阅读说明：本技术 弯管制造装置以及弯管制造方法 (Bent pipe manufacturing device and bent pipe manufacturing method ) 是由 山本幸一郎 岩濑広夫 于 2021-04-12 设计创作，主要内容包括：本公开提供一种在对双层管进行弯曲时能够抑制屈曲的弯管制造装置。本公开的一个方案是一种通过对双层管进行弯曲而获得弯管的弯管制造装置。弯管制造装置包括配置在第1配管内部的内侧芯棒、以及配置在第1配管与第2配管之间的中间芯棒。中间芯棒具有筒形的中间芯棒主体以及筒形的第1中间可动部,第1中间可动部与中间芯棒主体的于轴向上的端部连结,并且第1中间可动部以与中间芯棒主体的中心轴正交的第1中间摆动轴为中心而相对于中间芯棒主体进行摆动。中间芯棒主体中的在对双层管进行弯曲时靠近第1中间可动部的第1接近部的端缘与下述虚拟平面相交,该虚拟平面正交于第2配管中的和中间芯棒接触的部分处的中心轴。(The present disclosure provides a bent pipe manufacturing apparatus capable of suppressing buckling when bending a double-walled pipe. One aspect of the present disclosure is a bent pipe manufacturing apparatus that obtains a bent pipe by bending a double-walled pipe. The bent pipe manufacturing apparatus includes an inner mandrel disposed inside the 1 st pipe and an intermediate mandrel disposed between the 1 st pipe and the 2 nd pipe. The intermediate plug has a cylindrical intermediate plug main body and a cylindrical 1 st intermediate movable portion, the 1 st intermediate movable portion is connected to an end portion of the intermediate plug main body in the axial direction, and the 1 st intermediate movable portion swings with respect to the intermediate plug main body about a 1 st intermediate swing axis orthogonal to a central axis of the intermediate plug main body. An end edge of a 1 st approach portion of the intermediate plug main body, which is close to the 1 st intermediate movable portion when the double tube is bent, intersects a virtual plane orthogonal to a central axis of a portion of the 2 nd pipe which is in contact with the intermediate plug.)

1. A bent pipe manufacturing apparatus that obtains a bent pipe by bending a double pipe including a 1 st pipe and a 2 nd pipe in which the 1 st pipe is disposed, the bent pipe manufacturing apparatus comprising:

an inner plug configured to be disposed inside the 1 st pipe;

an intermediate plug configured to be disposed between the 1 st pipe and the 2 nd pipe; and

a bending die configured to bend the double tube in which the inner mandrel and the intermediate mandrel are arranged, and to bend the double tube

The intermediate plug has a cylindrical intermediate plug main body and a cylindrical 1 st intermediate movable portion, the 1 st intermediate movable portion is connected to an end portion of the intermediate plug main body in the axial direction, and the 1 st intermediate movable portion swings with respect to the intermediate plug main body about a 1 st intermediate swing axis orthogonal to a central axis of the intermediate plug main body,

an end edge of a 1 st approach portion of the intermediate plug main body, which is close to the 1 st intermediate movable portion when the double tube is bent by the bending die, intersects a virtual plane orthogonal to a central axis at a portion of the 2 nd pipe which is in contact with the intermediate plug.

2. The bent pipe manufacturing apparatus according to claim 1,

the 1 st approach portion protrudes toward the 1 st intermediate movable portion in the axial direction of the intermediate plug main body.

3. The bent pipe manufacturing apparatus according to claim 2,

the width of the 1 st approach portion in the circumferential direction of the intermediate plug main body becomes smaller toward the protruding end.

4. The bent pipe manufacturing apparatus according to claim 1,

the intermediate plug further includes a cylindrical 2 nd intermediate movable portion, the 2 nd intermediate movable portion being connected to the 1 st intermediate movable portion on a side opposite to the intermediate plug main body with the 1 st intermediate movable portion interposed therebetween, and the 2 nd intermediate movable portion being swingable with respect to the 1 st intermediate movable portion about a 2 nd intermediate swing axis orthogonal to a central axis of the 1 st intermediate movable portion,

an end edge of a 2 nd approach portion of the 1 st intermediate movable portion, which is close to the 2 nd intermediate movable portion when the double tube is bent by the bending die, intersects a virtual plane orthogonal to a central axis at a portion of the 2 nd pipe which is in contact with the intermediate mandrel.

