JPH06147386A - Connecting structure for two-layer pipe - Google Patents

Abstract

PURPOSE:To increase the mechanical strength of a connection section by connecting the end sections of two-layer tubes constituted of outer layers made of a high-rigidity material and inner layers made of a thermoplastic resin with a pipe coupling, and fusing the thermoplastic resins of the inner layers butted in the pipe coupling. CONSTITUTION:When two-layer pipes 1, 2 constituted of outer layers 11, 21 made of heat-resistant polyvinyl chloride and inner layers 12, 22 made of polyvinylidene fluoride are to be connected, tip portions of the outer layers 11, 21 of the two-layer pipes 1, 2 are removed to expose the inner layers 21, 22. End sections of the two-layer pipes 1, 2 are heated across a heater 3 to melt the inner layers 12, 22, and the two-layer pipes 1, 2 are butted to fuse the inner layers 12, 22 immediately after the heater 3 is removed. A pipe coupling 4 having a two-piece structure and buried with a heating element 5 made of a Nichrome wire near the inner periphery is covered and fastened with a fastening tool 6. After the pipe coupling 4 is fitted to the outer periphery of a connection section, the heating element 5 is excited to melt the inner periphery of the pipe coupling 4, and the outer peripheries of the two-layer pipes 1, 2 are fused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-layer pipe connecting structure. More specifically, the present invention relates to a two-layer pipe connecting structure in which an outer layer made of a material having high rigidity and an end portion of a two-layer pipe made of a thermoplastic resin in which a substance is hard to elute are connected by a pipe joint.

[0002]

2. Description of the Related Art Conventionally, there are various connection structures for connecting thermoplastic resin pipes with a pipe joint. For example, there is a connection structure in which an end portion of a thermoplastic resin pipe connected to a pipe opening of a pipe joint is inserted, or conversely, a pipe opening of a pipe joint is inserted into a tip end portion of a thermoplastic resin pipe. However, in the connection structure of such a thermoplastic resin pipe, a step is formed on the inner surface of the connection portion between the thermoplastic resin pipe and the pipe joint, and when water is flowed, stagnation of water can be made in this step portion, and therefore, There is a problem that bacteria grow in the stagnation and the water quality deteriorates. Particularly, in the piping of an apparatus or the like for producing ultrapure water, the growth of this bacterium may be fatal.

Therefore, the connection structure of the thermoplastic resin pipes to be connected to the apparatus for producing ultrapure water is disclosed in JP-A-1-110.
As described in Japanese Unexamined Patent Publication No. 128 and Japanese Unexamined Patent Publication No. 2-266191, the tips of the pipes to be connected are heated and melted, and the tips are abutted and fused to each other. And, for this thermoplastic resin tube, a resin such as polyvinyl chloride having high rigidity that is resistant to external pressure and external damage is often used. This thermoplastic resin tube made of polyvinyl chloride, etc., is used in various pipes because it has high rigidity and does not rust, but there is an extremely small amount, but the plasticizer and stabilizer contained in the thermoplastic resin In many cases, lubricants and the like elute, and metal ions and the like contained in the stabilizer elute, which causes a problem of deteriorating water quality.

Further, among the thermoplastic resins and the like, there are thermoplastic resins in which the above substances are hardly eluted, but there is a problem that they are low in rigidity and expensive. Therefore, in an apparatus or the like for producing ultrapure water, it is usually conceivable to use a two-layer pipe using a highly rigid material for the outer layer and a thermoplastic resin for which the substance is difficult to elute in the inner layer. In addition, there are metal pipes and the like as pipes of highly rigid material, but metal is not preferable because it rusts or substances such as metal ions are eluted, but this metal is used as an outer layer and a thermoplastic resin that is hard to elute substances is used. Two-layer tubes with inner layers are also used. A method described in Japanese Patent Application Laid-Open No. 1-93697 is known for connecting a composite pipe using this metal or the like as a core material.

[0005]

The above-mentioned method of connecting thermoplastic resin pipes in which the tips are butted against each other and fused together is a preferred method in which no recess is formed on the inner surface of the connecting portion of the pipe body as in the prior art and water stagnation is small. However, the inventor tried to apply it to a double-layer pipe, but could not connect it well. That is, even if the thermoplastic resin of the inner layer is fused, the outer layer is not connected at the connecting portion, so that there is a problem that the mechanical strength of this connecting portion is small and easily broken. In addition, the outer layer is made of highly rigid thermoplastic resin,
Even if you try to fuse both by using a thermoplastic resin that the substance is difficult to elute in the inner layer, both the inner layer and the outer layer are good due to the difference in the melting temperature between the outer layer thermoplastic resin and the inner layer thermoplastic resin It could not be fused into a perfect state.

