Waveform coated tubes and composite tubes

Abstract

To increase a movable load of a composite tube by enhancing the compression rigidity of a corrugated cladding tube in a radial direction.SOLUTION: A corrugated cladding tube 20 for cladding a flexible inner tube 10 comprises an annular crest part 21 and an annular trough part 22 which are alternately arranged in a tube axial direction, and holding protrusions 23 which are dispersed in the tube axial direction and a circumferential direction, and independently arranged. The holding protrusions 23 protrude toward the inside in the radial direction rather than the trough part 22, and hold an inner tube by their tips 230 so as to be substantially coaxial with a tube axis. The holding protrusions 23 are formed so as to traverse the crest part 21 and the trough part 22 in the tube axial direction, and dimensions L of the holding protrusions 23 in the tube axial direction are longer than one pitch P including the crest part 21 and the trough part 22.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a corrugated cladding pipe fitted over a flexible inner pipe suitable for fluid transportation, and a composite pipe including the inner pipe and the corrugated cladding pipe. [Background Art]

[0002] As a flexible cladding pipe for protecting a flexible pipe (inner pipe) for water supply and hot water supply, a corrugated cladding pipe in which crests and troughs are alternately arranged in the pipe axis direction is known (see, for example, Patent Documents 1 to 4). This corrugated cladding pipe is easily expandable and contractible in the pipe axis direction, since it is necessary to expose the inner pipe when connecting the inner pipe to a joint.

[0003] In the corrugated cladding pipes proposed in Patent Documents 1 to 4, retaining projections that further project radially inward from the troughs are dispersedly arranged, the lateral movement of the inner pipe is regulated by the tips of these retaining projections, and the inner pipe is held concentrically with the pipe axis of the corrugated cladding pipe. This suppresses the generation of flapping noise caused by water hammer due to thermal expansion / contraction noise or sudden closing of a faucet, and improves heat retention. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent No. 6945430 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2020-193691 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2010-210041 [Patent Document 4] Japanese Unexamined Patent Application Publication No. 2006-046407 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] In the cladding tubes proposed in Patent Documents 1 to 4, the retaining projections are formed to protrude radially inward from the valleys, and their dimensions in the axial direction of the tube are almost limited to the width of the valleys. As a result, the strength of the retaining projections against radial compressive loads is insufficient, and for example, when a composite tube with a cladding tube covering an inner tube is loaded, the cladding tube may collapse.

[0006] The present invention has been made in view of the above problems, and its purpose is to provide a corrugated coated pipe with high radial compressive strength and resistance to crushing, and a composite pipe that can increase the load capacity. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a corrugated covering tube for covering a flexible inner tube, comprising: annular peaks and annular valleys arranged alternately in the direction of the tube axis; and retaining projections dispersed in the direction of the tube axis and circumferentially, independently of each other, and protruding radially inward from the valleys, the tip of which holds the inner tube substantially concentrically with the tube axis, characterized in that the dimension of the retaining projections in the direction of the tube axis is longer than one pitch including one peak and one valley.

[0008] With this configuration, the retaining projections have a pipe axial dimension longer than one pitch between the peaks and valleys, which increases the strength of the retaining projections against radial compressive loads. As a result, the corrugated cladding is less likely to collapse even when a compressive load is applied to it from the radial outside. Therefore, the load capacity of the composite pipe, in which the cladding is placed over the inner pipe, can be increased.

[0009] Specifically, the retaining projection is formed such that it crosses at least one valley or at least one peak in the direction of the pipe axis.

[0010] Preferably, the retaining projection is formed such that it has one peak and two valleys that traverse the pipe axis direction. With this configuration, the dimension of the retaining projection in the pipe axis direction can be made sufficiently long, and the strength of the retaining projection can be reliably increased.

[0011] More preferably, the retaining projection is formed such that it has two peaks and three valleys that traverse the pipe axis direction. With this configuration, the dimension of the retaining projection in the pipe axis direction can be further increased, and the strength of the retaining projection can be further enhanced.

[0012] Preferably, the retaining projection has a pair of first side walls facing each other in the axial direction of the pipe and a pair of second side walls facing each other in the circumferential direction, the bases of the pair of first side walls are connected to the peaks, and the pair of second side walls are connected to the valleys and peaks that the retaining projection crosses.

