JP3293331B2 - Transition fitting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transition joint for connecting a metal pipe such as a steel pipe or a cast iron pipe to a thermoplastic resin pipe such as polyethylene.

[0002]

2. Description of the Related Art Transition joints are used to transfer steel pipes, cast iron pipes or metal pipes such as plastic lining pipes in a structure such as a building provided for transferring gas, water, and the like, and to the ground outside the structure. It is a type of mechanical joint that connects a buried thermoplastic resin tube such as polyethylene.

FIG. 3 shows an example of a standard transition joint currently used. In FIG. 3, 1 is a metal pipe (such as a steel pipe or a cast iron pipe), 2 is a resin pipe (such as a polyethylene pipe), 4 is a stiffener, and 5 is an O-ring. In order to join the metal pipe 1 and the resin pipe 2 in the joint, the resin pipe 2 is usually made of a tubular stiffener 4 made of the same material as the metal pipe 1.
Is fixed to the metal tube 1 from the inner surface side. Metal tube 1 of this part
A groove is formed on the inner surface of the resin tube 2 to prevent the resin tube 2 from coming off. The O-ring 5 is usually made of rubber, and prevents gas or water from leaking from the joint between the metal pipe 1 and the resin pipe 2 in the joint. The end on the side of the metal pipe 1 is connected to a metal pipe in a structure such as a building or a plastic lining pipe thereof by welding or the like, and the end on the side of the resin pipe 2 is connected via an electric fusion joint or the like. 2 is connected to an underground pipe made of the same thermoplastic resin.

When a large ground deformation occurs due to an earthquake or the like, the metal pipe 1 fixed to the structure side of the transition joint does not change, but the portion of the resin pipe 2 exposed from the metal pipe 1 changes. At this time, flattening of the exposed portion of the resin tube 2 progresses, and buckling or cracking that causes constriction of the tube occurs. For this reason, pressure fluctuations of gas, water, etc., exceed allowable values, and leakage of gas, water, etc. occurs, which is a serious problem.

[0005] In order to solve such a problem, a publication (Technical Data of Polyethylene Pipes for Gas: Japan Gas Association, 1991) discloses that a resin pipe exposed from a metal pipe is made of polyethylene or the like. A method of covering and protecting with a sleeve, and Japanese Unexamined Utility Model Publication No. Hei 5-42880, have proposed a joint provided with a bellows-shaped telescopic flexible tube made of a flexible material such as rubber.

[0006]

However, in the method described in the above publication, stress concentration occurs in the resin tube at the end of the protective sleeve, causing buckling and cracking. In the joint proposed in Japanese Utility Model Laid-Open Publication No. 5-42880, if the bellows-shaped telescopic flexible tube is made of a thermoplastic resin such as polyethylene, a crack is generated in the bellows ridge portion where a large stress is applied when the ground changes. . Further, it is difficult to connect a bellows-shaped telescopic flexible tube made of rubber or the like to a thermoplastic resin tube made of polyethylene or the like, and the structure becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a transition joint which is free from buckling or cracking even by a large ground deformation, has a simple structure, and is easy to manufacture. And

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a transition joint in which one is a metal pipe and the other is a resin pipe, and the other part is a resin pipe other than a part (fitting part) fitted with the metal pipe. The wall thickness increases over a predetermined length from the fitting portion toward the fitting portion, and a plurality of convex ring portions are provided on the outer peripheral surface of the resin pipe of the predetermined length portion, One of the ring-shaped portions is provided at a position adjacent to the fitting portion. In the above and the claims, the term "joint" includes not only a joint configured as a part for connecting pipes, but also a pipe having an end at the end of the pipe itself. It is.

[0009]

According to the present invention, the thickness of the resin tube other than the portion (fitting portion) fitted with the metal tube increases as approaching the fitting portion, and becomes thicker on the fitting portion side where a large stress is applied. Therefore, stress concentration does not occur in one place, and the amount of bending deformation can be made uniform over the entire pipe. In addition, since it serves as a reinforcing material for restraining the cross-sectional shape of the convex ring-shaped resin tube, it is possible to prevent a decrease in rigidity due to flattening of the resin tube. Further, the convex ring portion provided at a position adjacent to the fitting portion also has an action of restraining the bending deformation of the resin tube.

