Mounting structure for the cover to the access hole

Abstract

The objective is to provide a mounting structure for a cover to an access hole that reduces manufacturing costs, lessens the burden on workers, and makes it difficult for the cover to fall out of the access hole. [Solution] The device comprises a cylindrical access hole 110 and a cover 120 that is detachably installed in the access hole 110. The fixing portion 122 of the cover 120 is bolted to a bracket 130, so that the force required to push the cover 120 into the access hole 110 is eliminated, reducing the burden on the worker, while also making it difficult for the cover 120 to fall out of the access hole 110. Furthermore, the mounting structure of the cover 120 to the access hole 110 can be made relatively simple, thus reducing manufacturing costs.

Description

Technical Field

[0001] The present invention relates to an attachment structure of a cover to an access hole, and particularly to an attachment structure of a cover to an access hole that can reduce the manufacturing cost, reduce the burden on workers, and make it difficult for the cover to fall off from the access hole.

Background Art

[0002] There is known a tank including a tank body, a cylindrical skirt disposed below the tank body and provided with an access hole, and a cover capable of opening and closing the opening of the access hole (Patent Document 1). In the attachment structure of the cover to the access hole described in Patent Document 1, the cover is pivotally supported on the access hole by a hinge, and further, the cover is bolted to the access hole.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the attachment structure of the cover to the access hole described in Patent Document 1, it was difficult to suppress the manufacturing cost because a hinge was used.

[0005] Therefore, the applicant conceived of a cover mounting structure for an access hole that does not use hinges, but instead has claws that bias toward the inner circumferential surface of the access hole (not publicly known at the time of filing). However, with this cover mounting structure for an access hole, the worker needs to push the cover toward the access hole against the biasing force of the claws. If the biasing force of the claws is increased, a large force is required to attach it to the access hole, which increases the burden on the worker. Conversely, if the biasing force of the claws is decreased, the cover may be pushed from the inside of the skirt due to the pressure difference between the space inside and outside the skirt, and there is a risk that the cover will fall out of the access hole.

[0006] In other words, these conventional technologies described above had problems in that it was difficult to reduce manufacturing costs, lessen the burden on workers, and prevent the cover from falling off.

[0007] This invention was made to solve the above-mentioned problems, and aims to provide a cover mounting structure for access holes that reduces manufacturing costs, alleviates the burden on workers, and makes it difficult for the cover to fall out of the access hole. [Means for solving the problem]

[0008] To achieve this objective, the present invention provides a cover mounting structure for an access hole, comprising: a cylindrical skirt disposed below the tank body; a cylindrical access hole penetrating the skirt in the thickness direction and communicating the outer space of the skirt with a maintenance area inside the skirt; and a cover disposed at the outer end of the access hole protruding towards the outer space and configured to be detachably attached to the access hole, wherein the cover is to be opened and closed and attached to the access hole, and comprises a plurality of brackets disposed on the access hole or the skirt, wherein the cover comprises a cover body that covers the opening of the access hole in an openable and closable manner, and a plurality of fixing parts that protrude outward from the outer edge of the cover body and can be bolted to the brackets. [Effects of the Invention]

[0009] According to the cover mounting structure for an access hole described in claim 1, the cover comprises a plurality of brackets disposed in the access hole or skirt, and the cover comprises a cover body that covers the opening of the access hole in a manner that can be opened and closed, and a plurality of fixing parts that protrude outward from the outer edge of the cover body and can be bolted to the brackets. Therefore, the cover is detachably fixed to the access hole by bolting the plurality of brackets and the plurality of fixing parts together. Thus, the manufacturing cost can be made cheaper than a structure that uses a hinge to open and close the opening of the access hole.

[0010] Since the cover's fixing part and the bracket are bolted together, the cover is detachably secured to the access hole. Compared to a structure where the cover is held in the access hole by the biasing force of claws on the cover body, this eliminates the need for the worker to push the cover against the biasing force of the claws towards the access hole, while still securely fixing the cover to the access hole. Therefore, it reduces the burden on the worker and makes it less likely for the cover to fall out of the access hole.

[0011] As a result, manufacturing costs can be reduced, the burden on workers can be lessened, and the cover can be made less likely to fall off.

[0012] The cover mounting structure for the access hole described in claim 2 provides, in addition to the effects of the cover mounting structure for the access hole described in claim 1, the cover is provided with a cylindrical flange that protrudes rearward from the rear surface of the cover body and whose inner diameter is set to be larger than the outer diameter of the access hole, and the fixing part and bracket are provided with holes through which bolts are inserted, and in the holding state in which the cover is held in the access hole by bringing the inner surface of the flange into contact with the outer surface of the access hole from above downward, the holes of the fixing part and the holes of the bracket can be aligned, so that it is not necessary for the worker to lift the cover in the holding state when aligning the holes of the fixing part and the holes of the bracket. Thus, the burden on the worker can be reduced.

[0013] The mounting structure for the cover to the access hole described in claim 3 provides, in addition to the effects of the mounting structure for the cover to the access hole described in claim 1, the bracket is a plate that is substantially L-shaped in top view, and comprises a flat plate-shaped first part in which one end is welded to the outer surface of the skirt and rises from the outer surface of the skirt from one end to the other, and a flat plate-shaped second part in which the other end of the first part protrudes toward the outer surface of the access hole and can be bolted to a fixing part. Therefore, compared to the case in which one end of the first part is welded to the access hole, it is easier to secure space on both sides of one end of the first part in a top view. Thus, welding work can be made easier.

[0014] The cover mounting structure for the access hole described in claim 4 provides, in addition to the effects of the cover mounting structure for the access hole described in claim 3, the cover is provided with a cylindrical flange that protrudes rearward from the rear surface of the cover body and whose inner diameter is set to be larger than the outer diameter of the access hole, and in the holding state in which the cover is held in the access hole by bringing the inner surface of the flange into contact with the outer surface of the access hole from above downward, the second part is located on the skirt side of the fixing part, and the surface of the second part facing away from the skirt and the back surface of the fixing part facing the skirt side are separated in the thickness direction of the cover body, so that in the holding state before bolting the second part and the fixing part together, a gap is formed between the surface of the second part and the back surface of the fixing part. This makes it easier to tolerate variations in the dimensions of the bracket and the cover (fixing part), and variations in the welding accuracy of the bracket.

