JP7542827B2 - Manhole cover plug - Google Patents

Description

This disclosure relates to a manhole cover plug that is attached to a recess provided in a manhole cover.

Manhole covers often have a bag-shaped recess with a horizontal recess (see Figure 8) so that they can be easily opened and closed using a manhole key with a T-shaped or hook-shaped tip.

However, if a bag-shaped recess is provided in a manhole cover, once soil or sand enters the recess, it hardens instead of being discharged, and the manhole key cannot enter the recess, which can cause problems when opening and closing the manhole cover. Conventionally, therefore, a plug made of, for example, rubber has been attached to the bag-shaped recess to prevent soil or sand from entering the bag-shaped recess (for example, Non-Patent Document 1).

"Toyoyama Town Type Sewer Manhole Iron Cover Specifications", [online], 2010, [Retrieved January 7, 2021], Internet <URL: https://www.town.toyoyama.lg.jp/_res/projects/default_project/_page_/001/001/400/siyousyo.pdf>

However, when a plug is attached to a recess in a manhole cover, rain can get in and accumulate in the gap between the plug and the recess when it rains. From this perspective, it is preferable for the gap between the plug and the recess to be small, but in order to attach the plug to the recess, the dimensions of the recess must be made slightly larger than the plug, so a small gap had to be tolerated.

In cold regions where the temperature drops below freezing at night, rainwater that seeps into the gap between the plug and the recess freezes, and the frozen ice expands and pushes the plug upward. This expansion of the ice sometimes causes the plug to float upward and become dislodged from the recess. When the plug is removed, soil and sand accumulates in the recess, making it impossible to insert the manhole key, which can cause problems when opening and closing the manhole cover, so there is room for improvement in this regard.

Therefore, the objective of this disclosure, made in consideration of these points, is to provide a manhole cover plug that prevents rainwater or the like that has entered the gap with the manhole cover from floating up due to freezing.

In order to solve the above problems, the manhole cover plug according to the present disclosure is
A manhole cover plug to be attached to a bag-shaped recess provided in a manhole cover,
A hollow portion recessed upward from the bottom surface is provided ,
The volume of the hollow portion is equal to or greater than the volume that is increased by freezing of water that has entered the gap between the bag-shaped recess and the manhole cover plug,
The bag-shaped recess has an opening that opens upward, and a bottom wall on the side opposite the opening has no other opening .

According to the present disclosure, it is possible to provide a manhole cover plug that prevents rainwater or the like that has entered the gap with the manhole cover from floating up due to freezing.

FIG. 1 is a perspective view of a manhole cover plug according to one embodiment of the present disclosure. FIG. 2 is a front view of a manhole cover plug according to one embodiment of the present disclosure. FIG. 2 is a bottom view of a manhole cover plug according to one embodiment of the present disclosure. FIG. 2 is a right side view of a manhole cover plug according to one embodiment of the present disclosure. FIG. 2 is a left side view of a manhole cover plug according to one embodiment of the present disclosure. 5 is a cross-sectional view taken along line AA in FIG. 4. FIG. 2 is a plan view of a manhole cover to which a manhole cover plug according to an embodiment of the present disclosure is attached. FIG. 1 is a cross-sectional view (schematic diagram) showing a manhole cover plug according to one embodiment of the present disclosure being attached to a manhole cover. FIG. 11 is a diagram comparing the amount of lift depending on whether or not a manhole cover plug has a hollow portion.

Below, a manhole cover plug 100 according to one embodiment of the present disclosure will be described with reference to the drawings.

In this embodiment, the upward direction of the manhole cover plug 100 is the upward direction in FIG. 2, and the downward direction is the downward direction in FIG. 2. The radial direction is the direction along a straight line perpendicular to the central axis O of the manhole cover 200 shown in FIG. 7 to which the manhole cover plug 100 according to this embodiment is attached, and the radially outward direction is the direction away from the central axis O of the manhole cover 200 along the straight line, and the radially inward direction is the direction toward the central axis O of the manhole cover 200 along the straight line. The left direction in FIG. 2 is the radially outward direction, and the right direction in FIG. 2 is the radially inward direction. The direction perpendicular to the paper surface in FIG. 2 (the left-right direction in FIG. 4) is the circumferential direction of the manhole cover plug 100 and the manhole cover 200. The symbol C indicates the central axis of the manhole cover plug 100.

