JP2695133B2 - Double wall tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-walled pipe, in particular, an outer wall pipe having alternating peaks and valleys, and a flat wall heat-sealed to the outer wall pipe on the inner surface of the valley of the outer wall pipe. The present invention relates to a double-walled pipe having a pressure-resistant strength that can be used by being buried in the ground.

[0002]

2. Description of the Related Art Conventionally, double-walled pipes have been used as drainage pipes for underground burial. Japanese Examined Patent Publication No. 2-21477 discloses a double-walled pipe in which a tubular inner wall is heat-sealed to the inner surface of an outer wall having annular peaks and valleys alternately.
This double-walled tube has an insertion opening at one end and a receiving opening at the other end, and the inner surface of the valley portion of the outer wall is heat-sealed to the inner wall at the portion excluding the insertion opening to form a hollow integral structure with no unevenness on the inner surface. ing. The inner diameter of the inner wall is uniform except for the receiving opening, and is configured to have a large diameter so that the insertion opening can be inserted only in the receiving opening. Furthermore, on the outer surface of the insertion port,
A convex shape that is press-engaged with the inner wall of the receiving port is provided.

A double-walled pipe of this type pushes a synthetic resin for forming an outer wall from an extruder onto the concavo-convex molding surface while a pair of opposing half-molding dies are synchronously run at a constant speed. The molten resin outer layer having the above-mentioned peaks and valleys is continuously molded, and the inner surface of the valley of the outer layer is heat-fused to form the molten resin inner layer. The molded product thus obtained is released from the mold after curing, and then cut into pieces of a predetermined size and separated.

[0004]

In the above-mentioned double-walled pipe, since the inner surface of the inner wall of the receiving port is flat, the convex shape and the deformation of the inner wall are indispensable in the connected state, and the engagement is prevented. Deformation is working. Therefore, it is difficult to obtain a sufficient locking force. In addition, since the receiving port is also formed with a hollow integrated structure with the inner surface of the valley portion of the outer wall heat-sealed to the inner wall and with no unevenness on the inner surface, it has poor flexibility and is likely to be non-linear. There are difficulties.

An object of the present invention is to provide a double-walled pipe in which the insertion port and the reception port are surely connected to each other, and the connection portion has appropriate flexibility.

[0006]

According to the present invention, an outer wall tube having annular peaks and troughs alternately arranged in the axial direction, and an outer wall tube thermally fused to the inner surface of the trough of the outer wall tube. A double-walled pipe consisting of a flat inner-walled pipe, having an insertion opening at one end and a receiving opening at the other end, and the insertion opening is formed with a flat end portion of the outer-walled pipe so that the outer-walled pipe and the inner-walled pipe overlap each other. On the other hand, the receiving port is formed so that the inner wall pipe is closely attached along the inner surface of the outer wall pipe and is expanded in the radial direction so that the inner diameter of the valley portion of the inner wall pipe is substantially the same as the outer diameter of the insertion port. A heavy wall tube is provided.

According to the present invention, the double wall is composed of an outer wall tube having annular peaks and valleys alternately, and a flat inner wall tube heat-sealed to the outer wall on the inner surface of the valley of the outer wall tube. A wall tube having an insertion opening at one end and a receiving opening at the other end, and the insertion opening is formed such that the end portion of the outer wall tube is flat so that the outer wall tube and the inner wall tube overlap each other, while the receiving opening is the inner wall tube. A double-walled pipe is provided which is formed only from the outer-walled pipe so that the inner diameter of the valley portion of the outer-walled pipe is equal to the outer diameter of the insertion port.

The double-walled pipe according to the present invention has a predetermined compressive strength to be buried in the ground or laid on the ground surface and used as a drainage pipe, etc. A pipe material that can be sequentially connected by being fitted into the inner peripheral side. The double-walled pipe is a synthetic resin for forming the outer wall extruded from the extruder onto the concave-convex molding surface while the pair of endless half-molding halves facing each other are synchronously run at a constant speed. The molten resin outer layer having the above is continuously molded, and the inner surface of the valley portion of the outer layer is heat-fused to form the molten resin inner layer.
The molded product thus obtained is released from the mold after curing, and then cut into pieces of a predetermined size and separated.