5. A method for producing a bent pipe, the method being for obtaining a bent pipe by bending a double pipe having a 1 st pipe and a 2 nd pipe in which the 1 st pipe is disposed, the method comprising:

a disposing step of disposing an inner mandrel inside the 1 st pipe and disposing an intermediate mandrel between the 1 st pipe and the 2 nd pipe; and

a bending step of bending the double tube in which the inner mandrel and the intermediate mandrel are arranged, and bending the double tube

The intermediate plug has a cylindrical intermediate plug main body and a cylindrical 1 st intermediate movable portion, the 1 st intermediate movable portion is connected to an end portion of the intermediate plug main body in the axial direction, and the 1 st intermediate movable portion swings with respect to the intermediate plug main body about a 1 st intermediate swing axis orthogonal to a central axis of the intermediate plug main body,

an end edge of a 1 st approach portion of the intermediate plug main body, which is close to the 1 st intermediate movable portion when the double tube is bent, intersects a virtual plane orthogonal to a central axis of a portion of the 2 nd pipe which is in contact with the intermediate plug.

Technical Field

The present disclosure relates to a bent pipe manufacturing apparatus and a bent pipe manufacturing method.

Background

There is known a method of obtaining a bent pipe by pressing a bending die from the outside against a double tube into which a mandrel (i.e., a mandrel) is inserted (see japanese patent laid-open No. s 60-234723). The intermediate mandrel disposed between the inner tube and the outer tube is composed of a mandrel main body and a movable portion connected to the mandrel main body so as to be swingable with respect to the mandrel main body.

In the above method, the movable portion of the intermediate mandrel moves to follow the pipe when bending the pipe, thereby ensuring the bent shape of the pipe.

Disclosure of Invention

In the bending process using the above mandrel, the inner tube is compressed in the axial direction by the mandrel main body and the movable portion of the intermediate mandrel at the inner side of the bending. Therefore, buckling (i.e., wrinkles) due to axial compression of the inner tube is likely to occur.

An aspect of the present disclosure is to preferably provide a bent pipe manufacturing apparatus capable of suppressing buckling generated when a double-walled pipe is bent.

One aspect of the present disclosure is a bent pipe manufacturing apparatus that obtains a bent pipe by bending a double pipe including a 1 st pipe and a 2 nd pipe in which the 1 st pipe is disposed. The bent pipe manufacturing device comprises: an inner mandrel configured to be disposed inside the 1 st pipe; an intermediate plug configured to be disposed between the 1 st pipe and the 2 nd pipe; and a bending die configured to bend the double tube in which the inner mandrel and the intermediate mandrel are arranged.

The intermediate plug has a cylindrical intermediate plug main body and a cylindrical 1 st intermediate movable portion, the 1 st intermediate movable portion is connected to an end portion of the intermediate plug main body in the axial direction, and the 1 st intermediate movable portion swings with respect to the intermediate plug main body about a 1 st intermediate swing axis orthogonal to a central axis of the intermediate plug main body. An end edge of a 1 st approach portion of the intermediate plug main body, which is close to the 1 st intermediate movable portion when the double tube is bent by the bending die, intersects a virtual plane orthogonal to a central axis of a portion of the 2 nd pipe which is in contact with the intermediate plug.

According to the above configuration, since the end edge of the 1 st proximal portion of the intermediate plug main body is not parallel to the circumferential direction of the double tube, the axial compressive force generated by the bending of the 1 st pipe being sandwiched between the intermediate plug main body and the 1 st intermediate movable portion is dispersed in the axial direction of the 1 st pipe. As a result, the 1 st pipe can be prevented from buckling when the double pipe is bent.

In one aspect of the present disclosure, the 1 st approaching portion may protrude toward the 1 st intermediate movable portion in the axial direction of the intermediate mandrel body. According to the above configuration, when the double tube is bent, the 1 st approaching portion of the intermediate plug main body presses the portion of the 1 st tube where buckling is likely to occur, and therefore, buckling can be more reliably suppressed from occurring.

In one aspect of the present disclosure, the width of the 1 st approach portion in the circumferential direction of the intermediate mandrel main body may become smaller toward the protruding end. According to the above configuration, the effect of dispersing the compression force by the 1 st approach portion can be improved. As a result, the effect of suppressing the occurrence of buckling can be promoted.

In one aspect of the present disclosure, the intermediate plug may further include a 2 nd intermediate movable portion having a cylindrical shape, the 2 nd intermediate movable portion being connected to the 1 st intermediate movable portion at a side opposite to the intermediate plug main body with the 1 st intermediate movable portion interposed therebetween, and the 2 nd intermediate movable portion being swingable with respect to the 1 st intermediate movable portion about a 2 nd intermediate swing axis orthogonal to a central axis of the 1 st intermediate movable portion. The end edge of the 2 nd approach portion of the 1 st intermediate movable portion, which is close to the 2 nd intermediate movable portion when the double tube is bent by the bending die, may intersect a virtual plane orthogonal to the central axis at a portion of the 2 nd pipe which is in contact with the intermediate mandrel. According to the above configuration, the occurrence of buckling in the production of a bent pipe having a large bending angle can be reliably suppressed.

