JP7601351B2 - Manufacturing method of electric fusion joint - Google Patents

Description

The present invention relates to an electric fusion joint used to connect plastic pipes, and in particular to a method for manufacturing an electric fusion joint in which a heating wire is inserted into a groove formed on the inner circumference of a thermoplastic resin pipe.

Electric fusion joints are usually manufactured using an injection molding method, and an electric heating wire is embedded in the inner periphery of a joint body made of a thermoplastic resin such as polyethylene, polybutene, etc. Such electric fusion joints are sometimes called EF (ElectroFusion) joints, EF sockets, etc.
As such an electric fusion joint, a joint having a structure in which a groove is cut in a spiral shape along the inner surface of a tube material made of thermoplastic resin and an electric heating wire is fitted into the groove is provided, centering on a large-diameter electric fusion joint. The electric fusion joint of this structure is simple in terms of the manufacturing method, but the difficulty of mounting the electric heating wire so that it does not float up from the groove has been pointed out as a problem. In consideration of such problems, Japanese Patent No. 5035672 (Patent Document 1) discloses an electric fusion joint in which an electric heating wire is fitted into a groove formed on the inner circumference of a thermoplastic resin tube, in which the electric heating wire does not float up from the groove due to temperature changes in the storage environment and no voids are generated at the fusion interface with the plastic tube.

The electric fusion joint disclosed in Patent Document 1 has a thermoplastic resin tube into which a plastic tube is inserted, a U-shaped groove formed on the inner surface of the resin tube in a spiral shape with a small and large spiral pitch, tongues formed on both sides of the groove opening, and a heating wire inserted into the groove, the width of the groove is formed to be the same as or slightly narrower than the diameter of the heating wire, the depth of the groove is deeper than the diameter of the heating wire, the groove part with the small spiral pitch is shallower than the groove part with the large spiral pitch, the heating wire inserted into the groove part with the small spiral pitch is embedded in the groove with resin including the molten tongue, and the heating wire inserted into the groove part with the large spiral pitch is pressed into the groove with the pressed tongue.

Patent No. 5035672

However, as described in paragraphs 0016 to 0018 of Patent Document 1, the electric fusion joint disclosed in Patent Document 1 is manufactured through three steps: preparing a sleeve of thermoplastic resin, forming a U-shaped groove in a spiral shape on its inner surface by cutting, pressing a pressing tool while moving it along the groove to deform the side wall and form a burr-like tongue protruding from the inner surface, and then inserting a heating wire over the entire length of the groove. This tends to result in high manufacturing costs.

The electric fusion joint disclosed in Patent Document 1 is merely a joint for connecting two plastic pipes in series, as described in paragraph 0009 of Patent Document 1. More specifically, the inner peripheral surface of the sleeve is divided into a left fusion portion that melts and fuses the surface of the plastic pipe inserted from the left, a right fusion portion that melts and fuses the surface of the plastic pipe inserted from the right, a left winding end between the left fusion portion and the left connector pin (terminal pin), a right winding end between the right fusion portion and the right connector pin (terminal pin), and a transition portion between the left fusion portion and the right fusion portion, and a groove is formed continuously from the left winding end to the right winding end, in which a single continuous electric heating wire is installed. In other words, since it is assumed that plastic pipes are fused to the left and right sockets of the electric fusion joint at the same time, a single continuous electric heating wire is wound in the same direction from left to right (or right to left) on the inner surface of the joint.

In this structure, there are the following problems: (1) even if plastic pipes are fused to both the left and right sockets, they must be fused at the same time, and it is not possible to fuse one side at a time, (2) plastic pipes are fused to one of the sockets, not both, and the other socket cannot be connected to a plastic pipe or the like by another connection method (a single-seat type electric fusion joint cannot be realized), and (3) in general, in the case of both sockets, as described in (1) above, double the fusion energy is required as compared to a single socket because they must be fused at the same time, and the required power (generator) becomes very large when the aperture (size) is large. Furthermore, the above problems (1), (2), and (3) can be solved by arranging the left and right heating wires independently without providing a jumper, but in that case, one of the two terminal pins arranged at each of the left and right locations will be arranged in the center of the axial direction of the electric fusion joint. In this case, the terminal pin is installed in a through hole that passes through the sleeve of the electric fusion joint, so if the terminal pin is installed in the center of the electric fusion joint, there is a problem that this through hole may lead to water leakage. For this reason, a total of four terminal pins must be installed, two on each side, so as not to affect watertightness.

However, the electric fusion joint disclosed in Patent Document 1 is merely a joint for connecting two plastic pipes in series and simultaneously, and there is no mention or suggestion in Patent Document 1 of separating the left and right heating wires and arranging a total of four terminal pins, two on each side, without providing such a jumper section.
The present invention was developed in consideration of the above-mentioned problems, and its object is to provide an electric fusion joint which has a structure in which an electric heating wire is fitted into a groove formed on the inner circumference of a thermoplastic resin pipe, and which can electrically fuse a mating plastic pipe to the left and right sockets, not to both the left and right sockets at the same time, but to one of the left and right sockets at a time (it does not matter whether both the left and right sockets are electrically fused, or only one of the left and right sockets is electrically fused and the other is not), and which can perform electric fusion without increasing manufacturing costs and affecting watertightness.

In order to achieve the above object, the method for producing an electric fusion joint according to the present invention employs the following technical measures.
That is, the method for manufacturing an electric fusion joint according to the present invention is a method for manufacturing an electric fusion joint having a fusion part in which an electric heating wire is inserted into a notched groove formed in a spiral shape on the inner peripheral surface of a thermoplastic resin pipe into which a connecting resin pipe is inserted, the fusion part is provided on at least one end side in the axial direction of the electric fusion joint so that an electric current can be applied to the electric heating wire, and in the fusion part, a forward path in which a spiral advances in a forward direction from an opening side of the electric fusion joint to an opening side on the opposite side of the opening, and a return path in a direction opposite to the forward path are formed by a single electric heating wire, and the manufacturing method includes a joint setting step of setting the electric fusion joint on a lathe so as to rotate it on its axis, and a dedicated blade is set on the lathe. and a fusion portion forming step of moving the dedicated blade in the axial direction while contacting the inner peripheral surface of the electric fusion joint and rotating the electric fusion joint on its axis to form the fusion portion, wherein the fusion portion forming step includes a groove cutting step of cutting a notch groove in the inner peripheral surface with a cutting blade provided on the dedicated blade, an electric heating wire insertion step of inserting the electric heating wire into the notch groove from an electric heating wire supply hole provided on the dedicated blade, and an electric heating wire fixing step of pressing the notch groove into which the electric heating wire has been inserted together with the electric heating wire by a pressing guide provided on the dedicated blade to fix the electric heating wire in the notch groove.

Preferably, the lathe can be configured to be a general-purpose lathe or an NC lathe.
More preferably, the direction from the electric heating wire introduction hole (inlet) of the dedicated blade to the electric heating wire supply hole (outlet) can be configured to be the same as the direction in which the electric fusion joint rotates.
More preferably, the fusion portion forming step can be configured to further include a switching step of stopping the axial movement of the dedicated blade and the rotation of the electric fusion joint, and reversing the inner circumferential direction orientation of the dedicated blade by 180 degrees to switch from the forward path to the return path.

More preferably, the dedicated blade has a structure in which the cutting blade, the heating wire supply hole, and the pressure guide face the inner peripheral surface of the rotating electric fusion joint in this order, the cutting blade has an approximately V-shape when viewed from the direction along the inner peripheral surface, and the tip side of the approximately V-shape abuts against the inner peripheral surface to cut the notch groove, and the axial length of the dedicated blade is the blade width A, the axial width of the pressure guide is the pressure guide width E, and the wire diameter of the heating wire is the diameter d2, and the blade width A and the pressure guide width E are configured to be 10 times or more the diameter d2.

