JP7587438B2 - Corrugated cladding tube and its manufacturing equipment - Google Patents

Description

The present invention relates to a flexible corrugated cladding pipe that covers a flexible inner pipe and a manufacturing method thereof, and in particular to a corrugated cladding pipe suitable for covering an inner pipe for supplying cold water or hot water, and a manufacturing method thereof.

As a flexible covering pipe to protect flexible pipes (inner pipes) for hot and cold water supply, corrugated covering pipes with alternating large diameter peaks and small diameter valleys are well known and are widely used, for example, in the sheath header construction method. Flexible and easily stretchable corrugated covering pipes have also appeared. However, measures are needed to suppress the flapping noise caused by water hammer when the faucet is suddenly closed, etc. One way to do this is to wrap a cushioning material such as soundproofing tape around the inner pipe, but this is disadvantageous in terms of cost. Also, there is a demand for heat retention as well as scratch prevention.

Patent Document 1 discloses a method for manufacturing a composite pipe consisting of an inner pipe and a corrugated cladding pipe by forming and curing an inner pipe made of synthetic resin, and then forming a corrugated cladding pipe on its outer circumferential surface. According to this method, the previously formed inner pipe is sent out along the axis from the inner pipe outlet at the center of the extrusion nozzle and introduced into the corrugated pipe forming section. The corrugated pipe forming section is equipped with a large number of semi-split cylindrical corrugation split dies arranged on two elliptical annular tracks. While these corrugation split dies move in a circular manner along the two annular tracks, respectively, and move on a common track portion along the axis, the paired corrugation split dies are mated with each other to form a closed annular corrugation mold surface. The inner pipe is inserted along the central axis of the annular corrugation mold surface. The two layers of resin material are co-extruded from the extrusion port into a cylindrical shape, introduced into the inside of the annular corrugation mold surface, and expanded by vacuum to be in close contact with the corrugation mold surface, and formed into a corrugated cladding pipe.

In the corrugated cladding tube of Patent Document 2, small diameter valleys spaced at regular intervals in the tube axial direction protrude toward the tube axis over the entire circumference beyond the other annular valleys and contact the outer circumferential surface of the inner tube.

JP 2017-226144 A JP 2010-210041 A

In the composite pipe manufactured by the method of the above-mentioned Patent Document 1, a gap is formed not only between the large diameter part of the corrugated cladding pipe and the inner pipe, but also between the small diameter part and the inner pipe over the entire circumference. The gap is formed due to the thickness of the annular wall (inner pipe) that separates the inner pipe delivery port and the extrusion port of the extrusion nozzle, and due to the expansion of the diameter by vacuum or the like for forming the corrugated shape, and can be said to be unavoidable in the manufacturing process. If such a gap exists, when the pressure (internal pressure), flow rate, temperature, etc. of the fluid passing through the inside of the inner pipe suddenly changes, the inner pipe is likely to flap, causing water hammer noise or thermal expansion noise.
In the corrugated cladding tube of Patent Document 2, the small diameter valley portion needs to have a smaller diameter than the other valley portions over the entire circumference. Therefore, during molding, the resin that will become the small diameter valley portion gets caught in the joint of a pair of corrugation split dies, making molding difficult.
In view of the above circumstances, an object of the present invention is to provide a corrugated cladding tube which can suppress noise caused by flapping of the inner tube, can be reliably formed, and can also ensure heat retention.

In order to solve the above problems, the present invention provides
A flexible corrugated cladding tube covering a flexible inner tube,
The tube has a plurality of annular peaks and a plurality of annular valleys arranged alternately in the tube axial direction,
At least some of the valleys are formed with a plurality of retaining protrusions each protruding toward the tube axis, and these retaining protrusions are arranged spaced apart from one another in the circumferential direction of the tube. In other words, the retaining protrusions are discontinuous in the circumferential direction of the tube.
According to the corrugated cladding tube, the retaining protrusions are brought close to or into contact with the inner tube to retain the inner tube, thereby suppressing flapping of the inner tube and suppressing noise. The retaining protrusions are not continuous in the circumferential direction of the tube, which facilitates molding. In addition, the contact area between the retaining protrusions and the corrugated cladding tube and the inner tube is reduced, thereby reducing heat conduction and ensuring heat retention.

It is preferable that the retaining protrusions are arranged offset in the pipe circumferential direction with respect to a virtual parting cross section including the parting line position, and that valley portions between adjacent retaining protrusions in the pipe circumferential direction in the some of the valley portions straddle the parting cross section.
The parting line position and parting cross section correspond to the seam of a pair of corrugated split dies in the forming die. The valleys between the holding protrusions adjacent in the pipe circumferential direction (i.e., the valleys excluding the holding protrusions) straddle the seam. The holding protrusions are formed at positions shifted in the circumferential direction of the forming die from the seam. Therefore, the holding protrusions do not get caught in the seam during forming. This allows the corrugated cladding tube to be formed reliably and prevents burrs and dents due to the seam getting caught.
Preferably, the parting cross section passes through the tube axis of the corrugated cladding tube.
The parting line does not necessarily have to be present at the parting line position, and depending on the molding conditions, the parting line may not be formed.

Of the end faces on both sides in the pipe circumferential direction of each retaining protrusion, it is preferable that the end face on the side farther from the nearest parting line position of the retaining protrusion forms an angle of 90° or less with respect to the parting cross section on the side facing the parting cross section.
This makes it possible to prevent the holding protrusions from forming undercuts when the mold is removed after molding using the molding die, facilitating removal from the mold.

Of both end faces of each holding protrusion in the pipe circumferential direction, it is preferable that the end face closer to the parting line position nearest to the holding protrusion be aligned substantially along the parting cross section.
This makes demolding even easier.

The number of the retaining projections on both sides of the parting cross section is preferably the same, but may be different.

It is preferable that a cross section of the holding protrusion perpendicular to the tube axis direction is symmetrical with respect to a center line passing through the top of the holding protrusion and the tube axis.
This can prevent unevenness in the strength of the holding protrusions in the circumferential direction of the tube, making it possible to hold the inner tube more stably.

It is preferable that the end faces of the holding projection on both sides in the circumferential direction of the pipe form an angle of approximately 90°.
This makes it difficult for the retaining projections to bend in the circumferential direction of the tube, enabling the inner tube to be held firmly. Also, the contact area between the inner tube and the retaining projections can be reduced, ensuring heat retention.

It is preferable that the gradient of the side surface in the tube axis direction of the holding protrusion is equivalent to the gradient of the tube inner surface on the same side in the tube axis direction of the valley portion between adjacent holding protrusions in the tube circumferential direction in some of the valley portions.
This makes it possible to make the holding protrusion wider in the axial direction of the tube, making it less likely to break.

It is preferable that the width of the holding protrusion in the tube axial direction at the midpoint between the valley portion and the peak portion is wider than the width of the valley portion in the tube axial direction.
This makes it possible to make the holding protrusions wider in the tube axial direction, making them less likely to break in the tube axial direction, and to firmly hold the inner tube. Also, when the corrugated cladding tube is viewed from the outside, the recesses corresponding to the holding protrusions are larger than the valleys and extend to the peaks, so that a portion of the peaks appears to be missing. This makes it easy to check the position of the holding protrusions from the outside. Therefore, for example, when cutting the corrugated cladding tube to connect a joint, it becomes easier to cut while avoiding the holding protrusions.

The gradient of the side surface in the tube axis direction of the holding protrusion may be steeper than the gradient of the inner tube surface on the same side in the tube axis direction of the valley portion between adjacent holding protrusions in the tube circumferential direction in the part of the valley portion. This allows the width in the tube axis direction of the holding protrusion to be approximately the same as the width in the tube axis direction of the valley portion.

It is preferable that the axial width of the holding protrusion at the midpoint between the valley portion and the peak portion is equal to the axial width of the valley portion. This reduces the axial width of the holding protrusion and narrows the contact area with the inner tube, ensuring heat retention.

It is preferable that the gradient of the side surface of the holding protrusion on one side in the tube axis direction is gentler than the gradient of the side surface on the other side in the tube axis direction.
The forming mold for the corrugated cladding tube is preferably structured such that the corrugation split dies arranged in an annular manner on two annular tracks are moved along each annular track, and paired corrugation split dies are joined together to form an annular corrugation die surface on one track portion shared by the two annular tracks. The side surface on one side of the holding protrusion is preferably the side surface on the upstream side of the track portion in the feed direction of the corrugated cladding tube. This makes it possible to prevent the side surface on one side (preferably the upstream side) of the holding protrusion from interfering with and being deformed by the protruding die portion for the holding protrusion of the corrugation split mold when each corrugation split mold is removed while being rotated along the semicircular track portion of the downstream turnaround of the annular track.

