Electric fusion joint

Abstract

To provide an electric fusion joint capable of preventing occurrence of a kink even in a heating wire of which diameter is thin.SOLUTION: An electric fusion joint 1 includes a cylindrical part 11, a stopper part 12, side heating wires 31, 32 and a stopper heating wire 33. The cylindrical part 11 has joint socket parts 21, 22 into which a pipe including thermoplastic resin is inserted. The stopper part 12 is disposed on an inner surface of the cylindrical part 11 to expose inwardly, and when resin pipes 2, 3 are inserted to the inner sides of the joint socket parts 21, 22, regulates insertion positions of pipe ends of the resin pipes 2, 3. The side heating wires 31, 32 are disposed in the joint socket parts 21, 22. The stopper heating wire 33 is disposed in the stopper part 12. An angle in the circumferential direction between a first branch point P1 from the stopper heating wire 33 to the side heating wire 31 and a second branch point P2 from the side heating wire 31 to a pin 41b is in a range between -30° or larger and +30° or smaller.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] Electric fusion joints are often used to connect resin pipes, such as resin pipes and metal-reinforced composite pipes having a resin layer and a metal reinforcing layer. Electric fusion joints have pipe sockets at both ends and annular stoppers formed at the back of the pipe sockets, with heating wires provided in the pipe sockets and the stoppers.

[0003] When the number of heating wires in the circumferential direction of an electric fusion joint is different, the amount of heat is reduced in the area with fewer heating wires, making it difficult to heat the surrounding resin. This makes it easier for resin stress to be applied and kinking to occur. In particular, in the case of a large diameter joint, the difference between the buckling stress and the resin stress is small, making kinking more likely to occur. For example, in Patent Document 1, the wire diameter of the heating wire is increased to deal with this problem. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2023-046656 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the configuration shown in Patent Document 1, a heating wire with high rigidity and large wire diameter is used to prevent kinking when the aperture is increased, but the type of heating wire that can be used is limited.

[0006] An object of the present disclosure is to provide an electric fusion joint that is capable of preventing the occurrence of kinks even in an electric heating wire with a thin wire diameter. [Means for solving the problem]

[0007] In order to achieve the above object, the electric fusion joint according to the first disclosure includes a tubular portion, a stopper portion, a side heating wire, and a stopper heating wire. The tubular portion has a joint receptacle portion into which a tube containing thermoplastic resin is inserted. The stopper portion is disposed on the inner surface of the tubular portion so as to protrude inward, and regulates the insertion position of the tube end of the tube when the tube is inserted inside the joint receptacle portion. The side heating wire is disposed in the joint receptacle portion. The stopper heating wire is disposed in the stopper portion. The circumferential angle between a first branch point from the stopper heating wire to the side heating wire and a second branch point from the side heating wire to the terminal is in the range of -30° or more and +30° or less.

[0008] This reduces the area with a small number of heating wires in the circumferential direction, making it possible to heat the resin approximately uniformly in the circumferential direction, thereby reducing stress in the resin and suppressing the occurrence of kinking.

[0009] The electric fusion joint according to the second disclosure is the electric fusion joint according to the first disclosure, in which the number of the side heating wires in the portion outside the angular range in the circumferential direction is the same.

[0010] This allows the resin to be heated approximately uniformly in the circumferential direction, reducing stress in the resin and suppressing the occurrence of kinking.

[0011] The electric fusion joint according to the third disclosure is the electric fusion joint according to the second disclosure, wherein the number of side heating wires in the portion outside the angle range in the circumferential direction is two. This allows the resin to be heated substantially uniformly and sufficiently in the circumferential direction, and the stress in the resin can be reduced, thereby suppressing the occurrence of kinking.

[0012] An electric fusion joint according to a fourth disclosure is the electric fusion joint according to the first disclosure, wherein the first branch point and the second branch point coincide in the circumferential direction.

[0013] This allows the number of side heating wires to be the same in the circumferential direction, thereby reducing resin stress and suppressing the occurrence of kinking. Effect of the Invention

[0014] According to the present disclosure, it is possible to provide an electric fusion joint that is capable of preventing the occurrence of kinks even in an electric heating wire with a thin wire diameter. [Brief description of the drawings]

[0015] [Figure 1] 1A and 1B are diagrams showing a resin tube, an electric fusion joint, and a resin tube according to an embodiment of the present disclosure. [Diagram 2] 1 is a diagram showing a cross-sectional configuration of an electric fusion joint in an embodiment according to the present disclosure. [Diagram 3] 3 is a cross-sectional view showing a state in which a resin tube is inserted into the electric fusion joint of FIG. 2. [Figure 4] 4(a) is a perspective view of the electric fusion joint 1 shown in Fig. 2 as viewed from above, and Fig. 4(b) is a diagram showing the positional relationship between the first branch point and the second branch point when the electric fusion joint is viewed along the A1 direction shown in Fig. 4(a). [Diagram 5] 4(a) is a diagram showing a case where the first branch point and the second branch point are aligned in FIG. 4(a), and FIG. 4(b) is a diagram showing a case where the angle between the first branch point and the second branch point is changed from FIG. 4(a). [Figure 6] 6(a) is a perspective view of the electric fusion joint 1 shown in Fig. 2 as viewed from above on the rear side, and Fig. 6(b) is a view in which the angles of the first branch point and the second branch point are changed from those in Fig. 6(a). [Figure 7] 4 is a cross-sectional view showing a state in which an electric fusion joint and a resin tube are fused together. FIG. [Figure 8] FIG. 2 is a diagram showing a winding core. [Figure 9] FIG. 4 is a perspective view showing a state in which a heating wire is arranged on a winding core. [Figure 10] FIG. 4 is a cross-sectional view showing a state in which a heating wire is arranged on a winding core. [Figure 11]13 is a diagram for explaining how the winding core around which the heating wire is wound is inserted into a die. FIG. [Figure 12] FIG. 13 is a diagram for explaining the injection of resin into a mold. [Figure 13] FIG. 13 is a diagram showing a state in which a kink occurs. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0017] <Configuration> Fig. 1 is a diagram showing an electric fusion joint 1 according to an embodiment of the present disclosure, and a resin pipe 2 and a resin pipe 3 connected by the electric fusion joint. Fig. 1 can also be said to be an exploded view of a piping structure 110. The piping structure 110 has, for example, the electric fusion joint 1, the resin pipe 2, and the resin pipe 3.

