Piping structure

Abstract

To enable a coating pipe of a composite pipe to be mounted to a joint with high sealability.SOLUTION: A piping structure comprises a joint 1 and a composite pipe 5. The composite pipe 5 has a flexible resin inner pipe 30, and a covering pipe 40 made of a corrugated resin pipe having annular peak parts 41 and annular valley parts 42 alternating in a pipe axial direction. The joint 1 has a connection part 3 that connects the composite pipe 10. The connection part 3 includes an internal fixing structure 10 into which the inner pipe 30 is inserted and fixed. An outer periphery of the connection part 3 has an annular mounting surface 22a onto which an end part of the covering pipe 40 of the composite pipe 10 is mounted so as to cover it. An inner diameter Dy of the valley parts 42 of the covering pipe 5 is smaller than an outer diameter Dx of the mounting surface 22a, and the valley parts 42 are in close contact with the mounting surface 22a in a state where they are elastically expanded in diameter.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a piping structure in which a composite pipe made of resin is connected to a joint. [Background technology]

[0002] A resin composite pipe used for hot and cold water supply, etc., has an inner pipe and a covering pipe made of a corrugated pipe that covers the inner pipe. When connecting this composite pipe to a joint, as disclosed in Patent Document 1, it is common to insert and fix the end of the inner pipe into the joint in a state where the end of the covering pipe is moved back to expose the end of the inner pipe, and the end of the covering pipe is butted against the tip face of the joint. However, if the cladding pipe is cut at an angle, a gap will be created between the end of the cladding pipe and the end face of the joint, and the air layer between the inner pipe and the cladding pipe will be in communication with the outside. Also, if the end of the composite pipe is connected to the joint with the end facing upward, the end of the cladding pipe will slip down and separate from the joint, exposing the end of the inner pipe and allowing the air layer between the inner pipe and the cladding pipe to be in communication with the outside. Therefore, there is a possibility that a good heat retention effect cannot be maintained.

[0003] In the piping structure disclosed in Patent Document 2, the inner diameter of the cladding pipe is larger than the outer diameter of the joint, and the end of the cladding pipe is fitted over the outer periphery of the joint. In this piping structure, the sealing between the end of the cladding pipe and the outer periphery of the joint is insufficient, and the air layer between the inner pipe and the cladding pipe is not blocked from communicating with the outside. In addition, when the end of the composite pipe is connected to the joint with its end facing upward, the cladding pipe slides off the joint, exposing the end of the inner pipe.

[0004] In the piping structure disclosed in Patent Document 3, an annular locking projection is formed on the outer periphery of the tip of the connection part of the joint, and the valley part of the cladding pipe climbs over this locking projection and is attached to the outer periphery of the connection part. In this piping structure, even when the end of the composite pipe is connected to the joint with the end facing upward, the cladding pipe will not fall out of the connection part, but there is room for improvement in the sealing performance between the cladding pipe and the outer periphery of the connection part. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4190923 [Patent Document 2] JP 2020-193692 A [Patent Document 3] JP 2023-25475 A Summary of the Invention [Problem to be solved by the invention]

[0006] As a solution to the above-mentioned Patent Documents 1 to 3, a piping structure is conceivable in which the end of the cladding pipe is attached so as to cover the connection part of the joint, and in order to maintain this attached state and to improve the sealing between the two, the end of the cladding pipe is fastened to the outer periphery of the connection part with a fastening member such as an elastic ring or clip. However, the use of a fastening member increases costs. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a piping structure including a composite pipe having a flexible resin inner pipe, and a covering pipe made of a resin corrugated pipe having annular peaks and valleys alternately in the pipe axial direction and covering the inner pipe, and a joint having a connection part for connecting the composite pipes, the connection part including an internal fixing structure into which the inner pipe is inserted and fixed, the piping structure comprising: The connection portion is formed on an outer periphery with an annular mounting surface onto which the end of the cladding tube of the composite pipe is fitted, and the inner diameter of the valley portion of the cladding tube is smaller than the outer diameter of the mounting surface, so that the valley portion is elastically expanded in diameter and comes into close contact with the mounting surface.

