JP2024027304A - Composite pipe and its manufacturing method - Google Patents

Abstract

An object of the present invention is to provide a method for manufacturing a composite pipe in which flapping noise is less likely to occur. A method for manufacturing a composite tube 1 in which a flexible inner tube 9 is covered with a flexible corrugated tube 10 in which large diameter portions 11 and small diameter portions 12 are alternately formed in the tube axis direction. The inner tube 9 prepared in advance has a peelable buffer layer laminated on its outer periphery as a first coating, and this is sent out from the inner tube outlet 31c of the extrusion nozzle 31 to the corrugated tube forming section 32 to form a corrugated tube. 10 is supplied to the extrusion nozzle 31, the resin is made into a tube through the extrusion port 31d, and extruded to the corrugated tube forming section 32, and the corrugated tube forming section 32 molds the tubular resin into a corrugated cross section while expanding its diameter. At the same time as the molding, forming holding protrusions 13 distributed in the tube axis direction and circumferential direction on the inner peripheral surface of the corrugated tube 10, and bringing the holding protrusions 13 into contact with the peelable buffer layer on the outer periphery of the inner tube 9. This holds the inner tube 9 coaxially with the corrugated tube 10. [Selection diagram] Figure 3

Description

The present invention relates to a composite tube in which an inner tube is coated with a coating layer and a method for manufacturing the same, and more particularly to a composite tube in which a corrugated tube is used as a coating layer and a method for manufacturing the same.

For example, flexible pipes for water supply and hot water supply have a soft surface, so composite pipes with a coating layer are widely used. Composite pipes with a foamed resin coating layer are gaining popularity in the market because they are inexpensive, fit well, and are relatively resistant to scratches at corners. In addition, we have designed this composite pipe to make it slippery and less likely to get caught in corners, to improve its heat retention, to make the slack and wrinkles that occur on the inside of raw bends less noticeable, and to make it easier to connect joints. There is also a request to further improve the exposure of the inner tube.

The above requirements can be met by using a corrugated tube (corrugated tube) in which large diameter portions and small diameter portions are alternately formed in the tube axis direction as the coating layer.

Patent Document 1 proposes a manufacturing method in which a corrugated tube is molded while passing through an inner tube, and the inner tube is covered with the corrugated tube by coextruding a plurality of tubular coating layers each made of a resin material. It is said that this is done by However, this method is limited to a forming method that focuses on preventing the inner tube and the coating layer from adhering to each other, and does not lead to quality improvements such as suppressing the deflection of the tube due to water hammer, for example.

Patent No. 6706158

In the composite pipe manufactured by the method proposed in Patent Document 1, there is a gap between the inner pipe and the corrugated pipe, so there is a problem that flapping noise due to water hammer is likely to occur.

The present invention has been made in view of the above problems, and an object thereof is to provide a composite pipe in which flapping noise is less likely to occur and a method for manufacturing the same.

In order to solve the above problems, the method of the present invention manufactures a composite tube in which a flexible inner tube is covered with a flexible corrugated tube in which large diameter portions and small diameter portions are alternately formed in the tube axis direction. In this method, a corrugated tube is provided with an inner tube holding protrusion to suppress flapping of the inner tube due to water hammer. Furthermore, a cylindrical buffer layer is provided that bridges the part where there is no protrusion between the holding protrusions, and this combination prevents the corrugated pipe from sticking and reduces the flapping sound caused by water hammer (hereinafter referred to as "water hammer sound"). ) can be effectively suppressed.

The inner tube prepared in advance has a peelable buffer layer laminated on the outer periphery of the flexible inner tube as a first coating, and is sent to the corrugated tube forming section from the inner tube outlet in the center of the extrusion nozzle. , Supplying the resin that will become the corrugated tube to the extrusion nozzle so that it is foamed at a predetermined expansion ratio, and forming the resin into a tube through an annular extrusion port surrounding the inner tube outlet of the extrusion nozzle. extruded into a corrugated tube forming section, the tubular resin is expanded in diameter by the corrugated tube forming section and formed into the corrugated cross section, and simultaneously with the forming, the resin is distributed in the tube axis direction and the circumferential direction on the inner circumferential surface of the corrugated tube. The inner tube is held coaxially with respect to the corrugated tube by forming a retaining convex portion and bringing the retaining convex portion into contact with an outer peripheral surface buffer layer of the inner tube. In addition, the buffer layer may be provided with a plurality of protrusions in the circumferential direction on its inner diameter side, and the protrusions may extend in the longitudinal direction.

A gap is formed between the inner circumferential surface of the tubular resin and the outer circumferential surface of the inner tube during extrusion. Furthermore, the gap tends to further widen due to diameter expansion during molding into a wave-shaped cross section. Taking such a gap into consideration, the foaming ratio of the resin, the amount of protrusion of the holding convex portion toward the inside of the tube, etc. are adjusted. Thereby, the holding convex portion can be brought into contact with the inner tube, and the inner tube can be held coaxially with the corrugated tube at least during molding.

In the composite tube formed in this manner, displacement of the inner tube in the tube diameter direction can be suppressed by the holding convex portion. Furthermore, since the buffer layer gently bridges between the holding convex parts, even if the internal pressure suddenly changes when the composite pipe is in service, it can suppress the fluttering of the inner pipe and suppress the occurrence of water hammer noise. be able to.

It is preferable that the expansion ratio is 1.05 times to 4 times. This reduces the rigidity of the resin on the contact surface, thereby making it possible to further reduce the generated noise.

In the manufacturing method, it is preferable that at least a portion of the holding convex portion be formed in the small diameter portion. The small diameter portion itself may constitute the holding convex portion. A holding convex portion may protrude toward the inside of the tube from the small diameter portion.

In the manufacturing method, it is preferable that at least a portion of the holding convex portion be formed in an annular shape extending in the circumferential direction of the corrugated tube.

In the manufacturing method, it is preferable that at least some of the holding protrusions are formed at intervals in the circumferential direction of the corrugated tube.

In the manufacturing method, it is preferable that at least a portion of the holding convex portion be formed to extend along the tube axis direction.

It is preferable that the holding protrusion forming part includes a holding mold part provided on the small diameter mold surface part. This allows the holding convex portion to be formed in the small diameter portion of the corrugated tube.

A holding mold part may be provided on each small diameter mold surface part (all small diameter mold surface parts) of the corrugated tube forming part, or a holding mold part may be provided only on some (for example, every other small diameter mold surface part) of the small diameter mold surface part. You can. Further, the holding convex portion may extend beyond the small diameter portion and extend over the large diameter portion.

It is preferable that the holding mold part has an annular shape extending in the circumferential direction of the small diameter mold surface part. Thereby, it is possible to form an annular holding convex portion extending in the circumferential direction of the small diameter portion of the corrugated tube.

The holding mold part may have a closed annular shape covering the entire circumference of the corrugated tube, or may have an open annular shape with a part cut out in the circumferential direction.

