Pipe Fittings

Abstract

To provide a piping joint that is configured to constrain a telescopic part by a constraint member in normal time, and automatically releases the constraint by the constraint member in the event of a disaster such as an earthquake.SOLUTION: A restraint member 6 composed of a round bar member 6a is fixed to flanges 3, 3 on both sides of a telescopic part 2 in a region surrounding the outer peripheral part of the telescopic part 2. This fixed portion is formed by tightening nuts 6c, 6c to male screws 6b formed at each end part of the round bar member 6a with the flanges 3 sandwiched therebetween. A notch part 6d is formed in the middle part of the round bar member 6a, and the notch part 6d is broken by the action of predetermined external force for expanding and contracting the telescopic part 2, so that the restraint of the telescopic part 2 by the round bar member 6a is released.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a piping joint such as an expansion joint, an expansion flexible pipe, and a flexible tube. [Background technology]

[0002] As disclosed in Patent Document 1, for example, a pipe joint has a bellows-type expansion section, and connecting pipes are connected to both sides of the expansion section.

[0003] In such a pipe joint, the expansion and contraction portion expands and contracts due to pipe displacement, vibration, etc. in normal times. In general, the expansion and contraction of such an expansion portion is designed to have a strength that can withstand such pipe displacement, vibration, etc. in normal times. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 50-127047 Summary of the Invention [Problem to be solved by the invention]

[0005] However, since it is not known when a disaster such as an earthquake will occur, and since fatigue damage to the expansion and contraction of the expansion part during peacetime accumulates, there is a risk that the expansion part will not function adequately in the event of a disaster such as an earthquake.

[0006] The present invention has been made in consideration of these points, and aims to provide a pipe fitting in which the expansion section is restrained by a restraining member during peacetime, and this restraint by the restraining member is automatically released in the event of a disaster such as an earthquake. [Means for solving the problem]

[0007] In order to achieve this object, the present invention is configured as shown in (1) to (5).

[0008] (1) A pipe fitting characterized in that a restraining member is fixed to both sides of an expansion section in an area surrounding the outer periphery of the expansion section, and an intermediate portion of the restraining member or a fixed portion of the restraining member to both sides of the expansion section breaks or comes off when a predetermined external force is applied to the expansion section in a direction extending or contracting it.

[0009] (2) A pipe fitting characterized in that one end portion of a restraining member is slidably supported and the other end portion of the restraining member is fixed to a region surrounding the outer periphery of the expansion / contraction section at both sides of the expansion / contraction section, and a stopper is fixed to the end portion of the restraining member that is slidably supported, which will break or detach when a predetermined external force is applied to the expansion / contraction section in a direction extending it.

[0010] (3) A pipe fitting characterized in that both end portions of a restraining member are supported so as to be freely slidable on both sides of the stretchable portion in an area surrounding the outer periphery of the stretchable portion, and stoppers are fixed to both ends of the restraining member which are broken or detached when a predetermined external force is applied to the stretchable portion in a direction extending it.

[0011] (4) A pipe fitting comprising: an area surrounding the outer periphery of an expansion / contraction section, one end portion of a restraining member being slidably supported at both sides of the expansion / contraction section, and the other end portion of the restraining member being fixed; a stopper that is broken or detached when a predetermined external force is applied to the expansion / contraction section in a direction extending the expansion / contraction section is fixed to the end portion of the restraining member that is slidably supported, and a stopper that is broken or detached when a predetermined external force is applied to the expansion / contraction section in a direction contracting the expansion / contraction section is fixed to the middle portion of the restraining member.

[0012] (5) A pipe fitting characterized in that both end portions of a restraining member are supported so as to be freely slidable on both sides of the stretchable portion in an area surrounding the outer periphery of the stretchable portion, and stoppers are fixed to both ends of the restraining member which will break or come off when a predetermined external force is applied to the stretchable portion in a direction extending it, and two stoppers are fixed at a predetermined distance from each other to an intermediate portion of the restraining member which will break or come off when a predetermined external force is applied to the stretchable portion in a direction contracting it.