The manhole cover plug 100 according to this embodiment has a main body 10 that extends generally vertically and a protrusion 20 that extends generally horizontally (radially inward) from the lower portion of the main body 10.

The bottom of the main body 10 is provided with a main body cavity 11a (hollow portion) (see Figs. 3, 5, and 6) that is recessed upward from the main body lower surface 11 (lower surface). The bottom of the protruding portion 20 is provided with a protruding portion cavity 21a (hollow portion) (see Figs. 3 and 6) that is recessed upward from the protruding portion lower surface 21 (lower surface).

In this embodiment, the lower surface 11 of the main body is formed as an inclined surface that slopes upward toward the radially outward direction (to the left in FIG. 2) as shown in FIG. 2. With this configuration, as shown in FIG. 8, when the manhole cover plug 100 is attached to the bag-shaped recess 201 of the manhole cover 200, the manhole cover plug 100 can be attached smoothly without protruding radially outward from the manhole cover 200.

In addition, in this embodiment, as shown in Figures 1 and 2, a protrusion cavity 23a (side cavity) is also formed in the protrusion side surface 23 (the circumferential side surface of the protrusion 20).

As described below, when rainwater or the like that has entered the gap between the manhole cover plug body 100 and the bag-shaped recess 201 of the manhole cover 200 freezes and expands in cold regions, the expanded rainwater or the like enters this cavity, and serves the function of preventing the manhole cover plug body 100 from floating up.

In this embodiment, the hollow portion (main body hollow portion 11a and protruding portion hollow portion 21a) provided on the underside of the manhole cover plug body 100 is divided into two hollow regions by the main body partition wall 11c and the protruding portion partition wall 21c (see FIG. 3). In this way, by dividing the hollow portion into multiple hollow regions by the partition walls (main body partition wall 11c and protruding portion partition wall 21c), expanded rainwater, etc. can enter the hollow portion, preventing the manhole cover plug body 100 from floating up, while ensuring the rigidity of the manhole cover plug body 100.

In this embodiment, the hollows (main body hollow 11a and protruding hollow 21a) are recessed upward from the underside of the manhole cover plug 100, so that the hollows are filled with air and unfrozen rainwater, etc. do not enter the hollows. In addition, the volume of the hollows is configured to be equal to or greater than the volume that increases due to the freezing of water that has entered the gap between the bag-shaped recess 201 and the manhole cover plug 100. With this configuration, all of the ice that expands due to the freezing of rainwater, etc. that has entered the gap between the bag-shaped recess 201 and the manhole cover plug 100 can enter the hollows. Therefore, the manhole cover plug 100 is not lifted upward due to the freezing of rainwater, etc. that has entered the gap between the bag-shaped recess 201 and the manhole cover plug 100.

The protrusion partitions 21c, 23c (see Figures 2 and 3) provided between the protrusion cavity 21a and the protrusion cavity 23a are also thought to contribute to ensuring the rigidity of the manhole cover plug 100.

A top portion 15 that is circumferentially enlarged is provided on the upper portion of the main body portion 10. The shape of this top portion 15 in a plan view corresponds to the shape of the opening 203a (see Figures 7 and 8) of the recess 201 of the manhole cover 200. With this configuration, when the manhole cover plug body 100 is attached to the bag-shaped recess 201 of the manhole cover 200, the opening 203a of the bag-shaped recess 201 is closed by the top portion 15 of the manhole cover plug body 100, leaving a small gap.

The circumferential side of the main body 10, including the top 15 (main body side 13), is provided with pleated lateral grooves 13a, 15a extending in a substantially horizontal direction. Rainwater or the like that has entered between the manhole cover plug 100 and the bag-shaped recess 201 of the manhole cover 200 freezes in the lateral grooves 13a, 15a, causing the manhole cover plug 100 and the ice to become one, improving the frictional force with the bag-shaped recess 201 of the manhole cover 200 and preventing the manhole cover plug 100 from floating up.

In this embodiment, as shown in Figures 1 and 2, a pleated lateral groove 15a is also provided on the radially inner side of the top 15. This configuration further improves the frictional force between the top 15 and the opening 203a of the bag-shaped recess 201, effectively preventing the manhole cover plug 100 from floating up.

