Transport pipe and method for manufacturing a transport pipe

Abstract

To provide a transport pipe that can reliably fuse the inner surface of the receiving end with the outer surface of the spigot end while simplifying the structure for fusion bonding. [Solution] A transport pipe made of thermoplastic resin is provided with a receiving portion 4 into which the opening portion of the transport pipe to be connected is inserted. The receiving portion 4 has an inner surface 4a, which has a spiral groove 11 and a heating wire 6a inserted into the groove 11. The groove 11 has an open end 11a, a bottom 11b, and a side wall 11c connecting the open end 11a and the bottom 11b. The heating wire 6a is supported in contact with the side wall 11c by being pressed down by a projection 12 provided next to the open end 11a in the groove 11, and a gap 13 is formed between the heating wire 6a and the bottom 11b.

Description

Technical Field

[0001] The present invention relates to a transport pipe made of a thermoplastic resin and a method for manufacturing the transport pipe.

Background Art

[0002] For the joint of the resin pipe used for the transport pipe, an electric fusion joint as shown in Patent Document 1 is described. This electric fusion joint is provided with U-shaped concave grooves formed in a spiral shape on the inner peripheral surface of the resin pipe, with a small spiral pitch portion and a large spiral pitch portion. And an electric heating wire is inserted into the concave groove. And a tongue-like portion is used to block the concave groove into which the electric heating wire is inserted. Further, the groove portion includes a portion with a small spiral pitch that becomes a fusion portion and a portion with a large spiral pitch that becomes a winding end portion or the like. And the portion with a small spiral pitch is formed shallower than the portion with a large spiral pitch. And the electric heating wire inserted into the portion with a small spiral pitch is embedded in the concave groove with the resin including the melted tongue-like portion. The electric heating wire inserted into the portion with a large spiral pitch is pushed into the concave groove by the pressed tongue-like portion. In the portion with a small spiral pitch, the generation of voids in the concave groove is suppressed.

[0003] Also, Patent Document 2 describes another joint. In Patent Document 2, a configuration is described in which a cylindrical body in which a spiral electric heating wire is fixed to a thermoplastic resin is inserted into an inner concave circumferential groove provided on the inner surface of the receiving portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Patent Document 1 requires dividing the spiral pitch of the groove into a large and a small section for inserting the heating element. Furthermore, the depth of the spiral pitch needs to be varied between the large and small sections. This makes the groove machining complex.

[0006] Patent Document 2 states that there is a risk of trapping air inside the cylindrical body during manufacturing. There is also a risk of trapping air between the inner concave groove and the cylindrical body. When the heating wire is heated for thermal melting, the trapped air may expand and push the heating wire into the resin portion that constitutes the socket. The direction in which the heating wire is pushed is away from the socket portion. As a result, thermal melting between the socket portion and the socket portion may be insufficient, which may contribute to poor welding. [Means for solving the problem]

[0007] A transport pipe for solving the above problems is a transport pipe made of thermoplastic resin, comprising a receiving portion into which the socket portion of one transport pipe to be connected is inserted, and a socket portion into which the socket portion of another transport pipe to be connected is inserted, wherein the receiving portion has an inner surface, and the socket portion has an outer surface, and at least one of the inner surface and the outer surface comprises a spiral groove and a heating wire inserted into the groove, wherein the groove comprises an open end, a bottom, and a side wall connecting the open end and the bottom, and the heating wire is supported in contact with the side wall by being pressed in the groove by a projection provided next to the open end, and a gap is formed between the heating wire and the bottom.

[0008] With the above configuration, the groove is blocked by the projection, allowing the heating wire to be inserted without falling out of the groove until the joint is connected. When heat is generated to weld the inner and outer surfaces during joint connection, the air in the gap expands, and the heating wire is pressed in the direction of at least one surface of the outer and inner surfaces that are connected. This ensures that the inner surface of the receiving end and the outer surface of the spigot are reliably welded together. In this way, the structure for fusing the inner surface of the receiving end and the outer surface of the spigot is simplified while ensuring reliable fusion.

[0009] In the above transport pipe, the side wall portion may have a shape that narrows towards the bottom. With the above configuration, the heating element is supported by the side wall portion, thereby creating a gap between the heating element and the bottom.

