JP7397601B2 - Composite pipe manufacturing method and manufacturing device, and composite pipe - Google Patents

Description

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

For example, flexible pipes for water supply and hot water supply have soft surfaces, so composite pipes with a coating layer are widely used. Types in which the covering layer is a foamed resin layer are gaining popularity in the market because they are inexpensive, fit well, and are relatively resistant to scratches from scratches at corners. We want to make it more slippery and less likely to get caught in corners, to improve heat retention, to make the sag and wrinkles that occur on the inside of raw bends less noticeable, and to make the inner pipe more exposed when connecting the joint. There is also a request.
Such a request 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 discloses a method of manufacturing a composite tube by forming and curing an inner tube made of synthetic resin and then molding a corrugated tube on the outer peripheral surface of the inner tube. First, mold and harden the inner tube. The inner tube is sent out from the inner tube outlet at the center of the extrusion nozzle and introduced into the corrugated tube forming section.
The corrugated tube forming section includes a large number of half-cylindrical corrugating molds arranged on two oval annular orbits. While these corrugating molds circulate along each annular orbit, the pair of corrugating molds on the two annular orbits move about half a circle around the annular orbit. A pair of corrugated molds.
The inner tube is inserted into the corrugated mold pair. In addition, two coating layers made of synthetic resin are coextruded from a double annular extrusion port surrounding the inner pipe outlet of the extrusion nozzle. The coating layer is formed into a tubular shape surrounding the inner tube and introduced into the corrugated mold pair. Furthermore, the diameter of the coating layer is expanded by vacuuming, and the coating layer is brought into close contact with the corrugated mold surface on the inner circumference of the pair of corrugated molds. As a result, the coating layer is formed into a corrugated shape to form a corrugated tube.

Japanese Patent Application Publication No. 2017-226144

In the composite pipe manufactured by the method of the above-mentioned patent document, a gap is formed not only between the large diameter part of the corrugated pipe and the inner pipe, but also between the small diameter part and the inner pipe over the entire circumference. . The gap was formed due to the thickness of the annular wall (inner cylinder) that partitions the inner pipe outlet and extrusion port of the extrusion nozzle, and the diameter expansion by vacuum etc. to create a wave shape. This can be said to be unavoidable due to the process. If there is such a gap, when the pressure (internal pressure), flow rate, temperature, etc. of the fluid passing inside the inner tube suddenly changes, the inner tube will flap, causing water hammer noise and thermal expansion and contraction noise. Likely to happen.
In view of such circumstances, the present invention aims to suppress the fluttering of the inner tube due to sudden changes in internal pressure, temperature, etc., even in the case of a composite tube made by extruding a corrugated tube around the outer periphery of an already manufactured inner tube. shall be.

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. A method of
Sending out the inner tube prepared in advance from the inner tube outlet in the center of the extrusion nozzle to the corrugated tube forming section,
The resin that will become the corrugated tube is supplied to the extrusion nozzle so as to be foamed at a predetermined expansion ratio, and the resin is formed into a tube through an annular extrusion port surrounding the inner tube outlet of the extrusion nozzle to form the corrugated tube. Extrude to 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;
Simultaneously with the forming, holding convex portions distributed in the tube axis direction and circumferential direction are formed on the inner circumferential surface of the corrugated tube, and by bringing the holding convex portions into contact with the outer circumferential surface of the inner tube, the inner tube is It is characterized by being held coaxially with the corrugated tube.

A gap is formed between the inner circumferential surface of the tubular resin and the outer circumferential surface of the inner tube during extrusion. Moreover, 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. As a result, 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, the holding convex portion suppresses displacement of the inner tube in the tube diameter direction. Therefore, when the composite pipe is in service, even if the internal pressure or temperature suddenly changes, the inner pipe can be prevented from flapping, and the occurrence of water hammer noise, thermal expansion and contraction noise, etc. can be suppressed.

The expansion ratio is preferably 1.5 times to 4 times.
This ensures that the holding convex portion comes into contact with the inner tube during molding.

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.