In the above-mentioned molding, the endless half-molding die travels one round to form a standard length of a double-walled pipe having an insertion opening at one end and a receiving opening at the other end, and a molding die. It is preferable to use a device.

The material of the double-walled tube is synthetic resin, preferably,
It is an olefin resin or a vinyl chloride resin, and polyethylene is particularly preferable in terms of moldability, fusion property and mechanical strength.

It is preferable that at least a part of the insertion opening is formed by lacking the inner wall tube. It is preferable that the insertion port has a pipe connecting means for connecting a plurality of pipes, which is composed of a plurality of ridges protruding outward from the flat outer wall pipe surface and formed discontinuously in the circumferential direction. The ridge is preferably formed integrally with the outer wall tube. The ridge can be stored inside the mountain portion of the outer wall tube, and the cross section in the axial direction has a substantially triangular shape,
Further, it is preferable that 3 to 8 rings are formed. Providing at least three ridges enables uniform and firm engagement without blurring.

[0012]

In the double-walled pipe of the present invention, when the insertion port is fitted into the receiving port, the inner diameter of the trough portion of the inner wall pipe is almost the same as the outer diameter of the insertion port, so that the outer wall tube of the insertion port receives It is fitted into the inner wall of the mouth.
Here, if the receiving wall is formed so that the inner wall tube is in close contact with the inner surface of the outer wall tube, an appropriate bendability is secured in the tube connecting portion. Therefore, the laying work involving the connection of the double-walled pipes on site becomes easy.

In the double-walled pipe of the present invention, when the insertion port is fitted into the receiving port, the inner diameter of the trough portion of the inner wall pipe is substantially the same as the outer diameter of the insertion port, so that the outer wall tube of the insertion port receives It is fitted into the inner wall of the mouth. Here, if the receiving port is formed so as to lack the inner wall pipe, the pipe connecting portion can ensure appropriate flexibility. Therefore, the laying work involving the connection of the double-walled pipes on site becomes easy.

If at least a part of the insertion opening is formed by lacking the inner wall pipe, the pipe connecting portion can have appropriate flexibility, so that the laying work involving the connection of the double wall pipe at the site is easy. become. Further, when connecting these double-walled pipes to each other, the length of the pipes can be adjusted by the depth of insertion of the insertion port with respect to the receiving port, which facilitates the laying work involving the connection of the double-walled pipes. Become.

The insertion port has a pipe connecting means for connecting a plurality of pipes, which is composed of a plurality of ridges projecting outward from the flat outer wall pipe surface and formed discontinuously in the circumferential direction. With this configuration, when the insertion opening is inserted into the receiving opening, the ridges of the insertion opening engage with the inner surface of the receiving opening and are connected to each other. Therefore, it is not necessary to separately prepare a connection joint. The inner surface of the receiving port, the inner wall tube is formed so as to closely adhere to the inner surface of the outer wall tube, or because the inner wall tube is lacking and is formed only by the outer wall tube,
The ridge is engaged with the trough on the inner surface of the receptacle. In this connected state, since the ridge and the inner wall tube are not deformed, a sufficient locking force can be obtained in the insertion direction of the insertion opening.

If the ridge can be housed inside the ridge of the outer wall tube, has a substantially triangular cross section in the axial direction, and has three annular ridges, the ridge is inserted into the receptacle. The ridge easily passes the inner surface of the receiving opening, and a sufficient locking force can be obtained in the insertion direction of the insertion opening while ensuring appropriate flexibility at the insertion opening at a few locking points.

[0017]

【Example】

[Embodiment 1] FIG. 1 shows a double wall tube according to an embodiment of the present invention.
~ It demonstrates based on the sectional view of FIG. The double-walled pipe 1 has a cylindrical inner wall 2 made of polyethylene resin and an outer wall 3 made of polyethylene resin surrounding the outer periphery thereof, and has an insertion port 4 at one end and a receiving port 5 at the other end. ing. The outer wall 3 is alternately provided with annular peaks 3a and valleys 3b over the entire length except the flat portion 3c forming the insertion opening 4.

