Cover for underground structures

Abstract

To provide a lid body receiving frame for an underground structure that is designed to prevent unexpected damage to an anticorrosive sheet in installation construction of a receiving body and allow easy inspection of maintenance management.SOLUTION: A receiving frame 3 which defines an opening H connected to an underground structure and in which the opening is closed by a lid body 2, has a metallic frame body 5 having an inner peripheral surface 511 sloped downward in the direction of an inner diameter getting small, and an anticorrosive sheet 7 provided on the inner peripheral surface 511 with the lid body 2 coming into face contact thereto in a lid-closed state. Color of the frame body 5 is black, and the color of a front face 72 of the anticorrosive sheet 7 is different from the color of the frame body 5.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a cover body receiving frame for an underground structure that defines an opening leading to an underground structure and blocks the opening by closing it with a cover body for an underground structure. [Background technology]

[0002] At the location where underground structures such as underground buried objects and underground facilities for sewage, water supply, electricity, gas, and communications, etc., are connected to the ground, a lid receiving frame set for an underground structure may be installed, which includes a lid receiving frame for an underground structure that defines an opening connected to the underground structure, and a lid for an underground structure that is supported by the lid receiving frame for an underground structure to close the opening. In this specification, the lid receiving frame for an underground structure may be abbreviated to the receiving frame, the lid for an underground structure may be abbreviated to the lid receiving frame set, and the lid receiving frame set for an underground structure may be abbreviated to the lid receiving frame set. In addition, the state in which the lid is supported by the receiving frame and the opening is closed (the state in which the lid is fitted into the receiving frame) may be referred to as a closed lid state.

[0003] In the above-mentioned underground structures, hydrogen sulfide and the like are generated, particularly in places where sewage stagnates, such as sewerage pipeline facilities, and the atmosphere is prone to becoming corrosive. The lid and the frame are generally made of metal such as cast iron, and the back surface of the lid and the exposed parts of the frame when the lid is closed are exposed to a severe environment of a corrosive atmosphere, so they are required to have corrosion resistance that can withstand this. For this reason, measures such as providing an anticorrosive coating by electrostatically painting epoxy resin-based powder paint or the like on the back surface of the lid and the exposed parts of the frame are sometimes taken.

[0004] In addition, it is difficult to uniformly apply an anticorrosive coating to the outer peripheral surface of the lid body and the inner peripheral surface of the receiving frame (the mating portion of the lid body and the receiving frame), which are in surface contact when the lid is closed. Even if an anticorrosive coating is applied, it will come off due to interference (contact) when the lid body is opened and closed, and rusting (corrosion) is likely to occur. For this reason, the present applicant has proposed a receiving frame in which an anticorrosive sheet made of synthetic rubber or the like is provided on the inner peripheral surface of the receiving frame (see, for example, Patent Document 1, etc.). According to the receiving frame described in Patent Document 1, it is difficult for a corrosive atmosphere to enter between the outer peripheral surface of the lid body or the inner peripheral surface of the receiving frame and the anticorrosive sheet, making it possible to prevent corrosion of the outer peripheral surface of the lid body and the inner peripheral surface of the receiving frame. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-159113 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when installing the receiving frame, if a worker does not notice the presence of the anticorrosive sheet made of rubber or the like and mistakenly assumes that the anticorrosive sheet is made of metal like the frame body, there is a risk that the anticorrosive sheet may be inadvertently damaged. In addition, during maintenance inspections, a means is also desired that can easily and clearly determine whether the anticorrosive sheet is in a state where it is not damaged or peeled off. In this way, a new problem has been found for preventing corrosion of the outer peripheral surface of the lid body and the inner peripheral surface of the receiving frame in a more stable manner over the long term.

