Steel pipe connection device

Abstract

To provide a steel pipe connection device allowing easy connection work and having high work efficiency.SOLUTION: A steel pipe connection device has a box joint 1 and a pin joint 2 each provided at end parts facing with each other of steel pipes, a key 3 stored in a key groove 31 straddling a boundary of the joints 1, 2 formed by engaging the joints 1, 2 with each other and movable to a straddling position straddling the boundary of the joints 1, 2, and a pin 4 having a shaft part 41 and a head part 42. A through-hole 16 and a hole part 26 communicating with the key groove 31 are formed to the joint parts 1, 2, respectively, and a through-hole 32 facing the through-hole 16 and the hole part 26 is formed to the key 3. When the pin 4 is arranged at a setting position by inserting the shaft part 41 into the through-hole 32 and the hole part 26 and by inserting the head part 42 into the through-hole 16, the key 3 is positioned to the straddling part by the head part 42.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a steel pipe connecting device used to connect steel pipes that constitute a steel pipe pile. [Background technology]

[0002] A known example of the above-mentioned steel pipe connecting device is one in which a cylindrical portion welded to one steel pipe end and a shaft portion welded to the other steel pipe end are fitted together, and an arc key is positioned across a groove provided on the inner surface of the cylindrical portion and a groove provided on the outer surface of the shaft portion, thereby connecting the steel pipes in a non-disconnecting state (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-319874 Summary of the Invention [Problem to be solved by the invention]

[0004] The steel pipe connecting device of Patent Document 1 is provided with a means for preventing relative rotation between connected steel pipes. Specifically, a rotation prevention key is fitted into a notched recess formed across the outer circumferential surfaces of the fitted tubular and shank portions to prevent relative rotation between the tubular and shank portions, thereby connecting the steel pipes in a rotation-preventing state.

[0005] However, in the steel pipe connecting device of the above configuration, it is necessary to fix the rotation prevention key with a bolt or the like to prevent it from falling out of the notched recess, which makes the steel pipe connecting work time-consuming and reduces work efficiency.

[0006] The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a steel pipe connecting device that allows for easy connecting work and high work efficiency. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the steel pipe connecting device according to the present invention is a steel pipe connecting device comprising: a box joint provided at one of the opposing steel pipe end portions of steel pipes adjacent in the axial direction of the steel pipes, the box joint having an inward groove formed along the circumferential direction on the inner peripheral surface; a pin joint provided at the other steel pipe end portion, the pin joint having an outward groove formed along the circumferential direction on the outer peripheral surface that faces the inward groove when the box joint and the pin joint are fitted together; a load transmission key whose position can be changed between a stored position stored in the inward groove and a straddling position spanning the outward groove and the inward groove; and a pin having a shaft and a head connected to one end of the shaft, A box joint through hole is formed from the bottom of the outward groove portion and communicates with the outer peripheral surface of the box joint, and a pin joint hole portion that faces the box joint through hole when the box joint and the pin joint are fitted together is formed in the pin joint so as to extend from the bottom of the outward groove portion toward the inner peripheral surface of the pin joint, and the pin can be positioned in a set position where the shank is inserted into the pin joint hole portion from the outer peripheral surface of the box joint and the head is inserted into the box joint through hole, and the load transmission key is configured to be positioned in the spanning position by abutting against the head when the pin is positioned in the set position.

[0008] In the steel pipe connecting device configured as described above, when the box joint and pin joint are fitted together and the pin is placed in the set position, even if a rotational force is applied and the box joint and pin joint attempt to rotate relative to each other, the walls of the box joint through hole and the pin joint hole abut against the pin spanning these through holes from opposite directions, preventing relative rotation between the box joint and the pin joint. In other words, with the steel pipe connecting device configured as described above, the step of inserting the pin can transition the fitted box joint and pin joint from a state in which they are free to rotate relative to each other to a state in which they are prevented from rotating.

[0009] In contrast, with a conventional steel pipe connecting device such as that shown in Patent Document 1, in order to transition a box joint and a pin joint that are fitted together to a rotation-preventing state, it is necessary to perform at least the steps of fitting an anti-rotation key into a notched recess and fixing the anti-rotation key with a bolt. As such, compared to conventional steel pipe connecting devices, the steel pipe connecting device of the present invention simplifies the steps for connecting steel pipes, improving the efficiency of the connecting work.

