JP2009079838A - Duct connecting structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily connect a branch pipe to a main pipe, and to keep thermal insulation performance in its connecting part. <P>SOLUTION: An opening 2 is arranged in the main pipe 1 having a thermal insulation material layer 5, and a root part 12 of the branch pipe 11 is fixed to its opening 2. A freely bendable claw part 15 projecting in the pipe axis direction from the edge 12a of its root part 12 is arranged in the root part 12 of the branch pipe 11, and is projected to the claw part 15 side by arranging a thermal insulation material layer 13a on the outer periphery of the root part 12 of its branch pipe 11. By bending its claw part 15 to the outer diameter side by being inserted inside the opening 2, the thermal insulation material layer 13a is deformed and pressed to an inner peripheral surface of the main pipe 1, and a pin 16 fixed to its claw part 15 is pulled out to the outside of the main pipe 1, and is locked on a fixing member 17 arranged along an outer peripheral surface of the main pipe 1. With such a constitution, the thermal insulation performance is kept in the connecting part of the main pope 1 and the branch pipe 11, and these works can be performed from the outside of the main pipe 1, and can be easily performed with excellent workability. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a branching structure of piping (duct) for air conditioning equipment arranged in a building or the like.

  In order to ensure air conditioning efficiency, pipes (air ducts) for air conditioning equipment arranged in buildings and the like are provided with a heat insulating material around them. These ducts are arranged from the main body of the air conditioner arranged outdoors or outdoors to the room through the space behind the ceiling. Moreover, there are many cases where it is branched in the middle and distributed to each room.

As a tubular body used for these ducts, for example, a tubular body in which a heat insulating material layer made of glass wool or the like is provided on the outer periphery of a tubular metal member is used.
In some cases, a flexible tube called a flexible duct is used.

  For example, as shown in FIG. 9, in the flexible duct F, a heat insulating material layer 5 such as glass wool is provided on the outer periphery of a spiral metal core material 4, and the outer peripheral side of the heat insulating material layer 5 is a resin. It is covered with an exterior material 6 made of a manufactured sheet. In addition, since the inner peripheral side of the metal core material 4 is also covered with the interior material 3 made of a resin sheet, the heat insulating material layer 5 is not exposed to the outside except the end surface in the tube axis direction. Yes.

In addition, the narrowed portion 7 (see FIGS. 7A and 7B, which are explanatory diagrams of the embodiment of the present invention) is provided at the end of the flexible duct F so that it can be connected to other ducts.
In the narrowed portion 7, the heat insulating material layer 5 is slightly compressed to have a small diameter, and the interior material 3 and the exterior material 6 are sealed at the end of the narrowed portion 7. This sealing may be performed in advance in a factory, or after the flexible duct F is cut to a predetermined length in the field, the end face may be covered with an adhesive tape S or the like.

  When branching a duct, an opening for branching that penetrates the inside and outside of the pipe body is usually provided in the middle of the pipe body constituting the main pipe (hereinafter simply referred to as “main pipe”). A tube (hereinafter simply referred to as “branch tube”) is connected.

  An example of the configuration is shown in FIG. The branch structure shown in FIG. 10 will be described. First, the cylindrical support members 33 and 33 divided into two are inserted into the main pipe 1. The support members 33 and 33 are shaped along the inner peripheral surface of the main pipe 1. A base plate 32 having a shape along the outer peripheral surface of the main pipe 1 is integrally fixed to the base portion of the branch pipe 11.

Next, through holes having the same inner diameter are formed in the support members 33 and 33 and the base plate 32, respectively, and the support members 33 and 33 and the base plate 32 are screwed together by aligning the positions of both through holes. The main tube 1 is cut at the through hole. The incised portion becomes the opening 2, and the space in the main pipe 1 and the space in the branch pipe 11 communicate with each other through the opening 2. Further, another main pipe 21 is connected to the tip of the branch pipe 11, and the duct leads to each room.
At this time, the connection portion between the main pipe 1 and the branch pipe 11, that is, the base part of the branch pipe 11 and the outer peripheral surface of the base plate 32 are in a state in which the heat insulating material layer 5 is interrupted. It is repaired by etc. and the heat insulation of the connection part is hold | maintained (for example, refer patent document 1).