[0013] In preferred embodiments of the pipe joint of the present invention described in (1) to (5), the restraining member is made of a rigid member, and in preferred embodiments of the pipe joint of the present invention described in (1), the restraining member is made of a flexible member. Effect of the Invention

[0014] In the pipe joint of the present invention, the restraining member restrains the expansion section during normal times, and in the event of a disaster such as an earthquake in which a predetermined external force occurs, the restraint by the restraining member on the expansion section is automatically released. In other words, when a predetermined external force acts on the expansion section to extend it or when a predetermined external force acts on the expansion section to contract it, the fixed parts of the restraining member at both end positions or one end position of the expansion section, the notched parts of the restraining member, or the stoppers fixed to the restraining member are broken or separated, and the restraint of the expansion section by the restraining member is automatically released. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a side view showing an example of a pipe joint according to the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Diagram 3] FIG. 3 is a side view showing a state in which a predetermined external force is applied to the pipe joint. [Figure 4] FIG. 4 is a side view showing a modified example of a pipe joint according to the present invention. [Diagram 5] FIG. 5 is a side view showing another modified example of the pipe joint according to the present invention. [Figure 6]FIG. 6 is a side view showing still another modified example of the pipe joint according to the present invention. [Figure 7] FIG. 7 is a side view showing still another modified example of the pipe joint according to the present invention. [Figure 8] FIG. 8 is a side view showing still another modified example of the pipe joint according to the present invention. [Figure 9] FIG. 9 is a side view showing still another modified example of the pipe joint according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0017] FIG. 1 is a side view showing an example of a pipe joint according to the present invention, FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, and FIG. 3 is a side view showing the same pipe joint when a predetermined external force is applied thereto.

[0018] As shown in Fig. 1, the pipe joint 1 has a pair of flanges 3, 3 attached to both sides of an expansion section 2. The expansion section 2 is of a bellows type and can expand and contract in the axial direction. A connecting pipe 4 is connected to each end of the pipe joint 1 by means of bolts and nuts, welding, or other means. In this example, as shown in Figs. 1 to 3, the flange 3 of the pipe joint 1 is fastened to a flange 7 formed at the end of the connecting pipe 4 by a plurality of bolts and nuts 5, thereby connecting each end of the pipe joint 1 to the connecting pipe 4.

[0019] The pipe joint 1 is provided with restraining members 6 attached to both sides of the expansion section 2 in an area surrounding the outer periphery of the expansion section 2, which will break when a predetermined external force acts in a direction that expands or contracts the expansion section 2. The predetermined external force here refers to an external force that acts during a disaster such as an earthquake, and is determined by the number of restraining members 6 and the strength of the notched portions 6d of the round bar bodies 6a, which will be described later. In the following explanation, the predetermined external force in the direction that expands the expansion section 2 will be referred to as the "predetermined tensile force F1m," and the predetermined external force in the direction that contracts the expansion section 2 will be referred to as the "predetermined pressing force F2m."

[0020] As shown in FIG. 1, the restraining member 6 is made of a rigid or flexible member fixed to both sides of the telescopic section 2. In this example, it is made of a round bar 6a, which is a rigid member, and both ends of the round bar 6a are fixed to both sides of the telescopic section 2 with bolts and nuts. That is, male threads 6b, 6b are formed at both ends of the round bar 6a, and each male thread 6b is inserted into the flange 3 of the pipe joint 1, and nuts 6c, 6c arranged on both sides of the flange 3 are screwed and tightened onto the male threads 6b to restrain the telescopic section 2 in the most contracted state or in another state (in FIG. 1, the telescopic section 2 is restrained in the most contracted state). The round bar 6a is equally spaced at three locations on the flange 3.

[0021] The round bar 6a has a notch 6d formed in its middle, which is narrowed, and is broken when a predetermined tensile force F1m is applied to it, or when a predetermined pressing force F2m (not shown) is applied to it in the opposite direction to the predetermined tensile force F1m. That is, when a normal external force due to pipe displacement, vibration, etc. is applied to the telescopic section 2 of the pipe joint 1 (an external force that displaces the telescopic section 2 in the extension direction is called "normal tensile force F1" and an external force that displaces the telescopic section 2 in the contraction direction is called "normal pressing force F2"), the axial length of the round bar 6a does not change, and the telescopic section 2 restrained by the round bar 6a does not change, but when a predetermined tensile force F1m or a predetermined pressing force F2m due to an earthquake or the like is applied to the telescopic section 2, the round bar 6a breaks (breaks) from the notch 6d, and the telescopic section 2 is automatically released from the restraint of the round bar 6a.

