JP2013226598A - Method and device for twisting metal tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To process a twisting shape accurately and stably even if a twisting angle is large.SOLUTION: A recessed part 53 is formed by pressing each plane part 51 in a metal tube 5 toward a tube side by a roll pair 4a for forming a recessed part, when a metal tube 5 is transported in an order of a roll pair 4a for recessed part formation, a reference roll pair 4b, and a roll pair 4c for twisting, and a right edge or a left edge of the each plane part 51 is brought into contact with the plane from a substantially vertical direction by the reference roll pair 4b, the right edge or the left edge of each plane part 51 in the metal tube 5 is pressed by the roll pair 4c for twisting, which is provided by being rotated from a contact surface of the reference roll pair 4b to a circumferential direction outside the tube according to a desired twisting angle to a pitch of a pipe axis direction from the reference roll pair 4b.

Description

  The present invention relates to a torsion processing method and apparatus for a metal tube that twists in the outer peripheral direction of a metal tube having a polygonal cross section. is there.

  2. Description of the Related Art Conventionally, metal pipes having a polygonal cross section and twisted in the pipe outer peripheral direction around the pipe axis direction have been proposed. Such a twisted metal tube is expected to be applied to various applications such as vertical bars and piles of handrails, decorative members, and shock absorbing members.

  In order to actually twist the metal pipe having such a polygonal cross section in the pipe outer circumferential direction, for example, as shown in FIG. Four rolls 74 are arranged around the center. For example, the roll 74 is disposed at an angle such that the contact surface of the roll 74 and the flat portion 71 can be in surface contact with each other in parallel. Further, the contact position of the flat surface portion 71 with respect to the contact surface of the roll 74 is a portion of the flat surface portion 71 that is extremely close to the corner portion 72.

  A plurality of such roll pairs including four rolls 74 are provided in the tube axis direction. And about a mutual roll pair, the arrangement | positioning angle is shifted and arrange | positioned toward the pipe | tube outer peripheral direction centering | focusing on the pipe-axis direction. And the rotational force for conveying the metal pipe 7 to a pipe-axis direction is provided about at least one of the four rolls 74 in each roll pair, and this is driven. As a result, an external force in the direction of the arrow in the drawing is applied to the metal tube 7 and a clockwise torque is generated, which causes torsional deformation in the tube outer peripheral direction.

  By the way, when attention is paid to one flat surface portion 71a, this flat surface portion 71a can be considered as a model of a beam having one end fixed. The external force P actually applied to the flat surface portion 71a from the outside via the roll 74 is in the same direction as the extending direction of the flat surface portion 71a, as shown in FIG. As a result, when the external force applied to the flat portion 71 exceeds the buckling load (= Pcr), the flat portion 71 is buckled. This buckling load Pcr depends on the material strength and material, the length and thickness of the flat portion 71, and also the curvature at the corner portion 72, but until the flat portion 71 exceeds Pcr and starts buckling. A considerable external force P must be applied.

  And once buckling generate | occur | produces about this plane part 71, the plane part 71 begins to incline with respect to the load direction of the external force P, As a result, as shown in FIG. Crushing and deepening buckling. Further, as the buckling progresses and the difference in the inclination angle with respect to the load direction of the external force P of the flat surface portion 71 increases, the bending moment based on the external force P applied to the flat surface portion 71 further increases, and as a result, the buckling progresses rapidly. Will be. By repeating this, the flat surface portion 71 is rapidly bent, irregularly twisted and crushed, and eventually remains in the form of damage. In particular, since the metal tube 7 may be twisted and applied as a decorative member, it is necessary to prevent the flat portion 71 from being crushed irregularly by buckling as much as possible.

  As a conventional method for twisting a metal tube, for example, as shown in Patent Document 1, rolls are arranged radially, and a starting material is fed into this to perform twisting.

  However, in the disclosed technique of Patent Document 1, if the torsion angle is excessively increased, the inclination of the external force P of the flat portion 71 with respect to the load direction increases, and buckling occurs. For this reason, it is difficult for the disclosed technique of Patent Document 1 to perform a twisting process with a large torsion angle, and in order to twist without causing buckling, it is at best to set a torsion angle of 25 ° at most. there were.

  Moreover, according to the disclosed technique of Patent Document 2, a round pipe is passed in advance in a metal pipe (square pipe), and twisting is performed in this state. In the twisting process, the inner diameter of the square pipe becomes smaller, and when it hits the inner round pipe, no further twisting occurs, and the pitch can be made uniform. According to this method, it is possible to prevent the above-described buckling of the flat portion 71.

