JP7744787B2 - Corrugated cladding and composite pipes - Google Patents

Description

The present invention relates to a corrugated cladding pipe that is placed over a flexible inner pipe suitable for transporting fluids, and to a composite pipe that includes an inner pipe and a corrugated cladding pipe.

A corrugated cladding pipe with alternating peaks and valleys is known as a flexible cladding pipe for protecting flexible pipes (inner pipes) used in hot and cold water supply systems. Because this corrugated cladding pipe requires the inner pipe to be exposed when connecting it to a fitting, it is prone to expanding and contracting in the axial direction.

The corrugated cladding pipes of Patent Documents 1 to 3 have dispersed retaining protrusions that protrude radially inward from the valleys. The tips of these retaining protrusions restrict lateral movement of the inner pipe, holding the inner pipe concentric 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 thermal insulation.

Japanese Patent Application Laid-Open No. 2021-41539 Japanese Patent Application Laid-Open No. 2021-138140 JP 2021-139500 A

In the cladding tubes of Patent Documents 1 to 3, the retaining protrusions are formed to protrude further radially and inward from the valley portions, and their dimension in the tube axial direction is limited almost entirely by the width of the valley portions. As a result, the retaining protrusions lack the strength to withstand radial compressive loads, and for example, when a composite tube with a cladding tube placed on an inner tube is loaded, the cladding tube may be crushed.

In order to solve the above problems, the present invention provides a corrugated cladding pipe for covering a flexible inner pipe, comprising: annular peaks and valleys arranged alternately in the axial direction of the pipe; and retaining protrusions that are dispersed in the axial and circumferential directions of the pipe and are arranged independently of each other, protruding radially inward beyond the valleys, and whose tips hold the inner pipe substantially concentric with the pipe axis, wherein the dimension of the retaining protrusions in the axial direction of the pipe is longer than one pitch including one peak and one valley.
According to this configuration, since the retaining projections have an axial dimension longer than one pitch between the peaks and valleys, the strength of the retaining projections against radial compressive loads can be increased, making 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.

Specifically, the retaining protrusion is formed so as to cross at least one valley portion or at least one peak portion in the tube axial direction.

Preferably, the holding protrusion is formed so that one peak and two valleys cross the tube axis direction. This configuration allows the dimension of the holding protrusion in the tube axis direction to be sufficiently long, thereby reliably increasing the strength of the holding protrusion.

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

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.
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 crossed by the retaining protrusions, thereby further increasing strength against radial compressive loads.

Preferably, the pair of first side walls are inclined radially inward so as to approach each other, 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.

Preferably, the cross section of the holding protrusion along the tube axis direction is V-shaped due to the pair of first side walls.

The pair of second side walls are inclined radially inward 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.

Preferably, the tip of the retaining protrusion forms a concave curve when viewed in the axial direction of the tube. This allows the tip of the retaining protrusion to contact the outer periphery of the inner tube without slipping when subjected to a radial compressive load, thereby increasing strength against the compressive load.

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

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.

The present invention makes it possible to increase the strength of the corrugated cladding tube against radial compressive loads.

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. 2 is an enlarged side view showing a main part of FIG. 1 with only the upper half thereof in cross section. FIG. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. 2 of a composite pipe including a corrugated cladding pipe according to a second embodiment of the present invention. 3A and 3B are views of a composite pipe including a corrugated cladding pipe according to a third embodiment of the present invention.

First Embodiment
Hereinafter, an embodiment of the present invention will be described with reference to Figures 1 to 3. As shown in Figure 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 interior of the inner pipe 10 forms a fluid passage through which fluids such as cold water and hot water pass.

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 cross-linked polyethylene (PE-X) pipe, polybutene (PB) pipe, polyethylene (PE) pipe, heat-resistant polyethylene (PE-RT) pipe, or a resin pipe containing two or more of these resins. It can also be made of a metal-reinforced resin pipe containing at least one of the above resins and a metal. The above are examples, and there are no particular restrictions on the material of the inner pipe 10 as long as it can ensure the required performance, such as flexibility and fluid flow.

The corrugated cladding pipe 20 is made of a single-layer resin pipe, and can 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 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.

As shown in Figures 1 and 2, the corrugated cladding tube 20 has a corrugated cross section formed by alternating annular peaks 21 and annular valleys 22 at the same pitch in the axial direction of the tube. As shown in Figure 2, the peaks 21 are short cylindrical sections 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.

The corrugated cladding tube 20 further has retaining protrusions 23 that are dispersed and independent of each other in the axial and circumferential directions. In this embodiment, the retaining protrusions 23 are formed at equal intervals in the circumferential direction, with four retaining protrusions 23 formed at equal intervals in the axial direction. The retaining 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.

