JP2003320421A - Method and device for bending metal wire material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a metal wire material from being folded or broken after bending even when the metal wire material such as a steel pipe is bent at a small radius by the compressive bending. <P>SOLUTION: In a bending method, a metal wire material 1 is heated by a heating device 5 and advanced, a heated part (A point) is bent and deformed by turning a bending arm 3, and a part immediately after thereof is cooled. In the method, the load F toward the bending center O is applied to the metal wire material 1 during bending by a load application means 11, and the bending moment in the normal direction is applied to the base C of an arm clamp. One part of the bending moment in the reverse direction acting on the base C of the arm clamp by the propulsive force P is offsetted by the applied bending moment. Thus, the generation of the excessive bending moment in the reverse direction is prevented, as a result, the neck folding is prevented. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for continuously bending a metal strip such as a steel pipe or a shaped steel.

[0002]

2. Description of the Related Art Conventionally, as a method of bending a metal strip such as a steel pipe, as shown in FIG. 14, a heating device such as an induction coil for heating a metal strip 1 to be bent in a short section in the longitudinal direction. 2, the processing tip side is fixed to an arm clamp 4 provided on a bending arm 3 rotatable about a fulcrum O, and the metal strip 1 is heated by a heating device 2 while a strip propelling device (Fig. By propelling it in the longitudinal direction by (not shown), the heating part by the heating device 2 is moved in the longitudinal direction of the metal strip 1, and the heating part is deformed by applying a bending moment generated by the turning of the bending arm 3. A bending method is known in which the portion immediately after that is sprayed with cooling water 5 from the heating device 2 to cool it. Further, in this bending method, a force P _b in the direction opposite to the turning direction of the bending arm 3 accompanying the progress of bending is applied to the bending arm 3, and the metal strip 1 is longitudinally moved by that amount. There is also known a method (also referred to as a compression bending method) of increasing the propulsive force P to be applied and bending the metal strip 1 while applying a compressive force in the longitudinal direction. The compression bending method has an advantage that it is possible to suppress the thickness reduction on the outer circumferential side of bending. In the figure, 6 is a guide roller.

[0003]

By the way, recently, there has been a demand for making the bending radius as small as possible. For example, the outer diameter D
It has become necessary to bend the bending radius R of the steel pipe to 1.5D or less. However, when such a small R bend is performed by the compression bending method, as shown in an exaggerated manner in FIG. 15, the portion 1Aa held by the arm clamp of the steel pipe 1A after the bending process is changed to the arm clamp root (C At the position of the point), a phenomenon of bending in the direction opposite to the bending direction (called neck breaking) occurred, and there was a problem that the product did not become a product.

The present invention has been made in view of the above circumstances, and prevents bending of the neck even when a small R bend is performed by compression bending when bending a metal strip such as a steel pipe. This is an issue.

[0005]

Means for Solving the Problems As a result of examining the cause of neck breakage, the present inventors have found the following matters. That is, as shown in FIG. 14, the metal strip 1 is propelled and the bending arm 3 is swung, whereby the heating part (A
Bending moment M of the magnitude that causes bending deformation
_When bending is performed by acting _A in the clockwise direction, a counterclockwise bending moment M _A acts on the metal strip 1 at the base of the arm clamp (point C) by a reaction. Furthermore, this arm clamp base, moment M _G bending by thrust P which is applied to the metal strip material 1 is also acting, the bending moment M _G is acting in a clockwise direction. Therefore, during bending, the arm clamp root (point C) of the metal strip 1 is caused by the turning of the bending arm 3 and the propulsive force P.
When the counterclockwise direction is a positive direction, a bending moment M _C ′ represented by the following equation (4) is applied to the. _{M C '= M A -M G} ...... (4) below, this bending moment M _C' referred to as the basic bending moments. For normal bending (without applying a compressive force, or not so small even bending radius as performing bending compression is added when such compressive force is small therefore), the moment M _G bending by propulsion so large However, there was no problem, but in the case of performing a small R bend, the thinning rate on the outer circumferential side of the bend is large. Therefore, in order to reduce the thinning, the propulsive force P must be made extremely large and the compression amount should be large. Narazu a result, moment M _G bent by the thrust P becomes extremely large, the arm clamp base (C
A large bending moment acts in the opposite direction (clockwise direction) on the point), which causes permanent strain at the base of the arm clamp and causes neck breakage. Therefore, when the bending moment due to the propulsive force P becomes large and there is a risk of neck breakage, a neck bending can be prevented by applying a positive bending moment to the base of the arm clamp of the metal strip. Then, in order to give a positive bending moment to the base of the arm clamp, a linear portion near the heating portion of the metal strip being bent is included, and a region from the linear portion to the bending arm is in the bending plane. It is effective to apply a load in the direction toward the side where the bending arm has the center of rotation.