[0022] Therefore, according to the restraining member 6 configured as above, when the pipe fitting 1 is connected to the connecting pipes 4, 4 and buried underground, the expansion section 2 is held in the restrained state as shown in Fig. 1 when a normal tensile force F1 or a normal compressive force F2 acts on the pipe fitting 1, regardless of the magnitude and direction of the force. However, when a predetermined tensile force F1m acts on the pipe fitting 1 in the expansion direction of the expansion section 2 due to an earthquake or the like, the notch 6d of the round bar body 6a breaks as shown in Fig. 3 (or, although not shown, the notch 6d of the round bar body 6a breaks when a predetermined compressive force F2m acts on the contraction direction of the expansion section 2). When the round bar body 6a breaks in this way, the restraint by the round bar body 6a of the expansion section 2 is released, and the expansion section 2 changes in the expansion direction (or contraction direction). When this happens, if the damage to the pipe fitting 1 is significant, the part is replaced or repaired, but if the damage to the pipe fitting 1 is minor and it can still be used, it is either left as is or emergency repairs are made to the damaged part and then it is left as is or repaired and reinstalled.If the telescopic part 2 is restrained by the restraining member 6, which is a rigid body that cannot be stretched, then regardless of the restrained state (natural state, etc.), telescopic displacement will not occur unless a specified tensile force F1mm or a specified compressive force F2m is applied, so the telescopic part 2 will not suffer fatigue damage.

[0023] FIG. 4 is a side view showing a modified example of a pipe joint according to the present invention.

[0024] The pipe joint 1 shown in FIG. 4, for example, restrains the expandable section 2 in a natural state (a state in which no load is applied) by a restraining member 6, and the restraining member 6 uses a wire 6e that is a flexible member.

[0025] As shown in Fig. 4, the wire 6e is stretched in a tensile state between the flanges 3, 3 of the pipe joint 1, and is welded 6g, 6g to the bolts 6f, 6f screwed into the flanges 3, 3. One or both of the welded parts 6g, 6g that fasten both ends of the wire 6e are separated by a predetermined tensile force F1m. There are three wires 6e, and they are equally spaced at three locations on the flanges 3, 3.

[0026] Since the restraining member 6 is the wire 6e, which is a flexible member, when a normal pressing force F2 in the contraction direction acts on the telescopic portion 2 of the pipe joint 1, the telescopic portion 2 contracts, the wire 6 sags, and the telescopic portion 2 deforms in the contraction direction. Also, when a normal tensile force F1 in the extension direction acts on the telescopic portion 2 of the pipe joint 1, if the telescopic portion 2 contracts, the telescopic portion 2 expands within the range in which the wire 6 is tensed, or if the wire 6 is tensed, the telescopic portion 2 does not expand or contract due to the normal tensile force F1.

[0027] However, when a predetermined tensile force F1m acts on the telescopic part 2 in the extension direction, one or both of the welded parts 6g, 6g that fix both ends of the wire 6e are separated, and the telescopic part 2 changes in the extension direction. When this state occurs, if the damage to the pipe joint 1 is large, the parts are replaced or repaired, and if the damage to the pipe joint 1 is small and it can be used continuously, it is left as it is, or the damaged parts are repaired and then reinstalled after being left as it is or repaired. Note that when the restraining member 6 is composed of the wire 6e, the telescopic part 2 can be restrained in a state other than the natural state, but if the telescopic part 2 of the pipe joint 1 is restrained in the natural state as shown in Figure 4, the wire 6e does not sag when restrained, and tensioning such as welding can be easily performed.

[0028] FIG. 5 is a side view showing another modified example of a pipe joint according to the present invention.

[0029] The pipe joint 1 shown in FIG. 5, for example, restrains the expandable section 2 in a natural state by a restraining member 6, and the restraining member 6 is made of a belt-shaped member 6h that is a flexible member.

[0030] As shown in Fig. 5, the belt-shaped member 6h is stretched between the flanges 3, 3 of the pipe joint 1, and both ends of the belt-shaped member 6h are fixed under tension by bolts 6i, 6i screwed into the flanges 3, 3. One or both of the bolts 6i, 6i fixing both ends of the belt-shaped member 6h are broken or separated by a predetermined tensile force F1m. The belt-shaped members 6h are equally spaced at three locations on the flanges 3, 3.

