JP7366687B2 - Composite pipe and method for manufacturing composite pipe - Google Patents

Description

The present invention relates to a composite pipe and a method for manufacturing a composite pipe.

Patent Document 1 describes a composite pipe including a main pipe, a corrugated layer disposed on the outer peripheral side of the main pipe, and a buffer layer provided between the main pipe and the corrugated layer.

JP 2017-9072 Publication

In conventional composite pipes, the buffer layer is a foamed resin layer formed of foamed resin. In order to ensure heat retention of the fluid flowing through the main pipe of this composite pipe, the thickness of the foamed resin layer may be increased. Furthermore, in order to connect the composite pipe to a pipe joint or the like, the corrugated layer and foamed resin layer of the composite pipe may be shrunk in the axial direction to expose the end portion of the main pipe.

However, if the thickness of the foamed resin layer is increased, the corrugate layer (outer tube) and the foamed resin layer will not shrink sufficiently, making it difficult to expose the end portion of the main tube.

An object of the present invention is to easily expose the end portion of the main pipe while ensuring the heat retention of the fluid flowing through the main pipe.

The composite pipe of the first aspect includes a main pipe in which a fluid flows, an outer pipe that covers the main pipe from the outside in the radial direction of the main pipe and is expandable and contractible in the axial direction of the main pipe, and On the inside in the radial direction, the main pipe is covered from the outside in the radial direction, and the cut shape cut along the center line of the main pipe is an uneven shape, and between the outside pipe and the main pipe, there is a gap in the axial direction. and an inner tube formed of a resin material that forms a space extending continuously in at least a portion of the main tube in the circumferential direction.

According to the above configuration, the outer tube that covers the main pipe from the outside in the radial direction of the main pipe is expandable and retractable in the axial direction of the main pipe. Furthermore, the inner tube, which is radially inside the outer tube and covers the main tube from the outside in the radial direction of the main tube, is formed of a resin material, and the cut shape cut along the center line is an uneven shape. There is.

Further, the inner tube and the outer tube form a space that extends continuously in the axial direction in at least a portion of the main tube in the circumferential direction. In other words, a heat insulating space is formed between the inner pipe and the outer pipe to ensure heat retention of the fluid flowing through the main pipe. Further, as described above, the outer tube and the inner tube have an uneven shape when cut along a plane along the center line. That is, the outer tube and the inner tube are designed to contract in the axial direction.

As described above, in the composite pipe, the end portion of the main pipe can be easily exposed by contracting the outer pipe and the inner pipe in the axial direction while ensuring the heat retention of the fluid flowing through the main pipe.

The composite pipe of the second aspect is the composite tube of the first aspect, when viewed from the axial direction, the inner tube has a protrusion that protrudes toward the outer tube, and the protrusion extends toward the main tube. It is characterized in that a bulge portion is formed that bulges out.

According to the above configuration, when viewed from the axial direction, the inner tube is formed with a protrusion that protrudes toward the outer tube and a bulge that bulges from the protrusion toward the main tube. With this configuration, the amount of movement of the main tube relative to the outer tube can be reduced.

The composite tube of the third aspect is characterized in that, in the composite tube of the second aspect, the bulged portion is curved when viewed from the axial direction.

According to the above configuration, since the bulging portion is curved when viewed from the axial direction, the difference between the minimum thickness and the maximum thickness of the bulging portion is reduced when forming the inner tube by vacuum forming, for example. It is possible to suppress the increase in size.

In the composite pipe of the fourth aspect, in the composite pipe of the second or third aspect, a plurality of the bulges are formed, and at least a part of the bulges restricts movement of the main pipe in the radial direction. It is characterized by

According to the above configuration, the bulge restricts movement of the main pipe, thereby suppressing movement of the main pipe with respect to a designed target position. In other words, the bulge has a centering function of centering the main pipe.

A fifth aspect of the composite tube is the composite tube according to any one of the first to fourth aspects, in which, when viewed from the axial direction, the inner tube is lined with a line passing through the center of the inner tube. It is characterized by its symmetrical shape.

According to the above configuration, the inner tube has a shape that is line symmetrical with respect to a line passing through the center of the inner tube. For this reason, when vacuum forming an inner tube by butting a pair of molds together, it is possible to suppress an increase in the number of types of molds.

A composite tube according to a sixth aspect is the composite tube according to any one of the first to fifth aspects, wherein the outer tube has an uneven cut shape when cut along the center line, and the outer tube has an uneven shape when cut along the center line. The inner tube has a ridge portion that is convex toward the outside in the radial direction, and a trough portion that is concave on the outside in the radial direction and is composed of a pair of side walls and a bottom wall. The inner tube has a convex peak portion and a valley portion that is formed of a pair of side walls and a bottom wall and is concave on the outside in the radial direction, and the length of the peak portion of the inner tube in the axial direction is The outer tube is characterized by being longer than the distance between adjacent bottom walls in the axial direction.

According to the above configuration, the axial length of the peak portion of the inner tube is longer than the distance between the axially adjacent bottom walls of the outer tube. This prevents the peaks of the inner tube from fitting between axially adjacent valleys in the outer tube. That is, a heat insulating space that suppresses heat transfer can be formed between the inner tube and the outer tube.

