Pipe joint structure and assembly method of the same

Abstract

To provide a pipe joint structure which enables reduction of a possibility that a nut comes loose during use of a pipe, and to provide an assembly method of the pipe joint structure.SOLUTION: A pipe joint structure 1 includes: a nut 50; and a loosening inhibition ring 40 provided at an outer diameter part of a joint body 30 and having a partial ring shape. The nut 50 has a nut groove part 52 in which the loosening inhibition ring 40 is housed in an inner diameter part. When the nut 50 is not fastened, the loosening inhibition ring 40 has a large diameter part 42 having an inner diameter larger than an outer diameter of a joint groove part 32 in at least part thereof. When a first pipe 20 or a second pipe 21 and the joint body 30 are fastened by the nut 50, if the nut 50 is located in a temporarily fastened position, the large diameter part 42 of the loosening inhibition ring 40 is pressed by the inner diameter part of the nut 50. If the nut 50 is located at a fully fastened position where the nut 50 is further fastened than in the temporarily fastened position, the loosening inhibition ring 40 is housed in the nut groove part 52 to release pressing of the large diameter part 42.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pipe joint structure and an assembly method thereof. [Background technology]

[0002] A known example of an expansion type fitting is the one described in Patent Document 1, in which the vicinity of the end of a stainless steel pipe used for cold water and hot water supply piping is expanded (expanded) to form an expanded section, the end of the pipe is inserted into the fitting body, and a nut is tightened from above the expanded section, pressing the stainless steel pipe against the sealing material, thereby sealing the fitting body with water and preventing the pipe from coming loose. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-318459 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the pipe expansion joint described in Patent Document 1 had the problem that if the nut was not tightened properly or if excessive vibration, pressure changes, thermal contraction, or thermal expansion occurred during use of the piping, the nut could loosen, reducing the force pressing the stainless steel pipe against the sealing material, which could result in fluid leaking from the gap between the stainless steel pipe and the joint body.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide a pipe joint structure and an assembly method thereof that can reduce the possibility of nuts loosening during use of the pipe. [Means for solving the problem]

[0006] The pipe fitting structure according to the present invention comprises a pipe, a pipe fitting into which an end of the pipe is inserted, a nut that screws onto the pipe fitting and fastens the pipe and the pipe fitting together, and a loosening prevention member that is provided in a fitting groove formed on the outer diameter portion of the pipe fitting and has a partial ring-shaped shape including an open portion, the nut having a nut groove in its inner diameter portion in which the loosening prevention member is accommodated, and when the nut is not fastening the pipe and the pipe fitting together, the loosening prevention member has at least a portion that has a large diameter portion whose inner diameter is larger than the outer diameter of the fitting groove, and when the nut fastens the pipe and the pipe fitting together, when the nut is in a first position, the large diameter portion of the loosening prevention member is pressed by the inner diameter portion of the nut, and when the nut is in a second position that is tightened further than the first position, the loosening prevention member is accommodated in the nut groove and the pressure of the inner diameter portion of the nut against the large diameter portion of the loosening prevention member is released.

[0007] Furthermore, when the nut, which was in the second position, is loosened to release the fastening between the pipe and the pipe joint, the large diameter portion of the loosening preventive member may be pressed by the inner diameter portion of the nut in the first position. The loosening inhibiting member may be made of a metal material.

[0008] a nut having an inner diameter portion in which the loosening prevention member is accommodated, and a nut groove formed on the outer diameter portion of the pipe fitting, the nut having an inner diameter portion in which the loosening prevention member is accommodated, and when the nut is not fastening the pipe and the pipe fitting, at least a portion of the loosening prevention member has a large diameter portion whose inner diameter is larger than the outer diameter of the joint groove; [Effects of the Invention]

[0009] According to the present invention, a pipe fitting structure includes a loosening prevention member provided in a fitting groove formed in the outer diameter portion of the pipe fitting and having a partial ring-shaped shape including an open portion, and the nut has a nut groove portion in which the loosening prevention member is accommodated in its inner diameter portion, and when the nut is not fastening the pipe and the pipe fitting, the loosening prevention member has at least a portion having a large diameter portion whose inner diameter is larger than the outer diameter of the fitting groove, and when the nut fastens the pipe and the pipe fitting, when the nut is in a first position, the large diameter portion of the loosening prevention member is pressed by the inner diameter portion of the nut, and when the nut is in a second position tightened further than the first position, the loosening prevention member is accommodated in the nut groove and the pressure of the inner diameter portion of the nut on the large diameter portion of the loosening prevention member is released, thereby reducing the possibility of the nut loosening during use of the pipe.

