JP2016084897A - Double pipe - Google Patents

Abstract

CONSTITUTION: A double pipe 10 is used for supplying hot water or cold water and comprises a synthetic resin inner pipe 12 and a cladding tube 14 covering an outer peripheral surface of the inner pipe. The cladding tube has a thickness of tube wall formed uniformly or in a substantial uniform manner. In addition, the cladding tube is formed with a plurality of crest segments 16 protruding toward its outer peripheral direction. The crests are arranged in a circumferential direction under a desired spacing and extend in an axial direction of the cladding tube. A part between the adjoining crests acts as a supporting part 18 for supporting the outer peripheral surface of the inner pipe, its inner peripheral surface abuts against the outer peripheral surface of the inner pipe. The inner pipe is abutted against and supported by this supporting part over a full length in an axial direction of the cladding tube, i.e. irrespective of its axial position.EFFECT: Impact noise generated through contact between an inner peripheral surface of a cladding tube and an outer peripheral surface of the inner pipe can be reduced even if the inner pipe shows a substantial vibration due to water hammer phenomenon.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a double pipe, and more particularly to a double pipe including, for example, an inner pipe made of synthetic resin and a cladding pipe covering an outer peripheral surface of the inner pipe, and used for hot water supply or water supply, for example.

  An example of a conventional double tube of this type is disclosed in Patent Document 1. In the double tube of Patent Document 1, the cladding tube (corrugated tube) is a so-called sheath tube that is formed into a waveform in the axial direction by polyolefin. A gap continuous in the axial direction is formed between the inner peripheral surface of the cladding tube and the outer peripheral surface of the inner tube (smooth tube).

  In the double tube of Patent Document 2, the cladding tube (sheath tube) is formed of polyethylene or the like, and the outer peripheral surface is formed with a crest that extends in a ring shape in the circumferential direction and is aligned in the axial direction. Four concave portions having a triangular shape in the circumferential direction extending in the direction are formed. On the inner peripheral surface of the cladding tube at a position corresponding to the concave portion, a triangular convex portion (an inner tip of the concave portion) substantially the same as the concave portion is formed. The inner tube is in contact with all the convex portions, and is supported at a substantially concentric position in the cladding tube by the convex portions.

  In the double tube of Patent Document 3, the cladding tube (buffer layer) is formed of an olefin-based thermoplastic elastomer, and a plurality of protrusions having a triangular cross section extending in the axial direction are formed on the inner peripheral surface of the cladding tube. It is formed. The inner pipe (pipe main body) is supported in contact with all the protrusions. On the other hand, irregularities are not formed on the outer peripheral surface of the cladding tube.

  In the double pipes of Patent Documents 2 and 3, convex portions (projections) extending in the axial direction are formed on the inner peripheral surface of the cladding tube, and the inner tube is supported at substantially concentric positions in the cladding tube by all the convex portions. Therefore, even if the inner tube vibrates due to the water hammer phenomenon, the vibration can be buffered, and the impact sound caused by the contact between the cladding tube and the inner tube is suppressed.

Japanese Utility Model Publication No. 02-036687 [F16L 9/18, F16L 11/11] Japanese Patent Publication No. 07-043058 [F16L 11/11, F16L 9/18] Japanese Patent No. 4195146 [E03C 1/02, F16L 11/04]

  In the double pipe of Patent Document 1, when the pressure of water flowing in the inner pipe fluctuates rapidly and the inner pipe vibrates due to the water hammer phenomenon, a larger impact sound is generated at the contact between the cladding pipe and the inner pipe. .

  Further, in the double pipe of Patent Document 2, the cladding tube is easy to bend, but if the outer circumferential surface of the cladding tube is provided with irregularities aligned in the axial direction, the cladding tube is unintentionally locked to the surrounding structure, and There is a risk of breaking from the stop. Therefore, it is difficult to ensure the trauma prevention performance.

  Moreover, in the double pipe of patent document 3, although a cladding pipe | tube can be bent easily, since the olefin type thermoplastic elastomer has low hardness, its damage prevention performance is low.

  Therefore, the main object of the present invention is to provide a novel double tube.

  Another object of the present invention is to provide a double tube that can reduce the impact sound caused by the water hammer phenomenon and has high damage prevention performance.

  1st invention is a double pipe used for hot water supply or water supply provided with an inner pipe made of a synthetic resin and a cladding pipe covering the outer peripheral surface of the inner pipe, and the cladding pipe has a uniform wall thickness or It is substantially uniform and has a plurality of ridges arranged in the circumferential direction at predetermined intervals on the outer circumferential surface and extending in the axial direction, and the inner tube abuts and is supported by the inner circumferential surface of the cladding tube between adjacent ridges. Is a double tube.

