JP2017018963A - Manufacturing method for hollow tubes having u-shaped bent parts and manufacturing device for hollow tubes having u-shaped bent parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for efficiently manufacturing hollow tubes having U-shaped parts with a high productivity, as well as easily obtaining hollow tubes having small intervals between respective parallel parts, as well as small apex curvature radii.SOLUTION: A method for manufacturing hollow tubes uses a metal die having a groove into which a tube stock is inserted, and which is formed between a die member constituting an upper die and a die member constituting a lower die, wherein a recessed part is formed at one side of at least one of the upper and lower die members, continued to a space inside the groove, and recessed toward inside of at least the other one of the upper and lower die members, and an ejection member capable of move back and forth to the recessed part through the space inside the groove, is disposed at the other one of the die members. The method for manufacturing hollow tubes comprises: placing the tube stock in the groove; applying a liquid pressure into the tube stock: at the same time, while applying a pressure along an axis line (axial-pressing) from both end parts, advancing the ejection member from the other one of the die members toward the inside of the recessed part to push-in an intermediate part of the tube stock in a longitudinal direction into the recessed part, so as to form the U-shaped bent part of the tube-stock in the recessed part.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a hollow tube used for a heat exchanger, an automobile part, etc., in particular, a hollow tube (U-shaped bent tube) having a U-shaped bent portion (U-shaped bent portion). The invention relates to a method for applying and manufacturing, and to an apparatus used for its implementation.

  In heat exchangers, automobile parts, building interior materials / exterior materials, chemical plants, etc., use a hollow pipe having a U-shaped bent part of a straight pipe (straight pipe). There is. Here, the portion bent into a U-shape (a U-shaped bent portion) is projected between two or more straight pipe portions in a direction forming a predetermined angle with respect to the axial direction of each straight pipe portion. In other words, the protruding portion is a U-shaped portion. As a typical example, as shown in FIG. 33 (a) or (b), between two straight pipe portions 1A, 1B having a common axis O, the straight pipe portions 1A, 1B There is a hollow tube 5 having a U-shaped bent portion 3 protruding in a direction perpendicular to the axial direction. Here, in the case of the example of FIG. 33 (a), the first bent portion 7A that bends at a substantially right angle from one straight pipe portion 1A toward the U-shaped bent portion 3, and a substantially right angle within the U-shaped bent portion 3. The second and third bent portions 7B and 7C that are bent in a straight line and the fourth bent portion 7D that is bent at a substantially right angle from the U-shaped bent portion 3 toward the other straight pipe portion 1B are provided. doing. In the case of the example of FIG. 33 (b), the first bent portion 9A that bends substantially perpendicularly from one straight pipe portion 1A toward the U-shaped bent portion 3, and a predetermined curvature in the U-shaped bent portion 3. And has a total of three bent portions, a second bent portion 9B that bends at approximately 180 ° and a third bent portion 9C that is bent at a substantially right angle from the U-shaped bent portion 3 toward the other straight pipe portion 1B. ing.

  A hollow tube having a U-shaped bent portion (hereinafter simply referred to as a U-shaped bent tube), particularly a U-shaped bent tube made of a metal tube such as a steel tube, a copper tube, or an aluminum tube. As a conventional method, there is a method of repeatedly bending a straight pipe a plurality of times by a shear bending press. As a similar method, there is a method of bending a straight pipe using a so-called pipe bender. When a U-shaped bent pipe is formed by bending the straight pipe, it is usual to previously fill the hollow pipe with a filler such as sand so that the hollow pipe is not crushed by bending.

  A method of manufacturing a U-shaped bent pipe directly from a molten metal by casting or die casting is also known. In this case, the hollow portion is formed using a core.

In order to obtain a U-shaped bent pipe as shown in FIG. 33 (a) or (b) by a method of bending a straight pipe using a shear bending press or a pipe bender as described above, a plurality of times are required. Therefore, the productivity must be lowered. In addition, it is necessary to preliminarily fill with a filler such as sand, and the work for filling and removing the filler after processing also becomes an impediment to productivity improvement.
Furthermore, in these bending methods, the U-bend tube having a small interval S between the parallel portions in the U-bend portion 3, particularly 180 in the U-bend portion 3, as shown in FIG. It was extremely difficult to obtain a U-bend tube having a small radius of curvature r at the bent portion 9B, that is, the top of the U-shape.

  On the other hand, it is difficult to manufacture thin U-shaped bent pipes by casting or die casting directly from molten metal, and it is difficult to manufacture thin U-shaped bent pipes. There is a problem that takes time.

By the way, recently, hydroforming using hydraulic pressure is becoming widespread.
Hydroforming uses a hollow tubular material (material tube) such as a steel tube, stainless steel tube, or aluminum tube as a forming material. The material tube is set in a cavity of a mold, and water or the like is placed in the material tube. Fill the pressurizing liquid and apply a high hydraulic pressure to the material tube. At the same time, compress the material tube from both ends of the material tube along the axial direction as needed. In this process, a hollow member having a complicated shape can be integrally formed, and has recently been applied to the manufacture of various parts such as automobiles.
And the method of manufacturing the hollow tube which has a bending part, utilizing such hydroforming is proposed by patent document 1, patent document 2, etc., for example.

  The method proposed in Patent Document 1 uses a hydroforming method to manufacture a hollow tube having a bent portion and an enlarged diameter of the bent portion, that is, a bent tube with a bulging portion. The method disclosed in Patent Document 1 will be described with reference to FIGS.

  In FIG. 34A, the mold 10 is composed of an upper mold 10A and a lower mold 10B that can be separated vertically. A downward convex portion 12 is formed on the upper mold 10A, and an upward concave portion 13 is formed on the lower mold 10B corresponding to the convex portion 12 of the upper mold 10A. On the other hand, the pipe ends 14A and 14B at both ends of the material pipe 14 are sealed by the pipe end sealing members 15A and 15B (see FIG. 34C). These tube end sealing members 15A and 15B not only simply seal the space in the material tube 11, but also serve as shaft pushing members for compressing (axially pushing) the material tube 14 along its axial direction. At least one of them is connected to a shaft pushing drive device such as a hydraulic cylinder (not shown). Further, the pipe end sealing members 15A and 15B are formed with a flow path 17 for introducing a pressurizing liquid such as water into the material pipe 11 or discharging residual air in the material pipe 11. The

  Then, as shown in FIG. 34 (a), the material pipe 14 is disposed on the lower mold 10B in a state where the upper mold 10A and the lower mold 10B are separated (in the mold open state), and the pipe end portion 14A. , 14B are supported by the material pipe end support portions 16A, 16B of the lower mold 10B, and then, as shown in FIG. 34 (b), the upper mold 10A is lowered, and the intermediate portion of the material pipe 14 is moved to the upper mold 10A. Bends and deforms along the convex portion 12. Further, as shown in FIG. 34C, a pressurizing liquid is introduced into the material tube 14 (arrow), the material tube 14 is filled with the pressurizing liquid, and the material tube 14 is continuously filled with the pressurizing liquid. Pressurize to high pressure. At the same time, a load (axial pushing force) along the axial direction is applied to the material pipe 14 by the tube end sealing members 15A and 15B which also serve as the axial pushing member. As a result, the bent portion of the material tube 14 is expanded, and a bent tube with a bulge is obtained.

  Although the method disclosed in Patent Document 1 certainly applies hydroforming, it can be said that hydroforming using hydraulic pressure is only the latter diameter expansion process, and the former bending process. As such, it utilizes plastic deformation by physically pressing the convex portion 12 of the upper mold 10A against the material pipe, and does not utilize hydraulic pressure. In such a method, as in the case of using the above-described shear bending press machine or pipe bender, a U-shaped bent pipe having a small interval S between parallel portions in the U-shaped bent portion, particularly ( As shown in b), it was extremely difficult to obtain a U-shaped bent tube having a small radius of curvature r of the bent portion 9B of the 180 ° bent portion 3 in the U-shaped bent portion 3.

  Patent Document 2 discloses a method of manufacturing a metal tube having two or more bent portions and having a deformed cross section such as a square as the cross section of the bent portion using hydroforming. However, the method of Patent Document 2 also uses bending by physical pressing of the upper die in the former bending portion forming process, and only uses the hydraulic pressure for the first time in the subsequent sectional shape forming step. Therefore, similarly to the method shown in Patent Document 1, the radius of curvature r of the U-bend tube having a small interval S between the parallel parts in the U-bend portion, in particular, the bending portion 9B of the U-bend portion 3 which is bent by 180 °. It was extremely difficult to obtain a small U-bent tube.

JP 2003-103314 A JP 2004-50279 A

  The present invention has been made in the context of the above circumstances, and can efficiently manufacture a hollow tube having a U-shaped bent portion with high productivity, and the interval between the parallel portions and the top portion in the U-shaped bent portion. It is an object of the present invention to provide a method capable of easily obtaining a hollow tube having a small radius of curvature, and to provide an apparatus optimal for carrying out the method.

  In order to solve the above-mentioned problems, the present inventor has conducted various experiments and examinations. As a result, when bending a material pipe, the inventor has devised a mold structure for hydroforming to make hydroforming. It has been found that a U-shaped bent portion, particularly a U-shaped bent portion having a small interval between the parallel portions and a small radius of curvature can be easily formed by utilizing the axial pushing force and the hydraulic pressure application.