  Further, as shown in FIG. 11, a flange portion 34 projecting to the outer peripheral side is provided at the end portion of the branch pipe 11 so that the flange portion 34 contacts the inner peripheral surface around the opening 2 provided in the main pipe 1. Some branch pipes 11 are protruded from the main pipe 1 and fixed (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 10-9655 JP 2007-113803 A

10, after the branch pipe 11 is connected to the main pipe 1, the connection portion, that is, the root portion of the outer peripheral surface of the branch pipe 11 close to the base plate 32 and the outer periphery of the base plate 32. Each surface needs to be repaired with additional heat insulating material or tape so as not to be exposed to the outside air.
In the installation work of the flexible duct F that involves cutting at a large number of places, it is troublesome to carry out such a repair work of the heat insulating material layer 5 on the spot for each cutting place, and it is closed like a ceiling. In such a space, it may be difficult to perform such detailed work.

Further, according to the branch structure of the duct shown in FIG. 11, since the flange portion 34 of the branch pipe 11 is larger than the opening 2 provided in the main pipe 1, it is necessary to insert the branch pipe 11 from the inside of the main pipe 1. . For this reason, the operation | work required for the connection of the main pipe 1 and the branch pipe 11 must be performed inside the narrow main pipe 1, and the operation | work is complicated. Moreover, it can be said that it is a connection structure which cannot be employ | adopted when the main pipe 1 is long.
Further, after connecting the branch pipe 11 to the main pipe 1, the connection portion thereof, that is, the root portion near the main pipe 1 side of the outer peripheral surface of the branch pipe 11 and the periphery of the branch pipe 11 among the outer peripheral surface of the main pipe 1. This part needs to be repaired with an additional heat insulating material or a tape so as not to be exposed to the outside air as in the case of FIG.

In addition, in FIG. 11, when the main pipe 1 is a flexible duct F using a spiral core material 4, when the main pipe 1 is cut and the opening 2 is provided, the peripheral portion of the opening 2 is The core material 4 is cut. For this reason, there exists a problem that the cut surface of the core material 4 opposes the outer peripheral surface of the branch pipe 11. FIG.
Usually, since the cut surface of the core material 4 remains sharply pointed, when the branch pipe 11 is connected to the main pipe 1, the core material 4 is attached to the heat insulating material layer 5 provided on the outer periphery of the branch pipe 11. The tip may be slid and the heat insulating material layer 5 may be damaged. If the heat insulating material layer 5 is damaged, the heat insulating effect of the branch pipe 11 is inhibited, which is not preferable.

  Accordingly, an object of the present invention is to make it possible to easily connect a branch pipe to the main pipe and to maintain heat insulation at the connecting portion.

  In order to solve the above-mentioned problems, the present invention is provided with a heat insulating material layer on the outer periphery of a main pipe, an opening penetrating the inside and outside of the main pipe, and a branch pipe in the main pipe around the opening The space in the main pipe communicates with the space in the branch pipe through the opening, and a heat insulating material layer provided on the outer periphery of the branch pipe is spaced from the inside to the outside of the main pipe. In the connection structure of the ducts connected without any gaps, a foldable claw portion that protrudes in the tube axis direction from an end edge of the branch portion is provided at the root portion of the branch pipe, and at least the outer periphery of the root portion of the branch pipe is insulated. By providing a material layer and projecting the heat insulating material layer to the claw part side from the edge of the root part, inserting the claw part into the opening and bending it to the outer diameter side, the heat insulating material layer is Deform and press against the inner peripheral surface of the main Is fixed to the main pipe to branch pipes, adopted a configuration in which the heat insulating material layer provided on the outer periphery of the branch pipe was over outwardly to continuously without a gap from the inside of the main pipe.

