Covered pipe, method and apparatus of manufacturing the same

Abstract

To provide a suitable manufacturing method for a covered tube having a foam layer.SOLUTION: A covered pipe 12 comprises: a corrugated outer layer 20 in which ridges 21 and valleys 22 are alternately provided in an axial direction; and an inner layer 30 with a number of air bubbles formed inside. A method of manufacturing the covered pipe 12 has a multi-layer extrusion step of extruding a material for the outer layer from a discharge port 64 for the outer layer at a first position in an extruding direction E in a corrugator 53, and extruding a material for the inner layer from a discharge port 74 for the inner layer at a second position downstream of the first position.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a cladding tube, a method for manufacturing the same, and an apparatus for manufacturing the same. [Background technology]

[0002] For example, Patent Document 1 discloses a pipe for supplying hot and cold water, which has a foamed layer with many bubbles formed inside. The pipe in Patent Document 1 is a composite pipe that includes an inner pipe and a covering pipe disposed around the inner pipe. The covering pipe includes a corrugated outer layer and an inner layer made of foamed resin, and is formed by co-extrusion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-226144 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the manufacturing method described in Patent Document 1 is used, when the outer layer material and the inner layer material are extruded from the extrusion die, the inner layer material foams and expands while the shape of the outer layer is not stable, which can result in an unstable shape of the cladding tube.

[0005] An object of the present invention is to provide a suitable method and apparatus for manufacturing a cladding pipe having a foam layer, and a suitable cladding pipe having a foam layer. [Means for solving the problem]

[0006] A method for manufacturing a coated pipe that solves the above-mentioned problems is a method for manufacturing a coated pipe having a corrugated outer layer in which peaks and valleys are alternately arranged in the axial direction and an inner layer having a large number of bubbles formed therein, by extruding an outer layer material and an inner layer material containing a foaming agent in a corrugator, and includes a multi-layer extrusion process in which the outer layer material is extruded from an outer layer outlet at a first position in the extrusion direction, and the inner layer material is extruded from an inner layer outlet at a second position downstream of the first position.

[0007] In the method for manufacturing the coated tube, an outer layer die having a through hole extending in the axial direction is provided with the outer layer outlet, and an inner layer die is provided with the inner layer outlet, and the multi-layer extrusion process includes an arrangement step of extruding the outer layer material at a first temperature and extruding the inner layer material at a second temperature lower than the first temperature, and arranging the inner layer die in the through hole of the outer layer die so that the inner layer outlet of the inner layer die is located downstream in the extrusion direction from the outer layer outlet of the outer layer die, and so that a gap is formed between the outer peripheral surface of the inner layer die and the inner peripheral surface of the outer layer die.

[0008] The method for manufacturing the cladding tube includes an outer layer extrusion step of extruding the outer layer material at the first temperature, and after the outer layer extrusion step is started, the disposing step and the multi-layer extrusion step are carried out.

[0009] The coated pipe manufacturing apparatus that solves the above problem is a manufacturing apparatus that manufactures coated pipes having a corrugated outer layer in which peaks and valleys are alternately arranged in the axial direction, and an inner layer having a large number of bubbles formed therein, and is equipped with a corrugator that corrugates the outer layer, an outer layer outlet from which the outer layer material is extruded, and an inner layer outlet from which the inner layer material containing a foaming agent is extruded, and is capable of extruding the outer layer material from the outer layer outlet at a first position in the extrusion direction, and extruding the inner layer material from the inner layer outlet at a second position downstream of the first position.

[0010] The above-mentioned coated tube manufacturing apparatus comprises an outer layer die having a through hole extending in the axial direction and the outer layer outlet, and an inner layer die having the inner layer outlet, wherein the inner layer outlet of the inner layer die is located downstream in the extrusion direction from the outer layer outlet of the outer layer die, and the inner layer die can be arranged in the through hole of the outer layer die so that a gap is formed between the outer peripheral surface of the inner layer die and the inner peripheral surface of the outer layer die.

[0011] The cladding tube that solves the above-mentioned problems comprises: a corrugated outer layer formed from an outer layer material, with peaks and valleys alternately arranged in the axial direction; and an inner layer formed from an inner layer material, with numerous gas bubbles formed therein; the outer periphery of the valleys of the outer layer contains the outer layer material but does not contain the inner layer material; and a joint that contains the outer layer material and the inner layer material and melt-bonds the outer layer and the inner layer is formed between the valleys of the outer layer and the inner layer. [Brief explanation of the drawings]

[0012] [Figure 1] 1A is a longitudinal cross-sectional view of a portion of a compound pipe according to a first embodiment, and FIG. 1B is a transverse cross-sectional view of the compound pipe. [Figure 2] Schematic diagram showing a cladding tube manufacturing apparatus. [Figure 3] FIG. 2 is a plan view showing the molding surface of a corrugator die. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. 10 is a cross-sectional view showing the state in which the inner layer die is placed in the through hole of the outer layer die. [Figure 7] (a), (b), and (c) are schematic diagrams illustrating the manufacturing method of cladding tubes. [Figure 8] Schematic diagram showing the extrusion of the outer layer material. [Figure 9] Schematic diagram showing the extrusion of the outer layer material and the inner layer material. FIG. [Figure 10] FIG. 10 is a schematic view showing a manufacturing apparatus according to a second embodiment. [Figure 11]FIG. 10 is a schematic diagram showing how an outer layer material and an inner layer material are extruded in a manufacturing apparatus according to a second embodiment. [Figure 12] FIG. 10 is a longitudinal cross-sectional view of a portion of a composite pipe according to a third embodiment. [Figure 13] FIG. 10 is a schematic diagram showing how an outer layer material and an inner layer material are extruded in a manufacturing apparatus according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] [First embodiment] An embodiment of the present invention will be described below, which is embodied in a composite pipe for supplying hot and cold water having a cladding pipe. First, the configuration of the composite pipe 10 will be described. 1(a) and 1(b), a composite pipe 10 includes an inner pipe 11 for supplying cold and hot water, and a covering pipe 12 that covers the outer periphery of the inner pipe 11. The covering pipe 12 serves to protect the inner pipe 11 from external forces, protect the inner pipe 11 from ultraviolet rays, etc., and keep the hot water inside the inner pipe 11 warm. The axis P1 of the covering pipe 12 is common with the axis of the inner pipe 11 and is also the axis of the composite pipe 10.