As shown in Figure 2, the retaining protrusion 23 has a pair of first side walls 231, 231 facing each other in the tube axis direction, and as shown in Figure 3, a pair of second side walls 232, 232 facing each other in the circumferential direction. 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 retaining protrusion 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 retaining protrusion 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.

As shown in FIG. 2, the axial dimension L of the retaining protrusion 23 is longer than one pitch P, and in this embodiment is approximately 1.5P. The retaining protrusion 23 is formed so as to cross one peak 21 and two valleys 22 in the axial direction. The axial center of the retaining protrusion 23 coincides with the axial position of the peak 21. The pair of first side walls 231 are symmetrical with respect to the axial center of the retaining 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 retaining protrusion 23 are connected to the two peaks 21 adjacent to the two valleys 22 that crossed them.

As shown in Figure 3, the pair of second side walls 232 of the retaining protrusion 23 are symmetrical with respect to the circumferential center of the retaining protrusion 23 and are inclined at the same angle. The inclination angle Θ2 of the second side wall 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 crossed by the retaining protrusion 23, forming a wavy shape.

The corrugated cladding pipe 20 has retaining protrusions 23 that concentrically hold the inner pipe 10, thereby suppressing flapping of the inner pipe 10 and reducing noise, while also improving heat retention. Because the retaining protrusions 23 are distributed in the axial direction of the pipe, they do not affect the pipe's axial flexibility. Because the retaining protrusions 23 are distributed circumferentially, the risk of structures getting caught is reduced.

The retaining protrusions 23 have an axial dimension longer than one pitch P between the peaks 21 and valleys 22, and in this embodiment have a dimension of approximately 1.5P, which increases the radial compressive strength and therefore the strength of the corrugated cladding pipe 20 against radial compressive loads. As a result, when loading a composite pipe 1 with a corrugated cladding pipe 20 over the inner pipe 10, the load that can be loaded without the corrugated cladding pipe 20 collapsing can be increased.

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

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 increase 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 the corners of the structure from getting caught in it; for example, the groove width of the valley portions 22 is set to 35% or less of one pitch P. However, to ensure stretchability of the valley portions 22 in the tube axial direction (to ensure 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.

To prevent the corners of the structure from reaching the depths of the valleys 22, the groove depth of the valleys 22 is made greater than the groove width. Furthermore, the depth of the recesses of the retaining protrusions 23, which are approximately quadrangular pyramid-shaped, is made greater than the groove width of the valleys 22.

For reference, specific dimensions of the compound pipe 1 of the first embodiment described above will now be exemplified.
The outer diameter of the ridge 21 is 30.5 mm
The inner diameter of the valley portion 22 is 25.5 mm
The bottom (smallest diameter part) of the valley portion 22 has an outer diameter of 26.5 mm
The diameter of the inscribed circle of the holding projection 23 is 17.8 mm
The outer diameter of the inner pipe 10 made of cross-linked polyethylene is 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 the peak 21: 3.0 mm
Width of valley portion 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

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 axial 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 so as to cross the two peaks 21 and three valleys 22 in the tube axial direction. That is, the bases 232a of a pair of second side walls 232 are connected to the two peaks 21 and the three valleys 22, respectively. The bases 231a of a 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 axial direction, respectively. The inclination angle Θ1 of the first side walls 231 of this embodiment is approximately 45°.

In the second embodiment, the tube axial 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 increased, thereby further increasing the strength of the corrugated cladding tube 20 against radial compressive loads.

Third Embodiment
5, the shape of the tip 230 of the holding protrusion 23 as viewed in 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 the strength against the compressive load.

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 four circumferentially spaced retaining protrusions in the above-described embodiment may be offset in the axial direction of the tube.

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

1 Compound pipe 10 Inner pipe 20 Cladding pipe 21 Peak portion 22 Valley portion 23 Holding protrusion 231 First side wall 231a Root of first side wall 232 Second side wall 232a Root of second side wall P Pitch L Dimension of holding protrusion in pipe axis direction Θ1 Inclination angle of first side wall Θ2 Inclination angle of second side wall

Claims (11)

A corrugated cladding pipe covering a flexible inner pipe,
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. The corrugated cladding tube according to claim 1, wherein when viewed from an axial direction perpendicular to the tube axis and passing through the retaining projections outside the corrugated cladding tube, the roots of the pair of first side walls and the roots of the pair of second side walls extend linearly, and the roots of the pair of first side walls and the roots of the pair of second side walls form a rectangle. 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. 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. 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. The corrugated cladding tube according to claim 5 , wherein the pair of first side walls include flat plate portions connected to the base, and a cross section of the holding projection along the tube axis direction is V-shaped by the pair of first side walls. 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. The corrugated cladding tube according to claim 7, wherein the pair of second side walls have flat portions continuous with the root portion. 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. A corrugated cladding tube as described in any one of claims 1 to 9, 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 recess depth of the retaining protrusions is greater than the groove width of the valleys. 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.