The device of the present invention is a device 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,
a foamed resin supply unit that supplies the resin that will become the corrugated tube by foaming it at a predetermined expansion ratio;
an extrusion nozzle having an inner tube outlet for sending out the inner tube, and an extrusion port formed in an annular shape surrounding the inner tube outlet for extruding the resin into a tube;
The corrugated resin has a large-diameter surface portion that defines the large-diameter portion, and a small-diameter surface portion that defines the small-diameter portion, while expanding the diameter of the tubular resin on the downstream side of the extrusion direction of the extrusion nozzle. A corrugated tube forming part that is formed into a cross section;
a holding protrusion forming part provided on the corrugated tube forming part or the extrusion nozzle;
holding protrusions distributed in the tube axis direction and circumferential direction of the inner circumferential surface of the corrugated tube and in contact with the outer circumferential surface of the inner tube to hold the inner tube coaxially by the holding protrusion forming portion; It is characterized by forming a part.

In the composite pipe produced by the composite pipe manufacturing apparatus, the inner pipe is held by the holding convex portion, thereby suppressing displacement of the inner pipe in the pipe radial direction with respect to the corrugated pipe. This can prevent the inner tube from flapping.

It is preferable that the holding protrusion forming part includes a holding mold part provided on the small diameter mold surface part.
Thereby, the holding convex portion can 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. Good too.

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 protrusions 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.

It is preferable that the holding convex portion forming portion includes a notch recess formed on an 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 present invention is a composite tube comprising a flexible corrugated tube in which large diameter portions and small diameter portions are alternately formed in the tube axis direction, and a flexible inner tube covered by the corrugated tube. hand,
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 peripheral surface of the corrugated tube so as to be distributed in the tube axis direction and the circumferential direction, and the retaining convex portions hold the inner tube against the corrugated tube. It is characterized by being restrained in the pipe radial direction.

According to the composite tube, even if the internal pressure, temperature, etc. suddenly change, the inner tube can be restrained from flapping due to the restraint by the holding convex portion. As a result, the occurrence of water hammer noise, thermal expansion and contraction noise, etc. can be suppressed.
Preferably, the composite pipe is manufactured by the manufacturing method or the manufacturing apparatus. The corrugated tube preferably does not have a non-foamed resin layer, and is more preferably constructed 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 other 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.

Preferably, 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 or temperature of the inner tube in the composite tube, it is possible to suppress the inner tube from flapping.

