Ball forming device and pipe expansion processing method

Abstract

To provide a ball forming device which enables easy processing for expanding a diameter of an intermediate portion in an axial direction of a workpiece having a circular pipe shape, and to provide a pipe expansion processing method.SOLUTION: A ball forming device includes: a first insertion part and a second insertion part which can be inserted into a workpiece having a circular pipe shape along an axis; and a plurality of balls held between the first insertion part and the second insertion part. In the first insertion part, an inclined surface in which a diameter is reduced toward the second insertion part side in an axial direction is formed. The first insertion part and the second insertion part can rotate around the axis relative to each other. When the first insertion part and the second insertion part rotate relative to each other, the plurality of balls can rotate around the axis relative to the workpiece. Further, the first insertion part and the second insertion part move close to each other in the axial direction by operation of a screw mechanism to move the plurality of balls to a radial outer side along the inclined surface.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a ball forming apparatus and a tube expansion method. [Background technology]

[0002] Non-Patent Document 1 discloses a processing technology in which multiple rollers are pressed against the inner peripheral surface of a metal tube from the inner peripheral side and revolved to iron the wall of the metal tube and change (thin) its thickness (wall thickness). When processing the wall of the metal tube to be thin, the outer peripheral surface of the metal tube is supported by abutting against the inner peripheral surface of the processing equipment, preventing the wall from deforming toward the outer peripheral side due to the pressing force of each roller. In the technology of Non-Patent Document 1, the outer diameter of the metal tube remains constant. On the other hand, Non-Patent Document 2 discloses a processing technology in which a metal tube is placed inside a rotating die, a tool holding multiple rollers is inserted into the metal tube, and the rollers are pressed against the inner surface of the metal tube while it revolves, thereby squeezing the wall of the metal tube and changing (expanding) the diameter. This processing method, in which multiple rotating elements such as rollers rotate and revolve simultaneously to squeeze the tube wall and plastically deform the tube wall to create high-performance circular tubes, is called "planetary conical rolling" (PCR processing). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Eugen Wiens, Werner Homberg, “Internal Flow-Turning - a new approach for the manufacture of tailored tubes with a constant external diameter”, Procedia Engineering, 2017, p.1755-1760 [Non-Patent Document 2] Toshihiko Mori, Yuji Saito, Kunihiko Nakajima, "Effect of tube expansion in PCR processing", Transactions of the Japan Society of Mechanical Engineers, Vol. 62, No. 601, 1996, pp. 3676-3683 Summary of the Invention [Problem to be solved by the invention]

[0004] As mentioned above, the process of expanding the diameter of metal tubes is mainly used for the purposes of reducing the weight of heat exchanger joints and automobile shafts, and as a pretreatment for hydroforming, and various processing methods have been developed. However, existing processing methods require large processing equipment, and when considering pipe joints, for example, processing cannot be easily performed at the piping site, etc. In addition, it is difficult to expand the diameter of the axial middle part of the metal pipe. The present invention has been made in consideration of the above circumstances, and provides a ball forming apparatus and a tube expansion method that can easily perform processing to expand the diameter of the axial middle portion of a cylindrical workpiece. [Means for solving the problem]

[0005] As a means for solving the above problem, a first aspect of the present invention provides a ball forming device comprising: a first insertion portion that can be inserted along the axis into a tubular workpiece; a second insertion portion that is supported by the first insertion portion via a screw mechanism that converts rotational motion about the axis into axial movement along the axis and can be inserted into the workpiece alongside the first insertion portion in the axial direction; and a plurality of spheres that are held between the first insertion portion and the second insertion portion and can be inserted into the workpiece together with the first insertion portion and the second insertion portion, wherein at least one of the first insertion portion and the second insertion portion is formed with an inclined surface that inclines so that the diameter decreases as it approaches the other side in the axial direction, the first insertion portion and the second insertion portion are rotatable relative to each other about the axis, and during the relative rotation of the first insertion portion and the second insertion portion, the plurality of spheres can rotate about the axis with respect to the workpiece, and the first insertion portion and the second insertion portion approach each other in the axial direction by operation of the screw mechanism, moving the plurality of spheres radially outward along the inclined surface. According to this configuration, the first and second insertion parts are inserted into the workpiece, the plurality of spheres are disposed in the axial middle of the workpiece, and the first and second insertion parts are rotated relative to each other to move the plurality of spheres radially outward while rotating (revolving) relative to the workpiece. The plurality of spheres rotate relative to the workpiece and eventually press the pipe wall of the workpiece from the inner circumferential side. As a result, each sphere gradually bulges and deforms the pipe wall radially outward over the entire circumference of the workpiece, forming a bulge in the axial middle of the pipe wall. In this way, the pipe expansion process can be easily performed on the axial middle of the workpiece by a single operation of rotating the first and second insertion parts relative to each other using a tool or the like. In addition, since there is only one input, the configuration of the processing machine is simple and it can be easily used, for example, at a piping construction site.