  Further, if the heat insulating material layer provided on the outer periphery of the branch pipe has airtightness, the air flow in the main pipe does not leak along the outer periphery of the branch pipe, and higher heat insulation can be maintained. Moreover, it can function as a heat insulating material in a portion where the heat insulating material layer is exposed to the outside air.

  Further, the heat insulating material layer provided on the outer periphery of the branch pipe includes a heat insulating material layer provided on the outer periphery of the root portion, and a heat insulating material provided on the outer periphery of another tubular body connected to the tip side of the root portion. It can also be set as the structure currently formed so that a layer may continue without a gap.

  In this way, the connection work between the main pipe and the branch pipe can be performed from the outside of the main pipe, the workability is good, and it is easy to prevent the heat insulating material layer from being interrupted at the connection portion.

In these configurations, it is desirable to connect the two by an appropriate method so that the heat insulating material layer at the base and the heat insulating material layer of the main pipe are continuous.
In other words, the two heat-insulating material layers are brought into contact with each other so that there is no gap between them and brought into a continuous state, and in addition, the two are connected by an appropriate method so that the boundary between the two heat-insulating material layers is not expanded. . For example, if it is connected with an adhesive tape so as to block the boundary between the two heat insulating material layers, and the connection is made so that the heat insulating material layer of the base portion and the heat insulating material layer of the main pipe are continuous without a gap, the heat insulating effect Can be exhibited better. It is desirable that the adhesive tape is continuously applied over the entire circumference of the branch pipe or opening.
The same applies to the case where the heat insulating material layer provided on the outer periphery of the root portion and the heat insulating material layer provided on the outer periphery of another tubular body connected to the distal end side of the base portion are continuous without a gap. A connection method using an adhesive tape or the like can be employed.

Further, a pin is fixed to the claw portion, the pin is pulled out to the outside of the main pipe, and is locked to a fixing member provided with at least a part of the main pipe interposed therebetween, whereby the branch pipe is connected to the main pipe. The structure fixed to can be adopted.
The branch pipe and the main pipe can be fixed with a certain degree of strength by bending the claw part to the outer diameter side and along the inner peripheral surface of the main pipe. In this way, fixing means using pins are adopted. Then, the branch pipe and the main pipe can be fixed more firmly. In addition, since the fixing work using the pins can be performed from the outside of the main pipe, a wide working space can be secured, and therefore workability is good.
The fixing member may be, for example, a plate-like member along the outer peripheral surface of the main pipe having a function of locking the pin, or may be a rod-like member or a block-like member. Good. Further, the fixing member may be provided in a portion that enters the inner diameter side slightly from the outer peripheral surface of the main pipe. That is, it suffices that at least a part of the main constituent member is sandwiched between the claw portion and the fixing member.
Moreover, as the locking method, it is the structure which latches the latching | locking part provided in the pin to the to-be-latched part provided in the said fixing member, for example, the latching which provided the to-be-latched part in the said fixing member You may make it form the said latching | locking part by making it a hole and crimping the edge part of the pin penetrated in the latching hole.

  In the above configuration, if the edge of the root portion is formed along the inner peripheral surface of the main pipe, the branch pipe does not protrude inward from the inner peripheral surface of the main pipe in the space within the main pipe. Therefore, the flow of fluid in the duct becomes smooth.

Further, when the main pipe is a flexible duct, the above configuration works more advantageously.
In other words, a flexible duct is one in which a heat insulating material layer such as glass wool is provided on the outer periphery of a spiral metal core material. The core material is cut at the peripheral portion. For this reason, the cut surface of the core material faces the outer peripheral surface of the root portion of the branch pipe inserted into the opening.