The present invention has been made on the basis of such findings, and in a bending method using a bending arm, at least the bending of the bending arm and the propulsive force P are applied to the base of the arm clamp of the metal strip during the bending process. During the period when the bending moment acting, that is, the basic bending moment M _C ′ exceeds the allowable bending moment M _P of the metal strip, the absolute value of the total bending moment M _C acting on the arm clamp root of the metal strip is The allowable bending moment M
_The metal strip in the region from the straight portion to the bending arm includes a straight portion near the heating portion of the metal strip so as not to exceed _P. It is characterized in that bending is performed while applying a load in the direction toward the arm clamp and applying an additional bending moment to the base of the arm clamp, which prevents the neck from breaking.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to the embodiments of the drawings. FIG. 1 is a schematic plan view showing an example of a bending apparatus used for carrying out the method of the present invention in the state of being bent. The bending apparatus shown in FIG. 1 also heats a short section in the longitudinal direction of the metal strip 1 such as a steel pipe and sprays the cooling water 5 on one side (the right side in the drawing) of the heating portion, like the conventional bending apparatus. Bending arm 3 that has a heating device 2 such as a possible induction coil and an arm clamp 4 that clamps the processing tip side of the metal strip 1 and that can swivel about a fulcrum O, and the bending arm 3 A means (not shown) for exerting a force P _b in a direction opposite to the turning direction of the bending arm 3 accompanying the progress thereof and a longitudinal propulsion force P are applied to the metal strip 1 to advance the bending arm 3 toward the bending arm 3. It is provided with a strip propulsion device (not shown), a guide roller 6 and the like. Further, unlike the conventional bending apparatus, this bending apparatus includes a load applying device 11 for applying a bending moment in the forward direction (counterclockwise in the drawing) to the arm clamp root C of the metal strip 1. The load applying device 11 includes a pressing roller 12 and a hydraulic cylinder 13 that presses the pressing roller 12 against the metal strip 1. The load applying device 11 applies a bending arm to the metal strip 1 that is being bent in a direction perpendicular to its axis and in a bending plane. By applying a load F in the direction toward the side of the swivel center O of 3, the forward (counterclockwise) bending moment can be applied to the arm clamp root C of the metal strip 1. Here, the load applying device 11 is installed at a linear portion (specifically, the guide roller 6) near the heating portion (point A) of the metal strip 1.
To the heating device 2), and the load F can be applied to a desired position in a region from the straight part to the bending arm 3 (described in more detail later). In addition, as shown in FIG. 1, the load applying device 11 is connected to the metal strip 1.
When arranging so that the load F can be applied to the bent portion (area bent in an arc shape), the entire load applying device 11 or the push roller 12 is arranged so that the turning arm 3 can pass through the position without any hindrance. It is configured to be retracted.

Also in this bending apparatus, as in the conventional case, the metal strip 1 to be bent is passed through the heating device 2 and the processing tip side is fixed to the arm clamp 4 of the bending arm 3 to form the metal strip. By heating 1 with the heating device 2 and propelling it in the longitudinal direction, the heating part is continuously moved in the longitudinal direction of the metal strip 1, and at the same time, the bending arm 3 is swung to apply a bending moment to the heating part. A continuous bending process is performed in which the part is deformed by cooling and the part immediately after that is cooled. During a predetermined period during this bending process, the load applying device 11 operates to apply the load F to the metal strip 1, and the absolute value of the total bending moment M _C acting on the base of the arm clamp is allowed by the metal strip 1. Do not exceed the bending moment M _P. Hereinafter, the position where the load F is applied by the load applying device 11, the application period, the magnitude of the load F, and the like will be described. In this specification, when the position of the metal strip 1 in the bent portion is indicated by an angle, a straight line OA connecting the turning center O of the bending arm 3 and the heating center point A of the heating device 2 is used as a reference line, and the point O is The angle with respect to the reference line is used as the center. When the position of the bending arm 3 is indicated by an angle, the position occupied by the bending arm 3 at the start of bending is used as a reference line, and a turning angle (equal to the bending angle) from the reference line is used.

If the load applying device 11 is not operated during bending, only the basic bending moment M _C ′ acts on the arm clamp root (point C), and its magnitude is
As mentioned above, a _{M C '= M A -M G} ...... (4). Since the bending moment M _G due to the propulsive force P is a function of the angle (bending angle) θ of the bending arm 3,
Rewriting equation (4) gives equation (5) shown in equation 3.

[Equation 3]

Basic bending moment M _C ′ shown in equation (5)
2 is a pie chart showing an example of the relationship between the bending angle θ and the bending angle θ as shown in FIG.
Curves 15 (when the propulsive force P is small) and 16 (when the propulsive force P is large) are shown in FIG. In the figure, arc 1
7 in the positive direction of the permissible bending moment + M _P, the arc 18 is the allowable bending moment -M _P in the reverse direction, the arc 19 represents the bending moment 0. As can be seen from the curves 15 and 16 in FIG. 2, the basic bending moment M _C ′ acting on the root of the arm clamp is acting in the positive direction at the beginning of bending, but decreases as the bending progresses, and To the opposite direction and increase. When the propulsive force P is small, the basic bending moment M _C ′ is within the range of the allowable forward and reverse bending moments (+ _MP to _−MP ) as shown by the curve 15. When P is increased, as shown by the curve 16, the bending angle θ _C exceeds the allowable bending moment −M _P. For this reason, neck bending will occur when bending is performed beyond this bending angle θ _C. Therefore, in the present invention, a bending moment in the positive direction is applied by the load applying device 11 so that the bending moment acting on the root of the arm clamp does not exceed the allowable bending moment −M _P in the reverse direction. In the present specification, the bending angle θ _{C at} which the basic bending moment M _C ′ reaches the allowable bending moment −M _P in the opposite direction is referred to as the limit bending angle, and the bending moment applied by the load F is referred to as the additional bending moment.