[0010] Furthermore, according to the present invention, a method for assembling a pipe fitting structure includes the steps of providing a loosening prevention member in a fitting groove portion and inserting the end of a pipe provided with a nut into the pipe fitting; fastening the nut to the pipe fitting so that when the nut is in a first position, the large diameter portion of the loosening prevention member is pressed by the inner diameter portion of the nut; and when the nut is further tightened and in a second position, the loosening prevention member is accommodated in the nut groove portion, thereby reducing the possibility of the nut loosening during use of the pipe. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a half-sectional exploded view of a pipe joint structure according to an embodiment of the present invention; [Figure 2] 2 is a side view of the loosening restricting ring shown in FIG. 1, viewed in a direction along the central axis. [Figure 3] FIG. 3 is a perspective view of the loosening restricting ring shown in FIG. 2. [Figure 4] 1 is a partial cross-sectional view of a pipe joint structure when the nut is temporarily fastened to the joint body. [Figure 5] 10 is a side view of the loosening restricting ring when pressed radially inward. FIG. [Figure 6]1 is a half-sectional view of the pipe joint structure when the nut is fully tightened to the joint body. [Figure 7] 7 is a cross-sectional view of the second piping side loosening prevention ring and nut taken along line AA' in FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional exploded view of one side of a pipe joint structure according to an embodiment of the present invention. The pipe joint structure 1 is used in piping equipment installed in commercial facilities, homes, factories, etc., and includes a first pipe 20, a second pipe 21, and a joint body 30 connecting these pipes. The first pipe 20 and the second pipe 21 are metal pipes through which fluids, including various gases or liquids such as refrigerants, high-temperature or low-temperature gases, hot water, or cold water, flow. The first pipe 20 has a first expanded pipe section 22 with an expanded diameter, and the second pipe 21 has a second expanded pipe section 23 with an expanded diameter. The first expanded pipe section 22 and the second expanded pipe section 23 are formed by expanding the diameter of portions of the first pipe 20 and the second pipe 21 using a known expanding tool. The first pipe 20 and the second pipe 21 can be formed from any metal material, such as stainless steel, copper, or an aluminum alloy.

[0013] The joint body 30 is a tubular joint made of any metal material, such as stainless steel, copper, or aluminum alloy. The joint body 30 has a protruding portion 31 that protrudes radially outward at the center of the central axis. Ring-shaped joint grooves 32 are formed on both sides of the protruding portion 31. In the following description, the direction in which the radial central axes of the joint body 30, the first pipe 20, and the second pipe 21 extend is referred to as the X direction. In the following description, the X, Y, and Z directions are mutually orthogonal directions. Specifically, the Z direction is the vertical direction, and the X and Y directions are horizontal directions orthogonal to the vertical direction. The Z direction is referred to as the height direction, and the higher side in the Z direction is referred to as the upper side and the lower side in the Z direction is referred to as the lower side. A male thread portion 33 is provided adjacent to the joint groove 32. The joint groove 32 has a smaller outer diameter than the male thread portion 33 and is circular when viewed along the X direction. Furthermore, the end portion 34 adjacent to each male thread portion 33 of the joint body 30 is formed to have a smaller outer diameter than the male thread portion 33 .

[0014] At the inner diameter portion of the joint body 30, the inner diameter of the protruding portion 31 is formed to be smaller than the inner diameter of the male thread portion 33. Moreover, the inner diameter of the protruding portion 31 is formed to be smaller than the outer diameters of the first pipe 20 and the second pipe 21, and the inner diameter of the male thread portion 33 is formed so that the first pipe 20 and the second pipe 21 can be fitted thereto. Furthermore, annular rubber ring grooves 35 are formed in the inner diameter portions of each male thread portion 33 and each end portion 34.

[0015] A ring-shaped edge 36 that protrudes radially inward is formed on the inner diameter portion of each end 34. The inner diameter of the edge 36 is smaller than the outer diameter of the first expanded pipe portion 22 of the first pipe 20 and the second expanded pipe portion 23 of the second pipe 21.