[0007] In consideration of the above-mentioned circumstances, the present invention aims to provide a cover body receiving frame for underground structures that prevents inadvertent damage to the anti-corrosion sheet during frame installation work, etc., and that has been designed to facilitate inspection during maintenance and management. [Means for solving the problem]

[0008] The present invention provides a lid receiving frame for an underground structure that solves the above-mentioned object, In a frame for receiving a cover for an underground structure, the frame defines an opening leading to an underground structure, and the opening is blocked by being closed with a cover for an underground structure, a metal frame body having an inner peripheral surface that is inclined in a direction such that the inner diameter becomes narrower downward; On the inner circumferential surface Attached with adhesive and a corrosion prevention sheet with which the underground structure cover body comes into surface contact in a closed state, The frame body is black, The anticorrosive sheet is It is grey, The frame body and the front surface of the anticorrosive sheet have a brightness difference of 3.0 or more and less than 7.0 in the Munsell scale. It is characterized by:

[0009] Here, the anticorrosive sheet may be made of synthetic rubber or plastic. As synthetic rubber, NBR (nitrile rubber), CR (chloroprene rubber), and IIR (butyl rubber) are preferable, and as plastic, PP (polypropylene) and PVC (polyvinyl chloride) are preferable. In addition, the cover receiving frame for underground structures has a decades-long track record of being painted black so as not to spoil the scenery after installation, and the anticorrosive sheet as a whole is, gray Or, only the front side may be gray The frame body may be made of, for example, cast iron. The inclination angle of the inner peripheral surface is not particularly limited, and may be, for example, about 8° to 12°.

[0010] According to the cover receiving frame for an underground structure of the present invention, the corrosion prevention sheet is: Grey Since the anticorrosion sheet is made of a metal, it can be used to alert workers during installation work, etc. This can prevent mistakes such as accidentally damaging the anticorrosion sheet because the worker mistakenly believes it to be made of metal like the frame body. In addition, since the anticorrosion sheet is easy to distinguish from the frame body, defects such as damage or peeling of the anticorrosion sheet can be easily found during maintenance inspections.

[0012] In an embodiment in which the anticorrosive sheet is made of synthetic rubber such as NBR, if a pigment is added to give a predetermined color, the adhesive strength (bonding strength) of the anticorrosive sheet is reduced when the anticorrosive sheet is bonded to the frame body by, for example, a two-liquid mixed reactive adhesive. Therefore, if the anticorrosive sheet is gray, it can be formed by adding a white pigment to carbon black, and the amount of pigment used can be reduced. As a result, the adhesive strength of the anticorrosive sheet to the frame body can be prevented from decreasing. In addition, by making the brightness difference between the front surface of the frame body and the anticorrosive sheet 3.0 or more in the Munsell symbol, the anticorrosive sheet and the frame body can be clearly distinguished, and it is possible to fully ensure that workers are alerted during installation work and that inspections during maintenance and management are easy. Furthermore, if the brightness difference in Munsell symbols between the frame body and the front surface of the corrosion-prevention sheet exceeds 7.0, the distinguishability between the corrosion-prevention sheet and the frame body will be improved, but the amount of white pigment added to the corrosion-prevention sheet will increase accordingly, resulting in a decrease in adhesive strength, which is not preferable. In addition, in the cover receiving frame for an underground structure of the present invention, the frame body is made of cast iron and is painted black with an epoxy resin-based or acrylic resin-based paint, The anticorrosive sheet may be made of synthetic rubber and adhered to the inner peripheral surface by a two-part reactive adhesive.

[0013] Furthermore, in the underground structure cover receiving frame of the present invention, the anticorrosive sheet has a black upper end surface, The frame body and the upper end surface of the anticorrosive sheet may have a brightness difference of within 2.0 in Munsell symbols.

[0014] In the closed state, the upper end surface of the anticorrosive sheet is located between the frame body and the underground structure cover and is exposed above ground. Here, if the surface of the underground structure cover is also black like the frame body, if only the upper end surface of the anticorrosive sheet is a different color, it may cause an incongruity. In addition, the underground structure cover may have various designs or colors on its surface, but if the color of the upper end surface of the anticorrosive sheet is different from that of the frame body, there is a risk of losing the sense of unity in the design. Therefore, by adopting an embodiment in which the upper end surface of the anticorrosive sheet is black with a brightness difference of 2.0 or less in Munsell notation from that of the frame body, it is possible to reduce the sense of incongruity and the loss of the sense of unity in the design.

