Corrugated sheath pipe and composite pipe

Abstract

To maintain heat retention even when a corrugated coating pipe is bent.SOLUTION: A corrugated coating pipe 20 covering a flexible inner pipe 10 comprises annular peak parts 21 and annular valley parts 22 alternately arranged in a pipe axial direction, and a holding projections 23 arranged at equal intervals in the pipe axial direction. The holding projection 23 projects radially inward from the valley part 22 and holds the inner pipe substantially concentrically with the pipe axis by its tip 230. A distance D between the holding projections 23 is sufficiently short so that the inner pipe 10 does not come into contact with the valley part even when a coating pipe 1 is bent with the minimum bending radius R.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a corrugated coating pipe covering a flexible inner pipe suitable for fluid transportation, an inner pipe, and a composite pipe including the corrugated coating pipe and the inner pipe.

[0002] As a flexible coating pipe for protecting a flexible pipe (inner pipe) for water supply and hot water supply, a corrugated coating pipe in which mountain portions and valley portions are alternately arranged is known. Since it is necessary to expose the inner pipe when connecting the inner pipe to a joint, this corrugated coating pipe is liable to expand and contract in the pipe axis direction.

[0003] In the corrugated coating pipes of Patent Documents 1 to 3, holding protrusions protruding further radially inward from the valley portions are arranged at equal intervals in the pipe axis direction, and the lateral movement of the inner pipe is restricted at the tips of these holding protrusions, holding the inner pipe concentric with the pipe axis of the corrugated coating pipe. Thereby, an air heat insulation layer is formed between the corrugated coating pipe and the inner pipe, enhancing the heat retention property.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inventor of the present invention performed a simulation using analysis software on the heat insulation property of a corrugated coated pipe. The composite pipe includes an inner pipe made of a cross-linked polyethylene pipe with a nominal diameter of 13 mm, and a corrugated coated pipe made of a foamed polyethylene pipe with an outer diameter of 30.5 mm and a wall thickness of 0.5 mm. Assuming an ambient temperature of 5°C and the water in the inner pipe being stationary at a water temperature of 42°, the temperature drop of the water after 30 minutes was analyzed. As a result of the analysis, when the inner pipe was concentric with the corrugated coated pipe or eccentric within 1 mm, the water temperature dropped to 20°C. Based on this temperature, it was found that when the eccentricity was 3 mm, the temperature further dropped by 2 - 3°C, and when the inner pipe contacted the trough of the corrugated coated pipe, the temperature further dropped by 7°C. Thus, in order to enhance the heat insulation property of the corrugated coated pipe, it is important to avoid contact between the inner pipe and the trough of the corrugated coated pipe.

[0006] When the composite pipe is in a straight state, the holding protrusions of the corrugated coated pipe hold the inner pipe substantially concentrically with the corrugated coated pipe, so the heat insulation property can be exhibited. However, in a severe arrangement situation, that is, in a state bent at the minimum bending radius, it is not guaranteed whether the contact between the inner pipe and the trough of the corrugated coated pipe can be avoided to exhibit the heat insulation property. None of Patent Documents 1 to 3 teach regarding the heat insulation property from such a perspective.

Means for Solving the Problem

[0007] In order to solve the above problems, the present invention provides a corrugated coated pipe that covers a flexible inner pipe, the corrugated coated pipe including annular ridges and annular troughs alternately arranged in the pipe axis direction, and a plurality of holding protrusions arranged at equal intervals in the pipe axis direction and spaced apart in the circumferential direction, wherein the holding protrusions protrude radially inward from the troughs, and the inner pipe is held substantially concentrically with the pipe axis by the tips thereof, and the interval in the pipe axis direction of the holding protrusions is shorter than the limit value at which the inner pipe contacts the trough when the inner pipe is bent at the minimum bending radius. According to this configuration, even in a situation where the inner pipe is bent at the minimum bending radius, the contact between the inner pipe and the trough of the corrugated coated pipe can be avoided by the holding protrusions, and the heat insulation property can be maintained.

[0008] In the first aspect, when the distance between the holding protrusions in the tube axis direction is D and the minimum bending radius is R, the following formula is satisfied. D ≦ πR / 4 In the first aspect, preferably, D, the distance between the holding protrusions in the tube axis direction, satisfies the following formula. D ≧ πR / 8 In the first aspect, within the range of the size and material of the inner tube used in ordinary houses and the like, the distance between the holding protrusions in the tube axis direction is 534 mm or less.

