JP7847564B2 - box cover - Google Patents

Description

Applicable to Article 30, Paragraph 2 of the Patent Law. Sold by Act Co., Ltd. on May 25, 2023.

This invention relates to a manhole cover, and more particularly to a manhole cover that is attached to the upper end of the riser pipe of a manhole and has a decorative material on its upper surface.

An example of a conventional manhole cover is disclosed in Patent Document 1. The manhole cover of Patent Document 1 comprises a synthetic resin receiving frame having a projection on its lower inner surface and fitting its lower part to the upper end of a riser pipe; a synthetic resin upper cover having a recess on its upper surface into which a decorative material is fitted and detachably provided on the upper part of the receiving frame; a synthetic resin inner cover provided below the upper cover and detachably held inside the receiving frame by being locked to the projection; and a sealing ring provided on the outer surface of the inner cover.

Japanese Patent Publication No. 2018-197488

In the technology described in Patent Document 1, the height dimension (axial length) of the receiving frame (and consequently the manhole cover) is relatively large, requiring a large excavation depth during construction. Furthermore, in the technology described in Patent Document 1, the strength of the receiving opening of the receiving frame connected to the upper end of the riser pipe is relatively low. The ground surface (road surface) at the installation site of the manhole cover may be not only a horizontal surface but also an inclined surface with a water slope, etc. In this case, it is necessary to connect the receiving frame of the manhole cover at an angle relative to the upper end of the riser pipe. When connecting the receiving frame at an angle, the angle is adjusted by hammering it in with a plastic hammer or similar tool, but if the strength of the receiving opening is low, the receiving opening may break at this time. Therefore, further improvement in the constructability of the manhole cover is required.

Therefore, the primary objective of this invention is to provide a novel type of manhole cover.

Another objective of this invention is to provide a manhole cover with improved ease of installation.

The first invention is a manhole cover attached to the upper end of a riser pipe of a manhole, with a decorative material provided on its upper surface. It comprises a receiving frame having a lower cylindrical portion including a receiving opening connected to the upper end of the riser pipe, and an upper cover housing portion formed on the upper side of the lower cylindrical portion; and an upper cover having a recess on its upper surface into which the decorative material is fitted, and which is detachably held in the upper cover housing portion. The receiving frame has a projection formed on the inner surface of the upper end of the lower cylindrical portion that defines the inner end of the receiving opening, and a reinforcing rib formed on the outer surface of the receiving opening. The axial length of the lower cylindrical portion is smaller than the axial length of the upper cover housing portion.

In the first invention, the manhole cover is a cover capable of accommodating decorative materials such as interlocking blocks, tiles, stone, concrete (stamped concrete, etc.), and turf on its upper surface, and includes a receiving frame and an upper cover that is detachably attached to the receiving frame. The receiving frame has a lower cylindrical portion including a receiving opening connected to the upper end of a riser pipe, and an upper cover accommodating portion formed on the upper side of the lower cylindrical portion. The upper cover has a recess on its upper surface into which the decorative material is fitted, and is attached to the upper cover accommodating portion of the receiving frame. The receiving frame also has a projection (stopper) formed on the inner surface of the upper end of the lower cylindrical portion that defines the inner end of the receiving opening, and reinforcing ribs formed on the outer surface of the receiving opening. Furthermore, the axial length of the lower cylindrical portion of the receiving frame is set to be smaller than the axial length of the upper cover accommodating portion.

According to the first invention, the height dimension of the receiving frame (and consequently the manhole cover) can be reduced while ensuring sufficient height for installing decorative materials. This reduces the excavation depth required when installing the manhole cover, allowing for a neater and more compact installation. Furthermore, since the receiving opening of the receiving frame is reinforced with reinforcing ribs, it can appropriately accommodate connections when the receiving frame is tilted relative to the upper end of the riser pipe. Therefore, the ease of installation of the manhole cover is improved.