[0015] Furthermore, since the bracket is shaped like a roughly L-shaped plate when viewed from above, bolting the second part and the fixing part together causes the second part of the bracket to elastically deform toward the cover (fixing part). As a result, the elastic restoring force of the bracket acts on the cover via the fixing part, biasing it toward the access hole. This makes it easier to make the cover tightly adhere to the access hole. Therefore, it is possible to reduce the amount of rainwater and other debris that enters the maintenance area from between the cover body and the outer edge of the access hole.

[0016] The cover mounting structure for the access hole described in claim 5 provides, in addition to the effects of the cover mounting structure for the access hole described in claim 4, the fixing part is a separate component from the cover body, so the material and shape of the fixing part can be different from those of the cover body. This improves the design freedom of the cover. For example, by making the fixing part a plate parallel to the second part, the fixing part can be made elastically deformable, making it easier to absorb forces that would cause the cover to fall off through the elastic deformation of the fixing part. Therefore, the bracket and the fixing part are less likely to be damaged. [Brief explanation of the drawing]

[0017] [Figure 1] This is a side view of a tank equipped with a cover mounting structure for access holes in one embodiment. [Figure 2] (a) is a front view of the cover, and (b) is a cross-sectional view of the cover along the line IIb-IIb in (a). [Figure 3] (a) is a partial front view of the tank as seen from the direction of arrow IIIa in Figure 1, and (b) is a partial cross-sectional view of the tank along the line IIIb-IIIb in (a). [Figure 4] (a) is a partial cross-sectional view of the tank before the holding state along the line IVa-IVa in Figure 3(a), and (b) is a partial cross-sectional view of the tank in the holding state. [Figure 5] (a) is a rear view of the cover in the first modified example, (b) is a partial cross-sectional view of the tank in an aligned state with the cover mounting structure to the access hole, and (c) is a partial cross-sectional view of the tank with the cover mounting structure to the access hole in the second modified example. [Modes for carrying out the invention]

[0018] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a side view of a tank 100 having an attachment structure to an access hole 110 of a cover 120 in one embodiment. In FIG. 1, the arrows F-B, U-D, and L-R in the figure indicate the front-rear direction, the up-down direction (vertical up-down direction), and the left-right direction of the tank 100, respectively (the same applies in FIGS. 2 to 5). Note that in FIG. 1, the central portion in the up-down direction of the tank 100 is omitted and illustrated.

[0019] In this embodiment, the inner peripheral surface 123a of the flange 123 is brought into contact with the outer peripheral surface 111 of the access hole 110 from above to below, and the state in which the cover 120 is held (supported in the gravitational direction) by the access hole 110 (see FIG. 4(b)) is defined as the holding state, and the state in which the hole 122a of the fixing portion 122 and the hole 133 of the bracket 130 are aligned at a position where they can be bolted (see FIG. 3) is defined as the alignment state for explanation. Further, the state in which the bolt B is inserted through the hole 122a of the fixing portion 122 and the hole 133 of the bracket 130 from the alignment state and the fastening by the bolt B is completed is defined as the attachment state for explanation.

[0020] As shown in FIG. 1, the tank 100 is a vertical tank installed on a foundation G. The tank 100 includes a skirt 102 erected from the foundation G and a tank body 101 connected to the upper end of the skirt 102.

[0021] The tank body 101 is a steel member, and is formed in a cylindrical shape that extends in the up-down direction and has its upper and lower surfaces closed. In this embodiment, hydrogen gas is stored in a gaseous state inside the tank body 101. Note that in this embodiment, the tank body 101 is described as being cylindrical, but it may also be hollow spherical or rectangular cylindrical.

[0022] The skirt 102 is a cylindrical steel member with approximately the same diameter as the tank body 101, and forms a maintenance area S in the space between the tank body 101 and the foundation G (within the skirt 102). That is, the maintenance area S and the outer space, which is the space outside the maintenance area S, are separated by the skirt 102. The maintenance area S is a space for maintenance workers to enter in order to perform maintenance work on the tank 100. In this embodiment, the skirt 102 is described as being cylindrical, but for example, if the tank body 101 is rectangular, the skirt may be a rectangular tube with approximately the same outer shape as the tank body 101. That is, since the skirt 102 is provided for the purpose of preventing rainwater and the like from entering the maintenance area S, its outer shape is made to correspond to the outer shape of the tank body 101.

[0023] The skirt 102 includes a flange portion 102a that extends outward from the entire circumference of its lower end, and a gas vent hole 102b that connects the maintenance area S with the space outside the skirt 102. The skirt 102 is attached to the foundation G by fixing the flange portion 102a with anchor bolts (not shown) provided in the foundation G. The gas vent hole 102b is intended to prevent hydrogen gas that has leaked into the maintenance area S due to gas leakage from the tank body 101 from accumulating inside the skirt 102. As will be described in detail later, the outer circumferential surface 102c of the skirt 102 of the tank 100 is marked with a fixing position mark 103, which serves as a guide when attaching the cover 120 to the access hole 110.

[0024] The skirt 102 is provided with an access hole 110 that connects the outer space of the skirt 102 and the maintenance area S in the front-rear direction, with the outer end 113 protruding towards the outer space and the inner end 114 protruding towards the maintenance area S (see Figure 3(b)).

[0025] The access hole 110 is a cylindrical member that connects the outer space of the skirt 102 and the maintenance area S in the front-rear direction. A cover 120 is provided at the outer end 113 of the access hole 110, and is detachably fixed to the access hole 110 (see Figure 3(b)). Note that the shape of the access hole 110 is not limited to a cylindrical shape; it may also be a rectangular tube or an elliptical tube.

[0026] The cover 120 is designed to prevent debris, rain, snow (hereinafter referred to as "rainwater, etc.") from entering the maintenance area S from the outside space through the access hole 110. By attaching the cover 120 to the access hole 110, the opening of the access hole 110 is closed, suppressing the intrusion of rainwater, etc. into the maintenance area S. Conversely, by removing the cover 120 from the access hole 110, the opening of the access hole 110 is opened, allowing maintenance workers to enter the maintenance area S. In other words, the access hole 110 can be opened and closed by attaching and detaching the cover 120.

