Pipe forming apparatus

Abstract

To easily form not only a pipe body having a circular cross section of a small diameter but also a pipe body having a non-circular cross section including a straight line portion in at least a portion of the cross section from a work of a metallic rectangular flat plate.SOLUTION: A tubular body forming device 10 includes a core member 1 whose rotation around an axis is restricted, a contact member 2 that holds a central portion of a workpiece W between the contact member and the core member 1, a first pressing member 3A and a second pressing member 3B that are horizontally pressed against the core member 1 from both sides with the workpiece W interposed therebetween, a correction member 5 that is pressed against the core member 1 from an opposite side of the contact member 2 with both end portions of the workpiece W interposed therebetween, and a holding member 6 that is pressed against the peripheral surface of the core member 1 from an opposite side of the contact member 2. By pressing the work W from four directions orthogonal to each other of the core material 1, the work W is formed into a tubular body having an inner dimension corresponding to the outer dimension of the core material 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tube forming apparatus for bending a rectangular metal plate workpiece between a plurality of rolls to form the workpiece into a tube shape. [Background technology]

[0002] A known method for manufacturing a metal tube is to bend a workpiece, a rectangular metal plate, into a cylindrical shape using a roll forming device, and then join the two parallel ends using a welding device or the like. The roll forming device has multiple rolls, including one main roll and one or more sub-rolls, with their axial directions parallel to each other. As the workpiece passes between the main roll and the sub-rolls, it is plastically deformed by bending and formed into a cylindrical shape.

[0003] A typical conventional roll forming device is a three-roll forming device equipped with two auxiliary rolls made of a material with the same hardness as the main roll (see, for example, Patent Document 1). The three-roll forming device is suitable for bending relatively small diameters, and because the peripheral surfaces of the auxiliary rolls do not press against the peripheral surfaces of the main rolls with the work sandwiched between them, the bending diameter can be easily changed by adjusting the position of the auxiliary rolls relative to the main rolls.

[0004] However, conventional three-roll forming equipment has difficulty forming relatively hard metal workpieces, such as 1 mm thick SUS304, into small-diameter tubes with an outer diameter of approximately 22 mm. This is because large bending stress acts on the workpiece during bending, and when the workpiece is released from between the rolls, a springback phenomenon occurs in which the ends of the workpiece return to their original position due to elastic force. This springback phenomenon increases the gap between the ends of the workpiece, necessitating a tube-reducing process to ensure smooth joining.

[0005] Therefore, the applicant previously proposed a roll forming device equipped with a main roll, a pinch roll, two side rolls, an end bending plate, a first moving mechanism, a biasing mechanism, a second moving mechanism, a third moving mechanism, and a control unit (see Patent Document 2).

[0006] The main roll and pinch roll are arranged with their central axes parallel to each other and are supported on a shaft so that they can move independently along a main line connecting their centers. The two side rolls are supported on both sides of the main line so that they can move toward and away from the main roll with their central axes parallel to each other. The end bending plate is supported on the opposite side of the pinch roll across the main roll so that it can move freely along the main line, and its end face facing the circumferential surface of the main roll is shaped to fit along the circumferential surface of the main roll. The first moving mechanism moves the main roll toward the pinch roll. The biasing mechanism selectively biases the pinch roll in a direction that presses it against the main roll. The second moving mechanism moves the two side rolls at the same speed in directions that move them toward and away from each other. The third moving mechanism moves the end bending plate back and forth along the main line.

[0007] The control unit is configured to perform the following steps in order: a bending process in which the biasing mechanism and the first moving mechanism are operated to clamp the circumferential center of the metal plate workpiece in the thickness direction between the main roll and the pinch roll, and then the second moving mechanism is operated to move the two side rolls toward each other while moving the main roll along the main line toward the pinch roll; and an end bending process in which the second moving mechanism is operated to move the two side rolls away from each other and the third moving mechanism is operated to move the end face of the end bending plate along the main line toward the main roll.

[0008] With this configuration, a sufficient pressing force is applied from the two side rolls to the peripheral surface of the workpiece, which is a metal plate material with its circumferential center sandwiched between the main roll and the pinch roll, along the circumferential direction of the main roll during the bending process, and a sufficient pressing force is applied from the end bending plates to the peripheral surface of the main roll on both ends of the workpiece during the end bending process, thereby reliably forming the workpiece into a cylindrical shape. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-252546 [Patent Document 2] Japanese Patent Application Publication No. 2019-252546 Summary of the Invention [Problem to be solved by the invention]

[0010] However, the roll forming device described in Patent Document 2 can form a relatively hard workpiece into a small-diameter tube with a circular cross section, but cannot form it into a tube with a non-circular cross section, such as a rectangular cross section or a D-shaped cross section, which includes a straight section in at least part of the cross section.