[0031] The restraining member 6 is composed of a belt-shaped member 6h, which is a flexible member similar to the wire 6e. When a normal pressing force F2 in the contracting direction acts on the telescopic portion 2 of the pipe joint 1, the belt-shaped member 6h sags, and the telescopic portion 2 is displaced in the contracting direction. However, when a predetermined tensile force F1m acts, one or both of the bolts 6i, 6i that secure both ends of the belt-shaped member 6h are damaged or separated, and the telescopic portion 2 changes in the extension direction. When this happens, if the damage to the pipe joint 1 is significant, the part is replaced or repaired, but if the damage to the pipe joint 1 is minor and it can continue to be used, it is left as it is or the damaged part is repaired temporarily and then left or repaired and reinstalled. When the restraining member 6 is constructed of a belt-shaped member 6h, the restraint of the expansion section 2 can be performed in a state other than the natural state. However, if the expansion section 2 of the pipe fitting 1 is restrained in the natural state as shown in FIG. 5, no slack will be generated in the belt-shaped member 6h even when a normal tensile force F1 or a normal pressing force F2 is applied, and the tensioning can be easily performed.

[0032] FIG. 6 is a side view showing another modified example of a pipe joint according to the present invention.

[0033] 6, for example, the pipe joint 1 restrains the expansion section 2 in a natural state by the restraining member 6, and the restraining member 6 is composed of a round rod body 6j, which is a rigid member. The round rod body 6j is equally spaced at three positions on the flanges 3, 3.

[0034] That is, as shown in Fig. 6, the male thread 6k formed at one end of the round bar 6j is fixed to one flange 3 of the pipe joint 1 with nuts 6m, 6m, in the same manner as the round bar 6a, and the other end is slidably supported in a hole 6n formed in the other flange 3 of the pipe joint 1. A ring-shaped stopper 6o is fixed to the end of the sliding side of the round bar 6j with a rivet 6p. When a predetermined tensile force F1m is applied, the rivet 6p collides with the other flange 3, breaks, and comes off the round bar 6j. The rivet 6p may be a bolt, a welded joint, or the like.

[0035] Therefore, when a normal tensile force F1 acts on the telescopic portion 2 of the pipe joint 1, the telescopic portion 2 extends to the extent that the stopper 6o collides with the other flange 3, depending on the magnitude of the force, and when a normal pressing force F2 acts on the telescopic portion 2 of the pipe joint 1, the telescopic portion 2 is contracted to the extent that the stopper 6o collides with the other flange 3, depending on the magnitude of the force, and is contracted to the extent that the most contracted state is reached. However, when a predetermined tensile force F1m2 acts, the stopper 6o collides with the other flange 3, the rivet 6p is broken, the stopper 6o is separated, and the constraint of the telescopic portion 2 by the constraint member 6, i.e., the round rod body 6j, is released. In this state, if the damage to the pipe joint 1 is large, the part is replaced or repaired, and if the damage to the pipe joint 1 is small and it can be used continuously, it is left as it is, or the damaged part is repaired temporarily, and then it is left as it is or reinstalled after repair.

[0036] FIG. 7 is a side view showing another modified example of a pipe joint according to the present invention.

[0037] The pipe joint 1 shown in FIG. 7, for example, restrains the expansion section 2 in a natural state (a state in which no load is applied) by a restraining member 6, and the restraining member 6 is composed of a round rod body 6q, which is a rigid member.

[0038] That is, as shown in FIG. 7, both end portions of the round rod body 6q are slidably held in holes 6r, 6r provided in the flanges 3, 3 of the pipe fitting 1, and ring-shaped stoppers 6s, 6s are attached to both end portions protruding outside the flanges 3, 3. In this state, when a normal tensile force F1 or a normal pressing force F2 is applied to the stretchable portion 2, the stretchable portion 2 stretches or contracts in accordance with the magnitude of the force.

[0039] Each stopper 6s is fixed to the round bar body 6q by a rivet 6t, and when a predetermined tensile force F1m acts on the pipe joint 1, both stoppers 6r, 6r collide with the flanges 3, 3, and at least one of the rivets 6t, 6t is broken. That is, the stopper 6s is released from the round bar body 6q due to the breakage of the rivet 6t, and the restraint of the expansion part 2 by the restraint body 6 is released. In this state, if the damage to the pipe joint 1 is large, the part is replaced or repaired, and if the damage to the pipe joint 1 is small and it can be used continuously, it is left as it is or the damaged part is repaired and then reinstalled. The rivet 6t may be a bolt, a welded part, etc.

