Electric fusion joint

Abstract

To provide an electric fusion joint which can improve moldability and can reduce the cost.SOLUTION: An electric fusion joint 1 to be fused to tubes 11, 12 containing thermoplastic resin includes a joint body 2, and heating wires 31, 41. The joint body 2 contains thermoplastic resin. The heating wires 31, 41 are arranged in the joint body 2. The joint body 2 has heating wire arrangement portions 21a, 22a in which the heating wires 31, 41 are arranged along a circumferential direction C. When a thickness of the heating wire arrangement portions 21a, 22a is T1 and a diameter of the heating wires 31, 41 is d, the relation of 0.049≤d / T1<0.34 is satisfied.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to electrofusion joints. [Background technology]

[0002] 2. Description of the Related Art Electric fusion joints are used when connecting pipes made of resin, such as resin pipes and metal-reinforced composite pipes having a resin layer and a metal reinforcing layer.

[0003] For example, the electric fusion joint shown in Patent Document 1 has a joint body made of thermoplastic resin with pipe receptacles at both ends into which the pipe to be connected is inserted, and a positioning protrusion protruding inward from the inner peripheral surface of the joint body. The positioning protrusion positions the pipe inserted into the pipe receptacle. An electric heating wire is provided in the pipe receptacle, and by generating heat, the resin around the heating wire and the resin of the pipe are fused together, connecting the electric fusion joint and the pipe.

[0004] In the electric fusion process, kinks (twisting, twisting, etc.) may occur due to thermal expansion of the heating wire. If kinks occur during current flow, the heating wires are likely to come into contact with each other and short-circuit, which can lead to poor fusion.

[0005] In Patent Document 1, the occurrence of kinks is suppressed by ensuring the rigidity of the heating wire. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2023-46656 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in order to ensure the rigidity of the heating wire, it is necessary to use a heating wire with a large diameter, which makes it difficult to wind the heating wire when forming a joint, resulting in poor formability.

[0008] An object of the present disclosure is to provide an electric fusion joint that can improve moldability and reduce costs. [Means for solving the problem]

[0009] In order to achieve the above object, an electric fusion joint according to a first aspect is an electric fusion joint to be fused to a pipe containing a thermoplastic resin, and includes a joint body and a heating wire. The joint body contains a thermoplastic resin. The heating wire is disposed in the joint body. The joint body has a heating wire arrangement section in which the heating wire is arranged along the circumferential direction. If the wall thickness of the heating wire arrangement section is t and the diameter of the heating wire is d, the relationship 0.049≦d / t<0.34 is satisfied.

[0010] By setting d and t so as to satisfy 0.049≦d / t<0.34, the thickness of the portion where the heating wire is arranged can be reduced, and the stress generated in the portion where the heating wire is arranged during fusion can be reduced. Therefore, the occurrence of kinks can be suppressed without using a heating wire with a large diameter. By using a heating wire with a small diameter, costs can be reduced and moldability can be improved. In addition, when the diameter of the heating wire is reduced, the volume ratio of the heating wire to the resin in the thickness direction can be reduced, so strength can be ensured even if the overall thickness is thin.

[0011] The electric fusion joint according to the second aspect is the electric fusion joint according to the first aspect, in which, where the inner diameter of the heating wire arrangement portion is D and the diameter of the heating wire is d, the relationship 0.003≦d / D≦0.010 is satisfied.

[0012] This makes it possible to use a heating wire having a diameter that corresponds to the inner diameter of the heating wire arrangement portion.

[0013] An electric fusion joint according to a third aspect is the electric fusion joint according to the first aspect, wherein the joint body has a tubular portion and a stopper portion. The tubular portion includes a heating wire arrangement portion and a tube is inserted into the tubular portion. The stopper portion protrudes inward from an inner circumferential surface of the tubular portion and restricts the insertion of the tube.

[0014] By providing a stopper portion for positioning the tube, the thickness of the portion where no tube is present and where the pressure of the fluid is directly applied to the inner circumferential surface of the electric fusion joint is increased, thereby ensuring strength.

[0015] An electric fusion joint according to a fourth aspect is the electric fusion joint according to the first aspect, in which the thermoplastic resin is polyethylene.

[0016] This makes it possible to easily produce an electric fusion joint.

[0017] An electric fusion joint according to a fifth aspect is the electric fusion joint according to the third aspect, further comprising a heating wire disposed in the stopper portion.

[0018] This allows the stopper portion and the end of the pipe to be fused without any gaps. Also, by fusing without any gaps, water retention can be prevented, so the pipe can be used for piping for ultrapure water, for example. Effect of the Invention

[0019] According to the present disclosure, it is possible to provide an electric fusion joint that can improve moldability and reduce costs. [Brief description of the drawings]

[0020] [Figure 1] 1 is an external view showing an electric fusion joint and a tube connected to the electric fusion joint according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is a cross-sectional view showing the electric fusion joint of FIG. 1. [Diagram 3] FIG. 2 is a cross-sectional view showing the electric fusion joint of FIG. 1 in a state where a pipe is inserted. [Figure 4] FIG. 2 is a diagram for explaining how to obtain equations (1) and (2). [Diagram 5] FIG. 11 is a cross-sectional view showing an electric fusion joint according to a second embodiment of the present disclosure. [Figure 6]FIG. 11 is a cross-sectional view showing a state in which an electric fusion joint and a tube are connected in a second embodiment according to the present disclosure. [Figure 7] FIG. 4 is a cross-sectional view showing an electric fusion joint according to a modified example of the first embodiment. [Figure 8] FIG. 4 is a cross-sectional view of a single receiving pipe including a joint structure of a modified example of the first embodiment. [Figure 9] FIG. 2A is a partial cross-sectional view showing an elbow joint as a modified example of the first embodiment, and FIG. 2B is a partial cross-sectional view showing a Tee joint as a modified example of the first embodiment. [Figure 10] FIG. 11 is a cross-sectional view showing an electric fusion joint according to a modified example of the second embodiment. [Figure 11] FIG. 11 is a cross-sectional view showing an electric fusion joint according to a modified example of the second embodiment. [Figure 12] FIG. 1 is a graph showing the relationship between the inner diameter of the joint body of an electric fusion joint and the diameter of the heating wire. [Figure 13] FIG. 1 is a cross-sectional view showing the configuration of a conventional electric fusion joint. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0022] (Embodiment 1) (Outline of piping structure 100) Fig. 1 is a diagram showing an electric fusion joint 1 according to an embodiment of the present disclosure, a pipe 11 (an example of a pipe containing a thermoplastic resin) and a pipe 12 (an example of a pipe containing a thermoplastic resin) connected by the electric fusion joint 1. Fig. 1 can also be said to be an exploded view of a piping structure 100. The piping structure 100 has, for example, the electric fusion joint 1, the pipe 11, and the pipe 12.

[0023] As shown in the figure, electric fusion joint 1 is fused to pipe 11 and pipe 12 to connect pipe 11 and pipe 12 .

[0024] Each of the pipes 11 and 12 is formed of a thermoplastic resin composition. An example of the thermoplastic resin composition is a resin composition mainly composed of polyolefin. In this specification, the term "main component" means that the composition contains 50% by mass or more. For example, a resin composition made of one or more types of polyolefin, or a resin composition containing one or more types of polyolefin and additives as required, can be mentioned. Specifically, examples of the resin composition include polyethylene resin, high-density polyethylene resin, medium-density polyethylene resin, polybutene resin, polypropylene resin, etc.

