JP6173230B2 - Steel pipe connection structure - Google Patents

Description

  The present invention relates to a steel pipe mortar composite structure in which a steel pipe and a mortar are integrated with a natural ground reinforcing pile or the like, and a steel pipe connection structure in which steel pipes with irregularities on the steel pipe surface are sequentially connected by a pipe joint (joint).

Mainly in the field of civil engineering and construction, it is widely practiced to combine steel pipes and mortar to give a large strength. In recent years, in order to improve the adhesion strength between a steel pipe and a mortar, a steel pipe in which irregularities are processed on the inner surface and outer surface of the steel pipe has been developed, and in particular, it has been put to practical use in a field such as a pile having a large pulling force.
Conventionally, this steel pipe is used by connecting a plurality of pipes having a length of several meters, and since the surface of the steel pipe has irregularities, a general screw-type steel pipe connection structure (see Patent Document 1) can be used. There wasn't.
In view of this, the steel pipes are welded to each other and connected, or a screw-type joint is welded to the steel pipe and connected on site.

JP 2006-97272 A

However, when connecting steel pipes by welding, a welding machine was brought to the work site to carry out the welding work, but efficiency was lowered and it was difficult to confirm the welding quality. There was also a fire hazard.
In addition, when a screw-type joint is welded to a steel pipe, the joint is welded to the steel pipe at a factory. However, since the joint must be processed and welded to the steel pipe, the economic burden is large.

  In addition, as a conventional technique, there is a reinforcing bar and a reinforcing bar joint or welding, but when a reinforcing bar is used, the number of reinforcing bars increases and the structure is complicated.

  Then, an object of this invention is to provide the steel pipe connection structure which can connect a steel pipe easily, rapidly, and economically at low cost. In particular, another object of the present invention is to increase the adhesion of the steel pipe to the mortar and to exert a high supporting force in the steel pipe mortar composite structure of the uneven steel pipe and the mortar.

  A steel pipe connection structure according to the present invention includes a steel pipe in which a plurality of row-like convex groups including a plurality of convex portions arranged along the axial direction are arranged in parallel on the inner peripheral surface, an outer flange portion, and an insertion cylinder A steel pipe connection that includes a short cylindrical joint integrally formed with the part, and inserts and inserts the inner cylindrical part of the joint into ends of the steel pipes arranged close to each other and facing each other. The inner circumferential surface of the steel pipe is formed with a smooth concave portion in the longitudinal direction over the entire length in the axial direction between the row-like convex groups adjacent in the circumferential direction, and 180 ° opposite to the inner circumferential surface. In the row-shaped convex group, the convex portion is disposed in the same phase in the axial direction, and on the outer peripheral surface of the insertion tube portion, the retaining ring that is locked to the row-shaped convex group on the opposite side of 180 ° The circumferential positioning is such that the small projections are formed with a predetermined phase difference and shifted in the axial direction, and fitted into the longitudinal recesses. This is provided with a bulging portion.

In addition, a steel pipe in which a plurality of row-like convex groups composed of a plurality of convex portions arranged along the axial direction are arranged in parallel on the inner peripheral surface, a short having an outer flange portion and an insertion tube portion integrally. A steel pipe connection structure comprising: a cylindrical joint; and inserting and inserting the inserted cylindrical portion of the joint into ends facing each other close to each other of the steel pipes arranged on the same axis. On the inner peripheral surface, a smooth surface-like longitudinal concave portion is formed over the entire length in the axial direction between the row-like convex groups adjacent in the circumferential direction, and the row-like convex group on the opposite side of 180 ° The protrusions are arranged with a predetermined phase difference and shifted in the axial direction, and are retained on the outer peripheral surface of the insertion tube portion to be locked to the row-shaped protrusion group on the opposite side of 180 °. Small protrusions are formed in the same phase in the axial direction, and provided with a circumferential positioning bulge that fits into the longitudinal recess. It is.
Moreover, the hollow part is recessedly provided in the outer peripheral surface of the said steel pipe in the position corresponding to the said convex part.
In addition, when the convex portion is formed in a single-letter shape inclined in an oblique direction and a tensile force is applied to the steel pipe in the inserted and used state, the small protrusion is guided to the inclined convex portion and the joint In this state, the rotation force acts on the joint and the play between the joint and the steel pipe is eliminated.

