Electro-fusion fitting and method of manufacturing the same

Abstract

To surely connect a heating wire and a terminal pin in an electric fusion joint.SOLUTION: An electro-fusion fitting is an electro-fusion fitting including a fusion portion in which a heating wire 300 is inserted into a cutout groove formed in a spiral shape on an inner peripheral surface of a thermoplastic resin pipe into which a resin pipe to be connected is inserted, the electro-fusion fitting including a conductive terminal pin 2500 having a substantially columnar shape for supplying electricity from an external power supply to the heating wire 300, the terminal pin being provided in a through-hole drilled so as to reach the heating wire 300 from an outer peripheral surface of the thermoplastic resin pipe. The lower side (substantially cylindrical part 2530) connected to the heating wire 300 in the terminal pin 2500 has a different shape corresponding to the type of the heating wire 300, and the difference in shape can be visually distinguished from the outer peripheral surface of the thermoplastic resin tube.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an electric fusion joint used for connecting plastic pipes, and more particularly to an electric fusion joint having a structure in which an electric heating wire is inserted into a groove formed on the inner periphery of a thermoplastic resin pipe, and a method for manufacturing the same. [Background technology]

[0002] Electrofusion joints are typically manufactured using injection molding, with an electric heating wire embedded in the inner periphery of a joint body made of a thermoplastic resin such as polyethylene or polybutene. Such electrofusion joints are sometimes called EF (ElectroFusion) joints or EF sockets.

[0003] Such electrofusion joints, particularly those with large diameters, have been provided in which a spiral groove is cut along the inner surface of a tube made of thermoplastic resin, and a heating wire is fitted into this groove. While the manufacturing method for electrofusion joints of this structure is simple, it has been pointed out that there is a manufacturing difficulty in installing the heating wire so that it does not rise up from the groove.

[0004] In view of these problems, the applicant of the present invention has developed an electric fusion joint, which is disclosed in Japanese Patent Laid-Open Publication No. 2023-070444 (Patent Document 1). The electric fusion joint disclosed in Patent Document 1 is an electric fusion joint having a fusion portion in which an electric heating wire is inserted into a notched groove formed in a spiral shape on the inner surface of a thermoplastic resin pipe into which a connecting resin pipe is inserted, and the fusion portion is provided on at least one axial end side of the electric fusion joint so that electricity can be passed through the electric heating wire, and in the fusion portion, a single electric heating wire forms an outward path in which the spiral progresses in an outward direction from the opening side of the electric fusion joint to the opening side on the opposite side of the opening, and a return path in the opposite direction to the outward path, and the fusion portion includes, in both the outward path and the return path, a first area in the axial center of the fusion portion in which the spiral is formed at the same pitch, and a second area other than the center in which the spiral is formed at a pitch that is up to twice the same pitch (paragraphs 0017, 0018, 0039, and 0040 of Patent Document 1).

[0005] The electric fusion joint disclosed in Patent Document 1 has a structure in which an electric heating wire is fitted into a groove formed on the inner periphery of a thermoplastic resin pipe, and has been well received for providing an electric fusion joint that can electrically fuse the mating plastic pipe to the left and right sockets, not to both at the same time, but to one of the sockets at a time (even if both the left and right are electrically fused, it is not necessary that only one of the sockets is electrically fused and the other is not). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-070444 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, many electrofusion joints, including the electrofusion joint disclosed in Patent Document 1, use a terminal pin to supply power from an external power source to the heating wire. The electric fusion joint disclosed in Patent Document 1 includes a substantially cylindrical, electrically conductive terminal pin provided in a through hole drilled from the outer surface of the thermoplastic resin tube to reach the heating wire, for supplying electricity from an external power source to the heating wire, and a conductive connecting cylinder connecting the terminal pin and the heating wire. The terminal pin has a groove on the curved surface of the substantially cylindrical cylinder that corresponds to the diameter of the heating wire and is aligned with the central axis of the substantially cylindrical cylinder. The connecting cylinder is formed by bending a metal piece into a substantially cylindrical shape. The terminal pin, with the heating wire inserted in the groove, is inserted into the substantially cylindrical part of the connecting cylinder, and the heating wire is pressed against the terminal pin (Claim 1, paragraph

[0071] , Figure 12 of Patent Document 1). This securely connects the heating wire to the terminal pin, allowing power to be supplied from an external power source to the heating wire via the terminal pin.

