JP3153997B2 - Conversion joint between resin tube and metal tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a conversion joint between a resin tube and a metal tube used when connecting a resin tube to a metal tube or connecting a metal tube to a resin tube. About.

[Prior art] Conventionally, a pipe joint of a type in which resin pipes are continuously connected by a resin layer of the joint by heat-sealing the joint to the resin pipe, or a joint is screwed into a metal pipe such as a cast iron pipe or a steel pipe. There has been known a pipe joint of a type in which metal pipes are mechanically connected to each other by retaining them by a predetermined means.

On the other hand, recently, there is a demand to replace a part of a gas pipe using a metal pipe with a resin pipe.

[Problems to be Solved by the Invention] However, the conventional pipe joints do not have a function of interconnecting the resin pipe and the metal pipe, and thus have a problem that the above-mentioned demands cannot be sufficiently addressed.

The present invention has been made in view of this problem, and an object of the present invention is to provide a conversion joint between a resin pipe and a metal pipe having a function of connecting the resin pipe and the metal pipe while ensuring high airtight reliability. I do.

[Means for Solving the Problems] A conversion joint between a resin pipe and a metal pipe according to the first aspect of the present invention includes a female screw to which a male screw formed on the metal pipe is screwed and connected, and the outer surface of which has a plurality of threads. The metal pipe connection base formed in an uneven shape by the peaks and the valleys, and the cylindrical resin layer protruded to one side of the base and fitted with the synthetic resin pipe is melted into the resin layer by heat generation. A synthetic resin tube and a resin tube connection sleeve provided with a heating element for thermally fusing the resin layer to the resin layer, so that the sleeve and the ridge formed on the outer surface of the base are engaged with each other and engaged. A coating portion fitted to the outside of the base is provided, and an inner periphery of a tubular resin layer extending from the coating portion to the other side of the base and a metal tube connected to the base are provided therebetween. Synthetic resin configured so that the interposed seal ring is pinched And a seal ring which is fitted into the valley of the base and is pressed into contact with both the valley and the covering of the synthetic resin sleeve. is there.

The conversion joint between the resin pipe and the metal pipe according to the second aspect of the present invention includes a resin pipe connection sleeve having the same configuration as described above,
A tapered inclined surface that presses the seal packing between the metal pipe inside the one end of the metal pipe into which the metal pipe is inserted is provided on the inner circumference of one end of the metal pipe. On the outer periphery of one end of the body, a male screw into which a pressing ring for pressing the seal packing toward the inclined surface is provided, and the outer surface of the other end of the cylindrical body is formed by a plurality of peaks and valleys. The metal pipe connection base formed in an uneven shape and the resin pipe connection sleeve are extended to one side, and the outside of the cylindrical body is engaged with the ridges and valleys formed on the outer surface of the cylindrical body so as to be joined. And a sealing portion which is integrally fitted with a covering portion to be fitted to the base portion, and which is fitted into the valley portion of the base and pressed against both the valley portion and the covering portion. .

A conversion joint between a resin pipe and a metal pipe according to the third aspect of the present invention includes a resin pipe connection sleeve having the same configuration as described above,
A tapered inclined surface which presses the seal packing between the metal tube internally fitted to the metal tube and the metal tube internally fitted to the metal tube is provided on the inner periphery of one end of the metal cylinder to which the metal tube is internally fitted. On the inner periphery of one end of the cylindrical body outside the surface, a male screw into which a pressing ring for pressing the seal packing toward the inclined surface side is provided, and the outer surface of the other end of the cylindrical body has a plurality of threads. The metal pipe connection base formed in an uneven shape by the peaks and the valleys, the resin pipe connection sleeve extends to one side, and is meshed and connected to the peaks and the valleys formed on the outer surface of the cylindrical body. And a covering portion fitted to the outside of the cylindrical body so as to be integrally fitted thereto, and fitted into the valley portion of the base, and pressed against both the valley portion and the covering portion. Is provided.

