Electric fusion joint

Abstract

To secure a performance as an electric fusion joint while having an indicator.SOLUTION: An electric fusion joint 1 comprises a fusion part 20, at which a heating wire 21 is inserted in a notch groove spirally formed on an inner periphery of a thermoplastic resin pipe 10, in which a mating resin pipe 80 is inserted. In the electric fusion joint 1, the fusion part 20 is provided on at least one axial end side of the electric fusion joint 1 to conduct a current to the heating wire 21. At the fusion part 20, a forward passage, on which a spiral travels from an opening side of the electric fusion joint 1 to an opening side opposite to the opening, and a backward passage in a direction opposite to a forward direction are formed of one heating wire 21. An indicator 40 is provided on an outer periphery of the resin pipe 10, and the indicator 40 is arranged in a range of the resin pipe 10, in which the fusion part 20 is provided, nearer an end face 11d of the resin pipe 10 than a center of the range in a pipe axis O direction of the resin pipe 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrofusion joint. [Background technology]

[0002] Conventionally, for example, an electric fusion joint is known, as described in Patent Document 1. This electric fusion joint has a fusion part in which an electric heating wire is inserted into a notched groove formed in a spiral shape on the inner peripheral surface of a thermoplastic resin pipe into which a connecting resin pipe is inserted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO 93 / 14342 Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of electric fusion joint, it is desirable to provide an indicator while ensuring the performance of the electric fusion joint.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide an electric fusion joint that is provided with an indicator while ensuring the performance as an electric fusion joint. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention proposes the following means. An electric fusion joint according to one aspect of the present invention is an electric fusion joint having a fusion portion in which an electric heating wire is inserted into a notched groove formed in a spiral shape on the inner surface of a thermoplastic resin tube into which a connecting plastic tube is inserted, the fusion portion being provided on at least one end side in the axial direction of the electric fusion joint so that electricity can be passed through the electric heating wire, the fusion portion having an outward path in which a spiral progresses in a forward direction from the opening side of the electric fusion joint to the opening side opposite the opening, and a return path in a direction opposite to the outward direction, formed by a single electric heating wire, the outer peripheral surface of the plastic tube having an indicator which is disposed on the end face side of the plastic tube in the range in which the fusion portion is provided, in the axial direction of the plastic tube, closer to the center of the range. Effect of the Invention

[0007] The electrofusion joint of the present invention can ensure the performance required for an electrofusion joint while being provided with an indicator. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of an electric fusion joint according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a front view taken in the direction of the arrow II in FIG. [Diagram 3] FIG. 2 is a front view taken in the direction of an arrow III in FIG. [Figure 4] FIG. 2 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] 4 is a flowchart illustrating a method for manufacturing an electric fusion joint according to one embodiment of the present invention. [Figure 6] 13 is an explanatory view showing how the distance between the first fixing part and the second fixing part is widened to enable placement of a plastic tube in a joint setting step in the manufacturing method of an electric fusion joint. FIG. [Figure 7] 13 is an explanatory view showing how the resin pipe is temporarily fixed to the first fixing part in the joint setting step. FIG. [Figure 8] 11 is an explanatory view showing how a resin pipe is fixed to a first fixing portion and a second fixing portion in a joint setting step. FIG. [Figure 9]FIG. 4 is an explanatory diagram of a heating wire embedding portion used in a wire embedding portion cutting and embedding step in a manufacturing method for an electric fusion joint. [Figure 10] 13 is an explanatory view showing how a first heating wire is embedded in an inner peripheral surface of a first resin pipe portion in a wire-embedding portion cutting and embedding step. FIG. [Figure 11] FIG. 1 is a side view of a modified example 1(1) of an electric fusion joint. [Figure 12] FIG. 13 is an explanatory diagram showing how a first fixing mark is provided on a first resin pipe portion in the modified example 1(1). [Figure 13] FIG. 13 is a side view of a first modified example (2) of the electric fusion joint. [Figure 14] FIG. 11 is a side view of Modification 2 of the electric fusion joint. [Figure 15] 15 is a plan view seen from the direction of the arrow XV in FIG. 14. [Figure 16] FIG. 13 is a front view showing a first heating wire of a modified example 3(1) of an electric fusion joint. [Figure 17] FIG. 13 is a front view showing a first heating wire of a modified example 3(2) of the electric fusion joint. [Figure 18] FIG. 13 is a front view showing a first heating wire of a third modified example (3) of the electric fusion joint. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, one embodiment of an electric fusion joint and a method for manufacturing an electric fusion joint according to the present invention will be described with reference to FIGS.

[0010] <Electric fusion joint> As shown in Fig. 1, the electric fusion joint 1 has a fusion part on the inner peripheral surface of a thermoplastic resin pipe into which a connecting resin pipe is inserted. The fusion part has an electric heating wire inserted into a notched groove formed in a spiral shape on the inner peripheral surface of the resin pipe. Specifically, the electric fusion joint 1 has a thermoplastic resin pipe 10, a first fusion part (fusion part) 20, two first terminals (terminals) 30, 31, a first indicator (indicator) 40, a second fusion part (fusion part) 50, two second terminals (terminals) 60, 61, and a second indicator (indicator) 70.

[0011] The thermoplastic resin pipe 10 is formed in a hollow cylindrical shape. Examples of the thermoplastic resin constituting the resin pipe 10 include polyolefin resin, polyvinyl chloride, thermoplastic polyester (thermoplastic polyethylene terephthalate, etc.), etc. Among them, from the viewpoint of further improving earthquake resistance and durability, polyolefin resin is preferable as the thermoplastic resin constituting the resin pipe 10. Olefin resin pipes are more durable than rigid polyvinyl chloride pipes in accordance with JIS K 6815-1, JIS The tensile breaking elongation measured according to K 6815-3 is high. The tensile breaking elongation of rigid polyvinyl chloride pipes is 50 to 150%, while the tensile breaking elongation of olefin resin pipes is 350% or more. In particular, by the extrapolation method specified in ISO / TR9080, the tensile breaking elongation of PE100 high density polyethylene pipes is 500% or more, so they can better suppress damage caused by earthquakes. The polyolefin resin is not particularly limited, but examples thereof include polypropylene, polybutene, low-density polyethylene, high-density polyethylene, linear low-density polyethylene, atactic polypropylene, isotactic polypropylene, syndiotactic polypropylene, poly-α-olefin, and the like.

[0012] The melt mass flow rate (MFR) of the thermoplastic resin is not particularly limited, but is, for example, preferably from 0.1 to 25 g / 10 min, more preferably from 0.1 to 10 g / 10 min, and even more preferably from 0.29 to 1.00 g / 10 min. MFR can be measured in accordance with JIS K 7210:1999 at a test temperature of 220°C and a test load of 10 kg.

[0013] The specific gravity of the thermoplastic resin is not particularly limited, but is, for example, 942 to 953 kg / m3. The specific heat of the thermoplastic resin is not particularly limited, but is, for example, 1.9 to 2.3 kJ / kg·[K]. The thermal conductivity of the thermoplastic resin is not particularly limited, but is, for example, 0.46 to 0.5 W / m·K.

[0014] The thermoplastic resin may be a composition containing additives such as pigments, ultraviolet absorbers, antioxidants, and lubricants.

[0015] The melting point of the thermoplastic resin (ie, the melting temperature of the resin pipe 10) is not particularly limited, but is preferably 125 to 260°C, and more preferably 125 to 150°C.