The inner wall 2 is provided with a flat portion 2c heat-sealed to the outer wall 3 on the inner surface of the valley portion 3b of the outer wall 3, and further the flat portion 2
An annular peak 2a and a valley 2b are alternately provided in the receiving port 5 continuous to c. The insertion port 4 is formed so that the flat portions 3c, 2c of the outer wall 3 and the inner wall 2 overlap each other.
On the other hand, in the receiving port 5, the ridges 3a, 2a and the valleys 3b, 2b are in close contact with each other so that the inner wall 2 extends along the inner surface of the outer wall 3, and the inner surface thereof has irregularities.

As shown in FIG. 2, the receiving opening 5 has a structure in which it is expanded in the radial direction so that the inner diameter of the valley portion 2b of the inner wall 2 becomes substantially the same as the outer diameter of the insertion opening 4. . The flat portion 3c of the outer wall 3 is formed with a plurality of ridges 6 projecting outward from the wall surface and formed discontinuously in the circumferential direction (see FIG. 5). The ridge 6 serves as a pipe connecting means and is a mountain portion 2a of the inner wall 2.
It can be stored in the inner space without being deformed, and the cross section in the axial direction has a substantially triangular shape, and three annular members are formed at substantially equal intervals. The height of the ridge from the wall surface is formed in the range of 3 to 10 mm if the outer diameter of the insertion port 4 is 50 to 300 mm.

When connecting the above-mentioned double-walled pipes 1, as shown in FIG. 3, two double-walled pipes 1, which are connected to each other,
After the insertion opening 4 and the receiving opening 5 of 1 are butted, the insertion opening 4 is inserted into the receiving opening 5. The ridges 6 and the inner wall 2 are slightly deformed, and the ridges 6 pass while sliding along the valleys 2b of the inner wall 2. At this time, an adhesive or a sealing agent may be applied in advance to the joint surface between the insertion port 4 and the receiving port 5 as needed.

When the double-walled pipes 1 and 1 are connected, as shown in FIG. 4, the outer surface of the flat portion 3c of the insertion slot 4 is set so that the inner wall 2 is along the inner surface of the outer wall 3 in the receptacle 5. It adheres closely to the inner surface of the valley portion 2b of No. 5. Therefore, proper flexibility is secured. This flexibility facilitates the work of laying the double-walled tubes 1, 1 in the field.

When the above connection is made, the inner surface of the socket 5 is
As shown in FIG. 5 at part b, the tip 4a of the insertion port 4 has the inner wall 2
While contacting the end point of the flat portion 2c, the ridge 6 projects into the ridge portion 2a of the inner wall 2 and its locking surface 6a is engaged with the side surface of the valley portion 2b. In this connected state, the ridge 6 and the inner wall 2 are not deformed, so that a sufficient locking force can be obtained in the direction in which the insertion slot 4 is pulled out.

Since the ridge 6 has a substantially triangular cross section in the axial direction, the ridge 6 passes through the inner surface of the receptacle 5 with a small resistance when the insertion slot 4 is fitted into the receptacle 5. With
A sufficient locking force can be obtained in the direction in which the insertion slot 4 is pulled out.

A method of manufacturing the above-mentioned double-walled tube 1 will be described with reference to the molding apparatus 10 shown in FIGS. 6 and 7. In the figure, a molding apparatus 10 includes a molten resin extruding section 11, a molding die 12,
The cooling cylinder 13 is mainly included. The molten resin extruding section 11 is composed of a first extruding port 14 for extruding the outer wall, a second extruding port 15 for extruding the inner wall, and a nozzle 16. The extrusion ports 14 and 15 are connected to a resin extrusion device (not shown). At the tip of the nozzle 16 (right side in the figure),
A differential pressure portion 17 is formed between the molding die 12 and the molding die 12.