[0025] Flow paths 11f, 12f with circular cross sections extend inside tube 11 and tube 12. Flow path 1f with a circular cross section extends inside electric fusion joint 1. When tube 11 and tube 12 are connected by electric fusion joint 1, the axes of the flow paths of tube 11, tube 12, and electric fusion joint 1 are aligned on the same straight line.

[0026] The direction in which the axis of the electric fusion joint 1, pipe 11, and pipe 12 extends through the flow paths of the pipes is defined as an axial direction A. In the electric fusion joint 1, pipe 11, and pipe 12, the direction in which they approach or move away from each other perpendicularly to their respective axes is defined as a radial direction B, and the direction rotating around each axis is defined as a circumferential direction C.

[0027] Pipe 11 moves relative to electric fusion joint 1 in the direction of arrow A1 in axial direction A to be connected to electric fusion joint 1. Also, pipe 12 moves relative to electric fusion joint 1 in the direction of arrow A2 in axial direction A to be connected to electric fusion joint 1. The state in which pipes 11 and 12 are fused and connected to electric fusion joint 1 constitutes piping structure 100.

[0028] (Electric fusion joint 1) 2 is a diagram showing a cross-sectional configuration of the electric fusion joint 1. The electric fusion joint 1 has a joint body 2, heat generating portions 3 and 4, and a connector attachment portion 5.

[0029] (Joint body 2) The joint body 2 is formed of a thermoplastic resin composition. Examples of the thermoplastic resin composition include a resin composition mainly composed of polyolefin. Examples of the thermoplastic resin composition include a resin composition consisting of one or more types of polyolefin, or a resin composition containing one or more types of polyolefin and additives as required. Specifically, examples of the resin composition include polyethylene resin, high-density polyethylene resin, medium-density polyethylene resin, polybutene resin, polypropylene resin, etc.

[0030] The joint body 2 is cylindrical and has a joint socket portion 21, a joint socket portion 22, and a pipe end opposing portion 23. The pipe 11 is inserted into the inside of the joint socket portion 21. The pipe 12 is inserted into the inside of the joint socket portion 22.

[0031] FIG. 3 is a cross-sectional view showing the state in which the pipe 11 is inserted into the inside of the joint socket portion 21 of the electric fusion joint 1, and the pipe 12 is inserted into the inside of the joint socket portion 22. As shown in FIG.

[0032] The fitting socket 21 is cylindrical, and its inner diameter is greater than or equal to the outer diameter of the pipe 11. The fitting socket 22 is cylindrical, and its inner diameter is greater than or equal to the outer diameter of the pipe 12. If the outer diameter of the pipe 11 is greater than the inner diameter of the fitting socket 21, the pipe 11 can be inserted into the fitting socket 21 by scraping the outer periphery of the pipe 11 with a scraper or the like. If the outer diameter of the pipe 12 is greater than the inner diameter of the fitting socket 22, the pipe 12 can be inserted into the fitting socket 22 by scraping the outer periphery of the pipe 12 with a scraper or the like. In this embodiment, the inner diameters of the fitting socket 21 and the fitting socket 22 are the same, and are indicated by D in FIG. 2. The outer diameters of the fitting socket 21 and the fitting socket 22 are the same. The wall thickness of the fitting socket 21 and the wall thickness of the fitting socket 22 are set to the same size.

[0033] The joint receptacle portion 21 has a receptacle heating wire arrangement portion 21a and a receptacle heating wire non-arrangement portion 21b. The receptacle heating wire arrangement portion 21a is a portion of the joint receptacle portion 21 where the heating portion 3 described below is arranged. The receptacle heating wire non-arrangement portion 21b is a portion of the joint receptacle portion 21 where the heating portion 3 is not arranged. The receptacle heating wire non-arrangement portion 21b is arranged on the side of the joint receptacle portion 21 where the tube 11 is inserted. In the joint receptacle portion 21, the receptacle heating wire arrangement portion 21a is arranged on the tube end facing portion 23 side, and the receptacle heating wire non-arrangement portion 21b is arranged on the opposite side to the tube end facing portion 23. The receptacle heating wire arrangement portion 21a corresponds to an example of a heating wire arrangement portion of the present invention.

[0034] The joint receptacle portion 22 has a receptacle heating wire arrangement portion 22a and a receptacle heating wire non-arrangement portion 22b. The receptacle heating wire arrangement portion 22a is a portion of the joint receptacle portion 22 where the heating portion 4 described below is arranged. The receptacle heating wire non-arrangement portion 22b is a portion of the joint receptacle portion 22 where the heating portion 4 is not arranged. The receptacle heating wire non-arrangement portion 22b is arranged on the side of the joint receptacle portion 22 where the tube 12 is inserted. In the joint receptacle portion 22, the receptacle heating wire arrangement portion 22a is arranged on the tube end facing portion 23 side, and the receptacle heating wire non-arrangement portion 22b is arranged on the opposite side to the tube end facing portion 23. The receptacle heating wire arrangement portion 22a corresponds to an example of a heating wire arrangement portion of the present invention.

[0035] The pipe end facing portion 23 is disposed between the joint socket portion 21 and the joint socket portion 22. The pipe end facing portion 23 is connected to the joint socket portion 21 and the joint socket portion 22. The pipe end facing portion 23 is cylindrical. As shown in FIG. 3, the pipe end facing portion 23 faces the end 11e of the pipe 11 in the radial direction B. The pipe end facing portion 23 faces the end 12e of the pipe 12 in the radial direction B. As shown in FIG. 3, the inner diameter of the pipe end facing portion 23 is the same as that of the joint socket portion 21 and the joint socket portion 22. In the radial direction B, the position of the inner peripheral surface of the pipe end facing portion 23 is the same as that of the inner peripheral surfaces of the joint socket portion 21 and the joint socket portion. The inner peripheral surface 23c of the pipe end facing portion 23 is flush with the inner peripheral surface 21c of the joint socket portion 21 and the inner peripheral surface 22c of the joint socket portion 22. As will be described later, the thickness of the pipe end opposing portion 23 is greater than the thickness of the joint socket portion 21 and the thickness of the joint socket portion 22. The outer peripheral surface of the pipe end opposing portion 23 is located outward in the radial direction B than the outer peripheral surfaces of the joint socket portion 21 and the joint socket portion 22.

[0036] (heat generating parts 3 and 4) The heating part 3 is disposed in the joint receptacle 21. The heating part 3 is disposed in the receptacle heating wire disposing part 21a of the joint receptacle 21. The heating part 3 has a heating wire 31 wound in a coil shape a predetermined number of times along the circumferential direction C. As shown in FIG. 2, in the heating part 3 in this embodiment, the heating wire 31 is disposed so as to be wound five times in the circumferential direction along the inner circumferential surface 21c, but is not limited to five times. The heating wire 31 is disposed near the inner circumferential surface 21c. The heating wire 31 may be buried in the joint receptacle 21 so that a part of it is exposed on the flow path 1f side, or may be completely buried.

[0037] The heating part 4 is disposed in the joint receptacle 22. The heating part 4 is disposed in the receptacle heating wire disposing part 22a of the joint receptacle 22. The heating part 4 has a heating wire 41 wound in a coil shape a predetermined number of times along the circumferential direction C. As shown in FIG. 2, in the heating part 4 in this embodiment, the heating wire 41 is disposed so as to be wound five times in the circumferential direction along the inner circumferential surface 22c, but is not limited to five times. The heating wire 41 is disposed near the inner circumferential surface 22c. The heating wire 41 may be buried in the joint receptacle 21 so that a part of it is exposed on the flow path 1f side, or may be completely buried.

