Connection method

Abstract

To provide a connection method which can inhibit formation of gaps and uneven protrusion of a resin.SOLUTION: In a step S10 in a connection method of the disclosure, a tube end 11a of a resin tube 11 and a tube end 12a of a resin tube 12 are heated. In a step S11, a stopper heat generation part 7 which is disposed at a stopper part 22 of an electric fusion joint 500 and includes a heating wire is energized to be heated. In a step S14, after the step S11, the tube end 11a of the resin tube 11 inserted into a joint socket part 23 of a cylindrical part 21 and the tube end 12a of the resin tube 12 inserted into a joint socket part 24 are fused to the stopper part 22 heated in the step S11. In a step S15, a socket heat generation part 3 which is disposed at the joint socket part 23 and includes a heating wire 31 is energized to fuse the joint socket part 23 and the resin layer 11 to each other and a socket heat generation part 4 which is disposed at the joint socket part 24 and includes the heating wire 31 is energized to fuse the joint socket part 4 and the resin tube 12 to each other.SELECTED DRAWING: Figure 18

Description

[Technical field]

[0001] The present disclosure relates to an electric fusion joint, a pipe connecting method, and a piping structure. [Background technology]

[0002] 2. Description of the Related Art Electric fusion joints are often used to connect pipes made of resin, such as resin pipes and metal-reinforced composite pipes having a resin layer and a metal reinforcing layer (see, for example, Patent Documents 1 and 2).

[0003] For example, the electric fusion joint shown in Patent Document 1 has a joint body made of thermoplastic resin with pipe receptacles formed at both ends into which the pipe to be connected is inserted, and a stopper portion protruding inward from the inner peripheral surface of the joint body. The stopper portion regulates the position of the pipe inserted into the pipe receptacle. A heating element is provided in each of the pipe receptacle and the stopper portion, and by generating heat from the heating elements, the resin around the heating element and the resin of the pipe are fused together, connecting the electric fusion joint and the pipe.

[0004] For example, the electric fusion pipe joint shown in Patent Document 2 is a joint for butt-joining two thermoplastic pipes, and includes a ring-shaped body made of thermoplastic plastic having inner and outer diameters equal to those of the pipes to be joined, an electric heating wire laid on the end face of the ring-shaped body, and a terminal for supplying electricity to the electric heating wire. The joint and the pipes are fused by heating the electric heating wire with the pipes in contact with the ring-shaped body. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-87286 [Patent Document 2] Japanese Patent Application Publication No. 9-144983 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Patent Document 1, because two fusions are performed simultaneously at the stopper and the pipe socket, the air trapped between the two expands due to heat, making the resin more likely to spurt out, and the height of the resin swelling inward can become uneven in the circumferential direction. Also, if air gets mixed in with the resin and the mixed air expands and bursts, a depression can form in the resin swelling inward.

[0007] Furthermore, in Patent Document 2, butt fusion is performed using an electric fusion joint, which can make it difficult to heat sufficiently, resulting in the formation of gaps (crevices).

[0008] When uneven resin mounds or crevices are formed, turbulence occurs, which makes it easier for some water or chemicals to stagnate in the piping. This can lead to the proliferation of microorganisms, causing a deterioration in water quality, or the deterioration of chemicals, which can reduce purity, which can lead to a decrease in product yield in piping used in semiconductor manufacturing, etc.

[0009] An object of the present disclosure is to provide a connection method and a piping structure that can suppress the formation of gaps and uneven resin swelling. [Means for solving the problem]

[0010] In order to achieve the above object, a connection method according to a first aspect includes a tube end heating step, a first fusion step, a second fusion step, and a third fusion step. The tube end heating step heats a tube end of a first tube containing a thermoplastic resin and a tube end of a second tube containing a thermoplastic resin. The first fusion step, after the tube end heating step, brings the tube end of the first tube inserted inside a first joint socket provided at one of both ends of the electric fusion joint into contact with the tube end of the second tube inserted inside a second joint socket provided at the other end inside the electric fusion joint to fuse the tube ends together. The second fusion step passes electricity through a first socket heating section that is disposed in the first joint socket and includes a heating wire to fuse the first joint socket and the first tube. In the third fusion step, a current is passed through a second socket heating portion that is disposed in the second joint socket and includes a heating wire, thereby fusing the second joint socket and the second pipe.

[0011] In this way, after the pipe ends of the first pipe and the second pipe are fused together, the outer peripheral surface of the first pipe and the inner peripheral surface of the first fitting socket portion, and the outer peripheral surface of the second pipe and the inner peripheral surface of the second fitting socket portion are fused together, allowing the expanded air to escape and not be trapped, making it possible to make the height of the resin rising inward uniform.

[0012] Since the end of the first tube and the end of the second tube are joined by butt fusion, gaps are less likely to occur between the first tube and the second tube than in the past when fusion is performed only by heating an electric heating wire.

[0013] In addition, butt fusion can reduce the size of the bead because air is not trapped in the joint. Conventionally, resin in an electric fusion joint other than the stopper melts and is incorporated into the bead resin, but butt fusion suppresses melting of resin other than the stopper, allowing the bead to be smaller.

[0014] The connection method according to the second aspect includes a tube end heating step, a stopper heating step, a first fusion step, a second fusion step, and a third fusion step. The tube end heating step heats a tube end of a first tube containing a thermoplastic resin and a tube end of a second tube containing a thermoplastic resin. The stopper heating step heats the stopper by passing electricity through a stopper heating part including a heating wire, which is disposed on an inner surface of a cylindrical part of an electric fusion joint so as to protrude inward. The first fusion step fuses, to the stopper part, a tube end of the first tube inserted into a first fitting receptacle disposed on one of both ends of the cylindrical part, and a tube end of the second tube inserted into a second fitting receptacle disposed on the other end of the cylindrical part, after the tube end heating step. The second fusion step fuses the first fitting receptacle and the first tube by passing electricity through a first receptacle heating part disposed on the first fitting receptacle and including a heating wire. In the third fusion step, a current is passed through a second socket heating portion that is disposed in the second joint socket and includes a heating wire, thereby fusing the second joint socket and the second pipe.

[0015] In this way, after the pipe ends of the first pipe and the second pipe are fused to the stopper portion, the outer peripheral surface of the first pipe and the inner peripheral surface of the first fitting receptacle portion, and the outer peripheral surface of the second pipe and the inner peripheral surface of the second fitting receptacle portion are fused together, allowing the expanded air to escape and not be trapped, making it possible to make the height of the resin rising inward uniform.

[0016] Not only is the stopper portion heated, but the ends of the first and second tubes are also heated and fused to the stopper portion, making it less likely that gaps will form between the first and second tubes than in the conventional method of fusing them together by simply heating an electric heating wire.

[0017] Also, by performing butt welding, the beads can be made smaller.

[0018] A connecting method according to a third aspect is the connecting method according to the second aspect, in which the first fusion step is carried out after the current supply to the heat generating portion of the stopper in the stopper heating step is terminated.

[0019] In this manner, after the heating of the stopper portion is completed, the heated tube ends of the first tube and the second tube are fused to the stopper portion, so that the occurrence of gaps can be suppressed.

[0020] A connecting method according to a fourth aspect is the connecting method according to any one of the first to third aspects, in which the second fusion step and the third fusion step are carried out simultaneously. This makes it possible to simultaneously fuse the first joint socket portion and the first pipe, and the second joint socket portion and the second pipe. A piping structure according to a fifth aspect includes a first pipe, a second pipe, and an electric fusion joint. The first pipe includes a thermoplastic resin. The second pipe includes a thermoplastic resin. The electric fusion joint has a first joint socket portion into which the first pipe is inserted, a second joint socket portion into which the second pipe is inserted, a first socket heating portion disposed in the first joint socket portion and including a heating wire, and a second socket heating portion disposed in the second joint socket portion and including a heating wire. The pipe ends of the first pipe and the pipe ends of the second pipe are butted against each other inside the electric fusion joint and fused to each other.

[0021] After the pipe ends of the first pipe and the second pipe are fused together, the outer peripheral surface of the first pipe and the inner peripheral surface of the first fitting socket portion, and the outer peripheral surface of the second pipe and the inner peripheral surface of the second fitting socket portion can be fused together, so that air is not trapped and the height of the resin rising inward can be made uniform.

