JPH06105113B2 - Pipe fitting - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pipe joint to which a composite pipe in which at least an outer peripheral surface of a metal pipe is coated with a heat-meltable synthetic resin is connected.

(Prior Art) For synthetic resin pipes used for water supply pipes, hot water supply pipes, gas pipes, etc., in order to enhance the connection strength with the pipe joint to be connected, a method of connecting them by heat fusion is adopted. ing. Such a connection structure between the pipe and the pipe joint by heat fusion is disclosed in Japanese Utility Model Publication No. 60-23596, published Japanese Patent Publication No. 55-500479, and the like. In the connection structures for pipes and pipe joints disclosed in these publications, the outer peripheral surface of the end portion of the synthetic resin pipe to be connected is arranged on the inner peripheral surface of the pipe joint into which the end portion is fitted. The heating element is energized and heated to fuse the outer peripheral surface of the end portion of the synthetic resin pipe and the inner peripheral surface of the pipe joint.

In recent years, composite pipes made of synthetic resin with the inner and outer peripheral surfaces of thin metal pipes having a wall thickness of about 5% or less of the outer diameter have excellent corrosion resistance and durability. Piping,
Used in drainage pipes, etc. Also in the case of connecting such a composite pipe to a pipe joint, the fusion splicing method described above is adopted, and if the outer peripheral surface of the pipe and the inner peripheral surface of the pipe joint are heat-sealed, both are firmly bonded. This fusion splicing method has good workability in the field because it is sufficient to heat the heating element arranged in the pipe joint at the piping site. Moreover, the flange connection, which requires flare processing or diameter expansion processing at the pipe end, is excellent in workability in consideration of the fact that a force of several tons to tens of tons is required to process the pipe end.

(Problems to be Solved by the Invention) In such a fusion splicing method, in the state where the composite pipe is fusion-spliced to the pipe joint, for example, a fluid is caused to flow through the composite pipe at high pressure, and the composite pipe is When a force is applied to the composite pipe, the synthetic resin layer fused to the pipe joint on the outer peripheral side of the composite pipe may separate from the metal pipe portion of the composite pipe together with the pipe joint, and the composite pipe may fall out.

An object of the present invention is to provide a pipe joint that prevents such fusion-bonded composite pipes from falling off and is excellent in field workability.

(Means for Solving the Problems) In the pipe joint of the present invention, at least an outer peripheral surface of a metal pipe is externally fitted to an end portion of a composite pipe covered with a heat-meltable resin layer, and at least the end portion is externally fitted. The joint body is made of a heat-fusible resin, and the joint body is provided with a heating element in the portion, and the joint body is fitted to the end of the composite pipe fitted in the joint body. And a retaining member made of an annular shape memory alloy, which is fixed in the vicinity of the heating element and is reduced in diameter by being heated by the heating element, thereby achieving the above object.

(Example) Hereinafter, the present invention will be described with reference to Examples.

FIG. 1 is a partially cutaway sectional view showing a connection structure between a pipe joint and a composite pipe of the present invention. The composite pipe 10 has a structure in which an inner peripheral surface and an outer peripheral surface of a metal pipe 11 made of, for example, aluminum are covered with heat-meltable synthetic resin layers 12 and 13, respectively.

The pipe joint 20 to which the ends of the composite pipe 10 are joined has a straight tubular joint body 21 and a tightening nut 22 screwed to one end of the joint body 21.

An outer cylinder 21a and an inner cylinder 21b are coaxially formed at one end of the joint body 21 with a gap into which the end of the composite pipe 10 can fit. Then, the end of the composite pipe 10 is fitted into the gap.

At the other end of the joint body 21, a connecting portion 21c having an inner diameter slightly larger than the inner diameter of the inner cylinder 21b is provided, and a thread groove is formed on the outer peripheral surface of the connecting portion 21c. Then, by screwing the connecting portion 21c into a predetermined device or the like, the pipe joint 20 is connected to the device.

Such a joint body 21 is integrally formed of a heat-meltable resin.