Therefore, the gist of the present invention is as follows.
That is, a manufacturing method of a hollow tube having a U-shaped bent portion according to the basic aspect of the present invention (first aspect)
A method for producing a hollow tube having a U-shaped bent portion projecting in a direction forming a predetermined angle with respect to an axial direction of the straight pipe portion between two or more straight pipe portions,
Between the mold member that constitutes the upper mold and the mold member that constitutes the lower mold, a groove portion into which a material tube having a hollow tubular shape is inserted is formed, and at least one of the upper and lower mold members, At least one recess that is continuous with the space in the groove and is recessed toward the inside of the other mold member is formed, and at least the other mold member has a space in the recess through the space in the groove. Using a mold provided with at least one protruding member capable of moving forward and backward,
A material pipe is disposed in the groove, and both ends of the material pipe are sealed by a pipe end sealing member that also serves as a shaft pushing member, and a hydraulic pressure is applied to the inner space of the material pipe, and the material pipe is attached to both ends of the material pipe. From the side of the other mold member, the projecting member is advanced toward the inside of the concave portion while pressing in the direction along the axis thereof (that is, axially pushing), and the intermediate portion in the longitudinal direction of the material tube is It pushes in the said recessed part, The U-shaped bending part of a raw material pipe | tube is formed in the recessed part by this, It is characterized by the above-mentioned.

  In such a manufacturing method of the first aspect, while applying a hydraulic pressure in the material pipe and pushing the material pipe axially, the projecting member is advanced toward the concave portion so that the intermediate part in the longitudinal direction of the material pipe The U-bent portion can be efficiently formed in the intermediate portion of the material pipe by a simple process of pushing the material into the recess. And the space | interval between the parallel parts of the U-shaped bending part of the hollow tube obtained, or the curvature radius of the top part of a U-shaped bending part is the thickness (thickness of the direction along the axial direction of a raw material pipe | tube) or a protruding member Since it is determined by the radius of curvature of the tip, by setting the thickness of the protruding member or the radius of curvature of the protruding member tip to an appropriately small value, the interval between the parallel portions of the U-shaped bent portion or the top of the U-shaped bent portion A hollow tube having a small curvature radius can be easily obtained.

  Moreover, the manufacturing method of the hollow pipe | tube which has a U-shaped bending part by the 2nd aspect of this invention is a manufacturing method of the said 1st aspect, After stopping advance of the said pushing-up member, it is to the axial direction of a raw material pipe | tube. The U-bent portion in the concave portion is formed into a shape along the inner surface of the concave portion by increasing the hydraulic pressure applied to the inner space of the material tube while continuing the pressurization (shaft pushing) of It is what.

  In the manufacturing method of such a 2nd aspect, the outer surface shape of a U-shaped bending part can be shape | molded to a desired shape with high precision.

  According to a third aspect of the present invention, there is provided a method for manufacturing a hollow tube having a U-shaped bent portion. In the manufacturing method according to the first or second aspect, the protruding member is advanced to extend in the longitudinal direction of the material tube. In the middle of the process of pushing the intermediate part into the recess, the advancement of the protruding member is stopped, and the protruding member is subsequently retracted.After the advancement of the protruding member is stopped, the hydraulic pressure applied to the inner space of the material pipe and the material pipe The intermediate portion of the material pipe is pushed into the concave portion only by the pressure applied along the axial direction from the both end portions.

  In such a manufacturing method of the third aspect, in the latter half of the process of pushing the intermediate portion of the material pipe into the recess, the protruding member is not interposed inside the U-shaped bent portion. As a bent portion, a hollow tube having a curvature radius of zero or close to zero can be obtained.

  Furthermore, the manufacturing method of the hollow tube which has the U-shaped bending part by the 4th aspect of this invention WHEREIN: In the manufacturing method of the said 1st or 2nd aspect, as said metal mold | die, further on said one mold member, In the recess, a counter member that can be advanced and retracted toward the other mold member is used. The protruding member is advanced to push the intermediate portion of the material tube into the recess, and at the same time, the intermediate portion of the material tube. The counter member is retracted while bringing the outer surface of the portion into contact with the front end surface of the counter member.

  In such a manufacturing method of the fourth aspect, in the process in which the intermediate portion of the material pipe is pushed into the recess and bent, the bending is performed while the top surface of the bent portion of the material tube is in contact with the tip surface of the counter member. It is effective for the situation that the diameter of the material pipe expands locally or the material pipe deforms into an abnormal shape and the original correct bending shape cannot be obtained due to deformation. Can be prevented.

  A method for manufacturing a hollow tube having a U-shaped bent portion according to the fifth aspect of the present invention is the method for manufacturing a hollow tube according to the fourth aspect, wherein after the advancing member and the counter member are retracted, While increasing the pressure in the axial direction of the tube, by increasing the hydraulic pressure applied to the inner space of the material tube, the U-shaped bent portion is shaped along the tip surface of the counter member and the inner surface of the recess. It is characterized in that it is molded.

  In the manufacturing method of the fifth aspect as described above, the outer surface shape of the U-bent portion can be formed with high accuracy into a desired shape as in the manufacturing method of the second aspect.

  Moreover, the manufacturing method of the hollow pipe | tube which has a U-shaped bending part by the 6th aspect of this invention is a manufacturing method of the said any one aspect of the said 1st-5th. One mold member is formed with one concave portion that is continuous with the space in the groove portion and is recessed toward the inside of the other mold member, and at least the space in the groove portion on the other mold member side. And using a mold provided with one protruding member capable of moving forward and backward in the recess.

  According to the manufacturing method of such a 6th aspect, the hollow tube in which one U-shaped bending part was formed in the intermediate part of the raw material pipe | tube can be obtained.

  Moreover, the manufacturing method of the hollow pipe | tube which has a U-shaped bending part by the 7th aspect of this invention is a manufacturing method of the said any one of the 1st-5th aspect. One mold member is formed with two or more recesses that are continuous with the space in the groove and recessed toward the inside of the other mold member, and are spaced apart in the length direction of the groove. The member is characterized by using a mold provided with two or more projecting members that can be advanced and retracted into the respective recesses through the spaces in the grooves corresponding to the two or more recesses. is there.

  In the manufacturing method of such a 7th aspect, a U-shaped bending part can be simultaneously formed in two or more places which were separated in the length direction in a raw material pipe.

Moreover, the manufacturing method of the hollow tube which has a U-shaped bending part by the 8th aspect of this invention WHEREIN: In the manufacturing method of the said any one of the 1st-5th aspect,
As the mold, one or more first protruding members are disposed on the other mold member at a predetermined interval in the length direction of the groove portion, and one or more second members are disposed on the one mold member. The protruding member is disposed at a position shifted by a predetermined distance in the length direction of the groove portion with respect to the position of the first protruding member, and the one mold member corresponds to the first protruding member. A first recess is formed, and the other mold member is formed with a second recess corresponding to the second protruding member.
A material pipe is disposed in the groove, and both ends of the material pipe are sealed by a pipe end sealing member that also serves as a shaft pushing member, and a hydraulic pressure is applied to the inner space of the material pipe, and the material pipe is attached to both ends of the material pipe. From the side of the other mold member, the first projecting member is advanced from the side of the other mold member while pressing in the direction along the axis, and the intermediate portion in the longitudinal direction of the material tube is pushed into the first recess. Next, the second projecting member is advanced from the side of the one mold member, and the intermediate portion in the longitudinal direction of the material tube is pushed into the second recess, whereby the intermediate portion in the longitudinal direction of the material tube Two or more U-shaped bent portions that are continuously bent in the opposite direction are formed.

  In the manufacturing method according to the eighth aspect, a hollow tube having two or more U-shaped bent portions that are continuously bent in opposite directions alternately in the middle portion in the longitudinal direction can be efficiently produced by a simple process. Can get to.

According to a ninth aspect of the present invention, there is provided a method for manufacturing a hollow tube having a U-shaped bent portion. In the manufacturing method according to the eighth aspect, at least one mold member is further provided in the recess as the mold. Using a counter member capable of moving back and forth toward the other mold member in
The at least one protruding member is advanced to push the intermediate portion of the material pipe into the recess, and at the same time, the counter member is retracted while the outer surface of the pushed intermediate portion of the material pipe is brought into contact with the tip surface of the counter member. It is characterized by making it.

  In the manufacturing method of the ninth aspect as described above, the intermediate portion in the longitudinal direction has two or more U-bent portions that are continuously bent alternately in opposite directions, and the manufacturing method of the fourth aspect Similarly, since the counter member is used, the original correct bent shape can be easily obtained without causing local diameter expansion or abnormal deformation.

  According to a tenth aspect of the present invention, there is provided a method for manufacturing a hollow tube having a U-shaped bent portion, in the manufacturing method according to any one of the eighth and ninth aspects, wherein the other mold member is used as the mold. The two first protruding members are disposed at a predetermined interval in the length direction of the groove portion, and one second protruding member is provided on the one mold member with respect to the two first protruding members. The first mold member is provided with a first recess corresponding to the first protrusion member, and the other mold member corresponds to the second protrusion member. The second concave portion is formed, and three U-shaped bent portions that are continuously bent in the opposite direction are formed in the middle portion in the longitudinal direction of the material tube.

  In the manufacturing method according to the tenth aspect, the hollow tube having three U-shaped bent portions that are continuously bent in the opposite directions alternately in the middle portion in the longitudinal direction, that is, the substantially W-shaped bent portion. It is possible to efficiently obtain a hollow tube having a simple process.

  Moreover, the manufacturing method of the hollow pipe | tube which has a U-shaped bending part by the 11th aspect of this invention is 1 or 2 or more in the predetermined part of the intermediate part of the raw material pipe | tube by the method of the aspect in any one of the 1st-10th aspect. After forming the U-shaped bent portion, the step of forming one or more U-shaped bent portions in another part of the intermediate portion of the material pipe by the same method is performed one or more times. A hollow tube having a bent portion is manufactured.

