Fusing method, fusing system and fusing apparatus

Abstract

To provide a fusing method capable of preventing the occurrence of a kink even in electric heating wires with thin wire diameters.SOLUTION: The fusing method for fusing an electric fusion joint 1 and resin pipes 2 and 3, includes step S1, step S5, and step S6. Step S1 inserts the pipes into the inside of joint receiving portions 21 and 22 of the electric fusion joint 1. Step S5 energizes electric heating wires 31 to 33 of heating sections 13 to 15. Step S6 energizes the electric heating wires 31 to 33 of the heating sections 13 to 15 after step S5. The total heat value of step S5 is 0.14 or more and 0.70 or less of the total heat value of step S5 and step S6 combined, and an average value of Joule heat generated per second is less than 184 W when only a time of substantial heating in step S5 is calculated.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present disclosure relates to fusing methods, systems and apparatus. [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 a voltage is applied to the heating element with a tube inserted into the tube socket of the electric fusion joint to generate heat, the resin of the tube socket and stopper around the heating element fuses with the resin of the tube body, and the tube bodies are connected via the electric fusion joint (see, for example, Patent Document 1). However, with the electric fusion joint shown in Patent Document 1, when the temperature of the external environment is low, heating is insufficient and poor fusion may occur during fusion.

[0004] For this reason, for example, Patent Document 2 discloses a method of heating a resin product according to a heating pattern consisting of a preheating process in which a relatively large amount of electric power is supplied for a short period of time at the beginning to fill in the gap between the electric fusion joint and the tube body and to provide preheat, and then a main heating process.

[0005] However, in Patent Document 2, a large amount of power is initially supplied for a short period of time, which promotes thermal expansion of the heating wire and makes it prone to kinking. For this reason, a method of preventing short circuits by thickening the heating wire is used, as shown in Patent Document 3. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 5-318596 [Patent Document 2] Japanese Patent Application Publication No. 10-16062 [Patent Document 3] JP 2023-046656 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the configuration shown in Patent Document 3, a heating wire with high rigidity and large wire diameter is used to suppress kinking when the diameter is increased, but the design is restricted because the type of heating wire that can be used is limited.

[0008] An object of the present disclosure is to provide a fusion method, a fusion system, and a fusion device that are capable of preventing the occurrence of kinks even in an electric heating wire with a thin wire diameter. [Means for solving the problem]

[0009] In order to achieve the above object, the fusion method according to the first disclosure is a fusion method for fusing an electric fusion joint and a tube, and includes an insertion step, a first heating step, and a second heating step. The electric fusion joint includes a joint socket portion and a heat generating portion, and includes a thermoplastic resin. A tube including a thermoplastic resin is inserted into the joint socket portion. The heat generating portion has a heating wire. The insertion step includes inserting a tube into the inside of the joint socket portion of the electric fusion joint. The first heating step is energizing the heating wire of the heating portion. The second heating step is energizing the heating wire of the heating portion after the first heating step. The ratio of the total heat amount in the first heating step to the total heat amount in the first heating step and the second heating step combined is 0.14 or more and 0.70 or less, and the average value of Joule heat generated per second when calculating only the time during which heating is substantially performed in the first heating step is less than 184 W.

[0010] In this way, the ratio of the total heat amount of the first heating step to the total heat amount of the first heating step and the second heating step combined is set to 0.14 or more and 0.70 or less, and the average value of Joule heat generated per second when calculating only the time during which heating is actually performed in the first heating step is less than 184 W. By performing the first heating step, the elastic modulus of the thermoplastic resin around the heating wire can be reduced in advance. This makes it possible to reduce the stress of the resin and suppress the occurrence of kinking. Here, the time during which heating is actually performed refers to the time during which electricity is passed through the heating wire.

[0011] The fusion method according to the second disclosure is the fusion method according to the first disclosure, in which the total amount of heat given to the thermoplastic resin around the heat generating portion of the electric fusion joint in the first heating step is 16 KJ or more, thereby making it possible to reduce the elastic modulus of the thermoplastic resin.

[0012] The fusion method according to the third disclosure is the fusion method according to the first or second disclosure, in which the temperature of the thermoplastic resin around the heat generating portion of the electric fusion joint in the first heating step is equal to or lower than the melting point of the thermoplastic resin, thereby making it possible to suppress melting of the thermoplastic resin in the first heating step and reduce the elastic modulus, and to perform fusion in the second heating step.

[0013] The fusion method according to the fourth disclosure is the fusion method according to the third disclosure, in which in the first heating step, the temperature of the thermoplastic resin around the heat generating portion of the electric fusion joint is 70° C. or more and 130° C. or less. This makes it possible to reduce the elastic modulus in the first heating step when the thermoplastic resin is, for example, polyethylene.

[0014] The fusion method according to the fifth disclosure is the fusion method according to the first disclosure, in which in the second heating step, the temperature of the thermoplastic resin around the heat generating part of the electric fusion joint is equal to or higher than the temperature of the thermoplastic resin around the heat generating part of the electric fusion joint in the first heating step and is lower than the thermal decomposition starting temperature of the thermoplastic resin contained in the electric fusion joint, whereby in the second heating step, the thermoplastic resin of the electric fusion joint and the tube can be melted to perform fusion joining.

[0015] The fusion method according to the sixth disclosure is the fusion method according to the first disclosure, further comprising a heat retention step of maintaining the temperature of the thermoplastic resin around the heat generating part within a predetermined temperature range after the second heating step. By providing the heat retention step in this manner, the temperature at which the resin melts can be maintained, and overheating can be suppressed. Furthermore, by maintaining the temperature of the thermoplastic resin around the heat generating part within a predetermined temperature range, it becomes possible to stably exhibit fusion strength.

[0016] The fusion method according to the seventh disclosure is the fusion method according to the first disclosure, in which the voltage applied to the heating wire in the first heating step is 71.4% or less of the voltage applied to the heating wire in the second heating step, thereby making it possible to reduce the elastic modulus of the thermoplastic resin before fusion and suppress the occurrence of kinking.

[0017] A fusion method according to an eighth disclosure is the fusion method according to the first disclosure, wherein the electric fusion joint further has a main body including a joint socket, and a stopper provided on the inner surface of the main body so as to protrude inward and which regulates the insertion position of the tube end of the tube when the tube is inserted inside the joint socket. The fusion method further includes a pressurizing step of applying force to the tube toward the stopper.

[0018] This makes it possible to prevent kinking even when fusion splicing a tube to an electric fusion joint that has a stopper that regulates the tube position. It also makes it possible to prevent gaps from forming between the stopper and the tube end, making it possible to use the tube as a pipe for ultrapure water, for example.