The second invention is dependent on the first invention, wherein the ratio of the axial length of the socket to the outer diameter of the riser pipe is 15% or more and 25% or less.

According to the second invention, by reducing the axial length of the receiving opening, the inclination angle of the receiving frame can be increased when connecting it while tilted relative to the upper end of the riser pipe.

The third invention is dependent on the first or second invention and includes an inner lid provided below the upper lid, which is detachably held inside the lower cylindrical portion by being locked to a protruding portion.

According to the third invention, the intrusion of rainwater into the manhole and the leakage of odors from the riser pipe to the outside are effectively prevented.

The fourth invention is subordinate to the third invention, and uses an inner lid without a handle that protrudes above the top plate portion of the inner lid.

According to the fourth invention, since an inner lid without a handle protruding above the top wall is used, the axial length of the lower cylindrical portion can be appropriately reduced.

The fifth invention is dependent on the first or second invention, and the upper end of the riser pipe is provided with a frame for holding the inner lid, and the receiving port is connected to the upper end of the riser pipe including the frame for the inner lid.

According to the fifth invention, the variations in the inner lids used can be increased.

This invention allows for the height of the receiving frame (and consequently the manhole cover) to be reduced while ensuring sufficient height for installing decorative materials. This reduces the excavation depth required when installing the manhole cover, resulting in a neater and more compact installation. Furthermore, since the receiving opening of the receiving frame is reinforced with reinforcing ribs, it can appropriately accommodate connections when the receiving frame is tilted relative to the upper end of the riser pipe. Therefore, the ease of installation of the manhole cover is improved.

The aforementioned objectives, other objectives, features, and advantages of this invention will become even clearer from the detailed description of the embodiments described below with reference to the drawings.

This diagram shows the installation state of a manhole cover, which is one embodiment of this invention. This is an exploded perspective view showing a manhole cover. This is a cross-sectional view showing a manhole cover. This is a perspective view showing the receiving frame of the manhole cover. This is a front view showing the receiving frame. This is a plan view showing the receiving frame. This is a cross-sectional view showing the frame along the line VII-VII in Figure 5. This is a perspective view showing the top cover of the manhole cover. This is a plan view showing the top cover. Figure 9 is a cross-sectional view showing the top cover in X-X line. This is a perspective view showing the inner lid. This is a cross-sectional view showing the inner lid. This diagram shows how a manhole cover is connected straight to the upper end of a riser pipe. This diagram shows how the manhole cover is connected to the upper end of the riser pipe at an angle. This diagram shows how a manhole cover is connected straight to the upper end of a riser pipe, which is equipped with a frame for an inner cover. This diagram shows how a manhole cover is connected at an angle to the upper end of a riser pipe, which is equipped with a frame for an inner cover.

Referring to Figure 1, one embodiment of this invention, the manhole cover 10, comprises a receiving frame 12, an upper cover 14, and an inner cover 16, and is attached to the upper end of the riser pipe 102 of a manhole 100, such as a sewage manhole or rainwater manhole, installed on the premises of a building such as a detached house, apartment, or condominium. The manhole cover 10 is a decorative cover that can be fitted onto its upper surface with decorative material 106 similar to the surrounding decorative material 104 (paving material) such as interlocking blocks, tiles, stone, concrete (stamped concrete, etc.), and grass. The inner diameter of the riser pipe 102 to which the manhole cover 10 is attached is, for example, 40-300 mm. In this embodiment, the following explanation assumes a manhole cover 10 applicable to a riser pipe 102 with an inner diameter of 200 mm and an outer diameter of 216 mm.

As shown in Figures 1-3, the manhole cover 10 comprises a receiving frame 12 attached to the upper end of the riser pipe 102, and an upper cover 14 and an inner cover 16 that are detachably attached to the receiving frame 12. Each of these components—the receiving frame 12, the upper cover 14, and the inner cover 16—is made of a synthetic resin such as rigid polyvinyl chloride.