[Operation] In a conversion joint between a resin pipe and a metal pipe according to the first aspect of the invention (hereinafter, referred to as a conversion joint), after inserting a synthetic resin pipe into a sleeve for connecting a resin pipe, a heating element of the sleeve is inserted. When the synthetic resin tube and the resin layer are thermally fused by melting the molten layer of the cylindrical resin layer by causing heat to be generated, the conversion joint is connected to the resin tube and the connection portion is sealed at the same time. You. When the male screw formed on the metal tube is screwed into the female screw of the metal tube connection base, the conversion joint is connected to the metal tube. Then, the seal ring is sandwiched between the inner periphery of the cylindrical resin layer of the synthetic resin sleeve and the metal tube connected to the base, thereby sealing the connection between the metal tube and the conversion joint.

In the conversion joint according to the second aspect of the invention, the connection action with the resin pipe and the sealing action at the connection point are the same as those described above. Inserting a metal pipe into the metal pipe connection base, interposing a seal packing between the metal pipe and the inclined surface of the base, pressing the seal ring into the male screw of the base and pressing the seal packing, the metal pipe is converted At the same time as being connected to the joint, the connection point is sealed by a seal packing.

In the conversion joint according to the third aspect of the invention, the connection operation with the resin pipe and the sealing operation at the connection portion are the same as those described above. Inserting a metal pipe into the metal pipe connection base, interposing a seal packing between the metal pipe and the inclined surface of the base, pressing the seal ring into the male screw of the base and pressing the seal packing, the metal pipe is converted At the same time as being connected to the joint, the connection point is sealed by a seal packing.

In each of the conversion joints according to the first to third aspects of the present invention, the outer surface of the base is formed in an uneven shape, and the seal is interposed between the valley and the covering portion fitted to the outside of the base. Since the ring is pressed into contact with both the base and the cover, no gap is generated between the two even by heat generation or the like, and high airtight reliability is secured.

Embodiment FIG. 1 is a sectional view of a conversion joint A according to the first embodiment.

The conversion joint A includes a cylindrical metal pipe connecting base 1 having a female screw 11 on the inner periphery of a cast iron or steel cylindrical body, and a cylindrical resin layer 21 protruding to one side of the base 1. A resin tube connection sleeve (hereinafter, referred to as a connection sleeve) 2 having a heating element 22 provided along its inner surface, and a cylindrical resin 31 protruding to the other side of the base 1 radially inwardly. A synthetic resin sleeve (hereinafter referred to as a resin sleeve) 3 provided with a plurality of concentric bulging steps 32.

The base 1 is formed with a plurality of peaks 12 and valleys 13 in an uneven shape on the outer periphery, and the peaks 12 and valleys 13 are engaged with the synthetic resin coating 4 formed outside the base 1 to be strong. Is bound to The connection sleeve 2 extends from the covering portion 4 to one side of the base 1 and has a small-diameter portion 23 at a root portion thereof.
5 are formed. The outer surface of the cover 4 is polygonal, such as hexagonal or octagonal, so that engagement with a tightening tool such as a spanner is ensured. The heating element 22 provided on the connection sleeve 2 includes, in addition to a heating wire that is spirally wound around the resin layer 21 of the connection sleeve 2 and generates heat when energized, a conductive powder or a conductive short fiber of the connection sleeve 2. A heat-generating layer mixed in the resin layer 21 can be suitably used. In those cases, the electrode portion is exposed from the resin layer 21. The resin sleeve 3 extends from the coating portion 4 to the other side of the base 1. A plurality of the steps 32
The outer side in the axial direction has a larger diameter, and the protruding corner 32a of each step 32 is a right angle or a substantially right angle. As shown in FIG. 4, a seal ring 5 such as an O-ring is fitted into the valley 13 of the base 1 and the seal ring 5 is pressed into contact with both the base 1 and the cover 4 to cover the base 1 with the cover 1. A high airtightness is secured between the portion 4.