[0008] This connection structure between the heating wire and the terminal pin can potentially cause the following problems. Many electrofusion joints, including the electrofusion joint disclosed in Patent Document 1, require different types of heating wire (specifications, wire diameter, etc.) because the amount of energy required for fusion varies depending on the diameter. Therefore, it is necessary to manufacture terminal pins with different shapes depending on the type of heating wire. This requires the manufacture of terminal pins with different shapes for each type of heating wire (terminal pins with different shapes exist for each type of heating wire to be connected), which raises concerns about misassembly during the manufacturing process of connecting the heating wire to the terminal pin. Furthermore, once the terminal pin is assembled into the electrofusion joint (the terminal pin with the heating wire connected is inserted into the through-hole drilled from the outer surface of the thermoplastic resin pipe so that it reaches the heating wire from the outer surface), it is impossible to visually determine (visually distinguish) the shape of the terminal pin assembled from the outside (outer surface side) of the electrofusion joint after assembly. This makes it difficult to detect misassembly during or after the manufacturing process.

[0009] The present invention was developed in view of the above-mentioned problems, and its object is to provide an electric fusion joint and a method for manufacturing the same, which is an electric fusion joint having a structure in which an electric heating wire is fitted into a groove formed on the inner periphery of a thermoplastic resin pipe, which makes it possible to more reliably connect the terminal pin and the electric heating wire to perform electric fusion, and which makes it possible to visually detect any improper assembly even after the terminal pin has been assembled into the electric fusion joint. [Means for solving the problem]

[0010] In order to achieve the above object, the electrofusion joint according to the present invention employs the following technical means.

[0011] The electric fusion joint of the present invention is an electric fusion joint having a fusion portion in which an electric heating wire is inserted into a notched groove formed in a spiral on the inner surface of a thermoplastic resin pipe into which a connecting resin pipe is inserted, and includes a terminal pin having an approximately cylindrical shape and conductivity, which is provided in a through hole drilled from the outer surface of the thermoplastic resin pipe to reach the electric heating wire, for supplying electricity from an external power source to the electric heating wire, and the lower side of the terminal pin that is connected to the electric heating wire has a different shape corresponding to the type of the electric heating wire, and the difference in shape can be visually distinguished from the outer surface of the thermoplastic resin pipe. Preferably, the lower side of the terminal pin, which is connected to the heating wire, can be configured to have a different shape corresponding to the diameter of the heating wire. More preferably, the lower side of the terminal pin that is connected to the heating wire can be configured to have a different shape by cutting a portion of the curved surface of the approximately cylindrical shape into a flat surface by a thickness corresponding to the type of heating wire.

[0012] More preferably, the difference in shape can be distinguished by the color of the terminal pin. More preferably, the color can be developed by plating the terminal pin or by attaching a pigment thereto.

[0013] More preferably, the electric fusion joint further includes a connecting cylinder having electrical conductivity that connects the terminal pin and the heating wire, and the connecting cylinder is formed by bending a metal piece into an approximately cylindrical shape, and the terminal pin with the heating wire in contact with the flat surface is inserted into the approximately cylindrical part of the connecting cylinder, and the heating wire is pressed against the terminal pin. More preferably, the connecting cylinder can be configured as a crimp terminal or a terminal obtained by processing a crimp terminal. More preferably, the connecting cylinder can be configured to have the same shape regardless of the type of the heating wire.

[0014] More preferably, the remaining thickness cut off by the flat surface on the lower side of the terminal pin is t (mm), the diameter of the heating wire is D (mm), and the inner diameter of the connecting cylinder is d (mm), and the configuration can satisfy 0<((D+t)-d)<0.4.

[0015] Furthermore, a manufacturing method for an electrofusion joint according to another aspect of the present invention is a manufacturing method for any of the electrofusion joints described above, characterized in that it includes a drilling step of drilling a through hole corresponding to the shape of the terminal pin from the outer peripheral surface toward the inner peripheral surface of the electrofusion joint, a selection step of selecting and preparing the terminal pin corresponding to the type of heating wire, and a connection step of connecting the terminal pin and the heating wire within the through hole.

