JP2015045220A - Cover body for underground structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cast iron cover body for an underground structure, which has an undersurface on an underground side, which closes an opening communicating with the underground structure, and to which contrivance to suppress the progress of rust is applied.SOLUTION: A cover body for an underground structure has a protrusion 31 that protrudes downward from an undersurface 30. The protrusion 31 comprises a round part 32 that has a curved surface communicating with the undersurface 30. The round part 32 has an electrodeposition film 321 that is brought into contact with a casting surface and that includes a resin component, and a resin body 322 that is brought into contact with the electrodeposition film 321.

Description

  The present invention relates to a lid for an underground structure made of cast iron that has a lower surface on the underground side and closes an opening connected to the underground structure.

  Openings connected to underground structures such as underground and underground facilities such as sewers and waterworks, electric power, gas, and communications are closed by lids. This lid body is provided with a protruding portion such as a rib protruding downward from the lower surface on the underground side to improve the strength. However, if the lid is made of cast iron, there is a concern that rust will occur and the strength will be insufficient. Therefore, an electrodeposition coating is applied in order to enhance the rust prevention capability of the lid, and a rust-preventive coating is provided on the lower surface of the lid and the projecting portion (hereinafter referred to as the underground portion of the lid). (For example, see Patent Document 1).

  However, it has been found that due to recent changes in the living environment and social environment, in particular, the underground portion of the lid of the underground buried object in the sewer is faster than expected. This is considered to be influenced by hydrogen sulfide generated underground.

Japanese Patent Laid-Open No. 2005-120587

  As a result of further investigation and research by the present inventor, in the underground part of the lid, condensation of a corrosive solution such as hydrogen sulfide is likely to occur due to the humidity in the underground, and the underground part of the lid is corrosive. It was found that the solution was likely to remain. In particular, a corrosive solution such as hydrogen sulfide is likely to remain between the protrusion and the lower surface (hereinafter referred to as a root portion of the protrusion) without dripping due to the surface tension of the corrosive solution. Even if the rust preventive coating film is provided on the base portion of the protruding portion where the corrosive solution remains, rusting proceeds.

  In view of the above circumstances, an object of the present invention is to provide a lid for an underground structure that has been devised to suppress the progress of rust.

The lid for an underground structure of the present invention that solves the above object has a lower surface that becomes the underground side, and in the lid for an underground structure made of cast iron that closes an opening that leads to the underground structure,
Having a protrusion protruding downward from the lower surface;
The protruding portion includes an R portion having a curved surface connected to the lower surface,
The R portion has an electrodeposition coating film containing a resin component in contact with the casting surface and a resin body in contact with the electrodeposition coating film.

  Moreover, the lid for underground structures of this invention WHEREIN: The radius may be below the protrusion height of the said protrusion part in the said curved surface.

  Furthermore, in the lid for an underground structure according to the present invention, the R portion may have a surface arithmetic average roughness (Ra) of greater than 0 and less than 3 μm.

In addition, in the lid for a metal underground structure that has a lower surface that becomes the underground side and closes the opening that leads to the underground structure,
Having a protrusion protruding downward from the lower surface;
The projecting portion may include an R portion having a curved surface with a radius of 3 mm or more connected to the lower surface.

  According to this underground structure lid, the corrosive solution that tends to remain at the base portion of the protruding portion is likely to drip along the surface of the R portion, so that the corrosive solution remains in that portion. It is possible to suppress the progress of rust.

  Note that the R portion referred to here may have an open curved surface.

  Moreover, it is preferable that the radius of the curved surface in the R portion is not more than the protruding height of the protruding portion.

  The R portion preferably has a surface arithmetic average roughness (Ra) of more than 0 and less than 3 μm.

  By doing so, the corrosive solution that tends to remain at the base portion of the protruding portion is more likely to hang down along the R portion.

  Moreover, it is preferable that the said R part is the surface formed by the coating film.

  By forming the surface of the R portion with a coating film, it is possible to obtain a smooth surface on which the corrosive solution tends to sag.

  Moreover, it is one of the preferable aspects that the said R part is that the surface was formed with resin.

  According to this aspect, even if it takes some time for the corrosive solution to flow down the R portion, the progress of rust is suppressed because the surface of the R portion is formed of the resin.

Also, it has an upper surface that becomes the ground side,
The R portion may be an underground structure lid body whose surface is formed of a material having a higher hydrophobicity than the upper surface.

  By forming the surface with the material having high hydrophobicity, it becomes easy to play the corrosive solution, and the corrosive solution is prevented from remaining at the base portion of the protruding portion.