  According to the steel pipe connection structure of the present invention, a plurality of steel pipes can be easily connected via a joint. That is, it is no longer necessary to weld the end of the steel pipe, the labor for preparing welding power and large-scale equipment can be saved, the work of connecting the steel pipe can be simplified, and the working time can be greatly shortened, and Cost can be reduced. In addition, there is no risk of fire due to welding. The strength of the end of the steel pipe can be secured sufficiently large, or the thickness of the entire steel pipe can be reduced. During the connection work, it is not necessary to rotate the steel pipe many times as in the case of the connection structure of the screwing method. Further, the peripheral frictional force of the steel pipe can be increased, and the adhesion force to the solidified member can be increased. Further, the compressive strength in the direction perpendicular to the axis of the steel pipe end can be improved.

It is the front view which showed an example of the steel pipe used for this invention. It is the section front view showing one embodiment of the steel pipe connection structure concerning the present invention. It is a cross-sectional side view. It is the side view which looked at the joint of the 1st example from the axial center direction. It is the front view which showed the joint of 2nd Example. It is the top view which looked at the joint of 2nd Example from the axial center direction. It is the top view which looked at the joint of 3rd Example from the axial center direction. It is the cross-sectional front view which showed other embodiment of the steel pipe connection structure which concerns on this invention. It is the expanded view which showed the column-shaped convex group. It is the expanded view which showed the other row-shaped convex group. It is the expanded view which showed another row-shaped convex group. It is the expanded view which showed other row-shaped convex group. It is the cross-sectional side view which showed another embodiment of the steel pipe connection structure which concerns on this invention. It is a cross-sectional front view. It is action explanatory drawing of this invention, (A) is an action explanatory drawing which showed the convex part and the small protrusion, and (B) is action explanatory drawing which showed the steel pipe and the insertion cylinder part. It is action explanatory drawing of this invention, (A) is an action explanatory drawing which showed the convex part and the small protrusion, and (B) is action explanatory drawing which showed the steel pipe and the insertion cylinder part.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments.
As shown in FIG. 1 and FIG. 2, the present invention is a steel pipe 1 in which a plurality of row-like convex groups 15 composed of a plurality of convex portions 11 arranged along the axial direction are arranged in parallel on the inner peripheral surface 1B. And an end portion 2 of the steel pipes 1, 1 facing each other in close proximity to each other. , 2 is a steel pipe connection structure in which the insertion tube portions 4 and 4 of the joint 3 are inserted and connected.
The steel pipe connection structure of the present invention is used for reinforcing natural ground or for a steel pipe composite structure. Specifically, although not shown in the drawings, as for natural ground reinforcement, in order to prevent natural slopes and natural ground from collapsing, excavation holes are formed alternately in the horizontal direction or oblique direction toward the natural ground. A natural ground reinforcement method in which a plurality of steel pipes 1 and 1 are inserted into a hole while being connected in the longitudinal direction via a joint 3, and a solidified member such as mortar or soil cement is poured into the excavation hole and integrated with the ground. In, it is used as a core material of a composite pile composed of a solidified member and a steel pipe. Alternatively, in construction sites such as high-rise buildings and road / railway piers, the steel bars 1 are replaced with steel pipes 1 as the foundation of structures, and solidified members such as mortar or soil cement are assembled in the formwork. It can also be used for a steel pipe composite structure that is poured into and integrated with the steel pipe 1.