[0016] The resin pipe 10 may have a multi-layer structure having a surface layer on at least one of the outer and inner surfaces. For example, by having a surface layer containing an ethylene-vinyl alcohol copolymer resin, the resin pipe 10 is more suitable for air conditioning, hot water supply, gas, or fuel. This is because the surface layer containing an ethylene-vinyl alcohol copolymer resin makes it difficult for gases such as hydrogen, oxygen, propane, and butane, and hydrocarbons such as gasoline and benzene to permeate. The surface layer may contain, for example, at least one of inorganic fibers and organic fibers. Examples of inorganic fibers include glass fibers, carbon fibers, silicon-titanium-carbon composite fibers, boron fibers, and metal fibers. Examples of organic fibers include aramid fibers, vinylon fibers, polyester fibers, and polyamide fibers. When the surface layer contains these fibers, the tensile strength of the resin pipe 10 can be increased and thermal expansion can be further suppressed. The surface layer may also contain a fluororesin. When the surface layer contains fluorine, resistance (chemical resistance) to acids, alkalis, and the like can be increased. Moreover, a layer similar to the surface layer may be provided inside the wall of the resin pipe 10 .

[0017] Methods for forming the resin pipe 10 include extrusion molding and injection molding. In particular, extrusion molding is easy to form the resin pipe 10 into a long length or a large diameter. Therefore, for example, when the length of the resin pipe 10 in the pipe axis O direction is 2 m or more, or when the outer diameter of the resin pipe 10 is a large diameter such as 300 mm or more, it is preferable to form the resin pipe 10 by extrusion molding. In addition, in the case of extrusion molding, the inner diameter of the molded resin pipe 10 is the same from one end to the other end of the resin pipe 10, so that the inner surface cutting (dimension adjustment) step S3 when manufacturing the electric fusion joint 1 can be omitted, or the amount of resin discarded by the inner surface cutting (dimension adjustment) step S3 can be reduced. In particular, when manufacturing a large-diameter electric fusion joint 1 having an outer diameter of 400 mm or more, which is difficult to mold by injection molding, a long resin pipe 10 having an outer diameter of 400 mm or more and a length of 2 m or more can be molded by extrusion molding, and the long resin pipe 10 can be cut to an appropriate length and a fusion portion can be provided on the inner surface to form the electric fusion joint 1. Also, by enlarging one end of the long resin pipe 10 to form a socket, it is possible to manufacture an electric fusion joint 1 having a length of 2 m or more, which is difficult to mold by injection molding.

[0018] The thermoplastic resin pipe 10 has a first resin pipe section 11, a second resin pipe section 12, and a third resin pipe section 13. The first resin pipe section 11, the second resin pipe section 12, and the third resin pipe section 13 are provided along the pipe axis O direction of the resin pipe 10. Hereinafter, the pipe axis O direction of the resin pipe 10 may be abbreviated as the "pipe axis O direction". Also, the radial direction with respect to the pipe axis O may be abbreviated as the "radial direction". Furthermore, the circumferential direction with respect to the pipe axis O may be abbreviated as the "circumferential direction".

[0019] The first resin pipe section 11 is provided on one end side of the electric fusion joint 1 in the pipe axis O direction. The second resin pipe section 12 is provided on the other end side of the electric fusion joint 1 in the pipe axis O direction. The first resin pipe section 11 is formed with a larger diameter than the second resin pipe section 12. The first resin pipe section 11 and the second resin pipe section 12 are arranged at one end side and the other end side along the pipe axis O direction with a gap therebetween, and are connected by a third resin pipe section 13. The third resin pipe section 13 is formed in an inclined shape so that the diameter gradually becomes smaller from the first resin pipe section 11 toward the second resin pipe section 12.

[0020] A first resin pipe 80 as a connecting resin pipe is inserted into the first resin pipe section 11 from one end side in the pipe axis O direction. A second resin pipe 81 as a connecting resin pipe is inserted into the second resin pipe section 12 from the other end side in the pipe axis O direction. Both the first resin pipe section 11 and the second resin pipe section 12 function as receiving ports.

[0021] However, the resin pipe 10 is not limited to the above-mentioned form (so-called increaser or reducer). For example, the outer diameter of the resin pipe 10 may be constant, and it may be a so-called socket. For example, the resin pipe 10 may be bent at the center in the pipe axis O direction, and it may be a so-called elbow. For example, the resin pipe 10 may have a branch pipe, and it may be a so-called Tee. For example, the resin pipe 10 may be long enough to be usable not only as a simple joint but also as a general pipe material. An example of such a resin pipe 10 is a pipe material in which only the pipe end is expanded in diameter. More specifically, an example of such a resin pipe 10 is a pipe material in which one end is a socket that is expanded in diameter and provided with a fusion part 20, and the other end is a spigot that is inserted into the socket of another pipe material, and the distance between the socket and the spigot (between one end and the other end) is a long resin pipe, for example, 2 m or more.

[0022] A first fusion portion 20 is provided on the inner peripheral surface 11a of the first resin pipe portion 11. That is, the first fusion portion 20 is provided on one end side in the pipe axis O direction of the electric fusion joint 1. The first fusion portion 20 has a first heating wire (heating wire) 21 inserted into a first notched groove (notched groove) formed in a spiral shape on the inner peripheral surface 11a of the first resin pipe portion 11. The opening portion of the first notched groove that opens on the inner peripheral surface 11a of the first resin pipe portion 11 may be, for example, spiral in shape with the pipe axis O as the central axis and the distance from the central axis to the inner peripheral surface 11a as the radius.

[0023] The two first terminals 30, 31 are provided in the first resin pipe section 11 near the end 11b of the socket section with a gap therebetween in the circumferential direction (see FIG. 2). The first terminal 30 is disposed in the first wire outlet hole 33 and connected to one end of the first heating wire 21. The first terminal 31 is disposed in the first wire outlet hole 34 and connected to the other end of the first heating wire 21. The two first wire outlet holes 33, 34 penetrate the first resin pipe section 11 in the radial direction near the end 11b of the socket section. The two first terminals 30, 31 pass electricity through the first heating wire 21 when the first resin pipe 80 to be connected is electrically fused to the first fusion section 20.

[0024] The first indicator 40 is embedded in, for example, a first recess 41 provided on the outer circumferential surface 11c of the first resin pipe portion 11. The first indicator 40 protrudes radially outward from the first recess 41 during electrical fusion when power is supplied to the first heating wire 21 via the two first terminals 30, 31. The protrusion of the first indicator 40 allows confirmation that the first fusion portion 20 is electrically fused to the first resin pipe 80 to be connected. The first indicator 40 may be molded integrally with the plastic pipe 10 using the same material, or may be assembled to the plastic pipe 10 that is made of a different material from the plastic pipe 10. When the first indicator 40 is molded integrally with the plastic pipe 10 using the same material, for example, the first indicator 40 and the first recess 41 can be simultaneously post-machined in the plastic pipe 10. Specifically, the first recess 41 may be cut (bored) with a drill or the like while leaving the portion that will become the first indicator 40 so that the portion that will become the first indicator 40 remains in the first recess 41, and the first indicator 40 and the first recess 41 may be molded in the plastic pipe 10 at the same time.

