Anti-condensation composite pipe

Abstract

To provide a condensation-resistant composite pipe that can improve the condensation-resistant properties of the condensation-resistant composite pipe. [Solution] The anti-condensation composite pipe 5 comprises an inner pipe 20 containing a foam layer, a flexible corrugated coating pipe 21 covering the inner pipe 20, and an outer pipe 22 covering the corrugated coating pipe 21. The corrugated coating pipe 21 has annular peaks 21a and annular valleys 21b arranged alternately in the direction of the pipe axis, and retaining protrusions 21c that are spaced apart in the direction of the pipe axis and circumferentially, protruding radially inward from the valleys 21b, with their tips 21d holding the inner pipe 20 concentrically with the pipe axis. The outer pipe 22 is in movable contact with the surface of the peaks 21a.

Description

Technical Field

[0001] The present invention relates to a dew-proof composite pipe.

Background Art

[0002] Air-conditioning drain pipes and air-conditioning chilled water pipes are generally provided with a coating layer for dew prevention, for example. The coating layer commonly used in thermal insulation work is made by wrapping glass wool or rock wool and fixing it with wire mesh. However, this coating is applied after the piping work, which requires labor for construction period and process coordination. For this reason, equipment contractors demand the practical application of thermally insulated pipes that can complete the thermal insulation work during piping work.

[0003] The thermally insulated pipes desired for practical application can be summarized as follows. [1] The thermal insulation member does not interfere with the connection work between the pipe and the joint, and eliminates the need for tape application, wire mesh winding and the like after construction. [2] Since the outer diameter of the pipe increases and the piping work man-hour increases, the thermal insulation thickness is minimized to the necessary extent.

[0004] Accordingly, the inventor has researched a technology for further reducing costs and improving thermal insulation performance by making the foam layer of the pipe hollow to achieve air thermal insulation. In addition, the inventor has researched water supply and hot water supply pipes with thermal insulation properties by using an expandable corrugated pipe with holding protrusions as an air thermal insulation layer. However, dew prevention measures are required for the surfaces of the holding protrusions, and the water supply and hot water supply pipes cannot be horizontally applied to air-conditioning drain pipes and air-conditioning chilled water pipes.

[0005] For example, for some pipes, it is possible to solve the demand [1] by shrinking the coating during joint connection to easily expose the connection allowance. However, since dew condensation occurs on the holding protrusions, the performance is insufficient as an air-conditioning pipe (see, for example, Patent Document 1). In addition, since the holding protrusions are in contact with the inner pipe, heat conduction transmitted from the contact portions of the inner pipe to the crest portions of the pipe also poses a problem. As a countermeasure, it is conceivable to increase the outer diameter of the pipe. However, increasing the outer diameter of the pipe raises both the material cost and the piping man-hour cost, resulting in a significant increase in overall cost. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 7397601 [Overview of the project] [Problems that the invention aims to solve]

[0007] The pipe described in Patent Document 1 possesses some elements that make it suitable as a coated pipe for air conditioning, but there is a need for the practical application of technology to improve condensation prevention performance from the standpoint of heat transfer and other factors.

[0008] This invention has been made in view of the circumstances described above, and aims to provide a condensation-proof composite pipe that can improve condensation prevention performance. [Means for solving the problem]

[0009] To solve the aforementioned problems, the present invention proposes the following means. A condensation-proof composite pipe according to one aspect of the present invention comprises an inner pipe containing a foamed layer, a flexible corrugated coating pipe covering the inner pipe, and an outer pipe covering the corrugated coating pipe, wherein the corrugated coating pipe has annular peaks and annular valleys arranged alternately in the direction of the pipe axis, and retaining protrusions arranged at intervals in the circumferential direction in the direction of the pipe axis and protruding radially inward from the valleys, with their tips holding the inner pipe concentrically with the pipe axis, and the outer pipe is in movable contact with the surface of the peaks. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a condensation-resistant composite pipe that can improve condensation prevention. [Brief explanation of the drawing]

[0011] [Figure 1] This figure illustrates an example of a schematic configuration in which a condensation-proof composite pipe is provided for an air conditioning drain pipe according to the first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a state in which the dew-preventing composite pipe of FIG. 1 is connected to a drain pipe. [Figure 3] FIG. 3 is a perspective view showing an inner pipe and a corrugated cladding pipe provided in the dew-preventing composite pipe of FIG. 2. [Figure 4] FIG. 4 is a partially broken perspective view of the corrugated cladding pipe of FIG. 3. [Figure 5] FIG. 4 is a front view of the inner pipe and the corrugated cladding pipe of FIG. 3 as viewed from the direction of arrow A. [Figure 6] FIG. 4 is a cross-sectional view showing a state where the corrugated cladding pipe and the outer pipe are extended in the dew-preventing composite pipe of the first embodiment. [Figure 7] FIG. 4 is a schematic diagram showing a first study model of the inner pipe and the corrugated cladding pipe of the dew-preventing composite pipe. [Figure 8] FIG. 4 is a schematic diagram showing a second study model of the inner pipe and the corrugated cladding pipe of the dew-preventing composite pipe. [Figure 9] FIG. 4 is a schematic diagram showing a third study model of the inner pipe and the corrugated cladding pipe of the dew-preventing composite pipe. [Figure 10] FIG. 4 is a schematic diagram showing a fourth study model of the inner pipe and the corrugated cladding pipe of the dew-preventing composite pipe. [Figure 11] FIG. 4 is a cross-sectional view showing a state where the corrugated cladding pipe and the outer pipe of the dew-preventing composite pipe are contracted to expose the connection margin of the inner pipe. [Figure 12] FIG. 4 is a cross-sectional view showing a state where the outer pipe of the dew-preventing composite pipe is contracted to expose the corrugated cladding pipe. [Mode for Carrying Out the Invention]

[0012] Hereinafter, the dew-preventing composite pipe according to an embodiment of the present invention will be described with reference to the drawings. In the embodiment, an example in which the dew-preventing composite pipe is applied to an air conditioning drain pipe will be described, but the dew-preventing composite pipe may be applied to other facilities such as air conditioning cold water pipes and water supply and hot water supply pipes.