However, since the branch pipe is inserted into the opening from the outside of the main pipe, it is possible to minimize the sliding between the heat insulating material layer provided at the root portion and the cut end portion of the core material.
Further, since the core material is disposed in the portion near the inner diameter of the main pipe, the heat insulating material layer at the base portion deformed by bending the claw portion presses the cut end portion toward the outer diameter side. For this reason, it can prevent that a cutting | disconnection edge part moves and it protects so that another heat insulating material layer may not be damaged by the cutting | disconnection edge part.

Moreover, the heat insulating material layer of the said base part can be comprised with the foamed rubber sheet wound around the outer periphery of the said branch pipe.
As a heat insulating material layer provided at the root part of the branch pipe, for example, in the case of a configuration in which glass wool or the like is covered with an exterior material made of a resin sheet, the resin sheet is particularly fragile, so it is not preferable to touch the cut end of the core material directly. Cases are also conceivable.

  However, if the heat insulating material layer is a foamed rubber sheet, damage to the heat insulating material layer will affect the heat insulating performance even if the cut end portion of the core material touches or slides directly on the foamed rubber sheet. It can be said that it is hard to produce.

  Since the present invention is configured as described above, the branch pipe can be easily connected to the main pipe, and heat insulation can be secured at the connecting portion.

  An embodiment will be described with reference to the drawings. This embodiment is a branch structure of a duct in which another pipe body 21 made of a flexible duct F is connected to a main pipe 1 composed of a flexible duct F via a branch pipe 11. The main pipe 1 assumes a long flexible duct F having a certain length, and the duct is branched in the middle of the main pipe 1 in the pipe axis direction.

  The configuration of the flexible duct F is the same as that of the conventional example, and a heat insulating material layer 5 such as glass wool is provided on the outer periphery of a spiral metal core material 4, and the outer peripheral side of the heat insulating material layer 5 is a resin. It is covered with the exterior packaging material 6 made. Further, the inner peripheral side of the core material 4 is also covered with the resin interior material 3. Both the interior material 3 and the exterior material 6 are made of resin sheets.

  The branch pipe 11 is formed in a tubular shape by using a metal plate P punched as shown in FIG. 6 and joining the edges 11a and 11b thereof. For this joining, techniques such as welding, adhesion, and caulking can be employed.

The branch pipe 11 is provided with a claw part 15 which can be bent and protrudes in the pipe axis direction from an end edge 12a of the root part 12 at the root part 12 on the main pipe 1 side.
As shown in FIG. 1, the claw portions 15 are alternately provided with claw portions 15 a having a relatively long protruding length and claw portions 15 b having a short length along the circumferential direction. The claw portion 15a is provided with a pin insertion hole 15c. Each claw 15 is provided with a long hole 11c so that each claw 15 can be easily bent at the edge 12a of the root portion 12.
In addition, if the said long hole 11c is provided in two places in each said nail | claw 15a, 15b, those nail | claw 15a, 15b will become easier to bend.

  The attachment operation of the branch pipe 11 will be described. As shown in FIG. 1, the side peripheral surface of the main pipe 1 is cut and a circular opening 2 is provided. At this time, the interior material 3, the core material 4, the heat insulating material layer 5, and the exterior material 6 are each cut.

The heat insulating material layer 13a is wound around the entire outer periphery of the root portion 12 of the branch pipe 11 and fixed by adhesion. A foamed rubber sheet is used for the heat insulating material layer 13 a provided in the root portion 12.
The heat insulating material layer 13a made of the foamed rubber sheet protrudes toward the claw part 15 from the end edge 12a of the base part 12, and is fixed to a state positioned slightly in front of the tip of the claw part 15a.

