Corrugated coated pipes and composite pipes

Abstract

To increase a superimposed load on a composite pipe by enhancing the strength of a corrugated covering pipe against a radial compressive load.SOLUTION: A corrugated covering pipe 20 covering a flexible inner pipe 10 comprises annular crest parts 21 and annular trough parts 22 alternately arranged in a pipe axis direction, and holding protrusions 23 dispersed in the pipe axis direction and a circumferential direction, and arranged independently of each other. The holding protrusions 23 protrude in a radial inward direction from the trough parts 22, and hold the inner pipe substantially concentrically with a pipe axis by tips 230 thereof. The holding protrusions 23 are formed so as to cross the crest parts 21 and the trough parts 22 in the pipe axis direction, and a dimension L of the holding protrusions 23 in the pipe axis direction is 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 tube fitted over a flexible inner tube suitable for transporting fluids, and to a composite tube comprising an inner tube and a corrugated cladding tube.

[0002] A corrugated cladding pipe with alternating peaks and valleys is known as a flexible cladding pipe for protecting a flexible pipe (inner pipe) for hot and cold water supply. This corrugated cladding pipe is prone to expansion and contraction in the axial direction of the pipe because the inner pipe must be exposed when connecting the inner pipe to a joint.

[0003] The corrugated cladding pipes of Patent Documents 1 to 3 have retaining protrusions that protrude radially inward from the valleys, and the tips of these retaining protrusions restrict the lateral movement of the inner pipe, holding the inner pipe concentrically with the pipe axis of the corrugated cladding pipe. This suppresses the flapping noise caused by water hammer, such as when a water faucet is suddenly closed, and improves heat retention. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-41539 [Patent Document 2] Patent Publication No. 2021-138140 [Patent Document 3] Patent Publication No. 2021-139500 Summary of the Invention [Problem to be solved by the invention]

[0005] In the cladding pipes of Patent Documents 1 to 3, the retaining projections are formed so as to protrude further radially and inward from the roots, and the dimension in the tube axis direction is limited almost entirely by the width of the roots. Therefore, the retaining projections do not have sufficient strength against radial compressive loads, and for example, when a composite pipe in which a cladding pipe is placed on an inner pipe is loaded, the cladding pipe may be crushed. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a corrugated cladding tube that covers a flexible inner tube, comprising: annular peaks and valleys alternately arranged in the tube axial direction; and retaining protrusions that are dispersed in the tube axial and circumferential directions and arranged independently of each other, protruding radially inward beyond the valleys, and whose tips hold the inner tube substantially concentric with the tube axis, wherein the dimension in the tube axial direction of the retaining protrusions is longer than one pitch that includes one peak and one valley. According to this configuration, the retaining projections have an axial dimension longer than one pitch between the peaks and valleys, which increases the strength of the retaining projections against radial compressive loads and makes the corrugated cladding pipe less likely to collapse even when a compressive load is applied from the radial outside, thereby increasing the load capacity of the composite pipe in which the cladding pipe is fitted over the inner pipe.

[0007] Specifically, the holding protrusion is formed so as to cross at least one valley portion or at least one peak portion in the tube axis direction.

[0008] Preferably, the holding protrusion is formed so that one peak and two valleys cross the tube axis direction. With this configuration, the dimension of the holding protrusion in the tube axis direction can be made sufficiently long, and the strength of the holding protrusion can be reliably increased.

[0009] More preferably, the holding protrusion is formed so as to cross two peaks and three valleys in the tube axis direction. With this configuration, the dimension of the holding protrusion in the tube axis direction can be further increased, and the strength of the holding protrusion can be further increased.

[0010] Preferably, the retaining protrusion 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 bases of the pair of first side walls are connected to peak portions, and the pair of second side walls are connected to the valley portions and peak portions that the retaining protrusion crosses. According to 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 crossed by the retaining protrusions, thereby further increasing the strength against radial compressive loads.

[0011] Preferably, the pair of first side walls are inclined so as to approach each other in a 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 tube axis.

[0012] Preferably, the pair of first side walls form a V-shape in cross section of the holding projection along the tube axis direction.

[0013] The pair of second side walls are inclined radially inwardly so as to approach each other, and each of the second side walls has an inclination angle of more than 20° with respect to a plane passing through the tube axis.

[0014] Preferably, the tip of the retaining projection forms a concave curve when viewed from the axial direction of the tube, so that when a radial compressive load is applied, the tip of the retaining projection abuts against the outer periphery of the inner tube without slipping, thereby increasing the strength against the compressive load.