[0018] As shown in FIG. 1, an electric fusion joint 1 is fused to a resin pipe 2 and a resin pipe 3, and connects the resin pipe 2 and the resin pipe 3. The resin pipe 2 and the resin pipe 3 are each formed of a thermoplastic resin. The thermoplastic resin is not particularly limited, but may be a polyolefin such as polyethylene having a melting point of less than 230°C. PE (polyethylene), which has a low elution amount, may be used as the thermoplastic resin. HDPE (high density polyethylene resin), which has a melting point of about 130°C and has a low elution amount, may be used as the thermoplastic resin.

[0019] Flow paths 2f, 3f with circular cross sections extend inside the resin pipe 2 and the resin pipe 3. Flow path 1f with a circular cross section extends inside the electric fusion joint 1. When the resin pipe 2 and the resin pipe 3 are connected by the electric fusion joint 1, the axes of the respective flow paths of the resin pipe 2, the resin pipe 3, and the electric fusion joint 1 are arranged on the same straight line.

[0020] The direction in which the axis of each of the flow paths of the electric fusion joint 1, the plastic pipe 2, and the plastic pipe 3 extends is defined as the axial direction A. In addition, in the electric fusion joint 1, the plastic pipe 2, and the plastic pipe 3, the direction in which they approach or move away from each other perpendicularly to their respective axes is defined as the radial direction B, and the direction rotating around each of their axes is defined as the circumferential direction C.

[0021] The resin pipe 2 moves in the direction of arrow A1 relative to the electric fusion joint 1 in the axial direction A to be connected to the electric fusion joint 1. Furthermore, the resin pipe 3 moves in the direction of arrow A2 relative to the electric fusion joint 1 in the axial direction A to be connected to the electric fusion joint 1. The state in which the resin pipe 2 and the resin pipe 3 are fused and connected to the electric fusion joint 1 constitutes the piping structure 110.

[0022] (Electric fusion joint 1) Fig. 2 is a diagram showing a cross-sectional configuration of the electric fusion joint 1. The electric fusion joint 1 contains a thermoplastic resin. As shown in Fig. 2, the electric fusion joint 1 has a cylindrical portion 11, a stopper portion 12, side heating portions 13 and 14, a stopper heating portion 15, and a connector attachment portion 16.

[0023] (Cylindrical portion 11) The cylindrical portion 11 is formed of a thermoplastic resin. The cylindrical portion 11 is cylindrical and has a joint socket portion 21, a joint socket portion 22, and a continuous portion 23. The thermoplastic resin used in the cylindrical portion 11 is not particularly limited, but examples thereof include polyolefins such as polyethylene having a melting point of less than 230°C. As the thermoplastic resin, PE (polyethylene) with a small amount of elution may be used. As the thermoplastic resin, HDPE (high density polyethylene resin) with a melting point of about 130°C with a small amount of elution may be used.

[0024] The joint receptacle portion 21 is disposed on one end 11b side of the tubular portion 11. A plastic pipe 2 is inserted into the inside of the joint receptacle portion 21. The joint receptacle portion 22 is cylindrical. The joint receptacle portion 22 is disposed on the other end 11c side of the tubular portion 11. The joint receptacle portion 22 is cylindrical. A plastic pipe 3 is inserted into the inside of the joint receptacle portion 22.

[0025] 2, the connecting portion 23 is connected to the joint socket portion 21 and the joint socket portion 22, and connects the joint socket portion 21 and the joint socket portion 22. The connecting portion 23 is a portion that connects between the joint socket portion 21 and the joint socket portion 22, and the stopper portion 12 is provided on the inside in the radial direction B.

[0026] The joint socket portion 21 has a protruding portion 24 protruding from the inner surface 11a toward the inside in the radial direction B. The protruding portion 24 is annular. The protruding portion 24 is formed around the entire circumference along the circumferential direction C. The protruding portion 24 is arranged side by side with the stopper portion 12 in the axial direction A. The protruding portion 24 protrudes less radially inward than the stopper portion 12. The protruding portion 24 forms a stepped shape on the inner peripheral surface of the joint socket portion 21. The protruding portion 24 has a side surface 24a and a peripheral surface 24b. The side surface 24a is formed perpendicular to the axial direction A from the inner surface 11a of the cylindrical portion 11 toward the inside in the radial direction B. The peripheral surface 24b is a radially inner end surface of the protruding portion 24. The peripheral surface 24b is formed from the radially inner end of the side surface 24a toward the stopper portion 12 (toward the end 11c) and is connected to the stopper portion 12. The peripheral surface 25b is formed parallel to the axial direction A. In this specification, "perpendicular" may include design tolerance and includes a range that is generally accepted as perpendicular. In this specification, "parallel" may include design tolerance and includes a range that is generally accepted as parallel.