The composite tube according to a seventh aspect is the composite tube according to any one of the first to sixth aspects, wherein the outer tube has an uneven cut shape when cut along the center line, and the outer tube has an uneven shape when cut along the center line. The inner tube has a ridge portion that is convex toward the outside in the radial direction, and a trough portion that is concave on the outside in the radial direction and is composed of a pair of side walls and a bottom wall. The outer tube has a convex peak portion, and a valley portion that is concave on the outside in the radial direction, and is composed of a pair of side walls and a bottom wall, and the length of the bottom wall of the outer tube in the axial direction is The inner tube is characterized by being longer than the distance between adjacent peaks in the axial direction.

According to the above configuration, the length of the bottom wall of the outer tube in the axial direction is longer than the distance between adjacent peaks in the axial direction in the inner tube. Therefore, the valley portions of the outer tube are prevented from fitting between the axially adjacent peak portions of the inner tube. That is, a heat insulating space that suppresses heat transfer can be formed between the inner tube and the outer tube.

According to the method for manufacturing a composite pipe according to an eighth aspect, the method for manufacturing a composite pipe according to any one of the first to seventh aspects , wherein the main pipe is fed in the axial direction, and the main pipe is fed out in the axial direction. A first extrusion step in which a cylindrical molten resin is extruded to the outside of the main pipe in the radial direction, and the extruded cylindrical molten resin is adsorbed to a molding surface of a mold while being conveyed to form the inner tube. a second extrusion step of extruding a cylindrical molten resin to the outer side in the radial direction of the inner pipe being conveyed; and molding of a mold while conveying the extruded cylindrical molten resin. a second molding step of molding the outer tube by adsorption to a surface, and the cylindrical molten resin extruded in the first extrusion step has a cylindrical shape. It is characterized in that the shape is close to the molding surface of the mold before it is adsorbed to the molding surface of the mold.

According to the above configuration, the cylindrical molten resin extruded in the first extrusion step is in a state before being adsorbed to the molding surface of the mold for molding the inner tube, compared to the case where the molten resin is cylindrical. , the shape is close to the molding surface. Therefore, when the inner tube is molded by adsorption to the molding surface of the mold, it is possible to suppress the difference between the minimum thickness and the maximum thickness of the inner tube from increasing.

According to the composite pipe according to the present invention, the end portion of the main pipe can be easily exposed while ensuring the heat retention of the fluid flowing through the main pipe.

(A) and (B) are a front view and a perspective view showing a composite pipe according to a first embodiment. FIG. 1 is a cross-sectional view showing a composite pipe according to a first embodiment. FIG. 1 is a cross-sectional view showing a composite pipe according to a first embodiment. FIG. 2 is an enlarged sectional view showing the composite pipe according to the first embodiment. FIG. 2 is a process diagram showing a first extrusion step and a first molding step in the method for manufacturing a composite pipe according to the first embodiment. It is a manufacturing method of the composite pipe concerning a 1st embodiment, and is a process diagram showing a second extrusion process and a second molding process. 1 is a schematic process diagram showing the entire method of manufacturing a composite pipe according to a first embodiment; FIG. FIG. 2 is a cross-sectional view showing a mold used in a first molding step and a second molding step in the method for manufacturing a composite pipe according to the first embodiment. 1 is a perspective view showing a mold used in a first molding step in the method for manufacturing a composite pipe according to a first embodiment; FIG. It is a manufacturing method of the composite pipe concerning a 1st embodiment, and is a perspective view showing a metal mold used in a second forming process. FIG. 2 is a front view showing a mold used in a first molding step in the method for manufacturing a composite pipe according to the first embodiment. FIG. 3 is an explanatory diagram used to explain a method of comparing the bending rigidity of an outer tube and an inner tube included in the composite tube according to the first embodiment. (A) and (B) are front views showing a composite pipe according to a second embodiment and a composite pipe according to a third embodiment. (A) and (B) are front views showing a composite pipe according to a fourth embodiment and a composite pipe according to a fifth embodiment. It is a front view showing the compound pipe concerning a 6th embodiment.

<First embodiment>
An example of a composite pipe and a method for manufacturing the composite pipe according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 12. Note that the arrow S shown in the figure indicates the axial direction of the composite tube, and the arrow R indicates the radial direction of the composite tube.

Note that components shown using the same reference numerals in the drawings mean the same components. Further, overlapping explanations and symbols in the embodiments described below may be omitted. Furthermore, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present invention.

Furthermore, in this specification, the term "process" refers not only to an independent process, but also to a process that cannot be clearly distinguished from other processes, as long as the purpose is achieved. Included in this term. In the present specification, the amount of each component in the composition refers to the total amount of the multiple substances present in the composition, unless otherwise specified, when multiple substances corresponding to each component are present in the composition. means. In this specification, the term "main component" refers to the component having the highest content on a mass basis in the mixture, unless otherwise specified.

(Configuration of composite pipe 10)
As shown in FIGS. 1A and 1B, the composite pipe 10 includes a main pipe 12, an outer pipe 20 disposed to cover the main pipe 12 from the outside in the radial direction, and a An inner pipe 30 is arranged inside the main pipe 12 so as to cover the main pipe 12 from the outside in the radial direction.