Another aspect of the present disclosure is a method for producing a bent pipe, in which a bent pipe is obtained by bending a double pipe including a 1 st pipe and a 2 nd pipe in which the 1 st pipe is disposed. The bent pipe manufacturing method comprises the following steps: a disposing step of disposing an inner mandrel inside the 1 st pipe and disposing an intermediate mandrel between the 1 st pipe and the 2 nd pipe; and a bending step of bending the double tube in which the inner mandrel and the intermediate mandrel are arranged.

The intermediate plug has a cylindrical intermediate plug main body and a cylindrical 1 st intermediate movable portion, the 1 st intermediate movable portion is connected to an end portion of the intermediate plug main body in the axial direction, and the 1 st intermediate movable portion swings with respect to the intermediate plug main body about a 1 st intermediate swing axis orthogonal to a central axis of the intermediate plug main body. An end edge of a 1 st approach portion of the intermediate plug main body, which is close to the 1 st intermediate movable portion when the double tube is bent, intersects a virtual plane orthogonal to a central axis of a portion of the 2 nd pipe which is in contact with the intermediate plug.

According to the above configuration, since the compression force in the axial direction generated inside the bend of the 1 st pipe is dispersed in the circumferential direction, the 1 st pipe can be prevented from buckling when the double pipe is bent.

Drawings

Fig. 1 is a schematic view of an elbow manufacturing apparatus according to an embodiment.

Fig. 2A is a schematic side view of an inner mandrel in the bent pipe manufacturing apparatus of fig. 1.

Fig. 2B is a central cross-sectional view of the inner core rod of fig. 2A.

Fig. 3A is a schematic plan view of an intermediate core rod in the bent pipe manufacturing apparatus of fig. 2A.

Fig. 3B is a schematic cross-sectional view taken along line IIIB-IIIB of fig. 3A.

Fig. 4A is a schematic perspective view of the intermediate mandrel body of the intermediate mandrel of fig. 3A.

Fig. 4B is a schematic top view of the intermediate mandrel body of fig. 4A.

Fig. 5A is a schematic perspective view of the 1 st intermediate movable section of the intermediate mandrel of fig. 3A.

Fig. 5B is a schematic plan view of the 1 st intermediate movable portion of fig. 5A.

Fig. 6A is a schematic perspective view of the 2 nd intermediate movable portion of the intermediate mandrel of fig. 3A.

Fig. 6B is a schematic plan view of the 2 nd intermediate movable portion of fig. 6A.

Fig. 7 is a flowchart of a method for manufacturing the bent pipe according to the embodiment.

Fig. 8A is a schematic diagram illustrating steps of a method of manufacturing the bent pipe of fig. 7.

Fig. 8B is a schematic diagram illustrating the next step of fig. 8A.

Fig. 9A is a schematic diagram illustrating the next step of fig. 8B.

Fig. 9B is a schematic diagram for explaining the next step of fig. 9A.

Fig. 10A to 10K are schematic views showing the shape type of the proximity portion in the embodiment different from fig. 3A.

Detailed Description

Embodiments to which the present disclosure is applied are described below with reference to the drawings.

[1 ] embodiment 1 ]

[1-1. constitution ]

A bent pipe manufacturing apparatus 1 shown in fig. 1 (hereinafter also simply referred to as "manufacturing apparatus 1") is an apparatus for obtaining a bent pipe by bending a straight pipe.

The manufacturing apparatus 1 of the present embodiment manufactures a bent pipe from a double pipe 110 including a 1 st pipe 101 and a 2 nd pipe 102. The 2 nd pipe 102 is disposed so as to surround the outer peripheral surface of the 1 st pipe 101. That is, the 1 st pipe 101 is disposed inside the 2 nd pipe 102.

The 1 st pipe 101 and the 2 nd pipe 102 are joined at the 1 st end 111 of the double tube 110. On the other hand, the 1 st pipe 101 and the 2 nd pipe 102 are not joined at the 2 nd end 112 located on the opposite side of the 1 st end 111.

The 1 st pipe 101 and the 2 nd pipe 102 have circular outer shapes in cross sections perpendicular to the central axis. In the present embodiment, the central axis of the 1 st pipe 101 and the central axis of the 2 nd pipe 102 overlap each other, but the central axis of the 1 st pipe 101 and the central axis of the 2 nd pipe 102 may not overlap each other.

