JPH0247835Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the joint structure of a composite pipe formed by lining the inner surface of a metal pipe with a synthetic resin material. The present invention relates to a connection structure that prevents metal pipes from easily corroding and allows for easy joining work.

[Prior Art] Composite pipes are metal pipes with a synthetic resin layer formed on the inner surface for the purpose of preventing corrosion on the inner surface and further preventing the generation of red water and the elution of iron ions, etc.
It is beginning to be widely used in heating piping, water supply pipes, etc. However, when putting this type of composite pipe into practical use, the most important problem is the joining method. In other words, composite pipes are designed to extend the life of a metal pipe by lining the entire inner surface of the pipe with a synthetic resin material to prevent the fluid inside the pipe from coming into direct contact with the metal pipe. In the joining method, since the metal pipe layer is exposed at the joint end surface, water and the like enter the boundary between the metal pipe layer and the lining layer, causing rapid corrosion. For example, Figures 1 and 2 are vertical cross-sectional views of the upper half of a known composite pipe joining method, with Figure 1 showing an example of joining using a threaded socket, and Figure 2 showing an example of mechanical joining. In the figure, M indicates a metal layer, R indicates a lining layer, 1 indicates a double-receiving socket with screws, 2 indicates a double-flange joint, 3 indicates a push ring, and 4 indicates a sealing packing. That is, in FIG. 1, a male thread is cut on the outer periphery of the joint end of the composite pipe MR, and the pipes are connected to each other via a threaded double-receiving socket 1. In addition, in FIG. 2, the composite pipe MR is inserted through the large diameter portions on both sides of the double flange joint 2, and the sealing gasket 4 attached to the inner surface of the opening side of the flange joint 2 is tightened with the press ring 3 to make it watertight. is ensured. However, as is clear from the figure, the tip surface of the composite tube MR is exposed inside the tube, so when fluid is passed through this, the exposed end surface of the metal layer M, and furthermore, the interface between the metal layer M and the lining layer R. is rapidly corroded in a short period of time. In particular, once the interface between the metal layer M and the lining layer R is corroded, water will gradually penetrate from the corroded portion to the depths, causing the corrosion to propagate and cause a serious accident. As described above, the conventional joining method has a serious problem of corrosion deterioration starting from the joint.

Techniques for preventing corrosion from the tip of the composite pipe are disclosed in Japanese Utility Model Publication No. 56-95688 and Japanese Utility Model Publication No. 48-48.
There is a pipe joint structure disclosed in Publication No. 10483.

First, the former uses a pipe joint and a synthetic resin anti-corrosion ring, and the anti-rust ring consists of a head and a sleeve part, the threaded part of the head is screwed into the inner peripheral surface of the pipe joint, The protrusion formed on the sleeve portion is pressed against the inner circumferential surface of the composite tube to maintain airtightness. However, even with the above method, the sealing performance was insufficient because the seal portion formed by the inner circumferential surface of the composite tube and the protrusion was in line contact. Moreover, since a sealant is required at the threaded joint between the anti-rust ring and the pipe fitting and between the pipe fitting and the composite pipe, there are problems in that the reliability of the sealing performance is low and the workability during connection is poor. have.

On the other hand, the latter is a pipe joint that has an annular gap formed by a metal pipe and a synthetic resin material layer, and the end of the composite pipe is inserted into the annular gap, and the synthetic resin material layer at the end of the composite pipe and the pipe joint are connected. The synthetic resin material layers are bonded together using an adhesive. However, since the sealing surfaces of the synthetic resin material layers are adhesively bonded, the sealing performance of the joint depends on the performance of the adhesive, and there is a problem that reliable sealing performance cannot always be obtained.

[Problems to be solved by the invention] This invention was developed as a result of various studies focusing on the above-mentioned circumstances, and is a novel joint configured to prevent corrosion of composite pipes starting from the joint. It provides a partial structure.

[Means for solving the problem] In other words, the structure of the present invention that achieves the above purpose is as follows.
At the end of the composite pipe having the above structure, a socket with an enlarged diameter internal thread is formed in the metal layer, and an annular gap is formed between the metal layer and the synthetic resin material layer, and the outer circumferential side is the metal layer and the inner circumferential side is the synthetic resin material layer. A male threaded insertion tube formed of a material layer is screwed into the annular gap, and the contact surface of the synthetic resin material layer on the socket side or the insertion port side is formed in a tapered shape over the entire circumference. , the gist is to press-bond the inner surface of the synthetic resin material layer on the insertion port side and the synthetic resin material layer on the socket side with an interference fit surface.