[0011] The object of this invention is to provide a tube forming apparatus that can easily form not only small-diameter circular cross-section tubes from a metal rectangular flat plate workpiece, but also non-circular cross-section tubes that include at least a straight portion in the cross section. [Means for solving the problem]

[0012] The tube molding device of the present invention includes a core material, a contact body, a first pressing body and a second pressing body, a first rotation mechanism and a second rotation mechanism, a correcting body, a pressing mechanism, a displacement mechanism, a first biasing mechanism, a second biasing mechanism, and a third biasing mechanism.

[0013] The core material is a columnar body having a uniform cross-sectional shape along the axial direction and whose rotation around the axis is restricted. The abutment body is capable of moving toward and away from the core material along a reference direction, which is a specific radial direction of the core material, and has an abutment surface that faces the entire axial area of ​​the core material and clamps a plate-shaped workpiece between the abutment body and the core material along the reference direction. The first pressing material and the second pressing material are both columnar bodies having a uniform cross-sectional shape along the axial direction and a cross-sectional shape that includes straight and arc portions on the outer periphery, and are arranged parallel to the core material so as to be able to move toward and away from each other across the reference direction within a reference plane perpendicular to the reference direction. The first rotation mechanism and the second rotation mechanism selectively cause the straight portions or the arc portions of the first pressing material and the second pressing material to face the core material. The corrector has a correcting surface that faces the core material over the entire axial range on the opposite side of the abutting body across the core material, and that follows the peripheral surface of the workpiece sandwiched between the abutting surface and the core material, and is supported so as to be freely movable relative to the core material along the reference direction.

[0014] The pressing mechanism clamps the workpiece between the core material and the abutment surface. The displacement mechanism displaces the relative position in the reference direction between the workpiece clamped between the core material and the abutment surface and the reference surface. The first and second biasing mechanisms bias the first and second pressing members in directions toward each other while the workpiece clamped between the core material and the abutment surface moves from an initial position sandwiching the reference surface toward a completion position due to the displacement of the relative position. After the workpiece reaches the completion position, the third biasing mechanism clamps both ends of the workpiece between the first and second pressing members, which are spaced apart from each other, and presses the correction surface against the circumferential surface of the core material.

[0015] A portion of the workpiece, which is a rectangular flat metal plate, is clamped between the core material and the abutment surface by the pressing mechanism, and while the workpiece is moved from the initial position toward the completion position by the displacement mechanism, the first pressing material and the second pressing material, whose straight or arcuate portions are selectively opposed to the core material by the first rotation mechanism and the second rotation mechanism, are brought closer to each other by the first biasing mechanism and the second biasing mechanism.

[0016] When the pressing mechanism, displacement mechanism, first biasing mechanism, and second biasing mechanism continue to operate until the workpiece reaches the completion position, the straight or arcuate portions of the first pressing material and second pressing material sandwich the workpiece in the thickness direction and press it against the peripheral surface of the core material, causing the workpiece to deform to follow the shape of the peripheral surface of the core material.

[0017] When the straight or arcuate portions of the first and second pressing members are closest to each other and the workpiece reaches the completion position, and both ends of the workpiece are closest to each other, the first and second pressing members are separated from each other by the first and second contact / separation mechanisms. When the straight or arcuate portions of the first and second pressing members are pressed against the correcting surface and the circumferential surface of the core member by the third biasing mechanism, both ends of the workpiece are pressed against each other by the correcting surface and the circumferential surface of the core member, and the ends of the workpiece separated from the circumferential surface of the core member are pressed against each other and deformed along the circumferential surface of the core member. The workpiece is formed into a tubular body whose inner circumferential surface follows the circumferential surface of the core member along its entire circumference.

[0018] This configuration can also include a holding body and a fourth biasing mechanism. The holding body has a holding surface that faces the core material over the entire axial length on the opposite side of the abutting body with the core material sandwiched therebetween, and is supported so as to be movable relative to the core material along the reference direction. The fourth biasing mechanism presses the holding surface against the circumferential surface of the core material during the displacement of the relative position, from an initial position where the workpiece sandwiches the reference surface between the core material and the abutting surface, at least until the workpiece passes through the reference surface. By directly pressing the holding surface against the circumferential surface of the core material over the entire axial length when a portion of the workpiece is sandwiched between the abutting body and the core material, axial deflection of the core material can be prevented, and a long tube can be accurately formed.