[0014] The inner pipe 11 is made of a resin material. Examples of the resin material include polyolefins such as polybutene, polyethylene, cross-linked polyethylene, and polypropylene, as well as vinyl chloride. One type of resin material may be used alone, or two or more types may be used in combination. The resin material constituting the inner pipe 11 may also contain other additives. The inner pipe 11 of this embodiment is made of cross-linked polyethylene. The outer diameter D1 of the inner pipe 11 is, for example, 13 mm to 34 mm.

[0015] The cladding tube 12 includes an outer layer 20 and an inner layer 30 disposed inside the outer layer 20 . The outer layer 20 has a wave-like shape in which peaks 21 and valleys 22, each having an outer diameter and an inner diameter smaller than those of the peaks 21, are alternately arranged in the direction of the axis P1, allowing the outer layer 20 to expand and contract in the direction of the axis P1. The peaks 21 are thinner than the valleys 22.

[0016] The outer layer 20 is made of a resin material. Examples of the resin material include polyolefins such as polybutene, polyethylene, cross-linked polyethylene, and polypropylene, as well as vinyl chloride. Only one type of resin material may be used, or two or more types may be used in combination. The resin material constituting the outer layer 20 may also contain other additives. In this embodiment, the outer layer 20 is made of polyethylene colored blue or red, and is intended to enhance the appearance of the composite pipe 10, color-code the composite pipe 10 for cold water supply and hot water supply, and protect the outer surface of the inner layer 30 from external forces and the atmosphere.

[0017] The inner layer 30 of the covering pipe 12 is a foamed layer with many bubbles formed inside, and is made of a closed-cell foamed resin with an expansion ratio of 10 times or more (preferably 15 times or more, more preferably 20 to 30 times), making it expandable and contractible. The inner layer 30 improves the heat retention effect and shock absorption performance of the inner pipe 11 provided by the covering pipe 12.

[0018] The inner layer 30 has peaks 31 and valleys 32, each having a smaller outer diameter than the peaks 31, arranged alternately in the direction of the axis P1, and the outer circumferential surface of the inner layer 30 is corrugated. Meanwhile, the inner diameters of the peaks 31 and valleys 32 of the inner layer 30 are substantially the same, and the inner circumferential surface of the inner layer 30 is substantially cylindrical.

[0019] The outer diameter of the peaks 31 of the inner layer 30 is smaller than the inner diameter of the peaks 21 of the outer layer 20, and a space S is formed between the peaks 31 of the inner layer 30 and the peaks 21 of the outer layer 20. Meanwhile, the outer diameter of the valleys 32 of the inner layer 30 is substantially the same as the inner diameter of the valleys 22 of the outer layer 20, and the outer surfaces of the valleys 32 of the inner layer 30 are in close contact with the inner surfaces of the valleys 22 of the outer layer 20. When the outer layer 20 expands or contracts in the direction of the axis P1, the inner layer 30 also expands or contracts in the direction of the axis P1 together with the outer layer 20; that is, the cladding tube 12 expands or contracts in the direction of the axis P1. Note that the outer surfaces of the valleys 32 of the inner layer 30 and the inner surfaces of the valleys 22 of the outer layer 20 are not bonded or fused together.

[0020] Examples of resin materials constituting the inner layer 30 include polyolefins such as polybutene, polyethylene, cross-linked polyethylene, and polypropylene, polyurethane, ethylene propylene diene rubber, and mixtures thereof. The resin material constituting the inner layer 30 may contain other additives. The inner layer 30 of this embodiment is made of polyethylene.

[0021] Next, a manufacturing apparatus for the composite pipe 10 (particularly, a manufacturing apparatus for the cladding pipe 12) will be described. 2, the manufacturing apparatus 50 for the coated pipe 12 includes an outer layer extruder 51, an inner layer extruder 52, a corrugator 53, a cooling tank 54, a take-up machine 55, and a winding machine (not shown), and further includes an outer layer die 60 and an inner layer die 70. The crosshead type outer layer die 60 is attached to the outer layer extruder 51, and the straight head type inner layer die 70 is attached to the inner layer extruder 52. In addition to the manufacturing apparatus 50 for the coated pipe 12, the manufacturing apparatus for the composite pipe 10 further includes a pipe passing machine (not shown).

[0022] The outer layer extruder 51 is used to extrude a molten resin material (hereinafter referred to as "outer layer material") for forming the outer layer 20 of the cladding tube 12 through an outer layer die 60. The inner layer extruder 52 is used to extrude a molten resin material (hereinafter referred to as "inner layer material") for forming the inner layer 30 of the cladding tube 12 through an inner layer die 70. A foaming agent is injected into or mixed with the inner layer material to promote the foaming reaction of the inner layer material. The foaming agent may be a chemical foaming agent, a physical foaming agent, or a combination of a chemical foaming agent and a physical foaming agent.