In addition, instead of or in addition to the pleated lateral grooves 13a, 15a, a protrusion protruding in the circumferential direction may be provided on the circumferential side surface of the manhole cover plug body 100. This protrusion abuts against the side surface of the bag-shaped recess 201 of the manhole cover 200 to improve the frictional force with the bag-shaped recess 201, thereby preventing the manhole cover plug body 100 from floating up.

As shown in Figures 1 and 6, cutouts 17a and 17b are provided at both radial ends of the top 15, which extend downward from the top upper surface 15b to a height position higher than the lower surface (main body lower surface 11 and protrusion lower surface 21). When an operator removes the manhole cover plug 100 from the manhole cover 200, the operator can easily pull it out upward by inserting a crowbar or the like into the cutouts 17a and 17b.

In this embodiment, the cutouts 17a and 17b do not reach the underside of the manhole cover plug 100 (see FIG. 6) and are not connected to the inside of the manhole. Therefore, it is possible to prevent soil and sand from entering the manhole through the cutouts 17a and 17b.

The main body 10 and the protruding portion 20 may be made of rubber materials such as natural rubber, silicone rubber, urethane rubber, fluororubber, propylene rubber, butyl rubber, and nitrile rubber. The main body 10 and the protruding portion 20 are not limited to rubber materials, and may be thermoplastic elastomers such as polyester elastomers, polyamide elastomers, polyvinyl chloride, and polyethylene, or synthetic resins, and may be used in combination, such as by laminating them. The main body 10 and the protruding portion 20 may be made of the same material or different materials, and if made of the same material, they may be formed as one piece.

The manhole cover plug 100 having the above configuration is attached to the bag-shaped recesses 201 arranged in two opposing positions with respect to the central axis O of the manhole cover 200 shown in FIG. 7.

Figure 8 shows the state in which the manhole cover plug body 100 according to this embodiment is attached to the bag-shaped recess 201 of the manhole cover 200. Note that in Figure 8, details such as the horizontal grooves 13a and 15a are omitted. As shown in Figure 8, the bag-shaped recess 201 provided in the manhole cover 200 has a vertical recess 203 that opens on the upper surface of the manhole cover 200 and extends in a substantially vertical direction, and a horizontal recess 205 that extends in a substantially horizontal direction (radially inward direction) from the lower part of the vertical recess 203. In this embodiment, the vertical recess 203 extends downward from an opening 203a provided on the upper surface of the manhole cover 200, and a sloped surface 203b corresponding to the inclined main body lower surface 11 of the manhole cover plug body 100 is provided at the lower end. In addition, a horizontal recess 205 is formed from the lower part of the vertical recess 203 toward the radially inward direction (to the right in Figure 8). As a result, the bag-shaped recess 201 of the manhole cover 200 has a hook-like shape as shown in the cross-sectional view of FIG. 8, and the T-shaped or hook-shaped engagement portion at the tip of the manhole key can fit into the horizontal recess 205 extending radially inward. Then, when the worker rotates the manhole key around its axis, the T-shaped or hook-shaped engagement portion can be oriented perpendicular to the paper surface of FIG. 8 and can engage with the upper surface of the bag-shaped recess 201 in that direction. From this state, the worker can pull the manhole key upward to remove the manhole cover 200 from the manhole.

The worker tilts the manhole cover plug 100 so that the radially inner end of the protruding portion 20 is directed downward, then inserts the protruding portion 20 into the opening 203a, and then rotates the manhole cover plug 100 counterclockwise in FIG. 8 with the radially inner end of the opening 203a as a fulcrum. As a result, the protruding portion 20 of the manhole cover plug 100 enters the horizontal recess 205 in the radially inner direction, and as shown in FIG. 8, the manhole cover plug 100 is attached to the hook-shaped and bag-shaped recess 201. When the manhole cover plug 100 is attached so that the top upper surface 15b is approximately flush with the upper surface of the manhole cover 200, the lower surface 11 of the main body of the manhole cover plug 100 approaches the inclined surface 203b, and the main body 10 is positioned in the vertical recess 203 with almost no gap. In addition, the protrusion underside 21 is close to the underside of the horizontal recess 205, and there is a small space above the protrusion 20 within the horizontal recess 205. In this way, by approximating the shape of the manhole cover plug 100 to the shape of the bag-shaped recess 201, the gap when the manhole cover plug 100 is installed in the bag-shaped recess 201 is minimized.