[0006] A second aspect of the present invention is a workpiece holder capable of holding a workpiece in the first aspect described above, wherein the first insertion portion is supported on the workpiece holder via a second screw mechanism that converts rotational motion about the axis into axial movement, and the screw mechanism can be tightened to a specified stop position to fix the first insertion portion and the second insertion portion in an axially close state to each other, and the assembly including the first insertion portion and the second insertion portion fixed by the screw mechanism moves axially while rotating about the axis relative to the workpiece by operation of the second screw mechanism. According to this configuration, first, the assembly of the first and second insertion parts and each sphere is inserted into the inside of the workpiece, and while rotating (revolving) each sphere around the axis center with respect to the workpiece, it is moved radially outward along the inclined surface, and the pipe wall of the workpiece is pressed from the inner peripheral side to cause bulging deformation. After that, the screw mechanism is tightened to a stop position to fix the first and second insertion parts in a state close to each other, and in this state, the assembly including the first and second insertion parts is moved in the axial direction while rotating around the axis center with respect to the workpiece by the operation of the second screw mechanism, so that each sphere moves in the axial direction while squeezing the inner surface of the pipe wall of the workpiece from the inner peripheral side, and the pipe wall of the workpiece is bulged and deformed widely over a predetermined range in the axial direction. In this way, a single operation of rotating the assembly and the workpiece holder relative to each other using a tool or the like can easily perform a wide pipe expansion process on the axial middle part of the workpiece. In addition, since there is only one input, the configuration of the processing machine is simple and it can be easily used, for example, at a piping construction site.

[0007] A third aspect of the present invention is the same as the second aspect, further comprising a stop position adjustment mechanism that can adjust the stop position of the screw mechanism. According to this configuration, by making the stopping position of the screw mechanism adjustable, it becomes possible to adjust the axial position of the sphere (the position where the bulge of the workpiece is formed) when the first insertion portion and the second insertion portion are closest to each other in the axial direction, thereby improving the freedom of machining of the workpiece.

[0008] A fourth aspect of the present invention provides a tube expansion method in which a first insertion portion, a second insertion portion supported on the first insertion portion via a screw mechanism that converts rotational motion about the axis into axial movement along the axis, and a plurality of spheres held between the first insertion portion and the second insertion portion are inserted into a tubular workpiece, an inclined surface is formed on at least one of the first insertion portion and the second insertion portion such that the diameter decreases as it approaches the other in the axial direction, the first insertion portion and the second insertion portion are rotated relative to each other about the axis, the plurality of spheres are rotated about the axis with respect to the workpiece, and the first insertion portion and the second insertion portion are brought closer to each other in the axial direction by operating the screw mechanism, and the plurality of spheres are moved radially outward along the inclined surface. According to this configuration, the first and second insertion parts are rotated relative to each other, and the multiple spheres are moved radially outward while rotating (revolving) relative to the workpiece. As a result, each sphere gradually bulges and deforms the pipe wall radially outward over the entire circumference of the workpiece, forming a bulge in the axial middle portion of the pipe wall. In this way, a single operation of rotating the first and second insertion parts relative to each other using a tool or the like can easily perform pipe expansion processing on the axial middle portion of the workpiece. In addition, since there is only one input, the configuration of the processing machine is simple and it can be easily used, for example, at a piping construction site.

[0009] A fifth aspect of the present invention is a fourth aspect in which the first insertion portion is supported on a work holder that holds a workpiece via a second screw mechanism that converts rotational motion about the axis into axial movement, and the screw mechanism is tightened to fix the first insertion portion and the second insertion portion in an axially close position to each other. With the first insertion portion and the second insertion portion fixed in an axially close position to each other, the assembly including the first insertion portion and the second insertion portion is moved axially while being rotated about the axis relative to the workpiece by operating the second screw mechanism. According to this configuration, the pipe wall of the workpiece is pressed from the inner periphery side to cause a bulging deformation, and the assembly including the first and second insertion parts is moved axially while rotating about the axis center relative to the workpiece by operating the second screw mechanism, thereby causing the pipe wall of the workpiece to bulge widely over a predetermined range in the axial direction. In this way, a single operation of relatively rotating the assembly and the workpiece holder using a tool or the like can easily perform a wide pipe expansion process on the axial middle part of the workpiece. In addition, since there is only one input, the configuration of the processing machine is simple and it can be easily used, for example, at a piping construction site. Effect of the Invention

[0010] According to the present invention, it is possible to provide a ball forming apparatus and a tube expansion method that can easily perform processing to expand the diameter of the axial middle portion of a cylindrical workpiece. [Brief description of the drawings]

[0011] [Figure 1]FIG. 2 is an axial cross-sectional view of the ball forming apparatus according to the embodiment of the present invention, showing a state in which the sphere is in an inner position. [Diagram 2] FIG. 2 is a partially enlarged view of FIG. 1, showing the function of the inclined surface. [Diagram 3] FIG. 2 is a cross-sectional view corresponding to FIG. 1, showing the sphere in the outer position. [Figure 4] 4 is a cross-sectional view corresponding to FIG. 1, showing a state in which the sphere has moved axially from the expanded diameter state of FIG. 3. [Diagram 5] FIG. 2 is a side view of components of the ball forming device as viewed from a radial direction. [Figure 6] 3 is a side view of a metal tube seen from a radial direction before being expanded by the ball forming device. FIG. [Figure 7] 2 is a side view of a metal tube that has been subjected to a first expansion process by the ball forming device, as viewed from a radial direction. FIG. [Figure 8] 1 is a side view of a metal tube that has been subjected to a second expansion process by the ball forming device, as viewed from a radial direction. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An embodiment of the present invention will be described below with reference to the drawings, but the scope of the present invention is not limited to the embodiment described here, and various modifications can be made without departing from the spirit of the present invention. The term "middle" used in this embodiment includes not only the center between both ends of an object, but also an inner part and a predetermined range between both ends of an object.

