Composite pipe

Abstract

To provide a composite pipe which can improve heat retention and dew prevention properties and can be smoothly connected to a pipe joint. [Solution] The composite pipe comprises an inner pipe 1 and a cladding structure 2 that cladds the inner pipe 1. The cladding structure 2 includes a corrugated pipe 10 and an exterior tube 20. The corrugated pipe 10 is axially contractible and has peaks 11, valleys 12, and retaining projections 13. The retaining projections protrude radially inward from the valleys 12 to restrain the inner pipe 1 in the radial direction. An air insulating layer 30 is formed between the inner pipe 1 and the corrugated pipe 10. The exterior tube 20 contacts the outer surface of the peaks 11 of the corrugated pipe 10. Other air insulating layers 31 and 32 are formed between the exterior tube 20 and the valleys 12 and retaining projections 13 of the corrugated pipe 10. The exterior tube 20 is flexible so that it can expand and contract in accordance with the axial expansion and contraction of the corrugated pipe 10, or can be rolled up from its end to expose the corrugated pipe 10.

Description

[Technical Field]

[0001] The present invention relates to a composite pipe having an inner pipe covered with a cladding pipe structure. [Background technology]

[0002] Hot and cold water supply pipes and air conditioning refrigerant pipes are required to have insulation and moisture-proofing properties by covering the inner pipes through which the fluids pass. Typically, this is done by wrapping the pipes with glass wool, rock wool, polyethylene foam, urethane foam, or styrene foam, but this is done after the piping has been installed, making on-site installation difficult.

[0003] Patent Documents 1 and 2 disclose a composite pipe in which an inner pipe is covered with a corrugated pipe. This corrugated pipe has annular peaks and valleys alternately arranged in the pipe axial direction, and retaining protrusions that are dispersed in the pipe axial and circumferential directions, arranged independently of each other, and protrude radially inward from the valleys. By restraining the inner pipe in the pipe radial direction with the tips of the retaining protrusions of the corrugated pipe, the inner pipe is held substantially concentric with the corrugated pipe, and an air insulating layer is formed between the inner pipe and the corrugated pipe. This air insulating layer improves heat retention and moisture resistance.

[0004] When connecting the composite pipe to a pipe joint, the end of the corrugated pipe is retracted from the end of the inner pipe, compressing it in the axial direction. This exposes the connection margin of the inner pipe, allowing it to be connected to the pipe joint. After connecting the inner pipe to the joint, the force compressing the corrugated pipe is released, stretching it in the axial direction and eliminating the gap between the end of the corrugated pipe and the pipe joint. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-47542 [Patent Document 2] Japanese Patent Publication No. 2023-50382 Summary of the Invention [Problem to be solved by the invention]

[0006] In the composite pipes of Patent Documents 1 and 2, the retaining protrusions are in contact with or close to the inner pipe, which limits how much heat retention can be improved. Also, when a low-temperature fluid passes through the inner pipe, condensation can form on the outer surface of the retaining protrusions. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a composite pipe comprising an inner pipe and a covering pipe structure covering the inner pipe, wherein the covering pipe structure includes a corrugated pipe, the corrugated pipe being flexible and capable of being contracted in an axial direction, and having annular peaks and valleys alternately arranged in the pipe axial direction, and retaining protrusions that are dispersed in the pipe axial and circumferential directions, arranged independently of one another, and protrude radially inward from the valleys, wherein tips of the retaining protrusions of the corrugated pipe restrain the inner pipe in a pipe radial direction, thereby holding the inner pipe substantially concentrically with the corrugated pipe, and forming an air insulating layer between the inner pipe and the corrugated pipe, the covering pipe structure further including a cylindrical outer tube in contact with outer surfaces of the peaks of the corrugated pipe, and another air insulating layer is formed between the outer tube and the valleys and the retaining protrusions of the corrugated pipe, and the outer tube is flexible so that it can expand and contract in accordance with the axial expansion and contraction of the corrugated pipe, or can be rolled up from an end to expose the corrugated pipe.

[0008] In the composite pipe of the above configuration, the corrugated pipe is covered with an outer tube, so an air insulation layer can be formed not only between the inner pipe and the corrugated pipe, but also between the valleys and the retaining ridges of the corrugated pipe and the outer tube, further improving heat retention. Furthermore, the outer surfaces of the retaining ridges that restrain the inner pipe are covered by the outer tube and are not directly exposed to the outside air, so condensation on the retaining ridges of the corrugated pipe can be prevented. Furthermore, because a flexible outer tube is used, the axial expansion and contraction of the corrugated pipe is not hindered when connecting the inner pipe of the composite pipe to a pipe joint.