More preferably, the dedicated blade has a structure in which the cutting blade, the heating wire supply hole, and the pressure guide face the inner circumferential surface of the rotating electric fusion joint in this order, the cutting blade has an approximately V-shape when viewed from a direction along the inner circumferential surface, the tip side of the approximately V-shape abuts against the inner circumferential surface to cut the notch groove, the length from the cutting blade to the pressure guide in the inner circumferential surface direction is distance G, the wire diameter of the heating wire is diameter d2, and the blade width A and the pressure guide width E are configured to be four times or more the diameter d2.

More preferably, the dedicated blade has a structure that faces the inner peripheral surface of the rotating electric fusion joint in the order of the cutting blade, the heating wire supply hole, and the pressure guide, and the cutting blade has an approximately V-shaped shape when viewed from a direction along the inner peripheral surface, and the tip side of the approximately V-shaped shape abuts against the inner peripheral surface to cut the notch groove, and the tip bevel angle of the approximately V-shaped cutting blade is angle α, which can be configured to be less than 80 degrees.

More preferably, the dedicated blade has a structure that faces the inner peripheral surface of the rotating electric fusion joint in the order of the cutting blade, the heating wire supply hole, and the pressure guide, and the shape of the cutting blade when viewed from a direction along the inner peripheral surface is approximately V-shaped, and the tip side of the approximately V-shape abuts against the inner peripheral surface to cut the notch groove, and the width of the cutting blade in the axial direction on the side opposite the tip side is the cutting blade width B, and the height of the approximately V-shape of the cutting blade is the cutting blade height C, and the cutting blade width B is ≦ the cutting blade height C × 0.75.

More preferably, the dedicated blade has a structure that faces the inner peripheral surface of the rotating electric fusion joint in the order of the cutting blade, the heating wire supply hole, and the pressure guide, and the cutting blade has an approximately V-shaped shape when viewed from the direction along the inner peripheral surface, and the tip side of the approximately V-shaped shape abuts against the inner peripheral surface to cut the notch groove, and the width of the cutting blade in the axial direction on the side opposite the tip side is the cutting blade width B, the height of the approximately V-shaped shape of the cutting blade is the cutting blade height C, and the wire diameter of the heating wire is the diameter d2, where the cutting blade width B is 2.8 times or less than the diameter d2 and the cutting blade height C is 3.6 times or more than the diameter d2.

More preferably, the dedicated blade has a structure in which the cutting blade, the heating wire supply hole, and the pressure guide face the inner circumferential surface of the rotating electric fusion joint in this order, the cutting blade has an approximately V-shape when viewed from a direction along the inner circumferential surface, the tip side of the approximately V-shape abuts against the inner circumferential surface to cut the notch groove, the length of the cutting blade in the direction along the inner circumferential surface is the cutting blade length D, the wire diameter of the heating wire is the diameter d2, and the cutting blade length D is 10 times or less than the diameter d2.

More preferably, the dedicated blade has a structure that faces the inner peripheral surface of the rotating electric fusion joint in the order of the cutting blade, the electric heating wire supply hole, and the pressure guide, and the cutting blade has an approximately V-shaped shape when viewed from a direction along the inner peripheral surface, and the tip side of the approximately V-shaped shape abuts against the inner peripheral surface to cut the notch groove, and the diameter of the electric heating wire supply hole is diameter d1, the wire diameter of the electric heating wire is diameter d2, and the diameter d1 is at least twice the diameter d2.

According to the present invention, there is provided an electric fusion joint having a structure in which an electric heating wire is inserted into a groove formed on the inner circumference of a thermoplastic resin pipe, and which can electrically fuse a plastic pipe to the left and right sockets one at a time (it does not matter whether both the left and right are electrically fused or only one of the left and right sockets is electrically fused and the other is not), and which can be electrically fused without increasing manufacturing costs and affecting watertightness.

1A and 1B are a side view and a front view, respectively, of an electric fusion joint according to an embodiment of the present invention, and FIG. 1C is a cross-sectional view indicated by an arrow 1C, FIG. 1D is a cross-sectional view indicated by an arrow 1D, FIG. 1E is a cross-sectional view indicated by an arrow 1E, and FIG. 1F is a cross-sectional view indicated by an arrow 1F. FIG. 2 is a perspective view for explaining a method for manufacturing the electric fusion joint shown in FIG. 1 (part 1: outward path). FIG. 2 is a perspective view for explaining a method for manufacturing the electric fusion joint shown in FIG. 1 (part 2: return path). 4A is a front view (part 1: outward path) and FIG. 4B is a front view (part 2: return path) for explaining the relationship between a blade used in the method for producing an electric fusion joint shown in FIG. 2 and FIG. 3 and an electric fusion joint (here, a sleeve before processing). 4A to 4E are plan views and FIG. 4F to FIG. 4I are perspective views of a special blade used in the method for producing an electric fusion joint shown in FIG. 2 and FIG. 6A to 6C are perspective views for explaining the dimensions of each part of the special blade shown in FIG. 5, and FIG. 6D is a front view. 3A and 3B are diagrams for explaining the forward winding and the return winding of the electric fusion joint 100. FIG. 4A and 4B are diagrams for explaining the forward winding and the return winding of the electric fusion joint 200. FIG. 1A and 1B are diagrams for explaining an outgoing winding and a return winding of an electric fusion joint according to a comparative example. 1A to 1B are plan views for explaining a terminal pin provided in an electric fusion joint, FIG. 1C is a construction procedure diagram, and FIG. 1D to FIG. 1E are diagrams of connecting members.

An electrofusion joint and a method for manufacturing an electrofusion joint according to an embodiment of the present invention will now be described with reference to Figures 1 to 10. In Figures 1 to 10, the same components are designated by the same reference numerals and have the same functions, so that they may not be described repeatedly.
Here, the electric fusion joint according to the embodiment of the present invention is an electric fusion joint mainly having a medium to large diameter (for example, an inner diameter of 300 mm or more), and this electric fusion joint has a structure manufactured by a manufacturing method characterized by cutting a groove (the cross-sectional shape of this groove is a V-groove, as an example, because the push-cutting blade of a dedicated blade described later is V-shaped when viewed from the direction along the inner circumferential surface) spirally 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, or a single-supported type in which the electric heating wire is provided only on 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 a jumper section like that of Patent Document 1 at the center side in the axial direction, but instead has left and right heating wires separated and a total of four terminal pins are arranged on the end sides of the electric fusion joint, two on each side, at two locations on the left and right sides.Since there is no through hole (a hole that penetrates the outer peripheral surface and inner peripheral surface of the sleeve) for arranging a terminal pin at the center side, it has the characteristic that it does not affect watertightness.

As electric fusion joints according to this embodiment, electric fusion joint 100 and electric fusion joint 200 are shown in FIG. 1, which are two types of electric fusion joints with different winding structures (structures manufactured by winding methods with different winding start positions S and/or winding end positions E, and different winding pitches), with the electric fusion joint with the winding structure shown in FIG. 7 being electric fusion joint 100 shown in FIG. 1, and the electric fusion joint with the winding structure shown in FIG. 8 being electric fusion joint 200 shown in FIG. 1. The electric fusion joint with the winding structure shown in FIG. 9 is a comparative example.

As an example, by adopting the winding structure shown in any of Figures 7 to 8 and using the manufacturing method shown in Figures 2 to 4 with the dedicated blade shown in Figures 5 to 6, a spiral groove is cut along the inner surface of the tube (sleeve) and formed on the outward path from the end side to the center side of the sleeve and on the return path from the center side to the end side with the cutter blade of the dedicated blade, and at the same time, the heating wire is inserted (embedded or buried) in the groove, and then the terminal pin shown in Figure 10 and the inserted heating wire are securely connected, completing the electric fusion joint shown in Figure 1.