[0027] The joint socket portion 22 has a protruding portion 25 protruding from the inner surface 11a toward the inside in the radial direction B. The protruding portion 25 is annular. The protruding portion 25 is formed around the entire circumference along the circumferential direction C. The protruding portion 25 is arranged side by side with the stopper portion 12 in the axial direction A. The protruding portion 25 protrudes less radially inward than the stopper portion 12. The protruding portion 25 forms a stepped shape on the inner peripheral surface of the joint socket portion 21. The protruding portion 25 has a side surface 25a and a peripheral surface 25b. The side surface 25a is formed perpendicular to the axial direction A from the inner surface 11a of the cylindrical portion 11 toward the inside in the radial direction B. The peripheral surface 25b is a radially inner end surface of the protruding portion 25. The peripheral surface 25b is formed from the radially inner end of the side surface 25a toward the stopper portion 12 (toward the end 11b) and is connected to the stopper portion 12. The peripheral surface 25b is formed parallel to the axial direction A.

[0028] 4 is a cross-sectional view showing a state in which the resin pipe 2 is inserted into the inside of the joint socket 21 of the electric fusion joint 1, and the resin pipe 3 is inserted into the inside of the joint socket 22. As shown in Fig. 4, the resin pipe 2 is inserted into the inside of the protruding portion 24 of the joint socket 21. The resin pipe 3 is inserted into the inside of the protruding portion 25 of the joint socket 22.

[0029] (Stopper part 12) The stopper portion 12 is formed in an annular shape. The stopper portion 12 is formed on the inner surface 11a of the cylindrical portion 11 in the circumferential direction C as a ridge around the entire circumference. The stopper portion 12 contains a thermoplastic resin. The stopper portion 12 is preferably made of the same resin as the thermoplastic resin used in the cylindrical portion 11. Therefore, as the thermoplastic resin forming the stopper portion 12, a polyolefin such as polyethylene having a melting point of less than 230°C can be used, as in the cylindrical portion 11. As the thermoplastic resin, PE (polyethylene) with a small amount of elution may be used. As the thermoplastic resin, HDPE (high density polyethylene resin) with a melting point of about 130°C with a small amount of elution may be used.

[0030] 3, the stopper portion 12 is formed so as to protrude radially inward from the inner surface 11a of the cylindrical portion 11. The stopper portion 12 is disposed on the inner side of the connecting portion 23 of the cylindrical portion 11 in the radial direction B. The stopper portion 12 may be formed as one member together with the cylindrical portion 11, or may be formed as a separate member from the cylindrical portion 11.

[0031] 3, the stopper portion 12 is disposed between the protrusions 24 and 25. The stopper portion 12 has a first side surface 12a, a second side surface 12b, and a peripheral surface 12c. The peripheral surface 12c is an end surface of the stopper portion 12 on the radially inner side.

[0032] The first side surface 12a is formed from an end of the circumferential surface 24b of the protruding portion 24 opposite to the side surface 24a toward the inside in the radial direction B. The first side surface 12a is formed perpendicular to the axial direction A.

[0033] The second side surface 12b is formed from an end of the circumferential surface 25b of the protruding portion 25 opposite to the side surface 25a toward the inside in the radial direction B. The second side surface 12b is formed perpendicular to the axial direction A.

[0034] The peripheral surface 12c connects the radially inner end of the first side surface 12a to the radially inner end of the second side surface 12b. The peripheral surface 12c is formed parallel to the inner surface 11a of the cylindrical portion 11.

[0035] When the plastic pipe 2 is inserted into the fitting receptacle portion 21, the end face 2a of the plastic pipe 2 comes into contact with the first side face 12a of the stopper portion 12, and the insertion position of the end face 2a is restricted, as shown in Fig. 4. The end face 2a of the plastic pipe 2 coming into contact with the first side face 12a includes a case where the end face 2a comes into direct contact with the first side face 12a, and a case where the end face 2a comes into indirect contact with the first side face 12a via a heating wire 33 (described later) of the stopper heating portion 15.

[0036] When the plastic pipe 3 is inserted into the fitting receptacle 22, as shown in Fig. 4, the end face 3a of the plastic pipe 3 comes into contact with the second side face 12b of the stopper portion 12, and the insertion position of the end face 3a is restricted. The end face 3a coming into contact with the second side face 12b includes a case where the end face 3a comes into direct contact with the second side face 12b and a case where the end face 3a comes into indirect contact with the second side face 12b via a heating wire 33 (described later) of the stopper heating portion 15. When the plastic pipes 2, 3 are inserted into the fitting receptacle 21, 22, the protruding height of the stopper portion 12 is formed lower than the inner peripheral surfaces 2s, 3s of the plastic pipes 2, 3.