  In 1st invention, a double pipe is a double pipe used for hot-water supply or water supply, and is provided with the inner tube made from a synthetic resin, and the cladding tube which covers the outer peripheral surface of an inner tube. The cladding tube is formed so that the thickness of the tube wall is uniform or substantially uniform. In addition, the cladding tube is formed with a plurality of peaks that protrude in the outer circumferential direction (outside in the radial direction). The crests are arranged at predetermined intervals in the circumferential direction and extend in the axial direction of the cladding tube. Between the adjacent peak parts, it functions as a support part for supporting the outer peripheral surface of the inner tube, and the inner peripheral surface is in contact with the outer peripheral surface of the inner tube. The support portions are arranged so as to be alternately arranged in the circumferential direction with the mountain portions. By this support portion, the inner tube abuts and is supported over the entire axial position of the cladding tube, that is, regardless of the axial position.

  According to the first invention, since the inner pipe is in contact with and supported by the support portion regardless of the axial position of the cladding pipe, the pressure of the water flowing inside the inner pipe fluctuates rapidly, and the water hammer phenomenon Even when the inner tube vibrates greatly, the vibration is appropriately propagated and buffered through the support portion to the cladding tube. Thereby, the impact sound by contact with the inner peripheral surface of a cladding tube and the outer peripheral surface of an inner tube is reduced.

  Further, since the crest is formed in the cladding tube, the contact area between the outer peripheral surface of the cladding tube and the ground is reduced, and the frictional force against the movement of the double tube is reduced. Therefore, trauma when the double pipe is routed is suppressed or reduced. In addition, the crests are formed so as to be continuous in the axial direction, and no irregularities are formed in the axial direction of the outer peripheral surface of the cladding tube. Therefore, when the double tube is moved in the axial direction, the outer peripheral surface of the cladding tube is Even when it comes into contact with the structure, the structure can be overcome smoothly and is not unintentionally locked. Thereby, the breakage of the cladding tube starting from the locking portion can be prevented. Therefore, the trauma prevention performance is high.

  Further, since the crests and the support parts are arranged alternately in the circumferential direction in the cladding tube, the support part is reduced in diameter by the force applied to the crests when the cladding tube is gripped. The inner tube is reliably supported by the support portion, and the inner tube can be gripped at the same time. Therefore, it is excellent in workability.

  The second invention is dependent on the first invention, and the peak has a peak in the circumferential cross section.

  In the second invention, in the circumferential cross section, the peak portion is formed in, for example, a substantially isosceles triangle shape having the inner peripheral surface side of the cladding tube as a base and has one apex. In other words, the mountain has an apex angle.

  According to the second invention, since the apex angle is provided in the peak portion, when cutting the coated tube with a cutter knife or the like, the side of the peak portion (inclined surface) is not directed to the inner tube direction. A cut can be made and the cladding tube can be cut. Therefore, there is no risk of damaging the inner tube.

  3rd invention depends on 1st or 2nd invention, and the outer peripheral surface of a cladding tube is formed in the waveform containing a peak part and the trough part between them in the circumferential direction.

  In 3rd invention, a trough part is formed between adjacent peak parts, and a cladding tube is formed in a waveform in the circumferential direction.

  According to the third invention, since the valley portion is provided between the peak portions, the contact area between the outer peripheral surface of the cladding tube and the ground is further reduced, and the trauma when the double tube is routed is further suppressed. .

  The fourth invention is dependent on any one of the first to third inventions, and only a part of the inner peripheral surface of the cladding tube between a plurality of adjacent peaks is in contact with the inner tube, To support.

  In the fourth invention, only a part of the plurality of support portions is in contact with the inner tube to support the inner tube. For example, the inner tube abuts only half or less of the plurality of support portions. A gap is formed between the support portion that does not contact the inner tube and the outer peripheral surface of the inner tube.

  According to 4th invention, since a clearance gap is formed in the inside of a cladding tube, the followability with respect to a bending improves and it becomes easy to bend a double tube. Further, by utilizing this gap, it becomes easy to cut the coated tube with a cutter knife or the like, and it is difficult to damage the inner tube.

  The fifth invention is dependent on any one of the first to fourth inventions, and both the inner tube and the cladding tube are formed of a polyolefin resin.

  In the fifth invention, both the inner tube and the cladding tube are formed of a polyolefin resin.