<Overall structure of electric fusion joint>
First, the overall structure of the electric fusion joint manufactured as described above will be described. As shown in Fig. 1(A) and Fig. 1(B), the electric fusion joint 100 (having the winding structure shown in Fig. 7) and the electric fusion joint 200 (having the winding structure shown in Fig. 8) according to the present embodiment have 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 a nominal diameter of 250 (an electric fusion joint corresponding to an outer diameter of a resin pipe to be connected of 315 mm), for example. In the following, when absolute values of the numerical values of the electric fusion joint 100 including the dedicated blade 1000 are described, they are numerical values for the electric fusion joint with a nominal diameter of 250 (inner diameter 315 mm) even if not noted. In the following, the electric fusion joint 100 and the electric fusion joint 200 may be described as a representative of the electric fusion joint 100. And, the heating wire 300 is embedded in a spiral shape on the inner peripheral surface of the electric fusion joint.

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 peripheral 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 side in the axial direction of the electric fusion joint 100 so that electricity can be passed through the heating wire 300 (via the terminal pin 2000). In this fusion part, a forward path in which the spiral advances in the forward direction from the opening side of the electric fusion joint 100 to the opening side on the opposite side of the opening, and a return path in the opposite direction to the forward direction are formed by a single heating wire 300.

More specifically, as shown in Fig. 1(C) to Fig. 1(F), the electric fusion joint 100 has a terminal pin 2000 (S side) on the start position S side (start side of the outward path) of one electric heating wire 300 on each of the left and right sides, and a terminal pin 2000 (E side) on the end position E side (end side of the return path). The terminal pin 2000 is a metal processed product, the detailed structure of which will be described later, and is structured to be securely connected to the electric heating wire 300. The terminal pin 2000 in the electric fusion joint 100 is located at the same position in the circumferential direction on the start position S side and the end position E side, but is shifted in the axial direction. In contrast, the terminal pin 2000 in the electric fusion joint 200 is located at approximately the same position in the axial direction on the start position S side and the end position E side, but is shifted in the circumferential direction. In both electric fusion joints, a total of four terminal pins, two on each side, are placed on the ends (not the axial center side) of the electric fusion joint so as not to affect watertightness (because the electric fusion joint in this embodiment is a double-receiving type). In order to place the terminal pins 2000 in such positions, the winding structure includes an outward winding, a turn portion T, and a return winding, as shown in Figures 7 and 8.

The electric fusion joint 100 is equipped with an indicator 3000 in which an injection molded part is embedded, corresponding to the position of the left and right electric heating wires 300. When electric fusion is performed by supplying power to the electric heating wires 300 via the terminal pins 2000, the indicator 3000 rises, allowing confirmation that electric fusion has been performed.

<Method of manufacturing electric fusion joint>
The electric fusion joint 100 according to this embodiment having the above-mentioned winding structure is embedded in the inner peripheral surface of the electric fusion joint so that one heating wire 300 has a forward winding, a turn portion, and a return winding, by a manufacturing method for an electric fusion joint described below with reference to Figures 2 to 4. A dedicated blade 1000 used in the manufacturing method for an electric fusion joint described below is shown in Figures 5 and 6.

The manufacturing method of the electric fusion joint 100 according to this embodiment includes a joint setting step in which an electric fusion joint (here, a hollow cylindrical tubing material (sleeve) rather than an electric fusion joint as a finished product is set on a lathe so as to rotate on its axis, a blade setting step in which a dedicated blade (dedicated blade 1000 shown in Figures 2 to 6) is set on the lathe, and a fusion part forming step in which the dedicated blade 1000 is moved in the axial direction while being brought into contact with the inner peripheral surface of the electric fusion joint, and the electric fusion joint is rotated on its axis to form a fusion part. This fusion portion forming step includes a groove cutting step in which a notch groove is cut into the inner surface by the cutting blade 1200 provided on the dedicated blade 1000, a heating wire insertion step in which the heating wire 300 is inserted into the notch groove through the heating wire supply hole 1210 provided on the dedicated blade 1000 (more specifically, the heating wire 300 inserted through the heating wire introduction hole 1110 provided on the body portion 1100 of the dedicated blade 1000 is discharged through the heating wire supply hole 1210 provided on the cutting blade 1200 of the dedicated blade 1000 and inserted into the notch groove), and a heating wire fixing step in which the pressing guide 1300 provided on the dedicated blade 1000 presses the notch groove into which the heating wire 300 has been inserted together with the heating wire 300 to fix the heating wire 300 in the notch groove. Here, in the blade setting step, the dedicated blade 1000 is set on the lathe so that the direction of the inner circumference of the dedicated blade 1000 is reversed 180 degrees to switch from the forward path to the return path (forming the turn portion T described later) so that a switching step can be performed. Note that the electric heating wire supply portion may be described as being formed with the same diameter (d1 described later) formed by the electric heating wire introduction hole 1110, the electric heating wire supply hole 1210, and the communication hole provided inside the dedicated blade 1000 that connects these holes, or this same diameter d1 may be described as the diameter of the electric heating wire supply hole 1210.

Here, in the above-mentioned joint setting step, the lathe on which the electrofusion joint is set is preferably a general-purpose lathe or an NC (Numerical Control) lathe.
As shown in the relationship between the dedicated blade 1000 and the electric fusion joint on the outward path shown in Figure 4 (A) and the relationship between the dedicated blade 1000 and the electric fusion joint on the return path shown in Figure 4 (B), the dedicated blade 1000 has a structure in which the cutting blade 1200, the heating wire supply hole 1210, and the pressure guide 1300, in that order, face the inner surface of the rotating electric fusion joint, and it is preferable that the direction from the heating wire introduction hole 1110 (entrance) to the heating wire supply hole 1210 (exit) of the dedicated blade 1000 is the same as the direction in which the electric fusion joint rotates.

Furthermore, as shown in FIG. 2(C), it is preferable that the fusion portion forming step further includes a switching step of moving the dedicated blade 1000 in the axial direction (stopping parallel movement) and stopping the rotation of the electric fusion joint (stopping rotation), thereby reversing the orientation of the dedicated blade 1000 in the inner circumferential direction by 180 degrees, and switching from the forward path to the return path (forming the turn portion T described later).
With reference to FIG. 2, the fused portion forming step in this manufacturing method will be described separately for forming the outward winding and forming the return winding.

As shown in FIG. 2(A), the dedicated blade 1000 is positioned at the start position S of the forward path, and the dedicated blade 1000 starts to move in the axial direction (parallel movement) while in contact with the inner peripheral surface of the electric fusion joint, and starts to rotate the electric fusion joint (here, clockwise rotation as viewed from the opening on the left side). In this way, the dedicated blade 1000 starts to move in parallel and the electric fusion joint starts to rotate while in contact with the inner peripheral surface of the electric fusion joint, and the forward winding 300F starts to be embedded in the inner peripheral surface of the electric fusion joint from the start position S.

When the parallel movement speed of the dedicated blade 1000 and the rotation speed of the electric fusion joint are controlled so as to form the forward winding shown in Figures 7 and 8, the forward winding 300F (more specifically, the forward winding of either Figure 7(A) or Figure 8(A)) is formed as shown in Figure 2(B).
2C, when the outward winding 300F shown in Fig. 7 and Fig. 8 is formed until the dedicated blade 1000 reaches the end position of the outward path (the start position of the semicircle of the turn portion T), a switching step is executed. At this time, the translation of the dedicated blade 1000 and the rotation of the electric fusion joint are stopped, and the direction of the inner circumference of the dedicated blade 1000 is reversed by 180 degrees, forming the turn portion T for switching from the outward path to the return path.

Next, as shown in FIG. 3(A), the dedicated blade 1000, which is at the start position of the return path (the end position of the semicircle of the turn portion T), is brought into contact with the inner peripheral surface of the electric fusion joint and begins to move in the axial direction (parallel movement in the opposite direction to the forward path), and begins to rotate the electric fusion joint (here, counterclockwise rotation as viewed from the left opening). In this way, the dedicated blade 1000 is brought into contact with the inner peripheral surface of the electric fusion joint and parallel movement of the dedicated blade 1000 (parallel movement in the opposite direction to the forward path, so that the dedicated blade 1000 approaches the start position S) and rotation of the electric fusion joint (reverse rotation of the forward path) are started, and the return path winding 300R begins to be embedded in the inner peripheral surface of the electric fusion joint from the end position of the turn portion T.