[0010] Furthermore, in the steel pipe connecting device configured as described above, the box joint and pin joint are placed in a retained state by positioning the load transmission key in the spanning position during the pin insertion process. In other words, with the steel pipe connecting device configured as described above, the box joint and pin joint that are fitted together can be transitioned from a separable state to a retained state by performing the pin insertion process.

[0011] In contrast, with conventional steel pipe connecting devices, the process for transitioning to the anti-rotation state and the process for transitioning to the anti-slip state must be carried out separately. As such, compared to conventional steel pipe connecting devices, the steel pipe connecting device of the present invention simplifies the process for connecting steel pipes, thereby improving the efficiency of the connecting work.

[0012] In the steel pipe connecting device of the present invention, it is preferable that a key through hole is formed in the load transmission key that faces the box joint through hole and the pin joint hole portion when the box joint and the pin joint are fitted together, and when the pin is placed in the set position, the shank passes through the key through hole and is inserted into the pin joint hole portion, and the head abuts around the key through hole to position the load transmission key in the spanning position.

[0013] A plurality of load transmission keys are usually provided, and it is preferable to position these load transmission keys at the spanning position with equal circumferential spacing so that the load is evenly distributed. With the steel pipe connecting device configured as described above, the shank passes through the key through-hole when the pin is placed in the set position, so that the load transmission keys are less likely to shift circumferentially relative to the pin. In other words, it is easy to position the load transmission keys at the spanning position at the desired spacing.

[0014] In the steel pipe connecting device according to the present invention, it is preferable that the head of the pin has a tapered portion at one end connected to the shank portion, the diameter of which gradually decreases in the direction of the shank portion.

[0015] A bending moment acts on the pin that prevents relative rotation between the box joint and the pin joint, but the connection point between the head and shank of the pin is prone to fracture because stress concentrates due to changes in the cross-sectional shape.With the steel pipe connecting device configured as above, the change in cross-sectional shape at the connection point between the head and shank of the pin is gentler, so stress concentration is alleviated and fracture is less likely to occur.

[0016] In the steel pipe connecting device of the present invention, it is preferable that the load transmission key has a recess on its surface on the outer surface side of the box joint, which has a shape complementary to the tapered portion and accepts at least a portion of the tapered portion.

[0017] With the steel pipe connecting device configured as described above, when the pin is placed in the set position, the load transmission key is positioned in the spanning position by abutting the tapered portion of the head of the pin with its recess. Compared to when the load transmission key does not have a recess, the load transmission key abuts the head of the pin over a wider area, which makes it possible to reduce the force per unit area acting on the abutment area and, as a result, prevent damage to the abutment area.

[0018] In the steel pipe connecting device of the present invention, it is preferable that the device further comprises a stop ring that restricts movement of the pin positioned in the set position toward the outer peripheral surface of the box joint, and that the stop ring is attached to an attachment groove formed in the box joint through hole.

[0019] According to the steel pipe connecting device having the above configuration, it is possible to prevent the pin arranged in the set position from suddenly coming out toward the outer surface of the box joint, thereby preventing the connection of the steel pipes from being released.

[0020] The steel pipe connecting device according to the present invention is suitable for use in connecting steel pipes that make up a steel pipe pile in a construction method in which the steel pipe pile is pressed into the ground without applying a rotational force.