[0019] In this case, the corrector and the retainer are supported integrally and are movable along the reference direction, and a selection mechanism is provided for selectively facing either the corrector surface or the retainer surface to the core material, and the third biasing mechanism can also serve as the fourth biasing mechanism, thereby simplifying the configuration.

[0020] In addition, the core material is supported so as to be freely movable in the reference direction, and the displacement mechanism moves the core material between the initial position and the completion position, and the first pressing material, the second pressing material, the first rotation mechanism, and the second rotation mechanism are fixed in the reference direction, thereby simplifying the structure. [Effects of the Invention]

[0021] According to this invention, a rectangular metal plate workpiece can be easily formed into not only a small diameter circular cross-section tube, but also a non-circular cross-section tube that includes a straight line in at least part of its cross section. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view of a tube forming apparatus according to a first embodiment of the present invention. [Figure 2] 5(A) to 5(H) are schematic side views showing the operation of the tube forming device when forming a circular tube. [Figure 3] 5(A) to 5(H) are schematic side views showing the operation of the tube forming device when forming a rectangular tube. [Figure 4] 10(A) to 10(H) are schematic side views showing the operation of the tube forming device when forming a D-shaped tube. [Figure 5] FIG. 4 is a cross-sectional view of a tube forming apparatus according to a second embodiment of the present invention. [Figure 6] 5(A) to 5(H) are schematic side views showing the operation of the tube forming device when forming a circular tube. DETAILED DESCRIPTION OF THE INVENTION

[0023] A tube forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

[0024] As shown in FIG. 1, a tube forming apparatus 100 according to a first embodiment of the present invention includes a core material 1, a contact body 2, a first pressing member 3A, a second pressing member 3B, a first rotation mechanism 4A, a second rotation mechanism 4B, a straightening body 5, a holding body 6, a pressing mechanism 7, a displacement mechanism 8, a first biasing mechanism 9A, a second biasing mechanism 9B, a third biasing mechanism 10, and a selection mechanism 11.

[0025] The core material 1 is a columnar body with a uniform cross-sectional shape along the axial direction, and both axial ends are fixed to a slider 112 with their rotation restricted by chucks 111. The slider 112 is movable along a pair of slider guides 113 arranged on a frame (not shown). The longitudinal direction of the slider guides 113 coincides with a reference direction L1, which is a specific radial direction of the core material 1. The core material 1 moves along the reference direction L1 together with the slider 112. In this embodiment, the vertical direction is taken as the reference direction L1.

[0026] The tube forming apparatus 100 forms a tube by wrapping a rectangular metal flat workpiece around the circumferential surface of a core material 1. Therefore, the cross-sectional shape of the core material 1 matches the internal shape of the tube to be formed. The core material 1, whose cross-sectional shape corresponds to the internal shape of the tube to be formed, is fixed to a slider 112.

[0027] The abutment body 2 has an abutment surface 21 formed of a horizontal surface whose normal direction is the reference direction L1. The abutment surface 21 faces the circumferential surface of the core material 1 over the entire axial direction of the core material 1. The abutment surface 21 can also be formed in an arc shape that convex toward the circumferential surface of the core material 1. When the tube forming device 100 forms a tube, the abutment surface 21 presses against the circumferential surface of the core material 1 along the reference direction L1, sandwiching a portion of the workpiece in the thickness direction. The abutment body 2 is fixed to an abutment body base 22. The abutment body base 22 is movable up and down along the reference direction L1 via a pair of abutment body guides 23.

[0028] The first pressing member 3A and the second pressing member 3B are arranged parallel to the core member 1 across the reference direction L1 within a reference plane P1 that is perpendicular to the reference direction L1. The first pressing member 3A and the second pressing member 3B are axially supported by supports 33A and 31B, respectively. The first pressing member 3A and the second pressing member 3B are, for example, columnar bodies that have a uniform cross-sectional shape along the axial direction and include straight portions 31A and 31B and arc portions 32A and 32B.

[0029] The cross-sectional shapes of the first pressing member 3A and the second pressing member 3B can be such that the curvature of the arc portions 32A and 32B can be partially changed depending on the shape of the tube to be formed, or they can have a partially concave arc portion. When the tube forming apparatus 100 forms a tube, the straight portion 31A or 31B and the arc portion 32A or 32B are pressed against the peripheral surface of the core material 1 within the reference plane P1, sandwiching another part of the work in the thickness direction.

[0030] The first rotation mechanism 4A and the second rotation mechanism 4B are attached to a support base 33A and a support base 33B, respectively. The first rotation mechanism 4A and the second rotation mechanism 4B are formed by, for example, hydraulic cylinders, and their shafts 41A and 41B are connected to the rotation shaft 34A of the first pressing member 3A and the rotation shaft 34B of the second pressing member 3B via links 35A and 35B.