[0027] Here, since the skirt 102 is provided with a flange portion 102a and a gas vent hole 102b, for example, strong winds may cause air to enter the maintenance area S through the gap between the flange portion 102a and the foundation G or through the gas vent hole 102b, causing the pressure inside the maintenance area S to increase. Also, for example, tornadoes may cause the air pressure on the outside space to decrease. In other words, strong winds, tornadoes, and various other factors may cause a pressure difference between the outside space and the inside of the maintenance area S. As a result, if the cover 120 is not fixed to the skirt 102, the pressure inside the maintenance area S will be relatively larger than the air pressure on the outside space, causing pressure to be applied to the cover 120 in a direction that pushes it towards the outside space, and the cover 120 may fall out of the access hole 110.

[0028] In contrast, the mounting structure of the cover 120 to the access hole 110 in this embodiment, as will be described in detail later, involves bolting the bracket 130 and the fixing part 122 together (the cover 120 is fixed to the skirt 102), thereby reducing manufacturing costs, minimizing the burden on workers, and making it difficult for the cover 120 to fall out of the access hole 110.

[0029] Next, the mounting structure of the cover 120 to the access hole 110 will be described with reference to Figures 2 and 3. Figure 2(a) is a front view of the cover 120, and Figure 2(b) is a cross-sectional view of the cover 120 along the line IIb-IIb in Figure 2(a). Figure 3(a) is a partial front view of the tank 100 viewed from the direction of arrow IIIa in Figure 1, and Figure 3(b) is a partial cross-sectional view of the tank 100 along the line IIIb-IIIb in Figure 3(a).

[0030] In Figure 2, the vertical, horizontal, and front-to-back directions of the cover 120 are described in terms of their orientation in the installed state (similar to the cover 220 in Figure 5(a)). Figures 3(a) and 3(b) illustrate the aligned state and the state at which the head of the bolt B contacts the surface 122b of the fixing part 122 (i.e., the state before the fixing part 122 and bracket 130 are elastically deformed by the fastening of the bolt B and nut 134) (similar to the tank 300 in Figure 5(c)). In Figure 3(a), the tank 100 is shown with the parts other than the access hole 110 and bracket 130 located omitted, and in Figure 3(b), the part to the right of the center of the access hole 110 in the horizontal direction is omitted.

[0031] As shown in Figure 2(a), the cover 120 is a component that is bolted to the bracket 130 and is detachable from the access hole 110 (tank 100). The cover 120 comprises a disc-shaped cover body 121, a plurality (two in this embodiment) of fixing parts 122 whose one end is welded to the front surface 126, which is the front side (front side in Figure 2(a)) of the cover body 121, a cylindrical flange 123 that protrudes vertically (rearward) from near the outer edge 121a of the rear surface 125, which is the rear side (back side in Figure 2(a)) of the cover body 121 and is formed around the entire circumference, and a pair of gripping parts 124 arranged on the front surface 126 of the cover body 121. The cover body 121, fixing parts 122, flange 123, and gripping parts 124 are each made of steel. In this embodiment, the cover body 121 and the fixing parts 122 are separate components.

[0032] The cover body 121 is a disc-shaped member that is slightly larger than the diameter of the outer surface 111 of the access hole 110. When installed, it covers the opening of the access hole 110, and the cover 120 closes the opening of the access hole 110. When installed, the front surface 126 of the cover body 121 faces the outer space, and the rear surface 125 faces the access hole 110.

[0033] The front surface 126 of the cover body 121 is marked with a mark 127 that, when aligned with the fixing position mark 103 on the outer peripheral surface 102c of the skirt 102, serves as a guide for the position in which the cover 120 is attached to the access hole 110. As will be described in detail later, the mark 127 on the cover 120 and the fixing position mark 103 on the outer peripheral surface 102c of the skirt 102 are located in positions where the hole 122a of the fixing part 122 and the hole 133 of the bracket 130 correspond when the cover is attached.

[0034] The fixing portion 122 is a component that is bolted to the bracket 130 (described later) when the cover 120 is fixed to the access hole 110. The pair of fixing portions 122 are positioned in the center of the flange 123 in the vertical direction and opposite each other in the left-right direction of the cover body 121 when installed. That is, the fixing portions 122 are positioned in pairs so as to face each other at 180 degrees circumferentially on the cover body 121. The pair of fixing portions 122 have the same shape and the same Young's modulus. The back surface 122c of one end of the fixing portion 122 is welded to the front surface 126 of the cover body 121. The fixing portion 122 extends from one end to the other end toward the outer edge 121a of the cover body 121, with the other end protruding outward from the outer edge 121a of the cover body 121. The fixing portion 122 is a flat plate thinner than the thickness of the cover body 121 and is roughly rectangular in front view.

[0035] The fixing portion 122 is provided with a hole 122a through which a bolt B is inserted. The hole 122a is an elongated hole that extends vertically when installed. The distance L1 extending upward from the vertical center of the fixing portion 122 through the hole 122a and the distance L2 extending downward from the vertical center of the fixing portion 122 through the hole 122a are set to be the same distance. The width of the hole 122a in the short direction is set to a distance that is sufficiently large compared to the outer diameter of the male thread portion of the bolt B. The longitudinal center of the hole 122a of the fixing portion 122 is located at the vertical center of the flange 123 when installed.

[0036] As shown in Figure 2(b), the flange 123 is joined to the rear surface 125 of the cover body 121 by welding. The flange 123 may also be molded integrally with the cover body 121. The flange 123 is a component that covers the access hole 110 from above, from the holding state to the mounting state, and prevents rainwater and the like from directly entering from above between the cover body 121 and the outer end 113 of the access hole 110.

[0037] The diameter of the inner circumferential surface 123a of the flange 123 is set to be larger than the diameter of the outer circumferential surface 111 of the access hole 110 (see Figures 3(a) and 4). Also, the length to which the flange 123 is erected vertically from the rear surface 125 is set to be shorter than the length to which the access hole 110 protrudes from the outer circumferential surface 102c of the skirt 102 toward the outer space. By bringing the inner circumferential surface 123a of the flange 123 into contact with the outer circumferential surface 111 of the access hole 110 from above toward below, the cover 120 is held in the access hole 110 (held in place).

[0038] The gripping portion 124 is the part that is held by a person's hand to lift or adjust the position of the cover 120 when fixing the cover 120 to the access hole 110 or when removing the cover 120 from the access hole 110. The gripping portion 124 is formed in a roughly U-shape by bending a round bar at right angles at two arbitrary positions separated in the longitudinal direction.