[0010] In the above transport pipe, the spacing between adjacent heating elements may be constant in some areas. With this configuration, the area to be melted can be melted uniformly and without unevenness. In the above transport pipe, the projections may be provided opposite each other on both sides of the groove, and when bent in a direction that closes the groove, their tips may be spaced apart from each other. With this configuration, the projections can press the heating wire into the groove from both sides. This makes it even more difficult for the heating wire to fall out of the groove.

[0011] In the above-mentioned transport pipe, for example, it is a high-pressure resistant pipe for internal pressure. With the above configuration, even if a force due to internal pressure is applied inside the pipe, leakage from the joint portion between the socket and the spout can be suppressed. A method for manufacturing a transport pipe to solve the above problems is to provide a thermoplastic resin tube comprising a receiving portion into which the socket portion of one transport pipe to be connected is inserted, and a socket portion into which the receiving portion of another transport pipe to be connected is inserted, wherein the receiving portion has an inner surface and the socket portion has an outer surface, and when inserting a heating wire into at least one of the inner surface and the outer surface, a spiral groove portion is formed in at least one of the inner surface and the outer surface, the bottom of which is narrower than the diameter of the heating wire, and a projection portion is formed next to the groove portion, the heating wire is inserted into the groove portion, and then the projection portion is bent in a direction that closes the groove portion, pressing the heating wire into the groove portion, thereby causing the heating wire to contact and support the side wall portion of the groove portion.

[0012] According to the above configuration, the groove is formed as a cutting blade while the projection is also formed next to the groove. Then, the heating wire is inserted into the groove, and then the projection is bent to insert the heating wire into the groove. In this way, the formation of the groove and the insertion of the heating wire into the groove can be performed continuously. This allows the heating wire to be efficiently inserted into at least one of the receiving end and the insertion end. [Effects of the Invention]

[0013] According to the present invention, the structure for fusing the inner surface of the receiving end and the outer surface of the spigot is simplified while ensuring reliable fusion. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a side view of the transport pipeline in this embodiment. [Figure 2] Figure 2 is a cross-sectional view of the transport pipe in this embodiment. [Figure 3] Figure 3 is a schematic diagram showing the installation of the heating element. [Figure 4] Figure 4 is a schematic diagram showing the state in which the heating element is fixed. [Figure 5] Figure 5 is a schematic diagram illustrating the method of inserting the heating element into the groove. [Figure 6] Figure 6 is a schematic diagram illustrating the method for forming the grooves in the heating element. [Figure 7] Figure 7 is a schematic diagram showing the state in which the heating wire is inserted into the groove. [Modes for carrying out the invention]

[0015] The following describes a transport pipe to which the present invention is applied and a method for manufacturing the transport pipe, with reference to the drawings. [Structure of the transport pipe] As shown in Fig. 1, the transport pipeline 1 is an internal pressure pipeline used for agricultural water or the like, and a plurality of transport pipes 2 are joined and connected. Each transport pipe 2 is a resin pipe made of a thermoplastic resin containing glass fibers, and here a glass fiber reinforced polyethylene pipe is used. By using a high-density polyethylene material as the thermoplastic resin, the transport pipe 2 has excellent chemical resistance, corrosion resistance, wear resistance, impact resistance, and light weight. Furthermore, due to the orientation of the glass fibers, it is an internal pressure high-pressure resistant pipe with high rigidity in the circumferential direction of the pipe.

[0016] As shown in Fig. 2, each transport pipe 2 includes a pipe body 3, a receiving portion 4 formed at the first pipe end of the pipe body 3, and a spigot portion 5 formed at the second pipe end of the pipe body 3. The receiving portion 4 is configured such that its outer diameter and inner diameter are larger than those of the pipe body 3. The spigot portion 5 is configured such that its inner diameter is the same as that of the pipe body 3 and its outer diameter is formed by a thick wall portion larger than that of the pipe body 3. The receiving portion 4 and the spigot portion 5 are connected by an EF (electrofusion) joint.

[0017] The receiving portion 4 includes a heating portion 6 and a terminal 7 on the inner surface portion 4a. The heating portion 6 is configured by a heating wire 6a formed of a heating resistor extending in the circumferential direction of the pipe being wound around the inner surface portion 4a in a spiral shape. The end of the heating wire 6a is connected to the terminal 7, and is connected to a control device via this terminal 7.

