KR101308901B1 - Tube bending die - Google Patents

Abstract

PURPOSE: A tube bending die is provided to reduce high manufacturing costs due to manual welding and a thickness reduction rate of a tube bending portion, thereby improving durability and performance. CONSTITUTION: A tube bending die includes detachable upper and lower bending rolls (9a, 9b), an integrated clamp (9j), and a press die (9h). The roll molds of an elliptic curved shape is connected to a mold fixing shaft (9d) so that a bent portion of a tube (9f) is easily drawn out from the die when the tube is bent. The integrated clamp is arranged on sides of the upper and lower roll molds respectively. The press die is arranged on sides of the upper and lower molds respectively. The press die is formed into an elliptic curved shape and interlocked with a side booster cylinder (9k). [Reference numerals] (9a) Bending bottom roll mold mixed with a straight roll; (9b) Bending upper roll mold mixed with a straight roll; (9c,9i) Gap; (9d) Mold fixing shaft; (9e,9g) Oval curve shape; (9f,10f) Tube; (9h) Press die; (9j) Clamp; (9k) Side booster cylinder; (9L) Back booster clamp; (9m) Back booster cylinder; (AA) Bending roll mold mixed with a straight roll; (BB) Gap of the mold

Description

Tube Bending Molds {TUBE BENDING DIE}

In the present invention, the tube should be bent without a core (Mandrel) when the tube is bent (normal bending and hot bending), so that the roll-shaped mold (bending radius of less than 2.5 times the tube outer diameter should be manufactured in the egg-shaped mold, not the garden Depending on the outer diameter and thickness of the tube, if the bending radius of the tube is less than twice the outer diameter of the tube, hot bending shall be performed.

In the case of hot bending, the tube bending technology for bending the tube by heating the heating part of the tube to 800 ~ 1,100 degrees Celsius (different depending on the material and thickness) by gas heating device or electric heating device, and bending the tube accordingly Necessary tube bending is about the mold.

In general, when bending a tube, as shown in FIGS. 1 and 2, the tube is formed by forming a mold into molds (1a and 2a), pressing molds (1d and 2d), mandrel rods (1f and 2f), and corrugation shield (2h). The molds (1a, 2a) and the mold (1d, 2d) is made in the shape of a semi-circle, and used to prevent the wrinkles and protrusions (Fig. 4) and the wrinkle shield (Fig. 2h of Fig. 2), the tube of In order to maintain the quality of the ellipticity, the tube was bent using a mandrel (1f in FIG. 1 and 2f in FIG. 2). However, the thickness of the bent portion is very important in tubes with high temperature and high pressure fluid such as boiler tubes. Rather, it is difficult to apply to a facility subject to internal pressure because the inner side of the tube is thinner than 10%.

Korean Patent Registration (10-0658510) "Clamp manufacturing method for removing shape defects when tube bending" is not the shape of the bent portion of the tube, but the tube straight part clamp (1c in Figure 1) to bend the tube This is caused by the clamping force of the clamp that supports the bending moment of the tube. The shorter the clamp length, the greater the surface pressure per unit area received by the tube. By reducing the surface pressure of the clamp tube, the shape defect can be removed.

As described in Korean Patent Registration No. 10-1093192, "Pipe Bending Machine and Pipe Bending Method Using Pipe Bending Machine," two normal radiuses in which the shape of the second clamp is further cut to the shape of R where R is the radius of the tube. It is an oval shaped mold with R1 always equal to TR (TR is the radius of the outer diameter of the tube: hereinafter referred to as TR) and r1 is an ellipse consisting of two semi-circles with a radius of the garden smaller than R. The center of R1 is TR Since R1 and TR are the same as the method of bending located on the horizontal horizontal line of the center, the second clamp is in surface contact in the longitudinal direction of the tube, so the maximum point of the internal stress acting on the end face of the tube is 20 and 160 degrees in FIG. It is not able to pressurize intensively, and the change of ellipticity occurs a lot.

In addition, in claim 1 of Patent 10-1093192 it was characterized in that the wrinkles can be prevented, this method helps to improve the ellipticity rather than wrinkle prevention.