[0015] In addition, in the support frame for a lid for an underground structure of the present invention, the inner surface may be such that, when in a closed state, the corrosion prevention sheet is not provided in the portion facing the keyhole in the lid for the underground structure.

[0016] The part of the inner circumferential surface facing the keyhole in the underground structure cover is a part that does not come into contact with the outer circumferential surface of the underground structure cover (a part where the underground structure cover and the underground structure cover receiving frame do not fit together), and is less susceptible to corrosion even without the anticorrosive sheet. Furthermore, when the valve cover that closes the keyhole is rotated with an opening and closing tool or the like, the tip of the valve cover is likely to come into contact with the valve cover, and if the anticorrosive sheet is provided, it is likely to peel off due to contact with the tip of the valve cover. And peeling off of a part of the anticorrosive sheet may trigger peeling off of other parts of the anticorrosive sheet. Therefore, by adopting an embodiment in which the anticorrosive sheet is not provided on the part of the underground structure cover that faces the keyhole, peeling off due to contact with the tip of the valve cover, etc., can be prevented, and as a result, peeling off of other parts of the anticorrosive sheet can also be suppressed.

[0017] In addition, the portion of the inner surface that faces the pry hole in the cover for the underground structure when the cover is closed is also a portion that does not come into contact with the outer surface of the cover for the underground structure, and it is also possible to adopt an embodiment in which the corrosion prevention sheet is not provided. Effect of the Invention

[0018] According to the present invention, it is possible to provide a cover body receiving frame for underground structures which prevents inadvertent damage to the anti-corrosion sheet during frame installation work, etc., and which is designed to facilitate inspection during maintenance and management. [Brief description of the drawings]

[0019] [Figure 1] 1A is a cross-sectional view of a lid receiving frame set consisting of a receiving frame and a lid body, and FIG. 1B is a plan view of the lid receiving frame set shown in FIG. [Diagram 2] 1(a) is an enlarged view of part A surrounded by a dashed circle in Fig. 1(a), and Fig. 1(b) is a cross-sectional view taken along line CC in Fig. 1(b). [Diagram 3] 2A is a plan view of the receiving frame shown in FIG. 1, and FIG. 2B is an enlarged view of a portion D surrounded by a dashed-dotted circle in FIG. [Figure 4] FIG. 4 is a bottom view of the receiving frame shown in FIG. [Diagram 5] 3(a) is a front view (viewed from below) of the receiving frame shown in FIG. 3(a), and FIG. 3(b) is a rear view (viewed from above) of the receiving frame shown in FIG. 3(a). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] Fig. 1(a) is a cross-sectional view of a lid receiving frame set 10 consisting of a receiving frame 3 and a lid body 2, and Fig. 1(b) is a plan view of the lid receiving frame set 10 shown in Fig. 1(a). The cross-sectional view shown in Fig. 1(a) is a cross-sectional view taken along line BB in Fig. 1(b). Fig. 1(a) shows the ground G, but Fig. 1(b) omits the ground G.

[0022] FIG. 1 shows a cover frame set (cover frame set for underground structure) 10 including a cover (cover for underground structure) 2 according to one embodiment of the present invention and a frame (cover frame for underground structure) 3 supporting the cover 2. A sewerage drainage 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 sewerage drainage pipe. Both the sewerage drainage pipe and the manhole correspond to underground structures. The manhole is formed as a vertical hole leading from the sewerage drainage pipe to the ground surface by a framework in which prefabricated concrete molded products are piled up. The framework 3 is provided on the framework, and defines an opening H leading to the manhole, which is an underground structure. The inside of this underground structure is in a corrosive atmosphere due to the generated hydrogen sulfide and the like.

