CN118159747A

CN118159747A - Multi-segment insert joint, steel pipe with joint, structure, method for constructing same, method for designing multi-segment insert joint, and method for manufacturing multi-segment insert joint

Info

Publication number: CN118159747A
Application number: CN202280071415.0A
Authority: CN
Inventors: 大场雄登
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2021-10-29
Filing date: 2022-09-30
Publication date: 2024-06-07
Also published as: JP7484869B2; KR20240058185A; WO2023074257A1; JP2023066484A

Abstract

The object is to provide a multi-stage insert joint, a steel pipe with joint, a structure, a method for constructing the same, a method for designing a multi-stage insert joint, and a method for manufacturing the same, wherein engagement between a convex part and a concave part of a non-engagement object is prevented during insertion, and workability of a steel pipe joint is excellent. In a multi-stage plug-in joint (1), one of an inner joint pipe (3) and an outer joint pipe (5) has a split cylindrical part (11) composed of a plurality of split pieces (9) and convex parts (13) provided in a multi-stage manner to the split pieces, the other has a cylindrical part (17) and concave parts (19) provided in a multi-stage manner to the cylindrical part, the convex parts are engaged with the concave parts to join a steel pipe (7), the axial width of the convex parts of the multi-stage is gradually reduced from the convex part on the tip end side to the convex part on the base end side, the axial width of the concave parts of the multi-stage is gradually reduced from the concave part on the base end side to the concave part on the tip end side, and the axial width of each convex part is equal to or more than the axial width of the concave part located on the tip end side of the concave part engaged at the time of joint engagement.

Description

Multi-segment insert joint, steel pipe with joint, structure, method for constructing same, method for designing multi-segment insert joint, and method for manufacturing multi-segment insert joint

Technical Field

The present invention relates to a mechanical joint for joining steel pipes, and more particularly, to a multi-stage insert joint in which an inner joint pipe is inserted into and fitted to an outer joint pipe and a fastening portion is provided in a plurality of stages, a steel pipe with joint, a structure, a method of constructing the same, a method of designing a multi-stage insert joint, and a method of manufacturing the same.

Background

As a method of joining steel pipes instead of welding, various joining methods using mechanical joints have been proposed.

One type of mechanical joint is a plug-in joint in which an outer joint pipe and an inner joint pipe are provided at joint ends of steel pipes to be joined, respectively, and the steel pipes are connected to each other by inserting the inner joint pipe into the outer joint pipe. An example of such a plug-in connector is disclosed in patent document 1, for example.

The "joint structure of steel pipes" disclosed in patent document 1 includes a slit formed in one of the outer joint pipe and the inner joint pipe and dividing the same into a plurality of pieces in the circumferential direction, a convex portion formed on the outer peripheral surface of the inner joint pipe, and an engaging portion formed on the inner peripheral surface of the outer joint pipe and engaging with the convex portion in a state in which the inner joint pipe is inserted into the outer joint pipe and resisting a tensile load together with the convex portion (refer to claim 1 of patent document 1). Since the inner joint pipe is divided into a plurality of pieces by the slit, each piece divided at the time of insertion is elastically deformed inward, and when the insertion is completed, the elastic deformation is restored, and the convex portion of the inner joint pipe is engaged with the engaging portion of the outer joint pipe. In this state, the bolts are inserted into bolt holes provided in the base end side of the outer joint pipe and the tip end side of the inner joint pipe, respectively, and the bolts are fastened, whereby the connection is completed.

Since the convex portion of patent document 1 is a portion that resists a tensile load in cooperation with the engagement portion, when a large load is assumed, or when a high resistance is required such as a large diameter steel pipe, it is necessary to improve the strength of the convex portion and the like to improve the resistance to the tensile load. In order to increase the strength of the protruding portion, the protruding portion may be increased, but if the protruding portion is increased, the amount of elastic deformation during insertion becomes large, and thus the load required for fitting increases.

Therefore, there is a multi-stage type plug-in connector provided with two or more stages of protruding portions as a plug-in connector that improves resistance to load without enlarging the protruding portions (see fig. 11 and 12 of patent document 1). By providing the convex portions and the engaging portions corresponding to the convex portions in a plurality of stages, the load can be resisted by the plurality of convex portions, and thus the entire resistance can be improved without enlarging the respective convex portions.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 4600407

Disclosure of Invention

Problems to be solved by the invention

However, in the case where the protruding portion is provided in one of the inner joint pipe and the outer joint pipe in a plurality of stages, the recessed portion serving as the engagement portion is provided in the other of the inner joint pipe and the outer joint pipe in a plurality of stages, and therefore, the protruding portion, which is not the engagement target, is engaged with the recessed portion during insertion, and the hooking occurs, which may deteriorate workability. Such an example will be specifically described with reference to fig. 5A, 5B, and 6.

Fig. 5A and 5B are schematic views showing the insertion process of the conventional multi-stage insertion joint 27, and are sectional views showing portions corresponding to the section A-A of fig. 1 of patent document 1. In the example of fig. 5A and 5B, the inner joint pipe 3 is attached to the lower end of the upper steel pipe 7, and the outer joint pipe 5 is attached to the upper end of the lower steel pipe 7. The inner joint pipe 3 is provided with a split cylindrical portion 11 composed of a plurality of split pieces 9 split in the circumferential direction, and two radially outwardly projecting convex portions 13 are provided on the outer peripheral surface of the split cylindrical portion 11 in the axial direction. Further, the outer joint pipe 5 is provided with a cylindrical portion 17, and the inner peripheral surface of the cylindrical portion 17 is provided with two recessed portions 19 which engage with the protruding portions 13 in the axial direction. In the present description, the convex portion 13 and the concave portion 19 that engage at the same position in the axial direction at the time of fitting are referred to as one "step", and are counted as a first step and a second step from the lower side in the figure.

Hereinafter, the lower (distal end side of the inner joint pipe) convex portion 13 of the two convex portions 13 is referred to as a first-stage convex portion 131, and the upper (proximal end side of the inner joint pipe) convex portion 13 is referred to as a second-stage convex portion 132. Similarly, the lower recess 19 (the base end side of the outer joint pipe) of the two recesses 19 is defined as a first recess 191, and the upper recess 19 (the tip end side of the outer joint pipe) is defined as a second recess 192. In the joint fitted state, the convex portion 13 and the concave portion 19 in the engaged state are engaged with each other as the engaging portion 23.