[0013] 1 and 6 to 8, a ball forming apparatus 1 according to an embodiment is used as a tool for making pipe joints at a piping site of a heat exchanger, for example. The ball forming apparatus 1 has a substantially cylindrical appearance, and a cylindrical metal tube (hereinafter referred to as a workpiece W) of a predetermined length is coaxially arranged inside. The ball forming apparatus 1 is capable of forming bulging portions (enlarged diameter portions) WB1, WB2 (see Figs. 7 and 8) that bulge outward toward the outer periphery at the axially intermediate portion of the workpiece W. In the drawings, a line C1 indicates the central axis of the ball forming apparatus 1, a line C2 indicates the central axis of the workpiece W, and a symbol Wa indicates the cylindrical pipe wall of the workpiece W, respectively.

[0014] Unless otherwise specified, the following description will be made with reference to a state in which a workpiece W is coaxially arranged on the ball forming apparatus 1 (the state shown in Figs. 1 to 4). In this state, the direction along the central axis C1 (and C2) is the axial direction of the ball forming apparatus 1 (and workpiece W), the direction perpendicular to the axis C1 (and C2) is the radial direction of the ball forming apparatus 1 (and workpiece W), and the direction around the center of the axis C1 (and C2) is the circumferential direction of the ball forming apparatus 1 (and workpiece W). In addition, "around the axis C1 (and C2)" means "around the axis C1 (and C2)".

[0015] <Ball forming device 1> The ball forming apparatus 1 includes a workpiece retainer 10, a first assembly 20, a second assembly 30, and a plurality of (for example, four) spheres (balls) 41.

[0016] <Work holder 10> The workpiece holder 10 has a cylindrical shape capable of holding a predetermined length of workpiece W on its inner circumference. The workpiece holder 10 includes a cylindrical outer cylinder 11 centered on an axis C1, and an inner cylinder 15 that is cylindrical and coaxial with the outer cylinder 11 and is inserted into one axial end of the outer cylinder 11 with a clearance fit tolerance.

[0017] The outer tube 11 has a diameter dimension according to the outer diameter and the expansion dimension of the workpiece W. The inner tube 15 is inserted into the inside of one axial end side of the outer tube 11. A plurality of (four) first nut holes 12a are formed at one axial end side of the outer tube 11, penetrating the peripheral wall in the radial direction. The first nut holes 12a are arranged at equal intervals in the circumferential direction. An inner tube fixing bolt B1 is fastened into each of the first nut holes 12a from the outer periphery side of the outer tube 11. Each inner tube fixing bolt B1 abuts a tip t1 against the outer periphery surface of the inner tube 15 fitted into the outer tube 11. In this state, the inner tube fixing bolt B1 is fastened to fix the peripheral wall of the inner tube 15 at one axial end side within the outer tube 11.

[0018] In the embodiment, a step 12c is formed in the axial middle portion of the inner peripheral surface of the outer tube 11, against which the outer peripheral edge portion of the other axial end side of the inner tube 15 abuts. The step 12c allows the axial position of the inner tube 15 to be determined. The inner tube 15 can be disposed in an axial position where the tip t1 of each inner tube fixing bolt B1 can abut without interfering with the step 12c, etc., and can be fixed at this position by the inner tube fixing bolt B1. The inner tube 15 allows one axial end of the workpiece W to abut against the other axial end, and the axial position of the workpiece W can be determined. If the axial position of the inner tube 15 is changed, the axial position of the workpiece W can be changed, and the formation positions of the bulges WB1 and WB2 in the workpiece W can be adjusted.

[0019] At the other axial end of the outer tube 11, an outer tube reduced diameter portion 13 having an increased thickness on the inner circumferential side is formed. The outer tube reduced diameter portion 13 forms a cylindrical inner circumferential surface 13a centered on the axis C1. The workpiece W is inserted into the outer tube reduced diameter portion 13 with a clearance fit tolerance. At the other axial end side of the outer tube 11, a plurality of (for example, four) second nut holes 12b are formed radially penetrating a portion including the outer tube reduced diameter portion 13. The plurality of second nut holes 12b are formed in a line at equal intervals in the circumferential direction. A workpiece fixing bolt B2 is respectively fastened into each second nut hole 12b from the outer circumferential side of the outer tube 11. Each workpiece fixing bolt B2 abuts a tip t2 against the outer circumferential surface of the workpiece W fitted into the outer tube reduced diameter portion 13. By fastening each workpiece fixing bolt B2 in this state, the pipe wall Wa at the other axial end side of the workpiece W is fixed in the outer tube reduced diameter portion 13.