[0018] As shown in Figs. 3 and 4, the heating wire 6a is a linear member and is loaded onto the inner surface portion 4a in a spiral shape. As an example, the heating wire 6a has a circular cross-section and a diameter Φ of 1.2 mm. The heating wire 6a is loaded such that the interval C1 between adjacent heating wires 6a is constant. The inner surface portion 4a is formed with a groove portion 11 formed in a spiral shape, and the heating wire 6a is loaded into the groove portion 11.

[0019] As shown in Figures 5 and 7, the groove 11 comprises an open end 11a, a bottom 11b, and a side wall 11c. The groove 11 has a shape that narrows from the open end 11a towards the bottom 11b. The groove 11 has, for example, a V-shaped cross-section. The open end 11a has, for example, an opening width W that is wider than the diameter Φ of the heating element 6a. The bottom 11b is configured to be narrower than the diameter Φ of the heating element 6a. The heating element 6a will come into contact with the side wall 11c of the groove 11.

[0020] When the heating element 6a is inserted into the groove 11, the side wall portion 11c supports the heating element 6a, and the upper part of the heating element 6a protrudes slightly from the open end 11a. The amount of protrusion of the heating element 6a from the open end 11a is such that it does not obstruct the insertion of the insertion portion into the receiving portion 4. Furthermore, with the heating element 6a inserted, the groove 11 is closed by projections 12 that protrude from both sides of the open end 11a. As a result, the heating element 6a is pushed into the groove 11. In the groove 11, a gap portion 13 is formed below the heating element 6a. The gap portion 13 is a sealed space surrounded by the bottom portion 11b of the groove 11 and the heating element 6a.

[0021] [Manufacturing method] The raw pipe 2a of the transport pipe 2 comprises a pipe body 3, a receiving portion 4 formed at the first pipe end of the pipe body 3, and a spigot portion 5 formed at the second pipe end of the pipe body 3. The raw pipe 2a is in the state before the heating element 6 and terminal 7 are installed on the inner surface 4a.

[0022] As shown in Figures 5 and 6, the manufacturing apparatus for forming a groove 11 in the inner surface 4a of the receiving portion 4 and inserting a heating wire 6a comprises a main body 21, a moving portion 22 that moves the main body 21 in the direction of the tube axis of the raw tube, and a rotating portion 23 that rotates the raw tube around the tube axis. The main body 21 comprises cutting blades 24a, 24b and a holding portion 25.

[0023] The main body is equipped with two cutting blades 24a and 24b so as to be able to cut two grooves 11 simultaneously. The main body 21 rotates the raw pipe around the pipe axis by the rotating part 23, and moves sequentially from the opening end of the receiving part 4 to the insertion part 5 by the moving part 22. In this way, the cutting blades 24a and 24b cut the inner surface 4a, simultaneously forming two parallel grooves 11 in a spiral shape. At this time, as shown in Figure 7, the cutting blades 24a and 24b form protrusions 12 on both sides of each groove 11 by pushing up the resin in the cut portion. Alternatively, after forming the grooves 11 with the cutting blades 24a and 24b, an extrusion tool may be continuously pressed against the grooves 11 to deform the side walls 11c and form the protrusions 12.

[0024] The heating wires 6a are supplied sequentially from the supply unit. The heating wires 6a are supplied sequentially from the downstream side in the rotational direction of the raw tube 2a. The retaining part 25 is located adjacent to the cutting blades 24a and 24b on the upstream side in the rotational direction R. The heating wires 6a are supplied to the newly cut groove 11, and the retaining part 25 is a plate or roller that presses the heating wires 6a supplied to the groove 11 into the groove 11. At the same time, the projections 12 are also pressed inward by the retaining part 25, closing the open end 11a of the groove 11 and pressing the heating wires 6a toward the bottom 11b. The size of the projections 12 is such that they do not completely close the open end 11a even when bent, and their tips are spaced apart. As a result, the heating wires 6a are pressed toward the bottom 11b in the groove 11. The retaining portion 25 may be heated to make it easier to bend the projection portion 12.

[0025] The heating element 6a is supported at two points by the side wall portion 11c. A sealed gap 13 is formed between the lower surface of the heating element 6a and the bottom portion 11b. When the open end 11a is closed by the projection 12, the bent projection 12 and the heating element 6a protrude slightly from the portion of the inner surface 4a where the groove 11 is not formed, but the amount of protrusion is not such that it obstructs the insertion of the insertion portion 5 into the receiving portion 4. The heating element 6a may be pressed down with enough force to slightly indent the side wall portion 11c. This reduces the amount of protrusion of the bent projection 12 and the heating element 6a from the portion of the inner surface 4a where the groove 11 is not formed.