In the present invention, the load applying device 11 is made of metal.
The position where the load is applied to the strip 1 is the arm mark of the metal strip 1.
Position where a positive bending moment can be applied to the base of the ramp
Therefore, in FIG. 1, the guide roll 6
It may be in the region from the bending arm 3 to the bending arm 3,
Is from the guide roll 6 to the bending boundary point B on the bending tip side.
It should be within the area. With load by load applying device 11
The position to be given is not limited to one, but may be two or more.
Also, it is not necessary to fix the load application position at a fixed position.
Alternatively, it may be changed during bending. However, with load F
Given is at least the basic bending moment M_C′ Is negative
Before reaching the maximum bending moment, that is, the bending angle
Angle θ_CSo you have to start before you reach
At least one load application device 11 is as shown in FIG.
The bending arm 3 has a limit bending angle θ._CThe position corresponding to
When occupying, the bending arm 3 and the guide roller 6
Between the metal strip 1 at a position where a load F can be applied
There is. At least the basic bending mode is applied during the load F addition period.
Mento M_C′ Exceeds the allowable bending moment on the negative side
Anything that includes a period, specifically, load application
Is the limit bending angle θ _CIf you start before you reach
Good.

As described above, the limit bending angle θ _C is the bending angle at which the basic bending moment M _C ′ matches the allowable bending moment −M _P in the opposite direction.
It can be calculated by assuming that the absolute value of is equal to the allowable bending moment M _P. That is, the limit bending angle θ _C can be calculated by the equation (6) shown in the equation (4).

[Equation 4]

The limit bending angle θ _C can be calculated by the above equation (6), but a considerable amount of calculation is required. Therefore, it is preferable to create an approximate expression.
In the equation (6), the bending moment M _A is a function of the tensile strength σ _h of the metal strip 1 at the bending temperature, the section modulus Z and the compression rate, the propulsive force P is the function of the compression rate, and the compression rate is the bending rate. The function of the metal thinning rate α of the processed metal strip 1 and the allowable bending moment M _P are functions of the allowable bending stress σ _a and the section modulus Z. Considering these, the limit bending angle θ _C is mainly a function of the allowable bending stress σ _a of the material, the tensile strength σ _h at the bending temperature, and the wall thinning rate α. Therefore, in the case where the metal strip 1 is a circular pipe, an approximate expression using these factors as factors is obtained, and the expression (1) shown in the equation 5 is obtained. Therefore,
When performing bending on a circular pipe, if the limit bending angle θ _C is calculated using the formula (1), and at least the load F is started before the limit bending angle θ _C is reached, Good. The application of the load F may be started before the limit bending angle θ _C is reached, so that the limit bending angle θ _{C is} not always required.
The load application may be started at an appropriate time, which is considered to be before the critical bending angle θ _C.

[Equation 5]

The magnitude of the load applied by the load applying device 11 is the absolute value of the total bending moment M _C (the sum of the basic bending moment and the additional bending moment) that acts on the base of the arm clamp of the metal strip 1 during bending. Should not exceed the permissible bending moment M _P , but may be appropriately determined according to the bending conditions (specifically, the basic bending moment M _C ′). Hereinafter, specific examples of the position, the timing, the magnitude of the load, and the like for applying the load by the load applying device 11 will be described.

First, the case where one load applying device 11 arranged at a fixed position is used will be described. As shown in Figure 1,
If the load applying device 11 is arranged so as to apply the load F toward the bending center O at the position of the angle φ of the bent portion of the metal strip 1, the load F at the time when the bending angle becomes θ. Bending moment M to the base of the arm clamp by
_cr becomes like the formula (8) shown in Formula 6.

[Equation 6]

Since the total bending moment M _C acting on the root of the arm clamp is M _C = M _C ′ + M _cr (9), the total bending moment M _C can be calculated by calculating this equation (9). The magnitude of the load F and the angle φ of the applied position can be obtained so that the absolute value of the total bending moment M _C does not exceed the allowable bending moment M _P.