  Furthermore, in the method for producing a hollow tube having a U-shaped bent portion according to the twelfth aspect of the present invention, one or two or more are provided at predetermined positions in the intermediate portion of the material pipe by the method according to any one of the first to tenth aspects. After the U-curved portion is formed, another step of forming one or more U-curved portions in the middle portion of the U-curved portion by the same method is performed one or more times. A hollow tube having a bent portion is manufactured.

  On the other hand, the thirteenth and fourteenth aspects of the present invention relate to an apparatus for producing a hollow tube having a U-shaped bent portion.

That is, the manufacturing apparatus of a hollow tube having a U-shaped bent portion according to the thirteenth aspect of the present invention
An apparatus for producing a hollow tube having a U-shaped bent portion protruding in a direction forming a predetermined angle with respect to the axial direction of the straight pipe portion between two or more straight pipe portions,
A mold comprising a mold member constituting the upper mold and a mold member constituting the lower mold;
A groove portion into which a hollow tube-shaped material pipe is inserted is formed between the two mold members, and at least one of the two mold members is continuous with the space in the groove portion and the other At least one recess that is recessed toward the inside of the mold member, and at least one projecting member that can advance and retract toward the recess through the space in the groove on the side of the other mold member Is provided.

  According to a fourteenth aspect of the present invention, there is provided a manufacturing apparatus for a hollow tube having a U-shaped bent portion, in the manufacturing apparatus according to the thirteenth aspect, the one mold member in the mold and the other in the recess. A counter member capable of advancing and retreating toward the mold member is provided.

  According to the present invention, a hollow tube having a U-shaped bent portion can be efficiently manufactured with high productivity, and a hollow tube having a small space between the parallel portions and a small radius of curvature at the U-shaped bent portion. Can be easily obtained.

It is a vertical front view of the apparatus for implementing 1st Embodiment of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention. It is a vertical side view in the II-II line in FIG. It is a vertical side view in the III-III line in FIG. FIG. 4 is a transverse plan view taken along line IV-IV in FIG. 2. It is a typical longitudinal section front view which shows the situation which is implementing the 1st Embodiment of the method of this invention using the apparatus shown in FIGS. It is a perspective view which shows an example of the hollow tube which has the U-shaped bending part manufactured by 1st Embodiment of this invention method. It is a typical vertical front view which shows the condition which is implementing 2nd Embodiment of this invention method in steps. It is a perspective view which shows an example of the hollow tube which has the U-shaped bending part manufactured by 2nd Embodiment of this invention method. It is a vertical front view of the apparatus for implementing 3rd Embodiment of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention. It is a vertical side view in the XX line in FIG. It is a typical vertical front view which shows the condition which is implementing the 3rd Embodiment of the method of this invention using the apparatus shown in FIG. 9, FIG. 10 in steps. It is a vertical front view of the apparatus for implementing 4th Embodiment of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention. It is a vertical side view in the XIII-XIII line in FIG. It is a vertical side view in the XIV-XIV line | wire in FIG. It is a typical vertical front view which shows the condition which implements 4th Embodiment of the method of this invention using the apparatus shown in FIGS. 12-14 in steps. It is a perspective view which shows an example of the hollow tube which has the U-shaped bending part manufactured by 4th Embodiment of this invention method. It is a vertical front view of the apparatus for implementing 5th Embodiment of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention. It is a typical vertical front view which shows the condition which is implementing the 5th Embodiment of the method of this invention using the apparatus shown in FIG. 17 in steps. It is a perspective view which shows an example of the hollow tube which has the U-shaped bending part manufactured by 6th Embodiment of the manufacturing method of the hollow pipe which has a U-shaped bending part of this invention. It is a vertical front view of the apparatus for implementing 6th Embodiment of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention. It is a typical vertical front view which shows the condition which is implementing the 6th Embodiment of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention in steps. It is a perspective view which shows an example of the hollow tube which has the U-shaped bending part manufactured by 7th Embodiment of the manufacturing method of the hollow pipe which has a U-shaped bending part of this invention. It is a vertical front view of the apparatus for implementing 7th Embodiment of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention. It is a typical vertical front view which shows the condition which is implementing the 7th Embodiment of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention in steps. It is a vertical front view of the apparatus for implementing 8th Embodiment of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention. It is a vertical front view of the apparatus for implementing 9th Embodiment of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention. It is a vertical front view of the apparatus for implementing 10th Embodiment of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention. It is an approximate solution figure showing the situation where the 11th embodiment of the manufacturing method of the hollow tube which has the U character bent part of the present invention is implemented stepwise. It is a vertical side view which expands and shows the part of a metal mold | die and a protrusion member as another example of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention. FIG. 30 is a transverse plan view taken along line XXX-XXX in FIG. 29. It is a vertical side view which expands and shows the part of a metal mold | die and a protrusion member as another example of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention. FIG. 32 is a transverse plan view taken along line XXXII-XXXII in FIG. 31. It is a rough front view which shows two examples of the hollow tube which has a U-shaped bending part used as manufacture object by this invention. It is a schematic diagram which shows an example of the conventional method for manufacturing the hollow tube which has a bending part by applying hydroforming in steps.

  Next, the present invention will be described in detail.

  1 to 4 show an example of a main part of an apparatus configuration for carrying out the method of manufacturing a hollow tube having a U-shaped bent part according to the first embodiment of the present invention, particularly a mold part. 5 shows stepwise a method of manufacturing a hollow tube having a U-shaped bent portion in the first embodiment, and FIG. 6 shows a medium having a U-shaped bent portion manufactured by the first embodiment. An example of an empty tube is shown. 1 to 4 show a state in which the material pipe 37 is disposed at a required portion of the mold 31 and is clamped (a state before the start of processing).

  1 to 4, the mold 31 is composed of a mold member 33A constituting an upper mold and a mold member 33B constituting a lower mold. These mold members 33A and 33B are clamped (not shown). The mold is clamped by means. The material of the mold members 33A and 33B constituting the mold 31 is not particularly limited, and may be composed of FCD250, S50C, SKD11, and the like in the same manner as a normal hydroforming mold. In the following description, the mold member 33A constituting the upper mold is referred to as an upper mold member 33A, and the mold member 33B constituting the lower mold is referred to as a lower mold member 33B.

  In the present embodiment, the upper surface of the lower mold member 33B is formed to have a flat shape as a whole, and a half-groove (lower mold groove) 35B having a semicircular cross section is horizontal on the upper surface of the lower mold member 33B. It is formed upward along the direction. In addition, on the lower surface of the upper mold member 33A, a half groove (upper mold groove) 35A having a semicircular cross section is directed downward along the horizontal direction corresponding to the half groove (lower mold groove) 35B of the lower mold member 33B. Is formed. In the clamped state, the lower mold groove 35B and the upper mold groove 35A form a groove portion 35 having a circular cross section as a whole. This groove part 35 is for accommodating the hollow raw material pipe | tube 37 used as the application object of the manufacturing method of this invention. Therefore, the maximum diameter of the lower mold groove 35B and the upper mold groove 35A (that is, the inner diameter of the groove portion 35) is determined to be the same as or slightly larger than the outer diameter R of the material tube 37.

  Here, in the upper mold member 33A and the lower mold member 33B, the vicinity of both end portions of the groove portion 35 (upper mold groove 35A, lower mold groove 35B) is a tube end support portion for supporting both end portions 37A, 37B of the material tube 37. 43A and 43B. These tube end support portions 43A and 43B are in the vicinity of both end portions of the material tube 37 in a mold-clamping state (more precisely, both end portions 37A and 37B of the material tube 37 and subsequent tube end sealing members 45A and 45B). However, the material pipe 37 is supported so as to allow movement along the length direction of the material pipe 37. The tube end sealing members 45A and 45B are for sealing the space in the material tube 37, and pressurize the material tube 37 from its both end sides toward the intermediate portion along the axial direction (axis It also serves as a shaft pressing member for pressing. The pipe end sealing members 45A and 45B introduce a liquid such as water for applying a hydraulic pressure into the material pipe 37, and discharge (release air) residual air from the material pipe 37. One or two or more flow paths 47A, 47B for this purpose are formed along the axial direction.

  Further, the upper mold member 33A of the mold 31 is formed with a recess 39 that is continuous with the space in the upper mold groove 35A and is recessed upward (inside the upper mold member 33A). As shown in FIG. 1, the recess 39 is formed so that a cross section along the length direction of the upper mold groove 35A (and hence the length direction of the material tube 37) is substantially rectangular (and thus an inverted U-shape). The cross section perpendicular to the length direction of the upper mold groove 35A (and hence the length direction of the material tube 37) is formed in the upper mold groove 35A as shown in FIG. It has a shape that is recessed upward with substantially the same width W1 as the maximum width (thus the maximum width of the groove 35). Here, the width W2 of the concave portion 39 in the direction parallel to the length direction of the upper mold groove 35A, that is, the interval W2 between the two inner side surfaces 39A, 39B orthogonal to the length direction of the upper mold groove 35A is the material tube 37. More than twice the outer diameter R of the material tube 37, usually twice the outer diameter R of the material pipe 37, and the same or slightly larger than the dimension obtained by adding the thickness T of the protruding member 41 described later, preferably It is appropriate to set it to 1.0 times to 1.2 times [R × 2 + T]. The depth (the distance from the opening end of the recess 39 to the inner bottom surface 39A) D may be determined according to the height of the U-bend portion to be obtained.