Such a conversion joint A is a thermoplastic resin compatible with the resin tube 100 described later, such as a synthetic resin having compatibility with the polyethylene resin when the polyethylene tube is used as the resin tube 100, such as a polyethylene resin or a polybutene resin. Such a synthetic resin as a molding material for the covering portion 4, the connection sleeve 2, and the resin sleeve 3, and the base 1 is set at a predetermined position of a mold (not shown) and insert-molded, thereby easily manufacturing. However, the manufacturing method is not limited to this.
Alternatively, the resin layer composed of the connection sleeve 2 and the resin sleeve 3 may be injection-molded with a thermoplastic resin first, and then the die 1 and the die 1 may be press-fitted to each other to fit the die 1 to the covering portion 4. In addition, since the outer surface of the base 1 is uneven at the contact portion between the base 1 and the covering portion 4, a very large contact area is ensured, and it can be said that the structure is such that the two are not separated. Alternatively, in order to further increase the bonding strength at that location, the two may be bonded to each other with an adhesive such as a modified polyethylene adhesive interposed at the contact portion. It is preferable to use the base 1 having a rough skin surface by casting in order to further increase the contact area and improve the bonding strength with the covering portion 4. As shown in FIGS. 5A and 5B, a plurality of recesses are provided on the outer surface of the base 1 in the axial direction and the circumferential direction so that a circumferentially extending mountain portion 12 and an axially extending mountain portion 12a are provided. Is formed, the cover 1 is engaged with the ridges 12 and 12a in the axial direction and the circumferential direction, so that the base 1 and the cover 4 are reliably prevented from rotating.

When such a conversion joint A is used for a gas pipe, a high airtightness is required at a contact portion between the base 1 and the covering portion 4.
Therefore, in this embodiment, the outer surface of the base 1 is made uneven so as to have a very large contact area with the covering portion 4, particularly a long creepage length in the axial direction, and a gap crossing the contact portion in the axial direction. And the valley 13 and the covering 4
And a seal ring 5 is interposed therebetween. for that reason,
As compared with the case where the outer surface of the base 1 is a straight flat surface, the airtight reliability of the contact portion is extremely high.

FIG. 6 shows a state in which the resin pipe 100 and the metal pipe 200 are connected using the conversion joint A of FIG.

The end of the resin tube 100 inserted into the connection sleeve 2
By causing the heating element 22 to generate heat, the inner layer portion of the resin layer of the connection sleeve 2 is melted, and the outer layer portion of the resin layer of the resin tube 100 is heated by the heating element 22 or the connection sleeve 2.
And melting by the heat accompanying the melting of the resin layer. Since the interface between the overlapping portions of the connection sleeve 2 and the resin tube 100 thus heat-sealed disappears completely or almost completely due to the heat-sealing, the airtight reliability is extremely high at the connection portion. Suitable for gas piping.

The outer surface of the metal tube 200 except for the male screw 201 formed at the end is covered with an outer cover 210 made of a synthetic resin. Then, the end of the metal tube 200 in which the seal ring 6 such as an O-ring is previously inserted is inserted into the resin sleeve 3 so that the seal ring 6 is brought into contact with the protruding corner 32a of any one of the steps 32, and 201 is screwed into the female screw 11 of the base 1, and the seal ring 6 is compressed and deformed by being pressed between the metal tube 200 and the protruding corner 32a. When the conversion joint A and the metal tube 200 are connected in this manner, the seal ring 6 is connected to the step portion 32 of the metal tube 200 and the resin sleeve 3 at the connection point.
And the airtightness of the connection portion is maintained. In the case of a gas pipe, it is desirable that the female screw 11 of the base 1 and the male screw 201 of the metal pipe 200 screwed into it be tapered as shown in FIGS. 1 and 6, but depending on the type of pipe, the female screw 11 or It is also conceivable that the male screw 201 is a straight screw. Also, as shown in FIG.
As a 0, a cladding tube having an outer skin 210 is used.
If the seal ring 6 is tightly attached to the
200 metal pipe body 220 and metal fitting 1 for conversion joint A
Has the advantage that it does not come into contact with the outside air, moisture or rainwater, and its metal parts are effectively protected against corrosion.

FIG. 2 is a sectional view of the conversion joint B according to the second aspect.

The conversion joint B includes a metal base 1 and a connection sleeve 2.
And the connection sleeve 2 and the heating element 22 are the same as those of the conversion joint A in FIG.

The base 1 is a metal cylindrical body having a straight cylindrical portion 15 and a receiving portion 16 formed at the end of the cylindrical portion 15 so as to extend outward.
A tapered inclined surface 17 is provided on the inner circumference of one end of the socket 14, that is, the inner circumference of the socket 16, and a straight male screw 18 is formed on the outer circumference of one end of the cylindrical body 14, that is, the outer circumference of the socket 16. It was done. In addition, a short straight surface 19 is extended outside the inclined surface 17.

The cylindrical portion 15 of the base 1 is connected to the synthetic resin coating 4 formed on the outside thereof, and the connection sleeve 2 extends to one side of the coating 4. An annular groove 41 is formed at the other end of the cover 4.