[0023] The cover 2 is circular in plan view and freely closes an opening H that leads to a manhole, which is an underground structure, and the cover 2 shown in Fig. 1 closes the opening H. The cover 2 shown in Fig. 1 is made of cast iron formed by casting, for example, made of FCD700. The cover 2 may be made of iron other than cast iron, or may be made of metal other than iron.

[0024] FIG. 2(a) is an enlarged view of part A enclosed by a dashed circle in FIG. 1(a).

[0025] 1 and 2(a), the lid body 2 includes a disk-shaped top plate portion 21, an annular wall portion 22 provided on the outer periphery of the top plate portion 21 and surrounding the top plate portion 21, and a lid rib 23 protruding downward from the back surface of the top plate portion 21. An anticorrosive coating is formed by electrochemical coating on the back surface of the top plate portion 21 and the lid rib 23. On the outer periphery of the annular wall portion 22, an outer periphery surface 221 is formed that is inclined in a direction in which the outer diameter narrows downward.

[0026] As shown in FIG. 1 and FIG. 2(a), the receiving frame 3 includes a frame body 5 and an anticorrosive sheet 7. The frame body 5 is made of cast iron, for example, made of FCD700, and is painted black (for example, with a Munsell value of 1.5 (N1.5)) with an epoxy resin-based or acrylic resin-based paint. The frame body 5 includes a cylindrical body 51 formed in a ring shape in a plan view, a flange portion 52 protruding outward from the lower end portion of the cylindrical body 51, and a frame rib 53 provided on the upper surface of the flange portion 52. The inner peripheral portion of the cylindrical body 51 is provided with a stop portion 512 protruding in a ring shape toward the inside of the receiving frame 3. When the lid body 2 slides down due to long-term use, the lower end of the annular wall portion 22 of the lid body 2 abuts against the stop portion 512, preventing further sliding.

[0027] 2(a), an inner peripheral surface 511 is formed above a stop portion 512 in the inner peripheral portion of the cylindrical body 51, the inner peripheral surface 511 being inclined in a direction in which the inner diameter narrows downward, and an anticorrosion sheet 7 is provided on the surface of the inner peripheral surface 511. The inclination angle of the inner peripheral surface 511 is set to be substantially the same as the inclination angle of the outer peripheral surface 221 of the lid body 2 (for example, 8° to 9°).

[0028] In Fig. 2(a), the anticorrosive sheet 7 provided on the frame body 5 is shown enlarged and surrounded by a dashed-dotted circle. In this embodiment, the anticorrosive sheet 7 is made of synthetic rubber NBR, and is adjusted to gray (for example, a value of 6.5 (N6.5) in the Munsell scale) by adding carbon black and white pigment. The thickness of the anticorrosive sheet 7 is set in the range of 0.5 to 5.0 mm from the viewpoint of a thickness that is not cut or cracked by interference between the lid body 2 and the receiving frame 3 during the opening and closing operation of the lid body 2, and is not scratched to expose the cast iron base of the lid body 2 and the receiving frame 3.

[0029] The anticorrosion sheet 7 has its back surface 71 adhered to the inner peripheral surface 511 of the frame body 5 by an adhesive, with its lower end surface 74 supported by the stopper portion 512 of the frame body 5. The anticorrosion sheet 7 is not limited to being made of NBR, and may be made of other synthetic rubber such as CR or IIR, or may be made of plastic such as PP or PVC. Furthermore, it may be a combination of these materials.

[0030] 2(a), in the closed state, the outer peripheral surface 221 of the lid body 2 and the anticorrosive sheet 7 provided on the inner peripheral surface 511 of the frame body 5 are in surface contact with each other, and the lid body 2 is supported by the receiving frame 3. This makes it difficult for a corrosive atmosphere to get between the anticorrosive sheet 7 and the outer peripheral surface 221 of the lid body 2, thereby preventing corrosion of the outer peripheral surface 221 of the lid body 2. In addition, the inner peripheral surface 511 of the frame body 5 is prevented from corrosion by the anticorrosive sheet 7 provided on the surface.