FIG. 1(a) is a front view showing a composite pipe according to a first embodiment of the present invention, with a part thereof being a cross section along the pipe axis direction. FIG. 1(b) is a cross-sectional view of the composite pipe taken along line Ib-Ib in FIG. 1(a). FIG. 2(a) is a plan view showing an example of a composite pipe manufacturing apparatus. FIG. 2(b) is a plan view showing another example of the composite pipe manufacturing apparatus. FIG. 3 is an enlarged sectional view of the circular portion in FIG. 2(a). FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. FIG. 5 is a sectional view along the tube axis direction showing a modified form of the composite tube according to the first embodiment. FIG. 6 is a sectional view along the tube axis direction showing another modification of the composite tube according to the first embodiment. FIG. 7(a) is a sectional view orthogonal to the tube axis direction showing another modification of the composite tube according to the first embodiment. FIG. 7(b) is a sectional view orthogonal to the tube axis direction, showing another modification of the composite tube according to the first embodiment. FIG. 8(a) is a front view showing a composite pipe according to a second embodiment of the present invention, partially in cross section along line VIIIa-VIIIa in FIG. 8(b). FIG. 8(b) is a cross-sectional view of the composite pipe according to the second embodiment taken along line VIIIb-VIIIb in FIG. 8(a). FIG. 9 is a sectional view showing a pair of corrugating molds in the composite pipe manufacturing apparatus according to the second embodiment, taken along line IX-IX in FIG. 10. FIG. 10 is a cross-sectional view taken along line XX in FIG. FIG. 11(a) is a sectional view along the tube axis direction showing a modified form of the composite tube according to the second embodiment. FIG. 11(b) is a sectional view along the tube axis direction showing another modification of the composite tube according to the second embodiment. FIG. 12(a) is a front view showing another modification of the composite pipe according to the second embodiment, partially in cross section along the line XIIa-XIIa in FIG. 12(b). FIG. 12(b) is a sectional view taken along line XIIb-XIIb in FIG. 12(a). FIG. 13 is a sectional view perpendicular to the axis of the pair of corrugated molds in the composite pipe manufacturing apparatus of the embodiment shown in FIG. 12. FIG. 14(a) is a cross-sectional view along the tube axis direction showing another modification of the composite tube. FIG. 14(b) is a sectional view along the tube axis direction showing another modification of the composite tube. FIG. 15(a) is a sectional view perpendicular to the tube axis, showing another modification of the composite tube according to the second embodiment. FIG. 15(b) is a sectional view perpendicular to the tube axis, showing another modification of the composite tube according to the second embodiment. FIG. 16(a) is a front view showing another modification of the composite pipe according to the second embodiment. FIG. 16(b) is a sectional view taken along line bb in FIG. 16(a). FIG. 16(c) is a sectional view taken along line cc in FIG. 16(a). FIG. 16(d) is a cross-sectional view taken along line dd in FIG. 16(a). FIG. 16(e) is a sectional view taken along line ee in FIG. 16(a). FIG. 16(f) is a sectional view taken along line ff in FIG. 16(a). FIG. 17(a) shows another modification of the composite pipe according to the second embodiment, and is a sectional view perpendicular to the pipe axis. FIG. 17(b) shows another modification of the composite pipe according to the second embodiment, and is a sectional view perpendicular to the pipe axis. FIG. 17(c) shows another modification of the composite pipe according to the second embodiment, and is a sectional view perpendicular to the pipe axis. FIG. 18(a) shows another modification of the composite pipe according to the second embodiment, and is a sectional view perpendicular to the pipe axis. FIG. 18(b) shows another modification of the composite pipe according to the second embodiment, and is a sectional view perpendicular to the pipe axis. FIG. 18(c) is a sectional view perpendicular to the tube axis, showing another modification of the composite tube according to the second embodiment. FIG. 19 is a front view showing a composite pipe according to a third embodiment of the present invention, with a portion thereof in cross section. FIG. 20 is a cross-sectional view taken along line XX-XX in FIG. 19. FIG. 21 shows a pair of corrugating molds in the composite pipe manufacturing apparatus of the third embodiment, and is a sectional view taken along line XXI-XXI in FIG. 22. FIG. 22 is a cross-sectional view taken along line XXII-XXII in FIG. 21. FIG. 23 is a partially sectional front view showing a modified form of the composite pipe of the third embodiment. FIG. 24 is a cross-sectional view taken along line XXIV-XXIV in FIG. 23. FIG. 25 shows a pair of corrugating molds in a composite pipe manufacturing apparatus according to a modified version of the third embodiment (FIG. 23), and is a sectional view taken along line XXV-XXV in FIG. 26(a). FIG. 26(a) is a cross-sectional view taken along line XXVIa-XXVIa in FIG. 25. FIG. 26(b) is a cross-sectional view taken along line XXVIb-XXVIb in FIG. 25. FIG. 27 is a front view showing a composite pipe according to the fourth embodiment of the present invention, with a portion thereof taken in cross section along line XXVII-XXVII in FIG. 28. FIG. 28 is a cross-sectional view taken along line XXVIII-XXVIII in FIG. 27. FIG. 29 shows an extrusion nozzle in the composite pipe manufacturing apparatus of the fourth embodiment, and is a sectional view perpendicular to the axis. FIG. 30 is a cross-sectional view taken along the line XXX-XXX of FIG. 29, showing a state in which the resin and the inner tube are extruded from the extrusion nozzle.

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. The composite pipe 1 is used, for example, as piping for water supply and hot water supply. The composite tube 1 includes an inner tube 9 as a tube body and a corrugated tube 10 as a covering layer.