The lower mold member 33B is provided with a protruding member 41 at a position corresponding to the center of the recess 39 of the upper mold member 33A. The protruding member 41 is formed in a long plate shape or a rod shape along the vertical direction, and is moved in a vertical plane orthogonal to the length direction of the groove portion 35 by advancing / retreating drive means 42 such as a fluid pressure cylinder. It is configured to be able to advance and retract upward. And this protrusion member 41 is made so that the cross section (cross section along the length direction of the groove part 35) of the upper end 41A may be smoothly curved in a convex shape. Here, the thickness T of the protruding member 41 (thickness in the direction along the length direction of the groove portion 35) is not particularly limited, but this thickness T is used when a U-shaped bent portion is formed in the material tube 37 as will be described later. Since this corresponds to the space (space; see FIG. 6) S between the U-shaped parallel portions, it may be determined according to the space S of the U-shaped bent portion to be finally formed. In the case of the present embodiment, the thickness T of the protruding member 41 is set to be smaller than the outer diameter of the material pipe 37 (and therefore smaller than the maximum diameter of the groove portion 35) in order to make the space S smaller than the outer diameter of the material pipe 37. doing. In addition, it is desirable that the protruding member 41 has a smooth convex surface (convex curved surface) at its tip (upper end in the illustrated example) 41A. The desired radius of curvature of the tip 41A varies depending on the material, hardness, outer diameter and thickness of the material tube 37, but the outer diameter is about 21.7 to 114.3 mm and the thickness is 1.2 to 5.0 mm. When a general structural carbon steel pipe of a degree is targeted, it is desirable that the radius of curvature of the tip 41A of the protruding member 41 be 3.0 mm to 10.0 mm. Further, the material of the protruding member 41 is not particularly limited, but it may normally be made of the same material as that of the mold 31, for example, FCD250, S50C, SKD1, and the like.
In the initial state (when not operating), the protruding member 41 has its tip (upper end in the illustrated example) 41A positioned at the bottom surface of the lower mold groove 35B of the lower mold member 33B or a position slightly lower than that. doing.

Next, a method for forming a U-shaped bent portion in the material pipe 37 using the apparatus shown in FIGS. 1 to 4 will be described with reference to FIGS.
The material of the material tube 37 is not particularly limited as long as it is a material that can be cold or warm plastically processed. For example, carbon steel, stainless steel, copper or copper alloy, aluminum or aluminum alloy, titanium or A titanium alloy or the like can be applied.

  Tube end sealing members 45A and 45B that also serve as shaft pressing members are attached in advance to both end portions (tube end portions 37A and 37B) of the material tube 37. Then, as shown in FIG. 5A, the material pipe 37 is placed on the lower mold member 33B so that the lower half portion of the intermediate portion 37C is positioned in the lower mold groove 35B of the lower mold member 33B. . Further, the upper mold member 33A is lowered, and the mold is clamped in a state where the upper half portion of the intermediate portion of the material pipe 37 is inserted into the upper mold groove 35A of the upper mold member 33A. FIG. 5 (b) shows the clamped state.

  In the clamped state, the material pipe 37 is supported between the upper mold member 33A and the lower mold member 33B in such a manner that both end portions 37A and 37B are allowed to move in the axial direction. And the intermediate part of the raw material pipe | tube 37 is the state inserted in the groove part 35 which consists of 35 A of upper mold | type grooves, and the lower mold groove 35B. At this stage, the protruding member 41 is in a state where its tip has not yet protruded into the groove 35. Normally, at this stage, the material pipe 37 is filled with a liquid for applying a hydraulic pressure such as water. At this time, the liquid is filled while performing air bleeding so that air does not remain in the material tube 37. In some cases, the material tube 37 may be filled with liquid before the mold clamping.

  Next, as shown in FIG. 5 (c), the pipe end sealing members 45 </ b> A and 45 </ b> B are not shown in fluid pressure while applying a fluid pressure into the material pipe 37 through the flow paths 47 </ b> A and 47 </ b> B of the pipe end sealing member 45. Pressurization driving (that is, axial pressing) is performed along the axial direction from both sides by mechanical pressurizing means such as a cylinder, and at the same time, the protruding member 41 is advanced upward, and the material pipe 37 is extended by the tip of the protruding member 41. Push up the middle part. As a result, the intermediate portion of the material pipe 37 starts to bend and deform in a direction protruding upward in the recess 39. That is, the bending deformation portion 37D starts to be formed. Since the hydraulic pressure is applied in the material pipe 37, the bending deformation is started without being crushed.

  In this way, if the advancement of the protruding member 41 is continued while applying the hydraulic pressure and pushing the shaft, the intermediate portion of the material pipe 37 has an inverted U-shape as shown in FIG. It is pushed into the recess 39 while being deformed. Then, as shown in FIG. 5 (e), if the fluid pressure is further increased after the upper part of the deformation part (U-shaped bent part) 37D contacts the inner bottom surface 39C of the recess 39, as shown in FIG. The deformed portion is bent and deformed portion 37D is formed into a shape along substantially the entire inner surface of the recess 39.

  Thereafter, the application of the hydraulic pressure is stopped according to a conventional method, the axial pressing force is released, the protruding member 41 is returned (retracted) to the original position, and the mold 31 is opened. Further, before and after that, the pressurizing liquid in the material tube 37 is discharged, the material tube 37 is taken out from the mold 31, and the tube end sealing members 45A and 45B are removed from the material tube 37. The manufacturing process of the hollow tube having the bent portion) is completed (see FIG. 5G).

FIG. 6 shows an example of the hollow tube 5 that has been processed according to this embodiment.
As shown in FIG. 6, this hollow tube 5 is between two straight pipe portions 1A, 1B having a common axis O in a direction perpendicular to the axial direction of the straight pipe portions 1A, 1B. A protruding U-shaped bent portion 3 is provided. Here, the cross-sectional shape of the U-shaped bent portion 3 is determined by the inner surface shape of the recess 39 and the outer surface shape of the protruding member 41. In the case of the present embodiment, the cross section is formed to have a substantially rectangular shape. However, the present invention is not limited to this, and as will be described later, the inner surface shape of the recess 39 and the outer surface shape of the protruding member 41 are formed. Can be formed to have various different cross-sectional shapes.

  The rising speed (advance speed) when raising the protruding member 41 differs depending on the material, hardness, and dimensions (outer diameter and thickness) of the material pipe 37, but both side portions of the material pipe 37. It is desirable to be equal to the moving speed in the axial direction (shaft pushing speed). The shaft pushing speed is not particularly limited, and the optimum speed varies depending on the material, hardness, and dimensions (outer diameter and wall thickness) of the material tube 37, but the outer diameter is about 21.7 to 114.3 mm. When a general structural carbon steel pipe having a wall thickness of about 1.2 to 5.0 mm is targeted, it is desirable that the shaft pressing speed be determined to be about 1.0 to 10.0 mm / sec. The axial pushing force and the hydraulic pressure may be determined in consideration of the ascending speed of the protruding member 41, but the axial pushing force is usually preferably about 10 kN to 3000 kN, and the hydraulic pressure is preferably about 10 MPa to 200 MPa.

  In the above-described first embodiment, as illustrated in FIGS. 5B to 5F, the protruding member 41 is maintained until the upper surface of the bent portion of the intermediate portion of the material tube 37 contacts the inner bottom surface 39 </ b> C of the recess 39. However, in some cases, the protrusion member 41 may be stopped in the middle, and the protrusion member 41 may be subsequently retracted. An example in that case is shown in FIGS. 7A to 7D as a second embodiment.

  In this case, as shown in FIGS. 7A to 7B, while the hydraulic pressure is applied and the shaft is pushed, the protruding member 41 is advanced and its tip is slightly protruded toward the concave portion 39, whereby the material tube After a slight bending deformation is applied to the intermediate portion of 37, the advancement of the protruding member 41 is stopped while continuing the application of the hydraulic pressure and the axial pushing, and then the protruding member 41 is moved backward as shown in FIG. Further, the application of hydraulic pressure and the pushing of the shaft are continued. That is, the protruding member 41 is pulled out from the bent portion 37D formed in the initial stage, and the application of the hydraulic pressure and the axial pushing are continued as they are. In this way, the bending portion formed by the initial protrusion is bent by 180 ° or close to the state by the axial pressing force, and the bending portion is pushed upward in the recess 39. Then, the deformation is continued until the upper surface of the bent portion 37D in a state of 180 ° bending or close to the inner bottom surface 39C of the concave portion 39 is further formed along the inner surface of the concave portion. A letter-shaped bent portion is formed. In other words, if bending deformation is triggered by the initial protrusion (when initiated), the shaft is finally bent by 180 ° or close to the inner surface of the recess 39 by continuing to push the shaft and apply hydraulic pressure. The U-shaped portion can be formed.

  An example of the hollow tube 5 obtained in this way is shown in FIG. In this hollow tube 5, the space S between the parallel portions in the U-shaped bent portion 3 is zero or close thereto, in other words, the radius of curvature inside the bending of the U-shaped bent portion 3 is zero or close thereto. . In the case of the second embodiment, the width W2 (see FIG. 1) of the recess 39 in the direction parallel to the length direction of the upper mold groove 35A, that is, two inner portions orthogonal to the length direction of the upper mold groove 35A. It is desirable that the interval W2 between the side surfaces 39A and 39B is set to be relatively smaller than that in the first embodiment. Specifically, it is appropriate to set it to about 1.0 to 1.2 times [R × 2 + T] in relation to the outer diameter R of the material pipe 37 and the thickness T of the protruding member 41.

FIGS. 9 and 10 show a mold part of an apparatus used in the third embodiment of the present invention, and FIGS. 11A to 11D show the method of the third embodiment using the same. Shows the status of the implementation step by step. 9 and 10 show a state in which the material pipe 37 is arranged at a required portion of the mold 31 and is clamped (a state before the start of processing).
In addition, in FIG. 9, FIG. 10, the same code | symbol is attached | subjected about the same element as the apparatus used for 1st Embodiment shown in FIGS. 1-4, and the detail is abbreviate | omitted.