It is preferable that the gradient of the side surface on one side is at least 1 degree gentler than the gradient of the side surface on the other side.
This can reliably prevent deformation of the side surface on the one side (preferably the upstream side) of the retaining protrusion.

It is preferable that the angle of the one side surface with respect to the tube radial direction is 5° to 20°.
This can reliably prevent deformation of the side surface on the one side (preferably the upstream side) of the retaining protrusion.

It is preferable that the holding protrusion height from the top of the peak to the top of the holding protrusion is 1.5 to 5 times the valley height from the top of the peak to the inside pipe top of the valley portion excluding the holding protrusion.
This allows the inner tube to be reliably held by the holding protrusion, and also ensures that an air layer is reliably formed between the corrugated cladding tube and the inner tube, thereby reliably ensuring heat retention.

The corrugated cladding tube is preferably made of a single layer of foamed resin having a foaming ratio of 1.05 to 4 times.
It is more preferable that the corrugated cladding tube is made of a single layer of foamed resin having an expansion ratio of 1.2 to 2.5 times.
This reliably prevents noise caused by flapping of the inner tube and improves heat retention.

The foamed resin preferably contains a lubricant.
This can reduce the frictional resistance between the inner pipe and the corrugated cladding pipe, and can facilitate removal from the forming die during production of the corrugated cladding pipe.

The present invention relates to an apparatus for manufacturing the corrugated cladding tube, comprising:
a molding die having an annular corrugated surface for forming an outer surface of the corrugated cladding tube; and a supply unit for supplying a resin to be the corrugated cladding tube in a tubular shape to the molding die,
the mold includes a pair of corrugated split molds that mate together to form the corrugated mold surface;
The present invention is characterized in that the protruding mold portion for forming the holding protrusion on the corrugated mold surface is provided so as to avoid the joint between both circumferential ends of the corrugated split mold.
This prevents the resin parts that become the holding protrusions during molding from getting caught in the seams of the corrugated split mold, allowing for reliable molding and preventing burrs and dents caused by getting caught.

Of the end faces on both sides in the circumferential direction of the protruding mold portion, it is preferable that the end face farther from the nearest seam of the protruding mold portion forms an angle of 90° or less on the side facing the virtual cutting surface including the seam.
This makes it possible to prevent the holding protrusions from becoming undercut when the mold is removed from the molding die.

It is preferable that a cross section of the protruding mold portion perpendicular to the axis of the annular corrugated mold surface is symmetrical with respect to a center line passing through the apex of the protruding mold portion and the axis.
This can prevent unevenness in the strength of the retaining protrusion formed by the protruding mold portion in the circumferential direction of the tube, and enables the retaining protrusion to stably retain the inner tube.

Of the end faces on both sides of the protruding mold portion, it is preferable that the end face on the side closest to the nearest seam of the protruding mold portion is substantially parallel to the split surface.
This can prevent the holding protrusions from becoming undercut, facilitating demolding.

It is preferable that the end faces on both sides of the protruding portion form an angle of approximately 90° with each other.
This allows the angle between the end faces on both sides of the holding protrusion to be approximately 90°, making it possible to reliably prevent buckling (breaking) of the holding protrusion.

It is preferable that the protruding mold portion is provided on at least one of the pair of corrugated split molds.
In the pair of corrugation split dies, the number of protruding die portions provided on one corrugation split die may be different from the number of protruding die portions provided on the other corrugation split die.

The mold includes a plurality of wave-shaped split molds arranged on two circular tracks so as to be circulatively movable,
the two annular tracks share a common orbital portion along an axis of the annular corrugated surface;
The pair of corrugation split molds of the two annular tracks are mated with each other when moving on the track portion to form the annular corrugation mold surface;
The supply is connected to an upstream end of the track portion;
At the downstream end of the orbital portion, the pair of wave-shaped split dies rotate along respective annular orbits and move away from each other,
It is preferable that the slope of the side surface of the protruding portion facing the upstream side of the track portion is gentler than the slope of the side surface facing the downstream side.
This makes it possible to prevent, for example, the upstream side of the retaining protrusion from interfering with and being deformed by the protruding mold portion for the retaining protrusion of the corrugated split mold when each corrugated split mold is demolded while being rotated along the semicircular orbit portion of the downstream turn of the annular orbit.

It is preferable that the gradient of the side surface facing the upstream side is at least 1 degree gentler than the gradient of the side surface facing the downstream side.
This can reliably prevent deformation of the side surface on the one side (preferably the upstream side) of the retaining protrusion.

It is preferable that the angle of the side surface facing the upstream side with respect to a plane perpendicular to the axis is from 5° to 20°.
This can reliably prevent deformation of the side surface on the one side (preferably the upstream side) of the retaining protrusion.

It is preferable that the protruding height from the bottom of the concave mountain portion to the top of the protruding portion on the corrugated surface is 1.5 to 5 times the valley height from the bottom of the mountain portion to the top of the convex valley portion.
This allows the inner tube to be reliably held by the holding protrusion, and also ensures that an air layer is reliably formed between the corrugated cladding tube and the inner tube, thereby reliably ensuring heat retention.

According to the present invention, it is possible to reliably mold the corrugated cladding tube by preventing the resin from getting caught in the seams of the corrugated split mold. In addition, by holding the inner tube with the holding protrusions of the corrugated cladding tube, it is possible to suppress the flapping of the inner tube and suppress noise. Furthermore, it is possible to form an air insulating layer between the corrugated cladding tube and the inner tube, and by reducing the contact area between the holding protrusions and the inner tube, it is possible to ensure heat retention.

FIG. 1 is a side view showing a composite pipe including a corrugated cladding pipe according to a first embodiment of the present invention, a part of which is shown in cross section along line II in FIG. FIG. 2 is a front cross-sectional view of the compound pipe taken along line II-II in FIG. FIG. 3 is a front cross-sectional view of the compound pipe taken along line III-III in FIG. FIG. 4 is a plan view showing an example of an apparatus for manufacturing the composite pipe. FIG. 5 is a plan sectional view of the shared track portion and its surroundings of the composite pipe manufacturing apparatus. FIG. 6 is a front cross-sectional view of the forming die of the composite pipe manufacturing apparatus taken along line VI-VI in FIG. FIG. 7 is a front cross-sectional view showing the molding die in a slightly open state. FIG. 8 is a front cross-sectional view of a compound pipe according to a second embodiment of the present invention. FIG. 9 is a front cross-sectional view showing the molding die according to the second embodiment in a closed state. FIG. 10 is a front cross-sectional view of a compound pipe according to a third embodiment of the present invention. FIG. 11 is a front cross-sectional view showing the molding die according to the third embodiment in a closed state. FIG. 12 is a front cross-sectional view of a compound pipe according to a fourth embodiment of the present invention. FIG. 13 is a front cross-sectional view showing the molding die according to the fourth embodiment in a closed state. FIG. 14 is a front cross-sectional view of a compound pipe according to a fifth embodiment of the present invention. FIG. 15 is a front cross-sectional view showing the molding die according to the fifth embodiment in a closed state. FIG. 16 is a front cross-sectional view of a compound pipe according to a sixth embodiment of the present invention. FIG. 17 is a front cross-sectional view showing the molding die according to the sixth embodiment in a closed state. FIG. 18 is a front cross-sectional view of a compound pipe according to a seventh embodiment of the present invention. FIG. 19 is a front cross-sectional view showing the molding die according to the seventh embodiment in a closed state. FIG. 20 is a side view, partially in section, of a compound pipe according to an eighth embodiment of the present invention. FIG. 21 is a side view, partially in section, of a compound pipe according to a ninth embodiment of the present invention. FIG. 22 is a plan sectional view of a downstream portion of a shared orbit portion of the composite pipe manufacturing apparatus according to the ninth embodiment. FIG. 23 is a side cross-sectional view showing a modified aspect of the holding protrusion of the corrugated cladding tube according to the ninth embodiment. 24(a) is a side cross-sectional view showing a modified aspect of the holding protrusion of the corrugated cladding tube according to the ninth embodiment. FIG. 24(b) is a side cross-sectional view showing a modified aspect of the holding protrusion of the corrugated cladding tube according to the ninth embodiment. FIG. 25 is a front cross-sectional view showing a modified embodiment of the corrugated cladding tube. FIG. 26 is a front cross-sectional view showing a modified embodiment of the corrugated cladding tube.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First embodiment (FIGS. 1 to 7)
1 to 3 show a composite pipe 1 according to a first embodiment of the present invention. The composite pipe 1 includes an inner pipe 9 and an outer corrugated sheathing pipe 10 (corrugated pipe). The composite pipe 1 is used as a pipe for supplying hot and cold water, for example.