In order to prevent the bending of the bent portion, a crimp-proof mold (2h in FIG. 2) is used, or a roll mold is made into an elliptic curve shape, and the tube is deformed from a circular shape to an elliptical cross section by pressing force of the pressing mold when the tube is bent. As the buckling load is increased, the inner side of the tube bent portion becomes thicker under the compressive load, but when the buckling load becomes weaker, wrinkles are formed inside the bent portion.

In particular, when bending a thin tube is weak to the buckling load, when the bending operation without a core rod (Fig. 3), the elliptic curve roll mold is effective.

The present invention is to form a bending mold without a core as described above to bend the ellipticity and thickness reduction rate of the tube bending portion to the design quality (about 10% or less), to know the technical characteristics of the tube bending portion and to bend based on the characteristics By providing the manufacturing method of tube bending mold required to provide tube bending mold which can reduce manufacturing cost and operating cost by reducing raw material cost, reducing defective rate and improving durability by improving the quality of tube bending for boiler of power generation facilities. The purpose is.

Tube bending mold according to the present invention for achieving the object of the present invention, tube bending that can suppress the ellipticity and thickness reduction rate without the mandrel to insert a long length tube to the tube inner surface when bent to three times the tube diameter or less In the mold. A separate upper and lower roll mold connected by a mold fixing shaft and having an oval-shaped elliptic curve shape so that the bent portion of the tube is easily taken out of the mold when the tube is bent; An integrated clamp provided on one side of the detachable upper and lower roll molds; It is characterized in that it is provided; is provided on one side of the separate upper and lower roll molds, the pressing mold is interlocked by the side pressure cylinder while having an oval curved shape of the egg type.

A gap of a predetermined interval is formed between the separate elliptic curve-shaped separate upper and lower roll molds and the tube and between the elliptic curve-shaped mold and the tube.

The rear end of the bent tube of the present invention is characterized in that the rear end pressure clamp is interlocked by the rear end pressure cylinder to reduce the ellipticity and thickness reduction rate of the processed tube.

Another embodiment of the tube bending mold according to the present invention, in the tube bending mold that can suppress the ellipticity and the thickness reduction rate without the mandrel that inserts the long length tube to the tube inner surface when bending the tube three times or less. Upper and lower roll molds having an oval-shaped elliptic curve shape such that the bent portion of the tube is easily taken out from the mold when the tube is bent; A detachable clamp provided on one side of the upper and lower roll molds; It is characterized in that it is provided; is provided on one side of the separate upper and lower roll molds, the pressing mold is interlocked by the side pressure cylinder while having an oval curved shape of the egg type.

A gap of a predetermined interval is formed between the elliptic curved upper and lower roll molds and the tube and between the elliptic curved mold and the tube.

The rear end of the bent tube of the present invention is characterized in that the rear end pressure clamp is interlocked by the rear end pressure cylinder to reduce the ellipticity and thickness reduction rate of the processed tube.

Another embodiment of the tube bending mold according to the present invention is a tube bending mold that can suppress the ellipticity and the thickness reduction rate without the mandrel that inserts the long tube to the tube inner surface when the tube is bent to three times the tube diameter or less. Upper and lower roll molds having a circular shape that is easy to be pulled out of a mold when the tube is bent, and has an oval curve shape of an egg type; A detachable clamp provided on one side of the upper and lower roll molds; It is provided on one side of the separate upper and lower roll molds, a pressing mold having an oval curved shape of the egg type;

A gap of a predetermined interval is formed between the elliptic curved upper and lower roll molds and the tube and between the elliptic curved mold and the tube.

According to the tube bending mold of the present invention as described above has the following effects.

In other words, bending of tubes of long lengths (about 40m to 70m and longer), such as boiler tubes, can be done by bending long tubes without the use of core pipes. Therefore, it can contribute to durability and performance improvement by smoothing the fluid flow of boiler heat exchanger and reducing the thickness reduction rate of tube bent part by enormous reduction of manufacturing cost and improvement of ellipticity by manual welding.