  According to the fifth aspect, when the double pipe is discarded or recycled, it is possible to save the trouble of separating the double pipe into the cladding pipe and the inner pipe. Moreover, it is possible to increase the hardness of a cladding tube by using polyolefin resin. Thereby, the damage prevention performance of the inner pipe is further enhanced. Furthermore, if an inexpensive recycled polyethylene or the like is used, the manufacturing cost can be reduced.

  According to the present invention, the inner tube abuts and is supported by the support portion regardless of the axial position of the cladding tube, so even if the water hammer phenomenon occurs and the inner tube vibrates greatly, Impact noise due to contact between the peripheral surface and the outer peripheral surface of the inner tube is reduced.

  Further, since the crest is formed in the cladding tube, the frictional force with respect to the movement of the double tube is reduced, and trauma when the double tube is routed can be suppressed or reduced. Moreover, since the crests are formed so as to be continuous in the axial direction, and no irregularities are formed in the axial direction of the outer peripheral surface of the cladding tube, even when the outer peripheral surface of the cladding tube contacts the surrounding structure, it is not intended. It is not locked to. Thereby, the breakage of the cladding tube starting from the locking portion can be prevented. Therefore, the trauma prevention performance is high.

  Furthermore, since the cladding tube is arranged so that the crests and the support portions are alternately arranged in the circumferential direction, when the cladding tube is gripped, the inner tube is securely supported by the supporting portion, and at the same time, the inner tube is gripped. it can. Therefore, it is excellent in workability.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

It is a perspective view which shows the double tube of one Example of this invention. It is an illustration figure which shows the cross section in the circumferential direction of the double tube | pipe of FIG. It is an illustration figure which shows the cross section in the axial direction of the double pipe | tube of FIG. It is an illustration figure which shows a part of manufacturing process of the double pipe | tube of FIG. It is an illustration figure which shows the cross section in the VV line | wire of FIG. It is a front view which shows an example of the cutter knife used when cut | disconnecting the cladding tube with which the double pipe of FIG. 1 is provided. It is an illustration figure which shows a mode that the cladding tube with which the double tube | pipe of FIG. 1 is provided is cut | disconnected. It is an illustration figure which shows the cross section in the circumferential direction of the other Example of this invention. It is an illustration figure which shows the cross section in the circumferential direction of other Example of this invention.

  1 to 3, a double pipe 10 according to an embodiment of the present invention is a double pipe used for hot water supply or water supply, and covers the inner pipe 12 and the outer peripheral surface of the inner pipe 12. 14.

  The inner pipe 12 is a water passage pipe, and is formed in a cylindrical shape by a flexible polyolefin-based resin such as polybutene, polypropylene, polyethylene, and crosslinked polyethylene. The outer diameter of the inner tube 12 is, for example, 13 mm, and the inner diameter thereof is, for example, 10 mm.

  The cladding tube 14 is a tube for protecting the inner tube 12 and is formed in a cylindrical shape by the same polyolefin resin as the inner tube 12. The thickness of the tube wall of the cladding tube 14 is formed uniformly or substantially uniformly over the entire length in the circumferential direction and the axial direction, and is, for example, 0.2 mm. A plurality of peak portions 16 are formed on the outer peripheral surface of the cladding tube 14. In other words, the cladding tube 14 is formed with a plurality of ridges 16 that protrude in the outer circumferential direction (radially outward).

  The crests 16 are arranged so as to be arranged at predetermined intervals in the circumferential direction, and the crests 16 extend linearly continuously in the axial direction of the cladding tube 14. In this embodiment, ten peak portions 16 are arranged so as to be arranged at equal intervals in the circumferential direction. The outer diameter of the peak portion 16 is, for example, 17 mm, and the protruding height thereof is, for example, 1.2 mm. The crest 16 is formed in a substantially isosceles triangle shape with the inner peripheral surface side of the cladding tube 14 as a base in the circumferential cross section, and has one apex 16a. In other words, the peak 16 has an apex angle. The apex angle is formed in a rounded corner, and the angle is, for example, 90 °.

  In addition, a valley 20 is formed between the adjacent peaks 16. The valley portion 20 is formed in an arc shape that is recessed toward the inner circumferential direction in the circumferential cross section. The cladding 14 is formed into a waveform in the circumferential direction by the crests 16 and the troughs 20 arranged alternately and continuously.

  Since the thickness of the cladding tube 14 is uniform or substantially uniform, the inner circumferential surface of the cladding tube 14 at the position where the peak portion 16 is formed is formed with a recess that is recessed toward the outer circumferential direction.

  Further, the apex of the valley portion 20 and the vicinity thereof function as a support portion 18 that supports the outer peripheral surface of the inner tube 12, and the inner peripheral surface is in contact with the outer peripheral surface of the inner tube 12.