Note that the center line CL01 of the composite pipe 10 is also the center line of the main pipe 12, the outer pipe 20, and the inner pipe 30. Therefore, the axial direction of the composite pipe 10 is also the axial direction of the main pipe 12, the outer pipe 20, and the inner pipe 30. Furthermore, the radial direction of the composite pipe 10 is also the radial direction of the main pipe 12, the outer pipe 20, and the inner pipe 30.

[Main pipe 12]
The main pipe 12 is a resin pipe through which fluid flows, and extends in the axial direction. Examples of the resin used to form the main pipe 12 include polyolefins such as polybutene, polyethylene, crosslinked polyethylene, and polypropylene, and vinyl chloride, and only one type of resin can be used or two or more types can be used in combination. You may. Among them, polybutene is preferably used, and preferably contains polybutene as a main component, and more preferably contains 85% by mass or more in the resin material constituting the main pipe 12, for example. Further, the resin material constituting the main pipe 12 may contain other additives.

The diameter (outer diameter) of the main pipe 12 is not particularly limited, but may be, for example, in the range of 10 [mm] to 100 [mm], and 12 [mm] to 35 [mm]. The following ranges are preferred. Further, the thickness of the main pipe 12 is not particularly limited, but may be, for example, in the range of 1.0 [mm] or more and 5.0 [mm] or less, and 1.4 [mm] or more and 3. .2 [mm] or less is preferable.

[Outer tube 20]
The outer tube 20 is made of a resin material and extends in the axial direction, as shown in FIGS. 1(A) and 1(B).
The outer tube 20 has a circular shape when viewed from the axial direction. Furthermore, the cut shape of the outer tube 20 cut along the plane along the center line CL01 has an uneven shape, as shown in FIG. In other words, the cut shape obtained by cutting the outer tube 20 along the center line CL01 is a wave shape. In this way, the outer tube 20 is a corrugated tube.

Specifically, the outer tube 20 is composed of a peak portion 22 that is convex toward the outside in the radial direction (the side away from the center line CL01), a pair of side walls 26, and a bottom wall 28, and a It has a trough portion 24 whose outer side is concave. The peak portions 22 and the valley portions 24 are arranged alternately in the axial direction.

The diameter of the outer tube 20 (outer diameter of the outermost part) can be in the range of, for example, 13 [mm] or more and 130 [mm] or less. In order to shrink the outer tube 20 in the axial direction, the thickness of the outer tube 20 is preferably 0.25 [mm] or more at the thinnest part and 0.4 [mm] or less at the thickest part.

In addition, in this embodiment, as shown in FIG. 4, when the axial length of the bottom wall 28 (L01 in the figure) is "1", the axial length of the peak part 22 (L01 in the figure) is set to "1". L02) is set to "1.2", and the height of the side wall 26 (L03 in the figure) is set to "0.5". Further, when the length L01 is "1", the distance between the bottom walls 28 adjacent in the axial direction (L04 in the figure) is "1.3".

Further, examples of the resin used to form the outer tube 20 include polyolefins such as polybutene, polyethylene, polypropylene, and crosslinked polyethylene, and vinyl chloride, and even if only one type of resin is used, two or more types may be used. may be used together. Among them, low-density polyethylene is preferably used, and preferably contains low-density polyethylene as a main component, for example, it is more preferably contained in the resin material constituting the outer tube 20 in an amount of 80% by mass or more, and preferably contains 90% by mass or more. is even more preferable.

In this configuration, when a compressive force compressing in the axial direction is applied to the outer tube 20, the outer tube 20 contracts in the axial direction.

[Inner tube 30]
The inner tube 30 is made of a resin material and extends in the axial direction, as shown in FIGS. 1(A) and 1(B).
When viewed from the axial direction, the inner tube 30 has an irregular shape different from a circular shape. Specifically, when viewed from the axial direction, the inner tube 30 is formed with a protrusion 42 that protrudes toward the outer tube 20 and a bulge 44 that bulges from the protrusion 42 toward the main tube 12. has been done. “Protruding portion 42” refers to the inner tube 30 disposed within a range of 7 or more and 10 or less from the center line CL01 when the outermost diameter of the inner tube 30 from the center line CL01 is “10” when viewed from the axial direction. This is the part.
Four protrusions 42 are formed at equal intervals in the circumferential direction of the inner tube 30, and the bulge 44 is formed between a pair of adjacent protrusions 42. When viewed from the axial direction, the inner tube 30 has a shape that is symmetrical with respect to the line CL02 or CL03 shown in FIG. 1 passing through the center of the inner tube 30. In this embodiment, "bulge" refers to a state in which the bulge gradually narrows in width from the base end toward the distal end.

Furthermore, when viewed from the axial direction, the protruding portion 42 has a curved shape in which the radially outer side is convex, and contacts the outer tube 20 from the radially inner side (the side approaching the center line CL01). (See Figure 2).

Further, when viewed from the axial direction, the bulging portion 44 has a curved shape with a convex inner side in the radial direction, and contacts the main pipe 12 from the outer side in the radial direction (see FIG. 3). The curvature of the bulging portion 44 is made smaller than the curvature of the protruding portion 42.