[0013] With this configuration, the bases of the pair of first side walls are connected to the peaks, and the bases of the pair of second side walls are connected to the valleys and peaks through which the retaining projections cross, thereby further increasing the radial compressive strength of the retaining projections.

[0014] Preferably, the pair of first side walls are inclined to approach each other in the radially inward direction, and each of the first side walls has an inclination angle of more than 20° with respect to a plane perpendicular to the pipe axis.

[0015] Preferably, the cross-section of the retaining projection along the axial direction of the pipe is V-shaped due to the pair of first side walls.

[0016] The pair of second side walls are inclined so as to move closer to each other in the radially inward direction, and each of the second side walls has an inclination angle of more than 20° with respect to a plane passing through the pipe axis.

[0017] Preferably, the tip of the retaining projection has a concave curve when viewed from the direction of the pipe axis. This allows the tip of the retaining projection to contact the outer circumference of the inner pipe without slipping when subjected to a radial compressive load, thereby increasing the radial compressive strength of the corrugated coated pipe.

[0018] Preferably, the peaks have a short cylindrical shape, the groove width of the valleys is 25% or more of the pitch, and the depth of the recess of the retaining projection is greater than the groove width of the valleys.

[0019] The composite pipe according to the present invention comprises a flexible inner pipe and said corrugated covering pipe that covers said inner pipe.

Effects of the Invention

[0020] According to the present invention, it is possible to increase the radial compressive strength of the corrugated covering pipe to prevent the corrugated covering pipe from collapsing, and to increase the loading capacity of the composite pipe in which the inner pipe is covered with the corrugated covering pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] [Figure 1] FIG. 1 is a half-cut partial cross-sectional view of a composite pipe including a corrugated covering pipe according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view showing a main part of FIG. 1. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 4 is a half-cut partial cross-sectional view of a composite pipe including a corrugated covering pipe according to a second embodiment of the present invention. [Figure 5] FIG. 5 is a transverse cross-sectional view of a composite pipe including a corrugated covering pipe according to a third embodiment of the present invention. [Figure 6] FIG. 6 is a half-cut partial cross-sectional view of a composite pipe including a corrugated covering pipe according to a fourth embodiment of the present invention. [Figure 7] FIG. 7 is a half-cut partial cross-sectional view of a composite pipe including a corrugated covering pipe according to a fifth embodiment of the present invention. [Figure 8] FIG. 8 is a half-cut partial cross-sectional view of a composite pipe including a corrugated covering pipe according to a sixth embodiment of the present invention. [Figure 9] FIG. 9 is a half-cut partial cross-sectional view of a composite pipe including a corrugated covering pipe according to a seventh embodiment of the present invention. [Figure 10] FIG. 10 is a partial cross-sectional view showing a modified example of a holding projection of the corrugated covering pipe according to the seventh embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] <First Embodiment> The first embodiment of the present invention will be described below with reference to Figures 1 to 3.

[0023] As shown in Figure 1, the composite pipe 1 comprises a flexible inner pipe 10 and a flexible corrugated coating pipe (corrugated pipe) 20 that covers the inner pipe 10. This composite pipe 1 is used, for example, as piping for water supply and hot water supply. In this case, the inside of the inner pipe 10 becomes a fluid passage through which fluids such as water and hot water pass.

[0024] The inner tube 10 is formed with a constant circular cross-section along its entire length and is flexible. The inner tube 10 can be made of cross-linked polyethylene (PE-X), polybutene (PB), polyethylene (PE), heat-resistant polyethylene (PE-RT), or a resin tube containing two or more of these resins. Alternatively, a metal-reinforced resin tube containing at least one of the above resins and a metal can be used. The above are examples, and there are no particular restrictions on the material of the inner tube 10 as long as it can ensure the required performance, such as flexibility and fluid flow.

[0025] The corrugated coated pipe 20 consists of a single layer of resin pipe, and can be made of polyethylene (PE), cross-linked polyethylene (PE-X), polybutene (PB), heat-resistant polyethylene (PE-RT), or a resin pipe containing two or more of these resins. Furthermore, the flexibility of the coated pipe 20 may be improved by foaming. In this case, polyethylene (PE) is the main component, and a low foaming ratio of 1.05 to 4 times is preferable. Note that the above is an example, and there are no particular restrictions on the material of the corrugated coated pipe 20 as long as it can ensure the required performance, such as flexibility and protection for the inner pipe 10.