  The support portions 18 are arranged so as to be arranged at predetermined intervals in the circumferential direction, and each support portion 18 extends linearly continuously in the axial direction of the cladding tube 14. In this embodiment, ten support portions 18 are arranged at equal intervals in the circumferential direction so as to be alternately arranged with the mountain portions 16.

  Moreover, the internal diameter of the support part 18 is 15 mm, for example, and is set larger than the external diameter of the inner tube 12. When the inner tube 12 is inserted into the inside of the cladding tube 14, only some of the support portions 18 a out of the plurality of support portions 18 come into contact with the outer peripheral surface of the inner tube 12 to support the inner tube 12. In this embodiment, eight of the ten support portions 18 do not contact the inner tube 12, and the other two support portions 18 a contact the inner tube 12. Hereinafter, the support portion 18 that contacts the outer peripheral surface of the inner tube 12 is expressed as a support portion 18a, and the support portion 18 that does not contact the outer peripheral surface of the inner tube 12 is expressed as a support portion 18b.

  The two support portions 18 a support the inner tube 12 by contacting the outer peripheral surface of the inner tube 12 over the entire axial position of the cladding tube 14.

  Further, a gap is formed between the support portion 18 b that does not contact the inner tube 12 and the outer peripheral surface of the inner tube 12, and this gap becomes larger toward the opposite side of the inner tube 12 in the eccentric direction.

  Thus, by forming a gap inside the cladding tube 14, it is possible to ensure followability to bending and bending of the double tube 10, and the double tube 10 is easily bent. In addition, the followability of the double tube 10 improves as the gap formed inside the cladding tube 14 increases. According to the inventor's experiment, for example, only a half or less of the plurality of support portions 18 may be in contact with the outer peripheral surface of the inner tube 12. As a result, a large gap is formed inside the cladding tube 14 and the followability of the double tube 10 is improved.

  However, the size of the gap formed inside the cladding tube 14 is determined not only by the difference between the outer diameter of the inner tube 12 and the inner diameter of the support portion 18 but also by the circumferential length of the peak portion 16. That is, when the peripheral length of the peak portion 16 is increased, the gap between the outer peripheral surface of the inner tube 12 and the inner peripheral surface of the cladding tube 14 is increased accordingly.

  Such a double tube 10 is formed, for example, by double-layer extrusion in which the inner tube 12 and the cladding tube 14 are simultaneously extruded.

  4 and 5, the manufacturing apparatus 24 for the double pipe 10 includes, for example, a first extruder (not shown), a second extruder 30, a mold 32, an outer sizing 26, and cooling. Includes a water tank (not shown). The mold 32 is a crosshead die for multilayer (two-layer) extrusion, the first extruder is connected to the upstream side, and the tip of the second extruder 30 is connected to the upper end. . In addition, a cylindrical protrusion (inside sizing) 32 a is provided at the downstream end of the mold 32. Further, an annular outer sizing 26 is provided at the tip of the inner sizing 32a so as to cover the outer peripheral surface thereof. As can be seen from FIG. 5, the outer peripheral surface of the inner sizing 32a and the inner peripheral surface of the outer sizing 26 are each formed in a waveform in the circumferential direction, and a gap corresponding to the thickness of the cladding tube 14 is formed between them. Yes.

  When manufacturing the double pipe 10 using such a manufacturing apparatus 24, the first extruder supplies the mold 32 while extruding the heated and melted raw material into a cylindrical shape to form the inner pipe 12. . The inner tube 12 passes through the inside of the protrusion (inside sizing) 32a of the mold 32 and is pushed out from the outlet of the protrusion 32a. On the other hand, the second extruder 30 heats and melts the raw material of the cladding tube 14 and supplies it to the mold 32. In this mold 32, the molten material of the cladding tube 14 sequentially covers the outer peripheral surface of the inner tube 12 as it advances in the traveling direction, and the cladding tube 14 is pushed out through the outer surface of the protrusion (inner sizing) 32 a. At this time, the extruded cladding tube 14 is corrected by the outer shape of the inner sizing 32a and the inner shape of the outer sizing 26, and is formed into a waveform in the circumferential direction.

  Further, between each vertex of the valley 20 of the corrugated cladding tube 14, that is, between the inner peripheral surface of each support portion 18 and the outer peripheral surface of the inner tube 12 that has been sent through the protrusion 32a, A gap of about 0.8 mm is formed. Since the inner tube 12 and the cladding tube 14 are cooled and solidified after extrusion, the inner tube 12 and the coating layer 14 are not fused or bonded. That is, both are not integrated, and the inner peripheral surface of the cladding tube 14 and the outer peripheral surface of the inner tube 12 are not bonded. In this way, the double tube 10 including the inner tube 12 and the cladding tube 14 is formed.