[0008] According to the above-mentioned configuration, the valley portion of the cladding pipe is in close contact with the fitting surface of the joint in an elastically expanded state, so that the gap between the cladding pipe and the fitting is well sealed, the air layer between the cladding pipe and the inner pipe is reliably blocked from communication with the outside, and good heat retention is maintained. In addition, since the valley portion is in close contact with the fitting surface in an elastically expanded state, the fitting state can be stably maintained, and even when the end of the composite pipe is connected to the fitting with the end facing upward, for example, the cladding pipe can be prevented from slipping off the joint. Furthermore, since there is no need to use a separate fastening member or the like, an increase in costs can be avoided.

[0009] Preferably, the root portion of the end portion of the cladding tube is brought into close contact with the mounting surface in a state where the diameter of the root portion is expanded by 102% to 120% of the original inside diameter.

[0010] In one embodiment, the covering tube contains low-density polyethylene as a main material and has an expansion ratio of 1.05 to 4 times.

[0011] In one embodiment, the cladding tube has holding protrusions that are distributed axially and circumferentially and protrude radially inward from the valley portion, and the tips of the holding protrusions hold the inner tube approximately coaxially with the cladding tube, thereby forming an air layer between the inner tube and the valley portion, the holding protrusions are positioned away from the connection portion when the end of the cladding tube is attached to the attachment surface of the connection portion, and a recess corresponding to the holding protrusions is formed on the outer periphery of the cladding tube, and the width of this recess in the tube axial direction is 110% or more of the width of the valley portion in the tube axial direction. According to this configuration, the recess corresponding to the retaining protrusion is arranged so as to cut out at least a portion of the peak, making it easy to see and reliably preventing the retaining protrusion from being attached to the outer periphery of the connection part.

[0012] In one embodiment, a locking projection that projects radially outward from the mounting surface is formed on the connecting portion distal side of the mounting surface, and the valley portion rides over the locking projection and comes into close contact with the mounting surface. According to this configuration, the engagement between the valley portion and the locking projection can more reliably maintain the attachment state of the cladding tube end to the connection portion. Effect of the Invention

[0013] According to the present invention, by closely contacting the end of the cladding tube with the mounting surface on the outer periphery of the connection part of the joint in an expanded diameter state, it is possible to maintain the mounting state of the cladding tube and achieve high sealing performance without increasing costs. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a vertical cross-sectional view showing a joint of a piping structure according to a first embodiment of the present invention. [Diagram 2] 4 is a longitudinal sectional view showing the composite pipe of the piping structure, in which the end of the covering pipe has been moved in the pipe axial direction to expose the end of the inner pipe. FIG. [Diagram 3] FIG. 2 is a vertical cross-sectional view of a piping structure constructed by connecting the ends of a composite pipe to a joint. [Figure 4] FIG. 5 is a side view showing a piping structure according to a second embodiment of the present invention, in which a covering tube is shown in cross section. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A piping structure according to a first embodiment of the present invention will be described below with reference to Figures 1 to 3. The piping structure includes a joint 1 shown in Figure 1 and a composite pipe 5 shown in Figure 2 connected to the joint 1. <Joint configuration> As shown in Fig. 1, the joint 1 has a joint body 2. The joint body 2 can have various shapes, such as a straight pipe shape, an elbow pipe shape, a T-shaped pipe shape, etc. A connection part 3 for a compound pipe 5 is provided at one of the multiple ends of the joint body 2. This end is cylindrical, and its inner diameter increases stepwise toward the tip, with annular steps 2a, 2b, and 2c formed in sequence from the back to the tip.

[0016] The connection portion 3 includes an internal fixing structure 10 disposed radially inside the cylindrical end portion of the joint body 2, and a cap 20 disposed radially outside. The internal fixing structure 10 has an inner core 11, an O-ring 12, a ring base 13, a plurality of retaining rings 14, and a spacer 15.

[0017] The incore 11 has a long, thin cylindrical shape, and an insertion space 16 is formed between the incore 11 and the inner periphery of the end of the joint body 2. A flange 11a is formed at the inner end of the incore 11, and this flange 11a abuts against a step 2a of the joint body 2, thereby preventing the incore 11 from moving any further inward.