[0022] Since the end of the first tube and the end of the second tube are joined by butt fusion, gaps are less likely to occur between the first tube and the second tube than in the past when fusion is performed only by heating an electric heating wire. Effect of the Invention

[0023] According to the present disclosure, it is possible to provide a connection method and a piping structure that are capable of suppressing the formation of gaps and uneven resin swelling. [Brief description of the drawings]

[0024] [Figure 1] 1 is an external view showing an electric fusion joint, a resin tube connected to the electric fusion joint, and a resin tube in a first embodiment according to the present disclosure. FIG. [Diagram 2] 1 is a cross-sectional view showing an electric fusion joint according to a first embodiment of the present disclosure. [Diagram 3] 4 is a cross-sectional view showing a state in which a resin tube and a resin tube are inserted into an electric fusion joint according to the first embodiment of the present disclosure. FIG. [Figure 4] 3 is a schematic diagram of an electric fusion joint showing the connection relationship between a socket heating portion and a stopper heating portion of the electric fusion joint and a connector attachment portion in the first embodiment of the present disclosure. FIG. [Diagram 5] FIG. 2 is a perspective view showing a jig used in the connection method according to the first embodiment of the present disclosure. [Figure 6] 1 is a perspective view showing a state in which an electric fusion joint and two plastic tubes are attached to a jig in a connection method in a first embodiment according to the present disclosure. [Figure 7] 1 is a front view showing a state in which an electric fusion joint and two plastic tubes are attached to a jig in a connection method in a first embodiment according to the present disclosure. [Figure 8]FIG. 4 is a flow diagram showing a connection method according to the first embodiment of the present disclosure. [Figure 9] FIG. 1A is a diagram for explaining heating of a tube end of a plastic tube in the connection method according to the first embodiment of the present disclosure; FIG. 1B is a diagram for explaining insertion of a plastic tube into an electric fusion joint in the connection method according to the first embodiment of the present disclosure. [Figure 10] (a) A diagram for explaining the fusion of the pipe ends of plastic pipes in the connection method of embodiment 1 according to the present disclosure, and (b) A diagram for explaining the fusion between a fitting socket portion of an electric fusion fitting and a plastic pipe in the connection method of embodiment 1 according to the present disclosure. [Figure 11] Schematic diagram showing a bead of uniformly raised resin. [Figure 12] FIG. 11 is a cross-sectional view showing an electric fusion joint according to a second embodiment of the present disclosure. [Figure 13] FIG. 11 is a cross-sectional view showing a state in which a resin tube and a resin tube are inserted into an electric fusion joint according to a second embodiment of the present disclosure. [Figure 14] 11 is a schematic diagram of an electric fusion joint showing the connection relationship between a socket heating portion and a stopper heating portion of the electric fusion joint in a second embodiment according to the present disclosure and two connector attachment portions having a pair of pins. FIG. [Figure 15] FIG. 11 is a flow diagram showing a connection method according to a second embodiment of the present disclosure. [Figure 16] FIG. 13A is a diagram for explaining heating of a pipe end of a resin pipe in a connection method according to a second embodiment of the present disclosure; FIG. [Figure 17] (a) A diagram for explaining the insertion of a plastic tube into an electric fusion joint in a connection method of embodiment 2 according to the present disclosure, and (b) a diagram for explaining the fusion of a stopper portion of the electric fusion joint and a tube end of a plastic tube in a connection method of embodiment 2 according to the present disclosure. [Figure 18] 13 is a diagram for explaining fusion between a joint socket portion of an electric fusion joint and a pipe end of a plastic pipe in a connection method according to a second embodiment of the present disclosure. FIG. [Figure 19] FIG. 4 is a cross-sectional view showing the configuration of an electric fusion joint of a comparative example. [Figure 20]5(a) and 5(b) are diagrams for explaining the fusion process in an electric fusion joint of a comparative example. [Figure 21] FIG. 13 is a schematic diagram showing a state in which the resin is unevenly raised. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0026] (Embodiment 1) The piping structure and the connection method according to the first embodiment of the present disclosure will be described below.

[0027] <Configuration> (Outline of piping structure 100) 1 is an exploded view of a piping structure 100 according to a first embodiment of the present disclosure. The piping structure 100 according to the first embodiment includes an electric fusion joint 1, a resin pipe 11 (an example of a pipe containing a thermoplastic resin), and a resin pipe 12 (an example of a pipe containing a thermoplastic resin).

[0028] As shown in the figure, the electric fusion joint 1 is fused to a resin pipe 11 and a resin pipe 12 to connect the resin pipe 11 and the resin pipe 12 .

[0029] The resin pipe 11 and the resin pipe 12 are each made of a thermoplastic resin.

[0030] Flow paths 11f, 12f having a circular cross section extend inside resin pipe 11 and resin pipe 12. Flow path 1f having a circular cross section extends inside electric fusion joint 1. When resin pipe 11 and resin pipe 12 are connected by electric fusion joint 1, the axes of the flow paths of resin pipe 11, resin pipe 12, and electric fusion joint 1 are aligned on the same straight line.

[0031] The direction in which the axis of each of the flow paths of the electric fusion joint 1, the plastic pipe 11, and the plastic pipe 12 extends is defined as the axial direction A. In the electric fusion joint 1, the plastic pipe 11, and the plastic pipe 12, the direction perpendicular to each axis and moving toward or away from each other is defined as the radial direction B, and the direction rotating around each axis is defined as the circumferential direction C.

[0032] The resin pipe 11 moves in the direction of arrow A1 relative to the electric fusion joint 1 in the axial direction A to be connected to the electric fusion joint 1. Moreover, the resin pipe 12 moves in the direction of arrow A2 relative to the electric fusion joint 1 in the axial direction A to be connected to the electric fusion joint 1. The state in which the resin pipe 11 and the resin pipe 12 are connected to the electric fusion joint 1 constitutes the piping structure 100.

[0033] FIG. 2 is a diagram showing a cross-sectional configuration of the electric fusion joint 1. As shown in FIG.

[0034] As shown in FIGS. 1 and 2, the electric fusion joint 1 has a cylindrical portion 21, socket heating portions 3 and 4, and a connector attachment portion 5.

[0035] (Cylindrical portion 21) The cylindrical portion 21 is made of a thermoplastic resin, and is formed into a cylindrical shape as shown in FIG. 2. One end of the cylindrical portion 21 along the axial direction A is called end 21b, and the other end is called end 21c. The cylindrical portion 21 has a fitting receptacle portion 23 and a fitting receptacle portion 24. The resin pipe 11 is inserted into the inside of the fitting receptacle portion 23. The resin pipe 12 is inserted into the inside of the fitting receptacle portion 24. The fitting receptacle portion 23 is provided on the opposite side of the fitting receptacle portion 24. The fitting receptacle portion 23 is a portion of the cylindrical portion 21 on the end 21b side, and the fitting receptacle portion 24 is a portion of the cylindrical portion 21 on the end 21c side. The end of the fitting receptacle portion 23 opposite to the end 21b is connected to the end of the fitting receptacle portion 24 opposite to the end 21c.

[0036] The thermoplastic resin used in the cylindrical portion 21 is not particularly limited, but preferably has a melting point of less than 230° C. In the present embodiment 1, for example, polyethylene is used as the thermoplastic resin. In addition, the thermoplastic resin is not particularly limited, and for example, an olefin resin, polyvinyl chloride resin, etc. can be used.

[0037] The polyolefin resin is not particularly limited, but examples thereof include polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, and ethylene-α-olefin copolymer. From the viewpoint of more effectively increasing the strength, dimensional stability, and elongation at high temperatures of the multilayer pipe material, polyethylene or polypropylene is preferred, and polyethylene is more preferred.

[0038] Examples of the polyethylene (PE) include LDPE, LLDPE, HDPE, etc. From the viewpoint of more effectively increasing the strength of the multilayer pipe material, HDPE is more preferred.

[0039] FIG. 3 is a cross-sectional view showing the state in which the resin pipe 11 is inserted into the inside of the joint socket portion 23 of the electric fusion joint 1, and the resin pipe 12 is inserted into the inside of the joint socket portion 24. As shown in FIG.

[0040] The inner diameter of the joint socket portion 23 is formed to be equal to or larger than the outer diameter of the resin pipe 11. The inner diameter of the joint socket portion 24 is formed to be equal to or larger than the outer diameter of the resin pipe 12.

[0041] (Inlet heating parts 3 and 4) FIG. 4 is a schematic diagram of electric fusion joint 1 showing the connection relationship between socket heating parts 3 and 4 and connector attachment part 5.

[0042] 2 and 4, the socket heating portion 3 is provided in the joint socket portion 23. The socket heating portion 4 is provided in the joint socket portion 24.

