JP2022118098A - Vertical pipe structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vertical pipe structure allowing easy work of getting down from the inside of a shaft tube to the bottom face of a vertical shaft.

SOLUTION: A vertical pipe structure of the present invention is arranged in a vertical shaft connecting an upper water passage with a lower water passage, and comprises: a cylindrical vertical pipe having an upper end communicated with the upper water passage and a lower end communicated with the lower water passage; a cylindrical shaft tube arranged inside the vertical pipe and having a lower end at a position separated upward from the bottom face of the vertical shaft by a predetermined length; a guide plate spirally extended in the axial direction of the shaft tube so as to connect an outer peripheral surface of the shaft tube to an inner peripheral surface of the vertical pipe; a first ladder arranged on an inner wall face of the shaft tube so as to extend in the axial direction of the shaft tube; multiple scaffold members attached in the axial direction of the shaft tube with predetermined intervals; a second ladder composed to selectively take a first embodiment of arranged inside the shaft tube or a second embodiment of detachably bridged between the lower end of the shaft tube and the bottom face of the vertical shaft; and first holding means holding the second ladder in the first embodiment inside the shaft tube.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2022,JPO&INPIT

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical pipe structure arranged in a shaft connecting an upper waterway and a lower waterway.

Various underground structures have been proposed for treating sewage and rainwater. For example, Patent Literature 1 discloses a vertical pipe structure arranged in a shaft connecting an upper pipe line and a lower pipe line arranged below. The vertical pipe structure has a vertical pipe arranged in the vertical shaft, an axial pipe arranged inside the vertical pipe, and a helical guide plate attached to the outer peripheral surface of the axial pipe. there is The water that has flowed into the vertical pipe from the upper horizontal pipe flows through the vertical pipe into the lower pipe while drawing a spiral along the guide plate. Since water is allowed to flow downward along such a spiral guide plate, it is possible to prevent damage to vertical pipes, shafts, etc. due to the impact of falling water.

Further, in such a vertical pipe structure, a passage through which a worker can pass may be provided in the shaft pipe for maintenance, and a ladder for the worker to go up and down is provided in the shaft pipe. Workers can therefore reach the lower surface of the shaft along the ladder.

JP 2015-166522 A

By the way, in the vertical pipe structure as described above, there are cases where the shaft pipe does not reach the bottom surface of the shaft, and a gap is formed between the lower end portion of the shaft pipe and the shaft. In such a case, the worker has to jump down from the bottom end of the shaft tube to the bottom surface of the shaft, which may make the work difficult. SUMMARY OF THE INVENTION It is an object of the present invention to provide a vertical pipe structure that facilitates the work of descending from the inside of the shaft pipe to the bottom surface of the shaft.

The present invention relates to a vertical pipe structure arranged in a shaft that connects an upper water channel and a lower water channel, the vertical pipe structure having an upper end that communicates with the upper water channel and a lower end that communicates with the lower water channel. a cylindrical shaft pipe disposed in the vertical pipe and having a lower end at a position a predetermined distance upward from the bottom surface of the vertical hole; an outer peripheral surface of the shaft pipe and an inner surface of the vertical pipe a guide plate spirally extending in the axial direction of the axial tube so as to connect with the peripheral surface; a first ladder arranged on the inner wall surface of the axial tube so as to extend in the axial direction of the axial tube; A plurality of scaffolding members attached at predetermined intervals in the axial direction of the shaft pipe, a first aspect arranged in the shaft pipe, and detachable between the lower end portion of the shaft pipe and the lower surface of the shaft. and a first holding means for holding the second ladder in the first mode within the axial tube and have.

In the above vertical pipe structure, the first holding means may have a restricting portion that restricts vertical movement of the second ladder.

In the above vertical pipe structure, the second ladder can be arranged on the inner peripheral surface of the shaft pipe that is displaced from the first ladder by 45 degrees to 135 degrees in the circumferential direction by the first holding means. .

The vertical tube structure may further include second holding means for holding the second ladder in the second mode between the lower end of the shaft tube and the lower surface of the vertical hole.

In the vertical tube structure, the second holding means may be provided at a position on the shaft tube to which the guide plate is not attached.

The vertical pipe structure may further include a plurality of scaffolding members attached at predetermined intervals in the axial direction of the shaft pipe.

In the vertical pipe structure, the lowest scaffolding member, which is the lowest among the plurality of scaffolding members, is arranged near the lower end of the shaft pipe, and the first holding means holds the second ladder. , above the lowermost scaffolding member.