In the conventional multi-stage joint 27 configured as described above, when the inner joint pipe 3 is inserted into the outer joint pipe 5 while restraining the lower steel pipe 7, the first-stage convex portion 131 of the inner joint pipe 3 abuts against the inner surface of the cylindrical portion 17 of the outer joint pipe 5, and thereby the divided pieces 9 of the inner joint pipe 3 are elastically deformed radially inward by the horizontal force indicated by the hollow arrow in fig. 5A. The plurality of divided pieces 9 are elastically deformed radially inward, respectively, to thereby reduce the diameter of the divided cylindrical portion 11.

In this state, as shown in fig. 5B, when the first-stage convex portion 131 reaches the second-stage concave portion 192, the horizontal force applied temporarily disappears, and a restoring force for restoring the elastic deformation is generated in the divided pieces 9. When the diameter of the divided cylindrical portion 11 is increased by the restoring force, the outer peripheral portion of the first-stage convex portion 131 engages with the second-stage concave portion 192, and a hook is generated.

In the case of shallow engagement, a large press-in load may be applied to eliminate engagement, but in the case of deep engagement, continuation of the construction becomes difficult. In this case, if the divided cylindrical portion 11 is reduced in diameter again without using an auxiliary tool, the inner joint pipe 3 cannot be inserted, and the inner joint pipe 3 cannot be pulled out, which requires a large labor.

As described above, when the convex portion 13 and the concave portion 19, which are not the engagement targets during insertion, are engaged, there is a possibility that the workability is deteriorated by a large increase in the construction load, or a construction failure such as incapability of engagement is caused.

The example of fig. 5A and 5B is an example in which the pipe axes 3a and 5A of the inner joint pipe 3 and the outer joint pipe 5 coincide with each other, but the above-described problem is more likely to occur when the pipe axes 3a and 5A of the inner joint pipe 3 and the outer joint pipe 5 are offset. An example of this will be described with reference to fig. 6.

Fig. 6 is a view showing the insertion halfway of the conventional multistage insertion joint 27 similar to fig. 5A and 5B when the inner joint pipe 3 is inserted into the outer joint pipe 5 in a state where the pipe axis 3a of the inner joint pipe 3 is offset from the pipe axis 5A of the outer joint pipe 5. In the case of construction under conditions of poor connection environments (site, large diameter, long dimension, etc.), it is difficult to control the sagging of the inner joint pipe 3 and the outer joint pipe 5, and as shown in fig. 6, the construction may be performed in a state where the pipe axis 3a of the inner joint pipe 3 and the pipe axis 5a of the outer joint pipe 5 are offset.

In this case, as shown in fig. 6, the first-stage convex portion 131 is likely to collide with the lower side wall of the second-stage concave portion 192, and thus the problem of the foregoing poor work is more likely to occur.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a multi-stage insert joint, a steel pipe with joint, a structure, a method of constructing the same, a method of designing a multi-stage insert joint, and a method of manufacturing the same, which are excellent in workability of joining a steel pipe with joint, by preventing engagement of a convex portion and a concave portion, which are not engagement objects at the time of insertion.

Means for solving the problems

(1) The multi-stage joint for insertion of steel pipes includes an inner joint pipe and an outer joint pipe each of which is attached to an end portion of a steel pipe to be joined, wherein either one of the inner joint pipe and the outer joint pipe includes a split cylindrical portion formed of a plurality of split pieces split in a circumferential direction and a convex portion provided in the plurality of split pieces in a multi-stage manner in an axial direction and protruding radially, the other one of the inner joint pipe and the outer joint pipe includes an undivided cylindrical portion and a concave portion provided in the cylindrical portion in a multi-stage manner in the axial direction and engaged with the convex portion, and the inner joint pipe is inserted into the outer joint pipe while bending the split cylindrical portion in a radial direction to engage the convex portion with the concave portion, thereby joining the steel pipes.

(2) Further, in the multi-stage joint according to the present invention, the joint includes an inner joint pipe and an outer joint pipe each of which is attached to a cylindrical body of an end portion of a steel pipe to be joined, one of the inner joint pipe and the outer joint pipe includes a divided cylindrical portion formed of a plurality of divided pieces divided in a circumferential direction and a concave portion provided in the plurality of divided pieces in a multi-stage manner in an axial direction, the other of the inner joint pipe and the outer joint pipe includes an undivided cylindrical portion and a convex portion provided in the cylindrical portion in a multi-stage manner in the axial direction and protruding radially and engaging with the concave portion, and the inner joint pipe is inserted into the outer joint pipe while the divided cylindrical portion is flexed in the radial direction to engage the convex portion with the concave portion, whereby the steel pipe is joined, wherein an axial width of the convex portion of the multi-stage convex portion gradually decreases from a convex portion on a tip end side to a convex portion on a base end side, and an axial width of each convex portion of the multi-stage concave portion gradually decreases from the concave portion on the tip end side to a concave portion on a tip end side, and the axial width of each convex portion is larger than that of the concave portion on the tip side of the concave portion on which the joint is engaged.

(3) In the structure described in (1) or (2), the axial gap formed by the engaged convex portion and concave portion is the same in all the engaging portions in the joint fitted state.

(4) In the structure according to any one of (1) to (3), the protruding height of the protruding portion of the plurality of stages is set to be equal to or smaller than the protruding height of the protruding portion on the topmost side, and at least one of the protruding portions of the plurality of stages is set to have a lower protruding height than the protruding portion on the topmost side.

(5) In the structure described in (4), the protruding height of the convex portions of the plurality of stages gradually decreases from the convex portion on the distal end side to the convex portion on the proximal end side.

(6) The steel pipe with joint according to the present invention is provided with the inner joint pipe and/or the outer joint pipe in the multi-stage plug-in joint according to any one of (1) to (5) above at both ends or one end.

(7) The structure of the present invention further comprises a plurality of steel pipes connected by the multi-stage plug-in joint according to any one of (1) to (5).

(8) The construction method of the structure according to the present invention is the construction method of the structure according to (7) above, wherein the axial position of one of the steel pipe having the outer joint pipe attached to the end portion and the steel pipe having the inner joint pipe attached to the end portion is aligned with the other steel pipe and is inserted into the steel pipe while restraining the axial position of the other steel pipe.