[0038] Each of the heating wires 31, 41 has a conductor. The conductor may be, for example, a nichrome wire, an iron-chrome type 2 wire, an iron-chrome type 1 wire, a nickel-chrome wire, a kovar wire (iron-nickel-cobalt alloy), or a copper wire. The diameter of the conductor may be set to, for example, φ0.3 to 1.1 mm. If the diameter is less than φ0.3 mm, the conductor may stretch due to tension during winding, resulting in an unstable resistance value. The resistance value per unit length of the conductors 31a, 41a is about 2 to 21 Ω / m depending on the wire diameter.

[0039] Each of the heating wires 31, 41 may have an insulating coating covering the periphery of the conductor. The insulating coating is preferably set to a temperature that does not melt even at the temperature at which the thermoplastic resin melts (for example, in the case of polyethylene, the heating wire is heated to 220°C). The insulating coating can be made of, for example, a fluororesin or imide resin, but it is more preferable to make it of a polyimide resin. If the heating wire has an insulating coating, adjacent windings may be in contact with each other, but if it does not have an insulating coating, a predetermined gap is provided between adjacent windings.

[0040] The heat generating portion 4 is provided symmetrically to the heat generating portion 3 in FIG.

[0041] As shown in Fig. 2, in the axial direction A, the heat generating part 3 is arranged adjacent to the tube end facing part 23. Also, in the axial direction A, the heat generating part 4 is arranged adjacent to the tube end facing part 23.

[0042] (Connector attachment part 5) As shown in Fig. 2, the connector attachment part 5 has two pins 51. The two pins 51 are provided so as to project radially outward from the outer surface 2d of the joint body 2. One of the two pins 51 is arranged in the vicinity of the end 21d of the joint receiving part 21, and the other pin 51 is arranged in the vicinity of the end 22d of the joint receiving part 22, as shown in Fig. 2. Although not shown, the two pins 51 are connected to the heating wire 31 of the heat generating part 3 and the heating wire 41 of the heat generating part 4. When a connector of an electric fusion device is attached to the pin 51 and energized, the heating wire 31 and the heating wire 41 generate heat. In the present embodiment, the heating wire 31 and the heating wire 41 are connected and are a single heating wire. A portion of the single heating wire wound around the joint receiving part 21 in a coil shape a predetermined number of times (5 turns in Fig. 2) along the circumferential direction C constitutes the heat generating part 3, and a portion of the single heating wire wound around the joint receiving part 22 in a coil shape a predetermined number of times (5 turns in Fig. 2) along the circumferential direction C constitutes the heat generating part 4.

[0043] (Wall thickness T0, T1, inner diameter D and diameter d) As shown in Fig. 2, when the wall thickness of the receiving port heating wire arrangement part 21a and the receiving port heating wire arrangement part 22a is T1 (mm) and the wall thickness of the tube end facing part 23 is T0 (mm), T1 < T0 is satisfied. The wall thickness T1 of the receiving port heating wire arrangement part 21a and the diameter d of the heating wire 31 correspond to the wall thickness t of the heating wire arrangement part and the diameter d of the heating wire of the present invention. The wall thickness T1 of the receiving port heating wire arrangement part 22a and the diameter d of the heating wire 31 correspond to the wall thickness t of the heating wire arrangement part and the diameter d of the heating wire of the present invention. When the heating wires 31 and 41 are not covered with resin and are exposed on the flow path 1f side, or when resin sinks, the inner peripheral surface is uneven so as to follow the shapes of the heating wires 31 and 41. In that case, the top of the convex part protruding from the inner peripheral surface is taken as one end of the thickness of T0 and T1. Also, the top of the convex part protruding from the inner peripheral surface is taken as one end of the inner diameter D. The same applies to the configurations of Figs. 7 to 9 described later.

[0044] In this manner, in this embodiment, the wall thickness T1 of the receiving port heating wire arrangement parts 21a, 22a is made thin. This point will be described in more detail.

[0045] The stress generated in the resin is σ S The stress at which the heating wire buckles is σ cr If the stress generated in the resin exceeds the buckling stress of the heating wire, the heating wire will buckle and a kink will occur. S <σ cr When the above condition is satisfied, the occurrence of kinking can be suppressed.

[0046] Here, the linear expansion coefficient of the heating wires 31 and 41 is a, the temperature change (resin melting temperature minus environmental temperature) is ΔT, and the elastic coefficient of the resin is E P The thickness of the receiving-port heating wire arrangement parts 21a and 22a is T1, the diameter of the heating wires 31 and 41 is d, and the elastic modulus of the heating wire is E M Then, the stress generated in the resin is σ S =12aΔTE P T1 / πd···Equation (1), and the heating wire buckling stress is σ cr =4×16E M d 2 / D 2 ··· The inventors of the present application have found that this can be expressed as formula (2). Formulas (1) and (2) will now be described.

[0047] Resin stress σ Sis represented by the difference between the linear expansion and the actual increase in diameter, and can be approximated to the expansion inhibition force of the heating wire by the joint resin. FIG. 4(a) is a schematic cross-sectional view showing the joint part 2p in which one turn of the heating wire 31 is arranged in the joint body 2. FIG. 4(b) is a cross-sectional view taken along line AA in FIG. 4(a). The heating wire 31 includes a conductor 31a and a polyethylene coating 31b. The diameter d of the heating wire mentioned above represents the conductor 31a portion of the heating wire 31. The conductor 31a is coated with polyethylene, and the thickness of the polyethylene coating 31b is d. Therefore, the width of the joint part 2p can be represented as 3d. Furthermore, the expansion inhibition force σ of the heating wire by the joint resin is represented by the following formula: S affects the thickness of the portion of the joint part 2p outside the heating wire 31, but here it is approximated to the wall thickness T1. Fig. 4(c) is a diagram showing a state in which the annular shape of the joint part 2p is assumed to be a rectangular parallelepiped. If the joint part 2p is assumed to be a rectangular parallelepiped as shown in Fig. 4(c), the load P is generated in the direction of the arrow.

[0048] Heating wire expansion inhibition force σ due to joint resin S The load applied to the joint resin due to the thermal expansion of the heating wire is P, and the cross-sectional area of ​​the conductor 31a of the heating wire 31 is A. M Then, σ S =P / A M Here, the load P applied by the thermal expansion of the heating wire is expressed as the stress σ applied to the resin. P and resin cross-sectional area A p Using this, P = σ P Resin cross-sectional area A p A p = 3dT1, so the load P applied by the thermal expansion of the heating wire is P = σ P It is expressed as 3dT1. Stress applied to the resin σ P is σ P= εE p where ε is expressed as ε = aΔT. If the amount by which the length L expands due to thermal expansion is ΔL, then ε is expressed as ε = ΔL / L, and if the amount by which the diameter D increases is ΔD, then ε = ΔL / L = πΔD / πD. Thus, the load P caused by the thermal expansion of the heating wire is P = aΔTE p It is expressed as 3dT1. Cross-sectional area of ​​the conductor A MA M =(1 / 4)πd 2 Therefore, σ S =P / A M = aΔTE p 3dT1 / ((1 / 4)πd 2 )=12aΔTE p This is expressed as T1 / πd. This leads to equation (1).