Thereby, spaces 46 formed by separating the outer tube 20 and the inner tube 30 in the radial direction are lined up in the circumferential direction between the outer tube 20 and the inner tube 30. Further, between the inner tube 30 and the main tube 12, spaces 48 formed by the inner tube 30 and the main tube 12 being spaced apart in the radial direction are lined up in the circumferential direction. In this way, a space 46 that extends continuously in the axial direction is formed between the outer tube 20 and the inner tube 30, and a space 46 that extends continuously in the axial direction is formed between the inner tube 30 and the main tube 12. An extending space 48 is formed. The spaces 46 and 48 function as heat insulating spaces (so-called "insulating layers") that suppress the transfer of heat, and are formed alternately in the circumferential direction.

Furthermore, the cut shape of the inner tube 30 cut along the center line CL01 has an uneven shape, as shown in FIG. 3 . In other words, the cut shape obtained by cutting the inner tube 30 along the center line CL01 is a wave shape. In this way, the inner tube 30 is a corrugated tube.

Specifically, the inner tube 30 includes a peak portion 32 that is convex toward the outside in the radial direction, and a trough portion 34 that is concave on the outside in the radial direction and is composed of a pair of side walls 36 and a bottom wall 38; have. The peak portions 32 and the valley portions 34 are arranged alternately in the axial direction.

In order to shrink the inner tube 30 in the axial direction, the thickness of the inner tube 30 is preferably 0.1 [mm] or more at the thinnest part and 0.4 [mm] or less at the thickest part.

In addition, in this embodiment, as shown in FIG. 4, when the axial length L01 of the bottom wall 28 of the outer tube 20 is "1", the axial length of the peak part 32 of the inner tube 30 is The length (L12 in the figure) is "1.4". That is, the length L12 is longer than the distance L04 between the bottom walls 28 adjacent in the axial direction in the outer tube 20. In other words, the peak portion 32 of the inner tube 30 is prevented from fitting into the recess 52 of the outer tube 20 sandwiched between the pair of side walls 26 of the outer tube 20.

Further, when the axial length L01 of the bottom wall 28 of the outer tube 20 is "1", the axial length (L11 in the figure) of the bottom wall 38 of the inner tube 30 is "0.8". The height of the side wall 36 (L13 in the figure) is "0.7". Further, when the length L01 is set to "1", the distance between the peaks 32 adjacent in the axial direction (L14 in the figure) is set to "0.9". That is, the axial length L01 of the bottom wall 28 of the outer tube 20 is longer than the distance L14 between the axially adjacent peaks 32 in the inner tube 30. In other words, the trough 24 of the outer tube 20 does not fit into the recess 54 of the inner tube 30 sandwiched between the pair of side walls 36 of the inner tube 30.

Further, examples of the resin used to form the inner tube 30 include polyolefins such as polybutene, polyethylene, polypropylene, and crosslinked polyethylene, and vinyl chloride, and even if only one type of resin is used, two or more types may be used. may be used together. Among them, low-density polyethylene is preferably used, and preferably contains low-density polyethylene as a main component, for example, it is more preferably contained in the resin material constituting the inner tube 30 in an amount of 80% by mass or more, and preferably contains 90% by mass or more. is even more preferable.

Further, the bending rigidity of the inner tube 30 is made higher than that of the outer tube 20. A method of comparing bending rigidity will be explained below. Both ends of a rectangular test piece developed flat while maintaining its uneven shape are supported as shown in FIG. Then, the center portion of the test piece is pressed with a unit load F, and the displacement in the pressing direction at the load point is measured. Since the bending rigidity of the inner tube 30 is higher than that of the outer tube 20, the displacement of the test piece of the inner tube 30 in the pressing direction is in proportion to the displacement of the test piece of the outer tube 20 in the pressing direction. and become smaller.

Note that a calculation model of the test piece of the outer tube 20 and a calculation model of the test piece of the inner tube 30 may be created, and the bending rigidity may be compared by simulation analysis using the finite element method. Further, the size of the test piece may be the same shape in plan view, for example, 30 [mm] x 30 [mm].
In this configuration, when a compression force compressing in the axial direction is applied to the inner tube 30, the inner tube 30 contracts in the axial direction.

(Method for manufacturing composite pipe 10)
Next, a method for manufacturing the composite pipe 10 will be explained.
As shown in FIG. 7, the method for manufacturing the composite tube 10 includes a first extrusion step S1 in which a cylindrical resin is extruded onto the outside of the main tube 12 in the radial direction, which is conveyed in the axial direction, and an extruded resin tube. The method includes a first molding step S2 of forming the inner tube 30 into a corrugate shape by vacuum forming the cylindrical molten resin. Furthermore, the manufacturing method of the composite tube 10 includes a second extrusion step S3 in which a cylindrical resin is extruded to the outside of the inner tube 30 in the radial direction, and the extruded cylindrical resin is formed into a corrugate shape by vacuum forming. A second molding step S4 for molding the outer tube 20 is included.

As described above, in the method for manufacturing the composite pipe 10, the first extrusion step S1, the first forming step S2, the second extrusion step S3, and the second forming step S4 are performed on the main pipe 12 that is transported in the axial direction. It is done in this order.