[0015] Preferably, the peaks have a short cylindrical shape, the groove width of the valleys is 25% or more of one pitch, and the recess depth of the holding protrusion is greater than the groove width of the valleys.

[0016] Another aspect of the present invention is a composite pipe including a flexible inner pipe and the corrugated cladding pipe that covers the inner pipe. [Effects of the Invention]

[0017] According to the present invention, the strength of the corrugated cladding tube against radial compressive load can be increased. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a side view showing a cross section of only the upper half of a composite pipe including a corrugated cladding pipe according to a first embodiment of the present invention. [Figure 2] 2 is an enlarged side view showing the main part of FIG. 1, with only the upper half thereof being cross-sectional. [Figure 3] FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. [Figure 4] 2, showing a composite pipe including a corrugated cladding pipe according to a second embodiment of the present invention. [Figure 5] 3, showing a composite pipe including a corrugated cladding pipe according to a third embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] First Embodiment Hereinafter, an embodiment of the present invention will be described with reference to Figs. 1 to 3. As shown in Fig. 1, a composite pipe 1 includes a flexible inner pipe 10 and a flexible corrugated sheathing pipe 20 (corrugated pipe) that covers the inner pipe 10. The composite pipe 1 is used, for example, as a pipe for supplying cold water or hot water. The inside of the inner pipe 10 forms a fluid passage through which fluids such as water and hot water pass.

[0020] The inner pipe 10 has a constant circular cross section along its entire length and is flexible. The inner pipe 10 can be made of a cross-linked polyethylene (PE-X) pipe, a polybutene (PB) pipe, a polyethylene (PE) pipe, a heat-resistant polyethylene (PE-RT) pipe, or a resin pipe containing two or more of these resins. A metal-reinforced resin pipe containing at least one of the above resins and a metal can also be used. The above examples are merely examples, and there are no particular limitations on the material of the inner pipe 10 as long as it can ensure the required performance, such as flexibility and fluid flowability.

[0021] The corrugated cladding pipe 20 is made of a single-layer resin pipe, and may be a polyethylene (PE) pipe, a cross-linked polyethylene (PE-X) pipe, a polybutene (PB) pipe, a heat-resistant polyethylene (PE-RT) pipe, or a resin pipe containing two or more of these resins. The flexibility of the cladding pipe 20 may also be improved by foaming. In this case, it is preferable to use polyethylene (PE) as the main component and to have a low foaming ratio of 1.05 to 4 times. The above is merely an example, and there are no particular restrictions on the material of the corrugated cladding pipe 20 as long as it can ensure the required performance, such as flexibility and protection for the inner pipe 10.

[0022] 1 and 2, the corrugated cladding tube 20 has a corrugated cross section formed by alternately arranging annular peaks 21 and annular valleys 22 at a constant pitch in the axial direction of the tube. As shown in Fig. 2, the peaks 21 are short cylindrical with a constant diameter, and the valleys 22 have a U- or V-shaped cross section. One pitch P is defined as the axial dimension including one peak 21 and one valley 22.

[0023] The corrugated cladding tube 20 further has holding protrusions 23 that are dispersed and independent of each other in the axial and circumferential directions. In this embodiment, the holding protrusions 23 are formed at positions that are equally spaced in the axial direction, with four holding protrusions 23 being equally spaced in the circumferential direction. The holding protrusions 23 protrude radially inward beyond the valley portions 22, and their tip portions 230 are in contact with or close to the outer periphery of the inner tube 10, thereby holding the inner tube 10 substantially concentric with the tube axis of the corrugated cladding tube 20.

[0024] As shown in Fig. 2, the holding projection 23 has a pair of first side walls 231, 231 facing each other in the tube axis direction, and also has a pair of second side walls 232, 232 facing each other in the circumferential direction, as shown in Fig. 3. The pair of first side walls 231, 231 are inclined so as to approach each other in the radially inward direction, so that the cross section of the holding projection 23 along the tube axis direction is V-shaped. Similarly, the second side walls 232, 232 are inclined so as to approach each other in the radially inward direction, so that the cross section of the holding projection 23 perpendicular to the tube axis is approximately V-shaped. In this embodiment, the shape of the tip 230 when viewed from the tube axis direction is a convex curve.