The inner tube 9 has a constant circular cross section over its entire length and is flexible. 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.
The inside of the inner tube 9 becomes a fluid passage through which fluids such as water and hot water pass. The outer periphery of the inner tube 9 is covered with a corrugated tube 10 (corrugated tube).

The corrugated tube 10 has a large diameter portion 11 and a small diameter portion 12, and has a corrugated cross section. Large diameter portions 11 and small diameter portions 12 are alternately formed at a constant pitch _P10 in the tube axis direction.
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 pipe 10 is made of flexible foamed resin. Examples of resin materials for the corrugated pipe 10 include cross-linked polyethylene (PE-X), polyethylene (PE), high heat-resistant polyethylene (PE-RT), polybutene, polypropylene (PP), thermoplastic elastomer, thermosetting elastomer, plastomer, and others. Examples include synthetic resins, and the material is not limited to a single material, but may also be a composite resin containing a plurality of materials. 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. good. 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 1.5 times to 4 times, more preferably 2.5 times to 3.5 times.
The foaming agent functions to lower the specific gravity of the resin and thus of 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. For example, a high-precision electronic hydrometer may be used to measure the specific gravity.

An inner tube 9 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 peripheral surface portion of the small diameter portion 12 constitutes an annular holding convex portion 13 that holds the inner tube 9.
In other words, the holding convex portion 13 is formed on the inner peripheral surface of the corrugated tube 10. The inner tube 9 is restrained by the holding convex portion 13 so as not to be displaceable in the tube radial direction with respect to the corrugated tube 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 of the inner circumferential surface of the corrugated tube 10. Specifically, the annular holding convex portions 13 are distributed in the tube axis direction of the corrugated tube 10 at the same arrangement pitch as the small diameter portions 12. The annular holding convex portions 13 are distributed over the entire circumference of the corrugated tube 10 in the circumferential direction, and have a closed annular shape.

FIG. 2 shows an apparatus 3 for manufacturing the composite pipe 1. As shown in FIG. The manufacturing apparatus 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 includes a cylinder and a screw for extruding. 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 shape having an outer cylinder 31a and an inner cylinder 31b. The center hole of the inner tube 31b constitutes an inner tube outlet 31c. 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 cylinder 31a and the inner cylinder 31b constitutes an extrusion port 31d for the resin 19. The extrusion port 31d has an annular shape and surrounds the inner tube outlet 31c.
The thickness t _31b (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, about t _31b =0.5 mm to 2 mm. It is not limited to this.

As shown in FIGS. 2 and 3, a corrugated tube forming section 32 (corrugator) is arranged 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 orbits 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 extending from the axis of the extrusion nozzle 31 (extrusion direction).

First corrugating molds 33a are arranged in an annular manner on the first annular orbit 32a. Second corrugation molds 33b are arranged in an annular manner on the second annular track 32b.
These corrugation molds 33a, 33b are moved 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 a pair of two annular orbits 32a and 32b are moved in parallel along the axis _L33 , they come together to form a closed cylindrical corrugating mold pair 33. A plurality of corrugation die pairs 33 are arranged in a line on the axis _L33 .

A large-diameter die surface portion 34 and a small-diameter die surface portion 35 are formed on the inner circumferential surface (mold surface) of each of the corrugated molds 33a and 33b, and thus of 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. A small suction hole 36 is opened particularly in the large-diameter mold surface portion 34 among the mold surface portions 34 and 35 .

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 37 (a holding projection forming portion) 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. The holding mold part 37 has a closed annular shape extending all the way around the inner peripheral surface in the circumferential direction.

The composite pipe 1 is manufactured as follows.
The inner tube 9 is prepared in advance by being molded and hardened or obtained.
The inner tube 9 is introduced into the extrusion nozzle 31 and sent out from the inner tube outlet 31c in the center to the corrugated tube forming section 32. The inner tube 9 is introduced into the corrugated mold pair 33 and sent downstream in the feeding direction (to the right in FIG. 2).