(9) In the method of designing a multi-segment plug-in joint according to the present invention, the multi-segment plug-in joint includes an inner joint pipe and an outer joint pipe each of which is attached to a cylindrical body at an end portion of a steel pipe to be joined, one of the inner joint pipe and the outer joint pipe includes a split cylindrical portion formed of a plurality of split pieces split in a circumferential direction and a convex portion provided in the plurality of split pieces in a multi-segment manner in an axial direction and protruding in a radial direction, and the other of the inner joint pipe and the outer joint pipe includes an undivided cylindrical portion and a concave portion provided in the cylindrical portion in a multi-segment manner in the axial direction and engaging with the convex portion, and the inner joint pipe is inserted into the outer joint pipe while bending the split cylindrical portion in the radial direction to engage the convex portion with the concave portion, whereby the steel pipe is joined, wherein the method of designing the multi-segment plug-in joint is configured as follows: the axial width of the convex part of the multi-section gradually becomes smaller from the convex part on the top end side to the convex part on the base end side; the axial width of the multi-stage concave part gradually decreases from the concave part at the base end side to the concave part at the tip end side; and the width of each protruding portion in the axial direction is equal to or greater than the width of the recess portion located on the tip side of the recess portion engaged when the joint is engaged.

(10) The multi-stage insert joint includes an inner joint pipe and an outer joint pipe each of which is attached to a cylindrical body at an end portion of a steel pipe to be joined, one of the inner joint pipe and the outer joint pipe having a split cylindrical portion formed of a plurality of split pieces split in a circumferential direction and a concave portion provided in the plurality of split pieces in a multi-stage manner in an axial direction, the other of the inner joint pipe and the outer joint pipe having an undivided cylindrical portion and a convex portion provided in the cylindrical portion in a multi-stage manner in the axial direction and protruding in a radial direction and engaging with the concave portion, and the steel pipe being joined by inserting the inner joint pipe into the outer joint pipe while flexing the split cylindrical portion in the radial direction so that the convex portion engages with the concave portion, wherein a design method of the multi-stage insert joint is set as follows: the axial width of the convex part of the multi-section gradually becomes smaller from the convex part on the top end side to the convex part on the base end side; the axial width of the multi-stage concave part gradually decreases from the concave part at the base end side to the concave part at the tip end side; and the width of each protruding portion in the axial direction is equal to or greater than the width of the recess portion located on the tip side of the recess portion engaged when the joint is engaged.

(11) In the method for designing a multistage male joint according to (9) or (10), the axial widths of the convex portions and the concave portions are set so that the axial gaps formed by the convex portions and the concave portions engaged in the joint fitted state are the same in all the engaging portions.

(12) In the method for manufacturing a multi-segment plug-in joint according to the present invention, the multi-segment plug-in joint includes an inner joint pipe and an outer joint pipe each of which is attached to a cylindrical body at an end portion of a steel pipe to be joined, one of the inner joint pipe and the outer joint pipe includes a split cylindrical portion formed of a plurality of split pieces split in a circumferential direction and a convex portion provided in the plurality of split pieces in a multi-segment manner in an axial direction and protruding in a radial direction, the other of the inner joint pipe and the outer joint pipe includes an undivided cylindrical portion and a concave portion provided in the cylindrical portion in a multi-segment manner in the axial direction and engaging with the convex portion, and the inner joint pipe is inserted into the outer joint pipe while the split cylindrical portion is deflected in the radial direction to engage the convex portion with the concave portion, whereby the steel pipe is joined, wherein the multi-segment plug-in joint is manufactured such that: the convex parts of the multiple sections are formed so that the axial width becomes gradually smaller from the convex part on the tip end side to the convex part on the base end side; the recessed portions of the plurality of stages are formed so that the axial width becomes gradually smaller from the recessed portion on the base end side to the recessed portion on the tip end side; and the width of each protruding portion in the axial direction is equal to or greater than the width of the recessed portion located on the tip side of the recessed portion engaged when the joint is engaged.

(13) The multi-stage insert joint includes an inner joint pipe and an outer joint pipe each of which is attached to a cylindrical body at an end portion of a steel pipe to be joined, one of the inner joint pipe and the outer joint pipe having a split cylindrical portion formed of a plurality of split pieces split in a circumferential direction and a concave portion provided in the plurality of split pieces in a multi-stage manner in an axial direction, the other of the inner joint pipe and the outer joint pipe having an undivided cylindrical portion and a convex portion provided in the cylindrical portion in a multi-stage manner in the axial direction and protruding in a radial direction and engaging with the concave portion, the inner joint pipe being inserted into the outer joint pipe while flexing the split cylindrical portion in the radial direction to engage the convex portion with the concave portion, and the steel pipe being joined, wherein the multi-stage insert joint is manufactured such that: the convex parts of the multiple sections are formed so that the axial width becomes gradually smaller from the convex part on the tip end side to the convex part on the base end side; the recessed portions of the plurality of stages are formed so that the axial width becomes gradually smaller from the recessed portion on the base end side to the recessed portion on the tip end side; and the width of each protruding portion in the axial direction is equal to or greater than the width of the recessed portion located on the tip side of the recessed portion engaged when the joint is engaged.

(14) In the method for manufacturing a multi-stage plug-in connector according to (12) or (13), the projections and recesses are formed so that the axial gaps formed by the engaged projections and recesses are the same in all the engaging portions in the connector fitted state.

Effects of the invention

In the present invention, the axial width of the convex portions of the plurality of stages becomes smaller from the convex portion on the distal end side to the convex portion on the proximal end side, and the axial width of the concave portions of the plurality of stages becomes smaller from the concave portion on the proximal end side to the concave portion on the distal end side, and the axial width of each convex portion is larger than the axial width of the concave portion located on the distal end side of the concave portion engaged at the time of joint engagement, whereby engagement between the convex portion and the concave portion, which are not the engagement target at the time of insertion, can be prevented. This can suppress the hooking of the steel pipe joint, reduce the occurrence of construction failure such as deterioration of workability due to a large increase in construction load, or failure of fitting, and improve workability.

Drawings

Fig. 1 is an explanatory view of a multi-stage plug-in connector according to embodiment 1 of the present invention, and is a cross-sectional view of a part of the multi-stage plug-in connector in a fitted state.

Fig. 2 is a view showing a state in which the multistage plug-in connector shown in fig. 1 is fitted halfway (in the case of no axial misalignment).

Fig. 3 is a view showing a state in which the multi-stage plug-in connector shown in fig. 1 is fitted halfway (in the case of axial misalignment).

Fig. 4 is an explanatory view of a multi-stage plug-in connector according to embodiment 2 of the present invention, and is a cross-sectional view of a part of the multi-stage plug-in connector in a state of being fitted halfway.