[0043] The socket heating section 3 has a heating wire 31 embedded in the inner surface 21a at the joint socket section 23. The socket heating section 4 has a heating wire 31 embedded in the inner surface 21a at the joint socket section 24. The heating wire 31 is arranged so as to be wound circumferentially along the inner surface 21a at the joint socket section 23 and the joint socket section 24. The heating wire 31 is arranged in the vicinity of the inner surface 21a. The heating wire 31 may be embedded in the tubular section 21 so as to be partially exposed on the flow path 1f side, or may be completely embedded.

[0044] The portion of the heating wire 31 arranged at the joint receptacle 23 is referred to as heating wire portion 31a, and the portion of the heating wire 31 arranged at the joint receptacle 24 is referred to as heating wire portion 31b. The heating wire portion 31a and the heating wire portion 31b of the heating wire 31 are connected by heating wire portion 31c arranged to wind around in the circumferential direction. The heating wire portion 31c does not have to be arranged to wind around, and may be arranged parallel to the axial direction A, for example, as shown in Fig. 14 described later.

[0045] In this embodiment, a single heating wire 31 is arranged across the joint receptacle portion 23 and the joint receptacle portion 24, but each of the heating wire portion 31a and the heating wire portion 31b may be composed of separate heating wires, and these heating wires may be connected.

[0046] The heating wire 31 preferably has a conductor and an insulating coating, but may have only a conductor and not have an insulating coating. The conductor may be, for example, a nichrome wire, an iron-chromium type 2 wire, an iron-chromium type 1 wire, or a nickel-chromium wire. The insulating coating is provided so as to cover the periphery of the conductor. If the heating wire 31 is provided with an insulating coating, the melting point of the insulating coating is preferably 230 degrees or higher. This is because the melting point of the insulating coating is preferably set to a temperature at which the thermoplastic resin does not melt even at a temperature at which the thermoplastic resin melts in this embodiment (for example, in the case of polyethylene, the heating wire is heated to 220 degrees). The insulating coating can be formed of, for example, a fluorine-based resin or an imide-based resin, but it is more preferable to form it of a polyimide-based resin. For example, the thickness of the conductor may be set to 0.1 mm or more and 10 mm or less. The heating wire 31 generates heat at about 180 degrees to 230 degrees.

[0047] The following describes the arrangement of the heating wires 31 in the receiving port heating parts 3 and 4. The receiving port heating parts 3 and 4 are provided symmetrically with respect to the center of the cylindrical part 21.

[0048] In the joint socket portion 23, the heating wire 31 is wound eight times so as to come into contact with the joint socket portion 23. In the joint socket portion 24, the heating wire 31 is wound eight times so as to come into contact with the joint socket portion 23.

[0049] As shown in FIG. 2, a predetermined distance L0 is provided in the axial direction A between the heating wire portion 31a of the receiving port heating portion 3 and the heating wire portion 31b of the receiving port heating portion 4.

[0050] In order to generate heat in the receiving port heating portions 3 and 4, the clearance W1 (see Figure 3) between the inner surface 21a of the fitting receiving port portion 23 and the outer surface of the plastic pipe 11 and the clearance W1 between the inner surface 21a of the fitting receiving port portion 24 and the outer surface of the plastic pipe 12 are filled with molten resin, and the fitting receiving port portion 23 and the plastic pipe 11, as well as the fitting receiving port portion 24 and the plastic pipe 12 are fused together.

[0051] (Connector mounting part 5) 2 and 4, the connector attachment portion 5 has two pins 51b, 51c (one example of a pair of first terminals). The two pins 51b, 51c are provided so as to protrude radially outward from the outer surface 21d of the cylindrical portion 21. As shown in FIG. 2, one of the two pins 51b, 51c, the pin 51b, is disposed near the end 21b of the cylindrical portion 21, and the other pin 51c is disposed near the end 21c.

[0052] The end of heating wire portion 31a of heating wire 31 on the end 21b side is connected to pin 51b. The end of heating wire portion 31b of heating wire 31 on the end 21c side is connected to pin 51c. By attaching a connector of an electric fusion device to pins 51b and 51c and passing electricity through them, the socket heating parts 3 and 4 can be heated.

[0053] <Jig 200> Next, a jig 200 used in the connection method of the embodiment according to the present disclosure will be described. A plastic pipe 11, an electric fusion joint 1, and a plastic pipe 12 are arranged in the jig 200. Fig. 5 is a diagram showing the jig 200. Fig. 6 is a diagram showing the state in which the plastic pipe 11, the electric fusion joint 1, and the plastic pipe 12 are attached to the jig 200. Fig. 7 is a side view of Fig. 6.

[0054] The jig 200 includes a first clamp portion 210, a second clamp portion 220, a shaft portion 230, a pressing portion 240, a restricting portion 250, and a base 260.

[0055] (Pedestal 260) The base 260 is a plate-shaped member and supports the first clamp portion 210, the second clamp portion 220, the shaft portion 230, the pressing portion 240, and the restricting portion 250, which are arranged on the upper surface side of the base 260.

[0056] (First clamp portion 210) The first clamp portion 210 clamps and fixes the resin pipe 11. The first clamp portion 210 has a lower clamp portion 211, an upper clamp portion 212, a hinge portion 213, a fastening portion 214, and a bearing portion 215. The lower clamp portion 211 is a member having a semicircular recess 211a formed on its upper surface. In this embodiment, the lower clamp portion 211 is a roughly rectangular parallelepiped member having a semicircular recess formed on its upper surface.

[0057] The bearing portion 215 is provided in the lower clamp portion 211. The bearing portion 215 is inserted into a through hole formed in the lower clamp portion 211. The bearing portion 215 is disposed below the recessed portion 211a. The shaft portion 230, which will be described later, is inserted into the inside of the bearing portion 215. The axial direction of the bearing portion 215 is disposed parallel to the central axis of the recessed portion 211a. This allows the first clamp portion 210 to move along the shaft portion 230. In a state in which the resin tube 11, the resin tube 12, and the electric fusion joint 1 are placed in the jig, the axial direction of the bearing portion 215 is parallel to the axial direction A.

[0058] The upper clamping portion 212 is a member in which a semicircular recess 212a is formed. In this embodiment, the upper clamping portion 212 is a member in a roughly rectangular parallelepiped shape in which the semicircular recess 212a is formed on a predetermined surface. The upper clamp part 212 and the lower clamp part 211 can clamp the outer periphery of the resin pipe 11 with the recesses 212a and 211a formed therein. When the resin pipe 11 is clamped, the central axes of the recesses 212a and 211a roughly coincide. Furthermore, when the resin pipe 11 is clamped, this central axis coincides with the axial direction A described above.

[0059] The hinge portion 213 rotatably connects the ends of the lower clamp portion 211 and the upper clamp portion 212. The upper clamp portion 212 is configured to be rotatable relative to the lower clamp portion 211 around the hinge portion 213. The upper clamp portion 212 is attached to the lower clamp portion 211 via the hinge portion 213 such that, when the upper clamp portion 212 rotates around the hinge portion 213, its recess 212a faces the recess 211a of the lower clamp portion 211.

[0060] With the lower clamp part 211 and the upper clamp part 212 spaced apart about the hinge part 213, the resin pipe 11 is placed along the recess 211a of the lower clamp part 211. After that, the upper clamp part 212 rotates about the hinge part 213, and the resin pipe 11 is placed so as to fit into the recess 212a.

[0061] The fastening portion 214 is a so-called snap lock. The fastening portion 214 has a lock body 214a and a protrusion 214b. The fastening portion 214 is provided on the opposite side of the hinge portion 213 across the recesses 211a, 212a of the lower clamp portion 211 and the upper clamp portion 212. The lock body 214a is disposed on the side of the lower clamp portion 211, and the protrusion 214b is disposed on the side of the upper clamp portion 212. The lock body 214a has a lever 214c and an annular portion 214d. In a state where the upper clamp portion 212 is rotated to the upper side of the lower clamp portion 211, the annular portion 214d is hooked onto the protrusion 214b and the lever 214c is tilted downward, so that the upper clamp portion 212 can be fastened to the lower clamp portion 211 in a closed state.

[0062] (Second clamp portion 220) The second clamp part 220 clamps and fixes the resin pipe 12. The second clamp part 220 fixes the resin pipe 12 so that the central axis of the resin pipe 12 coincides with the central axis of the resin pipe 11.

[0063] The second clamp portion 220 has a lower clamp portion 221, an upper clamp portion 222, a hinge portion 223, and a fastening portion 224. The lower clamp portion 221 is a member having a semicircular recess 221a formed on its upper surface. In this embodiment, the lower clamp portion 221 is a roughly rectangular parallelepiped member having a semicircular recess formed on its upper surface. The lower clamp portion 211 is fixed to the base 260 via a bracket 270.