As shown in Figures 4-7, the receiving frame 12 comprises a cylindrical lower cylindrical portion 20 formed at the bottom and a rectangular cylindrical upper lid housing portion 22 (upper rectangular cylindrical portion) formed above the lower cylindrical portion. The connecting portion between the lower cylindrical portion 20 and the upper lid housing portion 22 is stepped in diameter toward the lower cylindrical portion 20, and the upper surface of this flange-like stepped portion is used as an upper lid support portion 24 that locks onto the lower surface of the upper lid 14. The length W1 of one side of the inner edge of the upper lid housing portion 22 is, for example, 300 mm, and the axial length H1 (height dimension) of the upper lid housing portion 22 is, for example, 87 mm.

The lower cylindrical portion 20 is used as a connection portion (receptacle 20a) to the riser pipe 102, and also as an inner lid housing portion that accommodates the inner lid 16. Specifically, an annular projection 26 extending in the circumferential direction is formed on the inner surface of the upper end of the lower cylindrical portion 20. This projection 26 defines the inner end of the receptacle 20a that connects to the upper end of the riser pipe 102, and the lower end surface of the projection 26 is used as a locking portion (stopper) that engages with the upper end surface of the riser pipe 102. Furthermore, the upper end surface of the projection 26 is used as an inner lid support portion that engages with the inner lid 16, which will be described later, and a short cylindrical space-forming portion 20b is provided above the projection 26, forming an internal space capable of accommodating the top plate portion 60 of the inner lid 16. In other words, the lower cylindrical portion 20 has a receiving opening 20a, which is the portion below the protruding portion 26, and a space-forming portion 20b, which is the portion above the protruding portion 26. However, the protruding portion 26 does not necessarily have to be formed in an annular shape; for example, it may be a plurality of protrusions arranged at predetermined intervals in the circumferential direction on the inner surface of the lower cylindrical portion 20.

A rectangular, annular flange 28 is formed at the connection point between the lower cylindrical portion 20 and the upper lid housing portion 22, extending outward. Furthermore, multiple triangular plate-shaped first ribs 30 (an example of reinforcing ribs) are formed on the lower cylindrical portion 20, extending vertically to connect its outer surface to the lower surface of the flange 28. These first ribs 30 are formed to extend over approximately the entire length of the lower cylindrical portion 20, including the receiving opening 20a. In other words, the receiving frame 12 has the first ribs 30 formed on the outer surface of the receiving opening 20a, thereby appropriately reinforcing the receiving opening 20a. In addition, multiple triangular plate-shaped second ribs 32 are formed on the upper lid housing portion 22, extending vertically to connect its outer surface to the upper surface of the flange 28. The second ribs 32 in the central part of the upper lid housing portion 22 are formed to be longer vertically than those on both sides. This allows for focused reinforcement of the central section, which is more prone to deformation than the sides, preventing deformation of the upper lid housing section 22, while simultaneously reducing the size of the second ribs 32 on both sides, thereby reducing the amount of resin used.

Furthermore, multiple drainage holes 34 are formed on the outer periphery (four corners) of the upper lid support portion 24. Water that flows into the upper lid housing portion 22 through the gap between the outer surface of the upper lid 14 and the inner surface of the upper lid housing portion 22, or through the drainage holes 56 of the upper lid 14, is discharged to the outside of the receiving frame 12 through these drainage holes 34. Additionally, a groove-shaped drainage section 36 extending vertically from the protruding portion 26 to the lower end is formed on the inner surface of the lower cylindrical portion 20. The circumferential position and number of the drainage sections 36 can be changed as appropriate, but in this embodiment, two drainage sections 36 are formed at 180-degree intervals. Water that flows into the lower cylindrical portion 20 without being discharged through the drainage holes 34 of the upper lid support portion 24 is discharged to the outside through the water passage formed by the drainage section 36 and the outer surface of the riser pipe 102. This prevents water from accumulating on the inner lid 16.