Japanese Patent Laid-Open No. 61-259838 Japanese Patent Laid-Open No. 7-80556

  However, in the technique disclosed in Patent Document 2 described above, a process of inserting a round pipe into the square pipe occurs, so that the manufacturing process is complicated, and the time required for attaching and detaching the round pipe is also required, thereby reducing the work time. There is a problem in that it is difficult to achieve this, and it is difficult to improve the production efficiency.

  Further, since it is not possible to generate any further twist when it hits the inner round pipe, even when it is desired to set a large twist angle, it eventually depends on the diameter of the inner round pipe. That is, the disclosed technique of Patent Document 2 has a problem in that it is not possible to set a large degree of freedom of a torsion angle to be machined during torsion.

  Therefore, the present invention has been devised in view of the above-described problems, and the object of the present invention is to accurately and stably process a torsional shape even when the torsion angle is large. Another object of the present invention is to provide a method and apparatus for twisting a metal pipe.

  The method for twisting a metal tube according to the present invention is a method for twisting a metal tube in which a metal tube having a polygonal cross section composed of a flat portion and a corner portion is twisted in the tube outer peripheral direction around the tube axis direction. A concave portion that is plastically deformed by pressing each flat portion of the tube toward the inside of the tube is formed, and then the twisting is performed.

  At this time, when transporting the metal tube in the order of the recess-forming roll pair, the reference roll pair, and the twisting roll pair, the planar portions of the metal tube are directed toward the inside of the tube by the recess-forming roll pair. The concave portion is formed by pressing, the right end or the left end of each plane portion is brought into contact with the plane from a substantially vertical direction by the reference roll pair, and a desired pitch relative to the pitch in the tube axis direction from the reference roll pair is set. According to the torsion angle, the right end or the left end of each flat portion of the metal tube is pressed by the twisting roll pair provided by rotating from the contact surface of the reference roll pair toward the outer periphery of the tube, and twisted. It may be processed.

In addition, a metal tube twisting device according to the present invention is a metal tube twisting device that twists in a tube outer peripheral direction around the tube axis direction, with respect to a polygonal cross-sectional metal tube composed of a flat portion and a corner portion. A recess-forming roll pair for conveying the metal tube, a reference roll pair, and a twisting roll pair are provided in order, and the recess-forming roll pair presses each flat portion of the metal tube toward the inside of the tube. And the reference roll pair has a right end or a left end of each plane portion in contact with the plane from a substantially vertical direction, and the twisting roll pair has the reference roll pair. According to the desired twist angle with respect to the pitch in the tube axis direction from the contact surface of the pair of reference rolls, and is provided by rotating in the tube outer peripheral direction. By pressing the, characterized by machining twisting the metal pipe.
At this time, the metal tube to be twisted may be formed of any one of a substantially square cross section, a substantially triangular cross section, and a substantially rhombus cross section.

  According to the present invention having the above-described configuration, the flat portion of the metal tube can be gradually deformed without buckling, and finally, the torsional shape of the metal tube in the torque direction is obtained. It becomes possible. In particular, in the present invention, since the twisted shape can be obtained without causing buckling, the twisted shape is irregularly twisted and does not remain in the form of damage. It becomes possible to do.

  In particular, according to the present invention, even if the torsion angle is large, buckling does not occur and the torsion processing can be realized more stably, and a highly accurate torsion shape can be obtained. For this reason, it becomes possible to improve the freedom degree about the twist angle which wants to twist. In addition, unlike the prior art, there is no need to insert a round pipe into the metal pipe, so that the working time can be shortened and the manufacturing efficiency can be improved.

It is a top view of the twist processing apparatus to which this invention is applied. It is a front view of the twist processing apparatus to which this invention is applied. In the twist processing apparatus to which this invention is applied, it is a figure which shows the detailed structure from a side surface. It is a front sectional view of a pair of rolls for forming recesses in a twist processing apparatus to which the present invention is applied. It is an enlarged plan view of the metal tube pressed by the pair of recess forming rolls. It is a front sectional view of a reference roll pair in a twist processing apparatus to which the present invention is applied. It is the figure which carried out the vector display of the external force loaded with a roll with respect to a metal pipe. It is a figure for demonstrating the roll pair for a twist process. (A) is a figure which shows the state before the rotation adjustment to the pipe | tube outer periphery direction of the twist pair for twist processing, (b) is a figure which shows the roll pair for twist processing in the state in which the rotation adjustment was made. is there. It is a figure which shows the external force state loaded with the roll pair for twist processing. It is a figure which shows the calculation result of the twist moment with respect to a twist angle. It is a figure for demonstrating other embodiment in the twist processing apparatus to which this invention is applied. It is a figure which shows the example in the case of processing the metal pipe which has a cross-sectional substantially triangular shape. It is a figure for demonstrating the detail of the deformation | transformation mode of the metal pipe which consists of cross-sectional substantially triangular shape. It is a figure which shows the example in the case of processing the metal pipe which consists of a cross-sectional substantially rhombus. It is a figure for demonstrating the detail of the deformation | transformation mode of the metal pipe which consists of a cross-sectional substantially rhombus. It is a figure for demonstrating the problem of a prior art.

