JP7609711B2 - Double tube molding method - Google Patents

Description

This disclosure relates to a method for forming a double-walled pipe in which the central axis is curved at least in part.

For example, Patent Document 1 describes a method for forming a double-walled pipe in which a filler is filled into the space inside the double-walled pipe to form the double-walled pipe into a predetermined shape.

JP 2005-180270 A

There are cases where it is desirable to apply a molding method using a filler as described in Patent Document 1 to a double-walled pipe that has at least a portion of its central axis curved. However, when filling the space inside such a double-walled pipe with a filler, the position of the inner pipe will shift relative to the outer pipe in the part where the central axis of the double-walled pipe is curved due to the difference in area between the side with the larger curvature along the axial direction and the side with the smaller curvature on the inner surface of the inner pipe. This poses the problem that it is difficult to mold the double-walled pipe into the designed shape.

One aspect of the present disclosure provides a technology that makes it easier to mold a double-walled pipe, at least partially having a curved central axis, into a designed shape when a molding method using a filler is applied to the double-walled pipe.

One aspect of the present disclosure is a method for forming a double-walled pipe having at least a portion of a curved central axis, the method comprising the steps of (i) to (iv) below.
(i) Inserting an insertion portion into the inner tube, the insertion portion being configured to be insertable into an inner tube of a double tube and configured to be able to change the outer diameter of the smallest including circle that contains the insertion portion when viewed from the insertion direction.

(ii) When the insertion portion is inserted into the inner tube, the outer diameter of the minimum including circle is enlarged to regulate the position of the inner tube.
(iii) The end of the outer tube in the double pipe on the side where the insertion portion is inserted is sealed with a sealing portion configured to be in contact with the outer tube over the entire circumference of the outer tube.

(iv) With the position of the inner tube regulated by the insertion portion and the end of the outer tube sealed by the sealing portion, fill the space inside the double tube with a filler and mold the double tube into a specified shape.

With this configuration, the position of the inner tube is regulated when filling with the filler, so the position of the inner tube is less likely to shift relative to the outer tube in the portion of the double tube where the central axis is curved. This makes it easier to mold the double tube into the designed shape.

In one aspect of the present disclosure, the method for molding a double tube may further include inserting a clamping section configured to be insertable between the inner tube and the outer tube, between the inner tube and the outer tube in a state in which the position is regulated by the insertion section, and then further expanding the outer diameter of the minimum containing circle to clamp the inner tube between the clamping section and the insertion section. In addition, the space inside the double tube may be filled with a filler while the inner tube is clamped between the clamping section and the insertion section.

With this configuration, when filling with the filler, the position of the inner tube is less likely to shift relative to the outer tube in the portion of the double tube where the central axis is curved. This makes it easier to mold the double tube into the designed shape.

In one aspect of the present disclosure, the end of the outer tube on the side where the insertion portion is inserted in the double tube may be sealed by molding the sealing portion into a shape corresponding to the sealing portion.
According to such a configuration, for example, even if the end of the outer tube is deformed or the diameter of the outer tube varies from one individual to another, it is possible to seal the end of the outer tube.

In one aspect of the present disclosure, the insertion portion may have a tapered end portion on the front side in the insertion direction.
With this configuration, it is possible to reduce the likelihood of the insertion portion being unable to be inserted into the inner tube due to interference with the inner tube.

FIG. 2 is a plan view showing the double pipe of the embodiment. FIG. 13 is a top view showing a state in which a double pipe is fitted into a groove in an outer circumferential mold. 3A and 3B are cross-sectional views that typically show a state in which an inner core bar is being inserted into an inner tube. 4A and 4B are cross-sectional views that typically show a state in which the position of the inner tube is regulated by the inner core bar. 5A and 5B are cross-sectional views showing a state where the clamping part is inserted between the inner tube and the outer tube, and Fig. 5C is a cross-sectional view showing a state where the end of the outer tube is sealed by the clamping part. Fig. 6A is a cross-sectional view showing a state in which a filler is being introduced into the space inside the double pipe, and Fig. 6B is a cross-sectional view showing a portion including a joint in the double pipe. 5 is a schematic diagram showing a comparison of the state before and after the double-walled pipe of the embodiment is deformed due to an increase in pressure of the filler. FIG. 1 is a schematic diagram showing the change in position of the inner tube relative to the outer tube when a filler is filled into a double tube having a partially curved central axis. FIG. 11 is a schematic diagram showing a comparison of a double pipe of a modified example before and after deformation due to an increase in pressure of the filler. FIG.

