Flight vehicle

Abstract

To provide a flying object having storage chambers separately above and below a main structure part, and allowing wiring to pass between the storage chambers without being exposed to the outside.SOLUTION: A main structural part, an upper chamber and a lower chamber, wherein the main structural part comprises a central joint, a plurality of beams extending radially from the central joint, and a rotor provided at an end of each of the beams opposite to the central joint, the central joint portion includes a central portion and a girder member support portion that supports an end portion of each of the girder members provided in the central portion on the central joint portion side, a central communication hole penetrating in a vertical direction is formed in the central portion, the upper storage chamber is provided on an upper side of the central joint portion, the lower storage chamber is provided on a lower side of the central joint portion, and an internal space of the upper storage chamber and an internal space of the lower storage chamber communicate with each other through the central communication hole.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an aircraft such as a drone having a rotor (rotating wing). [Background technology]

[0002] The general structure of unmanned aerial vehicles (also known as drones or UAVs), which have become widespread in recent years, has a centrally located main body, multiple frame parts extending radially from the main body, and rotors attached to the tips of the frame parts, as shown in Patent Document 1. The main body has a space inside in which units for control and communication are housed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-37347 Summary of the Invention [Problem to be solved by the invention]

[0004] In the aircraft of Patent Document 1, various units are housed in a single space, and the wiring connecting them is also housed therein, and these wirings are not exposed to the outside. However, there are cases where various devices such as such units are arranged in multiple spaces. In such cases, it is desirable to minimize the exposure of the wiring connecting the devices to the outside.

[0005] The present invention has been made in consideration of the above circumstances, and aims to provide an aircraft having separate storage compartments above and below the main structure, in which wiring can be passed between those storage compartments without being exposed to the outside. [Means for solving the problem]

[0006] One aspect of the aircraft of the present invention comprises a main structure, an upper storage compartment, and a lower storage compartment, the main structure having a central joint, a plurality of girders extending radially from the central joint, and a rotor attached to the end of each of the girders on the opposite side to the central joint, the central joint having a central portion and girder support portions that support the end of each of the girders attached to the central joint side, the central portion having a central communication hole that penetrates in the vertical direction, the upper storage compartment being provided above the central joint and the lower storage compartment being provided below the central joint, the internal space of the upper storage compartment and the internal space of the lower storage compartment being connected by the central communication hole.

[0007] One aspect of the aircraft of the present invention is an aircraft comprising a main structure, an upper storage compartment, and a lower storage compartment, the main structure having a plurality of central joints, connecting sections connecting the central joints together, a plurality of girders extending radially from the central joint, and a rotor provided at the end of each of the girders on the opposite side to the central joint side, the central joint having a central section and girder support sections supporting the end of each of the girders provided at the central section on the central joint side, the central section having a central section communication hole penetrating in the vertical direction, and the connecting sections having an upper rotor. A connecting portion communicating hole is formed through the bottom, a plurality of the central joints are arranged in a row, one above the other, the central portions located above and below are connected by the connecting portions, the central portion communicating hole and the connecting portion communicating hole are communicated, the upper storage chamber is provided above the central joint located at the top, and the lower storage chamber is provided below the central joint located at the bottom, and the internal space of the upper storage chamber and the internal space of the lower storage chamber are communicated by the central portion communicating hole and the connecting portion communicating hole. [Effects of the Invention]

[0008] According to the aircraft of the present invention, various devices can be stored in the upper storage compartment above the main structure and the lower storage compartment below. By passing wiring through the central communication hole (and the connection section communication hole if a connecting section is provided), the devices stored in the upper storage compartment and the lower storage compartment can be connected without the wiring being exposed to the outside. Not exposing the wiring to the outside prevents damage and improves the design. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is an explanatory diagram showing the internal structure of the first embodiment of the aircraft. [Figure 2] FIG. 1 is a perspective view of a first embodiment of an aircraft. [Figure 3] The central joint is shown in (a) a top view and (b) a side view. [Figure 4] FIG. [Figure 5] FIG. 2 is an exploded perspective view of the main structure, upper storage compartment, and lower storage compartment. [Figure 6] FIG. 10 is an explanatory diagram showing the internal structure of a second embodiment of the aircraft. DETAILED DESCRIPTION OF THE INVENTION

[0010] Specific details of the aircraft of the present invention will be described below. As shown in Figures 1, 2, and 5, the aircraft of the first embodiment comprises a main structure 100, an upper storage compartment 200, a lower storage compartment 300, and landing gear 400. However, in Figure 1, the upper storage compartment 200 and the lower storage compartment 300 are shown in a cross section along the central axis. The main structure 100 has one central joint 1, four girders 2 extending radially from the central joint 1, and rotors 3 attached to the tip of each girder 2. However, the end of the girder 2 on the side of the central joint 1 is referred to as the base end, and the end opposite the base end is referred to as the tip.