[First extrusion step S1]
In the first extrusion step S1, as shown in FIG. 5, a die 102 and an extruder 104 for extruding resin are used.
In the first extrusion step S1, a cylindrical molten resin is extruded from the extruder 104 through the mouthpiece 102 to the outside in the radial direction of the main pipe 12 that is conveyed in the axial direction. Note that the shape of the extruded cylindrical molten resin will be described later.

[First molding process S2]
In the first forming step S2, as shown in FIG. A guide device 120 is used to guide the molded body 60 in which the inner tube 30 is placed.

The molding machine 110 includes a mold group 114 in which a plurality of molds 112 are endlessly connected and arranged in an elliptical shape extending in the axial direction, and a pair of mold groups 114 wound around the mold group 114 spaced apart in the axial direction. A pair of mold units 118 having wheels 116 are provided.

The one mold unit 118 and the other mold unit 118 are arranged to face each other with the main pipe 12 being transported in between.

In one mold unit 118 (upper part in the figure), driving force from a drive means (not shown) is transmitted to wheels 116, and the mold group 114 rotates in the direction D01 in the figure. Specifically, the molds are moved so that the molds 112 of one mold unit 118 facing the other mold unit 118 (lower in the figure) move from the upstream side to the downstream side in the conveyance direction of the main pipe 12. The mold group 114 rotates in the direction D01 in the figure.

Further, in the other mold unit 118, driving force is transmitted from a drive means (not shown) to the wheels 116, and the mold group 114 rotates in the direction D02 in the figure. Specifically, the mold group 114 is arranged in a direction such that the molds 112 of one mold unit 118 and the other mold unit 118 facing each other move from the upstream side to the downstream side in the conveyance direction of the main pipe 12. Rotate in the direction of D02. More specifically, a pair of molds 112 in which a mold 112 of one mold unit 118 and a mold 112 of the other mold unit 118 are butted are connected to each other from the upstream side in the conveyance direction of the main pipe 12. Move downstream.

Then, with the molds 112 of one mold unit 118 and the molds 112 of the other mold unit 118 butted against each other, one mold 112 is formed so as to correspond to the outer peripheral shape of the inner tube 30. As shown in FIG. 9, a molding surface 112a is formed which has an uneven shape in the axial direction. Furthermore, as shown in FIG. 8, the mold 112 has suction holes 112b formed from the molding surface 112a to the opposite surface. This suction hole 112b is connected to a vacuum evacuation device (not shown), and the cylindrical molten resin extruded in the first extrusion step S1 is vacuum-adsorbed onto the molding surface 112a of the mold 112 through this suction hole 112b. It comes into close contact with the molding surface 112a.

In the first molding step S2, the mold group 114 of one mold unit 118 revolves in the D01 direction in the figure, and the mold group 114 of the other mold unit 118 revolves in the D02 direction in the figure. . Further, a pair of molds 112 in which the mold 112 of one mold unit 118 and the mold 112 of the other mold unit 118 are butted are moved from the upstream side to the downstream side in the conveyance direction of the main pipe 12. . The cylindrical molten resin formed in the first extrusion step S1 is extruded into the pair of butted molds 112.

This cylindrical molten resin is vacuum-adsorbed onto the molding surface 112a of the mold 112 through a suction hole 112b connected to a vacuum evacuation device, and is brought into close contact with the molding surface 112a. Thereby, the cylindrical molten resin is formed in the inner tube 30 while moving from the upstream side to the downstream side in the transport direction of the main tube 12. In this way, a molded body 60 is formed in which the inner tube 30 is disposed on the radially outer side of the main tube 12 being transported.

Here, the cylindrical molten resin extruded in the first extrusion step S1 will be explained. As shown in FIG. 11, the cylindrical molten resin 108 extruded into the pair of abutted molds 112 has a rectangular cylindrical shape, and is separated from the cylindrical molten resin 208 (see the two-dot chain line in the figure). In comparison, the shape is such that it approaches the molding surface 112a of the mold 112 before being attracted to the molding surface 112a. In this embodiment, the distance between the rectangular cylindrical molten resin 108 and the molding surface 112a at the outermost portion in the radial direction is a distance L21 shown in FIG. 11. On the other hand, the distance between the cylindrical molten resin 208 and the molding surface 112a at the outermost portion in the radial direction is a distance L22 shown in FIG. The distance L21 is shorter than the distance L22. In other words, as shown in FIG. 11, compared to the cylindrical molten resin 208, the cylindrical molten resin 108 is in a state before being adsorbed to the molding surface 112a of the mold 112. The shape is said to be close to .

Further, the guide device 120 shown in FIG. 5 guides the molded body 60 from the upstream side to the downstream side in the conveyance direction of the molded body 60.

[Second extrusion step S3]
In the second extrusion step S3, as shown in FIG. 6, a die 202 and an extruder 204 that extrudes the resin are used.
Then, in the second extrusion step S3, cylindrical molten resin is extruded from the extruder 204 through the mouthpiece 202 to the outside in the radial direction of the molded body 60 being conveyed.