The nozzle 16 has a first molten resin passage 21 which is annularly opened at the outer periphery of the tip end thereof and a second molten resin passage which is annularly opened at the tip of the nozzle 16 on the coaxial inner peripheral side of the passage 21.
In addition to having the molten resin passage 22, it also has a first air supply passage 31 and a second air supply passage 32 that communicate with the differential pressure section 17. The first air supply passage 31 opens in an annular shape inside the annular opening in the first molten resin passage 21. Further, the second air supply passage 32 opens in a ring shape further inside the ring opening in the second molten resin passage 22. Mold 12 to be described later
An exhaust passage 33 communicating with the pressure difference portion 17 through the mold 12 is formed on the back surface of the. At the tip of the nozzle 16,
The cooling cylinder 13 is arranged.

The cooling cylinder 13 is arranged coaxially with the nozzle 16 and is configured to supply cooling water through the cooling water flow port 13a. The molding die 12 includes a pipe body molding surface A, a socket molding surface B, and an insertion molding surface C (see FIG. 8). The socket molding surface B and the insertion molding surface C are formed so as to be continuous. There is. The tube body molding surface A has annular concave portions A1 and convex portions A2 alternately. Further, the socket molding surface B is the tube body molding surface A.
Similarly, the ring-shaped concave portions B1 and the convex portions B2 are alternately provided.

The convex portion B2 has a diameter larger than that of the convex portion A2 on the molding surface A of the tube body. The recess B1 is formed on the tube body molding surface A.
It has a cylindrical shape with the same diameter as the annular recess A1. Mold 12
Is divided into a pair of half molds, and each half mold has a large number of blocks connected endlessly, and these are surrounded by the molten resin extruding portion 11 and the cooling cylinder 13 by arrows in FIG. It is configured to travel in a fixed position in the same direction. Mold 12
Is a set of pipe body molding surfaces A, so that both half molds can travel once to form a fixed-length double-walled pipe having an insertion opening 4 at one end and a receiving opening 5 at the other end. It is a molding die provided with a socket molding surface B and an insertion molding surface C.

In the molding apparatus 10 as described above, the molten resin is continuously extruded through the first molten resin passage 21 and the second molten resin passage 22 while the molding die 12 is running in the direction of the arrow at a predetermined speed in the drawing, At the same time, air is supplied from the first air supply passage 31 into the differential pressure section 17 and is exhausted from the exhaust passage 33. Further, as shown in FIG. 7, in the air supply from the second air supply passage 32, the molten resin outer layer P1 formed by the inlet molding surface B passes around the opening of the second molten resin passage 22. Only during the hours that you are

The molten resin extruded in a cylindrical shape from the first molten resin passage 21 is formed by the internal and external differential pressure generated in the differential pressure portion 17, the pipe body molding surface A, the socket molding surface B and the insertion molding surface C.
Is pressed against to form a molten resin outer layer P1 and is molded into a shape along each molding surface. On the other hand, the second molten resin passage 22
The molten resin extruded from adheres to the inner surface of the already-molded molten resin outer layer P1 due to the suction effect of the exhaust from the exhaust passage 33 and heat-melts to form the molten resin inner layer P2.

When the inlet molding surface B passes through the outlet of the second air supply passage 32, air is supplied from the second air supply passage 32 and the exhaust pressure from the exhaust passage 33 is increased so that the inner layer P2 becomes the outer layer P1. It swells into the valley portion and is further extruded so that the molten resin inner layer P2 is in close contact with the inner surface of the molten resin outer layer P1.

Thermally melted inner and outer molten resin layers P1 and P2
Then, the resin is sequentially sent to the cooling cylinder 13 side as the molding die 12 travels, cooled and hardened, and then released. The obtained molded product P includes the insertion port equivalent part 104 and the receiving port equivalent part 105 which are continuous with each other at equal intervals in the axial direction of the pipe body equivalent part 106 (FIG. 8), and therefore, the insertion port equivalent part 104.
And the boundary portion of the receiving port equivalent portion 105 are cut along the cutting lines c-c and d-d to separate them. As a result, the standard double-walled tube 1
Is obtained. The standard length of the double-walled tube 1 is usually 4 to 5 m.
It is.