[0040] FIG. 8 is a side view showing still another modified example of a pipe joint according to the present invention.

[0041] The pipe joint 1 shown in Fig. 8, for example, restrains the expansion / contraction section 2 in a natural state (a state in which no load is applied) by a restraining member 6, and has a stopper 6u fixed to the middle part of the restraining member 6 shown in Fig. 6 by a rivet 6v. The rivet 6v breaks or comes off when a predetermined pressing force F2m is applied in a direction that contracts the expansion / contraction section 2. The rivet 6v may be a bolt, a welded member, or the like.

[0042] The restraining member 6 shown in FIG. 8 is a round bar body 6i with a stopper 6u in addition to the stopper 6o. When a predetermined pressing force F2m is applied to the telescopic portion 2, the stopper 6u collides with the flange 3 of the pipe joint 1, the rivet 6v is broken, and the restraint of the telescopic portion 2 in the contraction direction is released. When a predetermined tensile force F1m is applied to the telescopic portion 2, the stopper 6o provided at the end of the round bar body 6i is released by the flange 3, as shown in FIG. 6, and the restraint of the telescopic portion 2 in the extension direction is released. That is, when either the predetermined tensile force F1m or the predetermined pressing force F2m is applied, the restraint of the telescopic portion 2 is released. When this state occurs, if the damage to the pipe joint 1 is large, the part is replaced or repaired. When the damage to the pipe joint 1 is small and it can be used continuously, it is left as it is or the damaged part is repaired temporarily, and then it is left or repaired and reinstalled.

[0043] FIG. 9 is a side view showing still another modified example of a pipe joint according to the present invention.

[0044] The pipe joint 1 shown in Fig. 9, for example, restrains the expansion / contraction section 2 in a natural state (a state in which no load is applied) by a restraining member 6, and has stoppers 6w, 6x fixed at a predetermined distance from each other by rivets 6y, 6z at the middle part of the restraining member 6 shown in Fig. 7. The rivets 6y, 6z break when a predetermined pressing force F2m is applied in a direction to reduce the expansion / contraction section 2. The rivets 6y, 6z may be bolts, welding, etc.

[0045] In the restraining member 6 shown in FIG. 9, when a predetermined pressing force F2m is applied to the telescopic portion 2, the stoppers 6w, 6x collide with the flanges 3, 3 of the pipe joint 1, the rivets 6y, 6z are broken, and the restraint in the contraction direction of the telescopic portion 2 is released. Also, when a predetermined tensile force F1m is applied to the telescopic portion 2, the stoppers 6t, 6t provided at both ends of the round bar body 6q are released by collision with the flanges 3, 3, as shown in FIG. 7, and the restraint in the extension direction of the telescopic portion 2 is released. That is, when either the predetermined tensile force F1m or the predetermined pressing force F2m is applied, the restraint of the telescopic portion 2 is released. When this state occurs, if the damage to the pipe joint 1 is large, the parts are replaced or repaired, and when the damage to the pipe joint 1 is small and it can be used continuously, it is left as it is or the damaged parts are treated temporarily, and then it is left or repaired and reinstalled.

[0046] The present invention is not limited to the above-described embodiments, and can be appropriately improved or modified without departing from the basic principles of the present invention.

[0047] For example, as shown in FIG. 1 or FIGS. 6 to 8, when the restraint member 6 is composed of a rigid member, the rigid member is not limited to the above-mentioned round rods 6a, 6j, 6q, but may be a square rod, a round pipe, a square pipe, a plate-like body, or the like.

[0048] In addition, both ends of the rigid members such as the round rods 6a, 6j, 6q may be fixed to both ends of the expandable portion 2 other than the flanges 3, 3 or the flanges 3 (separately provided flanges, etc.), and the fixing parts may be the male screw 6b, nut 6c or male screw 6k, nut 6m, as well as bolts, rivets, welding, etc. In addition, the stoppers 6o, 6s, 6u, 6w, 6x do not have to be ring-shaped, and the fixing parts may be bolts, rivets, welding, etc. that are broken or separated by a predetermined tensile force F1m or a predetermined pressing force F2m, instead of the rivets 6p, 6t, 6y, 6z.