[0011] The beams 2 are made of CFRP and consist of long circular pipes. All four beams 2 have the same length and diameter. A motor 31 is attached to the upper end of each beam 2, and a rotor 3 is attached to the motor 31.

[0012] As shown in Figures 3 and 4, central joint 1 is made of metal, has a cross shape when viewed from above, and is divided into upper and lower parts. The upper part of the division is upper joint 4, and the lower part is lower joint 5. Upper joint 4 and lower joint 5 are approximately symmetrical in the vertical direction.

[0013] The upper joint 4 consists of a square upper central portion 41 located at the intersection of the cross in top view, and four upper support portions 42 connected to each of the four sides of the upper central portion 41. The upper central portion 41 and the four upper support portions 42 are integrally formed. The upper central portion 41 has a square rectangular parallelepiped shape in top view. A circular upper communication hole 411 penetrating vertically is formed in the center of the upper central portion 41. Female thread portions 412 extending vertically are formed at the four corners of the upper surface of the upper central portion 41. The upper support portions 42 are rectangular in top view, with the sides perpendicular to the sides of the upper central portion 41 longer than the sides parallel to them. The longitudinal direction of each upper support portion 42 is the direction perpendicular to the sides of the upper central portion 41 to which it is connected. The upper support portion 42 has an upper support portion main body 421, a recessed portion 422, and a protruding portion 423. The upper support body 421 has a rectangular parallelepiped shape with a semicircular recess 422 extending longitudinally, creating a roughly inverted U-shape when viewed longitudinally. The lower surface of the upper central portion 41 is also cut out as an extension of the recess 422. The upper surface of the upper central portion 41 is slightly higher than the upper surface of the upper support body 421. In other words, only the square upper central portion 41 protrudes from the upper surface of the upper joint 4. The recess 422 is shaped to fit the base end of the beam 2. The protrusions 423 are formed on the lower part of both longitudinal sides of the upper support body 421. The protrusions 423 are roughly rectangular parallelepiped and extend longitudinally. Their vertical length is shorter than that of the upper support body 421 and they are formed integrally with the upper support body 421. Each protrusion 423 has three insertion holes 424 aligned longitudinally. The insertion hole 424 passes through the protruding portion 423 in the vertical direction.

[0014] As described above, the lower joint portion 5 has a shape that is approximately symmetrical in the vertical direction to the upper joint portion 4, and is composed of a lower central portion 51 and four lower support portions 52. A lower communication hole 511 is formed in the center of the lower central portion 51. Female thread portions 512 are formed in the four corners of the lower surface of the lower central portion 51. The lower support portion 52 has a lower support portion main body 521, a recess 522, and a protrusion portion 523. Unlike the upper joint portion 4, each of the protrusion portions 523 has three female thread portions 524 formed therein. The female thread portions 524 pass vertically through the protrusion portions 523 and correspond to the positions of the insertion holes 424.

[0015] Then, the base ends of each of the four girder members 2 are sandwiched from above and below by the upper support portion 42 and the lower support portion 52. At this time, the base ends of the girder members 2 are fitted into the recesses 422 of the upper support portion 42 and the recesses 522 of the lower support portion 52. With the base ends of the girder members 2 fitted into the upper and lower recesses 422, 522, there is a slight gap between the lower surface of the upper support portion 42 and the upper surface of the lower support portion 52. In this state, the upper support portion 42 and the lower support portion 52 (i.e., the upper joint portion 4 and the lower joint portion 5) are bolted together. Bolts 43 are inserted from above into the insertion holes 424 of the upper support portion 42 and screwed into the female thread portion 524 of the lower support portion 52. Screwing in the bolts 43 tightens the upper support portion 42 and the lower support portion 52 so that they approach each other, thereby fixing the girder members 2 to the upper joint portion 4 and the lower joint portion 5. At this time, the openings at the base ends of the respective beams 2 face the space formed at the center of the central joint 1, with the upper communication hole 411 and the lower communication hole 511 positioned above and below this space, respectively.