1 and 2 are schematic views showing various embodiments of a conventional tube bending mold.
Figure 3 is a front view showing the mandrel used in a conventional bending mold.
Figure 4 is a front view showing a bad state occurring in a conventional bending mold.
5 is a stress distribution diagram generated around the tube cross-section during the tube bending operation.
6 to 8 are schematic views showing various embodiments of the tube bending mold according to the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred technical embodiment of the present invention.

The following description and the accompanying drawings are presented for a general understanding of the present invention, unless the technical scope of the present invention is limited to those described in the present invention, details of known configurations and functions that may unnecessarily obscure the contents of the present invention. The description will be omitted.

5 is a stress distribution diagram generated in the direction perpendicular to the length of the tube in the tube cross-section during the bending operation of the tube, the compressive stress occurs in the tube length direction at about one third of the tube diameter inside the bent portion. In addition, the tensile stress occurs in the tube length direction at the inner side of the tube at about 2/3 of the tube outer diameter.

As shown in FIG. 5, in the tube cross section perpendicular to the length of the tube when the tube is bent, the distribution of stress generated inside and outside the tube, the blue part is the stress that the tube flesh (thickness) moves to the inside of the tube when the tube is bent. The red part is the stress that the tube flesh (thickness) moves to the inside of the tube, and it is possible to lower the ellipticity and the thickness reduction rate of the high quality tube bend by making a tube bending mold that can understand and control the stress distribution.

It is possible to obtain a good ellipticity when bending a tube by forming a general bending mold as in the prior art, but there is an element that increases the thickness reduction rate because of the use of a mandrel.

Accordingly, as shown in FIG. 6, the shape of the roll molds 9a and 9b and the pressing mold 9h is formed into an oval curve shape 9e and 9g of an egg type to control the stress generated in the cross section when the tube is bent to control the quality of the tube bent portion. In order to maintain the linearly mixed bending mold, the roll molds 9a and 9b, the clamps 9j, the die molds 9h, the side pressure cylinder 9k, the rear end pressure clamp 9L and the rear end pressure cylinder 9m Consists of a tube bending device (hereinafter referred to as a bending machine) used to bend the tube to a certain radius to provide a tube bending mold that can be bent at the desired ellipticity and thickness reduction rate of the bend.

In more detail, as shown in Figure 6, the roll mold (9a, 9b), the pressing mold (9h), the roll mold (9a, 9b) and the clamp (9j) having an egg-shaped elliptic curve (9e, 9g) shape as shown in FIG. Side pressure cylinder (9k) that pushes the clamp-integral roll mold and press mold in one tube length in the longitudinal direction of the tube, and the rear pressure cylinder (9L) that secures the tube and pushes it in the tube length direction when the tube is bent. 9m).

When inserting the tube into the roll mold 9a, 9b and the pressing mold 9h, the gap 9c between the tube 9f and the roll mold 9a, 9b, the clearance between the tube 9f and the pressing mold 9h. (9i), the tube of the garden is transformed into an egg-shaped shape by the pressing force of the mold (9h) during tube bending to reduce the ellipticity.

At this time, when the mold die 9h is secured while the mold die 9h is pressurized and the tube 9f is moved toward the roll molds 9a and 9b, the bent tube section can be changed into an elliptical cross section in the garden. Make sure

When the roll molds 9a and 9b are integrated with the clamp 9j, the roll molds 9a and 9b must be separated into the lower roll mold 9a and the upper roll mold 9b to insert the tube into the roll molds 9a and 9b. After the clamp (9j) can be fixed and released.

In addition, the upper and lower separation molds of the roll molds 9a and 9b can be easily taken out of the roll molds 9a and 9b when the tube is bent at 180 degrees.

The fabrication of the mold 9h by the elliptic curve 9g and the gap 9i is as described in the above-mentioned (Solution Solution). Since the stress to move outward through the end face of the tube is the maximum, the mold die (9h) presses the tube at the point, and the mold die (9h) is pressed against the roll mold (9a, 9b). When the tube is deformed into an egg-shaped shape and the tube is bent by the rotational movement of the roll molds 9a and 9b, the bent section of the tube is bent into a tube having a good ellipticity having an egg-shaped shape.