The hollows (main body hollow 11a and protruding hollow 21a) are filled with air in the initial state before rainwater or the like has entered. Even if rainwater or the like enters the gap between the manhole cover plug 100 and the recess 201 when the manhole cover plug 100 is completely installed in the recess 201, the hollow is recessed upward from the underside of the manhole cover plug 100, so the rainwater or the like does not enter the hollow. When the rainwater or the like in the gap between the manhole cover plug 100 and the recess 201 freezes, the ice pushed out from the gap as the volume of the rainwater or the like increases enters the hollow, but in this embodiment, the volume of the hollow (the combined volume of the main body hollow 11a and the protruding hollow 21a) is configured to be greater than or equal to the volume increased by the freezing of the water that has entered the gap between the bag-shaped recess 201 and the manhole cover plug 100. Therefore, all of the ice that increases in volume due to the expansion of rainwater, etc. can enter the cavity. Therefore, even if rainwater, etc. freezes, the expanding ice does not push open the gap, so the manhole cover plug 100 can be effectively prevented from floating up.

In addition, in this embodiment, as shown in Figures 1 and 2, a protrusion cavity 23a (side cavity) is also provided on the circumferential side surface (protrusion side surface 23) of the protrusion 20. With this configuration, when rainwater or the like in the gap between the manhole cover plug 100 and the recess 201 freezes, it can also enter this protrusion cavity 23a, so that the manhole cover plug 100 can be more effectively prevented from floating up.

In addition, in this embodiment, the circumferential body side surface 13 (side surface) of the body 10 has pleated lateral grooves 13a, 15a extending in a substantially horizontal direction. Rainwater or the like that has entered between the manhole cover plug body 100 and the bag-shaped recess 201 of the manhole cover 200 freezes in these lateral grooves 13a, 15a, causing the manhole cover plug body 100 and the ice to become one, improving the frictional force with the bag-shaped recess 201 of the manhole cover 200 and effectively preventing the manhole cover plug body 100 from floating up.

As described above, this embodiment is a manhole cover plug 100 that is attached to a bag-shaped recess 201 provided in a manhole cover 200, and is configured to have a hollow portion that is recessed upward from the bottom (main body bottom surface 11 and protruding part bottom surface 21). By adopting such a configuration, when rainwater, etc. is not frozen, the hollow portion is filled with air, so that when rainwater, etc. in the gap between the manhole cover plug 100 and the recess 201 freezes, ice pushed out from the gap as the volume of the rainwater, etc. increases can enter the hollow portion. Therefore, even if rainwater, etc. freezes, the expanding ice can be prevented from pushing the gap wide, and the manhole cover plug 100 can be prevented from floating up.

In addition, in this embodiment, the volume of the hollow portion is configured to be equal to or greater than the volume that increases due to the freezing of water that has entered the gap between the bag-shaped recess 201 and the manhole cover plug 100. By adopting such a configuration, when rainwater or the like in the gap between the manhole cover plug 100 and the recess 201 freezes, all of the ice pushed out of the gap as the volume of the rainwater or the like increases can enter the hollow portion. Therefore, even if the rainwater or the like freezes, the expanding ice can be effectively prevented from pushing the gap open, and therefore the manhole cover plug 100 can be effectively prevented from floating up.

In addition, in this embodiment, the manhole cover plug 100 has a main body 10 that extends in a generally vertical direction and a protruding portion 20 that extends in a generally horizontal direction from the lower portion of the main body 10, and the hollow portion is configured to be provided in the main body 10 and the protruding portion 20. By adopting such a configuration, the manhole cover plug 100 has a main body 10 and a protruding portion 20 that correspond to the shape of the hook-shaped and bag-shaped recess 201, so that the volume of rainwater, etc. that gets into the gap between the manhole cover plug 100 and the bag-shaped recess 201 can be reduced, and the manhole cover plug 100 can be effectively prevented from floating up when the rainwater, etc. freezes.