[0016] The upper joint 4 and lower joint 5 connected in this manner form the central joint 1. The upper central portion 41 and lower central portion 51, which face each other vertically, form the central portion 11 of the central joint 1. The upper support portions 42 and lower support portions 52, which are connected vertically, form the girder support portions 12 that support the base ends of the respective girder members 2. The upper communication hole 411 and the lower communication hole 511 form the central portion communication hole 111 that passes through the central portion 11 in the vertical direction.

[0017] As shown in Figures 1 and 5, a flange 6 for attaching a hook (not shown) for hanging cargo is attached to the underside of the central joint 1. The flange 6 is made of metal and includes a base 61 that is a square, flat plate in top view, a cylindrical upper body section 62 extending downward from the base 61, an intermediate body section 63 that tapers downward from the lower end of the upper body section 62, and a cylindrical lower body section 64 extending downward from the lower end of the intermediate body section 63. The base 61, upper body section 62, intermediate body section 63, and lower body section 64 are integrally formed. A through-hole 65 is formed at the center of the base 61, upper body section 62, intermediate body section 63, and lower body section 64, penetrating vertically. The base 61 is the same size as the center section 11 of the central joint 1 in top view. Insertion holes 66 are formed at the four corners of the base 61, penetrating vertically. A window 67 communicating with the through-hole 65 is formed on the side surface of the upper body 62. The window 67 is formed in two opposing locations on the side surface of the upper body 62. A pin hole 68 is formed in the lower body 64, penetrating the lower body 64 in the horizontal direction. The upper surface of the base 61 of the flange 6 abuts against the underside of the central part 11 of the central joint 1 (the underside of the lower central part 51 of the lower joint 5), and is fastened with bolts. Bolts 69 are inserted into the insertion holes 66 of the base 61 from below, and screwed into the female threads 512 of the lower central part 51. The flange 6 covers the lower opening of the central communication hole 111 in the central portion 11 (the lower communication hole 511 in the lower central portion 51), but the central communication hole 111 communicates with the through hole 65 in the flange 6, and the through hole 65 also communicates with the window portion 67, so the central communication hole 111 communicates with the space below the central joint 1. The hook is attached to the lower end of the flange 6, and the shape and attachment structure of the hook itself will not be described here.

[0018] The upper storage chamber 200 is provided above the central joint 1. The upper storage chamber 200 has an upper base 210 attached to the central joint 1 and an upper cover 220 attached to the upper base 210.

[0019] The upper base 210 is made of resin and has a disk shape. The diameter of the upper base 210 is larger than the width of the central joint 1 (the distance from the tip of one girder support part 12 to the tip of the opposing girder support part 12). A circular central hole 211 that penetrates vertically is formed in the center of the upper base 210. Four insertion holes 213 for passing bolts 212 are formed around the central hole 211. The upper base 210 is fixed to the central joint 1 (upper joint 4) by passing the bolts 212 through the insertion holes 213 and screwing them into the female threaded parts 412 of the upper central part 41. The central hole 211 of the upper base 210 communicates with the central communication hole 111 of the central joint 1 (the upper communication hole 411 of the upper joint 4).

[0020] The upper cover 220 is made of resin and has a substantially cylindrical side portion 221, a ceiling portion 222 that covers the upper side of the side portion 221, and an extending portion 223 that extends inward from the lower end of the side portion 221. The side portion 221, the ceiling portion 222, and the extending portion 223 are integrally formed. The diameter of the side portion 221 is slightly larger than the diameter of the upper base 210, and is sized so that the upper base 210 fits exactly inside the side portion 221. When the upper base 210 fits inside the lower end of the side portion 221 of the upper cover 220, the extending portion 223 of the upper cover 220 overlaps the peripheral edge of the upper base 210, and the upper cover 220 is fixed to the upper base 210 by screwing this overlapping portion (screws not shown). Alternatively, a male screw portion may be formed on the periphery of upper base 210, and a female screw portion may be formed on the inner peripheral surface of the lower end of upper cover 220, so that upper cover 220 is screwed and fixed to upper base 210. In this way, an internal space surrounded by upper base 210 and upper cover 220 is formed in upper storage chamber 200.