[0025] A second fusion part 50 is provided on the inner peripheral surface 12a of the second resin pipe section 12. That is, the second fusion part 50 is provided on the other end side in the pipe axis O direction of the electric fusion joint 1. The second fusion part 50 has a second heating wire (heating wire) 51 inserted into a second notched groove (notched groove) formed in a spiral shape on the inner peripheral surface 12a of the second resin pipe section 12. The opening part of the second notched groove that opens on the inner peripheral surface 12a of the second resin pipe section 12 may be, for example, spiral in shape with the pipe axis O as the central axis and the distance from the central axis to the inner peripheral surface 12a as the radius.

[0026] The second fused portion 50 is configured substantially similarly to the first fused portion 20 . The winding direction of the spiral formed by the first heating wire 21 and the second heating wire 51 is not particularly limited. For example, when the winding direction is right-handed as viewed from the opening side of one of the sockets in the electric fusion joint 1, it is left-handed as viewed from the opening side of the other socket. In other words, the winding direction is right-handed or left-handed as viewed from the opening side of one of the sockets in the electric fusion joint 1, and when viewed from the opening side of the other socket, it is reversed from when viewed from one socket. Here, the winding direction (hereinafter also referred to as the first winding direction) of the first heating wire 21 as viewed from the opening side of the first resin pipe section 11 (the opening side of one of the receiving ports) and the winding direction (hereinafter also referred to as the second winding direction) of the second heating wire 51 as viewed from the opening side of the second resin pipe section 12 (the opening side of the other receiving port) may be the same or different. For example, the first winding direction and the second winding direction may be common to right-handed winding or common to left-handed winding. Furthermore, one of the first winding direction and the second winding direction may be right-handed winding and the other may be left-handed winding.

[0027] In the embodiment, an example in which the first fusion part 20 is provided on one end side of the electric fusion joint 1 and the second fusion part 50 is provided on the other end side of the electric fusion joint 1 will be described, but the present invention is not limited to this. As another example, a fusion part may be provided on at least one end side of the electric fusion joint 1. Here, when the fusion portion is only on one end (the socket portion) side, the winding direction of the heating wire may be clockwise or counterclockwise when viewed from the opening side of the socket portion.

[0028] The two second terminals 60, 61 are provided in the second resin pipe section 12 at a circumferential interval near the end 12b of the socket section (see FIG. 3). The second terminal 60 is connected to one end of the second heating wire 51 via a second wire outlet hole 63. The second terminal 61 is connected to the other end of the second heating wire 51 via a second wire outlet hole 64. The two second wire outlet holes 63, 64 are passed through the second resin pipe section 12 in the radial direction near the end 12b of the socket section. The two second terminals 60, 61 pass electricity through the second heating wire 51 when the second resin pipe 81 to be connected is electrically fused to the second fusion section 50. The two second terminals 60, 61 are configured substantially similarly to the two first terminals 30, 31.

[0029] The second indicator 70 is embedded in, for example, a second recess 71 provided on the outer circumferential surface 12c of the second resin pipe portion 12. The second indicator 70 protrudes radially outward from the second recess 71 during electrical fusion when power is supplied to the second heating wire 51 via the two second terminals 60, 61. The protrusion of the second indicator 70 allows confirmation that the second fusion portion 50 is electrically fused to the second resin pipe 81 that is the connection partner. The second indicator 70 may be integrally molded with the plastic pipe 10 using the same material, or may be assembled to the plastic pipe 10 using a material different from that of the plastic pipe 10. The second indicator 70 is configured in a manner substantially similar to that of the first indicator 40.

[0030] As described above, the second fusion section 50 is configured substantially similarly to the first fusion section 20. Moreover, the second terminals 60, 61 are configured substantially similarly to the first terminals 30, 31. Furthermore, the second indicator 70 is configured substantially similarly to the first indicator 40. Therefore, hereinafter, the resin tube 10, the first fusion section 20, the first terminals 30, 31, and the first indicator 40 will be described in detail, and descriptions of other configurations will be omitted. In this embodiment, both the first fusion portion 20 and the second fusion portion 50 are provided, but only one of the first fusion portion 20 and the second fusion portion 50 may be provided. That is, the electric fusion joint 1 may have a configuration in which only one end can be electrically fused.

[0031] <Resin pipe> As shown in Figs. 1 and 2, a plurality of first fixing marks (fixing marks) 15 are provided in a first portion of the first resin pipe section 11 located closer to the end face 11d of the first resin pipe section 11 than the first fusion section 20 in the pipe axis O direction. In the embodiment, the first portion located on the end face 11d side of the first resin pipe section 11 is described as the end face 11d of the first resin pipe section 11. Also, in the embodiment, an example in which four first fixing marks 15 are provided at equal intervals in the circumferential direction on the end face 11d of the first resin pipe section 11 as the plurality of first fixing marks 15 is described. However, the first fixing marks 15 do not have to be provided at equal intervals.

[0032] The four first fixing marks 15 are, for example, depressions formed by contact of four first needle portions 106 provided on a first device 102 (see FIG. 6) described later. The four first needle portions 106 contact the end face 11d of the first resin pipe portion 11, so that the end face 11d of the first resin pipe portion 11 is supported by the first device 102. In the embodiment, an example in which there are four first fixing marks 15 will be described, but the number of first fixing marks 15 can be arbitrarily selected from two or more. Furthermore, the location where the first fixing mark 15 is provided is not limited to the end surface 11d of the first resin pipe section 11. The location where the first fixing mark 15 is provided may be any first portion located on the end surface 11d side of the first resin pipe section 11. Note that modified examples of the first portion excluding the end surface 11d of the first resin pipe section 11 will be described in detail in Modification Example 1 of Figs. 11 to 13.

[0033] As shown in Fig. 1 and Fig. 3, a plurality of second fixing marks (fixing marks) 16 are provided in a first portion of the second resin pipe section 12 located closer to the end face 12d of the second resin pipe section 12 than the second fusion section 50 in the pipe axis O direction. In the embodiment, the first portion located on the end face 12d side of the second resin pipe section 12 is described as the end face 12d of the second resin pipe section 12. Also, in the embodiment, an example in which four second fixing marks 16 are provided at equal intervals in the circumferential direction on the end face 12d of the second resin pipe section 12 as the plurality of second fixing marks 16 is described. However, the second fixing marks 16 do not have to be provided at equal intervals.

[0034] The four second fixing marks 16 are, for example, depressions formed by contact of four second needle portions 107 provided in a first device 102 (see FIG. 6) described later. When the four second needle portions 107 contact the end face 12d of the second resin pipe portion 12, the end face 12d of the second resin pipe portion 12 is supported by the first device 102. Thus, the end face 11d of the first resin pipe portion 11 and the end face 12d of the second resin pipe portion 12 are supported by the first device 102. As a result, the resin pipe 10 is supported in a state in which it is positioned by the first device 102. In the embodiment, four second fixing marks 16 are described as an example, but the number of the second fixing marks 16 can be arbitrarily selected from two or more. Furthermore, the location where the second fixing mark 16 is provided is not limited to the end surface 12d of the second resin pipe section 12. The location where the second fixing mark 16 is provided may be any first portion located on the end surface 12d side of the second resin pipe section 12. Note that modified examples of the first portion excluding the end surface 12d of the second resin pipe section 12 will be described in detail in Modification Example 1 of Figs. 11 to 13.

