JP2000110981A - Joining method for resin pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the formation of a bead on the pipe inside surface, and to enhance mechanical strength of the joining part by diametrically fixing a cylindrical body and two resin pipes by butting and fusing the mutual resin pipes in a state of inserting the cylindrical body into the resin pipes in an almost central position of the opposed two resin pipe end parts. SOLUTION: The end parts of resin pipes 1, 2 are heated and melted by a heater 3 in a state of inserting a cylindrical body 4 into the resin pipes 1, 2 in an almost central position of the end parts of the opposed two resin pipes 1, 2. The mutual end parts of the melted resin pipes 1, 2 are butted so that the pipe shaft direction coincide with each other, and are butted and joined by pressing the end parts in the axial direction toward a joining place from the respective resin pipes 1, 2. In this butting joining, a pipe outside surface side melting resin protruding when pressed in the axial direction becomes a bead 5, but a pipe inside surface side melting resin does not become a bead, and is filled in clearance between the resin pipes 1, 2 and the cylindrical body 4, so that the cylindrical body 4 and the two resin pipes 1, 2 can be diametrically fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for joining thermoplastic resin tubes. More specifically, the present invention relates to a method for joining thermoplastic resin tubes by heating and melting the ends of two thermoplastic resin tubes and abutting and fusing the melted ends together.

[0002]

2. Description of the Related Art Conventionally, thermoplastic resin pipes such as polyethylene, polybutene, polypropylene, and polyvinylidene fluoride have been widely used as fluid transport pipes such as gas pipes, water pipes, and drain pipes. There are various methods for joining such a thermoplastic resin tube. Among these various joining methods, butt joining (butt joining), in which the ends of two thermoplastic resin tubes are heated and melted, and these melted ends are joined together and pressed in the tube axis direction to join them, is widely performed. ing.

[0003]

In the above-mentioned butt joint of the prior art, when the resin is pressed in the tube axis direction, the molten resin protrudes into the inner surface and the outer surface of the tube to form a projection called a beat. Will happen.
Specifically, beads protruding to the inner surface in particular obstruct the flow of the fluid and cause an increase in flow resistance, solids in the fluid are caught on the inner bead, and especially when the fluid is water or hot water. In such a case, water or warm water stays in the bead portion on the inner surface, and bacteria proliferate, resulting in deterioration of water quality due to decay or the like.

In the butt joining, there is a joining method in which a ridge portion at a boundary between an end face and a surface of a thermoplastic resin pipe is removed and heated and melted, and the melted end faces are joined to prevent bead formation. In this joining method, since the ridge portion of the boundary between the end face and the surface of the thermoplastic resin pipe is removed, the amount of the thermoplastic resin to be melted at the end is reduced, and the bead generated at the joint is reduced. This is a preferred joining method. However, in this joining method, since the ridge portion between the end face and the surface is removed in advance, there is a problem that the mechanical strength of the joined portion is small and the joined portion is easily broken.

On the other hand, without removing the ridge portion at the boundary between the end face and the surface of the thermoplastic resin pipe, the end faces of the thermoplastic resin pipe cut perpendicularly to the pipe axis direction are welded and butt-joined. Although the connection can be made firmly and firmly, there is a problem that the mechanical strength is still insufficient and the joint portion is easily broken when an excessive load is applied.

As a method of preventing harmful bead formation on the inner surface of the pipe, an expandable inner peripheral support device is inserted into the pipe at the joint to press the inner surface of the pipe so that the molten resin protrudes toward the inner surface of the pipe. There is a technique that prevents the inner peripheral support device from shrinking, restoring and deforming after the fusion of the pipe end is completed, and then pulls the inner peripheral supporting device to the outside. However, many of these inner peripheral support devices use pressurized air or a heat-expandable medium that is electrically heated in order to press-contact and contract and restore the inner periphery of the pipe at the joint, which complicates the device and complicates operation. There's a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and is a method of heating and melting the ends of two thermoplastic resin pipes, and joining the thermoplastic resin pipes by abutting each other. An object of the present invention is to provide a joining method capable of reliably preventing harmful beads from being formed on the inner surface of a pipe. Another object of the present invention is to provide a bonding method in which the mechanical strength of a bonding portion is large.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and to achieve the above object.
In a method for joining resin tubes by heating and melting the ends of the two resin tubes to be joined and abutting the fused ends together, the ends of the two resin tubes are heated and melted, and the two opposed resin tubes are heated and melted. In a state where the cylindrical body is inserted into the resin pipe at a substantially central position of the end of the resin pipe, the resin pipes are butted and fused together, and the cylindrical body and the two resin pipes are fixed across. Further, in the present invention, the outer diameter of the cylindrical body is smaller than the inner diameter of the resin tube, and it is preferable that a ridge is provided on a substantially central outer periphery of the cylindrical body.

[0009]

[Operation] In the present invention, first, a cylindrical body is inserted inside two resin pipes, and the cylindrical body is arranged at a substantially central position of two opposite ends of the resin pipes, and the axes of the two ends are aligned. Prepare for butt fusion. Next, the ends of both thermoplastic resin tubes are heated and melted by a heater to soften them. The heater is removed, and the ends are abutted against each other in the axial direction and pressed to be fused. At about the same time, the pressed molten resin protrudes into the inside of the tube and fills the gap between the outer periphery of the cylindrical body and the inner periphery of the two resin tubes, so that the cylindrical body and the two resin tubes can be inserted and fixed. At that time, the molten resin that protrudes into the inside of the tube is consumed for filling the cylindrical body and the resin tube, and does not become a bead that projects into the tube. Further, if there is a ridge provided substantially at the outer periphery of the center of the cylindrical body, the molten resin is also filled around the ridge, so if the molten resin is cooled and solidified, the ridge of the cylindrical body and the resin pipe are formed. Are engaged with each other, and as a result, the joining strength between the two resin tubes can be improved.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a procedure of a method of joining a resin tube according to one embodiment of the present invention, and (a) is an explanatory view showing a state in which a cylindrical body is inserted into the resin tube and the resin tube is arranged.
(B) is an explanatory view showing a state in which the end of the resin tube is heated and melted, and (c) is an explanatory view showing a state in which the joining of the resin tube is completed. FIG. 2 shows another embodiment of the present invention, and is an explanatory view showing a state in which the joining of the resin pipe has been completed.

