JP4312310B2 - Opening and closing structure of hollow cylindrical body and pier caisson - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
This invention includes a closing structure comprising a closing member capable of sealing the opening portion of the hollow cylindrical body and the hollow cylindrical body, to a Piakeson employing this closing structure hatch units.
[0002]
[Prior art]
Conventionally, various types of opening / closing structures including a hollow cylindrical body and an opening / closing body capable of sealing the opening of the hollow cylindrical body have been used in various technical fields. One of them is an open / close structure adopted in the pneumatic caisson method which is excavation work in the civil engineering field as shown in FIG.
[0003]
In the example shown in FIG. 12, the lower end portion of the caisson main body 1 has a work chamber 2 having a divergent shape in front view, and a ceiling slab 3 is provided on the work chamber 2. A hollow portion 4 is provided on the ceiling slab 3, and a top plate 5 is formed thereon.
[0004]
FIG. 12 shows what is generally called a pier caisson. The working chamber 2, the hollow portion 4, and the top plate 5 form a base portion 7 surrounded by a side wall 6. Compared with the base part 7, the cross section is formed small.
[0005]
In such a pier caisson, it is necessary to equip a hollow shaft 9 for securing a passage for raising and lowering workers and carrying out earth and sand, and a vertical opening for inserting the shaft 9 into the top plate 5 and the column 8. Part 10 is provided.
[0006]
In this type of conventional pier caisson, the shaft 9 is mounted by the following method.
[0007]
That is, the shaft 9 is inserted into the vertical opening 10 provided in the top plate 5 and the support column 8 of the caisson main body 1, and the lower end of the shaft 9 is provided in the ceiling slab 3 of the work chamber 2. 11, the lower end of the opening 11 of the ceiling slab 3 is closed with a disk-shaped bottom door 12.
[0008]
Moreover, the upper part of the shaft 9 communicates with the ground, the first lock 13 is connected, and the second lock 14 is connected thereon. The first lock 13 and the second lock 14 are provided with hatches 15 and 16, respectively.
[0009]
The hatch 15 of the first lock 13 and the hatch 16 of the second lock 14 are operated according to a predetermined procedure, and are used when adjusting the pressure in the shaft 9 and the work chamber 2.
[0010]
Before the installation work of the shaft 9, the bottom door 12 is divided into two parts on the ground so as not to hinder the loading into the work chamber 2 and the excavation work.
[0011]
The divided bottom door 12 is suspended by a wire 17 of a crane or the like (not shown) installed on the ground or the like, and is carried from the ground into the work chamber 2 through the shaft 9.
[0012]
The bottom door 12 carried into the work chamber 2 in a divided state is assembled integrally with a bolt or the like by abutting each joint surface. The integrated bottom door 12 is lifted by a wire 17 such as a crane and is brought into contact with the opening 11 of the ceiling slab 3. In this state, the inside of the shaft 9 is reduced to atmospheric pressure, so that the bottom door 12 is brought into close contact with and fixed to the opening 11 of the ceiling slab 3 by the action of the pressure difference between the working chamber 2 and the inside of the shaft 9.
[0013]
In the pneumatic caisson method as described above, the bottom door 12 independent of the shaft 9 is suspended from the opening 11 at the tip of the shaft 9 by a ground crane or the like, and the bottom door 12 is moved up and down, thereby The opening 11 was closed or opened.
[0014]
When the shaft 9 is installed, the first lock 13 and the second lock 14 are removed from the shaft 9 and temporarily placed on the ground.
[0015]
Next, a new shaft (not shown) is connected to the shaft 9, and the first lock 13 and the second lock 14 temporarily placed on the ground are connected to the upper portion of the new shaft, and the new shaft is installed. Is completed.
[0016]
Hereinafter, similarly, the excavation and subsidence work is advanced by repeating the shaft fitting procedure including the opening and closing work of the bottom door 12 which is the opening and closing body.