Further, the method of connecting a composite pipe having a metal or the like as a core material has the following problems. That is, when a high-rigidity thermoplastic resin is used for the pipe joint, the high-rigidity thermoplastic resin appears on the inner surface of the connection portion, and the substance elutes from the high-rigidity thermoplastic resin, and the substance is released to the pipe joint. The use of a thermoplastic resin that is difficult to elute has a problem that it is expensive and has low mechanical strength and is easily broken. Therefore, an object of the present invention is to provide a connection structure in which the thermoplastic resin of the inner layer of the two-layer pipe is integrally fused so that the outer layer is not exposed, and the mechanical strength of the connection portion is large.

[0007]

The present invention has been made to solve the above problems and achieve the above objects.
A connection structure of a two-layer pipe in which an end portion of a two-layer pipe composed of an outer layer made of a material having high rigidity and an inner layer made of a thermoplastic resin in which a substance is hard to elute is connected by a pipe joint. The ends of the two-layer pipes are inserted into the pipe openings at both ends of the pipe joint, the ends of the two inserted two-layer pipes are butted, and the thermoplastic resin of the inner layer is integrated at the butted parts. And the end portions of the two double-layer pipes are connected by the fusion of the thermoplastic resin and the pipe joint.

In the present invention, a highly rigid thermoplastic resin pipe joint is used for the pipe joint, the inner surface of the thermoplastic resin pipe joint is melted, and the inner surface of this pipe joint and the outer peripheral surface of the two-layer pipe are joined together. It is preferable to fuse them together, because the strength of this connecting portion is further increased. In the present invention, examples of the material having high rigidity include thermoplastic resins such as polyvinyl chloride and heat resistant polyvinyl chloride, and metals such as steel. Further, in the present invention, polyphenylene sulfide, polyvinylidene fluoride, etc. are suitable as the thermoplastic resin in which the substance is difficult to elute.

In the present invention, the ends of the two double-layer pipes are butted and the thermoplastic resin of the inner layer is integrally fused at the butted portions. However, the thermoplastic resin of the inner layer is fused to the outer layer. If you fold it into a brim to cover the end face of the and then fuse the flange face, the fusion area increases and the mechanical strength of the connection increases, and at the same time the end face of the outer layer is covered with the brim. In addition, the substance is not eluted from the outer layer, which is preferable. There are various construction methods for the connection structure of the two-layer pipe of the present invention,
Explaining a preferable method, the tip of the outer layer having high rigidity is removed, the thermoplastic resin of the inner layer is projected, and the thermoplastic resin is heated and melted. There is a method in which the thermoplastic resin of the inner layer is fused by inserting it into the pipe joint from the pipe opening of the above, butting the two-layer pipes against each other. At this time, the molten thermoplastic resin may be bent outward in a brim shape to cover the end face of the highly rigid outer layer, and then the thermoplastic resin of the inner layer may be fused.

As another method, first, the thermoplastic resin in the inner layer is melted, and the two-layer pipes are butted against each other and then fused.
There is also a method of attaching the pipe joint from the outside. At this time, using a thermoplastic resin pipe joint, after heating the inner surface of this pipe joint, immediately attached to the outer peripheral surface of the connection portion of the two-layer pipe,
The inner peripheral surface of the pipe joint and the outer peripheral surface of the two-layer pipe may be fused.
Furthermore, when using a pipe joint made of thermoplastic resin, a heating element such as a nichrome wire is embedded in the inner surface of the pipe joint, and after connecting the two-layer pipe by the above method, the heat generation of the nichrome wire or the like is performed. An electric current may be passed through the body to heat the body so that the inner surface of the pipe joint and the outer peripheral surface of the two-layer pipe are fused together.

[0011]

In the connecting portion of the two-layer pipe connecting structure of the present invention, since the two-layer pipes are butted and the thermoplastic resin in which the substance in the inner layer is difficult to elute is integrally fused, there is no step on the inner surface. ,
Therefore, the water quality does not deteriorate due to stagnation of water.
Further, since the thermoplastic resin in which the substance of the inner layer is difficult to elute is integrally fused as described above, the outer layer does not appear on the inner surface. Therefore, the substance does not elute from the outer layer and the water quality does not deteriorate.

