JPH05196187A - Connecting method of pipe and joint - Google Patents

Abstract

PURPOSE:To provide a connecting method of pipes and a joint where composite pipes having metal pipes and a synthetic resin layer are fusion-connected in an easy manner by a joint made of a normal thermo-plastic synthetic resin. CONSTITUTION:Pipe end parts and a joint 2 are fused by fitting the end parts of synthetic resin pipes having an induced exothermic layer 11 and the joint 2 made of a thermo-plastic synthetic resin, and generating heat of the induced exothemic layer 11 of the pipe end parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of connecting a pipe and a joint used for connecting a synthetic resin pipe having a metal layer or magnetic layer capable of induction heating.

[0002]

2. Description of the Related Art A metal pipe, for example, a composite pipe in which a steel pipe is protected by a synthetic resin layer is excellent in corrosion resistance, and the thickness of the metal pipe can be made thin, so that it is lightweight and easy to handle.
It is widely used for water supply pipes, hot water supply pipes, drainage pipes, etc.

Conventionally, this composite pipe has been connected according to a metal pipe, and a mechanical joint is usually used for the connection. However, this mechanical joint requires many bolts and nuts to be tightened, and the work is complicated. In addition, it is expensive and economically problematic.

In the composite pipe, however, since at least one of the inner and outer surfaces is made of a synthetic resin layer, it is possible to make connection in accordance with the connection of the synthetic resin pipe. The disadvantages of using the above mechanical joint can be eliminated.

For the connection of such synthetic resin pipes, a so-called TS joining method of connecting the pipe end portion and the joint with an adhesive is often used, but it is difficult to bond the synthetic resin pipe with an adhesive such as a polyethylene pipe. , The ends of the synthetic resin pipe and the surfaces to be joined of the thermoplastic synthetic resin sleeve are heated and melted by a heating jig, and then they are quickly detached from the heating jig and the pipe end is slid. -A so-called welding sleeve joining method of press-fitting into a sleeve is used.

[0006]

However, when the above composite pipes are connected by the welding sleeve joining method, the end of the composite pipe is joined to the joint while the synthetic resin layer at the pipe end is excessively heated. When press-fitting, peeling of the synthetic resin layer at the end of the pipe is likely to occur, while when press-fitting into the joint in a state of insufficient heating, it is difficult to sufficiently fuse the contact surface. Therefore, it is difficult to remove the heating jig and press the pipe end into the sleeve, which requires considerable skill.

In order to eliminate such disadvantages, a synthetic resin pipe end is fitted into a sleeve made of a thermoplastic synthetic resin in which a heating wire is embedded in an unheated state, and then the thermoplastic wire is heated to generate a thermoplastic composition. Method of fusing the contact interface between the resin sleeve and the end of the synthetic resin pipe, thermoplastic synthetic resin sleeve provided with a thermoplastic synthetic resin layer mixed with ferromagnetic powder on the innermost surface
Method in which the end of the synthetic resin pipe is fitted to the tube in an unheated state, and then the contact interface between the innermost surface of the sleeve made of the thermoplastic synthetic resin and the end of the synthetic resin pipe is fused by heating by heating the heating wire. (JP-A-3-129195) and the like have been proposed.

However, in these connection methods, it is necessary to manufacture a sleeve in which a heating wire is embedded or a synthetic resin resin layer containing magnetic powder is fixed, and it is not easy to manufacture the sleeve.

An object of the present invention is to provide a method for connecting a pipe and a joint, which allows a composite pipe having a metal pipe and a synthetic resin layer to be easily fusion-bonded to each other by a common thermoplastic synthetic resin joint. ..

[0010]

According to the method of connecting a pipe and a joint of the present invention, an end portion of a synthetic resin pipe having an induction heating layer and a thermoplastic synthetic resin joint are fitted to each other, and a pipe end portion is guided. The pipe end and the joint are fused by heating the heating layer.

[0011]

When a solenoid coil is arranged around the joint and an electric current is applied to the coil, an eddy current flows in the induction heating layer at the end of the pipe by electromagnetic induction, and the induction heating layer generates jule heat. The contact surface between the pipe end and the joint is fused.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

In FIG. 1, reference numerals 1 and 1 denote connected pipes,
It is a composite pipe in which synthetic resin layers 12 and 13 are coated on the inner and outer surfaces of a metal pipe 11, for example, a steel pipe. Reference numeral 2 denotes a thermoplastic synthetic resin joint, which has a sleeve portion 21 and a core portion 22. Reference numeral 3 is a solenoid coil arranged around the joint 2.

To connect the composite pipes according to the present invention, as shown in FIG. 1, the ends of the composite pipe 1 are fitted into the thermoplastic synthetic resin joint 2 and the solenoid coil 3 is arranged around the joint 2. Then, a high frequency current is passed through the coil 3 to generate a high frequency magnetic field. As a reaction to the change in the magnetic field, an eddy current in the direction of canceling the magnetic field flows in the circumferential direction of the pipe wall of the metal pipe portion 110 at the end of the composite pipe, and the metal pipe portion 11
Jul heat is generated at 0. As a result, the synthetic resin layer portion in contact with the metal pipe portion 110 at the end of the composite pipe and the thermoplastic synthetic resin joint portion in contact with the synthetic resin layer portion are heated and melted, and the synthetic resin layer portion and the joint portion. And are fused together.

