JP2000018461A - Connection structure for metal joint and plastic pipe, and method for connecting them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain connection structure for a metal joint and a plastic pipe with which they are inexpensively and surely connected to each other in a simple manner. SOLUTION: An outer diameter of a pipe insertion part 6 of a metal joint 2 is set a little larger than an inner diameter of a plastic pipe 3. An O-ring 8 is fitted to a portion near the base of the metal joint. An end of the plastic pipe 3 is press-fitted to the pipe insertion part 6. A metal cylindrical pressing member is externally press-fitted to the end of the plastic pipe 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection structure between a metal joint and a plastic pipe and a connection method therefor.

[0002]

2. Description of the Related Art A very difficult connection between a plastic pipe and a metal joint for passing high-pressure liquid is a problem due to the material of plastic. This is due to the poor precision of the plastic tube, loss of elasticity in the long run, and the formation of gaps due to differences in thermal expansion. As a conventional method of connecting a plastic pipe in consideration of such points, a heating element such as a heating wire is incorporated into a polyethylene joint, and an end of the plastic pipe is inserted into a pipe insertion portion of the joint. It is known that fusion bonding is performed by the heating element in a state.

[0003]

However, as described above, in the connection method using a polyethylene joint in which a heating element such as a heating wire is incorporated, the cost is inevitably increased due to the use of a special joint. Had to be high.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to propose a connection structure between a metal joint and a plastic pipe, which can be reliably and inexpensively connected by a particularly simple method, and a connection method thereof.

[0005]

According to a first aspect of the present invention, there is provided a connection structure between a metal joint and a plastic pipe according to the present invention. Is formed slightly larger than the inner diameter of the plastic pipe, and an O-ring is fitted near the base thereof, and the end of the plastic pipe is press-fitted into the pipe insertion portion, while the end of the plastic pipe is inserted outside the end. It is characterized in that a metal cylindrical pressing member is press-fitted.

A method for connecting a metal joint to a plastic pipe according to a second aspect of the present invention is characterized by comprising the following steps. (A) First step of heating the plastic pipe near its end by superheating means to make it softer. (B) The plastic pipe whose softened end is fitted with an O-ring near its base and the inner diameter of the plastic pipe Second step of press-fitting into the pipe insertion part of a metal joint having a slightly larger pipe insertion part. (C) Press-fitting the end of the plastic pipe into the pipe insertion part of the metal joint. A third step of press-fitting a metal cylindrical pressing member to the outer periphery of the pressing member through the pressing means in the state

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a connection structure between a metal joint and a plastic pipe according to the present invention. The connection structure 1 between the metal joint and the plastic pipe is a metal joint 2
, A plastic tube 3 and a metal-made cylindrical pressing member 4.

The plastic tube 3 will be described here. The material of the plastic tube 3 is formed of cross-linked polyethylene. A single-layer tube made entirely of cross-linked polyethylene, the inside is a cross-linked polyethylene layer, and the outside is Is constituted by a polyethylene layer which is not crosslinked.

[0010] The crosslinked polyethylene refers to polyethylene having a three-dimensional chemical bond (crosslinking) between molecules of polyethylene by using a specific means to increase the molecular weight.

Next, the metal joint 2 has a hollow shape, and a pipe insertion portion 6 is formed at a front portion with a polygonal flange portion 5 provided substantially at the center as a boundary, and at a rear portion. Is the pipe screwing part 7
Are formed.

The outer periphery of the pipe insertion portion 6 near the tip is formed in a substantially saw-tooth shape 6a in cross section, and a screw 7a is engraved on the outer circumference of the tube screwing portion 7 over the entire length. I have. A fitting groove 9 is provided around the outer periphery of the pipe insertion portion 6 near the rear, and an O-ring 8 is fitted in the fitting groove 9.

The joint 2 is preferably made of stainless steel or brass, but is not limited to this, and may be made of another metal. Further, the O-ring 8 is preferably formed of NBR (nitrile rubber), but is not limited thereto, and may be another rubber, resin, or the like.