[0064] The upper clamping portion 222 is a member in which a semicircular recess 222a is formed. In the present embodiment, the upper clamping portion 222 is a roughly rectangular parallelepiped member in which the semicircular recess 222a is formed on a predetermined surface. The upper clamp part 222 and the lower clamp part 221 can clamp the outer periphery of the resin pipe 12 with the recesses 222a and 221a formed therein. When the resin pipe 12 is clamped, the central axes of the recesses 222a and 221a roughly coincide. Furthermore, when the resin pipe 12 is clamped, this central axis coincides with the axial direction A described above.

[0065] The hinge portion 223 rotatably connects the ends of the lower clamp portion 221 and the upper clamp portion 222. The upper clamp portion 222 is configured to be rotatable relative to the lower clamp portion 221 around the hinge portion 223. The upper clamp portion 222 is attached to the lower clamp portion 221 via the hinge portion 223 such that, when the upper clamp portion 222 rotates around the hinge portion 223, its recess 222a faces the recess 221a of the lower clamp portion 221.

[0066] With the lower clamp part 221 and the upper clamp part 222 spaced apart about the hinge part 223, the resin pipe 12 is placed along the recess 221a of the lower clamp part 221. After that, the upper clamp part 222 rotates about the hinge part 223, and the resin pipe 12 is placed so as to fit into the recess 222a.

[0067] The fastening portion 224 is a so-called snap lock. The fastening portion 224 has a lock body 224a and a protrusion 224b. The fastening portion 224 is provided on the opposite side of the hinge portion 223 across the recesses 221a, 222a of the lower clamp portion 221 and the upper clamp portion 222. The lock body 224a is disposed on the side of the lower clamp portion 221, and the protrusion 224b is disposed on the side of the upper clamp portion 222. The lock body 224a has a lever 224c and an annular portion 224d. In a state where the upper clamp portion 222 is rotated to the upper side of the lower clamp portion 221, the annular portion 224d is hooked onto the protrusion 224b and the lever 224c is tilted downward, so that the upper clamp portion 222 can be fastened to the lower clamp portion 221 in a closed state.

[0068] With the resin pipe 11 and the resin pipe 12 inserted into the electric fusion joint 1, the resin pipe 11 can be clamped with the first clamp portion 210 and the resin pipe 12 can be clamped with the second clamp portion 220, thereby placing the resin pipe 11, the resin pipe 12 and the electric fusion joint 1 in the jig 200.

[0069] (Shaft portion 230) The shaft portion 230 is supported by the base 260. The shaft portion 230 is arranged parallel to the central axes of the recesses 211a and 212a of the first clamp portion 210. The shaft portion 230 is arranged parallel to the central axes of the recesses 221a and 222a of the second clamp portion 220. The shaft portion 230 is also arranged parallel to the central axes of the resin pipe 11 fixed to the first clamp portion 210 and the resin pipe 12 fixed to the second clamp portion 220. The shaft portion 230 is arranged along the axial direction A described above.

[0070] The shaft portion 230 extends from the second clamp portion 220 toward the first clamp portion 210. The first clamp portion 210 is attached to the shaft portion 230 so as to be movable along the shaft portion 230. The shaft portion 230 is disposed from the lower clamp portion 221 to the lower clamp portion 211. A bearing portion 215 is disposed below the recessed portion 211a of the lower clamp portion 211 of the first clamp portion 210, and the shaft portion 230 is inserted into the bearing portion 215.

[0071] (Pressing portion 240) The pressing portion 240 presses the first clamp portion 210 toward the second clamp portion 220 along the shaft portion 230. The pressing portion 240 has a spring 241 and a nut 242.

[0072] A spring 241 is disposed around the shaft portion 230 on the opposite side of the first clamp portion 210 to the second clamp portion 220 .

[0073] Nut 242 is disposed on shaft portion 230 on the opposite side of spring 241 from first clamp portion 210. A male screw is formed around the periphery of the end of shaft portion 230 opposite second clamp portion 220, and is screwed into a female screw formed on the inside of nut 242. Nut 242 can be moved along shaft portion 230 by rotating it.

[0074] The spring 241 is disposed between the nut 242 and the first clamping portion 210. The nut 242 is screwed onto the shaft portion 230 and its position on the shaft portion 230 is fixed, so that the spring 241 applies a load to the first clamping portion 210 toward the second clamping portion 220. The load can be set, for example, in the range of 1 to 50 kgf, and is more preferably in the range of 3 to 20 kgf. In addition, when the resin pipes 11, 12 and the electrofusion joint 1 are placed in the jig 200, the spring 241 is compressed when the nut 242 is rotated to move closer to the first clamping portion 210, so that the load applied to the first clamping portion 210 can be increased. On the other hand, when the nut 242 is rotated to move away from the first clamping portion 210, the spring 241 is expanded, so that the load applied to the first clamping portion 210 can be reduced.

[0075] As shown in FIG. 7, when the plastic pipe 11, the plastic pipe 12 and the electric fusion joint 1 are placed in the jig 200, a load is applied to the first clamp portion 210 by the pressing portion 240, so that the pipe end 11a of the plastic pipe 11 and the pipe end 12a of the plastic pipe 12 are pressed against the stopper portion 22.

[0076] (Regulatory section 250) The restricting portion 250 restricts the first clamping portion 210 from being moved too far toward the second clamping portion 220 by the pressing portion 240 .

[0077] The restricting portion 250 is disposed between the first clamp portion 210 and the second clamp portion 220 .

[0078] The restricting portion 250 has a fixed portion 251 and a contact portion 252. The fixed portion 251 is fixed to a base 260. The contact portion 252 is a portion that extends upward from the fixed portion 251, and is disposed around the shaft portion 230. When the bearing portion 215 of the first clamp portion 210 contacts the contact portion 252, it is possible to restrict the first clamp portion 210 from moving further toward the second clamp portion 220.

[0079] <Connection method> Next, a connection method according to an embodiment of the present invention will be described with reference to Fig. 8, which is a flow chart for explaining the connection method according to the present embodiment.

[0080] First, in step S1, the pipe end 11a of the resin pipe 11 and the pipe end 12a of the resin pipe 12 are heated by a heater. As shown in Fig. 9(a), the pipe end 11a of the resin pipe 11 and the pipe end 12a of the resin pipe 12 are pressed against a heater 300 to heat the pipe ends 11a and 12a. The temperature of the heating wire during heating may be any temperature capable of melting the cylindrical portion 21, and in the case of polyolefin, a temperature of 220°C or less is preferable.

[0081] Next, in step S2, as shown in Figure 9 (b), the tube end 11a of the resin tube 11 is inserted into the inside of the joint socket portion 23 of the electric fusion joint 1 (in the direction of arrow A1), and the tube end 12a of the resin tube 12 is inserted into the inside of the joint socket portion 24 of the electric fusion joint 1 (in the direction of arrow A2).

[0082] Next, in step S3, the plastic pipe 11, the electric fusion joint 1, and the plastic pipe 12 are attached to the jig 200 as shown in Fig. 6. A load is applied to the first clamping part 210 in the direction of the second clamping part 220 by the pressing part 240 of the jig 200, and the pipe end 11a of the plastic pipe 11 and the pipe end 12a of the plastic pipe 12 can be butted together while applying pressure as shown in Fig. 10(a). As a result, beads R of raised resin are formed on the inner and outer peripheries of the pipe ends 11a and 12a (see dotted line P1 in Fig. 10(a)). In this way, the plastic pipe 11 and the plastic pipe 12 are butt fused inside the electric fusion joint 1.

[0083] In step S3, since the pipe end 11a of the molten resin pipe 11 and the pipe end 12a of the molten resin pipe 12 are pressed against each other, the pressure by the pressing unit 240 gradually decreases, but for example, by moving the nut 242 toward the second clamp unit 220, the magnitude of the load applied to the first clamp unit 210 by the spring 241 can be maintained. In this manner, the pressure by the pressing unit 240 can be adjusted. For example, it is possible to apply pressure for a predetermined time, and then adjust the nut 242 so that no pressure is applied.

[0084] Next, in step S4, the connector 81 of the electric fusion device is attached to the two pins 51b, 51c of the connector attachment portion 5, and electricity is passed through the socket heating portions 3, 4 for a predetermined time. The temperature of the heating wire during the passage of electricity may be any temperature capable of melting the cylindrical portion 21, and in the case of polyolefin, the temperature is preferably 220°C or lower. Note that step S4 is preferably performed after the resin pipes 11, 12 fused in step S3 have cooled.