[0016] Preferably, the method may further include a visual confirmation step of visually checking the difference in shape of the terminal pin from the outer surface of the thermoplastic resin pipe after the connecting step, and confirming that the difference is consistent with the heating wire connected to the terminal pin in the connecting step. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide an electric fusion joint having a structure in which an electric heating wire is fitted into a groove formed on the inner periphery of a thermoplastic resin pipe, which makes it possible to more reliably connect the terminal pin and the electric heating wire for electric fusion, and which makes it possible to visually detect any incorrect assembly even after the terminal pin has been assembled into the electric fusion joint, as well as a method for manufacturing the same. [Brief explanation of the drawings]

[0018] [Figure 1] 1A and 1B are a side view and a front view, respectively, of an electrofusion joint 100 according to an embodiment of the present invention, and FIG. 1C is a cross-sectional view taken along arrows 1C-1C in FIG. 1B, and FIG. 1D is a cross-sectional view taken along arrows 1D-1D in FIG. 1C. [Figure 2]2 is a diagram showing the arrangement of the heating wire 300 and the position of the terminal pin 2500 in the fusion portion of the electrofusion joint 100 shown in FIG. [Figure 3] 1. FIG. 4 is a diagram for explaining a terminal pin 2500 (terminal pin 2501) provided in the electrofusion joint 100 shown in FIG. [Figure 4] 4 is a diagram for explaining a terminal pin 2500 (terminal pin 2502) that has a different shape from the terminal pin 2500 (2501) shown in FIG. [Figure 5] 10 is a diagram illustrating a connecting cylinder 2600 that connects a terminal pin 2500 and a heating wire 300 that are provided in the electric fusion joint 100. FIG. [Figure 6] 1A and 1B are diagrams showing the construction procedure for connecting a heating wire 300 to a terminal pin 2500 provided in an electric fusion joint 100 using a connecting cylinder 2600, and FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] An electrofusion joint and a method for manufacturing an electrofusion joint according to an embodiment of the present invention will be described below with reference to Figures 1 to 6. In Figures 1 to 6, the same components are designated by the same reference numerals and have the same functions, so they may not be described repeatedly. Note that for terminal pins whose shapes differ depending on the type of heating wire, terminal pins 2501 and 2502, which have different shapes, will be used as examples, and when describing common structures, they will be described as terminal pin 2500. Furthermore, because the electrofusion joint and its manufacturing method according to the present invention relate to the connection between such terminal pin 2500 and heating wire 300, there may be inconsistencies between the figures showing other electrofusion joints 100.

[0020] Here, the electrofusion joint according to the embodiment of the present invention is primarily an electrofusion joint of medium to large diameter (for example, an inner diameter of 300 mm or more), and has a structure manufactured by a manufacturing method characterized by cutting a spiral groove (the cross section of this groove is, for example, a V-groove because the cutting blade of a dedicated cutter is V-shaped when viewed along the inner circumferential surface) along the inner surface (sometimes referred to as the inner circumferential surface) of a resin pipe (sometimes referred to as a pipe material or a sleeve) made of thermoplastic resin, and simultaneously fitting an electric heating wire into this groove. Furthermore, the electric fusion joint according to the embodiment of the present invention may be a double-supported type in which the electric heating wire is provided independently on the left and right sides, or a single-supported type in which the electric heating wire is provided on only one of the left and right sides, but will be described below as a double-supported type. In other words, the electric fusion joint of this embodiment does not have left and right crossover sections on the central side in the axial direction (the same as the axial direction), but rather has left and right heating wires that are independent and have a total of four terminal pins, two on each side, on the end sides of the electric fusion joint.Since there are no through holes (holes that penetrate the outer and inner surfaces of the sleeve) for locating terminal pins on the central side, it has the characteristic that it does not affect watertightness.

[0021] <Overall structure of electric fusion joint> First, the overall structure of an electrofusion joint 100 according to this embodiment will be described. As shown in Figures 1(A) and 1(B), the electrofusion joint 100 according to this embodiment (having the winding structure shown in Figure 2) has, as an example, a hollow cylindrical shape with an inner diameter of 317 mm, an outer diameter of 400 mm, and an axial length of 300 mm in the case of an electrofusion joint with a nominal diameter of 250 (an electrofusion joint corresponding to an outer diameter of a plastic pipe to be connected of 315 mm). Then, as shown in Figure 2, an electric heating wire 300 is embedded in a spiral shape on the inner peripheral surface of the cylindrical shape.

[0022] That is, this electric fusion joint 100 has a fusion part in which a heating wire 300 is inserted into a notched groove formed in a spiral shape on the inner circumferential surface of a thermoplastic resin pipe (pipe material, sleeve) into which a connecting resin pipe is inserted. This fusion part is provided on at least one (here, both) end sides in the axial direction of the electric fusion joint 100 so that electricity can be applied to the heating wire 300 (via a terminal pin 2500). In this fusion part, a single electric heating wire 300 forms an outward path in which the spiral advances in the outward direction from the opening side of the electric fusion joint 100 to the opening side opposite the opening, and a return path in the opposite direction to the outward path.