[0021] The lower storage chamber 300 is provided below the central joint 1. The lower storage chamber 300 has a lower base 310 attached to the central joint 1 and a lower cover 320 attached to the lower base 310.

[0022] The lower base 310 is made of resin and has a disk shape. The diameter of the lower base 310 is smaller than the width of the central joint 1. A square central hole 311 that penetrates vertically is formed in the center of the lower base 310. The central hole 311 is sized so that the lower central portion 51 of the lower joint 5 fits into it. The lower base 310 is fixed to the central joint 1 (lower joint 5) by fitting the lower central portion 51 into the central hole 311. A hanging portion 312 that protrudes downward around the entire periphery is formed on the peripheral edge of the lower base 310.

[0023] Lower cover 320 is made of resin and has a substantially cylindrical side surface portion 321, a floor surface portion 322 covering the underside of side surface portion 321, a fixing hole 323 formed in the center of floor surface portion 322 and penetrating vertically, a cylindrical protrusion 324 protruding downward from the periphery of fixing hole 323, and a wiring hole 325 formed in floor surface portion 322 and penetrating vertically around fixing hole 323. Side surface portion 321, floor surface portion 322, and protrusion 324 are integrally formed. Wiring hole 325 is a circular hole and is formed in multiple locations (for example, two locations point-symmetrical with respect to the center of lower cover 320). The diameter of side surface portion 321 is slightly larger than the diameter of lower base 310, and is sized so that hanging portion 312 of lower base 310 fits exactly inside side surface portion 321. The height of side surface portion 221 is approximately the same as the combined height of base portion 61, upper body portion 62, and intermediate body portion 63 of flange 6. The diameter of fixing hole 323 is large enough to fit lower body portion 64 of flange 6 exactly. The height of protrusion 324 is lower than the height of lower body portion 64 of flange 6. Therefore, when hanging portion 312 of lower base 310 fits inside the upper end of side surface portion 321 of lower cover 320, lower body portion 64 of flange 6 is inserted into fixing hole 323, the side surface of the upper part of lower body portion 64 is covered by protrusion 324, and the lower part of lower body portion 64 protrudes downward from protrusion 324. Protrusion 324 has a pin hole 326 formed therein that passes horizontally through protrusion 324. By aligning the pin hole 68 of the lower body 64 with the pin hole 326 of the protrusion 324 and inserting a pin (not shown), the lower cover 320 is fixed to the flange 6, and the lower base 310 is also fixed. In this way, an internal space surrounded by the lower base 310 and the lower cover 320 is formed in the lower storage chamber 300.

[0024] In this way, the internal space of the upper storage chamber 200 and the internal space of the lower storage chamber 300 are in communication with each other through the central communication hole 111. More specifically, the internal space of the upper storage chamber 200 is in communication with the internal space of the lower storage chamber 300 through the central hole 211 of the upper base 210, the central communication hole 111 (upper communication hole 411 and lower communication hole 511), the through hole 65 of the flange 6, and the window portion 67.

[0025] As shown in FIG. 2 , the leg 400 includes struts 401 and crosspieces 402. The struts 401 and crosspieces 402 are both made of CFRP and are long, circular tubes. Four struts 401 extending in the vertical direction are arranged so as to be located at the four vertices of a square when viewed from above, and horizontally extending crosspieces 402 are laid between adjacent struts 401. The crosspieces 402 are located in the vertical middle of the struts 401, and there may be one or more crosspieces. In this way, the leg 400 is formed as a substantially rectangular parallelepiped frame structure by the struts 401 and crosspieces 402. The upper end of each strut 401 is attached to the longitudinal middle of each girder 2. The mounting structure may be such that a connecting fitting 403 is used for joining between the support material 401 and the beam material 2, as shown in Figure 2, or the support material 401 and the beam material 2 may be directly joined.

[0026] As shown in FIGS. 1 and 2, the aircraft further has a control device 501 (flight controller), a battery 502, and a distribution board 503. The control device 501 controls each device in accordance with operations to fly the aircraft. The battery 502 supplies electricity. The distribution board 503 distributes the electricity supplied from the battery 502 to various locations. The control device 501 is provided in the interior space of the upper storage compartment 200. The battery 502 is located in a space surrounded by the struts 401 and crosspieces 402 of the legs 400, outside the lower storage compartment 300, and is fixed to the struts 401, crosspieces 402, and main structure 100. The distribution board 503 is provided in the interior space of the lower storage compartment 300.