[0021] If the method involves pressing steel pipe piles into the ground without applying any rotational force, the rotational force transmitted between the steel pipes during installation is reduced or eliminated, making it possible to use pins with lower strength or to install fewer pins to prevent relative rotation between the steel pipes. Reducing the number of pins installed reduces the effort required for connecting the pipes, further improving work efficiency. Furthermore, whether lower strength pins are used or the number of pins installed is reduced, the cost of the pins can be reduced. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a partial cross-sectional view of a steel pipe pile constructed by connecting steel pipes with a steel pipe connecting mechanism. [Figure 2] 10A and 10B are diagrams illustrating a process of fitting a box joint to a pin joint. [Figure 3] FIG. 10 shows a load transmitting key held in a retracted position. [Figure 4] 10A and 10B are diagrams illustrating a process of releasing the hold of the load transmission key. [Figure 5] 10A and 10B are diagrams illustrating a process of placing a pin at a set position. [Figure 6]10A and 10B are diagrams illustrating a process of attaching a stop ring to a pin placed at a set position. [Figure 7] 10A and 10B are views showing a state in which relative rotation between the box joint and the pin joint is suppressed by the pin. [Figure 8] 10A and 10B show pins and load transfer keys according to another embodiment; [Figure 9] 10A and 10B are diagrams showing a steel pipe connecting mechanism according to another embodiment. [Figure 10] 10A and 10B are diagrams showing pins according to other embodiments; [Figure 11] 13A and 13B show a further embodiment of the pin before rotation; [Figure 12] 12A and 12B illustrate the rotation of the pin of the embodiment shown in FIG. [Figure 13] 12 shows the state of the pin of the embodiment shown in FIG. 11 after rotation. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of a steel pipe connecting device according to the present invention will be described with reference to the drawings.

[0024] The steel pipe connecting device J is used to connect the opposing ends of adjacent steel pipes S1 and S2 in the steel pipe axial direction X (the same direction as the up-down direction in this embodiment) to form a steel pipe pile P, and is equipped with a box joint 1, a pin joint 2, a load transmission key 3, a pin 4, and a stop ring 5 (see Figures 1, 2, and 6).

[0025] [Box joint] The box joint 1 is produced by processing a steel tubular body. The upper end of the box joint 1 is connected to the end of the steel pipe S1 by welding or the like. As shown in Figure 2, the box joint 1 has a ridge 11 at the lower end and a circumferential groove 13 formed near the upper end of the inner circumferential surface 12.

[0026] 2 and 3, two, but not limited to, inward grooves 14 are formed along the circumferential direction on the inner peripheral surface 12 of the box joint 1. Each inward groove 14 is configured to be deeper than the thickness of a load transmission key 3 (described later) along the radial direction of the steel pipe pile P, and higher than the height of the load transmission key 3 along the axial direction X of the steel pipe.

[0027] 1 to 3, the box joint 1 is provided with a plurality of box joint through holes 16, each having a circular cross section, that communicate from the bottom of the inward groove portion 14 to the outer peripheral surface 15 of the box joint 1, spaced equally apart in the circumferential direction in correspondence with the installation locations of the load transmission keys 3, which will be described later. Mounting grooves 17 are provided around the box joint through holes 16 near the outer peripheral surface 15 of the box joint 1, for mounting a stop ring 5, which will be described later.

[0028] [Pin joint] The pin joint 2 is produced by processing a steel cylindrical body, and has a shape that allows at least a portion of the axial direction to be inserted into the box joint 1. The portion that can be inserted into the box joint 1 has an outer peripheral surface 21 that is formed with a diameter that is approximately smaller than the inner peripheral surface 12 of the box joint 1.

[0029] The lower end of the pin joint 2 is connected to the end of the steel pipe S2 by welding or the like. As shown in Figure 2, the pin joint 2 is provided at its upper end with a rib 22 that can fit into the circumferential groove 13 of the box joint 1 when inserted into the box joint 1, and a circumferential groove 23 into which the rib 11 provided on the box joint 1 can fit is formed near the lower end of the outer circumferential surface 21. By fitting the ribs 22, 11 into the circumferential grooves 13, 23, respectively, the box joint 1 and the pin joint 2 are fitted to each other in a loose fit that is separable along the axial direction X of the steel pipe and allows relative rotation.

[0030] 2, 3, and 6, two, but not limited to, outward grooves 24 are formed along the circumferential direction on the outer peripheral surface 21 of the pin joint 2 so as to face the inward grooves 14 when the box joint 1 and the pin joint 2 are fitted together. Each outward groove 24 is configured to be shallower than the thickness of a load transmission key 3 (described later) (in this embodiment, the thickness is approximately half the thickness), and higher than the height of both the load transmission key 3 and the inward groove 14. When the box joint 1 and the pin joint 2 are fitted together, the lower side wall surface of the outward groove 24 is at approximately the same height as the lower side wall surface of the inward groove 14, while the upper side wall surface of the outward groove 24 is at a higher position than the upper side wall surface of the inward groove 14. The mutually opposing inward groove 14 and outward groove 24 form a keyway 31 for accommodating the load transmission key 3.