[0026] As shown in Figures 5 and 6, the distance C1 between the heating wires 6a inserted into the two grooves 11 formed by a pair of cutting blades 24a and 24b is constant. In contrast, the distance C2 between the heating wire 6a inserted into one groove 11x of a pair of grooves 11 formed in a predetermined circumference (nth circumference) and the heating wire 6a inserted into the other groove 11y of the grooves 11 formed in the next circumference (n+1th circumference) may be the same as or different from the distance C1. Figure 3 shows the case where the distance C2 is greater than the distance C1.

[0027] [Connection Method] As described above, the transport pipe 2, in which the electric heating element 6 is configured on the inner surface 4a of the receiving portion 4, is connected by joints as follows.

[0028] The socket portion 5 of the transport pipe 2, which will be connected to the other transport pipe 2, is inserted into the socket portion 4 of the other transport pipe 2. After this, a power line extending from the control device is connected to the terminal 7, and power is supplied to the heating wire 6a according to the set conditions. As a result, the heating wire 6a generates heat and heats and melts the inner surface 4a of the socket portion 4 and the outer surface 5a of the socket portion 5. At the same time, the air in the gap portion 13 in the groove portion 11 expands due to the heat. As a result, the heating wire 6a is pressed toward the outer surface of the socket portion 5. This allows the inner surface 4a of the socket portion 4 and the outer surface of the socket portion 5 to be firmly heat-welded together.

[0029] [Effects of the Embodiment] The transport pipe 2 described above can obtain the following effects: (1) In the socket portion 4, the groove portion 11 is closed by the projection portion 12, so that the heating wire 6a can be inserted without falling out of the groove portion 11 until the joint connection is made. When heat is generated to weld the inner surface portion 4a of the socket portion 4 and the outer surface portion 5a of the socket portion 5 during joint connection, the air in the gap portion 13 expands, and the heating wire 6a is pressed toward the outer surface portion 5a of the socket portion 5. This ensures that the inner surface portion 4a of the socket portion 4 and the outer surface portion 5a of the socket portion 5 are reliably welded together. In this way, the structure for fusing the inner surface portion 4a of the socket portion 4 and the outer surface portion 5a of the socket portion 5 is simplified while ensuring reliable fusion.

[0030] (2) The heating element 6a is supported by the side wall portion 11c of the groove portion 11. This allows a gap to be formed between the heating element 6a and the bottom portion 11b. (3) The spacing C1 of the heating elements is constant. This allows the areas to be melted on the inner surface 4a of the receiving portion 4 and the outer surface 5a of the insertion portion 5 to be melted uniformly without unevenness.

[0031] (4) The projection 12 allows the heating element 6a to be pressed against the groove 11 from both sides. This makes it even more difficult for the heating element 6a to fall out of the groove 11. (5) Even with high-pressure pipes for internal pressure, such as transport pipe 2, leakage from the joint between the receiving end 4 and the spigot end 5 can be suppressed.

[0032] (6) In the manufacturing method, the cutting blades 24a and 24b are formed in the groove 11, and the projection 12 is also formed next to the groove 11. Then, the heating wire 6a is inserted into the groove 11, and then the projection 12 is bent to insert the heating wire 6a into the groove 11. In this way, the formation of the groove 11 and the insertion of the heating wire 6a into the groove 11 can be performed continuously. This allows the heating wire 6a to be inserted into the receiving portion 4 efficiently.

[0033] [Variation] Furthermore, the transport pipe 2 described above may also be in the form of the modified versions shown below, or a combination of at least two mutually non-contradictory modified versions.

[0034] The projection 12 formed next to the groove 11 may be formed only on one side of the open end 11a. • When protrusions 12 are formed on both sides of the groove 11, the tips between the bent protrusions 12 may be spaced apart or may abut together to close the open end 11a.

[0035] The spacing C1 between adjacent heating elements 6a may be constant or not. Spacing C1 and spacing C2 may be the same. The heating element 6a may be, for example, in a wavy or spiral shape. The manufacturing apparatus was described in the case where two pairs of grooves 11 are simultaneously formed by a pair of cutting blades 24a and 24b. However, the number of grooves 11 formed simultaneously is not limited to two; it may be configured to form three, four, or more grooves simultaneously. The manufacturing apparatus should be configured so that the number of grooves 11 formed simultaneously is equal to the number of cutting blades.