[0026] As shown in Figures 1 and 2, the corrugated coated pipe 20 has a corrugated cross-section, formed by alternately arranging annular peaks 21 and annular valleys 22 at the same pitch in the direction of the pipe axis. As shown in Figure 2, the peaks 21 have a short cylindrical shape with a constant diameter, and the cross-sectional shape of the valleys 22 is U-shaped or V-shaped. Here, one pitch P is defined as the axial length of the pipe including one peak 21 and one valley 22.

[0027] The corrugated coated tube 20 further has retaining protrusions 23 that are distributed in the axial direction and circumferential direction and are independent of each other. In this embodiment, four retaining protrusions 23 are formed at equally spaced locations in the axial direction, and at equally spaced locations in the circumferential direction. Here, the retaining protrusions 23 protrude radially inward from the valleys 22, and their tips 230 are in contact with or close to the outer circumference of the inner tube 10, thereby holding the inner tube 10 substantially concentrically with the axial direction of the corrugated coated tube 20.

[0028] As shown in Figure 2, the retaining projection 23 has a pair of first side walls 231, 231 facing each other in the direction of the pipe axis, and as shown in Figure 3, it has a pair of second side walls 232, 232 facing each other in the direction of the circumferential axis. The pair of first side walls 231, 231 are inclined to approach each other in the radially inward direction, so that the cross section of the retaining projection 23 along the direction of the pipe axis is V-shaped. Similarly, the second side walls 232, 232 are inclined to approach each other in the radially inward direction, so that the cross section of the retaining projection 23 perpendicular to the pipe axis is approximately V-shaped. In this embodiment, the shape of the tip 230 of the retaining projection 23 as viewed from the direction of the pipe axis is a convex curve.

[0029] As shown in Figure 2, the axial dimension L of the retaining projection 23 is longer than one pitch P, and in this embodiment, it is set to approximately 1.5P. The retaining projection 23 is formed so as to traverse one peak 21 and two valleys 22 in the axial direction of the pipe. The axial center of the retaining projection 23 coincides with the axial position of the one peak 21. The pair of first side walls 231 are symmetrical with respect to the axial center of the retaining projection 23 and are inclined at the same angle. The inclination angle θ1 of the first side walls 23a with respect to a plane perpendicular to the pipe axis is 20° or more, and in this embodiment, it is set to approximately 30°. The bases 231a of the pair of first side walls 231 of the retaining projection 23 are connected to the two peaks 21 adjacent to the two valleys 22 that traverse it.

[0030] As shown in Figure 3, the pair of second side walls 232 of the retaining projection 23 are symmetrical with respect to the circumferential center of the retaining projection 23 and are inclined at the same angle. The inclination angle θ2 of the second side walls 232 with respect to the plane containing the pipe axis is 20° or more, and in this embodiment, it is set to approximately 45°. The base 232a of the second side walls 232 is connected to one peak 21 and two valleys 22 that the retaining projection 23 crosses, forming a wave shape.

[0031] The corrugated coated pipe 20 can suppress rattling of the inner pipe 10 and reduce noise, as well as improve heat retention, because the retaining protrusions 23 hold the inner pipe 10 concentrically. Since the retaining protrusions 23 are distributed in the direction of the pipe axis, they do not affect the expansion and contraction of the corrugated coated pipe 20 in the direction of the pipe axis. In addition, since the retaining protrusions 23 are distributed in the circumferential direction, the risk of structures getting caught on them can be reduced.

[0032] The retaining projection 23 has a pipe axial dimension that is longer than the pitch P of the peaks 21 and valleys 22. In this embodiment, it has a dimension of approximately 1.5P, which increases the radial compressive strength, and consequently increases the radial compressive strength of the corrugated coated pipe 20. As a result, when loading a composite pipe 1 in which the corrugated coated pipe 20 is placed over the inner pipe 10, the load that can be loaded without the corrugated coated pipe 20 being crushed can be increased.