An outer cylinder 21a and an inner cylinder 21b arranged at one end of the joint body 21.
Is a heating element composed of a linear resistor such as Cu or Nichrome.
1d is buried. The heat generating element 21d is arranged so that the heat generation thereof can heat the entire inner peripheral portion of the outer cylinder 21a and the outer peripheral portion of the inner cylinder 21b, and the tip portion of the outer cylinder 21a can be reliably heated. It In this embodiment, the heating element 21d is formed by winding a linear resistor along the inner peripheral surface of the outer cylinder 21a and the outer peripheral surface of the inner cylinder 21b with an appropriate gap in the axial direction. The heating element 21d is extended to the outside from the base ends of the outer cylinder 21a and the inner cylinder 21b, and the heating element 21d generates heat by applying a voltage between the ends of the heating element 21d. . The heating element 21d may be a sheet-like resistor regardless of such a linear resistor, or may be a resistor obtained by kneading a conductive powder material into a resin.

A thread groove is formed on the outer circumference of the tip of the outer cylinder 21a of the joint body 21, and a tightening nut 22 is screwed into the thread groove. The tightening nut 22 has a cylindrical shape with one end open, and the diameter is slightly tapered toward the open end, and a thread groove is formed on the inner peripheral surface on the open end side. . At the other end of the tightening nut 22, a locking portion 22a having a through hole having an outer diameter slightly larger than the outer diameter of the composite pipe 10 is formed in the central portion.
Is provided. The tightening nut 22 is externally fitted to the outer cylinder 21a of the joint body 20 from its open end, and the screw groove on the outer peripheral surface of the outer cylinder 21a and the screw groove on the inner peripheral surface of the tightening nut 22 are screwed together. Then, the tightening nut 22 is tightened into the outer cylinder 21a, so that the outer cylinder 21a is gradually reduced in diameter.

Between the tip of the outer cylinder 21a of the joint body 21 and the locking portion 22a of the tightening nut 22 screwed to the outer cylinder 21a, a retaining member 23 made of a shape memory alloy is arranged. There is. The retaining device
23 has a continuous annular shape as shown in FIG.
The cross-section is triangular with the inner circumference tapering inward. Regardless of such a shape, the retainer 23 may have a rectangular cross section with a flat inner peripheral surface as shown in FIG. 3, for example.

The retainer 23 is manufactured by cutting and punching a plate material or a cylindrical material made of a shape memory alloy such as Ni-Ti alloy and Cu-Zn-Al alloy, and then expanding the diameter. . Shape memory alloys have the property of undergoing reverse transformation and returning to the pre-deformation shape when they are heated above the austenite transformation point after undergoing plastic deformation at a low temperature below their martensitic transformation point, for example at room temperature. . The retainer 23 used in the pipe joint of the present invention is initially a metal pipe in the composite pipe 10.
It is manufactured by processing to an inner diameter smaller than the outer diameter of 11, and then expanding to an inner diameter larger than the outer diameter of the composite pipe 10 at a temperature below the martensitic transformation point of the material alloy. The shape memory alloy used for the retainer 23 has an austenite transformation temperature of the synthetic resin layers 12 and 13 of the composite pipe 10.
Also, the temperature is preferably equal to or lower than the melting point of the resin forming the joint body 21.

The pipe joint 20 having such a structure is joined to the end portion of the composite pipe 10 as follows. First, tighten the tightening nut 22
It is loosely screwed to the outer cylinder 21a. In such a state, the end of the composite pipe 10 is inserted into the through hole of the locking portion 22a of the tightening nut 22 and the retaining member 23, and is inserted into the gap between the outer cylinder 21a and the cylinder 21b. Then, the end face of the composite pipe 10 is attached to the outer cylinder 21a.
And the inner part 21b is brought into contact with the inner part in the gap. In this state, the tightening nut 22 is rotated, and the locking portion 22a is screw-fed so that it comes into contact with the retaining member 23. As a result, the outer cylinder 21a is tightened by the tightening nut 22, and the diameter of the outer cylinder 21a is gradually reduced from the portion where the tightening nut 22 is screwed. As a result, the composite pipe inserted in the gap between the outer cylinder 21a and the inner cylinder 21b.
The outer peripheral surface of the end portion of 10 is pressed against the inner peripheral surface of the outer cylinder 21a, and the inner peripheral surface thereof is pressed against the outer peripheral surface of the inner cylinder 21b.

Next, the heating elements arranged in the outer cylinder 21a and the inner cylinder 21b.
21d is energized to heat the heating element 21d. As a result, the outer cylinder 21a and the inner cylinder 21b made of the heat-meltable resin are heated and melted, and the heat-meltable resin layers 12 and 13 on the outer peripheral surface and the inner peripheral surface of the composite pipe 10 are also heat-melted, and both are melted. Be worn.