Next, the outer diameter of the pipe insertion portion 6 of the metal joint 2 is formed to be slightly larger than the inner diameter of the plastic pipe 3 into which the end 3a is press-fitted. A pressing member 4 made of metal and having a cylindrical shape is provided outside the end 3a of the plastic tube 3 press-fitted into the tube insertion portion 6.
Is press-fitted.

The pressing member 4 is preferably made of stainless steel or brass, similarly to the joint 2 made of metal, but is not limited to this and may be made of another metal.

According to the connection structure 1 between the metal joint and the plastic pipe having the above-described structure, the end 3a of the plastic pipe 3 is press-fitted into the pipe insertion portion 6 of the metal joint 2, and the outside of the end 3a is inserted. Is made of metal and has a simple structure in which a cylindrical pressing member 4 is simply press-fitted.
Can be connected, and the cost can be reduced.

Further, since the O-ring 8 is interposed between the pipe insertion portion 6 of the joint 2 and the plastic pipe 3, the plastic pipe 3 loses elasticity due to long-term use. The O-ring 8 can prevent leakage even when a gap is formed between the plug-in portion 6 and the insertion portion 6.

Although the plastic tube 3 is made of cross-linked polyethylene, it is not limited to this, and may be made of another resin material similar to this.

Next, FIG. 4 shows a process chart of a method for connecting a metal joint and a plastic pipe according to the present invention, and the method for connecting the metal joint and the plastic pipe will be described with reference to this process chart.

First, the first step will be described. The plastic tube 3 is rotated while rotating.
Is heated by an overheating means 11 such as a heater to soften the vicinity of the end 3a. In this case, the superheat temperature is 100 degrees to 1 degree.
Optimally, it is within the range of 80 degrees.

The heating means 11 is not necessarily limited to a heater, but other means may be used.

Next, in the second step, the O-ring 8 is fitted into the fitting groove 9 provided near the base, and the plastic pipe 3 is softened by the first step. 3 is press-fitted into the tube insertion portion 6 of the metal joint 2 having the tube insertion portion 6 formed slightly larger than the inner diameter.

As a press-fitting method, an operation of touching the plastic pipe 3 with the hand and press-fitting the end 3a thereof into the pipe insertion section 6 is generally used, but the present invention is not limited to this. There may be.

Next, in a third step, in a state where the end 3a of the plastic pipe 3 is press-fitted into the pipe insertion portion 6 of the metal joint 2, a metal cylindrical presser is provided on the outer periphery of the end 3a. What is necessary is just to press-fit the attaching member 4 by the pressing means 12.

The pressing means 12 includes a hydraulic cylinder 12a,
A piston rod 12b and a pressing member 12c provided at the tip of the piston rod 12b are attached to a base 15 having a concave shape in a front view.

That is, the hydraulic cylinder 12a of the pressing means 12 is fixed to the upper outer side of one side 15a of the base 15, and the piston rod 12b of the hydraulic cylinder 12a is fixed.
And the pressing member 12c provided at the front end are arranged inside one side 15a of the base 15.

On the other side 15b of the base 15, a recess 16 is formed from the upper portion to the center portion.
Is for accommodating and supporting the plastic tube 3. Also, a tube holding member 18 having a through hole 17 larger than the outer diameter of the plastic tube 3 inside the other side 15b.
Is arranged.

The pipe holding member 18 is formed by two members 18a and 18b which can be divided vertically from the center, and the two members 18a and 18b are provided with appropriate means such as screws when the plastic tube 3 is movably pressed. (Not shown)
Has been fixed by.

In short, in the third step, when the end portion 3a of the plastic pipe 3 is press-fitted into the pipe insertion portion 6 of the metal joint 2, a metal-made cylindrical portion is formed around the end portion 3a. The pressing member 4 is set, and the plastic tube 3 is stored and supported in the concave portion 16 provided on the other side 15b of the base 15.