[0039] The gripping portion 124 is positioned parallel to the fixing portion 122 at a predetermined distance apart, with its longitudinal direction perpendicular to the direction in which the fixing portion 122 faces (the left-right direction in the mounted state). Therefore, when the pair of gripping portions 124 are gripped so that the left-right direction of the cover 120 corresponds to the left-right direction of the access hole 110, and the cover 120 is attached to the access hole 110, it becomes easier to align the fixing portion 122 to a position that overlaps with the bracket 130.

[0040] Furthermore, when an operator grasps the pair of gripping parts 124 to attach the cover 120 to the access hole 110, the pair of gripping parts 124 are arranged side by side in the left-right direction, making it easier to hold the cover 120 with both hands when fixing the cover 120 to the access hole 110 or when removing the cover 120 from the access hole 110.

[0041] As shown in Figures 3(a) and 3(b), the bracket 130 is a member formed by bending a steel plate into an L-shape, and comprises a flat plate-shaped first part 131 whose one end 131a is welded to the outer peripheral surface 102c of the skirt 102, and a flat plate-shaped second part 132 which is bent at 90° from the other end 131b of the first part 131 and extends in a direction perpendicular to the direction in which the first part 131 extends. A pair of brackets 130 are arranged on both sides of the access hole 110 in the left-right direction and in the center of the access hole 110 in the vertical direction.

[0042] The second part 132 is provided with a hole 133 through which a bolt B is inserted in the thickness direction, and a nut 134 is welded to the back surface 132b, which is the surface facing the skirt 102, communicating with the hole 133 and screwed with the bolt B. With one surface of the first part 131, which is the surface connected to the back surface 132b of the second part 132, facing the outer surface 111 of the access hole 110, one end 131a of the first part 131 is welded to the outer surface 102c of the skirt 102. In other words, the bracket 130 is welded to the skirt 102 with the second part 132 extending toward the access hole 110. The center of the hole 133 in the second part 132 is located in the vertical center of the access hole 110. In other words, when the center of the access hole 110 and the center of the cover 120 coincide, and the left-right position of the cover 120 is aligned with the left-right position of the access hole 110, the hole 133 of the bracket 130 is positioned at the center of the longitudinal direction (vertical direction) of the hole 122a of the fixing part 122.

[0043] Here, we consider the case where the bracket 130 is welded to the outer circumferential surface 102c of the skirt 102, and the second part 132 of the bracket 130 extends away from the access hole 110. In this case, the hole 133 of the bracket 130 tends to be positioned far from the access hole 110 and the outer edge 121a of the cover body 121, and the distance at which the fixing part 122 protrudes from the outer edge 121a of the cover body 121 needs to be increased to correspond to the hole 133 of the bracket 130. To solve this, if the welding position between the bracket 130 and the skirt 102 is moved closer to the access hole 110, it becomes difficult to secure space for welding one end 131a of the first part 131 of the bracket 130 to the skirt 102. That is, when performing welding work, it becomes difficult to secure space to insert a welding tool such as a torch from above (or below) the gap and position the tip of the tool close to the welding location.

[0044] In contrast, in this embodiment, the bracket 130 is welded to the outer circumferential surface 102c of the skirt 102 with the direction in which the second part 132 extends facing the access hole 110, so that a gap is formed between one surface of the first part 131 and the outer circumferential surface 111 of the access hole 110. This makes it possible to secure space for welding work between one surface of the first part 131 and the outer circumferential surface 111 of the access hole 110 when welding one end 131a of the first part 131 to the tank 100 side. Thus, welding work can be made easier.

[0045] Furthermore, since the bracket 130 is welded to the skirt 102 with the direction in which the second part 132 extends facing the access hole 110, the hole 133 of the bracket 130 can be brought closer to the access hole 110 and the outer edge 121a of the cover body 121. This reduces the distance that the fixing part 122 protrudes from the cover body 121.

[0046] Furthermore, when attempting to weld one end 131a of the first part 131 to the outer circumferential surface 102c of the skirt 102, the end 131a of the first part 131 can be positioned along the vertical direction of the outer circumferential surface 102c of the skirt 102. Even when the skirt 102 is cylindrical with its axis extending in the vertical direction, as in this embodiment, the vertical direction of the outer circumferential surface 102c is straight, so the end 131a can be welded along a relatively flat surface. Therefore, compared to welding along the curved outer circumferential surface 102c of the skirt 102 or welding along the curved outer circumferential surface 111 of the access hole 110, welding can be made easier while ensuring welding strength.

[0047] Next, with reference to Figure 4, the method for attaching the cover 120 to the access hole 110 will be described. Note that the method for removing the cover 120 from the access hole 110 is the reverse of the procedure for attaching the cover 120 to the access hole 110, so the explanation for that will be omitted.

[0048] Figure 4(a) is a partial cross-sectional view of the tank 100 before the holding state along the line IVa-IVa in Figure 3(a), and Figure 4(b) is a partial cross-sectional view of the tank 100 in the holding state. Note that in Figure 4(a), for explanatory purposes, the center of the cover 120 and the center of the access hole 110 are shown to coincide.

[0049] As shown in Figure 4(a), first, the worker holds the cover 120 by the gripping part 124 so that the outer circumferential surface 111 of the access hole 110 is positioned inside the inner circumferential surface 123a of the flange 123 of the cover 120. At this time, in order to roughly align the hole 122a of the fixing part 122 and the hole 133 of the bracket 130, the worker aligns the mark 127 attached to the front surface 126 of the cover 120 with the fixing position mark 103 attached to the outer circumferential surface 102c of the skirt 102 when viewed from the front surface 126 side of the cover 120.

[0050] Next, as shown in Figure 4(b), the inner circumferential surface 123a of the flange 123 of the cover 120 is brought into contact with the outer circumferential surface 111 of the access hole 110 from above downwards, thereby placing the cover 120 on the access hole 110. This holds the cover 120 in a position where it is supported by gravity in the access hole 110. In this state, even when working alone, the operator can release their hand from the gripping part 124.

[0051] The distance L3 between the inner circumferential surface 123a of flange 123 and the outer circumferential surface 111 of access hole 110, when the center of the cover 120 and the center of the access hole 110 are aligned, is obtained by subtracting the diameter of the outer circumferential surface 111 of access hole 110 from the diameter of the inner circumferential surface 123a of flange 123 and dividing the result by 2 (see Figure 4(a)). Note that the distances L1 and L2 of the holes 122a of the fixing part 122 are set to be greater than the distance L3.