When the parallel movement speed of the dedicated blade 1000 and the rotation speed of the electric fusion joint are controlled so as to form the return winding shown in Figures 7 and 8, the return winding 300R (more specifically, the return winding of either Figure 7(B) or Figure 8(B)) is formed as shown in Figure 3(B).
Furthermore, as shown in FIG. 3(C), when the return winding 300R shown in FIG. 7 and FIG. 8 is formed until the dedicated blade 1000 reaches the end point of the return path (end position E), a single heating wire is embedded in the inner surface of the electric fusion joint from the start position S through the turn portion T to the end position E as the forward winding 300F, the turn portion T and the return winding 300R.

<Structure of the dedicated blade>
The structural features of the dedicated blade 1000 used in the above-described method for producing an electrofusion joint will be described in detail below with reference to FIGS.
As described above, the dedicated blade 1000 has a structure that faces the inner peripheral surface of the rotating electric fusion joint in the following order: the cutting blade 1200, the heating wire supply hole 1210, and the pressing guide 1300. Furthermore, the cutting blade has a substantially V-shape when viewed from the direction along the inner peripheral surface (the direction shown in Figs. 5 and 6), and the tip side of the substantially V-shape abuts against the inner peripheral surface to cut the notch groove.
Here, as shown in Figures 5 and 6, the axial length of the dedicated blade 1000 is the blade width A, the axial width of the pressure guide 1300 is the pressure guide width E, and the wire diameter of the heating wire 300 is the diameter d2, and it is preferable that the blade width A and the pressure guide width E are 10 times or more the diameter d2.

For an electric fusion joint with a nominal diameter of 250, the above-mentioned blade width A and pressure guide width E were set to 10 mm, but the load on the dedicated blade 1000 was large when embedding the heating wire 300 by pressing and when making a U-turn (when forming the turn part T), and the pressing blade 1200 was deformed and broken, so the blade width A and pressure guide width E were set to 15 mm for the purpose of improving strength. Here, these blade width A and pressure guide width E may vary depending on the nominal diameter of the electric fusion joint, but in the present invention, attention is paid to the relationship with the diameter d2, which is the wire diameter of the heating wire 300 embedded in the inner surface of the electric fusion joint. Generally, a diameter d2 of about 0.7 mm to 1.1 mm is preferably used. In the case of 0.7 mm, A = E = 15 mm, d2 = 0.7 mm, and 15/0.7 = 21.42. In the case of 1.1 mm, A = E = 15 mm, d2 = 1.1 mm, and 15/1.1 = 13.64. In either case, it is preferable that the blade width A and the pressure guide width E are 10 times or more the diameter d2.

Furthermore, the length in the inner circumferential direction from the cutting blade 1200 to the pressing guide 1300 is defined as distance G, and the wire diameter of the heating wire 300 is defined as diameter d2, and it is preferable that the distance G is four times or more the diameter d2.
When comparing distances G of 2 mm and 5 mm for an electric fusion joint with a nominal diameter of 250, the shorter distance is undesirable because the embedded position of the electric heating wire 300 is shallow (the embedded position is close to the inner surface of the joint, so the electric heating wire can be visually confirmed and is not hidden), while the longer distance is preferable because the suppression effect is greater (the electric heating wire cannot be visually confirmed and is hidden). Here, these distances G may vary depending on the nominal diameter of the electric fusion joint, but in the present invention, attention is paid to the relationship with the diameter d2, which is the wire diameter of the electric heating wire 300 embedded in the inner surface of the electric fusion joint. As described above, if the diameter d2 is 0.7 mm and 1.1 mm, in the case of 0.7 mm, G = 5 mm, d2 = 0.7 mm, and 5/0.7 = 7.143, and in the case of 1.1 mm, G = 5 mm, d2 = 1.1 mm, and 5/1.1 = 4.545, and in either case, it is preferable that the distance G is four times or more the diameter d2.

Furthermore, the tip bevel angle of the approximately V-shaped cutting blade 1200 is defined as angle α, and this angle α is preferably less than 80 degrees.
When comparing the angle α of the cutting blade 1200 of 80 degrees and 40 degrees for an electric fusion joint with a nominal diameter of 250, a larger angle α is not preferred because the groove width becomes larger when making a U-turn (when forming the turn portion T), which makes it easier for the heating wire 300 to float out of the groove and become detached from the groove (when the angle α is smaller, such a problem does not occur), and therefore in the present invention, it is preferable that the upper limit of the angle α is 80 degrees.
Furthermore, the axial width of the cutting blade 1200 on the side opposite the tip side is defined as the cutting blade width B, and the height of the approximately V-shaped cutting blade 1200 is defined as the cutting blade height C, and it is preferable that the cutting blade width B≦the cutting blade height C×0.75.

Regarding the tip groove angle (angle α) of the approximately V-shaped cutting blade 1200, when considered from another perspective, it can be determined as follows: For an electric fusion joint with a nominal diameter of 250, in order to prevent the problem that the groove width becomes large when making a U-turn (when forming the turn portion T) and the heating wire 300 tends to float out of the groove and become detached from the groove, it is preferable in the present invention that the cutting blade width B≦the cutting blade height C×0.75.
Furthermore, the axial width of the cutting blade 1200 on the side opposite the tip side is defined as the cutting blade width B, the height of the approximately V-shaped cutting blade 1200 is defined as the cutting blade height C, and the wire diameter of the heating wire 300 is defined as the diameter d2, and it is preferable that the cutting blade width B is 2.8 times or less than the diameter d2 and the cutting blade height C is 3.6 times or more than the diameter d2.

Regarding the tip groove angle (angle α) of the approximately V-shaped cutting blade 1200, the following can be determined from another viewpoint. As described above, in terms of preventing the problem of the electric heating wire 300 floating out of the groove and becoming easily dislodged from the groove due to the large groove width at the time of U-turn (when forming the turn portion T) for an electric fusion joint of nominal diameter 250, there is a possibility that it may change depending on the nominal diameter of the electric fusion joint, but in the present invention, attention is paid to the relationship between the outer dimensions of the cutting blade 1200 (cutting blade width B and cutting blade height C, where B = 3 mm and C = 4 mm for a nominal diameter of 250) and the diameter d2, which is the wire diameter of the electric heating wire 300 embedded in the inner peripheral surface of the electric fusion joint. As mentioned above, if the diameter d2 is 0.7 mm and 1.1 mm, then in the case of 0.7 mm, B/d2 = 3/0.7 = 4.285 (4.3: rounded up) and C/d2 = 4/0.7 = 5.714 (5.7: rounded down), and in the case of 1.1 mm, B/d2 = 3/1.1 = 2.727 (2.8: rounded up) and C/d2 = 4/1.1 = 3.636 (3.6: rounded down), and it is preferable that the cutting blade width B is 2.8 times or less the diameter d2 and the cutting blade height C is 3.6 times or more the diameter d2.

Furthermore, assuming that the length of the cutting blade 1200 in the inner circumferential direction is the cutting blade length D and the wire diameter of the heating wire 300 is the diameter d2, it is preferable that the cutting blade length D is 10 times or less than the diameter d2.
For an electric fusion joint with a nominal diameter of 250, it is assumed that the load during a U-turn (when forming the turn portion T) is reduced if the cutting blade length D is as short as possible. However, since the rigidity of the cutting blade 1200 decreases when the cutting blade length D is shortened, it is preferable to secure a length of about 6 to 7 mm. Here, the cutting blade length D may vary depending on the nominal diameter of the electric fusion joint, but in the present invention, attention is paid to the relationship with the diameter d2, which is the wire diameter of the heating wire 300 embedded in the inner peripheral surface of the electric fusion joint. As described above, if the diameter d2 is 0.7 mm or 1.1 mm, in the case of 0.7 mm, D = 6 to 7 mm, d2 = 0.7 mm, and 8.57 (= 6/0.7) to 10 (= 7/0.7), and in the case of 1.1 mm, 5.45 (= 6/1.1) to 6.36 (= 7/1.1), and in either case, the cutting blade length D is preferably 10 times or less than the diameter d2.