At the same time, 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 1.5 times to 4 times). After this, the resin 19 is supplied to the extrusion nozzle 31. Due to the high pressure inside the extrusion nozzle 31, the resin 19 has not yet started foaming.
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 extrusion, 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 inner tube 9. A gap d corresponding to the thickness t _31b of the inner tube 31b is formed between the inner circumferential surface of the tubular resin 19A and the outer circumferential surface of the 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 arranged 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 tubular resin 19A is expanded in diameter and brought into close contact with the mold surfaces 34 and 35 of the corrugated mold pair 33, and is molded into the corrugated tube 10 with a corrugated cross section. The inner tube 9 is covered by the corrugated tube 10.

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 . Moreover, the thickness of the corrugated pipe 10 is increased by foaming the resin 19A. As a result, the annular holding convex portion 13 comes into contact with the outer peripheral surface of the inner tube 9.
In other words, the expansion ratio of the resin 19 and the amount of protrusion of the holding mold part 37 toward the inside of the tube are adjusted so that the annular holding protrusion 13 of the corrugated tube 10 after foaming comes into contact with the inner tube 9. For example, if the wall thickness of the resin 19A at the time of extrusion is about 1 mm and the size of the gap d is about 0.5 mm, by setting the foaming ratio to 1.5 times or more, the annular holding protrusion 13 can be It can be ensured that it contacts the outer periphery.

The cross section of an actual corrugated tube is not a perfect circle but is slightly flattened. Therefore, even without setting a safety margin in the foaming ratio, the holding convex portion 13 on at least the short diameter side of the flattened cross section can be brought into contact with the inner tube 9, and there is no problem in practical use. By setting the upper limit of the expansion ratio to about 4 times, there is no problem in molding.

As a result, the inner tube 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. Therefore, displacement of the inner tube 9 in the tube diameter direction can be suppressed.
Since the corrugated tube 10 is molded on the outer circumference of the inner tube 9 prepared in advance, a part of the inner circumferential surface of the corrugated tube 10 (specifically, the holding mold part 37) has the shape of the outer circumferential surface of the inner tube 9. transcribed. 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. A fluid such as water or hot water passes through the interior of the inner tube 9. The pressure, flow rate, temperature, etc. of the fluid can change suddenly depending on usage conditions. On the other hand, since the inner tube 9 is restrained by the holding convex portion 13, even if the sudden change occurs, the inner tube 9 can be suppressed from fluttering, and water hammer noise and thermal expansion/contraction noise can be prevented from occurring. can.
Furthermore, since the foamed resin constituting the corrugated tube 10 absorbs impact, water hammer noise and thermal expansion/contraction noise can be more reliably prevented from occurring. Moreover, 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 can be suppressed and its flexibility can be improved. Moreover, 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 coating layer of the inner pipe 9, even if the composite pipe 1 gets caught in an angular obstacle during piping construction, it is easy to slip and the stuck state can 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, heat retention is enhanced. When the composite pipe 1 is raw bent, the slack and wrinkles that occur on the inner circumference become less noticeable. At the time of joint connection, by sliding the corrugated tube 10, which is a coating layer, in the tube axis direction with respect to the inner tube 9, the inner tube 9 to be connected can be exposed and the connection work can be performed.

Next, other embodiments of the present invention will be described. In the following embodiments, the same reference numerals are given to the same components in the drawings, and the explanation thereof will be 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, the small diameter portions 12A at intervals of several small diameter portions in the tube axis direction (horizontal direction in FIG. 5) protrude more toward the inner side of the tube than the other small diameter portions 12 and come into contact with the outer circumferential surface of the inner tube 9. The convex portion 13 may also be formed.
In FIG. 5, every two small diameter portions 12A constitute the holding convex portion 13, but the present invention is not limited to this, and the holding convex portion 13 may be composed of every one or three or more small diameter portions 12. 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 corresponding to the small-diameter portions 12A of the corrugated molds 33a, 33b, as well as the holding mold portions 37, 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, as well as the top portion of the holding mold portion 37 facing inside the tube, Form into a rounded semicircular cross section. As a result, the corrugated tube 10 shown by the 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.
As shown in FIG. 7(a), the annular holding convex portion 13 may be annular with a chip at one location 13c in the circumferential direction. As shown in FIG. 7(b), the annular holding convex portion 13 may have an annular shape that is chipped at two locations 13c, 13c 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. 7A and 7B 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 inner side 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 by 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 intervals in the circumferential direction of the small diameter portion 12. Here, four discrete holding protrusions 14 are provided at 90 degree intervals. Each discrete holding convex portion 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 W ₁₄ 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 dimension _L14 of the discrete holding protrusions 14 along the circumferential direction of the corrugated tube 10B is smaller than one quarter of the circumferential length of the small diameter portion 12 (one divided by the number of holding protrusions).