[0031] In addition, the frame body 5 is black, and in this embodiment, the front surface 72 of the anticorrosive sheet 7 is gray. This makes it possible to call the attention of workers during installation work, etc. This makes it possible to prevent mistakes such as accidentally damaging the anticorrosive sheet 7 by mistaking it for something made of metal like the frame body 5. In addition, since the anticorrosive sheet 7 is easy to distinguish from the frame body 5, defects such as damage and peeling that occur in the anticorrosive sheet 7 can be easily found during maintenance inspections. As a result, corrosion of the outer peripheral surface of the lid body 2 and the inner peripheral surface of the receiving frame 3 can be prevented more stably over a long period of time.

[0032] In particular, in this embodiment, the anticorrosive sheet 7 is gray, and can be formed by adding white pigment to carbon black as described above, thereby reducing the amount of pigment used. As a result, the adhesive strength of the anticorrosive sheet 7 to the frame body 5 can be prevented from decreasing.

[0033] Furthermore, in this embodiment, the brightness difference in the Munsell symbols between the frame body 5 and the anticorrosive sheet 7 is 3.0 or more (specifically, the frame body 5 is N1.5 and the anticorrosive sheet is N6.5, so the brightness difference is 5.0), so that the anticorrosive sheet 7 can be clearly distinguished from the frame body 5. Note that if the brightness difference in the Munsell symbols between the frame body 5 and the anticorrosive sheet 7 exceeds 7.0, the amount of white pigment added to the anticorrosive sheet 7 will increase, which is undesirable as it will reduce the adhesive strength.

[0034] 2(a), in the closed state, the upper end surface 73 of the corrosion prevention sheet 7 is located between the frame body 5 and the lid 2 and is exposed above ground. For this reason, it is preferable to color the upper end surface 73 of the corrosion prevention sheet 7 black, for example by painting, with a Munsell brightness difference of 2.0 or less from that of the frame body 5. This makes it less likely that a sense of incongruity will arise due to the difference in color between the frame body 5 and the upper end surface 73 of the corrosion prevention sheet 7.

[0035] The anticorrosion sheet 7 may be provided around the entire inner circumferential surface 511 of the frame body 5, but in this embodiment, the anticorrosion sheet 7 is not provided on the peripheral portion of the top plate portion 21, which faces the keyhole 211 formed on the upper side in Fig. 1(b). This keyhole 211 is a notched hole for inserting an opening / closing tool, and the portion of the receiving frame 3 facing the keyhole 211 is not in contact with the lid body 2. This point will be described in detail below.

[0036] FIG. 3(a) is a plan view of the frame 3 shown in FIG. 1, and FIG. 3(b) is an enlarged view of the D portion surrounded by a dashed line circle in FIG. 3(a). FIG. 4 is a bottom view of the frame 3 shown in FIG. 3(a). FIG. 5(a) is a front view (viewed from below) of the frame 3 shown in FIG. 3(a), and FIG. 5(b) is a rear view (viewed from above) of the frame 3 shown in FIG. 3(a). The right side view (viewed from the right side) of the frame 3 shown in FIG. 3(a) and the left side view (viewed from the left side) of the frame 3 shown in FIG. 3(a) are omitted because they are the same as those in FIG. 5(a). FIG. 5(c) is a cross-sectional view of the frame 3 shown in FIG. 3(a) along the line EE. In FIG. 3(b) and FIG. 5(c), the anticorrosive sheet 7 is shaded to distinguish it from the frame body 5.

[0037] 3(b) and 5(c), the anticorrosive sheet 7 is not provided in a keyhole facing region 511a facing the keyhole 211 (see FIG. 1(b)) in the frame body 5. The widthwise length S of the keyhole facing region 511a (the distance between both side end faces 75, 75 of the anticorrosive sheet 7) is set to be approximately the same as the widthwise length of the keyhole 211.