[0009] Preferably, the exterior tube is formed from an elastomer containing an olefin-based elastomer or a styrene-based elastomer, or a nonwoven fabric containing low-density polyethylene or polyester as a main material. According to this configuration, the flexibility of the exterior tube can be easily ensured.

[0010] Preferably, the outer tube is made of an elastomer, has a wall thickness of 1 mm or less, and a density of 0.91 g / cm 3 or less, and the durometer hardness A is less than 90. This configuration provides great flexibility.

[0011] Preferably, the corrugated pipe is made of a foamed resin, and the exterior tube is made of an elastomer. This configuration can increase the flexibility of the corrugated pipe and reduce the thermal conductivity, and also protect the corrugated pipe with the highly scratch-resistant outer tube.

[0012] Preferably, the corrugated pipe is characterized in that the foaming ratio of the outer layer is lower than that of the inner layer. With this configuration, even if the exterior tube is torn, the damage resistance of the corrugated pipe is not significantly reduced. [Effects of the Invention]

[0013] The composite pipe of the present invention has a simple structure, yet can improve heat retention and moisture resistance, and can be smoothly connected to a pipe joint. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a side view showing a compound pipe according to a first embodiment of the present invention, with the upper half thereof in cross section. [Figure 2] FIG. 2 is a cross-sectional view taken along the line II-II in FIG. [Figure 3] 4 is a cross-sectional view of the upper half of the composite pipe near the end connected to the pipe joint. FIG. [Figure 4]10 is a cross-sectional view of the upper half of the vicinity of the connection end, showing a method of exposing the inner tube by compressing the entire cladding tube structure in the axial direction. FIG. [Figure 5] 10 is a cross-sectional view of the upper half of the vicinity of the connection end of the same, showing a step of rolling up the outer tube from the end to expose the corrugated pipe in another method for exposing the inner pipe. FIG. [Figure 6] 6 is a cross-sectional view of the upper half of the vicinity of the connection end, showing the step of compressing the corrugated pipe in the axial direction to expose the inner pipe, following the step of FIG. 5. [Figure 7] FIG. 5 is a side view showing a compound pipe according to a second embodiment of the present invention, with the upper half thereof in cross section. DETAILED DESCRIPTION OF THE INVENTION

[0015] First Embodiment A first embodiment of the present invention will be described below with reference to Figs. 1 to 6. As shown in Fig. 1, a composite pipe comprises a flexible inner pipe 1 and a covering pipe structure 2 that covers the inner pipe 1. The composite pipe 1 is used, for example, as a pipe for cold water and hot water supply, a pipe for air conditioning, etc. The interior of the inner pipe 1 forms a fluid passage through which fluids such as water, hot water, and refrigerant pass. The inner pipe 1 is made of a round pipe and has a constant circular cross section along its entire length.

[0016] <Claying structure> The cladding pipe structure 2 of this embodiment includes a flexible, bellows-shaped corrugated pipe 10 (corrugated pipe) and a flexible exterior tube 20. The corrugated pipe 10 has annular peaks 11 and annular valleys 12 arranged alternately in the pipe axis direction. One pitch of the waves of the corrugated pipe 10 is defined as the dimension in the pipe axis direction that includes one peak 11 and one valley 12. The corrugated pipe 10 is expandable and contractible in the pipe axis direction.

[0017] The corrugated pipe 10 further has holding protrusions 13 that are dispersed in the pipe axis direction and circumferential direction and are independent of each other. In this embodiment, the holding protrusions 13 are formed at formation locations that are equally spaced (for example, 70 mm apart) in the pipe axis direction, with four holding protrusions 13 formed at equal intervals in the circumferential direction. The holding protrusions 13 in this embodiment have a pipe axis direction dimension that is longer than the pitch of the waves of the corrugated pipe 10.

[0018] The holding protrusions 13 protrude radially inward beyond the valleys 12, and their tips are in contact with or close to the outer periphery of the inner pipe 1, thereby holding the inner pipe 1 substantially concentrically with the pipe axis of the corrugated pipe 10. By holding the inner pipe 1 concentrically with the holding protrusions 13 of the corrugated pipe 10, flapping of the inner pipe 1 can be suppressed, thereby suppressing noise.