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.
[1. Configuration of double pipe]
First, a double pipe 1A (see FIG. 1 ) to which a molding method described later is applied will be described. The double pipe 1A has an outer pipe 11 and an inner pipe 12. Both the outer pipe 11 and the inner pipe 12 are tubular. The inner pipe 12 is disposed inside the outer pipe 11.

In this embodiment, the outer tube 11 is a circular tube with a substantially constant diameter. As shown in FIG. 4B, the outer tube 11 has a substantially perfect circle in cross section perpendicular to the axial direction. The inner tube 12 is also basically a circular tube with a substantially constant diameter, similar to the outer tube 11, and has a substantially perfect circle in cross section perpendicular to the axial direction. As shown in FIG. 1, there is a gap between the inner surface of the outer tube 11 and the outer surface of the inner tube 12.

The inner pipe 12 has an enlarged diameter portion 121 and a joint portion 122 at one end in the order of the end surface of the end. The enlarged diameter portion 121 expands in diameter toward the joint portion 122 side. As shown in FIG. 6B, the joint portion 122 is partially joined to the inner surface of the outer pipe 11 in the axial direction. The portion of the joint portion 122 that is not joined to the inner surface of the outer pipe 11 is separated from the inner surface of the outer pipe 11. That is, a gap is provided between the portion of the joint portion 122 that is not joined to the inner surface of the outer pipe 11 and the inner surface of the outer pipe 11. As shown in FIG. 1, the end portion of the outer pipe 11 that is on the joint portion 122 side of the inner pipe 12 is hereinafter referred to as end portion 11A. The end portion of the outer pipe 11 that is opposite the joint portion 122 side of the inner pipe 12 is hereinafter referred to as end portion 11B.

The double pipe 1A is partially curved in the central axis X due to a bending process being performed in advance. In other words, the double pipe 1 has at least one curved portion 13, which is a portion where the central axis X is curved. The double pipe 1A of this embodiment has one curved portion 13. In the double pipe 1A, due to the bending process, for example, the position of the inner pipe 12 relative to the outer pipe 11 is shifted, and the side of the outer pipe 11 with a larger curvature along the axial direction at the curved portion 13 has a flattened shape. In other words, in the double pipe 1A, the distance between the inner surface of the outer pipe 11 and the outer surface of the inner pipe 12 is biased around the axial direction of the inner pipe 12.

[2. Double tube molding method]
Next, a method for forming the double pipe 1A will be described with reference to Figs. 2 to 7. The method for forming the double pipe 1A includes an arrangement step, an insertion step, a position control step, a first sealing step, a clamping step, a second sealing step, and a filling step. In the following, as shown in Fig. 7, the finished product obtained after molding from the double pipe 1A is called a double pipe 1B. The method for forming the double pipe 1A is a method for forming the double pipe 1A into a shape designed as the double pipe 1B. The double pipe 1B does not have a significant difference in configuration compared to the double pipe 1A, but the distance between the inner surface of the outer pipe 11 and the outer surface of the inner pipe 12 is constant around the axial direction of the inner pipe 12. That is, in the method for forming the double pipe 1A, the configuration of the double pipe 1A is not significantly changed, and the shapes of the outer pipe 11 and the inner pipe 12 and the position of the inner pipe 12 relative to the outer pipe 11 are adjusted.