  Examples of the material include silicon-based materials.

  In addition, the R portion preferably includes an electrodeposition coating film containing a resin component in contact with a metal surface and a coating film of a resin material that forms a surface in contact with the electrodeposition coating film. One.

  According to this aspect, the electrodeposition coating film having high adhesion to the metal surface is formed of the material containing the resin component, and the coating film of the resin material is formed on the electrodeposition coating film. And a smooth surface on which the corrosive solution tends to sag can be obtained. Moreover, since a coating film having a two-layer structure of a coating film by electrodeposition coating and a coating film of a resin material is formed, the rust prevention ability is also enhanced.

  ADVANTAGE OF THE INVENTION According to this invention, the cover body for underground structures by which the device which suppresses advancing of rust was made | formed can be provided.

(A) is sectional drawing of the manhole iron cover corresponded to one Embodiment of the cover body for underground structures of this invention, (b) is a top view of the manhole iron cover shown to (a). It is a figure which shows a mode that the manhole iron cover shown in FIG. 1 was turned and the manhole iron cover 1 was opened. (A) is a bottom view of the manhole iron cover shown in FIG. 1 (a), (b) is a BB cross-sectional view of the manhole iron cover shown in FIG. 3 (a), and (c) is FIG. 6 is a partial cross-sectional view showing an enlarged periphery of a rib when a radius of an R portion 32 is made larger than a protruding height of the rib 31. (D) is an expanded sectional view showing a modification of R section. (A) is a bottom view of the manhole iron cover of 2nd Embodiment, (b) is a fragmentary sectional view which expands and shows the periphery of the protrusion of the manhole iron cover shown to (a). (A) is sectional drawing of the manhole iron cover of 3rd Embodiment, (b) is CC sectional drawing of (a). (A) is a bottom view of the manhole iron cover of 4th Embodiment, (b) is DD sectional drawing of (a), (c) is a cross section of the cyclic | annular rib shown to (a). It is a figure and (d) is a figure which shows the modification of the protrusion provided in the protrusion front end surface of the annular rib shown to (a). It is a fragmentary sectional view which expands and shows the periphery of the rib of the manhole iron cover of 5th Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  Fig.1 (a) is sectional drawing of the manhole iron cover corresponded to one Embodiment of the cover body for underground structures of this invention, FIG.1 (b) is the manhole iron cover shown to the same figure (a). It is a top view. The cross-sectional view shown in FIG. 1A is a cross-sectional view taken along the line AA in FIG.

  FIG. 1 shows a manhole iron lid 1 and a receiving frame 5 for receiving the manhole iron lid 1. A sewer drain pipe, which is an underground buried object, is buried at a predetermined depth from the ground surface, and a manhole is provided as an underground facility in the middle of the sewer drain pipe. Both sewer drains and manholes are equivalent to underground structures. The manhole is formed as a vertical hole from the sewer drain pipe to the surface of the earth by using a box made of ready-made concrete moldings. The receiving frame 5 is provided on the housing and defines an opening H (see FIG. 2) connected to a manhole that is an underground structure.

  A manhole iron cover 1 shown in FIG. 1 is made of cast iron formed by casting. The manhole iron cover 1 has a circular shape when viewed from above, which opens and closes an opening H connected to a manhole which is an underground structure, and the manhole iron cover 1 shown in FIG. 1 closes the opening H. In FIG. 1A, the upper side of the figure is the ground side, and the lower side of the figure is the underground side (the sewer drain pipe side). The manhole iron cover 1 has an upper surface 20 on the ground side, a horizontal lower surface 30 on the underground side, and a plurality of ribs 31 protruding downward from the lower surface 30. The rib 31 in the present embodiment corresponds to an example of a protruding portion in the present invention.

  As shown in FIG. 1A, a hinge member 33 is rotatably connected to a peripheral edge portion on one end side of the lower surface 30. Further, a hinge seat 51 is fixedly disposed on the receiving frame 5. The hinge seat 51 forms a through hole 511 through which the hinge member 33 penetrates in the vertical direction. At the lower end of the hinge member 33 penetrating the hinge seat 51, a protrusion 331 for preventing the removal is provided. On the other hand, a keyhole 11 is provided on the peripheral edge of the other end of the manhole iron lid 1. Further, a lock member 34 is provided on the other end side of the lower surface 30 so as to be rotatable about a rotation shaft 340. The lock member 34 includes a valve body 341 and a locking claw 342. The receiving frame 5 is provided with a locking piece 52. The lock member 34 is biased by a spring 343 so that the locking claw 342 is locked to the locking piece 52 when the manhole iron cover 1 is lifted. FIG. 1A shows the lock member 34 in the posture. In the posture of the lock member 34 shown in FIG. 1A, the valve body 341 enters the key hole 11 and closes the key hole 11.