[0019] An air insulation layer 30 is formed between the corrugated pipe 10 and the inner pipe 1. The average radial gap between the valley portions 12 of the corrugated pipe 10 and the inner pipe 1 is 4 mm or more. In other words, the protruding length of the holding protrusions 13 from the valley portions 12 is 4 mm or more. This ensures a large air insulation layer 30.

[0020] <Outer tube> The armor tube 20 of the cladding pipe structure 2 is flexible and is fitted in close contact with the outer surface of the crests 11 of the corrugated pipe 10. An air insulating layer 31 is formed between the armor tube 20 and the valleys 12, and an air insulating layer 32 is also formed between the armor tube 20 and the retaining protrusions 13. The composite pipe of this embodiment has a simple structure but has very high thermal insulation properties, not only because of the air insulation layer 30 formed between the inner pipe 1 and the corrugated pipe 10, but also because of the air insulation layers 31, 32 formed between the corrugated pipe 10 and the outer tube 20.

[0021] When a low-temperature fluid flows through the inner pipe 1, the temperature drops particularly near the tip of the retaining protrusion 13 of the corrugated pipe 10, which is in contact with or close to the inner pipe 1. However, the external air is blocked by the outer tube 20 and does not come into contact with the part near the tip of the retaining protrusion 13, so condensation can be suppressed or avoided.

[0022] <Connection to pipe fittings (part 1)> A method of connecting a composite pipe to a pipe joint (not shown) will be described. As shown in FIG. 3, the ends 10x and 20x of the connection side of the corrugated pipe 10 and the outer tube 20 of the cladding pipe structure 2 are aligned in the axial direction with the end 1x of the inner pipe 1. When connecting to the pipe joint, the end 10x of the corrugated pipe 10 is moved back from the end 1x of the inner pipe 1. This causes the corrugated pipe 10 to be contracted in the axial direction, as shown in FIG. 4. Specifically, the corrugated pipe 10 is contracted so as to reduce the gap between the ridges 11. As a result, a predetermined length (connection allowance) of the inner pipe 1 is exposed from the end 1x. Because the outer tube 20 is flexible, it follows the corrugated pipe 10 without interfering with the axial contraction of the corrugated pipe 10, and is contracted in the axial direction so that the end 20x is retracted together with the corrugated pipe 10.

[0023] When the armor tube 20 is fused to the outer surface of the crests 11 of the corrugated pipe 10, the armor tube 20 deforms so that the portions corresponding to the spaces between the crests 11 bulge outward, as shown in Fig. 4. When the armor tube 20 is not fused to the outer surface of the crests 11 of the corrugated pipe 10, the armor tube 20 deforms more irregularly than shown in Fig. 4, but similarly shrunk in an outward waving manner, following the corrugated pipe 10.

[0024] Next, the inner pipe 1 with the exposed connection tab is inserted into the pipe joint and connected to the pipe joint. After connecting the inner pipe 1, if you release the end 10x of the corrugated pipe 10 and the end 20x of the outer tube 20, the corrugated pipe 10 will extend in the axial direction due to its elastic restoring force, and its end 10x will come into contact with the pipe joint, eliminating the gap between them. The outer tube 20 will also extend following the corrugated pipe 10, and its end 20x will move toward the pipe joint. If the corrugated pipe 10 and the outer tube 20 do not return sufficiently, the ends 10x and 20x are pulled toward the pipe joint.

[0025] <Connection to pipe fittings (part 2)> In the above-described connection method, the outer tube 20 is shrunk in the axial direction together with the corrugated pipe 10 to expose the inner pipe 1, but another method can also be adopted. That is, in the first step, as shown in Fig. 5, the outer tube 20 is rolled up from its end 20x, and this rolled up portion 20y is positioned at a predetermined distance back from the ends 1x, 10x of the inner pipe 1 and the corrugated pipe 10, thereby exposing the corrugated pipe 10.

[0026] 6, the exposed corrugated pipe 10 is axially contracted to retract its end 10x from the end 1x of the inner pipe 1. As a result, the connecting margin of the inner pipe 10 is exposed. After connecting the inner pipe 1 to the pipe joint in the same manner as the above-described connection method, the end 10x of the corrugated pipe 10 is released, the corrugated pipe 10 is returned to its original position, and the end 10x is placed against the pipe joint. Next, the rolled-up portion 20y of the outer tube 20 is unrolled while being rolled toward the pipe joint, and the end 10x is placed against the pipe joint, or the remaining portion is placed over the outer tubular portion of the pipe joint.