[0018] The ring base 13 is engaged with the step 2c of the joint body 2, and the O-ring 12 is disposed between the ring base 13 and the step 2b. The retaining rings 14 are spaced apart by a spacer 15 and are disposed between the ring base 13 and an annular step 24 formed on the inner periphery of the cap 20.

[0019] The cap 20 has a first cylindrical portion 21 on the base end side and a second cylindrical portion 22 on the tip end side. The second cylindrical portion 22 has a smaller diameter than the first cylindrical portion 21. A threaded portion 23 is formed on the inner periphery of the first cylindrical portion 21 of the cap 20, and this threaded portion 23 screws into a threaded portion 2d formed on the outer periphery of the end of the joint body 2, thereby connecting the cap 20 to the end of the joint body 2. The above-mentioned annular step 24 is formed on the inner periphery of the cap 20. The outer periphery of the second tubular portion 22 of the cap 20 has a mounting surface 22a having a function described below. In this embodiment, the mounting surface 22a is a cylindrical surface and extends to the tip of the second tubular portion 22. The outer diameter of the mounting surface 22a is indicated by the symbol Dx in FIG.

[0020] <Composite pipe structure> As shown in FIG. 2, the composite pipe 5 includes a flexible inner pipe 30 made of resin and a covering pipe 40 made of resin that covers the inner pipe 30 . The inner tube 30 contains one or more resins selected from cross-linked polyethylene, polybutene, heat-resistant polyethylene, high-density polyethylene, low-density polyethylene, and polypropylene, or contains one or more of these resins and a metal.

[0021] The covering pipe 40 contains polyethylene, more preferably low-density polyethylene, as a main material, and has an expansion ratio of 1.05 to 4 times, and further preferably 1.2 to 2.5 times. The covering pipe 40 has an annular crest 41 and annular valley 42 arranged alternately in the pipe axis direction, forming a corrugated pipe shape. The covering pipe 40 is expandable in the pipe axis direction and elastically expandable in diameter. The inner diameter Dy of the valley 42 is larger than the outer diameter of the inner pipe 30 and smaller than the outer diameter Dx of the mounting surface 22a of the above-mentioned joint 1. The inner diameter of the crest 41 is larger than the outer diameter Dx of the mounting surface 22a.

[0022] The cladding tube 40 of this embodiment has holding protrusions 45 that are distributed in the tube axial direction and circumferential direction and are independent of each other. The holding protrusions 45 of this embodiment are arranged at three or more, for example four, at equal intervals in the circumferential direction at locations with a predetermined interval in the tube axial direction. The cross-sectional area of ​​each holding protrusion 45 is gradually reduced toward the radially inner side. The holding protrusions 45 protrude further radially inward than the valley portions 42, and their tips are arranged in contact with or close to the outer circumferential surface of the inner tube 30. As a result, the inner tube 30 is held approximately coaxially with the cladding tube 40, and an air layer (radial gap) 46 is formed between the inner tube 30 and the valley portions 42 of the cladding tube 40.

[0023] A recess 45x is formed on the outer circumferential surface of the cladding tube 40 in correspondence with the holding protrusion 45. The width Wa of the recess 45x in the tube axis direction is preferably set to 110% or more of the width Wb of the valley 42 in the tube axis direction, so that the peak 41 always has an appearance in which a part of the peak 41 is cut out, making it easy to see from the outside. In this embodiment, the recess 45x is formed so as to cross one peak 41 and two valleys 42 in the tube axis direction. The shape of the recess 45x as viewed from a direction perpendicular to the tube axis is a triangle, a square, a shape including a circular arc, or the like. The formation of three or more recesses 45x in the circumferential direction and the special shape make it even easier to see from the outside.

[0024] In this embodiment, the outer diameter of the covering tube 40 is 42 mm or less, the average wall thickness is 0.4 to 0.8 mm, and the average thickness of the air layer 26 is 4 mm or more. The interval between the holding protrusions 45 in the tube axial direction is 10 to 200 mm.