[0035] The first fixing marks 15 and the second fixing marks 16 may be arranged circumferentially offset from each other as shown in Figures 2 and 3, or may be arranged at the same position in the circumferential direction. Also, the number of the first fixing marks 15 and the number of the second fixing marks 16 may be the same as shown in Figures 2 and 3, or may be different.

[0036] <Heating wire> As shown in Figs. 1 and 4, the first heating wire 21 is inserted into a first notched groove (notched groove) formed in a spiral shape on the inner circumferential surface 11a of the first resin pipe portion 11 in the first fusion portion 20. The first heating wire 21 has an outward heating wire 21a, a folded portion 21b, and a return heating wire 21c in the first fusion portion 20. Hereinafter, the outward heating wire 21a may be referred to as the "outward portion 21a". Also, the return heating wire 21c may be referred to as the "return portion 21c".

[0037] The outgoing path section 21a is drawn out from the first wire drawing hole 33, and is formed by progressing in a spiral in the outgoing direction from the opening side of the first resin pipe section 11 to the opening side of the second resin pipe section 12. Here, the opening side of the first resin pipe section 11 is "one opening side of the electric fusion joint 1". The opening side of the second resin pipe section 12 is "the other opening side of the electric fusion joint 1 (the opening side opposite to the one opening)". In Figs. 1 and 4, the outgoing path section 21a is indicated by a solid line.

[0038] The folded-back portion 21b connects the outward path portion 21a and the return path portion 21c in the first heating wire 21. The folded-back portion 21b is curved in a front view of the folded-back portion 21b seen from the radially inner side of the first resin pipe portion 11. A modified example of the folded-back portion 21b will be described in detail in Modification Example 3 of Figs. 16 to 18.

[0039] The return path portion 21c is formed by a spiral that advances from the folded-back portion 21b where the forward path portion 21a is folded back in the return direction opposite to the forward direction. The return path portion 21c advances to the first wire drawing hole 34 at the opening side of the first resin pipe portion 11. That is, the first heating wire 21 is formed of a single heating wire including the forward path portion 21a in the forward direction, the folded-back portion 21b, and the return path portion 21c in the opposite direction to the forward path portion 21a. The diameter of the first heating wire 21 is 0.2 mm or more and 1.5 mm or less.

[0040] The Young's modulus of the first heating wire 21 is, for example, 65 kN / mm 2 More than 150kN / mm 2 The following is the Young's modulus of each material. The Young's modulus of copper is 117 kN / mm 2 Among copper alloys, the Young's modulus of copper-nickel 30 is 127.5 kN / mm 2 , Young's modulus of Cu-Ni-49 is 147.1kN / mm 2 , Young's modulus of Cu-Ni-69 is 147.1kN / mm 2 , Young's modulus of phosphor bronze (C5102) is 110kN / mm 2 , Young's modulus of brass (C2600) is 110kN / mm 2 The Young's modulus of aluminum is 69 kN / mm 2 The Young's modulus of aluminum alloy (A2024) is 74 kN / mm 2 Other materials that may be used for the first heating wire 21 include nichrome, iron-chrome alloy, copper-nickel alloy, copper-manganese alloy, iron-nickel alloy, manganese, copper-nickel-manganese alloy, nickel-chrome alloy, and chromel.

[0041] The first heating wire 21 may be covered or uncovered. Even if the first heating wire 21 is covered, the Young's modulus of the first heating wire 21 can be considered to be substantially the same as that of an uncovered heating wire in a bare wire state. When the first heating wire 21 is coated, polyurethane, modified polyester, polyester, polyesterimide, or polyamideimide is used as the coating resin for the first heating wire 21. The heat-resistant temperature of polyurethane is 130°C, that of modified polyester is 155 to 180°C, that of polyester is 155°C, that of polyesterimide is 180°C, and that of polyamideimide is 220°C. Preferably, an imide-based coating resin is used for the first heating wire 21, and more preferably, polyamideimide, which has excellent heat resistance, is used.

[0042] The Young's modulus of the first heating wire 21 can be measured by taking out the folded portion 21b from the electric fusion joint 1 and using the folded portion 21b as a sample. The measurement method is based on, for example, JIS C 2532:1999. For example, a test is performed according to JIS Z 2241 described in "8.2.3 Tensile test" in JIS C 2532:1999 to measure the Young's modulus.

[0043] <Terminal> In the first resin pipe section 11, two first wire drawing holes 33, 34 and two first terminals 30, 31 are provided at a circumferential distance near the end 11b of the socket section. In this state, the first heating wire 21 has an end 21a1 of the outward path section 21a connected to the first terminal 30. Also, the first heating wire 21 has an end 21c1 of the return path section 21c connected to the first terminal 31. The first heating wire 21 can be energized by the two first terminals 30, 31.

[0044] In the embodiment, an example in which the two first terminals 30, 31 are provided at an interval in the circumferential direction in the first resin pipe section 11 will be described, but the present invention is not limited thereto. For example, one protrusion (e.g., a rectangular parallelepiped protrusion) may be provided on the outer surface of the resin pipe 10, and the two first terminals 30, 31 may be arranged on this one protrusion. In this case, the two first terminals 30, 31 may be arranged adjacent to each other (adjacent) in the circumferential direction on the one protrusion. Furthermore, for example, the two first terminals 30, 31 may be provided at an interval in the pipe axis O direction. A modified example in which the two first terminals 30, 31 are provided at an interval in the pipe axis O direction will be described in detail in Modification 2 of Figs. 14 and 15.

[0045] <Indicator> The first indicator 40 is provided on the outer circumferential surface 11c of the first resin pipe portion 11. The circumferential position and the pipe axis O direction position of the first indicator 40 are as follows.

[0046] (Circumferential position of indicator) Plane X and plane Y are defined as references. The tube axis O passes through both plane X and plane Y. In other words, plane X and plane Y intersect at the tube axis O. Plane X passes through not only the tube axis O but also the midpoint in the circumferential direction of the line segment connecting the two first terminals 30, 31 in the circumferential direction. Meanwhile, plane Y passes through not only the tube axis O but also the first indicator 40. The first indicator 40 is disposed with respect to the first terminals 30, 31 such that the angle between the plane X and the plane Y in the circumferential direction is ±90° or less. However, the circumferential position of the first indicator 40 is not limited to this.

[0047] (Indicator tube axial position) The first indicator 40 is disposed on the end surface 11d side of the first resin pipe section 11 from the center of the range E in the tube axis O direction, in the range E in the tube axis O direction in which the first fusion section 20 is provided. Here, the range E in the tube axis O direction refers to the range in the tube axis O direction that extends from one end of the first heating wire 21 in the tube axis O direction to the other end of the first heating wire 21 in the tube axis O direction. The center of the range E refers to the midpoint of the range E in the tube axis O direction. In the embodiment, an example will be described in which the first indicator 40 is disposed closer to the end face 11d of the first resin pipe portion 11 than the center in the range E of the first fusion portion 20, but the present invention is not limited to this. For example, the first indicator 40 may be disposed between two first terminals in the direction of the tube axis O. A modified example in which the first indicator 40 is disposed between two first terminals in the direction of the tube axis O will be described in detail with reference to the modified examples in Figs. 14 and 15.