The inside of the inner pipe 9 becomes a fluid passage through which fluids such as water and hot water pass. The inner pipe 9 is formed to have a constant circular cross section over its entire length and is flexible. Examples of materials for the inner pipe 9 include synthetic resins such as cross-linked polyethylene (PE-X), polybutene, high heat resistant polyethylene (PE-RT), high density polyethylene (HDPE), low density polyethylene (LDPE), and polypropylene (PP). The inner pipe 9 may contain any one of these synthetic resins as a main component, or may contain a plurality of synthetic resins.
The inner tube 9 may include a plurality of resin layers, which may be laminated in the radial direction of the inner tube 9 .
The inner pipe 9 may be a composite resin pipe containing metal, such as a metal-reinforced multi-layer structure.
The above-mentioned materials for the inner tube 9 are merely examples, and there are no particular limitations as long as the required performance such as flexibility and fluid flowability can be ensured.

The inner pipe 9 is inserted into the corrugated cladding pipe 10. The outer periphery of the inner pipe 9 is clad with the corrugated cladding pipe 10. The central axes of the inner pipe 9 and the corrugated cladding pipe 10 are substantially aligned on a common axis (pipe axis L ₁ ).

The corrugated cladding pipe 10 is made of a flexible resin, and is preferably made of a single-layer foamed resin body. The foaming ratio of the foamed resin body is preferably 1.05 to 4 times, more preferably 1.2 to 2.5 times, from the viewpoints of noise suppression and heat retention. The resin material of the corrugated cladding pipe 10 is preferably mainly composed of polyethylene (50 wt% or more) and contains less than 50 wt% of polypropylene. From the viewpoint of flexibility, low-density polyethylene (LDPE) is preferable as the polyethylene of the main component of the corrugated cladding pipe 10. More preferably, the corrugated cladding pipe 10 contains a lubricant for ease of demolding, etc. The content of the lubricant in the foamed resin body is preferably 1 wt% or less.
The above-mentioned materials for the corrugated cladding tube 10 are merely examples, and there are no particular limitations on the material for the corrugated cladding tube 10 as long as it can ensure the required performance such as flexibility and protection for the inner tube 9 .

As shown in FIG. 1, the corrugated cladding tube 10 has a plurality of annular peaks 11 (large diameter portions) and a plurality of annular valleys 12 (small diameter portions), and has a corrugated cross section. The peaks 11 and the valleys 12 are alternately formed at a constant arrangement pitch in the tube axial direction. As shown in FIG. 2, the peaks 11 are annular convex portions when viewed from the outside of the corrugated cladding tube 10, and annular concave portions when viewed from the inside. The valleys 12 are annular concave portions when viewed from the outside of the corrugated cladding tube 10, and annular convex portions when viewed from the inside. The valleys 12 are thinner than the peaks 11, and the width W ₁₂ along the tube axis L ₁ is smaller than the width W ₁₁ of the peaks 11 along the tube axis L ₁ (W ₁₂ <W ₁₁ ). As a result, when the corrugated cladding tube 10 is expanded, contracted, or bent, the valleys 12 are more easily deformed than the peaks 11.
At an intermediate height H ₁₀ between the peaks 11 and the valleys 12, the peaks 11 have a width W ₁₁ along the tube axis L ₁ of, for example, W ₁₁ =about 2 mm to 4 mm, and the valleys 12 have a width W ₁₂ of, for example, W ₁ =about 0.5 mm to 1.5 mm.

As shown in Fig. 3, a plurality of holding protrusions 13 are formed in at least a portion (first) of the valleys 12A. The holding protrusions 13 protrude from the valleys 12A toward the tube axis _L1 (inward in the radial direction). A cross section of the holding protrusions 13 perpendicular to the tube axis _L1 is formed in a roughly fan shape with both bottom portions being linear. An apex 13p of the holding protrusions 13 facing the tube axis _L1 is arc-shaped and is almost in contact with the inner tube 9. The width of the apex 13p along the tube axis direction (direction perpendicular to the paper surface of Fig. 3) is smaller than the valley width _W12 .

The multiple holding protrusions 13 in the first valley portion 12A are arranged at intervals from each other in the tube circumferential direction. In this embodiment, four holding protrusions 13 are arranged at equal intervals in the tube circumferential direction. As shown in Fig. 1, the valley portions 12A having the holding protrusions 13 are arranged at regular intervals in the tube axial direction of the corrugated cladding tube 10. The holding protrusions 13 are not formed in the second valley portion 12B and the peak portions 11 other than the valley portion 12A, and therefore the holding protrusions 13 are discontinuous in the tube circumferential direction and the tube axial direction of the corrugated cladding tube 10.
In addition, all the valley portions 12 of the corrugated cladding tube 10 may be the first valley portions 12A having the holding protrusions 13.

2 and 3, the retaining protrusions 13 protrude toward the tube axis L1 side (radially inward) beyond the other valleys 12 (i.e., valley portions 14 between the retaining protrusions 13 adjacent in the circumferential direction in the first valleys _12A and the second valleys 12B). As shown in Fig. 1, a recess 16 corresponding to the retaining protrusion 13 is formed on the outer circumferential surface of the valleys 12A of the corrugated cladding tube 10.

1, the holding protrusion height H13 from the top of the peak 11 to the top 13p of the holding protrusion ₁₃ is preferably 1.5 to 5 times the valley height H12 from the top of the peak 11 to the inner apex 12p (the portion closest to the tube axis _L1 ) of the valley 12 (the valley portion 14 of the first valley 12A and the second valley 12B) other than the holding protrusion ( _H13 =1.5× _H12 to 5× _H12 ). More preferably, the holding protrusion height _H13 is about 3 times the valley height _H12 ( _{H13 =} 3× _H12 ).

As shown in Fig. 3, the holding protrusion 13 is arranged to be shifted in the pipe circumferential direction with respect to a virtual parting cross section _PL1 including a parting line position 15 of the corrugated cladding tube 10. The valley portion 14 is arranged on the parting cross section _PL1 and straddles the parting line position 15. The parting cross section _PL1 corresponds to a joint 38 of a pair of corrugated split dies 32 of a corrugated cladding tube manufacturing apparatus 3 described later, and the parting cross section _PL1 corresponds to a virtual split surface _PL38 including the joint 38 (Fig. 6). At the parting line position 15, a parting line due to the joint 38 can be formed.
It should be noted that the parting line does not necessarily have to appear at the parting line position 15, and depending on the molding conditions, the parting line may not be formed.

3, of the end faces 13e, 13f on both sides in the pipe circumferential direction of each holding protrusion 13, the end face 13f on the side farther from the nearest parting line position 15 of the holding protrusion 13 forms an angle of 90° with the parting cross section _PL1 . The end face 13e on the side closer to the parting line position 15 is parallel to the parting cross section _PL1 (angle 0°).

Here, the end faces 13e and 13f of the holding protrusion 13 refer to the surface portions that are approximately linear when viewed from the tube axis direction between the R-section 13r where the holding protrusion 13 is connected to the valley section 14 and the apex 13p. These end faces 13e and 13f form an angle of approximately 90° with each other. As shown in Fig. 3, the cross section of the holding protrusion 13 that is perpendicular to the tube axis direction is symmetrical with respect to the center line _L13c that passes through the apex 13p of the holding protrusion 13 and the tube axis _L1 .

1 , on the inner surface of the corrugated cladding tube 10, the gradient of the side surface 13a in the tube axis direction of the holding protrusion 13 is equivalent to the gradient of the tube inner side surface 14a on the same side in the tube axis direction of the valley portion 14. The width _W13 in the tube axis direction of the holding protrusion 13 at the intermediate height _H10 between the valley portion 14 and the peak portion 11 is wider than the width _W14 (= _W12 ) in the tube axis direction of the valley portion 14 and narrower than the pitch _P11 of the peak portions 11 ( _W14 < _W13 < _P11 ).