[0010]

FIG. 1 shows a transition joint as an example of the product of the present invention. In FIG. 1, the same portions as FIG.
The same reference numerals are given and the description is omitted. Reference numeral 3 denotes a convex portion having a rectangular cross section provided on the outer peripheral surface of the resin tube 2 in a ring shape. The thickness of the resin tube 2 other than the fitting portion with the metal tube 1 is increased in a tapered shape over a predetermined length as the fitting portion approaches the fitting portion. The convex portion 3 closest to the metal tube 1 is provided so as to be in contact with the end of the metal tube 1 (the end of the fitting portion). As a method of increasing the thickness, the thickness may be increased in a tapered manner, or may be increased stepwise each time the convex portion 3 appears. In addition, since the inner diameter of these joints is usually required to be constant, the outer diameter of the resin tube 2 is larger than that of the steady portion in the immediate vicinity of the fitting portion. Alternatively, the wall thickness may be changed by changing the inner diameter.

When a force is applied from a direction perpendicular to the pipe axis, stress concentrates near the boundary between the metal pipe 1 and the resin pipe 2 in the conventional joint as shown in FIG. 3, causing buckling and cracking. On the other hand, in the joint of the present invention shown in FIG. 1, the thickness of the resin pipe 2 exposed from the metal pipe 1 is increased near the fitting part where a large stress is applied, and is reduced in a tapered shape from there. Stress concentration does not occur in some places, and the amount of bending deformation can be made uniform over the entire pipe. In addition, since the convex portion 3 plays a role of a reinforcing material for restraining the cross-sectional shape of the resin tube 2, it is possible to prevent a decrease in rigidity due to the flattening of the resin tube 2.
Further, the convex portion 3 provided so as to be in contact with the end of the metal tube 1 also has an action of restraining the bending deformation of the resin tube 2.

The height and width of the projections 3 and the distance between the projections 3 may all be the same, but the stress applied to the resin tube 2 decreases as the distance from the end of the metal tube 1 decreases. Rigidity is not required as close to the end,
Therefore, there is no problem even if the height and width of the projections 3 are reduced as the distance from the end of the metal tube 1 increases, and the distance between the projections 3 is increased. Also, the cross-sectional shape does not necessarily need to be rectangular, and any shape may be used as long as rigidity can be secured.

FIG. 1 shows another example of the present invention, a transition joint (the present invention), FIG. 3 shows a conventional standard transition joint (the conventional product 1), and FIG. 4 shows another example of the conventional product. In addition, three types of transition joints, a transition joint (conventional product 2), in which a part of the resin pipe became bellows, were prepared and subjected to a bending test. In FIG. 4, reference numeral 18 denotes a bellows portion provided in a part of the resin tube, and other reference numerals represent the same components as those in FIG.

Each of the transition joints comprises a steel pipe and a polyethylene pipe, and is an electrofusion joint in which the polyethylene pipe is joined to the steel pipe, the polyethylene pipe in the steel pipe, and the polyethylene pipe exposed from the steel pipe on the side opposite to the steel pipe. The structure and dimensions of the portion that fits in the joint are the same. That is, each has a nominal diameter of 100 A and a wall thickness of 9.6 mm.
The nominal diameter of the tube is 100A, the wall thickness is 4.5mm, and the outer diameter of the portion joined to the polyethylene tube is 130mm.
φ, a steel pipe having a wall thickness of 8.5 mm is joined by a stiffener made of steel pipe. The length of the polyethylene pipe at the portion exposed from the steel pipe is 300 mm, and the length from the boundary with the steel pipe to the open end of the electrofusion joint is 225.
mm.