[0020] With the workpiece W fixed in the outer tube narrowing portion 13, the region formed between the outer tube narrowing portion 13 and the inner tube 15 in the axial direction becomes the tube expansion processing region R1. In the tube expansion processing region R1, a radial gap is formed between the tube wall Wa of the workpiece W and the peripheral wall of the outer tube 11. This gap makes it possible to form bulging portions WB1 and WB2 that bulge outward from the middle portion of the workpiece W held by the workpiece holder 10. In the tube expansion processing region R1, a tapered surface (inclined surface) 23 of the boss 21 described later is disposed. By causing each sphere 41 for tube expansion to ride up onto this tapered surface 23, each sphere 41 moves outward in the radial direction, and it is possible to bulge the axial middle portion of the tube wall Wa of the workpiece W.

[0021] At the other axial end of the inner tube 15, an inner tube reduced diameter portion 17 is formed with an increased thickness on the inner peripheral side. The inner tube reduced diameter portion 17 forms a cylindrical inner peripheral portion centered on the axis C1. The inner peripheral portion is a female screw portion 18 on which a screw thread is formed. The boss 21 of the first assembly 20 is disposed on the inner peripheral side of the female screw portion 18. The outer peripheral portion of the boss 21 is a male screw portion 24 on which a screw thread corresponding to the female screw portion 18 is formed. The female screw portion 18 of the inner tube 15 and the male screw portion 24 of the boss 21 form a second screw mechanism 45 that converts the rotational motion about the axis C1 into axial movement. The inner tube 15 (workpiece holder 10) supports the boss 21 (first insertion portion 21a) via the second screw mechanism 45.

[0022] 5, the inner cylinder 15 is inserted into and removed from the outer cylinder 11 along the axial direction while being connected to the first assembly 20 via the second screw mechanism 45. At this time, the second assembly 30 is connected to the first assembly 20 via the first screw mechanism 43, and a plurality of spheres 41 are held in the tubes of the first assembly 20 and the second assembly 30. This assembly is inserted into and removed from the outer cylinder 11 from one axial side (the left side in the figure).

[0023] <First assembly 20> 1 to 5, the first assembly 20 includes a boss 21, a first bolt 25, and a pair of nuts 27. The boss 21 is supported within the inner cylinder 15 and functions as a first insertion portion 21a that can be inserted along the axis C1 into the inside of the workpiece W. The boss 21 is cylindrical and centered on the axis C1, and has a nut hole 22 along the axial direction. The other axial end of the boss 21 is formed with a truncated cone-shaped tapered surface 23 that tapers in diameter as it approaches the second insertion portion 31a (ball holding portion 31) on the right side in the figure (as it is positioned to the right in the figure).

[0024] The tapered surface 23 faces in the axial direction the plurality of spheres 41 held between the first insertion portion 21a and the second insertion portion 31a. In the state shown in Fig. 1 and Fig. 5 (hereinafter referred to as the initial state S1), the tapered surface 23 is capable of moving away from the plurality of spheres 41 in the axial direction. At this time, each sphere 41 is capable of moving to an inner position P1 spaced away from the pipe wall Wa of the workpiece W toward the inner periphery, and is capable of being inserted into the workpiece W together with the first insertion portion 21a and the second insertion portion 31a.

[0025] In the state shown in Fig. 3 (hereinafter referred to as the expanded diameter state S2), the tapered surface 23 abuts the multiple spheres 41 in the axial direction and rides up radially outward. The state shown in Fig. 3 is a state in which the first screw mechanism 43 is tightened to move the multiple spheres 41 to an outer position P2 on the radially outer side, thereby forming a round bead-shaped bulging portion WB1 in the workpiece W. In the cross-sectional view of Fig. 3, the tapered surface 23 is linear, but the tapered surface 23 may have a curvature.

[0026] When the ball forming apparatus 1 is in the process of transitioning from the initial state S1 to the expanded diameter state S2, the first screw mechanism 43 is further tightened from the state in which the plurality of spheres 41 abut against the tapered surface 23, thereby achieving the following action. That is, the plurality of spheres 41 ride up onto the tapered surface 23, and move radially outward (toward the outer periphery) along the inclination of the tapered surface 23. The plurality of spheres 41 are driven by the ball holding portion 31 that rotates integrally with the second bolt 35 of the first screw mechanism 43, and move in the axial direction while rotating (revolving) (that is, rotate spirally along the thread of the second bolt 35).

[0027] The multiple spheres 41 move outward and come into contact with the inner peripheral surface of the workpiece W, and then the second bolt 35 is further tightened, causing the multiple spheres 41 to rotate integrally with the second bolt 35 while pressing the pipe wall Wa of the workpiece W outward with a force equal to or greater than a specified value. As a result, a bulging portion WB1 that bulges outward is formed in the axially intermediate portion of the pipe wall Wa of the workpiece W. The bulging portion WB1 is formed in a round bead shape along the circumferential direction by the multiple spheres 41 pressing the pipe wall Wa while rotating (revolving) about the axis C1.