As described above, in this double-walled pipe 1, when the insertion port 4 is fitted into the receiving port 5, the inner diameter of the valley portion 2b of the inner wall 2 is substantially the same as the outer diameter of the insertion port 4, Outer wall 3 of spigot 4
Is fitted into the inner surface of the receptacle 5. For this reason, when connecting these double-walled pipes 1 to each other, the length can be adjusted by the insertion depth of the insertion port 4 into the receiving port 5, so that the laying work involving the connection of the double-walled pipes 1 can be performed. Will be easier. Since the inner wall 2 of the receiving port 5 is formed in close contact with the inner surface of the outer wall 3, the receiving port 5 is easily bent at the connection portion, and appropriate flexibility is secured. Therefore, handling such as connecting the double-walled tubes 1 to each other in the field becomes easy.

Since the insertion slot 4 is provided with a plurality of protrusions 6 protruding outward from the surface of the flat outer wall 3, when the insertion slot 4 is fitted into the receiving port 5, the protrusions 6 of the insertion slot 4 are inserted. Engages with the inner surface of the receptacle 5. Since the inner wall 2 is formed in close contact with the inner surface of the receiving port 5 along the inner surface of the outer wall 3, the ridge 6 is engaged with the valley portion 2b of the inner surface of the receiving port 5. In this connected state, the ridge 6 and the inner wall 2 are not deformed, so that a sufficient locking force can be obtained in the direction in which the insertion slot 4 is pulled out.

Furthermore, since the ridge 6 has a substantially triangular cross section in the axial direction, it easily passes through the inner surface of the receiving port 5. If three ridges 6 are provided in an annular shape, when the double-walled pipes 1 are connected to each other, the double-walled pipes 1 do not shake each other while ensuring appropriate flexibility, and the insertion direction of the insertion port 4 is eliminated. A sufficient locking force can be obtained. The double-walled tube 1 does not need to separately prepare a joint for connection, and when it is connected, it is regarded as a single tube in appearance, and thus has a preferable form as a design.

[Embodiment 2] FIGS. 9 to 13 show an example of a double-walled pipe 41 having a receiving port lacking an inner wall pipe. Here, the inner wall 42 includes a flat portion 42c that is heat-sealed to the outer wall 43 on the inner surface of the valley portion 43b of the outer wall 43.
2c is missing at the socket 45. The insertion opening 44 is formed so that the flat portions 43c and 42c of the outer wall 43 and the inner wall 42 overlap each other. The receiving port 45 is the mountain portion 4 of the outer wall 43.
3a and the valley portion 43b form unevenness on the inner surface thereof.

As shown in FIG. 10, the e-portion of the receiving port 45 is
The inner wall 42 is omitted so that the inner diameter of the valley portion 43b of the outer wall 43 is substantially the same as the outer diameter of the insertion opening 44. The flat portion 43c of the outer wall 43 is provided with a plurality of protruding ridges 46 protruding outward from the wall surface and discontinuous in the circumferential direction.

When connecting the above-mentioned double-walled pipe 41,
As shown in FIG. 11, after the insertion ports 44 and the receiving ports 45 of the two double-walled pipes 41, 41 connected to each other are butted,
The insertion opening 44 is fitted into the receiving opening 45. Ridge 46 and outer wall 43
Is slightly deformed, and the ridge 46 passes while sliding on the inner surface of the valley portion 43b of the outer wall 43.

When the double wall tubes 41, 41 are connected, FIG.
2 and FIG. 13 showing the part f in FIG.
5, the outer surface of the flat portion 43c of the insertion opening 44 is
It closely adheres to the inner surface of the valley portion 43b. As a result, the connecting portion is easily bent, and this bendability causes the double-wall pipe 41 in the field.
Easy to handle such as connecting.

[Embodiment 3] FIGS. 14 to 17 show an example of a double-walled pipe 51 in which the insertion opening is formed by omitting the inner wall pipe. Here, as shown in FIG. 17, the inner wall 52 is a flat portion 52 heat-sealed to the outer wall 53 on the inner surface of the valley portion 53 b of the outer wall 53.
In the receiving port 55 which is provided with c and which is continuous with the flat portion 52c, annular peaks 52a and valleys 52b are alternately provided.
The tip of the insertion port 54 lacks the inner wall 52, and is formed only by the flat portion 53c of the outer wall 53. On the other hand, the socket 55 is
The inner wall 52 is formed so that the inner wall 52 extends along the inner surface of the outer wall 53.
The a and the troughs 53b and 52b are in close contact with each other, and irregularities are formed on the inner surface thereof.