  In order to open the manhole iron lid 1 with the opening closed as shown in FIG. 1, a rod-like opening / closing tool (not shown) is used. The tip portion of the rod-shaped opening / closing tool is T-shaped. First, the tip end portion of the opening / closing tool is inserted into the keyhole 11 closed by the valve body 341. The valve element 341 is pushed by the tip of the opening / closing tool, and the lock member 34 resists the biasing force of the spring 343 so that the locking claw 342 moves away from the locking piece 52 (counterclockwise in FIG. 1A). In the direction) about the rotation shaft 340. Next, the rod-shaped opening / closing tool is rotated about the axis, the T-shaped tip portion is engaged with the edge portion of the keyhole 11 on the lower surface 30 of the manhole iron lid 1, and the opening / closing tool is pulled up. Then, the other end side of the manhole iron lid 1 is lifted without the locking claw 342 being locked to the locking piece 52, and the manhole iron lid 1 can rotate together with the hinge member 33 with the hinge member 33 as a fulcrum. Become. That is, the manhole iron cover 1 can be turned in the substantially horizontal direction with the hinge member 33 as a fulcrum. The manhole iron cover 1 can be lifted until the projection 331 of the hinge member 33 is engaged with the hinge seat 51.

  FIG. 2 is a view showing a state where the manhole iron cover shown in FIG. 1 is turned and the manhole iron cover 1 is opened. Fig.2 (a) is sectional drawing which shows the mode, FIG.2 (b) is a top view of the manhole iron cover shown to the figure (a).

  In FIG. 2, the hinge member 33 and the lock member 34 are not shown. Moreover, the ground G is shown by Fig.2 (a). A manhole cover 1 shown in FIG. 2 is placed on the ground G.

  Fig.3 (a) is a bottom view of the manhole iron cover shown to Fig.1 (a).

  The ribs 31 are arranged in a cross pattern on the lower surface 30, a rectangular rib 311 surrounding the central region 300 </ b> C of the lower surface 30, and eight linear ribs extending from the rectangular rib 311 to the outer periphery of the lower surface 30. 312. Each rib 31 is formed integrally with the lower surface 30 when the manhole iron cover 1 is cast for the purpose of increasing the strength of the manhole iron cover 1. Each of the eight linear ribs 312 has a boundary portion with the rectangular rib 311 at the lowest position, and is inclined upward from the boundary portion toward the outer periphery of the lower surface 30. The rectangular rib 311 has the highest protruding height in the rib structure shown in FIG. 3A, and the protruding tip surface 311a of the rectangular rib 311 is located at the lowest position. The protruding height of the rectangular rib 311 in the present embodiment is 60 mm.

  An information display of the manhole cover 1 is cast out in a central region 300C surrounded by the rectangular rib 311 on the lower surface 30. That is, as shown in FIG. 3A, “FCD 700” and “T-25 600” are represented in two stages. “FCD” is information indicating the material of the manhole iron cover 1, “700” is information indicating the tensile strength (N / mm 2) of the manhole iron cover 1, and “T-25” is The information indicating the load resistance of the manhole iron cover 1, and “600” is information indicating the diameter (nominal diameter) of the manhole iron cover 1. Such information can be said to be a kind of identification information for identifying the manhole iron cover 1. The information displayed on the lower surface 30 is not limited to the information described here.

  FIG.3 (b) is BB sectional drawing of the manhole iron cover shown to Fig.3 (a). In FIG. 3B, the lower side of the figure is the ground side, and the upper side of the figure is the underground side (the sewer drain pipe side).

As shown in FIGS. 1A and 3B, each rib 31 is formed with an R portion 32 having a curved surface with a radius of 3 mm connected to the lower surface 30. Each R portion 32 is integrally formed with each rib 31. In the manhole, condensation of a corrosive solution such as hydrogen sulfide may occur due to the humidity in the manhole. When the R portion 32 is not formed, the corrosive solution tends to remain at the base portion of the rib 31 without dropping due to the surface tension of the corrosive solution. By forming the R portion 32 having a curved surface with a radius of 3 mm, the corrosive solution is likely to hang down on the lower side of the rib 31 along the R portion 32, and the remaining of the corrosive solution can be prevented. Therefore, the rib 31 is prevented from becoming thin due to rust, and the strength of the manhole iron lid 1 is kept at a high level for a very long time. In the manhole iron cover 1 of this embodiment, the curved surface of the R portion 32 is formed with a radius of 3 mm, but according to the study of the present inventor, this radius may be 3 mm or more, in order to make it easier to sag. It is preferable to set the radius to 5 mm or more, and to make it easier to sag in a short time, it has been found that the radius should be 6 mm or more. Table 1 shows the results of an experiment conducted by the inventors to evaluate the state in which water droplets hang down.