[0019] A fusion system according to a ninth disclosure includes a tube, an electric fusion joint, and a fusion device. The tube includes a thermoplastic resin. The electric fusion joint has a main body, a heat generating part, and a connector mounting part. The main body has a joint receptacle into which the tube is inserted. The heat generating part has a heating wire. The connector mounting part is disposed on the outer surface of the main body and connected to the heating wire. The fusion device has a connector and a control part. The connector is attached to the connector mounting part. The control part controls the supply of electricity to the heating wire via the connector mounting part. The control part executes a first heating control in which electricity is supplied to the heating wire, and a second heating control in which electricity is supplied to the heating wire after the first heating control. The ratio of the total heat amount of the first heating control to the total heat amount of the first heating control and the second heating control combined is 0.14 or more and 0.70 or less, and the average value of Joule heat generated per second when calculating only the time during which heating is substantially performed in the first heating control is less than 184 W.

[0020] In this way, by performing the first heating control with the ratio of the total heat amount of the first heating control to the total heat amount of the first heating process control step and the second heating control combined being 0.14 or more and 0.70 or less, and with the average value of the Joule heat generated per second when calculating only the time during which heating is actually performed in the first heating control being less than 184 W, the elastic modulus of the thermoplastic resin around the heating wire can be reduced in advance. This makes it possible to reduce the stress in the resin and suppress the occurrence of kinking.

[0021] The fusion device according to the tenth disclosure is a fusion device for fusing an electric fusion joint containing thermoplastic resin, the electric fusion joint having a main body having a joint receptacle into which a tube is inserted, a heating part having an electric heating wire, and a connector attachment part disposed on the outer surface of the main body and connected to the electric heating wire, to a tube containing thermoplastic resin, the fusion device comprising a connector and a control part. The connector is attached to the connector attachment part. The control part controls the supply of electricity to the electric heating wire via the connector attachment part. The control part executes a first heating control for supplying electricity to the electric heating wire, and a second heating control for supplying electricity to the electric heating wire after the first heating control. The ratio of the total heat amount of the first heating control to the total heat amount of the first heating control and the second heating control combined is 0.14 or more and 0.70 or less, and the average value of Joule heat generated per second when calculating only the time during which heating is substantially performed in the first heating control is less than 184 W.

[0022] In this way, by performing the first heating control with the ratio of the total heat amount of the first heating control to the total heat amount of the first heating control and the second heating control combined being 0.14 or more and 0.70 or less, and with the average value of the Joule heat generated per second when calculating only the time during which heating is actually performed being less than 184 W, the elastic modulus of the thermoplastic resin around the heating wire can be reduced in advance. This makes it possible to reduce the stress in the resin and suppress the occurrence of kinking. Effect of the Invention

[0023] According to the present disclosure, it is possible to provide a fusion method, a fusion system, and a fusion device that are capable of preventing the occurrence of kinks even in an electric heating wire with a thin wire diameter. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram showing a fusion system according to a first embodiment of the present disclosure. [Diagram 2] 1 is a diagram showing a resin pipe, an electric fusion joint, and a resin pipe according to a first embodiment of the present disclosure. [Diagram 3] 1 is a diagram showing a cross-sectional configuration of an electric fusion joint in a first embodiment according to the present disclosure. [Figure 4] 4 is a cross-sectional view showing a state in which a resin tube is inserted into the electric fusion joint of FIG. 3. FIG. [Diagram 5] FIG. 1 is a perspective view showing a jig according to a first embodiment of the present disclosure. [Figure 6] FIG. 6 is a schematic plan view showing the jig in FIG. 5. [Figure 7] A diagram showing the resin pipe, electric fusion joint, and resin pipe attached to a jig. [Figure 8] FIG. 8(a) is a graph showing the relationship between applied voltage and time, and FIG. 8(b) is a graph showing the temperature change of the thermoplastic resin when the voltage is applied as shown in FIG. 8(a). [Figure 9] FIG. 1 is a flow diagram showing a fusion method according to a first embodiment of the present disclosure. [Figure 10] 8 is a cross-sectional view showing the resin pipe, the electric fusion joint, and the resin pipe in FIG. 7 in a fused state. FIG. [Figure 11] FIG. 6 is a cross-sectional view of an electric fusion joint according to a second embodiment of the present disclosure. [Figure 12] 12 is a cross-sectional view showing a state in which a resin tube is inserted into the electric fusion joint of FIG. 11. FIG. [Figure 13] FIG. 13 is a diagram showing a state in which a kink occurs. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0026] (Embodiment 1) <Configuration> Fig. 1 is a diagram showing the configuration of a fusion system 100 according to an embodiment of the present disclosure. As shown in Fig. 1, the fusion system 100 includes an electric fusion joint 1, a resin pipe 2 (an example of a pipe), a resin pipe 3 (an example of a pipe), and a fusion device 4. The electric fusion joint 1, the resin pipe 2, and the resin pipe 3 are thermally fused together by the fusion device 4.

[0027] Fig. 2 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.

[0028] As shown in FIG. 2, 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. 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] (Electric fusion joint 1) Fig. 3 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. 3, the electric fusion joint 1 has a main body portion 11, a stopper portion 12, socket heating portions 13 and 14, a stopper heating portion 15, and a connector attachment portion 16.

[0033] (Main body 11) The main body 11 is made of a thermoplastic resin. The main body 11 is cylindrical and has a fitting socket portion 21, a fitting socket portion 22, and a connecting portion 23. The thermoplastic resin used in the main body 11 is not particularly limited, but may be a polyolefin such as polyethylene having a melting point of less than 230°C. As the thermoplastic resin, PE (polyethylene) with a low elution amount may be used. As the thermoplastic resin, HDPE (high density polyethylene resin) with a melting point of about 130°C with a low elution amount may be used.

[0034] The joint receptacle portion 21 is disposed on one end 11b side of the main body portion 11. The 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 main body portion 11. The joint receptacle portion 22 is cylindrical. The plastic pipe 3 is inserted into the inside of the joint receptacle portion 22.

[0035] 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.

[0036] 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 main body 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 24b 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.

[0037] 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 main body 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.

[0038] 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.

[0039] (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 main body 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 main body portion 11. Therefore, as with the main body portion 11, the thermoplastic resin forming the stopper portion 12 may be a polyolefin 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.

[0040] 3, the stopper portion 12 is formed so as to protrude radially inward from the inner surface 11a of the main body portion 11. The stopper portion 12 is disposed on the inner side of the connecting portion 23 of the main body portion 11 in the radial direction B. The stopper portion 12 may be formed as one member together with the main body portion 11, or may be formed as a separate member from the main body portion 11.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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 main body portion 11.

[0045] 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.

[0046] 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.

[0047] (Hot-air-generating parts 13 and 14) The socket heating parts 13, 14 are provided in the joint socket parts 21, 22 as shown in Fig. 3. The socket heating part 13 has a heating wire 31 embedded in the protruding part 24 of the joint socket part 21 as shown in Fig. 3. The heating wire 31 is arranged so as to be wound around the peripheral surface 24b for two revolutions in the circumferential direction. The heating wire 31 is arranged in the vicinity of the peripheral surface 24b. The heating wire 31 may be embedded in the protruding part 24 so that a part of the heating wire 31 is 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 revolutions in the axial direction A.