  Hereinafter, as an embodiment of the present invention, a metal tube twisting device for twisting a metal tube having a polygonal cross section in the tube outer peripheral direction will be described in detail with reference to the drawings.

  FIG. 1 is a plan view of a twisting apparatus 1 to which the present invention is applied, and FIG. 2 (a) is a front view thereof. The twist processing apparatus 1 includes a drive motor 19, a speed reducer 18 connected to the drive motor 19, and a drive shaft 16 connected to the speed reducer 18. The twist processing apparatus 1 includes the molding machine bed 3, a stand frame 10 erected on the molding machine bed 3, and a roll pair 4 including a plurality of rolls 2 provided on the stand frame 10. I have. As shown in FIG. 1, a plurality of stand frames 10 including these roll pairs 4 are provided at intervals in the direction of the tube axis of the metal tube 5.

  The metal tube 5 processed by the twist processing apparatus 1 is made of, for example, iron or an aluminum alloy, but may be made of any material as long as it is made of metal. Moreover, the metal tube 5 is comprised by the cross-sectional polygonal shape, and it is desirable to be comprised by the cross-sectional regular polygon. In the following example: A description will be given by taking the metal tube 5 having a regular square cross section as an example.

  The metal tube 5 having a square cross section includes a form in which corners 52 are rounded, as shown in FIG. 2B, for example. In such a case, the flat portion 51 formed between the corner portions 52 is not limited to a complete flat surface, and includes one having a certain degree of curvature. In other words, the metal tube 5 is not limited to a polygon having a cross section in a complete geometric sense, but is a substantially regular polygon in which the corner 52 and the plane 51 have a certain degree of curvature. May be.

  The drive motor 19 rotates the drive shaft 16 based on the supplied power. The power based on the drive shaft 16 that is rotationally driven by the drive motor 19 is transmitted to the stand frame 10 side via the speed reducer 18.

  The roll 2 provided in the stand frame 10 is incorporated by a roll shaft 21 provided in the stand frame 10, and is provided so as to be rotatable around the roll shaft 21. A rotational driving force from the drive shaft 16 is transmitted to any one or more of the roll shafts 21. Then, by rotating the roll shaft 21 to which the rotational driving force is transmitted, the roll 2 can rotate. As a result, the metal pipe 5 to be formed can be sent out from the upstream side to the downstream side in the pipe axis direction while performing desired processing as necessary. When actually forming the metal tube 5, the metal tube 5 is inserted into the central region surrounded by the rolls 2.

  A reduction adjusting bolt 20 is inserted and screwed from the outer peripheral surface of the stand frame 10. The insertion position of the reduction adjusting bolt 20 corresponds to the position where the roll 2 is disposed. The tip of the reduction adjustment bolt 20 can be brought into contact with the roll 2, and by tightening the reduction adjustment bolt 20, the roll 2 can be pushed inward to adjust the position. It is possible to adjust the pressing amount.

  FIG. 3 is a diagram showing a detailed configuration from the side in the twisting apparatus 1 to which the present invention is applied. In the twisting device 1, a concave forming roll pair 4a, a reference roll pair 4b, and a twisting roll pair 4c for conveying the metal tube 5 are provided in order from the upstream side to the downstream side in the tube axis direction.

  As shown in the front cross-sectional view shown in FIG. 4, the recess forming roll pair 4 a presses the metal tube 5 having a quadrangular cross section from the four directions toward the inside of the tube. FIG. 5 shows an enlarged plan view of the metal tube 5. The respective rolls 2a-1 to 2a-4 in the recess forming roll pair 4a are pressed against the respective flat portions 51 in the metal tube 5 having a quadrangular cross section composed of the flat portions 51 and the corner portions 52. The rolls 2a-1 to 2a-4 are provided according to the number of surfaces of the flat portion 51. In the metal tube 5 having a quadrangular cross section, the pressing directions are four directions with respect to each surface.