[0033] Furthermore, since the pair of first side walls 231 have an inclination angle θ1 greater than 20° (approximately 30° in this embodiment) and form a V-shaped cross-section, with their bases 231a connected to the peaks 21, and the pair of second wall portions 232 have an inclination angle θ2 greater than 20° (approximately 45° in this embodiment) and form a V-shaped cross-section, with their bases 232a connected to one peak 21 and two valleys 22, the radial compressive strength can be further increased.

[0034] As described above, the retaining projection 23 is set independently of the groove width of the valley section 22. In other words, the groove width of the valley section 22 does not need to be forcibly widened in order to increase the dimension of the retaining projection 23 in the pipe axis direction. Therefore, the groove width of the valley section 22 can be limited to a width that prevents the corners of structures from getting caught, for example, the groove width of the valley section 22 can be set to 35% or less of one pitch P. However, in order to ensure expansion and contraction in the pipe axis direction (to ensure compression allowance), the groove width of the valley section 22 is set to 25% or more of one pitch P. In this embodiment, the groove width of the valley section 22 is set to approximately 30% of one pitch P. This makes it possible to easily shorten a 200 mm corrugated coated pipe 20 by 50 mm or more.

[0035] To prevent the corners of the structure from reaching the back of the valley 22, the groove depth of the valley 22 is made greater than the groove width. Also, the depth of the recess of the retaining projection 23, which is roughly pyramidal, is made greater than the groove width of the valley 22.

[0036] Here, for reference, the specific dimensions of the composite pipe 1 according to the first embodiment described above are given as an example.

[0037] Outer diameter of Yamabe 21: 30.5 mm Inner diameter of valley section 22: 25.5 mm Outer diameter of the bottom (minimum diameter part) of the valley section 22: 26.5 mm Diameter of the inscribed circle of the retaining projection 23: 17.8 mm Outer diameter of inner tube 10 made of cross-linked polyethylene pipe: 17 mm Inner diameter (nominal diameter) of inner tube 10: 13 mm The pitch between the peak section 21 and the valley section 22 is P: 4.3 mm. Width of Yamabe 21: 3.0 mm Width of valley section 22: 1.3 mm The radius of the recess at the tip of the groove in the valley portion 22 and the tip of the retaining projection 23 is 0.5 mm. Next, other embodiments of the present invention will be described. In these embodiments, components corresponding to the first embodiment are denoted by the same reference numerals, and their detailed descriptions are omitted.

[0038] <Second Embodiment> In the second embodiment shown in Figure 4, the pipe axis dimension of the retaining projection 23 is longer than that of the first embodiment, and the retaining projection 23 is formed to traverse the two peaks 21 and three valleys 22 in the pipe axis direction. That is, the bases 232a of the pair of second side walls 232 are connected to the two peaks 21 and three valleys 22, respectively. The bases 231a of the pair of first wall portions 231 are connected to the two peaks 21 located on both sides of the pipe axis direction of the two peaks 21 and three valleys 22, respectively. The inclination angle θ1 of the first side wall 231 in this embodiment is approximately 45°.

[0039] In the second embodiment, the axial length of the retaining projection 23 is made even longer than in the first embodiment, and the inclination angle θ1 of the first side wall 231 is increased, thereby further increasing the radial compressive strength of the corrugated coated pipe 20.

[0040] <Third Embodiment> In the third embodiment shown in Figure 5, the shape of the tip 230 of the retaining projection 23, as viewed from the direction of the pipe axis, forms an arc (concave curve) corresponding to the inner pipe 10, allowing for more stable retention of the inner pipe 10. Furthermore, when subjected to a compressive load from the radially outer side, the tip 230 of the retaining projection 23 contacts the outer circumference of the inner pipe 10 without slipping, thereby increasing the strength against compressive loads.

[0041] <Fourth Embodiment> In the fourth embodiment shown in Figure 6, in the axial cross-section of the retaining projection 23, the inclination angles α1 and β1 of the pair of first side walls 231A and 231B constituting the projection with respect to the vertical plane (angles of inclination with respect to the pipe cross-section) are different from each other. The shape of the axial cross-section formed by these first side walls 231A and 231B is not an isosceles triangle, unlike in the first to third embodiments. Specifically, the inclination angle β1 of one of the first side walls 231B (right side in Figure 6) is set to be larger than the inclination angle α1 of the other first side wall 231A (left side in Figure 6) (β1>α1), but the relationship between these inclination angles α1 and β1 may be reversed (α1>β1).