In the above vertical pipe structure, the lowest scaffolding member, which is the lowest among the plurality of scaffolding members, is arranged near the lower end of the shaft pipe, and the second holding means comprises the lowest scaffolding member. and may be configured to hold the upper end of the second ladder.

In the vertical pipe structure, each of the scaffolding members is formed so as to partition the interior of the shaft pipe in the axial direction and is configured to allow liquid to pass therethrough. It has a large through hole and can have a cover member that detachably closes the through hole.

In the vertical pipe structure, the lid member can be detachably attached to the first ladder.

In the above vertical pipe structure, the center of the through hole can be formed closer to the first ladder than the center of the scaffold member.

ADVANTAGE OF THE INVENTION According to this invention, durability is high and designability can be hold|maintained.

1 is a cross-sectional view showing an embodiment of a vertical pipe structure according to the present invention; FIG. FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1; FIG. 3 is a cross-sectional view taken along line DD of FIG. 2; Fig. 2 is a plan view of a scaffolding member; FIG. 5 is a cross-sectional view taken along line BB of FIG. 4; FIG. 5 is a cross-sectional view taken along line CC of FIG. 4; It is a side view which shows the state where the 2nd ladder was attached to the shaft tube. FIG. 4 is a cross-sectional view of a vertical tube structure; It is a perspective view of a second holding member. FIG. 4 is a cross-sectional view showing the vicinity of the lower portion of the vertical pipe structure;

An embodiment of a vertical pipe structure according to the present invention will be described below with reference to the drawings.

<1. Overview of vertical tube structure>
A vertical pipe structure according to an embodiment of the present invention will be described below with reference to the drawings. 1 is a cross-sectional view of the vertical tube structure, and FIG. 2 is a cross-sectional view taken along the line AA of FIG. In addition, in these drawings, the inside of the vertical pipe structure is partially shown transparently for convenience of explanation.

As shown in FIGS. 1 and 2, this vertical tube structure, also called a drop shaft, is installed in a concrete underground structure. More specifically, water such as sewage, rainwater, etc. flows in a vertical shaft 300 that connects an upper pipeline 100 that extends horizontally and a lower pipeline 200 that is arranged below the upper pipeline 100 and extends horizontally. are placed in This vertical shaft 300 extends above the upper pipeline 100 and is connected to a manhole 400 provided on the ground. The manhole 400 allows inspection workers to enter the shaft structure. This vertical pipe structure has a cylindrical vertical pipe 1 extending vertically within a shaft 300 . This vertical pipe 1 extends downward from the lower end of the upper pipeline 100 and extends to the lower surface of the vertical pit 300 . A filler 500 such as air mortar is filled between the outer peripheral surface of the vertical pipe 1 and the inner peripheral surface of the vertical shaft 300, thereby fixing the vertical pipe 1 to the vertical shaft 300. there is A circular communication hole 11 communicating with the lower pipe line 200 is formed at the lower end of the vertical pipe 1 .

A cylindrical shaft tube 2 and a spiral guide plate 3 attached to the outer peripheral surface of the shaft tube 2 are provided inside the shaft 300 . Inside the shaft tube 2 are a plurality of scaffolding members 4, a first ladder 5 extending axially in the shaft tube 2, and a second ladder 6 detachably attached near the lower end of the shaft tube 2. is provided. These members will be described in detail below.

<2. Shaft tube and guide plate>
The shaft tube 2 extends along the central axis inside the vertical tube 1, and has an internal space inside thereof that is large enough for a worker to pass through. Further, the upper and lower ends of the shaft tube 2 are open. The upper end of the shaft tube 2 protrudes upward from the vertical tube 1 and extends slightly above the upper pipeline 100 . On the other hand, the lower end of the shaft tube 2 is not in contact with the lower surface of the vertical shaft 300 and is located at a predetermined distance (for example, about 2 m) above the lower surface of the vertical shaft 300 . The communication hole 11 of the vertical pipe 1 described above is formed below the axial pipe 2 . Further, the radial outer edge of the guide plate 3 is fixed to the inner peripheral surface of the vertical pipe 1 without any gap.

A shield plate 31 extending upward from the guide plate 3 is attached to the upper end of the shaft tube 2 . As shown in FIG. 3, the shielding plate 31 is attached to the outer peripheral surface of the shaft tube 2 so as to face the upper pipeline 100. As shown in FIG. More specifically, the shielding plate 31 extends radially so as to connect the outer peripheral surface of the shaft tube 2 and the inner peripheral surface of the shaft 300 and extends to near the upper end of the guide plate 3 .