[0031] When the first rotation mechanism 4A and the second rotation mechanism 4B move the shafts 41A and 41B back and forth in the axial direction, the rotation shafts 34A and 34B rotate via the links 35A and 35B. Depending on the amount of movement of the shafts 41A and 41B, the straight portion 31A or the arc portion 32A of the first pressing member 3A and the straight portion 31B or the arc portion 32B of the second pressing member 3B selectively face the circumferential surface of the core material 1.

[0032] The first and second urging mechanisms 9A and 9B are, for example, hydraulic cylinders fixed to a frame not shown, and cause the support bases 33A and 33B, which respectively support the first and second pressing members 3A and 3B, to move back and forth along the first and second pressing member guides 36A and 36B, and urge them toward the core material 1. The first and second pressing members 3A and 3B move toward or away from each other together with the support bases 33A and 33B.

[0033] The first and second urging mechanisms 9A and 9B can be configured, for example, by motors having pinion gears fixed to their rotation shafts that mesh with rack gears fixed to the support bases 33A and 33B, and can have only the function of moving the first and second pressing members 3A and 3B back and forth relative to the core material 1. In this case, a hydraulic cylinder or the like that urges the first and second pressing members 3A and 3B toward the core material 1 will be separately provided.

[0034] The straightening body 5 has a straightening surface 51 that selectively faces the core material 1. The straightening surface 51 is pressed against both ends of the workpiece that is held between the contact surface 21 and the core material 1 during tube molding. The straightening surface 51 is configured in a shape that follows the outer circumferential surface of the workpiece that is held between the contact surface 21 and the core material 1 during tube molding. For example, if the portion of the outer circumferential surface of the core material 1 that faces the straightening surface 51 is an arc that is convex outward, the cross section of the straightening surface 51 is configured as a concave arc with a radius equal to the radius of the outer circumferential surface of the molded workpiece, which is the radius of the core material 1 plus the thickness of the workpiece.

[0035] When the tube forming apparatus 100 is forming a tube, the straightener 5 moves to a position where the straightener surface 51 faces the peripheral surface of the core material 1 across the entire axial area of ​​the core material 1 on the opposite side of the abutting body 2 along the reference direction L1, sandwiching the core material 1. From this state, the straightener 5 approaches the core material 1 relatively along the reference direction L1, and the straightener surface 51 presses against both ends of the core material 1 along the reference direction L1, sandwiching both ends of the work in the thickness direction.

[0036] The holder 6 has a holding surface 61 that selectively faces the circumferential surface of the core material 1 over the entire axial direction. The holding surface 61 is pressed against the circumferential surface of the core material 1 during tube molding by the tube molding device 100. The holding surface 61 can be configured as a horizontal surface, taking into account that the cross-sectional shape of the core material 1 changes depending on the cross-sectional shape of the tube to be molded, and more preferably can be configured as an arc that is convex toward the circumferential surface of the core material 1.

[0037] When the tube forming apparatus 100 is forming a tube, the holding body 6 moves to a position where the straightening surface 51 faces the peripheral surface of the core material 1 across the entire axial area of ​​the core material 1 on the opposite side of the abutting body 2 along the reference direction L1, sandwiching the core material 1. From this state, the straightening body 5 approaches the core material 1 relatively along the reference direction L1, and the straightening surface 51 presses against both ends of the core material 1 along the reference direction L1, sandwiching both ends of the work in the thickness direction.

[0038] The pressing mechanism 7 is, for example, a hydraulic cylinder fixed to a frame (not shown). The pressing mechanism 7 reciprocates an abutment body base 22, to which the abutment body 2 is fixed, between a pair of abutment body guides 23 along a reference direction L1, and during tube molding, urges the abutment body 2 toward the core material 1 to sandwich a part of the workpiece between the abutment surface 21 and the circumferential surface of the core material 1. The uppermost position of the abutment surface 21 due to the urging force of the pressing mechanism 7 is predetermined as a start position above the reference plane P1.

[0039] The displacement mechanism 8 reciprocates the slider 112 along the slider guide 113. Before the start of tube forming, the workpiece is loaded between the core material 1 and the abutment body 2 above the reference plane P1, and during tube forming, the workpiece moves from above to below the reference plane P1 while being sandwiched between the circumferential surface of the core material 1 and the abutment surface 21. Before the start of tube forming, a sufficient gap must be provided between the core material 1 and the abutment surface 21 to load the workpiece, while after the start of tube forming, the workpiece must be sandwiched between the circumferential surface of the core material 1 and the abutment surface 21. The displacement mechanism 8 moves the core material 1 held by the slider 112 independently of the abutment body 2 along the reference direction L1 within a range in which it passes above and below the reference plane P1.