[0027] Since the exterior tube 20 is flexible, any of the above-mentioned connection methods can be employed, and the corrugated pipe 10 does not become impeded from expanding and contracting in the axial direction.

[0028] <Outer tube material> The outer tube 20 is formed of a flexible material so that it can follow the axial expansion and contraction of the corrugated pipe 10 as described above or so that its ends can be rolled up when the composite pipe is connected to the above-mentioned pipe joint. Preferably, it is formed of a nonwoven fabric mainly made of low-density polyethylene or polyester, or an elastomer containing an olefin-based elastomer or a styrene-based elastomer.

[0029] When the outer tube 20 is made of elastomer, its wall thickness can be 1 mm or less due to its high scratch resistance. It is also preferable that the density is 0.91 g / cm3 or less and the durometer hardness A is less than 90, thereby ensuring high flexibility. Furthermore, when the outer tube 20 is made of elastomer, it does not fuse to the peaks 11 of the corrugated pipe 10, making it suitable for rolling up by wrapping it from the end as described above.

[0030] <Corrugated pipe material> The corrugated pipe 10 is preferably formed from foamed resin to reduce thermal conductivity. The foaming ratio is preferably 1.05 to 4 times. More preferably, foamed polyethylene with an expansion ratio of 1.2 to 2.5 times is used. Foamed resin has high sound absorption properties, so it can absorb, for example, water hammer noise. In particular, by forming the resin from foamed polyethylene with an expansion ratio of 1.05 to 4 times, the apparent elastic modulus of the resin decreases, and the resin becomes more flexible for the same thickness. If the corrugated pipe 10 is made of foamed resin, its scratch resistance will be reduced, but if the outer tube 20 is made of an elastomer that has high scratch resistance, the corrugated pipe 10 can be protected.

[0031] When foamed polyethylene is used as the material for the corrugated pipe 10, the foaming ratio may be made to decrease continuously from the inner layer to the outer layer. Alternatively, the foaming ratio may be made to decrease discontinuously from the inner layer to the outer layer. In this case, even if the outer tube 20 is broken, the damage resistance of the corrugated pipe 10 can be ensured. If only the outer tube 20 is torn, it is preferable to apply a heat insulating material or the like to the torn portion, wrap it with tape, and then secure it with a wire mesh or an insulok.

[0032] <Inner tube 1 material> The inner tube 1 may be made primarily of polyvinyl chloride or polyvinyl chloride, cross-linked polyethylene, polybutene, heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, polypropylene, olefin-based elastomer, or styrene-based elastomer, or may be made of a resin composite of these, a metal-reinforced composite resin, or a composite material of the above resin and a foamed resin with an expansion ratio of 1.05 to 10, or a laminate of these. The above are examples of materials for the inner tube 1, and there are no particular restrictions as long as the required performance such as flexibility and fluid flow can be ensured.

[0033] <Other materials for corrugated pipes> The corrugated pipe 10 may be made primarily of heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, polyolefins other than polyethylene such as polybutene and polypropylene, olefin-based elastomers, styrene-based elastomers, polyvinyl chloride, etc., or may be a composite material of the above resins, or a laminate of the above resins. The above are examples of materials for the corrugated pipe, and there are no particular restrictions as long as the required performance such as flexibility and fluid flowability can be ensured.

[0034] The corrugated pipe 10 can also be obtained by expanding the diameter of a parison made primarily of a resin containing polyolefin, for example, low-density polyethylene having a tensile yield strength of 30 MPa or less, by blow molding or vacuum molding. In this case, an appropriate color masterbatch or the like may be added as an additive to the low-density polyethylene, which is the main polyethylene material, as needed. In this specification, the "main material" of a resin refers to the component that has the highest content by mass in a mixture.

[0035] Furthermore, the composite pipe may have a multi-layer structure, for example, the inner pipe 1 may be a cross-linked polyethylene pipe, the inner layer of the corrugated portions 10 may be an olefin-based elastomer, the outer layer of the corrugated portions 10 may be low-density polyethylene (LDPE), and the inner layer of the outer tube 20 may be an olefin-based elastomer. Alternatively, the inner pipe 1 may be a polyvinyl chloride pipe, the inner layer of the corrugated portions 10 may be a styrene-based elastomer, the outer layer of the corrugated portions 20 may be low-density polyethylene (LDPE), and at least the inner layer of the outer tube 20 may be an olefin-based elastomer. Because elastomers rarely fuse with polyethylene or polyvinyl chloride, it is preferable, especially when performing in-line molding, to form the corrugated portions 10 in a multi-layer structure with the layer in contact with the inner pipe 1 being an elastomer. As mentioned above, the corrugated pipe 10 may contain a resin other than polyethylene, such as a polyolefin such as polybutene or polypropylene, or vinyl chloride, either alone or in combination.