[2-1. Placement process]
As shown in Fig. 2, the arrangement step is a step of arranging the double pipe 1A in a space formed by two outer periphery molds 2 (one of which is not shown). The outer periphery mold 2 is made of metal. The mold 2 has a groove 21. The groove 21 is formed in a shape corresponding to the outer shape designed as a finished product, i.e., the outer shape designed as a double pipe 1B. is composed of a plurality of parts 2a, 2b, and 2c, the outer circumferential mold may be composed of a single part.

In the placement process, as shown in FIG. 2, the double pipe 1A is fitted into the groove 21 in one of the outer periphery dies 2, and the outer periphery dies 2 are abutted against each other so that the grooves 21 face each other, thereby placing the double pipe 1A in the space formed by the grooves 21. When placed in this space, the double pipe 1A is completely covered by the two outer periphery dies 2. However, both end faces of the double pipe 1A are not particularly covered.

[2-2. Insertion process]
As shown in Figures 3A and 3B, the insertion step is a step of inserting the inner core bar 3 into the inner tube 12 of the double tube 1A arranged in the space formed by the two outer periphery dies 2 from the end 11B side of the outer tube 11. Figure 3A is a cross-sectional view of a cut surface including the central axis Y of the outer tube 11 at the end 11B of the outer tube 11. The same applies to Figures 4A, 5A, and 5C. Figure 3B is a cross-sectional view of a cut surface perpendicular to the central axis Y of the outer tube 11 at the end 11B of the outer tube 11. The same applies to Figures 4B and 5B.

The inner core bar 3 is made of metal. The inner core bar 3 has an insertion portion 31. As shown in FIG. 3A, the insertion portion 31 is a portion designed to be located inside the inner tube 12 when the inner core bar 3 is inserted into the inner tube 12. The insertion portion 31 is configured to be insertable into the inner tube 12. That is, in the insertion process, specifically, the insertion portion 31 of the inner core bar 3 is inserted into the inner tube 12.

The insertion section 31 is also configured to be able to change the outer diameter of the minimum inclusive circle M shown in FIG. 3B. The minimum inclusive circle M refers to the circle with the smallest outer diameter among the circles that include the insertion section 31 as viewed from the insertion direction Z1 of the insertion section 31 into the inner tube 12. Hereinafter, the insertion direction Z1 of the insertion section 31 into the inner tube 12 is simply referred to as the insertion direction Z1. In this embodiment, the insertion direction Z1 is parallel to the central axis Y of the outer tube 11 at the end 11B of the outer tube 11.

As shown in Figures 3A and 3B, the insertion portion 31 of this embodiment is configured as a first plate-shaped portion 311 and a second plate-shaped portion 312, which are plate-shaped portions extending in the insertion direction Z1. The first plate-shaped portion 311 and the second plate-shaped portion 312 have tapered ends on the forward side in the insertion direction Z1. The first plate-shaped portion 311 and the second plate-shaped portion 312 have a half-moon cross-sectional shape perpendicular to the insertion direction Z1. In the insertion process, the first plate-shaped portion 311 and the second plate-shaped portion 312 are inserted into the inner tube 12 from the end portion 11B side of the outer tube 11 so that the central axis Y of the outer tube 11 passes through the center of the minimum inclusive circle M.

The first plate-shaped portion 311 and the second plate-shaped portion 312 are configured so that the distance between them can be changed when viewed from the insertion direction Z1. Specifically, the first plate-shaped portion 311 and the second plate-shaped portion 312 are configured so that they can move equally in directions away from and toward each other when viewed from the insertion direction Z1. For example, the first plate-shaped portion 311 and the second plate-shaped portion 312 can be moved equally in directions away from each other when viewed from the insertion direction Z1 to widen the distance between the first plate-shaped portion 311 and the second plate-shaped portion 312. This increases the outer diameter of the minimum inclusive circle M.

The outer diameter of the minimum inclusive circle M when the insertion portion 31 is inserted into the inner tube 12 is sufficiently smaller than the inner diameter of the inner tube 12. Therefore, even if the position of the inner tube 12 is misaligned relative to the outer tube 11, the insertion portion 31 is unlikely to collide with the end face of the inner tube 12 when inserted into the inner tube 12. In other words, in the insertion process, the insertion portion 31 can be inserted into the inner tube 12 without any problems.