It is preferable that the holding mold parts are provided at a plurality of positions spaced apart in the circumferential direction of the small diameter mold surface part. That is, a plurality of holding mold parts may be arranged at intervals in the circumferential direction of the small diameter mold surface part. Thereby, a plurality of holding convex portions can be formed at intervals in the circumferential direction of the small diameter portion of the corrugated tube.

It is preferable that the holding protrusion forming part includes a holding mold part extending in the extrusion direction. Thereby, a holding convex portion extending in the tube axis direction of the corrugated tube can be formed.

Preferably, the holding convex portion and the buffer layer forming portion include a notched recess formed at the inner peripheral edge of the annular extrusion port of the extrusion nozzle.

When extruding the resin from the extrusion port of the extrusion nozzle, a portion of the resin enters the notch recess. As a result, protrusions corresponding to the notch recesses are formed on the inner circumferential surface of the extruded tubular resin. Subsequently, by molding the resin into a corrugated tube in a corrugated tube molding section, vertical striped holding convex portions derived from the convex stripes are formed on the inner circumferential surface of the corrugated tube. The vertical stripes may be provided only on the holding protrusion, only on the buffer layer, or on both the holding protrusion and the buffer layer.

The composite tube according to the present invention includes a flexible corrugated tube in which large diameter portions and small diameter portions are alternately formed in the tube axis direction, a flexible inner tube covered by the corrugated tube, and a flexible corrugated tube. a peelable buffer layer on the outer circumference of the inner tube, the corrugated tube being made of foamed resin, and the inner circumferential surface of the corrugated tube being in contact with the outer circumferential surface of the inner tube. The holding convex portions are formed so as to be distributed in the tube axis direction and the circumferential direction, and the inner tube is restrained in the tube radial direction with respect to the corrugated tube by the holding convex portions.

According to the composite pipe, even if the internal pressure or the like suddenly changes, the fluttering of the inner pipe can be suppressed by the restraint by the holding convex portion. As a result, the occurrence of water hammer sounds and the like can be suppressed.

Preferably, the composite tube is manufactured by the manufacturing method described above. The corrugated pipe does not necessarily need to have a uniform foaming state as long as the foaming ratio is in the range of 1.05 to 4.0 according to method A (underwater displacement method) of JIS K7112, but it is preferable to have a non-foamed resin layer. It is more preferably composed of a single layer of foamed resin.

Preferably, at least a portion of the holding convex portion is provided in the small diameter portion.

The holding protrusions may be provided on each small diameter portion (all small diameter portions) of the corrugated tube, or the holding protrusions may be provided only on some (for example, every predetermined) small diameter portions.

It is preferable that at least a portion of the holding convex portion has an annular shape extending in the circumferential direction of the corrugated tube.

The holding convex portion may have a closed annular shape covering the entire circumference of the corrugated tube, or may have an open annular shape with a portion cut out in the circumferential direction.

It is preferable that at least some of the holding protrusions are arranged at intervals in the circumferential direction of the corrugated tube. Thereby, the inner tube can be held from multiple locations in the circumferential direction.

It is preferable that at least a portion of the holding convex portion extends along the tube axis direction.

The apex portion of the holding convex portion extending in the tube axis direction, which faces inside the tube, may have a wave shape that follows the cross section of the corrugated tube in the tube axis direction. It may be arranged at a constant height and extend straight in the tube axis direction.

According to the present invention, even if there is a sudden change in the internal pressure of the inner tube in the composite tube, it is possible to suppress the fluttering of the inner tube and prevent the occurrence of fluttering noise.

(a) is a front view showing a part of the composite pipe according to the first embodiment of the present invention in cross section along the tube axis direction, and (b) is a sectional view taken along the line Ib-Ib of (a). (a) is a plan view showing an example of a composite pipe manufacturing device, and (b) is a plan view showing another example of the composite pipe manufacturing device. FIG. 3 is an enlarged sectional view of part III in FIG. 2(a). 4 is a sectional view taken along the line IV-IV in FIG. 3. FIG. FIG. 3 is a cross-sectional view along the tube axis direction showing a modified form of the composite tube according to the first embodiment of the present invention. FIG. 7 is a sectional view along the tube axis direction showing another modification of the composite tube according to the first embodiment of the present invention. (a) is a sectional view orthogonal to the tube axis direction showing another modified form of the composite pipe according to the first embodiment of the present invention, (b) is a sectional view showing another modified form of the composite pipe in the pipe axial direction FIG. (a) is a front view showing a composite pipe according to the second embodiment of the present invention, partially in cross section along line VIIIa-VIIIa in FIG. FIG. 3 is a cross-sectional view taken along line VIIIb-VIIIb. 11 is a cross-sectional view showing a pair of corrugating molds in the composite pipe manufacturing apparatus along line IX-IX in FIG. 10. FIG. 9 is a sectional view taken along line XX in FIG. 9. FIG. (a) is a cross-sectional view along the tube axis direction showing a modified form of the composite pipe according to the second embodiment of the present invention, and (b) is a cross-sectional view along the pipe axis direction showing another modified form of the composite pipe. It is a diagram. (a) is a front view showing another modification of the composite pipe according to the second embodiment of the present invention, partially in cross section along the line XIIa-XIIa in FIG. 12(b); FIG. 3 is a cross-sectional view taken along line XIIb-XIIb in (a). FIG. 13 is a cross-sectional view perpendicular to the axis of a pair of corrugating molds in the composite pipe manufacturing apparatus of FIG. 12; (a) is a cross-sectional view along the tube axis direction showing another modified form of the composite pipe, and (b) is a cross-sectional view along the pipe axis direction showing another modified form of the composite pipe. (a) is a sectional view perpendicular to the tube axis showing another modified form of the composite pipe according to the second embodiment of the present invention; (b) is a sectional view perpendicular to the pipe axis showing another modified form of the composite pipe. FIG. (a) is a front view showing another modification of the composite pipe according to the second embodiment of the present invention, (b) is a cross-sectional view taken along line bb in FIG. 16(a), and (c) is FIG. (a) is a sectional view taken along line cc, (d) is a sectional view taken along line dd in FIG. 16(a), and (e) is a sectional view taken along line ee in FIG. 16(a). , (f) is a sectional view taken along line ff in FIG. 16(a). (a) is a sectional view orthogonal to the tube axis showing another modified form of the composite pipe according to the second embodiment of the present invention; (b) is a sectional view orthogonal to the pipe axis showing another modified form of the composite pipe. (c) is a cross-sectional view orthogonal to the tube axis, showing another modification of the composite tube. (a) is a sectional view perpendicular to the tube axis showing another modified form of the composite pipe according to the second embodiment of the present invention; (b) is a sectional view perpendicular to the pipe axis showing another modified form of the composite pipe. (c) is a cross-sectional view orthogonal to the tube axis, showing another modification of the composite tube. It is a front view showing a composite pipe according to a third embodiment of the present invention, with a portion thereof being in cross section. 20 is a sectional view taken along line XX-XX in FIG. 19. FIG. FIG. 23 is a sectional view taken along line XXI-XXI in FIG. 22 showing a pair of corrugated molds in the composite pipe manufacturing apparatus. 22 is a sectional view taken along line XXII-XXII in FIG. 21. FIG. FIG. 7 is a front view showing a modified form of a composite pipe according to a third embodiment of the present invention, with a portion thereof being in cross section. 24 is a sectional view taken along line XXIV-XXIV in FIG. 23. FIG. 26(a) is a cross-sectional view taken along the line XXV-XXV in FIG. 26(a), showing a pair of corrugated molds in a composite pipe manufacturing apparatus according to a modified example (FIG. 23) of the third embodiment of the present invention. FIG. (a) is a sectional view taken along line XXVIa-XXVIa in FIG. 25, and (b) is a sectional view taken along line XXVIb-XXVIb in FIG. 25. FIG. 29 is a front view showing a composite pipe according to a fourth embodiment of the present invention, partially in cross section along line XXVII-XXVII in FIG. 28; 28 is a sectional view taken along line XXVIII-XXVIII in FIG. 27. FIG. FIG. 7 is a cross-sectional view perpendicular to the axis showing an extrusion nozzle in a composite pipe manufacturing apparatus according to a fourth embodiment of the present invention. 30 is a sectional view taken along the XXX-XXX line in FIG. 29 showing a state in which the resin and the inner tube are extruded from the extrusion nozzle. FIG.