  As shown in FIG. 1, the steel pipe 1 is made of carbon steel or the like and has a fixed, substantially cylindrical shape, and a plurality of recesses 10 that are recessed in an elliptical shape are provided in the outer peripheral surface 1A thereof. . That is, the steel pipe 1 shown in FIG. 1 can be said to be a dimple steel pipe having dimples (recessed portions 10) on the outer peripheral surface 1A. The depressions 10 are arranged so as to form a row at a predetermined interval along the axial direction. In a place where the depression 10 is not formed, the smooth outer peripheral surface 1A remains cylindrical. A single-character recess 14 is formed at the center of each recess 10. In the manufacturing process, the recess 10 is formed simultaneously with the formation of the single-character recess 14, and the protrusion 11 on the inner peripheral surface 1 </ b> B side is formed corresponding to the recess 10. With this configuration, an uneven portion is formed on the outer peripheral surface 1A and the inner peripheral surface 1B of the steel pipe 1 (compared to a conventional straight pipe), the surface area is increased, and the adhesion to a solidified member such as mortar is increased. Can do.

  The steel pipe 1 is not shown in the drawing, but in the manufacturing process, the dimple (indentation portion 10) on the outer peripheral surface 1A has an outer peripheral surface from the opposite side of the projection of the steel pipe shaping roller (vertical single character type) 180 ° during hot rolling. As a result, the single-letter-shaped concave portion 14 and the hollow portion 10 are formed on the outer peripheral surface 1A by the (vertical single-letter type) protrusion of the steel pipe shaping roller, and at the same time, the inner peripheral surface 1B is formed on the inner peripheral surface 1B. The convex part 11 is formed. The steel pipe shaping roller is rotationally driven through a well-known synchronizing means, and the steel pipe 1 is configured to be sent and moved in accordance with the peripheral speed of the shaping roller. In this manner, the steel pipe 1 has the convex portions 11 and 11 arranged in the same phase in the axial direction on the row-like convex groups 15 and 15 on the opposite side of the inner peripheral surface 1B by 180 °.

As shown in FIG. 2 and FIG. 3, on the outer peripheral surface 4A of the insertion tube portion 4, there are provided small projections 9 and 9 for locking to the row-like convex groups 15 and 15 on the opposite side of 180.degree. The position is shifted in the axial direction with a phase difference.
Further, on the inner peripheral surface 1B of the steel pipe 1, a smooth surface-like longitudinal recess 20 is formed over the entire length in the axial direction between the row-like convex groups 15 and 15 adjacent in the circumferential direction (smooth inner periphery). Surface 1B remains). On the other hand, a circumferential positioning bulging portion 6 that fits in the longitudinal recess 20 is provided on the outer peripheral surface 4A of the insertion tube portion 4.
The joint 3 shown in FIG. 4 includes small protrusions 9 and 9 at two positions 180 ° opposite to the outer peripheral surface 4A of the insertion tube portion 4, and a pair of bulging portions adjacent to both sides of each small protrusion 9 6,6 are formed over the longitudinal direction. Further, the outer flange portion 5 is formed so as not to protrude radially outward from the outer peripheral surface 1A of the steel pipe 1 in the inserted and used state. Note that one of the bulging portions 6 and 6 adjacent to the small protrusion 9 may be omitted.

The design of the joint 3 can be changed, and in FIGS. 5 and 6, the bulging portions 6 and 6 are formed in the longitudinal direction at two locations on the opposite side of the outer peripheral surface 4A of the insertion tube portion 4 at 180 °. A pair of small protrusions 9 and 9 are formed adjacent to both sides of the bulging portion 6. That is, the small protrusions 9 and 9 are arranged at four positions on the opposite side of 180 °, and are formed so as to be displaced in the axial direction with a predetermined phase difference. 5 and 6, the number of the small protrusions 9 and 9 increases as compared with the joint 3 shown in FIG. 4, so that the resistance during insertion increases. be able to. The number of small protrusions 9 may be one row (one) for one bulging portion 6.
Further, for example, as shown in FIG. 7, bulging portions 6 and 6 are formed at two locations 180 ° opposite to the outer peripheral surface 4A of the inner tube portion 4, and two locations 180 ° opposite to the orthogonal direction. Small projections 9 and 9 may be provided.