  However, it is desirable that this radius be equal to or less than the protruding height of the rib 31. FIG. 3C is a partial cross-sectional view showing an enlarged periphery of the rib when the radius of the R portion 32 is larger than the protruding height of the rib 31. As shown in FIG. 3C, when the radius is larger than the protruding height, a corner portion is formed at a portion X where the lower surface 30 and the R portion 32 are connected or a portion Y where the side surface 31a of the rib 31 and the R portion 32 are connected. Will be formed. In FIG. 3C, a state in which a corner portion is formed at a portion X where the lower surface 30 and the R portion 32 are connected is shown on the left side of the rib 31, and a portion Y where the side surface 31a of the rib 31 and the R portion 32 are connected. A state in which the corner portion is formed is shown on the right side of the rib 31. At these corners, the corrosive solution tends to remain without flowing down due to its surface tension. By setting the radius of the curved surface of the R portion 32 to be equal to or less than the protruding height of the rib 31, the R portion 32 and the side surface 31a of the rib 31 and the R portion 32 and the lower surface 30 are smoothly connected to prevent the formation of corner portions. can do.

  Then, the modification of this embodiment is demonstrated. In the following description, components having the same names as those of the components described so far will be described with the same reference numerals as those used so far.

In the first modification, the arithmetic average roughness (Ra) of the surface of the R portion 32 is made larger than 0 and less than 3 μm by polishing the casting surface of the surface of the R portion 32. That is, the surface of the R portion 32 is formed into a smooth curved surface. The arithmetic average roughness (Ra) is a value measured based on JIS B 0601 (2001). By smoothing the surface of the R portion 32, the corrosive solution remaining in the R portion 32 is likely to hang down on the protruding tip end surface 311 a side of the rib 31 along the R portion 32. Therefore, the rib 31 is prevented from becoming thin due to rust, and the strength of the manhole iron lid 1 is kept at a high level for a very long time.

  Next, a second modification will be described. In the second modification, a coating film is formed on the R portion 32. This coating film is a rust preventive coating film formed by coating a resin such as an epoxy resin or a silicone resin on the surface of the R portion 32. By applying the coating on the casting surface, the surface of the R portion 32 can be made a smooth surface on which the corrosive solution is liable to drip with a simple operation. Although this coating film is not restricted to a rust prevention coating film, by making it a rust prevention coating film, the rust prevention capability of R part 32 can be improved and the progress of rust can be suppressed more. Further, as shown in the first modification, the arithmetic mean roughness (Ra) of the surface of the R portion 32 is larger than 0 and less than 3 μm before painting by polishing the casting surface of the surface of the R portion 32 or the like. You may paint after forming. By smoothing the surface of the R portion 32 before painting, the surface of the R portion 32 after painting can be made smoother. Further, after the coating, the arithmetic average roughness (Ra) of the surface of the R portion 32 may be made larger than 0 and less than 3 μm by polishing the coating film on the surface of the R portion 32. In addition, since electrodeposition coating forms a coating with a nearly uniform thickness on the metal surface before coating, it is difficult to obtain a smooth surface even if electrodeposition coating is applied to the cast surface as cast. . Therefore, when coating is performed on the cast surface as cast, it is desirable to form the coating film by a method other than electrodeposition coating such as spray coating or brush coating. A coating film may be formed on the entire surface of the rib 31 and the entire lower surface 30.

  Subsequently, a third modification will be described. In the third modification, the surface of the R portion 32 is formed by coating a silicon-based resin having higher hydrophobicity (versus hydrophilicity) than the upper surface 20. Due to the effect of the highly hydrophobic material, the corrosive solution is likely to be repelled, and the corrosive solution is likely to hang down on the protruding tip end surface 311 a side of the rib 31 through the R portion 32. The material that forms the surface of the R portion 32 may be any material that is more hydrophobic than the upper surface 20, and may be, for example, a resin or metal material other than silicon. Further, the method of forming the surface is not limited to coating, and may be formed by plating, for example.

  Furthermore, a fourth modification will be described.