[0040] The selection mechanism 11, for example, includes a straightener cylinder 12, a holder cylinder 13, and a selection mechanism support member 14. The selection mechanism support member 14 is movable along a reference direction L1 between a pair of selection mechanism guides 143. The straightener cylinder 12 and the holder cylinder 13 are fixed to a fixing portion 141 on the upper part of the selection mechanism support member 14. The selection mechanism support member 14 includes a pressing portion 142 that extends over the entire axial length of the core material 1.

[0041] A rotation shaft 151 of the corrector link 15 and a rotation shaft 161 of the holder link 16 are journaled at the lower part of the selection mechanism support member 14. The lower end of the piston rod 121 of the corrector cylinder 12 is journaled at one end of the corrector link 15, and the corrector 5 is fixed to the other end of the corrector link 15. The lower end of the piston rod 131 of the holder cylinder 13 is journaled at one end of the holder link 16, and the holder 6 is fixed to the other end of the holder link 16.

[0042] When the piston rod 121 of the corrector cylinder 12 or the piston rod 131 of the holder cylinder 13 is lowered, the corrector link 15 or the holder link 16 rotates to a position where the upper surface of the corrector 5 or the upper surface of the holder 6 abuts against the lower surface of the pressing part 142. When the piston rod 121 of the corrector cylinder 12 or the piston rod 131 of the holder cylinder 13 is raised, the corrector link 15 or the holder link 16 rotates to a position where the upper surface of the corrector 5 or the upper surface of the holder 6 is separated from the lower surface of the pressing part 142.

[0043] By selectively supplying fluid to the straightener cylinder 12 or the holder cylinder 13 of the selection mechanism 11, either the upper surface of the straightener 5 or the upper surface of the holder 6 comes into contact with the lower surface of the pressing portion 142, and either the straightening surface 51 or the holding surface 61 faces the circumferential surface of the core material 1. The tube forming device 100 selectively causes either the straightening surface 51 or the holding surface 61 to face the circumferential surface of the core material 1 via the selection mechanism 11 during tube forming.

[0044] The third biasing mechanism 10 is formed, for example, by a hydraulic cylinder, and the upper end of the pressing part 142 is engaged with the lower end of the rod 110. The third biasing mechanism 10 raises and lowers the upper end of the pressing part 142 by moving the rod 110 back and forth, causing the selection mechanism support member 14 to move back and forth in the reference direction L1 between a pair of selection mechanism guides 143. The relative position between the peripheral surface of the core material 1 and the correcting surface 51 or the holding surface 61 changes. The downward pressing force acting from the third biasing mechanism 10 on the corrector 5 or the holding body 6 is greater than the upward pressing force acting from the pressing mechanism 7 on the abutting body 2.

[0045] The tube forming apparatus 100 is equipped with multiple pairs of positioning rolls 17. The positioning rolls 17 are provided along the axial direction of the core material 1 and abut against both end surfaces of the workpiece carried into the tube forming apparatus 100, thereby determining the position of the workpiece before tube forming begins. The positioning rolls 17 are journaled by movable parts 172 of a movement mechanism 171 attached to the support tables 33A and 33B, outside the first pressing member 3A and the second pressing member 3B in the horizontal direction, with their peripheral surfaces facing the uppermost surfaces of the first pressing member 3A and the second pressing member 3B. The positioning rolls 17 move toward and away from both end surfaces of the workpiece as the movable parts 172 move forward and backward.

[0046] As shown in Figure 2, when a metal rectangular flat plate workpiece W is formed into a tube with a circular cross section using a tube forming apparatus 100, a core material 1 whose outer diameter is the same as the inner diameter of the tube to be formed and a straightener 5 having an arc-shaped straightening surface 51 with a diameter equal to the outer diameter of the tube to be formed are used. The first pressing member 3A and the second pressing member 3B are fixed in a rotational position where the straight portions 31A and 31B are horizontally facing upward, and where the tangent distance S1 to the core material 1 is the thickness of the workpiece W. In addition, the contact surface 21 of the contact body 2 is positioned at the same height as the positioning roll 17, and the core material 1 is spaced above the contact surface 21.