[0023] More specifically, as shown in FIG. 1(C), a cross-sectional view taken along arrows 1C-1C in FIG. 1(B), and FIG. 1(D), a cross-sectional view taken along arrows 1D-1D in FIG. 1(C), the electrofusion joint 100 includes a terminal pin 2500 (S side) on the start position S side (the start side of the forward path) of each of the left and right heating wires 300, and a terminal pin 2500 (E side) on the end position E side (the end side of the return path). The terminal pins 2500 are metalworked products, the detailed structure of which will be described later, and are configured to be securely connected to the heating wires 300. The terminal pins 2500 in the electrofusion joint 100 are arranged in approximately the same axial position at the start position S side and the end position E side, but are shifted in the circumferential direction. However, the terminal pins 2500 in the electrofusion joint 100 may be arranged in the same circumferential position at the start position S side and the end position E side, but shifted in the axial direction. In this electrofusion joint 100, a total of four terminal pins, two on each side, are located at the ends (not the axial center) of the electrofusion joint so as not to affect watertightness (because the electrofusion joint according to this embodiment is a double-receiving type). In order to position the terminal pins 2500 in such positions, the winding structure (the structure of the heating wire embedded in the inner peripheral surface of the electrofusion joint 100) includes an outward winding 300F, a turn portion T, and a return winding 300R, as shown in Figure 2.

[0024] The electrofusion joint 100 is provided with indicators 3000, which are injection-molded parts embedded in correspondence with the positions of the left and right heating wires 300. When electric power is supplied to the heating wires 300 via the terminal pins 2500 to perform electrofusion, the indicators 3000 bulge, making it possible to confirm that electrofusion has been achieved.

[0025] Here, the structure of the electrofusion joint 100 (excluding the connection structure between the terminal pin 2500 and the heating wire 300), the manufacturing method of the electrofusion joint 100 (excluding the step of connecting the terminal pin 2500 and the heating wire 300), the dedicated blade used in the manufacturing method, and the winding method and winding structure of the electrofusion joint 100 are described in Patent Document 1. For this reason, the following will describe in detail the structure of the terminal pin 2500 and the connection structure between the terminal pin 2500 and the heating wire 300 (the structure of the electrofusion joint 100 itself), as well as the manufacturing method of the electrofusion joint 100, which includes the step of connecting the terminal pin 2500 and the heating wire 300.

[0026] <Terminal pin structure> The structural features of the terminal pin 2500 constituting the above-mentioned electrofusion joint will be described in detail below with reference to Figures 3 and 4. Note that Figure 3(D) is a cross-sectional view (double-enlarged) taken along arrows 3D-3D in Figure 3(B), and Figure 4(D) is a cross-sectional view (double-enlarged) taken along arrows 4D-4D in Figure 4(B).

[0027] As described above, the electrofusion joint 100 according to this embodiment does not have a crossover section like that in Patent Document 1 at the center in the axial direction. Instead, the left and right heating wires are separated and a total of four terminal pins 2500 are arranged at two locations, two on each side, at the end of the electrofusion joint. Since there is no through-hole (a hole penetrating the inner and outer peripheral surfaces of the sleeve) for providing a terminal pin at the center, watertightness is not affected. This terminal pin 2500 is formed by cutting a spiral groove with a dedicated cutting blade. At the same time, the heating wire is inserted into the groove. Then, the terminal pin 2500 shown in FIGS. 3 and 4 is securely connected to the heating wire 300 embedded in the inner peripheral surface. Thus, the terminal pin 2500 of the electrofusion joint 100 according to this embodiment has a structure that securely connects to the heating wire 300 embedded in the inner peripheral surface.

[0028] 3 and 4 are both terminal pins 2500 included in the electrofusion joint 100 according to this embodiment. The types of terminal pins 2500, which differ in shape depending on the type of heating wire 300, are not limited to two, and an appropriate number of types of terminal pins 2500 is set depending on the type of heating wire 300 used in the electrofusion joint 100.

[0029] As described above, the electric fusion joint 100 according to this embodiment is an electric fusion joint having a fusion part in which the heating wire 300 is inserted into a notched groove formed in a spiral on the inner peripheral surface of a thermoplastic resin pipe into which a connecting resin pipe is inserted. The electric fusion joint includes a substantially cylindrical, electrically conductive terminal pin 2500 (more specifically, the terminal pin 2501 shown in FIG. 3 and the terminal pin 2502 shown in FIG. 4 , the shapes of which vary depending on the type of heating wire) provided (as shown in FIG. 6(A) (A5)) in a through hole (the hole shown in FIG. 6(A) (A3)) drilled from the outer peripheral surface of the thermoplastic resin pipe to reach the heating wire 300. The terminal pin 2500 has a shape that varies depending on the type of heating wire. The lower side of the terminal pin 2500 (the substantially cylindrical portion 2530), which is connected to the heating wire 300, has a different shape depending on the type of heating wire 300, and this difference in shape can be visually distinguished from the outer peripheral surface of the thermoplastic resin pipe.