[Second molding process S4]
In the second molding step S4, as shown in FIG. 6, a molding machine 210 that molds a cylindrical molten resin into an uneven shape to form the outer tube 20 and a guide device 220 that guides the composite tube 10 are used. It will be done.
The molding machine 210 includes a mold group 214 in which a plurality of molds 212 are endlessly connected and arranged in an elliptical shape extending in the axial direction, and a pair of mold groups 214 wound around the mold group 214 spaced apart in the axial direction. A pair of mold units 218 having wheels 216 are provided.

The one mold unit 218 and the other mold unit 218 are arranged to face each other with the molded object 60 being transported in between.

In one mold unit 218 (upper part in the figure), driving force is transmitted from a drive means (not shown) to wheels 216, and the mold group 214 rotates in the direction D11 in the figure. Specifically, the molds are moved so that the molds 212 of one mold unit 218 facing the other mold unit 218 (lower in the figure) move from the upstream side to the downstream side in the conveyance direction of the molded body 60. The mold group 214 rotates in the direction D11 in the figure.

Further, in the other mold unit 218, driving force is transmitted from a drive means (not shown) to wheels 216, and the mold group 214 rotates in the direction D12 in the figure. Specifically, the mold group 214 is arranged in a direction such that the molds 212 of one mold unit 218 and the other mold unit 218 facing each other move from the upstream side to the downstream side in the conveyance direction of the molded body 60. Rotate in the middle D12 direction. More specifically, a pair of molds 212, in which a mold 212 of one mold unit 218 and a mold 212 of the other mold unit 218 are butted, Move downstream.

Then, with the molds 212 of one mold unit 218 and the molds 212 of the other mold unit 218 butted against each other, one mold 212 is formed so as to correspond to the outer peripheral shape of the outer tube 20. As shown in FIG. 10, a molding surface 212a is formed which has an uneven shape in the axial direction.

Furthermore, as shown in FIG. 8, the mold 212 has suction holes 212b formed from the molding surface 212a to the opposite surface. The suction hole 212b is connected to a vacuum evacuation device (not shown), and the cylindrical molten resin extruded in the second extrusion step S3 is vacuum-adsorbed onto the molding surface 212a of the mold 212 through the suction hole 212b. It comes into close contact with the molding surface 212a.

In the second molding step S4, the mold group 214 of one mold unit 218 revolves in the direction D11 in the figure, and the mold group 214 of the other mold unit 218 revolves in the direction D12 in the figure. . Further, a pair of molds 212 in which the mold 212 of one mold unit 218 and the mold 212 of the other mold unit 218 are butted are moved from the upstream side to the downstream side in the conveyance direction of the molded body 60. . The cylindrical molten resin formed in the second extrusion step S3 is extruded into the pair of butted molds 212.

This cylindrical molten resin is vacuum-adsorbed onto the molding surface 212a of the mold 212 by a suction hole 212b connected to a vacuum evacuation device, and is brought into close contact with the molding surface 212a. Thereby, the cylindrical molten resin is formed in the outer tube 20 while moving from the upstream side to the downstream side in the conveyance direction of the molded body 60. Then, a composite tube 10 is manufactured in which the outer tube 20 is disposed on the radially outer side of the molded body 60 being transported.

Further, the guide device 220 guides the composite pipe 10 from the upstream side to the downstream side in the conveying direction of the composite pipe 10. Then, the composite pipe 10 is cut into a predetermined length by a cutting device (not shown).

(summary)
As explained above, in the composite tube 10, the outer tube 20 is formed of a resin material, and the cut shape of the outer tube 20 cut along the center line CL01 is an uneven shape. Moreover, the inner tube 30 is formed of a resin material, and the cut shape of the inner tube 30 cut along the center line CL01 is an uneven shape. Furthermore, a space 46 is formed between the inner tube 30 and the outer tube 20 to suppress the transfer of heat. In other words, the inner tube 30 is radially separated from the outer tube 20 at least in part in the circumferential direction of the inner tube 30 . For this reason, compared to the case where a foamed resin layer is provided between the outer pipe and the main pipe, the outer pipe 20 and the inner pipe 30 are contracted while ensuring the heat retention of the fluid flowing through the main pipe 12. The end portion of the main pipe 12 can be easily exposed.

In addition, in the composite pipe 10, when viewed from the axial direction, the inner pipe 30 has a protrusion 42 that protrudes toward the outer pipe 20, and a bulge 44 that bulges from the protrusion 42 toward the main pipe 12. is formed. By forming the bulge 44 on the inner tube 30, the amount of movement of the main tube 12 in the radial direction with respect to the outer tube 20 can be reduced compared to the case where the bulge is not formed.

Furthermore, in the composite tube 10, the bulging portion 44 of the inner tube 30 is curved when viewed from the axial direction. Therefore, when the inner tube 30 is formed by vacuum forming in the first forming process, the difference between the minimum thickness and the maximum thickness of the bulge 44 becomes larger than when the bulge is bent. can be suppressed.

Further, the composite pipe 10 has a plurality of bulges 44, and each bulge 44 contacts the main pipe 12 to restrict movement of the main pipe 12 in the radial direction. Therefore, compared to the case where there is only one bulge, movement of the main pipe 12 from the designed position can be suppressed.