[0037] (Side heating parts 13 and 14) The side heating parts 13, 14 are provided in the joint socket parts 21, 22 as shown in FIG. 3. The side heating part 13 has a side heating wire 31 embedded in the protruding part 24 of the joint socket part 21 as shown in FIG. 3. The side heating wire 31 is arranged so as to be wound around the peripheral surface 24b for two turns in the circumferential direction. The side heating wire 31 is arranged in the vicinity of the peripheral surface 24b. The side heating wire 31 may be embedded in the protruding part 24 so as to be partially exposed from the peripheral surface 24b or the side surface 24a to the flow path 1f side, or may be completely embedded. The protruding part 24 is formed to a length such that the heating wire 31 is wound around two turns in the axial direction A.

[0038] The side heating portion 14 has a side heating wire 32 embedded in the protruding portion 25 of the joint socket portion 22 as shown in Fig. 3. The side heating wire 32 is arranged so as to be wound around the peripheral surface 25b for two revolutions in the circumferential direction. The side heating wire 32 is arranged in the vicinity of the peripheral surface 25b. The side heating wire 32 may be embedded in the protruding portion 25 so as to be partially exposed from the peripheral surface 25b or the side surface 25a to the flow path 1f side, or may be completely embedded. The protruding portion 25 is formed to a length such that the side heating wire 32 is wound around two revolutions in the axial direction A.

[0039] The side heating wire 31 has, for example, a conductor 31a, an insulating film 31b, and a resin coating 31c. The heating wire 32 has, for example, a conductor 32a, an insulating film 31b, and a resin coating 32c. The conductor wires 31a and 32a can be, for example, nichrome wire, iron-chrome type 2 wire, iron-chrome type 1 wire, nickel-chrome wire, etc.

[0040] The insulating coatings 31b, 32b are provided so as to cover the periphery of the conductors 31a, 32a. The melting point of the insulating coatings 31b, 32b is 230° C. or higher. In this embodiment, it is preferable that the insulating coatings are set to a temperature at which the thermoplastic resin melts (for example, in the case of polyethylene, the heating wire is heated to 220° C.). The insulating coatings 31b, 32b can be formed of, for example, a fluorine-based resin or an imide-based resin, but it is more preferable to form them of a polyimide-based resin. Note that the side heating wires 31, 32 do not have to have the insulating coatings 31b, 32b. The coating resins 31c, 32c are provided so as to cover the periphery of the insulating coatings 31b, 32b. The coating resins 31c, 32c are formed of a thermoplastic resin. The same resin as the thermoplastic resin used in the cylindrical portion 11 may be used for the coating resins 31c, 32c. The thermoplastic resin may be a polyolefin such as polyethylene having a melting point of less than 230°C. The thermoplastic resin may be PE (polyethylene) which has a low elution amount. The thermoplastic resin may be HDPE (high density polyethylene resin) which has a melting point of about 130°C and has a low elution amount.

[0041] The side heating portion 13 is provided symmetrically with respect to the side heating portion 14 and the stopper portion 12. In this embodiment, the side heating wires 31 and 32 are wound so as to be in contact with each other in the axial direction A, but they may be provided with a gap so as not to be in contact with each other.

[0042] As shown in Fig. 2, the side heating portion 13 is disposed adjacent to the stopper portion 12 in the axial direction A. Also, the side heating portion 14 is disposed adjacent to the stopper portion 12 in the axial direction A. For example, as shown in Fig. 2, the heating wire 31 is disposed so as to be in contact with an imaginary surface M1 formed by extending the first side surface 12a outward in the radial direction B. Also, as shown in Fig. 2, the heating wire 32 is disposed so as to be in contact with an imaginary surface M2 formed by extending the second side surface 12b outward in the radial direction B.

[0043] In this way, the side heating portions 13, 14 are arranged next to the stopper portion 12 in the axial direction A so as to be in contact with the imaginary surfaces M1, M2, but a predetermined gap may be provided between the side heating portions 13, 14 and the stopper portion 12.

[0044] In addition, in each of the side heat generating parts 13, 14, the side heating wires 31, 32 are wound in contact with each other for two turns, but this is not limited to two turns. Also, a plurality of portions where a predetermined number of adjacent portions are provided may be provided.

[0045] Furthermore, while side heating portion 13 and side heating portion 14 are provided symmetrically on either side of stopper portion 12, this is not limiting. For example, side heating wire 31 may be wound two turns around one joint socket portion 21 across stopper portion 12, and side heating wire 32 may be wound three turns around the other joint socket portion 22.

[0046] (Stopper heating part 15) The stopper heating portion 15 is provided in the stopper portion 12. The stopper heating portion 15 has a stopper heating wire 33. The stopper heating wire 33 is provided in the stopper portion 12 so as to be wound in the circumferential direction C along the axial direction A. In this embodiment, the stopper heating wire 33 is wound around the stopper portion 12, for example, four times. In the stopper heating portion 15 of this embodiment, adjacent stopper heating wires 33 are all in contact with each other, but gaps may be provided.

[0047] The stopper heating wire 33 is embedded in the stopper portion 12 so as to be in contact with the peripheral surface 12c of the stopper portion 12, but may be embedded in the stopper portion 12 so as to be partially exposed to the flow path 1f side from the first side surface 12a, the second side surface 12b, or the peripheral surface 12c, or may be embedded at a predetermined distance from the peripheral surface 12c of the stopper portion 12. The stopper portion 12 is formed to a length such that the heating wire 33 is wound four times in the axial direction A.