Embodiments of the present invention will be described below with reference to the drawings.
<First embodiment (FIGS. 1 to 4)>
FIGS. 1A and 1B show a composite pipe 1 according to a first embodiment of the present invention, and this composite pipe 1 is used, for example, as a pipe for water supply and hot water supply. This composite pipe 1 includes an inner pipe 9 as a pipe body and a corrugated pipe (corrugated pipe) 10 as a coating layer, and the outer peripheral surface of the main body of the inner pipe 9 is not in close contact with the inner pipe 9. A removable buffer layer (not shown) is laminated thereon.

The inner tube 9 has a constant annular cross section over its entire length, and is made of an elastomer or a thermoplastic resin such as polyethylene (PE) or polypropylene (PP), which is flexible and can be peeled off. A buffer layer 9' is laminated on the outer peripheral surface of the main body.

Examples of the material for the inner tube 9 include crosslinked polyethylene (PE-X), polyethylene (PE), high heat resistant polyethylene (PE-RT), polybutene, polypropylene (PP), and other synthetic resins. Further, the inner tube 9 may be a cross-linked polyethylene tube (JIS K6769 class E) having a polyethylene layer on its outer skin, or may be a composite resin tube containing metal such as a metal-reinforced multilayer structure. As for the material of the inner tube 9, the above is just an example, and there is no particular restriction as long as it can ensure required performance such as flexibility and fluid circulation.

Furthermore, the material of the buffer layer is not particularly limited as long as it can ensure required performance such as flexibility and releasability.

The inside of the inner tube 9 serves as a fluid passage through which fluid such as water or hot water passes, and the outer periphery of the buffer layer 9' of the inner tube 9 is covered with a corrugated tube 10.

The corrugated tube 10 has a large diameter portion 11 and a small diameter portion 12, and has a corrugated cross section, and the large diameter portions 11 and the small diameter portions 12 are arranged alternately at a constant pitch in the tube axis direction. Here, the large diameter portion 11 is an annular convex portion (mountain portion) when viewed from the outside of the corrugated tube 10, and is an annular concave portion when viewed from the inside. The small diameter portion 12 is an annular concave portion (trough) when viewed from the outside of the corrugated tube 10, and is an annular convex portion when viewed from the inside.

The corrugated tube 10 is made of flexible foamed resin, and resin materials for the corrugated tube 10 include cross-linked polyethylene (PE-X), polyethylene (PE), and high heat-resistant polyethylene (PE-RT). ), polybutene, polypropylene (PP), thermoplastic elastomer, thermosetting elastomer, plastomer, and other synthetic resins, and may be a composite resin including not only a single material but a plurality of materials. Note that the above is an example of the material of the corrugated tube 10, and there is no particular restriction on the material of the corrugated tube 10 as long as it can ensure required performance such as flexibility and protection for the inner tube 9.

The corrugated tube 10 does not have a non-foamed resin layer and is composed of a single layer of foamed resin. As the foaming agent for the corrugated tube 10, for example, an inorganic chemical foaming agent or foaming microcapsules is used, but the present invention is not limited to these, and physical foaming agents such as fluorocarbons or supercritical fluids may be used. Also, the foaming ratio is adjusted by the blending ratio of the foaming agent. The foaming ratio of the foamed resin constituting the corrugated tube 10 is preferably 1.05 times to 4 times, more preferably 1.2 times to 3 times.

The foaming agent functions to lower the specific gravity of the resin and thus the corrugated tube 10 by foaming. The expansion ratio can be determined from the ratio of the specific gravity of the non-foamed material to the specific gravity of the foamed material. The specific gravity may be measured using, for example, method A (underwater displacement method) of JIS K7112.

An inner tube 9 on which a buffer layer is laminated is inserted into the corrugated tube 10. Preferably, the inner tube 9 and the corrugated tube 10 are arranged substantially coaxially.

The inner circumferential surface portion (the end protruding toward the inside of the tube) of the small diameter portion 12 is in contact with the outer circumferential surface of the inner tube 9 over the entire circumference. The inner circumferential surface of the small diameter portion 12 constitutes an annular holding convex portion 13 that holds the inner tube 9 .

In other words, the holding protrusion 13 is formed on the inner peripheral surface of the corrugated pipe 10, and the holding protrusion 13 restrains the inner pipe 9 from being displaced in the pipe radial direction relative to the corrugated pipe 10. . Preferably, the holding protrusion 13 holds the inner tube 9 coaxially with the corrugated tube 10.

The annular holding convex portions 13 are arranged for each small diameter portion 12 and are distributed in the tube axis direction and the circumferential direction on the inner circumferential surface of the corrugated tube 10 . Specifically, the annular holding protrusions 13 are distributed in the axial direction of the corrugated tube 10 at the same arrangement pitch as the small diameter portions 12, and are also distributed over the entire circumference of the corrugated tube 10 to form a closed annular shape. ing.

FIG. 2 shows an apparatus 3 for manufacturing the composite pipe 1. As shown in FIG. This manufacturing device 3 includes a foamed resin supply section 30, an extrusion nozzle 31, and a corrugated tube forming section 32.