Fig. 5A is a diagram (without axial offset) illustrating a problem of a conventional multi-stage plug-in connector.

Fig. 5B is a diagram (without axial offset) illustrating a problem of a conventional multi-stage plug-in connector.

Fig. 6 is a diagram (with shaft misalignment) illustrating a problem of a conventional multi-stage plug-in connector.

Detailed Description

Embodiment 1

The entire structure of the multi-stage plug-in connector in the present embodiment is substantially the same as that of fig. 12 of patent document 1, and therefore illustration is omitted, and only a partial cross-sectional view of the multi-stage plug-in connector is shown in fig. 1. Fig. 1 shows a section of a portion corresponding to section A-A of fig. 1 of patent document 1. The same reference numerals are given to the same parts and corresponding parts as those in fig. 5A, 5B and 6, which illustrate the conventional multistage plug-in connector 27.

The multi-stage joint 1 according to the present embodiment includes an inner joint pipe 3 and an outer joint pipe 5 which are attached to the ends of steel pipes to be joined, respectively, and fig. 1 shows an example in which the inner joint pipe 3 is attached to the lower end of an upper steel pipe 7 and the outer joint pipe 5 is attached to the upper end of a lower steel pipe 7. As shown in fig. 1, the inner joint pipe 3 is inserted into the outer joint pipe 5, and the inner joint pipe 3 is fitted into the outer joint pipe 5, whereby the upper and lower steel pipes 7 are joined. Hereinafter, the inner joint pipe 3 and the outer joint pipe 5 will be described in detail.

< Inside joint pipe >

The inner joint pipe 3 is formed of a substantially cylindrical body, and has a split cylindrical portion 11 formed of a plurality of split pieces 9 split in the circumferential direction. Two radially outwardly projecting convex portions 13 are provided on the outer peripheral surface of the split cylindrical portion 11 over the entire circumference thereof in the axial direction. As for the two-stage convex portion 13, similarly to fig. 5A, 5B and 6, the convex portion 13 on the lower side (the distal end side of the inner joint pipe 3) is referred to as a first-stage convex portion 131, and the convex portion 13 on the upper side (the proximal end side of the inner joint pipe 3) is referred to as a second-stage convex portion 132. Fig. 1 shows a cross section of one segment 9, but the cross section of the other segments 9 is also similar to fig. 1. A bolt hole 15 for bolt-engagement with the outer joint pipe 5 is provided at the tip end side of the first stage protrusion 131.

< Outside Joint pipe >

The outer joint pipe 5 is formed of a cylindrical body, and has an undivided cylindrical portion 17. Two recessed portions 19 recessed radially outward are provided on the inner peripheral surface of the cylindrical portion 17 over the entire circumference in the axial direction. As for the two-stage concave portion 19, the concave portion 19 on the lower side (the base end side of the outer joint pipe 5) is referred to as a first-stage concave portion 191, and the concave portion 19 on the upper side (the tip end side of the outer joint pipe 5) is referred to as a second-stage concave portion 192, similarly to the convex portion 13 of the inner joint pipe. As shown in fig. 1, in the joint fitted state, the first-stage concave portion 191 engages with the first-stage convex portion 131, and the second-stage concave portion 192 engages with the second-stage convex portion 132. A bolt hole 21 for inserting a bolt is provided at a position facing the bolt hole 15 of the inner joint pipe 3 on the base end side of the first step recess 191.

Here, as shown in the enlarged view of fig. 1, the axial width of the first-stage convex portion 131 is T1, the protruding height to the radial outside is H1, the axial width of the first-stage concave portion 191 is K1, and the recessed depth to the radial outside is L1. Similarly, the axial width of the second-stage convex portion 132 is T2, the protruding height to the radial outside is H2, the axial width of the second-stage concave portion 192 is K2, and the recessed depth to the radial outside is L2 (enlarged view is omitted). The T1 and T2 are axial widths of the top (tip end) of the convex portion 13. The above K1 and K2 are axial widths of the openings of the concave portions.

As described above, the axial widths T1 and T2 are axial widths of the top portions of the first-stage convex portion 131 and the second-stage convex portion 132, but the axial widths of the root portions of the first-stage convex portion 131 and the second-stage convex portion 132 may be set based on the shearing resistance required for the entire convex portion 13. In general, since the shearing resistance of the convex portion 13 can be set with a sufficient margin, even if the shearing resistance of the convex portion 13 slightly varies due to the change of the axial width of the top portion of the convex portion 13, the influence on the overall resistance of the joint is small.

The recess depth L1 of the first-stage concave portion 191 is larger than the protruding height H1 of the first-stage convex portion 131 so that the first-stage convex portion 131 and the first-stage concave portion 191 can be engaged (H1 < L1). Similarly, the depression depth L2 of the second-stage concave portion 192 is larger than the protrusion height H2 of the second-stage convex portion 132 (H2 < L2).

Further, the axial width T2 of the convex portion 13 (the second-stage convex portion 132) on the base end side of the two-stage convex portions 13 provided in the divided cylindrical portion 11 of the inner joint pipe 3 is smaller than the axial width T1 of the convex portion 13 (the first-stage convex portion 131) on the tip end side (T2 < T1). Further, of the two-stage concave portions 19 provided in the cylindrical portion 17 of the outer joint pipe 5, the axial width K2 of the concave portion 19 on the tip end side (the second-stage concave portion 192) is smaller than the axial width K1 of the concave portion 19 on the base end side (the first-stage concave portion 191) (K2 < K1). The axial width T1 of the first-stage convex portion 131 is equal to or greater than the axial width K2 of the concave portion 19 (the second-stage concave portion 192) located on the tip side of the concave portion 19 (the first-stage concave portion 191) engaged at the time of joint engagement (k2+.t1). As described above, the multistage plug-in connector 1 of the present embodiment satisfies the following relational expressions (1) to (3).

H1<L1...(1)

H2<L2...(2)

T2<K2≤T1<K1...(3)

As described above, the divided cylindrical portion 11 of the inner joint pipe 3 is constituted by the plurality of divided pieces 9 arranged in the circumferential direction, and the axial widths T1 and T2 and the protruding heights H1 and H2 of the two-stage convex portion 13 are formed equally in all the divided pieces 9. Further, two concave portions 19 provided in the cylindrical portion 17 of the outer joint pipe 5 are continuously provided in the circumferential direction on the inner peripheral surface of the cylindrical portion 17, and the magnitudes of the axial widths K1, K2 and the concave depths L1, L2 are constant over the entire circumference.