[0016] A metal loosening prevention ring 40 is attached to each joint groove 32. The loosening prevention ring 40 may be made of any metal, and preferably may be made of a metal such as stainless steel or copper that is less susceptible to rust than the metal materials such as stainless steel that make up the first pipe 20, the second pipe 21, the joint body 30, and the nut 50, which will be described in detail later. An annular rubber ring 38 is attached to each rubber ring groove 35. The rubber ring 38 is made of any rubber material, such as a ternary fluororubber.

[0017] A nut 50 is attached to the joint body 30. The nut 50 is made of any metal material, such as stainless steel, copper, or an aluminum alloy, and is used to secure the first pipe 20 and the second pipe 21 to the joint body 30. With the first pipe 20 and the second pipe 21 inserted into the joint body 30, the nut 50 is fastened to the joint body 30 by threading a female thread portion 51 formed inside the nut 50 onto a male thread portion 33 of the joint body 30, thereby securing and connecting the first pipe 20 and the second pipe 21 to the joint body 30. An annular nut groove 52 capable of accommodating the outer diameter portion of the loosening suppression ring 40 is formed in the inner diameter portion of the end of the nut 50 facing the joint body 30. The nut groove 52 is formed in a circular shape when viewed along the X direction.

[0018] FIG. 2 is a side view of the loosening prevention ring 40 shown in FIG. 1 , viewed along the X direction. In FIG. 2 , the deepest portion of the joint groove 32, i.e., the groove minimum diameter portion 32a, which is the portion with the smallest diameter, is indicated by a dashed line. FIG. 3 is a perspective view of the loosening prevention ring 40 shown in FIG. 2 . The loosening prevention ring 40 will be described below with reference to FIGS. 2 and 3 . The loosening prevention ring 40 has a ring-like shape and an open portion 41, where a portion of the circumference is interrupted. The loosening prevention ring 40 has a shape in which two ring-shaped members with circular cross sections are arranged in parallel. Furthermore, because the loosening prevention ring 40 has the open portion 41 and is made of an elastic metal material, the loosening prevention ring 40 can be bent to change its shape. The length of the open portion 41 is such that when an external force is applied to the loosening prevention ring 40 to deform it and open the open portion 41, the joint groove portion 32 of the joint main body 30 can be inserted into the open portion 41 and the loosening prevention ring 40 can be attached to the joint groove portion 32.

[0019] When no external force is applied, the shape of the loosening prevention ring 40 when viewed along the X direction shown in Figure 2 is not a circular arc, but rather has a large diameter portion 42 that is a portion with a larger radius than the groove minimum diameter portion 32a, which is a circular shape, and a small diameter portion 43 that is a portion with the same radius as the groove minimum diameter portion 32a.

[0020] Next, a method for connecting the first pipe 20 and the second pipe 21 of the pipe joint structure 1 using the joint body 30 will be described. First, loosening prevention rings 40 are placed in the two joint grooves 32 of the joint body 30 shown in FIG. 1 . As shown in FIG. 2 , the loosening prevention ring 40 is made of an elastic metal material and has an open portion 41. Therefore, the loosening prevention ring 40 can be placed in the joint groove 32 by inserting the joint groove 32 into the loosening prevention ring 40 while widening the open portion 41. Furthermore, as shown in FIG. 2 , the loosening prevention ring 40 does not have a circular arc shape when viewed along the X direction. Therefore, the loosening prevention ring 40 has a large diameter portion 42 midway between the Y direction and the Z direction. A gap 44 is formed between the large diameter portion 42 and the minimum diameter portion 32a, which is the deepest part of the joint groove 32.

[0021] Next, rubber rings 38 are placed in the two rubber ring grooves 35 of the joint body 30 shown in Figure 1. Next, the first pipe 20 is inserted into the nut 50, and the first expanded portion 22 is formed using a known pipe expanding tool. Furthermore, the second pipe 21 is inserted into the nut 50, and the second expanded portion 23 is formed using a known pipe expanding tool. The rubber rings 38 may be placed in advance before the pipe joint structure 1 is assembled.