  However, in the manufacturing method described above, the inner tube 12 and the cladding tube 14 are simultaneously extruded, but the manufacturing method of the double tube 10 is not limited to this method. Alternatively, the outer tube may be coated with the coating layer 14 to cover the outer peripheral surface of the inner tube 12.

  The double pipe 10 thus formed is wound in a coil shape at a factory or the like and cut to a required length at a construction site.

  When piping a hot water supply / water supply pipe using the double pipe 10, first, the double pipe 10 wound in a coil shape is carried into the construction site. Next, the double pipe 10 is pulled out from the coil at the construction site. At this time, the peak portion 16 formed on the cladding tube 14 becomes a non-slip, and the operator can easily grip the double tube 10. Further, since the crest 16 and the troughs 20 (supports 18) are arranged alternately in the circumferential direction, the clad 14 is gripped so as to wrap the clad 14 with a hand or a band. At this time, the support portion 18 is deformed so as to be reduced in diameter by the force applied to the peak portion 16, and the support portion 18 b that is not normally in contact with the inner tube 12 also comes into contact with the inner tube 12. Therefore, the inner tube 12 is reliably supported by more support portions 18a, and the inner tube 12 can be gripped at the same time.

  Subsequently, the double pipe 10 drawn out from the coil is drawn to a predetermined position on the pipe line and arranged. At this time, since the crest 16 is formed in the cladding tube 14, the contact area between the outer peripheral surface of the cladding tube 14 and the ground or slab surface is reduced, and the frictional force against the movement of the double tube 10 is reduced. The Therefore, trauma when the double pipe 10 is routed is suppressed or reduced. In particular, in this embodiment, since the cladding tube 14 is formed in a waveform in the circumferential direction, that is, the valley portion 20 is provided between the peak portions 16, the above-described effect is enhanced. Moreover, since the crest 16 is formed so as to be continuous in the axial direction, and there are no irregularities in the axial direction of the outer peripheral surface of the cladding tube 14, when the double tube 10 is moved in the axial direction, Even when the outer peripheral surface of the tube 14 comes into contact with a surrounding structure, the structure can be smoothly passed over and is not locked unintentionally. Thereby, the fracture | rupture of the cladding tube 14 from the latching | locking part is prevented.

  Here, when the double pipe 10 is wound in a coil shape and stored or carried in, the double pipe 10 is bent, and the shape of the peak portion 16 of the cladding pipe 14 is damaged, or the cladding pipe 14 is damaged. As a result, the above effects may be reduced. Therefore, in this embodiment, this is accommodated by providing a large gap between the outer peripheral surface of the inner tube 12 and the inner peripheral surface of the cladding tube 14. That is, if the gap between the inner peripheral surface and the outer peripheral surface of the cladding tube 14 is increased, the followability to bending and bending of the double tube 10 increases, and even if the cladding tube 14 is wound in a coil shape, the occurrence of bending is suppressed. Is done. Thereby, the shape of the peak part 16 is hard to be damaged, and it becomes difficult to make a ridge. Therefore, the effects as described above are appropriately exhibited.

  Further, when the double pipe 10 is disposed in the pipe line, the end thereof is connected to another pipe member such as a joint (not shown). When the double pipe 10 is connected to another pipe member such as a joint, the portion of the cladding tube 14 corresponding to the joint portion is removed. That is, the cladding tube 14 is cut in the circumferential direction with a cutter knife 100 or a dedicated tool (not shown) for removing the cladding tube.

  FIG. 6 shows an example of the cutter knife 100. The cutter knife 100 is formed in, for example, a flat and substantially rectangular shape, and its tip end portion is formed in an inclined shape obliquely downward from one side to the other side. The cutting edge 100a is provided at the inclined tip. Further, the angle between the blade edge 100a and one side of the cutter knife 100 is an acute angle, and the side surface on the acute angle side is the lower surface 100b of the cutter knife 100.

  Hereinafter, a method for cutting the cladding tube 14 in the circumferential direction using such a cutter knife 100 will be specifically described with reference to FIG.

  First, one end of the double pipe 10 is gripped, and the cutter knife 100 is directed in a direction crossing the axial direction at a predetermined position in the axial direction of the double pipe 10 as shown in FIG. 7A. The cutting edge 100a of the cutter knife 100 is digged into the side (inclined surface) of the ridge 16 and penetrated. At this time, the cutting edge 100 a of the cutter knife 100 is directed obliquely upward as viewed from the inner tube 12, and is not directed toward the inner tube 12. This prevents the inner tube 12 from being damaged. Further, the lower surface 100b of the cutter knife 100 is made to float from the outer peripheral surface of the inner tube 12 so as not to contact the inner tube 12.