  FIG. 3D is an enlarged cross-sectional view showing a fourth modification. FIG. 3D shows an enlarged surface portion of the R portion.

  In the fourth modified example, the R portion 32 includes an electrodeposition coating 321 containing a resin component provided on the casting surface M, and the electrodeposition coating 321 provided on the electrodeposition coating 321. And a coating 322 of a resin material that forms the surface. Even if a paint containing a resin component is directly applied to a metal surface such as the casting skin M, it is difficult to obtain adhesion between the metal surface and the material containing the resin component by a coating method other than electrodeposition coating. In contrast, electrodeposition coating can form a strong coating film with high adhesion even when a material containing a resin component is applied to a metal surface. However, as shown in FIG. 3 (d), the electrodeposition coating 321 is formed on the cast skin M before coating with a substantially uniform thickness. If only the film 321 is formed, the surface formed by the electrodeposition coating 321 becomes a rough surface similar to the casting surface M, and it is difficult to obtain a smooth surface. In the fourth modification, an electrodeposition coating 321 is formed on the casting surface M, and a resin material is applied on the electrodeposition coating 321 by a method other than electrodeposition coating such as spray coating or brush coating. Since the film 322 is formed, a smoother surface can be obtained. In addition, as described above, the electrodeposition coating 321 containing the resin material is firmly adhered to the casting surface M, and the resin coating 322 is firmly adhered to the electrodeposition coating 321 containing the resin material. As a whole, a strong coating film having high adhesion can be formed. Furthermore, since the coating film 322 of the resin material is formed on the surface, even if it takes some time for the corrosive solution to flow down the surface of the R portion 32, the surface is formed of the resin, so that rust progresses. Is suppressed. Further, since a coating film having a two-layer structure of the electrodeposition coating film 321 and the resin material coating film 322 is formed, the rust prevention ability is further enhanced. In addition, as resin used for these coating films, an epoxy resin and a silicon resin are mentioned.

  Next, the manhole iron cover from the second embodiment to the fourth embodiment will be described in order. Also in the following description of each embodiment, the same reference numerals as those used so far are attached to the components having the same names as the names of the components described so far. Moreover, the description which overlaps with the description of the manhole iron cover of 1st Embodiment may be abbreviate | omitted.

  FIG. 4A is a bottom view of the manhole cover of the second embodiment.

  Although the manhole iron cover of the first embodiment is provided with the cross-girder-shaped ribs 31 on the lower surface, the manhole iron cover 1 of the second embodiment includes the manhole iron cover 1 and the manhole iron cover 1 in the central region of the lower surface 30. Concentric circular ribs 35 are provided, and eight radial ribs 36 extending radially from the annular ribs 35 are also provided. By adopting such a rib structure, the strength of the manhole iron lid 1 is increased. The annular rib 35 and the radial rib 36 in the present embodiment correspond to an example of a protruding portion in the present invention. Each of the eight radial ribs 36 is inclined upward toward the outer periphery of the lower surface 30, and the protruding front end surface 35 a of the annular rib 35 is located at the lowest position in the rib structure shown in FIG. It becomes the bottom surface.

  Although not shown, like the ribs of the first embodiment, the annular ribs 35 and the radial ribs 36 are formed with R portions 32 having a curved surface with a radius of 3 mm connected to the lower surface 30. Each R portion 32 is integrally formed with the annular rib 35 and the radial rib 36.

  On the lower surface 30 of the manhole iron cover 1 of the second embodiment, protrusions 37 are provided between the radial ribs 36 adjacent in the circumferential direction. That is, a total of eight protrusions 37 are provided on the lower surface 30 shown in FIG. The protrusion height of these protrusions 37 is 10 mm.

  FIG. 4B is an enlarged partial cross-sectional view of the periphery of the manhole iron lid protrusion shown in FIG.

  As shown in FIG. 4B, the tip portion of the protrusion 37 has a hemispherical shape that becomes thinner toward the lower side. From each protrusion 37, the corrosive solution which tends to remain on the lower surface 30 is likely to drip, and the progress of rust on the lower surface 30 can be suppressed.

