JPH10311482A - Thermally fusing joining method of small diameter plastic pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively and directly connect pipes to each other by heating a prescribed width of a contact plane of the pipes by inserting a thin inner cylinder pipe, whose outside diameter is adjusted to an inside diameter of the pipes, into the pipes, and remolding a melting resin. SOLUTION: An inner cylinder pipe 6 is formed of a stainless steel pipe, and is inserted so that a contact plane of polybutene pipes 1 is positioned in a central part of this inner cylinder pipe 6. Next, joining parts are lightly contacted with each other, and a prescribed width of its parts is heated by a semicircular heater, and after heating finishes, the heater is removed, and when the pipes are press-fitted at once in the shaft direction, a melting resin swells upward. After this is instantly compacted and cooled for a prescribed time by a semicircular metal mold having a prescribed width, metal mold and a joining tool are removed. Therefore, a socket and the like is wholly obviated, and they can be joined together only by using the inner cylinder pipe as a material, and when an elbow or a cheese or the like is also set to the same diameter as the pipes to be joined, they can be wholly joined together by a straight pipe not by fitting, and can be joined together regardless of accuracy of the pipes by making the most of a characteristic of fusion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a method for connecting a small-diameter pipe in place of a socket joint, a cheese, an elbow, and the like used in a piping work of a plastic pipe.

2. Description of the Related Art In connection of the above-mentioned plastic tube,
1. 1. A so-called electrofusion method using a socket in which a heating wire is buried in a coil shape (FIG. 1, hereinafter referred to as EF); 2. A heat fusion method (hereinafter referred to as HF) in which only the injection-molded socket is used without using a heating wire, and the inner diameter of the socket and the outer diameter of the pipe to be inserted are heated by a heater to perform heat fusion. O inside the socket
A method such as a mechanical method in which a ring and a claw for preventing detachment are incorporated and mechanically joined is used.

In the EF method, it is important that the diameters of the socket and the pipe to be inserted coincide with each other. If the pipe is thick, it cannot be inserted naturally, and if it is thin, the fusion is incomplete. Therefore, sockets for EF are made smaller than the diameter of the pipe, and the outer diameter of the pipe to be inserted is physically cut to fit the socket. This operation is troublesome, and the resistance of the coil is not constant depending on the type of the socket, and it is necessary to adjust the supplied current, so that the overall operation is not complicated. Sockets are also expensive. In the HF method, fitting is still important, and furthermore, it is a manual operation to heat each of the socket and the pipe, and reliable joining is difficult without skill.

[0003] In particular, in a small-diameter pipe, due to a slight overheating, the entire insertion portion of the pipe is melted and bent, and the joining fails. 3. The method described above has the simplicity of one-touch joining, but this also has a problem with the accuracy of the outer diameter of the pipe, and if it is not a pipe with strict accuracy higher than JIS standards, it will be a poorly reliable joining method and will cause water leakage . Such mechanical joints are also more expensive than EF or HF.

SUMMARY OF THE INVENTION The present invention solves the above problems and provides an inexpensive method for directly connecting pipes. Further, it is possible to connect even if the pipes have different diameters, regardless of the outer diameter accuracy of the pipes.

Since the pipes are directly connected to each other, the joint does not become thick as in the case of using a socket (FIG. 1), and the present invention enables a slim joint as shown in FIG.

The simplest fusion bonding without using sockets is possible if the cut surfaces are heated and pressed. However, in this case, the cross section of the joining surface has burrs protruding from the inner and outer surfaces as shown in FIG. 3, the burrs 7 on the inner surface impede the flow of fluid, and the burrs 7 'on the outer surface significantly impair the appearance.
In simple joining of pipes, centering is difficult unless there is a guide for accurately adjusting the position of the cut surface. The present invention has been made in view of these circumstances and aims to provide a simple, safe and inexpensive method. To solve the problem, the following means were used. First, in order to prevent burrs of the molten resin from coming out inside the pipe, a thin inner cylindrical pipe having an outer diameter corresponding to the inner diameter of the pipe as shown in FIG. Insert stainless steel (preferably stainless steel) into the pipe.

[0005] The inner tube also has the purpose of accurately aligning the pipe. In order to prevent axial displacement of the inner tube itself, a projection 8 having a thickness of about 1/3 or less of the thickness of the pipe is preferably provided at the center of the inner tube. The projection need not be on the entire circumference, but may simply stop the axial movement. This inner tube can also be of a coiled spring type (FIG. 4) to cope with large variations in the inner diameter accuracy of the pipe.
By making the diameter slightly larger than the inner diameter of the pipe to be joined, it is possible to cope with variations in the pipe by reducing the diameter when inserting.