[0048] <Method of manufacturing electric fusion joint> Next, a manufacturing method of the electric fusion joint 1 will be described with reference to Figures 1 to 4 and 6 to 10 in addition to the flow chart of Figure 5. Note that in the manufacturing method of the electric fusion joint 1, an example of forming the first fusion portion 20 on the inner circumferential surface 11a of the first resin pipe portion 11 will be described, and a description of forming the second fusion portion 50 on the inner circumferential surface 12a of the second resin pipe portion 12 will be omitted. As shown in Figures 6 to 10, the electric fusion joint 1 is made by embedding a first heating wire 21 (see Figures 1 and 4) in a plastic pipe 10 using a heating wire laying device 100. The heating wire laying device 100 includes a first device 102 and a second device 103. The first device 102 includes a first fixing unit 104 and a second fixing unit 105. The second device 103 includes a cutting unit (not shown), a heating wire embedding unit 110, and a smoothing cutting unit (not shown).

[0049] As shown in FIG. 5, when manufacturing the electric fusion joint 1, first, in the pin position hole drilling process S1, two first wire withdrawal holes 33, 34 (see FIG. 4) are drilled in the electric fusion joint 1 (not the electric fusion joint 1 as a finished product, but a hollow cylindrical resin tube 10).

[0050] 5 and 6, in a joint setting step (first step) S2, the second fixing part 105 provided on the first device 102 is retreated from the first fixing part 104 to widen the gap between the first fixing part 104 and the second fixing part 105. This makes it possible to arrange the plastic pipe 10 in the gap between the first fixing part 104 and the second fixing part 105. 5 and 7, continuing with the joint setting step S2, the plastic pipe 10 is placed in the space between the first fixing portion 104 and the second fixing portion 105. The plastic pipe 10 is temporarily fixed in a state where one end face of the placed plastic pipe 10 (i.e., end face 11d of the first plastic pipe portion 11) is in contact with the four first needle portions 106 of the first fixing portion 104. After the plastic pipe 10 is temporarily fixed, the second fixing portion 105 is moved as indicated by arrow A toward the other end face of the plastic pipe 10 (i.e., end face 12d of the second plastic pipe portion 12). In the illustrated example, the resin pipe 10 is placed horizontally, but the first device 102 may be configured so that the resin pipe 10 is placed vertically.

[0051] 5 and 8, the joint setting step S2 is continued, and the four second needle portions 107 of the second fixing portion 105 are brought into contact with the end face 12d of the second resin pipe portion 12. As a result, in the joint setting step S2, the resin pipe 10 is fixed to the first fixing portion 104 and the second fixing portion 105 of the first device 102. In this state, the resin pipe 10 is set in the first device 102 so as to be rotatable (rotatable) about the pipe axis O as indicated by the arrow B (see FIG. 9).

[0052] In this manner, in the joint setting step S2, the end face 11d of the first resin pipe section 11 of the resin pipe 10 contacts (is pressed against) the first needle section 106 of the first fixing section 104 in the pipe axis O direction of the resin pipe 10. As a result, four first fixing marks 15 (see FIG. 2) are provided on the end face 11d of the first resin pipe section 11. Also, the end face 12d of the second resin pipe section 12 of the resin pipe 10 contacts (is pressed against) the second needle section 107 of the second fixing section 105 in the pipe axis O direction of the resin pipe 10. As a result, four second fixing marks 16 (see FIG. 3) are provided on the end face 12d of the second resin pipe section 12.

[0053] After the plastic pipe 10 is set in the first device 102, in the inner surface cutting (dimensioning) step S3, while the plastic pipe 10 is rotated on its axis as indicated by the arrow B in the first device 102, a cutting unit (not shown) is moved in the direction of the pipe axis O to cut the inner surface of the plastic pipe 10 with a cutting blade provided on the cutting unit. This allows the dimensions of the inner surface of the plastic pipe 10 to be determined. After the dimensions of the inner surface of the plastic pipe 10 have been determined, the rotation of the plastic pipe 10 is stopped. After the rotation of the plastic pipe 10 has been stopped, in a wire drawing step (1) S4 from the pin position, the outgoing path portion 21a of the first heating wire 21 (specifically, the end portion 21a1 of the outgoing path portion 21a) is drawn out from the first wire drawing hole 33 shown in FIG. 4.

[0054] Next, as shown in FIG. 5, FIG. 9, and FIG. 10, in the wire embedding portion cutting embedding step (second step) S5, the first heating wire 21 is embedded in the inner circumferential surface 11a of the first resin pipe portion 11 using the heating wire embedding portion 110 provided in the second device 103. The heating wire embedding portion 110 has cutting means 111 such as a cutter, heating wire guiding means 112, and sealing means 113. The cutting means 111 such as a cutter forms a first notch groove in the inner circumferential surface 11a of the first resin pipe portion 11. The cutting means 111 has a through hole or the like that guides the first heating wire 21 into the first notch groove. The heating wire guiding means 112 guides the first heating wire 21 into the first notch groove. The heating wire guiding means 112 is arranged so that the first heating wire 21 passes through the cutting means 111 and enters the notch. The containment means 113 closes the first notched groove to contain the first heating wire 21 within the first notched groove.

[0055] As shown in Figures 4, 9, and 10, the first heating wire 21 is laid on the inner circumferential surface 11a of the first resin pipe section 11 by the heating wire laying device 100. At this time, the resin pipe 10 is rotated on its axis as indicated by the arrow B by the first device 102, and the heating wire laying device 100 is moved in the pipe axis O direction from the end face 11d of the first resin pipe section 11 to the end face 12d of the second resin pipe section 12. As a result, the cutting means 111 of the heating wire laying device 100 is used to cut a first notch groove on the inner circumferential surface 11a of the first resin pipe section 11, while inserting the forward path portion 21a of the first heating wire 21 into the first notch groove. Next, the first notch groove is closed by the sealing means 113, and the forward path portion 21a is embedded in the inner circumferential surface 11a of the first resin pipe section 11.

[0056] After embedding the outward path 21a in the inner peripheral surface 11a of the first resin pipe section 11, the rotation angle of the cutting means 111 is adjusted in the reverse direction to fold back the outward path 21a and embed the folded back portion 21b in the inner peripheral surface 11a of the first resin pipe section 11. After reversing the cutting means 111, the electric heating wire laying device 100 is moved in the pipe axis O direction toward the end face 11d of the first resin pipe section 11, so that the return path 21c of the first electric heating wire 21 is embedded in the inner peripheral surface 11a of the first resin pipe section 11 in the same manner as the outward path 21a. Thus, the first electric heating wire 21 can be embedded in the inner peripheral surface 11a of the first resin pipe section 11 so as to draw a double spiral by the outward path 21a and the return path 21c. This allows the first fusion portion 20 to be formed on the inner peripheral surface 11a of the first resin pipe section 11.

[0057] 4 and 5, after the first fused portion 20 is formed on the inner peripheral surface 11a of the first resin pipe portion 11, the rotation of the resin pipe 10 is stopped in a wire drawing-out process (2) S6 from the pin position. After the rotation of the resin pipe 10 is stopped, the end portion 21c1 of the return path portion 21c is drawn out from the first wire drawing-out hole 34. Next, in the resin smoothing and thin film cutting process S7 of the wire embedded portion, while the resin pipe 10 is rotated on its axis as indicated by the arrow B by the first device 102, an embedded portion smoothing unit (not shown) is moved in the direction of the pipe axis O. As a result, the resin of the wire embedded portion is smoothed by the embedded portion smoothing unit, and the resin smoothed portion is thin-cut by a cutting blade provided on the embedded portion smoothing unit. By thin-cutting the resin smoothed portion, the dimensions of the inner circumferential surface 11a of the first resin pipe portion 11 in which the first heating wire 21 is embedded are determined.