[0013] [First Embodiment] As shown in Figure 1, the air conditioning drain pipe 1 includes, for example, a drain pipe 31 provided in an air conditioner 3 installed on the ceiling T of a building, a drain hose 5, a heat-insulating joint for drain 10, a flexible hose 6, and a drain piping 7. A dew-preventing composite pipe is used for the drain hose 5. Hereinafter, the drain hose 5 will be described as the "dew-preventing composite pipe 5". The drain pipe 31, the dew-preventing composite pipe 5, the heat-insulating joint for drain 10, the flexible hose 6, and the drain piping 7 are connected in this order from the air conditioner 3, and are configured to discharge drain generated from the air conditioner 3 to the outside. The air conditioner 3 and the air conditioning drain pipe 1 are suspended from the ceiling T by, for example, hanging members 8. Further, the drain pipe 31 is connected to the drain discharge port of the air conditioner 3.

[0014] The dew-preventing composite pipe 5 connects the drain pipe 31 and the heat-insulating joint for drain 10. Further, the dew-preventing composite pipe 5 is connected to, for example, an elbow-type joint member (drain joint) which will be described later and is disposed inside the heat-insulating joint for drain 10. Specifically, it is fitted and inserted into a socket member (not shown) constituting the elbow-type joint member (drain joint), and is attached to the elbow-type joint member.

[0015] The flexible hose 6 is preferably constituted by, for example, a coated hose with a two-layer structure formed by covering the outer periphery of a soft or relatively hard vinyl chloride hose with a heat insulating material such as urethane foam. Further, the flexible hose 6 is suspended from the ceiling T by the hanging member 8 via a mounting fitting 61. The flexible hose 6 is arranged so as to once rise upward from the heat-insulating joint for drain 10, and this rising portion constitutes a drain-up structure. Further, the flexible hose 6 is hung downward by the mounting fitting 61 and connected to the drain piping 7.

[0016] As shown in Figure 2, the drain pipe 31 includes a joint main body 12, an annular body 13, a retaining member 14, and a cap 15. The joint body 12 is made of a metal such as copper alloy or steel. The joint body 12 includes a first connecting part 12a and a second connecting part 12b. These connecting parts 12a and 12b are arranged in a line along the pipe axis. In Figure 2, the first connecting part 12a is located on the left side, and the second connecting part 12b is located on the right side. The first connecting part 12a is connected to the air conditioner 3, and the inner pipe 20 of the condensation-proof composite pipe 5 is connected to the second connecting part 12b.

[0017] An annular body 13 is provided on the outer circumference of the second connecting portion 12b. The annular body 13 surrounds the second connecting portion 12b, forming an annular receiving portion 13a between it and the second connecting portion 12b. The inner tube 20 is inserted into the receiving portion 13a, thereby fitting the inner tube 20 onto the outer circumference of the second connecting portion 12b. A retaining member 14 is provided in the receiving portion 13a. The retaining member 14 allows the inner tube 20 to be inserted into the receiving portion 13a, while preventing the inner tube 20 from being pulled out. An annular cap 15 is attached to the right end of the annular body 13.

[0018] Next, with reference to Figures 2 to 12, the condensation-proof composite pipe 5 according to the first embodiment will be described. As shown in Figure 2, the condensation-proof composite pipe 5 comprises an inner pipe 20, a corrugated coating pipe 21, and an outer pipe 22. The condensation-proof composite pipe 5 has, for example, an inner pipe 20 at the center of the corrugated coating pipe 21. In the condensation-proof composite pipe 5, the surface of the inner pipe 20 is covered with the corrugated coating pipe 21. Therefore, the inner pipe 20 is protected by the corrugated coating pipe 21, and the insulation performance of the corrugated coating pipe 21 is enhanced. In addition, the surface of the corrugated coating pipe 21 is covered with the outer pipe 22. Therefore, the corrugated coating pipe 21 is protected by the outer pipe 22. Furthermore, the insulation performance of the inner pipe 20 is further enhanced by the outer pipe 22. The corrugated coating pipe 21 and the outer pipe 22 constitute a corrugated pipe that can expand and contract in the axial direction of the pipe.

[0019] As shown in Figures 3 and 4, the inner pipe 20 is, for example, a pipe formed in the shape of a round pipe. The inner pipe 20 is not limited to a round pipe shape. The inner pipe 20 is made of a resin capable of forming, for example, an air conditioning drain hose (air conditioning drain pipe). The inner pipe 20 is used, for example, to transport chilled water such as drain water. In the first embodiment, the inner pipe 20 is described using an air conditioning drain pipe as an example, but it may also be applied to, for example, an air conditioning chilled / hot water pipe or an air conditioning chilled water pipe.

[0020] The inner tube 20 is made of a material containing one or more selected resins, such as polyvinyl chloride or polychlorinated polyvinyl chloride, crosslinked polyethylene, polybutene, heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, polypropylene, olefin-based elastomer, or styrene-based elastomer. Alternatively, the inner tube 20 can be made of a composite material containing one or more selected resins and a metal. Alternatively, the inner tube 20 can be made of a composite material containing one or more selected resins and a foamed layer with a foaming ratio of 1.05 to 10 times. As a result, the inner tube 20 has excellent performance in terms of heat insulation, fluid flow, etc. Alternatively, the inner tube 20 may be made of three components laminated radially. That is, the inner tube 20 may contain multiple resin layers laminated radially. There are no particular restrictions on the material of the inner tube 20 as long as it can ensure performance in terms of heat insulation, fluid flow, etc., and the material may also have flexibility.

[0021] The corrugated coated tube 21 is a flexible tube that covers the inner tube 20. The corrugated coated tube 21 consists of a bellows tube having alternating peaks 21a and valleys 21b on its surface along the tube axis. The peaks 21a are annular circumferential protrusions formed around the entire circumference of the corrugated coated tube 21. The valleys 21b are annular circumferential recesses formed around the entire circumference of the corrugated coated tube 21. The corrugated coated tube 21 also has a plurality of retaining protrusions 21c arranged at intervals in the tube axis direction and circumferential direction on the inner circumferential wall of the corrugated coated tube 21.

[0022] As shown in Figure 4, in the corrugated clad tube 21, retaining protrusions 21c are formed adjacent to each other at a predetermined interval in the inner circumferential direction of the corrugated clad tube 21, projecting toward the center of the corrugated clad tube 21 from the portion constituting the bottom of the valley 21b on the inner surface of the corrugated clad tube 21. The retaining protrusions 21c, 21c are formed along a direction perpendicular to the pipe axis of the corrugated clad tube 21. The retaining protrusions 21c are formed to project from the bottom toward the center of the corrugated clad tube 21 along the bottom of the valley 21b, which is a circumferential recess. That is, the retaining protrusions 21c are dispersed in the pipe axis direction and circumferential direction and are arranged independently of each other, and they project radially inward from the valley 21b. Preferably, four retaining protrusions 21c are arranged in the cross section.