Here, as shown in FIG. 3, in a plan view, the water flowing out from the upper pipeline 100 flows into both sides of the axial tube 2, but one side of the axial tube 2 is closed by the shielding plate 31. Therefore, the water that has flowed to one side of the shaft tube 2 is bounced off the shield plate 31 and flows downward from the other side of the shaft tube 2 . Moreover, the water that has flowed to the other side of the shaft tube 2 continues to flow downward. Thus, the water that has flowed downward flows downward while drawing a spiral along the guide plate 3 and flows through the communication hole 11 into the lower pipeline 200 .

<3. Scaffolding material>
Next, scaffold members will be described. 4 is a plan view of the scaffold member, FIG. 5 is a cross-sectional view taken along line BB of FIG. 4, and FIG. 6 is a cross-sectional view along line CC of FIG. Scaffolding members 4 are arranged in the inner space of the shaft tube 2 at predetermined intervals in the axial direction. As shown in FIG. 4, the scaffolding member 4 is formed in a disc shape that partitions the shaft tube 2 in the axial direction. More specifically, the scaffolding member 4 has a circular plate-like outer shape, a body portion 41 having a circular through hole 411 formed therein, and a circular body portion 41 detachably fitted into the through hole 411 of the body portion 41 . A plate-like lid member 42 is provided. The main body part 41 and the lid member 42 have a mesh structure so that water can pass through them.

The center of the through-hole 411 is shifted from the center of the body portion 41 and is close to the first ladder 5 on the inner peripheral surface of the shaft tube 2 . That is, the portion of the outer edge of the through-hole 411 closest to the first ladder 5 is arranged near the outer edge of the main body 41 .

The outer periphery of the body portion 41 is in contact with the inner peripheral surface of the shaft tube 2 . Further, as shown in FIG. 5, an annular support member 412 that supports the cover member 42 from below is arranged on the inner circumference of the through hole 411 . The support member 412 has a support surface 413 arranged along the inner circumference of the through hole 411 , and the support surface 413 supports the peripheral edge of the lower surface of the lid member 42 . That is, the cover member 42 is supported by the support member 412 so as not to fall downward from the through hole 411 .

As shown in FIG. 6 , on the upper surface of the body portion 41 , plate-shaped restricting plates 43 are attached to the periphery of the through hole 411 at a plurality of locations (four locations in this embodiment). The restricting plate 43 is rotatably attached to the upper surface of the main body portion 41 via a shaft member 44 , and is arranged to cover the upper surface of the lid member 42 at a first position. It is rotatable between the retracted second position and the retracted second position. Therefore, when the regulating plate 43 is at the first position, the lid member 42 is restricted from moving upward and cannot be removed from the body portion 41 . On the other hand, when the regulation plate 43 is at the second position, the lid member 42 can be removed from the body portion 41 . Further, a hook 45 is attached to the lower surface of the lid member 42, and the lid member 42 can be hooked on the first ladder 5 by this hook 45, as will be described later.

This scaffolding member 4 is designed so that a worker can rest when the through hole 411 is closed by the cover member 42 , and when the cover member 42 is removed, the worker can enter the shaft tube 2 through the through hole 411 . can be moved in the axial direction. A plurality of such scaffolding members 4 (four locations in this embodiment) are provided in the shaft pipe, and here, the scaffolding member 4 disposed at the lowest position is referred to as the lowest scaffolding member 40 . do. The bottom scaffolding member 40 is attached near the lower end of the shaft tube 2 .

<4. First ladder>
As shown in FIGS. 1 and 2, the first ladder 5 used when the worker moves up and down in the shaft tube 2 is a known ladder, and includes a pair of vertically extending pillars and a plurality of consists of treads. Each strut is fixed to the inner wall surface of the shaft tube 2 with a bracket. This first ladder 5 is divided at the location where the scaffold member 4 is arranged. However, as described above, the through-hole 411 of the scaffolding member 4 is formed so as to be close to the first ladder 5, so when the worker passes through the through-hole 411 of the scaffolding member 4, the first ladder 5 The first ladder 5 can be smoothly moved up and down without leaving too far from the . The lower end of the first ladder 5 is located slightly above the lowest scaffolding member 40 .