Furthermore, the diameter of the electric heating wire supply part (more specifically, the diameter of the electric heating wire introduction hole 1110, the electric heating wire supply hole 1210, and the communication hole provided inside the dedicated blade 1000 that connects these holes, which is the same diameter and may be described as the diameter of the electric heating wire supply hole 1210) is taken as diameter d1, and the wire diameter of the electric heating wire is taken as diameter d2, and it is preferable that diameter d1 is at least twice diameter d2.

Here, the relationship (difference, clearance) between diameter d1 and diameter d2 basically holds true for electric fusion joints with different nominal diameters. Regarding diameter d2, which is the wire diameter of the heating wire 300, when the difference between diameter d1, which is the diameter of the heating wire supply part in the dedicated blade 1000, and diameter d2, which is the wire diameter of the heating wire 300, is about 0.4 mm, the resistance when the heating wire 300 passes through the dedicated blade 1000 is large, and breakage of the heating wire was confirmed (diameter d1: 1.5 mm, diameter d2: 1.1 mm). When a clearance of about 0.8 mm was secured as the difference (diameter d1 - diameter d2) (diameter d1: 1.5 mm, diameter d2: 0.7 mm), breakage of the heating wire 300 was not confirmed. For these reasons, it is preferable to secure a clearance equivalent to diameter d2, which is the wire diameter of the heating wire 300.

<Winding structure>
The features of the winding method used in the above-mentioned manufacturing method of an electric fusion joint and the features of the winding structure of an electric fusion joint manufactured by the manufacturing method will be described in detail below with reference to Figures 7 to 9. Figures 7 and 8 are diagrams for explaining the winding structures of the electric fusion joint 100 and the electric fusion joint 200 according to this embodiment, and Figure 9 is a diagram for explaining the winding structure of an electric fusion joint according to a comparative example for comparison with the electric fusion joints. In the winding structures in Figures 7 and 8, the position of the turn portion T (the pitch of the turn portion T) can be changed as appropriate (within the range satisfying the conditions shown below) depending on the operating status of the manufacturing apparatus for the electric fusion joint according to this embodiment.

As described above, in the fusion section of the electric fusion joint, two terminal pins 2000 on each side, two on the left and right, totaling four, are arranged at the end side of the electric fusion joint (not at the axial center side), so that the electric fusion joint has a winding structure in which one heating wire 300 is embedded using a winding method in which the spiral advances from the opening side of the electric fusion joint 100 in the forward direction to the opening side on the opposite side of the opening, and the return path in the opposite direction to the forward direction, passing through the turn section T. This winding structure has the following characteristics.

The fusion portion of the electric fusion joint includes, on both the outbound and inbound paths, a first area in the axial center of the fusion portion where the helical pitch is formed at the same pitch, and a second area other than the center where the helical pitch is formed at a pitch that is up to twice the same pitch.
More specifically, the area of the fusion portion of the electric fusion joint is divided into a first area in the axial center of the fusion portion and a second area including the start position S and end position E of the heating wire 300 and the turn portion T other than the first area, which is the center, and the spiral winding pitch in the first area is formed at the same pitch, while the spiral winding pitch in the second area is formed at a maximum twice the same pitch of the first area.

As shown in FIG. 9, when the winding pitch of the second area is approximately 3 to 5 times that of the first area, the heating wire 300 tends to move outward during fusion, protruding to the outside of the electric fusion joint, and short circuits due to contact between the heating wires on the outward and return paths tend to occur. On the other hand, when the change in the winding pitch of the second area is small compared to the winding pitch of the first area (the winding pitch of the second area is the same as the same pitch of the first area, or up to twice as much as the same pitch of the first area), protruding or short circuits of the heating wire 300 tend not to occur. For this reason, it is preferable to keep the winding pitch of the second area the same (including the same) to approximately twice the winding pitch of the first area.

Although this is only an example for the case of an electric fusion joint having a nominal diameter of 250 shown in Figures 7 to 9, the winding pitch is divided into a first area and a second area and is shown below.
As shown in the forward winding of FIG. 9(A), which is the winding structure of the electric fusion joint according to the comparative example, the forward processing pitch is F(n) to F(n+1) = 9.0 mm (n = 1 to 5) in the first area, and F(0) to F(1) = 14.5 mm and F(6) to F(7) = 20.5 mm (turn portion T) in the second area. Since the winding pitch of the second area (here, F(6) to F(7) = 20.5 mm (turn portion T)) is 2.3 times the same pitch of the first area (here, F(n) to F(n+1) = 9.0 mm (n = 1 to 5)), the winding pitch of the second area is not the same as the same pitch of the first area, and is at most twice as unsatisfactory as the same pitch of the first area.

As shown in the return winding in Figure 9 (B), the return processing pitch is R(n) to R(n+1) = 9.0 mm (n = 1 to 5) in the first area, and R(0) to R(1) = 35.0 mm and F(6) to F(7) = 15.0 mm (turn section T) in the second area. The winding pitch of the second area (here, 35.0 mm for R(0) to R(1)) is 3.9 times the same pitch of the first area (here, 9.0 mm for R(n) to R(n+1) (n = 1 to 5)). Therefore, the winding pitch of the second area is not the same as the same pitch of the first area, and is at most twice as unsatisfactory as the same pitch of the first area.

In the winding structure shown in FIG. 9, the heating wire 300 tends to move outward during fusion, causing it to protrude to the outside of the electric fusion joint, and there is a tendency for a short circuit to occur due to contact between the outgoing and return heating wires.
Next, as shown in the forward winding of FIG. 7(A), which is the winding structure of the electric fusion joint 100 according to this embodiment, the forward processing pitch in the first area is F(n) to F(n+1) = 13.0 mm (n = 0 to 3), and in the second area is F(4) to F(5) = 16.5 mm (turn portion T), and the winding pitch in the second area satisfies (the same as the same pitch in the first area, or) a maximum of twice the same pitch in the first area.

As shown in the return winding of FIG. 7(B), the return processing pitch in the first and second areas is R(n) to R(n+1) = 13.0 mm (n = 0 to 6: including the turn portion), and the winding pitch in the second area is the same as the same pitch in the first area (or is up to twice the same pitch in the first area).
Furthermore, as shown in the forward winding of FIG. 8(A), which is the winding structure of the electric fusion joint 200 according to this embodiment, the forward processing pitch is F(n) to F(n+1) = 13.0 mm (n = 0 to 5: including turn portions) in the first and second areas, and the winding pitch in the second area is the same as the same pitch in the first area (or is up to twice the same pitch in the first area).

As shown in the return winding of FIG. 8(B), the return processing pitch in the first area is R(n) to R(n+1) = 13.0 mm (n = 0 to 4), and in the second area is R(5) to R(6) = 14.5 mm (turn portion T), and the winding pitch in the second area is (the same as the same pitch in the first area, or) up to twice the same pitch in the first area.
In the winding structures shown in FIG. 7 and FIG. 8, unlike the winding structure of the comparative example shown in FIG. 9, there was no tendency for the heating wire 300 to move outward during fusion and protrude to the outside of the electric fusion joint, or for a short circuit to occur due to contact between the outbound and inbound heating wires.