The axial gap δ of the first-stage engaging portion 23 (specifically, the distance from the position centered in the protruding direction of the side wall of the first-stage convex portion 131 to the side wall of the first-stage concave portion 191) shown in the enlarged view of fig. 1 is the same as the axial gap of the second-stage engaging portion 23. As described above, the axial gaps formed by the convex portion 13 and the concave portion 19 engaged in the joint fitted state are made the same in all the engaging portions 23, so that the load can be appropriately transmitted, and therefore, the multistage plug-in joint 1 is suitable for use as a part of a structure or the like.

The effects of the multi-stage plug-in connector 1 according to the present embodiment configured as described above will be specifically described below. In the conventional multistage plug-in connector 27, as described with reference to fig. 5A and 5B, when the first-stage convex portion 131 reaches the second-stage concave portion 192 during fitting, the tip end portion of the first-stage convex portion 131 enters the second-stage concave portion 192, and a hook is generated.

In this regard, the axial width T1 of the first-stage convex portion 131 of the multi-stage plug-in connector 1 according to the present embodiment is equal to or larger than the axial width K2 of the second-stage concave portion 192 (k2+.t1), and therefore the above-described problem does not occur. Specifically, as shown in fig. 2, even if the first-stage convex portion 131 reaches the second-stage concave portion 192, a part of the first-stage convex portion 131 always abuts against the inner peripheral surface of the cylindrical portion 17. Therefore, the first-stage convex portion 131 can pass over the second-stage concave portion 192 while maintaining the elastic deformation of the divided pieces 9 radially inward, and hooking is less likely to occur. Even if k2=t1, the entry is shallow and the hooking is small due to friction or the like, so that the above-described problem does not occur. In this regard, it is more preferable that the axial width T1 of each protruding portion is larger than the axial width K2 of the recessed portion located on the tip side of the recessed portion engaged at the time of fitting.

In the conventional multistage insertion joint 27, as illustrated in fig. 6, hooking occurs particularly when the construction is performed in a state in which the pipe axis 3a of the inner joint pipe 3 and the pipe axis 5a of the outer joint pipe 5 do not coincide with each other. In this regard, the present embodiment has an effect of suppressing hooking even when the construction is performed in the shaft-offset state as described above. This will be described with reference to fig. 3.

Fig. 3 is a diagram showing an insertion path when the inner joint pipe 3 is inserted into the outer joint pipe 5 in the multistage inserted joint 1 according to the present embodiment in a state where the pipe axis 3a of the inner joint pipe 3 is offset from the pipe axis 5a of the outer joint pipe 5. As shown in the enlarged view of fig. 3, when the outer joint pipe 5 is inclined, the first-stage convex portion 131 may collide with the lower side wall of the second-stage concave portion 192. In this case, in the conventional example, as shown in the enlarged view of fig. 6, the entire distal end portion of the first-stage convex portion 131 enters the second-stage concave portion 192 due to the restoring force to restore the elastic deformation, and therefore, the hooking may be deep, and the construction may not be continued. In the state of fig. 6, even if the inner joint pipe 3 is to be pulled out for the re-work, the first-stage convex portion 131 is caught by the upper side wall of the second-stage concave portion 192, and therefore, an auxiliary tool for reducing the diameter of the divided cylindrical portion 11 is required.

In this regard, the axial width T1 of the first-stage convex portion 131 of the multi-stage plug-in connector 1 according to the present embodiment is equal to or larger than the axial width K2 of the second-stage concave portion 192 (k2+.t1), and therefore the above-described problem does not occur. Specifically, as shown in the enlarged view of fig. 3, even if the first-stage convex portion 131 collides with the lower side wall of the second-stage concave portion 192, the entire tip end portion of the first-stage convex portion 131 does not enter the second-stage concave portion 192. Therefore, the hook is shallow, and the insertion load is slightly increased, so that the hook can be easily released and the construction can be continued. Even if k2=t1, the entry is shallow and the hooking is small due to friction or the like, so that the above-described problem does not occur. In this regard, it is more preferable that the axial width T1 of each protruding portion is larger than the axial width K2 of the recessed portion located on the tip side of the recessed portion engaged at the time of fitting.

Further, for example, even if the inner joint pipe 3 is to be pulled out for re-installation, the first-stage convex portion 131 is not caught by the upper side wall of the second-stage concave portion 192 as in the conventional example, and thus the inner joint pipe can be pulled out easily during the installation.

The above is an example of the case where the outer joint pipe 5 of the steel pipe 7 attached to the lower side is inclined, but the same effect is obtained even when the inner joint pipe 3 of the steel pipe 7 attached to the upper side is inclined.

As described above, according to the present embodiment, the axial width T2 of the second-stage convex portion 132 is smaller than the axial width T1 of the first-stage convex portion 131 (T2 < T1), and accordingly, the axial width K2 of the second-stage concave portion 192 is smaller than the axial width K1 of the first-stage concave portion 191 (K2 < K1). Thus, the axial width T1 of the first-stage convex portion 131 becomes equal to or greater than the axial width K1 of the concave portion 19 (the second-stage concave portion 192) located on the tip side of the concave portion 19 (the first-stage concave portion 191) engaged at the time of joint engagement (k1+.t1). Therefore, the convex portion 13 and the concave portion 19, which are not the engagement target at the time of insertion, can be prevented from engaging. Thus, even under the conditions that the connection environment is poor and the shaking is easy to occur, the occurrence of construction faults that the construction load is greatly increased and the workability is deteriorated or the fitting is impossible can be reduced, and the workability is improved.

The engaging portion 23 in embodiment 1 is two-stage, but the number of stages of the engaging portion 23 may be any number as long as it is within a processable range. In the case of 3 or more steps, the axial width gradually decreases from the convex portion 13 on the distal end side to the convex portion 13 on the proximal end side. In response, the axial width of the concave portion 19 from the base end side to the tip end side becomes gradually smaller. The axial width of each convex portion 13 is larger than the axial width of the concave portion 19 located on the tip side of the concave portion 19 engaged at the time of joint engagement. In the conventional multi-stage plug-in connector 27, the larger the number of stages of the engaging portion 23 is, the greater the risk of catching during insertion, but the multi-stage plug-in connector 1 of the present embodiment can suppress catching irrespective of the number of stages of the engaging portion 23. Therefore, the present invention is particularly suitable for a multi-stage plug-in connector having a large number of stages of engagement portions.