  Each protrusion 37 is formed with an R portion 38 having a curved surface with a radius of 3 mm, which is connected to the lower surface 30. The R portion 38 is integrally formed with the protrusion 37. The corrosive solution that tends to remain at the base of the protrusion 37 tends to sag to the tip side of the protrusion 37 along the R portion 38. Therefore, the protrusion 37 in the present embodiment also corresponds to an example of the protruding portion in the present invention. In this embodiment, the curved surface of the R portion 38 is formed with a radius of 3 mm, but it is sufficient that the radius is 3 mm or more. In order to make it more easy to sag, it is preferable to make the radius 5 mm or more. To make it easier, the radius should be 6 mm or more. However, it is desirable that this radius be equal to or less than the protrusion height of the protrusion 37. If the radius is larger than the protrusion height of the protrusion 37, a corner portion is formed at a portion where the lower surface 30 and the R portion 38 are connected or a portion where the side surface of the protrusion 37 and the R portion 38 are connected, and the corner portion is corroded. The residual solution tends to remain. By setting the radius of the curved surface of the R portion 38 to be equal to or less than the protruding height of the protrusion 37, formation of the corner portion can be prevented.

The portion between the radial ribs 36 on the lower surface 30 of the manhole cover 1 is inclined downward toward the protrusion 37 provided therebetween. That is, an inclined region 301 inclined downward toward the protrusion 37 is provided around the protrusion 37 provided between the radial ribs 36. In this embodiment, the inclined region 301 is a region that decreases at a rate of 1% with respect to the horizontal distance (an inclination angle of 0.57 degrees). The inclination angle may be 0.5 degrees or more, for example, 1 degree. The corrosive solution such as hydrogen sulfide generated due to the humidity in the underground actively gathers on the protrusion 37 by providing the inclined region 301, and the corrosive solution remaining on the lower surface 30 hangs down from the protrusion 37. It becomes easy.

  In the manhole iron lid 1 of the second embodiment, three hemispherical protrusions 37 ′ are provided on the protruding front end surface 35 a of the annular rib 35 at intervals of 120 degrees. Each protrusion 37 ′ is formed integrally with the annular rib 35 and protrudes further downward from the protruding tip surface 35 a of the annular rib 35. The diameter of the base of the protrusion 37 ′ is substantially the same as the thickness of the protruding tip surface 35 a of the annular rib 35. From the protrusion 37 ′ provided on the annular rib 35, the corrosive solution remaining on the annular rib 35 is likely to drip, and the progress of rust on the annular rib 35 can be suppressed.

  Fig.5 (a) is sectional drawing of the manhole iron cover of 3rd Embodiment, FIG.5 (b) is CC sectional drawing of the figure (a).

  The lower surface 30 of the manhole iron cover of the first embodiment is a flat region that is planar as a whole. On the other hand, the lower surface 30 of the manhole iron cover 1 of the third embodiment is provided with an inclined region 302 that is inclined downward toward the rectangular rib 311 and is not flat as a whole. As shown in FIG. 5A, the central region 300 </ b> C is also provided with an inclined region 302, and the inclined region 302 is inclined downward toward the four rectangular ribs 311. In this embodiment, the inclined region 302 is a region that decreases at a rate of 1% with respect to the horizontal distance (an inclination angle of 0.57 degrees). The inclination angle may be 0.5 degrees or more, for example, 1 degree. FIG. 5B shows an inclined region 302 that is inclined downward toward the rectangular rib 311. Further, in the inclined region 302 shown in FIG. 5B, the portion 3021 that is intermediate between the linear rib 312 and the linear rib 312 is lowest. In the third embodiment, the corrosive solution condensed on the lower surface 30 can be actively collected on the rectangular rib 311, and the corrosive solution can be prevented from remaining on the lower surface 30.

  Fig.6 (a) is a bottom view of the manhole iron cover of 4th Embodiment.

  The manhole iron cover 1 shown in FIG. 6A has an annular rib 35 and eight radial ribs 36 extending radially from the annular rib 35, similarly to the manhole iron cover shown in FIG. In addition, in the lower surface 30 of the manhole iron cover 1 shown in FIG. 6A, the region outside the annular rib 35 is an inclined region inclined downward toward the annular rib 35 (hereinafter referred to as an outer inclined region). The region inside the annular rib 35 is an inclined region (hereinafter referred to as an inner inclined region) 402 inclined downward from the central portion 1a of the manhole iron cover 1 toward the annular rib 35. Yes. The outer slope area 401 and the inner slope area 402 of this embodiment are areas that are lowered at a rate of 1% with respect to the horizontal distance (slope angle 0.57 degrees). The inclination angle may be 0.5 degrees or more, for example, 1 degree. Furthermore, the manhole iron lid 1 shown in FIG. 6A is provided with a flow path 39 extending in the radial direction between the radial ribs 36 adjacent in the circumferential direction. The flow path 39 is eight ridges extending radially from the annular rib 35, and is provided in the outer inclined region 401.