The use method (action) of the above-described steel pipe connection structure of the present invention will be described.
As shown in FIGS. 2 and 3, the insertion tube portion 4 of the joint 3 is inserted into the end portion 2 of the steel pipe 1. At this time, the circumferential positioning bulge 6 is inserted into the longitudinal recess 20 on the steel pipe 1 side. Further, at the time of insertion, one of the small projections 9 and 9 having a difference in phase is brought into sliding contact with the convex portion 11 by making use of a gap (play) between the insertion tube portion 4 and the inner peripheral surface 1B of the steel pipe 1. And while the other escapes to the trough part between the convex parts 11 and 11, it pushes in while inserting the insertion cylinder part 4 with respect to the steel pipe 1 at a slight angle (pitching). It is not necessary to insert until the end portion 2 of the steel pipe 1 hits the outer flange portion 5 of the joint 3. When the steel tube 1 is inserted to a certain depth, one small protrusion 9 comes into contact with the convex portion 11 and rides on the other side. The small projections 9 are engaged with the projections 11 whose phases are different from each other in the axial direction on the opposite side of 180 °, thereby preventing the steel pipe 1 from being pulled out. At this time, one of the small projections 9 rides on the convex portion 11, and the inner cylindrical portion 4 is eccentric with respect to the steel pipe 1, and the other small projection 9 is securely locked to the side surface of the convex portion 11. Make sure to keep it safe. Moreover, the bulging part 6 fits into the longitudinal direction recessed part 20, and rotation of the steel pipe 1 and the insertion cylinder part 4 is prevented. In addition, when inserting the insertion cylinder part 4 in the edge part 2 of the steel pipe 1, you may give a strong impact to an axial direction and may be struck. The small protrusions 9 and 9 are formed in a triangular shape or a trapezoidal shape having an inclined surface in the insertion direction of the insertion tube portion 4 so as to easily get over the convex portion 11 only when the insertion tube portion 4 is inserted. desirable.

Next, another embodiment of the present invention will be described with reference to FIG.
In FIG. 8, a steel pipe 1 in which a plurality of row-like convex groups 15 including a plurality of convex portions 11 arranged along the axial direction are arranged in parallel on the inner peripheral surface 1B, an outer flange portion 5 and an inner tube. And the short cylindrical joint 3 integrally having the portions 4 and 4, and the tube portions of the joint 3 at the end portions 2 and 2 of the steel pipes 1 and 1 arranged on the same axis and facing each other. 4 and 4 is a steel pipe connection structure in which the protrusions 11 and 11 are displaced in the axial direction with a predetermined phase difference in the row-like protrusion groups 15 and 15 on the opposite side of 180 °. On the outer peripheral surface 4A of the insertion tube portion 4, there are formed small projections 9 and 9 for locking to the row-like convex groups 15 and 15 on the opposite side of 180 ° in the same phase in the axial direction. ing.
On the inner peripheral surface 1B of the steel pipe 1, a smooth surface-like longitudinal concave portion 20 is formed over the entire length in the axial direction between the row-like convex groups 15 and 15 adjacent in the circumferential direction, and fitted into the longitudinal concave portion 20. A circumferential positioning bulging portion 6 is provided. About another structure, it is the same as that of the above-mentioned embodiment.