In the case of bending at 90 degrees, the basic bending moment M _C ′ at the base of the arm clamp is, as shown by a curve 21 in the pie chart of FIG. 3, an allowable bending moment −M near the end of bending. Slightly over _P. In this case, it is not necessary to increase the additional bending moment M _cr so much that the load F is applied at a point A in FIG. 1 (position at angle φ = 0, specifically, before or after the heating unit). ), A neck break can be prevented by adopting a method of continuously applying a small load F from the start of bending.
For example, in FIG. 3, when the bending angle θ = 90 degrees, the absolute value of the total bending moment M _C is the allowable bending moment M _P.
The load F that agrees with the above equations (8), (9)
The load F is added from the beginning of bending. Then, the additional bending moment M _cr due to the load F
Becomes as shown by the curve 22, and the total bending moment M _C
, As shown by curve 23, it is held within the allowable bending moment range within the whole bending range (within the range of _{+ M P ~-M P)} . Thus, the bending process can be performed without causing a neck break. The load applying position and the period are not limited to this, and may be changed as appropriate. For example, with the load F applying position kept at the position of the angle φ = 0, the load applying start timing is set to a point when the bending progresses to some extent. (However, before reaching the limit bending angle θ _C ), the position of applying the load F may be changed to any position below the limit bending angle θ _C.

Next, although there is a case where 90-degree bending is performed, a basic bending moment M _C ′ at the base of the arm clamp is used.
There, as shown by curve 26 in the pie chart in FIG. 4, beyond the relatively fast allowable bending moment -M _P, the end bend (bending angle theta = 90 degrees) is beyond the rather large allowable bending moment -M _P It may end up. In this case, the applied position of the load F is set to the position of the angle φ = 0, and when the bending angle θ = 90 degrees, the bending F is started so that the absolute value of the total bending moment M _C matches the allowable bending moment M _P. If the method of adding from time to time is adopted, the additional bending moment M _cr due to the load F becomes as shown by the curve 27, the total bending moment M _C changes as shown by the curve 28, and in the initial region of bending, it is positive. Since the allowable bending moment M _P on the side is exceeded, neck bending in the positive direction occurs. Therefore, in order to prevent this, the timing of applying the load F is set from the time when the total bending moment M _C becomes appropriately smaller than the allowable bending moment M _P. For example, as shown in FIG. 5A, application of the load F is started when the bending angle reaches θ _S.
As a result, the total bending moment M _C becomes equal to the bending angle θ = 0.
In the area of through? _S, varies as the curve 26, in the region of the bending angle θ = θ _S ~90 °, it becomes possible to change the curve 28, the allowable bending moment range within the whole bending range (+ M _It is kept in the range of _P to -MP) and can prevent neck breakage.

As shown in FIG. 5 (a), when a load F of a predetermined magnitude is started when the bending angle θ reaches θ _S , the total bending moment M _C suddenly increases at that time. May increase and adversely affect bending. If there is such a possibility, the load applied to the metal strip 1 should be 0.
It is preferable to adopt a method of gradually increasing the load to a predetermined load F. By adopting this method, FIG.
As shown in, the additional bending moment M _cr is
After the load reaches a predetermined magnitude F as shown by, the curve 27 becomes as shown in the curve 27, and the total bending moment M _C also changes as shown by the curve 28A, and then at the curve 28. As shown, the change in bending moment can be eliminated. The applied load F
Does not necessarily have to be constant during bending,
The form may be changed over the entire giving period.

In the embodiment shown in FIG. 5, the application position of the load F is set at the angle φ = 0, but instead of this, as shown in FIG. 5, the application position of the load F (angle φ) is It may be changed to an appropriate position within the range of 0 and the limit bending angle θ _C. Also in this case, for example, the bending angle θ = 9
At 0 degree, a load F is calculated so that the absolute value of the total bending moment M _C matches the allowable bending moment M _P, and the load F is calculated as shown in FIG. Angle θ that the bending angle is appropriately advanced from that angle φ
_When added at the time point when _S is reached, the additional bending moment M _cr due to the load F becomes as shown by the curve 31, and the total bending moment M _C after that changes as shown by the curve 32. Thus, can be held within the allowable bending moment range within the whole bending range (within the range of _{+ M P ~-M P)} , neck breakage can perform bending without causing. In addition,
Even in this case, the load F applied to the metal strip 1 is 0
Can be gradually increased to a predetermined load F. In that case, as shown in FIG. 6 (b), the additional bending moment M _cr and the total bending moment M _C are respectively curves 31A, 31B. 32A, it is possible to obtain an advantage that the total bending moment M _C does not change abruptly.

Next, the case where the bending angle is up to 180 degrees will be described. Now, it is assumed that the basic bending moment M _C ′ changes like a curve 36 in the pie chart of FIG. 7. It is assumed that the load F is applied to the position of φ = 0 (point A in FIG. 1), and when the load F is started to be applied when the bending angle θ _C is reached, the additional bending moment M _cr due to the load F is As shown by the curve 37, the bending angle from the load applying position suddenly decreases from around 90 degrees, becomes 0 at a certain angle θ _d that is considerably smaller than 180 degrees, and thereafter, the bending in the opposite direction occurs. It becomes a moment. For this reason,
The total bending moment M _C changes as shown by the curve 38, and even if the load F is selected to be large, the initial purpose of preventing neck breakage in the opposite direction cannot be achieved, and conversely it promotes neck breakage. I will end up. Therefore, in this case, the position where the load F is applied (angle φ) is set to a position greatly advanced in the bending progress direction as shown in FIGS.
Even when it reaches 0 degree), the additional bending moment M _cr can be maintained at a positive value. Then, by appropriately setting the magnitude of the load F, for example, when the bending angle reaches 180 degrees, the total bending moment M _C becomes equal to the allowable bending moment −M _P on the negative side.
The additional bending moment M _cr due to is changed as shown by the curve 40, and the total bending moment M _C to which the additional bending moment M _cr is added is changed as shown by the curve 41, so that the allowable bending moment is within the entire bending range. Within range (+ _MP to -M
(Within the range of _P ), it can be bent without causing neck breakage.