[0025] As shown in FIG. 2 , the tube axial direction dimension L of the holding protrusion 23 is longer than one pitch P, and in this embodiment, is approximately 1.5P. The holding protrusion 23 is formed so as to cross one peak 21 and two valleys 22 in the tube axial direction. The tube axial center of the holding protrusion 23 coincides with the tube axial position of the one peak 21. The pair of first side walls 231 are symmetrical with respect to the tube axial center of the holding protrusion 23 and are inclined at the same angle. The inclination angle Θ1 of the first side wall 23a with respect to a plane perpendicular to the tube axis is 20° or more, and in this embodiment, is approximately 30°. The bases 231a of the pair of first side walls 231 of the holding protrusion 23 are respectively connected to the two peaks 21 adjacent to the two valleys 22 that cross.

[0026] 3, the pair of second side walls 232 of the holding protrusion 23 are symmetrical with respect to the circumferential center of the holding protrusion 23 and are inclined at the same angle. The inclination angle Θ2 of the second side walls 232 with respect to a plane including the tube axis is 20° or more, and in this embodiment is approximately 45°. The base 232a of the second side wall 232 is connected to one peak 21 and two valleys 22 that the holding protrusion 23 crosses, forming a wavy shape.

[0027] The corrugated cladding pipe 20 has retaining protrusions 23 that concentrically hold the inner pipe 10, thereby suppressing flapping of the inner pipe 10, suppressing noise, and improving heat retention. The retaining protrusions 23 are distributed in the axial direction of the pipe, so they do not affect the pipe's axial flexibility. The retaining protrusions 23 are distributed in the circumferential direction, so the risk of structures getting caught can be reduced.

[0028] The holding protrusions 23 have a dimension in the tube axial direction that is longer than one pitch P between the peaks 21 and valleys 22, and in this embodiment has a dimension of approximately 1.5P, so that the radial compressive strength can be increased, and in turn, the strength of the corrugated cladding tube 20 against a radial compressive load can be increased. As a result, when the composite pipe 1 in which the corrugated cladding tube 20 is covered on the inner pipe 10 is loaded, the load that can be loaded without the corrugated cladding tube 20 being crushed can be increased.

[0029] Furthermore, the pair of first side walls 231 have a V-shaped cross section with an inclination angle Θ1 greater than 20° (approximately 30° in this embodiment) and their roots 231a are connected to the peaks 21, and the pair of second wall portions 232 have a V-shaped cross section with an inclination angle Θ2 greater than 20° (approximately 45° in this embodiment) and their roots 232a are connected to one peak 21 and two valleys 22, thereby further increasing the radial compression strength.

[0030] As described above, the retaining protrusions 23 are set independently of the groove width of the valley portions 22. In other words, there is no need to forcibly widen the groove width of the valley portions 22 in order to widen the dimension of the retaining protrusions 23 in the tube axial direction. Therefore, the groove width of the valley portions 22 can be limited to a width that prevents corners of a structure from getting caught in the groove, and for example, the groove width of the valley portions 22 is set to 35% or less of one pitch P. However, in order to ensure the stretchability of the valley portions 22 in the tube axial direction (to ensure a compression allowance), the groove width of the valley portions 22 is set to 25% or more of one pitch P. In this embodiment, the groove width of the valley portions 22 is approximately 30% of one pitch P. This allows the 200 mm corrugated cladding tube 20 to be easily shortened by 50 mm or more.

[0031] The groove depth of the valley portion 22 is made larger than the groove width so that the corners of the structure do not penetrate deep into the valley portion 22. In addition, the depth of the recess of the holding protrusion 23, which is approximately a quadrangular pyramid, is made larger than the groove width of the valley portion 22.

[0032] For reference, specific dimensions of the compound pipe 1 of the first embodiment described above will now be exemplified. Outer diameter of ridge 21: 30.5 mm Inner diameter of valley 22: 25.5 mm The outer diameter of the bottom (smallest diameter part) of the valley portion 22 is 26.5 mm The diameter of the inscribed circle of the retaining projection 23 is 17.8 mm The inner pipe 10 is made of cross-linked polyethylene and has an outer diameter of 17 mm. Inner diameter (nominal diameter) of inner pipe 10: 13 mm Pitch P between the peaks 21 and valleys 22: 4.3 mm Width of ridge 21: 3.0 mm Width of valley 22: 1.3 mm R of the groove tip of the valley portion 22 and the recess at the tip of the holding protrusion 23: 0.5 mm

[0033] Next, other embodiments of the present invention will be described. In these embodiments, components corresponding to those in the first embodiment are given the same reference numerals, and detailed descriptions thereof will be omitted. Second Embodiment The tube axis dimension of the holding protrusion 23 of the second embodiment shown in Fig. 4 is longer than that of the first embodiment, and the holding protrusion 23 is formed to cross the two peaks 21 and three valleys 22 in the tube axis direction. That is, the bases 232a of the pair of second side walls 232 are connected to the two peaks 21 and the 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 two peaks 21 and the three valleys 22 in the tube axis direction, respectively. The inclination angle Θ1 of the first side walls 231 of this embodiment is approximately 45°.