[0048] 2, the stopper heating wire 33 has a conductive wire 33a, an insulating coating 33b, and a coating resin 33c. The conductive wire 33a may be made of, for example, a nichrome wire, an iron-chrome type 2 wire, an iron-chrome type 1 wire, or a nickel-chrome wire.

[0049] The insulating coating 33b is provided so as to cover the periphery of the conductor 33a. The insulating coating 33b has a melting point of 230° C. or higher. In this embodiment, it is preferable that the insulating coating 33b is set to a temperature at which the thermoplastic resin does not melt (for example, in the case of polyethylene, the heating wire is heated to 220° C.). The insulating coating 33b can be formed of, for example, a fluorine-based resin or an imide-based resin, but it is more preferable to form it of a polyimide-based resin. The thickness of the insulating coating is preferably 10 μm to 100 μm, and from the viewpoint of fusion strength, it is preferably 100 μm or less. Note that the heating wire 33 does not need to have the insulating coating 33b. The coating resin 33c is provided so as to cover the periphery of the insulating coating 33b. The coating resin 33c is formed of a thermoplastic resin. The same resin as the thermoplastic resin used in the cylindrical portion 11 may be used for the coating resin 33c. Examples of the thermoplastic resin include polyolefins such as polyethylene having a melting point of less than 230° C. As the thermoplastic resin, PE (polyethylene) with a small amount of elution may be used. As the thermoplastic resin, HDPE (high density polyethylene resin) with a melting point of about 130° C. with a small amount of elution may be used.

[0050] In this embodiment, in the stopper heating portion 15, one stopper heating wire 33 is wound four times so as to contact the adjacent ones, but the number of turns is not limited to this and may be three turns or less or five turns or more. Also, the stopper heating portion 15 may be formed by winding two or more stopper heating wires 33, not limited to one.

[0051] (Connector mounting part 16) As shown in Fig. 3, the connector attachment portion 16 has two pins 41b, 41c. The two pins 41b, 41c are provided so as to protrude radially outward from the outer surface 11d of the cylindrical portion 11. As shown in Fig. 3, one of the two pins 41b, 41c, the pin 41b, is disposed near the end 11b of the cylindrical portion 11, and the other pin 41c is disposed near the end 11c.

[0052] Fig. 4(a) is a perspective view of the electric fusion joint 1 shown in Fig. 2 as viewed from above the front. In Fig. 4(a), the heating wire and pins 41b, 41c are indicated by solid lines, and the cylindrical portion 11 is indicated by dotted lines. As shown in Fig. 4(a), the pin 41b is connected to the side heating wire 31 of the side heating portion 13 by a connecting heating wire 34 (indicated by a two-dot chain line in Fig. 3). The pin 41c is connected to the side heating wire 32 of the side heating portion 14 by a connecting heating wire 35 (indicated by a dotted line in Fig. 3).

[0053] As shown in Fig. 4, the pin 41b, the connecting heating wire 34, the side heating wire 31, the stopper heating wire 33, the side heating wire 32, the connecting heating wire 35, and the pin 41c are connected in this order, and the heating wires 31 to 34 are a single heating wire. This single heating wire extends from the pin 41b to the side heating part 13 along the axial direction A by the connecting heating wire 34, forms the side heating part 13, the stopper heating part 15, and the side heating part 14 in this order, and extends to the pin 41c along the axial direction A by the connecting heating wire 35. When the connectors of the fusion device are attached to the pins 41b and 41c and electricity is applied, the heating wires 31, 32, 33, 34, and 35 generate heat. When describing a single heating wire, it is referred to as the heating wire 30.

[0054] (Branching of heating wire) As shown in Fig. 4(a), the electric fusion joint 1 is provided with a first branch point P1 where the stopper heating wire 33 branches off to the side heating wire 31, and a second branch point P2 where the side heating wire 31 branches off to the connection heating wire 34. Fig. 4(b) is a diagram showing the positional relationship between the first branch point P1 and the second branch point P2 when the electric fusion joint 1 is viewed along the direction A1 shown in Fig. 4(a).

[0055] As shown in FIG. 4(a), the heating wire 30 moves from the stopper heating part 15 to the side heating part 13 at the first branch point P1, and is wound around two adjacent turns in the clockwise direction shown in FIG. 4(b), and then branches off from the side heating part 13 toward the pin 41b at the second branch point P2. Here, as shown in FIG. 4(a), there is one region between the first branch point P1 and the second branch point P2 where there are no adjacent side heating wires 31 in the side heating part 13. This one region is shown as R. As shown in FIG. 4(b), the region R between the first branch point P1 and the second branch point P2 is formed on a circumference centered on the central axis O of the electric fusion joint 1. The central axis O is parallel to the axial direction A. The central axis O is the central axis of the cylindrical part 11.

[0056] The angle α of the region R between the first branch point P1 and the second branch point P2 about the central axis O is set to be -30° or more and +30° or less. For example, in FIG. 4(b), if the left-handed direction Cl is positive and the right-handed direction Cr is negative, the position of the second branch point P2 rotated 30° in the left-handed direction Cl from the first branch point P1 is +30°, and the position of the second branch point P2 rotated 30° in the right-handed direction Cr from the first branch point P1 is -30°. The second branch point P2 is disposed within a range of ±30° based on the first branch point P1. A range W of -30° or more and +30° or less based on the first branch point P1 is indicated by hatching.