As described above, the second area, which is divided into the first area and the second area, includes a switching portion (turn portion T) from the outward path to the return path.
Furthermore, the pitch of this switching portion (turn portion T) is preferably equal to or greater than the same pitch of the first area.
In the case of an electric fusion joint with a nominal diameter of 250, as one example, the pitch of the switching portion (turn portion T) is 16.5 mm compared to the same pitch of 13.0 mm in the first area as shown in the outgoing winding in FIG. 7(A), 13.0 mm compared to the same pitch of 13.0 mm in the first area as shown in the return winding in FIG. 7(B), 13.0 mm compared to the same pitch of 13.0 mm in the first area as shown in the outgoing winding in FIG. 8(A), and 14.5 mm compared to the same pitch of 13.0 mm in the first area as shown in the return winding in FIG. 8(B), satisfying that the pitch of the switching portion (turn portion T) is equal to or greater than the same pitch in the first area.

As described above, the pitch of the switching portion (turn portion T) in FIG. 9, which shows an undesirable winding structure in that the winding pitch of the second area is not the same as the same pitch of the first area or is not at most twice the same pitch of the first area, is 20.5 mm for the same pitch of 9.0 mm in the first area as shown in the outward winding in FIG. 9(A), and 15.0 mm for the same pitch of 9.0 mm in the first area as shown in the return winding in FIG. 9(B), and the pitch of the switching portion (turn portion T) satisfies that it is equal to or greater than the same pitch of the first area. For this reason, if the winding structure in FIG. 9 is changed so that the winding pitch of the second area is the same as the same pitch of the first area or is at most twice the same pitch of the first area, the tendency for the heating wire 300 to move outward during fusion and protrude outside the electric fusion joint, or the tendency for a short circuit to occur due to contact between the outward and return heating wires can be eliminated, and a preferable winding structure can be realized.

The changeover portion (turn portion T) is preferably formed in a semicircle having a diameter larger than half the diameter of the same pitch in the first area.
The changeover portion (turn portion T) is preferably formed in a semicircle having a diameter that is 150% or more of half the identical pitch in the first area.
It is preferred.

In the case of an electric fusion joint with a nominal diameter of 250, as an example, the diameter of the semicircle of the switching portion (turn portion T) is 10.0 mm for the same pitch of 13.0 mm in the first area as shown in the outgoing winding of FIG. 7(A), 10.0 mm for the same pitch of 13.0 mm in the first area as shown in the return winding of FIG. 7(B), 10.0 mm for the same pitch of 13.0 mm in the first area as shown in the outgoing winding of FIG. 8(A), and 10.0 mm for the same pitch of 13.0 mm in the first area as shown in the return winding of FIG. 8(B), and the switching portion (turn portion T) satisfies the requirement that the semicircle has a diameter larger than half the same pitch in the first area and a diameter that is 150% or more of half the same pitch in the first area.

As described above, the diameter of the semicircle of the switching portion (turn portion T) in Figure 9, which shows an undesirable winding structure in that the winding pitch of the second area is not the same as the same pitch of the first area or is not at most twice the same pitch of the first area, is 10.0 mm for the same pitch of 9.0 mm in the first area as shown in the outbound winding in Figure 9 (A), and 10.0 mm for the same pitch of 9.0 mm in the first area as shown in the return winding in Figure 9 (B), and the switching portion (turn portion T) satisfies the requirement that the semicircle has a diameter larger than half the same pitch in the first area and a diameter that is 150% or more of half the same pitch in the first area. Therefore, if the winding pitch of the second area in the winding structure in FIG. 9 is changed to be the same as the same pitch in the first area, or to be up to twice as large as the same pitch in the first area, the tendency for the heating wire 300 to move outward during fusion and protrude to the outside of the electric fusion joint, or for a short circuit to occur due to contact between the heating wires in the forward and return paths, can be eliminated, and a preferable winding structure can be realized.

<Terminal pin structure>
The structural features of the terminal pin 2000 constituting the above-mentioned electrofusion joint will be described in detail below with reference to FIG.
As described above, the electric fusion joint according to the present embodiment does not have a crossover portion like that of Patent Document 1 at the center side in the axial direction, and the left and right heating wires are separated and a total of four terminal pins 2000 are arranged at two locations on the left and right sides of the end side of the electric fusion joint, two on each side, and since there is no through hole (a hole that penetrates the outer peripheral surface and the inner peripheral surface of the sleeve) for providing a terminal pin at the center side, it has the characteristic that it does not affect watertightness. This terminal pin 2000 is provided by cutting a spiral groove with the cutting blade 1200 of the dedicated blade 1000, and at the same time, after the electric heating wire is inserted into the groove (after the process shown in Figures 2 and 3), the terminal pin 2000 shown in Figure 10 and the electric heating wire inserted into the inner peripheral surface are securely connected. In this way, the terminal pin 2000 provided in the electric fusion joint according to the present embodiment has a structure that is securely connected to the electric heating wire 300 embedded in the inner peripheral surface.

The terminal pin 2000 shown in FIG. 10(A) and the terminal pin 2100 shown in FIG. 10(B) are both terminal pins provided in the electric fusion joint according to this embodiment, and the shapes of the grooves provided at the end 2030 on the heating wire 300 side and enclosing the heating wire 300 along the longitudinal direction of the heating wire 300 are different. The terminal pin 2000 shown in FIG. 10(A) has a groove 2032 without a taper, and the terminal pin 2100 shown in FIG. 10(B) has a tapered groove 2132 with a taper. This is the only point that the terminal pin 2000 and the terminal pin 2100 differ from each other. Also, FIG. 10(C) shows the procedure of providing a perforation for inserting the terminal pin, and the procedure of inserting the terminal pin into the perforation to enclose the heating wire 300 in the groove provided at the end 2030 on the heating wire 300 side, thereby reliably connecting the terminal pin and the heating wire 300. In addition, terminal pin 2000 and terminal pin 2100 may be described as representative of terminal pin 2000.

The terminal pin 2000 is inserted into a hole drilled from the outer periphery of a thermoplastic resin pipe (pipe material, sleeve) to reach the heating wire 300, and is electrically conductive (one example is using copper, lead, etc. as the material of the terminal pin) for supplying electricity from an external power source to the heating wire 300. The end 2030 of the terminal pin 2000 on the heating wire 300 side (more specifically, this end 2030 is the lower end surface of the approximately cylindrical shape) is provided with a groove 2032 (tapered groove 2132 in the case of the terminal pin 2100) that contains the heating wire 300 along the longitudinal direction of the heating wire 300, and a mark indicating the direction of the groove 2032 (or tapered groove 2132) is attached at a position on the outer periphery side of the thermoplastic resin pipe opposite the end of the terminal pin 2000, which is visible from the outer periphery of the thermoplastic resin pipe when the terminal pin and the heating wire abut. In this case, this mark indicates the direction of the groove 2032 (or tapered groove 2132) and is visible from the outer surface of the thermoplastic resin tube when the terminal pin 2000 (or terminal pin 2100) and the heating wire 300 come into contact, so that the heating wire 300 can be reliably contained within the groove 2032 (or tapered groove 2132).

This mark is preferably a marker groove 2012 in the same direction as the groove 2032 (or tapered groove 2132) provided on the end 2010 on the outer peripheral surface side (more specifically, this end 2010 is the upper end surface of a substantially cylindrical shape). In this case, as shown in Figures 10(A) and 10(B), the groove 2032 (or tapered groove 2132) and the marker groove 2012 are in the same direction, and this marker groove 2012 is visible from the outer peripheral surface of the thermoplastic resin tube when the terminal pin 2000 (or terminal pin 2100) and the heating wire 300 come into contact, so that the heating wire 300 can be reliably contained within the groove 2032 (or tapered groove 2132).