As shown in FIG. 1, a ventilation gap 18 is formed between the corrugated cladding tube 10 and the inner tube 9. The ventilation gap 18 is continuous and uninterrupted throughout the entire axial direction of the composite pipe 1. The ventilation gap 18 acts as an air insulating layer, improving the thermal insulation of the composite pipe 1.

Figure 4 shows an apparatus 3 for manufacturing the corrugated cladding pipe 10 and thus the composite pipe 1. The corrugated cladding pipe manufacturing apparatus (composite pipe manufacturing apparatus) 3 is equipped with a supply section 4 and a corrugated pipe forming section 30. Although detailed illustration is omitted, the supply section 4 includes a hopper for receiving the resin 19 that is the raw material for the corrugated cladding pipe 10, a heater for heating and melting the resin 19, a section for adding a foaming agent, a section for adding a lubricant, an extrusion section 4a such as a screw for kneading and extruding the resin 19, the foaming agent, and the lubricant, and an annular extrusion nozzle 20.

As shown in FIG. 5, the extrusion nozzle 20 includes an inner tube outlet 21 consisting of a central hole, and an extrusion port 22. The inner diameter of the inner tube outlet 21 is larger than the outer diameter of the inner tube 9. The extrusion port 22 is annular so as to surround the inner tube outlet 21. The extrusion section 4a is connected to the upstream end of the extrusion port 22. The annular downstream end of the extrusion port 22 opens into the tip face of the extrusion nozzle 20.

As shown in FIG. 4, a corrugated pipe forming section 30 (corrugator) is disposed downstream of the extrusion nozzle 20 in the extrusion direction (on the right side in FIG. 4). The corrugated pipe forming section 30 includes two (a plurality of) oval circular tracks 31 and a plurality of half-cylinder corrugation split dies 32 for each of the circular tracks 31. The circular tracks 31 are disposed horizontally, but are not limited thereto, and may be disposed vertically or obliquely. These two circular tracks 31 share one track portion 31a. The track portion 31a is linear along the axis _L3 which is a straight extension of the axis (extrusion direction) of the extrusion nozzle 20. The supply section 4 is connected to the upstream end (left end in FIG. 4) of the track portion 31a by facing the extrusion nozzle 20.

As shown in FIG. 4, a plurality of corrugation dies 32 are arranged in a circular pattern on each annular track 31. Although not shown, the corrugation dies 32 are circulated on the corresponding annular track 31 by a moving mechanism including a motor, gears, or a chain, sprockets, etc. The movements of the corrugation dies 32 on the two annular tracks 31 are synchronized with each other.

As shown in Figures 4 and 5, the corrugation split dies 32 of the two annular tracks 31 are paired with each other on the track portion 31a. These pairs of corrugation split dies 32 join with each other while moving on the track portion 31a to form a closed cylindrical mold 33. A plurality of molds 33 are arranged in a line on the axis _L3 . The axis _L3 constitutes the central axis of the mold 33 on the track portion 31a. As shown in Figure 6, at two points 180 degrees apart on the mold 33, seams 38 are formed between both ends of the corrugation split dies 32 in the circumferential direction.
The pair of corrugated split dies 32 are arranged to approach and separate from each other in the horizontal direction (up and down in FIG. 4) at the upstream end (left end in FIG. 4) and the downstream end (right end in FIG. 4) of the track portion 31a, but may also be arranged to approach and separate from each other in the vertical direction, or may be arranged to approach and separate from each other in a diagonal direction relative to the horizontal or vertical direction.

As shown in Fig. 5, the inner peripheral surface of each corrugated split mold 32 and thus the forming mold 33 constitutes a corrugated mold surface 39. The corrugated mold surface 39 includes a mountain portion 34 and a valley portion 35. These mold portions 34, 35 are alternately arranged along the axis _L3 . As shown in Figs. 5 and 6, the mountain portion 34 is recessed radially outward and formed into a concave ring shape around the entire circumference of the forming mold 33. The inner peripheral diameter of the mountain portion 34 is larger than the outer peripheral diameter of the extrusion port 22. The valley portion 35 is formed into a convex ring shape that protrudes radially inward (toward the axis _L3 ) from the mountain portion 34.

As shown in Fig. 5, a portion (first) of the valley portions 35A is provided with a protruding portion 36 for forming the holding protrusion 13. A cross section of the protruding portion 36 perpendicular to the axis _L3 is formed in a roughly sector shape with linear end faces 36e, 36f and an arc-shaped apex 36p. The cross section of the protruding portion 36 is symmetrical with respect to a center line _LC36 passing through the apex 36p of the protruding portion 36.

The protruding portion 36 protrudes radially inward from the portion of the valley portion 35A other than the protruding portion 36 and from the other (second) valley portion 35B. The protruding height H36 from the bottom of the mountain portion 34 to the top 36p of the protruding portion ₃₆ is preferably 1.5 to 5 times the valley height _H35 from the bottom of the mountain portion 34 to the top of the valley portion 35A ( _H36 = 1.5 x _H35 to 5 x _H35 ). More preferably, the protruding height _H36 is about 3 times the valley height _H35 ( _H36 = 3 x _H35 ).

As shown in FIG. 6, four protruding portions 36 are arranged at intervals, preferably at equal intervals, in the circumferential direction of the mold 33. The protruding portions 36 are discontinuous in the circumferential direction of the mold 33.

As shown in FIG. 6, the portion between adjacent protruding mold portions 36 in the valley portion 35A constitutes a retractable mold portion 37. The retractable mold portion 37 is recessed radially outward from the protruding mold portion 36. As shown in FIG. 6 and FIG. 7, the retractable mold portion 37 is positioned so as to straddle the seam 38 between the corrugation split molds 32. The protruding mold portion 36 is offset from the seam 38 in the circumferential direction of the corrugation mold surface 39, and is positioned in the circumferential middle of each semi-split cylindrical corrugation split mold 32.

Specifically, the protruding portions 36 are arranged at 45° angles on both sides of the exact circumferential center of each corrugation split mold 32. Two protruding portions 36 are provided on each of the two corrugation split molds 22 that make up a pair. In other words, the number of protruding portions provided on one corrugation split mold 32 of the pair is the same as the number of protruding portions provided on the other corrugation split mold 32.

Of the end faces 36e, 36f on both sides in the pipe circumferential direction of each protruding mold portion 36, the end face 36f on the side farther from the nearest seam 38 of the protruding mold portion 36 is perpendicular to an imaginary plane (hereinafter, "cutting plane PL ₃₈ ") that includes the seam 38. The end face 13e on the side closer to the seam 38 is approximately parallel to the cutting plane PL _38. These end faces 13e, 13f on both sides form an angle of approximately 90° with each other.

5, the corrugated split mold 32 and thus the molding mold 33 may be constructed by combining a mold block 32a without a protruding mold portion 36 and a mold block 32b with a protruding mold portion 36. In this case, in order to facilitate the production of the molding mold 33, it is preferable that the mold block 32b and thus the protruding mold portion 36 are disposed at the end of each molding mold 33.
From the viewpoint of preventing the resin 19A from being caught between the adjacent molding dies 33 , the protruding die portion 36 may be disposed in the middle of each molding die 33 .

As shown in FIG. 5, a suction mechanism 50 is further added to the corrugated pipe forming section 30. The suction mechanism 50 includes a number of suction holes 52 and suction paths 53. The suction holes 52 are distributed and arranged on the corrugated mold surface 39. Suction paths 53 extend from the suction holes 52 and are connected to a vacuum pump 51. An opening and closing valve 54 is provided in the suction path 53.

The composite pipe 1 is manufactured as follows.
The inner tube 9 is prepared in advance by molding and curing it, obtaining it, or the like.
The inner pipe 9 is introduced into the extrusion nozzle 20 of the composite pipe manufacturing apparatus 3, and sent out from the inner pipe delivery port 21 toward the corrugated pipe forming section 30. The inner pipe 9 is introduced into the inside of the forming die 33 of the corrugated pipe forming section 30, and sent downstream in the feed direction (to the right in FIG. 5) along the axis _L3 .
An annular gas supply passage 1d is formed between the inner peripheral surface of the inner pipe delivery port 21 and the outer peripheral surface of the inner pipe 9. The upstream end of the gas supply passage 1d (left side in FIG. 5) is open to the atmosphere. A gas pressure-feeding device such as a compressor or a pump may be connected to the upstream end of the gas supply passage 1d to feed a gas such as air from the extrusion nozzle 20 toward the corrugated pipe forming section 30.