[0023] The corrugator 53 is used to corrugate the outer layer 20 of the cladding pipe 12. As shown in Fig. 8, the corrugator 53 has a mold block 80 that is divided into two parts. The corrugator 53 has a plurality of mold blocks 80 arranged side by side along circulation paths provided on both the left and right sides. The corrugator 53 also has a function of cooling the mold blocks 80.

[0024] 3 shows the molding surface 81 of one mold 80. The molding surface 81 of the mold 80 has a semicircular annular cross section. On the molding surface 81, semicircular annular recesses 82 for forming the peaks 21 of the outer layer 20 of the cladding tube 12 and semicircular annular protrusions 83 for forming the valleys 22 of the outer layer 20 are alternately provided in the axial direction. The recesses 82 are provided with suction grooves 82a for sucking air from within the recesses 82 by a suction device (not shown). The recesses 82 are also provided with a pair of annular walls 82b positioned opposite each other at the front and rear of the axial direction. The length L1 of one mold 80 is, for example, 40 mm to 90 mm.

[0025] The cooling tank 54 is for cooling the cladding pipe 12 delivered from the corrugator 53. The take-up machine 55 is for taking up the cladding pipe 12 and delivering it to a winding machine (not shown).

[0026] Next, the outer layer die 60 will be described. As shown in Fig. 4, the outer layer die 60 includes a main body 61 and a nozzle 62 provided at the tip side of the main body 61. The main body 61 has a cylindrical portion 61a located at the base end side and a conical portion 61b located at the tip side. The nozzle 62 has an elongated cylindrical shape.

[0027] The outer layer die 60 is formed with a passage 63 through which the outer layer material supplied from the outer layer extruder 51 passes. The tip of the passage 63 is an annular outer layer discharge port 64 through which the outer layer material is extruded.

[0028] Furthermore, the outer layer die 60 is formed with a through hole 65 extending in the direction of its axis P2. That is, the inner peripheral surface of the outer layer die 60 forms the through hole 65. The through hole 65 has a first cylindrical portion 65a with a relatively large diameter located on the base end side, a second cylindrical portion 65b with a relatively small diameter located on the tip end side, and a conical portion 65c located between these two cylindrical portions, and is shaped and sized so that the inner layer die 70 can be placed in the through hole 65. Furthermore, the through hole 65 has the effect of connecting the space on the inner peripheral side of the outer layer material extruded from the outer layer die 60 to the outside, thereby making it at atmospheric pressure.

[0029] Next, the inner layer die 70 will be described. As shown in FIG. 5, the inner layer die 70 includes a main body 71 and a nozzle 72 provided at the tip side of the main body 71. The main body 71 has a cylindrical portion 71a located at the base end side and a conical portion 71b located at the tip side. The nozzle 72 has an elongated cylindrical shape. The outer diameter D2 of the tip end of the inner layer die 70 (i.e., the tip end of the nozzle 72) is smaller than the outer diameter D1 of the inner tube 11. The outer diameter D2 is, for example, 10 mm to 30 mm. Compared to the outer layer die 60, the inner layer die 70 has an elongated shape overall.

[0030] The inner layer die 70 is formed with a passage 73 through which the inner layer material supplied from the inner layer extruder 52 passes. The tip of the passage 73 is an annular inner layer discharge port 74 through which the inner layer material is extruded. The inner layer die 70 is formed with a through hole 75 extending in the direction of its axis P3. This through hole 75 has the effect of connecting the space on the inner periphery of the inner layer material extruded from the inner layer die 70 with the outside, thereby making the pressure at atmospheric pressure.

[0031] The inner layer die 70 has a shape and dimensions that allow it to be placed in the through hole 65 of the outer layer die 60, and Figure 6 shows the inner layer die 70 placed in the through hole 65 of the outer layer die 60.

[0032] Next, a method for manufacturing the composite pipe 10 (particularly, a method for manufacturing the cladding pipe 12) will be described. As shown in FIG. 7(a), the outer layer die 60 is attached to the outer layer extruder 51, and the inner layer die 70 is attached to the inner layer extruder 52. From this position, either or both of the outer layer extruder 51, the outer layer die 60, and the corrugator 53 are moved, and the nozzle 62 (particularly the outer layer outlet 64) of the outer layer die 60 is positioned within the corrugator 53, as shown in FIG. 7(b) (first positioning step). Specifically, as shown in FIG. 8, the outer layer die 60 is positioned so that the outer layer outlet 64 of the nozzle 62 is located within the mold 80 that is most upstream (left side in FIG. 8) of the multiple closed mold sets 80 of the corrugator 53. The position of the outer layer outlet 64 in the extrusion direction E at this time is referred to as a first position.

[0033] 8, the outer layer extruder 51 extrudes the outer layer material at a predetermined first temperature from the outer layer die 60 (specifically, the outer layer outlet 64) into the corrugator 53 at the first position (outer layer extrusion step). The first temperature is set in consideration of the type of outer layer material, the shape of the outer layer 20, and the like, and may be 190°C to 250°C, and is preferably 200°C to 230°C.

[0034] The corrugator 53 circulates multiple dies 80 in synchronization with the extrusion of the outer layer material from the extruder 51 (outer layer die 60). The corrugator 53 brings the two left and right dies 80 close to each other and brings their molding surfaces 81 (see FIG. 3) into contact with the outer layer material. The dies 80 mold the outer layer material using their molding surfaces 81, and by circulating the dies 80, the outer layer material moves downstream. At this time, the corrugator 53 circulates the dies 80 while cooling them.