[0028] In the first assembly 20, a tip 25c side of a neck (screw shaft) 25b of a first bolt 25 coaxial with the boss 21 is fastened to one axial end side of a nut hole 22 of the boss 21. A pair of nuts 27 are screwed onto the first bolt 25 between a head 25a of the first bolt 25 and one axial end of the boss 21. The pair of nuts 27 are fixed to the first bolt 25 by the action of a double nut. The pair of nuts 27 make it possible to adjust the fastening depth of the first bolt 25 into the boss 21.

[0029] The position where the first bolt 25 is fastened into the nut hole 22 (the position of the tip 25c) defines a stop position 43a of the first screw mechanism 43, which will be described later. That is, the first bolt 25, the nut hole 22 of the boss 21, and the pair of nuts 27 are included in a stop position adjustment mechanism 29 that makes it possible to adjust the stop position 43a of the first screw mechanism 43. By fastening the first screw mechanism 43 to the stop position 43a, an assembly including the first assembly 20, the second assembly 30, and each of the spheres 41 is substantially integrated. The head 25a of the first bolt 25 protrudes toward one axial end of the work holder 10.

[0030] <Second assembly 30> 1 to 5, the second assembly 30 includes a ball holding portion 31, a second bolt 35, a collar 37, and a nut . The ball retaining portion 31 is disposed on the other axial side of the boss 21, and functions as a second insertion portion 31a that can be inserted axially together with the boss 21 into the workpiece W. The ball retaining portion 31 rotatably retains a plurality of spheres 41 between itself and the tapered surface 23 of the boss 21 in the axial direction, and also retains the plurality of spheres 41 so that they can revolve. The ball retaining portion 31 has retaining claws 32 extending between each pair of spheres 41 adjacent in the circumferential direction. The ball retaining portion 31 rotates integrally with the second bolt 35, thereby applying a driving force in the revolution direction to each sphere 41.

[0031] The ball retaining portion 31 has a bottom portion 33 that abuts against each of the spheres 41 from the other axial end side. The bottom portion 33 presses each of the spheres 41 toward the tapered surface 23 when the second bolt 35 is fastened. In a state in which the first assembly 20 and the second assembly 30 are assembled (see FIG. 5), the ball retaining portion 31 retains a plurality of spheres 41 between itself and the boss 21, and is inserted into the workpiece W together with each of the spheres 41. At this time, each of the spheres 41 is spaced from the tapered surface 23 of the boss 21 (initial state S1).

[0032] When each sphere 41 is inserted into the workpiece W, the first screw mechanism 43 is tightened, causing the ball holding portion 31 and the multiple spheres 41 to move to one axial side while rotating (revolving), until each sphere 41 abuts against the tapered surface 23. When the first screw mechanism 43 is further tightened after the multiple spheres 41 have come into contact with the tapered surface 23, each sphere 41 rides up onto the tapered surface 23 and moves radially outward (toward the outer periphery) and comes into contact with the inner surface of the pipe wall Wa of the workpiece W.

[0033] When the first screw mechanism 43 is further tightened from the state where each steel ball 41 is in contact with the pipe wall Wa of the work W, each ball 41 revolves while pressing the pipe wall Wa of the work W toward the outer periphery, gradually expanding the axial middle portion of the pipe wall Wa toward the outer periphery. As a result, an annular bulged portion WB1 is formed in the axial middle portion of the pipe wall Wa. This pipe expansion process is performed by a single operation input of tightening the head 35a of the second bolt 35. The head 35a of the second bolt 35 protrudes toward the other axial end side of the work holder 10.

[0034] The second assembly 30 has a ball retaining portion 31 screwed to a neck (screw shaft) 35b of a second bolt 35 that is coaxial with the boss 21 of the first assembly 20. A nut 38 is screwed to the head 35a side between the ball retaining portion 31 and the head 35a of the second bolt 35, and a collar 37 is attached to the ball retaining portion 31 side. The ball retaining portion 31 and the nut 38 are fixed to the second bolt 35 by the action of a double nut that sandwiches the collar 37. For example, the collar 37 is available in a plurality of axial lengths.

[0035] By changing the axial length of collar 37, it is possible to adjust the axial distance between tapered surface 23 of boss 21 and ball retaining portion 31 without relying on operation of first screw mechanism 43. In other words, it is possible to adjust the fixed position of ball retaining portion 31 relative to second bolt 35. Second bolt 35, ball retaining portion 31, collar 37 and nut 38 are included in distance adjustment mechanism 39 that makes it possible to adjust the axial distance between tapered surface 23 and ball retaining portion 31.

[0036] A tip 35c side of a neck portion 35b of the second bolt 35 is fastened to the other axial end side of a nut hole 22 of the boss 21. The second bolt 35 and the nut hole 22 constitute a first screw mechanism 43 that converts rotational motion about the axis C1 into axial movement. The boss 21 (first insertion portion 21a) supports (couples) the ball retaining portion 31 (second insertion portion 31a) via the first screw mechanism 43.