[0009] In the second aspect where conditions stricter than those of the first aspect are set, when the distance between the holding protrusions in the tube axis direction is D, the minimum bending radius is R, and the protruding height from the trough portion of the holding protrusion is H, the following formula is satisfied. D ≦ πR·ASIN{(H / 2R) 0.5} / 45 In the second aspect, preferably, D, the distance between the holding protrusions in the tube axis direction, satisfies the following formula. D ≧ πR·ASIN{(H / 2R) 0.5} / 90 In the second aspect, within the range of the size and material of the inner tube used in ordinary houses and the like, the installation interval in the tube axis direction of the holding protrusions of the coating tube is 142.9 mm or less.

[0010] The tip of the holding protrusion forms a concave curve when viewed from the tube axis direction. According to this, since the tip of the holding protrusion hits the outer periphery of the inner tube without slipping, the inner tube can be held well.

[0011] Another aspect of the present invention is a composite tube including a flexible inner tube and the corrugated coating tube that coats the inner tube.

Effect of the Invention

[0012] According to the present invention, even when the inner tube is bent at the minimum bending radius, the heat insulation function of the corrugated coating tube can be maintained.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the composite pipe 1 includes a flexible inner pipe 10 and a flexible corrugated coating pipe 20 (corrugated pipe) that covers the inner pipe 10. The composite pipe 1 is used, for example, as a pipe for water supply and hot water supply. The inside of the inner pipe 10 serves as a fluid passage through which fluids such as water and hot water pass.

[0015] The inner pipe 10 is formed with a constant circular cross-section over its entire length and has flexibility. As the inner pipe 10, 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 can be used. Also, a metal-reinforced resin pipe containing at least one of the above resins and metal can be used. The above are examples, and there is no particular limitation on the material of the inner pipe 10 as long as it can ensure required performances such as flexibility and fluid flowability.

[0016] The corrugated coating pipe 20 is made of a single-layer resin pipe, and a polyethylene (PE) pipe, a crosslinked 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 can be used. Further, the flexibility of the coating pipe 20 may be improved by foaming. In this case, it is preferable that the main component is polyethylene (PE) and the foaming ratio is low foaming of 1.05 times to 4 times. The above is an example, and there is no particular limitation on the material of the corrugated coating pipe 20 as long as the required performance such as flexibility and protection for the inner pipe 10 can be ensured.

[0017] As shown in FIGS. 1 and 2, the corrugated coating pipe 20 has a corrugated cross section by alternately arranging annular mountain portions 21 and annular valley portions 22 in the pipe axis direction. As shown in FIG. 2, the mountain portion 21 has a short cylindrical shape with a constant diameter, and the cross-sectional shape of the valley portion 22 is U-shaped or V-shaped.

[0018] The corrugated coating pipe 20 further has holding protrusions 23 that are dispersedly arranged in the pipe axis direction and the circumferential direction and are independent of each other. Specifically, at the formation positions at equal intervals D in the pipe axis direction, four holding protrusions 23 are formed at equal intervals in the circumferential direction. The holding protrusion 23 protrudes inward in the radial direction from the valley portion 22, and its tip portion 230 is in contact with or faces the outer periphery of the inner pipe 10 at a slight distance, thereby holding the inner pipe 10 substantially concentric with the pipe axis of the corrugated coating pipe 20.

[0019] The corrugated coating pipe 20 can suppress the rattling of the inner pipe 10 and suppress the sound by holding the inner pipe 10 concentrically with the holding protrusion 23. Further, the heat retention property can be improved by the air heat insulation layer formed between the corrugated coating pipe 20 and the inner pipe 10. Since the holding protrusions 23 are dispersed in the pipe axis direction, they do not affect the stretchability in the pipe axis direction. Since the holding protrusions 23 are dispersed in the circumferential direction, the risk of the structure getting caught can be suppressed.

[0020] When the composite pipe 1 is in a straight state, the air insulation layer between the inner pipe 10 and the corrugated covering pipe 20 exhibits an optimal heat preservation function. However, when the axial interval of the holding protrusions 23 is long, when the composite pipe 1 is bent, the inner pipe 10 may contact the trough 22 of the corrugated covering pipe 20, especially the trough 22 located at the center between the holding protrusions 23, and the heat preservation function may deteriorate. Therefore, the upper limit value of the axial interval of the holding protrusions 23, that is, the interval at which the inner pipe 10 does not contact the trough of the corrugated covering pipe 20 even when the composite pipe 1 is bent at the minimum bending radius, is obtained.