[0049] On the other hand, the buckling stress σ cr The moment of inertia is I and the effective buckling length is L. k Then, by using Euler's formula, σ cr = π 2 E M I / A M L k 2 The second moment of area I can be expressed as I=πd 4 / 64, and A M =πd 2 / 4. The effective buckling length L k , L k =πD / 16. Effective buckling length L k is the length at which buckling actually occurs, and was calculated as πD / 16 from the results of an experiment using an electric fusion joint 1 with a joint body 2 having a diameter of 75A. The buckling length is the length of the part that buckles under specified support conditions. From these formulas, σ cr =16E M d 2 / D 2 Since both ends of the heating wire are fixed by the resin of the joint, σ cr =4×16E M d 2 / D 2 This leads to equation (2).

[0050] Internal stress σ S is the buckling stress σ cr Since buckling occurs when it exceeds 12aΔTE P T1 / d<4×16E M d 2 / D 2By satisfying the above condition, the occurrence of buckling (kinking) can be suppressed. Fig. 4(d) shows a state where a kink has occurred in the heating wire 31. The heating wire 31 protrudes to the inside of the joint part 2p. The kinked part of the heating wire 31 is indicated by 31c.

[0051] This shows that by reducing the thickness T1, the stress generated in the resin can be reduced, and the occurrence of kinks can be suppressed.

[0052] The diameter d of the heating wires 31, 41 and the thickness T1 of the receiving-port heating-wire placement portions 21a, 22a satisfy 0.049≦d / T1<0.34, and more preferably 0.049≦d / T1≦0.22. Furthermore, it is preferable that the wall thickness T1 of the receiving port electric heating wire arrangement parts 21a, 22a is greater than 3 mm. If the wall thickness T1 is 3 mm or less, the receiving port electric heating wire arrangement parts 21a, 22a may melt. It is preferable that the wall thickness T1 of the receiving port electric heating wire arrangement parts 21a, 22a is smaller than 30 mm. This assumes the maximum wall thickness of electric fusion joints that can be used depending on the size of pipes currently in use.

[0053] It is preferable that the inner diameter D of the receiving port heating wire arrangement parts 21a, 22a and the diameter d of the heating wires 31, 41 satisfy 0.003≦d / D≦0.010. It is more preferable that they satisfy 0.003≦d / D≦0.008. In the electric fusion joint 1 of the present embodiment 1, the tube end opposing part 23 has a part that does not overlap with the tubes 11, 12 and is directly subjected to the pressure of the fluid, but the strength can be ensured by making the thickness of the tube end opposing part 23 larger than that of the receiving port heating wire arrangement parts 21a, 22a.

[0054] (Manufacturing of electric fusion joints) The electric fusion joint 1 can be manufactured by a known method. A core mold corresponding to the inner shape of the joint body 2 is prepared, and the heating wires 31, 41 are wound in a coil shape on the outer surface of the core mold. Then, the electric fusion joint can be manufactured by injection molding a resin composition into the space between the outer mold corresponding to the outer shape of the joint body 2 and the core mold around which the heating wires 31, 41 are wound.

[0055] The joint body 2 can also be manufactured by a method of molding the joint body 2 divided into an inner layer member and an outer layer member with the surface on which the heating wires 31, 41 are arranged as the boundary surface. For example, the inner layer member is molded by injection molding, and the heating wires 31, 41 are wound in a coil shape on the outer surface of the inner layer member. The electric fusion joint 1 can be manufactured by placing the inner layer member wound with the heating wires 31, 41 in a mold, molding the outer layer member by injection molding, and integrating the inner layer member and the outer layer member.

[0056] (Fusion splicing) First, the tubes 11 and 12 are inserted into the electric fusion joint 1. The tube 11 is inserted into the joint socket portion 21. As shown in Fig. 3, the tube 11 is inserted into the electric fusion joint 1 until the end 11e faces the tube end opposing portion 23 in the radial direction B. In addition, the tube 12 is inserted into the joint socket portion 22. The tube 12 is inserted into the electric fusion joint 1 until the end 12e faces the tube end opposing portion 23 in the radial direction B.

[0057] Next, a connector of an electric fusion device is attached to the two pins 51 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 any temperature that melts the joint body 2, and in the case of polyolefin, it is preferably 220°C or less.

[0058] This melts the resin around the heat generating part 3 of the electric fusion joint 1 and the resin of the pipe 11 facing the heat generating part 3, fusing the electric fusion joint 1 to the pipe 11. Also, the resin around the heat generating part 4 of the electric fusion joint 1 and the resin of the pipe 12 facing the heat generating part 4 melt, fusing the electric fusion joint 1 to the pipe 12. An indicator may be provided between the pins 51 to check the installation.

[0059] Thereafter, the connection is completed by cooling for a predetermined period of time.

[0060] (Embodiment 2) Next, an electric fusion joint according to the second embodiment will be described. Unlike the electric fusion joint 1 of the first embodiment, the electric fusion joint 101 of the second embodiment is provided with a stopper portion that restricts the insertion of the pipes 11 and 12. A piping structure 200 of the second embodiment is provided with the electric fusion joint 101, the pipe 11, and the pipe 12. In the second embodiment, the parts different from the first embodiment will be mainly described.

[0061] 5 is a cross-sectional view showing an electric fusion joint 101 of the present embodiment 2. The electric fusion joint 101 of the present embodiment 2 has a joint body 102, heat generating portions 103 and 104, a stopper heat generating portion 106, and a connector attachment portion 5.

[0062] (Joint body 102) The joint body 102 is formed of a thermoplastic resin composition as in the embodiment. The joint body 102 has a tubular portion 111 and a stopper portion 112. The tubular portion 111 is tubular and has a joint socket portion 121, a joint socket portion 22, and a connecting portion 123. The pipe 11 is inserted into the inside of the joint socket portion 121. The pipe 12 is inserted into the inside of the joint socket portion 122. The connecting portion 123 is disposed between the joint socket portion 121 and the joint socket portion 122.

[0063] The joint receptacle 121 has a receptacle heating wire arrangement section 121a and a receptacle heating wire non-arrangement section 121b. The receptacle heating wire arrangement section 121a is a section of the joint receptacle 121 where the heat generating section 103 is arranged. The receptacle heating wire non-arrangement section 121b is a section of the joint receptacle 121 where the heat generating section 103 is not arranged. The receptacle heating wire non-arrangement section 121b is arranged on the side of the joint receptacle 121 where the pipe 11 is inserted. In the joint receptacle 121, the receptacle heating wire arrangement section 121a is arranged on the connecting section 123 side, and the receptacle heating wire non-arrangement section 121b is arranged on the opposite side to the connecting section 123.

[0064] The joint receptacle 122 has a receptacle heating wire arrangement section 122a and a receptacle heating wire non-arrangement section 122b. The receptacle heating wire arrangement section 122a is a section of the joint receptacle 122 where the heating section 104 described below is arranged. The receptacle heating wire non-arrangement section 122b is a section of the joint receptacle 122 where the heating section 104 is not arranged. The receptacle heating wire non-arrangement section 122b is arranged on the side of the joint receptacle 122 where the pipe 12 is inserted. In the joint receptacle 122, the receptacle heating wire arrangement section 122a is arranged on the connecting section 123 side, and the receptacle heating wire non-arrangement section 122b is arranged on the opposite side to the connecting section 123.

[0065] 5, the connecting portion 123 is connected to the joint socket portion 121 and the joint socket portion 122, and connects the joint socket portion 121 and the joint socket portion 122. The connecting portion 123 is a portion that connects the joint socket portion 121 and the joint socket portion 122, and a stopper portion 112, which will be described later, is provided on the inside in the radial direction B.