The cross-sectional shape of the tapered groove 2132 is preferably an inverted V-shape in which the groove width at the open side is wider than the groove width at the bottom of the groove, thereby more reliably preventing electrical conduction failure when the heating wire 300 and the terminal pin 2000 are connected and fused by soldering.
As described above, the terminal pin 2000 shown in Fig. 10(A) and the terminal pin 2100 shown in Fig. 10(B) are substantially cylindrical and conductive, and the end 2030 (lower end face) on the heating wire 300 side is provided with a groove 2032 (or tapered groove 2132) that encloses the heating wire 300 along the longitudinal direction of the heating wire 300, and a mark groove 2012 is provided in the same direction as the groove 2032 (or tapered groove 2132) at a position on the outer circumferential surface side of the thermoplastic resin tube opposite to the end 2030 and visible from the outer circumferential surface of the thermoplastic resin tube when the terminal pin and the heating wire are in contact (end 2010 (upper end face)). Furthermore, a flange 2020 for preventing the end 2010 from coming off is provided in the middle between the end 2010 (upper end face) and the end 2030 (lower end face).

The procedure for installing the terminal pin 2000 having such a configuration will be described with reference to Fig. 10(C). In the procedure described below, (C1) to (C3) are performed before the winding is formed, and (C4) to (C5) are performed after the winding is formed (after the steps shown in Figs. 2 and 3). In addition, the dimensions of each part are taken as an example of an electrofusion joint with a nominal diameter of 250.
(C1) A hole is drilled from the outer circumferential surface of the electric fusion joint 100 toward the inner circumferential surface, the diameter of the hole corresponding to the size (diameter) of the flange 2020. At this time, the depth of the hole is determined according to the position of the flange 2020. For example, a hole having a diameter of 10 mm is drilled for a maximum diameter of the flange 2020 of 10.5 mm. Also, a hole having a depth of 18 mm is drilled for a position where the bottom end of the flange 2020 is 15 mm from the upper end face of the terminal pin 2000.

(C2) The drill is stopped at the depth determined in (C1) above, and the periphery of the hole on the outer periphery is chamfered, for example, to 2 mm.
(C3) A hole is drilled from the outer peripheral surface of the electric fusion joint 100 toward the inner peripheral surface, the diameter of which corresponds to the size (diameter) of the terminal pin 2000 below the flange 2020. For example, a hole with a diameter of 8 mm is drilled through to the inner peripheral surface, while the size (diameter) of the portion below the flange 2020 is 5 mm to 6 mm. The following steps (C4) and (C5) are processes after the winding process shown in Figures 2 and 3. (C4) The terminal pin 2000 is inserted into the through hole. At this time, the mark groove 2012 is visually confirmed, and the terminal pin 2000 is inserted into the through hole so that the groove 2032 provided in the same direction as the mark groove 2012 contains the heating wire 300 (so that the longitudinal direction of the heating wire 300 and the mark groove 2012 are parallel to each other, and the groove 2032 contains the heating wire 300).

(C5) With the terminal pin 2000 inserted into the through hole and the heating wire 300 contained within the groove 2032, the heating wire 300 is soldered to connect the terminal pin 2000 and the heating wire 300.
In this way, the heating wire 300 contained in the groove 2032 (or the tapered groove 2132) and the terminal pin 2000 (or the terminal pin 2100) are connected by soldering (as an example). However, the present invention is not limited to such a connection by soldering, and the following connection can be adopted. This connection other than soldering will be described with reference to Figs. 10(D) and 10(E). Note that Figs. 10(D) and 10(E) show the connection between the heating wire 300 and the terminal pin 2100, but the terminal pin 2000 may be used instead of the terminal pin 2100.

As shown in Figures 10 (D) and 10 (E), it is preferable that the joint between the terminal pin 2100 and the heating wire 300 in the tapered groove 2132 be achieved by abutting and joining the terminal pin 2100 and the heating wire 300 with a connecting member having conductivity and a shape that matches the shape of the tapered groove 2132 or the shape of the heating wire 300.
As such a connecting member, as shown in Fig. 10(D), the connecting member 2210 may have a generally hollow columnar shape that includes a hollow portion that contains the cross-sectional shape of the heating wire 300 in a vertical plane in the longitudinal direction and matches the groove width, or as shown in Fig. 10(E), the connecting member 2220 may have a generally rectangular columnar shape that matches the groove width. Note that the terminal pin 2100 is preferable to the terminal pin 2000 because the connecting members 2210 and 2220 are less likely to come out of the tapered groove 2132 when they are fitted into the tapered groove 2132.

<Effects of the above-described embodiment>
The manufacturing method of an electric fusion joint and the electric fusion joint having the above-described configuration provide the following advantageous effects.
(1-1) A dedicated blade is attached to a general-purpose normal lathe or NC lathe, and the sleeve is rotated to install (embed) the heating wire on the inner circumferential surface, so that the heating wire can be installed and fixed without using injection molding equipment or dedicated heating wire winding processing equipment. In particular, while injection molding requires a dedicated mold for each size, the manufacturing method of an electric fusion joint according to this embodiment makes it possible to relatively easily manufacture an electric fusion joint that matches the sleeve diameter of the base material.
(1-2) By cutting the inner circumferential surface of the sleeve with a cutting blade and inserting the heating wire while moving a special blade along the inner circumferential surface, it is possible to fix the heating wire when it passes through the holding guide, so that the groove can be excavated, the heating wire can be installed, and fixed in place in one process. As a result, it is possible to shorten the manufacturing time.
(1-3) Since it is relatively easy to change the height of the cutting blade and the diameter and position of the hole through which the heating wire passes within the dedicated blade, it is possible to arbitrarily and relatively easily adjust the embedding depth and heating wire diameter of the inner surface of the electric fusion joint.
(1-4) Since the shape of the cutting blade can be changed relatively easily to a shape other than a substantially V-shape, such as a cone-shape, it is possible to reduce the resistance acting on the cutting blade when the winding pitch of the heating wire is significantly changed or the winding direction is drastically changed (such as when the winding direction is reversed 180 degrees to form the turn portion T).

(2) In the electric fusion joint according to this embodiment, the area in the fusion part is divided into a first area in the axial center of the fusion part and a second area including the start and end positions of the heating wire other than the first area, which is the center, and a winding structure is adopted in which the spiral winding pitch in the first area is the same pitch, and the spiral winding pitch in the second area is a maximum of twice the same pitch as the first area. In other words, the winding pitch near the joint entrance (end) and turn part (second area) is not larger than the central part of the fusion part (first area), which is a general winding structure in electric fusion joints, but is set to be at most twice as large (to prevent the winding pitch from being large), so that the heating wire is less likely to move outward during fusion, and it is less likely to protrude outside the electric fusion joint, and a short circuit (short circuit) due to contact between the forward and return heating wires is less likely to occur. Furthermore, even if it does not significantly affect the joining quality, preventing the heating wire from protruding from the electric fusion joint also leads to an improved appearance. Also, when winding the heating wire, if the winding pitch is large, the load acting on the cutting blade of the dedicated blade increases because the force acts in an oblique direction. By keeping the winding pitch the same or not exceeding twice the pitch, wear and deformation of the cutting blade of the dedicated blade is also suppressed.

(3) When the terminal pin was inserted (driven) into the drilled hole, it was sometimes possible for the terminal pin to rotate and prevent the heating wire from fitting into the groove, making it impossible to reliably connect the terminal pin to the heating wire. However, by providing a mark (marker groove) indicating the direction of the groove in a position visible from the outer periphery of the electric fusion joint, it is possible to check whether the terminal pin is rotating while inserting it, and the heating wire can be reliably contained within the groove. In addition, by connecting the terminal pin to the heating wire by a method other than soldering, it is possible to more reliably prevent the solder from coming loose during current flow, causing the electric fusion process to be interrupted. As a result, by being able to reliably connect the terminal pin and the heating wire, it is possible to prevent fusion problems at the construction site.

As described above, according to the electric fusion joint and the manufacturing method of the electric fusion joint of this embodiment, it is possible to provide an electric fusion joint having a structure in which an electric heating wire is inserted into a groove formed on the inner circumference of a thermoplastic resin tube, and which can electrically fuse a plastic tube to one of the left and right receiving ports at a time (it does not matter whether both the left and right are electrically fused or only one of the left and right ports is electrically fused and the other is not), without increasing manufacturing costs and affecting watertightness, and with a more reliable connection between the terminal pin and the electric heating wire.