Here, the position where the load F is applied may be any position where the additional bending moment M _cr can be maintained at a positive value until the final bending angle (the bending angle of 180 ° in the embodiment of FIG. 8) is reached. . 8, 10, when the lower limit of the area of adding the load F and an angle theta _E, the position of the angle theta _E performs bending by applying a load F in position,
It is a position where the additional bending moment M _cr becomes 0 when the bending end (bending angle 180 °) is reached. This angle θ
_E is an equation (8) for _obtaining the additional bending moment M _cr described above.
Can be obtained using. Specifically, when determining the angle theta _D to a position which becomes the moment M _cr 0 flexural added from applying position of the load F in FIG. 7, it is the angle theta _D becomes as shown in Equation (10) shown in Formula 7 Therefore, the load F application position may be advanced so that the position of the angle θ _D coincides with the end position of bending. The lower limit angle θ _E of the load F application range is as shown in the equation (2). Therefore, θ
_When bending at a bending angle exceeding _D , metal strip 1
The position where the load F is applied with respect to
It is sufficient to set it as an area equal to or more than _E , which allows bending work that causes neck bending until the end of bending. The upper limit of the region to apply the load F, bending at the time the bending angle a load F it is necessary to impart to reach the critical bending angle theta _C, reaching the critical bending angle theta _C as described above the arm Position, preferably the critical bending angle θ _C. Therefore, when performing bending at a large angle exceeding 90 degrees, the region to which the load F is applied may be a region within the angles θ _{E to} θ _{C as shown} in FIG.

[Equation 7]

Also in the case shown in FIG. 8, it is preferable to adopt a method of gradually increasing the load applied to the metal strip 1 from 0 to a predetermined load F within an appropriate angle range. This method is adopted. Thus, as shown in FIG. 9, the additional bending moment M _cr and the total bending moment M _C
It can be gradually changed as indicated by 45. In the embodiment shown in FIG. 9, the load F is applied to a position slightly smaller than the limit bending angle θ _C , and the load application is started when the angle θ _S , which slightly exceeds the angle θ _C , is reached. .

As shown in the embodiment of FIGS. 8 and 9, 1
In case of bending 80 °, by applying a load F to a point, (in the range of + M _P ~-M _P) total total bending within the allowable bending moment range moment M _C in the range of bending
It is possible to hold at. However, if the bending angle from the load applying position becomes larger than a certain value, the additional bending moment due to the load F becomes small. Therefore, in order to prevent neck breakage, it is necessary to apply a considerably large load as the load F. However, this may deteriorate the accuracy of the bending radius. In order to prevent this, it is effective to change the position where the load F is applied when the bending progresses to a position near the root of the arm clamp, or to add the position. Hereinafter, an embodiment in that case will be described.

The bending apparatus shown in FIG. 11 includes a load applying device 11 (hereinafter referred to as a first load applying device) and a second load applying device 51 having a structure similar to that of the first load applying device 11. There is. The first load application device 11 is provided so that the load F can be applied before the bending angle reaches the limit bending angle θ _C , and the load application position (first load application) by the first load application device 11 (first load). The application position) is set between the guide roller 6 and the position of the limit bending angle θ _C. The second load applying device 51 is provided so that the load applying position (referred to as the second load applying position) is set within the region from the first load applying position to the bending arm 3. In the embodiment of the drawings, the first load applying position is set at a position of angle φ ₁ = 30 degrees, and the second load applying position is set at a position of angle φ ₂ = 90 degrees.