  FIG. 6B is a DD cross-sectional view shown in FIG.

  An R portion 40 having a curved surface with a radius of 3 mm connected to the lower surface 30 is formed in the flow path 39. The corrosive solution that tends to remain at the base portion of the flow path 39 is likely to hang down to the front end side of the flow path 39 through the R portion 40. Therefore, the flow path 39 in the present embodiment also corresponds to an example of the protruding portion in the present invention. Each R portion 40 is integrally formed with each flow path 39. In the manhole iron cover 1 of this embodiment, the curved surface of the R portion 40 is formed with a radius of 3 mm. However, the radius may be 3 mm or more. To make it easy to sag in a short time, the radius should be 6 mm or more. However, it is desirable that this radius be equal to or less than the protruding height of the flow path 39. If the radius is larger than the protruding height of the flow path 39, a corner is formed at a portion where the lower surface 30 and the R portion 38 are connected or a portion where the side surface of the flow channel 39 and the R portion 38 are connected. The corrosive solution tends to remain. By setting the radius of the curved surface of the R portion 40 to be equal to or less than the protruding height of the flow path 39, formation of corner portions can be prevented.

  The projecting height of the channel 39 which is a protrusion is substantially constant, and the channel 39 is inclined downward toward the annular rib 35 in accordance with the inclination of the outer inclined region 401. The corrosive solution remaining on the lower surface 30 tends to reach the annular rib 35 along these flow paths 39. In addition, you may adjust the inclination-angle of a flow path by making the protrusion height of the protrusion body which comprises the flow path 39 in the design stage, so that it may increase to the inner side and the outer side.

  The protrusion front end surface 351 of the annular rib 35 shown in FIG. 6A has unevenness arranged in the circumferential direction.

  FIG. 6C is a cross-sectional view of the annular rib shown in FIG.

  The protruding front end surface 351 of the annular rib 35 of the manhole cover 1 according to the fifth embodiment is formed in a zigzag shape in the vertical direction as shown in FIG. That is, the flat first inclined surface 3511 inclined downward in the counterclockwise direction and the flat second inclined surface 3512 inclined downward in the clockwise direction are alternately continued. A protrusion 350 is formed by the first inclined surface 3511 and the second inclined surface 3512. A plurality of the protrusions 350 are provided in the circumferential direction. That is, the tips of the protrusions 350 shown in FIG. 6C are dispersedly arranged with an interval of 15 mm or more in the circumferential direction.

  As described above, the corrosive solution that has reached the annular rib 35 through the flow path 39 reaches the protruding tip surface 351 of the annular rib 35 along the side surface of the annular rib 35, and the protrusion 350 formed on the protruding tip surface 351. Dripping from the tip. Thus, by providing the flow path 39, the corrosive solution is positively gathered on the protrusion 350, and the corrosive solution that is likely to remain on the lower surface 30 is likely to drip from the protrusion 350, thereby suppressing the progress of rust. .

  Further, the corrosive solution that has reached the annular rib 35 through the radial ribs 36 also drops from the protrusions 350 formed on the protruding tip surface 351. Further, the corrosive solution that has reached the annular rib 35 through the outer inclined region 401 and the inner inclined region 402 also drips from the protrusion 350 formed on the protruding tip surface 351.

  FIG.6 (d) is a figure which shows the modification of the protrusion provided in the protrusion front end surface of the cyclic | annular rib shown to Fig.6 (a).

  A protrusion 350 ′ shown in FIG. 6D is a protrusion extending in the circumferential direction of the annular rib 35. That is, when the central portion 1a of the manhole cover 1 is set to the inner side, the outer inclined surface 3511 ′ inclined downward from the outer side to the inner side and the inner inclined surface 3512 ′ inclined downward from the inner side to the outer side. A protrusion 350 ′ is formed. The corrosive solution that has reached the annular rib 35 can also be dripped down by the protrusion 350 '.

  In addition, you may provide the flow path extended in the circumferential direction of the manhole iron lid 1 in the outer side inclination area | region 401 shown to Fig.6 (a). In other words, a flow path connecting the radial rib 36 to the flow path 39 extending in the radial direction may be provided.

  Further, the inclination angle of the projecting tip surface of the radial rib 36 and the inclination angle of the outer inclined region 401 may be the same angle, or when the weight increase of the manhole iron cover 1 is not a problem, The inclination angle of the outer inclined area 401 may be increased, and when the weight increase of the manhole iron lid 1 becomes a problem, the inclination angle of the outer inclined area 401 may be decreased.