[2-3. Position regulation process]
As shown in FIGS. 4A and 4B , the position regulating step is a step of enlarging the outer diameter of the minimum inclusive circle M to regulate the position of the inner tube 12 in a state in which the insertion portion 31 is inserted into the inner tube 12. As described above, the insertion portion 31 of this embodiment is configured as the first plate-shaped portion 311 and the second plate-shaped portion 312. In the position regulating step of this embodiment, the first plate-shaped portion As the first plate-shaped portion 311 and the second plate-shaped portion 312 move in directions away from each other by equal amounts as viewed in the insertion direction Z1, the outer diameter of the minimum inclusive circle M is enlarged, and the position of the inner tube 12 is restricted. In this case, the outer diameter of the minimum inclusive circle M is enlarged until it coincides with the inner diameter of the inner tube 12, thereby restricting the position of the inner tube 12. When the insertion portion 31 is inserted into the inner tube 12, if the position of the inner tube 12 is shifted from the center of the outer tube 11 as shown in FIGS. 3A and 3B, the outer diameter of the minimum inclusive circle M is enlarged. 4A and 4B, the position of the inner tube 12 is restricted while being moved to the center of the outer tube 11.

[2-4. First sealing step]
As shown in FIG. 5A and FIG. 5B, the first sealing step is a step of sealing the end 11B of the outer pipe 11 on the side where the insertion portion 31 of the double pipe 1A is inserted, with the intermediate core bar 4. The intermediate core bar 4 is made of metal. The intermediate core bar 4 has a clamping portion 41 and a sealing portion 42. The clamping portion 41 is inserted between the outer tube 11 and the inner tube 12. Hereinafter, the insertion direction Z2 of the clamping portion 41 between the outer tube 11 and the inner tube 12 will be simply referred to as the insertion direction Z2. In this embodiment, the clamping portion 41 is configured to be inserted in the insertion direction Z2. The clamping portion 41 is a cylindrical portion having a predetermined thickness and an axial direction. The clamping portion 41 has a tapered shape at the front end in the insertion direction Z2. It coincides with the direction Z1.

The sealing portion 42 is configured to be able to contact the outer tube 11 over the entire circumference of the outer tube 11. In this embodiment, the sealing portion 42 is a cylindrical portion that continues from the clamping portion 41 rearward in the insertion direction Z2. Like the clamping portion 41, the sealing portion 42 also has an axial direction that is the insertion direction Z2 and has a predetermined thickness. However, as shown in FIG. 5C, the outer surface of the sealing portion 42 is inclined outward when viewed from the insertion direction Z2. In other words, the sealing portion 42 has an expanded diameter. Note that the shape of the sealing portion 42 is shown with emphasis in FIG. 5C.

In the first sealing step of this embodiment, more specifically, as shown in FIG. 5A, the intermediate core bar 4 moves along the insertion direction Z2, and the clamping portion 41 is inserted between the inner tube 12, whose position is regulated by the insertion portion 31, and the outer tube 11 from the end 11B side of the outer tube 11. When the intermediate core bar 4 advances a predetermined distance along the insertion direction Z2, the sealing portion 42 comes into contact with the end face of the end 11B of the outer tube 11. Then, as the intermediate core bar 4 advances further, the end 11B of the outer tube 11 is pressed against the outer peripheral mold 2 by the outer surface of the sealing portion 42, and is formed into a shape corresponding to the outer surface of the sealing portion 42. Specifically, the end 11B of the outer tube 11 is formed into a flare shape. As a result, the end 11B of the outer tube 11 is sealed.

[2-5. Clamping process]
As shown in FIG. 5C , the clamping step is a step of further expanding the outer diameter of the minimum inclusive circle M and clamping the inner tube 12 between the insertion part 31 and the clamping part 41. When the insertion portion 31 is pressed against the clamping portion 41 , the insertion portion 31 is clamped by the clamping portion 41 .