[0057] As shown in Fig. 4(a), when α is in the range of greater than 0° and less than +30°, a region R with one side heating wire 31 is formed. As shown in Fig. 5(b), when α is 0°, the positions of the first branch point P1 and the second branch point P2 in the circumferential direction C coincide, and two side heating wires 31 are arranged side by side over the entire circumference of the side heating portion 13. When α is greater than -30° and less than 0°, a region R with three side heating wires 31 arranged side by side is formed between the first branch point P1 and the second branch point P2.

[0058] 6(a) is a perspective view of the electric fusion joint 1 shown in FIG. 2, seen from above the rear. As shown in FIG. 6(a), the electric fusion joint 1 is also provided with a first branch point P1' where the stopper heating wire 33 branches into the side heating wire 32, and a second branch point P2' where the side heating wire 31 branches into the connection heating wire 35. The angle of the region R' between the first branch point P1' and the second branch point P2' about the central axis O is also set to be -30° or more and +30° or less. Note that the positive and negative rotation directions are reversed on the first branch point P1' and second branch point P2' sides compared to the first branch point P1 and the second branch point P2, and the position where the second branch point P2' is rotated 30° in the clockwise direction Cr from the first branch point P1' is +30°, and the position where the second branch point P2' is rotated 30° in the counterclockwise direction Cl from the first branch point P1' is -30°. As shown in Fig. 6(a), when α is in the range of greater than 0° and equal to or less than +30°, a region R' is formed in which there is one side heating wire 32. As shown in Fig. 6(b), when α is equal to or greater than -30° and less than 0°, a region R' in which three side heating wires 32 are lined up is formed between the first branch point P1' and the second branch point P2'. Although not shown, when α is 0°, the positions of the first branch point P1' and the second branch point P2' in the circumferential direction C match, and two side heating wires 32 are arranged side by side around the entire circumference of the side heating portion 14.

[0059] <Fusing method> Next, a fusion method according to an embodiment of the present disclosure will be described.

[0060] 3, the resin pipe 2 is inserted into the joint socket 21 of the electric fusion joint 1 until the relative movement of the end face 2a of the resin pipe 2 is restricted by the stopper portion 12. The resin pipe 3 is inserted into the joint socket 22 of the electric fusion joint 1 until the relative movement of the end face 3a of the resin pipe 3 is restricted by the stopper portion 12. When inserting the resin pipe 2 into the electric fusion joint 1, the end face 2a of the resin pipe 2 and the outer surface in the vicinity of the end face 2a, and the end face 3a of the resin pipe 3 and the outer surface in the vicinity of the end face 3a may be scraped.

[0061] Next, a connector of a fusion device is attached to the two pins 41 b and 41 c of the connector attachment portion 16 .

[0062] Next, an operator operates the fusion device to apply voltage to the side heating wires 31, 32 and the stopper heating wire 33 to fuse the electric fusion joint 1 to the plastic pipes 2, 3. At this time, it is preferable to press the plastic pipes 2, 3 against the stopper portion 12.

[0063] FIG. 7 is a cross-sectional view showing the state in which the plastic pipe 2, the electric fusion joint 1, and the plastic pipe 3 are fused. The stopper portion 12, the end face 2a of the plastic pipe 2, and the end face 3a of the plastic pipe 3 melt, and are pressed and narrowed by the plastic pipes 2 and 3, filling the gap between the plastic pipes 2 and 3 to form a bead V. The bead V is formed by melting the thermoplastic resin of the coating resin 33c of the electric heating wire 33, the stopper portion 12, the end face 2a of the plastic pipe 2, and the end face 3a of the plastic pipe 3. By pressing in a molten state, the plastic pipes 2 and 3 move toward the inside of the electric fusion joint 1 while crushing the stopper portion 12, and the bead V is formed according to the amount of movement. In addition, the outer surface 2d of the plastic pipe 2 and the resin around the electric heating wire 31 of the side heating portion 13 are fused, and the outer surface 3d of the plastic pipe 3 and the resin around the electric heating wire 32 of the side heating portion 14 are fused.

[0064] <Method of manufacturing electric fusion joint 1> Next, a method for producing the electric fusion joint 1 of the present disclosure will be described.

[0065] 8 is a diagram showing the winding core 200. The winding core 200 has a first member 201, a second member 202, and a third member 203. The first member 201, the second member 202, and the third member 203 are substantially cylindrical members, and are arranged side by side on the same axis.

[0066] The second member 202 is disposed between the first member 201 and the third member 203. The first member 201 forms the joint socket portion 21. The second member 202 forms the stopper portion 12. The third member 203 forms the joint socket portion 22. The second member 202 is formed to have a smaller diameter than the first member 201 and the third member 203.

[0067] Fig. 9 is a perspective view showing a state in which the heating wire 30 is arranged in the winding core 200. Fig. 10 is a cross-sectional view showing a state in which the heating wire 30 is arranged in the winding core 200.