[0030] Preferably, the lower side (approximately cylindrical portion 2530 ) of the terminal pin 2500 connected to the heating wire 300 has a different shape corresponding to the diameter of the heating wire 300 . More preferably, the lower side (approximately cylindrical portion 2530) of terminal pin 2500 that is connected to heating wire 300 has a different shape because a portion of the curved surface of the approximately cylinder (in approximately cylindrical portion 2530) is cut into a flat surface (flat surface 2531S shown in Figure 3 or flat surface 2532S shown in Figure 4) by a thickness corresponding to the type of heating wire 300.

[0031] 3 and 4, terminal pin 2500 has a generally cylindrical shape and is electrically conductive. It has an end 2510 on the outer peripheral surface side to which an external power source is connected, a lower side (generally cylindrical portion 2530) to which heating wire 300 is connected, and a flange 2520 to prevent it from coming off is provided between end 2510 and generally cylindrical portion 2530. Terminal pin 2500 is generally cylindrical and electrically conductive (for example, terminal pin 2500 is made of copper, lead, or the like) and is inserted into a hole drilled from the outer peripheral surface of a thermoplastic resin pipe (pipe material, sleeve) to reach heating wire 300, for supplying electricity from an external power source to heating wire 300.

[0032] And the lower side (the substantially cylindrical portion 2530) connected to the heating wire 300 in the terminal pin 2501 shown in FIG. 3 has a part of the curved surface of the substantially cylindrical column in the (substantially cylindrical portion 2530) cut by a thickness corresponding to the type of the heating wire 300 on the plane 2531S, and the lower side (the substantially cylindrical portion 2530) connected to the heating wire 300 in the terminal pin 2502 shown in FIG. 4 has a part of the curved surface of the substantially cylindrical column in the (substantially cylindrical portion 2530) cut by a thickness corresponding to the type of the heating wire 300 on the plane 2532S, so that their shapes are different as prominently shown in FIGS. 3(B), 3(D), 4(B), and 4(D).

[0033] Here, for the terminal pin 2501 shown in FIG. 3 and the terminal pin 2502 shown in FIG. 4, the terminal pin 2501 is cut more than the terminal pin 2502, and for the remaining thickness t(1) in the terminal pin 2501 and the remaining thickness t(2) in the terminal pin 2502, the relationship of t(1) < t(2) holds. The terminal pin 2501 with a smaller remaining thickness t is used for a large-capacity type (thicker wire diameter) heating wire 300, and the terminal pin 2502 with a larger thickness t is used for a small-capacity type (thinner wire diameter) heating wire 300, and they are used separately in a distinguished manner.

[0034] Note that the shapes different due to the type of the heating wire 300 are not limited to those due to the difference in the cutting amount of such a plane cutting shape. For example, a groove with a width corresponding to the type of the heating wire 300 is provided from the lower end of the lower side (the substantially cylindrical portion 2530) connected to the heating wire 300 through the central axis of the substantially cylindrical portion 2530 (the groove is provided to bifurcate), and the heating wire 300 is locked in the groove (wound and fixed, or fixed by soldering, welding, etc.) for connection; or a through hole with a diameter corresponding to the type of the heating wire 300 (perpendicular to the central axis of the substantially cylindrical portion 2530) is provided in the lower side (the substantially cylindrical portion 2530) connected to the heating wire 300 through the central axis of the substantially cylindrical portion 2530, and the heating wire is passed through the through hole (wound and fixed, or fixed by soldering, welding, etc.) for connection (the connecting cylindrical body 2600 described later is an arbitrary configuration in these examples).

[0035] This difference in shape can be visually distinguished from the outer circumferential surface of the thermoplastic resin pipe. As shown in (A5) of Figure 6(A), even after the terminal pin 2500 connected to the heating wire 300 is attached to the electric fusion joint 100, the (upper) end 2510 of the terminal pin 2500 is visible through the hole (the hole drilled from the outer circumferential surface of the thermoplastic resin pipe (pipe material, sleeve) to reach the heating wire 300).