[0037] <Sphere 41> 1 to 5, the plurality of spheres 41 are sandwiched and held between the tapered surface 23 of the boss 21 and the bottom portion 33 of the ball holding portion 31 in the axial direction. In an initial state S1 (see FIGS. 1 and 2) before the first screw mechanism 43 is fastened, the plurality of spheres 41 can be inserted into the workpiece W along the axis C1 together with the first insertion portion 21a and the second insertion portion 31a. In the initial state S1, the second bolt 35 is fastened into the boss 21 by a specified amount, and the first assembly 20 and the second assembly 30 can be handled in an assembled state.

[0038] In a state where the first assembly 20 and the second assembly 30 are assembled together (see FIG. 5), the plurality of spheres 41 are restricted from coming off radially outward by the plurality of holding claws 32, so that the first assembly 20, the second assembly 30, and the plurality of spheres 41 can be handled as a whole. For example, the holding claws 32 may only restrict the circumferential movement of the spheres 41, and the radially outward coming off of the spheres 41 may be restricted on the inside of the tube when the spheres 41 are inserted into the workpiece W. For example, each sphere 41 is a steel ball, but any material may be used as long as it is capable of expanding and deforming the workpiece W.

[0039] <effect> In the first processing stage, the ball forming apparatus 1 of the embodiment moves each sphere 41 mainly radially outward (toward the outer periphery) while revolving (more specifically, moves each sphere 41 radially outward along the tapered surface 23). By moving toward the outer periphery while revolving, each sphere 41 presses the pipe wall Wa of the workpiece W from the inner periphery side to the outer periphery side while moving in the circumferential direction, and gradually causes the pipe wall Wa of the axially intermediate portion of the metal pipe to bulge (plastically deform) toward the outer periphery.

[0040] When the tip 35c of the second bolt 35 abuts against the tip 25c of the first bolt 25, the first screw mechanism 43 is restricted from being further tightened, and each sphere 41 moves to its maximum outer periphery position (expanded diameter state S2). The tip 25c of the first bolt 25 defines a stop position 43a for tightening the first screw mechanism 43. This stop position 43a can be adjusted according to conditions such as the height of the bulges WB1, WB2 to be formed in the workpiece W.

[0041] After each sphere 41 reaches its maximum outer periphery position, the ball forming apparatus 1 operates the second screw mechanism 45 as a second processing stage, and moves the first assembly 20, the second assembly 30, and each sphere 41 in the axial direction while rotating (revolving) them together. Since the assembly including the first assembly 20, the second assembly 30, and each sphere 41 is integrated by tightening the first screw mechanism 43 to the stop position 43a, the assembly can be easily rotated by rotating the first bolt 25.

[0042] At this time, the assembly can move within a predetermined range in the axial direction while rotating in the expanded diameter state S2. The state after this movement is shown in Fig. 4 as an axial movement state S3. In the axial movement state S3, a wide and flat bulging portion WB2 that forms a top surface parallel to the axis C1 is formed in a predetermined range in the axial middle portion of the workpiece W.

[0043] When performing the above-mentioned tube expansion process, the revolution, radial movement, and axial movement of the multiple spheres 41 are each realized by one input (rotation operation) at each processing stage. In this way, by using the ball forming device 1 with a simple mechanism, it is possible to perform tube expansion of the workpiece W at, for example, a piping construction site. Furthermore, the present invention can be widely used in industry to manufacture various tube parts such as automobile shafts and exhaust manifolds, as well as various tube parts for medical equipment, etc.

[0044] As described above, the ball forming apparatus 1 in the above embodiment includes the workpiece holder 10 capable of holding a tubular workpiece W, the first insertion portion 21a supported by the workpiece holder 10 and capable of being inserted into the workpiece W along the axis C1, the second insertion portion 31a supported by the first insertion portion 21a via a first screw mechanism 43 that converts rotational motion about the axis C1 into axial movement along the axis C1 and capable of being inserted into the workpiece W side by side with the first insertion portion 21a in the axial direction, and the second insertion portion 31a held between the first insertion portion 21a and the second insertion portion 31a and capable of being inserted into the workpiece W together with the first insertion portion 21a and the second insertion portion 31a. and a plurality of insertable spheres 41, and at least one of the first insertion portion 21a and the second insertion portion 31a has a tapered surface 23 that is inclined so that the diameter decreases as it is positioned toward the other side in the axial direction, and the first insertion portion 21a and the second insertion portion 31a are rotatable relative to each other about the axis C1, and when the first insertion portion 21a and the second insertion portion 31a rotate relative to each other, the plurality of spheres 41 can rotate about the axis C1 with respect to the workpiece W, and operation of the first screw mechanism 43 brings the first insertion portion 21a and the second insertion portion 31a closer to each other in the axial direction, moving the plurality of spheres 41 radially outward along the tapered surface 23.