  9 and 10, for example, a thick plate-like counter member 49 is disposed in the recess 39 of the upper mold member 33A. The counter member 49 has a shape similar to the shape of the horizontal section of the recess 39 as the shape of the horizontal section of the counter member 49, and can be moved up and down (lifted and lowered) in the recess 39 from the dimension of the horizontal section of the recess 39. Also made to slightly smaller dimensions. Further, the lower surface (tip surface) 49A of the counter member 49 is a substantially horizontal plane. The counter member 49 is configured to be moved up and down in the recess 39 by the second forward / backward drive means 51 such as a fluid pressure cylinder.

  In such a method of the third embodiment, at the stage before the start of processing just by performing mold clamping, as shown in FIG. 11A, the protruding member 41 is retracted, and the counter member 49 is The lower surface 49A is advanced (lowered) so as to contact the upper surface of the material tube 37. Then, as shown in FIGS. 11B to 11C, the protruding member 41 is advanced (raised), and at the same time, the counter member 49 is retracted (raised) at the same speed as the advanced speed of the protruding member 41. As a result, the intermediate portion of the material pipe 37 is bent and deformed while its upper surface is in contact with the lower surface 49 </ b> A of the counter member 49. In other words, while there is no extra space above the bending part during bending deformation, the diameter of the material pipe is locally expanded or deformed into an abnormal shape, resulting in the original correct bending. It is possible to effectively prevent a situation in which the shape cannot be obtained.

FIGS. 12 to 14 show an example of a main part of an apparatus configuration for carrying out the method for manufacturing a hollow tube having a U-shaped bent part according to the fourth embodiment of the present invention, particularly an example of a mold part. 15 shows a step-by-step manufacturing method of a hollow tube having a U-shaped bent portion in the fourth embodiment, and FIG. 16 shows a medium having a U-shaped bent portion manufactured by the fourth embodiment. An example of an empty tube is shown. 12 to 14 show a state in which the material pipe 37 is arranged at a required portion of the mold 31 and clamped (a state before the start of processing).
In addition, in FIGS. 12-14, the same code | symbol is attached | subjected about the same element as the apparatus used for 1st Embodiment shown in FIGS. 1-4, and the detail is abbreviate | omitted.

  12-14, the upper mold member 33A has a first recess 53A (hereinafter referred to as the upper mold recess) 53A, and the lower mold member 33B has a second recess (hereinafter referred to as this). (Denoted as a lower mold recess) 53B is formed.

The upper mold recess 53A, like the recess 39 in the first embodiment (see FIGS. 1 to 3), forms a space continuous above the upper mold groove 35A, and has an overall shape. Is formed in a substantially rectangular shape. The width of the upper mold recess 33A (the length in the direction along the length direction of the groove 35; accordingly, the length along the axial direction of the material tube 37) W2 is slightly larger than four times the outer diameter R of the material tube 37. To the extent that it is large, more precisely, it is the same as the dimension obtained by adding the total thickness of a first protruding member 55A and two second protruding members 55B ₁ and 55B ₂ described later to four times the outer diameter R of the material tube 37. If the thickness of the first protruding member 55A and the two second protruding members 55B ₁ , 55B ₂ is T respectively, or [R × 4 + T × 3] or more It is set to a slightly larger extent. Further, the front-rear interval W1 (see FIG. 13) of the upper mold recess 53A is determined to be the same as or slightly larger than the outer diameter R of the material pipe 37.

The lower mold recess 53B forms a space continuous downward from the lower mold groove 35B, and the overall shape thereof is formed to be substantially rectangular. The width of the lower mold recess 53B (the length in the direction along the length direction of the groove 35; thus, the length along the axial direction of the material tube 37) W3 is slightly larger than twice the outer diameter R of the material tube 37. To the extent that it is large, more precisely, it is about the same as the dimension obtained by adding the total thickness of the first protruding member 55A and the two second protruding members 55B ₁ and 55B ₂ described later to twice the outer diameter of the material tube 37. If the thickness of the first protruding member 55A and the two second protruding members 55B ₁ and 55B ₂ is T, respectively, or [R × 4 + T × 3] or more It is determined to be slightly larger. Further, the space W4 (see FIG. 14) before and after the lower mold recess 53B is determined to be the same as or slightly larger than the outer diameter R of the material pipe 37.

Further, in the upper mold recess 53A of the upper mold member 33A, a first protruding member (hereinafter referred to as an upper mold protruding member) 55A is disposed so as to be able to advance and retreat downward. A pair of second protruding members (hereinafter referred to as lower mold protruding members) 55B ₁ and 55B ₂ are disposed in the mold recess 53B so as to be able to advance and retract upward.

The upper mold projecting member 55A and the pair of lower mold projecting members 55B ₁ , 55B ₂ are each in the vertical direction (therefore, the direction orthogonal to the axial direction of the material tube 37), like the projecting member 41 in the first embodiment. ) Along a long plate or rod. The upper die protrusion member 55A is advanced and retracted along the vertical direction by the advancing / retreating drive means 57A such as a fluid pressure cylinder in the central portion of the upper die recess 53A (the central portion of the upper die recess 53A in the length direction of the groove portion 35). It is comprised so that. The pair of lower die protruding member _55B 1, 55B ₂ are both end portions of the lower die recess 53B in (a lower die recess 53B at both ends in the length direction of the groove 35), advancing drive means _57B 1, such as a fluid pressure cylinder, 57B ₂ is configured to be advanced and retracted along the vertical direction.

Next, a process for performing the method of the fourth embodiment using the apparatus shown in FIGS. 12 to 14 will be described with reference to FIGS. In this embodiment, at the stage prior to the start of processing after the mold clamping, as shown in FIG. 15A, the lower mold protruding members 55B ₁ and 55B ₂ have their tips on the lower surface of the material pipe 37. It is set in a state of being retracted so as to be in a contact position or a position below it. On the other hand, as shown by the solid line in FIG. 15 (a), the upper die protruding member 55A is usually set in a state of being retracted to the position of the inner bottom surface of the upper die recess 53A. In the previous stage, as shown by the chain line in FIG. 15A, it is allowed to lower the tip (lower end) of the upper die protruding member 55A to a position where it contacts the upper surface of the material tube 37.

  Then, after the material pipe 37 is filled with a liquid for applying a hydraulic pressure such as water, the upper die protruding member 55A is lowered as shown in FIG. 15B while applying the hydraulic pressure and pushing the shaft. Let As a result, the intermediate portion of the material pipe 37 is bent and deformed downward, and is pushed into the lower mold recess 53B. That is, a first bending portion 37E that protrudes downward is formed.

Next, as shown in FIG. 15C, the pair of lower mold protruding members 55B ₁ and 55B ₂ are simultaneously raised at a constant speed. As a result, the portions on both sides of the first bending portion 37E in the intermediate portion of the material tube 37 are bent and deformed upward and pushed into the upper mold recess 53A. That is, a pair of second bending portions 37F and 37G protruding upward are formed on both sides of the first bending portion 37E.

After the upper surfaces of the second bent portions 37F and 37G are in contact with the inner bottom surface of the upper mold recess 53A in this way, if the hydraulic pressure is increased while further pushing the shaft, finally, as shown in FIG. As described above, the outer surface of the first bending portion 37E is along the inner bottom surface of the lower mold recess 53B and the side surfaces of the lower mold protruding members 55B ₁ and 55B ₂ , and the outer surfaces of the pair of second bending portions 37F and 37G are the upper mold. It is molded so as to have a shape along the inner bottom surface and side surface of the recess 53A and the side surface of the upper die protruding member 55A.

  FIG. 16 shows the appearance of the hollow tube having a bent portion thus obtained. As shown in FIG. 16, the hollow tube 5 is formed between two straight tube portions 1A and 1B having a common axis O at right angles to the axial directions of the straight tube portions 1A and 1B and alternately. It has three U-shaped bent portions 3A, 3B, 3C protruding in the reverse direction. That is, it has a portion bent into an inverted W shape as a whole.

Although the counter member is not used in the fourth embodiment, a counter member may be used as in the third embodiment (see FIGS. 9 to 11). 17 and 18 show the fifth embodiment.
17 is the same as the embodiment shown in FIGS. 9 to 11 except for the counter members and the advance / retreat driving means for driving the counter members.

In FIG. 17, in the upper mold recess 53A, a pair of counter members (hereinafter referred to as upper mold counter members) 49A ₁ and 49A ₂ are disposed at portions corresponding to both sides of the upper mold protruding member 55A. In the lower mold recess 53B, a counter member (hereinafter referred to as a lower mold counter member) 49B is disposed at a position between the pair of lower mold protrusion members 55B ₁ and 55B ₂ . Each of these counter members 49A ₁ , 49A ₂ , 49B is configured to be advanced and retracted by an advancing / retreating drive means such as a fluid pressure cylinder (not shown).

A process for implementing the method of the fifth embodiment using the apparatus shown in FIG. 17 will be described with reference to FIGS. In this embodiment, as shown in FIG. 18 (a), the lower mold projecting members 55B ₁ and 55B ₂ have their tips (upper ends) at the material tube 37 at the stage before the start of processing after only performing mold clamping. The lower mold counter member 49 </ b> B is advanced to a position where the upper surface thereof contacts the lower surface of the material pipe 37. On the other hand, the upper die protruding member 55A is positioned so that the tip (lower end) thereof is in contact with the upper surface of the material tube 37, and the upper die counter members 49A ₁ and 49A ₂ are also positioned so that the lower surface thereof is in contact with the upper surface of the material tube 37. Keep it.