The manufacturing apparatus 1 simultaneously bends the 1 st pipe 101 and the 2 nd pipe 102 while securing a gap between the 1 st pipe 101 and the 2 nd pipe 102, thereby obtaining a bent double pipe 110.

The manufacturing apparatus 1 includes an inner mandrel 2, an intermediate mandrel 3, and a bending die 5.

< inner mandrel >

As shown in fig. 2A, the inner plug 2 is arranged inside the 1 st pipe 101. As shown in fig. 2B, the inner plug 2 includes an inner plug main body 21, a 1 st inner movable portion 22, and a 2 nd inner movable portion 23.

(inner core rod body)

The inner core rod main body 21 is a member having a cylindrical shape or a cylindrical shape. The inner mandrel main body 21 is disposed in a straight tube portion (i.e., a portion that is not bent) of the double tube 110.

The outer diameter of the inner core rod main body 21 is constant in the axial direction. The outer diameter of the inner plug main body 21 is substantially equal to the inner diameter of the 1 st pipe 101. The axial length of the inner plug main body 21 is longer than the axial lengths of the 1 st inner movable portion 22 and the 2 nd inner movable portion 23.

(1 st inner movable part)

The 1 st inner movable portion 22 is a cylindrical or columnar member connected to one end portion of the inner plug main body 21 in the axial direction.

The 1 st inner movable portion 22 swings with respect to the inner plug main body 21 about a 1 st inner swing axis L11 orthogonal to the central axis of the inner plug main body 21. The 1 st inner swing axis L1 passes through an intersection where a straight line including the center axis of the inner mandrel main body 21 and a straight line including the center axis of the 1 st inner movable portion 22 intersect.

A part of the 1 st inner movable portion 22 is held inside the inner plug main body 21. The 1 st inner swing axis L11 is located inside the inner mandrel main body 21.

(2 nd inner movable part)

The 2 nd inner movable portion 23 is a member having a cylindrical or columnar shape, and is connected to the 1 st inner movable portion 22 at a side opposite to the inner plug main body 21 with the 1 st inner movable portion 22 interposed therebetween.

The 2 nd inner movable part 23 swings with respect to the 1 st inner movable part 22 about a 2 nd inner swing axis L2 parallel to the 1 st inner swing axis L1 of the 1 st inner movable part 22. The 2 nd inner swing axis L2 passes through an intersection where a straight line including the center axis of the 1 st inner movable portion 22 and a straight line including the center axis of the 2 nd inner movable portion 23 intersect.

A part of the 2 nd inner movable portion 23 is held inside the 1 st inner movable portion 22. The 2 nd inner swing shaft L2 is located inside the 1 st inner movable portion 22.

< intermediate core rod >

The intermediate mandrel 3 shown in fig. 1 is disposed between the 1 st pipe 101 and the 2 nd pipe 102.

The intermediate plug 3 is disposed so as to radially sandwich the 1 st pipe 101 together with the inner plug body 21 at the bent portion of the double tube 110. The intermediate plug 3 is sandwiched between the 1 st pipe 101 and the 2 nd pipe 102 in the radial direction of the 1 st pipe 101.

As shown in fig. 3A and 3B, the intermediate plug 3 includes an intermediate plug main body 31, a 1 st intermediate movable portion 32, and a 2 nd intermediate movable portion 33.

(middle core rod main body)

As shown in fig. 4A, the intermediate core rod main body 31 is a member having a cylindrical shape. The intermediate plug body 31 is disposed in a straight tube portion of the double tube 110.

The inner diameter and the outer diameter of the intermediate core rod main body 31 are constant in the axial direction. The inner diameter of the intermediate plug main body 31 is substantially equal to the outer diameter of the 1 st pipe 101. The outer diameter of the intermediate plug main body 31 is substantially equal to the inner diameter of the 2 nd pipe 102. The length of the intermediate plug main body 31 in the axial direction is longer than the length of the 1 st intermediate movable portion 32 and the 2 nd intermediate movable portion 33 in the axial direction.

The intermediate plug body 31 has two engaged portions 31B provided at a 1 st end portion 31A that is one end in the axial direction. The engaged portion 31B is a notch recessed inward in the axial direction of the center rod main body 31.

As shown in fig. 4B, the end edge of the 1 st approach portion 31C of the intermediate plug main body 31 that is close to the 1 st intermediate movable portion 32 when the double tube 110 is bent by the bending die 5 intersects a virtual plane S1 that is orthogonal to the central axis of the portion of the 2 nd pipe 102 that is in contact with the 1 st approach portion 31C (i.e., the central axis C1 of the intermediate plug main body 31).