Here, the operation sequence of the bending mold is described. The tube 9f is inserted into the lower roll mold 9a, the upper roll mold 9b is lowered downward, and the tube is clamped while the upper and lower roll molds are brought into close contact with each other. The die 9h to the roll dies 9a and 9b to press the tube 9f to the roll dies 9a and 9b, and then rotate the roll dies 9a and 9b clockwise. , The mold die 9h is advanced by the side pressure cylinder 9k in the tube length direction to bend the tube.

When the tube is bent at the desired angle, the roll molds (9a, 9b) and the dies (9h) stop working, and the dies (9h) are reversed to the roll molds (9a, 9b) and back to secure space. The upper roll mold 9b is raised to unwind the tube fixed to the clamp 9j and take out the tube.

Here, in order to reduce the ellipticity and thickness reduction rate of the tube according to the bending radius of the tube, the tube is pressurized in the longitudinal direction from the back of the bend to the roll molds (9a, 9b) in the longitudinal direction during the bending operation using the rear pressure cylinder. It is possible to reduce the thickness reduction rate by reducing the tensile stress generated in the.

In Fig. 7, there is a bending machine that requires roll molds 10a and 10b and an integral clamp (9j in Fig. 6), which is a body, and a bending machine that requires a separate clamp 10j.

Therefore, this drawing consists of a separate clamp 10j in a form in which the bending rolls 10a and 10b and the clamp 10j are separated.

In the clamp integral type of FIG. 6, the tube is fixed to the clamp 9j by the up and down operation of the upper roll mold 9b. However, in FIG. 7, the clamp 10j is separately positioned at the right ends of the roll molds 10a and 10b. The tube 10f can be fixed and loosened to the roll molds 10a and 10b by the forward operation.

Here, the roll molds 10a and 10b may be manufactured as a roll mold unit in which the lower roll mold 10a and the upper roll mold 10b are one body, and the tube bent portion may be formed by bending the tube when the tube is bent 180 degrees and hot bent. If it is difficult to take out in the roll mold, the upper roll mold (10a), the lower roll mold (10b) to separate the upper roll mold (10b) up and down to facilitate tube extraction.

Here, the roll molds of FIGS. 6 and 7 are made of a straight linear mixing roll mold on the opposite side of the clamps 9j and 10j and subjected to compressive stress in the longitudinal direction of the tube at the inside of the bent end when the tube is bent 180 degrees. As the thickness of the tube is compressed, the roll mold is circular, so that when the tube is bent, the thickness of the tube protrudes as shown in FIG. 4 due to the gap between the tube and the circular roll mold, and the roll mold (9a, 9b, 10a, 10b) If the straight part is made at the end of the bending, the protrusion is pushed into the tube by the straight line of the roll mold, and the inner part of the tube is smooth.

FIG. 8 shows the roll molds 11a and 11b separated from the clamp 11j, and the roll molds 11a and 11b also include the roll mold integrated body in which the upper roll mold 11b and the lower roll mold 11a are one body. The upper roll mold 11b and the lower roll mold 11a are separated, and the upper roll mold 11b can be operated up and down to bend the tube, and then it can be easily taken out from the roll mold.

This roll die is circular, and the difference between the straight mixed roll die of FIGS. 6 and 7 is that when the bending radius of the tube is 2.5DR or more, the inner shape of the tube bent portion is not formed or is generated very little. If the quality is not a problem, it is economical to manufacture and use a roll mold having a circular shape which is cheaper than a straight mixing roll mold and which is easy to manufacture.

On the other hand, if the bending radius of the tube is less than 2DR, there is a difference depending on the outer diameter and thickness of the tube, but the hot bending work to locally heat the inside of the bent portion of the tube should be performed.

That is, the smaller the bending radius, the greater the ratio of the inner and outer circumferential lengths of the tube bend, so the compressive stress section is about 1/3 of the tube diameter and the tensile stress section is about 2/3 of the tube diameter. Adjusting the liver can reduce the thickness reduction rate.

Also, the displacement (the position of the straight line of the tube and the position of the same arc length when the tube is bent) is generally one third of the diameter of the tube, and the non-displacement point is moved out of the tube where the tensile stress is generated. Less tension on the outside of the tube will reduce the rate of thickness reduction.