[0036] As described above, even after the terminal pin 2500 connected to the heating wire 300 is attached to the electrofusion joint 100, the (upper) end 2510 of the terminal pin 2500 is visible through the hole, and therefore the difference in shape can be distinguished by the color of the terminal pin 2500. In this case, if the shape of the lower side (approximately cylindrical portion 2530) of the terminal pin 2500 is different, it is sufficient that at least the color of the end 2510 is different, but it is also possible to make the color of the entire terminal pin 2500 different.

[0037] This color may be achieved by plating the terminal pin 2500 (to color the entire surface) or by applying a pigment (by applying paint, etc.). In the latter case, the pigment must be applied to at least the end 2510.

[0038] More preferably, the terminal pin 2500 and the heating wire 300 are connected using a connecting cylinder 2600 shown in Fig. 5. That is, the electrofusion joint 100 according to this embodiment includes not only the terminal pin 2500, the shape of the lower side (the substantially cylindrical portion 2530) of which differs depending on the type of heating wire 300 as described above, but also the connecting cylinder 2600 shown in Fig. 5, which has electrical conductivity and connects the terminal pin 2500 and the heating wire 300. This connecting cylinder 2600 is formed by bending a metal piece into a substantially cylindrical shape, and the lower side (the substantially cylindrical portion 2530) of the terminal pin 2500, with the heating wire 300 in contact with its flat surfaces (flat surfaces 2531S and 2532S), is inserted into the substantially cylindrical portion of the connecting cylinder 2600, and the heating wire 300 is pressure-welded to the terminal pin 2500.

[0039] Furthermore, the connecting cylinder 2600 can employ a crimp terminal or a terminal obtained by processing a crimp terminal. Here, an example of a crimp terminal is a terminal called a bare crimp terminal for copper wire, as defined in JIS C 2805. In the case of a crimp terminal such as a round crimp terminal, a Y-type crimp terminal, or a rod-shaped crimp terminal, for example, as shown in FIG. 5(B), the crimp terminal is formed by cutting off the dotted line portion of the crimp terminal (the round portion in the case of a round crimp terminal, the Y-type portion in the case of a Y-type crimp terminal, and the rod-shaped portion in the case of a rod-shaped crimp terminal) to leave only the crimp portion. Furthermore, in the case of a crimp terminal called a crimp sleeve, as shown in FIG. 5(A), the dotted line portion shown in FIG. 5(B) is not included in the first place, and therefore it can be used without processing. In this way, a crimp terminal or a terminal obtained by processing a crimp terminal can be employed as the connecting cylinder 2600. In this case, it is also preferable that the connecting cylinder 2600 has the same shape regardless of the type (wire diameter, etc.) of the heating wire 300. This is advantageous in that it is not necessary to prepare connecting cylinders with different shapes (particularly inner diameters) for each type of terminal pin 2500 and / or each type of heating wire 300.

[0040] As described above, the shape of the lower side (approximately cylindrical portion 2530) connected to the heating wire 300 varies depending on the type of heating wire 300. Between the terminal pin 2500, the heating wire 300, and the connecting cylinder 2600, the remaining thickness cut off by the lower flat surface (here, flat surface 2531S or flat surface 2532S) of the terminal pin 2500 is t (mm), the diameter of the heating wire is D (mm), and the inner diameter of the connecting cylinder is d (mm), and the relationship 0<((D+t)-d)<0.4 is satisfied.

[0041] If ((D+t)-d) is 0.4 or more, it is difficult to manually insert the connecting cylinder 2600 into the terminal pin 2500 with the heating wire 300 in contact with its flat surface (the insertion load is large and it may not be possible to assemble the connecting cylinder 2600 to the terminal pin 2500 with the heating wire 300 connected). On the other hand, if ((D+t)-d) is 0 or less, even if it is possible to assemble the connecting cylinder 2600 to the terminal pin 2500, the heating wire 300 will come out with a small force (a gap may be generated at the joint, making it impossible to reliably assemble the connecting cylinder 2600 to the terminal pin 2500 with the heating wire 300 connected).

[0042] As an example, t(1) = 2.35 ± 0.05 mm, t(2) = 2.75 ± 0.05 mm, D = 0.714 mm (t(2) used), 1.1 mm (t(1) used), d = 3.21 mm. The material of terminal pin 2500 is C3604 specified in JIS H 3250, and one of terminal pins 2501 and 2502 is plated with trivalent chromium (black), and the other is plated with electroless nickel (silver).