[0031] Furthermore, the pin joint 2 is provided with a plurality of pin joint holes 26, each having a circular cross section and extending from the bottom of the outward groove 24 toward the inner circumferential surface 25 of the pin joint 2, at equal intervals in the circumferential direction, in correspondence with the installation locations of the load transmission keys 3, which will be described later. The pin joint holes 26 have a smaller diameter than the box joint through hole 16, and are provided so as to face the box joint through hole 16 via the key groove 31 when the box joint 1 and the pin joint 2 are fitted together. In this embodiment, the pin joint hole 26 is a through hole that communicates from the bottom of the outward groove 24 to the inner circumferential surface 25. However, the pin joint hole 26 may be a blind hole that does not communicate with the inner circumferential surface 25.

[0032] [Load transmission key] The load transmission key 3 is a member for connecting the box joint 1 and the pin joint 2 in a non-disconnecting state when the box joint 1 and the pin joint 2 are fitted together. As shown in Figures 2 and 3, the load transmission key 3 is made of an arc-shaped steel member with a rectangular cross section, and in this embodiment, although not limited to this, eight load transmission keys 3 are arranged in the key groove 31 at intervals around the steel pipe axis X. Therefore, corresponding to the number of load transmission keys 3, eight box joint through holes 16 of the box joint 1 and eight pin joint holes 26 of the pin joint 2 are also provided.

[0033] A key through hole 32 is drilled in the center of the load transmission key 3 in the longitudinal and height directions, penetrating the load transmission key 3 in the thickness direction. The key through hole 32 has a female threaded portion 321 located on the outer peripheral surface 15 side of the box joint 1, and an unthreaded portion 322 located on the inner peripheral surface 25 side of the pin joint 2. When the box joint 1 and the pin joint 2 are fitted together, the female threaded portion 321 faces the box joint through hole 16, and the unthreaded portion 322 faces the pin joint hole 26. The female threaded portion 321 has a smaller diameter than the box joint through hole 16, and the unthreaded portion 322 has a smaller diameter than the female threaded portion 321 and the pin joint hole 26.

[0034] Within the keyway 31, the load transmission key 3 can be moved between a stored position (see Figures 2 and 3) in which the entire thickness of the load transmission key 3 is inserted into the inward groove portion 14, and a spanning position (see Figures 6 and 7) in which the load transmission key 3 straddles the inward groove portion 14 and the outward groove portion 24. When the load transmission key 3 is placed in the spanning position, the box joint 1 and the pin joint 2, which are in a loose fit state, are connected in a locked state.

[0035] 〔pin〕 6 and 7 , the pin 4 is a steel member having a longitudinal shank 41 with a substantially circular cross section and a head 42 connected to one end of the shank 41. The head 42 has an end face 421 connected to the shank 41 that is substantially perpendicular to the longitudinal direction of the shank 41. The shank 41 is formed to have a diameter substantially smaller than the pin joint hole 26 and the unthreaded portion 322 of the key-through hole 32, and is longer than the length of the key-through hole 32. On the other hand, the head 42 is formed to have a diameter larger than the key-through hole 32 and a diameter substantially smaller than the box joint through hole 16, and is formed so that the sum of the length of the head 42 and the thickness of the load transmission key 3 is greater than the sum of the depths of the inward grooves 14 and the outward grooves 24.

[0036] When the pin 4 formed in this manner is inserted into the box joint through-hole 16 from the outer peripheral surface 15 of the box joint 1, the load transmission key 3 is pushed into the bottom of the outward groove portion 24 by abutting against the end face 421 of the head 42, and is positioned in the spanning position. In addition, the shank 41 passes through the key through-hole 32 and is inserted into the pin joint hole portion 26, and at least a portion of the head 42 on the outer peripheral surface 15 side of the box joint 1 is held within the box joint through-hole 16. The position of the pin 4 at this time corresponds to the set position according to the present invention.