  Then, after filling the material pipe 37 with a liquid for applying a hydraulic pressure such as water, the upper die protruding member 55A is lowered as shown in FIG. 18B while applying the hydraulic pressure and pushing the shaft. At the same time, the lower mold counter member 49B is lowered at a constant speed. Thus, the intermediate portion of the material pipe 37 is bent and deformed downward while the lower surface thereof is in contact with the upper surface of the lower mold counter member 49B, and is pushed into the lower mold recess 53B. That is, a first bending portion 37E that protrudes downward is formed.

Next, as shown in FIG. 18C, the pair of lower mold protrusion members 55B ₁ and 55B ₂ are simultaneously raised at a constant speed, and at the same time, the pair of upper mold counter members 49A ₁ and 49A ₂ are raised at the same speed. . As a result, the portions on both sides of the first bending portion 37E in the intermediate portion of the material pipe 37 are bent and deformed upward while in contact with the upper surfaces of the upper mold counter members 49A ₁ and 49A ₂ , thereby Is pushed into. That is, a pair of second bending portions 37F and 37G protruding upward are formed on both sides of the first bending portion 37E.

Thus, after the upper mold counter members 49A ₁ and 49A ₂ reach the upper limit position (the position where the upper surfaces of the upper mold counter members 49A ₁ and 49A ₂ are in contact with the inner bottom surface of the upper mold recess 53A), the shafts are further pressed. If the hydraulic pressure is increased, finally, as shown in FIG. 18D, the outer surface of the first bending portion 37E is brought into contact with the side surfaces of the lower mold protruding members 55B ₁ and 55B ₂ and the upper surface of the lower mold counter member 49B. And the outer surfaces of the pair of second bent portions 37F and 37G are shaped along the inner surface of the upper mold recess 53A, the side surfaces of the upper mold protrusion member 55A, and the lower surfaces of the upper mold counter members 49A ₁ and 49A _2. To be molded.
As described above, in the fifth embodiment, since the counter member is used as in the third embodiment, there is no extra space above or below the bending portion during the bending deformation. It is possible to effectively prevent a situation in which the original correct bending shape cannot be obtained due to the local expansion of the diameter of the material pipe or the deformation to an abnormal shape.

Furthermore, according to the method of the present invention, a hollow tube having a portion in which two U-shaped bent portions continuously protrude in opposite directions, for example, two straight tube portions 1A having a common axis O as shown in FIG. 1B, the first U-curved portion 3A projecting in one direction perpendicular to the axial direction of the straight pipe portions 1A, 1B, and opposite to the projecting direction of the U-curved portion 3A It is also possible to manufacture a hollow tube in which the second U-shaped bent portion 3B protruding in the direction is continuously formed, that is, a hollow tube having a portion bent in a substantially S shape.
Examples of such cases are shown in FIGS. 20 and 21 as a sixth embodiment.

The apparatus shown in FIG. 20 basically has one (55B ₂ ) of the pair of lower mold protruding members 55B ₁ and 55B ₂ in the fifth embodiment (see FIGS. 17 and 18), and an upper mold counter. It can be said that _{one of} the members 49A ₁ and 49A ₂ (49A ₂ ) is omitted.
The material pipe 37 is processed using the apparatus having such a configuration, and the process is shown in FIG. The machining process shown in FIG. 21 basically conforms to the machining process in the fifth embodiment shown in FIG. 18, and therefore a detailed description thereof will be omitted here.
Here, as shown in FIG. 21B, after the upper die protruding member 55A and the lower die counter member 49B are lowered to form the lower U-shaped bent portion, as shown in FIG. 21C again. raising the lower mold projecting member 55B ₁ and the upper mold counter member 49A _1, but forms an upper U-shaped bend, in some cases, a lowering of the upper mold ejection member 55A and the lower mold counter member 49B, by performing the rise of the lower mold ejector member 55B ₁ and the upper mold counter member 49A ₁ at the same time at a constant speed, the upper and lower U-shaped bend portions may be formed at the same time.

  Furthermore, according to the method of the present invention, the hollow tube 5 having a two-stage U-shaped bent portion, that is, between two straight tube portions 1A and 1B having a common axis O as shown in FIG. In addition, a relatively large U-shaped bent portion 3H protruding in a direction perpendicular to the axial direction of the straight pipe portions 1A and 1B is formed, and further, an intermediate portion in the relatively large U-shaped bent portion 3H is formed. It is also possible to manufacture the hollow tube 5 in which a relatively small U-shaped bent portion 3I is formed at the portion (top portion). An example of manufacturing a hollow tube having such a two-stage U-shaped bent portion is shown in FIGS. 23 and 24 as a seventh embodiment.

In FIG. 23, a recess (hereinafter referred to as a large recess) 57 having a relatively large width W2a in the length direction of the groove 35 is formed in the upper mold member 33A as a recess continuous with the upper mold groove 35A. Further, a recess (hereinafter referred to as a small recess) 59 having a relatively small width W2b in the length direction of the groove 35 is formed as a recess recessed from the inner bottom surface of the large recess 57. In the small recess 59, a counter member 49C that is advanced and retracted in the vertical direction by an advancing and retracting drive means 61 such as a fluid pressure cylinder is disposed.
On the other hand, a protruding block 63 is provided on the lower mold member 33B so as to be movable up and down. The protruding block 63 is moved up and down by an advancing / retreating drive means 65 such as a fluid pressure cylinder. The protruding block 63 further includes a protruding member 67 similar to the protruding member 41 in the first embodiment. The projecting member 67 can be moved forward and backward relative to the projecting block 63 by an advancing / retreating drive means 69 such as a fluid pressure cylinder fixed to the projecting block 63.

FIGS. 24A to 24D show a process of forming a two-stage U-shaped bent portion in the material pipe 37 using the apparatus shown in FIG.
At the stage where the material pipe 37 is set in the mold 31 and the material pipe 37 is filled with a liquid such as water for applying a hydraulic pressure and the mold is clamped (see FIG. 24A), the protruding block 63 has an upper surface. Is in contact with the lower surface of the material tube 37, and the lower surface (tip surface) of the counter member 49C is flush with the inner bottom surface of the large recess 57.

  Then, while applying the hydraulic pressure and pushing the shaft, as shown in FIG. 24B, if the protruding block 63 is entirely raised, the intermediate portion of the material pipe 37 is pushed into the large recess 57, A relatively large U-shaped bent portion 3H is formed.

  Next, as shown in FIG. 24C, while continuing to apply the hydraulic pressure and pushing the shaft, the protruding member 67 is raised relative to the protruding block 63 and the counter member 49C can be raised at a constant speed. For example, the intermediate portion of the relatively large U-shaped bent portion 3A in the material pipe 37 is pushed into the small recess 59, and a relatively small U-shaped bent portion 3I is formed. Thereafter, when the shaft is further pushed and the hydraulic pressure is applied, as shown in FIG. 24D, the U-shaped bent portions 3H and 3I are formed on the inner surfaces of the large recess 57 and the small recess 59 and the lower surface of the counter member 49C. Shaped along the shape.

  In each of the above embodiments, the material pipe 37 before processing is shown as a straight one, but may be provided with a bend in advance by pre-processing. In that case, the shapes of the upper mold member 33A and the lower mold member 33B constituting the mold 31, particularly the shapes of the upper mold groove 35A and the lower mold groove 35B constituting the groove portion 35 are adapted to the bent shape by the pre-processing. Set it. An example in that case (an example according to the first embodiment) is shown in FIG. 25 as an eighth embodiment.

  In addition, as described above, with respect to the hollow tube having the U-shaped bent portion to be finally obtained, with reference to FIG. 33 (a) or (b), two straight tube portions 1A having a common axis O, The hollow tube 5 having the U-shaped bent portion 3 protruding in a direction perpendicular to the axial direction of the straight pipe portions 1A and 1B is described between 1B and 1B. The two straight pipe portions 1A and 1B do not necessarily have the common axis O, and the axis of one straight pipe portion 1A and the axis of the other straight pipe portion 1B form an angle. Is also applicable. An example of an apparatus for forming a bent portion in that case is shown in FIG. 26 as a ninth embodiment.

  Furthermore, in the method of the present invention, it is also possible to simultaneously form U-bent portions at two or more locations in the material pipe 37 that are separated in the length direction. An example of the device configuration in that case is shown in FIG. 27 as a tenth embodiment. In the tenth embodiment, basically, the same components as those in the first embodiment are arranged side by side in the same mold 31 at positions separated in the length direction of the groove 35. Is. That is, two concave portions 39 are formed at positions separated in the length direction of the groove portion 35 in the upper mold member 33A, and the protruding members 41 are respectively disposed at positions corresponding to the concave portions 39 in the lower mold member 33B. The arrangement is arranged.

  In addition, as a method for forming U-shaped bent portions at two or more locations separated in the length direction of the material pipe 37, for example, as shown in FIG. The first U-bent portion 3J is formed in the portion by the method of the present invention (for example, the method according to the first embodiment), and then the method of the present invention (for example, the first If the second U-bent portion 3K is formed by the method according to the embodiment, and this process is repeated sequentially, a hollow tube having a large number of U-bent portions 3J, 3K, and 3L can be manufactured. .

  Further, in each of the above-described embodiments, the inner bottom surface and the side surface of the concave portion 39 are substantially flat surfaces, and the outer surface of the protruding member 41 is also a substantially flat surface except for the curved surface at the tip, whereby U A hollow tube having a rectangular cross-sectional shape of the bent portion 3 is manufactured. However, in the method of the present invention, the shape of the inner bottom surface and the side surface of the recess 39 and the shape of the outer surface of the protruding member 41 are changed. Thus, U-shaped bent portions having various cross-sectional shapes can be formed.