[0042] In this embodiment as well, similar to the second embodiment, the axial length L of the retaining projection 23 is longer than in the first embodiment, and the retaining projection 23 is formed to traverse the two peaks 21 and three valleys 22 in the axial direction of the pipe.

[0043] As described above, by setting the inclination angles α1 and β1 of the pair of first side walls 231A and 231B with respect to the vertical plane to different values ​​in the axial cross-section of the retaining projection 23, the radial compressive strength of the corrugated coating tube 20 can be further increased.

[0044] <Fifth Embodiment> In the fifth embodiment shown in Figure 7, in the axial cross-section of the retaining projection 23, a stepped portion 231B1 is formed by a horizontal surface on the inclined portion of one of the pair of first side walls 231A and 231B constituting the projection (the right side in Figure 7). The stepped portion may also be formed on the inclined portion of the other first side wall 231A (the left side in Figure 7).

[0045] In this embodiment, the inclination angles α2 and β2 of the pair of first side walls 231A and 231B constituting the protrusion with respect to the vertical plane (angle of inclination with respect to the pipe cross-section) are set to the same value (α2 = β2).

[0046] Furthermore, in this embodiment, the retaining projection 23 is formed to traverse one peak 21 and two valleys 22 in the direction of the pipe axis.

[0047] As described above, in the axial cross-section of the retaining projection 23, by forming a stepped portion 231B1 with a horizontal surface on the inclined portion of one of the pair of first side walls 231A and 231B constituting the projection (the right side in Figure 7), the radial compressive strength of the corrugated coating pipe 20 can be further increased. In this embodiment, the stepped portion 231B1 is formed on one of the first side walls 231B (the right side in Figure 7), but the stepped portion may also be formed on the other first side wall 231A (the left side in Figure 2), or stepped portions may be formed on both first side walls 231A and 231B, respectively.

[0048] Furthermore, the surface length per unit length in the axial direction of the pipe is long for the first side walls 231A and 231B of the retaining projection 23, which tends to stretch the resin and reduce its wall thickness. However, by forming a stepped portion 231B1 on the inclined portion of the first side wall 231B, the surface length per unit length of the first side wall 231B becomes relatively shorter, thereby improving the wall thickness stability of the retaining projection 23.

[0049] <Sixth Embodiment> In the sixth embodiment shown in Figure 8, similar to the fourth embodiment, in the axial cross-section of the retaining projection 23, the inclination angles α3 and β3 of the pair of first side walls 231A and 231B constituting the projection with respect to the vertical plane (angle of inclination with respect to the pipe cross-section) are different from each other, and stepped portions 231A1 and 231B1 formed by horizontal surfaces are formed at the connection points of these first side walls 231A and 231B with the valley portions 22.

[0050] Furthermore, in this embodiment as well, similar to the second embodiment, the axial length L of the retaining projection 23 is longer than in the first embodiment, and the retaining projection 23 is formed to traverse two peaks 21 and three valleys 22 in the axial direction of the pipe.

[0051] As described above, in this embodiment, stepped portions 231A1 and 231B1 are formed by horizontal surfaces at the connection points between the first side walls 231A and 231B and the valley portions 22, respectively, thereby further increasing the radial compressive strength of the corrugated coating pipe 20. Note that in the axial cross-section of the retaining projection 23, the inclination angles α3 and β3 of the pair of first side walls 231A and 231B constituting the projection with respect to the vertical surface (inclination angles with respect to the pipe cross-section) may be set to the same value (α3 = β3).

[0052] <Seventh Embodiment> In the seventh embodiment shown in Figure 9, in the axial cross-section of the retaining projection 23, a plurality of horizontal stepped portions 231A1, 231B1 are formed on the pair of first side walls 231A, 231B that constitute the projection, respectively (two of each in the illustrated example).

[0053] Furthermore, in this embodiment, in the axial cross-section of the retaining projection 23, the inclination angles α4 and β4 of the pair of first side walls 231A and 231B constituting the projection with respect to the vertical plane (angle of inclination with respect to the pipe cross-section) are set to the same value (α4 = β4). The axial dimension L of the retaining projection 23 is longer than in the first embodiment, and the retaining projection 23 is formed to traverse two peaks 21 and three valleys 22 in the direction of the pipe axis.