[0022] FIG. 4 is a partial cross-sectional view of the pipe fitting structure 1 with the nuts 50 temporarily fastened to the fitting body 30. After the first expanded pipe portion 22 and the second expanded pipe portion 23 are formed, the first pipe 20 and the second pipe 21 are inserted into the fitting body 30. Next, the female thread portion 51 of the nut 50 on the first pipe 20 side is manually threaded onto the male thread portion 33 of the fitting body 30, and the female thread portion 51 of the nut 50 on the second pipe 21 side is manually threaded onto the male thread portion 33 of the fitting body 30. This attaches each nut 50 to the fitting body 30 in a temporarily fastened state. The temporarily fastened position of each nut 50 at this time constitutes the first position.

[0023] In the pre-tightened state before the nuts 50 are tightened, the loosening prevention ring 40 has a large diameter portion 42 between the Y direction and the Z direction as shown in Figure 2, and a gap 44 is formed between the loosening prevention ring 40 and the minimum diameter portion 32a of the joint groove portion 32 of the joint body 30.

[0024] Furthermore, when the nut 50 is temporarily fastened to the fitting body 30, the rubber rings 38, which are sealing materials, are not in close contact with the first expanded pipe portion 22 and the second expanded pipe portion 23, and therefore fluids such as refrigerant, high-temperature or low-temperature gas, hot or cold water, etc., flowing through the first pipe 20 or the second pipe 21 leak from the gap between the first expanded pipe portion 22 and the fitting body 30, and from the gap between the second expanded pipe portion 23 and the fitting body 30. Therefore, if a fluid is allowed to flow through the first pipe 20 or the second pipe 21 in this state, the fact that the nut 50 is temporarily fastened can be detected by the leakage of the fluid.

[0025] Each nut 50 is provisionally tightened to the joint body 30, and then fully tightened with a tool such as a pipe wrench. As a result, each nut 50 is tightened while moving toward the protruding portion 31 of the joint body 30 (in the tightening direction). At this time, the edge of the nut groove 52 of the nut 50 comes into contact with the outer diameter portion of the loosening prevention ring 40, and the loosening prevention ring 40 is pressed radially inward.

[0026] Fig. 5 is a side view of the loosening prevention ring 40 when it is pressed radially inward. When each nut 50 is tightened, the edge of the nut groove 52 presses the loosening prevention ring 40 radially inward in the direction of arrow F, reducing the diameter of the large diameter portion 42 and eliminating the gap 44, as shown in Fig. 6.

[0027] FIG. 6 is a half-side cross-sectional view of the pipe fitting structure with the nuts 50 fully tightened to the fitting body 30. As shown in FIG. 6, when the nuts 50 are further tightened and moved toward the protruding portion 31, the edges of the nut grooves 52 move over the reduced diameter of the loosening prevention ring 40, the loosening prevention ring 40 is accommodated in the nut grooves 52, and the loosening prevention ring 40 is no longer pressed radially inward. As a result, the loosening prevention ring 40 elastically returns to its original shape shown in FIG. 2. At this time, the rubber rings 38, which serve as sealing materials, are pressed and crushed by the first expansion portion 22 and the second expansion portion 23, sealing the gap between the first pipe 20 and the fitting body 30 and the gap between the second pipe 21 and the fitting body 30, preventing leakage of fluid flowing through the first pipe 20 and the second pipe 21. The fully tightened position of each nut 50 at this time constitutes the second position.

[0028] 7 is a cross-sectional view of the loosening prevention ring 40 and the nut 50 on the second pipe 21 side shown in FIG. 6 taken along line A-A' extending in the Z direction. Due to the elasticity of the loosening prevention ring 40, the large-diameter portion 42 is pressed radially outward at position B of the nut groove 52. This pressing force increases the frictional force between the loosening prevention ring 40 and the nut groove 52 at position B. Furthermore, when loosening the nut 50 after final tightening, the large-diameter portion 42 of the elastic loosening prevention ring 40 is pressed by the edge of the nut groove 52 of the nut 50 moving in a direction away from the protruding portion 31 (loosening direction) to reduce its diameter, and the edge of the nut groove 52 must overcome the loosening prevention ring 40. This increases the torque required to loosen the nut 50. Although the loosening prevention ring 40 and the nut 50 on the second pipe 21 side have been described with reference to FIG. 7, the loosening prevention ring 40 and the nut 50 on the first pipe 20 side are the same.