[0023] As shown in Figures 4 and 5, when the corrugated coating tube 21 is viewed in cross-section, the retaining projection 21c is formed in the shape of a low isosceles triangle with a rounded corner 21d at its apex. Hereinafter, the rounded corner 21d at the apex may be referred to as the "tip 21d". The two adjacent retaining projections 21c are formed at positions 90° apart around the circumference of the corrugated coating tube 21 when viewed in cross-section, as described below. In the corrugated coated tube 21, two additional retaining protrusions 21c are formed at a second position, which is a predetermined distance apart in the axial direction of the corrugated coated tube 21 from the first position where two retaining protrusions 21c are formed adjacent to each other. The two adjacent retaining protrusions 21c at the second position have the same shape as the first two retaining protrusions 21c.

[0024] However, as shown in Figure 5, when the corrugated coated tube 21 is viewed in cross-section and the four retaining protrusions 21c are seen, the four retaining protrusions 21c, consisting of two retaining protrusions 21c at the first position and two retaining protrusions 21c at the second position, are formed such that they are arranged at 90° intervals around the inner circumference of the corrugated coated tube 21. Along the axial direction of the corrugated coated tube 21, the first and second positions are repeatedly defined, and two retaining protrusions 21c are formed at each position. The inner tube 20 is supported along the entire length of the corrugated coated tube 21 by these retaining protrusions 21c that are repeatedly formed at each position.

[0025] The retaining projection 21c protrudes radially by 4 mm or more toward the pipe axis relative to the bottom of the valley portion 21b. Therefore, the inner tube 20 is supported so as to be located at the center of the corrugated coating tube 21, with a gap of 4 mm or more between it and the inner surface of the corrugated coating tube 21 secured by the multiple retaining projections 21c arranged in the circumferential direction. The inner tube 20 is concentric with respect to the corrugated coating tube 21. Note that the retention of the inner tube 20 by the tip 21d of the retaining projection 21c does not need to be perfectly concentric with respect to the pipe axis. Hereinafter, the gap formed between the bottom of the valley 21b in the corrugated coated pipe 21 and the inner pipe 20 may be referred to as the "radial gap δ". That is, the radial gap δ formed between the bottom of the valley 21b and the surface of the inner pipe 20 is set to 4 mm or more. The corrugated coated pipe 21 allows movement in the axial direction of the inner pipe 20, while restricting movement in the radial direction of the inner pipe 20.

[0026] In the first embodiment, in the corrugated coated pipe 21, a plurality of retaining protrusions 21c for concentrically holding the inner pipe 20 are integrally provided projecting radially inward from the inner surface of the corrugated coated pipe 21 at regular intervals in the pipe axis direction. In addition, four retaining protrusions 21c are provided projecting circumferentially from the inner surface of the corrugated coated pipe 21 at equal angular pitches (90° pitches). The number of retaining protrusions 21c is arbitrary as long as there are multiple. In particular, considering the function of holding the inner pipe 20 concentrically by the retaining protrusions 21c, it is desirable to have three or more retaining protrusions 21c. Furthermore, the spacing of the retaining protrusions 21c in the pipe axis direction is preferably 70 mm or less from the viewpoint of flattening strength and suppression of contact between the inner pipe 20 and the corrugated coated pipe 21 when the inner pipe 20 is bent.

[0027] As shown in Figures 5 and 6, the retaining projection 21c has a conical shape with a chamfered tip 21d. The retaining projection 21c has a maximum virtual apex angle θ of tip 21d of 60 degrees or more, and the shortest path A is set to be more than 5% longer than the line segment B that connects the inner tube 20 and the peak 21a with a perpendicular line. Hereinafter, the line segment B that connects the inner tube 20 and the peak 21a with a perpendicular line may be referred to as the shortest distance B. The virtual apex angle θ of tip 21d is the maximum angle among the angles formed by any two generatrixes of the conical shape. The shortest path A is the shortest path from the point on tip 21d that is tangent to the inner tube 20 to the peak 21a.

[0028] Here, the reason for making the shortest path A more than 5% longer than the shortest distance B by setting the virtual vertex angle θ to 60 degrees or more will be explained based on Figures 7 to 10 and Tables 1 and 2. Figures 7 to 10 show the study models for the inner pipe 20 and the corrugated coated pipe 21. Figure 7 shows the first study model of the outer shape D1 of the inner pipe 20 and the outer shape D2 of the corrugated coated pipe 21. Figure 8 shows the second study model of the outer shape D3 of the inner pipe 20 and the outer shape D4 of the corrugated coated pipe 21. Figure 9 shows the third study model of the outer shape D5 of the inner pipe 20 and the outer shape D6 of the corrugated coated pipe 21. Figure 10 shows the fourth study model of the outer shape D7 of the inner pipe 20 and the outer shape D8 of the corrugated coated pipe 21. The inner pipe 20 is a cross-linked polyethylene pipe. The corrugated coated pipe 21 is a cone pipe used in the cone pipe header method. The retaining protrusion 21c of the corrugated coated pipe 21 is assumed to be formed in a conical shape and in contact with the inner pipe 20 without chamfering. Table 1 shows the outer diameters of the inner pipe 20 and corrugated coated pipe 21 at their nominal diameters in the study model shown in Figures 1 to 10.

[0029] [Table 1]

[0030] Table 2 shows the results of the study of the models shown in Figures 1 to 10.

[0031] [Table 2]

[0032] According to the results of the study model shown in Figures 1 to 10, Table 2 shows that when the virtual vertex angle θ is 20 degrees, the angle between the rotation axis and the generatrix is ​​10 degrees. In this case, the ratio of the shortest distance B to the shortest path A is 101%, indicating that the difference is only at the level of error.

[0033] On the other hand, when the virtual vertex angle θ is 60 degrees, the angle between the axis of rotation and the generatrix becomes 30 degrees. In this case, the ratio of the shortest distance B to the shortest path A becomes 107% to 109%. Therefore, for example, in a situation where condensation and dripping occur on the air conditioning piping 180 minutes after the start of operation of the air conditioner, the occurrence of condensation and dripping can be delayed by 7% to 9%. This delays the occurrence of condensation and dripping by 12.6 minutes to 16.2 minutes over 180 minutes.

[0034] Furthermore, when the virtual vertex angle θ is 90°, the angle between the axis of rotation and the generatrix becomes 45°. In this case, the ratio of the shortest distance B to the shortest path A becomes 115% to 122%. Therefore, for example, in a situation where condensation and dripping occur 180 minutes after the start of air conditioning operation, the occurrence of condensation and dripping can be delayed by 15% to 22%. This delays the occurrence of condensation and dripping by 27 minutes to 39.6 minutes relative to 180 minutes.