[0035] At this time, a suction device (not shown) sucks air from inside the recessed portion 82 of the mold 80 through the suction grooves 82a, thereby creating a negative pressure inside the recessed portion 82 of the mold 80. As a result, the outer layer material deforms radially outward, and the outer peripheral surface is shaped by the recessed portion 82. This results in the formation of a corrugated outer layer 20 in which peaks 21 and valleys 22 are alternately arranged in the direction of the axis P1.

[0036] While continuing the outer layer extrusion process, either or both of the outer layer extruder 51, outer layer die 60 and corrugator 53 and the inner layer extruder 52 and inner layer die 70 are moved, and the nozzle 72 (particularly the inner layer outlet 74) of the inner layer die 70 is positioned within the corrugator 53 while passing through the outer layer die 60, as shown in Figure 7(c) (second positioning process).

[0037] At this time, as shown in Figure 6, the inner layer die 70 is positioned in the through hole 65 of the outer layer die 60 so that the axis P3 of the inner layer die 70 coincides with the axis P2 of the outer layer die 60, and so that a gap G is formed between the outer peripheral surface of the inner layer die 70 and the inner peripheral surface of the outer layer die 60. In this state, the inner layer die 70 is not in contact with the outer layer die 60. Furthermore, the tip of the inner layer die 70 is protruded from the through hole 65 of the outer layer die 60 so that the inner layer discharge port 74 of the inner layer die 70 is located downstream in the extrusion direction E of the outer layer discharge port 64 of the outer layer die 60. The position of the inner layer discharge port 74 in the extrusion direction E at this time is referred to as the second position.

[0038] The length L2 of the inner layer die 70 protruding from the tip of the outer layer die 60, i.e., the length L2 from the first position to the second position, may be at least half the length L1 of the mold 80 of the corrugator 53, preferably at least the length L1 of the mold 80, and more preferably at least twice the length L1 of the mold 80. In this embodiment, the length L2 is at least the length L1 of the mold 80.

[0039] Alternatively, the length L2 from the first position to the second position may be 20 mm to 200 mm, preferably 30 mm to 150 mm, and more preferably 40 mm to 100 mm. In this embodiment, the length L2 is 60 mm to 80 mm.

[0040] More specifically, as shown in Figure 6, the cylindrical portion 71a and conical portion 71b of the main body 71 of the inner layer die 70, and the nozzle 72, have smaller diameters than the first cylindrical portion 65a, conical portion 65c, and second cylindrical portion 65b of the through hole 65 of the outer layer die 60, respectively, and the cylindrical portion 71a and conical portion 71b of the main body 71 of the inner layer die 70, and the nozzle 72 are arranged to correspond to the first cylindrical portion 65a, conical portion 65c, and second cylindrical portion 65b of the through hole 65 of the outer layer die 60, respectively.

[0041] After the second placement step is completed as described above, as shown in FIG. 9, extrusion of the inner layer material from the inner layer die 70 begins while continuing to extrude the outer layer material from the outer layer die 60. That is, within the corrugator 53, the outer layer material is extruded from the outer layer outlet 64 at a first position, and the inner layer material is extruded from the inner layer outlet 74 at a second position downstream of the first position (multi-layer extrusion step). At this time, the outer layer material is extruded at a first temperature, and the inner layer material is extruded at a predetermined second temperature lower than the first temperature. For example, the second temperature is a temperature that is 100°C or more lower than the first temperature. The second temperature is set taking into consideration the type of inner layer material, the shape of the inner layer 30, and the like, and may be, for example, 80°C to 140°C, and preferably 90°C to 120°C.

[0042] The inner layer material extruded from the inner layer discharge port 74 foams and expands. The expanded inner layer material spreads radially outward and is pressed against the outer layer material, which has been corrugated by the mold 80. At this time, the inner layer material is in close contact with the portions of the outer layer material that correspond to the valleys 22 of the outer layer 20, and these portions of the inner layer material correspond to the valleys 32 of the inner layer 30. However, the inner layer material is not in contact with the portions of the outer layer material that correspond to the peaks 21 of the outer layer 20, and these portions of the inner layer material correspond to the peaks 31 of the inner layer 30, forming spaces S between the inner layer material and the outer layer material at these locations.

[0043] When the inner layer material expands and comes into contact with the outer layer material, the temperature of the outer layer material is somewhat lower than the first temperature, so the shape of the outer layer material is relatively stable, and the outer layer material and the inner layer material do not mix or melt and bond, even in the portions corresponding to the valley portions 22 of the outer layer 20. The inner layer material thus extruded moves downstream together with the outer layer material by circulation through the die 80, and the cladding tube 12 is formed.

[0044] The cladding pipe 12 delivered from the corrugator 53 is cooled using water or the like while passing through a cooling bath 54 (cooling process). This cooling process hardens the cladding pipe 12. The cladding pipe 12 is taken up by a take-up machine 55 (take-up process), and is wound up by a winding machine (not shown) (winding process). In this way, the cladding pipe 12 is completed.

[0045] To manufacture the composite pipe 10 using this cladding pipe 12, after the winding step, a separately manufactured inner pipe 11 is passed through the cladding pipe 12 using a pipe passing machine (not shown) (pipe passing step). In this way, the composite pipe 10 is completed.

[0046] Next, the effects of this embodiment will be described. (1) In the multi-layer extrusion process, an outer layer material is extruded from an outer layer outlet 64 at a first position in the extrusion direction E, and an inner layer material is extruded from an inner layer outlet 74 at a second position downstream of the first position.

[0047] The shape of the extruded outer layer material stabilizes as it moves downstream in the extrusion direction E, so that the shape is more stable when it is at the second position than when it is at the first position. The inner layer material is extruded on the inner circumferential side of the outer layer material, expands due to foaming, and is pressed against the outer layer material, which has a relatively stable shape. This stabilizes the shapes of the outer layer 20 and the inner layer 30, i.e., the shape of the cladding tube 12.