At the same time, in the resin supply section 4, the resin 19 is heated and melted, and a predetermined amount of a foaming agent or the like is added so that the resin 19 is foamed at a predetermined foaming ratio (preferably 1.05 to 4 times). The resin 19 is supplied to the extrusion nozzle 20 and extruded from the extrusion port 22 toward the corrugated pipe forming section 30.
The resin 19A during extrusion is in a tubular shape having substantially the same inner and outer diameters as the extrusion port 22. The tubular resin 19A becomes a coating layer surrounding the inner tube 9.

In the corrugated pipe forming section 30, the corrugation split dies 32 are circulated along a circular track 31. In the vicinity of the extrusion port 22, the corresponding corrugation split dies 32 come close to each other and come together to form a cylindrical forming die 33.
A tubular resin 19A is introduced into the molding die 3. Since the protruding die portion 36 is offset from a seam 38 between the corrugated split dies 32 and the inscribed circle diameter of the corrugated die surface 39 at the seam 38 is relatively large, the resin 19A can be prevented from getting caught in the seam 38.

Then, the suction mechanism 50 sucks the resin 19A from the suction hole 52 of the corrugated pipe forming section 30. This causes the tubular resin 19A to be tightly attached to the corrugated mold surface 39 of the mold 33, and the corrugated cladding pipe 10 with a corrugated cross section is formed. An air gap 18 is formed between the corrugated cladding pipe 10 and the inner pipe 9, and the air gap 18 is connected to the gas supply path 1d. This causes the outside air (air) to be supplied from the gas supply path 1d to the entire area of the air gap 18 in conjunction with the vacuum. As a result, the resin 19A can be reliably sucked to the corrugated mold surface 39, and the corrugated cladding pipe 10 can be reliably formed.

The peak portion 11 is formed by the peak portion 34. The valley portion 12 is formed by the valley portion 35. The first valley portion 35A is formed by the first valley portion 12A, and the second valley portion 35B is formed by the second valley portion 12B. Furthermore, in the valley portion 35A, the retractable portion 37 forms the valley portion 14, and the protruding portion 36 forms the retaining protrusion 13. The protruding portion 36 and thus the retaining protrusion 13 are arranged discontinuously in the circumferential direction of the pipe and are not continuous around the entire circumference, which facilitates molding.

In addition, the valley portion 14 straddles the seam 38 between the corrugated split molds 32. The holding protrusion 13 is formed avoiding the seam 38. Therefore, as described above, the resin 19A does not get caught in the seam 38. In particular, the resin portion that becomes the holding protrusion 13 does not get caught in the seam 38. This makes it possible to prevent burrs and dents due to resin being caught, and the corrugated cladding tube 10 can be molded well and reliably. A parting line can be formed at a position 15 corresponding to the seam 38 on the corrugated cladding tube 10. A parting surface PL ₃₈ including the seam 38 on the molding mold 33 coincides with the parting cross section PL ₁ of the corrugated cladding tube 10.

As the forming die 33 is moved along the track portion 31a so as to move away from the extrusion port 22, the corrugated cladding tube 10 and hence the composite tube 1 inside the forming die 33 are moved in the same direction.
At the downstream end of the orbital portion 31a (the right end in FIG. 4), as shown by the white arrows in FIG. 4 and FIG. 5, the pair of corrugated split dies 32 of the forming die 33 move in parallel in the opposite direction to the facing direction (the demolding direction perpendicular to the split surface PL ₃₈ ) and rotate along the downstream turn-back semicircular orbital portion 31b of each annular orbit 31, and are separated from each other. This causes the corrugated cladding tube 10 to be released from the forming die 33. At this time, the valley portion 35 including the protruding portion 36 is not undercut. In particular, the end faces 36e and 36f of the protruding portion 36 are not undercut in the demolding direction perpendicular to the split surface PL ₃₈ , so that the mold can be easily released. By including a lubricant in the resin 19A, the frictional resistance during demolding can be reduced, and the mold release can be facilitated.
After being released from the mold, the composite pipe 1 is sent out from the corrugated pipe forming section 30 along the axis _L3 to the downstream side in the sending direction (to the right in FIG. 4).

In the composite pipe 1 thus manufactured, the apex 13p of each holding protrusion 13 of the corrugated cladding pipe 10 is in close proximity to or in contact with the outer circumferential surface of the inner pipe 9, thereby holding the inner pipe 9 from shifting from the pipe axis _L1 . This makes it possible to prevent the inner pipe 9 from flapping due to a sudden change in internal pressure or temperature. In addition, when a fluid such as water is flowed inside the inner pipe 9, the generation of noise such as a ringing sound can be suppressed or prevented. Furthermore, by preventing the formation of burrs at the parting line position 15, noise caused by burrs can be reliably prevented.
There is no need to interpose a foamed resin intermediate layer or sound-deadening tape between the corrugated cladding pipe 10 and the inner pipe 9 to prevent abnormal noise, and this can prevent costs from increasing.

The holding protrusion 13 has a cross-sectional shape symmetrical with respect to the center line _L13C, which prevents bias in strength. In addition, the two end faces 13e, 13f form an angle of 90° with each other, which makes it difficult for the holding protrusion 13 to break in the circumferential direction of the tube. Furthermore, by making the width _W13 of the holding protrusion 13 in the tube axial direction larger than the width _W14 of the valley portion 14, it is possible to make the holding protrusion 13 difficult to break in the tube axial direction. This makes it possible to suppress buckling of the holding protrusion 13, and to hold the inner tube 9 more stably.

Also, when the corrugated cladding tube 10 is viewed from the outside, the recesses 16 corresponding to the holding protrusions 13 are recessed larger than the valley portions 14 and extend to the crests 11, and a part of the crests 11 appears to be missing, so that the position of the holding protrusions 13 can be easily confirmed from the outside. Therefore, when cutting the corrugated cladding tube 10 for joint connection or the like, it is easy to cut while avoiding the holding protrusions 13. Since the width W ₁₃ of the holding protrusions 13 in the tube axial direction is wider than the width W ₁₄ of the valley portions 14, the position of the holding protrusions 13 can be easily known by visual inspection or touch. When the corrugated cladding tube 10 is contracted in the tube axial direction, it is possible to avoid gripping the holding protrusions 13, and it is not necessary to apply much force. When the inner tube 9 is inserted into the corrugated cladding tube 10, the inner tube 9 may get caught by the holding protrusions 13, but the position of the catch is known, and the inner tube 9 can be inserted while being positioned while holding the vicinity of the holding protrusions 13, so that the catch can be suppressed.

Since the corrugated covering tube 10 is composed of a single layer of foamed resin having an expansion ratio preferably of 1.05 to 4 times, and more preferably of 1.2 to 2.5 times, noise caused by flapping of the inner tube 9 can be reliably suppressed and heat retention can be improved.
In addition, since a heat insulating layer is formed by the ventilation gap 18 between the corrugated cladding tube 10 and the inner tube 9, the heat retention of the composite tube 1 can be ensured.
By setting the holding protrusion height _H13 to be 1.5 to 5 times the valley height _H12 , the inner tube 9 can be securely held, the ventilation gap 18 can be securely formed, and heat retention can be securely ensured.
The top 13p of the holding protrusion 13 comes into spot contact with the inner pipe 9, thereby reducing the contact area between the inner pipe 9 and the holding protrusion 13, and therefore the corrugated cladding tube 10. Therefore, the heat conduction between the inner pipe 9 and the corrugated cladding tube 10 can be suppressed, and the heat retention can be further improved.
By incorporating a lubricant in the corrugated cladding tube 10, the frictional resistance between the inner tube 9 and the corrugated cladding tube 10 can be reduced, thereby facilitating the work of shrinking the end of the corrugated cladding tube 10 to expose the end of the inner tube 9 for joint connection, etc., or of pulling the composite pipe 1 around.

Next, another embodiment of the present invention will be described. In the following embodiment, the same components as those in the above-described embodiment will be denoted by the same reference numerals in the drawings and the description thereof will be omitted.
Second embodiment (FIGS. 8 and 9)
As shown in Fig. 8, in the corrugated cladding tube 10B according to the second embodiment, the cross section of the holding protrusion 13 perpendicular to the tube axis is approximately trapezoidal. The top 13p of the holding protrusion 13 is recessed in an arc-shaped concave shape so as to fit the outer periphery of the inner tube 9. The recess of the top 13p may be formed by the forming die 33B (Fig. 9) or by the inner tube 9. The outer periphery of the inner tube 9 fits into the recess of the top 13p, thereby enabling the inner tube 9 to be firmly held.