[0035] In this way, by making the holding projection 21c conical and setting the virtual apex angle θ of the tip 21d to 60 degrees or more, the angle between the axis of rotation and the generatrix becomes 30 degrees or more. In this case, according to the drawing of the study model, the path to the surface of the corrugated coating tube 21 can be extended by 5% or more compared to the shortest distance B by the perpendicular.

[0036] Here, as shown in Figure 1, the condensation-proof composite pipe 5, which includes an inner pipe 20 and a corrugated coated pipe 21, is connected to the air conditioner 3 (see Figure 1). The space above the ceiling where the air conditioner 3 is installed is hot and humid when the air conditioner operation is started. On the other hand, the humidity in the space above the ceiling decreases as the air conditioner 3 is operated, and the dew point also gradually decreases. Therefore, by delaying the conditions under which condensation and dripping occur, it becomes possible to suppress condensation and dripping. For this reason, it is very important to set the virtual apex angle θ to 60 degrees or more in the condensation-proof composite pipe 5 to lengthen the shortest path A.

[0037] Next, we will explain, based on Tables 3 and 4, why setting the virtual apex angle θ to 60 degrees or more and lengthening the shortest path A can slow down the decrease in surface temperature in the inner tube 20. First, let's explain "condensation." In other words, the amount of water vapor that air can hold, known as "saturation vapor pressure," varies depending on the temperature; warmer air can hold more water vapor. The ratio of the actual amount of water vapor (absolute humidity) to the "saturation vapor pressure" is called "relative humidity." When warm air full of water vapor cools and exceeds the "saturation vapor pressure," the excess water vapor turns into water, causing condensation. Condensation occurs due to the balance between temperature and the amount of water vapor. The temperature at which excess water vapor turns into water is called the "dew point."

[0038] Table 3 shows examples of dew point temperatures at a room temperature of 30°C.

[0039] [Table 3]

[0040] Table 4 shows the results of condensation determination when the surface temperature of the air conditioning drain pipe is 30°C.

[0041] [Table 4]

[0042] As shown in Tables 3 and 4, for example, let's assume the room temperature is 30°C and the surface temperature of the air conditioning drain pipe is 26.5°C. In this case, if the relative humidity is high, the dew point rises and condensation occurs at the surface temperature of the air conditioning drain pipe. On the other hand, if the relative humidity is low, the dew point falls, and condensation due to the surface temperature of the air conditioning drain pipe can be suppressed.

[0043] Here, for example, let's start the air conditioning system with a room temperature of 30°C and a relative humidity of 85% (dew point 27.2°C). When the air conditioning system is started, the moisture in the room is discharged as condensation water through the air conditioning drain pipe, causing the room temperature and relative humidity to decrease. In this state, the temperature and relative humidity inside the ceiling also decrease in conjunction. As an example, let's assume that the temperature inside the ceiling becomes 30°C and the relative humidity becomes 80%.

[0044] Furthermore, when the air conditioning is running, condensate water at 10°C to 15°C flows into the air conditioning drain pipe, and the surface of the air conditioning drain pipe is cooled by the condensate water. Let's assume that the surface temperature reaches 26.5°C due to the continuous cooling of the air conditioning drain pipe. If the surface temperature never falls below the dew point temperature until it reaches 26.5°C, condensation will not form on the surface of the air conditioning drain pipe, as shown in Table 4. In this way, by delaying the time it takes for the surface temperature to cool, the risk of condensation can be reduced even if the final surface temperature is the same.

[0045] Next, we will explain why lengthening the shortest path A can slow down the decrease in the surface temperature of the inner tube 20. Let's explain using air conditioning chilled water pipes and air conditioning drain pipes as examples. In air conditioning chilled water pipes, chilled water flows through the pipes during air conditioning operation, and the coolness from the chilled water gradually transfers to the surface of the pipes. Similarly, in air conditioning drain pipes, cold drain water flows through the pipes, and the coolness from the drain water gradually transfers to the surface of the pipes. When the surface temperature of the air conditioning chilled water pipes and air conditioning drain pipes is below the dew point, condensation and dripping can be suppressed. Also, the dew point of the ambient environment gradually decreases. Therefore, by lengthening the shortest path A (see Figures 7 to 10) and slowing down the decrease in the surface temperature of the air conditioning chilled water pipes and air conditioning drain pipes, it is possible to reduce the risk of condensation and dripping.

[0046] Here, the conduction heat transfer rate Q can be determined by Fourier's law, as shown in equation (1). Q = -λA(ΔT / Δx) ... (1) however, Δx: Distance between two points [m] λ: Thermal conductivity (thermal conductivity) [W / (m·K)] A: Heat transfer area [m²] 2 ] ΔT: temperature difference Equation (1) shows that the conduction heat transfer rate Q slows down as Δx increases. Δx represents the distance between two points. By setting the virtual apex angle θ to 60 degrees or more and lengthening the shortest path A, the decrease in the surface temperature of the inner tube 20 can be slowed down.

[0047] In the first embodiment, the conical shape of the retaining projection 21c shown in Figures 5 and 6 is described using a right circular cone as an example, but the conical shape is not limited to a right circular cone. The conical shape may be, for example, an oblique cone, or a shape that combines a right circular cone and an oblique cone by changing the angle or base length midway. In this case as well, the shortest path A is set to be at least 5% longer than the shortest distance B.

[0048] As shown in Figure 6, the corrugated coated tube 21 has excellent properties such as flexibility and scratch resistance. The corrugated coated tube 21 is made of a material containing one or more resins selected from, for example, heat-resistant polyethylene, high-density polyethylene, low-density polyethylene (LDPE), polypropylene, olefin-based elastomer, styrene-based elastomer, rayon (regenerated fiber), and polyester. There are no particular restrictions on the material of the corrugated coated tube 21 as long as it can ensure properties such as flexibility and scratch resistance.

[0049] As an example, the corrugated coated tube 21 is obtained by expanding the diameter of a parison made primarily from a polyolefin resin, such as low-density polyethylene with a tensile yield strength of 30 MPa or less, by blow molding or vacuum molding. In this case, the low-density polyethylene, which is the main component, may be molded with an appropriate color masterbatch or the like as an additive as needed. The "main component" of the resin refers to the component that has the highest mass-based content in the mixture.