Specifically, the 1 st approach portion 31C is a part of the 1 st end portion 31A. The 1 st approach portion 31C overlaps the center axis C1 of the intermediate plug main body 31 when viewed from a direction orthogonal to the 1 st intermediate swing axis L21 and the center axis C1 of the intermediate plug main body 31, which will be described later. The 1 st approach portion 31C is disposed inside a bend when the double tube 110 is bent.

The 1 st approach portion 31C is a tongue-shaped portion that protrudes toward the 1 st intermediate movable portion 32 in the axial direction of the intermediate plug main body 31. The 1 st approach portion 31C is the most projecting portion in the 1 st end portion 31A in the axial direction. Further, the width of the 1 st approach portion 31C in the circumferential direction of the intermediate plug main body 31 gradually becomes smaller as it goes toward the protruding end (i.e., as it goes closer to the 1 st intermediate movable portion 32). The end edge of the 1 st approach portion 31C is formed by curves connected to form an arc.

(1 st intermediate movable part)

As shown in fig. 3B, the 1 st intermediate movable portion 32 is a cylindrical member directly connected to the 1 st end portion 31A of the intermediate plug main body 31.

The 1 st intermediate movable portion 32 swings with respect to the intermediate plug main body 31 about a 1 st intermediate swing axis L21 orthogonal to the central axis C1 of the intermediate plug main body 31. The 1 st intermediate swing axis L21 passes through an intersection point where a straight line including the center axis C1 of the intermediate plug main body 31 intersects a straight line including the center axis C2 of the 1 st intermediate movable portion 32.

As shown in fig. 5A, the 1 st intermediate movable portion 32 has a ring portion 32A, two engaging portions 32B, and two engaged portions 32C. The inner diameter and the outer diameter of the ring portion 32A are constant in the axial direction of the 1 st intermediate movable portion 32.

The two engagement portions 32B each protrude from the ring portion 32A toward the center rod main body 31. The two engagement portions 32B face each other in the radial direction of the 1 st intermediate movable portion 32. The two engaging portions 32B are each swingably engaged with the engaged portion 31B of the middle core rod main body 31.

The two engaged portions 32C are provided at the end portions of the ring portion 32A on the opposite side to the engaging portion 32B. The engaged portion 32C is a notch recessed inward in the axial direction of the 1 st intermediate movable portion 32.

As shown in fig. 5B, the end edge of the 2 nd approach portion 32D of the 1 st intermediate movable portion 32, which is close to the 2 nd intermediate movable portion 33 when the double tube 110 is bent by the bending die 5, intersects a virtual plane S2, which is orthogonal to the central axis of the portion of the 2 nd pipe 102 that contacts the 2 nd approach portion 32D (i.e., the central axis C2 of the 1 st intermediate movable portion 32).

Specifically, the 2 nd approach portion 32D is a portion of the end portion of the ring portion 32A where the engaged portion 32C is provided. The 2 nd approaching portion 32D overlaps the center axis C2 of the 1 st intermediate movable portion 32 as viewed from a direction orthogonal to the 2 nd intermediate swing axis L22 and the center axis C2 of the 1 st intermediate movable portion 32, which will be described later. The 2 nd approach portion 32D is disposed inside the bend when the double tube 110 is bent.

The 2 nd approach portion 32D is a tongue-shaped portion that protrudes toward the 2 nd intermediate movable portion 33 in the axial direction of the 1 st intermediate movable portion 32. Further, the width of the 2 nd approach portion 32D in the circumferential direction of the 1 st intermediate movable portion 32 is gently smaller toward the projecting end (i.e., as approaching the 2 nd intermediate movable portion 33). The end edge of the 2 nd approach portion 32D is formed by curves connected to form an arc.

The end edge of the 3 rd proximate part 32E of the 1 st intermediate movable part 32, which is proximate to the 1 st proximate part 31C of the intermediate plug main body 31 when the double tube 110 is bent by the bending die 5, intersects a virtual plane S3 orthogonal to the central axis at the portion of the 2 nd pipe 102 that is in contact with the 3 rd proximate part 32E.

Specifically, the 3 rd approach portion 32E is a portion of the end portion of the ring portion 32A where the engagement portion 32B is provided. The 3 rd approach portion 32E overlaps the center axis C2 of the 1 st intermediate movable portion 32 as viewed from the direction orthogonal to the 1 st intermediate swinging axis L21 and the center axis C2 of the 1 st intermediate movable portion 32. The 3 rd approach portion 32E is disposed inside the bend when the double tube 110 is bent.