[0036] The shape of the groove 11 may not be a V-shape in cross-section, but a trapezoidal shape in which the upper base is longer than the lower base. In this case, the lower base is set to be shorter than the diameter Φ of the heating element 6a. Even in this case, the side wall 11c is configured as an inclined surface and can support the heating element 6a.

[0037] - In the inner surface 4a of the socket portion 4, heating element regions 6 may be provided in both the first region near the opening end of the socket portion 4 and the second region near the pipe body 3. In this case, the space between the heating element of the first region and the heating element of the second region, which are aligned in the direction of the pipe axis in the inner surface 4a, is either a gap where no heating wire is inserted, or a wiring is inserted to connect the heating wire of the heating element of the first region and the heating wire of the second region. The heating element 6 may be provided on the outer surface 5a of the socket portion 5 and not on the inner surface 4a of the receiving portion 4. If the heating element 6 is provided on the outer surface 5a, a groove 11 may be provided on the outer surface 5a, the heating wire 6a may be inserted into the groove 11, and the heating wire 6a may be held down by the projection 12. With such a configuration, the state of the heating wire 6a is stable in the socket portion 5, and the detachment of the heating wire 6a from the groove 11 can be suppressed when inserting it into the receiving portion 4. The heating elements 6 may be provided on the inner surface 4a of the receiving portion 4 and the outer surface 5a of the insertion portion 5. In this case, it is preferable that the positions of the heating elements 6 provided on the inner surface 4a of the receiving portion 4 and the positions of the heating elements 6 provided on the outer surface 5a of the insertion portion 5 do not overlap in the direction of the pipe axis. This allows for uniform welding across the entire area to be fused.

[0038] The thermoplastic resin constituting the transport pipe 2 is not limited to high-density polyethylene material. Furthermore, it does not need to contain glass fibers. • Transport pipeline 1 may be applied not only to agricultural pipelines but also to water pressure pipelines for hydroelectric power plants, water treatment facilities, sewage treatment facilities, and circulating water pipes within factories. It can be applied to the installation of heating wires 6a in EF joints in various types of resin pipes. [Explanation of Symbols]

[0039] 2…Transport pipe 2a…Main pipe 3... Pipe body 4... Socket 4a...Inner surface 5... Socket part 5a…External part 6…Electric heating part 6a…Heating wire 7… Terminals 11… Groove 11a...Open end 11b...bottom 11c...Side wall part 12...Protrusion 13...Void part

Claims

1. A transport pipe made of thermoplastic resin, It comprises a receiving portion into which the socket portion of one transport pipe to be connected is inserted, and a socket portion into which the socket portion of the other transport pipe to be connected is inserted, The receiving portion has an inner surface, and the insertion portion has an outer surface. At least one of the inner surface and the outer surface comprises a spiral groove and a heating element inserted into the groove, The groove comprises an open end, a bottom, and a side wall connecting the open end and the bottom. The heating element is supported in contact with the side wall by being held down in the groove by a projection provided next to the open end. A gap is formed between the heating element and the bottom. transport pipe.

2. The side wall portion has a shape that narrows towards the bottom. The transport pipe according to claim 1.

3. The spacing between adjacent heating elements is constant in some parts. The transport pipe according to claim 1.

4. The aforementioned protrusions are provided opposite each other on both sides of the groove, When the groove is bent in a direction that closes it, the ends of the grooves are separated from each other. The transport pipe according to claim 1.

5. It is a high-pressure resistant pipe for internal pressure applications. The transport pipe according to claim 1.

6. A thermoplastic resin tube comprises a receiving portion into which the socket portion of one transport pipe to be connected is inserted, and a socket portion into which the receiving portion of another transport pipe to be connected is inserted, wherein the receiving portion has an inner surface and the socket portion has an outer surface, and when inserting an electric heating wire into at least one of the inner surface and the outer surface, A spiral groove is formed in at least one of the inner and outer surfaces, the bottom of which is narrower than the diameter of the heating element, and a projection is formed next to the groove. The heating wire is inserted into the groove, and then the projection is bent in a direction that closes the groove, pressing the heating wire against the groove, thereby supporting the heating wire in contact with the side wall of the groove. A method for manufacturing transport pipes.

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