  At this time, it is desirable that the pressing position of each of the rolls 2a-1 to 2a-4 with respect to the plane portion 51 is exactly the center of the cross section of the plane portion 51 as shown in FIG. This is because the torsional external force applied in the subsequent stage is applied more evenly, and a torsional shape with consistency can be obtained. However, it is not indispensable that the pressing position of each of the rolls 2a-1 to 2a-4 is the center of the cross section of the plane portion 51, and it may be any other location.

  The shape of the contact surface of the rolls 2a-1 to 2a-4 with the flat surface 51 may be provided with a curvature as shown in FIG. 4, but is not limited to this and is a flat shape. It may also be a tapered shape.

  Further, in the present invention, through pressing of the rolls 2a-1 to 2a-4 against the flat portion 51, the flat portion 51 is plastically deformed toward the inside of the tube as shown in FIG. Let it form. That is, it is not sufficient to press the flat portion 51 in a mere elastic range, and a pressing amount is required to the extent that plastic deformation occurs and the concave portion 53 is formed. And the location corresponding to the recessed part 53 formed through such plastic deformation has produced work hardening, and has hardened compared with the other location.

  In this way, as shown in FIG. 5B, the metal pipe 5 having the recess 53 formed in the flat part 51 is conveyed from the upstream side to the downstream side in the pipe axis direction and reaches the reference roll pair 4b. To do.

  FIG. 6 is a configuration diagram of the reference roll pair 4b. In FIG. 6 which shows this reference | standard roll 4b, about the same component and member as FIG. 2 mentioned above, the description below is abbreviate | omitted by attaching | subjecting the same code | symbol.

  The reference roll 4 b includes a drive motor 19, a speed reducer 18 connected to the drive motor 19, and a drive shaft 16 connected to the speed reducer 18, and a roll to which power from the drive shaft 16 is further transmitted. The shaft 21 and the rolls 2b-1 to 2b-4 in the reference roll pair 4b connected to the roll shaft 21 are provided in the stand frame 10. The stand frame 10 is further provided with a reduction adjusting bolt 20 that can push the roll 2 inward.

  The rotational driving force from the drive motor 19 is transmitted to the rolls 2b-1 and 2b-3 in the reference roll pair 4b, and the rolls 2b-1 and 2b-3 can rotate to transport the metal tube 5. Become. Incidentally, the rotational driving force from the drive motor 19 is sufficient for conveying the metal tube 5 as long as it is provided at least in the recess forming roll pair 4a in FIG. 3 described above. May not be particularly arranged.

  With the rolls 2b-1 to 2b-4 in the reference roll pair 4b, as shown in the front sectional view of FIG. 6, the left end when viewed to the center of the metal tube in each flat portion 51 of the metal tube 5 is the plane. It is made to contact from a substantially vertical direction. It is desirable that the contact position is extremely near the corner 52 at the left end of the flat portion 51. Moreover, the contact position of each roll 2b-1 to 2b-4 to the metal tube 5 may be the right end when viewed from the center of the metal tube of each flat portion 51. Even in such a case, the contact position needs to be the right end of all the plane portions 51, not the right end of one plane portion 51. Each of the rolls 2b-1 to 2b-4 is provided according to the number of surfaces of the flat portion 51.

  FIG. 7 is a vector display of the external force applied to the metal tube 5 by the rolls 2b-1 to 2b-4. As long as the vector direction of the external force loaded on the metal tube 5 by the rolls 2b-1 to 2b-4 can support the flat portions 51, the flat portion before the formation of the concave portion 53 shown by the dotted line is shown. 51 may be inclined.

  The external force applied by the reference roll pair 4b is set to a small external force that is within the elastic deformation range. That is, the reference roll pair 4b may simply have a pressing force that can support the flat portions 51 of the metal tube 5.

  Thus, the metal pipe 5 in which the plane portion 51 is supported by the rolls 2b-1 to 2b-4 is conveyed from the upstream side to the downstream side in the pipe axis direction, and reaches the twisting roll pair 4c. It will be.

  In this twisting roll pair 4c, the rolls 2c-1 to 2c-4 constituting the twisting roll pair 4c are rotated and adjusted in the pipe outer peripheral direction according to the desired twist angle θ as shown in the side view of FIG. 3 and FIG. A turntable 9 provided and a fixing plate 11 for fixing the turntable 9 are provided on a pedestal 17. The turntable 9 has a gear 9a formed on a part of the outer periphery thereof, and a rotation control unit 13 configured to be able to rotate the gear 9a in the outer peripheral direction. Further, a lock mechanism 12 for fixing the rotational position of the rotary disk 9 is provided.