  Then, as shown in FIG. 7B, the lower surface 100 b of the cutter knife 100 is moved from the outer peripheral surface of the inner tube 12 using a gap between the outer peripheral surface of the inner tube 12 and the inner peripheral surface of the cladding tube 14. The cutter knife 100 is moved along the circumferential direction of the cladding tube 14 so as to slide on the outer peripheral surface of the inner tube 12 while being floated, and the cladding tube 14 is cut open in the circumferential direction. At this time, a force is applied from the outside of the cladding tube 14 by human power or a machine, so that the gap between the outer peripheral surface of the inner tube 12 and the inner peripheral surface of the cladding tube 14 is widened in the traveling direction of the cutter knife 100. It is good to transform. Thus, the cladding tube 14 is easily cut by using the gap between the outer circumferential surface of the inner tube 12 and the inner circumferential surface of the cladding tube 14.

  Then, by directly rotating the cutter knife 100 in the circumferential direction, the cladding tube 14 is pushed out as shown in FIG. Thereby, the cladding tube 14 corresponding to the joining portion is removed.

  Thus, when cutting the cladding tube 14, the cutting edge 100 a can be bitten into the side (inclined surface) of the peak portion 16 without directing the cutting edge 100 a of the cutter knife 100 toward the inner tube 12. This is because the crest 16 having one apex 16a (vertical angle) is provided in the cladding tube 14. If the outer peripheral surface of the cladding tube 14 is a smooth surface without unevenness, when cutting the cladding tube 14 with the cutter knife 100, it is necessary to point the cutting edge 100a toward the inner circumferential direction, that is, the inner tube 12, The inner tube 12 may be damaged.

  When the cladding tube 14 is removed as described above, a clean joint portion of the inner tube 12 can be obtained. Therefore, the end portion of the double tube 10 is connected to a receiving port such as a joint by using this joint portion. Insert and join to complete the connection.

  By the way, in the double pipe 10 used for such a hot water supply / water supply conduit, for example, when the hot water supply / water tap is opened and closed, the pressure of the water flowing inside the inner pipe 12 changes abruptly. A water hammer phenomenon occurs that collides with the tube wall of the inner tube 12, and the inner tube 12 tends to vibrate greatly. Further, the inner tube 12 may be wavy, and a collision sound may be generated due to the collision between the inner tube 12 and the cladding tube 14. Therefore, in this embodiment, a support portion 18a that contacts the outer peripheral surface of the inner tube 12 over the entire length in the axial direction is provided on the cladding tube 14, and the inner tube 12 is supported by the support portion 18a regardless of the position in the axial direction. It was to so. Thereby, even when the water hammer phenomenon occurs and the inner tube 12 vibrates greatly, the vibration is appropriately propagated and buffered to the cladding tube 14 via the support portion 18a, so that the cladding tube 14 and the inner tube 12 The impact sound caused by the contact of the

  Further, as described above, in this embodiment, the peak portion 16 is formed so as to be continuous in the axial direction, and no irregularities are formed in the axial direction of the outer peripheral surface of the cladding tube 14. Even if the outer peripheral surface of the lens contacts the surrounding structure, it is not unintentionally locked. As a result, the breakage of the cladding tube 14 starting from the locking portion can be prevented. Therefore, the trauma prevention performance is high.

  Furthermore, since the double tube 10 has high damage prevention performance, the thickness of the tube wall of the cladding tube 14 can be reduced, and the double tube 10 can be reduced in weight and cost.

  Further, since the apex angle is formed in the peak portion 16, when the cladding tube 14 is cut with the cutter knife 100 or the like, the side of the peak portion 16 (inclined surface) is directed without directing the blade edge 100 a toward the inner tube 12. ) Can be cut. Therefore, there is no possibility of damaging the inner tube 12.

  Further, the inner tube 12 is supported by a part of the plurality of support portions 18, and a gap is formed between the support portion 18 b that does not contact the inner tube 12 and the outer peripheral surface of the inner tube 12. The By forming a gap inside the cladding tube 14, the followability to bending is improved and the double tube 10 is easily bent. In addition, by utilizing this gap, the cladding tube 14 can be easily cut with the cutter knife 100 or the like, and the inner tube 12 is hardly damaged.