The branch pipe 11 is inserted into the opening 2 from the root portion 12 thereof. The hand is inserted from the inside of the branch pipe 11 and the opening 2, and the claw portions 15a and 15b are bent to the outer diameter side to deform the heat insulating material layer 13a and press it against the inner peripheral surface of the main pipe 1 ( (See FIG. 2).
At this time, if a double-sided tape is attached to the outer peripheral surface of the front end of the foamed rubber sheet, when the foamed rubber sheet is pressed against the inner peripheral surface of the main pipe 1, the inner circumference of the main pipe 1 is more firmly secured. Adhering to the surface increases airtightness.
Subsequently, the pin 16 is inserted into the hole 15c of the claw portion 15a. The head portion 16 a of the pin 16 is sized so as not to pass through the hole 15 c, and the shaft portion 16 b of the pin 16 penetrates the interior material 3, the heat insulating material layer 5, and the exterior material 6 to the outside of the main pipe 1. Pulled out. Since the interior material 3, the heat insulating material layer 5, and the exterior material 6 are soft, the pin 16 can penetrate the main pipe 1 manually.

The tip 16c of the pin 16 is inserted into a hole of a plate-like fixing member 17 provided along the outer peripheral surface of the main pipe 1, and the pin 16 is crimped while pulling the pin 16 to the outer diameter side. Is prevented from coming out of the hole of the fixing member 17. The claw portion 15 a is immovable with respect to the main pipe 1 via the fixing member 17 and the pin 16, and as a result, the branch pipe 11 is fixed to the main pipe 1.
Since the pulling and caulking of the pin 16 can be performed in a wide space outside the main pipe 1, it can be said that the workability is good.

  The fixing member 17 can also be provided inside the exterior material 6. If the fixing member 17 is inside the exterior material 6, the aesthetic appearance is improved and condensation of the fixing member 17 due to heat transfer from the pin 16 can be prevented. At this time, as shown in FIG. 8, the fixing member 17 may be provided between the outer peripheral surface of the heat insulating material layer 5 and the exterior material 6, or may be embedded in the heat insulating material layer 5. Moreover, if the pin 16 and the fixing member 17 are made of resin, the heat transfer can be more effectively suppressed.

In place of the caulking and fixing of the pin 16, the pin 16 may be prevented from being detached from the fixing member 17 by bending the tip of the pin 16, or the pin 16 may be a bolt shaft and the bolt shaft It is also conceivable that the tip of the screw is inserted into the hole of the fixing member 17 and tightened with a nut.
That is, as a method of locking the pin 16 and the fixing member 17, the locking portion provided on the pin side is locked to the locked portion provided on the fixing member side, and the pin 16 is fixed to the fixing member 17. Any configuration that is fixed so as not to come off may be used.

  In this embodiment, as shown in FIGS. 4 and 5, the boundary between the heat insulating material layer 13 a provided on the outer periphery of the root portion 12 and the heat insulating material layer 5 around the opening 2 of the main pipe 1 is further closed. Since the adhesive tape T is affixed, a gap is formed at the boundary between the heat insulating material layer 13a of the root portion 12 and the heat insulating material layer 5 of the main pipe 1 during or after the duct is disposed. This prevents the heat insulation from deteriorating.

Further, since the heat insulating material layer 13a is a foamed rubber sheet, even if the cut end portion of the core material 4 directly touches or slides on the foamed rubber sheet, the heat insulating material affects the heat insulating performance. It can be said that the layer 13a is hardly damaged.
Moreover, since the foamed rubber sheet has airtightness, the airflow in the main pipe 1 does not leak along the outer periphery of the branch pipe 11. For this reason, higher heat insulation can be maintained in the connecting portion of the branch pipe. Further, even in a portion where the heat insulating material layer 13a is exposed to the outside air, it can function as a heat insulating material.

Further, since the end edge 12 a of the root portion 12 is formed along the inner peripheral surface 1 a of the main pipe 1, the end edge 12 a is inward from the inner peripheral surface 1 a in the space in the main pipe 1. It does not protrude. For this reason, the smooth gas flow in the duct is not obstructed.
Such an effect is made possible by forming the edge 12a shown on the right side in the figure in a wave shape in the metal plate P shown in FIG.