[2-6. Second sealing process]
As shown in FIG. 6A, the second sealing step is a step of sealing the end 11A of the outer tube 11 on the side opposite to the side where the insertion part 31 of the double pipe 1A is inserted, with a contact mold 5. 6A is a cross-sectional view of a cut surface including the central axis Y of the outer tube 11 at the end 11A of the outer tube 11. FIG. 6B is a cross-sectional view of a cut surface including the central axis Y of the outer tube 11 at the end 11A of the outer tube 11. FIG.

The contact type 5 is made of metal. The contact type 5 is configured to be able to contact the outer tube 11 over the entire circumference of the outer tube 11. For example, the contact type 5 may seal the end 11A of the outer tube 11 by molding the end 11A of the outer tube 11, similar to the sealing portion 42 described above.

The order of the second sealing step and the aforementioned insertion step, position control step, first sealing step, and clamping step is not particularly limited. The second sealing step may be performed before or after these aforementioned steps, or may overlap with any of these steps.

[2-7. Filling process]
As shown in FIG. 6A, the filling step is a step of filling the space inside the double pipe 1A with a filler and forming the double pipe 1A into a shape designed as a finished product after molding. For example, the filling step is a step of forming the double pipe 1A into a shape designed as the double pipe 1B.

In this embodiment, as shown by the arrow in FIG. 6A, the filler is filled into the space inside the double tube 1A from the end 11A side of the outer tube 11. The space inside the double tube 1A here includes both the space inside the inner tube 12 and the space between the outer tube 11 and the inner tube 12. The filler in this embodiment is a liquid agent. When the pressure of the filler (liquid pressure in this embodiment) increases in the space inside the double tube 1A, the outer tube 11 is pressed from the inner side and deformed as shown in FIG. 7. As described above, the outer surface side of the double tube 1 is covered by the grooves 21 in the two outer periphery molds 2. Therefore, the outer tube 11 is molded into a shape corresponding to the grooves 21, that is, a shape designed as the outer shape of the double tube 1B.

The double pipe 1B, which is a finished product after molding, is used, for example, as an exhaust pipe that forms a flow path for exhaust gas from an internal combustion engine of an automobile.
3. Effects
According to the embodiment described above in detail, the following effects can be obtained.

(3a) When applying a molding method using a filler to a double pipe having a curved portion such as double pipe 1A, if the filler is filled into the space inside the double pipe without any particular restrictions on the position of the inner pipe relative to the outer pipe, as shown in Figure 8, the position of the inner pipe will shift relative to the outer pipe due to the area difference between the side with the larger curvature along the axial direction and the side with the smaller curvature on the inner surface of the inner pipe at the curved portion. This makes it difficult to mold the double pipe into the designed shape.

In contrast, the method of molding the double pipe 1A involves filling the space inside the double pipe 1A with a filler while the position of the inner pipe 12 is regulated by the insertion portion 31 and the end portion 11B of the outer pipe 11 is sealed by the sealing portion 42, and molding the double pipe 1A into the shape designed for the double pipe 1B. With this configuration, because the position of the inner pipe 12 is regulated when filling with the filler, the position of the inner pipe 12 is less likely to shift relative to the outer pipe 11 at the curved portion 13. This makes it easier to mold the double pipe 1A into the shape designed for the double pipe 1B.

(3b) In the method for forming the double pipe 1A, the inner space of the double pipe 1A is filled with a filler while the inner pipe 12 is clamped between the clamping portion 41 and the insertion portion 31. With this configuration, when filling with the filler, the position of the inner pipe 12 is less likely to shift relative to the outer pipe 11 at the curved portion 13. This makes it easier to mold the double pipe 1A into the shape designed for the double pipe 1B.

(3c) In the method for forming the double pipe 1A, the end 11B of the outer pipe 11 is sealed by molding it into a shape corresponding to the sealing portion 42 with the sealing portion 42. With this configuration, for example, even if the end 11B of the outer pipe 11 is deformed due to bending or the diameter of the outer pipe 11 varies from one individual to another, the end 11B of the outer pipe 11 can be sealed. Therefore, even in such cases, leakage of the filler from the end 11B of the outer pipe 11 can be suppressed.