In this embodiment, the axial length H2 of the lower cylindrical portion 20 is set to be smaller than the axial length H1 of the upper lid housing portion 22. This is to ensure sufficient height for installing the decorative material 106 while suppressing the height of the receiving frame 12 (and consequently the manhole cover 10). In this embodiment, the axial length H1 of the upper lid housing portion 22 is, for example, 87 mm, while the axial length H2 of the lower cylindrical portion 20 is set to, for example, 58 mm. Therefore, the axial length (height dimension) of the receiving frame 12 is, for example, 145 mm.

Specifically, the ratio of the axial length H3 of the socket 20a to the outer diameter of the riser pipe 102 is set to 15% to 25%, thereby reducing the axial length H3 of the socket 20a and suppressing the axial length H2 of the lower cylindrical portion 20. In this embodiment, the axial length H3 of the socket 20a is, for example, 40 mm. Note that this axial length H3 of the socket 20a is less than half the axial length of the socket used in conventional synthetic resin pipe members. Furthermore, in this embodiment, by employing an inner lid 16 without a handle protruding above the top plate portion 60, as described later, the axial length of the space-forming portion 20b is also reduced, thereby suppressing the axial length H2 of the lower cylindrical portion 20.

Furthermore, the inner surface of the socket 20a is formed in a tapered shape, expanding in diameter from the back to the front. In this case, the inner diameter W2 of the socket 20a is set to be larger than the outer diameter of the riser pipe 102 at the front (inlet) portion and smaller than the outer diameter of the riser pipe 102 at the back end portion. In this embodiment, while the outer diameter of the riser pipe 102 is 216.0 mm, the inner diameter W2 of the socket 20a is, for example, 217.3 mm at the front and 215.3 mm at the back end. By making the inner diameter W2 of the back end portion of the socket 20a smaller than the outer diameter of the riser pipe 102, and providing a tightening allowance when the socket 20a is fitted onto the upper end of the riser pipe 102, the receiving frame 12 can be properly temporarily fixed to the riser pipe 102. This prevents the receiving frame 12 from floating up due to buoyancy when concrete or mortar is applied around the receiving frame 12 during the construction of the manhole cover 10.

As shown in Figures 8-10, the top cover 14 is formed in a bottomed rectangular tubular shape with a recessed portion 40 on its upper surface. Specifically, the top cover 14 has a rectangular cylindrical side wall 42 and a rectangular plate-shaped bottom wall 44 that seals the lower end of the side wall 42.

At the two opposing corners of the side wall 42, L-shaped wall portions 46 are formed, projecting inward. These wall portions 46 and the corners of the side wall 42 form a rectangular cylindrical portion. At the upper end of this rectangular cylindrical portion, a rectangular plate-shaped hanging portion 50 with a jig hole 48 is formed. In this embodiment, the jig hole 48 is formed as an elongated hole, elongated diagonally. A jig (not shown) with a T-shaped tip is used to attach and detach the top cover 14. The specific details, such as the position and shape of the jig hole 48, can be changed as appropriate; the jig hole 48 only needs to allow the jig to be inserted and the top cover 14 to be attached and detached.

Furthermore, the lower surface of the bottom wall 44 is formed with bottom ribs 52, including multiple circular ribs arranged concentrically and multiple linear ribs arranged radially. In addition, the upper surface of the bottom wall 44 (the bottom surface of the recessed portion 40) is formed with protrusions 54 that form a space for water guidance between it and the lower surface of the decorative material 106, such as concrete. In this embodiment, the protrusions 54 include first protrusions 54a distributed in a predetermined arrangement across substantially the entire upper surface of the bottom wall 44, and second protrusions 54b formed to extend along substantially the entire length of the upper peripheral edge of the bottom wall 44. However, the arrangement of the protrusions 54 can be changed as appropriate.

