JPH041024A - Method for molding receiving port of composite pipe - Google Patents

Abstract

PURPOSE:To mold the receiving port of a composite pipe not generating possibility such that a synthetic resin layer is released from the inner peripheral surface of a metal pipe by providing elastic force not breaking an adhesive layer at the time of diametric expansion to the adhesive layer and expanding the diameter of the synthetic resin layer in the quantity corresponding to the diametrically reduced quantity of the adhesive layer by the diameter reducing force remaining in the adhesive layer by diametric expansion. CONSTITUTION:In a cold state, diameter expanding force is internally applied to the end part of a composite pipe 10 whose receiving port must be molded to expand the diameter of the metal pipe 11 and synthetic resin layer 13 at the end part of the composite pipe 10. At this time, since the adhesive layer 12 interposed between the metal pipe 11 and the synthetic resin layer 13 can be elastically deformed, the adhesive layer 12 is pressed to the inner peripheral surface of the metal pipe 11 by the diametric expansion of the synthetic resin layer 13 to be compressed in the diametric direction and stretched in the peripheral direction. When the diameter expanding force is removed from the end part of the composite pipe 10, the metal pipe 11 at the end part is reduced in its diameter by spring back and the synthetic resin layer 13 is reduced in its diameter by this diameter reducing force and the adhesive layer 12 becomes an expanded state from the state compressed in the diameter direction by the diameter reducing force of the synthetic resin layer 13. By this method, there is no possibility such that the bonding surface of the metal pipe 11 and the adhesive layer 12 and the bonding surface of the adhesive layer 12 and the synthetic resin layer 13 are released.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for forming a socket for a composite pipe, which forms a socket constituting a pipe joint at the end of a composite pipe used for a drainage pipe, etc. .

(Prior Art) Composite pipes in which the inner peripheral surface of a metal pipe is coated with a synthetic resin layer have recently been used as a piping material for draining water from buildings and the like. In the composite tube, an adhesive layer is interposed between the synthetic resin layer coated on the inner circumferential surface of the metal tube and the metal tube in order to firmly adhere the two. Such an adhesive layer usually uses a rubber adhesive, a hot melt adhesive, an epoxy adhesive, or the like.

For such composite pipes, a plug-in type pipe joint is used, in which the end of the composite pipe to be connected is inserted into a socket configured by expanding the diameter of one of the ends of the composite pipe. . The socket formed at the end of a composite pipe is, for example, formed by coating the inner peripheral surface of a metal pipe with an adhesive layer and a synthetic resin layer. It is formed by cold diameter expansion processing which applies radial force to expand the diameter of the end portion.

(Problems to be Solved by the Invention) In such a conventional socket forming method, when a diameter expanding force is applied to the end of the composite pipe, 1, as the diameter of the synthetic resin layer expands,
The adhesive layer interposed between the synthetic resin layer and the metal tube is expanded in diameter and stretched in the circumferential direction.

Therefore, if the amount of diameter expansion is large, there is a risk that the adhesive layer will break. When the adhesive layer breaks, the adhesive layer is not interposed between the metal pipe and the synthetic resin layer at the broken part, and the adhesive force between the metal pipe and the synthetic resin layer decreases, causing the synthetic resin layer to become metal. There is a risk of it peeling off from the pipe.

Moreover, when the diameter expanding force is removed from the end portion of the composite pipe after the end portion is expanded in diameter, the diameter of the metal tube is contracted due to springback. However, since the amount of diameter reduction is small, the expanded diameter dimensions of the metal tube are almost the same as the dimensions immediately after diameter expansion.
is rarely reduced in diameter. On the other hand, the synthetic resin layer
By expanding the diameter and stretching in the circumferential direction, in addition to permanent elongation due to plastic deformation, a contractile force larger than the springback of the metal tube remains. Therefore, when the diameter expansion force is removed, a large diameter contraction force acts inside the synthetic resin layer, and if the adhesive force of the adhesive layer is weak, the diameter contraction of the synthetic resin layer The force may cause the synthetic resin layer to peel off from the inner peripheral surface of the metal tube. If the adhesive layer is in a broken state, the synthetic resin layer will more easily peel off from the metal tube.