An end face 13e of the holding protrusion 13 on the side closer to the parting line position 15 is inclined with respect to the parting cross section _PL1 so as to approach the imaginary parting cross section _PL1 toward the apex 13p. An end face 13f on the side farther from the parting line position 15 forms an angle of 90° or _less with respect to the parting cross section _PL1 on the side facing the parting cross section PL1, and is preferably substantially perpendicular to the parting cross section _PL1 , as in the first embodiment.

As shown in Fig. 9, in the molding die 33B according to the second embodiment, the cross section of the protruding mold portion 36 perpendicular to the tube axis is approximately trapezoidal. The top 36p of the protruding mold portion 36 is an arc-shaped concave surface along the outer periphery of the inner tube 9. The end face 36e on the side close to the seam 38 of the protruding mold portion ₃₆ is inclined with respect to the imaginary cutting surface _PL38 so as to approach the top 36p. The end face 36f on the side farther from the seam 38 forms an angle of 90° or less with respect to the cutting surface _PL38 on the side facing the cutting surface _PL38 , and is preferably approximately perpendicular to the cutting surface _PL38 , as in the first embodiment.
In the molding die 33B, the protruding die portion 36 does not become an undercut when released from the die, and ease of molding can be ensured.

Third embodiment (FIGS. 10 and 11)
As shown in Fig. 10, in the corrugated cladding tube 10C according to the third embodiment, a pair (two) of holding protrusions 13 are arranged at positions spaced apart from each other by 180° in the circumferential direction of the valley portion 12A. As in the first embodiment, the cross-sectional shape of the holding protrusion 13 is formed in a roughly arc-shaped sector shape with a top 13p. Both end faces 13g of the holding protrusion 13 form an angle of 45° with respect to the imaginary parting cross section _PL1 . By minimizing the number of holding protrusions 13, the contact area with the inner tube 9 can be reduced to ensure heat retention.

As shown in Fig. 11, in the molding die 33C according to the third embodiment, one protruding die portion 36 is provided in the center of each semicircular corrugated split die 32. The protruding die portions 36 of the pair of corrugated split dies 32 face each other at a distance of 180° in the circumferential direction of the molding die 33C. The cross-sectional shape of the protruding die portion 36 is formed in a roughly fan shape with both end faces 36g being linear and the top portion 36p being arc-shaped. Both end faces 36g of the protruding die portion 36 form an angle of 45° with the split surface PL _38. In the molding die 33C, the protruding die portion 36 does not become an undercut when demolded, and ease of molding can be ensured.

Fourth embodiment (FIGS. 12 and 13)
As shown in Fig. 12, in the corrugated cladding tube 10D according to the fourth embodiment, the numbers of the holding protrusions 13 on both sides of the imaginary parting cross section _PL1 are different from each other. In detail, two holding protrusions 13 are arranged at a distance of 90° from each other on one half of the circumference (left side in Fig. 12) of the valley portion 12A across the parting cross section _PL1 . One holding protrusion 13 is arranged at the center in the circumferential direction on the other half of the circumference (right side in Fig. 12). The cross-sectional shape of these holding protrusions 13 is formed in a roughly sector shape with linear end faces and an arc-shaped apex 13p, as in the first embodiment.

The opposing end faces 13f of the two holding protrusions 13 on one side (the left side in FIG. 12) are perpendicular to the parting cross section _PL1 , and the opposite end faces 13e are parallel to the parting cross section _PL1 . Both end faces 13g of the holding protrusion 13 on the other side (the right side in FIG. 12) in the semicircular portion form an angle of 45° with the imaginary parting cross section _PL1 .
In addition, the arrangement or number of the holding protrusions 13 in the valleys 12A adjacent to each other in the tube axial direction (perpendicular to the paper surface of FIG. 12) of the corrugated cladding tube 10D may be different from each other. For example, the arrangements of the holding protrusions 13 in the adjacent valleys 12A may be reversed by 180° from each other.

As shown in FIG. 13, in the molding die 33D according to the fourth embodiment, the number of protruding die portions 36 of the pair of corrugated split dies 32 is different from each other. In one corrugated split die 32 (left side in FIG. 13), two protruding die portions 36 are arranged at an angle of 90° from each other. In the other corrugated split die 32 (right side in FIG. 13), one protruding die portion 36 is arranged in the circumferential center. The cross-sectional shape of these protruding die portions 36 is formed in a roughly sector shape with an arc-shaped apex 36p, as in the first embodiment.

The opposing end faces 36f of the two protruding mold portions 36 in one of the corrugated split molds 32 (the left side in FIG. 13) are perpendicular to the parting surface PL ₃₈ , and the opposite end faces 36e are parallel to the parting surface PL _38. The two end faces 36g of the protruding mold portions 36 in the other of the corrugated split molds 32 (the right side in FIG. 13) are at an angle of 45° to the parting surface PL _38. In the molding mold 33D, the protruding mold portions 36 do not become undercut when released, and ease of molding can be ensured.
The protruding portion 36 may be provided on at least one of the pair of corrugated split dies 32 in the forming die 33. The numbers of protruding portions 36 of adjacent corrugated split dies 32 on the annular track 31 may be different from each other.

Fifth embodiment (FIGS. 14 and 15)
As shown in Fig. 14, in the corrugated cladding tube 10E according to the fifth embodiment, the apex 13p of the holding protrusion 13 is formed in a straight line parallel to the imaginary parting cross section _PL1 and extends over the entire area of the holding protrusion 13. Both ends of the apex 13p are directly connected to the valley 12A. In other words, both end faces 13g of the holding protrusion 13 are arranged on a straight line by forming an angle of 180° with each other. The angle between each end face 13g and the parting cross section _PL1 is 0°. The inner pipe 9 is sandwiched between the pair of holding protrusions 13. This allows the inner pipe 9 to be stably held.

As shown in Fig. 15, in the molding die 33E according to the fifth embodiment, the top 36p of the protruding portion 36 is formed in a straight line parallel to the cut surface PL ₃₈ and extends over the entire area of the protruding portion 36. Both ends of the top 36p are directly connected to the valley portion 35A. In other words, both end faces 36g of the protruding portion 36 are arranged in a straight line by forming an angle of 180° with each other. The angle between each end face 36g and the cut surface PL ₃₈ is 0°. In the molding die 33E, the protruding portion 36 does not become an undercut when released from the mold, and ease of molding can be ensured.

Sixth embodiment (FIGS. 16 and 17)
As shown in FIG. 16, in the corrugated cladding tube 10F according to the sixth embodiment, the cross-sectional shape of the holding protrusion 13 is an acute triangle. The arrangement and number of the holding protrusions 13 in the valley portion 12A are the same as those in the first embodiment. Each holding protrusion 13 protrudes from the valley portion 12A toward the inner pipe 9 along a direction perpendicular to the imaginary parting cross section _PL1 . Both end faces 13e, 13f are at angles of 90° to 0° with respect to the parting cross section _PL1 on the side facing the parting cross section _PL1 , and approach each other toward the apex 13p. The tapered apex 13p is almost in contact with the inner pipe 9. This makes it possible to minimize the contact area between the holding protrusion 13 and the inner pipe 13, thereby ensuring heat retention.

As shown in Fig. 17, in the molding die 33F according to the sixth embodiment, the cross-sectional shape of the protruding mold portion 36 is an acute triangle. The arrangement and number of the protruding mold portions 36 in the valley portion 35A are the same as those in the first embodiment. Each protruding mold portion 36 protrudes from the valley portion 35A in a direction perpendicular to the cut surface PL _38. Both end faces 36e, 36f of the protruding mold portion 36 are at an angle of 90° to 0° with respect to the cut surface PL ₃₈ on the side facing the cut surface PL _38. In the molding die 33F, the protruding mold portion 36 does not become an undercut when demolded, and ease of molding can be ensured.

Seventh embodiment (FIGS. 18 to 19)
As shown in Fig. 18, in the corrugated cladding tube 10G according to the seventh embodiment, the cross-sectional shape of the holding protrusion 13 is U-shaped. The arrangement and number of the holding protrusions 13 in the valley portion 12A are the same as those in the first embodiment. Each holding protrusion 13 protrudes from the valley portion 12A toward the inner pipe 9 along a direction perpendicular to the imaginary parting cross section _PL1 . Both end faces 13e, 13f are parallel to each other and perpendicular to the parting cross section _PL1 . The apex 13p of the semicircular cross section is almost in contact with the inner pipe 9. This makes it possible to reduce the contact area between the holding protrusion 13 and the inner pipe 13, thereby ensuring heat retention.