[0050] Furthermore, the corrugated coating tube 21 is made of foamed resin with a foaming ratio of 1.05 to 4 times. Preferably, the corrugated coating tube 21 is made of foamed polyethylene with a foaming ratio of 1.2 to 2.5 times. Also, as will be described later, the corrugated coating tube 21 may be subdivided into a multilayer structure so that the surface of the ridges 21a is made of non-foamed resin. This prevents damage such as tearing of the corrugated coating tube 21 and a decrease in appearance.

[0051] Furthermore, the corrugated coated tube 21 may be subdivided into a multilayer structure, thereby incorporating multiple resin layers stacked radially. When foamed polyethylene is used as the material, the foaming ratio of the foamed polyethylene may be continuously lower than that of the inner layer as it approaches the outer layer, or it may be discontinuously different in its foaming ratio from the inner layer to the outer layer. In addition, the corrugated coated tube 21 may also contain a portion of resins other than polyethylene, such as polyolefins like polybutene and polypropylene, olefin-based elastomers, styrene-based elastomers, and vinyl chloride, either individually, foamed, or in combination thereof.

[0052] The outer tube 22 is, for example, a cylindrical bellows tube that covers the corrugated coated tube 21. The outer tube 22 is formed to be expandable and contractible in the direction of the tube axis. In the first embodiment, the outer tube 22 is described as a cylindrical bellows tube, but the outer tube 22 may be of other shapes. The outer tube 22 is made of a material containing one or more resins selected from heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, polypropylene, olefin-based elastomer, styrene-based elastomer, rayon, and polyester, similar to the corrugated coated tube 21. The corrugated coated tube 21 has excellent properties such as flexibility and scratch resistance. There are no particular restrictions on the material of the corrugated coated tube 21 as long as it can ensure properties such as flexibility and scratch resistance.

[0053] Furthermore, the outer tube 22 may be subdivided into multiple layers to form multiple resin layers stacked radially. When foamed polyethylene is used as the material, the foaming ratio of the foamed polyethylene may be continuously lower than that of the inner layer as it approaches the outer layer, or it may be discontinuously changed from the inner layer to the outer layer. The outer tube 22 and the corrugated coating tube 21 may each be made of different materials.

[0054] Furthermore, the outer tube 22 may be made of a nonwoven fabric using heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, polypropylene, olefin-based elastomer, styrene-based elastomer, rayon, or polyester. This makes it possible to improve the flexibility, heat retention, and breathability of the outer tube 22.

[0055] The thickness of the outer tube 22 is set to 2 mm or less. Furthermore, it is desirable that the thickness of the outer tube 22 be set to 1 mm or less. Therefore, the outer tube 22 can expand and contract in accordance with the corrugated coating tube 21 when the corrugated coating tube 21 expands and contracts in the axial direction of the tube. As a result, the outer tube 22 does not hinder the expansion and contraction of the corrugated coating tube 21, which is preferable. Furthermore, the outer tube 22 is in close, movable contact with the surface of the peaks 21a of the corrugated coating tube 21. Specifically, the outer tube 22 is kept in a state of close contact with the corrugated coating tube 21 without fusing, or in a state of incomplete fusion. Therefore, the outer tube 22 can be expanded and contracted, flipped over, or rolled up without expanding or contracting the corrugated coating tube 21. This further reduces the resistance of the outer tube 22 to the corrugated coating tube 21 when the corrugated coating tube 21 expands and contracts.

[0056] Next, the procedure for connecting the condensation-proof composite pipe 5 to the drain pipe 31 will be explained based on Figures 2, 11, and 12. As shown in Figure 11, when connecting the condensation-proof composite pipe 5 to the drain pipe 31, the corrugated coating pipe 21 is compressed by sliding it in the axial direction relative to the inner pipe 20 at the holding protrusion 21c (see Figure 6) of the corrugated coating pipe 21. By compressing the corrugated coating pipe 21, the connection allowance 20a of the inner pipe 20 is exposed. At this time, the outer pipe 22, which is in close contact with the peaks 21a of the corrugated coating pipe 21, is also compressed and folded in the axial direction along with the corrugated coating pipe 21.

[0057] As shown in Figure 12, the outer tube 22 is formed of, for example, an elastomer. The elastomer has a density of 0.19 g / cm³. 3 Preferably, the durohardness A is less than 90. The elastomer has the property of hardly fusing with polyethylene. Therefore, it is possible to shift the outer tube 22 relative to the corrugated coating tube 21. By shifting the outer tube 22, the outer tube 22 can be pre-contracted in the axial direction of the tube to expose the corrugated coating tube 21. After exposing the corrugated coating tube 21, as shown in Figure 11, the corrugated coating tube 21 can be contracted to easily expose the inner tube 20. In this state, as shown in Figure 2, the inner pipe 20 is connected to the drain pipe 31. This completes the procedure for connecting the condensation-proof composite pipe 5 to the drain pipe 31.

[0058] Here, the corrugated coated pipe 21 is made of a flexible resin mainly composed of polyethylene. The outer pipe 22 is made of a material including, for example, an elastomer. Therefore, the inner pipe 20 can be easily and quickly connected to the drain pipe 31 without hindering the contraction of the corrugated coated pipe 21 and the outer pipe 22. Furthermore, the elastomer hardly fuses to the olefin-based corrugated coating tube 21 during molding. In addition, the elastomer utilizes its rubber-like elasticity to pre-shrink the elastomer outer tube 22 individually in the axial direction of the tube. Therefore, the resistance to shrinking the corrugated coating tube 21 can be reduced.

[0059] After connecting the inner tube 20 to the drain tube 31, the corrugated coated tube 21 comes into contact with the cap 15 of the drain tube 31 and contracts slightly in the direction of the tube axis. As a result, the outer tube 22 may be left over in the direction of the tube axis. In this case, the outer tube 22 may be unwound to the end of the tube and the excess portion may be left coiled. Alternatively, the outer casing of the drain tube 31 may be covered with the outer tube 22.

[0060] Furthermore, the corrugated coating tube 21 and the outer tube 22 contract in the direction of the pressure applied (in the direction of the tube axis) when pressure is applied in the direction of the tube axis. When the pressure is released, the corrugated coating tube 21 and the outer tube 22 attempt to return to their original length due to their own elastic restoring force. However, the corrugated coating tube 21 and the outer tube 22 may not return completely to their original length. On the other hand, the corrugated coating tube 21 and the outer tube 22 are elastic. Therefore, the corrugated coating tube 21 and the outer tube 22 can be returned to their original length by pulling them in the opposite direction to the direction of the pressure.