The present invention solves the above-mentioned conventional problems, and its purpose is to expand the diameter of the end of a composite pipe whose inner peripheral surface is covered with a synthetic resin layer via an adhesive layer to form a socket. Provides a method for forming a socket for a composite pipe in which there is no risk of the synthetic resin layer peeling off from the inner circumferential surface of the metal pipe, even when the diameter of the metal pipe is large or the adhesive strength of the adhesive layer is weak. There is something for every thing you do.

(Means for Solving the Problems) The method for forming a socket for a composite pipe of the present invention includes:
A method for forming a socket for a composite pipe in which the diameter of the end of the composite pipe coated with a synthetic resin layer via an adhesive layer is expanded by applying a diameter expanding force from inside the pipe in the cold to form a socket. The adhesive layer has an elastic force that does not break when the diameter is expanded, and due to the diameter-reducing force that remains inside due to the diameter expansion, the adhesive layer follows and reduces the diameter of the synthetic resin. The layer is characterized by being expanded in diameter by an amount corresponding to the amount by which the layer is reduced in diameter, thereby achieving the above object.

(Example) The present invention will be described below with reference to Examples.

The method of forming a socket for a composite pipe according to the present invention is carried out when the end of the composite pipe 10 shown in FIG. 1 is expanded in diameter to form a socket.

In the composite tube 10, the inner peripheral surface of a metal tube 11 is covered with a synthetic resin layer 13 with an adhesive layer 12 interposed therebetween. Composite pipe 1
The metal tube 11 in 0 is made of, for example, copper, aluminum,
A metal material, such as brass, that is stretched in the circumferential direction and expanded in diameter when a diameter expansion force is applied is used.

The synthetic resin layer 13 covering the metal tube 11 is made of PvC (polyvinyl chloride), PE (polyethylene), PP (polypropylene), nylon, etc., which has a larger elongation in the circumferential direction in the cold than the material of the metal tube 11. resin is used. The synthetic resin layer 13 is stretched in the circumferential direction and expanded in diameter by applying a diameter expanding force to the end of the composite pipe 10. When the synthetic resin is expanded in diameter, in addition to permanent elongation due to plastic deformation, a contraction force larger than the spring hole of the metal tube 11 remains. Therefore, after the diameter expansion force is removed from the end of the composite pipe 10, the diameter contraction force acts on the synthetic resin layer 13.

The adhesive layer 1z interposed between the metal tube 11 and the synthetic resin layer 13 is formed by applying a diameter expanding force to the end of the composite tube 10 and stretching the synthetic resin layer 13 in the circumferential direction. An elastic adhesive is used that is elastically compressed in the radial direction by the outer peripheral surface of the synthetic resin layer 13 and the inner peripheral surface of the metal tube 11. Therefore, when the diameter of the synthetic resin layer 13 is reduced by the diameter-reducing force remaining in the synthetic resin layer 13 after the diameter-expanding force is removed from the end of the composite pipe 10, the elastic adhesive layer 12 Following the diameter reduction, the state changes from a radially compressed state to an expanded state. Such an adhesive layer 12 is made of, for example, urethane foam, rubber foam, or the like. The adhesive layer 12 is
The thickness is 0.5m or more, and the volume change rate is 2/3
~115 times.

Methods for expanding the diameter of the end of the composite pipe 10 include methods that can apply a diameter expanding force from inside the end of the composite pipe 10, such as 1<rugi molding method, shell expand molding method, punch molding method, etc. will be adopted.

In the method of the present invention, the amount of diameter expansion at the end of the composite pipe 10 is
With the diameter expanding force applied, the inner diameter of the synthetic resin layer 13 is made slightly larger than the specified dimension.