  Further, as shown in FIG. 4, another pipe body 21 made of a flexible duct F is connected to the distal end side of the branch pipe 11. This tubular body 21 has a narrowed portion 7 at an end portion facing the main tube 1, and the configuration thereof includes an interior material 3, a core material 4, a heat insulating material layer 13 b, an exterior, as shown in FIG. The material 6 and the tape S of the narrowed portion 7 are the same as the flexible duct F constituting the main pipe 1.

As shown in FIG. 5, the heat insulating material layer 13 b of the tubular body 21 includes a heat insulating material layer 13 a provided on the outer periphery of the root portion 12 by fitting the tubular body 21 to the outer periphery on the distal end side of the branch pipe 11. It becomes the heat insulating material layer 13 which adheres closely without a gap and continues along the outer periphery of the branch pipe 11.
In addition, you may affix the adhesive tape T so that the boundary of the contact | adherence part of the heat insulating material layer 13a provided in the outer periphery of the said base part 12 and the heat insulating material layer 13b provided in the outer periphery of the tubular body 21 may be plugged up.
Further, as shown in FIG. 5, if the throttle portion 7 of the pipe body 21 is connected so as to overlap the heat insulating material layer 13 a provided on the outer periphery of the root portion 12 of the branch pipe 11, a metal is formed from the outer periphery of the throttle portion 7. The branch pipe 11 and the pipe body 21 can be fixed by winding and tightening a band.

In the above-described embodiment, the case where the main pipe 1 is a long flexible duct F has been described. In addition, as shown in FIGS. 7A and 7B, the main pipe 1 has a relatively short length. Even in the case of the flexible duct F, the duct connection structure of the present invention can be adopted.
7 (a) and 7 (b), the narrowed portions 7 and 7 at both ends of the main pipe 1 are fitted on the outer periphery of a joint pipe (not shown) and connected to the next main pipe 1 through the joint pipe. It has come to be.

The duct connection structure of the present invention is also applicable when the main pipe 1 is formed of a pipe body other than the flexible duct F. For example, the duct connection structure of the present invention can be employed even in a configuration in which the main pipe 1 is fixed by wrapping a heat insulating material layer 5 such as glass wool around the outer periphery of a tubular body made of a cylindrical metal such as a spiral duct.
When a spiral duct or the like is used, it is difficult to manually penetrate the pin 16 through the main pipe 1. Therefore, before inserting the pin 16, a hole is drilled from the outside of the main pipe 1 with a drill or the like. Is desirable.

  Further, in each of the above embodiments, the heat insulating material layer 13 provided on the outer periphery of the branch pipe 11 is connected to the heat insulating material layer 13a provided on the outer periphery of the root portion 12 and the tip side from the root portion 12. In addition, the heat insulating material layer 13b provided on the outer periphery of the other pipe body 21 is continuously formed without a gap, but as another embodiment, for example, on the outer periphery of the branch pipe 11, from the root portion 12 After providing the heat insulating material layer 13 in the entire region up to the distal end side, the connection work to the main pipe 1 may be performed.

At this time, the other pipe body 21 connected to the distal end side of the branch pipe 11 may be the pipe body 21 that is connected to the outer periphery of the heat insulating material layer 13 of the branch pipe 11. It may be a tube body 21 that is connected to the inner periphery of the tube 21.
In addition to the flexible duct F, this tubular body 21 is a tubular body 21 in which a heat insulating material layer 5 such as glass wool is wound around the outer periphery of a tubular body made of a cylindrical metal such as a spiral duct, or another tubular body 21. It may be a pipe body 21 of a joint pipe used for connecting to the pipe.
Further, the heat insulating material layer 13a of the branch pipe 11 is not limited to the foamed rubber sheet shown in the above embodiment, and a rubber sheet without foaming can also be used. Moreover, common heat insulating materials, such as glass wool, can also be used.