[0037] When the pin 4 is placed in the set position, the load transmission key 3 is positioned in the straddling position, and the box joint 1 and the pin joint 2 are connected in a non-disconnected state. Furthermore, when a counterclockwise rotational force as shown in Figure 7 as an example is applied to the box joint 1, causing the box joint 1 to rotate relative to the pin joint 2, the walls of the box joint through hole 16 and the pin joint hole portion 26 abut against the pin 4 spanning these through holes 16, 26 from opposite directions (in the form shown in Figure 7, the wall of the box joint through hole 16 abuts against the head portion 42 from the counterclockwise direction, and the wall of the pin joint hole portion 26 abuts against the shaft portion 41 from the clockwise direction), so the rotational force acting on the box joint 1 is transmitted to the pin joint 2 via the pin 4, and relative rotation between the box joint 1 and the pin joint 2 is suppressed. As a result, the box joint 1 and the pin joint 2 are connected in a non-rotational state.

[0038] As shown in Figure 6, before a tensile load acts on the steel pipe pile P, the distance between the upper wall surface of the outward groove 24 and the upper side surface of the load transmission key 3 is smaller than the distance between the upper outer peripheral surface of the shank 41 of the pin 4 and the upper wall surface of the pin joint hole 26. As a result, when a tensile load acts on the steel pipe pile P, the load transmission key 3 rises together with the box joint 1 and eventually comes into contact with the upper wall surface of the outward groove 24. However, even at this time, the shank 41 of the pin 4 does not come into contact with the upper wall surface of the pin joint hole 26, so the tensile load is transmitted only by the load transmission key 3. This makes it possible to prevent the shank 41 of the pin 4, which has lower strength than the load transmission key 3, from being broken by the tensile load.

[0039] [Stop ring] 6 and 7, the stop ring 5 can be attached to the attachment groove 17 by reducing its diameter with an attachment jig. By attaching the stop ring 5 to the attachment groove 17, which is formed on the outer peripheral surface 15 side of the box joint 1 relative to the head 42 of the pin 4 that is positioned in the set position, movement of the pin 4 toward the outer peripheral surface 15 of the box joint 1 is restricted, so there is no risk of the pin 4 moving away from the set position due to vibration or the like and releasing the connection between the box joint 1 and the pin joint 2.

[0040] <Steel pipe connection method> Hereinafter, a method for connecting steel pipes S1 and S2 using the steel pipe connecting device J according to the present invention configured as described above will be described. Note that an explanation of the steps for connecting the box joint 1 and the pin joint 2 to the ends of the steel pipes S1 and S2 will be omitted.

[0041] First, as shown in Figures 2 and 3, the box joint 1 is moved above the pin joint 2 using a crane or the like. Within the inward grooves 14 of the box joint 1, each load transmission key 3 is held in advance in a storage position by a bolt 6 that is inserted from the outer peripheral surface 15 side of the box joint 1 into the box joint through hole 16 and threaded into the female thread portion 321 in the key through hole 32 of the load transmission key 3.

[0042] Next, the steel pipe S1 is lowered to fit the box joint 1 and the pin joint 2 in a loose fit state. When lowering the steel pipe S1, the steel pipe S1 is rotated appropriately so that the key through hole 32 of the load transmission key 3 roughly faces the pin joint hole portion 26 of the pin joint 2.

[0043] Then, as shown in FIG. 4, the bolts 6 are removed from the box joint 1, and the load transmission keys 3 are released from the bolts 6.

[0044] Thereafter, as shown in FIG. 5, the pin 4 is inserted through the box joint through-hole 16 and placed in the set position, thereby connecting the box joint 1 and the pin joint 2, which are in a loosely fitted state, in a locked state and in a locked state.

[0045] 6, the stop ring 5 is attached to the attachment groove 17 to hold the pin 4 in the set position. Through the above steps, the steel pipes S1 and S2 are connected.

[0046] Note that when separating the steel pipes S1 and S2, the above steps can be performed in reverse order. Specifically, first, the stop ring 5 is removed from the mounting groove 17. Next, a tool such as a hex wrench is fitted into the hole 422 formed in the head 42 of the pin 4, and the pin 4 is removed from the box joint through-hole 16. Then, the bolt 6 is inserted through the box joint through-hole 16 and screwed into the key through-hole 32 of the load transmission key 3, and the load transmission key 3 is pulled back to the storage position. This places the box joint 1 and the pin joint 2 in a loose-fit state, making it possible to separate the steel pipes S1 and S2.