  The fixed plate 11 is erected on the pedestal 17 and is provided with a hole 14 through which the metal tube 5 is inserted. A locking mechanism 12 is attached to the fixed plate 11.

  As shown in FIG. 3, the lock mechanism 12 may be configured in any shape that can grip the rotating disk 9. The gripping of the turntable 9 by the lock mechanism 12 may be realized through tightening of the screws 15.

  The rotation control unit 13 is continuously provided with a concavo-convex portion 13 a that can be fitted to a gear 9 a formed on the outer periphery of the rotating disk 9. By rotating the rotation control unit 13, it is possible to control the turntable 9 to be rotatable in the outer peripheral direction via a gear 9 a fitted to the rotation control unit 13.

  FIG. 9A shows a state before the rotation adjustment of the twisting roll pair 4c in the pipe outer peripheral direction. Incidentally, the configuration of the gear 9a is omitted in FIG. The torsion angle θ is set with reference to the reference line A in the rolls 2c-1 to 2c-4 before the rotation adjustment. The twist angle θ is adjusted based on a desired twist angle with respect to the interval (pitch length) between the reference roll pair 4b and the twisting roll pair 4c. And this is adjusted by rotating the turntable 9 which comprises this twisting roll pair 4c to the pipe | tube outer peripheral direction over twist angle (theta). FIG. 9B shows the twisting roll pair 4c in a state where the rotation is adjusted. It is shown that it is rotated from the reference line A toward the outer periphery of the tube by the twist angle θ.

  By passing the metal tube 5 through the twisting roll pair 4c that has been adjusted in this way, an external force as shown in FIG. 10 is applied to the metal tube 5 from the rolls 2c-1 to 2c-4. The Rukoto. The rolls 2c-1 to 2c-4 are brought into contact with and pressed against the right end when viewed from the center of the metal tube in all the flat portions 51. As a result, an external force having a vector direction as shown in FIG. 10 is applied to the right end of the flat portion 51, and a counterclockwise torque is generated in the metal tube 5.

  At this time, the recess 53 has undergone plastic deformation and is work-hardened. For this reason, when the external force which consists of such a vector direction is loaded to the right end in the plane part 51, the plane part 51 will deform | transform as shown by the dotted line in the figure.

  That is, the metal tube 5 is bent inward because the recess 53 is formed in advance. When an external force is applied from the rolls 2c-1 to 2c-4 in such a state, the external force is applied in an oblique direction with respect to the flat portion 51 as shown in FIG. When an external force is applied from such a direction, the corner 52 in the metal tube 5 rotates with the recess 53 as a fulcrum. At this time, the concave portion 53 plastically deformed in the flat portion 51 hardly undergoes deformation because it is work-hardened, and the flat portion 51 other than the bending point of the concave portion 53 that has not yet undergone plastic deformation is the roll 2c. It will be deformed by pressing with -1 to 2c-4. The side pressed by the rolls 2c-1 to 2c-4 in the flat surface portion 51 in the vicinity of the corner portion 52 is plastically deformed so as to extend in the rotation direction. The side which is not pressed by the rolls 2c-1 to 2c-4 in the flat surface portion 51 in the vicinity of the corner portion 52 is plastically deformed so as to be crushed in the rotation direction.

  In particular, since the work-hardened recess 53 serves as a fulcrum, it can be easily bent by being pressed by the rolls 2c-1 to 2c-4. As a result, a rotational bending moment is applied to the corner portion 52 and the flat portion 51 in the vicinity of the corner portion 52, but the bending load based on this bending moment can be suppressed to a lower level. The buckling load Pcr of the flat surface portion 51 is hardly exceeded.

  As a result, the flat portion 51 of the metal tube 5 can be gradually deformed toward the torque direction in the figure without buckling, and finally the metal tube 5 is directed in the torque direction. A twisted shape can be obtained. In particular, in the present invention, since the twisted shape can be obtained without causing buckling, the twisted shape is irregularly twisted and does not remain in the form of damage. It becomes possible to do.

  In particular, according to the present invention, even if the torsion angle is large, buckling does not occur and the torsion processing can be realized more stably, and a highly accurate torsion shape can be obtained. For this reason, it becomes possible to improve the freedom degree about the twist angle which wants to twist. Moreover, unlike the prior art, there is no need to insert a round pipe into the metal tube 5, so that the working time can be shortened and the production efficiency can be improved.