[0058] After the dimensions of the inner surface 11a of the first resin pipe section 11 are determined, in the fitting removal process S8, the second fixing section 105 provided on the first device 102 is retracted from the resin pipe 10, and the resin pipe 10 with the first heating wire 21 embedded therein is removed from the first device 102. As shown in Figures 1, 4 and 5, after the plastic pipe 10 is removed from the first device 102, in the indicator step S9, the first indicator 40 is formed on the outer peripheral surface 11c of the first plastic pipe section 11. When the first indicator 40 is integral with the plastic pipe 10, in the indicator step S9, a cylindrical drill is used to cut a recess in the outer peripheral surface 11c, leaving a protrusion that will become the first indicator 40, thereby forming the first indicator 40. When the first indicator 40 is a member separate from the plastic pipe 10, the first indicator 40 can be formed by forming a through hole or a recess (a non-through recess) in the outer peripheral surface 11c, and then assembling a member that will become the first indicator 40 into the through hole or recess.

[0059] After forming the first indicator 40 on the outer circumferential surface 11c of the first resin pipe portion 11, in a terminal pin positioning process S10, two first terminals 30, 31 are provided on the first resin pipe portion 11. The end portion 21a1 of the outgoing path portion 21a is connected to the first terminal 30. In addition, the end portion 21c1 of the return path portion 21c is connected to the first terminal 31. In this way, by carrying out the steps S1 to S10, the electrofusion joint 1 can be manufactured, and the manufacturing method for the electrofusion joint 1 is completed. However, the manufacturing method is not limited to this. For example, as in the embodiment, both the indicator step S9 and the terminal pin position step S10 may be carried out after the joint removal step S8, and at least one of the indicator step S9 and the terminal pin position step S10 may be carried out before the joint removal step S8.

[0060] As described above, according to the embodiment of the electric fusion joint 1, as shown in Figs. 1 to 3 and 8, four first fixing marks 15 are provided on the end surface 11d of the first resin pipe section 11. In addition, four second fixing marks 16 are provided on the end surface 12d of the second resin pipe section 12. The first fixing marks 15 and the second fixing marks 16 are provided by contacting the first needle section 106 and the second needle section 107 of the first device 102 with the resin pipe 10 when the first resin pipe section 11 is provided with the first fusion section 20 and the second resin pipe section 12 is provided with the second fusion section 50. In this way, by sandwiching the resin pipe 10 with the first device 102 from the pipe axis O direction, the first needle section 106 and the second needle section 107 of the first device 102 contact the resin pipe 10. Therefore, the resin pipe 10 can be positioned with high accuracy by the first device 102. This can improve the molding accuracy of the electric fusion joint 1.

[0061] Also, the first fixing mark 15 is provided on the end face 11d of the first resin pipe section 11. Furthermore, the second fixing mark 16 is provided on the end face 12d of the second resin pipe section 12. As a result, when the resin pipe 10 is positioned by the first device 102, there is no risk of the first device 102 interfering with the wire-embedding section cutting and embedding step of providing the first fusion section 20 on the first resin pipe section 11 and the second fusion section 50 on the second resin pipe section 12.

[0062] According to the manufacturing method of the electric fusion joint 1 in the embodiment, as shown in Figs. 1 to 3 and 8, the first needle 106 of the first device 102 contacts the end face 11d of the first resin pipe section 11 to provide four first fixing marks 15 on the end face 11d of the first resin pipe section 11. The second needle 107 of the second device 103 contacts the end face 12d of the second resin pipe section 12 to provide four second fixing marks 16 on the end face 12d of the second resin pipe section 12. Thus, the resin pipe 10 can be positioned with high accuracy by the first device 102. This allows the molding accuracy of the electric fusion joint 1 to be improved.

[0063] Moreover, four first fixing marks 15 are provided on the end face 11d of the first resin pipe portion 11. Furthermore, four second fixing marks 16 are provided on the end face 12d of the second resin pipe portion 12. As a result, with the plastic pipe 10 positioned by the first device 102, there is no risk of the first device 102 interfering with the wire embedding portion cutting and embedding process S5, in which the first heating wire 21 is inserted into the first notch groove using the second device 103.

[0064] 4, the first heating wire 21 is folded back at the folded back portion 21b to switch the spiral direction from the forward direction (i.e., the forward portion 21a) to the backward direction (i.e., the backward portion 21c). It is preferable that the folded back portion 21b secures folding accuracy of the first heating wire 21, taking into consideration, for example, the pitch P of the heating wire 21 in the tube axis O direction. Therefore, the Young's modulus of the first heating wire 21 is set to 150 kN / mm 2 As a result, the rigidity of the heating wire can be suitably kept low, thereby ensuring the folding accuracy of the folded-back portion 21b and improving the forming accuracy of the electric fusion joint 1.

[0065] Furthermore, if the rigidity of the first heating wire 21 is too low, the first heating wire 21 may break when the first heating wire 21 is folded back. Therefore, the Young's modulus of the first heating wire 21 is set to 65 kN / mm 2As a result, when the first heating wire 21 is folded back, the first heating wire 21 can be prevented from breaking at the folded back portion 21b.

[0066] Furthermore, by setting the diameter of the first heating wire 21 to be 0.2 mm or more and 1.5 mm or less, when the first heating wire 21 is folded back, the folding back accuracy of the first heating wire 21 can be ensured and breakage of the first heating wire 21 can be prevented.

[0067] In addition, by folding back the folded-back portion 21b of the first heating wire 21 in a curved manner, the first heating wire 21 can be folded back smoothly at the folded-back portion 21b, making the first heating wire 21 less likely to break.

[0068] 1 and 4, the first indicator 40 is embedded in, for example, a first recess 41 provided on the outer circumferential surface 11c of the first resin pipe portion 11. The first indicator 40 protrudes radially outward from the first recess 41 during electrical fusion when power is supplied to the first heating wire 21 via the two first terminals 30, 31. The protrusion of the first indicator 40 makes it possible to confirm that the electrical fusion joint 1 is electrically fused to the first resin pipe 80 as a connection partner.

[0069] Here, it is considered that the first resin pipe section 11 expands relatively greatly radially outward at the center 11e in the pipe axis O direction of the first fusion section 20 during electrical fusion. Therefore, for example, if the first indicator 40 is provided at the center of the first fusion section 20 on the outer circumferential surface 11c of the first resin pipe section 11, it is considered that resin leakage occurs during fusion or the first indicator 40 protrudes too much during fusion. For this reason, it is desired to ensure the performance of the electrical fusion joint 1 while providing the first indicator 40 on the outer circumferential surface 11c of the first resin pipe section 11.

[0070] Therefore, the first indicator 40 is arranged, in the direction of the pipe axis O, closer to the end face 11d of the first resin pipe section 11 than the center of the range E in the direction of the pipe axis O in which the first fusion section 20 is provided. Therefore, it is possible to confirm by the first indicator 40 that the electric fusion joint 1 is electrically fused to the first resin pipe 80 as a connection partner. As a result, the performance of the electric fusion joint 1 can be ensured while providing the first indicator 40 to the electric fusion joint 1.