[0017]
[Problems to be solved by the invention]
As described above, when proceeding with the excavation and subsidence work using the conventional pier caisson, a bottom door that is an opening / closing body closer to the work chamber is repeated each time the outfitting work of adding a hollow cylindrical body such as a shaft is repeated. The opening and closing operation of the machine is complicated and takes time.
[0019]
Accordingly, a first object of the present invention is to provide an opening / closing structure that can quickly open and close the opening / closing body in a limited space, in an opening / closing structure comprising an opening / closing body that can seal a hollow cylindrical body such as a shaft. It is an issue.
[0020]
The second object of the present invention is to provide a pier caisson equipped with a hollow cylindrical body opening / closing structure capable of quickly performing a fitting operation of a shaft which is a hollow cylindrical body .
[0022]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is an opening / closing structure comprising a substantially cylindrical hollow cylindrical body and an opening / closing body capable of sealing the opening of the hollow cylindrical body, in the vicinity of the opening. The opening is opened and closed by rotating the opening / closing body around a rotation axis provided on the opening, and viewed from the central axis direction of the hollow cylindrical body in a state where the opening is sealed. The shape of the opening and the opening / closing body is substantially circular with substantially the same diameter, and the shape of the opening / closing body viewed from the central axis direction in a state where the opening is fully opened is substantially U-shaped , The curvature of the substantially U-shaped inner peripheral surface of the opening / closing body is made substantially equal to the curvature of the shape of the opening viewed from the central axis direction, so that the opening / closing body is crossed when the opening / closing body is fully opened. The opening / closing body does not block the area.
[0023]
In addition to the structure of Claim 1 , the invention of Claim 2 has a housing | casing which covers the said hollow cylindrical body from the said radial direction outer side, The said opening part vicinity of the inner surface of this housing | casing The opening / closing body is attached to the inner surface of the housing via the rotation shaft, and the opening / closing body includes all states including a state where the opening is sealed and a state where the opening is fully opened. In the state, it is characterized in that it is within the radial direction with respect to the casing .
[0024]
According to a third aspect of the present invention, there is provided a work chamber provided at a lower end portion of the caisson main body, a vertical opening communicating the work chamber and the ground, a hollow shaft inserted into the vertical opening, And a hatch unit that employs the opening and closing structure of the hollow cylindrical body according to claim 2, wherein the hatch unit is provided at a lower portion of the shaft as the housing. An attached unit housing, and as the hollow cylindrical body, a receiving ring provided inside the unit housing in a cross section of the vertical opening, and provided as the opening on the receiving ring. A communication port that communicates with the shaft; and a hatch that opens and closes the communication port as the opening and closing body, and the unit housing and the receiving ring in the transverse section of the vertical opening. A gap is formed between the gap and the rotation shaft that locks the hatch in the gap near the communication opening on the inner surface of the unit housing. A drive device that rotates the hatch via the rotation shaft by an operation is provided .
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0026]
Embodiment 1 of the Invention
1 to 4 show a first embodiment of the present invention.
[0027]
First, the structure will be described. Reference numeral 1 in the figure denotes a caisson body used in a pneumatic caisson method.
[0028]
The lower end of the caisson body 1 is provided with a work chamber 2 to form a longitudinal opening 10 which communicates with said working chamber 2 and ground.
[0029]
A hollow shaft 9 is inserted into the vertical opening 10 of the caisson body 1. A hatch unit 18 is provided between the lower portion of the shaft 9 and the ceiling slab 3 of the work chamber 2.
[0030]
The hatch unit 18 is attached with an opening / closing body 21 that opens and closes around a rotation shaft 20 provided on the inner surface of a unit housing 19 forming a hollow body. The opening / closing body 21 has a structure capable of completely closing the lower open end 23 of the receiving ring 22 provided inside the unit casing 19.
[0031]
A communication port 24 that communicates with the shaft 9 is provided on the upper portion of the receiving ring 22.