For example, when it is desired to obtain a U-shaped bent portion having a circular cross-sectional shape, the cross-sectional shapes of the tip 41A and the side surfaces 41B and 41C of the protruding member 41 are concavely curved as shown in FIGS. In addition, the inner bottom surface 39C and the side surfaces 39D and 39E of the concave portion 39 may be formed into a semicircular shape having a concave curve. For example, when it is desired to obtain a U-shaped bent portion having a polygonal cross-sectional shape, as shown in FIGS. 31 and 32, the cross-sectional shapes of the tip 41A and the side surfaces 41B and 41C of the protruding member 41 are concave multiple. In addition, the inner bottom surface 39C and the side surfaces 39D and 39E of the concave portion 39 may be formed into a concave polygon. In addition, a U-shaped bent portion having various cross-sectional shapes can be formed as necessary.
When the counter member is disposed in the recess, the cross-sectional shape of the tip surface of the counter member is replaced with a concave-curved semicircle or concave polygon as described above instead of the cross-sectional shape of the inner bottom surface of the recess. Of course, it should be set to.

  Examples of the present invention are shown below. In addition, the following examples are for confirming the operation and effect of the present invention, and it is needless to say that the conditions described in the examples do not limit the technical scope of the present invention.

[Example 1]
This Example 1 corresponds to the first embodiment, and as a mold, a material as shown in FIGS. 1 to 4 is used, and a material according to the method shown in FIGS. 5 (a) to 5 (g). The tube was processed to produce a hollow tube with a U-bend. Here, the groove portion 35 in the mold 31 has a circular cross section as a whole and an inner diameter of 38.1 mm. Further, the recess 39 of the upper mold member 33A has a width (interval between the inner side surfaces 39A, 39B) W2 of 85.0 mm along the length direction of the groove portion 35, and an inner surface in a direction orthogonal to the length direction of the groove portion 35. The distance W1 was 40.0 mm and the depth was 120.0 mm. On the other hand, as the protruding member 41, a member having a thickness T of 5.0 mm and a tip surface curved in a convex shape with a radius of curvature of 2.5 mm was used. As the material pipe 37, a hollow pipe made of STKM13B having a carbon steel pipe for mechanical structure having an outer diameter of 38.1 mm and a wall thickness of 2.3 mm was used.

  Specifically, pipe end sealing members 45A and 45B are attached to both ends of the raw material pipe 37, arranged in the groove part 35, filled with water as a pressurizing liquid in the raw material pipe, and arranged in the groove part 35. After tightening, a pressure of 50 kN (axial pushing force) was applied to the tube end sealing member in the axial direction, and a pressure of 20 MPa was applied to the pressurizing liquid in the material tube 37. Then, the material pipe 37 was axially driven from both sides thereof at a speed of 5.0 mm / sec while the axial push and hydraulic pressure were continuously applied, and the protruding member 41 was raised at a speed of 5.0 mm / sec. . Then, at the stage where a part of the material tube was in contact with the inner bottom surface of the recess 39, the raising of the protruding member 41 was stopped and the hydraulic pressure was raised to 80 MPa.

  As a result, a hollow tube having a U-shaped bend as shown in FIG. 6 was obtained. Here, when the molded hollow tube product was examined, it was confirmed that it was precisely processed into a shape along the inner surface of the recess. Furthermore, the appearance of the outer peripheral surface of the U-shaped bent portion was also confirmed to have good appearance quality, particularly without occurrence of cracks, irregularities, and wrinkles.

[Example 2]
This Example 2 corresponds to the second embodiment, and the same manufacturing apparatus as that of Example 1 is used as the manufacturing apparatus, and the carbon steel pipe for machine structure similar to that of Example 1 is used as the material pipe. : Using STKM13B with an outer diameter of 38.1 mm and a wall thickness of 2.3 mm, the material tube is processed according to the method shown in FIGS. 7A to 7D, and has a U-shaped bend. A tube was manufactured. Here, the groove part 35 in the mold 31 has a circular cross section as a whole and an inner diameter of 38.1 mm. Further, the recess 39 of the upper mold member 33A has a width (interval between the inner side surfaces 39A, 39B) W2 of 85.0 mm along the length direction of the groove portion 35, and an inner surface in a direction orthogonal to the length direction of the groove portion 35. The distance W1 was 40.0 mm and the depth was 120.0 mm. On the other hand, as the protruding member 41, a member having a thickness T of 5.0 mm and a tip surface curved in a convex shape with a radius of curvature of 2.5 mm was used.

  As in Example 1, pipe end sealing members 45A and 45B are attached to both ends of the raw material pipe 37, placed in the groove 35, filled with water as a pressurizing liquid in the raw material pipe, and placed in the groove 35, After clamping and clamping, a pressure of 50 kN (axial pushing force) was applied to the tube end sealing member in the axial direction, and a pressure of 20 MPa was applied to the pressurizing liquid in the material tube 37. . Then, the material pipe 37 is axially driven at a speed of 5.0 mm / sec from both sides of the material pipe 37 while the axial pressing and the application of the hydraulic pressure are continued, and the protruding member 41 is raised at a speed of 5.0 mm / sec. At a point before the material tube contacts the inner bottom surface of 39, the protruding member 41 was lowered. Subsequently, the axial push and the application of the fluid pressure were continued, and the fluid pressure was increased to 80 MPa when a part of the material tube was in contact with the inner bottom surface of the recess 39.

  As a result, it was possible to obtain a hollow tube having a U-shaped bent portion as shown in FIG. 8, that is, a hollow tube having a substantially zero inner curvature radius. Here, when the molded hollow tube product was examined, it was confirmed that the hollow tube product was processed into a shape along the inner surface of the recess with high accuracy. Furthermore, the appearance of the outer peripheral surface of the U-shaped bent portion was also confirmed to have good appearance quality, particularly without occurrence of cracks, irregularities, and wrinkles.

Example 3
This Example 3 corresponds to the third embodiment, and a mold having a counter member 49 as shown in FIGS. 9 and 10 is used, and FIGS. The material tube was processed in accordance with the method shown in FIG. 3 to produce a hollow tube having a U-shaped bent portion.

Here, the groove portion 35 in the mold 31 has a circular cross section as a whole and an inner diameter of 38.1 mm. Further, the recess 39 of the upper mold member 33A has a width W2 in the direction along the length direction of the groove portion 35 (interval between the inner side surfaces 39A and 39B) W2 of 85.0 mm and a direction orthogonal to the length direction of the groove portion 35. The inner surface distance W1 was 40.0 mm, the depth was 140.0 mm, and the counter member 49 had a thickness of 20.0 mm. Therefore, the depth from the opening end of the recess 39 to the tip end surface of the counter member 49 in the state in which the counter member 49 is most retracted is 120.0 mm.
On the other hand, as the protruding member 41, a member having a thickness T of 5.0 mm and a tip surface curved in a convex shape with a radius of curvature of 2.5 mm was used. As the material pipe 37, a hollow pipe made of STKM13B having a carbon steel pipe for mechanical structure having an outer diameter of 38.1 mm and a wall thickness of 2.3 mm was used.

  As in Example 1, pipe end sealing members 45A and 45B are attached to both ends of the raw material pipe 37, placed in the groove 35, filled with water as a pressurizing liquid in the raw material pipe, and placed in the groove 35, After clamping and clamping, a pressure of 50 kN (axial pushing force) was applied to the tube end sealing member in the axial direction, and a pressure of 20 MPa was applied to the pressurizing liquid in the material tube 37. . The material tube 37 is axially driven at a speed of 5.0 mm / sec from both sides while the axial push and the hydraulic pressure are continuously applied, and the protruding member 41 is raised at a speed of 5.0 mm / sec. The counter member 49 is also raised at a speed of 5.0 mm / sec. When the upper surface of the counter member 49 is in contact with the inner bottom surface of the recess 39, the raising of the protruding member 41 is stopped and the hydraulic pressure is increased to 80 MPa. I let you.

  As a result, a hollow tube having a U-shaped bent portion as shown in FIG. Here, when the molded hollow tube product was examined, it was confirmed that it was precisely processed into a shape along the inner surface of the recess. Furthermore, the appearance of the outer peripheral surface of the U-shaped bent portion was also confirmed to have good appearance quality, particularly without occurrence of cracks, irregularities, and wrinkles.

Example 4
This Example 4 corresponds to the fourth embodiment. As the mold, the one shown in FIGS. 12 to 14 is used, and the material is manufactured according to the method shown in FIGS. 15 (a) to (d). The tube was processed to produce a hollow tube having a plurality of U-shaped bent portions having a substantially W shape as shown in FIG. Here, the groove portion 35 in the mold 31 has a circular cross section as a whole and an inner diameter of 38.1 mm. Further, the upper mold recess 53A of the upper mold member 33A has a width (interval between the inner side surfaces 39A, 39B) W2 in the direction along the length direction of the groove 35 of 175.0 mm and a direction orthogonal to the length direction of the groove 35. The inner surface distance W1 was 40.0 mm and the depth was 120.0 mm. On the other hand, the lower mold recess 53B of the lower mold member 33B has a width W3 (interval between the inner side surfaces 39A and 39B) W3 of 85.0 mm along the length direction of the groove 35, and is orthogonal to the length direction of the groove 35. The distance between inner surfaces W4 in the direction was 40.0 mm, and the depth was 120.0 mm. Each of the protruding members (upper mold protruding member 55A, lower mold protruding members 55B ₁ and 55B ₂ ) has a thickness T of 5.0 mm and a tip surface curved in a convex shape with a radius of curvature of 2.5 mm. Was used. As the material pipe 37, a hollow pipe made of STKM13B having a carbon steel pipe for mechanical structure having an outer diameter of 38.1 mm and a wall thickness of 2.3 mm was used.