[0045] The tube expansion method using the ball forming apparatus 1 includes inserting a first insertion portion 21a, a second insertion portion 31a supported by the first insertion portion 21a via a first screw mechanism 43 that converts rotational motion about the axis C1 into axial movement along the axis C1, and a plurality of spheres 41 held between the first insertion portion 21a and the second insertion portion 31a into a cylindrical workpiece W, forming a tapered surface 23 on at least one of the first insertion portion 21a and the second insertion portion 31a that is inclined so that the diameter decreases as it approaches the other side in the axial direction, and rotating the first insertion portion 21a and the second insertion portion 31a relatively around the axis C1 to rotate the plurality of spheres 41 around the axis C1 with respect to the workpiece W, and operating the first screw mechanism 43 to bring the first insertion portion 21a and the second insertion portion 31a closer to each other in the axial direction, and moving the plurality of spheres 41 radially outward along the tapered surface 23.

[0046] According to this configuration, the first inserting portion 21a and the second inserting portion 31a are inserted into the workpiece W, the plurality of spheres 41 are disposed in the axial middle portion of the workpiece W, and the first inserting portion 21a and the second inserting portion 31a are rotated relative to each other, so that the plurality of spheres 41 are moved radially outward while rotating (revolving) relative to the workpiece W. The plurality of spheres 41 rotate relative to the workpiece W and eventually press the pipe wall Wa of the workpiece W from the inner circumferential side. As a result, each sphere 41 gradually bulges and deforms the pipe wall Wa radially outward over the entire circumference of the workpiece W, forming a bulging portion WB1 in the axial middle portion of the pipe wall Wa. In this way, the pipe expansion processing can be easily performed in the axial middle portion of the workpiece W by a single operation of relatively rotating the first inserting portion 21a and the second inserting portion 31a using a tool or the like. In addition, since there is only one input, the configuration of the processing machine is simple and it can be easily used, for example, at a piping construction site.

[0047] In addition, in the above-mentioned ball forming apparatus 1, the first insertion portion 21a is supported on the work holder 10 via a second screw mechanism 45 that converts rotational motion about the axis C1 into axial movement, and the first screw mechanism 43 can be tightened to a specified stop position 43a to fix the first insertion portion 21a and the second insertion portion 31a in an axially close state to each other, and the assembly including the first insertion portion 21a and the second insertion portion 31a fixed by the first screw mechanism 43 moves axially while rotating about the axis C1 relative to the work W by operation of the second screw mechanism 45.

[0048] In the tube expansion processing method using the above-mentioned ball forming apparatus 1, the first insertion portion 21a is supported on the work holder 10 holding the workpiece W via a second screw mechanism 45 which converts the rotational motion about the axis C1 into axial movement, and the first screw mechanism 43 is tightened to fix the first insertion portion 21a and the second insertion portion 31a in an axially close position to each other. Then, by operating the second screw mechanism 45, the assembly including the first insertion portion 21a and the second insertion portion 31a is moved axially while being rotated about the axis C1 relative to the workpiece W.

[0049] According to this configuration, first, the assembly of the first insertion portion 21a, the second insertion portion 31a and the spheres 41 is inserted into the inside of the workpiece W, and while rotating (revolving) the spheres 41 around the axis C1 with respect to the workpiece W, they are moved radially outward along the tapered surface 23, pressing the pipe wall Wa of the workpiece W from the inner peripheral side to form the bulging portion WB1. Thereafter, the first screw mechanism 43 is tightened to the stop position 43a to fix the first insertion portion 21a and the second insertion portion 31a in a state close to each other, and in this state, the assembly is moved axially while rotating around the axis C1 by operating the second screw mechanism 45, so that the spheres 41 move axially while squeezing the inner surface of the pipe wall Wa of the workpiece W from the inner peripheral side, forming the bulging portion WB2 in which the pipe wall Wa of the workpiece W is bulged widely over a predetermined range in the axial direction. In this way, by a single operation of relatively rotating the assembly and the workpiece holder 10 using a tool or the like, it is possible to easily perform wide tube expansion processing on the axially middle portion of the workpiece W. Also, since there is only one input, the configuration of the processing machine is simple and it can be easily used, for example, at a piping construction site.

[0050] The ball forming apparatus 1 further includes a stop position adjustment mechanism 29 capable of adjusting the stop position 43a of the first screw mechanism 43. According to this configuration, by making the stop position 43a of the first screw mechanism 43 adjustable, it becomes possible to adjust the axial position of the sphere 41 (the position where the bulge portion of the workpiece W is formed) when the first insertion portion 21a and the second insertion portion 31a are closest to each other in the axial direction, thereby improving the freedom of machining the workpiece W.

[0051] In addition, the above-mentioned ball forming device 1 is provided with a distance adjustment mechanism 39 that can adjust the axial distance between one tapered surface 23 of the first insertion portion 21a and the second insertion portion 31a and the opposing insertion portion when the first screw mechanism 43 is in a specified tightening position. According to this configuration, by making it possible to adjust the axial distance between one of the tapered surfaces 23 of the first insertion portion 21a and the second insertion portion 31a and the opposing insertion portion, even if the tightening amount of the first screw mechanism 43 is the same, it becomes possible to adjust the amount of radially outward movement along the tapered surface 23 of each sphere 41, thereby improving the freedom of machining the workpiece W.