Embodiment 2

In embodiment 1 described above, the protruding height of the protruding portion 13 is all the same (h1=h2), but in this embodiment, an example will be described in which the protruding height H1 of the first-stage protruding portion 131 is larger than the protruding height H2 of the second-stage protruding portion 132. Fig. 4 shows a multi-stage plug-in connector according to the present embodiment, and the same reference numerals are given to the same and corresponding parts as in fig. 1 to 3.

As shown in fig. 4, the protruding height H1 of the first-stage protruding portion 131 of the multi-stage male joint 25 of the present embodiment is larger than the protruding height H2 of the second-stage protruding portion 132 (H2 < H1). In addition, as the protrusion height H1 of the first-stage protrusion 131 increases, the recess depth L1 of the first-stage recess 191 also increases so that H1 < L1. Except for the above-described aspects, the multi-stage plug-in connector 25 of the present embodiment satisfies the following relational expression (4) in addition to the relational expressions (1) to (3) described in embodiment 1, as in the multi-stage plug-in connector 1 of embodiment 1.

H2<H1...(4)

The protruding height H1 of the first-stage protrusions 131 is greater than the protruding height H2 of the second-stage protrusions 132. In other words, the protruding height H2 of the second-stage protrusions 132 is smaller than the protruding height H1 of the first-stage protrusions 131. As a result, during the process of inserting the inner joint pipe 3 into the outer joint pipe 5, as shown in fig. 4, a gap is generated between the second-stage convex portion 132 and the inner peripheral surface of the cylindrical portion 17. By this clearance, friction does not occur between the second-stage convex portion 132 and the inner peripheral surface of the cylindrical portion 17, and therefore, the construction resistance when the inner joint pipe 3 is inserted into the outer joint pipe 5 can be reduced.

The engaging portion of embodiment 2 is two-stage, but the number of stages of the engaging portion 23 may be any as long as it is within a processable range. For example, in the case where the engaging portion has three steps, the second-step protruding portion passes over the third-step recessed portion and then engages with the second-step recessed portion at the time of insertion, and therefore, if the second-step protruding portion does not come into contact with the inner peripheral surface of the cylindrical portion 17, it is difficult for the second-step protruding portion to be caught in the third-step recessed portion, as shown in fig. 4.

In the case of having 3 or more protruding portions 13, the protruding height of the protruding portion 13 may be set to be equal to or less than the protruding height of the protruding portion 13 on the most distal side, and at least one of the protruding portions 13 may be set to have a protruding height lower than the protruding portion 13 on the most distal side. That is, the protruding portions 13 having the same protruding height as the protruding portions 131 of the first stage may be arranged at intervals of several stages, and in this case, the construction resistance is reduced as compared with the case where the protruding heights of the protruding portions 13 are all the same. In addition, with respect to the convex portion 13 having a lower protruding height than the first-stage convex portion 131, hooking in the middle of insertion is more difficult to occur than the convex portion 13 having the same protruding height as the first-stage convex portion 131. However, since the first-stage convex portion 131 and the other convex portion 13 having the same protruding height as the first-stage convex portion 131 have a larger axial width than the concave portion 19 passing over in the middle of insertion, the hooking is less likely to occur than in the conventional example.

In the above description, since at least one of the plurality of protruding portions 13 is set to have a lower protruding height than the protruding height of the protruding portion 13 on the most distal side, the protruding height may be gradually reduced from the protruding portion 13 on the distal side to the protruding portion 13 on the proximal side, for example.

The height of the convex portion 13 is determined by checking the thickness of the steel material required for the joint pipe having the corresponding concave portion 19, and the lower limit value is determined by the support pressure required for preventing the falling-off damage of the convex portion 13 and the concave portion 19. The height of each convex portion 13 may be changed within the ranges of the upper limit value and the lower limit value, and the total support pressure of the plurality of stages may be equal to or greater than the desired support pressure.

While embodiments 1 and 2 described above are examples in which the side (inner joint pipe 3) to be inserted into the inside is divided, the present invention is not limited to this, and the side (outer joint pipe 5) to be disposed on the outside may be divided. That is, the outer joint pipe 5 having the divided cylindrical portion 11 with the convex portions 13 formed in a plurality of stages on the inner peripheral surface and the inner joint pipe 3 having the cylindrical portion 17 with the concave portions 19 formed in a plurality of stages on the outer peripheral surface may be constituted. In this case, the axial width of the convex portion 13 of the plurality of stages also gradually decreases from the convex portion 13 on the distal end side to the convex portion 13 on the proximal end side. The axial width of the recess 19 of the plurality of stages gradually decreases from the recess 19 on the base end side to the recess 19 on the tip end side. The width of each protruding portion 13 in the axial direction is equal to or greater than the width of the recessed portion 19 located on the tip end side of the recessed portion 19 engaged at the time of fitting the joint.

The above-described example is an example in which the convex portion 13 is formed in a plurality of stages on one side (the split cylindrical portion 11) and the concave portion 19 is formed in a plurality of stages on the other side (the cylindrical portion 17) which is not split, but the present invention is not limited to this. That is, a plurality of concave portions 19 may be provided in the divided cylindrical portion 11, and a plurality of convex portions 13 may be provided in the cylindrical portion 17. That is, as shown in fig. 11 of patent document 1, the outer joint pipe 5 having the divided cylindrical portion 11 formed with the multi-stage concave portion 19 and the inner joint pipe 3 having the cylindrical portion 17 formed with the multi-stage convex portion 13 may be constituted. The inner joint pipe 3 having the divided cylindrical portion 11 formed with the concave portions 19 of the plurality of stages and the outer joint pipe 5 having the cylindrical portion 17 formed with the convex portions 13 of the plurality of stages may be constituted. In this case, the axial width of the convex portion 13 of the plurality of stages also gradually decreases from the convex portion 13 on the distal end side to the convex portion 13 on the proximal end side. The axial width of the recess 19 of the plurality of stages gradually decreases from the recess 19 on the base end side to the recess 19 on the tip end side. The width of each protruding portion 13 in the axial direction is equal to or greater than the width of the recessed portion 19 located on the tip end side of the recessed portion 19 engaged at the time of fitting the joint. In either case, the same effects as those of embodiments 1 and 2 can be exhibited.

Further, although the above embodiments 1 and 2 show the connection by vertical movement, the movement direction may be any direction of the steel pipe axis, and the connection by diagonal piles or horizontal cross connection may be performed.