Furthermore, in the composite tube 10, the inner tube 30 has a shape that is symmetrical with respect to a line passing through the center of the inner tube 30 when viewed from the axial direction. For this reason, compared to the case where the inner tube is asymmetrical, when vacuum forming the inner tube 30 by butting the pair of molds 112 against each other, the pair of molds have the same shape, so the type of mold can be changed. It is possible to suppress the increase.

Further, in the composite tube 10, the peak portion 32 of the inner tube 30 does not fit into the recess 52 of the outer tube 20 sandwiched between the pair of side walls 26 of the outer tube 20. Therefore, a heat insulating space that suppresses heat transfer can be formed between the outer tube 20 and the inner tube 30.

Further, in the composite tube 10, the valley portion 24 of the outer tube 20 does not fit into the recess 54 of the inner tube 30 sandwiched between the pair of side walls 36 of the inner tube 30. Therefore, a heat insulating space that suppresses heat transfer can be formed between the outer tube 20 and the inner tube 30.

Furthermore, in the composite tube 10, the bending rigidity of the inner tube 30 is made higher than that of the outer tube 20. Therefore, it is possible to suppress the main pipe 12 from moving in the radial direction due to the deformation of the inner pipe 30.

In addition, in the method for manufacturing the composite pipe 10, the cylindrical molten resin 108 extruded in the first extrusion step S1 is in a state before being adsorbed to the molding surface 112a, compared to the case of the cylindrical molten resin 208. , the shape is close to the molding surface 112a of the mold 112 for molding the inner tube 30. For this reason, when the inner tube 30 is molded by adsorption to the molding surface 112a of the mold 112, it is possible to suppress the difference between the minimum thickness and the maximum thickness of the inner tube 30 from increasing.

<Second embodiment>
An example of a composite pipe and a method for manufacturing the composite pipe according to the second embodiment of the present invention will be described using FIG. 13(A). Note that, regarding the second embodiment, the differences from the first embodiment will be mainly described.

As shown in FIG. 13(A), a composite pipe 310 of the second embodiment includes a main pipe 12, an outer pipe 20, and an inner pipe 330. When viewed from the axial direction, the inner tube 330 has a star shape, and the cut shape cut along the center line CL01 has an uneven shape. The action of the composite pipe 310 of the second embodiment is similar to the action of the composite pipe 10 of the first embodiment, except for the action caused by the curving of the bulging portion.

<Third embodiment>
An example of a composite pipe and a method for manufacturing the composite pipe according to the third embodiment of the present invention will be described using FIG. 13(B). Note that, regarding the third embodiment, parts that are different from the first embodiment will be mainly described.

As shown in FIG. 13(B), a composite pipe 410 of the third embodiment includes a main pipe 12, an outer pipe 20, and an inner pipe 430. When viewed from the axial direction, the inner tube 430 has a cross shape, and the cut shape cut along the center line CL01 has an uneven shape. The action of the composite pipe 410 of the third embodiment is similar to the action of the composite pipe 10 of the first embodiment, except for the action caused by the curving of the bulging portion.

<Fourth embodiment>
An example of a composite pipe and a method for manufacturing the composite pipe according to the fourth embodiment of the present invention will be described using FIG. 14(A). Note that, regarding the fourth embodiment, the parts that are different from the first embodiment will be mainly described.

As shown in FIG. 14(A), a composite pipe 510 of the fourth embodiment includes a main pipe 12, an outer pipe 20, and an inner pipe 530. When viewed from the axial direction, five protrusions 542 and five bulges 544 are formed in the inner tube 530, and the inner tube 530 is cut along the center line CL01. The cut shape is an uneven shape. Further, in the first molding step S2, the inner tube 530 is molded by butting the three molds together. The action of the composite pipe 510 of the fourth embodiment is similar to the action of the composite pipe 10 of the first embodiment.

<Fifth embodiment>
An example of a composite pipe and a method for manufacturing the composite pipe according to the fifth embodiment of the present invention will be described using FIG. 14(B). Note that, regarding the fifth embodiment, parts that are different from the first embodiment will be mainly described.

As shown in FIG. 14(B), a composite pipe 610 of the fifth embodiment includes a main pipe 12, an outer pipe 20, and an inner pipe 630. When viewed from the axial direction, the inner tube 630 is formed with six protrusions 642 and six bulges 644, and the inner tube 630 is cut along the center line CL01. The cut shape is an uneven shape. Furthermore, in the first molding step S2, the inner tube 630 is molded by butting the three molds together. The action of the composite pipe 610 of the fifth embodiment is similar to the action of the composite pipe 10 of the first embodiment.

<Sixth embodiment>
An example of a composite pipe and a method for manufacturing the composite pipe according to the sixth embodiment of the present invention will be described using FIG. 15. Note that, regarding the sixth embodiment, the differences from the first embodiment will be mainly described.

As shown in FIG. 15, a composite pipe 710 according to the sixth embodiment includes a main pipe 712 having a larger diameter than the main pipe 12, an outer pipe 20, and an inner pipe 730. When viewed from the axial direction, the inner tube 730 has a rectangular shape, and the cut shape cut along the center line CL01 has an uneven shape. The action of the composite pipe 710 of the sixth embodiment is similar to the action of the composite pipe 10 of the first embodiment, except for the action caused by the curving of the bulging portion.