Next, the bending by the bending apparatus shown in FIG.
Fig. 12 shows the load application and bending moment change during buffing.
This will be explained using the pie chart of. In the figure, 36 is a basic bending model.
Statement M_CIt is a curve showing the change of ′. Open bending
After starting, the bending angle is the first load applying position (angle φ₁= 3
A little over 0 degree (bending angle θ_S1) With first load
First load F to applied position₁To start adding. At this time,
One load F₁Gradually increases from 0. By this
The additional bending moment M as shown by the curve 53A._crBut
Applied, total bending moment M_CIs like curve 54A
Varies and stays within the permissible bending moment. That
The bending progresses, the bending angle slightly exceeds 90 degrees, and the second
When the load can be applied by the load applying device 51
(Bending angle _θS2), The first load applied position
One load F₁At the same time as removing the second
Load F₂Starts to add and then a constant second load F₂To
Continue to add. Second load F applied here₂Is, for example,
At the end of bending (bending angle θ = 180 degrees), all bending
Statement M_CIs the negative allowable bending moment-M_PEqual to
Set so that Also, to the first load application position
First load F₁At the time of switching the load application
The first load F₁Additional bending moment M due to_crIs the second
Load F₂Additional bending moment M due to_crWill be equal to
To be set. As a result, after switching the load application
Is the additional bending moment M as shown by the curve 53B._crBut
Applied, total bending moment M_CIs like curve 54B
Varies and stays within the permissible bending moment. Write
And the total bending moment M over the entire bending range._CIs acceptable
Keeping within the range of bending moment and causing neck breakage
It can be bent without bending. As in this embodiment
The second load application position is set to the position where the bending angle is large.
The second load F at that position₂If you add
Second load F₂To act on the base of the arm clamp
Additional bending moment M_crCan be increased
In other words, a small second load F₂To prevent neck breakage
You can Thus, a relatively small load F₁, F₂Add
The total bending moment M_CIs kept within the allowable range
Yes, while maintaining high bending radius accuracy, prevent neck breakage
Bending can be performed.

In the above description, the addition of the first load F ₁ to the first load application position and the application of the second load F ₂ to the second load application position are switched, but the first load F ₁ The second load F ₂ may be added in parallel with the application of the second load F ₁ , and in that case, the first load F ₁ may be gradually decreased and the second load F ₂ may be gradually increased. May be Further, in the above description, the load F ₁ is changed so as to gradually increase from 0, but the present invention is not limited to this, and it may be changed so that a constant amount of load F ₁ is applied from the start of application. Similarly, the load F ₂ is not limited to the case where the load having a constant magnitude is applied from the beginning, and may be applied while being appropriately changed.

In each of the embodiments described above, the load applying devices 11 and 51 are installed at fixed positions to apply a load to a constant bending angle position during bending. It is also possible to adopt a configuration that moves with the progress. FIG. 13 shows an embodiment in that case. In this embodiment, the turning arm 61 is provided so as to turn about the turning center O of the bending arm 3, and the turning arm 61 holds the load applying device 11. In this bending device starts bending in a state of not operating the load applying device 11, a suitable time before the bending angle reaches a critical bending angle theta _C, load the limit bending angle theta _C is smaller than the angular position The application device 11 is positioned and operated to start applying the load F. After that, as the bending progresses, the turning arm 61 also turns in the turning direction of the bending arm 3 to advance the load applying position. As a result, the bending moment due to the load F can be effectively applied to the base of the clamp even when the bending angle becomes large, and by applying a relatively small load F, the total bending moment M _C is kept within the allowable range. Yes, while keeping the bending radius accuracy high,
Bending that prevents neck breakage can be performed. In addition,
The swivel arm 61 may be continuously swung in synchronization with the bending arm 3 during the bending process, or may be stopped at one position for a certain period during the bending process, and when the bending process proceeds, You may make it perform an intermittent turning, such as turning to a position and stopping. Also, the load F applied in this embodiment
Also, the size may be constant or may change.

[0029]

As described above, according to the present invention, at least during the bending process, the absolute value of the bending moment M _C ′ acting on the arm clamp root of the metal strip by the turning and the propulsive force P of the bending arm. During a period in which the allowable bending moment M _P of the metal strip exceeds the allowable bending moment M _P , the absolute value of the total bending moment M _C acting on the base of the arm clamp of the metal strip does not exceed the allowable bending moment M _P. An arm is formed by applying a load in the direction toward the side having the turning center of the bending arm in the bending plane to a metal strip in a region including the straight portion near the heating portion of the strip and extending from the straight portion to the bending arm. By bending the clamp base while applying an additional bending moment, it is possible to prevent neck breakage that tends to occur when performing compression bending with a small bending radius and to prevent neck breakage. Has such an effect can be obtained.

Here, it is assumed that the period for applying a load to the metal strip is started at least before the turning angle of the bending arm reaches the limit bending angle θ _C shown in the above equation (1). , The absolute value of the total bending moment M _C acting on the base of the arm clamp is the allowable bending moment M _P
The effect of being able to start applying the load before the load exceeds the value and preventing the neck from breaking can be obtained, and the timing of applying the load can be obtained by a simple calculation.

Further, when performing bending such that the bending angle exceeds 90 degrees, it is assumed that the position where the load is applied to the metal strip is a region equal to or greater than the angle θ _E shown in the above equation (2). Even when the bending angle becomes large, an additional bending moment in the positive direction can be applied to the base of the arm clamp, and neck bending can be prevented even when bending a large bending angle such as a bending angle of 180 degrees. The effect is obtained.