In addition, in this embodiment, the cavity is configured to be divided into multiple cavity regions (main body cavity 11a and protruding portion cavity 21a) by partitions (main body partition 11c and protruding portion partition 21c). By adopting such a configuration, expanded rainwater, etc. can enter the cavity, suppressing the floating of the manhole cover plug body 100, while ensuring the rigidity of the manhole cover plug body 100.

In addition, in this embodiment, the multiple hollow regions are configured to be formed in the main body 10 and the protruding portion 20, respectively. By adopting such a configuration, the hollow portions can be arranged evenly within the manhole cover plug body 100, so that even if rainwater or the like that has entered the gap freezes, the expanding ice can be effectively prevented from pushing the gap wider, and the manhole cover plug body 100 can be effectively prevented from floating up.

In addition, in this embodiment, the side of the protrusion 20 is further configured to have a side cavity (protrusion cavity 23a). By adopting such a configuration, when rainwater or the like in the gap between the manhole cover plug 100 and the recess 201 freezes, ice can enter this side cavity in addition to the cavity (main body cavity 11a and protrusion cavity 21a), so that the manhole cover plug 100 can be more effectively prevented from floating up.

In addition, in this embodiment, the side surface (main body side surface 13) of the main body 10 is configured to have horizontal grooves 13a, 15a extending in a substantially horizontal direction. By adopting this configuration, rainwater or the like that has entered the gap between the manhole cover plug 100 and the bag-shaped recess 201 of the manhole cover 200 freezes in these horizontal grooves 13a, 15a, and the manhole cover plug 100 and the ice become one, improving the frictional force with the bag-shaped recess 201 of the manhole cover 200. Therefore, the manhole cover plug 100 can be effectively prevented from floating up.

In addition, in this embodiment, the radial end of the main body 10 is configured to have cutouts 17a, 17b that extend downward from the upper surface (top upper surface 15b) to a height position higher than the lower surface. By adopting such a configuration, when removing the manhole cover plug 100 from the manhole cover 200, it is possible to easily pull it out upward by inserting a crowbar or the like into the cutouts 17a, 17b. In addition, the cutouts 17a, 17b do not reach the lower surface of the manhole cover plug 100 (see Figure 6) and do not communicate with the inside of the manhole, so that it is possible to prevent soil and sand from entering the manhole through the cutouts 17a, 17b.

Although the present disclosure has been described based on various drawings and examples, it should be noted that a person skilled in the art would be able to easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these modifications and corrections are included in the scope of the present invention. For example, the functions contained in each component can be rearranged so as not to cause logical inconsistencies, and multiple components can be combined into one or divided.

For example, in this embodiment, the hollow portion is configured to be provided on the underside of the main body portion 10 and the protruding portion 20 (main body portion underside 11 and protruding portion underside 21), respectively, but this is not limited to this aspect. It is sufficient that the hollow portion is provided on at least one of the main body portion 10 and the protruding portion 20.

In addition, in this embodiment, the cavity is configured to be divided into two cavity regions by a partition wall, but this is not limited to the above. The cavity may be divided into three or more cavity regions by a partition wall. Also, the cavity may not be divided by a partition wall.

In addition, in this embodiment, the side surface of the protrusion 20 (protrusion side surface 23) is configured to have a side cavity (protrusion cavity 23a), but this is not limited to the above embodiment. The side cavity may be provided on the side surface of the main body 10 in addition to the side surface of the protrusion 20, or may be provided only on the side surface of the main body 10. Also, the configuration may not have a side cavity.

In addition, in this embodiment, the lateral grooves 13a, 15a are provided on almost the entire area of the circumferential side surface of the main body 10, but this is not limited to the embodiment. The lateral grooves 13a, 15a may be provided only on a part of the circumferential side surface, or the lateral grooves 13a, 15a may not be provided.

In addition, in this embodiment, the cutouts 17a and 17b are provided at the radial end of the top 15 of the main body 10, but this is not limited to the embodiment. The cutouts 17a and 17b may be provided in an area other than the radial end of the top 15, or the cutouts 17a and 17b may not be provided. The cutouts 17a and 17b may also be configured to reach the underside of the manhole cover plug 100.