Although detailed illustrations are omitted, the foamed resin supply section 30 includes a hopper that receives the resin 19 that is the raw material for the corrugated tube 10, a heater that heats and melts the resin 19, a foaming agent addition section, and a foaming agent adding section that kneads the resin 19 and the foaming agent. It consists of a cylinder and a screw for extruding. Here, a foaming agent may be included in the raw resin 19 before being introduced into the hopper.

As shown in FIG. 2(a), the foamed resin supply section 30 and the extrusion nozzle 31 may constitute a crosshead die, or as shown in FIG. 2(b), they may constitute an offset die. good.

As shown in FIGS. 3 and 4, the extrusion nozzle 31 has a double cylinder structure including an outer cylinder 31a and an inner cylinder 31b. The center hole of the inner tube 31b constitutes an inner tube outlet 31c. Note that the diameter of the inner tube outlet 31c is approximately equal to the outer diameter of the inner tube 9.

The annular space between the outer tube 31a and the inner tube 31b constitutes an extrusion port 31d for the resin 19, and the extrusion port 31d has an annular shape and surrounds the inner tube outlet 31c.

The thickness t31b (the difference between the inner radius of the extrusion port 31d and the radius of the inner tube outlet 31c) at least at the tip of the inner tube 31b is, for example, approximately t31b=0.5 mm to 2 mm. It is not limited.

As shown in FIGS. 2 and 3, a corrugated tube forming section (corrugator) 32 is disposed downstream of the extrusion nozzle 31 in the extrusion direction (on the right side in FIG. 2). The corrugated tube forming section 32 includes two oval annular tracks 32a, 32b and a large number of half-cylindrical corrugating molds 33a, 33b. The two annular orbits 32a and 32b are arranged in parallel so as to touch on an axis L33 that is an extension of the axis (extrusion direction) of the extrusion nozzle 31.

First corrugation molds 33a are arranged in an annular manner on the first annular orbit 32a, and second corrugation molds 33b are arranged in an annular manner on the second annular orbit 32b. These corrugation molds 33a, 33b move in synchronization with each other so as to circulate along the corresponding annular orbits 32a, 32b. During a period in which the corrugating molds 33a and 33b forming the pair of the two annular orbits 32a and 32b move in parallel along the axis L33, they come together to form a closed cylindrical corrugating mold pair 33. A plurality of corrugated mold pairs 33 are arranged in a line on the axis L33.

A large-diameter mold surface portion 34 and a small-diameter mold surface portion 35 are formed on the inner peripheral surface (mold surface) of each of the corrugated molds 33a, 33b and the corrugated mold pair 33. The large diameter mold surface portion 34 is concave to the outside in the radial direction and has a concave annular shape extending over the entire circumference of the corrugated mold pair 33, and forms the large diameter portion 11. Among the mold face parts 34 and 35, a small suction hole 36 is opened particularly in the large diameter mold face part 34.

The small-diameter mold surface portion 35 protrudes toward the inside of the tube and has a convex annular shape covering the entire circumference of the corrugated mold pair 33, and forms the small-diameter portion 12. The protruding end portion of each small-diameter mold surface portion 35 toward the inside of the tube constitutes a holding mold portion (holding projection forming portion) 37 for forming the annular holding projection 13 . In short, the holding mold part 37 is provided on the inner peripheral surface (mold surface) of the corrugated tube forming part 32. This holding mold part 37 has a closed ring shape extending all the way around the inner peripheral surface in the circumferential direction.

The composite pipe 1 is manufactured as follows.

That is, the inner tube 9 is prepared in advance by being molded and hardened or obtained. A peelable buffer layer is laminated on the outer circumference of the inner tube 9 in contact with the outer circumferential surface of the main body of the inner tube 9, and is introduced into the extrusion nozzle 31, and formed into a corrugated tube from the inner tube outlet 31c in the center. Send it to Department 32. The laminated inner tubes 9 are introduced into the corrugated mold pair 33 and sent downstream in the feeding direction (to the right in FIG. 2).

In parallel, in the foamed resin supply section 30, the resin 19 is heated and melted and a foaming agent of a predetermined blending ratio is added so that the resin 19 is foamed at a predetermined expansion ratio (preferably 1.05 times to 4 times). After this, the resin 19 is supplied to the extrusion nozzle 31. Inside the extrusion nozzle 31, the resin 19 has not yet started foaming due to the high pressure.

The resin 19 is extruded from the extrusion port 31d of the extrusion nozzle 31 toward the corrugated tube forming section 32. Since the pressure applied to the resin 19 is reduced by extruding the resin 19, foaming starts immediately after extrusion.

The resin 19A during extrusion has a tubular shape with substantially the same inner and outer diameters as the extrusion port 31d. The tubular resin 19A serves as a covering layer surrounding the laminated inner tube 9. A gap d corresponding to the thickness t31b of the inner tube 31b is formed between the inner circumferential surface of the tubular resin 19A and the outer circumferential surface of the laminated inner tube 9. The thickness of the resin 19A during extrusion is, for example, 0.5 mm to 2 mm, but is not limited thereto.

The tubular resin 19A is introduced into a pair of corrugating molds 33 that are aligned in a row on the axis L33 of the corrugated tube molding section 32. The outer circumferential surface of the tubular resin 19A immediately after introduction is away from the corrugation mold pair 33.

Subsequently, vacuum is applied from the suction hole 36 of the corrugated tube forming section 32. As a result, the diameter of the tubular tree 19A is expanded and brought into close contact with the mold surfaces 34 and 35 of the corrugated mold pair 33, forming the corrugated pipe 10 with a corrugated cross section. The corrugated tube 10 covers the inner tube 9 covered with a buffer layer.

Simultaneously with the molding, the annular holding convex portion 13 that is integrated with the small diameter portion 12 is formed by the holding mold portion 37 that is integrated with the small diameter mold surface portion 35 . Then, the thickness of the corrugated pipe 10 increases due to the foaming of the resin 19A. As a result, the annular holding protrusion 13 comes into contact with the outer peripheral surface of the inner tube 9 on which the buffer layer is laminated. Conversely, the expansion ratio of the resin 19 and the amount of protrusion of the holding mold part 37 to the inside of the pipe are adjusted so that the annular holding convex part 13 of the corrugated pipe 10 after foam molding comes into contact with the inner pipe 9 on which the buffer layer is laminated. is adjusted.

The annular holding convex portion 13 does not necessarily need to come into contact with the laminated inner tube 9, and in order to practically effectively suppress water hammer sound, 1) the corrugated tube 10 should be made of foamed LDPE, etc. 2) the size of the gap d between the inner tube 9 on which the buffer layer is laminated and the corrugated tube 10, and 3) the spacing between the holding protrusions 13.

For example, in the case of a 1.2 times foamed product of LDPE with a wall thickness of 0.5 mm, the difference between the inner diameter of the tip of the holding protrusion 13 and the outer diameter of the surface of the inner tube 9 on which the buffer layer is laminated is 1 mm, and the holding protrusion 13 It has been confirmed that the generated sound can be effectively suppressed even when the distance is between 66 mm and 198 mm. The present buffer layer is suitable because it has the effect of suppressing the fluttering of sound generation.