The disassembled perspective view which shows the state before connecting a branch pipe to the main pipe in one Embodiment. The perspective view which shows the inside of the main after connecting a branch pipe to the main in the same embodiment Cross-sectional view of the same embodiment The perspective view which shows the state which connects another pipe body to the branch pipe fixed to the main pipe 3 is an enlarged view of the main part of FIG. Branch pipe development An exploded perspective view showing a state before the branch pipe is connected to the main pipe Is a perspective view showing a state after the connection The principal part enlarged view of other embodiment Explanatory drawing showing the configuration of the flexible duct Disassembled perspective view of conventional example Cross section of conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main pipe 2 Opening 3 Interior material 4 Core material 5, 13, 13a, 13b Heat insulation material layer 6 Exterior material 7 Restriction part 11 Branch pipe 12 Base part 15, 15a, 15b Claw part 16 Pin 17 Fixing member 21 Other pipe body F Flexible duct P Metal plate

Claims (8)

A heat insulating material layer 5 is provided on the outer periphery of the main pipe 1, an opening 2 penetrating the inside and outside of the main pipe 1 is provided, and a root portion 12 of the branch pipe 11 is fixed to the main pipe 1 around the opening 2. Then, the space in the main pipe 1 and the space in the branch pipe 11 communicate with each other through the opening 2, and the heat insulating material layer 13 provided on the outer periphery of the branch pipe 11 extends from the inner side to the outer side of the main pipe 1. In the duct connection structure that is continuous without gaps,
The root portion 12 of the branch pipe 11 is provided with a bendable claw portion 15 projecting from the edge 12a of the root portion 12 in the tube axis direction, and at least the heat insulating material layer 13a on the outer periphery of the root portion 12 of the branch pipe 12. And the heat insulating material layer 13a protrudes toward the claw 15 from the edge 12a of the base 12, and the claw 15 is inserted into the opening 2 and bent to the outer diameter side. The heat insulating material layer 13a is deformed and pressed against the inner peripheral surface of the main pipe 1 to fix the branch pipe 11 to the main pipe 1, and the heat insulating material layer 13a provided on the outer periphery of the branch pipe 11 A duct connection structure characterized in that it is continuous without gaps from the inside to the outside of the main pipe 1.   The duct connection structure according to claim 1, wherein the heat insulating material layer 13 a provided on the outer periphery of the branch pipe 11 has airtightness.   The heat insulating material layer 13 provided on the outer periphery of the branch pipe 11 is provided on the outer periphery of the heat insulating material layer 13a provided on the outer periphery of the root portion 12 and the other tubular body 21 connected to the tip side of the root portion 12. The duct connection structure according to claim 1 or 2, wherein the heat insulating material layer (13b) to be provided is formed continuously without a gap.   The heat insulating material layer 13a of the base portion 12 and the heat insulating material layer 5 of the main tube 1 are connected by the adhesive tape T, so that the heat insulating material layer 13a of the root portion 12 and the heat insulating material layer 5 of the main tube 1 are connected. 4. The duct connection structure according to claim 1, wherein the duct connection structure is continuous without a gap.   A pin 16 is fixed to the claw portion 15, the pin 16 is pulled out to the outside of the main pipe 1, and locked to a fixing member 17 provided with at least a part of the main pipe 1 interposed therebetween. 11. The duct connection structure according to claim 1, wherein 11 is fixed to the main pipe 1.   6. The duct connection structure according to claim 1, wherein an end edge 12 a of the root portion 12 is formed along an inner peripheral surface 1 a of the main pipe 1.   The duct connection structure according to claim 1, wherein the main pipe 1 is a flexible duct.   The duct connection structure according to claim 7, wherein the heat insulating material layer 13 a of the root portion 12 is a foamed rubber sheet wound around an outer periphery of the branch pipe 11.

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