[0048] (2) In the second arrangement step, the inner layer die 70 is arranged in the through hole 65 of the outer layer die 60 so as to create a gap G between the outer peripheral surface of the inner layer die 70 and the inner peripheral surface of the outer layer die 60. Depending on the resin and foaming agent contained in the inner layer material, the higher the temperature, the more likely cell breakage (bubble rupture) may occur. Here, in this embodiment, the first temperature of the outer layer material is higher than the second temperature of the inner layer material, but because there is a gap G between the inner layer die 70 and the outer layer die 60, heat from the outer layer die 60 is less likely to be transferred to the inner layer die 70, preventing the inner layer material from becoming unintentionally hot. As a result, cell breakage can be prevented.

[0049] (3) After the outer layer extrusion process is initiated, the second placement process and the multi-layer extrusion process are performed. In the early stages of extrusion of the outer layer material, the outer layer material may not adhere to the entire circumference of the mold 80 and may sag downward due to gravity. If the tip of the inner layer die 70 (nozzle 72) protrudes from the tip of the outer layer die 60, the outer layer material may adhere to the protruding tip. In this embodiment, the inner layer die 70 does not protrude from the tip of the outer layer die 60 at the start of extrusion of the outer layer material, which prevents the outer layer material from adhering to the inner layer die 70.

[0050] (4) The length L2 from the first position to the second position is set to be equal to or greater than the length L1 of the mold 80. Therefore, the mold 80 at the second position is a different mold from the mold 80 at the first position. The outer layer material at the first temperature immediately after being extruded is not in direct contact with the mold 80 at the second position, and therefore the temperature of the outer layer material at the mold 80 at the second position tends to be low. Because the temperature of the outer layer material that comes into contact with the inner layer material as it expands tends to be low, the inner layer material is less likely to become too hot, which can prevent cells from breaking.

[0051] (5) The length L2 from the first position to the second position is set to 60 mm to 80 mm. The longer the length L2, the more stable the shape of the outer layer material that can be brought into contact with the inner layer material. On the other hand, the longer the length L2, the more likely the tip of the nozzle 72 of the inner layer die 70, i.e., the inner layer discharge port 74, is to become misaligned, resulting in less stable shape of the inner layer 30. Therefore, in this embodiment, the length L2 is set with this balance in mind.

[0052] (6) The length L2 from the first position to the second position is set so that, in the multi-layer extrusion process, the inner layer material comes into contact with the outer layer material, whose shape is stable enough to prevent the outer layer material and the inner layer material from mixing, even in the portions corresponding to the valley portions 22 of the outer layer 20. This makes it possible to further stabilize the shapes of the outer layer 20 and the inner layer 30, i.e., the shape of the cladding tube 12.

[0053] [Second embodiment] Next, a second embodiment will be described with reference to Figures 10 and 11. In the first embodiment, the composite pipe 10 is manufactured by manufacturing the cladding pipe 12 and then passing the inner pipe 11 through the cladding pipe 12. Instead, in the manufacturing method of this embodiment, the composite pipe 10 is manufactured by manufacturing the cladding pipe 12 on the outer periphery of the inner pipe 11. In this embodiment, a manufacturing apparatus 90 shown in Figure 10 is used. Note that the same components as in the first embodiment are denoted by the same reference numerals, and redundant explanations will be omitted.

[0054] The manufacturing apparatus 90 for the composite pipe 10 (which is also the manufacturing apparatus for the coated pipe 12) includes a payout machine 91, an outer layer extruder 51, an outer layer die 60', an inner layer extruder 52, an inner layer die 70', a corrugator 53, a cooling tank 54, a take-up machine 55, and a winding machine (not shown). The payout machine 91 is used to pay out the inner pipe 11 downstream.

[0055] The inner layer die 70' is a crosshead type, and as shown in Fig. 11, its through hole 75' is formed larger than the outer diameter D1 of the inner tube 11 so that the inner tube 11 can pass through the through hole 75' of the inner layer die 70'. Furthermore, as the through hole 75' is larger in diameter, the inner layer die 70' of this embodiment has a larger diameter overall than the inner layer die 70 of the first embodiment. Furthermore, the through hole 65' of the outer layer die 60' of this embodiment has a larger diameter than the through hole 65 of the outer layer die 60 of the first embodiment.

[0056] Next, a manufacturing method using the manufacturing apparatus 90 will be described with reference to FIGS. First, in this embodiment, as in the first embodiment, the first arrangement step, outer layer extrusion step, second arrangement step, and multi-layer extrusion step are performed in sequence. In the first arrangement step, the nozzle 62' of the outer layer die 60' is arranged inside the corrugator 53 so that the outer layer discharge port 64' is at a first position. In the outer layer extrusion step, the outer layer extruder 51 extrudes the outer layer material from the outer layer die 60' into the corrugator 53 at a first temperature. In the second arrangement step, the inner layer die 70' is arranged in the through hole 65' of the outer layer die 60' so that the inner layer discharge port 74' is at a second position and a gap G is formed between the outer layer die 60' and the inner layer die 70'. In the multi-layer extrusion process, an inner layer material containing a foaming agent is extruded onto the outer periphery of the inner tube 11 from an inner layer die 70' (nozzle 72') at a second temperature, and an outer layer material is extruded from an outer layer die 60' (nozzle 62') at a first temperature.