As a result, the inner tube 9 laminated with the buffer layer 9' is held by the holding convex portion 13 and restrained with respect to the corrugated tube forming portion 32 in the tube radial direction. Further, since the buffer layer bridges between the holding convex portions 13 and covers the outer surface of the inner tube 9, displacement of the inner tube 9 in the tube diameter direction can be further suppressed.

In addition, regarding the composite pipe 1 formed in this way, since the corrugated pipe 10 is formed on the outer periphery of the inner pipe 9 on which the buffer layer prepared in advance is laminated, one part of the inner peripheral surface of the corrugated pipe 10 is The shape of the buffer layer 9' on the outer circumferential surface of the inner tube 9 is transferred to the part (specifically, the holding mold part 37), and traces of molding can be seen on the buffer layer. Thereby, the molding method can be specified.

The composite pipe 1 produced in this manner is used, for example, as a pipe for supplying hot water and water, and a fluid such as water or hot water passes through the inner pipe 9 on which a buffer layer is laminated. Here, the pressure, flow rate, temperature, etc. of the fluid may change suddenly depending on the usage conditions, but since the inner tube 9 on which the buffer is laminated is restrained by the holding protrusion 13, the pressure, flow rate, temperature, etc. of the fluid may change suddenly. Even if a sudden change occurs, the fluttering of the inner tube 9 on which the buffer layer is laminated can be suppressed, and water hammer noise can be prevented from occurring.

Furthermore, since the foamed resin constituting the corrugated tube 10 absorbs impact, water hammer noise can be more reliably prevented from occurring. Furthermore, since the corrugated tube 10 is made of only a single layer of foamed resin and does not have a non-foamed surface layer, its rigidity is suppressed and its flexibility can be improved. Furthermore, since the corrugated tube 10 is made thicker by foaming, it can ensure tear resistance against dragging and the like equivalent to that of a tube having a non-foamed surface layer.

By using the corrugated pipe 10 with a corrugated cross section as the covering layer of the inner pipe 9 on which the buffer layer is laminated, even if the composite pipe 1 gets caught in an angular obstacle during piping construction, it will easily slip and the stuck state will be easily released. .

Since an air heat insulating layer is formed between at least the inner circumferential surface of the large diameter portion 11 of the corrugated tube 10 and the outer circumferential surface of the inner tube 9 on which the buffer layer is laminated, heat retention is enhanced. When the composite pipe 1 is bent, the slack and wrinkles generated on the inner circumference become less noticeable. When connecting a joint, by sliding the corrugated pipe 10, which is a coating layer, in the pipe axial direction against the inner pipe 9 on which a buffer layer is laminated, the laminated inner pipe 9 to be connected can be exposed and the connection work can be performed. can.

It is assumed that the buffer layer on the outer surface of the inner tube 9 on which the buffer layer is laminated will shrink while forming folds when the inner tube of the corrugated tube 10 is exposed.

If this is not possible, it may be possible to shrink the buffer layer in the tube axis direction following the corrugated tube 10 to expose the inner tube 9. In addition, if the material cannot be followed, other than the shrinking method, methods such as rolling it up, flipping it over, or splitting it open may be used.

Next, other embodiments of the present invention will be described. In addition, regarding the structure which overlaps with the already-mentioned form in the following embodiment, the same code|symbol is attached to drawing and description is omitted.
<Modification (1) of the first embodiment (annular holding convex portion)>
As shown in FIG. 5, the holding protrusion 13 may be provided only in some small diameter portions 12A of the corrugated tube 10 of the first embodiment having the annular holding protrusion 13. For example, several small-diameter portions 12A in the tube axis direction (horizontal direction in FIG. 5) protrude more toward the inside of the tube than other small-diameter portions 12, and come into contact with the outer circumferential surface of the inner tube 9 on which the buffer layer is laminated. The holding convex portion 13 may also be formed by this.

In FIG. 5, every two small diameter portions 12A constitute the holding convex portion 13; however, the holding convex portion 13 is not limited to this. You can.

As shown by the two-dot chain line in FIG. 5, in the composite pipe manufacturing apparatus, the mold surfaces of the inner peripheries of the corrugated molds 33a and 33b are formed to correspond to the desired shape of the corrugated pipe 10. In particular, the small-diameter mold surface portions 35 and the holding mold portions 37 corresponding to the small-diameter portions 12A of the corrugated molds 33a and 33b are made to protrude from the other small-diameter mold surface portions 35. As a result, the corrugated tube 10 shown by the solid line in FIG. 5 can be manufactured.
<Modification (2) of the first embodiment (annular holding convex portion)>
The cross-sectional shape of the small diameter portion 12 constituting the holding convex portion 13 may be changed as appropriate. In FIGS. 1 and 5, the valley portion facing the inside of the tube has a flat trapezoidal shape, but as shown in FIG. It may have a circular cross section.

As shown by the two-dot chain line in FIG. 6, in the composite pipe manufacturing apparatus, the small diameter mold surface portion 35 corresponding to the small diameter portion 12B of the corrugated molds 33a, 33b extends to the top of the holding mold portion 37 facing inside the tube. is formed into a rounded semicircular cross section. As a result, the corrugated tube 10 shown in solid line in FIG. 6 can be manufactured.
<Modification (3) of the first embodiment (annular holding convex portion)>
The holding protrusion 13 does not necessarily have to have a closed ring shape that extends around the entire circumference of the corrugated tube 10. That is, as shown in FIG. 7(a), the annular holding convex portion 13 may be annular with only one portion 13c missing in the circumferential direction. As shown in FIG. 7(b), the annular holding convex portion 13 may have an annular shape with two portions 13c and 13c chipped in the circumferential direction. Although not shown, the annular holding convex portion 13 may have an annular shape with three or more holes in the circumferential direction.

The two-dot chain line in FIGS. 7(a) and 7(b) hypothetically shows the small diameter portion 12 when the holding convex portion 13 is not formed. In a portion other than the chipped portion 13c, the annular holding convex portion 13 protrudes further toward the inside of the tube than the imaginary small diameter portion 12.

Although not shown in the drawings, in the composite pipe manufacturing apparatus, the holding mold portions 37 of the corrugating molds 33a and 33b are formed into an annular shape with only one portion missing in the circumferential direction. As a result, the corrugated tube 10 shown in solid lines in FIGS. 7(a) and 7(b) can be manufactured.