[0032]
A driving device 25 for opening and closing the opening / closing body 21 is provided between the unit housing 19 of the hatch unit 18 and the receiving ring 22.
[0033]
The driving device 25 and the operation panel 26 provided on the ground are connected via a communication means 27, and the opening / closing operation of the opening / closing body 21 from the ground is enabled.
[0034]
By the way, the cross section of the vertical opening 10 of the caisson main body 1 is specified to have a specific size because of the demand for strength. Therefore, the size of the cross section of the shaft 9 inserted into the vertical opening 10 is It is smaller than the size of the cross section of the portion 10.
[0035]
Since the hatch unit 18 is finally carried out from the vertical opening 10, the size of its cross section must be smaller than the size of the cross section of the vertical opening 10.
[0036]
On the other hand, the communication port 24 of the receiving ring 22 that communicates with the shaft 9 serves as a bucket for storing earth and sand and a worker's passage, so that the cross section must have a sufficient size.
[0037]
Therefore, it is necessary to devise a method for forming the receiving ring 22 having a size as large as possible in the cross section of the hatch unit 18 having a limited size and housing the driving device 25 for opening and closing the opening / closing body 21.
[0038]
Therefore, in the first embodiment of the present invention, the lower portion of the receiving ring 22 is opened in the unit housing 19 of the hatch unit 18, and the opening lower end 23 cut out in a semicircular shape in front view as shown in FIG. Is forming. Here, the semicircular diameter line 28 of the opening lower end 23 is positioned in the horizontal direction.
[0039]
The shape of the receiving ring 22 in a plan view is a circular ring shape as shown in FIG. 3, and the communication port 24 communicating with the shaft 9 and the opening lower end 23 opened in the unit housing 19 of the hatch unit 18 are: It has the same circular shape in plan view.
[0040]
The opening / closing body 21 has a semicircular shape when viewed from the front as shown in FIG. 2, and has a semicircular ring shape when viewed from the top as shown in FIG. Here, the curvature R1 of the inner peripheral surface of the semicircular ring shape of the opening / closing body 21 is substantially the same as the curvature R2 of the outer periphery of the receiving ring 22.
[0041]
When the opening / closing body 21 is in a fully open state, as shown in FIG. 2, the longest twill line portion 29 equal to the semicircular diameter coincides with the vertical direction when the opening / closing body 21 is viewed from the front. Thus, the opening / closing body 21 does not block the cross-sectional area in plan view of the communication port 24 of the receiving ring 22.
[0042]
In the fully closed state of the opening / closing body 21, as shown in FIG. 4, the opening peripheral edge 30 of the opening lower end 23 of the receiving ring 22 and the opening / closing peripheral edge 31 of the opening / closing body 21 come into contact over the entire circumference. ing.
[0043]
Here, the cross section of the opening / closing body 21 is a semicircular ring shape that is substantially U-shaped, but may be a semipolygonal ring shape similar to the semicircular ring shape. However, even in this case, the shape of the opening lower end 23 of the receiving ring 22 should be made to correspond to this, and the opening lower end 23 needs to be able to be completely closed.
[0044]
In addition, packing 32 is affixed to the opening peripheral part 30 of the receiving ring 22 previously so that the opening peripheral part 30 and the opening-and-closing body peripheral part 31 can contact | adhere. The location where the packing 32 is affixed is not limited to the opening periphery 30 side of the receiving ring 22, and may be affixed to the opening / closing body periphery 31 of the opening / closing body 21, or the opening periphery 30 and the opening / closing body periphery 31. And may be attached to both.
[0045]
The unit housing 19 of the hatch unit 18 has a circular ring shape in cross section as shown in FIG. As shown in FIG. 3, the center of the receiving ring 22 and the center of the unit casing 19 are shifted from each other by a dimension B in plan view, so that the gap between the receiving ring 22 and the unit casing 19 is the largest. The maximum gap portion 33 is secured. A driving device 25 that opens and closes the opening / closing body 21 using the maximum gap 33 is incorporated in the unit casing 19.