[0021] <The first calculation method> Hereinafter, the first calculation method for obtaining the upper limit of the interval between the holding protrusions 23 will be described with reference to FIG. 4. Since the composite pipe 1 is almost always bent at an angle of 90° or less, it is assumed that the most severe bending condition, that is, the inner pipe 10 is bent at the minimum bending radius R and a bending angle of 90°. In FIG. 4, the corrugated covering pipe 20 is schematically shown. That is, the circumscribed circle 22A of the trough 22 located on the curved inner side and the inscribed circle 22B of the trough 22 located on the curved outer side are shown, and the holding protrusions 23 protruding from the trough 22 are shown as short straight lines. The corrugated covering pipe 20 is fixed to the building structure by a fixture and maintained in the above-mentioned bent state, and the inner pipe 10 is not restrained.

[0022] In the bent state shown in FIG. 4, when the holding protrusions 23 are provided at an angular interval of 90°, the inner pipe 10 is most likely to approach and contact the trough 22 of the covering pipe 20 at the central position between the holding protrusions 23 (a position 45° away from the holding protrusions 23) as shown by the broken line in the figure. Therefore, by arranging the holding protrusions 23 at this intermediate position, the possibility of avoiding the contact between the holding protrusions 23 and the trough 22 is highly increased. The interval Do of the holding protrusions 23 at this time is set as the upper limit value. The interval Do can be expressed by the following formula. Do = 2πR(45 / 360) ··· (1) When the above formula (1) is arranged, the following formula is obtained. Do = πR / 4 ··· (2) If the distance D between the holding protrusions 23 is made equal to or less than the above distance Do, it is highly likely that contact between the inner tube 10 and the trough portion 22 can be surely avoided, and a high heat-insulating function can be exhibited.

[0023] In FIG. 4, if the holding protrusions 23 are arranged at an angle of 45°, contact between the inner tube 10 and the trough portion 22 of the corrugated coating tube 20 can be more surely avoided, and narrowing of the radial distance between the inner tube 10 and the trough portion 22 between the holding protrusions 23 can be suppressed. The distance between the holding protrusions 23 at this time is Do / 2. The distance obtained by this calculation can also be used as the lower limit value for reducing the number of the holding protrusions 23 and reducing the contact between the holding protrusions 23 and the inner tube 10. In that case, the distance D can be expressed by the following formula. D≧πR / 8 ···(3)

[0024] Specific examples will be given. When a cross-linked polyethylene tube, a polybutene tube, or a metal-reinforced resin tube is used as the inner tube 10, it is difficult to perform field bending because the wall thickness increases as the size increases. However, when it is used for the piping at the end of a living room, a toilet in a house or a hotel, the nominal diameter of the inner tube 10 is 10 mm to 25 mm, and the piping is performed in a field-bent state.

[0025] If the size and material of the inner tube 10 are different, the minimum bending radius is also different. For example, the minimum bending radius in the case where the inner tube 10 is a cross-linked polyethylene tube is as follows. Nominal diameter 10 mm, outer diameter 13 mm... minimum bending radius 150 mm Nominal diameter 13 mm, outer diameter 17 mm... minimum bending radius 150 mm Nominal diameter 16 mm, outer diameter 21.5 mm... minimum bending radius 200 mm Nominal diameter 20 mm, outer diameter 27 mm... minimum bending radius 300 mm Nominal diameter 25 mm, outer diameter 34 mm... minimum bending radius 350 mm

[0026] Further, the minimum bending radius in the case where the inner tube 10 is a polybutene tube is as follows. Nominal diameter 10 mm, outer diameter 13 mm... minimum bending radius 130 mm Nominal diameter 13 mm, outer diameter 17 mm... minimum bending radius 170 mm Nominal diameter 16 mm, outer diameter 22 mm ··· Minimum bending radius 220 mm Nominal diameter 20 mm, outer diameter 27 mm ··· Minimum bending radius 270 mm Nominal diameter 25 mm, outer diameter 34 mm ··· Minimum bending radius 680 mm

[0027] In the above examples, the case where the minimum bending radius is the largest is when the inner tube 10 is a polybutene tube with a nominal diameter of 25 mm and an outer diameter of 34 mm (the outer diameter of the corrugated coating tube 20 is 52 mm). The minimum bending radius R of the inner tube 10 is 680 mm. Substituting this minimum bending radius R = 680 mm into the above formula (2), the interval D between the holding protrusions 13 becomes 534 mm or less.