[0068] The end of the outer peripheral surface 201a of the first member 201 on the second member 202 side is provided with a heating wire arrangement portion 201b around which the heating wire 31 of the side heating portion 13 is wound. The heating wire arrangement portion 201b is formed by recessing the outer peripheral surface 201a toward the center. The heating wire arrangement portion 201b is formed in a stepped shape on the outer peripheral surface 201a. The diameter of the heating wire arrangement portion 201b of the outer peripheral surface 201a is smaller than the diameter of the portion other than the heating wire arrangement portion 201b. It is preferable that the size of the step d of the heating wire arrangement portion 201b is larger than 0 mm and equal to or smaller than the tube thickness. If d is small, the heating wire is likely to be misaligned, and if d is large, it is difficult to insert the tube during scraping. From the above, it is preferable that it is 1.0 mm or less, and preferably 0.5 mm or less. It is also preferable that it is up to about 50% of the diameter of the heating wire 31. The outer diameter of the portion of the first member 201 where the heating wire arrangement portion 201b is formed is larger than the outer diameter of the second member 202.

[0069] As shown in FIG. 9, the heating wire 33 of the stopper heat generating portion 15 is wound around the outer circumferential surface 202a of the second member 202.

[0070] The end of the outer peripheral surface 203a of the third member 203 on the second member 202 side is provided with a heating wire arrangement portion 203b around which the heating wire 32 of the side heating portion 14 is wound. The heating wire arrangement portion 203b is formed by recessing the outer peripheral surface 203a toward the center. The heating wire arrangement portion 203b is formed in a stepped shape on the outer peripheral surface 203a. The diameter of the heating wire arrangement portion 2203b of the outer peripheral surface 203a is smaller than the diameter of the portion other than the heating wire arrangement portion 2203b. The size of the step d of the heating wire arrangement portion 203b is preferably up to about 20% of the diameter of the heating wire 32. The outer diameter of the portion of the third member 203 where the heating wire arrangement portion 203b is formed is larger than the outer diameter of the second member 202.

[0071] Such a winding core 200 is used to manufacture the electric fusion joint 1.

[0072] The heating wires 31 to 35 are connected to each other to form a single heating wire 30.

[0073] First, the heating wire 30 is wound around the winding core 200. Because the heating wires 31, 32, and 33 are a single connected heating wire, the heating wire is wound from left to right or from right to left as shown in Fig. 9. At this time, because the heating wire arrangement portion 201b and the heating wire arrangement portion 203b are stepped, it is easy to see where to start winding the first turn.

[0074] After the heating wire is wound around the winding core 200, the winding core 200 with the heating wire wound thereon is inserted into a mold 300 as shown in FIG. 11. The mold 300 is divided into a first mold 301 and a second mold 302 as shown in FIGS. 11 and 12, and the winding core 200 is inserted into the mold 300. A gate 303 for injecting resin into the mold 300 is disposed so as to face the outer peripheral surface 202a of the second member 202. The gate 303 is formed on the front side of the mold 300 in FIGS. 11 and 12. The gate 303 is indicated by a two-dot chain line in FIG. 12. The gate 303 is provided at a position rotated 90° in the circumferential direction from the pin forming portions 304b, 304c where the pins 41b, 41c are formed.

[0075] Next, as shown in Fig. 12, resin is injected from a gate 303 formed in a first mold 301 to form an electric fusion joint 1. The resin flowing in from the gate 303 spreads toward the first member 201 and the second member 202 (left and right directions, see arrows F1 and F2). At this time, the heating wires 31 and 32 are pushed by the flow of resin (see arrows F1 and F2). However, since the heating wire arrangement parts 201b and 203b are formed in a stepped shape, the heating wires 31 and 32 are held down by the stepped surfaces 201c and 203c on the opposite side of the second member 202, and it is possible to prevent the heating wires 31 and 32 from flowing outward (to the side of arrows F1 and F2). In Fig. 12, the arrow F1 indicates the right direction as viewed from the gate 303, and the arrow F2 indicates the left direction.

[0076] In this manner, the electric fusion joint 1 can be manufactured.

[0077] <Ultrapure water use of piping structure 110> In the piping structure 110 of the first embodiment, no gap is formed between the resin pipe 2 and the resin pipe 3, and therefore the retention of liquid is suppressed. For this reason, the piping structure 110 of the first embodiment can be used, for example, for transporting ultrapure water. Specifically, the piping structure 110 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, and the like.

[0078] 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.

[0079] The piping structure 110 of the embodiment according to 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.

[0080] Furthermore, the piping structure 110 according to the embodiment of the present disclosure may have, for example, a polyethylene-based resin layer, and is excellent in workability. For example, fusion work such as EF (electrical fusion) bonding can be easily performed at a relatively low temperature.

[0081] When the electric fusion joint 1 is used for ultrapure water applications, the bead V is the only part of the electric fusion joint 1 that comes into contact with ultrapure water. For this reason, it is preferable to use HDPE (high density polyethylene resin), which has a low elution amount, for the coating resin 33c of the heating wire 33 that forms the bead V and the thermoplastic resin that forms the stopper portion 12.

[0082] <Other embodiments> Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0083] (A) In the above embodiment, the heating wires 30 (side heating wires 31, 32, stopper heating wire 33, connecting heating wires 34, 35) are provided with an insulating coating, and although this is not limiting, it is preferable that the heating wires 30 are provided with an insulating coating. This is because the heating wires are pressurized by the resin pipes 2 and 3 at the stopper portion 12, and are likely to come into contact with each other.

[0084] (B) In the above embodiment, the side heat generating portion 13 and the side heat generating portion 14 are provided at positions symmetrical on the left and right sides of the stopper portion 12, but this is not limiting.