[0057] 10 and 11 , while continuing the multilayer extrusion process, the inner tube 11 is passed through the through-hole 75′ of the inner layer die 70′ by the unwinding machine 91, and is unwound via the inner layer die 70′ and the outer layer die 60′ into the corrugator 53 (unwinding process). In this way, the inner tube 11 is passed through the inside of the outer layer material and the inner layer material stuck to the mold 80 of the corrugator 53. Thereafter, a cooling process, a taking-up process, and a winding process are carried out, and the composite pipe 10 is completed.

[0058] Next, the effects of this embodiment will be described. In addition to the effects (1) to (6) of the first embodiment, this embodiment has the following effects. (7) In this embodiment, the outer layer material and the inner layer material are extruded around the outer periphery of the inner pipe 11 to form the cladding pipe 12. Therefore, unlike the first embodiment, the pipe passing step after manufacturing the cladding pipe 12 is not required, and the production efficiency of the composite pipe 10 can be improved.

[0059] [Third embodiment] Next, a third embodiment will be described with reference to Figures 12 and 13. In the first embodiment, the outer layer 20 and the inner layer 30 of the cladding tube 12 are not bonded or melt-bonded. Instead, in this embodiment, the outer layer 20' and the inner layer 30' are melt-bonded at a portion thereof. Note that the same components as those in the first embodiment are designated by the same reference numerals, and redundant description will be omitted.

[0060] As shown in Figure 12, the cladding pipe 12' of the composite pipe 10' of this embodiment includes an outer layer 20' and an inner layer 30'. At least the outer peripheral portions of the valley portions 22' of the outer layer 20' are formed only from the outer layer material and do not contain the inner layer material. At least the inner peripheral portions of the peak portions 31' of the inner layer 30' are formed only from the inner layer material and do not contain the outer layer material. A joint 13' that melt-bonds the outer layer 20' and the inner layer 30' is formed between the valley portions 22' of the outer layer 20' and the inner layer 30' (specifically, the valley portions 32'). The joint 13' includes the outer layer material and the inner layer material.

[0061] Next, the manufacturing apparatus of this embodiment will be described. As shown in Fig. 13, in the manufacturing apparatus of this embodiment, the nozzle 72'' of the inner layer die 70'' is shorter than that of the manufacturing apparatus 50 of the first embodiment, but other parts of the manufacturing apparatus have the same configuration.

[0062] Next, the manufacturing method of this embodiment will be described. The manufacturing method of this embodiment is the same as the manufacturing method of the first embodiment, except that the nozzle 72'' of the inner layer die 70'' is shorter, and therefore the length by which the tip of the inner layer die 70'' protrudes from the through hole 65 of the outer layer die 60'' is shorter.

[0063] In the second positioning step, the position of the inner layer discharge port 74'' in the extrusion direction E, i.e., the second position, is located upstream of the second position in the first embodiment. The length L2' by which the inner layer die 70'' protrudes from the tip of the outer layer die 60'', i.e., the length L2' from the first position to the second position, may be equal to or less than twice the length L1 of the mold 80 of the corrugator 53, preferably equal to or less than the length L1, and more preferably equal to or less than half the length L1. Alternatively, the length L2' from the first position to the second position may be 10 mm to 100 mm, preferably 15 mm to 80 mm, and more preferably 20 mm to 50 mm. In this embodiment, the length L2' is 25 mm to 35 mm.

[0064] In the multi-layer extrusion process, as shown in FIG. 13 , while the outer layer material continues to be extruded through the outer layer die 60″, extrusion of the inner layer material begins through the inner layer die 70″. The inner layer material extruded through the inner layer outlet 74″ foams and expands. The expanded inner layer material spreads radially outward and is pressed against the corrugated outer layer material by the mold 80. At this time, the inner layer material adheres to the portions of the outer layer material that correspond to the valleys 22′ of the outer layer 20′, and these adhered portions of the inner layer material correspond to the valleys 32′ of the inner layer 30′. Meanwhile, the inner layer material does not contact the portions of the outer layer material that correspond to the peaks 21′ of the outer layer 20′. Instead, these portions of the inner layer material correspond to the peaks 31′ of the inner layer 30′, and a space S is formed between the inner layer material and the outer layer material at these locations.

[0065] When the inner layer material expands and comes into contact with the outer layer material, the temperature of the outer layer material's peripheral portion is somewhat lower than the first temperature, and the shape of the outer layer material's peripheral portion is relatively stable. Therefore, the outer layer material's peripheral portion does not mix with the inner layer material, even in the portions corresponding to the valleys 22' of the outer layer 20'. Meanwhile, the inner layer material's temperature is higher than the outer peripheral portion, and its shape is not yet stable. Therefore, the portions corresponding to the valleys 22' of the outer layer 20' mix with the inner layer material.

[0066] As the extruded outer layer material and inner layer material move downstream by circulation through the die 80, the temperature of the mixed portion decreases and the mixed state becomes stable. In this way, the cladding tube 12' of this embodiment is formed, and the mixed portion becomes the bonded portion 13' that melt-bonds the outer layer 20' and the inner layer 30'.

[0067] Next, the effects of this embodiment will be described. In addition to the effects (1) to (3) of the first embodiment, this embodiment has the following effects. (8) The cladding tube 12' has a joining portion 13' that melt-bonds the outer layer 20' and the inner layer 30', making it even more difficult for the relative positions of the outer layer 20' and the inner layer 30' to shift, that is, it is possible to more reliably make the outer layer 20' and the inner layer 30' expand and contract integrally.

[0068] (9) The length L2' from the first position to the second position is set so that, in the multi-layer extrusion process, the outer peripheral portion of the outer layer material at the location corresponding to the valley portion 22' of the outer layer 20' is relatively stable in shape and does not mix with the inner layer material, while the inner peripheral portion of the outer layer material mixes with the inner layer material that it comes into contact with. This allows the effects of (1) and (8) above to be achieved together.