  Note that the twisting roll pair 4c may be provided not only in one stage but also in a plurality of stages from upstream to downstream in the tube axis direction. In such a case, adjustment is made so that the angle θ from the reference line A increases as it goes downstream so that the shape is finished with the same twist angle.

  Incidentally, it is desirable that the distance between the reference roll pair 4b and the twisting roll pair 4c is as close as possible. This is because the closer these distances are, the smaller the elastic deformation can be achieved, and the twisting can be effectively realized by increasing the amount of plastic deformation.

  FIG. 11 shows the calculation result of the torsional moment with respect to the torsional angle. The horizontal axis represents the twist angle (°), and the vertical axis represents the twist moment (kg · m). An analysis was performed on the right end of each planar portion 51 with an external force applied to the two types of the metal tube 5 having a square cross section in which the recess 53 was provided in advance and the metal tube 5 in which the recess 53 was not provided. As a result, the one not provided with the recess 53 requires a large torsional moment when twisting, whereas the one provided with the recess 53 twists with the lower torsional moment than the former when twisting the same twist angle. Has been shown to be possible. Further, it was also shown that the structure provided with the recess 53 has a stable behavior because the lowering of the torsional moment is stopped lower than in the case where the recess 53 is not provided, particularly in a region where the torsion angle is high.

  In addition, according to this invention, it becomes possible to control so that it may become the optimum also about an actual twist shape. The shape of the recess 53 formed by the recess forming roll pair 4a is based on the shape of the contact surface of the rolls 2a-1 to 2a-4 with the flat surface 51, but the torsional shape actually formed. Is controlled by the shape of the recess 53. Therefore, conversely, by optimizing the shape of the concave portion 53 in accordance with the target torsional shape, the final torsional shape itself can be controlled. Similarly, the depth and width of the recess 53 can be optimized according to the target twist shape.

  In the above-described embodiment, the case where the metal tube 5 having a square cross section is twisted has been described as an example. However, the present invention is not limited to this, and any other metal tube having a polygonal cross section. 5 can be twisted by using the same principle. In such a case, needless to say, it is necessary to arrange the rolls 2 according to the number of faces of the metal tube having a polygonal cross section.

  In the above-described embodiment, the case of twisting in the counterclockwise direction is described as an example. However, the present invention is not limited to this, and the case of twisting in the clockwise direction can be realized based on the same method. . In such a case, the right end of the plane portion 51 is pressed by the reference roll pair 4b, and the left end of the plane portion 51 is pressed by the processing roll pair 4c.

  The configurations of the reference roll pair 4b and the twisting roll pair 4c are not limited to the above-described embodiments. For example, for the reference roll pair 4b, as shown in FIG. 12A, a fitting groove 61 in which the tip of the roll 2b is recessed in a concave shape may be provided. Then, this fitting groove 61 may be supported by loosely fitting the corner portion 52 of the metal tube 5.

  Similarly, as shown in FIG. 12B, the twisting roll 4c may also be provided with a fitting groove 62 whose tip is recessed in the roll 2c constituting the twisting roll 4c. Then, the fitting groove 62 may be loosely fitted to the corner portion 52 of the metal tube 5. FIG. 12C shows a state after the twisting roll 4c is rotated over the rotation angle θ. By fitting the corner portion 52 of the metal tube 5 with the fitting groove 62, the same effect as described above can be obtained because the concave portion 53 is formed in advance even if the corner portion 52 is twisted.

  Moreover, in embodiment mentioned above, although the case where it comprised by the cross-sectional regular polygon was demonstrated as an example as an example of the metal pipe 5 processed by the twist processing apparatus 1, it is not limited to this. Of course.

  FIG. 13 shows an example in which a metal tube 5a having a substantially triangular cross section is processed as the metal tube 5 to be processed based on the above-described method.

  First, as shown in FIG. 13A, a metal tube 5a having a substantially triangular cross section having a flat portion 51a and a corner portion 52a is prepared. Next, it presses with respect to each plane part 51a in the metal pipe 5a. In this example, although the pressing position with respect to the plane part 51a is the exact center of the cross section of the plane part 51a, it is not limited to this. Similarly, in the case of the metal tube 5a, the pressing position to the flat surface portion 51a is exactly the center of the cross section of the flat surface portion 51a, so that the torsional external force is applied more evenly and a consistent torsion shape is obtained. It becomes possible.

  By pressing in this way, as shown in FIG. 13B, the metal tube 5a is plastically deformed toward the inside of the tube to form a recess 53a.