[0006] Thus, the width of about 1 cm of the joint surface of the pipe into which the inner tube is inserted is heated. This state is schematically shown in FIG. Originally, it is theoretically necessary to heat only the circumferential joining surface. However, a thin pipe with a small diameter and a thin wall is melted to the periphery by heat conduction. In the present invention, this phenomenon is used in reverse to increase the heating width and re-mold the melted resin. Since it is meaningless if the heating width is too wide, a width appropriate for this joining step is set to 1/3 or less of the inner tube. Although various heating means are conceivable, here, it is assumed that a half heater (FIGS. 6 and 10) is applied to heat and melt. The size is about the same as a clothespin, and it is more convenient to incorporate a spring of appropriate strength.

This heating differs from the conventional delicate method in which only the skin of the fusion surface is melted like EF and HF, so that the entire wall thickness of the pipe is melted, so that the strength of the pipe in this portion becomes zero. Since the inner tube is at least three times as long as the fused portion, even in this molten state, it contributes to the alignment of the pipe. The temperature of the heater can be controlled by a thermostat or ordinary electronic control, but a simpler method is to use a PTC (self-control ceramic heater). The heater temperature is set to a melting temperature suitable for each resin. At the time of melting, remove the heater from the pipe. If the surface of the heater is subjected to Teflon processing or the like, it can be easily released from the molten resin. As soon as the heater is removed, the pipe is pressed so as to be pressed in the axial direction.
It becomes like 9.

Since the metal inner tube 6 is provided inside the pipe, entry of the molten resin is prevented. Although the purpose of joining can be achieved for the time being cooled in this state, it is not preferable from the viewpoint of aesthetics, and it is better not to have such bumps in handling the pipe. Therefore, when the mold shown in FIG. 5 is further sandwiched by a half mold at room temperature as shown in FIG. 6 and cooled, and the mold is removed, the shape shown in FIG. 2 is obtained. Of course, by changing the shape of the mold, the outer diameter of the joint portion 5 of the pipe can be arbitrarily set. If there is excess molten resin in the scale, it will protrude from the mold as burrs, which can be easily scraped off.
In addition, by providing a gap in the mold in advance, excess molten resin can be easily protruded.

In a more special case, the diameter of the joint (5 in FIG. 2) can be the same as that of the pipe. When the joint has the same diameter as the pipe, the area of the joint is reduced, so that the strength of the joint is usually uneasy. However, in the joining according to the present invention, the molten resin is remolded by applying pressure instead of mere fusion, and has the same strength as a pipe even with the same thickness as the pipe. But if you want to be more secure, you can do the following: That is to build up inside the pipe. In other words, when the inner tube is made into a spring type as shown in FIG. 4 and the protrusion of burrs from the cooling mold is reduced, excess molten resin is pressed into the inner tube and flows into the pipe as shown in FIG. Thicken the part.

[0010] According to this method, it is possible to perform joining without leaving any trace outside the pipe. Inside the pipe thickness 1
However, the resistance of the fluid that maintains strength and overcomes does not increase so much. The function of the inner tube according to the present invention ends when the fusion is completed. It is unnecessary, but the embedded one cannot be removed and will be permanently in the pipe. Therefore, the material of the inner cylinder should be selected so as to minimize the fluid resistance and to prevent corrosion. In the present invention, a thin stainless steel plate was selected. In this joining step, it is preferable to use a joining tool as shown in FIG. 7 to support the pipes mutually.

Reference numeral 14 denotes a pipe fixed by a fastener, and after heating is completed, the screw 12 is rotated so that the fasteners come closer to each other and press-fit the pipe. It exerts its power when an abnormal force is applied to a pipe at a work site or when work is performed at an unstable position.

In the method of joining straight pipes according to the present invention, no sockets are required at all, and the material is completed by using only the inner cylindrical pipe. If the elbow or the cheese is made to have the same diameter as the pipe to be joined, it can be carried out not by fitting but by joining all the straight pipes according to the present invention. The present invention, which makes full use of the characteristics of fusion, enables joining regardless of the accuracy of the pipe, and the conventional method of incomplete joining if there is no matching between the inner diameter of the sockets and the outer diameter of the pipe ( (EF, HF, mechanical).