[0046]
An opening / closing body bearing 34 is integrally provided at one end of the longest twill line portion 29 of the opening / closing body 21. A rotation shaft 20 is fixed to the opening / closing body bearing 34, and a pinion 35 is fixed to the rotation shaft 20.
[0047]
A bearing 36 for rotatably supporting the rotary shaft 20 is provided at a portion of the inner wall of the unit housing 19 that corresponds to the maximum gap 33, and a rack guide 38 having a rack 37 that meshes with the pinion 35 is provided in a vertical direction. It is attached to match. The rack 37 can slide in the rack guide 38.
[0048]
A cylinder bearing 39 is fixed to the lower portion of the rack 37, and is connected to the cylinder bearing 39 by a cylinder shaft 41 and a cylinder pin 42 that can be projected and retracted with respect to the cylinder body 40.
[0049]
The cylinder main body 40 is attached to the inner wall of the unit housing 19 that contacts the lower side of the rack guide 38 via an attachment pin 43.
[0050]
The cylinder body 40 is connected to an operation panel 26 arranged on the ground via a communication means 27. Where the connecting means 27 penetrates the unit housing 19 of the hatch unit 18, a sealing 46 is provided to prevent air leakage.
[0051]
Here, if the cylinder body 40 is a pneumatic cylinder, the communication means 27 is connected to the operation panel 26 as an air feed pipe. If the cylinder body 40 is a hydraulic cylinder, the operation means 26 is used as the communication means 27 as an oil feed pipe. Connected. If the cylinder body 40 is an electric cylinder, the connecting means 27 is connected to the operation panel 26 using electric wiring.
[0052]
In the first embodiment of the present invention, the opening / closing body 21 has a complicated three-dimensional shape as described above so that the size of the cross section of the unit housing 19 of the hatch unit 18 and the size of the cross section of the receiving ring 22 are as close as possible. The opening lower end 23 of the receiving ring 22 closed by the opening / closing body 21 has a three-dimensional shape corresponding to the shape of the opening / closing body 21.
[0053]
Hereinafter, the operation of the first embodiment will be described.
[0054]
First, the hatch unit 18 is suspended by a crane or the like, installed on the ceiling slab 3, the shaft 9 is inserted, and the hatch unit 18 is connected to the lower portion of the shaft 9. On the ground side, the first lock 13 is connected to the upper part of the shaft 9, the second lock 14 is connected to the first lock 13, and the operation panel 26 on the ground and the cylinder body 40 in the hatch unit 18 are connected by the communication means 27. .
[0055]
Therefore, the rack 37 is pulled by the cylinder shaft 41 along the rack guide 38 by operating the ground operation panel 26 and feeding air so that the cylinder shaft 41 moves in the direction in which the cylinder shaft 41 is pulled into the cylinder body 40. Descend.
[0056]
Then, the pinion 35 meshed with the rack 37 rotates in the clockwise direction, and the rotating shaft 20 and the opening / closing body bearing 34 fixed to the pinion 35 rotate in the clockwise direction, so that the opening / closing body bearing 34 is integrated. The opening / closing body 21 fixed to the rotating shaft 20 rotates clockwise about the rotation shaft 20, and the opening / closing body peripheral edge 31 of the opening / closing body 21 contacts the opening peripheral edge 30 of the opening lower end 23 of the receiving ring 22. Fully closed and the closing operation is completed. In this state, the air supply to the cylinder body 40 is stopped.
[0057]
If it can be confirmed that the opening / closing body 21 in the hatch unit 18 is in the fully closed state, the internal pressure of the shaft 9 is reduced to the same pressure as the atmospheric pressure.
[0058]
When the decompression is completed, the first lock 13 and the second lock 14 are removed from the upper part of the shaft 9, and these are temporarily placed on the ground.
