JP5525872B2 - Cover for underground structure - Google Patents

Description

  The present invention relates to an underground structure in which a concavo-convex structure is formed on the surface of the lid body in order to increase frictional resistance between the ground contact portion of the tire or the bottom of shoes passing through the surface of the lid body and prevent slipping. It relates to a lid for use.

  Many of the lids for underground structures known as so-called manhole covers are made of cast iron, but the coefficient of friction decreases when wet by rain, etc., compared to the surrounding asphalt pavement surface and concrete pavement surface. It becomes a slippery state and tends to cause a fall accident such as a two-wheeled vehicle. Therefore, many independent small protrusions made of a geometric pattern are formed on the surface of the iron lid to secure a friction coefficient substantially equal to that of a paved surface such as asphalt, thereby preventing slipping. The inventions to this effect include Patent Nos. 3094008, 3356694, 2878663, 2799687, 3564005, etc., each of which has its own improvement in the shape, structure and arrangement of independent small protrusions. It is trying to secure a coefficient of friction that is almost the same as that of paved surfaces such as asphalt.

  The iron lid with the above-mentioned independent small protrusions has almost achieved its intended purpose in terms of preventing slipping, and there is no problem, but since it consists only of geometric patterns, the surface pattern is visually monotonous. There is an opinion that it is not interesting. Around the time of securing the coefficient of friction against the iron lid surface, what is commonly called a design iron lid with a design on the surface of the iron lid has become widespread. There exists patent 4167619 in invention of this meaning. Most of the design iron lids are designed with motifs of flowers, plants, animals, festivals, landscapes, etc. that represent the city, mainly to publicize the existence of iron lids to citizens. However, the design iron cover generally has a high anti-slip effect because the design is generally prioritized. For example, Japanese Patent Application Laid-Open No. 2006-16895 and Japanese Patent No. 3343102 belong to the design iron lid, but these inventions show that the improvement of the anti-slip in the design iron lid is still performed.

  In this way, when design is prioritized, the anti-slip effect declines, and if the anti-slip effect is pursued, the situation is still monotonous. Therefore, in the situation where the anti-slip effect is prioritized, visual In fact, there is no choice but to adopt a non-slip material consisting of a monotonous geometric pattern. In other words, the design iron lid cannot be used in a place where the anti-slip effect is prioritized. Against this backdrop, the inventor of the present case has intensively studied to achieve both slip prevention and aesthetic problems, and as a result has reached the present invention.

Japanese Patent No. 3094008 Japanese Patent No. 3356694 Japanese Patent No. 4167619 JP 2006-16895 Japanese Patent No. 2878663 Japanese Patent No. 2796087 Japanese Patent No. 3564005 Japanese Patent No. 3343102

  The present invention has been made paying attention to the above points, and its problem is to provide a lid for an underground structure having a necessary and sufficient anti-slip effect and a visually appealing aesthetic. is there. Another object of the present invention is to clarify an arrangement method of design protrusions that does not substantially impair the anti-slip effect even if the design protrusions are provided on the surface of the lid body.

In order to solve the above problem, the present invention increases the frictional resistance between the ground contact portion of the tire passing through the surface of the lid body or the bottom of the shoes, and prevents the slip structure from forming the concavo-convex structure. As for the lid for underground structures formed on the surface of the surface, a pattern consisting of a non-geometric pattern that forms a number of independent small protrusions consisting of geometric patterns on the surface of the lid body as a concavo-convex structure and causes aesthetics through vision One or two or more design protrusions having the above-mentioned independent small protrusions of the lid main body are arranged, and the design protrusions are approximately the length of the contact surface shape of the small-diameter tire. the 125 mm × width of about 55mm and a reference, together with one portion of the diameter or diagonal length L1 of about 50 to 100 mm, the diameter or diagonal length of the design projections L1, the shortest among the plurality of design projections When the separation is L2, and the length of the ground contact portion of the small-diameter tire passing through the surface of the lid body is L3, the diameter of the design protrusion or the length of the diagonal line is shorter than the length of the tire contact portion (L1 <L3). In addition, the shortest distance between the design protrusions is a means that the relationship is greater than half the length of the tire ground contact portion (L2> 0.5L3) .