[0071] <Modification> Next, Modifications 1, 2, and 3 of the embodiment will be described with reference to Figures 11 to 18. Note that in Modifications 1, 2, and 3, the same or similar configurations as those of the electric fusion joint 1 of the embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0072] <Variation 1> A first modification of the first fixing mark 15 and the second fixing mark 16 in the embodiment will be described with reference to Figs. 11 and 12, in the modified example 1(1), a plurality of first fixing marks (fixing marks) 201 are provided on the outer circumferential surface (peripheral surface) 11c of the first resin pipe section 11 as a first portion located closer to the end surface 11d side of the first resin pipe section 11 than the first fusion section 20. An example of the plurality of first fixing marks 201 will be described using four marks. The first fixing marks 201 are provided by contact with the first needle section 206 of the first fixing section 205. In the first modification, four first fixing marks 201 are described as an example, but the number of first fixing marks 201 can be arbitrarily selected from two or more.

[0073] In addition, in the modified example 1(1), the multiple second fixing marks (fixing marks) 202 are provided on the outer circumferential surface (peripheral surface) 12c of the second resin pipe section 12 as a first portion located closer to the end surface 12d side of the second resin pipe section 12 than the second fusion section 50. An example of the multiple second fixing marks 202 will be described using four marks. The second fixing marks 202 are provided by contact with the second needle portion of the second fixing section (not shown). In the first modification, four second fixing marks 202 are described as an example, but the number of second fixing marks 202 can be arbitrarily selected from two or more.

[0074] According to the modified example 1(1) shown in Figs. 11 and 12, four first fixing marks 201 are provided on the outer peripheral surface 11c of the first resin pipe section 11, and four second fixing marks 202 are provided on the outer peripheral surface 12c of the second resin pipe section 12. Therefore, the resin pipe 10 can be accurately positioned by supporting it from the radially outside of the resin pipe 10. This allows the molding accuracy of the electric fusion joint 1 to be improved without the first fixing portion 205 or the second fixing portion interfering with the manufacturing process of providing the first fusion portion 20 on the inner peripheral surface 11a of the first resin pipe section 11 and the second fusion portion 50 on the inner peripheral surface 12a of the second resin pipe section 12. The first fixing marks 201 and the second fixing marks 202 may be arranged circumferentially offset from each other as shown in Figures 11 and 12, or may be arranged at the same position in the circumferential direction. Also, the number of the first fixing marks 201 and the number of the second fixing marks 202 may be the same as in Figures 11 and 12, or may be different.

[0075] 13, in the modified example 1(2), the multiple first fixing marks (fixing marks) 211 are provided by contacting (pressing, gripping, clamping) a first chuck (not shown). Although four first fixing marks 211 are described as an example, the multiple first fixing marks 211 can be arbitrarily selected from two or more. Furthermore, the multiple second fixing marks (fixing marks) 212 are provided by contacting a second chuck (not shown). Although four second fixing marks 212 are described as an example, the multiple second fixing marks 212 can be arbitrarily selected from two or more.

[0076] 13, the resin pipe 10 can be accurately positioned by supporting the resin pipe 10 from the radially outer or inner side of the resin pipe 10 with the first chuck and the second chuck. This improves the molding accuracy of the electric fusion joint 1 without interfering with the manufacturing process of providing the first fusion portion 20 on the inner circumferential surface 11a of the first resin pipe portion 11 and the second fusion portion 50 on the inner circumferential surface 12a of the second resin pipe portion 12 with the first chuck and the second chuck. The first fixing marks 211 and the second fixing marks 212 may be arranged circumferentially offset from each other as shown in Fig. 13, or may be arranged at the same position in the circumferential direction. Also, the number of the first fixing marks 211 and the number of the second fixing marks 212 may be the same as in Fig. 13, or may be different.

[0077] <Variation 2> A second modification of the first indicator 40 and the second indicator 70 in the embodiment will be described with reference to Figs. 14 and 15, in the second modification, two first terminals (terminals) 221, 222 are provided on the outer peripheral surface 11c of the first resin pipe section 11. The two first terminals 221, 222 are arranged at an interval from each other in the direction of the pipe axis O on the outer peripheral surface 11c of the first resin pipe section 11. The two first terminals 221, 222 are connected to both ends of the first heating wire 21, respectively.

[0078] The first heating wire 21 is folded back at the folded back portion 21b (see FIG. 4). Therefore, both ends of the first heating wire 21 are located closer to the end face 11d of the first resin pipe section 11 than the center of the range E of the first fusion section 20. As a result, the two first terminals 221, 222 are located closer to the end face 11d of the first resin pipe section 11 than the center of the range E of the first fusion section 20. Therefore, the first indicator (indicator) 224 is disposed between the two first terminals 221, 222 in the direction of the tube axis O. This allows the first indicator 224 to be disposed closer to the end face 11d of the first resin tube section 11 than the center of the range E of the first fusion section 20.

[0079] 14 and 15, it is possible to confirm with the first indicator 224 that the electrofusion joint 1 is electrically fused to the first resin tube 80 as a connection partner. This makes it possible to provide the first indicator 224 to the electrofusion joint 1 while ensuring the performance of the electrofusion joint 1.

[0080] 14, two second terminals (terminals) 231, 232 are provided on the outer circumferential surface 12c of the second resin pipe portion 12. The two second terminals 231, 232 are connected to both ends of the second heating wire 51, similar to the two first terminals 221, 222. Between the two second terminals 231, 232, a second indicator (indicator) 234 is disposed in the direction of the tube axis O. That is, the second indicator 234 is disposed in the same manner as the first indicator 224. As a result, according to the second indicator 234 of the second modification shown in FIG. 14, the performance of the electric fusion joint 1 can be ensured while providing the second indicator 234 to the electric fusion joint 1.

[0081] The circumferential positions of the two first terminals 221, 222 do not have to coincide with each other, and the circumferential positions of the two second terminals 231, 232 do not have to coincide with each other. In other words, the two first terminals 221, 222 do not have to be arranged side by side in the tube axis O direction, and the two second terminals 231, 232 do not have to be arranged side by side in the tube axis O direction. For example, the two first terminals 221, 222 may be arranged at an interval from each other in the circumferential direction and also at an interval from each other in the direction of the tube axis O. In this case, the position of the first indicator 224 in the direction of the tube axis O is disposed between the two first terminals 221, 222 in the direction of the tube axis O. For example, the two second terminals 231, 232 may be arranged at an interval from each other in the circumferential direction and also at an interval from each other in the direction of the tube axis O. In this case, the position of the second indicator 234 in the direction of the tube axis O is disposed between the two second terminals 231, 232 in the direction of the tube axis O.

[0082] <Modification 3> A third modification of the folded-back portion 21b of the first heating wire 21 in the embodiment will be described with reference to Figs. 16, in the modification 3(1), the folded-back portion 21b1 of the first heating wire 21 has a shape including a plurality of arcs having different curvatures when viewed from the front. The folded-back portion 21b1 includes two arcs, a first arc Ca1 and a second arc Ca2.

[0083] The first arc Ca1 is folded back at a radius of curvature R1 in a semicircle or greater. The center of curvature C1 of the first arc Ca1 is located inside the folded back portion 21b1. The second arc Ca2 is folded back at a radius of curvature R2. The center of curvature C2 of the second arc Ca2 is located outside the folded back portion 21b1. That is, the center of curvature C1 of the first arc Ca1 and the center of curvature C2 of the second arc Ca2 are located on opposite sides of the folded back portion 21b1 in a front view.