[0034] In the second embodiment, the tube axis dimension of the holding protrusion 23 is made longer than in the first embodiment, and the inclination angle Θ1 of the first side wall 231 is made larger, thereby further increasing the strength of the corrugated cladding tube 20 against radial compressive loads.

[0035] Third Embodiment 5, the shape of the tip 230 of the holding protrusion 23 when viewed from the tube axial direction is an arc (concave curve) corresponding to the inner tube 10, enabling more stable holding of the inner tube 10. Furthermore, when a compressive load is applied from the radially outer side, the tip 230 of the holding protrusion 23 abuts against the outer periphery of the inner tube 10 without slipping, thereby increasing strength against the compressive load.

[0036] The present invention is not limited to the above-described embodiment, and various modifications can be adopted within the scope of the present invention. For example, the four holding protrusions spaced apart in the circumferential direction in the above-described embodiment may be offset in the axial direction of the tube. [Industrial Applicability]

[0037] The present invention can be applied to, for example, cold and hot water supply pipes. [Explanation of symbols]

[0038] 1 Composite pipe 10 Inner tube 20 Cladding tube 21 Yamabe 22 Valley 23 Retaining protrusion 231 First side wall 231a Base of the first side wall 232 Second Side Wall 232a Base of second side wall Pitch L Dimension of the retaining projection in the pipe axis direction Θ1 inclination angle of the first side wall Θ2 Slope angle of the second side wall

Claims

1. A corrugated cladding tube covering a flexible inner tube, annular peaks and valleys alternately arranged in the tube axial direction; holding protrusions that are dispersed in the tube axial direction and the circumferential direction, are arranged independently of one another, protrude radially inward from the valley portions, and hold the inner tube substantially concentrically with the tube axis by their tips; Equipped with the holding protrusion has a dimension in the tube axis direction longer than one pitch including one each of the peaks and valleys, and is formed so as to cross at least one peak and at least two valleys in the tube axis direction; The holding projection has a pair of first side walls facing each other in the tube axis direction and a pair of second side walls facing each other in the circumferential direction, The pair of first side walls have roots extending in the circumferential direction and connected to the peak portions along their entire lengths, the roots of the pair of second side walls extend in the tube axis direction and are connected to the at least one peak portion and at least two valley portions, and the roots of the pair of first side walls extend to the peak portion to which they are connected and are connected to a part of the peak portion; a second side wall of the pair of second side walls, both ends of which are connected to one end of the base of the pair of first side walls, and a second side wall of the other of the pair of second side walls, both ends of which are connected to the other end of the base of the pair of first side walls.

2. A corrugated coated tube as described in claim 1, characterized in that when viewed from an axial direction outside the corrugated coated tube that is perpendicular to the tube axis and passes through the retaining protrusion, the roots of the pair of first side walls and the roots of the pair of second side walls extend in a straight line, and a rectangle is formed by the roots of the pair of first side walls and the roots of the pair of second side walls.

3. 3. The corrugated cladding tube according to claim 1, wherein the holding projection is formed so as to cross one peak and two valleys in the axial direction of the tube.

4. 3. The corrugated cladding tube according to claim 1, wherein the holding projections are formed so as to cross two peaks and three valleys in the axial direction of the tube.

5. 5. The corrugated cladding tube according to claim 1, wherein the pair of first side walls are inclined so as to approach each other in a 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 tube axis.

6. A corrugated coated tube as described in Claim 5, characterized in that the pair of first side walls include a flat portion connected to the base, and the cross section of the retaining protrusion along the tube axial direction forms a V-shape due to the pair of first side walls.

7. 7. The corrugated cladding tube according to claim 1, wherein the pair of second side walls are inclined so as to approach each other in a 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 tube axis.

8. A corrugated coated tube as described in Claim 7, characterized in that the pair of second side walls have flat portions connected to the root.

9. 9. The corrugated cladding tube according to claim 7, wherein the tip of the holding projection forms a concave curve along the outer circumferential surface of the inner tube when viewed in the axial direction of the tube.

10. 10. The corrugated cladding tube according to claim 1, wherein the peaks have a short cylindrical shape, the groove width of the valleys is 25% or more of the one pitch, and the recess depth of the retaining projection is greater than the groove width of the valleys.

11. A composite pipe comprising a flexible inner pipe and the corrugated cladding pipe according to any one of claims 1 to 10 that covers the inner pipe.

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