<5. Second ladder and its holding mechanism>
Next, the second ladder will be explained. FIG. 7 is a side view showing a state in which the second ladder is attached to the shaft tube. As shown in FIG. 7, the second ladder 6 is a known ladder, and has a plurality of treads 62 attached between a pair of vertically extending posts 61 . Hooks 63 are attached to the upper ends of both struts 61, respectively. In addition, a non-slip member 64 made of rubber such as butyl rubber or plastic is attached to the lower ends of both columns. The second ladder 6 is hung between the lower end of the shaft tube 2 and the lower surface of the vertical shaft 300, and the worker descends from the lower end of the shaft tube 2 to the lower surface of the vertical shaft 300. Used. However, it is detachably held inside the shaft tube 2 as shown in FIG. 7 except during work. A mechanism for holding the second ladder 6 inside the shaft tube 2 except during work will be described below.

FIG. 8 is a plan view of the shaft tube. As shown in FIG. 8, in the shaft tube 2, the first holding member 7 and the second holding member 8 that hold the second ladder 6 are above the lowest scaffolding member 40 and around the first ladder 5. It is arranged on the inner wall surface shifted by 90 degrees in the direction. At the position where the second ladder 6 is held on the inner wall surface of the shaft tube 2 , the first holding member 7 is a member formed in a U shape, and both ends of the first holding member 7 extend inside the shaft tube 2 . It is fixed to the wall surface and protrudes into the inner space of the shaft tube 2 . A hook 63 at the upper end of the second ladder 6 is hooked on the first holding member 7 .

On the other hand, the second holding member 8 is attached below the first holding member 7 on the inner wall surface of the shaft tube 2 so as to be hooked on one of the treads 62 of the second ladder 6 . The second holding member 8 will be described in detail below.

FIG. 9 is a perspective view of the second holding member. As shown in FIG. 9, the second holding member 8 includes an L-shaped substrate 81 protruding from the inner wall surface of the shaft tube 2 and a pair of support plates extending in parallel from the vicinity of the tip of the substrate 81 with a predetermined gap therebetween. 82 and . A pair of support plates 82 are formed to extend upward from the base plate 81, and one of the treads 62 of the second ladder 6 is fitted between the support plates 82 from above. That is, the distance between the support plates 82 is such that the treads 62 are fitted therein.

A shaft member 83 is attached to the base plate 81 and extends upward from the support plate 82 toward the inner wall surface of the shaft tube 2 . is rotatably mounted. The regulation plate 84 rotates around the shaft member 83 and can selectively take a first position covering the space between the two support plates 82 from above and a second position retracted from the two support plates 82 . there is Therefore, when the regulating plate 84 is at the second position, the tread 62 can be fitted between the two support plates 82 and removed. On the other hand, when the tread 62 is fitted between the support plates 82, if the regulating plate 84 is placed at the first position, the tread 62 is supported because the regulating plate 84 covers the top of the tread 62. Detachment upward from the plate 82 can be prevented.

Thus, the first holding member 7 and the second holding member 8 are mechanisms for holding the second ladder 6 inside the shaft tube 2 .

Next, a mechanism for holding the second ladder 6 during work will be described. As shown in FIG. 10, on the inner wall surface of the shaft tube 2, below the second holding member 8, a third holding member 9 having the same structure as the first holding member 7 and having a U-shape is attached. there is The third holding member 9 is provided slightly above the lowest scaffolding member 40 , just below the first ladder 5 and slightly below the lower end of the first ladder 5 . The hook 63 of the second ladder 6 removed from the first and second holding members 7 and 8 is hooked on the third holding member 9 . Thereby, when the second ladder 6 is arranged between the lower end of the shaft tube 2 and the lower surface of the shaft 300, the second ladder 6 is fixed so as not to move.

<6. Working with a Vertical Pipe Structure>
Next, a description will be given of operations performed on the vertical pipe structure configured as described above. A worker enters the shaft 300 from the ground through the manhole 400 . Then, it enters into the shaft tube 2 through the upper opening of the shaft tube 2 and goes down along the first ladder 5 . Then, each time the scaffolding member 4 is reached, the regulation plate 43 of the scaffolding member 4 is rotated to the second position, and the cover member 42 is removed. Then, the removed lid member 42 is hooked on the first ladder 5 by the hook 45 . Then, after removing the cover member 42 from the lowermost scaffolding member 40, the second ladder 6 is removed from the inner wall surface of the shaft tube 2. As shown in FIG. That is, after rotating the regulating plate 84 of the second holding member 8 from the first position to the second position, the second ladder 6 is lifted upward, and the second ladder is lifted from the first and second holding members 7 and 8. Remove 6.