[0048] The socket heating portion 14 has a heating wire 32 embedded in the protruding portion 25 of the joint socket portion 22 as shown in Fig. 3. The heating wire 32 is arranged so as to be wound around the peripheral surface 25b in two circumferential turns. The heating wire 32 is arranged in the vicinity of the peripheral surface 25b. The 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 heating wire 32 is wound around two turns in the axial direction A.

[0049] The 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 conductors 31a and 32a can be made of, for example, nichrome wire, iron-chrome type 2 wire, iron-chrome type 1 wire, nickel-chrome wire, etc.

[0050] The insulating coatings 31b, 32b are provided so as to cover the periphery of the conductors 31a, 32a. The insulating coatings 31b, 32b have a melting point of 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 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 main body 11 may be used for the coating resins 31c, 32c. As the thermoplastic resin, a polyolefin such as polyethylene having a melting point of less than 230° C. can be used. 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.

[0051] The socket heating part 13 is provided symmetrically with respect to the socket heating part 14 and the stopper part 12. In this embodiment, the heating wires 31, 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.

[0052] As shown in Fig. 3, the socket heating portion 13 is disposed adjacent to the stopper portion 12 in the axial direction A. Also, the socket heating portion 14 is disposed adjacent to the stopper portion 12 in the axial direction A. For example, as shown in Fig. 3, 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. 3, 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.

[0053] In this way, the socket 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 distance may be provided between the socket heating portions 13, 14 and the stopper portion 12.

[0054] In addition, in each of the receiving port heating parts 13, 14, the heating wires 31, 32 are wound in contact with each other for two turns, but this is not limited to two turns. In addition, all or part of the wires may not be in contact. In addition, a plurality of parts may be provided in which a predetermined number of wires are adjacent to each other.

[0055] Furthermore, although the socket heating portion 13 and the socket heating portion 14 are provided symmetrically on the left and right sides of the stopper portion 12, this is not limiting. For example, the heating wire 31 may be wound two turns around one joint socket portion 21 with the stopper portion 12 in between, and the heating wire 32 may be wound three turns around the other joint socket portion 22.

[0056] (Stopper heating part 15) The stopper heating portion 15 is provided in the stopper portion 12. The stopper heating portion 15 has a heating wire 33. The 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 heating wire 33 is wound around the stopper portion 12, for example, four times. In the stopper heating portion 15 of this embodiment, adjacent heating wires 33 are all in contact with each other, but gaps may be provided.

[0057] The 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.

[0058] The heating wire 33 has a conductive wire 33a, an insulating coating 33b, and a coating resin 33c, as shown in Fig. 3. 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.

[0059] The insulating film 33b is provided so as to cover the periphery of the conductor 33a. The melting point of the insulating film 33b is 230° C. or higher. In this embodiment, it is preferable that the insulating film 33b is 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 film 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 heating wire 33 does not need to have the insulating film 33b. The coating resin 33c is provided so as to cover the periphery of the insulating film 33b. The coating resin 33c is formed of a thermoplastic resin. The same resin as the thermoplastic resin used in the main body 11 may be used for the coating resin 33c. As the thermoplastic resin, a polyolefin such as polyethylene having a melting point of less than 230° C. may be used. As the thermoplastic resin, PE (polyethylene) having a small amount of elution may be used. As the thermoplastic resin, HDPE (high density polyethylene resin) having a melting point of about 130° C. and a small amount of elution may be used.

[0060] In this embodiment, in the stopper heating portion 15, one heating wire 33 is wound four times so as to contact the adjacent wires, but this is not limited to this and may be three or fewer turns or five or more turns. Also, instead of being limited to one wire, two or more heating wires 33 may be wound to form the stopper heating portion 15. The heating wire 33 may be wound so that all or part of it does not contact the adjacent wires.

[0061] (Connector mounting part 16) As shown in FIG. 3, the connector mounting portion 16 has two pins 41b and 41c. The two pins 41b and 41c are provided so as to protrude radially outward from the outer surface 11d of the main body portion 11. As shown in FIG. 3, one of the two pins 41b and 41c, the pin 41b, is disposed near the end 11b of the main body portion 11, and the other pin 41c is disposed near the end 11c. Although not shown, the two pins 41b and 41c are connected to the heating wires 31 and 32 of the socket heating portions 13 and 14 and the heating wire 33 of the stopper heating portion 15. The pin 41b, the heating wire 31, the heating wire 32, the heating wire 33, and the pin 41c are connected in this order. In this embodiment, the heating wire 31, the heating wire 32, and the heating wire 33 are a single heating wire. This single heating wire extends from pin 41b to socket heating portion 13, forms socket heating portion 13, stopper heating portion 15 and socket heating portion 14 in that order, and then extends to pin 41c. When connectors of fusion device 4 are attached to pins 41b and 41c and electricity is applied, heating wires 31, 32 and 33 generate heat.

[0062] (Jig 5) When the resin pipe 2 and the resin pipe 3 are fusion-jointed using the electric fusion joint 1, a jig 5 for supporting the electric fusion joint 1, the resin pipe 2, and the resin pipe 3 is used.

[0063] The jig 5 will be described below. The resin pipe 2, the electric fusion joint 1, and the resin pipe 3 are arranged in the jig 5. Fig. 5 is a diagram showing the jig 5. Fig. 6 is a schematic plan view showing the jig 5. Fig. 7 is a diagram showing the state in which the resin pipe 2, the electric fusion joint 1, and the resin pipe 3 are attached to the jig 5.

[0064] The jig 5 includes a first clamp portion 210, a second clamp portion 220, a shaft portion 230, a pressing portion 240, and a base 250.

[0065] (Pedestal 250) The base 250 is a plate-shaped member. The base 250 supports the first clamp portion 210, the second clamp portion 220, and the shaft portion 230, which are arranged on the upper surface side of the base 250. In addition, the base 250 supports the pressing portion 240.

[0066] (First clamp portion 210) The first clamp portion 210 clamps and fixes the resin pipe 2. The first clamp portion 210 has a lower clamp portion 211, an upper clamp portion 212, a hinge portion 213, a fastening portion 214, and a bearing portion 215. The lower clamp portion 211 is a member having a semicircular recess 211a formed on its upper surface. In this embodiment, the lower clamp portion 211 is a roughly rectangular parallelepiped member having a semicircular recess formed on its upper surface.

[0067] The bearing portion 215 is provided in the lower clamp portion 211. The bearing portion 215 is inserted into a through hole formed in the lower clamp portion 211. The bearing portion 215 is disposed below the recessed portion 211a. A shaft portion 230, which will be described later, is inserted into the inside of the bearing portion 215. The axial direction of the bearing portion 215 is disposed parallel to the central axis of the recessed portion 211a. This allows the first clamp portion 210 to move along the shaft portion 230. In a state in which the resin tube 2, the resin tube 3, and the electric fusion joint 1 are disposed in the jig 5, the axial direction of the bearing portion 215 is parallel to the axial direction A.

[0068] The upper clamp portion 212 is a member having a semicircular recess 212a formed therein. In this embodiment, the upper clamp portion 212 is a roughly rectangular parallelepiped member having the semicircular recess 212a formed on a predetermined surface thereof.