Further, the steel pipe 1 may be a striped steel plate having a convex portion 11 on the inner peripheral surface 1B. The striped steel plate is made of a steel plate in which a plurality of convex portions 11 are formed in a striped pattern on one surface by hot rolling, and the convex portions 11 are formed on the inner peripheral surface 1B by rolling the steel plate into a steel pipe. Is formed.
For example, in FIG. 9, the convex portion 11 is formed in a single character shape inclined in an oblique direction. A plurality of row-like convex groups 15 in which a plurality of obliquely inclined convex portions 11 are arranged along the axial direction are arranged in parallel. The inclination direction of the convex portion 11 may be different for each row as shown in the figure, or all may be the same direction. Moreover, as shown in FIG. 10, it is also preferable that the convex portions 11 have a single character shape inclined in an oblique direction, and are arranged in a staggered manner in which the inclination directions are alternately different in a row.
Moreover, in FIG. 11, the convex part 11 is formed in the shape of one character along the axial direction, and arranged in multiple rows in series. As shown in FIG. 12, it is also preferable that the convex portion 11 is formed in a single letter shape in the circumferential direction.

As shown in FIGS. 13 and 14, the steel pipe 1 may be one in which a recess is not formed on the outer peripheral surface 1A.
In FIG. 13 and FIG. 14, a plurality of row-like convex groups 15 composed of a plurality of convex portions 11 arranged along the axial direction are arranged in parallel on the inner peripheral surface 1B of the steel pipe 1, and 180 ° opposite to each other. In the row-like convex groups 15, 15, the convex portions 11, 11 are arranged in the same phase in the axial direction. In the joint 3, the small projections 9 and 9 for locking to the row-like convex groups 15 and 15 on the opposite side of 180 ° are positioned in the axial direction with a predetermined phase difference on the outer peripheral surface 4A of the insertion tube portion 4. It is formed by shifting. Further, in the inner peripheral surface 1B of the steel pipe 1, a smooth surface-like longitudinal concave portion 20 is formed over the entire length in the axial direction between the row-like convex groups 15 and 15 adjacent in the circumferential direction, and the insertion tube On the outer peripheral surface 4A of the portion 4, a circumferential positioning bulging portion 6 that fits into the longitudinal recess 20 is projected. Although not shown in the drawings, the convex portions 11 and 11 are formed on the columnar convex groups 15 and 15 on the opposite side of 180 ° by shifting the position in the axial direction with a predetermined phase difference. On the surface 4A, the small protrusions 9 and 9 for retaining to be locked to the row-like convex groups 15 and 15 on the opposite side of 180 ° may be arranged in the same phase.

  As shown in FIG. 15 and FIG. 16, the steel pipe 1 is inserted and inserted into the steel pipe 1 in which the convex portion 11 is formed in a single-letter shape inclined in an oblique direction. When a tensile force is applied, the small protrusion 9 is guided by the inclined convex portion 11 so that a rotational force is applied to the joint 3, so that the play between the joint 3 and the steel pipe 1 is eliminated and is firmly retained. Has been.

As shown in FIG. 15, when the small protrusion 9 hits the inclined convex portion 11 when the insertion tube portion 4 of the joint 3 is inserted into the steel pipe 1, the small protrusion 9 guides along the slope of the convex portion 11. Then, the joint 3 rotates within a backlash range between the longitudinal recess 20 of the steel pipe 1 and the bulging portion 6 of the insertion tube portion 4.
Next, as shown in FIG. 16, the bulging portion 6 comes into contact with one side end surface (side surface of the convex portion 11) of the longitudinal concave portion 20 and cannot rotate (see FIG. 16B). It stops and the small protrusion 9 gets over the convex part 11. When a tensile force is applied to the steel pipe 1, the small protrusion 9 is guided in the reverse direction along the slope of the convex portion 11, and the joint 3 is inserted by the amount of play between the longitudinal concave portion 20 and the bulging portion 6. Rotate in the opposite direction of time. In a state where the bulging portion 6 is in contact with the other side end surface of the longitudinal concave portion 20 and cannot be rotated, the small protrusion 9 is locked to the slope of the convex portion 11 and does not rattle and firmly holds out. . At the time of insertion, the small protrusion 9 easily passes through the convex portion 11. On the other hand, in the inserted and used state, even if a tensile force is applied to the steel pipe 1, the small protrusion 9 is free from play in the steel pipe 1 and the joint 3. Since 9 is locked to the convex portion 11, the prevention of disconnection is strong. Moreover, since the location where the small protrusion 9 gets over the convex portion 11 is different from the location where it is locked, the convex portion 11 is not broken and crushed.