[0085] When electricity is applied, the socket heating portions 3, 4 generate heat, and as shown in FIG. 10(b), the inner surfaces 21a of the joint socket portions 23, 24 and the outer circumferential surfaces of the plastic pipes 11, 12 melt (see dotted line P2).

[0086] Next, in step S5, the supply of current to the socket heating parts 3, 4 is stopped and they are cooled, completing the fusion of the inner surfaces 21a of the joint socket parts 23, 24 and the outer circumferential surfaces of the plastic pipes 11, 12.

[0087] <Ultrapure water use of piping structure 100> The piping structure 100 according to the embodiment of the present disclosure can be used, for example, for transporting ultrapure water. Specifically, the piping structure 100 for ultrapure water according to the embodiment of the present disclosure can be used as piping in an ultrapure water production apparatus, piping for transporting ultrapure water from the ultrapure water production apparatus to a point of use, piping for returning ultrapure water from the point of use, etc.

[0088] Ultrapure water is water with extremely high purity, and is suitable for use in cleaning electronic devices such as semiconductor devices. There are many indices for expressing the grade of ultrapure water, but in this embodiment, the electrical resistivity of ultrapure water is 18.2 MΩ cm or more, and the TOC is 50 ppb or less.

[0089] The piping structure 100 according to the embodiment of the present disclosure is preferably a water piping for nuclear power generation, which has particularly strict water quality requirements for ultrapure water, or a piping for transporting ultrapure water used in wet processing steps such as cleaning in the manufacturing process of pharmaceuticals, semiconductor elements or liquid crystals, and more preferably in the manufacturing process of semiconductor elements. The semiconductor elements are preferably those with a higher degree of integration, and more specifically, are more preferably used in the manufacturing process of semiconductor elements with a minimum line width of 65 nm or less. An example of a standard for the quality of ultrapure water used in semiconductor manufacturing is SEMI F75.

[0090] In addition, the piping structure 100 according to the embodiment of the present disclosure has a polyethylene resin layer, and therefore has excellent workability. For example, fusion work such as EF (electrical fusion) bonding can be easily performed at a relatively low temperature.

[0091] <Features> The connection method in this embodiment includes step S1 (an example of a pipe end heating step), step S3 (an example of a first fusion step), and step S4 (an example of a second fusion step and an example of a third fusion step). In step S1, a pipe end 11a of a resin pipe 11 (an example of a first pipe) containing a thermoplastic resin and a pipe end 12a of a resin pipe 12 (an example of a second pipe) containing a thermoplastic resin are heated. In step S3, after step S1, the pipe end 11a of the resin pipe 11 inserted inside a joint socket 23 (an example of a first joint socket) provided at one of both ends of the electric fusion joint 1 and the pipe end 12a of the resin pipe 12 inserted inside a joint socket 24 (an example of a second joint socket) provided at the other end are brought into contact with each other inside the electric fusion joint 1 to fuse the pipe ends 11a and 12a together. In step S4, electricity is passed through a receptacle heating part 3 (an example of a first receptacle heating part) which is arranged in the fitting receptacle portion 23 and includes a heating wire 31 to fuse the fitting receptacle portion 23 and the plastic pipe 11, and electricity is passed through a receptacle heating part 4 (an example of a second receptacle heating part) which is arranged in the fitting receptacle portion 24 and includes a heating wire 31 to fuse the second fitting receptacle portion and the plastic pipe 12.

[0092] The piping structure 100 in this embodiment includes a resin pipe 11 (an example of a first pipe), a resin pipe 12 (an example of a second pipe), and an electric fusion joint 1. The resin pipe 11 includes a thermoplastic resin. The resin pipe 12 includes a thermoplastic resin. The electric fusion joint 1 includes a joint socket portion 23 (an example of a first joint socket portion) into which the resin pipe 11 is inserted, a joint socket portion 24 (an example of a second joint socket portion) into which the resin pipe 12 is inserted, a socket heating portion 3 (an example of a first socket heating portion) disposed in the joint socket portion 23 and including a heating wire 31, and a socket heating portion 4 (an example of a second socket heating portion) disposed in the joint socket portion 24 and including a heating wire 31. A pipe end 11a of the resin pipe 11 and a pipe end 12a of the resin pipe 12 are butted against each other inside the electric fusion joint 1 and fused to each other.

[0093] In this way, after the pipe ends of the resin pipe 11 and the resin pipe 12 are fused together, the outer surface of the resin pipe 11 is fused to the inner surface 21a of the joint socket 23 of the electric fusion joint 1, and the outer surface of the resin pipe 12 is fused to the inner surface 21a of the joint socket 24, so that air is not trapped and the height of the resin swelling inward can be made uniform. FIG. 11 is a diagram showing a state in which the height of the resin swelling inward is uniform. FIG. 11 is a diagram showing the piping structure 100 as viewed from the resin pipe 11 side. As shown in the figure, a bead R in which the resin is uniformly swelling in the circumferential direction C is formed.

[0094] Since the pipe end 11a of the resin pipe 11 and the pipe end 12a of the resin pipe 12 are joined by butt fusion, gaps are less likely to occur between the resin pipes 11 and 12 than in the conventional method of fusion using only heating by an electric heating wire.

[0095] In addition, by performing butt welding, the bead R can be made smaller.

[0096] (Embodiment 2) Next, a piping structure 400 in a second embodiment according to the present disclosure will be described. The piping structure 400 in the second embodiment has an electric fusion joint 500 having a different configuration from that in the first embodiment. In the description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted.

[0097] FIG. 12 is a cross-sectional view showing the configuration of an electric fusion joint 500 according to the second embodiment.

[0098] Unlike the electric fusion joint 1 of the first embodiment, the electric fusion joint 500 of the second embodiment is provided with a stopper portion 22 that regulates the inserted resin pipes 11, 12. The stopper portion 22 is disposed between the joint socket portion 23 and the joint socket portion 24.

[0099] As shown in FIG. 12, the electric fusion joint 1 has a main body portion 2, socket heating portions 3 and 4, a stopper heating portion 7, a connector mounting portion 5, and a connector mounting portion 6.

[0100] (Main body 2) The main body 2 is formed of a thermoplastic resin, and as shown in Fig. 12, has a tubular portion 21 and a stopper portion 22. The tubular portion 21 is cylindrical and has a fitting receptacle portion 23, a fitting receptacle portion 24, and a connecting portion 25. The resin pipe 11 is inserted into the inside of the fitting receptacle portion 23. The resin pipe 12 is inserted into the inside of the fitting receptacle portion 24.

[0101] The thermoplastic resin used in the main body 2 is not particularly limited, but one having a melting point of less than 230° C. is preferable.

[0102] FIG. 13 is a cross-sectional view showing the state in which the resin pipe 11 is inserted into the inside of the joint socket portion 23 of the electric fusion joint 500, and the resin pipe 12 is inserted into the inside of the joint socket portion 24. As shown in FIG.

[0103] The inner diameter of the joint socket portion 23 is formed to be equal to or larger than the outer diameter of the resin pipe 11. The inner diameter of the joint socket portion 24 is formed to be equal to or larger than the outer diameter of the resin pipe 12.

[0104] 12, the connecting portion 25 is connected to the joint socket portion 23 and the joint socket portion 24, and connects the joint socket portion 23 and the joint socket portion 24. The connecting portion 25 is a portion that connects the joint socket portion 23 and the joint socket portion 24, and a stopper portion 22, which will be described later, is provided on the inside in the radial direction B. The connecting portion 25 is disposed between the opposite side of the end 21b of the joint socket portion 23 and the opposite side of the end 21c of the joint socket portion 24.

[0105] (Stopper portion 22) The stopper portion 22 is an annular portion. The stopper portion 22 is a protrusion formed on the inner surface 21a of the cylindrical portion 21 along the circumferential direction C, and is formed around the entire circumference. The stopper portion 22 also contains a thermoplastic resin, and is preferably formed of the same resin as the thermoplastic resin used for the cylindrical portion 21.

[0106] 12, the stopper portion 22 is formed so as to protrude radially inward from the inner surface 21a of the cylindrical portion 21. The stopper portion 22 is disposed on the inner side of the connecting portion 25 of the cylindrical portion 21 in the radial direction B. The stopper portion 22 may be formed as one member together with the cylindrical portion 21, or may be formed as a separate member from the cylindrical portion 21.

[0107] The stopper portion 22 has a first side surface 22a, a second side surface 22b, and a peripheral surface 22c. The peripheral surface 22c is an end surface of the stopper portion 22 on the inner side in the radial direction.