[0052] In the held state, the cover 120 is supported by the flange 123 in the access hole 110, so the center of the cover 120 is lowered by a distance L3 from the center of the access hole 110. Therefore, the gap between the inner circumferential surface 123a of the flange 123 and the outer circumferential surface 111 of the access hole 110 at the top of the access hole 110 is approximately 0, and the gap L4 between the inner circumferential surface 123a of the flange 123 and the outer circumferential surface 111 of the access hole 110 at the bottom of the access hole 110 is approximately twice the distance L3.

[0053] In this state, the hole 122a of the fixing part 122 and the hole 133 of the second part 132 of the bracket 130 do not necessarily coincide. However, even in this case, while maintaining the holding state (that is, while maintaining the state in which the cover 120 is supported in the access hole 110 by bringing one part of the inner circumferential surface 123a of the flange 123 into contact with the outer circumferential surface 111 of the access hole 110 from above downwards), the cover 120 can be moved circumferentially or horizontally to the left and right relative to the access hole 110, or swung from side to side using the part where the inner circumferential surface 123a of the flange 123 and the outer circumferential surface 111 of the access hole 110 contact as a pivot point, thereby aligning the hole 122a of the fixing part 122 and the hole 133 of the second part 132 of the bracket 130.

[0054] In this case, the cover 120 can maintain its supported position in the access hole 110, eliminating the need for the worker to lift the cover 120 to align the hole 122a in the fixing part 122 with the hole 133 in the bracket 130. As a result, the burden on the worker can be reduced.

[0055] Here, we consider the case where the center of the access hole 110 and the center of the cover 120 coincide, and the hole 133 of the bracket 130 is positioned in the longitudinal center of the hole 122a of the fixing part 122, and the unit is then held in place. In this case, the cover 120 is lowered by a distance L3 relative to the access hole 110, so the hole 133 of the bracket 130 is positioned L3 above the longitudinal (vertical) center of the hole 122a of the fixing part 122. Since the distance L1 of the hole 122a of the fixing part 122 is set to be greater than the distance L3, in this state, there can be vertical clearance between the hole 122a of the fixing part 122 and the hole 133 of the bracket 130. This makes it easier to insert the bolt B through the holes 122a and 133. Therefore, the work of aligning the hole 122a of the fixing part 122 and the hole 133 of the bracket 130 while maintaining the held state can be made easy or unnecessary.

[0056] Even if the cover 120 is rotated 180 degrees relative to the access hole 110, thereby reversing the vertical orientation of the cover 120, the cover body 121 and flange 123 are formed in a vertically symmetrical cylindrical shape, and the fixing part 122 is positioned vertically and horizontally symmetrically, so the position of the fixing part 122 can be aligned with the bracket 130. Furthermore, since the distance L2 of the hole 122a in the fixing part 122 is set to be larger than the distance L3, even if the cover 120 is reversed vertically, there is still vertical clearance in the hole 122a of the fixing part 122 relative to the hole 133 of the bracket 130. This makes it easier to insert the bolt B through the holes 122a and 133, just as when the cover 120 is not reversed vertically. It is preferable that, even when the cover 120 is reversed vertically, a mark (not shown) corresponding to the fixing position mark 103 of the skirt 102 is added to facilitate alignment of the holes 122a and 133 when the cover 120 is reversed vertically.

[0057] Now, let's consider the case where the hole positions of the hole 122a in the fixing part 122 and the hole 133 in the bracket 130 do not coincide in the held state. Even in this case, since the hole 122a in the fixing part 122 is an elongated hole extending in the vertical direction, it is easier to align the hole positions of the hole 122a in the fixing part 122 and the hole 133 in the bracket 130 when changing from the held state to the alignment state.

[0058] To explain in detail, when moving from the holding state to the alignment state, the cover 120 is moved circumferentially or horizontally to the left and right relative to the access hole 110, or it is swung from side to side using the point where the inner circumferential surface 123a of the flange 123 and the outer circumferential surface 111 of the access hole 110 come into contact as a pivot point. At this time, since the hole 122a of the fixing part 122 is an elongated hole that extends in the vertical direction, the trajectory through which the hole 122a of the fixing part 122 passes can be made wider compared to when it is a round hole. This makes it easier to tolerate misalignment between the holes 122a and 133. In other words, the precision required to align the hole positions of 122a and 133 can be relaxed. Therefore, the work of aligning the positions of the holes 122a and 133 can be made easier. As a result, the workability when attaching the cover 120 to the access hole 110 can be improved.

[0059] From the alignment state until the head of bolt B comes into contact with the surface 122b of the fixing part 122, a gap D1 is formed between the surface 132a of the second part 132 of the bracket 130 and the back surface 122c of the fixing part 122 (see Figure 3(b)).

[0060] As bolt B is screwed onto nut 134 to move from that state to the installed state, a force is applied to the fixing part 122 and bracket 130 in a direction that reduces the gap D1. That is, a force is applied to the fixing part 122 in a direction toward bracket 130, and a force is applied to the bracket 130 in a direction toward fixing part 122. As a result, the fixing part 122 and bracket 130 are elastically deformed in a direction that brings them closer together.

[0061] The fixing part 122 is a flat plate with one end fixed to the cover body 121 and the other end extending outward from the outer edge 121a of the cover body 121 (i.e., cantilevered), and the bracket 130 is a plate that is roughly L-shaped when viewed from above. Therefore, compared to solid block-shaped or cylindrical fixing parts 122 and bracket 130, the fixing part 122 and bracket 130 can be more easily elastically deformed in the direction that brings them closer together.

[0062] As bolt B is screwed onto nut 134, the fixing part 122 and bracket 130 are elastically deformed in a direction that brings them closer to each other. The fixing part 122 is elastically deformed so that the other end approaches the bracket 130, with the one end fixed to the cover body 121 acting as a fulcrum. The bracket 130 is elastically deformed so that the second part 132 approaches the fixing part 122, with the other end 131b of the first part 131 acting as a fulcrum.

[0063] In the installed state, the fixing part 122 and the bracket 130 are elastically deformed in close proximity, so the elastic restoring force of the bracket 130 and the elastic restoring force of the fixing part 122 each act in a direction that moves the cover 120 toward the access hole 110. As a result, the cover 120 is tightly pressed against the access hole 110. Therefore, it is possible to prevent rainwater and the like from entering the access hole 110 and the maintenance area S from between the cover body 121 and the outer end 113 of the access hole 110.