In this conversion joint B, the base 1 is made of cast iron or steel, the peaks 12 and the valleys 13 of the base 1 are meshed with the covering part 4 and are firmly connected. A point that a heating wire or the like that generates heat by energizing the body 22 can be used; a point that the covering portion 4 and the connection sleeve 2 are made of a thermoplastic resin compatible with the resin tube 100; An adhesive is used so that the contact portion between the base 1 and the covering portion 4 is hardly peeled off.
A sealing ring 5 such as an O-ring as shown in FIG. 4 is fitted into the valley portion 13 of the base member, and the sealing ring 5 is pressed into contact with both the base 1 and the covering portion 4 to provide a gap between the base 1 and the covering portion 4. The point that high airtightness is ensured is the same as that described in FIG.

FIG. 7 shows a state where the resin pipe 100 and the metal pipe 200 are connected using the conversion joint B of FIG.

The connection state between the connection sleeve 2 and the resin tube 100 is the same as that described with reference to FIG. And the illustrated metal tube
Reference numeral 200 denotes a structure in which the tube main body 220 is covered with an outer cover 210 made of a synthetic resin, and a mechanical structure having a function of preventing the metal tube 200 from being pulled out is adopted as a connection structure between the metal tube 200 and the conversion joint B. . That is, an end of a metal tube 200 in which a pipe tightening member 7 and a pressing ring 8 each including a retaining ring 71 in which a plurality of spheres 71a are held by an annular holder 71b, a retainer 72, and a seal packing 73 such as a gasket are previously fitted. Part is inserted into the base 1 and the female screw 81 of the press ring 8 is screwed into the male screw 18 of the base 1, thereby pressing the seal packing 73 against the inclined surface 17 side of the base 1 at the stepped portion 82 of the press ring 8 via the retainer 72. The seal packing 73 is pressed between the metal tube 200 and the inclined surface 17 by the force generated by the pressing, and at the same time, the sphere 71 a of the retaining ring 71 is bitten into the metal tube 200 by the wedge action of the inclined surface 83 of the pressing ring 8. There is not.

When such a mechanical system is adopted, the seal packing 73 is in close contact with the inclined surface 17 of the base 1 and the metal tube 200 to ensure reliable airtightness, and at the same time, the metal ring 200 is pulled out by the retaining ring 71. In addition to being prevented, the vibration generated during an earthquake or the like is absorbed by the relative movement of the base 1 and the metal tube 200 in the direction of the pull-out, so that the metal tube 200 has a seismic function.

The pressing ring 8 covers a metal pressing ring main body 84 with a resin layer 85, and a thick portion 85 a formed at one end of the resin layer 85.
An annular groove 86 is formed, and a seal ring 9 having a substantially T-shaped end face housed in the annular groove 86 is closely attached to the metal tube 200. In addition, a cylindrical extension 87 formed at the other end of the resin layer 85 is closely fitted to the seal ring 10 fitted in the annular groove 41 of the covering portion 4 in an external fitting manner. By doing so, the pipe fastening device 7 is actuated by the sealing action of the seal rings 9 and 10.
The base 1 and the base 1 do not come into contact with the outside air, moisture, rainwater, or the like, and there is an advantage that their metal parts are effectively protected from corrosion.

The connection sleeve 2 and the resin tube 100 are integrally heat-sealed as described with reference to FIG.

FIG. 3 is a sectional view of the conversion joint C according to the third aspect.

This conversion joint C is integrally provided with a metal base 1 and a connection sleeve 2. The connection sleeve 2 and the heating element 22 are the same as those of the conversion joint A in FIG. The configuration is substantially the same as that of the conversion joint B described in the drawing. However, a straight cylindrical extending portion 16a is provided in the receiving portion 16 of the base 1 and a straight female screw 18a is formed on the inner periphery of the extending portion 16a. This is different from the conversion joint B described with reference to FIG. 2 in that the formed cylindrical extension 42 is projected to the other side of the base 1. Also, the fact that the base 1 is made of cast iron or steel, and the ridges 12 and the valleys 13 of the base 1 are firmly engaged with the covering part 4 is clearly shown in FIG. O to do
FIG. 1 shows that a seal ring 5 such as a ring is fitted and the seal ring 5 is pressed against both the base 1 and the cover 4 to ensure high airtightness between the base 1 and the cover 4. Are the same as those described in FIG. It should be noted that the male thread 18 and the annular groove 41 of the conversion joint B described with reference to FIG.