Furthermore, multiple drainage holes 56 are formed in the bottom wall 44. These drainage holes 56 include a first drainage hole 56a and a second drainage hole 56b. The first drainage holes 56a are arranged in an annular pattern at the location of the recess (groove) formed between the protrusions 54. The second drainage holes 56b, on the other hand, are located at the recess and on the periphery of the bottom wall 44. These drainage holes 56 prevent rainwater and other liquids from accumulating in the recessed area 40.

As described above, the top cover 14 is held within the top cover housing 22 of the receiving frame 12 by being locked to the top cover support portion 24 (see Figure 3). The height of the top cover 14 is set to be the same as the axial length H1 of the top cover housing 22 of the receiving frame 12, so that when the top cover 14 is attached to the receiving frame 12, the upper end surface of the side wall 42 and the upper end surface of the top cover housing 22 are flush. The length of one side of the outer edge of the side wall 42 is set to be the same as or slightly smaller than the length W1 of one side of the inner edge of the top cover housing 22. The depth of the recess 40 is set considering the thickness of a typical interlocking block, for example, 60 mm.

As shown in Figures 11 and 12, the inner lid 16 is a component that seals the upper end opening of the riser pipe 102 to prevent leakage of foul odors and wastewater from the riser pipe 102 to the outside, and is made of a synthetic resin such as rigid polyvinyl chloride. The inner lid 16 has a circular top plate portion 60 and a short cylindrical fitting portion 62 formed along the lower peripheral edge of the top plate portion 60. The top plate portion 60 has a recess 60a in its center, and a grip portion (handle) 64 is formed so as to span this recess 60a. Having such a grip portion 64 makes it easy to attach and detach the inner lid 16. Furthermore, by using an inner lid 16 with a grip portion 64 formed in the recess 60a, that is, by using an inner lid 16 without a handle that protrudes above the top plate portion 60, the axial length of the space-forming portion 20b of the receiving frame 12 can be suppressed.

Furthermore, an annular groove 66 extending in the circumferential direction is formed on the outer surface of the inner lid 16, specifically on the outer surface of the fitting portion 62, and a seal ring 68 is fitted into this groove 66. The inner lid 16 is held within the lower cylindrical portion 20 of the receiving frame 12 by the lower peripheral edge of the top plate portion 60 being locked to the protruding portion 26. When the manhole cover 10 is attached to the upper end of the riser pipe 102, the seal ring 68 is compressed between the outer surface of the inner lid 16 and the inner surface of the riser pipe 102 (see Figure 13). This ensures airtightness and watertightness in this area, and the upper opening of the riser pipe 102 is properly sealed by the inner lid 16, effectively preventing leakage of odors and drainage from the riser pipe 102 to the outside.

Next, the installation method for the manhole cover 10 will be explained. When attaching the manhole cover 10 to the riser pipe 102 of the manhole 100, as shown in Figures 1 and 13, first, the upper end of the riser pipe 102 is fitted into the receiving opening 20a of the receiving frame 12. At this time, the receiving frame 12 is forcibly fitted by hammering it in using a jig such as a plastic hammer until the lower end surface of the protruding part 26 of the receiving frame 12 is locked (butts against) the upper end surface of the riser pipe 102. This connects (temporarily fixes) the receiving frame 12 in a positioned state relative to the riser pipe 102. In other words, the installation height of the receiving frame 12 is determined by the position of the upper end surface of the riser pipe 102, so in order to install the receiving frame 12 at a predetermined height, it is only necessary to cut the riser pipe 102 to a predetermined length. Therefore, the height position of the receiving frame 12 (and by extension the manhole cover 10) can be easily adjusted. Furthermore, since there is no need to separately install a base or other components, the installation process is simplified. In addition, in this embodiment, the axial length (height dimension) of the receiving frame 12 is reduced, allowing for a reduction in the excavation depth of the ground around the upper end of the riser pipe 102. Therefore, the construction of the receiving frame 12 (and consequently the manhole cover 10) becomes easier. Note that the receiving opening 20a of the receiving frame 12 and the upper end of the riser pipe 102 may be joined simply by fitting them together (hammer-in joint) or by adhesive bonding.