[0108] The first side surface 22a is formed approximately perpendicular to the axial direction A from the inner surface 21a of the cylindrical portion 21 toward the inside in the radial direction B.

[0109] The second side surface 22b is formed approximately perpendicular to the axial direction A from the inner surface 21a of the cylindrical portion 21 toward the inside in the radial direction B.

[0110] The peripheral surface 22c connects the radially inner end of the first side surface 22a and the radially inner end of the second side surface 22b. The peripheral surface 22c is formed generally parallel to the inner surface 21a of the cylindrical portion 21.

[0111] When the plastic pipe 11 is inserted into the fitting receptacle 23, the stopper portion 22 restricts the insertion position of the pipe end 11a, as shown in Fig. 13. Restricting the insertion position of the pipe end 11a includes a case in which the stopper portion 22 directly restricts the insertion position by causing the pipe end 11a to come into contact with the first side surface 22a of the stopper portion 22 as shown in Fig. 13, and a case in which the stopper portion 22 indirectly restricts the insertion position by causing the pipe end 11a to come into contact with a heating wire 41 (described later) of the stopper heating portion 7.

[0112] When the plastic pipe 12 is inserted into the fitting receptacle 24, the stopper portion 22 regulates the insertion position of the pipe end 12a, as shown in Fig. 13. Regulating the insertion position of the pipe end 12a includes a case in which the stopper portion 22 directly regulates the insertion position by causing the pipe end 12a to come into contact with the second side surface 22b of the stopper portion 22 as shown in Fig. 13, and a case in which the stopper portion 22 indirectly regulates the insertion position by causing the pipe end 12a to come into contact with a heating wire 41 (described later) of the stopper heating portion 7.

[0113] In this embodiment, the occurrence of crevices between the pipe end 11a and the first side surface 22a and between the pipe end 12a and the second side surface 22b (see position V) is suppressed.

[0114] (Stopper heating part 7) The stopper heating part 7 is provided in the stopper part 22. The stopper heating part 7 has a heating wire 41. The heating wire 41 is provided in the stopper part 22 so as to be wound in the circumferential direction C along the axial direction A. In this embodiment, the heating wire 41 is wound around the stopper part 22 for example four times, but this is not limited to four times, and may be five times or more, or three times or less. In the stopper heating part 7 of this embodiment, all adjacent heating wires 41 are in contact with each other, but a gap may be provided between all or part of adjacent heating wires 41.

[0115] The heating wire 41 may be made of the same material and have the same structure as the heating wire 31. The heating wire 41 generates heat at about 180 degrees to 230 degrees.

[0116] 12, a predetermined distance L1 is provided along the axial direction A between the stopper heating portion 7 and the heating wire portion 31a closest to the stopper heating portion 7. Also, a predetermined distance L1 is provided along the axial direction A between the stopper heating portion 7 and the heating wire portion 31b closest to the stopper heating portion 7. In this embodiment, the socket heating portion 3 and the socket heating portion 4 are provided symmetrically, but they do not have to be symmetrical.

[0117] The diameter of the wound heating wire 41 in the stopper heating portion 7 is set to be smaller than the diameter of the wound heating wire 31 in the socket heating portions 3, 4.

[0118] Further, the diameter of the wound heating wire 41 in the stopper heating portion 7 is set so that the position of the heating wire 41 falls within the thickness of the pipe walls of the resin pipes 11, 12 into which the heating wire 41 is inserted.

[0119] In order to generate heat in the stopper heating portion 7, the space between the first side surface 22a of the stopper portion 22 and the tube end 11a of the resin tube 11 (see position V in Figure 13) and the space between the second side surface 22b of the stopper portion 22 and the tube end 12a of the resin tube 12 (see position V in Figure 13) are filled with molten resin, and the stopper portion 22 and the resin tube 11, as well as the stopper portion 22 and the resin tube 12, are fused together.

[0120] (Connector mounting part 6) 12, the connector attachment portion 6 has two pins 61b, 61c (an example of a pair of second terminals). The two pins 61b, 61c are provided so as to protrude radially outward from the outer surface 21d of the cylindrical portion 21. The two pins 61b, 61c are arranged side by side along the axial direction A near the center of the cylindrical portion 21.

[0121] Of the two pins 61b and 61c, one pin 61b is disposed on the end 21b side, and the other pin 61c is disposed on the end 21c side.

[0122] FIG. 14 is a schematic diagram showing the connection relationship between the connector attachment parts 5, 6 and the heating wires 31, 41.

[0123] 14, one end of the heating wire 41 is connected to the pin 61b, and the other end of the heating wire 41 is connected to the pin 61c. The stopper heating part 7 can be heated by attaching a connector of an electric fusion device to the pins 61b and 61c and passing electricity through them.

[0124] 14, the receptacle heating part 3 has a heating wire 31 wound eight times, and the receptacle heating part 4 has a heating wire 31 wound eight times. The receptacle heating part 3 and the receptacle heating part 4 are connected by a single heating wire 31, both ends of which are connected to pins 51b and 51c. Of the heating wire 31, a heating wire portion 31c that connects between the heating wire portion 31a constituting the receptacle heating part 3 and the heating wire portion 31b constituting the receptacle heating part 4 is embedded in the connecting part 25. In the second embodiment, the heating wire portion 31c is embedded in the connecting part 25 along the axial direction A, rather than being wound in the circumferential direction as in the first embodiment, but may be wound and embedded in the connecting part 25 as in the first embodiment.

[0125] In this way, since the connector mounting portion 5 for generating heat in the receptacle heating portions 3, 4 and the connector mounting portion 6 for generating heat in the stopper heating portion 7 are provided separately, the timing of supplying electricity to the receptacle heating portion 3 and the timing of supplying electricity to the stopper heating portion 7 can be changed.

[0126] <Connection method> Next, a connection method according to an embodiment of the present disclosure will be described with reference to Fig. 15, which is a flow diagram for explaining the connection method according to the present embodiment.

[0127] First, in step S10, the pipe end 11a of the resin pipe 11 and the pipe end 12a of the resin pipe 12 are heated by a heater. As shown in Fig. 16(a), the pipe end 11a of the resin pipe 11 and the pipe end 12a of the resin pipe 12 are pressed against a heater 300 to heat the pipe ends 11a and 12a. The temperature of the heating wire during heating may be any temperature that can melt the cylindrical portion 21, and in the case of polyolefin, a temperature of 220 degrees or less is preferable.

[0128] 16(b), the connector 81 of the electric fusion device is attached to the two pins 61b, 61c of the connector attachment portion 6, and electricity is started to be applied to the stopper heating portion 7. This heats the stopper portion 22 (see dotted line P3). Note that steps S10 and S11 may be performed simultaneously.

[0129] After a predetermined time has elapsed, in step S12, the power supply to the stopper heating portion 7 is stopped.

[0130] 17(a), the resin pipe 11 is inserted into the receiving port heating part 3 from the heated pipe end 11a until it is restricted by the stopper part 22, and the resin pipe 12 is inserted into the receiving port heating part 4 from the heated pipe end 12a until it is restricted by the stopper part 22. In step S11, by warming the stopper part 22, it is possible to suppress a decrease in temperature of the pipe ends 11a, 12a. In addition, it is preferable to perform step S13 as soon as possible after the completion of the energization of the stopper heating part 7 in step S12.

[0131] Next, in step S14, the resin pipe 11, the electric fusion joint 500 and the resin pipe 12 are attached to the jig 200 described in the first embodiment.

[0132] 17(b), the pipe end 11a of the resin pipe 11 is pressed against the first side surface 22a of the stopper portion 22, and the first side surface 22a of the stopper portion 22 and the pipe end 11a of the resin pipe 11 are fused together, and the pipe end 12a of the resin pipe 12 is pressed against the second side surface 22b of the stopper portion 22, and the second side surface 22b of the stopper portion 22 and the pipe end 12a of the resin pipe 12 are fused together. In step S14, the pipe end 11a of the molten resin pipe 11 and the pipe end 12a of the molten resin pipe 12 are pressed against the molten stopper portion 22, so that the pressure by the pressing portion 240 gradually decreases. However, for example, by moving the nut 242 toward the second clamp portion 220, the magnitude of the load applied to the first clamp portion 210 by the spring 241 can be maintained. In this manner, the pressure by the pressing portion 240 can be adjusted. For example, pressure may be applied for a predetermined period of time, and then the nut 242 may be adjusted so that pressure is no longer applied.