The amount of floating of the manhole cover plug 100 (Example) according to the present embodiment shown in Figures 1 to 6 and a manhole cover plug (Comparative Example) that does not have a cavity (main body cavity 11a and protruding cavity 21a, 23a) was measured when rainwater that entered the gap between the plug and the bag-shaped recess 201 froze.

The measurements were taken every week for four weeks from February 24, 2020 in Morioka City, Iwate Prefecture, measuring the height of the top surface of the plug relative to the top surface of the manhole cover 200.

In Figure 9, the horizontal axis plots the time elapsed since the plug was installed (mounted) on the manhole cover 200, and the vertical axis plots the height [mm] of the top surface of the plug relative to the top surface of the manhole cover 200, for both the case with a hollow portion (Example) and the case without a hollow portion (Comparative Example).

In the comparative example, a rise of about 2 mm was observed two weeks after the plug was installed. Then, three weeks after the plug was installed, the amount of rise increased to about 11 mm. Two weeks after the plug was installed, some of the rainwater in the gap between the plug and the bag-shaped recess 201 froze, causing the plug to rise about 2 mm, and three weeks later, most of the rainwater in the gap froze, causing the plug to rise about 11 mm. Note that friction acts between the horizontal grooves 13a, 15a of the plug and the bag-shaped recess 201, so the rise of the plug is an irreversible change (even if the ice in the gap melts, the plug will not move downward). Therefore, the amount of rise of the plug in Figure 9 increases over time, and it is thought that no change in the amount of rise is observed after three weeks when most of the rainwater in the gap has frozen.

On the other hand, in the embodiment, no floating of the plug was observed up to four weeks after installation. Even if rainwater or the like in the gap between the plug and the bag-shaped recess 201 freezes and expands, the expanding ice enters the cavity (main body cavity 11a and protruding cavity 21a, 23a) and does not push up the plug, which is thought to suppress the plug from floating up.

10 Main body part 11 Lower surface of main body (bottom surface)
11a Body cavity (cavity)
11c Main body partition wall (partition wall)
13 Main body side (side)
13a Horizontal groove 15 Top 15a Horizontal groove 15b Top upper surface 17a, 17b Notch 20 Projection 21 Projection lower surface (lower surface)
21a Projection cavity part (cavity part)
21c Projection partition wall (partition wall)
23 Side surface of protrusion (side surface)
23a: protruding cavity (side cavity)
23c Projection partition wall (partition wall)
REFERENCE SIGNS LIST 100 Manhole cover plug 200 Manhole cover 201 Bag-shaped recess 203 Vertical recess 203a Opening 203b Inclined surface 205 Horizontal recess C Central axis of plug O Central axis of manhole cover

Claims (7)

A manhole cover plug to be attached to a bag-shaped recess provided in a manhole cover,
A hollow portion recessed upward from the bottom surface is provided ,
The volume of the hollow portion is equal to or greater than the volume that is increased by freezing of water that has entered the gap between the bag-shaped recess and the manhole cover plug,
The bag-shaped recess has an opening that opens upward, and no other openings are provided in the bottom wall on the side opposite the opening. The manhole cover has a main body extending in a generally vertical direction with a direction along a straight line perpendicular to the central axis of the manhole cover as a radial direction, and a protrusion extending generally horizontally in the radial direction from a lower portion of the main body,
The manhole cover plug according to claim 1 , wherein the cavity is provided in at least one of the main body and the protrusion. 3. The manhole cover plug according to claim 1 , wherein the cavity is divided into a plurality of cavity regions by partition walls extending downward from an upper end of the cavity . The manhole cover plug according to claim 3 when dependent on claim 2 , wherein the plurality of hollow regions are formed in the main body portion and the protruding portion, respectively. 5. The manhole cover plug according to claim 2 , wherein a side cavity portion opening laterally is further provided on at least one side surface of the main body portion and the protrusion portion. The manhole cover plug according to any one of claims 2 , 4 and 5 , wherein a lateral groove extending in a substantially horizontal direction is provided on a side surface of the main body. A manhole cover plug as claimed in any one of claims 2 , 4 , 5 and 6 , wherein the radial end of the main body is provided with a notch extending downward from the upper surface to a height position higher than the lower surface.

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