Thereafter, the hook 63 at the upper end of the second ladder 6 is hooked to the third holding member 9 while lowering the second ladder 6 from the through hole 411 of the lowermost scaffolding member 40 . Thereby, the second ladder 6 is suspended between the lower end of the shaft tube 2 and the lower surface of the shaft 300 . Also, the second ladder 6 is stretched diagonally or vertically away from the first ladder 5 so that the lowest scaffold member 40 does not interfere. Subsequently, the worker descends along the second ladder 6 to the lower surface of the shaft 300 to perform the work.

When the work is completed, climb the second ladder 6 and enter the shaft pipe 2 through the through hole 411 of the lowest scaffolding member 40 . Then, the second ladder 6 is lifted upward, removed from the third holding member 9, and pulled up into the shaft tube 2. - 特許庁Next, the hook 63 of the second ladder 6 is hooked to the first holding member 7 and one of the treads 62 is fitted between the support plates 82 of the second holding member 8 . After that, the restricting plate 84 is rotated to be placed at the first position so as to cover the top of the tread 62 . This restricts the second ladder 6 from moving upward and downward.

Subsequently, the lid member 42 hooked on the first ladder 5 is removed and fitted into the through hole 411 of the lowest scaffolding member 40 . Then, the regulation plate 43 is rotated to be arranged at the first position. As a result, the lid member 42 is restricted from moving upward and is fixed to the body portion 41 . Then, each time the first ladder 5 is climbed and the through hole 411 of the scaffolding member 4 is passed through, the through hole 411 is closed with the cover member 42 . In this way, after exiting from the upper opening of the shaft tube 2, it exits from the manhole 400 to the ground.

<7. Flow of Water in Vertical Pipe Structure>
As described above, water flowing from the upper pipeline 100 flows into the upper opening of the vertical pipe 1 . The water flows downward along the guide plate 3 and flows into the lower pipe line 200 through the communication hole 11 of the vertical pipe 1 . A part of the internal air pushed by water is returned to the upper pipeline 100 through the shaft tube 2 and the scaffold member 4 . In addition, water may flow backwards, and in this case, the water may flow upward along the guide plate 3 or may enter the inside of the shaft tube 2 from the lower opening of the shaft tube 2 . At this time, since the scaffold member 4 is formed in a mesh shape, the water that has flowed into the axial pipe 2 passes through the scaffold member 4 and flows upward. However, even if it flows backward, it is normal that it does not reach the upper pipeline 100 .

<8. Features>
The vertical tube structure configured as described above has the following effects.
(1) Since the second ladder 6 can be stretched over the space between the lower end of the shaft tube 2 and the lower surface of the shaft 300, the work can be performed safely. Further, when the work is not performed, the second ladder 6 is held in the shaft tube 2 by the first and second holding members 7 and 8, so that the flow of water flowing downward along the guide plate 3 is suppressed. can be prevented from being obstructed, and the second ladder 6 can be prevented from being damaged.

(2) The second ladder 6 is held by the first and second holding members 7 and 8 on the inner wall surface of the shaft tube 2 so as not to move vertically. Therefore, it is possible to prevent the second ladder 6 from coming off the inner wall surface of the shaft tube 2 due to vibration or the like. Also, even if water flows backward in the shaft tube 2, the second ladder 6 can be prevented from being washed away.

(3) The lower end of the first ladder 5 is positioned close to the lowest scaffolding member 40, and the third holding member 9 is arranged between the lower end of the first ladder 5 and the lowest scaffolding member 40. , after descending the first ladder 5, the work of attaching the second ladder 6 to the third holding member 9 can be easily performed.

(4) The second ladder 6 is not arranged on the opposite side of the first ladder 5 on the inner wall surface of the shaft tube 2, but is arranged at a position offset by 90 degrees from the first ladder 5 in the circumferential direction. there is Therefore, for example, when a worker carrying a load on his back moves up and down the first ladder 5, it is possible to prevent the worker from being caught in the second ladder 6.

(5) The first to third holding members 7 to 9 are not attached to the shaft tube 2 at the position where the guide plate 3 is attached. Therefore, it is possible to prevent the strength of the shaft tube 2 from decreasing.

<9. Variation>
Although one embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications are possible without departing from the gist of the present invention. It should be noted that the following modified examples can be combined as appropriate.