In variant form (3), the missing portion of the annular holding convex portion 13 does not need to be at a fixed position in the circumferential direction of the corrugated tube 10, but is located at an annular holding convex portion adjacent to the tube axis direction (direction perpendicular to the paper plane in FIG. 7). The missing portions of the convex portions 13 may be shifted from each other in the circumferential direction.
<Second embodiment (discrete holding convex portions, FIGS. 8 to 10)>
FIGS. 8(a) and 8(b) show a composite pipe 1B according to a second embodiment of the present invention. In the corrugated tube 10B of the composite tube 1B, each small diameter portion 12 is provided with a plurality of discrete holding convex portions 14. A plurality of discrete holding convex portions 14 are arranged at predetermined intervals in the circumferential direction of the small diameter portion 12. Here, four discrete holding protrusions 14 are provided at angular intervals of 90° in the circumferential direction, and each discrete holding protrusion 14 projects from the small diameter portion 12 toward the inside of the tube. Preferably, the shape and arrangement of the discrete holding protrusions 14 are set to avoid undercuts in order to facilitate die cutting (the same applies to the following variants).

The width dimension W14 of the discrete holding convex portions 14 along the tube axis direction of the corrugated tube 10B is smaller than the width dimension of the small diameter portion 12 along the same direction. The length L14 of the discrete holding protrusions 14 along the circumferential direction of the corrugated tube 10B is smaller than one quarter of the circumference of the small diameter portion 12 (one divided by the number of holding protrusions 14).

As shown in FIG. 8A, when the corrugated tube 10B is viewed from the outside, grooves 15 are formed in the small diameter portion 12 where the discrete holding convex portions 14 are arranged.

As shown in FIG. 8(b), the top portion 14e (end portion inside the tube) of each discrete holding convex portion 14 is flat. This top portion 14e is in contact with the outer peripheral surface of the inner tube 9 on which the buffer layer is laminated. These discrete holding protrusions 14 restrain the inner tube 9 on which the buffer layer is laminated in the radial direction of the corrugated tube 10B. As a result, even if the internal pressure or the like suddenly changes, fluttering of the inner tube 9 is suppressed, and the generation of water hammer noise can be suppressed.

In the composite tube 1B of the second embodiment, a gap is formed not only between the large diameter portion 11 and the inner tube 9 but also between the small diameter portion 12 and the inner tube 9. Thereby, the heat retention of the composite tube 1B can be further improved.

9 and 10 show the corrugated tube forming section 32 of the composite tube manufacturing apparatus in the second embodiment. In each of the corrugating molds 33a and 33b of the corrugated tube forming section 32, a holding mold part (holding protrusion forming part) 38 is formed on the small diameter mold surface part 35. The holding mold part 38 projects from the small diameter mold surface part 35 toward the inside of the tube. As shown in FIG. 10, four holding mold parts 38 are provided at angular intervals of 90 degrees in the circumferential direction of the small diameter mold surface part 35. The shape and arrangement of the holding mold part 38 are set to avoid undercuts (the same applies to the following variations). The holding mold part 38 forms the discrete holding protrusions 14 and grooves 15 shown in FIG.
<Modification of second embodiment (discrete holding convex portion) (1)>
As shown in FIG. 11, discrete holding convex portions 14 may be provided only in some small diameter portions 12 of the corrugated tube 10B. For example, in FIG. 11(a), discrete holding convex portions 14 are provided in every small diameter portion 12 in the tube axis direction (left and right direction in the figure). In FIG. 11(b), discrete holding convex portions 14 are provided in every two small diameter portions 12. Although not shown, discrete holding convex portions 14 may be provided at every three or more small diameter portions 12.

As shown by two-dot chain lines in FIGS. 11(a) and 11(b), in the composite pipe manufacturing apparatus, the holding mold portions 38 of the corrugated molds 33a, 33b are arranged so as to correspond to the arrangement of the discrete holding convex portions 14. Form it. As a result, a corrugated tube 10B shown in solid lines in FIGS. 11(a) and 11(b) can be manufactured.
<Modification of second embodiment (discrete holding convex portion) (2)>
The length of the discrete holding convex portions 14 along the circumferential direction of the corrugated tube 10B can be set as appropriate. In the embodiment shown in FIG. 12, the circumferential length of the discrete holding convex portions 14 is shorter than in the embodiment shown in FIG. 8(a).

As shown in FIG. 13, in the composite pipe manufacturing apparatus, the holding mold portions 38 of the corrugating molds 33a, 33b are formed shorter in the circumferential direction than in FIG. As a result, the corrugated tube 10B shown in FIG. 12 can be manufactured.
<Variation of the second embodiment (3)>
As shown by two-dot chain lines in FIGS. 14(a) and 14(b), the width dimension of the holding mold part 38 of the corrugating molds 33a and 33b is set narrowly (as shown in FIG. 14(a)) or wide. ((b) in the same figure).
<Modification of second embodiment (discrete holding convex portion) (4)>
The number of discrete holding protrusions 14 arranged in the circumferential direction of the corrugated tube 10B can be set as appropriate. In the embodiment shown in FIG. 15(a), three discrete holding convex portions 14 are arranged at intervals of 120° in the circumferential direction. In the embodiment shown in FIG. 15(b), eight discrete holding convex portions 14 are arranged at intervals of 45° in the circumferential direction.
<Modification of second embodiment (discrete holding convex portion) (5)>
In the embodiment shown in FIG. 16, the arrangement angle of the discrete holding convex portions 14 changes depending on the position of the corrugated tube 10B in the tube axis direction. Specifically, in FIG. 16, for example, three discrete holding convex portions 14 are arranged at 120° intervals per one small diameter portion 12, and as shown in FIG. Each time the small diameter portion 12 is successively traced, the arrangement angle of the discrete holding convex portions 14 is rotated, for example, by 30 degrees. The arrangement of the discrete holding convex portions 14 of four (n) adjacent small diameter portions 12 is the same. As a result, when the composite pipe 1B is green bent, the bending resistance can be prevented from greatly varying depending on the direction of bending, and high piping workability can be ensured.

In the composite pipe manufacturing apparatus of this aspect, it is preferable that the number of small diameter mold surface parts 35 of each corrugated mold 33a, 33b is a multiple of n (=4) (for example, 8 pieces in FIG. 16). By doing so, the corrugating molds 33a and 33b can be arranged along the annular orbits 32a and 32b without considering the order of arrangement.

The angle of deviation between the discrete holding convex portions 14 adjacent to each other in the tube axis direction can be set as appropriate. Preferably, in order to avoid undercutting, the shapes of the discrete holding protrusions 14 differ depending on the arrangement angle. The number of discrete holding convex portions 14 may be different for each small diameter portion 12. Further, the arrangement pattern of the discrete holding convex portions 14 does not necessarily have to be regular, and may be random.
<Modification of second embodiment (discrete holding convex portion) (5)>
The cross-sectional shape of the discrete holding convex portions 14 can be modified as appropriate.

In the embodiment of FIG. 17, the discrete holding protrusions 14 have a bifurcated cross-sectional shape with bulges 19b on both sides. The top portion 14e is in surface contact with the inner tube 9 by following the outer peripheral surface of the inner tube 9 on which the buffer layer is laminated.