Next, in this state, the pipe threaded portion 7 of the joint 2 press-fitted into the end of the plastic pipe 3 is pressed by a pressing member 12c provided at the tip of the piston rod 12b of the hydraulic cylinder 12a. The plastic tube 3 is pushed rightward and moves. At this time, the rightward movement of the holding member 4 against the pipe holding member 18 is suppressed.

Further, by pressing the plastic tube 3 with the piston rod 12b, the pressing member 4 can be pressed into the outside of the end 3a of the plastic tube 3.

In this manner, the end 3 of the plastic tube 3
By press-fitting the pressing member 4 to the outside of the metal pipe 2, the inner surface of the end 3 a of the plastic pipe 3 becomes substantially saw-tooth-shaped in cross section 6 a formed on the outer circumference of the pipe insertion portion 6 of the metal joint 2. , So that the end 3a can be prevented from coming off and water can be stopped at the same time.

According to the method for connecting the metal joint to the plastic pipe in the above step, the vicinity of the end 3a of the plastic pipe 3 is heated by the heating means 11 to soften the end, and then the end 3a is connected to the pipe of the metal joint. Press into the insertion part 6. Then, the fitting and the plastic pipe can be easily connected only by press-fitting the metal-made cylindrical pressing member 4 to the outer periphery of the end portion 3a via the pressing means 12.

[0034]

As described above, according to the connection structure of the metal joint and the plastic pipe according to the first aspect, the end of the plastic pipe is press-fitted into the pipe insertion portion of the metal joint 2, and this end is inserted. With a simple structure in which a metal cylindrical pressing member is simply press-fitted to the outside of the portion, the joint and the plastic pipe can be reliably connected, and the cost can be reduced.

Further, since the O-ring is interposed between the pipe insertion part of the joint and the plastic pipe, the plastic pipe loses its elasticity due to long-term use, and a gap is formed between the plastic pipe and the pipe insertion part. When the O-ring occurs, leakage can be prevented by the O-ring.

According to the method for connecting a metal joint to a plastic pipe according to the second aspect, the vicinity of the end of the plastic pipe is overheated by an overheating means to soften the end, and the end is inserted into the pipe insertion portion of the metal joint. It can be easily connected by press-fitting and press-fitting a metal cylindrical pressing member to the outer periphery of the press-fitting member via pressing means.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a connection structure between a metal joint and a plastic pipe according to the present invention.

FIG. 2 is a longitudinal sectional view of a connection structure between the metal joint and a plastic pipe.

FIG. 3 is an enlarged view of a main part of a connection structure between a metal joint and a plastic pipe shown in FIG. 2;

FIG. 4 is a process diagram showing a method for connecting a metal joint and a plastic pipe according to the present invention.

[Explanation of symbols]

 2 Metal joint 3 Plastic tube 3a End 4 Pressing member 6 Pipe insertion portion 8 O-ring 12 Pressing means

Claims (2)

[Claims] 1. An outer diameter of a pipe insertion portion of a metal joint is formed to be slightly larger than an inner diameter of a plastic pipe, and an O-ring is fitted near a base thereof, and the pipe insertion portion is provided with the O-ring. A connection structure between a metal joint and a plastic pipe, characterized in that an end of the plastic pipe is press-fitted, and a metal cylindrical pressing member is press-fitted outside the end. 2. A method for connecting a metal joint to a plastic pipe, comprising the following steps. (A) First step of heating the plastic pipe near its end by superheating means to make it softer. (B) The plastic pipe whose softened end is fitted with an O-ring near its base and the inner diameter of the plastic pipe Second step of press-fitting into the pipe insertion part of a metal joint having a slightly larger pipe insertion part. (C) Press-fitting the end of the plastic pipe into the pipe insertion part of the metal joint. A third step of press-fitting a metal cylindrical pressing member to the outer periphery of the pressing member through the pressing means in the state