[0047] In this state, the workpiece W is placed on the contact body 2 via the positioning roll 17 so that its center coincides with the reference direction L1 (see FIG. 2(A)), and the core material 1 is lowered via the displacement mechanism 8 so that the center of the workpiece W is sandwiched between the core material 1 and the contact body 2 (see FIG. 2(B)). At this time, the vertical position of the core material 1 is fixed by the displacement mechanism 8, and a biasing force is applied from the pressing mechanism 7 to the contact body 2 so that the contact surface 21 moves toward the core material 1.

[0048] Next, the selection mechanism 11 causes the holding surface 61 of the holding body 6 to face the circumferential surface of the core material 1 (see FIG. 2(C)), and the third biasing mechanism 10 causes the holding body 6 to descend together with the selection mechanism 11. At the same time that the holding surface 61 abuts against the circumferential surface of the core material 1, the vertical position of the core material 1 fixed by the displacement mechanism 8 is released.

[0049] The downward pressing force acting on the holder 6 from the third biasing mechanism 10 is greater than the upward pressing force acting on the abutment body 2 from the pressing mechanism 7. When the downward pressing force from the third biasing mechanism 10 continues to act on the holder 6, the core material 1 descends integrally with the workpiece W and the abutment body 2, with the central portion of the workpiece W sandwiched between the core material 1 and the abutment surface 21, on which the upward pressing force from the pressing mechanism 7 is acting. When the center of the core material 1 reaches the reference plane P1, the workpiece W from its central portion to both end sides abuts against the arc portion 32A of the first pressing member 3A and the arc portion 32B of the second pressing member 3B, and deforms into a semicircular shape along the circumferential surface of the core material 1 (see FIG. 2(D)).

[0050] When the center of the core material 1 reaches the reference plane P1, the first and second biasing mechanisms 9A and 9B apply pressing forces to the first and second pressing members 3A and 3B in directions that bring them closer to each other. Pressing forces act on the core material 1 in a total of four directions from the holding surface 61, the abutting surface 21, the arc portion 32A of the first pressing member 3A, and the arc portion 32B of the second pressing member 3B. The pressing force from the holding surface 61 and the pressing force from the abutting surface 21 oppose each other along the reference direction L1. The pressing force from the arc portion 32A and the pressing force from the arc portion 32B oppose each other across the reference direction L1.

[0051] As the supply of pressing force from the pressing mechanism 7, the first biasing mechanism 9A, the second biasing mechanism 9B, and the third biasing mechanism 10 continues, the portions of the workpiece W closer to both ends than the semicircularly deformed portion deform into an arc shape along the circumferential surface of the core material 1 while abutting against the arc portions 32A and 32B. Just before the arc portions 32A and 32B abut against the holder 6, the supply of pressing force from the first biasing mechanism 9A, the second biasing mechanism 9B, and the third biasing mechanism 10 is stopped while the supply of pressing force from the pressing mechanism 7 continues. The positions of the first pressing member 3C and the second pressing member 3B are fixed in the reference direction L1, and the descent of the core material 1 stops (see FIG. 2(E)).

[0052] Next, the third biasing mechanism 10 moves the holding body 6 upward, and the selection mechanism 11 moves the holding surface 61 back to a position where it does not face the core material 1, and the supply of pressing force from the first biasing mechanism 9A and the second biasing mechanism 9B is resumed. As the core material 1 resumes its descent, the first pressing member 3A and the second pressing member 3B come closest to each other (see FIG. 2(F)).

[0053] When the first pressing member 3A and the second pressing member 3B are closest to each other, the portions of the workpiece W on both ends of the position where the arc portions 32A and 32B abut are not pressed by the arc portions 32A and 32B and are separated in the tangential direction from the peripheral surface of the core material 1. In addition, stress generated in the workpiece W by deformation acts on the portions of the workpiece W at both ends where the arc portions 32A and 32B abut in a direction separating them from the peripheral surface of the core material 1, further separating both ends of the workpiece W from the peripheral surface of the core material 1.

[0054] Therefore, the first pressing member 3A and the second pressing member 3B are separated from each other, and the selection mechanism 11 is used to make the straightening surface 51 of the straightener 5 face the core material 1 (see FIG. 2(G)), and the third biasing mechanism 10 is used to lower the straightener 5 toward the core material 1 (see FIG. 2(H)). Both ends of the workpiece W are pressed by the straightening surfaces 51 and deformed along the circumferential surface of the core material 1, and the workpiece W is formed into a cylindrical tube whose inner circumferential surface follows the circumferential surface of the core material 1 over its entire length.

[0055] Thereafter, the vertical position of the core material 1 is fixed by the displacement mechanism 8, the first pressing member 3A and the second pressing member 3B are separated from each other by the first biasing mechanism 9A and the second biasing mechanism 9B, and the contact body 2 is separated from the core material 1 by the pressing mechanism 7. The workpiece W formed into a cylindrical tube can be pulled out from one end side of the core material 1 along the axial direction of the core material 1.