  In this way, an external force is applied in the vector direction shown in FIG. 13C on the metal tube 5a in which the concave portion 53a is previously formed in the flat portion 51a. As a result, a counterclockwise torque is generated in the metal tube 5a. At this time, the recess 53a has undergone plastic deformation and is work-hardened. For this reason, when the external force which consists of such a vector direction is loaded to the plane part 51a, it will deform | transform similarly to the mechanism mentioned above.

  FIG. 14 is a diagram for explaining the details of the deformation mode of the metal tube 5a having a substantially triangular cross section. The metal tube 5a is bent inward because the recess 53a is formed in advance. When an external force is applied in such a state, the external force is also applied in an oblique direction to the flat portion 51a in the metal tube 5a having a substantially triangular cross section. As shown in FIG. 14, the extending direction of the flat portion 51a and the vector direction of the external force constitute an acute angle. When an external force is applied from such a direction, the corner 52a of the metal tube 5a rotates with the recess 53a as a fulcrum. At this time, since plastic deformation has not yet occurred, the flat portion 51a-1 to which an external force is directly applied other than the bending point of the concave portion 53a is plastically deformed so as to extend in the rotation direction. Further, the flat portion 51a-2 other than the bending point of the concave portion 53a, to which no external force is directly applied, is plastically deformed so as to be crushed in the rotational direction.

  As a result, the flat portion 51a of the metal tube 5a having a substantially triangular cross section can be gradually deformed in the torque direction without buckling, and finally, FIG. ) As shown by the solid line in the figure, it is possible to obtain a twisted shape in the torque direction for the metal tube 5a.

  FIG. 15 shows an example in which a metal tube 5b having a substantially rhombic cross section is processed as the metal tube 5 to be processed based on the above-described method.

  First, as shown in FIG. 15A, a metal tube 5b having a substantially rhombic cross section having a flat portion 51b and a corner portion 52b is prepared. Next, it presses with respect to each plane part 51b in the metal pipe 5b. In this example, although the pressing position with respect to the plane part 51b is just the center of the cross section of the plane part 51b, it is not limited to this. By pressing in this way, as shown in FIG. 15B, the metal tube 5b is plastically deformed toward the inside of the tube to form a recess 53b.

  In this way, an external force is applied in the vector direction shown in FIG. 15C on the metal tube 5b in which the concave portion 53b is formed in the flat portion 51b in advance. As a result, clockwise torque is generated in the metal tube 5b. At this time, the recess 53b has undergone plastic deformation and is work hardened. For this reason, when the external force which consists of such a vector direction is loaded to the plane part 51b, it will deform | transform similarly to the mechanism mentioned above.

  FIG. 16 is a diagram for explaining the details of the deformation mode of the metal tube 5b having a substantially diamond-shaped cross section. The metal tube 5b is bent inward because the recess 53b is formed in advance. When an external force is applied in such a state, the external force is applied in an oblique direction to the flat portion 51b in the metal tube 5b having a substantially rhombic cross section. As shown in FIG. 16, the extending direction of the flat portion 51b and the vector direction of the external force form an acute angle with each other. When an external force is applied from such a direction, the corner 52b of the metal tube 5b rotates with the recess 53b as a fulcrum. At this time, since plastic deformation has not yet occurred, the flat surface portion 51b-1 to which an external force is directly applied other than the bending point of the concave portion 53b is plastically deformed so as to extend in the rotation direction. Further, the flat surface portion 51b-2 to which an external force is not directly applied other than the bending point of the concave portion 53b is plastically deformed so as to be crushed in the rotation direction.

  As a result, the flat portion 51b of the metal tube 5b having a substantially rhombic cross section can be gradually deformed in the torque direction without buckling, and finally, FIG. ) As shown by the solid line in the figure, it is possible to obtain a twisted shape in the torque direction for the metal tube 5b.

  Note that the above-described triangular triangular metal tube 5a and rhombic metal tube b are not limited to the polygonal cross section in a complete geometric sense, but include corners 52a, 52b, and planar portions. 51a and 51b may be substantially polygonal with a certain degree of curvature.

  In order to realize the twisting method to which the present invention is applied, it is not essential to use the twisting device 1 described above. That is, it is not essential to convey the metal pipe 5 from the upstream side to the downstream side by the concave portion forming roll pair 4a, the reference roll pair 4b, and the twisting roll pair 4c. Any method can be used in the same manner as long as it forms a concave portion plastically deformed by simply pressing each flat portion 51 in the metal tube 5 toward the inside of the tube, and then twists it.