In the present invention, a pipe joint is provided outside the connecting portion, and the ends of the two two-layer pipes are connected by this pipe joint and the fusion of the thermoplastic resin of the inner layer. The mechanical strength of the connecting portion is large, and the connecting portion does not break. In the present invention, when a pipe joint made of a highly rigid thermoplastic resin is used and the inner surface of the pipe joint is fused with the outer peripheral surface of the double-layer pipe, the mechanical strength of this connection portion becomes large.

[0013]

EXAMPLES Next, examples of the present invention will be shown. 1 and 2 show an embodiment of the present invention, FIG. 1 is a cross-sectional view showing a part of a connecting portion connecting two-layer pipes, and FIG. 2 shows a construction procedure of the connecting portion shown in FIG. Then, (a) is an explanatory view showing a state in which the end portion of the two-layer pipe is being heated, (b) is an explanatory diagram showing a state in which the two-layer pipes are butted, and (c) is a pipe joint attached to the connection part. It is explanatory drawing which shows the state which was opened. FIG. 3 shows another embodiment of the present invention and is an explanatory view showing a state in which a pipe joint is attached to a connecting portion of a two-layer pipe. FIG. 4 shows another embodiment of the present invention and is an explanatory view showing a state in which a two-layer pipe is connected. FIG. 5 shows still another embodiment of the present invention and is an explanatory view showing a state in which a two-layer pipe is connected.

1 and 2, reference numeral 1 denotes one of the two-layer pipes to be connected, and the two-layer pipe 1 comprises an outer layer 11 of heat-resistant polyvinyl chloride and an inner layer 12 of polyvinylidene fluoride. Two
Is the other two-layer pipe to be connected, and like the two-layer pipe 1, the two-layer pipe 2 is composed of an outer layer 21 of heat-resistant polyvinyl chloride and an inner layer 22 of polyvinylidene fluoride. 3 is a heater. Reference numeral 4 denotes a heat-resistant polyvinyl chloride pipe joint, and this pipe joint 4 has two cracks, and a heating element 5 made of a nichrome wire is embedded near the inner peripheral surface. 6
Is a fastener.

Next, this construction method will be described. As shown in FIG. 2A, the tip portions of the outer layers 11 and 12 of the two-layer pipes 1 and 2 are removed, and the inner layers 12 and 22 are projected on the end faces. Next, the heaters 3 are sandwiched, and the ends of the two-layer tubes 1 and 2 are heated to melt the inner layers 12 and 22. After that, the heater 3 was removed, and immediately, as shown in (b) of FIG.
The two-layer tubes 1 and 2 are butted against each other and the inner layers 12 and 22 are fused. As shown in (c) of FIG. 2, the outer peripheral surface of this connecting portion is covered with the pipe joint 4 and is tightened with the fastener 6, so that the pipe joint 4
After attaching to the outer peripheral surface of the connecting portion, an electric current is passed through the heating element 5.

Then, the inner peripheral surface of the pipe joint 4 is melted and the inner peripheral surface of the pipe joint 4 and the outer peripheral surface of the connecting portion of the two-layer pipes 1 and 2 are fused, and the mechanical strength of this connecting portion is large. Becomes In the connection structure thus connected, since the inner layers 12 and 22 are fused at the connection portion of the two-layer pipes 1 and 2, there is no step, and therefore, there is no stagnation of water and the water quality deteriorates. Never. Further, since the inner layers 12 and 22 are fused and the outer layers 11 and 21 are not exposed on the inner surface in this manner, the substance does not elute from the outer layer, and therefore the water quality does not deteriorate. or,
In this connection portion, since the fusion is connected to the pipe joint 4, the mechanical strength becomes large and this portion does not break.

Next, the embodiment shown in FIG. 3 will be described. Comparing the embodiment shown in FIG. 3 with the embodiment shown in FIGS. 1 and 2, the pipe joint 4a is formed by rotatably connecting side edges of a polyvinyl chloride component having a semicircular cross section, and a heating element is provided inside. The difference is that the outer layers 11a and 21a of the two-layer tubes 1a and 2a are made of polyvinyl chloride and the inner layers 12a and 22a are made of polyphenylene sulfide.