Although the present invention has been described in detail with respect to a specific embodiment, it is understood that the present invention is not limited to such embodiments, and that various other embodiments are possible within the scope of the present invention. It is clear to the trader. For example, in the first embodiment, all the bulges 44 contact the main pipe 12 to restrict movement of the main pipe 12 in the radial direction, but at least some of the bulges 44 contact the main pipe 12. The radial movement of the main pipe 12 may be restricted by contacting with the main pipe 12 . However, in this case, the effect caused by all the bulges 44 coming into contact with the main pipe 12 does not occur.

Further, in the first embodiment, the inner tube 30 has a shape that is line symmetrical with respect to a line passing through the center of the inner tube 30, but the shape does not have to be line symmetrical. However, in this case, the effect caused by the line-symmetrical shape of the inner tube does not occur.

Further, although not specifically described in the above embodiment, the inner tube may be spaced apart from the outer tube 20, which has at least a portion of a circular shape in the circumferential direction. For this reason, the inner tube may have an irregular shape different from a circular shape when viewed from the axial direction. For example, the inner tube may have a polygonal shape having a plurality of sides when viewed from the axial direction.

Further, although not particularly described in the above embodiment, the protruding portion and the bulging portion may or may not be formed on the inner tube.

DESCRIPTION OF SYMBOLS 10... Composite pipe, 12... Main pipe, 20... Outer pipe, 22... Peak part, 24... Valley part, 26... Side wall, 28... Bottom wall, 30... Inner pipe, 32... Peak part, 34... Valley part, 36 ...Side wall, 38...Bottom wall, 42...Protrusion, 44...Bulging part, 46...Space, 112...Mold, 112a...Molding surface, 212...Mold, 212a...Molding surface, 310...Composite pipe, 330... Inner tube, 410...Composite tube, 430...Inner tube, 510...Compound tube, 530...Inner tube, 542...Protrusion part, 544...Bulging part, 610...Composite tube, 630...Inner tube, 642...Protrusion part, 644 ...Bulging part, 710...Composite tube, 712...Main pipe, 730...Inner tube, S1...First extrusion process, S2...First forming process, S3...Second extrusion process, S4...Second forming process

Claims (7)

A main pipe through which fluid flows;
an outer pipe that covers the main pipe from the outside in the radial direction of the main pipe and is expandable and retractable in the axial direction of the main pipe;
On the inside of the outer pipe in the radial direction, the main pipe is covered from the outside in the radial direction, and the cut shape cut along the center line of the main pipe is an uneven shape, and there is a gap between the outer pipe and the outer pipe. an inner tube formed of a resin material that forms a space that extends continuously in the axial direction in at least a part of the main tube in the circumferential direction ;
When viewed from the axial direction, the inner tube is formed with a protrusion that protrudes toward the outer tube and a bulge that bulges from the protrusion toward the main tube.
Composite tube. The composite tube according to claim 1 , wherein the bulged portion is curved when viewed from the axial direction. The composite pipe according to claim 1 or 2 , wherein a plurality of the bulges are formed, and at least a part of the bulges restricts movement of the main pipe in the radial direction. The composite tube according to any one of claims 1 to 3 , wherein the inner tube has a shape that is symmetrical with respect to a line passing through the center of the inner tube when viewed from the axial direction. The outer tube has an uneven cut shape when cut along a plane along the center line, and is composed of a mountain portion that is convex outward in the radial direction, and a pair of side walls and a bottom wall, and has a trough with a concave outer side,
The inner tube has a peak portion that is convex toward the outside in the radial direction, and a valley portion that is configured from a pair of side walls and a bottom wall and is concave on the outside in the radial direction,
The composite tube according to any one of claims 1 to 4 , wherein the length of the peak portion of the inner tube in the axial direction is longer than the distance between adjacent bottom walls in the axial direction in the outer tube. . The outer tube has an uneven cut shape when cut along a plane along the center line, and is composed of a mountain portion that is convex outward in the radial direction, and a pair of side walls and a bottom wall, and has a trough with a concave outer side,
The inner tube has a peak portion that is convex toward the outside in the radial direction, and a valley portion that is configured from a pair of side walls and a bottom wall and is concave on the outside in the radial direction,
The composite pipe according to any one of claims 1 to 5 , wherein the length of the bottom wall of the outer pipe in the axial direction is longer than the distance between adjacent peaks in the axial direction in the inner pipe. . A method for manufacturing a composite pipe according to any one of claims 1 to 6 , comprising:
a first extrusion step of feeding the main pipe in the axial direction and extruding a cylindrical molten resin to the outside of the fed main pipe in the radial direction;
a first molding step of molding the inner tube by adsorbing the extruded cylindrical molten resin to the molding surface of the mold while conveying it;
a second extrusion step of extruding a cylindrical molten resin to the outside of the inner tube in the radial direction;
a second molding step of molding the outer tube by adsorbing the extruded cylindrical molten resin to the molding surface of the mold while conveying it;
Compared to the case where the molten resin is cylindrical, the cylindrical molten resin extruded in the first extrusion step is not adsorbed to the molding surface of the mold for molding the inner tube. A method for manufacturing composite pipes with a shape that is approaching.