[0061] Furthermore, by constructing the corrugated clad tube 21 and the outer tube 22 from foamed polyethylene with low thermal conductivity, it is possible to improve the heat insulation and heat retention properties of the corrugated clad tube 21 and the outer tube 22. Therefore, temperature changes of the fluid flowing through the inner tube 20 can be kept to a minimum. In addition, foamed polyethylene has high sound absorption properties. Therefore, for example, it can absorb water hammer noise. In particular, by constructing the resin from foamed polyethylene with a foaming ratio of 1.05 to 4 times, the apparent modulus of elasticity of the resin can be reduced. Therefore, the corrugated clad tube 21 and the outer tube 22 can be made more flexible while maintaining rigidity at the same wall thickness. It is preferable to use foamed polyethylene with a foaming ratio of 1.2 to 2.5 times for the corrugated clad tube 21 and the outer tube 22. Furthermore, foaming of the resin reduces scratch resistance. To address this, the outer tube 22 can be made thicker, or a non-foamed elastomer or similar material can be used as a non-foamed resin to prevent damage such as tearing of the outer tube 22 and a decrease in its appearance.

[0062] Furthermore, when foamed polyethylene is used as the resin constituting the corrugated coated pipe 21, as mentioned above, the foaming ratio may be continuously lower than that of the inner layer as one approaches the outer layer. Alternatively, the foaming ratio may change discontinuously from the inner layer to the outer layer. Therefore, for example, even if the outer pipe 22 is subjected to an external force that causes it to break, superior scratch resistance of the corrugated coated pipe 21 can be expected, and the protection of the inner pipe 20 can be ensured. If only the outer pipe 22 is broken, it is preferable to apply insulating material to the broken part, wrap the broken part with tape, and then secure it with wire mesh or cable ties (registered trademark). Furthermore, the broken outer pipe 22 may be replaced with another outer pipe 22.

[0063] Alternatively, the corrugated coated pipe 21 and the outer pipe may be made into a multilayer structure, for example, the inner pipe 20 may be a cross-linked polyethylene pipe, the inner layer of the corrugated coated pipe 21 may be an olefin-based elastomer, the outer layer of the corrugated coated pipe 21 may be low-density polyethylene, and the inner surface layer of the outer pipe 22 may be an olefin-based elastomer. Alternatively, the inner pipe 20 may be a polyvinyl chloride pipe, the inner layer of the corrugated coated pipe 21 may be a styrene-based elastomer, the outer layer of the corrugated coated pipe 21 may be low-density polyethylene, and the inner surface layer of the outer pipe 22 may be an olefin-based elastomer.

[0064] Elastomers have the property of hardly fusing with polyethylene or polyvinyl chloride. Therefore, when molding the corrugated coated pipe 21 in-line, it is preferable to make the corrugated coated pipe 21 multilayered and make the layer that comes into contact with the inner pipe 20 an elastomer. In addition, as mentioned above, the corrugated coated pipe 21 and the outer pipe may contain in part resins other than polyethylene, such as polyolefins such as polybutene and polypropylene, or polyvinyl chloride, either individually or in combination with these resins.

[0065] According to the condensation-proof composite pipe 5 of the first embodiment described above, the inner pipe 20 is covered with a corrugated coating pipe 21. A retaining projection 21c is provided on the corrugated coating pipe 21, and the tip 21d of the retaining projection 21c holds the inner pipe 20 concentrically with the pipe axis. The tip 21d of the retaining projection 21c is in contact with (closely in contact with) the inner pipe 20, or positioned close to the inner pipe 20, in order to hold the inner pipe 20 concentrically with the pipe axis. As a result, the outside temperature is easily transmitted to the inner pipe 20 via the tip 21d of the retaining projection 21c.

[0066] Therefore, the corrugated coated pipe 21 is covered with the outer pipe 22, and the outer pipe 22 is made to be movable and in close contact with the surface of the peak portion 21a. Thus, an air insulation layer can be formed between the surface of the valley portion 21b and the surface of the retaining protrusion 21c and the outer pipe 22. By forming an air insulation layer, the surface of the retaining protrusion 21c in particular can be prevented from coming into contact with the outside air. As a result, the heat retention of the condensation-proof composite pipe 5 can be improved by the air insulation layer. Therefore, the occurrence of condensation on the condensation-proof composite pipe 5 can be suppressed, and the condensation-proof performance of the condensation-proof composite pipe can be improved.

[0067] Furthermore, the retaining projection 21c was made conical. The maximum angle of the virtual apex angle θ of the tip 21d of the retaining projection 21c was set to 60 degrees or more, and the shortest path A from the point of the tip 21d in contact with the inner tube 20 to the peak 21a was made more than 5% longer than the shortest distance B. By making the shortest path A more than 5% longer than the shortest distance B, the heat transfer rate by the retaining projection 21c can be slowed down. Therefore, the heat retention performance of the inner tube 20 can be further improved. As a result, condensation on the condensation-proof composite tube can be suppressed more effectively, and the condensation-proof performance of the condensation-proof composite tube can be further improved.

[0068] Furthermore, the retaining protrusion 21c is made to protrude radially by 4 mm or more toward the pipe axis relative to the bottom of the valley 21b. Therefore, the radial gap δ formed between the bottom of the valley 21b in the corrugated coated pipe 21 and the surface of the inner pipe 20 can be set to 4 mm or more. As a result, the heat retention of the inner pipe 20 can be improved by the insulating air layer formed by the radial gap δ. Consequently, the temperature change of the fluid flowing through the inner pipe 20 can be kept to a minimum.

[0069] Furthermore, the anti-condensation composite pipe 5 can have its radial gap δ set to 4 mm or more by the holding protrusions 21c of the corrugated coating pipe 21. Therefore, it is not necessary to provide an intermediate material between the inner pipe 20 and the corrugated coating pipe 21 in order to set the radial gap δ to 4 mm or more. This simplifies the structure of the anti-condensation composite pipe 5 and keeps manufacturing costs low.

[0070] Furthermore, the corrugated cladding tube 21 was constructed from foamed resin with a viscosity of 1.05 to 4 times. By constructing the corrugated cladding tube 21 from foamed resin, the thermal conductivity of the corrugated cladding tube 21 can be reduced. On the other hand, it is conceivable that constructing the corrugated cladding tube 21 from foamed resin would reduce its rigidity. Therefore, the corrugated cladding tube 21 was constructed from foamed resin with a viscosity of 1.05 to 4 times. This ensures the rigidity of the corrugated cladding tube 21.