The 3 rd approach portion 32E is recessed in the axial direction of the 1 st intermediate movable portion 32 so as to be apart from the intermediate plug main body 31. Further, the width of the concave portion of the 3 rd approach portion 32E in the 1 st intermediate movable portion 32 circumferential direction is gently reduced as being distant from the intermediate plug main body 31. The end edge of the 3 rd approach portion 32E is formed by curves connected to form an arc.

The 3 rd approach portion 32E has the following shape: when the double tube 110 is bent, the 3 rd approach portion 32E does not abut on the 1 st approach portion 31C, and the gap between the 3 rd approach portion 32E and the 1 st approach portion 31C does not become large. The end edge of the 3 rd proximity portion 32E and the end edge of the 1 st proximity portion 31C have substantially similar shapes.

(2 nd intermediate movable part)

As shown in fig. 3B, the 2 nd intermediate movable portion 33 is a member having a cylindrical shape, and the 2 nd intermediate movable portion 33 is directly connected to the 1 st intermediate movable portion 32 on the opposite side of the intermediate mandrel main body 31 with the 1 st intermediate movable portion 32 interposed therebetween.

The 2 nd intermediate movable portion 33 swings with respect to the 1 st intermediate movable portion 32 about a 2 nd intermediate swing axis L22 parallel to the 1 st intermediate swing axis L21 of the 1 st intermediate movable portion 32. The 2 nd intermediate swing axis L22 passes through an intersection point where a straight line including the center axis C2 of the 1 st intermediate movable portion 32 intersects a straight line including the center axis C3 of the 2 nd intermediate movable portion 33.

As shown in fig. 6A, the 2 nd intermediate movable portion 33 has a ring portion 33A and two engaging portions 33B. The inner diameter and the outer diameter of the ring portion 33A are constant in the axial direction of the 2 nd intermediate movable portion 33.

The two engaging portions 33B each protrude from the ring portion 33A toward the 1 st intermediate movable portion 32. The two engaging portions 33B face each other in the radial direction of the 2 nd intermediate movable portion 33. The two engaging portions 33B are each swingably engaged with an engaged portion 32C provided at an end of the 1 st intermediate movable portion 32.

The end edge of the 4 th approaching portion 33C of the 2 nd intermediate movable portion 33, which is close to the 2 nd approaching portion 32D of the 1 st intermediate movable portion 32 when the double tube 110 is bent by the bending die 5, intersects a virtual plane S4, which is described below, and the virtual plane S4 is orthogonal to the central axis at the portion of the 2 nd pipe 102 that contacts the 4 th approaching portion 33C (i.e., the central axis C3 of the 2 nd intermediate movable portion 33).

Specifically, the 4 th approach portion 33C is a portion of the end portion of the ring portion 33A where the engagement portion 33B is provided. The 4 th approaching portion 33C overlaps the central axis C3 of the 2 nd intermediate movable portion 33 as viewed from the direction orthogonal to the 2 nd intermediate swinging axis L22 and the central axis C3 of the 2 nd intermediate movable portion 33. The 4 th approaching portion 33C is disposed inside the bend when the double tube 110 is bent.

The 4 th approaching portion 33C is recessed in the axial direction of the 2 nd intermediate movable portion 33 so as to be apart from the 1 st intermediate movable portion 32. Further, the width of the concave portion of the 4 th approaching portion 33C in the circumferential direction of the 2 nd intermediate movable portion 33 gradually becomes smaller as it goes away from the 1 st intermediate movable portion 32. The end edge of the 4 th approach portion 33C is formed by curves connected to form an arc.

The 4 th approach portion 33C has the following shape: when the double tube 110 is bent, the 4 th approaching portion 33C does not abut on the 2 nd approaching portion 32D, and the gap between the 4 th approaching portion 33C and the 2 nd approaching portion 32D does not become large. The end edge of the 4 th proximity portion 33C and the end edge of the 2 nd proximity portion 32D have substantially similar shapes.

< bending die >

The bending die 5 shown in fig. 1 is configured to bend the double tube 110 in a region where the inner plug 2 and the intermediate plug 3 are arranged.

Specifically, the bending die 5 radially sandwiches the 1 st pipe 101 and the 2 nd pipe 102 together with the inner plug 2 and the intermediate plug 3, and the bending die 5 rotates and moves to bend the 1 st pipe 101 and the 2 nd pipe 102. The bending die 5 includes a rotating portion 51, a clamping portion 52, a sliding portion 53, and a conveying portion 54.