(3d) In the double pipe 1A, the bending process may cause the position of the inner pipe 12 to shift relative to the outer pipe 11 at the end 11B of the outer pipe 11. In such a case, the insertion portion 31 may interfere with the inner pipe 12, causing a problem that the insertion portion 31 cannot be inserted into the inner pipe 12.

However, the insertion portion 31 is configured to be able to change the outer diameter of the minimum inclusive circle M. With this configuration, the insertion portion 31 is less likely to interfere with the inner tube 12. This makes it less likely that the insertion portion 31 will be unable to be inserted into the inner tube 12 due to interference with the inner tube 12.

(3e) The end of the insertion portion 31 on the forward side in the insertion direction Z1 is tapered. With this configuration, the insertion portion 31 is less likely to interfere with the inner tube 12. This makes it even less likely that the insertion portion 31 will be unable to be inserted into the inner tube 12 due to interference with the inner tube 12.

4. Other embodiments
Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments and can take various forms.

(4a) In the above embodiment, the double pipe 1A in which a gap is provided between the inner surface of the outer pipe 11 and the outer surface of the inner pipe 12 is exemplified as an application target of the molding method. However, the molding method may be applied to a double pipe having a different structure from the double pipe 1A, for example, the double pipe 1C shown in FIG. 9. In the double pipe 1C, there is no gap between the inner surface of the outer pipe 11S and the inner surface of the inner pipe 12S, except for the end of the inner pipe 12S. Even when the above-mentioned molding method is applied to such a double pipe 1C, the filler is filled with the position of the inner pipe 12S being regulated, so that the double pipe 1C can be easily molded into a shape as designed. In the example shown in FIG. 9, the double pipe 1C is molded into a shape designed as the double pipe 1D. The double pipe 1D has a shape in which a gap is provided between the outer surface of the inner pipe 12S and the inner surface of the outer pipe 11S, as in the above-mentioned double pipe 1B. The gap is constant around the axial direction of the inner pipe 12S.

(4b) In the above embodiment, the insertion portion 31 is configured as two parts, the first plate-shaped portion 311 and the second plate-shaped portion 312, but the configuration of the insertion portion is not particularly limited. The insertion portion may be configured as a single part, or may be configured as three or more parts. The shape of the insertion portion is also not limited to a plate shape like the first plate-shaped portion 311 and the second plate-shaped portion 312, and may be, for example, a rod shape. In addition, the end of the insertion portion on the forward side in the insertion direction into the inner tube does not have to be tapered like the first plate-shaped portion 311 and the second plate-shaped portion 312.

(4c) In the above embodiment, the insertion portion 31 changes the outer diameter of the minimum inclusive circle M by the relative movement of the first plate-shaped portion 311 and the second plate-shaped portion 312. However, the change in the outer diameter of the minimum inclusive circle M may be achieved in a manner other than the relative movement of multiple parts.

(4d) In the above embodiment, in the position restriction process, the outer diameter of the minimum inclusive circle M is expanded until it matches the inner diameter of the inner tube 12, and the position of the inner tube 12 is restricted. However, the degree of expansion of the outer diameter of the minimum inclusive circle M in the position restriction process may be limited to a degree that allows the position of the inner tube 12 to be restricted. In other words, the outer diameter of the minimum inclusive circle M does not necessarily have to be expanded until it matches the inner diameter of the inner tube 12 in the position restriction process.

(4e) In the above embodiment, the clamping portion 41 is a cylindrical portion, but the shape of the clamping portion is not particularly limited. In other words, in the above embodiment, the clamping portion 41 is configured to cover the entire circumference of the inner tube 12 when inserted between the outer tube 11 and the inner tube 12, but the clamping portion may be configured to cover a portion of the axial circumference of the inner tube in this state.