[0133] Next, in step S15, as shown in Fig. 18, the connector 81 of the electric fusion device is attached to the two pins 51b, 51c of the connector attachment portion 5, and electricity is passed for a predetermined time. The temperature of the heating wire during the passage of electricity may be a temperature capable of melting the cylindrical portion 21, and in the case of polyolefin, a temperature of 220°C or less is preferable. Step S15 is preferably performed after the resin pipes 11, 12 fused in step S14 have cooled.

[0134] This current flow causes the socket heating portions 3, 4 to generate heat, and the inner surfaces 21a of the joint socket portions 23, 24 and the outer circumferential surfaces of the plastic pipes 11, 12 melt (see dotted line P2).

[0135] Next, in step S16, the supply of current to the socket heating parts 3, 4 is stopped and they are cooled, completing the fusion of the inner surfaces 21a of the joint socket parts 23, 24 and the outer circumferential surfaces of the plastic pipes 11, 12.

[0136] The piping structure 400 of the second embodiment can be used for transporting ultrapure water, similarly to the case described in the first embodiment.

[0137] <Features> The connection method in the second embodiment of the present disclosure includes step S10 (an example of a tube end heating step), step S11 (an example of a stopper heating step), step S14 (an example of a first fusion step), and step S15 (an example of a second fusion step and a third fusion step). Step S10 heats the tube end 11a of the resin tube 11 (an example of a first tube) containing thermoplastic resin and the tube end 12a of the resin tube 12 (an example of a second tube) containing thermoplastic resin. Step S11 heats the stopper heating part 7 including the heating wire 41, which is disposed in the stopper part 22 provided on the inner surface of the cylindrical part 21 of the electric fusion joint 500 so as to protrude inward. In step S14, after step S11, the pipe end 11a of the resin pipe 11 inserted inside the fitting receptacle 23 (an example of a first fitting receptacle) provided at one of the ends of the tubular portion 21 and the pipe end 12a of the resin pipe 12 inserted inside the fitting receptacle 24 (an example of a second fitting receptacle) provided at the other end are fused to the stopper portion 22. In step S15, electricity is applied to the receptacle heating portion 3 (an example of a first receptacle heating portion) that is arranged at the fitting receptacle 23 and includes the heating wire 31 to fuse the receptacle heating portion 3 and the resin pipe 12, and electricity is applied to the receptacle heating portion 4 (an example of a second fitting receptacle) that is arranged at the receptacle heating portion 4 (an example of a second fitting receptacle) and includes the heating wire 31 to fuse the receptacle heating portion 4 and the resin pipe 12.

[0138] In this way, after the pipe ends 11a, 12a of the resin pipe 11 and the resin pipe 12 are fused to the stopper portion 22, the outer surface of the resin pipe 11 is fused to the inner surface 21a of the fitting socket portion 23, and the outer surface of the resin pipe 12 is fused to the inner surface 21a of the fitting socket portion 24, so that air is not trapped and the height of the resin swelling inward can be made uniform.

[0139] Not only is the stopper portion 22 heated, but the pipe end 11a of the resin pipe 11 and the pipe end 12a of the resin pipe 12 are also heated and fused to the stopper portion 22, so that gaps are less likely to occur between the resin pipe 11 and the resin pipe 12 than in the conventional method of fusion using only heating with an electric heating wire.

[0140] In addition, by performing butt welding, the bead R can be made smaller.

[0141] In the connection method according to the second embodiment of the present disclosure, step S14 (an example of a first fusion step) is performed after step S12 of terminating the energization of stopper heat generating portion 7 in step S11 (an example of a stopper heating step).

[0142] In this way, after the heating of the stopper portion 22 is completed, the pipe end 11a of the heated resin pipe 11 and the pipe end 12a of the heated resin pipe 12 are fused to the stopper portion 22, thereby suppressing the occurrence of gaps.

[0143] <Other embodiments> Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0144] (A) In the above embodiment 2, the tube end 11a of the resin pipe 11 and the tube end 12a of the resin pipe 12 are pressed against the stopper portion 22 after the current supply to the stopper heating portion 7 is stopped, but this is not limited to this, and the tube end 11a of the resin pipe 11 and the tube end 12a of the resin pipe 12 may be pressed against the stopper portion 22 while current is being supplied to the stopper heating portion 7.

[0145] (B) In the above-mentioned second embodiment, when viewed along the axial direction A, the outer diameter of the stopper portion 22 is circular, but this is not limited to a circle and may be polygonal.

[0146] (C) In the above-mentioned first and second embodiments, all of the heating wires 31 are wound so that adjacent portions are in contact with each other in the receptacle heating parts 3 and 4, but all or some of them do not have to be in contact. Also, as in the comparative example 1 described later, adjacent heating wire portions may be in contact with each other at a predetermined interval and every predetermined number of adjacent portions, or the intervals and / or the number of contacts may be different in the receptacle heating parts 3 and 4.

[0147] (D) In the above embodiment, the socket heating portion 3 and the socket heating portion 4 are provided symmetrically on the left and right sides of the stopper portion 22, but this is not limited to the above. For example, the heating wire 31 may be wound seven times around one joint socket portion 23 with the stopper portion 22 in between, and the heating wire 31 may be wound eight times around the other joint socket portion 24.

[0148] (E) In the above embodiment, all of the flow paths of the electric fusion joint 1 are formed straight, but the flow paths may be curved, that is, an elbow joint.

[0149] (F) In the above-mentioned second embodiment, the same electric heating wire 31 of the socket heating part 3 and the electric heating wire 41 of the stopper heating part 7 are used, so all of the electric heating wires 31, 41 are provided with an insulating coating, but this is not limited to this. However, it is preferable that at least the electric heating wire 41 is provided with an insulating coating. This is because the electric heating wires 41 are easily brought into contact with each other due to pressure being applied by the resin pipes 11 and 12.

[0150] (G) In the above embodiment, the resin pipes 11 and 12 are used as an example of the pipes, but the pipes are not limited to this and may be pipes made of resin, such as a metal-reinforced composite pipe having a metal reinforcing layer.

[0151] (H) In the above embodiments 1 and 2, the receptacle heating portion 3 and the receptacle heating portion 4 are heated simultaneously, but if a connector connection portion is provided for each of the receptacle heating portion 3 and the receptacle heating portion 4, it is possible to heat one of the receptacle heating portion 3 and the receptacle heating portion 4 before heating the other.

[0152] (I) In the above-mentioned first and second embodiments, the spring 241 and the nut 242 are used as a pressing part for applying a load to the first clamp part 210, but this is not limited thereto and may be a motor, a cylinder, etc. In addition, the pressing of the tube ends 11a, 12a against the stopper part 22 may be by either the application of a load to the first clamp part 210 or the amount of movement.

[0153] In addition, when a load is applied using a motor or a cylinder, the motor or cylinder may be controlled in conjunction with the electric fusion device. For example, the motor or cylinder may be controlled according to a preset program in accordance with the elapsed heating time of the electric fusion device so that a load equal to or greater than a predetermined value is maintained.

[0154] (Example) The above-mentioned first and second embodiments will be described in detail below using examples.

[0155] Example 1 In Example 1, resin pipes 11 and 12 were joined using the electric fusion joint 1 having the configuration shown in the first embodiment.

[0156] The material of the electric fusion joint 1 is olefin resin. The total length of the electric fusion joint 1 is 70-300 mm. The material of the resin pipes 11, 12 is olefin resin. The insulating coating of the heating wire 31 is made of imide or amide-imide. The diameter of the heating wire 31 is 0.3-2.0 mm. The nominal diameter of the resin pipes 11, 12 is 20-200 A. The length L0 is at least twice the diameter of the coated heating wire.

[0157] In Example 1, the electric fusion joint 1 and the resin pipes 11 and 12 were connected in accordance with the flow diagram of FIG.

[0158] The heating conditions for the pipe ends 11a, 12a of the plastic pipes 11, 12 in Fig. 9(a) are to control the heating time and voltage so that the entire pipe end exceeds 230 degrees (approximately 40-76V, 70-500s). The pressure used when pad welding the plastic pipes 11 and 12 is 0.15MPa x cross-sectional area. The heating conditions for the receiving port heating parts 3, 4 are to apply a heating time and voltage that exceeds 230 degrees.