As shown in Fig. 19, in a molding die 33G according to the seventh embodiment, a protruding portion 36 protrudes from a valley portion 35A in a direction perpendicular to the cut surface PL _38. Both end faces 36e, 36f of the protruding portion 36 are each at an angle of 90° with respect to the cut surface PL _38. A top portion 36p has a semicircular cross section. In the molding die 33G, the protruding portion 36 does not become an undercut when released from the mold, and ease of molding can be ensured.

Eighth embodiment (FIG. 20)
As shown in Fig. 20, in the corrugated cladding tube 10H according to the eighth embodiment, the gradient of the side surface 13a of the holding protrusion 13 in the tube axis direction is steeper than the gradient of the inner tube side surface 14a on the same side of the valley portion 14. The width _W13 in the tube axis direction of the holding protrusion 13 at the intermediate height _H10 between the peak portion 11 and the valley portion 12 is equal to the width _W14 in the tube axis direction of the valley portion 14 ( _W13 = _W14 ). According to the corrugated cladding tube 10H, the recess 16 appearing on the outer surface by the holding protrusion 13 can be prevented from reaching the peak portion 11, and chipping of the peak portion 11 can be prevented.

Ninth embodiment (FIGS. 21 and 22)
21 , in the corrugated cladding tube 10I according to the ninth embodiment, the cross-sectional shape of the holding protrusion 13 along the tube axis _L1 is asymmetric with respect to a center line _L13I along the tube diameter passing through the apex 13p of the holding protrusion 13. In detail, the gradient of the side surface 13b of the holding protrusion 13 on one side in the tube axis direction (the left side in FIG. 21 ) is gentler than the gradient of the side surface 13d on the other side in the tube axis direction (the right side in FIG. 21 ).

Here, the side surfaces 13b and 13d of the holding protrusion 13 refer to the surface portions between the R portion 13q where the holding protrusion 13 is connected to the mountain portion 11 or the valley portion 14 and the apex 13p, where the cross section along the tube axis _L1 is approximately linear. The R portion 13q has an arc-shaped cross section, but is not limited thereto, and may have a linear cross section with a gentler gradient than the side surfaces 13b and 13d, as shown in Fig. 23. The apex 13p has an arc-shaped cross section, but is not limited thereto, and may be a flat surface intersecting (perpendicular to) the protruding direction of the holding protrusion 13, as shown in Fig. 24(a), or may be sharply pointed at an acute angle by the side surfaces 13b and 13d directly intersecting each other, as shown in Fig. 24(b).

Preferably, the gradient of the gently sloping side surface 13b is gentler than the gradient of the steeply sloping side surface 13d by 1° or more. Preferably, the angle of the gently sloping side surface 13b with respect to the center line L _13I (in the pipe radial direction) is 5° to 20°.

As shown in FIG. 22, in the protruding mold portion 36 of the forming mold 33I according to the ninth embodiment, the gradient of the side surface 36b facing the upstream side in the feed direction of the track portion 31a is gentler than the gradient of the side surface 36d facing the downstream side. Preferably, the gradient of the gentle gradient side surface 36b is 1° or more gentler than the gradient of the steep gradient side surface 36d. Preferably, the angle of the gentle gradient side surface 36b with respect to the radial direction of the forming mold 33I is 5° to 20°.

As shown in FIG. 22, the gently sloping side 13b of the holding protrusion 13 is formed by the gently sloping side 36b facing the upstream side of the protruding mold portion 36. The steeply sloping side 13d is formed by the steeply sloping side 36d facing the downstream side. By making the upstream side 36b of the protruding mold portion 36 and therefore the side 13b of the holding protrusion 13 gently sloping, it is possible to prevent the upstream side 13b of the holding protrusion 13 from interfering with the protruding mold portion 36 and being deformed so as to be concave when the mold is demolded along the semicircular orbit portion 31b of the downstream turnaround.

As shown by the two-dot chain line in FIG. 22, if the upstream side 13b of the holding protrusion 13 had the same slope as the downstream side 13d, when the corrugated split mold 32 rotates along the downstream semicircular portion of the annular track 31 for demolding, the protruding mold portion 36 will be more likely to come into contact with the upstream side 13b of the holding protrusion 13.

The present invention is not limited to the above-described embodiment, and various modifications can be adopted without departing from the spirit of the present invention.
For example, the corrugated cladding tube according to the present invention is not limited to a circular cross section. As shown in Fig. 25, the corrugated cladding tube 10J may have an elliptical cross section. As shown in Fig. 26, the corrugated cladding tube 10K may have a rectangular cross section.
The above-mentioned embodiments may be combined with each other. For example, the cross-sectional shape perpendicular to the tube axis _L1 of the holding protrusion 13 of the eighth embodiment (FIG. 20) or the ninth embodiment (FIG. 21) may be any of the cross-sectional shapes of the first to seventh embodiments (FIGS. 1 to 19).

The present invention can be applied to, for example, water and hot water supply pipes.

L ₁ Pipe axis L _13c center line L _13I center line LC ₃₆ center line PL ₁ Parting section PL ₃₈₀ sectional surface H ₁₀ Intermediate height 1 Composite pipe 3 Composite pipe manufacturing equipment (corrugated cladding pipe manufacturing equipment)
4: supply section 4a; extrusion section 9: inner pipe 10: corrugated cladding pipe 10B to 10K; corrugated cladding pipe 11: peak section 12: valley section 12A; partial valley section 12B; other valley section 12p; pipe inner top section 13: holding protrusion section 13a; side surface 13b; one side The gently sloping side surface 13d (upstream side) The steeply sloping side surface on the other side (downstream side) Right 13e Near end surface 13f Far end surface 13g End surface 13p Peaks 13r, 13q R portion 14 Valley portion 14a Pipe inner surface 15 Parting Line position 19 Raw resin 19A Tubular resin 20 Extrusion nozzle 31 Annular orbit 31a Shared orbit portion 31b Downstream folded semicircular orbit portion 32 Waved split mold 33 Forming mold 34 Mountain portion 35 Valley portion 35A Part (first 1) Valley-shaped portion 35B Another (second) valley portion 36, protruding portion 36b, upstream side surface 36d, downstream side surface 36e, near end surface 36f, far end surface 36g, end surface 36p, peak 37, recessed portion 38, seam 39, corrugated surface 50 Suction Mechanism

Claims (27)