[0027] At this time, the control device 501 and the switchboard 503 are connected by a first wiring 601. The first wiring 601 extends from the control device 501 provided in the internal space of the upper storage chamber 200 through the central hole 211, central communication hole 111 (upper communication hole 411 and lower communication hole 511) of the upper base 210, and the through-hole 65 and window 67 of the flange 6 to the switchboard 503 provided in the internal space of the lower storage chamber 300. The switchboard 503 and the battery 502 are also connected by a second wiring 602. The second wiring 602 extends from the switchboard 503 provided in the internal space of the lower storage chamber 300 through the wiring hole 325 of the lower cover 320 to the battery 502 provided outside the lower storage chamber 300. The switchboard 503 and the motor 31 that drives the rotor 3 are also connected by a third wiring 603. The third wiring 603 extends from the distribution board 503 provided in the internal space of the lower storage chamber 300, through the window portion 67 and through hole 65 of the flange 6, the lower communication hole 511 and the inside of each girder 2, to the motor 31 provided at the tip of each girder 2.

[0028] According to the first embodiment of the aircraft of the present invention configured as described above, the control device 501 can be stored in the upper storage compartment 200 above the main structure 100, and the distribution board 503 can be stored in the lower storage compartment 300 below. The first wiring 601 connecting the control device 501 and the distribution board 503 is not exposed to the outside by passing through the center hole 211 and central communication hole 111 (upper communication hole 411 and lower communication hole 511) of the upper base 210, as well as the through-hole 65 and window 67 of the flange 6. The second wiring 602 connecting the distribution board 503 and the battery 502 is not exposed to the outside, except for the portion between the battery 502 and the lower storage compartment 300. The third wiring 603 connecting the distribution board 503 and the motor 31 is not exposed to the outside by passing through the window 67 and through-hole 65 of the flange 6, the lower communication hole 511, and the inside of each girder 2. By not exposing these wires to the outside, damage is prevented and the design is good.

[0029] Next, an aircraft according to a second embodiment will be described. The second embodiment differs from the first embodiment in the configuration of the main structure 100. Only the differences from the first embodiment will be described below. As shown in FIG. 6, the main structure 100 according to the second embodiment has two central joints 1, a connecting portion 7 that connects the central joints 1 together, a total of eight beams 2, four of which extend radially from each central joint 1, and a rotor 3 provided at the tip of each beam 2.

[0030] The two central joints 1 are arranged side by side, one above the other, and the upper central joint 1 and the four beams 2 and rotor 3 extending from it are the same as in the first embodiment. The lower central joint 1 and the four beams 2 and rotor 3 extending from it differ from the first embodiment only in that the motors 31 and rotors 3 are attached to the undersides of the tips of the beams 2, respectively. When viewed from above, the extension directions of the upper and lower beams 2 and the positions of the rotors 3 are the same.

[0031] The central joints 1 located above and below are connected to each other by a connecting portion 7. The connecting portion 7 is made of metal and has a cylindrical connecting portion main body 71 that extends vertically, and flange portions 72 formed at the upper and lower ends of the connecting portion main body 71. The flange portion 72 is square in top view and is the same size as the central portion 11 of the central joint 1. Insertion holes that penetrate vertically are formed at the four corners of the flange portion 72. The height of the connecting portion 7 is the same as the height of the central joints 1. The inner portion of the connecting portion main body 71 forms a connecting portion communication hole 73 that penetrates vertically. The upper end surface of the connecting portion 7 abuts against the lower surface of the central portion 11 (lower central portion 51) of the upper central joint 1, and the lower end surface of the connecting portion 7 abuts against the upper surface of the central portion 11 (upper central portion 41) of the lower central joint 1, and they are each fastened with a bolt. Bolts 74 are inserted into the insertion holes and screwed into the female thread portions 412, 512. At this time, the central communication hole 111 of the upper central joint 1, the connecting portion communication hole 73 of the connecting portion 7, and the central communication hole 111 of the lower central joint 1 are in communication with each other.