  FIG. 7 is an enlarged partial cross-sectional view showing the periphery of the rib 31 of the manhole cover according to the fifth embodiment.

  The manhole iron cover 1 of this embodiment differs in the material of the R part 32 from the manhole iron cover of 1st Embodiment. The R portion 32 of the manhole cover of the first embodiment is made of cast iron integrally formed with the rib 31. On the other hand, the R portion 32 of the manhole iron cover 1 of the fifth embodiment is made of a resin molded separately from the ribs 31. In this embodiment, the molten resin is injected into the cast manhole iron lid 1 and pressed against the base portion of the rib 31 at a high pressure to form the R portion 32. The resin constituting the R portion 32 is a polyamide resin. In this embodiment, since the entire R portion 32 is made of resin, even if a corrosive solution remains at the base portion of the R portion 32, the progress of rust is suppressed. In addition, as long as the resin has strong resistance to the corrosive solution, the resin constituting the R portion 32 may be a resin other than the polyamide resin. Moreover, you may shape | mold the R part 32 by methods other than injecting resin, such as a hand layup method.

  Next, a modification of the fifth embodiment will be described. In this modification, before the R portion 32 is molded, a material containing a resin component is electrodeposited, molten resin is injected onto the electrodeposition-coated film, and pressed at a high pressure to form the R portion 32. Is molded. Since the electrodeposition coating film formed of the material containing the resin component is in close contact with the casting surface and the R portion 32 is formed by pressing the electrodeposition coating film containing the resin material and the resin material having high adhesion, the lower surface 30 As a result, the R portion 32 having higher adhesion to the rib 31 is obtained.

  Even if the configuration requirements are included only in the description of each embodiment or modification described above, the configuration requirements may be applied to other embodiments or variations.

  In the description here, the manhole iron lid that pivots in a substantially horizontal direction around the fulcrum at the time of opening and closing has been described as an example, but the present invention is reversed so that the front and back are reversed around the fulcrum when opening and closing. It can also be applied to manhole iron lids. In addition, the underground structure is not limited to a manhole, and the present invention can be widely applied to a lid for an underground structure that closes an opening connected to an underground structure other than a mannhole, and the shape and size of the lid are not limited at all. Never happen. Furthermore, the lid for an underground structure is not limited to a cast iron but may be a metal.

(Appendix 1)
In a lid for a metal underground structure that has a lower surface that becomes an underground side and closes an opening that leads to the underground structure,
Having a protrusion protruding downward from the lower surface;
The protruding portion includes an R portion having a curved surface with a radius of 3 mm or more connected to the lower surface,
The lid for an underground structure, wherein the lower surface has an inclined region inclined downward toward the R portion.

(Appendix 2)
The lid for an underground structure according to supplementary note 1, wherein the R portion has a surface arithmetic average roughness (Ra) of greater than 0 and less than 3 μm.

(Appendix 3)
The lid for an underground structure according to appendix 1 or 2, wherein the R portion has a surface formed by a coating film.

(Appendix 4)
4. The lid for an underground structure according to any one of Supplementary notes 1 to 3, wherein the R portion has a surface formed of a resin.

(Appendix 5)
It has an upper surface that becomes the ground side,
The said R part is a lid | cover for underground structures as described in any one of the additional remarks 1-4 characterized by the surface being formed with the material whose hydrophobicity is higher than the said upper surface.

(Appendix 6)
The R portion includes an electrodeposition coating film containing a resin component in contact with a metal surface, and a coating film of a resin material in contact with the electrodeposition coating film to form a surface. To 5. The lid for an underground structure according to any one of 5 to 5.

DESCRIPTION OF SYMBOLS 1 Manhole iron cover 20 Upper surface 30 Lower surface 31 Rib 32, 38, 40 R part 35 Annular rib 36 Radial rib 37 Protrusion 39 Channel 5 Receptacle frame H Opening

Claims (3)

In the lid for an underground structure made of cast iron that has a lower surface that becomes the underground side and closes the opening that leads to the underground structure,
Having a protrusion protruding downward from the lower surface;
The protruding portion includes an R portion having a curved surface connected to the lower surface,
The said R part has the electrodeposition coating film containing the resin component which contacted the casting surface, and the resin body which contact | connected the electrodeposition coating film, The lid | cover for underground structures characterized by the above-mentioned.   The lid for an underground structure according to claim 1, wherein the curved surface has a radius equal to or less than a protruding height of the protruding portion.   The lid for an underground structure according to claim 1 or 2, wherein the R portion has a surface arithmetic average roughness (Ra) of more than 0 and less than 3 µm.