The shapes of the convex portion 13 and the concave portion 19 are not particularly limited as long as the above-described relational expressions (1) to (3) or relational expression (4) are satisfied (in the case where the engaging portion 23 is two-stage). Even in a shape different from the shapes exemplified in embodiments 1 and 2, effects can be exerted.

In the above-described embodiment, the multi-stage plug-in joints 1 and 25 attached to the end portions of the steel pipes 7 are described, but the inner joint pipe 3 and/or the outer joint pipe 5 of the multi-stage plug-in joints 1 and 25 may be attached to the end portions of the steel pipes 7 by welding or the like in a factory or the like in advance to manufacture a jointed steel pipe. That is, the steel pipe with joint may be provided with the inner joint pipe 3 and/or the outer joint pipe 5 of the multi-stage plug-in joints 1 and 25 described in embodiments 1 and 2 at both ends or one end.

Further, in a construction site or the like, a plurality of joined steel pipes are connected to each other, whereby a steel pipe pile, a steel pipe sheet pile wall formed by connecting steel pipe sheet piles, a steel pipe column, a steel pipe beam, or the like can be formed. That is, these structures include a plurality of steel pipes connected by the multi-stage plug-in joints 1 and 25 described in embodiments 1 and 2.

In the case of constructing these structures, it is sufficient to align and insert and fit the axial position of one steel pipe 7 with the axial position of the other steel pipe 7 in a state where the axial position of either one of the steel pipe 7 having the outer joint pipe 5 attached to the end and the steel pipe 7 having the inner joint pipe 3 attached to the end is restrained.

Further, embodiments 1 and 2 relate to the multi-stage plug-in connector of the invention as an article, but the invention may be modified into an invention of a design method and an invention of a manufacturing method, and the cases are as follows.

< Invention of design method 1>

A method for designing a multi-segment plug-in joint comprising an inner joint pipe and an outer joint pipe each of which is attached to a cylindrical body at an end portion of a steel pipe to be joined, wherein either one of the inner joint pipe and the outer joint pipe has a split cylindrical portion formed of a plurality of split pieces split in a circumferential direction and a convex portion provided in the plurality of split pieces in a multi-segment manner in an axial direction and protruding in a radial direction, and the other one of the inner joint pipe and the outer joint pipe has an undivided cylindrical portion and a concave portion provided in the cylindrical portion in a multi-segment manner in the axial direction and engaging with the convex portion, and the inner joint pipe is inserted into the outer joint pipe while bending the split cylindrical portion in a radial direction to engage the convex portion with the concave portion, thereby joining the steel pipe, wherein the method for designing a multi-segment plug-in joint is configured in such a manner that: the axial width of the convex part of the multi-section gradually becomes smaller from the convex part on the top end side to the convex part on the base end side; the axial width of the multi-stage concave part gradually decreases from the concave part at the base end side to the concave part at the tip end side; and the width of each protruding portion in the axial direction is equal to or greater than the width of the recess portion located on the tip side of the recess portion engaged when the joint is engaged.

< Invention of design method 2>

A method for designing a multi-stage stab joint comprising an inner joint pipe and an outer joint pipe each of which is attached to a cylindrical body at an end portion of a steel pipe to be joined, wherein either one of the inner joint pipe and the outer joint pipe has a split cylindrical portion formed of a plurality of split pieces split in a circumferential direction and a concave portion provided in the plurality of split pieces in a multi-stage manner in an axial direction, and the other one of the inner joint pipe and the outer joint pipe has an undivided cylindrical portion and a convex portion provided in the cylindrical portion in a multi-stage manner in the axial direction and protruding in a radial direction and engaging with the concave portion, and the inner joint pipe is inserted into the outer joint pipe while bending the split cylindrical portion in the radial direction to engage the convex portion with the concave portion, thereby joining the steel pipe, wherein the method for designing a multi-stage stab joint is configured in such a manner that: the axial width of the convex part of the multi-section gradually becomes smaller from the convex part on the top end side to the convex part on the base end side; the axial width of the multi-stage concave part gradually decreases from the concave part at the base end side to the concave part at the tip end side; and the width of each protruding portion in the axial direction is equal to or greater than the width of the recess portion located on the tip side of the recess portion engaged when the joint is engaged.

< Invention of design method 3>

The method for designing a multistage plug-in connector according to the invention 1 or 2 of the above-described design method, wherein the axial widths of the convex portions and the concave portions are set so that the axial gaps formed by the convex portions and the concave portions that are engaged are the same in all the engaging portions in the joint fitted state.

< Invention of production method 1>

A method for manufacturing a multi-stage plug-in joint comprising an inner joint pipe and an outer joint pipe each of which is attached to a cylindrical body at an end portion of a steel pipe to be joined, wherein either one of the inner joint pipe and the outer joint pipe has a divided cylindrical portion formed of a plurality of divided pieces divided in a circumferential direction and a convex portion provided in the plurality of divided pieces in a multi-stage manner in an axial direction and protruding in a radial direction, and the other one of the inner joint pipe and the outer joint pipe has an undivided cylindrical portion and a concave portion provided in the cylindrical portion in a multi-stage manner in the axial direction and engaging with the convex portion, and the inner joint pipe is inserted into the outer joint pipe while the divided cylindrical portion is deflected in a radial direction to engage the convex portion with the concave portion, thereby joining the steel pipe, wherein the method comprises: the convex parts of the multiple sections are formed so that the axial width becomes gradually smaller from the convex part on the tip end side to the convex part on the base end side; the recessed portions of the plurality of stages are formed so that the axial width becomes gradually smaller from the recessed portion on the base end side to the recessed portion on the tip end side; and the width of each protruding portion in the axial direction is equal to or greater than the width of the recessed portion located on the tip side of the recessed portion engaged when the joint is engaged.