[0066] (Stopper portion 112) The stopper portion 112 is annular. The stopper portion 112 is formed as a protrusion on the inner peripheral surface 111a of the cylindrical portion 111 along the circumferential direction C over the entire circumference. The stopper portion 112 is also formed of a thermoplastic resin composition, and is preferably formed of the same resin composition as the thermoplastic resin composition used for the cylindrical portion 111.

[0067] The stopper portion 112 is formed so as to protrude radially inward from the inner circumferential surface 111a of the cylindrical portion 111. The stopper portion 112 is disposed on the inner side of the connecting portion 123 of the cylindrical portion 111 in the radial direction B. The stopper portion 112 may be formed as one member together with the cylindrical portion 111, or may be formed as a separate member from the cylindrical portion 111.

[0068] The stopper portion 112 has a first side surface 112a, a second side surface 112b, and a peripheral surface 112c. The peripheral surface 112c is an end surface of the stopper portion 112 on the inner side in the radial direction.

[0069] The first side surface 112a is a side surface of the stopper portion 112 on the side of the joint socket portion 121. The first side surface 112a is formed approximately perpendicular to the axial direction A from the inner circumferential surface 111a of the cylindrical portion 111 toward the inside in the radial direction B.

[0070] The second side surface 112b is a side surface of the stopper portion 112 on the side of the joint socket portion 122. The second side surface 112b is formed approximately perpendicular to the axial direction A from the inner circumferential surface 111a of the cylindrical portion 111 toward the inside in the radial direction B.

[0071] The peripheral surface 112c connects the radially inner end of the first side surface 112a and the radially inner end of the second side surface 112b. The peripheral surface 112c is formed generally parallel to the inner peripheral surface 111a of the cylindrical portion 111. The protruding height of the stopper portion 112 is lower than the inner peripheral surfaces of the plastic pipes 11 and 12 when the plastic pipes 11 and 12 are inserted.

[0072] (heat generating parts 103, 104) The heat generating part 103 is disposed in the joint receptacle 121. The heat generating part 103 is disposed in the receptacle heating wire arrangement part 121a of the joint receptacle 121. The heat generating part 103 is disposed next to the stopper part 112 in the axial direction A. The heat generating part 103 has a heating wire 31 wound in a coil shape a predetermined number of times along the circumferential direction C. As shown in FIG. 5, in the heat generating part 103 in this embodiment, the heating wire 131 is disposed so as to be wound around the inner circumferential surface 121c in the circumferential direction two times, but is not limited to two turns. The heating wire 131 is disposed near the inner circumferential surface 121c. The heating wire 131 may be buried in the joint receptacle 121 so as to be partially exposed to the flow path 101f side, or may be completely buried.

[0073] The heat generating part 104 is disposed in the joint receptacle 122. The heat generating part 104 is disposed in the receptacle heating wire arrangement part 122a of the joint receptacle 122. The heat generating part 104 is disposed next to the stopper part 112 in the axial direction A. The heat generating part 104 has a heating wire 141 wound in a coil shape a predetermined number of times along the circumferential direction C. As shown in FIG. 5, in the heat generating part 104 in this embodiment, the heating wire 141 is disposed so as to be wound around the inner circumferential surface 122c in the circumferential direction two times, but is not limited to two turns. The heating wire 141 is disposed near the inner circumferential surface 122c. The heating wire 131 may be buried in the joint receptacle 21 so as to be partially exposed to the flow path 101f side, or may be completely buried.

[0074] The heating wires 131 and 141 may be the same type of heating wire as that described in the first embodiment.

[0075] (Stopper heating part 106) The stopper heating part 106 is provided in the stopper part 112. The stopper heating part 106 has a heating wire 161. The heating wire 161 is wound a predetermined number of times in the circumferential direction C along the axial direction A and is provided in the stopper part 112. In this embodiment, the heating wire 161 is wound around the stopper part 112 four times, for example, but is not limited to four times.

[0076] The heating wire 161 is embedded in the stopper portion 112, but may be embedded in the stopper portion 112 so that a portion of the heating wire 161 is exposed on the flow path 101f side from the first side surface 112a, the second side surface 112b, or the peripheral surface 112c.

[0077] The heating wire 161 may be of the same type as the heating wires 31 and 41 of the first embodiment.

[0078] (Thickness of joint body 102) As shown in FIG. 5, a recess 125 is formed on the outer peripheral surface 111b of the tubular portion 111 of the joint body 102 along the circumferential direction C over the entire circumference. The recess 125 is formed over the receptacle heating wire arrangement portion 121a, the connecting portion 123, and the receptacle heating wire arrangement portion 122a in the axial direction A. The recess 125 makes the wall thickness T3 of the receptacle heating wire arrangement portions 121a and 122a thinner than the wall thickness T2 of the receptacle heating wire non-arrangement portions 121b and 122b. As in the first embodiment, the wall thickness T3 of the receptacle heating wire arrangement portions 121a and 122a is preferably greater than 3 mm. The inner diameter D of the receptacle heating wire arrangement portions 121a and 122a and the diameter d of the heating wires 31 and 41 preferably satisfy 0.003≦d / D≦0.010.

[0079] If the combined thickness of the stopper portion 112 and the connecting portion 123 is T1, the relationship 0.049≦d / T1<0.34 is satisfied, and 0.049≦d / T1≦0.22 is more preferable. The thickness T1 is greater than the thickness T3 of the socket heating wire arrangement parts 121a, 122a. The thickness T3 satisfies 0.049≦d / T3<0.34. It is more preferable that 0.049≦d / T3≦0.22. In the electric fusion joint 101 of the second embodiment, the pressure of the fluid is directly applied to the stopper part 112, but the strength can be ensured by making the thickness T1 of the stopper part 112 and the connecting part 123 together greater than that of the socket heating wire arrangement parts 121a, 122a. More preferably, the thickness of the stopper part 112 is set so that the thickness T1' of the connecting part 123 and the bead R together is greater than that of the socket heating wire arrangement parts 121a, 122a. In addition, the length from the peripheral surface 112c to the outer peripheral surface 111b of the stopper part 112 perpendicular to the axial direction A is defined as T0.

[0080] The combined portion of the stopper portion 112 and the connecting portion 123 corresponds to an example of the heating wire arrangement portion of the present invention. The combined thickness T1 of the stopper portion 112 and the connecting portion 123 of the electric fusion joint 101 and the diameter d of the heating wire 161 correspond to the thickness t of the heating wire arrangement portion and the diameter d of the heating wire of the present invention.

[0081] The receiving port heating wire arrangement parts 121a and 122a also correspond to an example of the heating wire arrangement part of the present invention. The wall thickness T3 of the receiving port heating wire arrangement part 121a of the electric fusion joint 101 and the diameter d of the heating wire 131 correspond to the wall thickness t of the heating wire arrangement part and the diameter d of the heating wire of the present invention. The wall thickness T3 of the receiving port heating wire arrangement part 122a of the electric fusion joint 101 and the diameter d of the heating wire 141 correspond to the wall thickness t of the heating wire arrangement part and the diameter d of the heating wire of the present invention.

[0082] In the second embodiment, the same heating wire diameter d is used in the stopper portion 112 and the socket heating wire arrangement portions 121a and 122a, and the thickness T1 of the combined portion of the stopper portion 112 and the connecting portion 123 is greater than the thickness T3 of the socket heating wire arrangement portions 121a and 122a. As described in the first embodiment, by reducing the thickness of the resin in the portion where the heating wire is arranged, the stress generated in the resin can be reduced, and the occurrence of kinks can be suppressed. Therefore, in the electric fusion joint 101 of the second embodiment, kinks are more likely to occur in the stopper heating portion 106 than in the heating portions 103 and 104 arranged in the joint socket portions 121 and 122. In other words, if kinks do not occur in the stopper heating portion 106, it can be said that kinks do not occur in the heating portions 103 and 104 either. When the heating wires 131, 141, 161 are not covered with resin and are exposed on the flow path 101f side, or when the resin is drawn, the inner circumferential surface becomes uneven to match the shape of the heating wires 131, 141, 161. In this case, the top of the protrusion protruding from the inner circumferential surface is one end of the thicknesses T0 to T3, and the top of the protrusion protruding from the inner circumferential surface is one end of the inner diameter D. This is also true for the configurations shown in Figs. 10 and 11 described below.