[0029] After the nut 50 has been fully tightened, torque may be generated in a direction that loosens the nut 50 due to factors such as excessive vibration of the first pipe 20 and the second pipe 21, pressure changes in the fluid within the pipes, thermal contraction and expansion, and the like that occur during operation of the piping equipment in which the pipe fitting structure 1 is installed. However, the torque in the direction that loosens the nut 50 that is generated due to such factors is not large enough to press the edge of the nut groove 52 against the loosening preventive ring 40 and reduce its diameter, and therefore the nut 50 cannot be loosened. In other words, the loosening preventive ring 40 of this embodiment improves the torque for loosening the nut 50, and therefore loosening of the nut 50 due to various factors that loosen the torque of the nut 50 that occur during operation of the piping equipment, as described above, is suppressed.

[0030] Furthermore, after the nut 50 has been fully tightened, when the connection between the nut 50 and the fitting body 30 needs to be released in order to disconnect the first pipe 20 and the second pipe 21, a tool is used to press the loosening prevention ring 40 with the edge of the nut groove 52 to reduce its diameter, and the nut 50 is loosened with a torque equal to or greater than that required to loosen the nut 50. As a result, as shown in FIG. 5 , the large-diameter portion 42 of the loosening prevention ring 40 is pressed radially inward by the edge of the nut groove 52, reducing its diameter, causing the nut groove 52 to clear the loosening prevention ring 40 and allowing the nut 50 to move in the loosening direction. This allows the connection between the nut 50 and the fitting body 30 to be released. Furthermore, when the nut 50 is loosened with a tool, the loosening prevention ring 40, which is made of a metal material, reduces its diameter. This prevents damage to the loosening prevention ring 40, and the same loosening prevention ring 40 can be reused when reconnecting the first pipe 20 and the second pipe 21 to the fitting body 30.

[0031] As described above, the pipe joint structure 1 according to this embodiment includes the first pipe 20 or the second pipe 21, the joint body 30 into which the end of the first pipe 20 or the second pipe 21 is inserted, the nut 50 that is threaded onto the joint body 30 and fastens the first pipe 20 or the second pipe 21 to the joint body 30, and the loosening prevention ring 40 that is provided in the joint groove 32 formed on the outer diameter part of the joint body 30 and has a partial ring shape including the open part 41. The nut 50 has the nut groove 52 in which the loosening prevention ring 40 is housed on the inner diameter part, and when the nut 50 is not fastening the first pipe 20 or the second pipe 21 to the joint body 30, the loosening prevention ring 40 is The ring 40 has at least a portion thereof having a large diameter portion 42 whose inner diameter is larger than the outer diameter of the fitting groove portion 32. When the nut 50 fastens the first pipe 20 or the second pipe 21 to the fitting body 30, when the nut 50 is in a pre-tightening position, the large diameter portion 42 of the anti-loosening ring 40 is pressed by the inner diameter portion of the nut 50. When the nut 50 is in a final tightening position, which is tightened further than the pre-tightening position, the anti-loosening ring 40 is accommodated in the nut groove portion 52, and the pressure on the large diameter portion 42 of the anti-loosening ring 40 by the inner diameter portion of the nut 50 is released. This reduces the possibility of the nut 50 loosening during use of the pipe fitting structure 1.

[0032] Furthermore, when the nut 50, which was in the fully tightened position, is loosened to release the fastening between the first pipe 20 or the second pipe 21 and the fitting body 30, the large diameter portion 42 of the anti-loosening ring 40 is pressed by the inner diameter portion of the nut 50 in the pre-tightened position, so that the fastening between the first pipe 20 or the second pipe 21 and the fitting body 30 can be released by loosening the nut 50 with a tool.

[0033] Furthermore, since the loosening prevention ring 40 is made of a metal material, the possibility of the loosening prevention ring 40 being damaged due to deterioration over time is reduced.