[0038] Fig. 2(b) is a cross-sectional view taken along line CC in Fig. 1(b), which shows a side end surface 75 on one side (the right side in Figs. 3(b) and 5(c)) of the anticorrosive sheet 7.

[0039] 2(b), a locking member 9 is provided on the back side of the keyhole 211. The locking member 9 has a pair of shafts 92, 92 supported on the back side of the lid 2, a valve cover 91 that closes the keyhole 211, a locking claw 93 provided below the valve cover 91, a weight 94, and a spring 95 as a biasing means. In addition, a claw receiving piece 514 that protrudes obliquely downward is provided in a position below the inner circumferential surface 511 in a portion of the frame main body 5 corresponding to the locking member 9, and a space R is formed below the claw receiving piece 514.

[0040] The locking member 9 is rotatable about a pair of shafts 92, 92 between a closed state in which the valve cover 91 closes the keyhole 211 and an open state in which the valve cover 91 opens the keyhole 211. The locking member 9 is given a force toward the closed state by the weight 94 and is biased toward the closed state by the spring 95, and the locking claw 93 is inserted into the space R. Therefore, when the lid body 2 floats up, the locking claw 93 engages with the claw receiving piece 514, preventing the opening from being opened.

[0041] In order to open the lid 2, the valve lid 91 is pushed down with an opening / closing tool (not shown) and the locking member 9 is rotated counterclockwise, whereby the keyhole 211 is opened and the locking claw 93 retracts from below the claw receiving piece 514 and moves out of the space R. This allows the lid 2 to be opened. In Fig. 2(b), in order to simplify the drawing, only the valve lid 91 is shown with a dashed line with respect to the rotated locking member 9.

[0042] When the locking member 9 rotates, the tip of the valve cover 91 approaches the frame body 5, and if an anticorrosive sheet 7 is provided in the keyhole-facing region 511a of the inner circumferential surface 511, the tip of the valve cover 91 will come into contact with it and will likely peel off. Peeling off a portion of the anticorrosive sheet 7 may trigger peeling off of other portions of the anticorrosive sheet 7.

[0043] In this embodiment, the anti-corrosion sheet 7 is not provided in the keyhole-facing region 511a of the inner surface 511, so it will not peel off due to contact with the tip of the valve lid 91, and as a result, peeling off of the entire anti-corrosion sheet 7 can be prevented.

[0044] In FIG. 1(b), the cover 2 is likened to a clock face, and pry holes 212 are provided near the 4 o'clock and 8 o'clock positions. The pry holes 212 are holes for inserting a rod-shaped opening / closing tool (not shown) to pry the cover 2 when the cover 2 is not opened for a long time and the cover 2 and the receiving frame 3 are tightly fitted together due to rust or repeated loads such as the passing of vehicles, making it difficult to open the cover 2. Since the pry holes 212, 212 are also formed in a notch shape like the keyhole 211, the portion of the receiving frame 3 facing the pry hole 212 is not in contact with the cover 2. For this reason, the portion of the inner circumferential surface 511 facing the pry hole 212 may also be provided with no anticorrosive sheet 7.

[0045] Next, an example of a process for attaching the anticorrosive sheet 7 to the frame body 5 will be described.

[0046] For example, anticorrosion sheet 7 is prepared by using synthetic rubber NBR as the material and adding carbon black and white pigment to give it a gray color (for example, N6.5). The height dimension of anticorrosion sheet 7 is the same as the height dimension of inner circumferential surface 511 of frame body 5, and the total length of anticorrosion sheet 7 is formed to be approximately the same as or slightly longer than the total perimeter length of inner circumferential surface 511 of frame body 5. If necessary, upper end surface 73 of anticorrosion sheet 7 is painted black.

[0047] Next, with the inner circumferential surface 511 of the frame body 5 except for the keyhole facing region 511a and the front surface 72 covered with masking tape, a two-part reactive adhesive, for example, is applied to the back surface 71 of the anticorrosive sheet 7. The thickness of the anticorrosive sheet 7 and the adhesive are adjusted taking into consideration functionality, workability, etc., and the thickness of the anticorrosive sheet 7 may be about 1.5 mm, for example.