[0083] (Connection method) First, the tubes 11 and 12 are inserted into the electric fusion joint 101. The tube 11 is inserted into the inside of the joint socket portion 121 of the electric fusion joint 101 until the relative movement of the end 11e of the tube 11 is restricted by the stopper portion 112. Next, the tube 12 is inserted into the inside of the joint socket portion 122 of the electric fusion joint 101 until the relative movement of the end 12e of the tube 12 is restricted by the stopper portion 112. Note that, prior to insertion into the electric fusion joint 101, it is preferable to scrape the end faces (the faces facing the stopper portion 112) of the tubes 11 and 12 and then insert them into the electric fusion joint 101, as this improves the strength of fusion.

[0084] Next, a connector of an electric fusion device is attached to the two pins 51 of the connector attachment portion 5, and electricity is passed through the connector for a predetermined period of time. At this time, the tubes 11, 12 may be heated while being pressed against the stopper portion 112.

[0085] This current flow causes the heating wires 131, 141, and 161 to generate heat, melting the receiving port heating wire arrangement portions 121a and 122a, the stopper portion 112, the pipes 11, and the pipes 12, and connecting the electric fusion joint 101 to the pipes 11 and 12. Fig. 6 is a diagram showing the state in which the electric fusion joint 101 and the pipes 11 and 12 are connected. Fig. 6 can also be considered a cross-sectional view showing the configuration of a piping structure 200 of the second embodiment.

[0086] 6, the stopper portion 112 and the ends of the tubes 11 and 12 melt to form a bead R that bulges inward. This bead R fills the gap between the tubes 11 and 12, preventing gaps from forming between the tubes 11 and 12, preventing water stagnation and enabling use for ultrapure water applications.

[0087] (Ultrapure water application for piping structure 200) The piping structure 200 of the second embodiment can be used, for example, for transporting ultrapure water. Specifically, the piping structure 200 for ultrapure water of the embodiment according to 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 200 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 transport piping for 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] (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.

[0091] (A) In the electric fusion joint 1 of the above-mentioned embodiment 1, the wall thickness of the socket heating wire non-arrangement parts 21b, 22b is T1, which is the same as that of the socket heating wire arrangement parts 21a, 22a, but this is not limited thereto. FIG. 7 is a cross-sectional view showing the configuration of an electric fusion joint 201 of a modified embodiment of the embodiment 1. The electric fusion joint 201 has socket heating wire non-arrangement parts 221b, 222b with different thicknesses, instead of the socket heating wire non-arrangement parts 21b, 22b of the embodiment 1. The wall thickness of the socket heating wire non-arrangement parts 221b, 222b is set to T0, which is larger than T1. In the socket heating wire non-arrangement parts 221b, 222b in which the heating wire is not wound in a coil shape, large stress is unlikely to occur even if the wall thickness of the resin is high. The socket heating wire arrangement part 21a in the electric fusion joint 201 shown in FIG. 7 corresponds to an example of the heating wire arrangement part of the present invention. The wall thickness T1 of the receiving port heating wire arrangement portion 21a and the diameter d of the heating wire 31 correspond to the wall thickness t of the heating wire arrangement portion and the diameter d of the heating wire of the present invention. The receiving port heating wire arrangement portion 22a in the electrically fused joint 201 shown in FIG. 7 corresponds to one example of the heating wire arrangement portion of the present invention. The wall thickness T1 of the receiving port heating wire arrangement portion 22a and the diameter d of the heating wire 41 correspond to the wall thickness t of the heating wire arrangement portion and the diameter d of the heating wire of the present invention. The wall thickness T1 and the diameter d satisfy 0.049≦d / T1<0.34. It is more preferable that 0.049≦d / T1≦0.22.

[0092] (B) The electric fusion joint 1 of the above-mentioned embodiment 1 connects two pipes 11, 12, but may have a single-receiving structure connected to one pipe. FIG. 8 is a diagram showing a single-receiving pipe 300. The single-receiving pipe 300 has a joint portion 301 and a pipe portion 312. The joint portion 301 corresponds to an example of an electric fusion joint of the present invention. For example, the pipe 12 is connected to the joint portion 301. The pipe portion 312 is cylindrical. The joint portion 301 is connected to an end of the pipe portion 311. Unlike the electric fusion joint 1 of embodiment 1, the joint portion 301 does not have a joint socket portion 21 and a heating portion 3.

[0093] The joint part 301 includes a joint body 302, a heating part 4, and a stopper part 306. The joint body 302 has a joint receiving port part 322 and a pipe end facing part 323. The pipe 12 is inserted into the joint receiving port part 322 (shown by a two-dot chain line). The joint receiving port part 322 has a receiving port heating wire arranging part 322a where the heating part 4 is arranged and a receiving port heating wire non-arranging part 322b where the heating part 4 is not arranged. If the end on the side opposite to the pipe part 311 of the joint part 301 is 301e, then from the end 301e towards the pipe part 311, the receiving port heating wire non-arranging part 322b, the receiving port heating wire arranging part 322a, the pipe end facing part 323, and the stopper part 306 are arranged in order. The stopper part 306 is a part that protrudes inward from the inner peripheral surface of the pipe end facing part 323. The pipe 11 inserted into the joint receiving port part 322 abuts against the stopper part 306 and is positioned. The inner peripheral surface of the pipe part 312 is provided at the same position as the inner peripheral surface of the stopper part 306 in the radial direction B and is formed flush. In the joint part 301 shown in Fig. 8, the connector mounting part 5 is omitted.

[0094] Here, the wall thickness of the pipe end facing part 323 is indicated by T0, the wall thickness of the receiving port heating wire arranging part 322a is indicated by T1, and T1 < T0 is set. In the joint part 301 shown in Fig. 8, the wall thickness of the receiving port heating wire non-arranging part 322b is also set to T0. The receiving port heating wire arranging part 322a in the single-receiving pipe 300 shown in Fig. 8 corresponds to an example of the heating wire arranging part of the present invention. The wall thickness T1 of the receiving port heating wire arranging part 322a and the diameter d of the heating wire 41 correspond to the wall thickness t of the heating wire arranging part of the present invention and the diameter d of the heating wire. The wall thickness T1 and the diameter d satisfy 0.049 ≦ d / T1 < 0.34. It should be noted that 0.049 ≦ d / T1 ≦ 0.22 is more preferable.

[0095] (C) The electric fusion joint 1 of the above-mentioned embodiment 1 is configured to connect two pipes 11, 12, but the configuration of this embodiment may be applied to an elbow joint 401 shown in FIG. 9(a) or a tee joint 501 shown in FIG. 9(b). In the elbow joint 401 and the tee joint 501, the receiving port heating wire arrangement parts 422a, 522a in which the heat generating part 4 is arranged, the pipe end opposing parts 423, 523 opposing the end of the inserted pipe, and the stopper parts 406, 506 are indicated by lead lines. The receiving port heating wire arrangement part 422a corresponds to an example of the heating wire arrangement part of the present invention. The receiving port heating wire arrangement part 522a corresponds to an example of the heating wire arrangement part of the present invention.