[0043] <Connection procedure> The procedure for connecting the terminal pin 2500 and the heating wire 300 using the connecting cylinder 2600 having such a configuration (the method for manufacturing the electrofusion joint 100, including the step of connecting the terminal pin 2500 and the heating wire 300) will be described with reference to FIGS. 6(A) and 6(B). In the procedure described below, steps (A1) to (A3) in FIG. 6(A) are performed before the winding is formed, and steps (A4) to (A5) are performed after the winding is formed. The dimensions of each part are shown using an electrofusion joint with a nominal diameter of 250 as an example. Steps (B1) to (B3) in FIG. 6(B) are specific steps for connecting the terminal pin 2500 to the heating wire 300 using the connecting cylinder 2600 as a step before step (A4). However, the electrofusion joint and its manufacturing method according to the present invention are not limited to those using the connecting cylinder 2600.

[0044] (A1) A hole is drilled from the outer peripheral surface of the electrofusion joint 100 toward the inner peripheral surface, with a diameter corresponding to the size (diameter) of the flange 2520. At this time, the depth of the hole is determined according to the position of the flange 2520. For example, a hole with a diameter of 10 mm is drilled for a flange 2520 with a maximum diameter of 10.5 mm. Furthermore, a hole with a depth of 18 mm is drilled for a flange 2520 with its lowest point located 15 mm from the upper end face of the terminal pin 2500. (A2) Stop the drill at the depth determined in (A1) above and chamfer the periphery of the hole. For example, chamfer to 2 mm.

[0045] (A3) A hole is drilled from the outer peripheral surface of the electrofusion joint 100 toward the inner peripheral surface, with a diameter corresponding to the size (diameter) of the portion below the flange 2520 of the terminal pin 2500. For example, if the size (diameter) of the portion below the flange 2520 is 5 mm to 6 mm, a hole with a diameter of 8 mm is drilled all the way to the inner peripheral surface. This is the drilling step. The following steps (A4) and (A5) are processes after the winding is formed. ((B1) to (B3) are the pre-processes for A4)

[0046] (B1) In the selection step, a terminal pin 2500 corresponding to the type of heating wire 300 is selected and prepared. At this time, the remaining thickness after cutting on the lower flat surface of the terminal pin 2500 (here, flat surface 2531S or flat surface 2532S) is defined as t (mm), the diameter of the heating wire is defined as D (mm), and the inner diameter of the connecting cylinder is defined as d (mm), and a terminal pin that satisfies 0<((D+t)-d)<0.4 is prepared. As mentioned above, the inner diameter d (mm) of the connecting cylinder is 3.21 mm.

[0047] (B2) The connecting cylinder 2600 is brought close from below to the terminal pin 2500 with the heating wire 300 in contact with the lower flat surface of the terminal pin 2500 (here, the flat surface 2531S or the flat surface 2532S).

[0048] (B3) The terminal pin 2500, to which the heating wire 300 is in contact, is covered with the connecting cylinder 2600, and the heating wire 300 is pressed against the flat surface (here, flat surface 2531S or flat surface 2532S) of the terminal pin 2500. At this time, although not limited thereto, it is also preferable to press the heating wire 300 against the terminal pin 2500 by crimping and crimping using a crimping tool or electrician's pliers, as shown by the black arrow in (B3) of Fig. 6(B). However, in the present invention, in order to satisfy the above-mentioned 0<((D+t)-d)<0.4, the heating wire 300 is preferably pressed against the terminal pin 2500 without crimping as described above (although crimping is acceptable), and the terminal pin 2500 and the heating wire 300 are reliably connected.

[0049] (C4) (C5) In the connection steps, the terminal pin 2500, in which the end of the heating wire 300 in contact with the flat surface (here, flat surface 2531S or flat surface 2532S) of the terminal pin 2500 is crimped by the connecting cylinder 2600, is inserted into the through hole as shown by the gray arrows in (A4) and (A5) of Figure 6(A), and the terminal pin 2500 and the heating wire 300 are connected within the through hole via the connecting cylinder 2600.

[0050] Although not shown, from the viewpoint of preventing incorrect assembly, it is also preferable to perform the following visual inspection step in the manufacturing method of the electrofusion joint 100. In this visual inspection step, after the above-mentioned connecting step, the difference in shape of the terminal pin 2500 is visually confirmed from the outer circumferential surface of the thermoplastic resin tube, and it is confirmed that the difference matches the heating wire 300 connected to the terminal pin 2500 in the connecting step.

[0051] In this way, the heating wire 300 in contact with the flat surface of the terminal pin 2500 and the connecting cylinder 2600 are pressed together, and the end of the heating wire 300 is securely connected to the terminal pin 2500 without using soldering or the like.