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. The top portion 14e is in contact with the outer peripheral surface of the inner tube 9. These discrete holding convex portions 14 restrain the inner tube 9 in the tube diameter direction with respect to the corrugated tube 10B. As a result, even if the internal pressure or temperature suddenly changes, the inner tube 9 can be prevented from flapping, and the generation of water hammer noise and thermal expansion and contraction 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 38 (holding protrusion forming part) 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 90 degree intervals 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, the discrete holding convex portions 14 may be provided only in some of the 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 three or more small diameter portions 12.
As shown by the two-dot chain lines in FIGS. 11(a) and 11(b), in the composite pipe manufacturing apparatus, the holding mold parts 38 of the corrugated molds 33a, 33b are arranged so as to correspond to the arrangement of the discrete holding protrusions 14. Form it. As a result, the corrugated tube 10B shown by the solid line 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 length of the discrete holding convex portions 14 in the circumferential direction 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 the two-dot chain line in FIGS. 14(a) and 14(b), the width of the holding mold part 38 of the corrugating molds 33a and 33b is set narrow (as shown in FIG. 14(a)), It can be set widely (see figure (b)).
The three-dot chain lines in FIGS. 14(a) and 14(b) indicate the discrete holding protrusions 14 formed by the holding mold part 38, assuming that the inner tube 9 is not provided.
As shown by solid lines in FIGS. 14(a) and 14(b), the actual discrete holding convex portions 14 in the modified form (3) are compressed by the inner tube 9 and integrated with the small diameter portion 12. There is. The top surfaces of the discrete holding convex portions 14 and the small diameter portion 12 facing inside the tube are flush with each other and in contact with the inner tube 9. In FIG. 14(b), since the discrete holding convex portions 14 are wide, the resin compressed by the inner tube 9 becomes the bulged portions 19b and bulges out to both sides of the small diameter portion 12.

<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°. The arrangement of the discrete holding convex portions 14 of four (n) adjacent small diameter portions 12 is the same.
Thereby, when the composite pipe 1B is green bent, the bending resistance can be prevented from greatly varying depending on the direction of bending, and 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 the above 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 protrusions 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.
In FIG. 17(a), three bifurcated discrete holding convex portions 14 are arranged at 120° intervals in the circumferential direction of the corrugated tube 10B.
In FIG. 17(b), four bifurcated discrete holding protrusions 14 are arranged at 90° intervals in the circumferential direction of the corrugated tube 10B.
In FIG. 17(c), eight bifurcated discrete holding convex portions 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 are tapered toward the inner side of the tube, and the top portions 14e are in contact with the inner tube 9 in a substantially dotted 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 parts 38 of the corrugating molds 33a and 33b are formed in a shape corresponding to the discrete holding convex parts 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 striped holding convex portion 16 has a vertical striped 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 striped holding convex portions 16 are arranged at intervals in the circumferential direction of the inner peripheral surface of the corrugated tube 10C. Preferably, the shape and arrangement of the vertical striped holding convex portions 16 are set 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 .
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 or temperature suddenly changes, the inner tube 9 can be prevented from flapping, and the generation of water hammer noise and thermal expansion and contraction noise can be suppressed.
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 portions 39 are formed on the mold surfaces of the inner peripheries of the corrugated molds 33a and 33b. . The vertically 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 corrugated molds 33a and 33b (the extrusion direction of the extrusion nozzle 31). It has a wave shape that follows the wave cross sections of the large-diameter surface portion 34 and the small-diameter surface portion 35. The shape and arrangement of the vertical 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. . The top portion 16e is in contact with the outer peripheral surface of the inner tube 9 over its 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 FIG. 25, as well as FIGS. 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 corrugated molds 33a and 33b. and extends straight along the axial direction (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.
The groove 17 (see FIGS. 19 and 20) is not formed on the outer peripheral surface of the corrugated tube 10D.