The receiving port 55 is expanded in the radial direction so that the inner diameter of the valley portion 52b of the inner wall 52 is substantially the same as the outer diameter of the insertion port 54. In the flat portion 53c of the outer wall 53,
A plurality of protrusions 56 are formed so as to project outward from the wall surface and are discontinuous in the circumferential direction.

When connecting the above-mentioned double-walled pipe 51,
As shown in FIG. 15, after the insertion ports 54 and the receiving ports 55 of the two double-walled tubes 51, 51 connected to each other are butted,
The insertion port 54 is fitted into the receiving port 55. Ridge 56 and inner wall 52
Is slightly deformed, and the ridge 56 passes while sliding along the valley portion 52b of the inner wall 52.

When the double-walled tubes 51, 51 are connected, FIG.
6 and FIG. 17 showing part g of FIG.
5, the outer surface of the flat portion 53c of the insertion port 54 is
The inner surface of the inner wall 52 is closely attached to the inner surface of the valley portion 52b. As a result, the connecting portion is easily bent, and this bendability further facilitates handling such as connecting the double-walled pipe 51 in the field.

When molding the above-mentioned double-walled pipes 41 and 51, when the receiving port molding surface B or the insertion port molding surface C passes through the pressure difference portion 17, the pressure from the second molten resin passage 22 is increased. By temporarily stopping the extrusion of the molten resin, only the molten resin outer layer P1 corresponding to each outer wall is formed.

[0044]

According to the double-walled pipe of the present invention, when the insertion port is fitted into the receiving port, the inner diameter of the trough portion of the inner wall pipe is substantially the same as the outer diameter of the insertion port, so that the outer wall of the insertion port is The tube is fitted into the inner wall tube of the receptacle. Here, if the receiving wall is formed so that the inner wall tube is in close contact with the inner surface of the outer wall tube, the receiving port has a proper flexibility. Therefore, the laying work involving the connection of the double-walled pipes on site becomes easy.

In the double-walled pipe of the present invention, when the insertion port is fitted into the receiving port, the inner diameter of the trough portion of the inner wall pipe is almost the same as the outer diameter of the insertion port, so that the outer wall tube of the insertion port receives It is fitted into the inner wall of the mouth. Here, if the receiving port is formed so as to lack the inner wall tube, the receiving port has a proper flexibility. Therefore, the laying work involving the connection of the double-walled pipes on site becomes easy.

If at least a part of the insertion port is formed by lacking the inner wall pipe, the insertion port can ensure appropriate flexibility, so that the laying work involving the connection of the double wall pipe at the site is easy. become. Further, when connecting these double-walled pipes to each other, the length of the pipes can be adjusted by the depth of insertion of the insertion port with respect to the receiving port, which facilitates the laying work involving the connection of the double-walled pipes. Become.

The insertion port has a pipe connecting means for connecting a plurality of pipes, which is formed of a plurality of convex strips projecting outward from the flat outer wall pipe surface and formed discontinuously in the circumferential direction. With this configuration, when the insertion opening is inserted into the receiving opening, the ridges of the insertion opening engage with the inner surface of the receiving opening and are connected to each other. Therefore, it is not necessary to separately prepare a connection joint.

The inner surface of the receiving port is formed so that the inner wall tube is closely attached along the inner surface of the outer wall tube or is formed only by the outer wall tube without the inner wall tube. Are engaged in the valleys of the. In this connected state, since the ridge and the inner wall tube are not deformed, a sufficient locking force can be obtained in the insertion direction of the insertion opening.

When the ridge can be stored inside the mountain portion of the outer wall tube and has a cross section in the axial direction of a substantially triangular shape, and further, three ridges are formed in an annular shape, when the insertion port is fitted into the receiving port. The ridge easily passes the inner surface of the receiving opening, and a sufficient locking force can be obtained in the insertion direction of the insertion opening while ensuring appropriate flexibility at the insertion opening at a few locking points.