The amount of diameter expansion is the amount by which the diameter of the synthetic resin layer 13 is reduced based on the contraction force remaining inside the synthetic resin layer 13 after the diameter expansion force is removed from the end of the composite pipe 10.

According to such a socket forming method, in a cold state, a diameter expanding force is applied from inside to the end of the composite pipe 1o in which the socket is to be formed, and the metal pipe 11 and the synthetic resin layer at the end are 13 is expanded in diameter. At this time, since the adhesive layer 12 interposed between the metal tube 11 and the synthetic resin layer 13 can be elastically deformed, it is pressed against the inner peripheral surface of the metal tube 11 by the diameter expansion of the synthetic resin layer 13. It is compressed in the radial direction and stretched in the circumferential direction. The adhesive layer 12 has a thickness such that it will not break due to this compression.

When the diameter expanding force is removed from the end of the composite tube 10, the diameter of the metal tube 11 at the end is contracted due to springback. The amount of diameter reduction due to springback is 0.1 to 0.2%.
The size of the metal tube 11 is approximately the same as that at the time of diameter expansion. On the other hand, the synthetic resin layer 13 at the diameter-expanded end is stretched in the circumferential direction due to the diameter expansion, and in addition to permanent elongation due to plastic deformation, the metal tube 11
Since a contractile force larger than the springback remains, the diameter-expanding force is removed from the end of the composite pipe 10, and a diameter-reducing force is applied within the synthetic resin layer 13. When the expanding force is removed from the end of the composite tube lO,
The diameter of the synthetic resin layer 13 is reduced by this diameter reduction force, and the metal tube 1
The adhesive layer 12 interposed between the adhesive layer 1 and the synthetic resin layer 13 changes from a radially compressed state to an expanded state due to the diameter-reducing force of the synthetic resin layer 13. As a result, the synthetic resin layer 13
At the same time, the inner peripheral surface of the adhesive layer 12 is reduced in diameter following the diameter reduction of the synthetic resin layer 13. When expanding the diameter of the synthetic resin layer 13, the diameter of the synthetic resin layer 13 is expanded in consideration of the amount of diameter reduction, so that when the synthetic resin layer 13 contracts, its inner diameter becomes approximately equal to the inner diameter of the socket to be formed. .

Since the adhesive layer 12 is interposed between the metal tube 11 and the synthetic resin layer 13 due to elastic deformation, the bonding surface between the metal tube 11 and the adhesive layer 12 and the adhesive layer 12 and the synthetic resin layer 13 There is no risk of the joint surface peeling off. Therefore, even when the diameter of the synthetic resin layer 13 is reduced, the metal tube 11 and the synthetic resin layer 13 are firmly adhered to each other by the adhesive layer 12, and the synthetic resin layer is formed from the inner peripheral surface of the metal tube 11. There is no risk that 13 will peel off.

Next, a specific example of the method of the present invention will be explained. For example, metal pipe 1
1 is a steel pipe with an inner diameter of 106 m, adhesive layer 12 is a foamed urethane layer (3 times foamed) with a thickness of 3 m, and synthetic resin layer 1
By the method of the present invention, a hard vinyl chloride pipe with an outer diameter of Loom is used at the end of the composite pipe 10 as shown in Fig. 3.
%.

When the diameter expanding force is applied, the outer diameter of the synthetic resin layer 13 becomes 120 m, the adhesive layer 12 is compressed from a thickness of 3 m to a thickness of 1 cm, and the inner diameter of the metal tube 11 becomes 120 m. , 106
It became 122 easy from m. When the expanding force is removed from the expanded end, the inner diameter of the metal tube 11 remains 122 mm, but the outer diameter of the synthetic resin layer 13 changes from 120 m to 116 mm due to the shrinkage force remaining inside due to the expanded diameter. It decreased to 1111. However, since the thickness of the adhesive layer 12 was changed from 1 m to 3 m, the space between the metal tube 11 and the synthetic resin layer 13 remained filled with the adhesive layer 12. At this time, the adhesive layer 12 is in a state where no tensile force is applied in the circumferential direction and the radial direction.