[0054] As described above, in this embodiment, in the axial cross-section of the retaining projection 23, multiple (two each in the illustrated example) horizontal stepped portions 231A1, 231B1 are formed on the pair of first side walls 231A, 231B that constitute the projection. Therefore, similar to the fifth and sixth embodiments, the radial compressive strength of the corrugated coating tube 20 is further increased, and the wall thickness stability of the retaining projection 23 is enhanced.

[0055] In the axial cross-section of the retaining projection 23, the number of horizontal stepped portions 231A1, 231B1 formed on the pair of first side walls 231A, 231B is arbitrary. For example, as shown in Figure 10, four stepped portions 231A1, 231B1 may be formed on each of the first side walls 231A, 231B.

[0056] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the technical idea described in the claims, specification, and drawings. [Industrial applicability]

[0057] The present invention can be applied, for example, to water supply and hot water pipes. [Explanation of symbols]

[0058] 1 Composite pipe 10 Inner tube 20 Cladding tube 21 Yamabe 22 Tanibe 23 Retaining protrusion 231 First side wall 231A,231B 1st side wall 231A1, 231B1 Stepped section 231a Base of the first side wall 232 Second side wall 232a Base of the second side wall P pitch Dimension of the retaining projection in the axial direction of the tube. θ1 Inclination angle of the first side wall α1~α4 Inclination angle of the first side wall β1~β4 Inclination angle of the first side wall θ2 Inclination angle of the second side wall

Claims

1. A corrugated coating tube that covers a flexible inner tube, Annular peaks and annular valleys are arranged alternately in the direction of the pipe axis, Retaining protrusions are dispersed in the axial and circumferential directions of the pipe, arranged independently of each other, and protrude radially inward from the valley portion, with their tips holding the inner pipe substantially concentrically with the pipe axis. Equipped with, The dimension of the retaining projection in the axial direction of the pipe is longer than one pitch including one peak and one valley. The retaining projection has a pair of first side walls facing each other in the axial direction of the pipe and a pair of second side walls facing each other in the circumferential direction, and the pair of first side walls are inclined to move toward each other in the radially inward direction. A corrugated coating tube characterized in that a stepped portion is formed at a radially intermediate position of at least one of the pair of first side walls.

2. The corrugated coated pipe according to Claim 1, characterized in that the retaining projection crosses at least one peak and the valleys on both sides of the at least one peak, and the pair of first side walls are connected to the pair of peaks located on the outer side of the tube axis direction of the valleys on both sides.

3. The corrugated coated pipe according to claim 1, characterized in that the stepped portion is formed at a position radially inward from the inner circumference of the valley portion.

4. The corrugated coating tube according to claim 1, characterized in that the stepped portion is formed on both of the pair of first side walls.

5. A corrugated coating tube for covering a flexible inner tube, Annular peaks and annular valleys are arranged alternately in the direction of the pipe axis, Retaining protrusions are dispersed in the axial and circumferential directions of the pipe, arranged independently of each other, and protrude radially inward from the valley portion, with their tips holding the inner pipe substantially concentrically with the pipe axis. Equipped with, The dimension of the retaining projection in the axial direction of the pipe is longer than one pitch including one peak and one valley. The retaining projection has a pair of first side walls facing each other in the axial direction of the pipe and a pair of second side walls facing each other in the circumferential direction, and the pair of first side walls are inclined to move toward each other in the radially inward direction. The corrugated coating tube is characterized in that the retaining projection crosses at least one peak, the pair of first side walls are connected to the inner circumference of the valleys located on both sides of the at least one peak, and a stepped portion is formed at the connected portion.

6. The corrugated coated pipe according to any one of claims 1 to 5, characterized in that the pair of second side walls are inclined to approach each other radially inward, each of the first side walls has an inclination angle of more than 20° with respect to a plane perpendicular to the pipe axis, and each of the second side walls has an inclination angle of more than 20° with respect to a plane passing through the pipe axis.

7. The corrugated coated tube according to any one of claims 1 to 5, characterized in that the peaks have a short cylindrical shape, the groove width of the valleys is 25% or more of the pitch, and the depth of the recess of the retaining projection is greater than the groove width of the valleys.

8. A composite tube comprising a flexible inner tube and a corrugated covering tube according to any one of claims 1 to 5 for covering the inner tube.

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