  Although not shown, the steel pipe 1 may be manufactured by pressing the outer peripheral surface 1A from three directions at a pitch of 120 ° by three shaping rollers in the manufacturing process. In this case, it is also preferable to form small protrusions 9, 9, 9 on the outer peripheral surface 4 </ b> A of the insertion tube portion 4 at three locations with a 120 ° pitch in the circumferential direction.

  As described above, in the steel pipe connection structure according to the present invention, the steel pipe 1 in which the row-like convex group 15 composed of the plurality of convex portions 11 arranged along the axial direction is arranged in a plurality of rows on the inner peripheral surface 1B. And an end portion 2 of the steel pipes 1, 1 facing each other in close proximity to each other. , 2 is a steel pipe connection structure in which the insertion tube portions 4 and 4 of the joint 3 are inserted and connected to each other, and the inner peripheral surface 1B of the steel pipe 1 is connected between the row-like convex groups 15 and 15 adjacent in the circumferential direction A longitudinal concave portion 20 having a smooth surface is formed over the entire length in the axial direction, and the convex portions 11, 11 are arranged in phase in the axial direction in the columnar convex groups 15, 15 on the opposite side of 180 °. On the outer peripheral surface 4A of the insertion tube portion 4, the retaining small projections 9, 9 that are locked to the row-like convex groups 15, 15 on the opposite side of 180 ° have a predetermined phase difference. Thus, since the circumferential positioning bulging portion 6 that is formed so as to be shifted in the axial direction and fitted in the longitudinal recess 20 is provided, a plurality of steel pipes 1 can be easily connected via the joint 3. . That is, it is no longer necessary to weld the end 2 of the steel pipe 1, and it is possible to save the labor for preparing welding power and large-scale equipment, simplifying the connecting work of the steel pipe 1 and greatly shortening the work time. And cost can be reduced. In addition, there is no risk of fire due to welding. The strength of the end 2 of the steel pipe 1 can be secured sufficiently large, or the thickness of the entire steel pipe 1 can be reduced. It is not necessary to rotate the steel pipe 1 many times during the connecting operation. Furthermore, the peripheral surface friction force of the inner peripheral surface 1B of the steel pipe 1 can be increased, and the adhesion force to the solidified member can be increased.

  Further, a steel pipe 1 in which a plurality of row-like convex groups 15 composed of a plurality of convex portions 11 arranged along the axial direction are arranged in parallel on the inner peripheral surface 1B, an outer flange portion 5, and an insertion tube portion 4 , 4 and a short tubular joint 3 integrally formed, and at the end portions 2, 2 of the steel pipes 1, 1 arranged on the same axis and facing each other close to each other, the insertion tubular portion 4, 4 is a steel pipe connection structure in which 4 is inserted and connected to the inner peripheral surface 1B of the steel pipe 1 between the row-like convex groups 15 and 15 adjacent in the circumferential direction and the longitudinal direction of the smooth surface over the entire length in the axial direction. Concave portions 20 are formed, and the convex portions 11 and 11 are arranged on the columnar convex groups 15 and 15 on the opposite side of 180 ° with the predetermined phase difference being shifted in the axial direction. 4 are formed in the same phase in the axial direction on the outer peripheral surface 4A. In addition, since the circumferential positioning bulge 6 that fits into the longitudinal recess 20 is provided, a plurality of steel pipes 1 can be easily connected via the joint 3. That is, it is no longer necessary to weld the end 2 of the steel pipe 1, and it is possible to save the labor for preparing welding power and large-scale equipment, simplifying the connecting work of the steel pipe 1 and greatly shortening the work time. And cost can be reduced. In addition, there is no risk of fire due to welding. The strength of the end 2 of the steel pipe 1 can be secured sufficiently large, or the thickness of the entire steel pipe 1 can be reduced. It is not necessary to rotate the steel pipe 1 many times during the connecting operation. Furthermore, the peripheral surface friction force of the inner peripheral surface 1B of the steel pipe 1 can be increased, and the adhesion force to the solidified member can be increased.