[0034] Furthermore, a method for assembling a pipe joint structure according to this embodiment includes a first pipe 20 or a second pipe 21, a joint body 30 into which an end of the first pipe 20 or the second pipe 21 is inserted, a nut 50 that threads onto the joint body 30 and fastens the first pipe 20 or the second pipe 21 to the joint body 30, and a loosening preventive ring 40 that is provided in a joint groove 32 formed in the outer diameter part of the joint body 30 and has a partial annular shape including an open part 41, the nut 50 having a nut groove 52 in which the loosening preventive ring 40 is housed on its inner diameter part, and when the nut 50 is not fastening the first pipe 20 or the second pipe 21 to the joint body 30, at least a part of the loosening preventive ring 40 has an inner diameter larger than the outer diameter of the joint groove 32. In the pipe fitting structure 1 having a diameter portion 42, the steps include providing a loosening prevention ring 40 in the fitting groove portion 32 and inserting the end of the first pipe 20 or the second pipe 21, on which the nut 50 is provided, into the fitting body 30; fastening the nut 50 to the fitting body 30, so that when the nut 50 is in a first position, the large diameter portion 42 of the loosening prevention ring 40 is pressed by the inner diameter portion of the nut 50; and when the nut 50 is further tightened to a second position, the loosening prevention ring 40 is accommodated in the nut groove portion 52, and the pressure on the large diameter portion by the inner diameter portion of the nut 50 is released. This reduces the possibility of the nut 50 loosening during use of the pipe fitting structure 1 having the first pipe 20 or the second pipe 21.

[0035] Although the pipe joint structure 1 according to the present embodiment has the joint body 30 that connects the first pipe 20 and the second pipe 21 in a straight line, the configuration of the joint body is not limited to this. For example, a curved joint body may be used to connect the second pipe in a direction perpendicular to the first pipe, or a joint body that connects three or more pipes may be used.

[0036] Furthermore, although the loosening prevention ring 40 is made of a metal material, it may be made of a resin material that has sufficient elasticity and strength. [Explanation of symbols]

[0037] 20 first pipe, 21 second pipe, 30 joint body (pipe joint), 32 joint groove portion, 40 loosening prevention ring (loosening prevention member), 41 open portion, 42 large diameter portion, 50 nut (fastening member), 52 nut groove portion.

Claims

1. Piping and a pipe joint into which the end of the pipe is inserted; a nut that is threaded onto the pipe joint and fastens the pipe and the pipe joint; a loosening suppression member provided in a joint groove formed in an outer diameter portion of the pipe joint and having a partial ring shape including an open portion; Equipped with The nut has an inner diameter portion having a nut groove portion in which the loosening suppression member is accommodated, When the nut is not fastening the pipe and the pipe joint, the loosening suppression member has at least a part of a large diameter portion whose inner diameter is larger than the outer diameter of the joint groove portion, A pipe fitting structure in which, when the nut is in a first position to fasten the pipe and the pipe fitting, the large diameter portion of the loosening prevention member is pressed by the inner diameter portion of the nut, and when the nut is in a second position that is tightened further than the first position, the loosening prevention member is accommodated in the nut groove portion, and the pressure of the inner diameter portion of the nut against the large diameter portion of the loosening prevention member is released.

2. 2. The pipe fitting structure according to claim 1, wherein when the nut in the second position is loosened to release the fastening between the pipe and the pipe fitting, the large diameter portion of the loosening suppression member is pressed by the inner diameter portion of the nut in the first position.

3. The pipe joint structure according to claim 1 or 2, wherein the loosening inhibiting member is made of a metal material.

4. Piping and a pipe joint into which the end of the pipe is inserted; a nut that is threaded onto the pipe joint and fastens the pipe and the pipe joint; a loosening suppression member provided in a joint groove formed in an outer diameter portion of the pipe joint and having a partial ring shape including an open portion; Equipped with The nut has an inner diameter portion having a nut groove portion in which the loosening suppression member is accommodated, In a pipe joint structure, when the nut is not fastening the pipe and the pipe joint, the loosening suppression member has at least a part of a large diameter portion whose inner diameter is larger than the outer diameter of the joint groove portion, providing the loosening suppression member in the joint groove portion, and inserting the end of the pipe provided with the nut into the pipe joint; a step of fastening the nut to the pipe joint, and when the nut is in a first position, the large diameter portion of the loosening suppression member is pressed by the inner diameter portion of the nut; and when the nut is further tightened to a second position, the loosening prevention member is accommodated in the nut groove portion, and the inner diameter portion of the nut is released from pressing the loosening prevention member against the large diameter portion.

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