[0059]
A new shaft (not shown) is connected to the upper portion of the shaft 9 from which the first lock 13 and the second lock 14 have been removed, and the first lock temporarily placed on the ground above the new shaft. 13 and the second lock 14 are connected, and the internal pressure of the first lock 13 and the shaft 9 is increased to the same pressure as the internal pressure of the working chamber 2.
[0060]
Then, in order to open the opening / closing body 21 from the fully closed state, the opening / closing body 21 moves in the direction in which the cylinder shaft 41 is pushed out from the cylinder body 40, so that the opening / closing body 21 operates in the opposite direction to closing the opening / closing body 21. Eventually, the operation of opening the longest ridge line portion 29 of the opening / closing body 21 in the fully open state that coincides with the vertical direction is completed.
[0061]
Thereby, the outfitting work of the shaft 9 is completed.
[0062]
(Embodiment 2 of the invention)
In the second embodiment of the invention shown in FIG. 5, a worm gear 55 is used instead of the pinion 35 of the first embodiment of the invention, and a worm 44 is used instead of the rack 37. In this case, a motor 45 for driving the worm 44 is fixed to the unit housing 19 and connected to the operation panel 26 arranged on the ground by the communication means 27.
[0063]
The motor 45 is not limited to an electric motor. For example, a pneumatic motor or a hydraulic motor may be used.
[0064]
(Embodiment 3 of the invention)
In the third embodiment of the present invention shown in FIG. 6, one cylinder body 40 is arranged at a symmetrical position around the maximum gap 33 as viewed from above as shown in FIG.
[0065]
Thereby, the attachment state of the opening / closing body 21 and the cylinder shaft 41 is different from that of the first embodiment.
[0066]
That is, a spherical body 47 is provided on the upper portion of the cylinder shaft 41, and a spherical bearing 48 that supports the spherical body 47 is provided at a location where the spherical body 47 and the opening / closing body 21 are in contact with each other.
[0067]
In the case of the third embodiment of the present invention, not only the capacity of one cylinder body 40 is small, but also drive parts such as a rack excluding the cylinder body 40, a rack guide and pinion, or a worm and worm gear are provided. It becomes unnecessary.
[0068]
(Embodiment 4 of the Invention)
In the first embodiment of the invention, the longest twill line portion 29 of the opening / closing body 21 is set to the horizontal position in the fully closed state. However, in the fourth embodiment of the invention, the opening / closing body 21 is fully moved as shown in FIG. The position was set to be inclined in front view in the closed state.
[0069]
In this case, the end of the opening / closing body 21 is set to a position that contacts the peripheral wall of the receiving ring 22 that is opposite to the maximum gap 33 so as not to block the cross-sectional area of the communication port 24 of the receiving ring 22. I am doing so.
[0070]
In the case of the fourth embodiment, since the operating range of the opening / closing body 21 can be reduced, the operation from fully open to fully closed or from fully closed to fully open can be performed quickly.
[0071]
( Reference example )
Embodiments 1 to 4 of the invention have been described with respect to a pier caisson in which an opening / closing structure comprising a hollow cylindrical body and an opening / closing body capable of sealing the opening of the hollow cylindrical body is employed in a hatch unit. Hereinafter, a reference example in which the opening / closing structure is used for opening / closing a roof of a structure will be described.
[0072]
9 to 11 show schematic views of an opening / closing structure in which a hollow cylindrical body is used as a structure main body, and an opening / closing body is used as a roof of the structure main body.
[0073]
FIG. 9 shows a state where the roof of the structure is fully closed, and FIGS. 10 and 11 show a state where the roof of the structure is fully open.
[0074]
The upper opening portion (opening portion) 51 of the hollow cylindrical body 50 standing on the ground 49 has a substantially semicircular cutout that swells downward in a front view as shown in FIG. An original opening peripheral edge 30 is formed.