In three types of transition joints,
The only difference is the structure of the resin pipe from the end of the steel pipe to the open end of the electrofusion joint. This part of the product of the present invention has a height of 25 mm measured from the inner surface of the tube, and has three convex portions having a rectangular cross-sectional shape in a ring shape, and the width of the convex portion is defined by the boundary with the steel pipe. 30, 20, as you move away from
It has been reduced to 10 mm. Further, the protrusion having a width of 30 mm is provided so as to be in contact with the steel pipe. The distance between the width centers of the protrusions is 70 mm, and the distance from the width center of the protrusion having a width of 10 mm to the open end of the electrofusion joint is also 70 mm. The thickness of the polyethylene pipe is 30 mm from the end of the steel pipe
Is 15m (where the 30mm wide protrusion ends)
m, it is 9.6 mm at 225 mm from the end of the steel pipe (the open end of the electrofusion joint) and is tapered to 9.6 mm.
The structure of this part of the conventional product 1 is the same as the structure of the other parts. That is, the nominal diameter is 100A and the wall thickness is 9.
6 mm. This portion of the conventional product 2 has a bellows-like structure including three peaks. The thickness of the bellows is 5.0 mm at the peak and 9.6 mm at the valley. The height of the peak is 25 mm measured from the inner surface of the pipe at the valley of the bellows, and the interval between the peaks is 70.
mm. The distance from the peak farthest from the end of the steel pipe to the open end of the electrofusion joint is 55 mm.

FIG. 2 shows a bending test apparatus used in this test. In FIG. 2, 6 is a steel pipe portion of the transition joint,
7 is a polyethylene pipe part of a transition joint, 8 is a polyethylene electrofusion joint, 9 is a polyethylene pipe, 10 is a support, 11 is a welded part, 12 is a bogie, 13 is a rail, 14
Is an actuator, 15 is a slide tube fixing jig, 16
Is a slide groove, and 17 is a guide. The steel pipe part 6 of the transition joint is welded to the support 11 on the carriage 16, and the polyethylene pipe part 7 of the transition joint is joined to the polyethylene pipe 9 via the polyethylene electric fusion joint 8. Then, the polyethylene pipe 9 is fixed to a slide type pipe fixing jig 15. The distance from the end of the steel pipe portion 6 of the transition joint to the end of the slide type pipe fixing jig 15 on the polyethylene pipe 9 side is 1000 mm. Now, when the slide-type fixing jig 15 is moved up and down along the slide groove 16 provided in the guide 17 by the actuator 14, bending deformation is given to the polyethylene pipe portion 7 of the transition joint. At this time, since the steel pipe portion 6 of the transition joint is fixed to the column 11 on the carriage 16, the steel tube portion 6 moves along the rail 13 so as to approach the guide 17. Therefore, no stress is applied in the pipe axis direction of the transition joint, and only pure bending deformation is applied to the transition joint.

The transition joint is attached to the transition joints (6 and 7) shown in FIG.
The deformation state of the polyethylene pipe portion 7 of the transition joint was observed while changing the amount of displacement of. Table 1 shows the results. In the product of the present invention, even when the displacement amount was increased to 300 mm, flattening, buckling, and cracking were not observed in the polyethylene pipe portion 7. On the other hand, in the conventional product 1, flattening occurs even when the displacement amount is as small as about 100 mm, and the displacement amount is 200 m.
When it is increased to m or more, buckling occurs. In the case of the conventional product 2, there is no problem when the displacement amount is as small as about 100 mm. However, as the displacement amount increases to 200 mm and 300 mm, buckling and cracks occur.

In this embodiment, the convex portions are provided in a ring shape, but the effect is not changed even if they are provided in a spiral shape.

[0019]

[Table 1]

[0020]

Since the present invention is constructed as described above, it is possible to provide a transition joint which does not cause buckling or cracking even by a large ground deformation, has a simple structure and is easy to manufacture.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a transition joint according to an embodiment of the present invention.

FIG. 2 is a diagram showing a transition joint bending test apparatus.

FIG. 3 is a diagram illustrating an example of a conventional standard transition joint.

FIG. 4 is a diagram illustrating a transition joint as another example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal tube 2 Resin tube 3 Convex part

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16L 1/02 F16L 21/00-21/02 F16L 27/10 F16L 47/06

Claims (1)

(57) [Claims] 1. A transition joint comprising a metal pipe on one side and a resin pipe on the other side, wherein a thickness of the resin pipe other than a part (fitting part) fitted with the metal pipe is increased from the fitting part. A plurality of convex loops are provided on the outer peripheral surface of the resin tube of the predetermined length portion, the convex loops increasing with approaching the fitting portion over a predetermined length, and one of the convex loops is fitted. A transition joint, which is provided at a position adjacent to a joint.