[0049] The notch 6d formed in the rigid member such as the round bar 6a is not limited to one, and may be provided in multiple places. Instead of the notch 6d, the rigid member may be made of a brittle material that is weak in terms of tensile strength and breaks when a predetermined tensile force F1m is applied.

[0050] Furthermore, when a part of a rigid member such as the round bar 6a is not made of the notch 6d or a similar brittle material, both ends of the rigid member may be fixed to both ends of the expandable portion 2 other than the flanges 3, 3 or the flanges 3 (separately provided flanges, etc.), and the fixed parts may be separated by a predetermined tensile force F1m. For example, when the fixed parts are bolts, rivets, welding, etc., in addition to the male screws 6b and nuts 6c described above, the fixed parts may be separated by a predetermined tensile force F1m.

[0051] Furthermore, when the restraining member 6 is constructed of a rigid member such as a round rod body 6a, the expansion portion 2 of the pipe joint 1 is restrained in the most contracted state as shown in FIG. 1, but the expansion portion 2 may be restrained in its natural state or in another state.

[0052] 4 or 5, when the restraining member 6 is made of a flexible member such as a wire 6e or a belt-shaped member 6h, it may be made of a flexible member other than the wire 6e or the belt-shaped member 6h. The flexible member may be configured to break the welded portion 6g or the bolt 6i, or may be configured to have a notch formed in a part of it so that the notch breaks when a predetermined tensile force F1m is applied to the flexible member.

[0053] Furthermore, when the restraining member 6 is made up of rigid members such as the round rods 6a, 6j, 6q, or flexible members such as the wire 6e and the band 6h, these need not be arranged in three equal parts, but may be arranged arbitrarily.

[0054] The restraint member 6 is fixed to or supported by the flange 3 of the pipe joint 1, but it may be fixed to or supported by a member other than the flange 3, and may be a separate member attached to the member of the pipe joint 1 or may be formed integrally therewith. [Explanation of symbols]

[0055] 1. Pipe fittings 2 Telescopic part 3 Flanges (on both sides of the extension section) 6 Restraint member 6a Round bar material 6b Male thread 6c Nut 6e Wire 6f Bolt 6g welded part 6h Belt-shaped member 6i Bolt 6j round bar 6k male thread 6m nut 6n hole 6o Stopper 6p rivet 6q Round bar material 6r hole 6s stopper 6t rivet 6u stopper 6v Rivet 6w stopper 6x stopper 6y Rivet 6z Rivet

Claims

1. A pipe fitting characterized in that both end side portions of a restraining member are slidably supported in holes provided in one and the other flanges of the pipe fitting at both sides of the stretchable portion in a region surrounding the outer periphery of the stretchable portion, and stoppers are fixed to both ends of the restraining member protruding outside the one and the other flanges, which are broken or detached when a predetermined external force is applied to the stretchable portion in a direction extending it.

2. A pipe fitting characterized in that both end side portions of a restraining member are supported so as to be freely slidable in holes provided in one and the other flanges of the pipe fitting at both sides of the stretchable portion in an area surrounding the outer periphery of the stretchable portion, and stoppers that are broken or detached when a predetermined external force is applied to the stretchable portion in a direction extending it are fixed to both end portions of the restraining member that protrude outside the one and the other flanges, and two stoppers that are broken or detached when a predetermined external force is applied to the stretchable portion in a direction contracting it are fixed at a predetermined interval to an intermediate portion of the restraining member.

3. 3. The pipe joint according to claim 1, wherein the restraining member is made of a rigid member.

4. 3. The pipe joint according to claim 1, wherein the restraining member is made of a flexible material.

5. A pipe fitting characterized in that a restraining member has both ends fixed to both sides of the stretchable portion in an area surrounding the outer periphery of the stretchable portion, and an intermediate portion of the restraining member or the fixed portions of the restraining member to both sides of the stretchable portion breaks or detaches when a predetermined external force is applied to the stretchable portion in a direction extending it, and the restraining member is a flexible wire or band-shaped member.

6. A pipe fitting as described in claim 5, wherein the restraining member is a wire or band-shaped member that restrains the expansion portion in a natural state.

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