[0084] According to the folded portion 21b1 of the modified example 3(1), the folded portion 21b1 has a shape including two circular arcs, a first circular arc Ca1 and a second circular arc Ca2, each having a different curvature. This allows the first heating wire 21 to be folded back smoothly at the folded portion 21b1, making it difficult for the first heating wire 21 to break.

[0085] In addition, the center of curvature C1 of the first arc Ca1 and the center of curvature C2 of the second arc Ca2 are positioned on opposite sides of the turn-back portion 21b1 in a front view. Therefore, the return path portion 21c turned back at the turn-back portion 21b1 can be brought closer to the outgoing path portion 21a in the direction of the tube axis O. As a result, the turn-back portion 21b1 can turn the outgoing path portion 21a back to the return path portion 21c without changing the pitch P between the outgoing path portion 21a and the return path portion 21c.

[0086] 17, in the modification 3(2), the folded-back portion 21b2 of the first heating wire 21 has a shape including a plurality of arcs having different curvatures in a front view. The folded-back portion 21b2 includes four arcs, namely, a first arc Ca3, a second arc Ca4, a third arc Ca5, and a fourth arc Ca6.

[0087] The first arc Ca3, the second arc Ca4, and the third arc Ca5 fold back the convex corners of the folded-back portion 21b2 to form a rounded corner shape. The center of curvature C3 of the first arc Ca3, the center of curvature C4 of the second arc Ca4, and the center of curvature C5 of the third arc Ca5 are located inside the folded-back portion 21b2. The fourth arc Ca6 is folded back at a curvature radius R6. The center of curvature C6 of the fourth arc Ca6 is located outside the folded-back portion 21b2. That is, the center of curvature C3 of the first arc Ca3, the center of curvature C4 of the second arc Ca4, and the center of curvature C5 of the third arc Ca5 are located on the opposite side of the folded-back portion 21b2 in a front view.

[0088] According to the folded-back portion 21b2 of the modified example 3(2), the folded-back portion 21b2 has a shape including four arcs, a first arc Ca3, a second arc Ca4, a third arc Ca5, and a fourth arc Ca6, each having a different curvature. This allows the first heating wire 21 to be folded back smoothly at the folded-back portion 21b2, making the first heating wire 21 less likely to break.

[0089] In addition, the center of curvature C3 of the first arc Ca3, the center of curvature C4 of the second arc Ca4, the center of curvature C5 of the third arc Ca5, and the center of curvature C6 of the fourth arc Ca6 are positioned on opposite sides of the turn-back portion 21b2 in a front view. Therefore, the return path portion 21c turned back at the turn-back portion 21b2 can be brought closer to the outgoing path portion 21a in the direction of the tube axis O. As a result, the turn-back portion 21b2 can turn the outgoing path portion 21a back to the return path portion 21c without changing the pitch P between the outgoing path portion 21a and the return path portion 21c.

[0090] As shown in FIG. 18, in the modified example 3(3), the folded portion 21b3 of the first heating wire 21 has a shape including a plurality of arcs having different curvatures in a front view. The folded portion 21b3 has two arcs, a first arc Ca7 and a second arc Ca8. The first arc Ca7 is folded back with a radius of curvature R7. The center of curvature C7 of the first arc Ca7 is located inside the folded portion 21b3. The second arc Ca8 is folded back with a radius of curvature R8. The center of curvature C8 of the second arc Ca8 is located inside the folded portion 21b3.

[0091] Here, the connecting end (end) 21a2 of the outgoing path portion 21a and the connecting end (end) 21c2 of the returning path portion 21c are both linearly inclined with respect to the tube axis O direction in a front view. The connecting end 21a2 is connected to the turn-back portion 21b3. The connecting end 21c2 is connected to the turn-back portion 21b3. Furthermore, the inclination angle θ1 that the connecting end 21a2 of the outgoing path portion 21a makes with respect to the tube axis O direction is different from the inclination angle θ2 that the connecting end 21c2 of the returning path portion 21c makes with respect to the tube axis O direction. However, the inclination angle θ1 and the inclination angle θ2 may be the same. The inclination angle θ1 that the connecting end 21a2 makes with respect to the tube axis O direction indicates the angle of the connecting end 21a2 with respect to the imaginary line Vl perpendicular to the tube axis O. The inclination angle θ2 that the connecting end 21c2 makes with respect to the tube axis O direction indicates the angle of the connecting end 21c2 with respect to the imaginary line Vl perpendicular to the tube axis O.

[0092] According to the folded portion 21b3 of the modified example 3(3), the folded portion 21b3 has a shape including two arcs, a first arc Ca7 and a second arc Ca8, each having a different curvature. This allows the first heating wire 21 to be folded back smoothly at the folded portion 21b3, making it difficult for the first heating wire 21 to break. In addition, the inclination angle θ1 that the connecting end 21a2 of the outgoing path portion 21a makes with respect to the tube axis O direction is made different from the inclination angle θ2 that the connecting end 21c2 of the return path portion 21c makes with respect to the tube axis O direction. Therefore, the return path portion 21c folded back at the folded back portion 21b3 can be brought closer to the outgoing path portion 21a in the tube axis O direction. As a result, the folded back portion 21b3 can fold back the outgoing path portion 21a to the return path portion 21c without changing the pitch P between the outgoing path portion 21a and the return path portion 21c.

[0093] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and changes, combinations, deletions, etc. of the configuration are also included within the scope that does not deviate from the gist of the present invention.

[0094] For example, there may be no fixing marks. For example, the Young's modulus of a heating wire is 65 kN / mm 2 It may be less than 150kN / mm 2 It may be super. For example, the indicator does not have to be disposed closer to the end face of the resin tube than the center of the range in the tube axial direction in which the fused portion is provided.

[0095] In addition, the components in this embodiment can be replaced with well-known components as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0096] 1 Electric fusion joint 10 Plastic pipe 20 1st fusion part (fusion part) 21 1st heating wire (heating wire) 50 Second fused part (fused part) 51 2nd heating wire (heating wire) 80 First resin pipe (connection partner resin pipe) 81 Second resin pipe (connection partner resin pipe) O tube shaft

Claims

1. An electric fusion joint having a fusion part in which an electric heating wire is inserted into a notched groove formed in a spiral shape on the inner peripheral surface of a thermoplastic resin pipe into which a connecting resin pipe is inserted, The fusion portion is provided on at least one end side in the axial direction of the electric fusion joint so as to be capable of passing electricity through the heating wire, In the fusion portion, an outward path in which a spiral advances in an outward direction from the opening side of the electric fusion joint to the opening side on the opposite side of the opening, and a return path in a direction opposite to the outward direction are formed by a single heating wire, An indicator is provided on the outer circumferential surface of the resin pipe, The indicator is arranged in the range of the plastic tube in which the fusion portion is provided, toward the end face of the plastic tube rather than the center of the range in the axial direction of the plastic tube.

2. The resin pipe is provided with two terminals to be connected to both ends of the heating wire, The two terminals are arranged side by side in the tube axis direction, The electric fusion joint according to claim 1 , wherein the indicator is disposed between the two terminals in the tube axial direction.

Images