In FIG. 1, reference numeral 1 denotes one resin pipe to be connected, and 2 denotes another resin pipe to be connected. The material used for the resin tubes 1 and 2 is a thermoplastic resin. Examples of the thermoplastic resin include polyethylene, polybutene, polyvinyl chloride, and polypropylene. Polybutene is widely used for water supply and hot water supply. 3 is a heater. Reference numeral 4 denotes a cylindrical body, which is made of engineering plastic (for example, polyphenylene oxide) having a higher heat deformation temperature than the resin pipes 1 and 2 or a metal (for example, brass) having a high mechanical strength. Suitable.

Next, a method of joining the resin tubes 1 and 2 will be described. It is confirmed that the ends of the resin pipes 1 and 2 to be joined are cut at substantially right angles in the pipe axis direction. If it is not cut at a substantially right angle, the end of the resin tube is cut again to make a right angle, and as shown in FIG. 1, the cylindrical body 4 is inserted into the resin tube at a substantially central position between the ends of the two resin tubes. And resin pipes 1, 2
Are arranged to face each other. Next, the resin pipe 1,
2 and the heater 3 is disposed between the resin pipe 1 and the heater 3.
Then, as shown in FIG. 1B, the end of the resin tube is heated and melted. After that, the heater 3 is removed, and as shown in FIG. 1 (c), the ends of the melted resin pipes are butted so that the pipe axes coincide with each other. And butt-joined.

In this butt joining, the molten resin on the outer surface of the tube which is pressed and protruded in the axial direction becomes a bead 5, but the molten resin on the inner surface of the tube does not become a bead.
The gap between the cylinder 2 and the cylindrical body 4 is filled, and the cylindrical body 4 and the two resin tubes 1 and 2 can be fixed across. In this embodiment, as a method of heating and melting the ends of the two resin tubes, a method of heating by contacting a heated heater (heating plate) to both tube ends has been described. Either a method of heating with radiant heat or a method of heating by blowing hot air may be used, but a contact method that is not easily affected by ambient temperature or wind is more preferable.

Next, another embodiment shown in FIG. 2 will be described. Comparing the embodiment shown in FIG. 2 with the embodiment shown in FIG. 1, the embodiment shown in FIG. 2 is different from the embodiment shown in FIG.

In this embodiment, in the same manner as shown in FIG. 1, after melting the thermoplastic resin tube, the ends of the molten resin tube are butted together and pressed in the axial direction to make a butt-joint. The molten resin protruding to the surface side is filled in the gap between the resin pipes 1 and 2 and the cylindrical body 4, and is also filled around the ridge 4 a of the cylindrical body 4. 4 and the two resin tubes 1 and 2 can be more firmly inserted and fixed.

[0016]

As described above, according to the resin pipe joining method of the present invention, the ends of the resin pipes are abutted and fused, and at the same time, the cylindrical body is fixed across the two resin pipes. The mechanical strength of the joint can be increased by the synergistic effect, and the variation in the mechanical strength can be reduced. Further, by providing a protruding ridge having a saw-tooth shape substantially at the outer periphery of the center of the cylindrical body, the joining strength can be further increased. In addition, even when an external bending force is applied to the pipe after the pipe is laid, there is an effect that stress concentration at the joint can be prevented. On the other hand, as another effect, since the cylindrical body is inserted in advance into the two resin pipes, it is possible to eliminate the deviation of the axis between the ends.

Furthermore, since the molten resin that protrudes into the inside of the tube is consumed for filling the cylindrical body and the resin tube, and no bead protruding into the tube is generated, the flow resistance increases due to the bead and solid matter is deposited on the bead portion. It does not cause germ propagation or decay due to bacteria. Further, the presence of the cylindrical body makes it possible to easily prevent harmful bead formation on the inner surface of the pipe, and eliminates the need for a complicated inner peripheral support device and complicated operation required for preventing bead formation.

[Brief description of the drawings]

FIG. 1 is a view showing a procedure of a method of joining a resin pipe according to an embodiment of the present invention, wherein (a) is an explanatory view showing a state where a cylindrical body is inserted into the resin pipe and the resin pipe is arranged; () Is an explanatory view showing a state in which the end of the resin pipe is heated and melted, and (c) is an explanatory view showing a state in which the joining of the resin pipe is completed.

FIG. 2 illustrates another embodiment of the present invention, and is an explanatory view showing a state where joining of a resin tube is completed.

[Explanation of symbols]

1: One resin tube to be connected 2: The other resin tube to be connected 3: Heater 4: Cylindrical body 4a: Ridge 5: Bead

Claims (2)

[Claims] 1. A method for joining two resin tubes, wherein the ends of the two resin tubes to be joined are heated and melted, and the ends of the two melted resin tubes are abutted and fused. In a state where the cylindrical body is inserted into the resin pipe at substantially the center position of the two resin pipe ends facing each other, the resin pipes are butted and fused together and the cylindrical body and the two resin pipes are fixed across. To join resin pipes. 2. The joining of resin pipes according to claim 1, wherein an outer diameter of said cylindrical body is smaller than an inner diameter of said resin pipe, and a ridge is provided on a substantially central outer periphery of said cylindrical body. Method.