[0064] In this case, a hard material such as cast iron may be used for the cover body 121 to ensure rigidity. If the fixing part 122 is integrated with the cover body 121, the fixing part 122 is also made of a relatively hard material, making it difficult to ensure the elastic deformability of the fixing part 122 even if it is made in the shape of a plate. The same applies when the outer edge 121a side of the cover body 121 is expanded and the fixing part 122 is machined into that expanded portion.

[0065] In contrast, in this embodiment, the fixing part 122 is made of a separate component from the cover body 121, thereby improving the design freedom of the cover 120. For example, the cover body 121 can be made of a hard material such as cast iron to ensure rigidity, while the fixing part 122 can be made of a plate-like or easily elastically deformable material to ensure elastic deformation to fill the gap D1.

[0066] In the installed state, the fixing part 122 and the second part 132 of the bracket 130 are bolted together, thereby supporting the cover 120 in the front-rear direction relative to the access hole 110 (in the direction that causes the cover 120 to fall out of the access hole 110 and in the direction that causes the cover 120 to be tightly attached to the access hole 110). Compared to an installation structure in which the cover 120 and the access hole 110 are pivotally supported by a hinge to open and close the opening of the access hole 110, the cost of the parts used in the installation structure can be reduced, and the structure can be simplified. Therefore, the manufacturing cost can be reduced.

[0067] Furthermore, compared to a mounting structure in which the cover 120 is held in the access hole 110 by the biasing force of claws provided on the cover body 121, this method eliminates the need for the worker to push the cover 120 towards the access hole 110 against the biasing force of the claws, while still securely fixing the cover 120 to the access hole 110. Therefore, it reduces the burden on the worker while making it difficult for the cover 120 to fall out of the access hole 110.

[0068] As a result, the manufacturing cost of providing the tank 100 with a mounting structure for the cover 120 to the access hole 110 can be reduced, the burden on the worker when attaching the cover 120 to the access hole 110 can be reduced, and even if a force is applied that would cause the cover 120 to fall off due to the pressure difference between the inside of the skirt 102 (maintenance area S) and the space outside the skirt 102, the cover 120 can be made less likely to fall off the access hole 110.

[0069] Although the present invention has been described above based on embodiments, it can be easily inferred that the present invention is not limited in any way to the above embodiments, and that various improvements and modifications are possible without departing from the spirit of the present invention.

[0070] In the above embodiment, we have described the case in which, from the holding state to the alignment state, the inner circumferential surface 123a of the flange 123 abuts against the outer circumferential surface 111 of the access hole 110 from above downwards, thereby supporting the cover 120 in the access hole 110. In addition to this, in the alignment state, we will describe, with reference to Figures 5(a) and 5(b), the case in which the flange 123 and the access hole 110 are engaged to prevent the cover 120 from falling out of the access hole 110, as the mounting structure of the cover 220 to the access hole 210 in the first modified example.

[0071] Figure 5(a) is a rear view of the cover 220 in the first modified example, and Figure 5(b) is a partial cross-sectional view of the tank 200 in an aligned state with the mounting structure for the cover 220 to the access hole 210. In Figure 5(b), the cross-section of the tank 200 is shown in the upper part of the access hole 210, obtained by cutting the center of the access hole 210 in the left-right direction vertically. The same reference numerals are used for parts that are the same as those described in the above embodiment, and the following description is omitted (the same applies to Figure 5(c)).

[0072] As shown in Figures 5(a) and 5(b), the flange 223 of the cover 220 is provided with a convex engaging portion 228 that protrudes inward from the inner circumferential surface 223a. The engaging portion 228 is located on the apex side of the cover 220 when it is aligned. The lower end surface of the engaging portion 228 is flat.

[0073] As shown in Figure 5(b), the outer circumferential surface 211 of the access hole 210 is provided with a concave engaged portion 215 that is recessed inward and penetrates in the left-right direction, at a position corresponding to the position of the engaging portion 228 in the aligned state (towards the apex of the access hole 210). The bottom surface of the engaged portion 215 is flat. In the aligned state, the engaged portion 215 engages with the engaging portion 228 by inserting the convex engaging portion 228 into the inside of its recess. The engaging portion 228 and the engaged portion 215 are set so that a small gap is formed between the lower end surface of the engaging portion 228 and the bottom surface of the engaged portion 215 when the lower end surface of the engaging portion 228 and the bottom surface of the engaged portion 215 are parallel.

[0074] According to the mounting structure of the cover 220 to the access hole 210 of the first modified example, in the alignment state, the engaged portion 215 has a structure in which a convex engaging portion 228 is inserted into the inside of its recess and engages with the engaging portion 228. Therefore, even in the state before bolting the fixing portion 122 and the bracket 130 together (alignment state), the cover 220 can be prevented from falling out of the access hole 210. Thus, safety can be improved when performing tasks that require releasing the gripping portion 124 (for example, bolting from the alignment state by one person, or removing bolt B by one person and removing the cover 120 from the access hole 110).

[0075] In the mounting structure of the cover 220 to the access hole 210 of the first modified example, an engaging portion 228 is provided on the apex side of the cover 220, and a engaged portion 215 corresponding to the engaging portion 228 is provided on the apex side of the access hole 210. Furthermore, the lower end surface of the engaging portion 228 is flat, and the bottom surface of the engaged portion 215 that engages with the engaging portion 228 is also flat. In the aligned state, the lower end surface of the engaging portion 228 and the bottom surface of the engaged portion 215 face each other with the inner circumferential surface 223a of the flange 223 supported by the outer circumferential surface 211 of the access hole 210.

[0076] When the lower end surface of the engaging portion 228 and the bottom surface of the engaged portion 215 are engaged so that they are parallel, a small gap is formed between them, allowing the cover 220 to swing relative to the access hole 210 by the amount of this gap (swinging with the part of the flange 223 that is supported by the access hole 210 as the pivot point). Furthermore, by the contact between the lower end surface of the engaging portion 228 and the bottom surface of the engaged portion 215, the rotation of the cover 220 relative to the access hole 210 can be restricted to a certain range including the position in which the hole 122a of the fixing portion 122 and the hole 133 of the bracket 130 are aligned. Therefore, it is easier to align the hole 122a of the fixing portion 122 with the hole 133 of the bracket 130.

[0077] The gap formed between the lower end surface of the engaging portion 228 and the bottom surface of the engaged portion 215 may be large enough not to restrict the swinging and rotation of the cover 220 relative to the access hole 210.