[0071] Furthermore, the inner tube 20 is made of a material containing one or more resins selected from polyvinyl chloride or polychlorinated polyvinyl chloride, crosslinked polyethylene, polybutene, heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, polypropylene, olefin-based elastomer, and styrene-based elastomer. Alternatively, the inner tube 20 can be constructed as a composite tube using a material containing one or more selected resins and metal. Furthermore, the inner tube 20 can be constructed as a composite tube using a material containing one or more selected resins and a foamed layer with a foaming ratio of 1.05 to 10 times. This ensures that the inner tube 20 has properties such as thermal insulation and fluid flow.

[0072] Furthermore, the corrugated coated tube 21 is constructed using a material containing one or more resins selected from heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, polypropylene, olefin-based elastomer, styrene-based elastomer, rayon, and polyester. This ensures that the corrugated coated tube 21 has properties such as flexibility and scratch resistance.

[0073] Furthermore, the inner tube 20 contains multiple resin layers laminated radially. This ensures that the inner tube 20 has appropriate properties such as thermal insulation and fluid flow. Additionally, the corrugated cladding tube 21 contains multiple resin layers laminated radially. This effectively prevents the inner surface of the corrugated cladding tube 21 from fusing to the surface of the inner tube 20. Furthermore, it effectively prevents damage and deterioration of appearance on the surface of the corrugated cladding tube 21.

[0074] [Second Embodiment] Next, the condensation-proof composite pipe 5 of the second embodiment will be described. In the second embodiment, the outer tube 22 of the condensation-proof composite tube 5 is made of nonwoven fabric. Nonwoven fabrics have a porous structure, and one of their basic properties is heat retention. On the other hand, nonwoven fabrics can be manufactured in cloth-like or flexible forms depending on the combination of raw materials and manufacturing methods. By using nonwoven fabric for the outer tube 22, heat retention can be ensured without the outer tube 22 hindering the contraction of the flexible corrugated coated tube 21. The nonwoven fabric used for the outer tube 22 is not limited in terms of raw materials or manufacturing method, as long as it does not hinder the contraction of the corrugated coated tube 21 and ensures heat retention.

[0075] Preferably, the nonwoven fabric used for the outer tube 22 has an average fiber diameter of 20 ± 10 μm, a fiber porosity of 90 ± 5%, and a thickness of 1 mm or less. This prevents the corrugated coated tube 21 and the outer tube 22 from sticking together and allows for easy expansion and contraction.

[0076] Furthermore, it is conceivable that condensation may occur due to capillary action in the porous portion of the nonwoven fabric of the outer tube 22, causing the surface temperature to drop below the dew point. In this case, the design may be modified to effectively suppress dripping by diffusing the condensed water in the thickness direction of the nonwoven fabric or by using rayon for the nonwoven fabric to absorb the water.

[0077] According to the condensation-proof composite pipe 5 of the second embodiment described above, by constructing the outer pipe 22 of the condensation-proof composite pipe 5 from a nonwoven fabric, it is possible to achieve both heat retention and expandability of the condensation-proof composite pipe 5 while suppressing the expansion of the outer diameter of the condensation-proof composite pipe 5.

[0078] It should be noted that the technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention.

[0079] The maximum angle of the virtual vertex angle θ does not need to be less than 60 degrees, and the shortest path A does not need to be more than 5% longer than the shortest distance B. The retaining projection 21c may protrude radially from the bottom of the valley portion 21b toward the pipe axis by a range of less than 4 mm. The corrugated coated pipe 21 does not have to be made of foamed resin with a thickness of 1.05 to 4 times. The materials of the inner tube 20, the corrugated coated tube 21, and the outer tube 22 are not limited to the examples described above.

[0080] Furthermore, it is possible to replace the components in this embodiment with well-known components as appropriate, without departing from the spirit of the present invention.

[0081] (Note) The above embodiment can be understood, for example, as follows:

[0082] <1> A condensation-proof composite pipe according to one aspect of the present invention comprises an inner pipe containing a foamed layer, a flexible corrugated coating pipe covering the inner pipe, and an outer pipe covering the corrugated coating pipe, wherein the corrugated coating pipe has annular peaks and annular valleys arranged alternately in the direction of the pipe axis, and retaining protrusions arranged at intervals in the circumferential direction in the direction of the pipe axis and protruding radially inward from the valleys, with their tips holding the inner pipe concentrically with the pipe axis, and the outer pipe is in movable contact with the surface of the peaks.

[0083] In the condensation-proof composite pipe, the inner pipe is covered with a corrugated coating pipe. A retaining projection is provided on the corrugated coating pipe, and the tip of the retaining projection holds the inner pipe concentrically with the pipe axis. The tip of the retaining projection is positioned in contact with or close to the inner pipe in order to hold the inner pipe concentrically with the pipe axis. As a result, the outside temperature is easily transmitted to the inner pipe via the tip of the retaining projection.

[0084] Therefore, the corrugated coated pipe was covered with an outer pipe, and the outer pipe was made to be in movable contact with the surface of the peaks. As a result, an air insulation layer can be formed between the surface of the valleys and the surface of the retaining protrusions and the outer pipe. By forming an air insulation layer, the surface of the retaining protrusions in particular can be prevented from coming into contact with the outside air. This improves the heat retention of the condensation-proof composite pipe with the air insulation layer. Consequently, the occurrence of condensation in the condensation-proof composite pipe can be suppressed, and the condensation-proof performance of the condensation-proof composite pipe can be improved.

[0085] <2> the above <1> In the condensation-proof composite pipe relating to the present invention, the retaining protrusion allows the corrugated coating pipe to move in the axial direction relative to the inner pipe, while constraining the inner pipe in the radial direction relative to the corrugated coating pipe, and the tip is a chamfered cone shape, the maximum angle of the virtual apex angle of the tip is 60 degrees or more, and the shortest path from the point of the tip in contact with the inner pipe to the peak may be longer than 5% of the line segment connecting the inner pipe and the peak with a perpendicular line.

[0086] In the anti-condensation composite pipe, the retaining protrusion is conical in shape. The maximum virtual apex angle of the tip of the retaining protrusion is set to 60 degrees or more, and the shortest path from the point of contact with the inner pipe to the peak is made to be more than 5% longer than the line segment connecting the inner pipe and the peak with a perpendicular line. The virtual apex angle of the tip is the maximum angle among the angles formed by any two generatrixes of the cone shape. By making the shortest path more than 5% longer than the line segment connecting the inner tube and the peaks with perpendicular lines, the heat transfer rate due to the retaining protrusions can be slowed down. Therefore, the heat insulation performance of the inner tube can be further improved. As a result, condensation can be more effectively suppressed in the condensation-proof composite tube, and the condensation-proof performance of the condensation-proof composite tube can be further improved.