FIG. 8 shows a state in which the resin pipe 100 and the metal pipe 200 are connected using the conversion joint C of FIG.

The connection state between the connection sleeve 2 and the resin tube 100 is the same as that described with reference to FIG. And the illustrated metal tube
Reference numeral 200 denotes a structure in which the tube main body 220 is covered with a synthetic resin outer skin 210, and a mechanical system having a function of preventing the metal tube 200 from being pulled out is employed in a connection structure between the metal tube 200 and the conversion joint C. Then, the connection structure is the same as that of FIG. However, the structure for screwing the press ring 8 and the base 1 is different from the connection structure of FIG. That is, the connection structure between the metal tube 200 and the conversion joint C in FIG.
The end of a metal tube 200 in which a pipe tightening member 7 composed of a retaining ring 71, a retainer 72 and a seal packing 73 and a pressing ring 8 are previously fitted is inserted into the base 1, and a male screw 8 of the pressing ring 8 is inserted.
1 ′ is screwed into the female screw 18 ′ of the base 1 to
The seal packing 73 is pressed against the inclined surface 17 side of the base 1 via the retainer 72 at the tip 82 ′ of the base, and the seal packing 73 is pressed between the metal tube 200 and the inclined surface 17 by the force generated by the pressing. The sphere 71 a of the retaining ring 71 is bitten into the metal tube 200 by the wedge action of the inclined surface 83 of the press wheel 8. In addition, a seal ring 10 ′ is interposed between the resin layer 85 covering the metal push ring main body 84 of the push ring 8 and the extending portion 42 of the coating portion 4 in a compressed state.

The connection sleeve 2 and the resin tube 100 are integrally heat-sealed as described with reference to FIG.

According to the structure described above, at the connection point between the metal pipe 200 and the conversion joint C connected by the mechanical method,
The sealing gasket 73 closely adheres to the inclined surface 17 of the base 1 and the metal tube 200 to ensure reliable airtightness, and at the same time, prevents the metal tube 200 from being pulled out by the retaining ring 71, and at the time of an earthquake. Vibration generated in the base is absorbed by the relative movement of the base 1 and the metal tube 200 in the direction in which the metal tube 200 is pulled out, so that the metal tube 200 has a seismic function. In addition, the sealing action of the seal rings 9 'and 10' prevents the pipe fastener 7 and the base 1 from coming into contact with the outside air, moisture or rainwater in the outside air, and the metal parts thereof are effectively protected.

Although the conversion joints A, B, and C described in FIGS. 1 to 3 are all socket type, these can be easily configured as other types of conversion joints such as an elbow type and a cheese type. Of course, they are also included in the present invention.

In FIGS. 1 to 8, the same parts or corresponding parts are denoted by the same reference numerals or reference numerals with '' added thereto for convenience of explanation.

[Effects of the Invention] According to the conversion joint according to the first to third aspects of the present invention, there is an effect that a resin pipe and a metal pipe can be connected. The connection between the resin pipe and the conversion joint is sealed by heat-sealing the resin pipe and the resin pipe connection sleeve, and the connection between the metal pipe and the metal pipe connection base is sealed with a seal ring or seal packing. A seal ring that is pressed against both of the metal pipe connection base and the synthetic resin covering portion fitted on the outside of the base is formed between the base and the base for connection, thereby creating a gap between the base and the base. Therefore, there is an effect that the sealing performance when the resin pipe and the metal pipe are connected to each other is ensured.

In addition, the conversion joint of the present invention can sufficiently cope with a demand for replacing a part of the gas pipe using a metal pipe with a resin pipe in order to exhibit these effects, and also can provide a gas pipe. And other various pipes, it is also possible to sufficiently cope with a request to replace a middle part of a pipe formed of a resin pipe with a metal pipe and a request to connect a resin pipe and a metal pipe. Become like