[0056] As shown in Figure 3, when a workpiece W, which is a rectangular metal plate, is formed into a square tube with a rectangular cross section using a tube forming device 100, a core material 101 having outer dimensions equal to the inside dimensions of the square tube to be formed is held by a displacement mechanism 8, and a straightener 105 having a flat straightening surface 1051 is attached to a selection mechanism 11. In this state, by performing the same process as in Figures 2(A) to (F), the inner peripheral surface of the workpiece W is deformed into a shape that conforms to the three peripheral surfaces of the core material 101. At this time, the vicinity of both ends of the workpiece W approaches the top surface of the core material 101 (see Figures 3(A) to (F)).

[0057] Since internal stress occurs in the workpiece W due to deformation, both ends of the workpiece W move away from the upper surface of the core material 101 as the first pressing member 3A and the second pressing member 3B move away from each other. Therefore, the contact member 2 is raised by the pressing mechanism 7 until the upper surface of the core material 101 reaches above the reference plane P1, and the first pressing member 3A and the second pressing member 3B are rotated so that the linear portions 31A and 31B face the core material 101 with the workpiece W sandwiched between them. Furthermore, the first pressing member 3A and the second pressing member 3B are biased toward each other, and the selection mechanism 11 causes the straightening surface 1051 of the straightening body 105 to face the core material 101 (see FIG. 3(G)).

[0058] From this state, the third biasing mechanism 10 lowers the straightening body 105 toward the core material 101, whereby both ends of the workpiece W are pressed by the straightening surfaces 1051 and deformed so as to come into close contact with the upper surface of the core material 101. The close contact state of the workpiece W on both side surfaces of the core material 101 is maintained by the pressing forces of the linear portions 31A and 31B of the first pressing member 3A and the second pressing member 3B, and the workpiece W is formed into a square tube whose inner dimensions follow the outer dimensions of the core material 101 (see FIG. 3(H)).

[0059] As shown in Figure 4, when a workpiece W, which is a rectangular metal plate, is formed into a D-shaped cross-section deformed pipe using the pipe forming device 100, a core material 201 having outer dimensions equal to the inside dimensions of the square pipe to be formed is held by a displacement mechanism 8, and a straightener 205 having a flat straightening surface 2051 is attached to a selection mechanism 11. In this state, by performing the same process as in Figures 2(A) to (F), a part of the inner peripheral surface of the workpiece W is deformed into a shape that follows the two continuous flat surfaces and part of the curved surface of the peripheral surface of the core material 201. At this time, the vicinity of both ends of the workpiece W approaches the upper surface of the core material 101 (see Figures 4(A) to (F)).

[0060] Since internal stress occurs in the workpiece W due to deformation, both ends of the workpiece W move away from the upper surface of the core material 201 as the first pressing member 3A and the second pressing member 3B move away from each other. Therefore, the contact member 2 is raised by the pressing mechanism 7 until the upper surface of the core material 201 reaches above the reference plane P1, and the first pressing member 3A and the second pressing member 3B are rotated so that the linear portion 31A and the arc portion 32B face the core material 201 with the workpiece W sandwiched between them. Furthermore, the first pressing member 3A and the second pressing member 3B are biased toward each other, and the selection mechanism 11 causes the straightening surface 2051 of the straightening body 205 to face the core material 201 (see FIG. 4(G)).

[0061] From this state, the third biasing mechanism 10 lowers the straightening body 205 toward the core material 201, whereby both ends of the workpiece W are pressed by the straightening surfaces 2051 and deformed so as to adhere to the upper surface of the core material 201. The adherence state of the workpiece W on both sides of the core material 201 is maintained by the pressing forces of the straight portions 31A and arc portions 32B of the first pressing member 3A and the second pressing member 3B, and the workpiece W is formed into a deformed pipe whose inner dimensions follow the outer dimensions of the core material 201 (see FIG. 4(H)).

[0062] As described above, the tube forming apparatus 100 uses a core material 1 that corresponds to the cross-sectional shape of the tube to be formed, making it possible to form tubes of any non-circular cross-sectional shape, not limited to circular, rectangular, or D-shaped. Furthermore, by using a holder 6 whose length matches the axial length of the tube to be formed, it is possible to prevent the core material 1 from bending even when the workpiece W has a high hardness, and it is possible to reliably form a long tube of any non-circular cross-sectional shape.