[0036] Second Embodiment 7 shows a compound pipe according to a second embodiment of the present invention. In this compound pipe, the axial dimension of the retaining protrusions 13A of the corrugated pipe 10 is shorter than the pitch of the waves of the corrugated pipe 10 and is the same as or slightly larger than the axial dimension of the valleys 12. Since the other components are the same as those in the first embodiment, the same reference numerals are used and detailed descriptions thereof are omitted.

[0037] <Condensation conditions> The composite pipe of the second embodiment described above is used as an example model, and a composite pipe obtained by omitting the outer tube 20 from this example model is used as a comparison example to compare condensation conditions. The inner pipe 1 of the example model and the comparison example is a cross-linked polyethylene pipe with a nominal diameter of 13 (outer diameter 17 mm), the outer diameter of the corrugated pipe 10 is 30.5 mm, the inscribed circle diameter of the holding protrusion 13 is 17.6 mm, and the wall thickness of the holding protrusion 13 is 0.915 mm.

[0038] When the condensation conditions for the comparative example were calculated under conditions of an outside temperature of 30°C and a relative humidity of 85%, the temperature of the fluid in the inner tube 1 when condensation occurred on the outer surface of the tip of the holding protrusion 13 was 26°C.

[0039] The example model is fitted with an outer tube 20 made of elastomer or low-density polyethylene with a thickness of 1 mm. In this example model, the temperature of the fluid in the inner tube 1 when condensation occurs under the same outdoor temperature and relative humidity conditions as the comparative example is 19°C, which is expected to be a significant improvement over the comparative example.

[0040] The present invention is not limited to the above-described embodiment, and various modifications are possible. The number of holding protrusions arranged in the circumferential direction may be any number as long as it is plural, but considering the function, three or more is preferable. The outer tube may have a plurality of axially extending ribs formed on its inner periphery at equal intervals in the circumferential direction. In this case, the outer tube body may be made of a non-foaming resin, and the inner ribs may be made of a foaming resin. [Industrial Applicability]

[0041] The present invention can be applied to composite pipes used for cold water supply, hot water supply, air conditioning, etc. [Explanation of symbols]

[0042] 1 inner tube 2 Cladding structure 10 corrugated tube 11 Yamabe 12 Valley 13, 13A Retaining protrusion 20 outer tube 30, 31, 32 Air insulation layer

Claims

1. an inner tube and a covering tube structure covering the inner tube; the cladding tube structure includes a corrugated tube; The corrugated pipe is flexible and can be contracted in the axial direction, and has annular peaks and valleys alternately arranged in the pipe axial direction, and holding protrusions that are dispersed in the pipe axial direction and circumferential direction, are arranged independently of each other, and protrude radially inward from the valleys, By constraining the inner pipe in the pipe diameter direction with the tip of the holding protrusion of the corrugated pipe, the inner pipe is held substantially concentric with the corrugated pipe, and an air insulating layer is formed between the inner pipe and the corrugated pipe, The cladding pipe structure further includes a cylindrical outer tube in contact with the outer surface of the crest portion of the corrugated pipe, and another air insulating layer is formed between the outer tube and the valley portion and the retaining protrusion of the corrugated pipe, The composite pipe is characterized in that the outer tube is flexible so that it can expand and contract in accordance with the axial expansion and contraction of the corrugated pipe, or can be rolled up from an end to expose the corrugated pipe.

2. 2. The composite pipe according to claim 1, wherein the outer tube is formed from an elastomer containing an olefin-based elastomer or a styrene-based elastomer, or a nonwoven fabric containing low-density polyethylene or polyester as a main material.

3. The outer tube is made of an elastomer, has a wall thickness of 1 mm or less, and a density of 0.91 g / cm ３ 2. The composite pipe according to claim 1, characterized in that it has a durometer A of less than 90 and a durometer A of less than 90.

4. 2. The composite pipe according to claim 1, wherein the corrugated pipe is made of a foamed resin, and the outer tube is made of an elastomer.

5. 5. The composite pipe according to claim 4, wherein the foaming ratio of the outer layer is lower than that of the inner layer of the corrugated pipe.

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