Further, the position where the load is applied to the metal strip is set within the region from the straight pipe portion in the vicinity of the heating portion of the metal strip to the bending arm at that time when the load is started to be applied. If the configuration is such that the first load application position is changed to a second load application position that is advanced in the bending direction from the first load application position at a time when a predetermined amount of bending has proceeded thereafter, it is relatively small. By applying a load, all bending moments acting on the base of the arm clamp can be maintained within the allowable bending moment, and the neck bending can be prevented without deteriorating the accuracy of the bending radius.

If the position where the load is applied to the metal strip is moved in the swivel direction of the bending arm as the bending process progresses, a relatively small load is applied to the base of the arm clamp. The effect is that all the bending moments that act can be kept within the allowable bending moment, and neck bending can be prevented without degrading the accuracy of the bending radius.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a bending apparatus according to an embodiment of the present invention.

[Fig. 2] A pie chart showing changes in bending moment acting on the base of the arm clamp of the metal strip during bending, with respect to the bending angle.

3 is a circle showing a change of a bending moment acting on a root of an arm clamp of a metal strip with respect to a bending angle in a bending method according to an embodiment of the present invention using the apparatus of FIG. Graph

FIG. 4 shows a state in which a large load F is applied to the bending start position,
Pie chart showing changes in bending moment acting on the base of arm clamp of metal strip with bending angle

5 (a) and 5 (b) are pie charts each showing a change in bending moment with respect to a bending angle of a bending moment acting on an arm clamp root of a metal strip in a bending method according to another embodiment of the present invention.

6 (a) and 6 (b) are pie charts showing changes in bending moment acting on a root of an arm clamp of a metal strip with respect to a bending angle in a bending method according to still another embodiment of the present invention.

FIG. 7 is a pie chart showing a change in a bending moment acting on a root of an arm clamp of a metal strip with respect to a bending angle when a load F is applied to a bending start position when the bending angle is 180 degrees.

FIG. 8 is a pie chart showing a change of a bending moment acting on a root of an arm clamp of a metal strip with respect to a bending angle in a bending method according to still another embodiment of the present invention.

FIG. 9 is a pie chart showing a change of a bending moment acting on a root of an arm clamp of a metal strip with respect to a bending angle in a bending method according to still another embodiment of the present invention.

FIG. 10 is a schematic plan view of a bending apparatus showing a load application area when performing bending at a large bending angle.

FIG. 11 is a schematic plan view of a bending apparatus according to another embodiment of the present invention.

FIG. 12 is a pie chart showing a change of a bending moment acting on a root of an arm clamp of a metal strip with respect to a bending angle in a bending method according to an embodiment of the present invention using the apparatus of FIG. 11.

FIG. 13 is a schematic plan view of a bending apparatus according to still another embodiment of the present invention.

FIG. 14 is a schematic plan view of a conventional bending apparatus.

FIG. 15: Metal strip (steel pipe) bent by a conventional device
Schematic plan view showing

[Explanation of symbols]

1 metal strip 2 heating device 3 bending arm 4 arm clamp 5 cooling water 6 Guide roller 11 Load application device (first load application device) 12 push rollers 13 hydraulic cylinder 51 Second load applying device

[Procedure amendment]

[Submission date] August 29, 2002 (2002.8.2)
9)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

Next, the case where the bending angle is up to 180 degrees will be described. Now, it is assumed that the basic bending moment M _C ′ changes like a curve 36 in the pie chart of FIG. 7. It is assumed that the load F is applied to the position of φ = 0 (point A in FIG. 1), and when the load F is started to be applied when the bending angle θ _C is reached, the additional bending moment M _cr due to the load F is As shown by the curve 37, the bending angle from the load applying position suddenly becomes smaller when it exceeds 90 degrees, becomes 0 at a certain angle θ _D that is considerably smaller than 180 degrees, and thereafter, the bending in the opposite direction occurs. It becomes a moment. For this reason,
The total bending moment M _C changes as shown by the curve 38, and even if the load F is selected to be large, the initial purpose of preventing neck breakage in the opposite direction cannot be achieved, and conversely it promotes neck breakage. I will end up. Therefore, in this case, the position where the load F is applied (angle φ) is set to a position greatly advanced in the bending progress direction as shown in FIGS.
Even when it reaches 0 degree), the additional bending moment M _cr can be maintained at a positive value. Then, by appropriately setting the magnitude of the load F, for example, when the bending angle reaches 180 degrees, the total bending moment M _C becomes equal to the allowable bending moment −M _P on the negative side.
The additional bending moment M _cr due to is changed as shown by the curve 40, and the total bending moment M _C to which the additional bending moment M _cr is added is changed as shown by the curve 41, so that the allowable bending moment is within the entire bending range. Within range (+ _MP to -M
(Within the range of _P ), it can be bent without causing neck breakage.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