[0085] (C) In the above embodiment, all of the flow paths of the electric fusion joint 1 are formed straight, but the electric fusion joint 1 may be an elbow joint in which the flow paths are curved.

[0086] (D) In the electric fusion joint 1 of the above embodiment, the heating wire 31 is wound two times in the side heating portion 13 so as to be adjacent to each other in the axial direction, the heating wire 33 is wound four times in the stopper heating portion 15 so as to be adjacent to each other in the axial direction, and the heating wire 32 is wound two times in the side heating portion 14 so as to be adjacent to each other in the axial direction, but the number of times the heating wire is wound is not limited to these.

[0087] (Example) Next, the electric fusion joint of this embodiment will be described in detail using examples.

[0088] In the examples, the angle between the first branch point P1 and the second branch point P2 and the angle between the first branch point P1' and the second branch point P2' were changed to create an electric fusion joint, which was used to fuse the resin pipes 2 and 3 to examine whether kinking occurs. Note that in the following, the angle was changed from 0 to a positive value, and negative values ​​were not used. This is because negative values ​​increase the number of heating wires as described above, making kinking less likely to occur than positive values.

[0089] In the following (Table 1), an electric fusion joint 1 of a size corresponding to the diameter of the 75A was used. That is, the inner diameter D of the protruding portion 24 of the electric fusion joint 1 shown in FIG. 3 is equal to the outer diameter of the 75A resin pipe. The wall thickness of the joint socket of the electric fusion joint 1 was 5.6 mm, and the heating wire 30 was an iron-chromium type 2 wire whose surface was insulated with polyimide and the insulating coating was then coated with HE222D. The wire diameter of the iron-chromium type 2 wire was 0.6 mm, the wire diameter including the iron-chromium type 2 wire and polyimide was 0.64 mm, and the wire diameter including the iron-chromium type 2 wire, polyimide, and HE222D was 1.8 mm.

[0090] For example, in Example 1, the angle between the first branch point P1 and the second branch point P2 was set to 65°, and the angle between the first branch point P1' and the second branch point P2' was set to 13°, and it was confirmed whether a kink occurred in the side heating portion 13 where the first branch point P1 and the second branch point P2 are provided, and whether a kink occurred in the side heating portion 14 where the first branch point P1' and the second branch point P2' are provided.

[0091] 13 is a cross-sectional view showing a state in which a kink has occurred in the side heating part 13. Fig. 13 is a cross-sectional view passing through the side heating part 13 and perpendicular to the axial direction A. As shown in Fig. 13, when a kink occurs, the heating wire 31 protrudes to the inside of the electric fusion joint 1.

[0092] (Table 1) TIFF2025053954000002.tif21154 As shown in conditions 1 to 26 where the angle is changed as described above, it can be seen that no kink occurs when the angle between the first branch point P1 and the second branch point P2 is in the range of 0° to 30°. It can also be seen that no kink occurs when the angle between the first branch point P1' and the second branch point P2' is in the range of 0° to 30°.

[0093] In the following (Table 2), an electric fusion joint 1 of a size corresponding to the diameter of 200A was used. That is, the inner diameter D of the protruding part 24 of the electric fusion joint 1 shown in FIG. 3 is equal to the outer diameter of the 200A resin pipe. The wall thickness of the joint socket of the electric fusion joint 1 was 6 mm, and the heating wire 30 was an iron-chromium type 2 wire whose surface was insulated with polyamide-imide, and the insulating coating was then coated with HE222D. The wire diameter of the iron-chromium type 2 wire was 0.8 mm, the wire diameter including the iron-chromium type 2 wire and polyamide-imide was 0.84 mm, and the wire diameter including the iron-chromium type 2 wire, polyamide-imide, and HE222D was 2.4 mm.

[0094] (Table 2) TIFF2025053954000003.tif39147As shown in conditions 1 to 6 where the angle was changed as above, even with a diameter of 200A, it can be seen that when the angle between the first branch point P1' and the second branch point P2' exceeds 30°, a kink occurs, but when the angle is in the range of 0° to 30°, no kink occurs. It can also be seen that when the angle between the first branch point P1 and the second branch point P2 is in the range of 0° to 30°, no kink occurs. [Explanation of symbols]

[0095] 1: Electric fusion joint 11: Cylindrical part 12: Stopper part 31: Side heating wire 32: Side heating wire P1: First branch point P2: Second branch point

Claims

1. a tubular portion having a fitting receiving portion into which a tube containing a thermoplastic resin is inserted; a stopper portion disposed on an inner surface of the cylindrical portion so as to protrude inward, the stopper portion regulating an insertion position of a pipe end of the pipe when the pipe is inserted into the fitting socket portion; A side heating wire disposed in the joint socket; A stopper heating wire is disposed in the stopper portion, an angle in the circumferential direction between a first branch point from the stopper heating wire to the side heating wire and a second branch point from the side heating wire to the terminal is in the angle range of -30° or more and +30° or less.

2. The number of the side heating wires in the portion other than the angle range in the circumferential direction is the same. The electric fusion joint according to claim 1.

3. The number of the side heating wires in the portion outside the angle range in the circumferential direction is two.

3. The electric fusion joint according to claim 2.

4. The first branch point and the second branch point coincide with each other in the circumferential direction. The electric fusion joint according to claim 1.

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