It should be noted that the embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope of the claims.

The present invention is preferable for an electric fusion joint having a structure in which an electric heating wire is fitted into a groove formed on the inner circumference of a thermoplastic resin pipe, and is particularly preferable in that it can provide an electric fusion joint that can electrically fuse the connecting plastic pipe to the left and right sockets one at a time (it does not matter whether both the left and right are electrically fused or only one of the left and right sockets is electrically fused and the other is not), without increasing manufacturing costs and affecting watertightness, and with a more reliable connection between the terminal pin and the electric heating wire.

100 Electric fusion joint 200 Electric fusion joint 300 Heating wire 300F Forward winding 300R Return winding 1000 Dedicated blade 1100 Body 1110 Heating wire introduction hole 1200 Pressing blade 1300 Pressing guide 1600 Housing joint 2000 Terminal pin 3000 Indicator

Claims (11)

A method for manufacturing an electric fusion joint having a fusion part in which an electric heating wire is inserted into a notched groove formed in a spiral shape on the inner peripheral surface of a thermoplastic resin pipe into which a connecting resin pipe is inserted, comprising:
The fusion portion is provided on at least one end side in the axial direction of the electric fusion joint so as to be capable of passing electricity through the heating wire,
In the fusion portion, a forward path in which a spiral advances in a forward direction from the opening side of the electric fusion joint to the opening side on the opposite side of the opening and a return path in a direction opposite to the forward direction are formed by a single heating wire,
The manufacturing method includes:
a joint setting step of setting the electric fusion joint on a lathe so as to rotate the joint;
a blade setting step of setting a dedicated blade on the lathe so that the direction of the notch groove in the inner circumferential direction can be reversed by 180 degrees ;
a fusion portion forming step of moving the dedicated blade in the axial direction while contacting an inner circumferential surface of the electric fusion joint and rotating the electric fusion joint to form the fusion portion,
The fusion portion forming step includes:
A groove cutting step of cutting a notch groove on the inner circumferential surface by a cutting blade provided on the dedicated blade;
a heating wire insertion step of inserting the heating wire into the notch groove through a heating wire supply hole provided in the dedicated blade;
a heating wire fixing step of pressing the notch groove into which the heating wire is inserted together with the heating wire by a pressing guide provided on the dedicated blade to fix the heating wire in the notch groove;
and a switching step of stopping the axial movement of the dedicated blade and the rotation of the electric fusion joint, reversing the orientation of the dedicated blade in the inner circumferential direction by 180 degrees to form a semicircular turn portion in which the heating wire is fixed within the notch groove, and switching from the outward path to the return path . The method for manufacturing an electric fusion joint according to claim 1, characterized in that the lathe is a general-purpose lathe or an NC lathe. The method for manufacturing an electric fusion joint according to claim 1 or 2, characterized in that the direction from the electric heating wire introduction hole (inlet) of the dedicated blade to the electric heating wire supply hole (outlet) is the same as the direction in which the electric fusion joint rotates. The turn portion is
The fusion portion is formed into a semicircle having a diameter larger than half the pitch of the heating wire.
or
The method for manufacturing an electric fusion joint according to any one of claims 1 to 3, characterized in that the fusion portion is formed into a semicircle having a diameter that is 150% or more of half the same pitch of the heating wire in the fusion portion. The dedicated blade has a structure in which the cutting blade, the heating wire supply hole, and the pressing guide face the inner peripheral surface of the rotating electric fusion joint in this order,
The shape of the cutting blade as viewed from a direction along the inner circumferential surface is substantially V-shaped, and a tip side of the substantially V-shaped shape abuts against the inner circumferential surface to cut the notch groove,
The axial length of the dedicated blade is defined as a blade width A, the axial width of the pressing guide is defined as a pressing guide width E, and the wire diameter of the heating wire is defined as a diameter d2.
The method for manufacturing an electric fusion joint according to any one of claims 1 to 4, characterized in that the blade width A and the pressing guide width E are 10 times or more larger than the diameter d2. The dedicated blade has a structure in which the cutting blade, the heating wire supply hole, and the pressing guide face the inner peripheral surface of the rotating electric fusion joint in this order,
The shape of the cutting blade as viewed from a direction along the inner circumferential surface is substantially V-shaped, and a tip side of the substantially V-shaped shape abuts against the inner circumferential surface to cut the notch groove,
The length from the cutting blade to the pressing guide in the inner circumferential direction is a distance G, and the wire diameter of the heating wire is a diameter d2.
The method for manufacturing an electric fusion joint according to any one of claims 1 to 4, wherein the distance G is four times or more the diameter d2. The dedicated blade has a structure in which the cutting blade, the heating wire supply hole, and the pressing guide face the inner peripheral surface of the rotating electric fusion joint in this order,
The shape of the cutting blade as viewed from a direction along the inner circumferential surface is substantially V-shaped, and a tip side of the substantially V-shaped shape abuts against the inner circumferential surface to cut the notch groove,
The tip bevel angle of the approximately V-shaped tip of the cutting blade is defined as angle α,
The method for producing an electric fusion joint according to any one of claims 1 to 4, wherein the angle α is less than 80 degrees. The dedicated blade has a structure in which the cutting blade, the heating wire supply hole, and the pressing guide face the inner peripheral surface of the rotating electric fusion joint in this order,
The shape of the cutting blade as viewed from a direction along the inner circumferential surface is substantially V-shaped, and a tip side of the substantially V-shaped shape abuts against the inner circumferential surface to cut the notch groove,
The width of the cutting blade in the axial direction on the side opposite to the tip side is defined as a cutting blade width B, and the height of the approximately V-shaped shape of the cutting blade is defined as a cutting blade height C.
The method for producing an electric fusion joint according to any one of claims 1 to 4, characterized in that the cutting edge width B≦the cutting edge height C×0.75. The dedicated blade has a structure in which the cutting blade, the heating wire supply hole, and the pressing guide face the inner peripheral surface of the rotating electric fusion joint in this order,
The shape of the cutting blade as viewed from a direction along the inner circumferential surface is substantially V-shaped, and a tip side of the substantially V-shaped shape abuts against the inner circumferential surface to cut the notch groove,
The width of the cutting blade in the axial direction on the side opposite to the tip side is defined as a cutting blade width B, the height of the approximately V-shaped shape of the cutting blade is defined as a cutting blade height C, and the wire diameter of the heating wire is defined as a diameter d2.
A method for manufacturing an electric fusion joint according to any one of claims 1 to 4, characterized in that the cutting blade width B is 2.8 times or less than the diameter d2, and the cutting blade height C is 3.6 times or more than the diameter d2. The dedicated blade has a structure in which the cutting blade, the heating wire supply hole, and the pressing guide face the inner peripheral surface of the rotating electric fusion joint in this order,
The shape of the cutting blade as viewed from a direction along the inner circumferential surface is substantially V-shaped, and a tip side of the substantially V-shaped shape abuts against the inner circumferential surface to cut the notch groove,
The length of the cutting blade in the direction of the inner circumferential surface is defined as a cutting blade length D, and the wire diameter of the heating wire is defined as a diameter d2.
The method for manufacturing an electric fusion joint according to any one of claims 1 to 4, characterized in that the length D of the cutting blade is 10 times or less than the diameter d2. The dedicated blade has a structure in which the cutting blade, the heating wire supply hole, and the pressing guide face the inner peripheral surface of the rotating electric fusion joint in this order,
The shape of the cutting blade as viewed from a direction along the inner circumferential surface is substantially V-shaped, and a tip side of the substantially V-shaped shape abuts against the inner circumferential surface to cut the notch groove,
The diameter of the heating wire supply hole is d1, and the wire diameter of the heating wire is d2.
The method for manufacturing an electric fusion joint according to any one of claims 1 to 4, characterized in that the diameter d1 is at least twice the diameter d2.

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