[0078] In the first modified example, the mounting structure of the cover 220 to the access hole 210 was described in which a gap is formed between the lower end surface of the engaging portion 228 and the bottom surface of the engaged portion 215 when they are engaged in a parallel manner in the alignment state. However, it is also possible to have a structure in which the lower end surface of the engaging portion 228 and the bottom surface of the engaged portion 215 are in contact in the alignment state and no gap is formed. In this case, the vertical position of the cover 220 (fixing portion 122) relative to the access hole 210 (bracket 130) can be set to a constant position. This allows the position of the hole 122a of the fixing portion 122 and the hole 133 of the bracket 130 to be aligned by moving the cover 220 horizontally left and right so that the hole 122a of the fixing portion 122 aligns with the hole 133 of the bracket 130.

[0079] In the first modified example, the case in which the engaging portion 228 is convex and the engaged portion 215 is concave was described, but it is also possible for the engaging portion 228 to be concave and the engaged portion 215 to be convex. Furthermore, the case in which the engaging portion 228 and the engaged portion 215 are provided at the apex of the cover 220 and the access hole 210 in the held state was described, but the positions in which the engaging portion 228 and the engaged portion 215 are provided do not have to be at their respective apex, as long as they are positions in which the engaging portion 228 and the engaged portion 215 can engage with each other in the held state.

[0080] In the above embodiment, the case in which the bracket 130 is approximately L-shaped when viewed from above was described. However, the case in which the bracket 330 is approximately U-shaped when viewed from above will be described as the mounting structure for the cover 120 to the access hole 110 in the second modified example, with reference to Figure 5(c). Figure 5(c) is a partial cross-sectional view of a tank 300 equipped with the mounting structure for the cover 120 to the access hole 110 in the second modified example. In Figure 5(c), the part and state (alignment state) corresponding to the enlarged view of the part of the tank 300 in which the bracket 130 and the fixing part 122 are bolted together in Figure 3(b) are shown.

[0081] As shown in Figure 5(c), the bracket 330 is a plate-shaped steel member that is curved in a roughly U-shape when viewed from above. The bracket 330 comprises a flat first part 331, one end 331a of which is welded to the outer circumferential surface 111 of the access hole 110; a plate-shaped curved part 335 connected to the other end 331b of the first part 331 and curved 180 degrees toward the outer circumferential surface 111 of the access hole 110 and toward away from the skirt 102; and a flat second part 332 extending toward the outer circumferential surface 111 of the access hole 110 from the end of the curved part 335 opposite to the side to which the first part 331 is connected. A pair of brackets 330 are arranged on either side of the access hole 110 in the left-right direction and in the center of the access hole 110 in the vertical direction, with the access hole 110 in the center.

[0082] The second part 332 is provided with a hole 333 through which a bolt B is inserted in the thickness direction of the plate, and a nut 334 is welded to the back surface 332b side, communicating with the hole 333 and screwed onto the bolt B. When one end 331a of the first part 331 is welded to the outer circumferential surface 111 of the access hole 110, the surface 332a of the second part 332 faces away from the skirt 102.

[0083] In the aligned state and the state in which the head of bolt B contacts the surface 122b of the fixing part 122, a gap D2 is formed between the surface 332a of the second part 332 of the bracket 330 and the back surface 122c of the fixing part 122.

[0084] According to the mounting structure of the cover 120 to the access hole 110 of the second modified example, the cover is a plate that is approximately U-shaped when viewed from above as described above. In the aligned state, a gap D2 is formed between the surface 332a of the second part 332 of the bracket 330 and the back surface 122c of the fixing part 122. Therefore, even if the bracket 330 elastically deforms to fill the gap D2, the entire bracket 330 can elastically deform. Thus, damage to the bracket 330 due to deformation concentrating at one point of the bracket 330 can be suppressed.

[0085] Furthermore, if a force is applied to the cover 120 in a direction that would cause it to detach from the access hole 110 due to the pressure difference between the inside of the skirt 102 (maintenance area S) and the space outside the skirt 102, that force is transmitted to the bracket 330 via the fixing part 122. Even in this case, since the bracket 330 is shaped in such a way that it is easily elastically deformed, the force can be easily absorbed by the elastic deformation of the entire bracket 330. Therefore, the force can be prevented from concentrating deformation at a single point in the bolted portion between the bracket 330 and the fixing part 122, the bolt B, the welded portion between the bracket 330 and the access hole 110, and the bracket 330 itself, thereby preventing damage.

[0086] In the above embodiment, the case where tank 100 is vertical was described, but tanks 100, 200, and 300 may also be horizontal.

[0087] In the above embodiment, the case in which hydrogen gas is stored in the tank body 101 was described, but nitrogen gas or oxygen gas may also be stored, or solid materials such as powders like cement or grains may be stored. Alternatively, liquids (liquefied gases) such as liquefied petroleum gas, liquefied ammonia, liquefied hydrogen, liquefied nitrogen, or liquefied oxygen may be stored.

[0088] In the above embodiment, the case in which the access hole 110 connects the outer space and the maintenance area S in a horizontal direction perpendicular to the vertical direction was described. However, the access hole 110 may also be inclined with respect to the horizontal direction in which it connects the outer space and the maintenance area S.

[0089] In the above embodiment, the case in which a pair of brackets 130 are arranged at 180 degrees in the left-right direction of the access hole 110 was described. However, they may also be arranged at 180 degrees in the up-down direction of the access hole 110, or at positions that divide the access hole 110 into three equal parts in the circumferential direction.

[0090] In the above embodiment, the case in which the flange 123 is arranged around the entire circumference of the cover 120 has been described, but the flange 123 may be arranged in a C-shape only on the upper part of the cover 120. Also, the flange 123 may be omitted. If the flange 123 is omitted, it is preferable to have a structure in which a bolt B welded to the second part 132 of the bracket 130 abuts against the inner circumferential surface above the hole 122a of the fixing part 122 to hold the cover 120, or a structure in which a bolt B welded to the fixing part 122 abuts against the inner circumferential surface below the hole 133 of the bracket 130 to hold the cover 120.

[0091] In the above embodiment, the case in which the cover 120 is fixed to the access hole 110 and the pair of gripping portions 124 extend in the vertical direction and are arranged side by side in the left-right direction was described. However, the case in which the cover 120 is fixed to the access hole 110 and the pair of gripping portions 124 extend in the left-right direction and are arranged side by side in the vertical direction is also possible.