[0052] The present invention is not limited to the above embodiment. For example, the present invention is not limited to the configuration in which the tapered surface 23 is provided on the other axial side of the first insertion portion 21a, but may have the tapered surface 23 on one axial end of the second insertion portion 31a, or may have the tapered surface 23 on both the first insertion portion 21a and the second insertion portion 31a. The first screw mechanism 43 is not limited to a configuration in which the first insertion portion 21a side is fixed and the second insertion portion 31a side is rotated, but may be configured to fix the second insertion portion 31a side and rotate the first insertion portion 21a side. That is, it is sufficient that the first insertion portion 21a and the second insertion portion 31a are configured to be relatively rotatable. Similarly, the second screw mechanism 45 is not limited to a configuration in which the work holder 10 side is fixed and the first insertion portion 21a side is rotated, but may be configured to fix the first insertion portion 21a side and rotate the work holder 10 side. That is, it is sufficient that the work holder 10 and the first insertion portion 21a are configured to be relatively rotatable.

[0053] The ball forming apparatus 1 is not limited to a configuration capable of forming a flat bulge portion WB2 (capable of performing the second processing stage), but may be a configuration capable of forming only a bead-shaped bulge portion WB1 (capable of performing only the first processing stage). In other words, the second screw mechanism 45 may be omitted. The first assembly 20 is not limited to a configuration having a pair of nuts 27, and may be a configuration having a nut and a collar like the second assembly 30. Similarly, the second assembly 30 is not limited to a configuration having a nut 38 and a collar 37, and may be a configuration having a pair of nuts like the first assembly 20. The configurations in the above-described embodiments are merely examples of the present invention, and various modifications are possible without departing from the gist of the present invention, such as replacing the components of the embodiments with well-known components. [Explanation of symbols]

[0054] 1 Ball forming equipment 20 First assembly 21 Boss 21a First insertion part 23 Tapered surface (inclined surface) 29 Stop position adjustment mechanism 30 Second assembly 31 Ball holding section 31a Second insertion part 39 Distance adjustment mechanism 41 Sphere (Ball) 43 First screw mechanism (screw mechanism) 43a Stop position 45 Second screw mechanism WB1,WB2 Bulging part (expanded diameter part) C1,C2 Center axis line (axis line) W Work (metal pipe) Wa Pipe Wall

Claims

1. A first insertion portion that can be inserted into a tubular workpiece along an axis line; A second insertion portion that is supported by the first insertion portion via a screw mechanism that converts rotational motion about the axis line into axial movement along the axis line and can be inserted into the workpiece in line with the first insertion portion in the axial direction; A plurality of spheres are held between the first insertion portion and the second insertion portion and can be inserted into the workpiece together with the first insertion portion and the second insertion portion, At least one of the first insertion portion and the second insertion portion is formed with an inclined surface that is inclined so as to decrease in diameter toward the other side in the axial direction, The first insertion portion and the second insertion portion are relatively rotatable about the axis center, A ball forming device in which, when the first insertion portion and the second insertion portion rotate relative to each other, the multiple spheres can rotate around the axis center relative to the workpiece, and the first insertion portion and the second insertion portion approach each other in the axial direction by operation of the screw mechanism, moving the multiple spheres radially outward along the inclined surface.

2. A work holder capable of holding the workpiece is provided, The first insertion portion is supported by the workpiece retainer via a second screw mechanism that converts the rotational motion about the axis line into the movement in the axial direction, The screw mechanism can fix the first insertion portion and the second insertion portion in a state in which they are close to each other in the axial direction by being tightened to a specified stop position, The ball forming apparatus of claim 1, wherein an assembly including the first insertion portion and the second insertion portion fixed by the screw mechanism moves axially while rotating about the axis center relative to the workpiece by operation of the second screw mechanism.

3. The ball forming apparatus according to claim 2 , further comprising a stop position adjustment mechanism capable of adjusting the stop position of the screw mechanism.

4. A first insertion portion, a second insertion portion supported by the first insertion portion via a screw mechanism that converts rotational motion about an axis line into axial motion along the axis line, and a plurality of spheres held between the first insertion portion and the second insertion portion are inserted into a tubular workpiece; At least one of the first insertion portion and the second insertion portion is formed with an inclined surface that is inclined so as to decrease in diameter toward the other side in the axial direction, A tube expansion method is provided in which the first insertion portion and the second insertion portion are rotated relative to each other around the axis, the multiple spheres are rotated around the axis relative to the workpiece, and the screw mechanism is operated to bring the first insertion portion and the second insertion portion closer to each other in the axial direction, and the multiple spheres are moved radially outward along the inclined surface.

5. The first insertion portion is supported on a workpiece holder that holds the workpiece via a second screw mechanism that converts the rotational motion about the axis line into the movement in the axial direction; A tube expansion method as described in claim 4, wherein the screw mechanism is tightened to fix the first insertion portion and the second insertion portion in a position close to each other in the axial direction, and an assembly including the first insertion portion and the second insertion portion is moved axially while being rotated about the axis center relative to the workpiece by operating the second screw mechanism.

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