[0032] A flange 6 is attached to the underside of the lower central joint 1. An upper storage chamber 200 is provided above the upper central joint 1. A lower storage chamber 300 is provided below the lower central joint 1. A leg 400 is attached to the lower girder 2. The flange 6, upper storage chamber 200, lower storage chamber 300, and leg 400 are the same as in the first embodiment. In addition, a member may be provided to connect the middle portions of the upper and lower girder members 2 in the longitudinal direction.

[0033] In this way, the internal space of the upper storage chamber 200 and the internal space of the lower storage chamber 300 are in communication with each other via the central communication hole 111 and the connecting portion communication hole 73. More specifically, the internal space of the upper storage chamber 200 is in communication with the internal space of the lower storage chamber 300 via the central hole 211 of the upper base 210, the upper central communication hole 111, the connecting portion communication hole 73, the lower central communication hole 111, the through hole 65 of the flange 6, and the window portion 67.

[0034] The control device 501, the battery 502, and the distribution board 503 are also the same as in the first embodiment. As described above, since the internal space of the upper storage chamber 200 and the internal space of the lower storage chamber 300 are connected, the first wiring 601 connecting the control device 501 and the distribution board 503 is not exposed to the outside. The second wiring 602 connecting the distribution board 503 and the battery 502 is also the same as in the first embodiment. Furthermore, the third wiring 603 connecting the distribution board 503 and the motor 31 is also the same as in the first embodiment for the lower motor 31, but for the upper motor 31, it is not exposed to the outside because it passes through the window portion 67 and through hole 65 of the flange 6, the lower central communication hole 111, the connecting portion communication hole 73, the upper lower communication hole 511, and the inside of each girder member 2.

[0035] The aircraft of the second embodiment also achieves the same effects as the aircraft of the first embodiment. Furthermore, an aircraft with eight rotors 3 can be constructed using parts common to the aircraft with four rotors 3 (first embodiment), thereby reducing costs.

[0036] The present invention is not limited to the above-described embodiments, and the shape and structure of each part can be modified as appropriate within the spirit of the invention. For example, the shapes of the upper and lower storage compartments can be modified as appropriate, taking into account the type of equipment to be stored in the internal space and the design. Furthermore, when connecting central joints vertically, the extension directions of the upper and lower beams do not need to be the same. For example, when four beams form a cross, the extension direction of the upper beam and the extension direction of the lower beam may be 45 degrees different from each other when viewed from above. In this case, the flange of the connecting part may be provided with insertion holes that can accommodate both cases where the beams extend in the same direction and cases where they extend in different directions, allowing for appropriate selection when connecting central joints using the connecting part. Furthermore, three or more central joints may be connected vertically. [Explanation of symbols]

[0037] 1 Center joint 2 Girder material 3 rotors 7 Connecting part 11 Central part 12 Girder support 73 Connection hole 100 Main structure 111 Central communication hole 200 Upper storage room 300 Lower storage compartment

Claims

1. It comprises a main structure, an upper storage room and a lower storage room, the main structure includes a central joint, a plurality of beams extending radially from the central joint, and rotors provided at the ends of the beams on the opposite side to the central joint, The central joint has a central portion and a girder support portion that supports the end portion of each of the girder members provided in the central portion on the central joint side, and a central portion communication hole that penetrates in the vertical direction is formed in the central portion, The upper storage chamber is provided above the central joint, and the lower storage chamber is provided below the central joint, An aircraft characterized in that the internal space of the upper storage compartment and the internal space of the lower storage compartment are connected to each other through the central communication hole.

2. It comprises a main structure, an upper storage room and a lower storage room, the main structure includes a plurality of central joints, connecting portions that connect the central joints to each other, a plurality of beams that extend radially from the central joints, and rotors that are provided at the ends of the beams on the opposite side to the central joints, The central joint has a central portion and a girder support portion that supports the end portion of each of the girder members provided in the central portion on the central joint side, and a central portion communication hole that penetrates in the vertical direction is formed in the central portion, A connecting portion communication hole is formed in the connecting portion, penetrating in the vertical direction, a plurality of the central joint portions are arranged vertically, the vertically positioned central portions are connected to each other by the connecting portion, and the central portion communicating hole and the connecting portion communicating hole are in communication with each other; the upper storage chamber is provided above the uppermost central joint, and the lower storage chamber is provided below the lowermost central joint, an internal space of the upper storage compartment and an internal space of the lower storage compartment communicate with each other via the central communication hole and the connecting portion communication hole;

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