  Furthermore, since both the inner tube 12 and the coated tube 14 are formed of the same polyolefin-based resin, it is possible to save the trouble of separating the double tube 10 into the coated tube 14 and the inner tube 12 when the double tube 10 is discarded or recycled. Moreover, the hardness of the cladding tube 14 can be increased by using a polyolefin-based resin. Thereby, the damage prevention performance of the inner tube 12 is further enhanced.

  In the above-described embodiment, the apex angle of the peak portion 16 is set to 90 °. However, the apex angle of the peak portion 16 is obtuse as shown in FIG. May be. The embodiment shown in FIG. 8 is the same as the above-described embodiment except for the following points, and a duplicate description will be omitted.

  In the embodiment shown in FIG. 8, the peak 16 is formed in a substantially isosceles triangle shape having a rounded apex angle in the circumferential cross section, but the apex angle is an obtuse angle, for example, set to 120 °. . Each inclined surface of the mountain portion 16 is gently inclined, and the distance between the adjacent mountain portions 16 is increased. Moreover, the protrusion height of the peak part 16 is 1 mm, for example. As described above, when the cladding tube 14 is cut with the cutter knife 100 or the like, the peak is set when the distance between the peak 16 and the peak 16 is set to be large and the protruding height of the peak 16 is lowered. It becomes even easier to make a cut in the side of the part 16. Therefore, the covering tube 14 can be cut more easily without damaging the inner tube 12.

  Further, in each of the above-described embodiments, the cladding tube 14 is formed in a waveform in the circumferential cross section, but the present invention is not limited to this. As the circumferential sectional shape of the cladding tube 14, various shapes such as a square shape and a star shape are conceivable. For example, as shown in FIG. 9, the cladding tube 14 may be formed in a hexagonal shape in the circumferential cross section. Hereinafter, a specific description will be given with reference to FIG. 9, but the same reference numerals are used for the same parts as in the above-described embodiment, and the description thereof is omitted or simplified.

  In the embodiment shown in FIG. 9, six crests 16 are arranged on the cladding tube 14 so as to be arranged at equal intervals in the circumferential direction, and extend linearly in the axial direction of the cladding tube 14. The crest 16 is formed in a substantially isosceles triangular shape with the inner peripheral surface side of the cladding tube 14 as a base in the circumferential cross section, and has one apex angle. The angle of the apex angle is 120 °, for example.

  A flat portion 22 that connects the mountain portions 16 in a straight line is formed between the adjacent mountain portions 16. The cladding tube 14 is formed in a hexagonal shape in the circumferential direction by the alternately arranged peak portions 16 and flat portions 22.

  Since the thickness of the tube wall of the cladding tube 14 is uniform or substantially uniform, the inner peripheral surface of the cladding tube 14 at the position where the peak portion 16 is formed has a substantially isosceles triangular shape substantially the same as the convex shape of the peak portion 16. A recess is formed.

  The central portion of the flat portion 22 and the vicinity thereof function as a support portion 18 that supports the inner tube 12, and the inner peripheral surface thereof abuts on the outer peripheral surface of the inner tube 12. In this embodiment, the six support portions 18 are arranged at equal intervals in the circumferential direction and extend in the axial direction of the cladding tube 14.

  Also in this embodiment, the inner tube 12 is supported by the support portion 18a regardless of the axial position of the cladding tube 14 as in the above-described embodiments, so that a water hammer phenomenon occurs and the inner tube 12 is Even when it vibrates greatly, the impact sound due to the contact between the cladding tube 14 and the inner tube 12 is reduced. Moreover, since the peak part 16 is formed in the cladding tube 14, the frictional force with respect to the movement of the double pipe 10 is reduced, and the damage at the time of drawing the double pipe 10 can be suppressed or reduced. In addition, since irregularities are not formed in the axial direction of the outer peripheral surface of the cladding tube 14, the outer peripheral surface of the cladding tube 14 is not unintentionally locked to the surrounding structure. Thereby, the breakage of the cladding tube starting from the locking portion can be prevented. Therefore, the trauma prevention performance is high.

  In the above-described embodiment, the inner tube 12 and the coated tube 14 are made of polyolefin resin such as polybutene, polypropylene, polyethylene, and cross-linked polyethylene, but the material of the inner tube 12 and the coated tube 14 is, for example, Recycled polyethylene may be used. By using inexpensive recycled polyethylene, the manufacturing cost of the double pipe 10 can be reduced.

  The inner tube 12 and the cladding tube 14 do not necessarily need to be formed of a polyolefin-based resin, and may be formed of a flexible synthetic resin such as a polyolefin foam, an elastomer, or an elastomer foam. . Further, the inner tube 12 and the cladding tube 14 are not necessarily formed of the same material.