At this time, the retainer 23 is also heated by the heating element 21d at the same time. When the retainer 23 reaches a temperature equal to or higher than the austenite transformation point of the material alloy by this heating, the retainer 23 undergoes reverse transformation, and the retainer 23 has an inner diameter of the metal pipe of the composite pipe 10. It is smaller than the outer diameter of the 11th part.
Therefore, this reverse transformation causes the retainer 23 to enter the heat-meltable resin layer 12 on the outer peripheral surface of the composite pipe 10 which is melted by heating.
The metal pipe 11 of the composite pipe 10 is embedded in the outer peripheral surface of the metal pipe 11. If the austenite transformation temperature of the material alloy of the retainer 23 is not higher than the melting points of the synthetic resin layers 12 and 13 of the composite pipe 10 and the resin forming the joint body 21, the heating required for melting the resin is sufficient. The retainer 23 undergoes reverse transformation, so that the metal pipe 11 is swallowed quickly and reliably.

In such a state, tap water or the like flows through the pipe joint 20 and the composite pipe 10, and the composite water 10 causes the composite pipe 10 to flow through the joint body 20.
Even if a force is applied in the direction of coming off, the composite pipe 10 is firmly locked to the retaining member 23, and the retaining member 23 is locked to the retaining portion 22a of the tightening nut 22, so that The composite pipe 10 does not separate from the resin layer 12 on the outer peripheral side and the metal pipe 11, and there is no risk of falling out of the pipe joint 20. Further, since the inner peripheral surface of the composite pipe 10 and the outer peripheral surface of the inner cylinder 21b are integrally fused, and the outer peripheral surface of the composite pipe 10 and the inner peripheral surface of the outer cylinder 21a are integrally fused, the pipe joint 20 There is no risk of water leakage at the joint between the and the composite pipe 10. Moreover, the metal pipe 11 of the composite pipe 10 does not come into contact with water, and there is no risk of corrosion.

Thermofusible resin layer covering the metal tube 11 in the composite tube 10.
12 and 13 include polyethylene, polypropylene,
An olefin resin such as polybutene, or a mixture or copolymer of these resins is used. In particular, a crosslinked olefin resin is suitable because it has a large adhesive force with a metal.

The joint body 21 of the pipe joint 20 is also made of the same synthetic resin as the resin layers 12 and 13 of the composite pipe 10.

FIG. 4 is a partially cutaway side view of another embodiment of the pipe joint of the present invention. In this embodiment, the joint body 21 has a flange 21e instead of the tubular connecting portion 21c of the above embodiment. A bolt insertion hole 21f is formed in the flange 21e. By bolting the flange 21e to a predetermined device or the like, the pipe joint 20 is connected and fixed to the device or the like. The pipe joint of this embodiment has the same structure as that of the embodiment shown in FIG. 1 except that the joint body 21 has the flange 21e. Therefore, the same components are designated by the same reference numerals and detailed description thereof will be omitted.

FIG. 5 is a partially cutaway side view of another embodiment of the pipe joint of the present invention. In this embodiment, a spring coil-shaped retainer formed by winding a wire having a circular cross section shown in FIG.
23 'is used. The spring coil-shaped retainer 23 'is made of the same shape memory alloy as the ring-shaped retainer 23 of the above embodiment. When the retainer 23 'is heated by the heating element 21d, the retainer 2'
The diameter of the entire 3'is reduced, and the retainer 23 'is locked in the composite pipe 10 over its entire axial direction. As a result, composite pipe
It is possible to more effectively prevent 10 from falling out of the pipe joint 20.

In general, shape memory alloys have extremely poor machinability, and are barely cut by cemented carbide tools. Therefore, it is not easy to manufacture the ring-shaped retainer 23 of the above embodiment. On the other hand, the spring coil-shaped retainer of this embodiment
23 'is manufactured by simply winding the wire. Since it is easy to process the shape memory alloy into a wire rod, the spring coil retainer 23 'can be easily manufactured. Further, the spring coil-shaped retainer 23 'can easily change the number of turns, and the locking force to the composite pipe 10 can be adjusted by changing the number of turns. Therefore, the retainer 23 'can reliably prevent the composite pipe 10 from falling off the joint body 20. The spring coil retainer 23 'is not limited to have a circular cross section,
For example, as shown in FIG. 7, the inner peripheral side surface may have a cross-sectional shape protruding inward. The retainer 23 'having such a cross-sectional shape can be easily manufactured by changing the shape of the processing die.