  The lid for underground structures of the present invention belongs to a so-called manhole iron lid made of cast iron such as ductile cast iron. As an uneven structure for preventing slip, in the present invention, a large number of independent small protrusions are formed on the surface of the lid body, and a design protrusion having a design that causes aesthetic appearance through vision is formed by a group of the independent small protrusions of the lid body. One or more are arranged inside. The independent small protrusion has, for example, a truncated pyramid shape having a convex polygonal planar shape as a basic shape having a large lower portion and a small upper portion like the protrusion described in Patent Document 1 or 2, Those having a concave or convex part extending from the lower part to the upper part of the inclined side surface of each protrusion are suitable, and such independent small protrusions maintain the similar shape of the planar shape of the protruding surface due to wear, Or it has the feature that it enlarges gradually while changing, and can obtain the frictional resistance equivalent to a paved road surface.

  The said design projection part shall set the diameter L of one piece or the length L1 of a diagonal to about 50-100 mm. The reason why the diameter or diagonal length L1 is about 50 to 100 mm is that the traditional emblems of municipalities etc. are about 50 mm in diameter, but this is not conspicuous, and about 50 mm is judged to be the smallest This is the lower limit. In addition, the upper limit is determined on the basis of the length of the contact surface shape of the small-diameter tire of the moped bicycle, which is about 125 mm long and about 55 mm wide, which has been found to cause a slip accident as a result of research. In the course of the research leading to the present invention, the contact portions of various tires and the like were examined. The contact surface shape of the small-diameter tire is an average value, and a numerical value of about 125 mm in length × about 55 mm in width is obtained. Even when the tire is in the range of the design protrusion, a part of the tire needs to be applied to the independent small protrusion, and the length of the independent small protrusion is at least 20% (based on the above value of about 125 mm). 25 mm) is determined to be necessary for preventing slipping, and therefore the subtraction of about 100 mm is the maximum value of the design protrusion.

  Study that the numerical value of about 50 to 100 mm related to the diameter of one design protrusion or the length L1 of the diagonal line is optimal for providing a design effect by providing a plurality of design protrusions of about 80 to 100 mm. It overlaps with the result. Therefore, if the diameter or diagonal length L1 is a planar design projection having a size of 50 to 100 mm, the slip prevention effect of the independent small projection is not impaired, and the size is aesthetically pleasing through vision. It can be judged that it can be secured. To supplement the explanation about the point that slip accidents are likely to occur, the number of mopeds using this type of tire is large, the user's age group and driving skills vary widely, and it is used regardless of the weather such as commuting to work or school. It is presumed that the accident rate will increase due to the large number of opportunities to do so.

  The method of arranging the design protrusions in the present invention can be determined on the basis of a small-diameter tire of a moped bicycle as described above, and can be described more generally as follows. That is, when the length of the ground contact portion of the passing tire is L3, the diameter of the design protrusion or the length of the diagonal line is L1, and the shortest distance between the plurality of design protrusions is L2, the diameter of the design protrusion or the diagonal line The length is shorter than the length of the tire ground contact portion (L1 <L3), and the shortest distance between the design protrusions is greater than half the length of the tire ground contact portion (L2> 0.5L3). It is desirable that By making the diameter of the design protrusion or the length of the diagonal line shorter than the length of the tire ground contact part (L1 <L3), the minimum necessary frictional resistance is ensured by the independent small protrusion even when the tire rides on the design protrusion. By making the shortest distance between the design projections larger than one half of the length of the tire contact portion (L2> 0.5L3), the length L3 of the tire contact portion is between the adjacent design projections. There will be a non-slip part by an independent small protrusion of 1/2 or more. Since the condition involving the design protrusion is minimal, the slip prevention effect by the independent small protrusion is not substantially impaired. More specifically, when the length L3 of the ground contact portion of the tire is 125 mm, it is desirable that the shortest distance L2 between the plurality of design protrusions is about one half of 63 mm or more.