[0028] The case where the minimum bending radius is the smallest is when the inner tube 10 is a polybutene tube with a nominal diameter of 10 mm and an outer diameter of 13 mm, and the minimum bending radius R is 130 mm. Substituting this minimum bending radius R = 130 mm into the above formula (2), the interval D between the holding protrusions 13 becomes 102 mm or less.

[0029] <Second calculation method> Next, a second calculation method for obtaining the upper limit of the interval between the holding protrusions 23 will be described with reference to FIG. 5. The second calculation method assumes more severe conditions than the first calculation method. FIG. 5 is a schematic view of the coating tube 1 when the inner tube 10 is bent at the minimum bending radius. Similar to FIG. 4, for the corrugated coating tube 20, the circumscribed circle 22A and the inscribed circle 22B of the valley portion 22 are shown, and the holding protrusion 23 protruding from the valley portion 22 is shown as a short straight line. Assume the worst situation that can actually occur. That is, the inner tube 10 forms a straight tube shape between the two holding protrusions 23, 23 and contacts the valley portion 22. This straight inner tube 10 is denoted by reference numeral 10'. The contact point between the straight inner tube 10' and the circumscribed circle 22A of the valley portion 22 is denoted by reference numeral P in the figure. Also, the displacement amount from the ideal shape in which the inner tube 10 is concentric with the corrugated coating tube 20 and is bent at the minimum bending radius to the above straight shape is denoted by reference numeral H'. This displacement amount H' is equal to the protrusion height H of the holding protrusion 23 from the valley portion 22. The minimum bending radius (the radius of the inscribed circle of the bent inner tube 10) is denoted by R.

[0030] To obtain the arithmetic expression, a straight line of length L is defined in FIG. 5. This straight line is the line connecting the tip of the holding projection 23 and the contact point P. The triangle formed by this straight line of length L, the short straight line representing the displacement amount H’, and another straight line is defined as the “small triangle”. Let the angle between the straight line of length L and the other straight line be Θ. Furthermore, the triangle formed by the straight line connecting the center of the radius of curvature of the composite tube 1 and the contact point P, the straight line of length L, and another straight line (the straight line having the length of the minimum bending radius R and including the holding projection 23) is defined as the “large triangle”. In the “large triangle”, the angle between the straight line connecting the center of the radius of curvature and the contact point P and the other straight line (the angle between the contact point P and the holding projection 23) is 2Θ. The angle between the holding projections 23 arranged on both sides of the contact point P is 4Θ.

[0031] For the “small triangle” in FIG. 5, the following equation holds. tanΘ = H’ / L = H / L ···(4) For the “large triangle”, the following equation holds. sin2Θ = L / R ···(5) The following equation can be derived from the above (4) and (5). L = H / tanΘ = Rsin2Θ···(6) Furthermore, when rewritten, the following equation is obtained. tanΘ·sin2Θ = H / R···(7) Here, substituting tanΘ = sinΘ / cosΘ and sin2Θ = 2sinΘ·cosΘ into equation (7), the following equation is obtained. (sinΘ) 2 = H / 2R···(8) Θ can be expressed as follows from equation (8). Θ = ASIN{(H / 2R) 0.5}···(9)

[0032] As described above, the angular interval of the holding projections 23 can be expressed as 4Θ, and when expressed in terms of distance, the upper limit interval Dc at which the inner tube 10 contacts the trough 22 of the covering tube 20 can be expressed by the following equation. Dc = 2πR·(4Θ / 360) = πRΘ / 45···(10) By substituting the above-described formula (9) into formula (10), the following formula is obtained. Dc = πR·ASIN{(H / 2R) 0.5} / 45 ···(11) In order to avoid the inner tube 10 from contacting the trough portion 22 of the covering tube 20, it is required that the interval D between the holding protrusions 23 be equal to or less than the upper limit interval Dc. In terms of an equation, it is as follows. D ≦ πR·ASIN{(H / 2R) 0.5} / 45 ···(12)

[0033] In FIG. 5, if the holding protrusions 23 are also arranged at the contact point P, it is possible to more reliably avoid the contact between the inner tube 10 and the trough portion 22 of the corrugated covering tube 20, and it is possible to suppress the narrowing of the radial interval between the inner tube 10 and the trough portion 22 between the holding protrusions 23. The interval between the holding protrusions 23 at this time is 1 / 2 of formula (10) and can be expressed by the following formula. Dc’ = πR·ASIN{(H / 2R) 0.5} / 90 ···(13)