[0075]
In the upper opening (opening) 51 of the structure main body 50, a pair of left and right symmetrical roofs (opening and closing bodies) 52, 52 are the lowest part (structure) in the front view of the upper opening (opening) 51. It can be opened and closed in a double-sided manner with the pivot shaft 20 provided on the center line of the main body 50 as the center.
[0076]
The roof (opening / closing body) 52 has a substantially U-shaped cross section, and when the opening / closing operation is performed, the inner peripheral surface 53 of the roof (opening / closing body) 53 is the opening peripheral edge 30 of the upper opening (opening) 51 of the structure body 50. The curvature of the structure body 50 is substantially equal to the curvature of the outer periphery of the cross section of the structure body 50.
[0077]
The outer periphery on the inner surface side of the opening / closing body 21 forms a linear peripheral edge 54, and the outer periphery on the outer surface side of the roof (opening / closing body) 52 is a substantially quarter circle (see FIG. 9) that bulges downward in a front view and is upward in a side view. A three-dimensional opening / closing body peripheral portion 31 that is a substantially semicircular shape (not shown) that swells is formed.
[0078]
Therefore, in the fully closed state of FIG. 9, the linear peripheral edges 54 and 54 of the left and right roofs (opening and closing bodies) 52 and 52 are in close contact with each other at the center, and at the same time the opening and closing body periphery of the roofs (opening and closing bodies) 52 and 52 The portions 31, 31 can be brought into close contact with the opening peripheral edge 30 of the structure body 50.
[0079]
On the other hand, in the fully open state shown in FIGS. 10 and 11, the linear peripheral edges 54, 54 of the left and right roofs (opening / closing bodies) 52, 52 coincide with the highest part of the opening peripheral edge 30 in the front view of the structure body 50. The roof (opening / closing body) 52 does not block the cross-sectional area of the upper opening (opening) 51 in spite of a small opening / closing operation.
According to such a structure, in the structure of the hollow cylindrical body opened to the upper part which has the roof which is an opening / closing body, the said roof can be opened / closed rapidly in the limited space.
[0080]
【The invention's effect】
As described above, according to the invention described in claim 1 or 2 , in the opening / closing structure comprising the hollow cylindrical body and the opening / closing body capable of sealing the opening of the hollow cylindrical body, in a limited space. The opening / closing body can be opened and closed quickly.
[0081]
According to the invention described in claim 3 , in addition to the effects of the inventions described in claims 1 and 2 , since the opening / closing operation of the bottom door as the opening / closing body is not required, the shaft mounting operation in the pneumatic caisson method can be quickly performed. It became possible to do.
[0082]
In addition, since the opening and closing body can be opened and closed from the ground, it is no longer necessary for an operator to enter the caisson each time the opening and closing body is opened and closed, thus making it possible to work safely.
[0083]
Further, conventionally, when the caisson main body has oversunk during excavation work, if the worker evacuates urgently, the worker must ascend the shaft and reach the ground lock (first lock) that hits the evacuation site. Although not easy, in the configuration where the hatch unit is set on the ceiling slab immediately above the work room as in the above embodiment , in an emergency, the hatch unit is located in the hatch unit immediately above the work room. Evacuation is sufficient, and workers can now easily evacuate.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a usage state of Embodiment 1 of the present invention.
FIG. 2 is an enlarged longitudinal sectional view of a main part in a state where the opening / closing body according to the first embodiment is fully opened.
FIG. 3 is an enlarged cross-sectional view of a main part in a state where the opening / closing body according to the first embodiment is fully opened.
4 is an enlarged longitudinal sectional view of a main part in a state where the opening / closing body according to Embodiment 1 is fully closed. FIG.
FIG. 5 is an enlarged longitudinal sectional view of a main part in a state in which the opening / closing body according to the second embodiment is fully opened.