In the above, the induced current (eddy current) flowing in the metal pipe portion at the end of the composite pipe flows only in the skin portion of the metal pipe portion due to the high frequency skin effect, and the skin thickness σ is theoretically expressed by Given.

[0016]

[Equation 1]

Where ρ is the resistivity of the metal tube (μΩcm),
μr: relative permeability, f: frequency. Therefore, the skin thickness of the steel pipe is about 3.0 mm, and by making the thickness of the steel pipe in the composite pipe about 3 mm (2 to 4 mm), the entire steel pipe portion at the end of the composite pipe is heated by the juule heat. It can be heated only by itself, and only the synthetic resin part near the pipe end steel pipe can be melted, and the composite pipe end and the joint can be fusion-bonded well (the thickness of the steel pipe is much larger than 3.0 mm above). If the thickness is too thick, the jule heat generated only by the skin thickness σ above escapes to the steel pipe thickness part other than that thickness by heat conduction, the temperature rising speed of the pipe end steel pipe becomes slow, and that much time is required for heating. In short, since the melting range of the synthetic resin around the pipe end steel pipe becomes wide, thermal deformation easily occurs at the connection portion).

In the above description, it is necessary to use a resin having a good compatibility for the synthetic resin layer of the thermoplastic synthetic resin joint and the synthetic resin layer of the composite pipe contacting the joint, and it is preferable to use the same type of resin. For example, polyethylene or vinyl chloride resin can be used. The thickness of this synthetic resin layer is usually 1 to 3 mm.

In addition, as shown in FIG.
Using the thermoplastic synthetic resin joint 2 having only the sleeve portion 21 to heat-bond the outer thermoplastic synthetic resin layer portion 120 of the end portion of the composite pipe and the inner surface of the sleeve portion 21 to each other, or in FIG. Using the thermoplastic synthetic resin joint 2 having only the core portion 22 as shown in (b), the inner thermoplastic synthetic resin layer portion 130 of the composite pipe end portion and the outer surface of the core portion 22 are heat-sealed. Is also possible. In FIG. 2 (a), the inner synthetic resin layer 13 is a non-thermoplastic synthetic resin layer, for example, a cross-linked polyethylene layer (in this case, it is preferably used as a hot water supply pipe due to the excellent heat resistance of the cross-linked polyethylene). it can)
Alternatively, the inner synthetic resin layer 13 can be omitted, and in FIG. 2B, the outer synthetic resin layer 1 can be omitted.
2 can be a non-thermoplastic synthetic resin layer, for example a cross-linked polyethylene layer, or the outer synthetic resin layer 12 can be omitted.

In the above, water-crosslinkable polyethylene is used for the synthetic resin layer 12 or 13 of the joint 2 and the composite pipe 1 fused to the joint 2, and both are fused in an uncrosslinked thermoplastic state, During use, it is also possible to crosslink by passing water.

In the above, the metal pipe 11 of the composite pipe 1 is
Any material may be used as long as it has an induction heating layer that can easily generate heat by an induction current due to a high frequency magnetic field, and an aluminum tube, a copper tube, a braided tube of a resistance wire, a winding layer of a resistance wire, or the like can be used.

In the above, when the composite tube has a structure in which a synthetic resin layer is provided only on the outer or inner surface of the induction heating layer, the induction heating layer 11 is made of a thermoplastic synthetic resin mixed with a ferromagnetic powder, As shown in (a) of FIG. 3 or (b) of FIG. 3, the thermoplastic synthetic resin joint 2 is fitted in the induction heating layer portion 110 at the end of the composite pipe, and the induction heating layer portion 110 is guided. It is also possible to generate heat and fuse the induction heating layer portion 110 and the joint 2.

[0023]

According to the method for connecting a pipe and a joint of the present invention, as described above, the end portion of the composite pipe having the synthetic resin layer on at least one of the inner and outer surfaces of the metal pipe and the thermoplastic synthetic resin joint. Can be rapidly fused by inductively heating the metal pipe at the end of the composite pipe by utilizing the induction heat generation property of the metal pipe. Therefore, it is not necessary to attach an electric heating means (electric heating wire, dielectric heating layer, etc.) to the thermoplastic synthetic resin joint, and the composite pipe can be easily fusion-spliced using an ordinary thermoplastic synthetic resin joint. ..

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a vertical sectional view showing another embodiment different from the above according to the present invention.

FIG. 3 is a vertical sectional view showing another embodiment different from the above according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Connected pipe 11 Induction heating layer 12 Synthetic resin layer 13 Synthetic resin layer 2 Joint 3 Solenoid coil

Claims (1)

[Claims] 1. An end portion of a synthetic resin pipe having an induction heating layer and a thermoplastic synthetic resin joint are fitted to each other to generate heat in the induction heating layer at the pipe end portion, thereby melting the pipe end portion and the joint. A method of connecting a pipe and a joint, characterized by wearing.