Explaining this construction method, the inner layer 12a is heated by a heater as in the embodiment shown in FIGS.
After bonding 22a, the outer peripheral surfaces of the connecting portions of the two-layer pipes 1a and 2a are heated and melted, and at the same time, the inner peripheral surface of the pipe joint 4a is heated and melted. Immediately thereafter, the pipe joint 4a is covered on the outer peripheral surface of the connecting portion, and the inner peripheral surface of the pipe joint 4a and the two-layer pipes 1a, 2
The outer peripheral surface of a is fused. As shown in FIG. 1, the inner peripheral surface of the pipe joint 4a is fused to the outer peripheral surfaces of the two-layer pipes 1a and 2a.
There is no deterioration in water quality as in the examples shown in FIGS.
The mechanical strength of this connection was great and it did not break.

Next, the embodiment shown in FIG. 4 will be described. In the embodiment shown in FIG.
After connecting in the same manner as in the embodiment shown in FIG. 2, the pipe joint 4b is attached to the connecting portion, the pull-out ring 7 is sandwiched, and the fastener 6b made of a cap nut is screwed into the pipe joint 4b and tightened.
Different to connect. Others are the same as the embodiment shown in FIGS.

Next, the embodiment shown in FIG. 5 will be described. In FIG. 5, the inner layers 12c and 22c of the two-layer pipes 1c and 2c are bent in a flange shape on the end faces of the outer layers 11c and 21c. Therefore, the fusion area of the inner layers 12c and 22c becomes large, and this mechanical strength is increased. Is large, the outer layers 11c and 21
Since the end of c is completely covered, the outer 11c is surely
21c differs from the examples shown in FIGS. 1 and 2 in that the substance is not eluted from 21c. Others are the same as the embodiment shown in FIGS.

[0021]

EFFECTS OF THE INVENTION In the connection portion of the double-layer pipe connection structure of the present invention, since the inner layer is integrally fused, there is no step, and since the outer layer is not exposed on this inner surface, the substance does not elute. Therefore, the water quality does not deteriorate, and it can be used with confidence in the piping of an apparatus or the like for producing ultrapure water. In addition, since the pipe joint and the fusion of the thermoplastic resin of the inner layer are connected at this connecting portion, the mechanical strength is high, and there is no fear of breaking at this connecting portion, which is safe.

If a pipe joint with high rigidity is used and the inner surface of this pipe joint and the outer peripheral surface of the double-layer pipe are fused, the mechanical strength of this connection portion becomes large, and therefore this connection portion is It is safe because it will not break or come off. in this way,
The connection structure of the double-layer pipe of the present invention is extremely valuable.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is a cross-sectional view showing a part of a connecting portion to which a two-layer pipe is connected.

FIG. 2 shows a procedure for constructing the connecting portion shown in FIG. 1, (a) is an explanatory view showing a state in which an end portion of the two-layer pipe is being heated, and (b) is a two-layer pipe. FIG. 3 is an explanatory view showing a state where they are butted, and (c) is an explanatory view showing a state where a pipe joint is attached to a connecting portion.

FIG. 3 shows another embodiment of the present invention and is an explanatory view showing a state in which a pipe joint is attached to a connecting portion of a two-layer pipe.

FIG. 4 shows another embodiment of the present invention and is an explanatory view showing a state in which a two-layer pipe is connected.

FIG. 5 shows still another embodiment of the present invention,
It is explanatory drawing which shows the state which connected the two-layer pipe.

[Explanation of symbols]

 1, 1a, 2c One-sided two-layer tube connected 11, 11a, 11c Outer layer 12, 12a, 12c Inner layer 2, 2a, 2c Another two-layered tube connected 21, 21a, 21c Outer layer 22, 22a, 22c Inner layer 3 Heater 4, 4a, 4b Pipe joint 5 Heating element 6, 6b Fastener

Claims (2)

[Claims] 1. A connection structure of a two-layer pipe in which an end portion of a two-layer pipe composed of an outer layer made of a material having high rigidity and an inner layer made of a thermoplastic resin in which a substance is difficult to elute is connected by a pipe joint. The ends of the two two-layer pipes to be connected are respectively inserted into the pipe openings at both ends of the pipe joint, the ends of the two inserted two-layer pipes are butted, and the butted portions of the inner layer A structure for connecting a two-layer pipe, characterized in that thermoplastic resins are fused together, and the ends of the two two-layer pipes are connected by the fusion of the thermoplastic resin and the pipe joint. 2. The pipe joint according to claim 1, wherein the pipe joint is made of a highly rigid thermoplastic resin, and the outer peripheral surface of the two-layer pipe and the inner peripheral surface of the pipe joint are fused to each other. Layered tube connection structure.