  Further, the torsion processing may be realized simply by pressing the right end or the left end of each flat portion 51 in the metal tube 5.

  Furthermore, in the twisting device 1, the concave forming roll pair 4a may be omitted, and only the reference roll pair 4b and the twisting roll pair 4c may be configured. Even in such a case, since it is assumed that the concave portion 53 is always formed before being inserted into the reference roll pair 4b, the concave portion 53 is formed by pressing the flat portion 51 of the metal tube 5 by some means in advance. Of course, it is necessary to be done.

  Furthermore, in the twisting apparatus 1, the reference roll pair 4b may be omitted, and only the recess forming roll pair 4a and the twisting roll pair 4c may be configured. This is because, even if the reference roll pair 4b does not exist, the reference position alignment by the reference roll pair 4b can be realized through the recess forming roll pair 4a. Of course, the above-described effects can be obtained even in such a case.

DESCRIPTION OF SYMBOLS 1 Processing apparatus 2 Roll 3 Forming machine bed 4 Roll pair 5 Metal tube 9 Turntable 10 Stand frame 11 Fixing plate 14 Hole part 16 Drive shaft 17 Base 18 Reduction gear 19 Drive motor 20 Reduction adjustment bolt 21 Roll shaft 51 Flat part 52 Angle Part 53 Recess 61, 62 Fitting groove

Claims (7)

For a metal tube having a polygonal cross section composed of a flat surface portion and a corner portion, in a twisting method of the metal tube that twists in the tube outer peripheral direction around the tube axis direction,
Forming a concave portion plastically deformed by pressing each flat portion of the metal tube toward the inside of the tube;
Then, the twisting method for a metal pipe, characterized by performing the twisting process. The method of twisting a metal tube according to claim 1, wherein in the twisting process, a right end or a left end of each flat portion of the metal tube is pressed. When transporting the metal tube in the order of the recess-forming roll pair, the reference roll pair, and the twisting roll pair,
Pressing each flat portion of the metal tube toward the inside of the tube with the pair of recess-forming rolls to form the recess,
With the reference roll pair, the right end or the left end of each plane portion is brought into contact with the plane from a substantially vertical direction,
According to a desired twist angle with respect to the pitch in the tube axis direction from the reference roll pair, the metal pipe is rotated by the twisting roll pair provided by rotating from the contact surface of the reference roll pair in the tube outer peripheral direction. The twisting method for a metal tube according to claim 1 or 2, wherein the twisting process is performed by pressing a right end or a left end of each of the flat portions in the method. In the twisting process, the metal pipe is transported in the order of a reference roll pair and a twisting roll pair,
With the reference roll pair, the right end or the left end of each plane portion is brought into contact with the plane from a substantially vertical direction,
According to a desired twist angle with respect to the pitch in the tube axis direction from the reference roll pair, the metal pipe is rotated by the twisting roll pair provided by rotating from the contact surface of the reference roll pair in the tube outer peripheral direction. The twisting method for a metal tube according to claim 1 or 2, wherein the twisting process is performed by pressing a right end or a left end of each of the flat portions in the method. When transporting the metal tube in the order of the recess-forming roll pair and the twisting roll pair,
Pressing each flat portion of the metal tube toward the inside of the tube with the pair of recess-forming rolls to form the recess,
The twisting process is performed by pressing the right end or the left end of each flat portion of the metal pipe with the twisting roll pair provided by rotating the pipe in the outer circumferential direction according to a desired twist angle. The method for twisting a metal pipe according to claim 1 or 2. The method of twisting a metal tube according to any one of claims 1 to 5, wherein the metal tube having any one of a substantially quadrangular cross section, a substantially triangular cross section, and a substantially rhombic cross section is twisted. For a metal tube with a polygonal cross section consisting of a flat portion and a corner portion, in a torsion processing device for a metal tube that twists in the tube outer peripheral direction around the tube axis direction,
A pair of concave forming rolls for conveying the metal tube, a reference roll pair, and a twisting roll pair are provided in this order,
The recess-forming roll pair forms a recess that is plastically deformed by pressing each flat portion of the metal tube toward the inside of the tube,
The reference roll pair has the right end or the left end of each plane part abutted from the plane substantially perpendicular to the plane,
The twisting roll pair is provided by rotating from the contact surface of the reference roll pair toward the outer periphery of the pipe according to a desired twist angle with respect to the pitch in the pipe axis direction from the reference roll pair, and the metal pipe A metal tube twisting apparatus, wherein the metal tube is twisted by pressing a right end or a left end of each of the flat portions in the above.