FIGS. 29 and 30 show an extrusion nozzle 40 in a composite pipe manufacturing apparatus according to the 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 (for example, four) of cutout recesses 45 (holding protrusion forming portions) are formed on the outer peripheral surface of the inner cylinder 41 (inner peripheral 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 cutout 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, ridges 19d are formed on the inner peripheral surface of the extruded tubular resin 19A. The protrusion 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 protrusions 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 may have both the annular holding convex portion 13 and the vertical striped holding convex portion 16, or may have both the discrete holding convex portion 14 and the vertical striped holding convex portion 16. good.
The corrugated tube forming section 32 may be of a blow type that applies pressure between the tubular resin 19A and the inner tube 9 instead of a vacuum type.
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.
Unique configurations of two or more embodiments (including variations) may be combined.
For example, the holding convex portion may not face the tube core.
The composite pipe may be used not only as a water/hot water supply pipe but also as a pipe 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 HD (registered trademark) HE121 manufactured by Japan Polyethylene Co., Ltd.). As the foaming agent, foaming agent MB5885 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. 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. Furthermore, no abnormal noise was found in the 60°C thermal expansion and contraction evaluation of the same composite pipe.

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

1, 1B, 1C, 1D Composite tube 9 Inner tube 10, 10B, 10C, 10D Corrugated tube 11 Large diameter section 12 Small diameter section 12A, 12B Small diameter section (holding protrusion)
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 3 during extrusion Composite pipe manufacturing apparatus 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 portion 35 Small diameter mold surface portions 37, 38, 39 Holding mold portion (holding protrusion forming portion)
40 Extrusion nozzle 43 Inner pipe outlet 44 Extrusion port 45 Notch recess (holding protrusion forming part)

Claims (15)