[0047] Methods for burying steel pipes include the driving method, pre-boring method, inner excavation method, and rotary buried pile method. A steel pipe pile constructed using the steel pipe connecting device J of the present invention can be used regardless of the construction method, but is preferably used in construction methods that do not apply a rotational force to the steel pipe pile, such as the driving method. In this construction method, the rotational force acting on the pins 4 during the embedding of the steel pipe pile P is reduced or eliminated, reducing the risk of the pins 4 breaking. However, by using pins 4 with higher strength or increasing the number of pins 4, it becomes possible to transmit the rotational force without worrying about breakage, so the steel pipe connecting device J of the present invention may also be used to construct a steel pipe pile P used in a construction method that applies a rotational force.

[0048] <Other embodiments> (1) In the steel pipe connecting device J of the above-described embodiment, the head 42 of the pin 4 is formed so that the end surface 421 that connects to the shank 41 is approximately perpendicular to the longitudinal direction of the shank 41. However, the present invention is not limited to this. As shown in FIG. 8 , the head 42 of the pin 4 may have a tapered portion 423 at one end that connects to the shank 41, the diameter of which gradually decreases toward the shank 41. Correspondingly, the load transmission key 3 may have a recess 33 on its surface on the outer peripheral surface 15 side of the box joint 1, the recess 33 having a shape complementary to the tapered portion 423 and formed to receive a portion of the tapered portion 423. In this embodiment, the pin 4 positions the load transmission key 3 in the straddling position by the tapered portion 423 abutting against the recess 33. Note that the recess 33 may be formed to receive the entire tapered portion 423.

[0049] (2) In the steel pipe connecting device J of the above-described embodiment, the pin 4 is configured so that the shank 41 passes through the key through hole 32 and is inserted into the pin joint hole 26, and the head 42 abuts against the periphery of the key through hole 32, allowing the pin 4 to be positioned in a set position where the load transmission key 3 is positioned in a straddling position. However, the steel pipe connecting device J of the present invention is not limited to this. As shown in FIG. 9 , a box joint through hole 16′ and a pin joint hole 26′ may be provided to face the gap between adjacent end portions 34 of the load transmission keys 3 arranged around the steel pipe axis X with a gap between them, and the pin 4 may be configured so that the shank 41 passes through the gap between the end portions 34 and is inserted into the pin joint hole 26′, allowing the head 42 to abut against the end portions 34, allowing the pin 4 to be positioned in a set position where the load transmission key 3 is positioned in a straddling position. In the steel pipe connecting device J of this embodiment, steel pipes can be connected or separated by performing the same steps as in the steel pipe connecting device J of the above-described embodiment. In this embodiment as well, it is necessary to provide the through hole 18 in the box joint 1 for inserting the bolt 6, but the through hole 18 can be made to have a diameter substantially larger than the outer diameter of the bolt 6.

[0050] (3) In the steel pipe connecting device J of the above-described embodiment, the pin 4 is held in the set position by the stop ring 5, but the means for restricting the movement of the pin 4 toward the outer surface 15 of the box joint 1 is not limited to this. For example, by forming the box joint through hole 16 as a female-threaded hole and the head 42 of the pin 4 as a male-threaded hole, the movement of the pin 4 can be restricted by the frictional force generated between the box joint through hole 16 and the head 42, which are threaded together. 10, a so-called drop-out prevention bolt can be used as the pin 4, in which a male thread portion 411 is provided only on the tip side of the shaft portion 41 and the head 42 side of the shaft portion 41 is recessed, and the pin joint hole 26 is formed as a female threaded hole. In this configuration, the pin 4 is positioned in the set position so that the male thread portion 411 on the tip side of the shaft portion 41 screws through the pin joint hole 26 and penetrates all the way to the inner circumferential surface 25 of the pin joint 2. With the pin 4 positioned in this manner, the male thread portion 411 of the pin 4 gets caught in the female thread portion of the pin joint hole 26, thereby restricting movement toward the outer circumferential surface 15 of the box joint 1. 11 to 13 (the pin 4 is shown in a non-cross-sectional view for ease of explanation), two protrusions 424 extending in the axial direction of the pin 4 can be provided at equal intervals in the circumferential direction on the shaft portion 41 side of the outer peripheral surface of the head 42 of the pin 4, and a groove 161 that slides and guides the protrusions 424 of the head 42 can be provided in the box joint through-hole 16. Here, the protrusions 424 are configured to pass through the groove 161 of the box joint through-hole 16 and be housed in the inward groove 14 when the pin 4 is inserted to the set position. In this embodiment, when installing the pin 4, the pin 4 is inserted into the set position with the protrusion 424 of the head 42 guided by the groove 161 of the box joint through-hole 16, but after the protrusion 424 of the head 42 passes through the groove 161 and moves to the inward groove 14 (see FIG. 11), the pin 4 can be rotated a predetermined angle (for example, 90 degrees) to shift the position of the protrusion 424 to a position where it does not face the groove 161 (see FIGS. 12 and 13), and the movement of the pin 4 toward the outer peripheral surface 15 of the box joint 1 will be restricted by the protrusion 424 abutting against the bottom of the inward groove 14 (the portion indicated by the two-dot chain line in FIG. 13). The number of protrusions 424 is not limited to two, and may be one, or three or more. [Explanation of symbols]