The rotating portion 51 is disposed radially outward of the bent portion of the double tube 110. The rotating portion 51 is configured to rotate about the rotation axis P in a state where the clamping portion 51A is pressed against the outer peripheral surface of the double tube 110. The rotation axis P of the rotating portion 51 is parallel to the 1 st inner swing axis L11 of the 1 st inner movable portion 22.

The rotating portion 51 is configured to press the inner surface of the 1 st pipe 101 against the 1 st inner movable portion 22 and the 2 nd inner movable portion 23, and press the inner surface of the 2 nd pipe 102 against the 1 st intermediate movable portion 32 and the 2 nd intermediate movable portion 33.

The clamp portion 52 is disposed on the opposite side of the rotating portion 51 with the double tube 110 interposed therebetween. The clamp portion 52 is configured to clamp the double tube 110 together with the clamp portion 51A of the rotating portion 51. The clamp portion 52 swings about the rotation axis P of the rotating portion 51 as the rotating portion 51 rotates.

The sliding portion 53 is disposed adjacent to the rotating portion 51. The sliding portion 53 functions as a guide for conveying the double pipe 110 in the rotation direction of the rotating portion 51 by sliding relative to the outer peripheral surface of the straight cylindrical portion of the double pipe 110 during bending.

The conveying portion 54 is disposed on the opposite side of the sliding portion 53 with the double tube 110 interposed therebetween and adjacent to the clamping portion 52. The conveying portion 54 is configured to move along the central axis of the double pipe 110 while pressing the straight cylindrical portion of the double pipe 110 in the radial direction. The feeding unit 54 feeds the double tube 110 to the rotating unit 51 so that the double tube 110 is pressed against the sliding unit 53.

[1-2. production method ]

A method for producing a bent pipe using the bent pipe production apparatus 1 of fig. 1 will be described below. As shown in fig. 7, the bent pipe manufacturing method of the present embodiment includes a disposing step S10, a bending step S20, and a taking-out step S30.

< disposing step >

In this step, the inner plug 2 is disposed inside the 1 st pipe 101, and the intermediate plug 3 is disposed between the 1 st pipe 101 and the 2 nd pipe 102. Specifically, the double tube 110 is inserted in the axial direction into the inner mandrel 2 and the intermediate mandrel 3 held between the rotating portion 51 and the clamping portion 52 of the bending die 5.

In this step, the inner plug 2 is held so that the center axis of the inner plug main body 21, the center axis of the 1 st inner movable portion 22, and the center axis of the 2 nd inner movable portion 23 are aligned on the same straight line. Similarly, the intermediate plug 3 is held such that the center axis of the intermediate plug main body 31, the center axis of the 1 st intermediate movable portion 32, and the center axis of the 2 nd intermediate movable portion 33 are on the same straight line.

The 1 st inner movable portion 22 is disposed so as to overlap the intermediate mandrel 3 in the radial direction of the 1 st pipe 101. The 2 nd inner movable portion 23 is disposed so that at least a part of the 2 nd inner movable portion 23 overlaps the intermediate core rod 3 in the radial direction of the 1 st pipe 101.

< bending step >

In this step, the 1 st pipe 101 and the 2 nd pipe 102 are bent by the bending die 5 in the region where the inner plug 2 and the intermediate plug 3 are arranged in the double tube 110.

Specifically, as shown in fig. 8A, the double tube 110 having the inner mandrel 2 and the intermediate mandrel 3 arranged therein is pressurized in the radial direction by the clamp section 52 and the conveying section 54. Thereby, the double tube 110 slides in the radial direction toward the rotating portion 51 together with the inner mandrel 2 and the intermediate mandrel 3. The double tube 110 is pressed against the chucking portion 51A of the rotating portion 51 by the clamping portion 52, and the double tube 110 is pressed against the sliding portion 53 by the conveying portion 54.

Next, as shown in fig. 8B, the rotating portion 51 is rotated in a direction in which the chucking portion 51A is away from the sliding portion 53 (i.e., toward the 1 st end portion 111), and the conveying portion 54 is slid in a direction following the clamping portion 52.

Thereby, the gripping portion 51A and the clamping portion 52 slide on the outer peripheral surface of the double tube 110 toward the 1 st end 111 while sandwiching the double tube 110. As a result, the portion of the double tube 110 sandwiched between the clamping portion 51A and the clamping portion 52 is plastically deformed so as to bend around the rotation axis P of the rotation portion 51.