[0069] [Other embodiments] The above embodiment can be modified as follows, for example: The above embodiment and the following modifications can be combined and implemented within the scope of technical compatibility. The outer layer extruder 51 and the outer layer dies 60, 60′ may be configured to extrude multiple resin layers, and the inner layer extruder 52 and the inner layer dies 70, 70′, 70″ may be configured to extrude multiple resin layers.

[0070] The number of extruders 51, 52 and the number of dies 60, 60′, 70, 70′, 70″ is not limited to two. For example, the coating tube 12 may be produced by co-extrusion using one extruder and one die. In this case, the inner layer outlet of the one die may be located at a position spaced a distance L2 from the outer layer outlet in the extrusion direction E.

[0071] The outer layer die 60, 60' and the inner layer die 70, 70', 70'' may be in contact with each other, or the gap G may not be formed between the outer layer die 60, 60' and the inner layer die 70, 70', 70''. For example, the outer layer die 60, 60' and the inner layer die 70, 70', 70'' may be in partial contact with each other, or the through-hole 65, 65' of the outer layer die 60, 60' may be formed in a shape that makes contact entirely with the outer peripheral surface of the inner layer die 70, 70', 70''.

[0072] In the second disposing step and the multi-layer extrusion step, the position of the inner layer outlet in the extrusion direction E may be the same as the position of the outer layer outlet. The outer layer extrusion step may be omitted, and the extrusion of the outer layer material and the inner layer material may be started simultaneously.

[0073] The covering of the covering pipes 12, 12' is not limited to the inner pipe 11. For example, the covering pipes 12, 12' may be used to cover a metal pipe or an electric wire.

[0074] [Note] The technical concept that can be understood from the above embodiment will be described. (1) A method for producing a cladding pipe having a corrugated outer layer in which peaks and valleys are alternately provided in the axial direction and an inner layer in which a large number of bubbles are formed, by extruding an outer layer material through an outer layer die having through-holes extending in the axial direction and extruding an inner layer material containing a foaming agent through an inner layer die in a corrugator, an arrangement step of arranging the inner layer die in the through hole of the outer layer die so that a gap is formed between an outer peripheral surface of the inner layer die and an inner peripheral surface of the outer layer die; a multi-layer extrusion process in which, in the corrugator, the outer layer material is extruded through the outer layer die at a first temperature and the inner layer material is extruded through the inner layer die at a second temperature lower than the first temperature; A method for manufacturing a cladding tube comprising:

[0075] (2) The method for manufacturing a cladding tube according to the technical idea (1), wherein the positioning step is performed by protruding the tip of the inner layer die from the through hole of the outer layer die so that the inner layer outlet of the inner layer die is located downstream in the extrusion direction from the outer layer outlet of the outer layer die.

[0076] (3) an outer layer extrusion step of extruding the outer layer at the first temperature; The method for manufacturing a cladding tube according to technical idea (2), wherein the disposing step and the multi-layer extrusion step are carried out after the outer layer extrusion step is started.

[0077] (4) A manufacturing apparatus for manufacturing a cladding tube having a corrugated outer layer in which peaks and valleys are alternately provided in the axial direction and an inner layer in which a large number of bubbles are formed, a corrugator that corrugates the outer layer; an outer layer die having a through hole extending in an axial direction and extruding an outer layer material into the corrugator; an inner layer die for extruding an inner layer material containing a foaming agent into the corrugator; Equipped with an outer layer die disposed in the through hole of the outer layer die so as to form a gap between the outer peripheral surface of the inner layer die and the inner peripheral surface of the outer layer die, the outer layer material being extruded from the outer layer die at a first temperature, and the inner layer material being extruded from the inner layer die at a second temperature lower than the first temperature.

[0078] (5) A coated tube manufacturing apparatus according to technical idea (4), in which, with the inner layer die positioned in the through hole of the outer layer die, the tip of the inner layer die can be protruded from the through hole of the outer layer die so that the inner layer outlet of the inner layer die is located downstream in the extrusion direction from the outer layer outlet of the outer layer die.

[0079] (6) A method for producing a composite pipe comprising a coating pipe having a corrugated outer layer in which peaks and valleys are alternately provided in the axial direction and an inner layer having a large number of bubbles formed therein, by extruding an outer layer material through an outer layer die having a through-hole extending in an axial direction and extruding an inner layer material containing a foaming agent through an inner layer die in a corrugator, and passing an inner pipe through the coating pipe, an arrangement step of arranging the inner layer die in the through hole of the outer layer die; a multi-layer extrusion process in which, in the corrugator, the outer layer material is extruded through the outer layer die and the inner layer material is extruded through the inner layer die; a tube passing step of passing an inner tube having an outer diameter larger than that of a tip end of the inner layer die into the cladding tube manufactured through the disposing step and the multilayer extrusion step; A method for manufacturing a composite pipe comprising: According to the method of technical idea (6), a composite pipe having a large diameter inner pipe can be produced compared to a method in which a covering pipe is directly produced around an inner pipe while the inner pipe is being fed into an inner layer die.

[0080] (7) A manufacturing method for a composite pipe including a covering pipe and an inner pipe, the covering pipe having a corrugated outer layer in which peaks and valleys are alternately provided in the axial direction and an inner layer in which a large number of bubbles are formed, by extruding an outer layer material and an inner layer material containing a foaming agent onto the outer periphery of an inner pipe in a corrugator, A method for manufacturing a composite pipe, comprising a multi-layer extrusion process in which an outer layer material is extruded from an outer layer outlet at a first position in the extrusion direction, and an inner layer material is extruded from an inner layer outlet at a second position downstream of the first position.