In FIG. 17(a), three bifurcated discrete holding convex portions 14 are arranged at intervals of 120° in the circumferential direction of the corrugated tube 10B.

In FIG. 17(b), four bifurcated discrete holding convex portions 14 are arranged at 90° intervals in the circumferential direction of the corrugated tube 10B.

In FIG. 17(c), eight bifurcated discrete holding protrusions 14 are arranged at 45° intervals in the circumferential direction of the corrugated tube 10B.

In the embodiment shown in FIG. 18, the discrete holding protrusions 14 have a tapered protrusion shape toward the inner side of the tube, and the top portions 14e are in contact with the laminated inner tube 9 in a substantially point-like manner.

In FIG. 18(a), three protruding discrete holding convex portions 14 are arranged at intervals of 120° in the circumferential direction of the corrugated tube 10B.

In FIG. 18(b), four protruding discrete holding convex portions 14 are arranged at 90° intervals in the circumferential direction of the corrugated tube 10B.

In FIG. 18(c), eight protruding discrete holding convex portions 14 are arranged at 45° intervals in the circumferential direction of the corrugated tube 10B.

In the composite pipe manufacturing apparatus, the holding mold portions 38 of the corrugating molds 33a and 33b are formed in a shape corresponding to the discrete holding convex portions 14. As a result, the corrugated tube 10B shown in FIGS. 17(a) to 17(c) and FIGS. 18(a) to 18(c) can be manufactured.
<Third embodiment (vertical striped holding convex portion formed by corrugated mold, FIGS. 19 to 22)>
19 and 20 show a composite pipe 1C according to a third embodiment of the present invention. A vertically striped holding convex portion 16 is formed on the inner circumferential surface of the corrugated tube 10C in the composite tube 1C. The vertical stripe-shaped holding convex portion 16 has a vertical stripe shape extending along the tube axis direction of the corrugated tube 10C, and traverses the large diameter portion 11 and the small diameter portion 12. Four (plural) vertical stripe-like holding protrusions 16 are arranged at intervals in the circumferential direction of the inner circumferential surface of the corrugated tube 10C. Preferably, the shape and arrangement of the vertical striped holding convex portions 16 are set so as to avoid undercuts in order to facilitate die cutting (the same applies to the following modifications).

The top portion 16e of each vertical striped holding convex portion 16 facing toward the inside of the tube has a wave shape that follows the wave cross section of the corrugated tube 10C in the tube axis direction. The protruding portion of each vertically striped holding convex portion 16 from the small diameter portion 12 is in contact with the outer circumferential surface of the inner tube 9 on which the buffer layer is laminated. The inner tube 9 is restrained in the tube radial direction with respect to the corrugated tube 10C by these vertical striped holding convex portions 16. As a result, even if the internal pressure suddenly changes, it is possible to suppress the fluttering of the inner tube 9, and the generation of water hammer noise can be suppressed. Note that the number of vertical striped holding convex portions 16 in the circumferential direction can be changed as appropriate.

A vertically striped groove 17 is formed on the outer peripheral surface of the corrugated tube 10C. The grooves 17 are arranged at four (plural) circumferential positions corresponding to the vertical striped holding convex portions 16 and extend in the tube axis direction. The groove bottom of the groove 17 has a wave shape that follows the wave cross section of the corrugated tube 10C in the tube axis direction.

As shown in FIGS. 21 and 22, in the composite pipe manufacturing apparatus of the third embodiment, vertical strip-like holding mold parts 39 are formed on the mold surfaces of the inner peripheries of the corrugated molds 33a and 33b. This vertical striped holding mold part 39 longitudinally cuts through the large diameter mold surface part 34 and the small diameter mold surface part 35 and extends in the axial direction of the corrugating molds 33a and 33b (the extrusion direction of the extrusion nozzle 31), and its top part is It has a wavy shape that follows the wavy cross sections of the large-diameter surface portion 34 and the small-diameter surface portion 35.

Here, the shape and arrangement of the vertically striped holding mold part 39 are set so as to avoid undercuts (the same applies to the following modifications). The vertical striped holding mold portion 39 forms the vertical striped holding convex portion 16 and the groove 17 (FIGS. 19 and 20).

<Variations of the third embodiment (vertical striped holding convex portion)>
In the embodiments shown in FIGS. 23 and 24, the apex 16e of the vertical striped holding convex portion 16 facing inward is arranged at a constant height in the radial direction of the corrugated tube 10C and extends straight in the tube axis direction. . This top portion 16e is in contact with the outer circumferential surface of the inner tube 9 on which the buffer layer is laminated over the entire length. The groove bottom of the groove 17 is arranged at a fixed position in the tube radial direction and extends straight in the tube axis direction.

As shown in FIGS. 25, 26(a) and 26(b), the tops of the corresponding vertical striped holding mold parts 39 are arranged at a constant height in the radial direction of the corrugating molds 33a and 33b, and (in the left-right direction in FIG. 25).
<Fourth embodiment (vertical striped holding convex portion formed by extrusion nozzle, FIGS. 27 to 30)>
27 and 28 show a composite pipe 1D according to a fourth embodiment of the present invention. On the inner circumferential surface of the corrugated tube 10D in the composite tube 1D, a plurality of vertically striped holding convex portions 16D similar to those in the third embodiment (FIG. 19) are formed at equal intervals in the circumferential direction.

The apex 16e of the vertical striped holding convex portion 16D facing toward the inside of the tube has a wave shape that follows the wave cross section of the corrugated tube 10D in the tube axis direction. The protruding portion of each vertical striped holding convex portion 16D from the small diameter portion 12 is in contact with the outer circumferential surface of the inner tube 9 on which the buffer layer is laminated. Here, the groove 17 (see FIGS. 19 and 20) is not formed on the outer peripheral surface of the corrugated tube 10D.

29 and 30 show an extrusion nozzle 40 in a composite pipe manufacturing apparatus according to a fourth embodiment. The extrusion nozzle 40 includes an inner cylinder 41 and an outer cylinder 42. The center hole of the inner tube 41 constitutes the inner tube outlet 43, and the annular space between the inner tube 41 and the outer tube 42 constitutes the extrusion port 44.

A plurality of (for example, four) notched recesses (holding protrusion forming portions) 45 are formed on the outer circumferential surface of the inner cylinder 41 (inner circumferential edge of the extrusion port 44). These cutout recesses 45 are arranged at equal intervals (for example, at 90° intervals) in the circumferential direction of the inner cylinder 41. Each notch recess 45 extends in the axial direction of the inner cylinder 41 and reaches the front end surface of the inner cylinder 41 while gradually increasing in depth toward the front end surface of the inner cylinder 41 . Note that the depth of the notch recess 45 may be constant regardless of the axial position of the inner cylinder 41.