[0096] (D) In the heat generating parts 3 and 4 of the above embodiment 1, the heating wires 31 and 41 are wound five times, in the heat generating parts 103 and 104 of embodiment 2, the heating wires 131 and 141 are wound two times, and in the stopper heat generating part 106, the heating wire 161 is wound four times, but the number of turns is not limited to these.

[0097] (E) In the electric fusion joint 101 of the second embodiment, the wall thickness T2 of the socket heating wire non-placement parts 121b, 122b is thicker than the wall thickness T3 of the socket heating wire placement parts 121a, 122a, but this is not limited thereto, and the wall thickness T2 of the socket heating wire non-placement parts 121b, 122b may be formed thin and may be formed to be the same size as the wall thickness T3 of the socket heating wire placement parts 121a, 122a. Such an electric fusion joint 601 is shown in FIG. 10. In the electric fusion joint 601 shown in FIG. 10, the wall thickness T2 of the socket heating wire non-placement parts 121b, 122b is formed thin so as to be the same size as the wall thickness T3 of the socket heating wire placement parts 121a, 122a. For this reason, T0=T1.

[0098] (F) In the electric fusion joint 601 shown in FIG. 10, the outer peripheral surface of the connecting portion 123, the outer main surface of the joint socket portion 121, and the outer peripheral surface of the joint socket portion 122 are on the same plane, and the connecting portion 123, the joint socket portion 121, and the joint socket portion 122 have the same thickness T3. However, as in the electric fusion joint 701 shown in FIG. 11, the thickness T4 of the connecting portion 123 may be thinner than the thickness T3. In the electric fusion joint 701 shown in FIG. 11, a recess 625 is formed on the outer peripheral surface of the connecting portion 123, compared to the electric fusion joint 601 in FIG. 10. The recess 625 is formed in the connecting portion 123, and is not formed up to the socket heating wire arrangement portions 121a and 122a. In this way, the thickness T4 of the connecting portion 123 may be thinner than the thickness T3 of the joint socket portion 121 and the joint socket portion 122. The thicknesses T1 and T3 are preferably 3 mm or more. The thickness T4 is preferably a diameter d or more from the viewpoint of moldability. The combined stopper portion 112 and the connecting portion 123 of the electric fusion joint 601 shown in FIG. 10 and the electric fusion joint 701 shown in FIG. 11 correspond to an example of the electric heating wire arrangement portion of the present invention. The combined thickness T1 of the stopper portion 112 and the connecting portion 123 of the electric fusion joint 601 shown in FIG. 10 and the electric fusion joint 701 shown in FIG. 11 and the diameter d of the electric heating wire 161 correspond to the thickness t of the electric heating wire arrangement portion and the diameter d of the electric heating wire of the present invention. The thickness T1 and the diameter d satisfy 0.049≦d / T1<0.34. It is more preferable that 0.049≦d / T1≦0.22. The socket heating wire arrangement portion 121a of the electric fusion joint 601 shown in FIG. 10 and the electric fusion joint 701 shown in FIG. 11 corresponds to an example of the heating wire arrangement portion of the present invention. The wall thickness T3 of the socket heating wire arrangement portion 121a of the electric fusion joint 601 shown in FIG. 10 and the diameter d of the heating wire 131 of the electric fusion joint 701 shown in FIG. 11 correspond to the wall thickness t of the heating wire arrangement portion and the diameter d of the heating wire of the present invention. The wall thickness T3 and the diameter d satisfy 0.049≦d / T3<0.34. It is more preferable that 0.049≦d / T3≦0.22. The socket heating wire arrangement portion 122a of the electric fusion joint 601 shown in FIG. 10 and the electric fusion joint 701 shown in FIG. 11 correspond to an example of the heating wire arrangement portion of the present invention. The thickness T3 of the receiving port heating wire arrangement portion 122a and the diameter d of the heating wire 141 of each of the electric fusion joint 601 shown in Figure 10 and the electric fusion joint 701 shown in Figure 11 correspond to the thickness t of the heating wire arrangement portion and the diameter d of the heating wire of the present invention.It is desirable that the receiving port heating wire placement parts 121a, 122a where the heating wire is inserted are thicker than the receiving port heating wire non-placement parts 121b, 122b. As with thicknesses T0 to T3, when the heating wires 131, 141 are not covered with resin and are exposed on the flow path 701f side, or when the resin is drawn, the inner circumferential surface will be uneven to follow the shape of the heating wires 131, 141. In this case, the apex of the protrusion protruding from the inner circumferential surface is regarded as one end of thickness T4.

[0099] (G) In the above-mentioned embodiment 1, the heat generating portion 3 and the heat generating portion 4 are provided symmetrically, but this is not limited thereto, and the number of turns of the heating wire may be different between the heat generating portion 3 and the heat generating portion 4. The same applies to the embodiment 2.

[0100] (H) In the above-mentioned embodiment 1, the inner diameter of the joint socket portion 21 and the inner diameter of the joint socket portion 22 are the same, but they may be different.

[0101] (I) In the above embodiment, the electric fusion joints 1, 101 and the pipes 11, 12 are formed from a resin composition, but are not limited to this and may be pipes made of resin, such as metal-reinforced composite pipes having a metal reinforcing layer.

[0102] (Example) Next, a more detailed explanation will be given using an example.

[0103] In Examples 1 to 4 and 7 to 9, an electric fusion joint 101 (see FIG. 5) having the configuration described in embodiment 2 was used. In Examples 5 and 6 and Comparative Examples 1 to 5, an electric fusion joint 601 having the configuration described in FIG.

[0104] In Examples 1 to 6 and Comparative Examples 1 to 3, the diameter D of the joint body 2 was 75A (=90.4mm). The current flow conditions during connection were a voltage of 35V applied for 50 seconds. Iron chrome was used as the conductor of the heating wire. In the following, a polyethylene coating layer was provided around the conductor, but the diameter of the conductor is taken as the heating wire diameter. For example, in the case of a conductor with a diameter of Φ0.6mm, the diameter of the coating layer including the coating layer is Φ1.8mm.

[0105] Under the above conditions, the thickness T0 from the outermost surface to the innermost surface of the electric fusion joint, the thickness T1 of the stopper portion 112 and the connecting portion 123 combined, the thickness T2 of the socket heating wire non-placed portion, the thickness T3 of the socket heating wire-placed portion, and the heating wire diameter d were changed to verify the number of kinks occurring in the heating wire 161 of the stopper heating portion 106. Note that the heating wire has the same diameter in the heating portions 103, 104 of the joint socket portions 121, 122 and the stopper heating portion 106, and the thickness T1 is greater than the thickness T3, so that kinks are more likely to occur in the stopper heating portion 106 than in the heating portions 103, 104 of the joint socket portions 121, 122, as described above. For this reason, the occurrence of kinks was verified for the stopper heat generating part 106 arranged on the stopper part 112, and if kinks do not occur in the stopper heat generating part 106, it is considered that kinks will not occur in the heat generating parts 103, 104 of the joint socket parts 121, 122 either. The results of the verification are shown in Table 1 below. Table 1 also shows the resin generation stress calculated by the above-mentioned formula (1) and the buckling stress calculated by the formula (2) for the combined part of the stopper part 112 and the connecting part 123. In Comparative Examples 1 to 3, since T2=T3 and T1=T0, values ​​changed from those of the electric fusion joint having the shape shown in FIG. 10 were used. (Table 1) TIFF2025051607000002.tif40164 From the above Examples 1 to 6 and Comparative Examples 1 to 3, it can be seen that even though the heating wire diameter d is the same 0.6 mm, in Examples 1 to 4 where the wall thickness T1 is thinner, the stress generated in the resin is smaller than the buckling stress, and the occurrence of kinks can be suppressed, whereas in Comparative Examples 1 to 3 where the wall thickness T1 is the same as the wall thickness T0, the stress generated in the resin is equal to or larger than the buckling stress, and kinks occur. In the table, the number of kinks that occurred is represented as n / N, which indicates that kinks occurred n times during N tests.