  Moreover, since the recessed part 10 is recessedly provided in the outer peripheral surface 1A of the steel pipe 1 in the position corresponding to the convex part 11, the surface areas of the outer peripheral surface 1A and the inner peripheral surface 1B of the steel pipe 1 increase, and mortar etc. The adhesion force to the solidified member can be increased.

  Moreover, the convex part 11 is formed in the shape of one character inclined in the oblique direction, and when a tensile force is applied to the steel pipe 1 in the inserted and used state, the small protrusion 9 is guided by the inclined convex part 11 and is connected to the joint 3. Since the rotation force is applied to the joint 3 and the steel pipe 1 is free of play, the small protrusion 9 is securely locked to the convex portion 11 and the rattle is not loose. There is no, and can be firmly removed. Since the location where the small protrusion 9 gets over the convex portion 11 is different from the location where it is locked, the convex portion 11 can be firmly prevented from coming out without being destroyed and crushed.

DESCRIPTION OF SYMBOLS 1 Steel pipe 1A Outer peripheral surface 1B Inner peripheral surface 2 End part 3 Joint 4 Insertion cylinder part 4A Outer peripheral surface 5 Outer flange part 6 Swelling part 9 Small protrusion 10 Depression part 11 Convex part 15 Columnar convex group 20 Longitudinal concave part

Claims (6)