< Invention of production method 2>

A method for manufacturing a multi-stage insert joint comprising an inner joint pipe and an outer joint pipe each of which is attached to a cylindrical body at an end portion of a steel pipe to be joined, wherein either one of the inner joint pipe and the outer joint pipe has a divided cylindrical portion formed of a plurality of divided pieces divided in a circumferential direction and a concave portion provided in the plurality of divided pieces in a multi-stage manner in an axial direction, and the other one of the inner joint pipe and the outer joint pipe has an undivided cylindrical portion and a convex portion provided in the cylindrical portion in a multi-stage manner in the axial direction and protruding in a radial direction and engaging with the concave portion, and the inner joint pipe is inserted into the outer joint pipe while bending the divided cylindrical portion in the radial direction to engage the convex portion with the concave portion, thereby joining the steel pipe, wherein the method comprises: the convex parts of the multiple sections are formed so that the axial width becomes gradually smaller from the convex part on the tip end side to the convex part on the base end side; the recessed portions of the plurality of stages are formed so that the axial width becomes gradually smaller from the recessed portion on the base end side to the recessed portion on the tip end side; and the width of each protruding portion in the axial direction is equal to or greater than the width of the recessed portion located on the tip side of the recessed portion engaged when the joint is engaged.

< Invention of production method 3>

According to the method for manufacturing a multi-stage male joint described in invention 1 or 2 of the above manufacturing method, the projections and the recesses are formed so that the axial gaps formed by the engaged projections and recesses are the same in all the engaging portions in the joint fitted state.

[ Possibility of industrial use ]

The invention is suitable for the joint of steel pipes.

[ Description of reference numerals ]

1 Multistage plug-in connector (embodiment 1)

3 Inside joint pipe

3A tube shaft

5 Outside joint pipe

5A tube shaft

7 Steel pipe

9 Dividing sheet

11 Split cylindrical portion

13 Convex part

131 First segment of convex part

132 Second section of convex part

15 Bolt hole (inner joint pipe)

17 Cylinder part

19 Recess portion

191 First segment recess

192 Second section recess

21 Bolt hole (outside joint pipe)

23 Engaging portion

25 Multistage plug-in connector (embodiment 2)

27 Multi-stage plug-in connector (conventional example).

Claims

1. A multi-stage plug-in joint is provided with an inner joint pipe and an outer joint pipe which are respectively installed on the end parts of steel pipes to be joined,

Either one of the inner joint pipe and the outer joint pipe has a split cylindrical portion composed of a plurality of split pieces split in a circumferential direction and a convex portion provided in the plurality of split pieces in a multistage manner in an axial direction and protruding in the radial direction,

The other of the inner joint pipe and the outer joint pipe has an undivided cylindrical portion and a concave portion provided in the cylindrical portion in a plurality of stages in an axial direction and engaged with the convex portion,

The steel pipe is joined by inserting the inner joint pipe into the outer joint pipe while bending the split cylindrical portion in the radial direction to engage the convex portion with the concave portion,

The axial width of the convex part of the multi-stage is gradually reduced from the convex part at the top end side to the convex part at the base end side,

The axial width of the multi-stage concave part gradually decreases from the concave part at the base end side to the concave part at the tip end side,

The width of each protrusion in the axial direction is equal to or greater than the width of the recess at the tip end side of the recess engaged at the time of fitting.

2. A multi-stage plug-in joint is provided with an inner joint pipe and an outer joint pipe which are respectively installed on the end parts of steel pipes to be joined,

Either one of the inner joint pipe and the outer joint pipe has a split cylindrical portion composed of a plurality of split pieces split in a circumferential direction and concave portions provided in the plurality of split pieces in a multistage manner in an axial direction,

The other of the inner joint pipe and the outer joint pipe has an undivided cylindrical portion and a convex portion provided in the cylindrical portion in a plurality of stages in an axial direction and protruding radially and engaging with the concave portion,

3. A multi-segment stab connector according to claim 1 or 2,

In the joint fitted state, the axial gap formed by the engaged convex portion and concave portion is the same in all the engaging portions.

4. A multi-segment plug-in connector according to any of claim 1 to 3,

The protruding height of the protruding portions of the plurality of stages is set to be equal to or less than the protruding height of the protruding portions on the topmost side, and at least one of the protruding portions of the plurality of stages is set to have a lower protruding height than the protruding portion on the topmost side.

5. The multi-segment stab connector of claim 4,

The protruding height of the convex portions of the plurality of stages gradually decreases from the convex portion on the distal end side to the convex portion on the proximal end side.

6. A steel pipe with joint, comprising the inner joint pipe and/or the outer joint pipe in the multi-stage insert joint according to any one of claims 1 to 5 at both ends or one end.

7. A structure comprising a plurality of steel pipes connected by the multi-stage plug-in joint according to any one of claims 1 to 5.

8. A construction method of a structure according to claim 7, wherein,

In a state where the axial position of either one of the steel pipe having the outer joint pipe attached to the end portion and the steel pipe having the inner joint pipe attached to the end portion is restrained, the axial position of the other steel pipe is aligned with the one steel pipe and is inserted and fitted.

9. A method for designing a multi-stage joint, comprising an inner joint pipe and an outer joint pipe each of which is attached to a cylindrical body at an end of a steel pipe to be joined,

The design method of the multi-section plug-in connector is set as follows:

the axial width of the convex part of the multi-section gradually becomes smaller from the convex part on the top end side to the convex part on the base end side;

The axial width of the multi-stage concave part gradually decreases from the concave part at the base end side to the concave part at the tip end side; and

10. A method for designing a multi-stage joint, comprising an inner joint pipe and an outer joint pipe each of which is attached to a cylindrical body at an end of a steel pipe to be joined,

The design method of the multi-section plug-in connector is set as follows:

11. The method for designing a multi-segment stab joint according to claim 9 or 10,

The axial widths of the projections and recesses are set so that the axial gaps formed by the engaged projections and recesses are the same in all the engaging portions in the joint fitted state.

12. A method for manufacturing a multi-stage joint insert comprising an inner joint pipe and an outer joint pipe each of which is attached to a cylindrical body at an end of a steel pipe to be joined,

The manufacturing method of the multi-section plug-in connector comprises the following steps:

the convex parts of the multiple sections are formed so that the axial width becomes gradually smaller from the convex part on the tip end side to the convex part on the base end side;

The recessed portions of the plurality of stages are formed so that the axial width becomes gradually smaller from the recessed portion on the base end side to the recessed portion on the tip end side; and

The width of each protrusion in the axial direction is equal to or greater than the width of the recess in the axial direction at the tip end side of the recess engaged when the joint is engaged.

13. A method for manufacturing a multi-stage joint insert comprising an inner joint pipe and an outer joint pipe each of which is attached to a cylindrical body at an end of a steel pipe to be joined,

14. A method of manufacturing a multi-segment stab connector according to claim 12 or 13,

The projections and recesses are formed such that the axial gaps formed by the engaged projections and recesses are identical in all engagement portions in the joint fitted state.