FIG. 6 is an enlarged longitudinal sectional view of a main part in a state in which the opening / closing body according to the third embodiment is fully opened.
FIG. 7 is an enlarged cross-sectional view of a main part in a state where the opening / closing body according to the third embodiment is fully opened.
FIG. 8 is an enlarged longitudinal sectional view of a main part in a state where the opening / closing body according to the fourth embodiment is fully opened.
FIG. 9 is a schematic front view of a state in which an opening / closing body according to a reference example is fully closed.
FIG. 10 is a schematic front view of a state in which an opening / closing body according to a reference example is fully opened.
FIG. 11 is a schematic plan view of a state in which an opening / closing body according to a reference example is fully opened.
FIG. 12 is a longitudinal sectional view showing a use state of the opening / closing structure in the conventional pneumatic caisson method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Caisson main body 2 Working room 3 Ceiling slab 9 Shaft 10 Vertical opening part 13 1st lock 14 2nd locks 15 and 16 Hatch 17 Wire 18 Hatch unit 19 Unit housing 20 Rotating shaft 21 Opening and closing body 22 Receiving ring (hollow cylindrical shape) body)
23 Opening lower end 24 Communication port (opening)
25 driving device 26 operation panel 27 communication means 28 diameter line 29 longest ridge line part 30 opening peripheral part 31 opening / closing body peripheral part 32 packing 33 maximum gap part R1 curvature of inner periphery of opening / closing body R2 curvature of outer periphery of receiving ring 50 structure body (Hollow tube)
51 Upper opening (opening)
52 Roof (Opening and closing body)
53 Inner peripheral surface 54 Linear peripheral edge

Claims (3)

A hollow cylindrical body of substantially cylindrical, in closing structure comprising a closing member capable of sealing the opening portion of the hollow cylindrical body,
The opening is opened and closed by rotating the opening / closing body around a rotation shaft provided in the vicinity of the opening,
In the state where the opening is sealed, the shape of the opening and the opening / closing body viewed from the central axis direction of the hollow cylindrical body is a substantially circular shape having substantially the same diameter,
In the state where the opening is fully opened, the shape of the opening / closing body viewed from the central axis direction is substantially U-shaped ,
By making the curvature of the substantially U-shaped inner peripheral surface of the opening / closing body substantially equal to the curvature of the shape of the opening as seen from the central axis direction ,
An opening / closing structure for a hollow cylindrical body, wherein the opening / closing body is configured not to block a cross-sectional area of the opening when the opening / closing body is fully opened. A housing that covers the hollow cylindrical body from the outside in the radial direction; the pivot shaft is provided near the opening on the inner surface of the housing; The opening / closing body is attached to the inner surface,
  2. The hollow cylindrical shape according to claim 1, wherein the opening / closing body fits inside the radial direction with respect to the housing in all states including a state where the opening is sealed and a state where the opening is fully opened. Body opening and closing structure.   A working chamber provided at the lower end of the caisson body,
  A vertical opening communicating the working chamber and the ground;
  A hollow shaft inserted into the longitudinal opening;
  A hatch unit provided at a lower portion of the shaft,
  In the peer caisson employing the opening and closing structure of the hollow cylindrical body according to claim 2 in the hatch unit,
  The hatch unit is
  As the case, comprising a unit case attached to the lower part of the shaft,
  As the hollow cylindrical body, comprising a receiving ring provided inside the unit housing in the cross section of the vertical opening,
  As the opening, provided with a communication port provided in the receiving ring and communicating with the shaft,
  As the opening and closing body, provided with a hatch that opens and closes the communication port,
  A gap is formed between the unit housing in the transverse section of the vertical opening and the communication port of the receiving ring,
  In the gap, in the vicinity of the communication opening of the inner surface of the unit housing, the rotation shaft for locking the hatch,
  A pier caisson provided with a driving device for rotating the hatch via the rotating shaft in the gap by an operation from the ground.

Images