A steel pipe (1) in which a plurality of row-like convex groups (15) composed of a plurality of convex portions (11) arranged along the axial direction are arranged in parallel on the inner peripheral surface (1B), and an outer flange portion ( 5) and a short cylindrical joint (3) integrally including the insertion tube portions (4) and (4), and the steel pipes (1) and (1) arranged on the same axis are close to each other. A steel pipe connection structure for inserting and connecting the inner cylindrical portions (4) and (4) of the joint (3) to the opposite end portions (2) and (2),
On the inner peripheral surface (1B) of the steel pipe (1), a longitudinal concave portion (20) having a smooth surface is formed over the entire length in the axial direction between the row-shaped convex groups (15) (15) adjacent in the circumferential direction. The columnar convex groups (15) and (15) formed on the opposite side of 180 ° are provided with the convex portions (11) and (11) in the same phase in the axial direction,
On the outer peripheral surface (4A) of the insertion tube portion (4), there are predetermined small projections (9) and (9) for retaining on the columnar convex groups (15) and (15) on the opposite side of 180 °. A steel pipe coupling structure characterized by being provided with a circumferential positioning bulging portion (6) which is formed by shifting the position in the axial direction with a phase difference of 5 mm and fitted into the longitudinal recess (20). A steel pipe (1) in which a plurality of row-like convex groups (15) composed of a plurality of convex portions (11) arranged along the axial direction are arranged in parallel on the inner peripheral surface (1B), and an outer flange portion ( 5) and a short cylindrical joint (3) integrally including the insertion tube portions (4) and (4), and the steel pipes (1) and (1) arranged on the same axis are close to each other. A steel pipe connection structure for inserting and connecting the inner cylindrical portions (4) and (4) of the joint (3) to the opposite end portions (2) and (2),
On the inner peripheral surface (1B) of the steel pipe (1), a longitudinal concave portion (20) having a smooth surface is formed over the entire length in the axial direction between the row-shaped convex groups (15) (15) adjacent in the circumferential direction. In the row-shaped convex groups (15) and (15) formed on the opposite side of 180 °, the convex portions (11) and (11) are arranged with a predetermined phase difference and shifted in the axial direction. ,
On the outer peripheral surface (4A) of the insertion tube portion (4), there are provided small projections (9) and (9) for retaining which are locked to the row-like convex groups (15) and (15) on the opposite side of 180 °. A steel pipe coupling structure characterized by being provided with a circumferential positioning bulging portion (6) that is formed in the same phase in the center direction and fits in the longitudinal recess (20). A steel pipe (1) in which a plurality of row-like convex groups (15) composed of a plurality of convex portions (11) arranged along the axial direction are arranged in parallel on the inner peripheral surface (1B), and an outer flange portion ( 5) and a short cylindrical joint (3) integrally including the insertion tube portions (4) and (4), and the steel pipes (1) and (1) arranged on the same axis are close to each other. A steel pipe connection structure for inserting and connecting the inner cylindrical portions (4) and (4) of the joint (3) to the opposite end portions (2) and (2),
On the inner peripheral surface (1B) of the steel pipe (1), a longitudinal concave portion (20) having a smooth surface is formed over the entire length in the axial direction between the row-shaped convex groups (15) (15) adjacent in the circumferential direction. In addition, the row-shaped convex groups (15) are arranged in three rows at a circumferential pitch of 120 °, and the convex portions (11), (11) in the three rows of row-shaped convex groups (15) are axes. Arranged in the same direction in the direction of the heart,
On the outer peripheral surface (4A) of the insertion tube portion (4), there are small protrusions (9) for retaining that are engaged with the row-shaped convex groups (15) (15) disposed at a circumferential pitch of 120 °. (9) is characterized by being provided with a circumferential positioning bulging portion (6) which is formed with a predetermined phase difference and shifted in the axial direction and fitted into the longitudinal recess (20). steel pipe connecting structure to be. A steel pipe (1) in which a plurality of row-like convex groups (15) composed of a plurality of convex portions (11) arranged along the axial direction are arranged in parallel on the inner peripheral surface (1B), and an outer flange portion ( 5) and a short cylindrical joint (3) integrally including the insertion tube portions (4) and (4), and the steel pipes (1) and (1) arranged on the same axis are close to each other. A steel pipe connection structure for inserting and connecting the inner cylindrical portions (4) and (4) of the joint (3) to the opposite end portions (2) and (2),
On the inner peripheral surface (1B) of the steel pipe (1), a longitudinal concave portion (20) having a smooth surface is formed over the entire length in the axial direction between the row-shaped convex groups (15) (15) adjacent in the circumferential direction. In addition, the row-shaped convex groups (15) are arranged in three rows at a circumferential pitch of 120 °, and the convex portions (11), (11) in the three rows of row-shaped convex groups (15) are predetermined. The position is shifted in the axial direction with a phase difference of
On the outer peripheral surface (4A) of the insertion tube portion (4), there are small protrusions (9) for retaining that are engaged with the row-shaped convex groups (15) (15) disposed at a circumferential pitch of 120 °. (9) A steel pipe coupling structure characterized in that a circumferential positioning bulging portion (6) is provided which is formed in the same phase in the axial direction and fits in the longitudinal recess (20) . The steel pipe connection structure according to claim 1, 2, 3, or 4, wherein a hollow portion (10) is recessed in a position corresponding to the convex portion (11) on the outer peripheral surface (1A) of the steel pipe (1). . When the convex portion (11) is formed in a single-letter shape inclined in an oblique direction and a tensile force is applied to the steel pipe (1) in the inserted and used state, the small protrusion (9) is inclined to the convex shape. It is configured to be firmly retained in a state in which a rotational force acts on the joint (3) by being guided by the portion (11) and there is no play between the joint (3) and the steel pipe (1). Item 6. A steel pipe connection structure according to item 1, 2, 3, 4 or 5.

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