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment according to the first aspect of the present invention,
FIG. 2 is a sectional view of an embodiment according to the second aspect of the present invention,
FIG. 3 is a sectional view of an embodiment according to the third aspect of the present invention,
FIG. 4 is an enlarged cross-sectional view of a main part showing a contact portion between the base and the covering part, FIG. 5A is an enlarged cross-sectional view of a main part showing a structure for preventing rotation of the base and the covering part, and FIG. FIG. 5B is a sectional view taken along the line VB-VB in FIG. 5A. 6 is a partial cross-sectional view showing the use state of the conversion joint of FIG. 1, FIG. 7 is a partial cross-sectional view showing the use state of the conversion joint of FIG. 2, and FIG. 8 is use of the conversion joint of FIG. It is a fragmentary sectional view showing a state. A, B, C ... conversion fitting, 1 ... base (base for metal pipe connection), 2 ... connection sleeve (sleeve for connection to resin pipe),
3 ... Resin sleeve (synthetic resin sleeve), 4 ... Coating part, 5 ... Seal ring, 6 ... Seal packing, 8
… Pressing ring, 11… Female screw of base, 12 … Crest, 13 … Valley, 14… Cylindrical body, 17… Inclined surface, 18… Male screw of base
18a ... female screw up to the base, 21 ... resin layer of connection sleeve, 22 ... heating element, 73 ... seal packing, 100 ... resin pipe (synthetic resin pipe), 200 ... metal pipe, 201 ... metal Male pipe thread.

Continuation of the front page (56) References JP-A 2-16898 (JP, U) JP-A 59-75986 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16L 15 / 04 F16L 19/08 F16L 47/02

Claims (3)

(57) [Claims] 1. A metal pipe connection base provided with a female screw into which a male screw formed in a metal pipe is screwed and connected, and having an outer surface formed in an uneven shape by a plurality of ridges and valleys; A heating element is provided on the tubular resin layer protruding to one side and fitted with the synthetic resin tube, for melting the resin layer by heat generation and for heat-sealing the synthetic resin tube and the resin layer. A resin pipe connection sleeve, and a covering portion fitted to the outside of the base so as to be engaged with and joined to the crests and valleys formed on the outer surface of the base, and from the covering portion to the other side of the base. An inner periphery of the extended cylindrical resin layer and a metal tube connected to the base are integrally formed with a synthetic resin sleeve configured so that a seal ring interposed therebetween is pressed. And fitted into the valley of the base, Conversion joint between the resin pipes and the metal tube parts and the seal ring is pressed against the both the cover portion of the synthetic resin sleeve is provided. 2. A tubular resin layer in which a synthetic resin tube is fitted,
A resin tube connection sleeve provided with a heating element for causing the synthetic resin tube and the resin layer to be thermally fused by being melted into the resin layer by heat generation; and a metal cylinder into which a metal tube is fitted. A tapered inclined surface that presses the seal packing between the metal pipe fitted into the cylindrical body at one end inner circumference is provided, and the seal packing is provided on the outer circumference at one end of the cylindrical body. An external thread into which a pressing wheel for screwing to the inclined surface side is screwed is provided, and the outer surface of the other end of the cylindrical body is formed with a plurality of ridges and valleys, and the metal pipe connection base is formed in an uneven shape. A synthetic resin covering portion that extends the resin tube connection sleeve to one side, and is fitted to the outside of the cylindrical body so as to be meshed and coupled with the ridges and valleys formed on the outer surface of the cylindrical body; , And fitted into the valley of the base, Conversion joint between the resin pipes and the metal tube sealing is pressed against the both the valley and the cover portion. 3. A cylindrical resin layer into which a synthetic resin pipe is fitted,
A resin tube connection sleeve provided with a heating element for causing the synthetic resin tube and the resin layer to be thermally fused by being melted into the resin layer by heat generation; and a metal cylinder into which a metal tube is fitted. The inner circumference of one end is provided with a tapered inclined surface that presses the seal packing between the metal pipe and the metal pipe fitted inside the cylindrical body, and the inner circumference of one end of the cylindrical body outside the inclined surface is provided. A male screw into which a pressing ring for pressing the seal packing is pressed toward the inclined surface is provided, and the outer surface of the other end of the cylindrical body is formed in an uneven shape by a plurality of peaks and valleys. The metal pipe connection base and the resin pipe connection sleeve extend to one side, and are fitted to the outside of the cylinder so as to be engaged with and coupled to the peaks and valleys formed on the outer surface of the cylinder. And a synthetic resin covering part. Fitted into valleys of the base, the conversion fitting with its valleys and the resin tube sealing ring is provided which is pressed against the both the cover portion and the metal pipe.