[0012]

【Example】

Example 1 A polybutene pipe of 13 A (inner diameter 13, outer diameter 17) was joined. The inner tube is a stainless steel pipe having a thickness of 0.1 mm (length 50 mm, outer diameter 12.8). The polybutene pipe is inserted so that its joint is located at the center of the inner tube. Next, the joined portion was lightly contacted, and a portion having a width of 10 mm was heated by a semicircular heater (10 in FIG. 6). The inner diameter of the heater was 17 mm and the temperature was 240 ° C. The heating time is about 15 seconds. Immediately after the removal of the heater, when the pipe is pressed in the axial direction by about 5 mm, the molten resin rises as shown in FIG.

At this time, the mold was immediately pressed and cooled for about 15 seconds in a mold having a semicircular diameter of 30 mm in width. When the mold and the joining tool were removed, joining was completed in a shape as shown in FIG. Example 2 A polybutene pipe of 13A (inner diameter 13, outer diameter 17) and 10A (inner diameter 10, outer diameter 13) were joined. The inner tube may be modified, but in this case a straight tube of 10A was used. The thickness is a 0.1 mm stainless steel plate, and the length is 50 mm. The heater has a width of 5 for each of 13A and 10A.
mm and a stepped semicircular heater. Temperature is 250
° C, the heating time is 13 seconds,
mm and pressed and molded with a 30 mm wide tapered half mold.

The cooling time was 15 seconds, the result was as shown in FIG. 10, and different diameter joining was possible without a joint. Example 3 A 20 A (inner diameter 22, outer diameter 27) polybutene pipe was joined. The inner tube was a 0.12 mm stainless steel plate, a coiled spring as shown in FIG. 4, and a small projection 8 having a height of about 0.5 mm was provided at the center. The inner tube has an outer diameter of 23 mm and a length of 70 mm. The inner tube was reduced in diameter and inserted into the pipe, and a connector as shown in FIG. 7 was attached. Next, a heater 1 with a width of 15 mm
Heated at 1. The temperature was 260 ° C., and the pipe was crimped by removing the screw after 20 seconds, turning the screw 12 and pulling the fourteen fasteners by about 10 mm. Immediately, molding and cooling were performed using a semicircular mold 10 having a width of 30 mm in FIG. Twenty seconds later, it was removed and the joining was completed in the shape shown in FIG.

According to the present invention, the joining operation is improved in reliability,
The simplicity and economic efficiency were improved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a fusion model of a conventional electrofusion method.

FIG. 2 is an explanatory view of an embodiment according to the present invention.

FIG. 3 is an explanatory view of an embodiment before the fusion is improved.

FIG. 4 is an explanatory view of an inner tube essential to the present invention.

FIG. 5 is an explanatory view in the middle of a fusing step of the present invention.

FIG. 6 is an explanatory model diagram of a heater and a cooling mold according to the present invention.

FIG. 7 is a heating model diagram using the connector of the present invention.

FIG. 8 is a schematic diagram of a model using the connector of the present invention when cooled.

FIG. 9 is an explanatory view of another embodiment of the present invention.

FIG. 10 is an explanatory view of an embodiment of joining different diameter pipes according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pipe to be joined 2 Socket for EF 3 Terminal for heater 4 Heating wire 5 Fusion part according to the present invention 6 Inner tube 7 Outer burr 7 'Inner burr 8 Projection of inner tube 9 Molten resin in the process of carrying out the present invention 10 Heater And mold 11 Heater explanatory drawing 12 Screw 13 Heating wire 14 Pipe fixing fastener 15 Cooling mold model drawing 16 Molded fused resin inside pipe according to the present invention

Claims (5)

[Claims] 1. An inner tube is inserted between pipes to be joined, and after heating the joint of the pipes to the melting point of the plastic, the pipes are pressed in the axial direction, and the raised resin is clamped by a mold. And heat-bonding of small-diameter plastic pipes for molding and cooling. 2. Two semicircular heaters 10 are used as heating means, and the width of the heaters is about 1 / the width of the inner tube inserted into the pipes.
3. The fusion method according to claim 1, wherein the number is 3 or less. 3. The fusion welding method according to claim 1, wherein the pipes to be joined are fixed with fasteners, the fasteners are connected by support rods, and the pipes have a function of drawing them in the axial direction. 4. The fusion welding method according to claim 1, wherein a small projection (8 in FIG. 4) having a thickness of 1/3 or less of the pipe thickness is provided at a central portion of the inner cylindrical tube to prevent displacement. . 5. The method according to claim 1, wherein the inner tube is a coiled spring (FIG. 4).