[0087] <3> the above <1> or <2> In the condensation-proof composite pipe relating to the present invention, the corrugated coating pipe may have the holding protrusions protruding 4 mm or more radially toward the pipe axis relative to the bottom of the valleys, the corrugated coating pipe may be made of foamed resin with a thickness of 1.05 to 4 times, and the outer pipe (the surface of the peaks) may be made of non-foamed resin.

[0088] In the anti-condensation composite pipe, the retaining protrusions are projected radially by 4 mm or more toward the pipe axis relative to the bottom of the valleys. Therefore, the radial gap formed between the bottom of the valleys and the surface of the inner pipe in the corrugated coated pipe can be set to 4 mm or more. As a result, the insulating air layer formed by the radial gap can improve the heat retention of the inner pipe. Consequently, the temperature change of the fluid flowing through the inner pipe can be kept to a minimum.

[0089] Furthermore, the condensation-proof composite pipe allows for a radial gap of 4 mm or more due to the holding protrusions of the corrugated coating pipe. Therefore, it is not necessary to provide an intermediate material between the inner pipe and the corrugated coating pipe in order to set the radial gap to 4 mm or more. This simplifies the structure of the condensation-proof composite pipe and keeps manufacturing costs low.

[0090] Furthermore, the corrugated cladding was constructed using foamed resin with a viscosity of 1.05 to 4 times its original strength. Using foamed resin for the corrugated cladding reduces its thermal conductivity. However, this also reduces its rigidity. Therefore, the corrugated cladding was constructed using foamed resin with a viscosity of 1.05 to 4 times its original strength. This ensures the rigidity of the corrugated cladding.

[0091] <4> the above <1> from <3> In a condensation-proof composite pipe according to any one embodiment of the above, the inner pipe may contain one or more resins selected from polyvinyl chloride or polychlorinated polyvinyl chloride, crosslinked polyethylene, polybutene, heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, polypropylene, olefin-based elastomer, and styrene-based elastomer, or it may contain the one or more resins and a metal or the one or more resins and a foamed layer with a foaming ratio of 1.05 to 10 times.

[0092] According to the condensation-proof composite pipe, the inner pipe is made of a material containing one or more resins selected from polyvinyl chloride or polychlorinated polyvinyl chloride, crosslinked polyethylene, polybutene, heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, polypropylene, olefin-based elastomer, and styrene-based elastomer. Alternatively, the inner pipe can be constructed as a composite pipe using a material containing one or more selected resins and a metal. Furthermore, the inner pipe can be constructed as a composite pipe using a material containing one or more selected resins and a foamed layer with a foaming ratio of 1.05 to 10 times. This ensures that the inner pipe has properties such as thermal insulation and fluid flow.

[0093] <5> the above <1> from <4> In a condensation-proof composite pipe according to any one embodiment, the corrugated coating pipe may contain one or more resins selected from heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, polypropylene, olefin-based elastomer, styrene-based elastomer, rayon, and polyester.

[0094] According to the anti-condensation composite pipe, the corrugated coated pipe is constructed using a material containing one or more resins selected from heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, polypropylene, olefin-based elastomer, styrene-based elastomer, rayon, and polyester. This ensures that the corrugated coated pipe has properties such as flexibility and scratch resistance.

[0095] <6> the above <1> from <5> In a condensation-proof composite pipe according to any one of the embodiments, at least one of the inner pipe and the corrugated coating pipe may include a plurality of resin layers stacked in the radial direction.

[0096] In the condensation-proof composite pipe, the inner pipe contains multiple resin layers laminated radially. This ensures that the inner pipe has appropriate properties such as thermal insulation and fluid flow. Furthermore, the corrugated cladding pipe also contains multiple resin layers laminated radially. This effectively prevents, for example, the inner surface of the corrugated cladding pipe from fusing to the surface of the inner pipe. In addition, it effectively prevents damage and deterioration of the appearance of the corrugated cladding pipe's surface. [Explanation of Symbols]

[0097] 5… Condensation-proof composite pipe 20…Inner pipe 21…Corrugated cladding tube 21a... Yamabe 21b…Tanibe 21c...Retaining protrusion 21d...tip 22…Outer tube A... Shortest route B...Shortest distance (the line segment connecting the inner pipe and the aforementioned peak with a perpendicular line) θ... virtual vertex angle δ... Radial clearance

Claims

1. An inner tube containing a foam layer, A flexible corrugated covering tube that covers the inner tube, The corrugated covering tube comprises an outer tube that covers the corrugated covering tube, The aforementioned corrugated coated tube is Annular peaks and annular valleys are arranged alternately in the direction of the pipe axis, The tube has a holding projection that is spaced apart in the axial and circumferential directions of the tube, protruding radially inward from the valley portion, and whose tip holds the inner tube concentrically with the tube axis, The outer tube is in movable contact with the surface of the ridge. Condensation-proof composite pipe.

2. The aforementioned retaining projection is The corrugated coating tube allows movement of the inner tube in the axial direction of the tube, and constrains the inner tube in the radial direction relative to the corrugated coating tube. Furthermore, the tip is a chamfered cone shape, the maximum angle of the virtual apex angle of the tip is 60 degrees or more, and the shortest path from the point of the tip touching the inner tube to the peak is more than 5% longer than the line segment connecting the inner tube and the peak with a perpendicular line. The condensation-proof composite pipe according to claim 1.

3. The corrugated coated tube has a holding projection that protrudes 4 mm or more radially toward the tube axis relative to the bottom of the valley, The corrugated coating tube is made of foamed resin with a volume of 1.05 to 4 times its original volume. The outer tube is made of non-foamed resin. The condensation-proof composite pipe according to claim 1.

4. The inner tube is, It comprises one or more resins selected from polyvinyl chloride or polychlorinated polyvinyl chloride, crosslinked polyethylene, polybutene, heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, polypropylene, olefin-based elastomers, and styrene-based elastomers, or comprises the one or more resins and a metal or the one or more resins and a foamed layer with a foaming ratio of 1.05 to 10 times. The condensation-proof composite pipe according to claim 1.

5. The aforementioned corrugated coated tube is It contains one or more resins selected from heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, polypropylene, olefin-based elastomers, styrene-based elastomers, rayon, and polyester. The condensation-proof composite pipe according to claim 1.

6. At least one of the inner tube and the corrugated coating tube includes a plurality of resin layers stacked in the radial direction. The condensation-proof composite pipe according to claim 1.

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