[0081] (8) A method for producing a composite pipe including a covering pipe and an inner pipe, the covering pipe having a corrugated outer layer in which peaks and valleys are alternately provided in the axial direction and an inner layer in which a large number of bubbles are formed, by extruding an inner layer material containing a foaming agent from an inner layer die onto the outer periphery of an inner pipe in a corrugator, and extruding an outer layer material from an outer layer die having through holes extending in the axial direction, an arrangement step of arranging the inner layer die in the through hole of the outer layer die so that a gap is formed between an outer peripheral surface of the inner layer die and an inner peripheral surface of the outer layer die; a multi-layer extrusion process in which, in the corrugator, the outer layer material is extruded through the outer layer die at a first temperature and the inner layer material is extruded through the inner layer die at a second temperature lower than the first temperature; A method for manufacturing a composite pipe comprising:

[0082] (9) A manufacturing apparatus for manufacturing a cladding tube having a corrugated outer layer in which peaks and valleys are alternately provided in the axial direction and an inner layer in which a large number of bubbles are formed, a corrugator that corrugates the outer layer; a die having an outer layer discharge port through which an outer layer material is extruded and an inner layer discharge port through which an inner layer material containing a foaming agent is extruded; an extruder to which the die is attached and which supplies the outer layer material and the inner layer material to the die; Equipped with The cladding tube manufacturing apparatus, wherein the inner layer discharge port is provided downstream of the outer layer discharge port in the extrusion direction. [Explanation of symbols]

[0083] 10,10'...Composite pipe, 11...Inner pipe, 12,12'...Coating pipe, 13'...Joining part. 20,20'...outer layer, 21,21'...peak portion, 22,22'...valley portion. 30,30'...inner layer, 31,31'...peak section, 32,32'...valley section. 50... manufacturing equipment, 51... outer layer extruder, 52... inner layer extruder, 53... corrugator, 54... cooling tank, 55... take-up machine. 60, 60', 60''... die for outer layer, 61... main body, 61a... cylindrical portion, 61b... conical portion, 62, 62'... nozzle, 63... passage, 64, 64'... discharge port for outer layer, 65, 65'... through hole, 65a... first cylindrical portion, 65b... second cylindrical portion, 65c... conical portion. 70, 70', 70''... die for inner layer, 71... main body, 71a... cylindrical portion, 71b... conical portion, 72, 72', 72''... nozzle, 73... passage, 74, 74', 74''... discharge port for inner layer, 75, 75'... through hole. 80... mold, 81... molding surface, 82... recess, 82a... suction groove, 82b... wall, 83... protrusion. 90...Manufacturing equipment, 91...Delivery machine. D1, D2...outer diameter, E...extrusion direction, G...gap, P1~P3...axis, S...space.

Claims

1. A method for producing a cladding pipe having a corrugated outer layer in which peaks and valleys are alternately provided in the axial direction and an inner layer in which a large number of bubbles are formed, by extruding an outer layer material and an inner layer material containing a foaming agent in a corrugator, comprising: A method for manufacturing a cladding tube, comprising a multi-layer extrusion process in which an outer layer material is extruded from an outer layer outlet at a first position in the extrusion direction, and an inner layer material is extruded from an inner layer outlet at a second position downstream of the first position.

2. an outer layer die having a through hole extending in an axial direction and equipped with the outer layer discharge port; an inner layer die having the inner layer discharge port; The multi-layer extrusion step includes extruding the outer layer material at a first temperature and extruding the inner layer material at a second temperature lower than the first temperature; 2. The method for manufacturing a cladding tube according to claim 1, further comprising an arrangement step of arranging the inner layer die in the through hole of the outer layer die so that the inner layer outlet of the inner layer die is located downstream in the extrusion direction from the outer layer outlet of the outer layer die, and so that a gap is formed between the outer peripheral surface of the inner layer die and the inner peripheral surface of the outer layer die.

3. an outer layer extrusion step of extruding the outer layer material at the first temperature; The method for manufacturing a cladding tube according to claim 2 , wherein the disposing step and the multi-layer extrusion step are carried out after the outer layer extrusion step is started.

4. A manufacturing apparatus for manufacturing a cladding tube having a corrugated outer layer in which peaks and valleys are alternately provided in the axial direction and an inner layer in which a large number of bubbles are formed, a corrugator that corrugates the outer layer; an outer layer discharge port through which the outer layer material is extruded; an inner layer discharge port through which an inner layer material containing a foaming agent is extruded; Equipped with An apparatus for manufacturing a cladding tube, which is capable of extruding the outer layer material from the outer layer outlet at a first position in the extrusion direction, and extruding the inner layer material from the inner layer outlet at a second position downstream of the first position.

5. an outer layer die having a through hole extending in the axial direction and the outer layer discharge port; the inner layer die having the inner layer discharge port; Equipped with 5. The apparatus for manufacturing a coated tube according to claim 4, wherein the inner layer die can be positioned in the through hole of the outer layer die so that the inner layer outlet of the inner layer die is located downstream in the extrusion direction from the outer layer outlet of the outer layer die, and so that a gap is formed between the outer peripheral surface of the inner layer die and the inner peripheral surface of the outer layer die.

6. A cladding tube, a corrugated outer layer formed from an outer layer material and having peaks and valleys alternately provided in the axial direction; an inner layer formed from an inner layer material and having a large number of bubbles formed therein; Equipped with an outer periphery of the valley portion of the outer layer contains the outer layer material but does not contain the inner layer material; a cladding pipe in which a joint portion is formed between the valley portion of the outer layer and the inner layer, the joint portion including the outer layer material and the inner layer material, and the outer layer and the inner layer are fused together.

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