[0051] 1: Box joint 2: Pin joint 3: Load transmission key 4: Pin 5: Stop ring 6: Bolt 11: Projection 12: Inner surface 13: Peripheral groove 14: Inward groove 15: Outer surface 16, 16': Box joint through hole 161: Groove 17: Mounting groove 18:Through hole 21: Outer surface 22: Projection 23: Peripheral groove 24: Outward groove 25: Inner surface 26, 26': Pin joint hole 31: Keyway 32: Key through hole 321: Female thread 322: Non-screw part 33: Recess 34: Edge 41: Shaft 411: Male thread 42:Head 421: End face 422: Hole 423: Tapered section 424:Protrusion J: Steel pipe connection device P: Steel pipe pile S1: Steel pipe S2: Steel pipe X: Steel pipe axial direction

Claims

1. a box joint provided at one of the opposing steel pipe ends of steel pipes adjacent to each other in the axial direction of the steel pipes, the box joint having an inward groove formed along the circumferential direction on the inner circumferential surface; a pin joint provided at the other steel pipe end, the pin joint having an outward groove formed along the circumferential direction on the outer peripheral surface thereof, the outward groove facing the inward groove when the pin joint and the box joint are fitted together; a load transmission key whose position can be changed between a storage position stored in the inward groove portion and a spanning position spanning the outward groove portion and the inward groove portion; A steel pipe connecting device comprising a shaft portion and a pin having a head connected to one end of the shaft portion, A box joint through hole is formed in the box joint, the box joint communicating from a bottom of the inward groove portion to an outer peripheral surface of the box joint, a pin joint hole portion that faces the box joint through hole when the box joint and the pin joint are fitted together is formed in the pin joint so as to extend from a bottom of the outward groove portion toward an inner circumferential surface of the pin joint, The pin can be arranged at a set position where the shank is inserted into the pin joint hole from the outer peripheral surface of the box joint and the head is inserted into the box joint through-hole, The load transmission key is a steel pipe connecting device configured so that when the pin is placed in the set position, the head of the load transmission key abuts against the surface on the outer surface side of the box joint of the load transmission key, thereby positioning it in the spanning position.

2. a key through hole is formed in the load transmission key, the key through hole facing the box joint through hole and the pin joint hole portion when the box joint and the pin joint are fitted together; When the pin is placed in the set position, The shaft portion passes through the key through hole and is inserted into the pin joint hole portion, The steel pipe connecting device according to claim 1 , wherein the head abuts around the key through hole to position the load transmission key at the spanning position.

3. 3. The steel pipe connecting device according to claim 2, wherein the head of the pin has a tapered portion at one end connected to the shank, the tapered portion gradually reducing in diameter in the direction of the shank.

4. The steel pipe connecting device according to claim 3, wherein the load transmission key has a recess on its outer peripheral surface of the box joint, the recess having a shape complementary to the tapered portion and receiving at least a portion of the tapered portion.

5. A stop ring is further provided to restrict movement of the pin arranged at the set position toward the outer peripheral surface of the box joint, The steel pipe connecting device according to claim 1 , wherein the stop ring is attached to an attachment groove formed in the box joint through hole.

6. The steel pipe connecting device according to any one of claims 1 to 4, which is used to connect steel pipes that constitute a steel pipe pile in a construction method of pressing a steel pipe pile into the ground without applying a rotational force.

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