Therefore, if the compressive stress section can be extended inversely, the tension section is relatively reduced.

The compressive stress section is heated by the arc length of the bent portion with a heater to reduce the compressive stress in the tube compression section, so that the non-displacement point is moved to the right. The thickness reduction rate can be reduced.

In addition, when the side pressure device (9k, 10k) and the rear end pressure device (9m, 10m) is used to pressurize the roll mold (9a, 9b) from the side and back of the tube, the ellipticity and thickness reduction rate of the tube bent portion There is an effect to reduce.

9a, 9b, 10a, 10b, 11a, 11b: Roll Mold
9h, 10h, 11h: Tooling mold
9j, 10j, 11j: clamp
9k, 10k: Side pressure device
9m, 10m: Rear stage pressure device

Claims (8)

In a tube bending mold capable of suppressing an ellipticity and a thickness reduction rate without a mandrel inserted into an inner surface of a tube when the long tube 9f is bent to three times the tube diameter or less.
When the tube 9f is bent, the separate upper and lower roll molds having an oval curved shape 9e of an egg shape type and connected by a mold fixing shaft 9d so that the bent portion of the tube 9f is easily taken out of the mold ( 9a, 9b);
An integrated clamp 9j provided at one side of the separate upper and lower roll molds 9a and 9b;
It is provided on one side of the separate upper and lower roll molds (9a, 9b), the pressing die (9h) is interlocked by the side pressure cylinder (9k) while having an oval-shaped elliptic curve (9g); Tube bending mold, characterized in that.
The method of claim 1,
The clearance gaps 9c and 9i of predetermined intervals are formed between the elliptic curved separated upper and lower roll molds 9a and 9b and the tube 9f and between the elliptic curved press mold 9h and the tube 9f. Tube bending mold, characterized in that.
The method of claim 1,
The rear end of the bent tube (9f) tube is characterized in that the rear end of the pressure clamp (9L) which is interlocked by the rear end pressure cylinder (9m) in order to reduce the ellipticity and thickness reduction rate of the processed tube (9f) Bending mold.
In a tube bending mold capable of suppressing an ellipticity and a thickness reduction rate without a mandrel inserted into an inner surface of a tube when the long tube 10f is bent to three times the tube diameter or less.
Upper and lower roll molds (10a, 10b) having an oval-shaped elliptic curve (10e) so that the bent portion of the tube (10f) is easily taken out from the mold when the tube (10f) is bent;
A separate clamp 10j provided at one side of the upper and lower roll molds 10a and 10b;
It is provided on one side of the separate upper and lower roll molds (10a, 10b), the pressing mold (10h) interlocked by the side pressure cylinder (10k) having an oval-shaped elliptic curve (10g); including Tube bending mold, characterized in that.
5. The method of claim 4,
The clearance gaps 10c and 10i of predetermined intervals are formed between the elliptic curved upper and lower roll molds 10a and 10b and the tube 10f and between the elliptic curved mold die 10h and the tube 10f. Tube bending mold, characterized in that.
5. The method of claim 4,
The rear end of the bent tube (10f) is a tube characterized in that the rear end pressure clamp (10L) is interlocked by the rear end pressure cylinder (10m) in order to reduce the ellipticity and thickness reduction rate of the processed tube (10f) Bending mold.
In the tube bending mold which can suppress ellipticity and thickness reduction, without having to insert a long tube (11f) to 3 times or less of a tube diameter to the inner tube surface.
Upper and lower roll molds 11a and 11b having a circular shape that is easy to be pulled out of a mold and an egg-shaped elliptic curve shape 11e when the tube 11f is bent;
A detachable clamp 11j provided at one side of the upper and lower roll molds 11a and 11b;
And a pressing mold (11h) provided at one side of the separate upper and lower roll molds (11a, 11b) and having an oval-shaped elliptic curve (11g).
The method of claim 7, wherein
The gaps 11c and 11i of predetermined intervals are formed between the elliptic curved upper and lower roll molds 11a and 11b and the tube 11f and between the elliptic curved press mold 11h and the tube 11f. Tube bending mold, characterized in that.

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