The 1 st inner movable portion 22 swings with respect to the inner plug main body 21 in accordance with bending of the double tube 110 caused by rotation of the rotating portion 51. Similarly, the 2 nd inner movable portion 23 swings relative to the 1 st inner movable portion 22 in accordance with the bending of the double tube 110 caused by the rotation of the rotating portion 51.

As the double tube 110 is bent by the rotation of the rotating portion 51, the 1 st intermediate movable portion 32 and the 2 nd intermediate movable portion 33 are swung so as to eliminate a gap between the two portions in the axial direction inside the bend. That is, inside the bent 2 nd pipe 102, the 1 st intermediate movable portion 32 and the 2 nd intermediate movable portion 33 move to positions where no gap is generated in the region facing the outer surface of the 1 st pipe 101 on the inside of the bend between the 1 st intermediate movable portion 32 and the 2 nd intermediate movable portion 33.

The inner plug main body 21 and the intermediate plug main body 31 are held so as not to move in the bending step. Therefore, the double tube 110 moves so as to extend in the moving direction of the clamp 52 while sliding with respect to the inner mandrel 2 and the intermediate mandrel 3.

< taking out Process >

In this step, the double tube 110 after bending is taken out from the inner plug 2, the intermediate plug 3, and the bending die 5.

Specifically, first, as shown in fig. 9A, after the inner mandrel 2 and the intermediate mandrel 3 are pulled back to positions not overlapping with the bent portions of the double tube 110, the clamping portion 52 and the conveying portion 54 are separated from the double tube 110 in the radial direction, and the double tube 110 is separated from the rotating portion 51 and the sliding portion 53.

Finally, as shown in fig. 9B, the inner core rod 2, the intermediate core rod 3, and the bending die 5 are returned to the initial positions (i.e., positions where the double tube 110 can be inserted before the bending process).

[1-3. Effect ]

According to the embodiments described in detail above, the following effects can be obtained.

(1a) Since the end edge of the 1 st approach portion 31C of the intermediate plug main body 31 is not parallel to the circumferential direction of the double tube 110, the axial compressive force generated by the bent inner side of the 1 st pipe 101 being sandwiched between the intermediate plug main body 31 and the 1 st intermediate movable portion 32 is dispersed in the circumferential direction of the 1 st pipe 101. As a result, buckling of the 1 st pipe 101 can be suppressed when the double pipe 110 is bent.

(1b) Since the 1 st approaching portion 31C protrudes toward the 1 st intermediate movable portion 32, the 1 st approaching portion 31C of the intermediate plug main body 31 presses the portion of the 1 st pipe 101 where buckling is likely to occur when the double tube is bent, and therefore, the occurrence of buckling can be more reliably suppressed.

(1c) The width of the 1 st approach portion 31C in the circumferential direction of the intermediate mandrel main body 31 becomes smaller as it goes toward the protruding end, whereby the effect of dispersing the compressive force through the 1 st approach portion 31C can be enhanced. As a result, the effect of suppressing the occurrence of buckling can be promoted.

(1d) The intermediate plug 3 has the 2 nd intermediate movable portion 33, and the end edge of the 2 nd approach portion 32D that is close to the 2 nd intermediate movable portion 33 during bending of the double tube intersects a virtual plane that is orthogonal to the central axis at the portion of the 2 nd pipe 102 that contacts the intermediate plug 3, whereby buckling can be reliably suppressed from occurring during production of a bent tube having a large bending angle.

[2 ] other embodiments ]

The embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above embodiments and can be implemented in various ways.

(2a) In the bent pipe manufacturing apparatus according to the above embodiment, the width of the 1 st approach portion may not be decreased as it goes toward the protruding end. Further, the 1 st approach portion may not protrude toward the 1 st intermediate movable portion. The same applies to the 2 nd access portion.

For example, the shape of the approach portion 131 shown in fig. 10A to 10K may be applied to the 1 st approach portion or the 2 nd approach portion, and the shape of the approach portion 132 shown in fig. 10A to 10K may be applied to the 3 rd approach portion or the 4 th approach portion.

(2b) In the bent pipe manufacturing apparatus according to the above embodiment, the inner plug may have one or three or more inner movable portions. The intermediate mandrel may have one or three or more intermediate movable portions.

(2c) The functions included in one constituent element in the above-described embodiments may be dispersed into a plurality of constituent elements, or the functions included in a plurality of constituent elements may be integrated into one constituent element. In addition, a part of the configuration of the above embodiment may be omitted. Further, the structure of the other embodiments may be added or replaced with at least a part of the structure of the above embodiment. All the aspects included in the technical idea defined by the terms described in the claims are embodiments of the present disclosure.