(4f) In the above embodiment, the intermediate core bar 4 has both the clamping portion 41 and the sealing portion 42, but the clamping portion and the sealing portion may each be provided in a separate member. Also, the clamping portion does not necessarily have to be provided. In other words, the method for forming the double pipe does not necessarily have to include a clamping process.

(4g) In the above embodiment, the end 11B of the outer tube 11 is sealed by molding the sealing portion 42 into a shape corresponding to the sealing portion 42. However, the sealing of the end of the outer tube may be achieved in a manner other than molding with a sealing portion. For example, the end of the outer tube may be sealed by simply pressing in the axial direction of the outer tube. Also, for example, the end of the outer tube may be sealed by pressing from the radial outside of the outer tube, or may be sealed by a method using an O-ring.

(4h) In the above embodiment, the space inside the double pipe 1A is filled with a filler from the end 11A side of the outer pipe 11. However, the method of filling the filler is not particularly limited, and for example, the filler may be filled from the end 11B side of the outer pipe 11.

(4i) The functions of one component in the above embodiments may be distributed among multiple components, or the functions of multiple components may be integrated into one component. In addition, part of the configuration of the above embodiments may be omitted. In addition, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

1A...Double tube, 11...Outer tube, 12...Inner tube, 121...Expanded diameter part, 122...Joining part, 13...Curved part, 2...Outer periphery type, 21...Groove part, 3...Inner core bar, 31...Insertion 311...First plate-like part, 312...Second plate-like part, 4...Intermediate metal core, 41...Snipping part, 42...Sealing part, 5...Contact type, M...Minimum enclosing circle.

Claims (4)

A method for forming a double-walled pipe having at least a part of a curved central axis, comprising the steps of:
An insertion portion configured to be insertable into an inner pipe of the double pipe, the insertion portion being configured to be capable of changing an outer diameter of a minimum including circle including the insertion portion as viewed from an insertion direction, into the inner pipe;
In a state in which the insertion portion is inserted into the inner tube, the outer diameter is enlarged to regulate a position of the inner tube;
a clamping portion configured to be insertable between the inner pipe and the outer pipe of the double pipe is inserted between the inner pipe and the outer pipe whose position is regulated by the insertion portion, and then the outer diameter is further expanded to clamp the inner pipe between the clamping portion and the insertion portion;
sealing an end of the outer tube on a side where the insertion portion is inserted in the double tube with a sealing portion configured to be in contact with the outer tube over an entire circumference of the outer tube;
In a state in which the inner tube is clamped by the clamping portion and the insertion portion and the end of the outer tube is sealed by the sealing portion, filling a space inside the double tube with a filler and forming the double tube into a predetermined shape;
A method for forming a double pipe comprising the steps of: The method for forming a double pipe according to claim 1 ,
A method for molding a double pipe, wherein an end of the outer pipe on the side where the insertion portion is inserted in the double pipe is sealed by molding the sealing portion into a shape corresponding to the sealing portion. A method for forming a double-walled pipe having at least a portion of a curved central axis, comprising the steps of:
An insertion portion configured to be insertable into an inner pipe of the double pipe, the insertion portion being configured to be capable of changing an outer diameter of a minimum including circle including the insertion portion as viewed from an insertion direction, into the inner pipe;
In a state in which the insertion portion is inserted into the inner tube, the outer diameter is enlarged to regulate a position of the inner tube;
sealing an end of the outer tube on a side where the insertion portion is inserted in the double pipe with a sealing portion configured to be in contact with the outer tube over an entire circumference of the outer tube;
In a state in which the position of the inner tube is regulated by the insertion portion and the end of the outer tube is sealed by the sealing portion, a filler is filled into the space inside the double tube, and the double tube is molded into a predetermined shape;
Equipped with
A method for molding a double pipe, wherein an end of the outer pipe on the side where the insertion portion is inserted in the double pipe is sealed by molding the sealing portion into a shape corresponding to the sealing portion . A method for forming a double-walled pipe according to any one of claims 1 to 3,
The method for molding a double pipe, wherein the insertion portion has a tapered end portion on a front side in the insertion direction.

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