Next, the inner lid 16 is installed inside the receiving frame 12. At this time, the lower peripheral edge of the top plate portion 60 of the inner lid 16 is locked to the upper end surface of the protruding portion 26, thereby holding the inner lid 16 within the lower cylindrical portion 20 of the receiving frame 12. Furthermore, as can be clearly seen in Figure 13, the seal ring 68 provided on the outer surface of the inner lid 16 is compressed between the outer surface of the inner lid 16 and the inner surface of the riser pipe 102. This ensures airtightness and watertightness in this area, and the upper opening of the riser pipe 102 is properly sealed by the inner lid 16, effectively preventing leakage of odors and wastewater from the riser pipe 102 to the outside.

Next, the top lid 14 is attached to the receiving frame 12. At this time, the top lid 14 is held within the top lid housing 22 with its upper end surface of its side wall 42 flush with the upper end surface of the receiving frame 12, by being locked to the top lid support portion 24.

Subsequently, concrete or mortar is applied around the upper end of the riser pipe 102 and the lower end of the receiving frame 12. At the same time, decorative material 104 is applied around the manhole cover 10 (receiving frame 12 and upper cover 14) so that it is flush with the upper end surface of the manhole cover 10. The receiving frame 12 is completely fixed once the concrete or mortar hardens. Furthermore, decorative material 106 is fitted into the recess 40 of the upper cover 14 via a fixing material 108 such as adhesive or bedding mortar. This ensures that the decorative material 106 fitted inside the upper cover 14 is held flush with the surrounding decorative material 104.

Furthermore, in the construction method shown in Figure 13, the receiving frame 12 of the manhole cover 10 is connected straight to the riser pipe 102. However, as shown in Figure 14, by adjusting the angle using a jig such as a plastic hammer and forcibly fitting the receiving opening 20a of the receiving frame 12 at an angle to the upper end of the riser pipe 102, the receiving frame 12 of the manhole cover 10 can also be connected (temporarily fixed) at an angle to the riser pipe 102. In other words, it is possible to install the manhole cover 10 in construction sites where the ground surface is sloped. In this embodiment, since the axial length H3 of the receiving opening 20a is set small, interference between the tip (lower end) of the receiving opening 20a and the riser pipe 102 is reduced, and the inclination angle of the receiving frame 12 relative to the riser pipe 102 can be increased. Furthermore, when connecting the socket 20a and the riser pipe 102 by hammering without applying adhesive, fine adjustments to the height position and inclination angle of the receiving frame 12 can be easily made until the surrounding concrete or mortar hardens. Moreover, in this embodiment, since the first rib 30 is formed on the outer surface of the socket 20a to reinforce it, damage to the socket 20a is prevented even when the receiving frame 12 is connected to the riser pipe 102 at an angle.

As described above, in this embodiment, since the axial length H2 of the lower cylindrical portion 20 is set to be smaller than the axial length H1 of the upper cover housing portion 22, the height dimension of the receiving frame 12 (and consequently the manhole cover 10) can be suppressed while ensuring the height dimension for installing the decorative material 106. This reduces the excavation depth when installing the manhole cover 10, allowing for a neat and tidy installation. Furthermore, since the receiving opening 20a of the receiving frame 12 is reinforced by the first rib 30, it can appropriately accommodate connections when the receiving frame 12 is tilted relative to the upper end of the riser pipe 102. Therefore, the ease of installation of the manhole cover 10 is improved.