[0069] The upper clamp part 212 and the lower clamp part 211 can clamp the outer periphery of the resin pipe 2 with the recesses 212a and 211a formed therein. When the resin pipe 2 is clamped, the central axes of the recesses 212a and 211a roughly coincide. Furthermore, when the resin pipe 2 is clamped, this central axis coincides with the axial direction A described above.

[0070] The hinge portion 213 rotatably connects the ends of the lower clamp portion 211 and the upper clamp portion 212. The upper clamp portion 212 is configured to be rotatable relative to the lower clamp portion 211 around the hinge portion 213. The upper clamp portion 212 is attached to the lower clamp portion 211 via the hinge portion 213 such that, when the upper clamp portion 212 rotates around the hinge portion 213, its recess 212a faces the recess 211a of the lower clamp portion 211.

[0071] With the lower clamp part 211 and the upper clamp part 212 spaced apart about the hinge part 213, the resin pipe 2 is placed along the recess 211a of the lower clamp part 211. After that, the upper clamp part 212 rotates about the hinge part 213, and the resin pipe 2 is placed so as to fit into the recess 212a.

[0072] The fastening portion 214 is a so-called snap lock. The fastening portion 214 has a lock body 214a and a protrusion 214b. The fastening portion 214 is provided on the opposite side of the hinge portion 213 across the recesses 211a, 212a of the lower clamp portion 211 and the upper clamp portion 212. The lock body 214a is disposed on the side of the lower clamp portion 211, and the protrusion 214b is disposed on the side of the upper clamp portion 212. The lock body 214a has a lever 214c and an annular portion 214d. In a state where the upper clamp portion 212 is rotated to the upper side of the lower clamp portion 211, the annular portion 214d is hooked onto the protrusion 214b and the lever 214c is tilted downward, so that the upper clamp portion 212 can be fastened to the lower clamp portion 211 in a closed state.

[0073] (Second clamp portion 220) The second clamp part 220 clamps and fixes the resin pipe 3. The second clamp part 220 fixes the resin pipe 3 so that the central axis of the resin pipe 3 coincides with the central axis of the resin pipe 2.

[0074] The second clamp portion 220 has a lower clamp portion 221, an upper clamp portion 222, a hinge portion 223, and a fastening portion 224. The lower clamp portion 221 is a member having a semicircular recess 221a formed on its upper surface. In this embodiment, the lower clamp portion 221 is a roughly rectangular parallelepiped member having a semicircular recess formed on its upper surface. The lower clamp portion 211 is fixed to the base 250 via a bracket 270.

[0075] The upper clamping portion 222 is a member in which a semicircular recess 222a is formed. In the present embodiment, the upper clamping portion 222 is a roughly rectangular parallelepiped member in which the semicircular recess 222a is formed on a predetermined surface.

[0076] The upper clamp part 222 and the lower clamp part 221 can clamp the outer periphery of the resin pipe 3 with the recesses 222a and 221a formed therein. When the resin pipe 3 is clamped, the central axes of the recesses 222a and 221a roughly coincide. Furthermore, when the resin pipe 3 is clamped, this central axis coincides with the axial direction A described above.

[0077] The hinge portion 223 rotatably connects the ends of the lower clamp portion 221 and the upper clamp portion 222. The upper clamp portion 222 is configured to be rotatable relative to the lower clamp portion 221 around the hinge portion 223. The upper clamp portion 222 is attached to the lower clamp portion 221 via the hinge portion 223 such that, when the upper clamp portion 222 rotates around the hinge portion 223, its recess 222a faces the recess 221a of the lower clamp portion 221.

[0078] With the lower clamp part 221 and the upper clamp part 222 spaced apart about the hinge part 223, the resin pipe 3 is placed along the recess 221a of the lower clamp part 221. After that, the upper clamp part 222 rotates about the hinge part 223, and the resin pipe 3 is placed so as to fit into the recess 222a.

[0079] The fastening portion 224 is a so-called snap lock. The fastening portion 224 has a lock body 224a and a protrusion 224b. The fastening portion 224 is provided on the opposite side of the hinge portion 223 across the recesses 221a, 222a of the lower clamp portion 221 and the upper clamp portion 222. The lock body 224a is disposed on the side of the lower clamp portion 221, and the protrusion 224b is disposed on the side of the upper clamp portion 222. The lock body 224a has a lever 224c and an annular portion 224d. In a state where the upper clamp portion 222 is rotated to the upper side of the lower clamp portion 221, the annular portion 224d is hooked onto the protrusion 224b and the lever 224c is tilted downward, so that the upper clamp portion 222 can be fastened to the lower clamp portion 221 in a closed state.

[0080] With the resin pipe 2 and the resin pipe 3 inserted into the electric fusion joint 1, the resin pipe 2 can be clamped with the first clamp portion 210 and the resin pipe 3 can be clamped with the second clamp portion 220, thereby placing the resin pipe 2, the resin pipe 3 and the electric fusion joint 1 in the jig 5.

[0081] (Shaft portion 230) The shaft portion 230 is supported by the base 250. The shaft portion 230 is arranged parallel to the central axes of the recesses 211a and 212a of the first clamp portion 210. The shaft portion 230 is arranged parallel to the central axes of the recesses 221a and 222a of the second clamp portion 220. The shaft portion 230 is also arranged parallel to the central axes of the resin pipe 2 fixed to the first clamp portion 210 and the resin pipe 3 fixed to the second clamp portion 220. The shaft portion 230 is arranged along the axial direction A described above.

[0082] The shaft portion 230 extends from the second clamp portion 220 toward the first clamp portion 210. The first clamp portion 210 is attached to the shaft portion 230 so as to be movable along the shaft portion 230. The shaft portion 230 is disposed from the lower clamp portion 221 to the lower clamp portion 211. A bearing portion 215 is disposed below the recessed portion 211a of the lower clamp portion 211 of the first clamp portion 210, and the shaft portion 230 is inserted into the bearing portion 215.

[0083] (Pressing portion 240) The pressing portion 240 presses the first clamp portion 210 toward the second clamp portion 220 along the shaft portion 230. The pressing portion 240 has, for example, an electric cylinder 241 and a connecting portion 242, as shown in FIG.

[0084] 6, the electric cylinder 241 is disposed on the side of the base 250. The electric cylinder 241 has a motor (not shown), a rod 243, and a cylinder 244. The rod 243 is disposed parallel to the axial direction A. The rod 243 is movable relative to the cylinder 244 in a direction parallel to the axial direction A by driving the motor.

[0085] The connecting portion 242 connects the rod 243 and the lower clamp portion 211. The connecting portion 242 is a substantially plate-shaped member. The connecting portion 242 is disposed in a direction (width direction) perpendicular to the axial direction A in a plan view. One end 242a of the connecting portion 242 in the width direction is fixed to the rod 243. The other end 242b of the connecting portion 242 in the width direction is passed through the shaft portion 230. The end 242b is fixed to the lower clamp portion 211.

[0086] When the rod 243 moves toward the cylinder 244, the first clamp portion 210 including the lower clamp portion 211 moves along the shaft portion 230 toward the second clamp portion 220 (in the A1 direction).