[0063] 5, a tube forming apparatus 200 according to a second embodiment of the present invention includes a selection mechanism 211 instead of the selection mechanism 11 of the tube forming apparatus 100, and the holder 6 of the tube forming apparatus 100 is eliminated, but other configurations are the same as those of the tube forming apparatus 100. In accordance with the elimination of the holder 6, the selection mechanism 211 omits the holder cylinder 13 and holder link 16 from the selection mechanism 11. The tube forming apparatus 200 forms a workpiece W, which is a rectangular flat plate made of low-hardness metal, into a short tube with a circular cross section.

[0064] In the selection mechanism 11, by selectively supplying fluid to the straightener cylinder 12, the upper surface of the straightener 5 comes into contact with the lower surface of the pressing part 142, and the straightening surface 51 faces the circumferential surface of the core material 1. The tube forming device 200, via the selection mechanism 211, selectively causes the straightening surface 51 to face the circumferential surface of the core material 1 during tube forming.

[0065] When a workpiece W, which is a rectangular flat plate made of low-hardness metal, is formed into a short pipe with a circular cross section using the pipe forming apparatus 200, no bending occurs in the core material 1. Therefore, when forming a pipe using the pipe forming apparatus 200, the pressing of the core material 1 by the holder 6 shown in Figures 2(C) to (E) is omitted, as shown in Figure 6. When a workpiece W, which is a rectangular flat plate made of low-hardness metal, is formed into a short square pipe or a short irregular pipe with a D-shaped cross section, the pressing of the core material 1 by the holder 6 shown in Figures 3(C) to (E) and 4(C) to (E) can also be omitted. [Explanation of symbols]

[0066] 1-Core material 2-Abutting body 3A-First pressing material 3B-Second pressing material 4A-1st rotation mechanism 4B - Second rotation mechanism 5- Correction body 6-Holding body 7-Pressing mechanism 8-Displacement mechanism 9A-1st biasing mechanism 9B-Second biasing mechanism 10-Third biasing mechanism 11-Selection mechanism

Claims

1. a columnar core material having a uniform cross-sectional shape along its axial direction and restricted from rotating about its axis; a contact body that is capable of moving relatively toward and away from the core material along a reference direction that is a specific radial direction of the core material, and that has a contact surface that faces the entire axial direction of the core material and that clamps a plate-shaped workpiece between the core material and the contact surface along the reference direction; a first pressing member and a second pressing member, each of which is a columnar body having a uniform cross-sectional shape along the axial direction and a cross-sectional shape including a straight portion and an arc portion on the outer periphery, the first pressing member and the second pressing member being arranged parallel to the core member and being movable toward and away from each other across the reference direction within a reference plane perpendicular to the reference direction; a first rotation mechanism and a second rotation mechanism that selectively cause the linear portion or the arc portion of the first pressing member and the second pressing member to face the core member; a corrector supported on the core material so as to be movable relative to the core material along the reference direction, the corrector including a correcting surface that faces the core material across the entire axial range on the opposite side of the contact body with the core material sandwiched therebetween and that follows the peripheral surface of the workpiece sandwiched between the contact surface and the core material; and a pressing mechanism that clamps the workpiece between the core material and the contact surface; a displacement mechanism that displaces a relative position in the reference direction between the workpiece sandwiched between the core material and the abutment surface and the reference surface; a first biasing mechanism and a second biasing mechanism that bias the first pressing member and the second pressing member in directions toward each other while the workpiece sandwiched between the core member and the abutment surface moves from an initial position sandwiching the reference surface toward a completion position due to the displacement of the relative positions; a third biasing mechanism that sandwiches both ends of the work between the first pressing member and the second pressing member that are spaced apart from each other after the work reaches the completion position, and presses the correction surface against the circumferential surface of the core member; A tube forming device comprising:

2. A tube molding device as described in claim 1, comprising: a holding body having a holding surface that faces the core material over the entire axial range on the opposite side of the abutment body across the core material, and supported so as to be freely movable relative to the core material along the reference direction; and a fourth biasing mechanism that presses the holding surface against the peripheral surface of the core material by displacement of the relative position, from an initial position where the work clamped between the core material and the abutment surface sandwiches the reference surface, at least until it passes through the reference surface.

3. A tube molding device as described in claim 2, further comprising a selection member that supports the straightening body and the holding body so that they can be moved freely along the reference direction and that selectively faces either the straightening surface or the holding surface toward the core material, and the third biasing mechanism also serves as the fourth biasing mechanism.

4. 4. The tube forming apparatus according to claim 1, wherein the displacement mechanism moves the core material between the initial position and the completed position of the workpiece along the reference direction.

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