[0159] Comparative Example 1 In Comparative Example 1, the resin pipes 11 and 12 were joined using an electric fusion joint 1100 having a configuration shown in FIG. 19. In the electric fusion joint 1100 shown in FIG. 19, the stopper heating part 1007, the socket heating part 1003, and the socket heating part 1004 are configured with a single connected heating wire 31, the connector attachment part 6 is not provided, and the winding configuration of the heating wire in the socket heating part 1003 and the socket heating part 1004 is different from that of the electric fusion joint 500 of the second embodiment. In the socket heating part 1003 of the electric fusion joint 1100 of Comparative Example 1, the heating wire 31 is wound two times so that the heating wire 31 contacts, and two times the heating wire 31 is wound along the axial direction A with a predetermined interval L3 between them, and this is repeated. In the socket heating part 1003, for example, the heating wire 31 is wound eight times as shown in FIG. 19. In addition, in the receiving port heat generating part 1004, the heating wire 31 is wound two times so as to come into contact with the heating wire 31, and two more times are repeatedly wound so as to come into contact with the heating wire 31 with a predetermined interval L3 in between along the axial direction A. In the receiving port heat generating part 1004, as shown in Fig. 19, for example, the heating wire 31 is wound eight times.

[0160] In the electric fusion joint 1100, the stopper heating part 1007 is formed by winding four turns of the heating wire 31. If the part of the heating wire 31 that constitutes the socket heating part 1003 is referred to as heating wire part 31a, the part that constitutes the socket heating part 1004 is referred to as heating wire part 31b, and the part that constitutes the stopper heating part 1007 is referred to as heating wire part 31d, then the heating wire part 31a, the heating wire part 31d, and the heating wire part 31b are connected in this order.

[0161] The end of heating wire portion 31a on the end 21b side is connected to pin 51b, and the end of heating wire portion 31b on the end 21c side is connected to pin 51c. That is, by passing electricity through pins 51b and 51c, stopper heating portion 1007, socket heating portion 1003, and socket heating portion 1004 are heated simultaneously.

[0162] In addition, a gap L2 is provided along the axial direction A between the stopper heating portion 1007 and the two adjacent heating wire portions 31a arranged closest to the stopper heating portion 1007, and a gap L2 is provided along the axial direction A between the stopper heating portion 1007 and the two adjacent heating wire portions 31b arranged closest to the stopper heating portion 1007.

[0163] The material of the electric fusion joint 1100 is olefin resin. The total length of the electric fusion joint 1100 is 70-300 mm. The material of the resin pipes 11, 12 is olefin resin. The insulating coating of the heating wire 31 is made of imide or amide-imide. The nominal diameter of the resin pipes 11, 12 is 20-200 A. The lengths of L2 and L3 are at least twice the diameter of the coated heating wire.

[0164] In Comparative Example 1, a structure in which a resin tube 11 was inserted into the joint socket portion 23 of the electric fusion joint 1100 and a resin tube 12 was inserted into the joint socket portion 24 was attached to the above-mentioned jig 200, and while applying a pressure of 0.15 MPa × cross-sectional area, electricity was passed through pins 51b and 51c to heat the socket heating portions 1003 and 1004 and the stopper heating portion 1007.

[0165] The piping structures of Example 1 and Comparative Example 1 were cut, and visually inspected to see whether or not a bead had erupted or a depression had occurred.

[0166] The results are shown below (Table 1).

[0167] (Table 1) TIFF2025019296000002.tif29141 In Comparative Example 1, bead ejection or the occurrence of depressions was observed, whereas in Example 1, no bead ejection or the occurrence of depressions was observed.

[0168] The occurrence of ejection of the bead R or depression in Comparative Example 1 will be described with reference to Figures 20(a) and 20(b). Figure 20(a) is a partially enlarged view for explaining fusion between the electric fusion joint 1100 and the plastic pipe 11 in Comparative Example 1. As shown in Figure 20(a), in the portion (cold zone) of the interval L2 between the stopper heating part 1007 and the socket heating part 1003, air is present in the clearance (indicated by E in the figure) between the inner surface of the electric fusion joint 1100 and the outer surface of the plastic pipe 11. When fusion begins, fusion between the stopper heating part 1007 and the pipe end 11a of the resin pipe 11 (the fused part is shown as Q2 in the figure) and fusion between the inner surface of the part where the receiving port heating part 1003 is provided and the outer surface of the resin pipe 11 (the fused part is shown as Q1 in the figure) proceed simultaneously, so that the air in the clearance E is trapped between the two fused parts Q1 and Q2 and expands due to the heat, pushing up the molten resin in the process of forming the bead R and ejecting the bead R, as shown in Figure 20(b). Also, air bubbles are mixed into the resin due to the expansion of the air, and when the mixed air bubbles burst due to further expansion, a dent is formed in the bead R.

[0169] Fig. 21 is a diagram showing an example of the ejection and depression of the bead R. Fig. 21 is a diagram seen from the end 21b side. In Fig. 21, the resin protruding inward from the stopper portion 22 and the inner peripheral surface of the resin pipe 11 is indicated by R, and the depression is indicated by Q.

[0170] In contrast, in Example 1, after the pipe end 11a of the resin pipe 11 and the pipe end 12a of the resin pipe 12 are joined by butt fusion, the outer surface of the resin pipe 11 is fused to the inner surface 21a of the fitting socket portion 23 of the electric fusion joint 1, and the outer surface of the resin pipe 12 is fused to the inner surface 21a of the fitting socket portion 24. As a result, no air is trapped, and the height of the resin (bead R) that bulges inward can be made uniform, as shown in Figure 11.

[0171] Example 2 In Example 2, resin pipes 11 and 12 were joined using electric fusion joint 500 having the configuration shown in the second embodiment.

[0172] The material of the electric fusion joint 500 is olefin resin. The total length of the electric fusion joint 500 is 70-300 mm. The material of the resin pipes 11, 12 is olefin resin. The insulating coating of the heating wire 31 is made of imide or amide-imide. The nominal diameter of the resin pipes 11, 12 is 20-200 A. The length L1 is at least twice the diameter of the coated heating wire.

[0173] In Example 2, the electric fusion joint 1 and the resin pipes 11 and 12 were connected in accordance with the flow diagram of FIG.

[0174] The heating conditions for the pipe ends 11a, 12a of the resin pipes 11, 12 in FIG. 16(a) are to apply a heating time and voltage that exceeds 230 degrees. The pressure for pad welding the resin pipes 11 and 12 is 0.15 MPa x cross-sectional area. The heating conditions for the stopper heating part 7 in FIG. 16(b) are: The condition for heating the socket heating parts 3 and 4 in Fig. 18 is to apply a heating time and voltage that exceeds 230 degrees. The pressure applied to the electric fusion joint 500 of the resin pipes 11 and 12 in Fig. 17(a) and Fig. 17(b) is 0.15 MPa x cross-sectional area. The condition for heating the socket heating parts 3 and 4 in Fig. 18 is to apply a heating time and voltage that exceeds 230 degrees.

[0175] The piping structure of Example 2 thus prepared was cut, and visually inspected for the presence or absence of bead ejection or depression. The results of Example 2 together with the results of Comparative Example 1 are shown in Table 2 below.

[0176] (Table 2) TIFF2025019296000003.tif28141 In Example 2, after the pipe ends 11a, 12a of the resin pipe 11 and the resin pipe 12 are fused to the stopper portion 22, the outer surface of the resin pipe 11 is fused to the inner surface 21a of the fitting socket portion 23, and the outer surface of the resin pipe 12 is fused to the inner surface 21a of the fitting socket portion 24. As a result, air is not trapped and the height of the resin swelling inward can be made uniform. [Explanation of symbols]

[0177] 1: Electric fusion joint 3: Heat generating part 4: Heat generating part 11: Plastic pipe 11a: Pipe end 12: Plastic pipe 12a: Pipe end

Claims

1. a tube end heating step of heating a tube end of a first tube containing a thermoplastic resin and a tube end of a second tube containing a thermoplastic resin; a stopper heating step of applying electricity to a stopper heating portion including a heating wire, the stopper portion being disposed on the inner surface of the cylindrical portion of the electric fusion joint so as to protrude inward; a first fusion step of fusing, after the tube end heating step, a tube end of the first tube inserted into a first fitting socket provided at one of the two ends of the tubular portion and a tube end of the second tube inserted into a second fitting socket provided at the other end of the tubular portion, to the stopper portion heated in the stopper heating step; a second fusion step of applying electricity to a first socket heating portion including a heating wire disposed in the first fitting socket portion after the first fusion step, thereby fusing the first fitting socket portion and the first pipe; a third fusion step of, after the first fusion step, passing electricity through a second socket heating part that is arranged in the second fitting socket and includes a heating wire to fuse the second fitting socket part and the second pipe.

2. The first fusion step is performed after the current supply to the heat generating portion of the stopper is terminated in the stopper heating step. The connection method according to claim 1 .

3. The second fusion step and the third fusion step are performed simultaneously.

3. The connection method according to claim 1 or 2.

Images