[0087] As shown in Figure 7, when the plastic pipe 2, the plastic pipe 3, and the electric fusion joint 1 are placed in the jig 5, a load is applied to the first clamp portion 210 by the pressing portion 240, so that the end face 2a of the plastic pipe 2 and the end face 3a of the plastic pipe 3 are pressed against the stopper portion 12.

[0088] (fusion device 4) Next, the fusion device 4 that applies electricity to the electric fusion joint 1 will be described.

[0089] As shown in FIG. 1, the fusion device 4 has a pair of connectors 51b, 51c and a main body 52. ​​The pair of connectors 51b, 51c are attached to the pins 41b, 41c of the connector attachment portion 16 of the electric fusion joint 1. The main body 52 has an operation unit 53, an input unit 54, and a control unit 55. The operation unit 53 is operated by an operator. The operation unit 53 includes, for example, a start button for starting energization. The input unit 54 inputs information about the electric fusion joint 1. The input unit 54 is shown as, for example, a barcode reader that reads a barcode attached to the electric fusion joint 1, but is not limited to this, and may be a touch panel that the operator manually inputs. There are multiple types of electric fusion joints 1 that differ in outer diameter, inner diameter, thickness, or material. The fusion device 4 identifies the type of electric fusion joint 1 by reading information about the electric fusion joint 1 via the input unit 54, and controls energization according to the type.

[0090] The control unit 55 controls the power supplied to the electrofusion joint 1. The control unit 55 includes a processor and a storage device. The processor is, for example, a CPU (Central Processing Unit). Alternatively, the processor may be a processor different from the CPU. The processor executes processing for controlling energization according to a program. The storage device includes a nonvolatile memory such as a ROM (Read Only Memory) and a volatile memory such as a RAM (Random Access Memory). The storage device may include an auxiliary storage device such as a hard disk or an SSD (Solid State Drive). The storage device is an example of a non-transitory computer-readable recording medium. The storage device stores programs and data for controlling energization. The storage device stores an energization program for each type of electrofusion joint 1.

[0091] Fig. 8(a) is a graph showing the relationship between applied voltage and time. Fig. 8(b) is a diagram showing the temperature change when a voltage is applied as shown in Fig. 8(a). The temperature is the temperature at position P1 in Fig. 3. Position P1 is a position on the peripheral surface 12C of the stopper portion 12. Position P1 is a position around the heating wire 33.

[0092] As shown in FIG. 8(a), the control unit 55 applies a first predetermined voltage V1 to the electric fusion joint 1 from time t0 when the current supply is started to time t1 to time t1, thereby performing preheating control (an example of first heating control). Next, the control unit 55 switches the voltage to be applied from V1 to V2 at time t1, and applies a second predetermined voltage V2 to the electric fusion joint 1 from time t1 to time t2, thereby performing main heating control (an example of second heating control). The second predetermined voltage V2 is set to a voltage higher than the first predetermined voltage V1. Next, the control unit 55 applies a third predetermined voltage V3 lower than the second predetermined voltage V2 to the electric fusion joint 1 to keep it warm. Next, the control unit 55 turns off the voltage at time t3, maintains the off state until time t4, performs cooling, and ends the control of the current supply. The control unit 55 can notify the user of the end of the control of the current supply by a buzzer, a liquid crystal display, or the like.

[0093] Preheating is performed by applying a first predetermined voltage V1 for a predetermined time D1 (from time t0 to time t1), and the temperature of the resin around the heating wires 31-33 (for example, at position P1 shown in FIG. 3) rises to temperature T1. This reduces the elastic modulus of the resin around the heating wires 31-33, making it possible to suppress the occurrence of kinking due to the subsequent main heating. Temperature T1 is set to a temperature that results in an elastic modulus that does not cause kinking due to main heating. Temperature T1 can be set, for example, to 70 degrees or higher and 130 degrees or lower.

[0094] By applying the second predetermined voltage V2 for a predetermined time D2 (from time t1 to time t2), main heating is performed, and the temperature of the resin around the heating wires 31 to 33 rises to temperature T2, which becomes a temperature suitable for fusing between the electric fusion joint 1 and the resin pipes 2 and 3, and fusing is performed. The temperature T2 can be set to a temperature suitable for fusing. The temperature T2 can be set to, for example, 160 degrees or more and 250 degrees or less.

[0095] By applying the third predetermined voltage V3 for a predetermined time D3 (from time t2 to time t3), the temperature of the resin surrounding the heating wires 31 to 33 can be kept within a temperature range suitable for fusion (the range of the above-mentioned temperature T2).

[0096] The voltage-off state is maintained for a predetermined time D4 (from time t3 to time t4), thereby cooling the fused electric fusion joint 1 and the resin pipes 2 and 3. At time t4, the temperature of the resin around the heating wires 31 to 33 reaches T3, and the cooling ends. The temperature T3 can be set to 100°C or higher and 120°C or lower.

[0097] The first predetermined voltage V1, the predetermined time D1, the second predetermined voltage V2, the predetermined time D2, the predetermined time D3, and the predetermined time D4 that make the temperatures at the position P1 of the thermoplastic resin T1, T2, and T3 are determined in advance by experiments and stored in a storage device for each type of electric fusion joint 1. Since each data is stored in the storage device in this way, appropriate fusion can be performed without providing, for example, a temperature sensor.

[0098] <Fusing method> Next, a fusion method according to an embodiment of the present disclosure will be described with reference to Fig. 9, which is a flow diagram for explaining the fusion method according to the present embodiment.

[0099] First, in step S1, 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. FIG. 4 shows the state in which the resin pipe 2 and the resin pipe 3 are inserted into the electric fusion joint 1. When inserting 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 outer surface in the vicinity of the end face 3a of the resin pipe 3 may be scraped. Step S1 corresponds to an example of an insertion process.

[0100] Next, in step S2, as shown in FIG. 7, the resin pipe 2 is clamped and fixed by the first clamp portion 210, and the resin pipe 3 is clamped and fixed by the second clamp portion 220, and the resin pipe 2, the electric fusion joint 1 and the resin pipe 3 are placed in the jig 5.

[0101] Next, in step S3, the connectors 51b and 51c of the fusion device 4 are attached to the two pins 41b and 41c of the connector attachment portion 16.

[0102] Next, in step S 4 , the operator uses the input unit 54 to cause the control unit 55 to obtain information about the electric fusion joint 1 .

[0103] Next, in step S5, the operator operates the operation unit 53, whereby the control unit 55 executes preheating control. In the preheating control, the control unit 55 applies a first predetermined voltage V1, which is set in advance according to the type of the electric fusion joint 1, to the electric fusion joint 1 for a predetermined time D1. By applying the first predetermined voltage V1 for the predetermined time D1, the temperature of the resin surrounding the heating wires 31-33 increases and the elastic modulus decreases, making it possible to suppress the occurrence of kinking due to the subsequent main heating. Step S5 corresponds to an example of a first heating step.