Specifically, pipe end sealing members 45A and 45B are attached to both ends of the raw material pipe 37, arranged in the groove part 35, filled with water as a pressurizing liquid in the raw material pipe, and arranged in the groove part 35. After tightening, a pressure of 50 kN (axial pushing force) was applied to the tube end sealing member in the axial direction, and a pressure of 20 MPa was applied to the pressurizing liquid in the material tube 37. Then, the material tube 37 is axially driven from both sides at a speed of 5.0 mm / sec while continuing the axial pushing and hydraulic pressure application, and the upper die protruding member 55A is lowered at a speed of 5.0 m / sec. I let you. Then, when a part of the material tube comes into contact with the inner bottom surface of the lower mold recess 53B, the lowering of the upper mold protruding member 55A is stopped, and the lower mold protruding members 55B ₁ and 55B ₂ are moved upward (the rising speed is 5.0 mm / sec). ) Was started. Next, at the stage where a part of the material tube was in contact with the inner bottom surface of the upper mold recess 53A, the lower mold protrusion members 55B ₁ and 55B ₂ were stopped from rising and the hydraulic pressure was increased to 80 MPa.

  As a result, a hollow tube having a substantially W-shaped bent portion in which a plurality of U-shaped bent portions continued as shown in FIG. 16 could be obtained. Here, when the molded hollow tube product was examined, it was confirmed that it was precisely processed into a shape along the inner surface of the recess. Furthermore, the appearance of the outer peripheral surface of the U-shaped bent portion was also confirmed to have good appearance quality, particularly without occurrence of cracks, irregularities, and wrinkles.

  The preferred embodiments and examples of the present invention have been described above, but the present invention is not limited to these embodiments and examples, and additions and omissions of configurations are within the scope of the present invention. , Substitutions, and other changes are possible.

  The manufacturing method and apparatus of the U-shaped bent pipe of the present invention includes a heat exchanger, an automotive part, an architectural interior part, an architectural exterior part, an outdoor device such as a gate, other chemical plant parts, and various liquid processing equipment parts. Suitable for manufacturing hollow tubes used in

1A, 1B Straight pipe part 3, 3A-3L U-shaped bent part 5 Hollow pipe 31 Mold 33A Upper mold member 33B Lower mold member 35 Groove part 37 Material pipe 37A, 37B Both end parts 39, 53A, 53B Recessed parts 41, 55A, 55B ₁ , 55B ₂ protruding member 42, 42A ₁ , 42A ₂ , 42B advance / retreat driving means 45A, 45B pipe end sealing member 49, 49A ₁ , 49A ₂ , 49B counter member

Claims (14)

A method for producing a hollow tube having a U-shaped bent portion projecting in a direction forming a predetermined angle with respect to an axial direction of the straight pipe portion between two or more straight pipe portions,
Between the mold member that constitutes the upper mold and the mold member that constitutes the lower mold, a groove portion into which a material tube having a hollow tubular shape is inserted is formed, and at least one of the upper and lower mold members, At least one recess that is continuous with the space in the groove and is recessed toward the inside of the other mold member is formed, and at least the other mold member has a space in the recess through the space in the groove. Using a mold provided with at least one protruding member capable of moving forward and backward,
A material pipe is disposed in the groove, and both ends of the material pipe are sealed by a pipe end sealing member that also serves as a shaft pushing member, and a hydraulic pressure is applied to the inner space of the material pipe, and the material pipe is attached to both ends of the material pipe. While pushing in the direction along the axis, the protruding member is advanced from the side of the other mold member into the recess, and the intermediate portion in the longitudinal direction of the material tube is pushed into the recess. A method of manufacturing a hollow tube having a U-shaped bent portion, characterized in that a U-shaped bent portion of a material pipe is formed in the recess.   After stopping the advancement of the push-up member, the U-bent portion in the recess is increased by increasing the hydraulic pressure applied to the inner space of the material tube while continuing to press the material tube in the axial direction. The method for producing a hollow tube having a U-shaped bent portion according to claim 1, wherein the hollow tube is formed into a shape along the inner surface of the concave portion.   In the middle of the process of advancing the protruding member and pushing the intermediate portion in the longitudinal direction of the material pipe into the recess, the advancement of the protruding member is stopped, and the protruding member is subsequently retracted. The intermediate portion of the material pipe is pushed into the concave portion only by the hydraulic pressure applied to the inner space of the material pipe and the pressure applied to the material pipe along the axial direction from both ends thereof. The manufacturing method of the hollow tube which has a U-shaped bending part as described in any one of Claim 2. As the mold, further, the one mold member is provided with a counter member capable of moving back and forth toward the other mold member in the recess,
The protruding member is advanced to push the intermediate portion of the material pipe into the recess, and at the same time, the counter member is moved backward while the outer surface of the intermediate portion of the material pipe is brought into contact with the front end surface of the counter member. A method of manufacturing a hollow tube having a U-shaped bent portion according to claim 1 or 2.   After stopping the advancement of the push-up member and the backward movement of the counter member, the U-bent portion is increased by increasing the fluid pressure applied to the inner space of the material tube while continuing to pressurize the material tube in the axial direction. 5. The method for manufacturing a hollow tube having a U-shaped bent portion according to claim 4, wherein the counter member is formed into a shape along a tip surface of the counter member and an inner surface of the recess.   As the mold, one mold member of the upper and lower mold members is formed with one concave portion that is continuous with the space in the groove and is recessed toward the inside of the other mold member, and at least the other mold member is formed. 6. The mold according to claim 1, wherein the mold member is provided with one projecting member that can move forward and backward in the recess through the space in the groove. The manufacturing method of the hollow tube which has a U-shaped bending part of Claim.   As the mold, one mold member of the upper and lower mold members has two or more concave portions that are continuous in the space in the groove portion and are recessed toward the inside of the other mold member in the length direction of the groove portion. The other mold member is provided with two or more projecting members that can advance and retreat into the respective concave portions through the spaces in the groove portions, corresponding to the two or more concave portions. A method for producing a hollow tube having a U-shaped bent portion according to any one of claims 1 to 5, wherein a mold is used. As the mold, one or more first protruding members are disposed on the other mold member at a predetermined interval in the length direction of the groove portion, and one or more second members are disposed on the one mold member. The protruding member is disposed at a position shifted by a predetermined distance in the length direction of the groove portion with respect to the position of the first protruding member, and the one mold member corresponds to the first protruding member. A first recess is formed, and the other mold member is formed with a second recess corresponding to the second protruding member.
A material pipe is disposed in the groove, and both ends of the material pipe are sealed by a pipe end sealing member that also serves as a shaft pushing member, and a hydraulic pressure is applied to the inner space of the material pipe, and the material pipe is attached to both ends of the material pipe. From the side of the other mold member, the first projecting member is advanced from the side of the other mold member while pressing in the direction along the axis, and the intermediate portion in the longitudinal direction of the material tube is pushed into the first recess. Next, the second projecting member is advanced from the side of the one mold member, and the intermediate portion in the longitudinal direction of the material tube is pushed into the second recess, whereby the intermediate portion in the longitudinal direction of the material tube 6. A hollow tube having a U-shaped bent portion according to any one of claims 1 to 5, wherein two or more U-shaped bent portions that are continuously bent in the opposite direction to each other are formed. Manufacturing method. As the mold, further, at least one mold member provided with a counter member capable of moving back and forth toward the other mold member in the recess,
The at least one protruding member is advanced to push the intermediate portion of the material pipe into the recess, and at the same time, the counter member is retracted while the outer surface of the pushed intermediate portion of the material pipe is brought into contact with the tip surface of the counter member. The manufacturing method of the hollow tube which has a U-shaped bending part of Claim 8 characterized by the above-mentioned. As the mold, two first projecting members are disposed on the other mold member at a predetermined interval in the length direction of the groove portion, and one second projecting member is disposed on the one mold member. A member is disposed at an intermediate position between the two first protruding members, and the first mold member has a first recess corresponding to the first protruding member, and the other mold member. Is used in which a second recess corresponding to the second protruding member is formed,
10. The U-shape according to claim 8, wherein three U-shaped bent portions that are continuously bent in opposite directions are formed in an intermediate portion in a longitudinal direction of the material tube. A method for producing a hollow tube having a bent portion.   After forming one or two or more U-shaped bent portions at predetermined locations in the intermediate portion of the material pipe by the method according to any one of claims 1 to 10, further separating the intermediate portion of the material pipe The step of forming one or two or more U-shaped bent portions in the same place by the same method is performed one or more times, thereby manufacturing a hollow tube having a large number of U-shaped bent portions. A method for producing a hollow tube having a bent portion.   After forming one or two or more U-curved portions at a predetermined portion of the intermediate portion of the material pipe by the method according to any one of claims 1 to 10, the intermediate portion of the U-curved portion is further formed. Forming one or more U-curved portions in a portion by the same method one or more times, thereby producing a hollow tube having a large number of bent portions A method for producing a hollow tube having a portion. An apparatus for producing a hollow tube having a U-shaped bent portion protruding in a direction forming a predetermined angle with respect to the axial direction of the straight pipe portion between two or more straight pipe portions,
A mold comprising a mold member constituting the upper mold and a mold member constituting the lower mold;
A groove portion into which a hollow tube-shaped material pipe is inserted is formed between the two mold members, and at least one of the two mold members is continuous with the space in the groove portion and the other At least one recess that is recessed toward the inside of the mold member, and at least one projecting member that can advance and retract toward the recess through the space in the groove on the side of the other mold member An apparatus for producing a hollow tube having a U-shaped bent portion.   14. The U-shaped bent portion according to claim 13, wherein the one mold member of the mold is provided with a counter member capable of moving forward and backward in the recess toward the other mold member. Hollow tube manufacturing equipment.

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