Furthermore, in this embodiment, the ratio of the axial length of the receiving opening 20a of the receiving frame 12 to the outer diameter of the riser pipe 102 is set to 15% to 25%, thereby reducing the axial length H3 of the receiving opening 20a. This allows for a larger inclination angle of the receiving frame 12 when connecting it to the upper end of the riser pipe 102 at an angle, and facilitates fine adjustments to the height position and inclination angle of the receiving frame 12. Therefore, it is possible to more appropriately handle the case where the receiving frame 12 is connected to the upper end of the riser pipe 102 at an angle, improving the ease of installation of the manhole cover 10.

Furthermore, the specific configuration of the manhole cover 10 is not limited to that described above, and can be modified as appropriate without departing from the spirit of this invention.

For example, in the above embodiment, the top lid 14 and the top lid housing section 22 that accommodates the top lid 14 are formed in a rectangular cylindrical shape (square cylindrical shape), but the top lid 14 and the top lid housing section 22 can also be formed in a cylindrical shape.

Furthermore, in the above-described embodiment, an inner cover 16 is provided to seal the upper end of the riser pipe 102. However, if the manhole 100 is a rainwater manhole (i.e., not for sewage use), the inner cover 16 is not necessarily required.

Furthermore, in the above-described embodiment, the inner lid 16 is secured by a projection 26 formed on the lower cylindrical portion 20 of the receiving frame 12, but the embodiment is not limited to this. For example, as shown in the embodiments in Figures 15 and 16, an inner lid receiving frame 110 may be provided at the upper end of the riser pipe 102, and the inner lid 16 may be held by this inner lid receiving frame 110. In this case, the receiving opening 20a of the receiving frame 12 is connected to the upper end of the riser pipe 102, including the inner lid receiving frame 110. The projection 26 of the receiving frame 12 is then secured to the outer peripheral edge of the inner lid receiving frame 110, thereby connecting (temporarily fixing) the receiving frame 12 in a positioned state relative to the riser pipe 102. In this case as well, as shown in Figure 15, the receiving frame 12 (and thus the manhole cover 10) can be connected straight to the upper end of the riser pipe 102, or as shown in Figure 16, the receiving frame 12 can be connected at an angle to the upper end of the riser pipe 102. In this way, by making the inner lid 16, which is held by the inner lid receiving frame 110, usable, the variations of the inner lid 16 that can be used can be increased.

Please note that the specific dimensions and configurations mentioned above are merely examples and can be modified as needed according to product specifications and other requirements.

10... Manhole cover 12... Receiving frame 14... Top cover 16... Inner cover 20... Lower cylindrical part 20a... Receiving opening 20b... Space forming part 22... Top cover housing part 26... Protruding part 30... First rib (reinforcement rib)
40... recessed area 100... box 102... riser pipe 104, 106... decorative material 110... frame for inner cover

Claims (5)

A manhole cover that is attached to the upper end of the riser pipe of a manhole and has a decorative material on its upper surface,
A receiving frame having a lower cylindrical portion including a receiving opening connected to the upper end of the riser pipe, and an upper lid housing portion formed on the upper side of the lower cylindrical portion, and an upper lid having a recess on its upper surface into which the decorative material is fitted, and which is detachably held in the upper lid housing portion,
The receiving frame has a projection formed on the inner surface of the upper end of the lower cylindrical portion that defines the inner end of the receiving opening, and a reinforcing rib formed on the outer surface of the receiving opening.
A box cover in which the axial length of the lower cylindrical portion is smaller than the axial length of the upper lid housing portion. The manhole cover according to claim 1, wherein the ratio of the axial length of the socket to the outer diameter of the riser pipe is 15% or more and 25% or less. The manhole cover according to claim 1 or 2, further comprising an inner cover provided below the upper cover and detachably held inside the lower cylindrical portion by being locked to the protruding portion. The box cover according to claim 3, wherein the inner cover is a cover without a handle that protrudes above the top plate portion of the inner cover. An inner lid support frame is provided at the upper end of the aforementioned riser pipe for holding the inner lid.
The manhole cover according to claim 1 or 2, wherein the receiving opening is connected to the upper end of the riser pipe including the inner cover receiving frame.