Next, the load application and bending moment change during bending by the bending apparatus shown in FIG. 11 are shown in FIG.
This will be explained using the pie chart of. In the figure, 36 is a curve showing the change in the basic bending moment M _C ′. After the bending process is started, the bending angle is the first load applying position (angle φ ₁ = 3
At a point slightly beyond 0 degree (bending angle θ _S1 ), application of the first load F ₁ to the first load application position is started. At this time, the first load F ₁ is gradually increased from 0. As a result, the additional bending moment M _cr is applied as shown by the curve 53A, the total bending moment M _C changes as shown by the curve 54A, and is kept within the range of the allowable bending moment. When the bending progresses, the bending angle slightly exceeds 90 degrees, and the load can be applied by the second load applying device 51 (bending angle θ _S2 ), the first load applying position is added. At the same time as eliminating the load F ₁ , the second load F ₂ is started to be added to the second load applying position, and thereafter the constant second load F ₂ is continuously added. The second load F ₂ applied here is, for example,
At the end of bending (bending angle θ = 180 degrees), the total bending moment M _C is set to be equal to the negative side allowable bending moment −M _P. Further, the first load F ₁ to the first load applying position is such that the additional bending moment M _cr due to the first load F ₁ becomes equal to the additional bending moment M _cr due to the second load F ₂ at the time of switching the _application of the load. Set to. As a result, after the load application is switched, the additional bending moment M _cr is added as shown by the curve 53B, and the total bending moment M _C changes as shown by the curve 54B, and is maintained within the range of the allowable bending moment. Thus, the total bending moment M _C is kept within the range of the allowable bending moment over the entire bending range, and bending can be performed without causing neck bending. As in this embodiment, it is bending to set the second load applying position to position greater angle, when configured to apply a second force F ₂ in position, additional to act on the base arm clamped by the second load F ₂ The bending moment M _cr can be increased, in other words, the neck can be prevented from being broken with a small second load F ₂ . Thus, by applying relatively small loads F ₁ and F ₂ , the total bending moment M _C can be held within the allowable range, and bending can be performed while preventing the neck from bending while keeping the accuracy of the bending radius high. .

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenshi Yatabe             2-17-8 Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa               Dai-ichi Kogyo Kogyo Co., Ltd. (72) Inventor Tadanobu Miyagawa             2-17-8 Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa               Dai-ichi Kogyo Kogyo Co., Ltd. F-term (reference) 4E063 AA03 AA04 BC11 CA03 JA02                       KA02 KA05

Claims (8)

[Claims] 1. A metal strip to be bent is passed through a heating device that heats a short section in the longitudinal direction, and is fixed to an arm clamp provided on a rotatable bending arm, the working tip side of which is fixed.
By bending the metal strip in the longitudinal direction while heating it with the heating device, the bending moment generated by the turning of the bending arm in the heating part while moving the heating part by the heating device in the longitudinal direction of the metal strip. In the method for bending a metal strip, in which a portion of the metal strip is bent by applying a force to cool the portion immediately after that, a bend acting on the root of the arm clamp of the metal strip by at least the turning of the bending arm and the propulsive force P during the bending process. During the period when the absolute value of the moment M _C ′ exceeds the allowable bending moment M _P of the metal strip,
In order to prevent the absolute value of the total bending moment M _C acting on the base of the arm clamp of the metal strip from exceeding the permissible bending moment M _P , including a straight portion near the heating portion of the metal strip, from the straight portion It is possible to perform bending while applying a load in the direction toward the side having the turning center of the bending arm in the bending plane to the metal strip in the region reaching the bending arm while applying an additional bending moment to the base of the arm clamp. Characteristic method of bending metal strip. 2. The metal strip material according to claim 1, wherein the period for applying the load is started at least before the bending angle reaches θ _C shown in the following expression (1). Bending method. [Equation 1] 3. The metal according to claim 1, wherein the position where the load is applied to the metal strip is set to a position equal to or greater than the angle θ _E shown in the equation (2) in the following mathematical expression 2. Bending method for strips. [Equation 2] 4. The position where the load is applied to the metal strip is within a region from a straight pipe portion near the heating portion of the metal strip to the bending arm at that time when the load starts to be applied. The first load application position set to
At the time when a predetermined amount of bending has progressed, it is changed to a second load applying position set to a position advanced in the advancing direction of the bending arm from the first load applying position, or a load is applied to the second load applying position. The method for bending a metal strip according to any one of claims 1 to 3, further comprising: 5. The position for applying the load to the metal strip is moved in the turning direction of the bending arm as the bending process progresses. Method of bending metal strip. 6. A heating device for heating a short section of a metal strip to be bent in the longitudinal direction, a strip propelling device for propelling the metal strip passed through the heating device in the longitudinal direction, and the metal strip. A swivel bending arm having an arm clamp for fixing the working tip side of the material, and a metal in a region from the straight part to the bending arm including a straight part near the heating part of the metal strip during bending. A metal strip having a load applying device provided so as to apply a load in the bending plane toward the side having the pivot center of the bending arm to apply an additional bending moment to the base of the arm clamp. Material bending equipment. 7. The metal according to claim 6, wherein a plurality of the load applying devices are provided so that a load can be applied to each of a plurality of positions separated from each other in the longitudinal direction of the metal strip. Bending equipment for strips. 8. The bending apparatus for a metal strip according to claim 6 or 7, wherein one load applying device is provided so as to be rotatable about a center of rotation of the bending arm.