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:
preparing in advance the shaped inner tube having a constant circular cross section over its entire length;
sending the inner tube from an inner tube outlet in the center of the extrusion nozzle to a corrugated tube forming section;
The resin that will become the corrugated tube is melted and supplied to the extrusion nozzle so as to be foamed at a predetermined expansion ratio, and the resin is formed into a tube through an annular extrusion port surrounding the inner tube outlet of the extrusion nozzle. extruding into the corrugated tube forming section and foaming ;
The tubular resin is formed into a corrugated cross section by the corrugated tube forming section while expanding its diameter;
Simultaneously with the forming, holding convex portions distributed in the tube axis direction and circumferential direction are formed on the inner circumferential surface of the corrugated tube, and the retaining convex portions are expanded toward the outer circumferential surface of the inner tube by foaming . contacting the outer peripheral surface of the tube , thereby holding the inner tube coaxially with respect to the corrugated tube while allowing the corrugated tube to slide in the tube axis direction relative to the inner tube. Characteristic method for manufacturing composite pipes. The manufacturing method according to claim 1, wherein the foaming ratio is 1.5 times to 4 times. 3. The manufacturing method according to claim 1, wherein at least a portion of the holding convex portion is formed in the small diameter portion. The manufacturing method according to any one of claims 1 to 3, characterized in that at least a portion of the holding convex portion is formed in an annular shape extending in the circumferential direction of the corrugated tube. 4. The manufacturing method 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 manufacturing method according to claim 1 , wherein at least a portion of the holding convex portion is formed to extend along the tube axis direction. An apparatus 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,
a foamed resin supply unit that melts the resin that will become the corrugated tube and supplies it so that it is foamed at a predetermined expansion ratio;
An inner tube outlet for sending out the molded inner tube having a constant circular cross section over its entire length, and an annular shape surrounding the inner tube outlet, which converts the resin in a molten state from the foamed resin supply section into a tube. an extrusion nozzle having an extrusion port that starts foaming while extruding;
The tube-shaped resin has a large-diameter surface portion that defines the large-diameter portion and a small-diameter surface portion that defines the small-diameter portion, and has a corrugated cross section while expanding the diameter of the tubular resin on the downstream side of the extrusion direction of the extrusion nozzle. a corrugated tube forming section to be formed into;
a holding protrusion forming portion provided on the corrugated tube forming portion;
The holding protrusion forming portion forms holding protrusions distributed in the tube axis direction and the circumferential direction of the inner circumferential surface of the corrugated tube, and the holding protrusions are formed toward the outer circumferential surface of the inner tube by foaming. and inflate the inner tube into contact with the outer circumferential surface of the inner tube, thereby causing the inner tube to be coaxial with the corrugated tube while allowing the corrugated tube to slide in the tube axis direction relative to the inner tube. A manufacturing device for a composite pipe, which is characterized by holding the composite pipe so that it is 8. The manufacturing apparatus according to claim 7, wherein the holding protrusion forming part includes a holding mold part provided on the small diameter mold surface part. 9. The manufacturing apparatus according to claim 8, wherein the holding mold part has an annular shape extending in a circumferential direction of the small diameter mold surface part. 9. The manufacturing apparatus according to claim 8, wherein the holding mold part is provided at a plurality of positions spaced apart in the circumferential direction of the small diameter mold surface part. 8. The manufacturing apparatus according to claim 7 , wherein the holding protrusion forming section includes a holding mold section extending in the extrusion direction. An apparatus 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,
a foamed resin supply unit that melts the resin that will become the corrugated tube and supplies it so that it is foamed at a predetermined expansion ratio;
An inner tube outlet for sending out the molded inner tube having a constant circular cross section over its entire length, and an annular shape surrounding the inner tube outlet, which converts the resin in a molten state from the foamed resin supply section into a tube. an extrusion nozzle having an extrusion port that starts foaming while extruding;
The tube-shaped resin has a large-diameter surface portion that defines the large-diameter portion and a small-diameter surface portion that defines the small-diameter portion, and has a corrugated cross section while expanding the diameter of the tubular resin on the downstream side of the extrusion direction of the extrusion nozzle. a corrugated tube forming section to be formed into;
a notched recess as a holding protrusion forming portion formed on the inner peripheral edge of the annular extrusion port of the extrusion nozzle;
The notched recesses form holding protrusions distributed in the tube axis direction and the circumferential direction of the inner circumferential surface of the corrugated tube, and the holding protrusions are expanded toward the outer circumferential surface of the inner tube by foaming. contact with the outer circumferential surface of the inner tube, thereby holding the inner tube coaxially with respect to the corrugated tube while allowing the corrugated tube to slide in the tube axis direction with respect to the inner tube. A composite pipe manufacturing device characterized by: A composite tube comprising a flexible corrugated tube in which large diameter portions and small diameter portions are alternately formed in the tube axis direction, and a flexible inner tube covered by the corrugated tube,
the corrugated tube is made of foamed resin;
Holding convex portions contacting 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,
At least some of the holding convex portions are arranged at intervals in the circumferential direction of the corrugated tube,
The composite tube is characterized in that the holding convex portion restrains the inner tube in the tube radial direction with respect to the corrugated tube while allowing the corrugated tube to slide in the tube axial direction with respect to the inner tube. . 14. The composite pipe according to claim 13, wherein at least a portion of the holding convex portion is provided in the small diameter portion. A composite tube comprising a flexible corrugated tube in which large diameter portions and small diameter portions are alternately formed in the tube axis direction, and a flexible inner tube covered by the corrugated tube,
the corrugated tube is made of foamed resin;
Holding convex portions contacting 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,
At least a portion of the holding convex portion extends along the tube axis direction ,
The composite tube is characterized in that the holding convex portion restrains the inner tube in the tube radial direction with respect to the corrugated tube while allowing the corrugated tube to slide in the tube axial direction with respect to the inner tube. .

Images