. It turns out that it is thicker than that.

Furthermore, we will discuss the results of investigating the processing conditions.

First, FIG. 9 shows the relationship between the curvature and the rolling height when a circular pipe with a wall thickness of 1.51 ffl is horizontally bent.

The curvature is determined only by the position of the pressing means such as restraint rolls, but as shown in Figure 9, in the region where the reduction rate of the rolling height is extremely small, a decrease in the curvature due to springback was observed, so this point is important. It is necessary to take this into consideration when determining the position of the pressing means.

Next, Fig. 10 shows the relationship between the restraining moment required for bending acting on the pressing means and the curvature, and the rolling height is Ul (= 29
．． 301111), U2 (=29.0OIIIl)
, U3 (=28.24mm), U4 (=27.2
0111) shows the case of horizontal bending. It can be seen that the restraining moment increases as the curvature and wall thickness S0 of the tube increases, and decreases as the rolling height decreases.

Thirdly, Fig. 11 shows the results of investigating the relationship between the rolling blade and the curvature by changing the wall thickness of the pipe, and the rolling height U, (= 29.
30 mm) and U4 (=27.20 mm) are constant, the rolling force for both horizontal bending and vertical bending increases as the wall thickness increases, but it is found that it does not depend on the curvature and bending direction.

Therefore, by determining the rolling height and the position of the restraining means according to the outer diameter and target curvature of the tube to be processed, it is possible to process a tube that is accurately bent to the target curvature. Conversely, it is also possible to straighten a bent tube by bending it in the opposite direction according to the bend.

(Effects of the Invention) As described above, according to the present invention, a tube can be bent to a desired curvature extremely easily with a small external force by a combination of a rolling means and a pressing means on the exit side thereof, and the tube can be bent to a desired curvature very easily with a small external force. Since the entire outer circumferential surface is rolled and rolled almost uniformly in the circumferential direction, and the entire circumference is bent in a plastic state, it can be bent in any direction while maintaining a predetermined cross-sectional shape without wrinkles or flattening. Therefore, it is possible to easily manufacture bent pipes and straight pipes used in a wide range of fields such as building construction members and various types of piping.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an example of an apparatus for carrying out the present invention;
FIG. 2 is a cross-sectional view of FIG. 1, FIGS. 3 and 4 are diagrams showing examples of arrangement of rolling rolls, and FIG. 5 is an enlarged partial view of the rolling roll shown in FIG. Figure 6 is a diagram explaining the hole shape and bending direction by the rolling rolls shown in Figure 1.2; Figures 7A, B, C, and D are diagrams showing the measurement results of the cross-sectional shape of the bent pipe; Figures 8A and B are diagrams showing the measurement results of the wall thickness distribution of a bent pipe, Figure 9 is a diagram showing the relationship between curvature and rolling height, Figure 10 is a diagram showing the relationship between restraint moment and curvature, and Figure 11 is a diagram showing the relationship between restraint moment and curvature.
The figure is a diagram showing the relationship between rolling force and curvature. P...Pipe, 1.4, 13.14.15.17.18.
19.20... Rolling roll, 7, 16.21... Groove shape, 8... Restraining roll. Figure 1 Figure 5 Figure 6 Figure 8

Claims (1)

[Claims] The method is characterized in that the tube is rolled almost evenly in the circumferential direction from almost the entire outer peripheral surface, and the rolled tube is pressed from one side, thereby bending and deforming the portion that is in a plastic state due to rolling. Method for bending pipes.