[0104] Next, in step S6, the control unit 55 executes the main heating control. In the main heating control, the control unit 55 switches the applied voltage from the first predetermined voltage V1 to the second predetermined voltage V2, and applies the second predetermined voltage V2 for a predetermined time D2. This increases the temperature of the resin around the heating wires 31-33, and the temperature becomes suitable for fusion. Step S6 corresponds to an example of the second heating step.

[0105] Next, in step S7, the control unit 55 switches the applied voltage from the second predetermined voltage V2 to the third predetermined voltage V3, and applies the third predetermined voltage V3 for a predetermined time D3. This keeps the temperature of the resin around the heating wires 31-33 in a temperature range suitable for fusion, and provides the amount of heat required for fusion to the thermoplastic resin. Step S7 corresponds to an example of a heat-keeping process.

[0106] In steps S5 to S7, the electric cylinder 241 is driven to move the rod 243 toward the A1 side, whereby a load is applied to the first clamp section 210 toward the second clamp section 220. By applying a load from the first clamp section 210 toward the second clamp section 220, the end face 2a of the resin pipe 2 is pressed against the first side face 12a of the stopper section 12, and the end face 3a of the resin pipe 3 is pressed against the second side face 12b of the stopper section 12. The amount of heat required for fusion is applied to the electric fusion joint 1, and the resin pipes 2 and 3 are pressed against the electric fusion joint 1, thereby performing fusion between the electric fusion joint 1 and the resin pipes 2 and 3. Steps S5 to S7 correspond to an example of a pressurizing step.

[0107] Next, in step S8, cooling is performed for a predetermined time D4 of the molten resin pipe 2, the electric fusion joint 1, and the resin pipe 3. Note that the pressing may be continued until the cooling in step S8 is completed, or may be stopped together with the stopping of the heating in step S7.

[0108] Here, the ratio of the total heat amount by heating in step S5 to the total heat amount by combining steps S5 and S6 is 0.14 or more and 0.70 or less, and the average value of Joule heat generated per second when only the time during which heating is substantially performed in step S5 is calculated is less than 184 W. The average value of Joule heat generated per second when only the time during which heating is substantially performed is preferably 160 W or less. The time during which heating is substantially performed means, for example, the time during which a voltage is applied to the heating wires 31 to 33. In this embodiment, heating is performed continuously for the predetermined time D1, so the time during which heating is substantially performed corresponds to the predetermined time D1.

[0109] In step S5, the total amount of heat given to the thermoplastic resin around the heat generating portions 13 to 15 of the electric fusion joint 1 is 16 KJ or more.

[0110] In step S5, the temperature of the thermoplastic resin around the heat generating parts 13-15 of the electric fusion joint 1 is equal to or lower than the melting point of the thermoplastic resin. The temperature T1 shown in Fig. 8(b) described above is set to equal to or lower than the melting point of the thermoplastic resin of the electric fusion joint 1 and the resin pipes 2 and 3. Furthermore, when polyethylene is used as the thermoplastic resin of the electric fusion joint 1 and the resin pipes 2 and 3, the temperature T1 is set to equal to or higher than 70°C and equal to or lower than 130°C.

[0111] In step S6, the temperature of the thermoplastic resin around the heat generating portions 13 to 15 of the electric fusion joint 1 is set to be equal to or higher than the melting point of the thermoplastic resin and lower than the thermal decomposition starting temperature of the thermoplastic resin.

[0112] The voltage applied to the heating wires 31 to 33 in step S5 is set to 71.4% or less of the voltage applied to the heating wires 31 to 33 in step S6.

[0113] FIG. 10 is a cross-sectional view showing a 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 R. The bead R is formed by melting the thermoplastic resin of the coating resin 33c of the 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. When the resin is in a molten state, the pressing portion 240 presses the plastic pipes 2 and 3, crushing the stopper portion 12, and the plastic pipes 2 and 3 move toward the inside of the electric fusion joint 1, and the bead R is formed according to the amount of movement. In addition, the outer surface 2d of the plastic pipe 2 and the resin around the heating wire 31 of the receiving port heating portion 13 are fused, and the outer surface 3d of the plastic pipe 3 and the resin around the heating wire 32 of the receiving port heating portion 14 are fused.

[0114] (Ultrapure water use of piping structure 110) The piping structure 110 of the first embodiment differs from that of the second embodiment described later in that no gap is formed between the resin pipe 2 and the resin pipe 3, and therefore liquid retention is suppressed. Therefore, 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] When the electric fusion joint 1 is used for ultrapure water applications, the bead R 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 R and the thermoplastic resin that forms the stopper portion 12.

[0119] (Embodiment 2) Next, an electric fusion joint 300 according to a second embodiment of the present disclosure will be described. Fig. 11 is a cross-sectional view showing the electric fusion joint 300 according to the second embodiment.

[0120] Unlike the electric fusion joint 1 of the first embodiment, the electric fusion joint 300 of the second embodiment is not provided with a stopper portion 12. Also, the number of turns of the heating wires 31, 32 in the socket heating portion is different from that of the first embodiment.

[0121] The electric fusion joint 300 has a main body 311, socket heating portions 313 and 314, and a connector attachment portion 16. The main body 311 is cylindrical and has a joint socket portion 321, a joint socket portion 322, and a connecting portion 323. The main body 311 contains a thermoplastic resin. There are no particular limitations on the thermoplastic resin used in the main body 311, but a melting point of less than 230° C. is preferred. Examples of thermoplastic resins include polyolefins such as polyethylene.

[0122] The joint socket 321 is disposed on one end 311b side of the main body 311. The resin pipe 2 is inserted into the inside of the joint socket 321. The joint socket 322 is cylindrical. The joint socket 322 is disposed on the other end 311c side of the main body 311. The joint socket 322 is cylindrical. The resin pipe 3 is inserted into the inside of the joint socket 322. The connecting portion 323 is connected to the joint socket 321 and the joint socket 322 as shown in FIG. 11, and connects the joint socket 321 and the joint socket 322. The connecting portion 323 is a portion that connects the joint socket 321 and the joint socket 322.

[0123] The joint socket 321 has a protruding portion 324 protruding from the inner surface 311a of the main body 311 toward the inside in the radial direction B. The protruding portion 324 is annular. The protruding portion 324 is formed over the entire circumference in the circumferential direction C. The protruding portion 324 forms a stepped shape on the inner circumferential surface of the joint socket 21. The protruding portion 324 has a first side surface 324a, a second side surface 324b, and a circumferential surface 324c. The first side surface 324a is formed perpendicular to the axial direction A from the inner surface 311a of the main body 311 toward the inside in the radial direction B. The second side surface 324b is formed perpendicular to the axial direction A from the inner surface 311a of the main body 311 toward the inside in the radial direction B. The first side surface 324a is disposed closer to the end 311b than the second side surface 324b. The peripheral surface 324c connects an inner end of the first side surface 324a in the radial direction B to an inner end of the second side surface 324b in the radial direction B. The peripheral surface 324c is formed parallel to the axial direction A.