This embodiment is the same as the embodiment shown in FIG. 1 except that a spring coil-shaped retainer 23 'is used, and therefore the same parts are allotted with the same reference numerals and detailed description thereof is omitted. Also in this embodiment, a flange may be provided instead of the connecting portion 21c of the joint body 21 as in the embodiment of FIG.

Although the above-mentioned embodiments are all examples of straight pipe type pipe joints, the present invention is not limited to such pipe joints and can be applied to elbow type pipe joints and the like. Further, the joint body 21 and the device are not limited to the connection by the screw-in type connection portion 21c but may be connected by using the flange 21e, and further, a socket type or the like can be adopted. The retainer may be arranged inside the joint body 21.

The composite pipe was actually connected to the pipe joint in the embodiment of FIG. 4 and the pull-out strength was tested. The details will be described below.

As the composite pipe 10, a metal pipe 11 made of aluminum, the inner and outer surfaces of which were coated with polyethylene resin, was used. Composite pipe 10
Has an outer diameter of 40 mm and the metal tube 11 has an outer diameter of 39 mm. Fitting body 2
1 was molded with the same resin as the coating resin of the composite pipe 10. A nichrome wire with a wire diameter of 1.0 mm was used as the heating element 21d. The retainer 23 is formed by cutting a 49.8% Ni-Ti shape memory alloy plate into a ring shape with an inner diameter of 38.6 mm and a wall thickness of 2 mm, and then expanding it with a mandrel so that the inner diameter becomes 40.5 mm at room temperature. Diameter processed.

Insert the composite pipe 10 into the joint body 20, energize the heating element 21d, fuse the composite pipe 10 to the pipe joint 20, and then drop the composite pipe 10 with an autograph (Shimadzu; load 5 tons). The performance was investigated. As a result, it became clear that it could withstand pulling out of 100 kg / cm ² , and it was confirmed that the retainer 23 effectively contributed to holding the composite pipe 10.

A similar test was conducted using a spring coil-shaped retainer 23 'shown in FIG. 6 in place of the ring-shaped retainer 23. The wire diameter of the retainer 23 'is 1.5 mm, and the material and inner diameter thereof are the same as those of the ring retainer 23. If the number of turns of the coil is 3 times in the case of 60kg / cm ^2, 5 times was confirmed that the withstand pulling forces of 80 kg / cm ^2.

(Effects of the Invention) In the pipe joint of the present invention, the joint body and the composite pipe are integrally fused as described above, and the retaining member made of the shape memory alloy is simple and easy to use by utilizing the fusion heat. Since it is firmly locked to the composite pipe, the composite pipe can be firmly fixed to the joint body. Moreover, since it is only necessary to apply a voltage to the heating element at the piping site, workability is excellent.

[Brief description of drawings]

FIG. 1 is a partially broken longitudinal view showing an example of the pipe joint of the present invention together with a composite pipe, FIGS. 2 and 3 are sectional views showing an example of a retaining member, and FIGS. 4 and 5 are respectively. FIG. 6 and FIG. 7 are sectional views showing a partly broken longitudinal section showing another embodiment of the present invention together with a composite pipe. 10 …… Composite tube, 11 …… Metal tube, 12,13 …… Heat melting resin layer,
20 …… Pipe joint, 21 …… Coupling body, 21a …… Outer cylinder, 21b …… Inner cylinder, 21d …… Heating element, 22 …… Tightening nut, 23,23 ′ …… Retainer.

Claims (1)

[Claims] 1. A metal pipe, at least the outer peripheral surface of which is externally fitted to an end of a composite pipe covered with a heat-fusible resin layer, at least a portion of which the end is externally fitted is made of a hot-melt resin , A joint body having a heating element disposed in that portion, and a fitting body fixed to the joint body in the vicinity of the heating element so that the joint tube can be externally fitted to the end portion of the composite pipe. A pipe joint comprising: an annular shape memory alloy retainer that is heated by a heating element to reduce its diameter.