Although the composite pipe 1o used in the above embodiment has a synthetic resin layer 13 with no unevenness on its outer peripheral surface, it is not limited to the composite pipe 1o having such a structure. As shown, it may be a composite pipe 10 in which a plurality of protrusions 13a extending continuously or intermittently in the axial direction are provided on the outer peripheral surface of the synthetic resin layer 13 at appropriate intervals in the circumferential direction. .

When such a composite pipe 10 is used, each protrusion 13 in the synthetic resin layer 13 is removed when the end portion is expanded in diameter.
By crushing a, the portion where each protrusion 13a was provided can extend in the circumferential direction by a larger amount than other portions, and the amount of elongation in the circumferential direction in other portions can be reduced. As a result, the diameter reduction rate of the synthetic resin layer I3 after the diameter expansion force is removed from the diameter expanded end portion becomes small.

For example, in the case where the synthetic resin layer 13 is a hard vinyl chloride pipe with an outer diameter of 100+ am, when a diameter expansion force is applied so that the diameter expansion rate is 20%, each protrusion 13a is provided and each protrusion 13a is When the synthetic resin layer 13 is allowed to elongate in the circumferential direction by 30 to 50%, the change in the outer diameter of the synthetic resin layer 13 after the diameter expansion force is removed can be suppressed from 120 days to 118 days. As a result, peeling of the synthetic resin layer 13 is more reliably prevented, and furthermore, the adhesive layer 12 can be made thinner.

In order to suppress the diameter reduction of the synthetic resin layer 13 by causing the synthetic resin layer 13 to locally extend largely in the circumferential direction, a protrusion may be provided on the outer circumferential surface of the metal tube 11. As shown in FIG. 3, protrusions 21 may be provided on the outer peripheral surface of a mold 20 in shell expand molding, punch molding, or the like. No matter where the protrusion is provided, the synthetic resin layer 13 is locally crushed by the protrusion, and a larger elongation in the circumferential direction occurs in that part than in other parts, thereby reducing elongation in the circumferential direction in other parts. This suppresses the amount of diameter reduction of the synthetic resin layer 13 after the diameter expansion force is removed from the diameter expanded end.

(Effects of the Invention) As described above, the method for forming a socket for a composite pipe of the present invention has the advantage that the adhesive layer of the composite pipe in which the socket is to be formed at the end is an elastic adhesive layer that can be compressively deformed. Even if a cold diameter expanding force is applied to the end of the composite pipe, there is no risk of the adhesive layer breaking. In addition, since the adhesive layer can be elastically deformed, after the diameter expansion force is removed from the end of the composite pipe, the contraction force that remains inside the synthetic resin layer acts, causing the adhesive layer to follow suit. The diameter is reduced without any diameter-reducing force remaining inside the synthetic resin layer. As a result, there is no fear that the synthetic resin layer of the molded socket will peel off from the metal tube.

Figure 1 is a sectional view showing an example of the composite pipe used in the method of the present invention, and Figures 2 and 3 are respectively illustrative of other embodiments of the composite pipe used in the method of the present invention. FIG.

DESCRIPTION OF SYMBOLS 10... Composite pipe, 11... Metal tube, 12... Adhesive layer, 13... Synthetic resin layer, 20... Mold.

that's all

Claims (1)

[Claims] 1. By applying a diameter expanding force from inside the end of a composite pipe whose inner circumferential surface is coated with a synthetic resin layer via an adhesive layer in a cold state. A method for forming a socket of a composite pipe in which the diameter is expanded to form a socket, wherein the adhesive layer has an elastic force that does not break during diameter expansion, and the diameter reduction force that remains inside due to diameter expansion is suppressed. A method for forming a socket for a composite pipe, characterized in that the diameter is expanded by an amount corresponding to the amount by which the synthetic resin layer is reduced in diameter by following the adhesive layer and reduced in diameter by the adhesive layer.