[Operations and Examples] The configuration and operation effects of the present invention will be explained below based on the drawings of the embodiments. FIG. 3 is a cross-sectional view of a main part illustrating the structure of a connecting part of a composite pipe according to the present invention, and numeral 5 indicates the socket of the composite pipe MR1, and 6 indicates the socket of the composite pipe MR2. That is, the socket part 5 is composed of a female threaded socket 5M formed by expanding the diameter of the metal layer M, and a core part 5R formed so as to extend the lining layer R toward the socket opening side, The annular gap 10 is defined by the inner circumferential side of the female threaded socket 5M and the outer circumferential side of the core portion 5R. In addition, a tapered interference fit surface 8R is formed on the outer peripheral surface side of the core portion 5R, and the diameter gradually increases from the tip 5b to the inner portion 5c of the core portion 5R.
It is configured such that the inner surface on the distal end side and the tapered interference fit surface 8R are in contact with each other. In this way, the composite pipe
The inner surface of the lining layer R of MR2 has the same inner diameter in the longitudinal direction, except for a slight chamfer 6a formed at the tip, but the outer diameter of the tapered interference fit surface 8R and the composite pipe are different. It is necessary that the following relationship exists between the inner diameter dimensions of MR2. That is, the inner diameter of the lining layer 6 of the composite pipe MR2 is larger than the outer diameter of the tip 5b, and
It is formed to have a smaller diameter than the outer diameter of c. Further, a convex portion 5a (which may be formed continuously or discontinuously along the circumferential direction) that sinks into the metal layer M is formed on the root side 5d of the illustrated example core portion 5R,
The integrity of the metal layer M and the lining layer R is enhanced. In addition, the female thread 8M formed in the female threaded socket 5M
The male thread 6M formed in the insertion port 6 may be a tapered thread for pipe connection or a simple parallel thread.

Both composite pipes MR1 and MR2 configured as above
When connecting, as shown in FIG. 4, a male thread 6M is screwed along a female threaded socket 5M. When the lining surface 6R on the tip end side of the insertion port 6 is screwed together until it contacts the core portion 5R, the lining surface 6R begins to push the tapered interference fit surface 8R in the direction of arrow A. When the socket 6 is further screwed in, the inner circumferential surface on the distal end side of the lining layer 6R is further pushed down in the direction of arrow A, so that the core part 5R is deformed so as to curve toward the axis of the socket 5. Since a reaction force against the pressing force in the direction of arrow A acts on the lining surface 6R of the core portion 5R, a strong pressure contact state is obtained between the tapered interference fit surface 8R and the lining surface 6R. That is, the tapered interference fit surface 8R receives an interference fit with the lining surface 6R, and the adhesion between the core portion 5R and the lining layer R of the composite pipe MR2 becomes extremely strong, and the fluid in the pipe line is Tapered interference fit surface 8R (lining surface 6R)
Since there is no leakage from the metal pipe M to the annular gap 10 side, corrosion of the metal pipe M can be prevented as much as possible. In the above embodiment, the tapered female thread is 8M.
The lining surface 6 of the insertion port 6 is used to reduce the diameter of the insertion port 6.
Since the tip surface including R presses the tapered tight fit surface 8R in the direction along the axis, the state of pressure contact between the tapered tight fit surface 8R and the lining surface 6R is improved as a result. As a supplementary structure for preventing leakage of the fluid in the pipe, for example, as shown in FIG.
A seal 9 may be attached to the base of the inlet tube so that the sealing effect is enhanced by deformation due to compression of the inlet tube. Further, in the above embodiment, the core portion 5R is formed with a tapered interference fit surface 8R, but as shown in FIG. , or may be formed on both the core portion 5R and the lining surface 6R.

[Effects of the invention] Since the present invention is configured as described above, the following effects can be obtained.

The interface between the metal layer and the lining layer does not corrode.

Corrosion and deterioration of the composite pipe starting from the composite pipe joint can be prevented.

The joining operation is extremely simple.

Good sealing properties.

The corrosion prevention structure is simpler than the conventional technology.

[Brief explanation of drawings]

1 and 2 are cross-sectional explanatory diagrams illustrating the conventional connection structure, FIG. 3 is a sectional view of the main part showing the joint of a composite pipe according to the present invention, and FIG. 4 is a composite pipe according to the present invention. FIGS. 5 and 6 are cross-sectional views showing other embodiments of the present invention. MR...Composite pipe, M...Metal layer, R...Lining layer, 5...Socket part, 6...Socket part, 10...
Annular gap.

Claims (1)

[Scope of utility model registration request] This is a composite pipe connection structure in which the outer peripheral side is formed of a metal layer and the inner peripheral side is formed of a synthetic resin material layer, and a female threaded socket is formed at the end of the metal layer, and a female threaded socket is formed inside the female threaded socket. The synthetic resin layer is integrally fitted, and the end of the synthetic resin layer extends along the longitudinal direction of the female threaded socket, and an annular shape is formed between the synthetic resin layer and the female threaded socket. A gap is formed, and a male threaded socket tube with a metal layer on the outer circumference and a synthetic resin layer on the inner circumference is screwed into the annular gap, and a synthetic resin layer on the socket or insertion side. The abutment surface is tapered around the entire circumference,
A composite pipe connection structure characterized in that the inner surface of the synthetic resin material layer on the insertion port side and the synthetic resin material layer on the socket side are crimped and joined with an interference fit surface.