  Further, in each of the above-described embodiments, the circumferential cross-sectional shape of the cladding tube 14 is formed to be rotationally symmetric, but the cladding tube 14 may be asymmetrical in the circumferential direction.

  Furthermore, the shape and size of the peak portion 16 and the support portion 18 (the valley portion 20) need not be limited to those described above.

  For example, the peak 16 can be formed in an arc shape in the circumferential cross section. In this case, the outermost position of the arc-shaped peak 16 (the position where the outer diameter of the cladding tube 14 is the largest) is the apex 16a of the peak 16. That is, the apex angle may be arcuate. Further, the apex angle of the peak 16 may be changed. For example, the apex angle of the peak 16 may be smaller than 90 ° or larger than 120 °. Furthermore, the peak 16 does not necessarily have the apex 16a (vertical angle). For example, the mountain portion 16 may have a rectangular shape. However, when the crest 16 is formed in a square shape, if the distance between the crests 16 adjacent to each other is small, it is difficult to cut the side of the crest 16 with a cutter knife 100 or the like. Become. In order to solve such a problem, it is preferable to form the peak portion 16 in a trapezoidal shape and to gently set the inclination angle of each inclined surface of the peak portion 16.

  Moreover, you may form the support part 18 in the shape of a triangle which protrudes toward inner peripheral direction, for example in the shape of a rectangle. Even in this case, the inner tube 12 can be supported by the support portion 18a.

  Furthermore, the angle of the apex angle of the valley 20 can be changed as appropriate.

  Furthermore, in each of the above-described embodiments, the peak portions 16 and the support portions 26 (the valley portions 20) are arranged at equal intervals in the circumferential direction, but the arrangement mode of the peak portions 16 and the support portions 18 is not limited to this, They may be arranged at unequal intervals.

  Further, the number of the peak portions 16 and the support portions 18 (the valley portions 20) is not particularly limited, but in order to form the cladding tube 14 having the peak portions 16 and the support portions 18 alternately arranged in the circumferential direction, at least each It is necessary to provide three or more.

  Furthermore, the number of the support portions 18a that abut on the inner tube 12 in normal times is not particularly limited. For example, the inner tube 12 may be supported by one support portion 18a. Alternatively, it may be set to be supported by more than half of the plurality of support portions 18. In short, it is only necessary that the support portion 18a and the inner tube 12 are in contact with each other regardless of the position in the axial direction, and the contact range in the circumferential direction is not limited. In addition, when the number of the support parts 18a which contact | abut with the inner tube | pipe 12 is set more than half, the clearance gap between the support part 18b and the outer peripheral surface of the inner pipe | tube 12 becomes small. However, even in that case, if the inner space is increased by setting the peripheral length of the peak portion 16 to be large, a sufficient gap is secured between the outer peripheral surface of the inner tube 12 and the inner peripheral surface of the cladding tube 14. The following effect with respect to bending and bending of the double pipe 10 can be exhibited.

  Moreover, as the cutter knife 100 used when cutting the cladding tube 14, it is sufficient if the cutting edge 100a does not face in the direction of the inner tube 12 as long as it can cut into the side of the peak portion 16, It is not necessary to be limited to those shown in the above-described embodiments.

  Note that the specific numerical values such as the dimensions described above are merely examples, and can be appropriately changed as necessary.

DESCRIPTION OF SYMBOLS 10 ... Double pipe 12 ... Inner pipe 14 ... Cladding pipe 16 ... Peak part 16a ... Peak of peak part 18 (18a, 18b) ... Support part 20 ... Valley part 22 ... Flat part

Claims (5)

A double pipe used for hot water supply or water supply comprising an inner pipe made of synthetic resin and a cladding pipe covering the outer peripheral surface of the inner pipe,
The cladding tube has a plurality of crests that are uniform or substantially uniform in the thickness of the tube wall and that are arranged on the outer peripheral surface at predetermined intervals in the circumferential direction and extend in the axial direction.
A double pipe in which the inner pipe is supported by being in contact with an inner peripheral surface of the cladding pipe between the adjacent peak portions.   The double pipe according to claim 1, wherein in the circumferential cross section, the peak has an apex.   3. The double tube according to claim 1, wherein an outer peripheral surface of the cladding tube is formed in a corrugated shape including the peak portion and a valley portion therebetween in the circumferential direction.   The duplex according to any one of claims 1 to 3, wherein only a part of an inner peripheral surface of the cladding tube between a plurality of the adjacent peak portions is in contact with the inner tube to support the inner tube. tube.   The double pipe according to any one of claims 1 to 4, wherein each of the inner pipe and the cladding pipe is formed of a polyolefin resin.

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