[0124] The joint socket 322 has a protruding portion 325 protruding from the inner surface 311a of the main body 311 toward the inside in the radial direction B. The protruding portion 325 is annular. The protruding portion 325 is formed over the entire circumference in the circumferential direction C. The protruding portion 325 forms a stepped shape on the inner circumferential surface of the joint socket 22. The protruding portion 325 has a first side surface 325a, a second side surface 325b, and a circumferential surface 325c. The first side surface 325a is formed perpendicular to the axial direction A from the inner surface 311a of the main body 311 toward the inside in the radial direction B. The second side surface 325b is formed perpendicular to the axial direction A from the inner surface 311a of the main body 311 toward the inside in the radial direction B. The first side surface 325a is disposed closer to the end 311c than the second side surface 325b. The peripheral surface 325c connects an inner end of the first side surface 325a in the radial direction B to an inner end of the second side surface 325b in the radial direction B. The peripheral surface 325c is formed parallel to the axial direction A.

[0125] The socket heating part 313 is disposed in the protruding part 324 of the joint socket part 321 as shown in FIG. 11. The socket heating part 313 has a heating wire 31 embedded in the protruding part 324 as shown in FIG. 11. The heating wire 31 is disposed so as to be wound eight times in the circumferential direction C along the circumferential surface 324c of the protruding part 324. The heating wire 31 is disposed in the vicinity of the circumferential surface 324c. The heating wire 31 may be embedded in the joint socket part 321 so as to be partially exposed from the circumferential surface 324c to the flow passage 300f side, or may be completely embedded. The protruding part 324 is formed to a length such that the heating wire 31 is wound eight times in the axial direction A.

[0126] The socket heating part 314 is disposed in the protruding part 325 of the joint socket part 322. The socket heating part 314 has a heating wire 32 embedded in the protruding part 325 as shown in FIG. 11. The heating wire 32 is disposed so as to be wound eight times in the circumferential direction C along the circumferential surface 325c of the protruding part 325. The heating wire 32 is disposed in the vicinity of the circumferential surface 325c. The heating wire 32 may be embedded in the joint socket part 321 so as to be partially exposed from the circumferential surface 325c to the flow passage 300f side, or may be completely embedded. The protruding part 325 is formed to a length such that the heating wire 32 is wound eight times in the axial direction A. The heating wires 31 and 32 have the same configuration as in the first embodiment.

[0127] The receptacle heating part 313 and the receptacle heating part 314 are formed in line symmetry with respect to the center of the main body part 311 in the axial direction A. The heating wire 31 of the receptacle heating part 313 and the heating wire 32 of the receptacle heating part 314 are connected. They are connected in the order of pin 41b, heating wire 31, heating wire 32, and pin 41c. In this embodiment, the heating wires 31 and 32 are a single heating wire. This single heating wire extends from pin 41b to the receptacle heating part 313, forms the receptacle heating part 313 and the receptacle heating part 314 in that order, and extends to pin 41c. When connectors of an electric fusion device are attached to the pins 41b and 41c and electricity is applied, the heating wires 31 and 32 generate heat.

[0128] 12 is a diagram showing a state in which a resin tube 2 and a resin tube 3 are inserted into an electric fusion joint 300 of the second embodiment. The resin tube 2 is inserted into the joint socket portion 321 to the inner side, beyond the socket heat generating portion 313. The resin tube 3 is inserted into the joint socket portion 322 to the inner side, beyond the socket heat generating portion 314. Fixed in this state, the connectors 51b, 51c of the fusion device 4 are attached to the pins 41b, 41c of the connector attachment portion 16, and electricity is passed through. The method of controlling power in the second embodiment is the same as that in the first embodiment.

[0129] In the second embodiment, the positions of the resin pipes 2 and 3 relative to the electric fusion joint 300 may be fixed using the jig 5 of the first embodiment, but since it is not necessary to press the resin pipes 2 and 3 against the stopper portion, the jig 5 may not be provided with the pressing portion 240. That is, in the second embodiment, the resin pipes 2 and 3 do not need to be pressed against the electric fusion joint 300 in steps S5, S6, and S7. In the second embodiment, by applying electricity, the outer surface 2d of the resin pipe 2 and the resin around the heating wire 31 of the socket heating portion 313 are fused, and the outer surface 3d of the resin pipe 3 and the resin around the heating wire 32 of the socket heating portion 314 are fused. In this embodiment, the first predetermined voltage V1, the predetermined time D1, the second predetermined voltage V2, and the predetermined time D2 are set so that the resin temperature at the position P2 is kept within a range of temperatures T1°C or higher and T2°C or lower. The position P2 is a position on the peripheral surface 324c of the protruding portion 324. Position P2 is a position around the heating wire 31.

[0130] <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.

[0131] (A) In the above-mentioned embodiments 1 and 2, as shown in FIG. 8(b), the temperature of the heat-transferable resin is constant between time t2 and time t3, but as long as the amount of heat required for fusion can be supplied, the temperature may increase or decrease within a temperature range suitable for fusion.

[0132] (B) In the above-mentioned first and second embodiments, as shown in Fig. 8(a), the voltage is applied continuously for a predetermined time D1, but there may be a period during which the application of the voltage is stopped, or the voltage may be applied periodically. In addition, a constant first predetermined voltage V1 is applied for the predetermined time D1, but the voltage may be increased or decreased as long as the temperature can be raised to a temperature T1 at which no kinking occurs by main heating. It is sufficient that the average value of Joule heat generated per second when only the time during which the voltage is applied is calculated is less than 184 W.

[0133] (C) In the above first and second embodiments, the voltage is changed, but this is not limiting and the current may be changed. In short, it is only necessary that the power supplied to the electric fusion joints 1, 300 can be changed.

[0134] (D) In the above embodiment, when viewed along the axial direction A, the outer diameter of the stopper portion 12 is circular, but this is not limited to a circle and may be polygonal.

[0135] (E) In the above embodiment, socket heating portion 13 and socket heating portion 14 are provided symmetrically on the left and right sides of stopper portion 12, but this is not limiting.

[0136] (F) In the above embodiment, all of the flow paths of the electric fusion joint 1 are formed straight, but the flow paths may be curved, that is, an elbow joint.

[0137] (G) In the above-mentioned embodiment 1, the same heating wires 31, 32, 33 are used for the socket heating parts 13, 14 and the stopper heating part 15, so all of the heating wires 31, 32, 33 are provided with an insulating coating, but this is not limited to this. However, it is preferable that at least the heating wire 33 is provided with an insulating coating. This is because the heating wires 33 are easily brought into contact with each other when pressurized by the resin pipes 2 and 3. The heating wires 31, 32 in embodiment 2 do not need to be provided with an insulating coating either.

[0138] (H) In the electric fusion joint 1, the heating wire 33 is wound four times in the socket heating part 13 so as to be adjacent to each other in the axial direction, the heating wire 31 is wound two times in the stopper heating part 15 so as to be adjacent to each other in the axial direction, and the heating wire 32 is wound two times in the socket heating part 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. Also, in the electric fusion joint 300, the heating wire 31 is wound eight times in the heating part 313 so as to be adjacent to each other in the axial direction, and the heating wire 32 is wound eight times in the heating part 314 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.