[0048] Then, after the anticorrosion sheet 7 is overlapped on the inner peripheral surface 511 of the frame body 5 using the stopper portion 512 of the frame body 5 as a support, the portion of the anticorrosion sheet 7 that overlaps the keyhole facing region 511a is cut. Here, in a mode in which the anticorrosion sheet 7 is provided around the entire inner peripheral surface 511 of the frame body 5, the anticorrosion sheet 7 must be cut at the overlapping portions, which may make the work difficult. In contrast, in a mode in which the anticorrosion sheet 7 is not provided in the keyhole facing region 511a as in this embodiment, the work of cutting the anticorrosion sheet 7 becomes easier.

[0049] Next, the frame body 5 and the anticorrosive sheet 7 are clamped with clips or the like and left to cure until adhesion is complete. Here, instead of using clips or the like, the lid body 2 may be set in a closed state to cure. In other words, the lid body 2 may be used as a jig for curing.

[0050] Once the preparation is complete, the masking tape is removed and the attachment of the anti-corrosion sheet 7 to the frame body 5 is complete.

[0051] According to the receiving frame 3 described above, it is possible to provide a receiving frame for a lid body for underground structures which prevents inadvertent damage to the anti-corrosion sheet during receiving frame installation work, etc., and which is designed to facilitate inspection for maintenance and management.

[0052] The present invention is not limited to the above-mentioned embodiment, and various modifications can be made within the scope of the claims. For example, in the above-mentioned embodiment, a gray anticorrosive sheet 7 is used as an example, but a non-gray anticorrosive sheet 7 may be used as long as it is a color that can be sufficiently distinguished from the frame body 5. In addition, although an embodiment in which the entire anticorrosive sheet 7 is gray has been described, a black anticorrosive sheet 7 in which only the front surface 72 is painted gray may be used. If this embodiment is adopted, the gray paint may peel off due to interference (contact) caused by the opening and closing operation of the lid body, but since it can be configured without adding pigment, a decrease in adhesive strength due to the addition of pigment is prevented, and the black paint of the upper end surface 73 is also unnecessary. [Explanation of symbols]

[0053] 10 Lid holder frame set 2 Lid 21 Top plate 211 Keyhole 22 Annular wall 221 Outer surface 3. Receiving slots 5 Frame body 511 Inner surface 511a Keyhole facing area 512 Stop part 7. Anti-corrosion sheet 73 Upper end surface 75 Side end face 9 Locking member 91 Opercula H opening

Claims

1. In a frame for receiving a cover for an underground structure, the frame defines an opening leading to an underground structure, and the opening is blocked by being closed with a cover for an underground structure, a metal frame body having an inner peripheral surface that is inclined in a direction such that the inner diameter becomes narrower downward; and a corrosion prevention sheet that is adhered to the inner peripheral surface by an adhesive and that comes into surface contact with the underground structure cover in a closed state. The frame body is black, The anticorrosive sheet is gray in color, A lid receiving frame for underground structures, characterized in that the frame body and the front surface of the corrosion prevention sheet have a brightness difference in Munsell symbols of 3.0 or more and less than 7.

0.

2. The frame body is made of cast iron and painted black with an epoxy resin or acrylic resin paint, 2. The lid receiving frame for underground structures according to claim 1, wherein the anticorrosive sheet is made of synthetic rubber and is adhered to the inner peripheral surface by a two-part reactive adhesive.

3. The anticorrosive sheet has a black upper end surface, 3. The lid receiving frame for underground structures according to claim 1 or 2, characterized in that the difference in brightness between the frame body and the upper end surface of the corrosion protection sheet is within 2.0 in Munsell symbols.

4. A support frame for a lid for an underground structure as described in any one of claims 1 to 3, characterized in that when the lid is closed, the inner surface does not have the corrosion protection sheet provided in the portion facing the keyhole in the lid for the underground structure.

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