[0052] The present invention does not exclude the step of inserting and pressing the connecting cylinder 2600 into the terminal pin 2500 having the heating wire 300 in contact with a flat surface (here, flat surface 2531S or flat surface 2532S) in a through hole as in (A4). That is, the substantially cylindrical portion of the connecting cylinder 2600 may be inserted into the terminal pin 2500 having the heating wire 300 in contact with a flat surface in the through hole so that the heating wire 300 is pressed against the terminal pin 2500.

[0053] As described above, the electric fusion joint and the method for manufacturing an electric fusion joint according to the present embodiment can provide an electric fusion joint having a structure in which an electric heating wire is fitted into a groove formed on the inner periphery of a thermoplastic resin tube, which can more reliably connect the terminal pin and the electric heating wire for electric fusion, and which allows for visual detection of improper assembly even after the terminal pin has been assembled into the electric fusion joint, and a method for manufacturing the same.

[0054] It should be noted that the embodiments including the modifications disclosed herein are to be considered as illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Industrial Applicability]

[0055] The present invention is preferred for an electric fusion joint having a structure in which an electric heating wire is fitted into a groove formed on the inner periphery of a thermoplastic resin pipe, and is particularly preferred in that it allows for a more secure connection between the terminal pin and the electric heating wire for electric fusion, and that even once the terminal pin has been assembled into the electric fusion joint, any misassembly can be detected visually. [Explanation of symbols]

[0056] 100 Electric fusion joint 300 heating wire 300F forward winding 300R return winding 2500 terminal pins 3000 indicator

Claims

1. An electric fusion joint having a fusion part in which an electric heating wire is inserted into a notched groove formed in a spiral on the inner circumferential surface of a thermoplastic resin pipe into which a connecting resin pipe is inserted, a substantially cylindrical, electrically conductive terminal pin provided in a through hole drilled from the outer circumferential surface of the thermoplastic resin pipe to reach the heating wire, for supplying electricity from an external power source to the heating wire; The lower part of the terminal pin, which is connected to the heating wire, has a different shape depending on the type of the heating wire. An electric fusion joint, characterized in that the difference in shape can be visually distinguished from the outer circumferential surface of the thermoplastic resin pipe.

2. 2. The electric fusion joint according to claim 1, wherein the lower side of the terminal pin connected to the heating wire has a different shape corresponding to the diameter of the heating wire.

3. 2. The electric fusion joint according to claim 1, wherein the lower side of the terminal pin, which is connected to the heating wire, has a different shape in that a portion of the curved surface of the approximately cylindrical shape is cut into a flat surface by a thickness corresponding to the type of heating wire.

4. 2. The electrofusion joint according to claim 1, wherein the difference in shape can be distinguished by the color of the terminal pin.

5. 5. The electrofusion joint according to claim 4, wherein the color is developed by plating the terminal pin or by attaching a dye to the terminal pin.

6. the electric fusion joint further includes a connecting cylinder having electrical conductivity that connects the terminal pin and the heating wire, The connecting cylinder is formed by bending a metal piece into a substantially cylindrical shape, 4. The electric fusion joint according to claim 3, wherein the terminal pin with the heating wire in contact with the flat surface is inserted into the substantially cylindrical portion of the connecting cylinder, and the heating wire is pressure-welded to the terminal pin.

7. 7. The electrofusion joint according to claim 6, wherein the connecting cylindrical body is a crimp terminal or a terminal obtained by processing a crimp terminal.

8. 7. The electric fusion joint according to claim 6, wherein the connecting cylinder has the same shape regardless of the type of the heating wire.

9. 7. The electric fusion joint according to claim 6, wherein t (mm) is the remaining thickness after cutting at the flat surface on the lower side of the terminal pin, D (mm) is the diameter of the heating wire, and d (mm) is the inner diameter of the connecting cylinder, and the relationship 0<((D+t)-d)<0.4 is satisfied.

10. The method for manufacturing an electric fusion joint according to any one of claims 1 to 9, a drilling step of drilling a through hole corresponding to the shape of the terminal pin from the outer peripheral surface to the inner peripheral surface of the electric fusion joint; a selection step of selecting and preparing the terminal pin corresponding to the type of the heating wire; a connecting step of connecting the terminal pin and the heating wire within the through hole.

11. 11. The method for manufacturing an electric fusion joint according to claim 10, further comprising a visual confirmation step, after the connecting step, of visually confirming the difference in shape of the terminal pin from the outer peripheral surface of the thermoplastic resin tube to confirm that the difference matches the heating wire connected to the terminal pin in the connecting step.

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