As shown in FIG. 30, when the resin 19 is extruded from the extrusion port 44 of the extrusion nozzle 40, a portion of the resin 10 enters the notch recess 45. As a result, protrusions 19d are formed on the inner peripheral surface of the extruded tubular resin 19A. This ridge 19d extends straight along the extrusion direction (tube axis direction of the tubular resin 19A). The protrusion height of the protrusion 19d has a constant size depending on the depth of the notch recess 45 on the distal end surface of the inner cylinder 41.

The tubular resin 19A including the ridges 19d is introduced into the corrugated tube forming section 32 while being foamed, and is formed into a corrugated shape. As a result, the tubular resin 19A becomes a corrugated tube 10D, and the protrusions 19d become vertically striped holding protrusions 16D (FIGS. 27 and 28).

The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit thereof. For example, the corrugated tube 10 may have both the annular holding protrusion 13 and the vertical striped holding protrusion 16, or may have both the discrete holding protrusion 14 and the vertical striped holding protrusion 16. Good too. The corrugated tube forming section 32 may be of a blow type, instead of a vacuum type, which applies pressure between the tubular resin 19A and the inner tube 9 on which the buffer layer is laminated.

Further, the holding convex portion may have a spiral shape along the circumferential direction of the inner circumferential surface of the corrugated tube and the tube axis direction. Furthermore, unique configurations of two or more embodiments (including modified versions) may be combined. For example, the holding convex portion may not face the tube core.

Moreover, the composite pipe is not limited to water supply piping, and may be used as piping for passing electric wires and the like.

An example will be explained. The invention is not limited to the following examples.

A composite tube having the cross-sectional structure shown in FIG. 15(a) was manufactured.

The resin material of the corrugated pipe of the composite pipe was high-density polyethylene (Novatec LD (registered trademark) LF244E, manufactured by Japan Polyethylene Co., Ltd.). As the foaming agent, foaming agent MB3074P manufactured by Sankyo Kasei Co., Ltd. was used.

The prepared composite pipe was inserted into one hole of a fixed three-hole hollow concrete block and pulled up, so that the surface of the composite pipe rubbed against the upper edge of the one hole. The pulling force was measured using a hand scale, and the appearance of the composite tube when pulled up with a force of 15 kgf was visually observed. No breakage on the surface (outer surface of the corrugated tube) was observed.

Separately, prepare a composite pipe with a total length of 5 m with the same structure as above, stretch the composite pipe on the floor, bend it horizontally at two points in the length direction, and vertically at one point, and stand it up. Connected to faucet. After running water at an original pressure of 0.2 MPa, the faucet was quickly closed, and no particularly loud water hammer sound was generated.

The present invention can be applied to, for example, a water supply pipe.

1, 1B, 1C, 1D Composite pipe 9 Inner pipe with a buffer layer laminated on its outer surface 10, 10B, 10C, 10D Corrugated pipe 11 Large diameter part 12 Small diameter part 12A, 12B Small diameter part (holding convex part)
13 Annular holding protrusion (holding protrusion)
14 Discrete holding protrusion (holding protrusion)
16, 16D Vertical striped holding protrusion (holding protrusion)
19 Raw material resin 19A Tubular resin during extrusion 3 Composite pipe manufacturing device 30 Foamed resin supply section 31 Extrusion nozzle 31c Inner tube outlet 31d Extrusion port 32 Corrugated tube forming section 33a, 33b Corrugated mold 33 Corrugated mold pair 34 Large Diameter mold surface part 35 Small diameter mold surface part 37, 38, 39 Holding mold part (holding protrusion forming part)
40 Extrusion nozzle 43 Inner pipe outlet 44 Extrusion port 45 Notch recess (holding protrusion forming part)

Claims (13)

A method for manufacturing a composite tube in which a flexible inner tube is covered with a flexible corrugated tube in which large diameter portions and small diameter portions are alternately formed in the tube axis direction, the method comprising:
The inner tube prepared in advance has a peelable buffer layer laminated on the outer periphery of the flexible inner tube as a first coating, and this is formed into a corrugated tube from the inner tube outlet in the center of the extrusion nozzle. Send it to the department,
supplying a resin that will become the corrugated tube to the extrusion nozzle, forming the resin into a tube from an annular extrusion port surrounding the inner tube outlet of the extrusion nozzle, and extruding the resin to the corrugated tube forming section;
molding the tubular resin into the wavy cross section while expanding the diameter of the tubular resin by the wavy tube forming section;
At the same time as the forming, holding protrusions are formed on the inner circumferential surface of the corrugated tube and are distributed in the tube axis direction and the circumferential direction, and the holding protrusions are brought into contact with a peelable buffer layer on the outer periphery of the inner tube. . A method for manufacturing a composite tube, characterized in that the inner tube is held coaxially with the corrugated tube. 2. The composite pipe according to claim 1, wherein the first coating is provided with protrusions at regular intervals along its inner circumferential direction, and the protrusions abut linearly on the outer circumferential surface of the tube body in the longitudinal direction. manufacturing method. The manufacturing of a composite pipe according to claim 1 or 2, wherein the corrugated pipe is foamed at a predetermined foaming ratio, and the foaming ratio is 1.05 times to 4 times. Method. 3. The method for manufacturing a composite pipe according to claim 1, wherein at least a portion of the holding convex portion is formed in the small diameter portion. 3. The method for manufacturing a composite tube according to claim 1, wherein at least a portion of the holding convex portion is formed in an annular shape extending in the circumferential direction of the corrugated tube. 3. The method for manufacturing a composite tube according to claim 1, wherein at least some of the holding convex portions are formed at intervals in the circumferential direction of the corrugated tube. 3. The method for manufacturing a composite tube according to claim 1, wherein at least a portion of the holding convex portion is formed to extend along the tube axis direction. A flexible corrugated tube in which large-diameter portions and small-diameter portions are alternately formed in the tube axis direction, a flexible inner tube covered by the corrugated tube, and an outer circumference of the flexible inner tube that can be peeled off. A composite pipe comprising a buffer layer,
the corrugated tube is made of foamed resin;
Holding convex portions in contact with the outer circumferential surface of the inner tube are formed on the inner circumferential surface of the corrugated tube so as to be distributed in the tube axis direction and the circumferential direction, and the holding convex portions protect the inner tube and the peelable buffer layer. is restrained in the pipe radial direction with respect to the corrugated pipe. The composite pipe according to claim 8, wherein at least a portion of the holding convex portion is provided in the small diameter portion. The composite pipe according to claim 8 or 9, wherein at least a part of the holding convex portion has an annular shape extending in the circumferential direction of the corrugated pipe. The composite pipe according to claim 8 or 9, wherein at least some of the holding convex portions are arranged at intervals in the circumferential direction of the corrugated pipe. The composite tube according to claim 8 or 9, wherein at least a portion of the holding convex portion extends along the tube axis direction. The composite pipe according to claim 8 or 9, wherein at least a portion of the holding convex portion is fused to the buffer layer.

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