When the insertion opening is inserted into the receiving opening, the inner diameter of the trough portion of the inner wall opening is substantially the same as the outer diameter of the insertion opening, so that the outer wall opening of the insertion opening is inserted into the inner wall opening of the receiving opening. Here, if the receiving port is formed in close contact with the inner wall pipe along the inner surface of the outer wall pipe,
The socket has a proper flexibility. Therefore, the laying work involving the connection of the double-walled pipes on site becomes easy.

As described above, according to the present invention, there is provided a double-walled pipe in which the insertion port and the reception port are surely connected to each other and the connection portion has an appropriate flexibility.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a double wall tube according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a portion of the double-walled tube in FIG.

FIG. 3 is a cross-sectional view showing a connection procedure of the double-walled pipe of FIG.

FIG. 4 is a cross-sectional view showing a connected state of the double-walled pipe of FIG.

5 is an enlarged view of a portion b of the double-walled pipe in FIG.

6 is a schematic cross-sectional view of a molding apparatus that forms the double-walled tube of FIG.

7 is a partially enlarged cross-sectional view showing the vicinity of the nozzle tip of the molding apparatus of FIG.

8 is a cross-sectional view of a molded product and its molding surface by the double-walled pipe molding apparatus of FIG.

FIG. 9 is a cross-sectional view of a double wall tube according to another embodiment of the present invention.

10 is an enlarged view of an e portion of the double-walled pipe in FIG.

11 is a cross-sectional view showing a connection procedure of the double-walled pipe of FIG.

12 is a cross-sectional view showing a connected state of the double-walled pipe of FIG.

13 is an enlarged view of an f portion of the double-walled pipe in FIG.

FIG. 14 is a cross-sectional view of a double wall tube according to still another embodiment of the present invention.

15 is a cross-sectional view showing a connection procedure of the double-walled pipe of FIG.

16 is a cross-sectional view showing a connected state of the double-walled pipe of FIG.

FIG. 17 is an enlarged view of part g of the double-walled tube of FIG.

[Explanation of Codes] 1 double wall pipe 2 inner wall 2a mountain part 2b valley part 3 outer wall 3a mountain part 3b valley part 4 insertion port 5 receiving port 6 convex strip 41 double wall pipe 51 double wall pipe

Claims (5)

(57) [Claims] 1. A double wall composed of an outer wall tube having annular peaks and troughs alternately arranged in the axial direction, and a flat inner wall tube heat-sealed to the outer wall tube on the inner surface of the trough of the outer wall tube. A pipe having an insertion port at one end and a receiving port at the other end, the insertion port having a flat end portion of the outer wall pipe so that the outer wall pipe and the inner wall pipe overlap each other, while the receiving port has an inner wall pipe. A double-walled pipe which is closely attached along the inner surface of the outer wall pipe and is radially expanded so that the inner diameter of the valley portion of the inner wall pipe is substantially the same as the outer diameter of the insertion opening. 2. A double-walled pipe comprising an outer wall pipe having alternating annular peaks and valleys, and a flat inner wall pipe heat-sealed to the outer wall at the inner surface of the valley of the outer wall pipe. The end of the outer wall pipe is formed flat so that the outer wall pipe and the inner wall pipe overlap with each other, while the receiving end lacks the inner wall pipe and the outer wall. A double-walled pipe formed only from an outer wall pipe so that an inner diameter of a valley portion of the pipe is substantially equal to an outer diameter of the insertion opening. 3. The method according to claim 1, wherein at least a part of the insertion opening is formed by lacking the inner wall tube.
Double wall tube as described. 4. A pipe connecting means for connecting a plurality of pipes, wherein the insertion port is composed of a plurality of ridges projecting outward from the flat outer wall pipe surface and formed discontinuously in the circumferential direction. The double-walled pipe according to any one of claims 1 to 3, which has. 5. The ridge can be housed inside the mountain portion of the outer wall pipe, has a cross section in the axial direction of a substantially triangular shape, and further has a ring shape of 3 to 3.
The double-walled pipe according to claim 4, wherein eight double-walled pipes are formed.