<9-1>
The structures of the first and second holding members 7 and 8 are not particularly limited as long as they have a structure capable of holding the second ladder 6 on the inner wall surface of the shaft tube 2 . Thus, for example, one or more than three retaining members may be provided. Moreover, as long as the second ladder 6 can be held, the structure may be such that the second ladder 6 is held at any position. Furthermore, a member like the restricting plate 84 of the second holding member 8 may be provided on the first holding member 7 to prevent the second ladder 6 from moving upward. Note that these first and second holding members 7 and 8 correspond to the first holding means of the present invention.

The first and second holding members 7 and 8 are attached at positions offset by 90 degrees from the first ladder 5 in the circumferential direction, but the present invention is not limited to this. For example, if the inner space of the shaft tube 2 is large, it may be installed at any position. In the above-described embodiment, the first ladder 5 is composed of a pair of vertically extending posts and a plurality of treads bridged over the struts, but may be composed of U-shaped steps without providing a pair of posts.
<9-2>
The structure of the third holding member 9 is also not particularly limited. Any structure may be employed as long as it can fix the second ladder 6 so that it does not move when it is handed over.

<9-3>
The structure of the scaffold members 4 is not particularly limited, and it is sufficient that they are provided inside the shaft tube 2 at predetermined intervals so that workers can rest. Therefore, the structure does not necessarily have to partition the inside of the shaft tube 2 . Moreover, even if the structure partitions the shaft tube 2, the configuration of the through hole 411 and the lid member 42 is not particularly limited as described above. When the shaft tube 2 is short, one scaffolding member 4 may be provided below the shaft tube 2, or none may be provided.

<9-4>
The structure of the second ladder 6 is also not particularly limited, and may be any structure as long as it can be attached to the first to third holding members 7 to 9, for example.

<9-5>
The vertical pipe 1 may be arranged at any position in the vertical pit 300, and its length and position in the vertical direction are not particularly limited. Therefore, for example, the vertical pipe 1 may extend to a position covering the upper pipe line 100 , and in this case, a communication passage communicating with the upper pipe line 100 may be formed in the vertical pipe 1 . Also, the length and position of the shaft tube 2 are not particularly limited, and can be appropriately set within the vertical tube 1 . For example, the upper end of the shaft tube 2 may be positioned at the upper end of the inner surface of the upper pipeline 100 . Furthermore, the upper pipeline 100 and the lower pipeline 200 do not have to extend horizontally, and may be inclined. Thus, the underground structure in which the vertical pipe structure is installed is also not particularly limited. The guide plate 3 does not have to have a spiral shape with a continuous constant inclination, but may have a spiral shape as a whole. For example, the guide plate 3 may be stepped.

1 Vertical pipe 2 Axial pipe 3 Guide plate 4 Scaffold member 40 Bottom scaffold member 5 First ladder 6 Second ladder 7 First holding member (first holding means)
8 second holding member (first holding means)
84 regulation plate (regulation part)
9 Third holding member (second holding means)

Claims (4)

A vertical pipe structure arranged in a shaft that connects an upper waterway and a lower waterway,
a cylindrical vertical pipe having an upper end communicating with the upper water channel and a lower end communicating with the lower water channel;
a cylindrical axial tube disposed in the vertical tube and having a lower end at a position a predetermined distance upward from the lower surface of the vertical hole;
a guide plate spirally extending in the axial direction of the axial tube so as to connect the outer peripheral surface of the axial tube and the inner peripheral surface of the vertical tube;
a first ladder arranged on the inner wall surface of the axial tube so as to extend in the axial direction of the axial tube;
It is configured so as to be able to selectively take either a first mode in which it is arranged inside the shaft tube, or a second mode in which it is detachably spanned between the lower end of the shaft tube and the bottom surface of the shaft. a second ladder, and
a first holding means for holding the second ladder in the first mode on the inner wall surface of the axial tube at a position displaced from the first ladder in the circumferential direction;
with
A longitudinal tubular structure, wherein said second ladder is configured to be detached from said first retaining means and arranged below said first ladder in said second aspect. 2. The vertical tube structure according to claim 1, wherein said first holding means has a restricting portion that restricts vertical movement of said second ladder. 3. A downpipe according to claim 1 or 2, further comprising second retaining means for retaining said second ladder in said second configuration between a lower end of said axial tube and a lower surface of said shaft. Structure. 4. The vertical tube structure according to claim 3, wherein said second holding means is provided at a position of said shaft tube to which said guide plate is not attached.

Images