A flexible corrugated cladding tube covering a flexible inner tube,
The tube has a plurality of annular peaks and a plurality of annular valleys arranged alternately in the tube axial direction,
At least some of the valleys are formed with a plurality of holding protrusions each protruding toward the tube axis, and these holding protrusions are arranged spaced apart from each other in the tube circumferential direction ;
the holding protrusions are arranged to be shifted in a pipe circumferential direction with respect to a virtual parting cross section including a parting line position, and valley portions between the holding protrusions adjacent in the pipe circumferential direction in the partial valley portion straddle the parting cross section,
a parting line position of the proximal end of the retaining protrusion, the parting line position being located at an angle of 90° or less with respect to the parting cross section, the parting line position being located at an angle of 90° or less with respect to the parting cross section . A flexible corrugated cladding tube covering a flexible inner tube,
The tube has a plurality of annular peaks and a plurality of annular valleys arranged alternately in the tube axial direction,
At least some of the valleys are formed with a plurality of holding protrusions each protruding toward the tube axis, and these holding protrusions are arranged spaced apart from each other in the tube circumferential direction;
the holding protrusions are arranged to be shifted in a pipe circumferential direction with respect to a virtual parting cross section including a parting line position, and valley portions between the holding protrusions adjacent in the pipe circumferential direction in the partial valley portion straddle the parting cross section,
a parting line extending from the outer circumferential surface of the retaining protrusion to the outer circumferential surface of the retaining protrusion, the parting line extending from the outer circumferential surface of the retaining protrusion to the outer circumferential surface of the retaining protrusion, A flexible corrugated cladding tube covering a flexible inner tube,
The tube has a plurality of annular peaks and a plurality of annular valleys arranged alternately in the tube axial direction,
At least some of the valleys are formed with a plurality of holding protrusions each protruding toward the tube axis, and these holding protrusions are arranged spaced apart from each other in the tube circumferential direction;
2. A corrugated cladding tube, wherein the end faces of the retaining protrusions on both sides in the circumferential direction of the tube form an angle of approximately 90° with each other. A flexible corrugated cladding tube covering a flexible inner tube,
The tube has a plurality of annular peaks and a plurality of annular valleys arranged alternately in the tube axial direction,
At least some of the valleys are formed with a plurality of holding protrusions each protruding toward the tube axis, and these holding protrusions are arranged spaced apart from each other in the tube circumferential direction;
a gradient of a side surface of the retaining protrusion in the tube axial direction is equivalent to a gradient of an inner surface of the tube on the same side in the tube axial direction of a valley portion between adjacent retaining protrusions in the tube circumferential direction in some of the valley portions. 5. The corrugated cladding tube according to claim 4 , wherein the width of the holding protrusion in the tube axial direction at an intermediate height between the valley portion and the crest portion is wider than the width of the valley portion in the tube axial direction. A flexible corrugated cladding tube covering a flexible inner tube,
The tube has a plurality of annular peaks and a plurality of annular valleys arranged alternately in the tube axial direction,
At least some of the valleys are formed with a plurality of holding protrusions each protruding toward the tube axis, and these holding protrusions are arranged spaced apart from each other in the tube circumferential direction;
a gradient of a side surface of the retaining protrusion in the tube axial direction is steeper than a gradient of an inner surface of the tube on the same side in the tube axial direction of a valley portion between adjacent retaining protrusions in the tube circumferential direction in the some of the valley portions. 7. The corrugated cladding tube according to claim 6 , wherein a width of the holding protrusion in the tube axial direction at an intermediate height between the valley portion and the crest portion is equal to a width of the valley portion in the tube axial direction. A flexible corrugated cladding tube covering a flexible inner tube,
The tube has a plurality of annular peaks and a plurality of annular valleys arranged alternately in the tube axial direction,
At least some of the valleys are formed with a plurality of holding protrusions each protruding toward the tube axis, and these holding protrusions are arranged spaced apart from each other in the tube circumferential direction;
2. A corrugated cladding tube, wherein the gradient of a side surface of the holding protrusion on one side in the axial direction of the tube is gentler than the gradient of a side surface of the holding protrusion on the other side in the axial direction of the tube. 9. The corrugated cladding tube according to claim 8 , wherein the slope of the side surface on one side is at least 1 degree gentler than the slope of the side surface on the other side. 10. The corrugated cladding tube according to claim 8 , wherein an angle of the side surface on one side with respect to a radial direction of the tube is 5° to 20°. A flexible corrugated cladding tube covering a flexible inner tube,
The tube has a plurality of annular peaks and a plurality of annular valleys arranged alternately in the tube axial direction,
At least some of the valleys are formed with a plurality of holding protrusions each protruding toward the tube axis, and these holding protrusions are arranged spaced apart from each other in the tube circumferential direction;
A corrugated cladding pipe, characterized in that it is made of a single layer of foamed resin having a foaming ratio of 1.05 to 4 times. A flexible corrugated cladding tube covering a flexible inner tube,
The tube has a plurality of annular peaks and a plurality of annular valleys arranged alternately in the tube axial direction,
At least some of the valleys are formed with a plurality of holding protrusions each protruding toward the tube axis, and these holding protrusions are arranged spaced apart from each other in the tube circumferential direction;
A corrugated cladding pipe, characterized in that it is made of a single layer of foamed resin having a foaming ratio of 1.2 to 2.5 times. The corrugated cladding tube according to claim 11 or 12 , characterized in that the foamed resin body contains a lubricant. 14. The corrugated cladding tube according to claim 3, characterized in that the retaining protrusions are arranged at positions shifted in a pipe circumferential direction with respect to a virtual parting cross section including a parting line position, and a valley portion between the retaining protrusions adjacent in the pipe circumferential direction in the some of the valley portions straddles the parting cross section. 15. The corrugated cladding tube according to claim 1, 2 or 14 , characterized in that the numbers of the holding protrusions on both sides of the parting cross section are different from each other. The corrugated cladding tube according to any one of claims 1 to 15 , characterized in that a cross section of the holding protrusion perpendicular to the tube axis direction is symmetrical with respect to a center line passing through the apex of the holding protrusion and the tube axis. 17. The corrugated cladding tube according to any one of claims 1 to 16, characterized in that a retaining protrusion height from a top of the crest to a top of the retaining protrusion is 1.5 to 5 times a valley height from a top of the crest to an inner top of the valley excluding the retaining protrusion. A manufacturing apparatus for a corrugated cladding tube, the corrugated cladding tube covering a flexible inner tube, the corrugated cladding tube having a plurality of annular peaks and a plurality of annular valleys alternately arranged in an axial direction of the tube, at least some of the valleys having a plurality of holding protrusions each protruding toward the tube axis, the holding protrusions being arranged spaced apart from one another in a circumferential direction of the tube ,
a molding die having an annular corrugated surface for forming an outer surface of the corrugated cladding tube; and a supply unit for supplying a resin to be the corrugated cladding tube in a tubular shape to the molding die,
the mold includes a pair of corrugated split molds that mate together to form the corrugated mold surface;
A protruding mold portion for forming the holding protrusion on the corrugated mold surface is provided to avoid a joint between both ends of the corrugated split mold in the circumferential direction ,
the end face on the opposite circumferential side of the protruding mold portion which is farther from a nearest seam of the protruding mold portion forms an angle of 90° or less with respect to a virtual cutting plane including the seam on a side facing the cutting plane . 20. The manufacturing apparatus according to claim 18 , wherein a cross section of the protruding mold portion perpendicular to the axis of the annular corrugated mold surface is symmetrical with respect to a center line passing through the apex of the protruding mold portion and the axis. 20. The manufacturing apparatus according to claim 18, wherein, of the end faces on both sides of the protruding mold portion, the end face closest to the nearest seam of the protruding mold portion is substantially parallel to the split surface. 21. The manufacturing apparatus according to claim 18 , wherein the end faces on both sides of the protruding portion form an angle of approximately 90 degrees with each other. A manufacturing apparatus for a corrugated cladding tube, the corrugated cladding tube covering a flexible inner tube, the corrugated cladding tube having a plurality of annular peaks and a plurality of annular valleys alternately arranged in an axial direction of the tube, at least some of the valleys having a plurality of holding protrusions each protruding toward the tube axis, the holding protrusions being arranged spaced apart from one another in a circumferential direction of the tube,
a molding die having an annular corrugated surface for forming an outer surface of the corrugated cladding tube; and a supply unit for supplying a resin to be the corrugated cladding tube in a tubular shape to the molding die,
the mold includes a pair of corrugated split molds that mate together to form the corrugated mold surface;
A protruding mold portion for forming the holding protrusion on the corrugated mold surface is provided to avoid a joint between both ends of the corrugated split mold in the circumferential direction,
The mold includes a plurality of wave-shaped split molds arranged on two circular tracks so as to be circulatively movable,
the two annular tracks share a common orbital portion along an axis of the annular corrugated surface;
The pair of corrugation split molds of the two annular tracks are mated with each other when moving on the track portion to form the annular corrugation mold surface;
The supply is connected to an upstream end of the track portion;
At the downstream end of the orbital portion, the pair of wave-shaped split dies rotate along respective annular orbits and move away from each other,
2. A manufacturing apparatus for a corrugated cladding tube , wherein the slope of a side surface of the projecting mold portion facing the upstream side of the track portion is gentler than the slope of a side surface of the projecting mold portion facing the downstream side. 23. The manufacturing apparatus according to claim 22 , wherein the inclination of the side surface facing the upstream side is at least 1 degree gentler than the inclination of the side surface facing the downstream side. 24. The manufacturing apparatus according to claim 22 or 23 , characterized in that the angle of the side surface facing the upstream side with respect to a plane perpendicular to the axis is 5° to 20°. 25. The manufacturing apparatus according to claim 18 , wherein the protruding portion is provided on at least one of the pair of corrugated split dies. The manufacturing apparatus according to any one of claims 18 to 25, characterized in that in the pair of corrugated split dies, the number of protruding die portions provided on one corrugated split die is different from the number of protruding die portions provided on the other corrugated split die . A manufacturing apparatus as described in any one of claims 18 to 26, characterized in that the protruding height from the bottom of the concave mountain portion to the top of the protruding portion on the corrugated mold surface is 1.5 to 5 times the valley height from the bottom of the mountain portion to the top of the convex valley portion.

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