[0025] <Connection to composite pipe fittings> The piping structure shown in Fig. 3 is constructed by connecting the composite pipe 5 having the above-mentioned configuration to the connection portion 3 of the joint 1. This will be described in detail below. First, the end of the covering pipe 40 of the composite pipe 5 is moved back in the pipe axial direction to expose the end of the inner pipe 30. The incore 11 is removed from the connection part 3 in Fig. 1 and inserted into the end of the inner pipe 30. In this state, the end of the inner pipe 30 is inserted into the connection part 3 of the joint 1 and pushed in until the flange part 11a of the incore 11 hits the step 2a of the joint body 2. The O-ring 12 adheres closely to the outer circumferential surface of the inner pipe 30, thereby sealing between the inner pipe 30 and the joint 1. The locking claws of the retaining ring 14 bite into the outer periphery of the inner pipe 30, so that the inner pipe 30 is inserted and fixed into the connection part 3 in a retained state.

[0026] As described above, when the inner tube 30 is inserted and fixed into the connection portion 3, the valley portion 42 of the covering tube 40 abuts on the tip surface of the second cylindrical portion 22 of the cap 20. This is because the inner diameter Dy of the valley portion 42 is smaller than the outer diameter Dx of the mounting surface 22a of the second cylindrical portion 22.

[0027] Next, the end of the cladding tube 40 is moved in the tube axial direction while being elastically expanded in diameter, and is covered with the second tubular portion 22 of the connection portion 3. As a result, the valley portion 42 is in close contact with the mounting surface 22a. As described above, since the inner diameter Dy of the valley portion 42 is smaller than the outer diameter Dx of the mounting surface 22a, the valley portion 42 is mainly in close contact with the mounting surface 22a in an elastically deformed state. As a result, the gap between the cladding tube 40 and the joint 1 can be well sealed, the air layer 46 can be isolated from the outside, and a good heat retention function can be maintained. In addition, since the valley portion 42 is in close contact with the mounting surface 22a with elastic force, the cladding tube 40 can be stably maintained in a mounted state on the joint 1. For example, even when the end of the composite pipe 5 is connected to the joint 1 upward, the end of the cladding tube 40 does not slip off the connection portion 3 of the joint 1 to expose the inner tube, and a good heat retention function can be stably maintained. The mounting surface 22a preferably has an axial length of at least one pitch of the valley portion 42 so that at least one valley portion 42 can be mounted.

[0028] In this embodiment, the inner pipe 30 has a holding protrusion 45 for holding the inner pipe 30 approximately coaxially with the cladding pipe 40, but it is necessary to prevent this holding protrusion 45 from being attached to the attachment surface 22a. As described above, the recess 45x corresponding to the holding protrusion 45 can be easily seen from the outside, so that this recess 45x (holding protrusion 45) can be cut so as not to be positioned at the end of the composite pipe 5, and it is possible to reliably prevent the holding protrusion 45 from being disposed on the attachment surface 22a.

[0029] <Test to confirm the expansion performance of cladding tube> The main material is low density polyethylene with a specific gravity of 0.921. By expanding the end of the corrugated pipe (covering pipe) with an outer diameter of 30.5 mm and an inner diameter of 25.5 mm, which is expanded by 1.2 times, it was possible to attach it to the attachment surface with an outer diameter of 26.0 mm (expansion rate 102%). By expanding the end of a corrugated pipe (cladding pipe) made of the same material with an outer diameter of 36.5 mm and an inner diameter of 30.7 mm, it was possible to attach it to the attachment surface with an outer diameter of 32 mm (expansion rate 104.2%). By expanding the end of a corrugated pipe (cladding pipe) made of the same material with an outer diameter of 30.5 mm and an inner diameter of 25.5 mm, it was possible to attach it to the attachment surface with an outer diameter of 28.0 mm (expansion rate 110%). By expanding the end of a corrugated pipe (cladding pipe) made of the same material with an outer diameter of 36.5 mm and an inner diameter of 30.7 mm, it was possible to attach it to the attachment surface with an outer diameter of 33 mm (expansion rate 107%).