[0106] In Examples 7 to 12 and Comparative Examples 4, 5, and 6, the diameter D of the joint body 2 was 200A (=226.45 mm). In Examples 7 to 9, and 11, the electrofusion joint 101 (see FIG. 5) having the configuration described in the second embodiment was used. In Examples 10 and 12, the electrofusion joint 601 having the configuration described in FIG. 10 was used. In Comparative Examples 4 and 5, since T2=T3 and T1=T0, the electrofusion joint having the shape shown in FIG. 10 was used with the numerical values ​​changed. In Comparative Example 6, the electrofusion joint 101 (see FIG. 5) having the numerical values ​​changed was used. The conditions for the current flow during connection included applying a voltage of 70V for 100 seconds. Iron chrome was used for the conductor of the heating wire. In the following, a polyethylene coating layer is provided around the conductor, but the diameter of the conductor is taken as the heating wire diameter. For example, in the case of a conductor with a diameter of 0.8 mm, the diameter of the coating layer including the coating layer is 2.4 mm.

[0107] Under the above conditions, the thickness T0 from the outermost surface to the innermost surface of the electric fusion joint, the thickness T1 of the stopper portion 112 and the connecting portion 123 combined, the thickness T2 of the socket heating wire non-placed portion, the thickness T3 of the heating wire-placed portion, and the heating wire diameter d were changed to verify the number of kinks that occurred in the heating wire 161 of the stopper heat generating portion 106. The number of kinks that occurred was verified. The results of the verification are shown in Table 2 below. Table 2 also shows the resin generation stress calculated using the above-mentioned formula (1) and the buckling stress calculated using formula (2). (Table 2) TIFF2025051607000003.tif41164 In Comparative Example 6, no kinking occurred, but the resin melted at the thickness T3 during fusion, causing defects. For example, when comparing the above-mentioned Examples 7 and 8 with Comparative Example 4, even though the heating wire diameter d is the same 0.8 mm, in Examples 7 and 8, in which the thickness T1 is thinner, the stress generated in the resin is smaller than the buckling stress, and the occurrence of kinking can be suppressed, whereas in Comparative Example 4, in which the thickness T1 is larger than those of Examples 7 and 8, the stress generated in the resin is larger than the buckling stress, and kinking occurs.

[0108] From Table 1 above, it can be seen that when the inner diameter D of the joint body 2 is 75 A, in this embodiment, buckling does not occur when the heating wire diameter d is 0.6 mm. Also, from Table 2, it can be seen that when the inner diameter D of the joint body 2 is 100 A, in this embodiment, buckling does not occur when the heating wire diameter d is 0.8 mm. Thus, in this embodiment, even when a heating wire with a relatively small diameter, such as 0.6 mm or 0.8 mm, is used, the occurrence of buckling can be suppressed.

[0109] From the above Examples 1 to 12 and Comparative Examples 1 to 6, in the values ​​including both d / T3 and d / T1 in Examples 1 to 13 where kinks do not occur, the lower limit is 0.049 for d / T1 in Example 12. Also, from d / T3 in Comparative Example 6, the upper limit is less than 0.34. This shows that the occurrence of kinks can be suppressed by arranging a heating wire with a diameter d and setting the wall thickness t and diameter d in the heating wire arrangement part to 0.049≦d / t<0.34. Also, from the value of d / T3 in Example 9, 0.049≦d / t≦0.22 is more preferable.

[0110] Fig. 12 is a graph showing the relationship between the inner diameter D of the joint body and the heating wire diameter d. In Fig. 12, the horizontal axis shows the inner diameter D of the joint body, and the vertical axis shows the diameter d of the heating wire. Fig. 12 plots a point where the heating wire diameter d is 0.6 mm when the inner diameter D is 75 A, and a point where the heating wire diameter d is 0.8 mm when the inner diameter D is 200 A. A line L1 is shown connecting these two points. It can be said that buckling does not occur at least in the region above line L1.

[0111] Next, the setting of the conventional heating wire will be described. FIG. 13 is a diagram showing a conventional electric fusion joint 1000. The electric fusion joint 1001 is different from the electric fusion joint 1 of this embodiment in that the wall thickness T1 of the socket heating wire arrangement parts 1021a and 1022a is thickened and is the same thickness as the wall thickness T0 of the tube end facing part 23. The electric fusion joint 1000 shown in FIG. 13 has a joint body 1002, heat generating parts 3 and 4, and a connector mounting part 5, like the electric fusion joint 1. The joint body 1002 has a joint socket part 1021, a joint socket part 1022, and a tube end facing part 23. The joint socket part 1021 has a socket heating wire arrangement part 1021a and a socket heating wire non-arrangement part 1021b. The joint socket portion 1022 has a socket heating wire arrangement portion 1022a and a socket heating wire non-arrangement portion 1022b.

[0112] In an electric fusion joint 1001 configured as described above, the wall thickness T0 is determined by the ratio (outer diameter / wall thickness=SDR) of the diameters of the pipes 11, 12 used (inner diameter D of the joint socket portions 1021, 1022). Taking into account the pressure conditions used, for example, in Japan, the SDR is designed to be 11 or less. The diameter d of the heating wire is designed according to the inner diameter D as shown in the graph indicated by the square points in Figure 12. The approximation line of the multiple square points is indicated as L2. Conventionally, it can be said that buckling of the heating wire does not occur, at least in the upper region including the wire L2.

[0113] Comparing line L1 and line L2 in Figure 12, it can be seen that in this embodiment, by reducing the thickness T1 of the receiving port heating wire arrangement sections 21a, 22a, the threshold value at which buckling does not occur can be lowered, making it possible to use a heating wire with a smaller diameter. [Explanation of symbols]

[0114] 1: Electric fusion joint 11:Tube 12: tube 21a: Socket heating wire arrangement part 22a: Socket heating wire arrangement part 23: Tube end facing part 31: Heating wire 41: Heating wire

Claims

1. An electric fusion joint to be fused to a tube containing a thermoplastic resin, A joint body including a thermoplastic resin; A heating wire is disposed in the joint body, The joint body has a heating wire arrangement portion in which the heating wire is arranged along a circumferential direction, If the thickness of the heating wire arrangement portion is t and the diameter of the heating wire is d, 0.049≦d / t<0.34 is satisfied; Electric fusion joint.

2. If the inner diameter of the heating wire arrangement portion is D and the diameter of the heating wire is d, 0.003≦d / D≦0.010 is satisfied; The electric fusion joint according to claim 1.

3. The joint body includes: a cylindrical portion including the heating wire arrangement portion and into which the tube is inserted; A stopper portion protruding inward from an inner circumferential surface of the cylindrical portion and restricting insertion of the tube. The electric fusion joint according to claim 1.

4. The thermoplastic resin is polyethylene. The electric fusion joint according to claim 1.

5. Further comprising a heating wire disposed in the stopper portion, The electric fusion joint according to claim 3.

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