[0139] (Example) Next, the fusion method of this embodiment will be described in detail using examples.

[0140] In the examples and comparative examples, the electric fusion joint 1 and the resin pipes 2 and 3 described in the first embodiment were fused. The material of the resin pipes 2 and 3 and the electric fusion joint 1 was HDPE (High-density polyethylene). In the examples 1 to 7 and the comparative examples 1 to 4, as shown in the following (Table 1), the resin pipes 2 and 3 with a diameter of 200A were used, and the electric fusion joint 1 with 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 coincides with the outer diameter of the resin pipe of 200A. In the example 8, as shown in the following (Table 1), the resin pipes 2 and 3 with a diameter of 150A were used, and the electric fusion joint 1 with a size corresponding to the diameter of 150A was used. In the example 9 and the comparative examples 5 and 6, as shown in the following (Table 1), the resin pipes 2 and 3 with a diameter of 75A were used, and the electric fusion joint 1 with a size corresponding to the diameter of 75A was used. Table 1 shows values ​​of wall thicknesses d1, d2 and wall thickness d3 of the resin pipe for the electric fusion joints used in Examples 1 to 9 and Comparative Examples 1 to 5. d1 (see FIG. 3) indicates the wall thickness of the heat generating portions 13, 14 of the joint socket portions 21, 22. d2 (see FIG. 3) indicates the wall thickness of the stopper portion 12 and the connecting portion 23. d3 (see FIG. 4) indicates the wall thickness of the resin pipes 2, 3. Note that in Comparative Examples 1 and 5, only main heating was performed, and in Comparative Examples 2, 3, and 6, only preheating was performed.

[0141] The electric fusion joint 1, the resin pipe 2, and the resin pipe 3 were fused under the conditions of Examples 1 to 9 and Comparative Examples 1 to 6, and it was observed whether or not kinking occurred. The occurrence of kinking is indicated by "x", and the absence of kinking is indicated by "o". FIG. 13 is a cross-sectional view showing a state in which kinking has occurred. FIG. 13 is a cross-sectional view passing through the stopper portion 12 and perpendicular to the axial direction A. As shown in FIG. 13, when kinking occurs, the heating wire 33 protrudes to the inside of the electric fusion joint 1.

[0142] (Table 1) TIFF2025054190000002.tif25578As shown in Table 1, it can be seen that the occurrence of kinks can be suppressed if the ratio of the total heat amount from preheating to the total heat amount from preheating and main heating combined is 0.14 or more and 0.70 or less, and the average value of Joule heat generated per second in preheating is less than 184 W. It can also be seen that it is preferable for the average value of Joule heat generated per second in preheating to be 160 W or less. It can also be seen that it is more preferable for the ratio of the total heat amount from preheating to the total heat amount from preheating and main heating combined to be 0.63 or less.

[0143] It is also found that the total heat quantity in preheating is preferably 16 KJ or more, and the voltage in preheating is preferably 71.4% or less of the voltage in main heating. [Explanation of symbols]

[0144] 1: Electric fusion joint 2: Plastic pipe 3: Plastic pipe 13: Heat generating part 14: Heat generating part 21: Joint socket 22: Joint socket

Claims

1. a fitting socket into which a tube containing a thermoplastic resin is inserted; A heat generating portion having a heating wire, and an electric fusion joint including a thermoplastic resin; A fusion method for fusing the tube, comprising the steps of: an insertion step of inserting the tube into the joint socket of the electric fusion joint; a first heating step of energizing the heating wire of the heat generating portion; A second heating step of passing electricity through the heating wire of the heat generating portion after the first heating step, The ratio of the total heat amount of the first heating step to the total heat amount of the first heating step and the second heating step combined is 0.14 or more and 0.70 or less, and The average value of Joule heat generated per second when only the time during which heating is substantially performed in the first heating step is calculated is less than 184 W. Fusion method.

2. In the first heating step, the total amount of heat applied to the thermoplastic resin around the heat generating portion of the electric fusion joint is 16 KJ or more. The fusing method according to claim 1.

3. In the first heating step, the temperature of the thermoplastic resin around the heat generating portion of the electric fusion joint is equal to or lower than the melting point of the thermoplastic resin. The fusion method according to claim 1 or 2.

4. In the first heating step, the temperature of the thermoplastic resin around the heat generating portion of the electric fusion joint is 70 degrees or more and 130 degrees or less. The fusing method according to claim 3.

5. In the second heating step, the temperature of the thermoplastic resin around the heat generating portion of the electric fusion joint is equal to or higher than the temperature of the thermoplastic resin around the heat generating portion of the electric fusion joint in the first heating step, and is lower than the thermal decomposition starting temperature of the thermoplastic resin contained in the electric fusion joint. The fusing method according to claim 1.

6. The method further includes a heat retention step of maintaining the temperature of the thermoplastic resin around the heat generating portion within a predetermined temperature range after the second heating step. The fusing method according to claim 1.

7. The voltage applied to the heating wire in the first heating step is 71.4% or less of the voltage applied to the heating wire in the second heating step. The fusing method according to claim 1.

8. The electric fusion joint is a body portion including the fitting socket portion; a stopper portion provided on an inner surface of the main body portion so as to protrude inward, the stopper portion restricting an insertion position of a pipe end of the pipe when the pipe is inserted into the fitting socket portion, The method further includes a pressurizing step of applying a force to the tube toward the stopper portion. The fusing method according to claim 1.

9. A tube comprising a thermoplastic resin; an electric fusion joint including a thermoplastic resin, the electric fusion joint having a body having a joint socket into which the pipe is inserted, a heating part having a heating wire, and a connector attachment part disposed on an outer surface of the body and connected to the heating wire; a fusion device including a connector attached to the connector attachment portion and a control portion that controls the supply of electricity to the heating wire via the connector attachment portion; Equipped with The control unit executes a first heating control in which current is applied to the heating wire, and a second heating control in which current is applied to the heating wire after the first heating control, A ratio of a total heat amount of the first heating control to a total heat amount of the first heating control and the second heating control combined is 0.14 or more and 0.70 or less, and an average value of Joule heat generated per second when only the time during which heating is substantially performed in the first heating control is calculated is less than 184 W; Fusion system.

10. A fusion device for fusing an electric fusion joint containing thermoplastic resin to a tube containing thermoplastic resin, the electric fusion joint having a main body having a joint socket into which a tube is inserted, a heating unit having an electric heating wire, and a connector attachment unit disposed on an outer surface of the main body and connected to the electric heating wire, a connector attached to the connector attachment portion; A control unit that controls the supply of electricity to the heating wire via the connector attachment portion, The control unit executes a first heating control in which current is applied to the heating wire, and a second heating control in which current is applied to the heating wire after the first heating control, A ratio of a total heat amount of the first heating control to a total heat amount of the first heating control and the second heating control combined is 0.14 or more and 0.70 or less, and an average value of Joule heat generated per second when only the time during which heating is substantially performed in the first heating control is calculated is less than 184 W; Fusion device.

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