[0092] In the above embodiment, the case in which the cover body 121 and the fixing part 122 are separate components was described, but the cover body 121 and the fixing part 122 may be integrated. For example, the portion of the cover body 121 on the outer edge side of the flange 123 may be made wider, and that portion may be used as the fixing part 122. In this case, the widened portion may be further machined and shaped so that it consists only of the part that is fixed to the bracket 130. Alternatively, the portion that is fixed to the bracket 130 (fixing part 122) and its base may be formed using a mold with a shape that protrudes outward from a part of the circumferential direction of the outer peripheral surface of the base of the disc-shaped cover body 121.

[0093] In the above embodiment, the case was described in which there is a gap D1 between the back surface 122c of the fixing part 122 and the surface 132a of the second part 132 of the bracket 130 in the holding state before bolting. However, the back surface 122c of the fixing part 122 and the surface 132a of the second part 132 of the bracket 130 may be in contact with each other. In this case, the flange 123 allows the cover 120 to be supported (held) in the access hole 110 while the rear surface 125 of the cover body 121 and the outer end 113 of the access hole 110 can be brought into contact or separated without being in close contact. In particular, when separated, a portion of the pressure acting on the cover 120 from inside the skirt 102 can be released through the gap between the cover 120 and the access hole 110, making it difficult for the cover 120 to fall out of the access hole 110.

[0094] In the above embodiment, the case where the hole 122a of the fixing part 122 is an elongated hole was described, but in the holding state, the hole 133 (round hole) of the bracket 130 and the hole 122a of the fixing part 122 may be round holes that coincide at a predetermined position.

[0095] In the above embodiment, the case in which the hole 122a of the fixing part 122 is an elongated hole extending in the vertical direction was described, but the hole 122a of the fixing part 122 may also be an elongated hole extending in the left-right direction or an elongated hole extending in the diagonal direction. When the hole 122a of the fixing part 122 is an elongated hole extending in the diagonal direction, it is preferable that the elongated hole extends downward from one end of the fixing part 122 (the side welded to the cover body 121) to the other end. In this case, it is easier to widen the trajectory that the hole 122a passes through when the cover 120 is swung with the point where the inner circumferential surface 123a of the flange 123 and the outer circumferential surface 111 of the access hole 110 come into contact. Alternatively, instead of the fixing part 122, the hole 133 of the bracket 130 may be an elongated hole extending in the vertical, left-right, or diagonal direction. Furthermore, when attaching the cover 120 to the access hole 110, the flange 123 is hooked onto the outer surface 111 of the access hole 110 from above while aligning the mark 127 with the fixing position mark 103. Therefore, it is preferable that the hole 133 of the bracket 130 be an elongated hole extending in the vertical direction (direction of gravity) to facilitate alignment between the hole 133 of the bracket 130 and the hole 122a of the fixing part 122.

[0096] In the above embodiment, the case where the bracket 130 is a plate that is roughly L-shaped (or roughly U-shaped in the second modified example) was described, but it may also be a plate that is roughly Z-shaped or roughly S-shaped. Also, although the bracket 130 is assumed to be a bent steel plate, it may also be a steel material that has been extruded into the respective shape.

[0097] In the above embodiment, the case where the fixing part 122 is a flat plate was described, but it may also be approximately L-shaped, approximately U-shaped, approximately Z-shaped, or approximately S-shaped.

[0098] In the above embodiment, the case in which the bracket 130 and the fixing part 122 are plate-shaped was described, but the bracket 130 and the fixing part 122 may also be solid block-shaped, hollow box-shaped, or cylindrical.

[0099] In the above embodiment, the case where the distance L1 and distance L2 of the holes 122a of the fixing part 122 are approximately the same was described, but it is also possible for distance L1 to be greater than distance L2 or distance L1 to be smaller than distance L2. [Explanation of Symbols]

[0100] 100, 200, 300 tanks 101 Tank body 102 Skirt 102c Outer surface (outer surface) 110,210 Access Hall 111,211 Outer surface (outer surface) 113 Outer edge 120,220 covers 121 Cover body 121a Outer edge 122 Fixed part 122a hole 122c back side 123,223 flange 123a, 223a Inner peripheral surface (inner surface) 125 Rear 130,330 brackets 131,331 Part 1 131a,331a one end 131b, 331b Other end 132,332 Part 2 132a,332a surface 133,333 holes S Maintenance Area

Claims

1. A cover mounting structure for an access hole, comprising: a cylindrical skirt disposed below the tank body; a cylindrical access hole that penetrates the skirt in the thickness direction and communicates the outer space of the skirt with a maintenance area inside the skirt; and a cover disposed at the outer end of the access hole that protrudes towards the outer space and is configured to be detachably attached to the access hole, wherein the cover is attached to the access hole in an openable and closable manner, The access hole or the skirt is equipped with a plurality of brackets, The cover is characterized by comprising a cover body that covers the opening of the access hole in a manner that can be opened and closed, and a plurality of fixing parts that protrude outward from the outer edge of the cover body and can be bolted to the bracket, and is a mounting structure for a cover to an access hole.

2. The cover is provided with a cylindrical flange that protrudes rearward from the rear surface of the cover body and whose inner diameter is set to be larger than the outer diameter of the access hole. The fixing portion and the bracket are provided with holes through which bolts are inserted. The mounting structure for a cover to an access hole according to claim 1, characterized in that, in a holding state in which the inner surface of the flange is brought into contact with the outer surface of the access hole from above to below, the hole of the fixing part and the hole of the bracket can be aligned.

3. The bracket is a plate that is substantially L-shaped when viewed from above, and comprises a flat plate-shaped first part that is welded at one end to the outer surface of the skirt and erected from the outer surface of the skirt from the one end toward the other end, and a flat plate-shaped second part that extends from the other end of the first part toward the outer surface of the access hole and can be bolted to the fixing part, characterized in that the cover mounting structure to the access hole according to claim 1.

4. The cover is provided with a cylindrical flange that protrudes rearward from the rear surface of the cover body and whose inner diameter is set to be larger than the outer diameter of the access hole. The cover mounting structure for an access hole according to claim 3, characterized in that, in a holding state in which the inner surface of the flange is brought into contact with the outer surface of the access hole from above to below, the second part is located on the skirt side of the fixing part, and the surface of the second part facing away from the skirt and the back surface of the fixing part facing the skirt side are separated in the thickness direction of the cover body.

5. The mounting structure for the cover to the access hole according to claim 4, characterized in that the fixing part is a separate component from the cover body.

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