[0030] <Second embodiment> Next, a piping structure according to a second embodiment of the present invention will be described with reference to FIG. 4. The second tubular portion 22 of the cap 20 of the joint 1 has annular locking projections 25, 26 formed at the tip and base ends of the mounting surface 22a. The outer diameters of these locking projections 25, 26 are larger than the outer diameter Dx of the mounting surface 22a. When the end of the covering tube 40 is placed on the second tubular portion 22, the expanded valley portion 42 passes over the locking projection 25 on the tip side and is tightly attached to the mounting surface 22a. In this embodiment, the inner diameter Dy of the valley portion 42 is also smaller than the outer diameter Dx of the mounting surface 22a, so that the valley portion 42 can be elastically deformed and tightly attached to the mounting surface 22a, thereby providing a sealing function. A part of the cut valley portion 42 at the tip of the covering tube 40 passes over the locking projection 26 and is attached to the outer periphery of the second tubular portion 22.

[0031] In this embodiment, the engagement of the valley portion 42, which is in intimate contact with the mounting surface 22a, with the locking projection 25 on the tip side can more reliably prevent the covering tube 40 from slipping off the connection portion 3. The locking projections 25, 26 do not have to be continuous annular over the entire circumference, and multiple locking projections may be formed at intervals in the circumferential direction. The locking projection 26 on the base end side may be omitted.

[0032] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the first embodiment, the mounting surface 22a extends to the tip of the second cylindrical portion 22, but a guide surface that tapers toward a narrower point may be formed between the mounting surface and the tip of the second cylindrical portion 22. The mounting surface may be a gently tapered surface.

[0033] The recess 45x of the holding protrusion 45 may be formed so as to cross one valley portion 42 and a part of one or two peak portions 41, or may be formed so as to cross one peak portion 41 and a part of one or two valley portions 42. Also, the holding protrusion 45 may be omitted. [Industrial Applicability]

[0034] INDUSTRIAL APPLICABILITY The present invention is applicable to a piping structure in which a composite pipe having an inner pipe and a corrugated covering pipe is connected to a joint. [Explanation of symbols]

[0035] 1. Joint 3 Connection 5 Composite pipe 10 Internal fixed structure 20 Cap 22 Second cylinder part (cylindrical part) 22a Mounting surface 25 Locking protrusion 30 Inner tube 40 Cladding tube 41 Yamabe 42 Valley 45 Retaining protrusion 45x recess Dx Outer diameter of mounting surface Dy Inner diameter of valley

Claims

1. a composite pipe including a flexible resin inner pipe and a covering pipe made of a resin corrugated pipe having annular peaks and valleys alternately in an axial direction and covering the inner pipe; a joint having a connection portion for connecting the composite pipes, the connection portion including an internal fixing structure into which the inner pipe is inserted and fixed; In a piping structure comprising: an annular mounting surface is formed on an outer periphery of the connection portion so that the end portion of the covering tube of the composite tube is fitted thereon; A piping structure, characterized in that an inner diameter of a root portion of the cladding tube is smaller than an outer diameter of the mounting surface, and the root portion is in close contact with the mounting surface in a state where it is elastically expanded in diameter.

2. 2. The piping structure according to claim 1, wherein the valley portion of the end portion of the covering tube is brought into close contact with the mounting surface in a state where the diameter of the valley portion is expanded by 102% to 120% of the original inner diameter.

3. 2. The piping structure according to claim 1, wherein the covering pipe contains low-density polyethylene as a main material and has an expansion ratio of 1.05 to 4 times.

4. the cladding tube has holding protrusions that are distributed in the axial and circumferential directions and protrude radially inward from the valley portions, and the tips of the holding protrusions hold the inner tube so as to be substantially coaxial with the cladding tube, thereby forming an air layer between the inner tube and the valley portions, the holding protrusion is disposed away from the connection portion in a state in which the end of the cladding tube is attached to the attachment surface of the connection portion, 2. The piping structure according to claim 1, characterized in that a recess corresponding to the retaining protrusion is formed on the outer periphery of the covering tube, and the width of this recess in the tube axial direction is 110% or more of the width of the valley portion in the tube axial direction.

5. The piping structure according to claim 1, characterized in that a locking protrusion protruding radially outward from the mounting surface is formed on the tip side of the mounting surface of the connection portion, and the valley portion overcomes the locking protrusion and comes into close contact with the mounting surface.

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