[0034] The interval D calculated by formula (13) can be used as the upper limit when the contact conditions are made strict, but it can also be used as the lower limit value for reducing the number of the holding protrusions 23 and reducing the contact between the holding protrusions 23 and the inner tube 10. In the latter case, the interval D can be expressed by the following formula. D ≧ πR·ASIN{(H / 2R) 0.5} / 90 ···(14)

[0035] A specific example will be given for explanation. Among the above-described exemplified sizes and materials, the inner tube 10 is a polybutene tube with a nominal diameter of 25 mm and an outer diameter of 34 mm, for which the upper limit interval Dc of the holding protrusions 23 is the largest. In this case, the inner diameter of the corrugated covering tube 20 (excluding the holding protrusions 23) is 42.5 mm, the height H of the holding protrusions is 3.75 mm, and the minimum bending radius R is 680 mm. By substituting the height H of the holding protrusions and the minimum bending radius R into formula (11) for calculation, the upper limit interval Dc of the holding protrusions 23 is 142.9 mm.

[0036] The upper limit interval Dc is the smallest when the inner tube 10 is a polybutene tube with a nominal diameter of 10 mm and an outer diameter of 13 mm. In this case, the inner diameter of the corrugated coating tube 20 is 22.5 mm, the protrusion height H = 4.25 mm, and the minimum bending radius R = 130 mm. Substituting the holding protrusion height H and the minimum bending radius R into Equation (11) for calculation, the upper limit interval Dc of the holding protrusion 23 is 66.7 mm. Note that the lower limit interval Dc' calculated by Equation (13) for this size is 33.3 mm.

[0037] As shown in FIG. 6, the shape of the tip 230 of the holding protrusion 23 viewed from the tube axis direction may be an arc (concave curve) shape corresponding to the inner tube 10. In this case, the inner tube 10 can be held more stably.

[0038] The present invention is not limited to the above-described embodiments, and various forms can be adopted without departing from the gist thereof. For example, the axial dimension of the holding protrusion may be equal to or greater than the groove width of the valley portion.

Industrial Applicability

[0039] The present invention can be applied to, for example, a water supply and hot water supply pipe.

Explanation of Reference Numerals

[0040] 1 Composite pipe 10 Inner tube 20 Coating tube 21 Crest 22 Trough 23 Holding protrusion D Interval between holding protrusions R Minimum bending radius H Height from the trough of the holding protrusion

Claims

1. A corrugated coating tube that coats a flexible inner tube, comprising annular ridges and annular valleys alternately arranged in the tube axis direction, and a plurality of holding protrusions arranged at equal intervals in the tube axis direction and spaced apart in the circumferential direction, wherein the holding protrusions protrude radially inward from the valleys, and the inner tube is held substantially concentric with the tube axis by the tips thereof, and the interval of the holding protrusions in the tube axis direction is shorter than the limit value at which the inner tube contacts the valleys when the inner tube is bent at the minimum bending radius, characterized in that it is a corrugated coating tube.

2. The corrugated coating tube according to claim 1, characterized in that when the interval of the holding protrusions in the tube axis direction is D and the minimum bending radius is R, the following formula is satisfied. D ≦ πR / 4

3. The corrugated coating tube according to claim 2, characterized in that D of the interval of the holding protrusions in the tube axis direction satisfies the following formula. D ≧ πR / 8

4. The corrugated coating tube according to claim 2, characterized in that the interval of the holding protrusions in the tube axis direction is 534 mm or less.

5. The corrugated coating tube according to claim 1, characterized in that when the interval of the holding protrusions in the tube axis direction is D, the minimum bending radius is R, and the protruding height of the holding protrusions from the valleys is H, the following formula is satisfied. D ≤ πR·ASIN{(H / 2R) ０.５} / 45

6. The corrugated coating tube according to claim 5, characterized in that D of the interval of the holding protrusions in the tube axis direction satisfies the following formula. D ≥ πR · ASIN{(H / 2R) ０.５} / 90

7. The corrugated coating tube according to claim 5, characterized in that the installation interval of the holding protrusions of the coating tube in the tube axis direction is 142.9 mm or less.

8. The corrugated coating tube according to any one of claims 1 to 7, characterized in that the tip of the holding protrusion forms a concave curve when viewed from the tube axis direction.

9. A composite tube including a flexible inner tube and the corrugated coating tube according to any one of claims 1 to 8 that coats the inner tube.

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