  The above arrangement method can be applied without problem to a circular underground structure lid of φ600. However, there is also a φ900 circular lid, which is commonly called a parent-child lid, as a lid for an underground structure. In that case, a small lid is arranged at an eccentric position of the parent lid, and a space for providing sufficient design protrusions May not be secured on the lid (see FIG. 8). Even in such a case, it is natural that it is necessary to prevent slipping. Therefore, in the present invention, when the shortest distance between the design projection and the peripheral edge of the lid body is L4, the design projection and the lid body. By making the shortest distance L4 with the peripheral edge of the tire larger than one quarter of the length L3 of the tire ground contact portion (L4> 0.25L3), the minimum slip prevention is obtained. Since it has been found that the length of a part of the tire that needs to be applied to the independent small protrusion for preventing slipping is about 20% of the contact surface shape length of the small-diameter tire as described above, about 25 mm. As a specific numerical value of the space to be secured between the design protrusion and the peripheral edge of the lid body, a space of at least about 25 mm, preferably about 30 mm or more should be provided.

  In the case where the design protrusion as described above is surrounded by a protruding edging, it is desirable to form a drainage groove through the protruding edging through the inside and outside of the edging portion. It does not mean that all design protrusions must be surrounded by a border, but in the case of design protrusions that have a design surrounded by a border, the drainage is a problem, so the drainage groove should be This means that it is necessary to provide the border portion. Even when the design protrusion has a rim of the ridge, the rim of the ridge is not always closed like a circular ring, and it is also free to provide a drain groove on such an rim. .

  Also, when considering the depth (or height) of the independent small protrusion and the design protrusion, the depth of the independent small protrusion from the surface to the space between the independent small protrusion where the root is located is about 6mm, the surface of the design protrusion is flush with the surface of the independent small protrusion, and the depth from the surface of the design protrusion to the root is about 3mm or more and less than the depth of the independent small protrusion. Can be set to The numerical value of about 6 mm is based on the standard depth and height of the uneven structure for preventing slippage provided on the surface of the so-called manhole iron lid, where the independent small protrusion has a height of about 6 mm. It is a judgment that it is necessary. The design protrusion has a depth (height) of about one-half or more that of the independent small protrusion. The reason for this depends on the service life (wear) and design of the design protrusion described below.

  In other words, the service life of the manhole cover installed in the roadway is 15 years or more according to the notification of the Ministry of Land, Infrastructure, Transport and Tourism (Kokusai Shiga No. 77, June 19, 2003). In addition, the surface wear rate of manhole iron lids is described as 0.1 mm to 0.3 mm / year in the “Maintenance manual for manhole lids for sewerage (draft)” published by Japan Sewerage Association, If calculated at 0.2 mm / year, it will wear 3 mm in 15 years. Therefore, a pattern depth (height) of 3 mm or more is required to achieve the service life determined by the Ministry of Land, Infrastructure, Transport and Tourism. Of course, it may be the same as the depth of about 6 mm to the surface of the space between the independent small protrusions where the roots of the independent small protrusions are located. However, in the sand casting method, which is the mainstream of the manufacturing method currently in progress, hot water in which cast iron is melted is poured into a sand mold to manufacture a manhole iron lid. The sand mold is pressed into the sand by pressing the wooden pattern carved into the sand, and then transferred to the sand. There is a draft of about 20 degrees in the (height) direction. When a pattern with a draft of 20 degrees and a depth (height) of 6 mm is carved, a draft of 6 x tan 20 ° = 2.1 mm is required, and the distance between the pattern on the iron lid surface and the pattern is 2.1 mm x two gradients = 4.2 mm or more is necessary. Therefore, even when trying to design a fine pattern, the design is limited because the distance between the patterns is too far away. Therefore, by setting the pattern depth (height) of only the design protrusions to 3 mm, the pitch between the patterns is reduced to 3 × tan 20 ° × 2 locations = 1.1 × 2 = 2.2 mm, which is fine. Design is possible.

In the present invention, non-slip related to small-diameter tires that are considered to have more opportunities to pass over manhole iron covers are mainly described, but here it is another important object to the bottom of shoes A comparative study is as follows. First, the ground contact part of the small-diameter tire is about 125 mm long x about 55 mm wide, while the bottom of the shoes is for adults with a length of 250-
Assuming 300 mm and a width of 60 to 100 mm, the average is 275 × 80 mm. The weight of the motorbike is the sum of the body weight and the driver's weight, which is almost twice the weight of the person. However, only one of the front and rear wheels is mounted on the manhole cover. Because there is no, half of the total weight hangs on the iron lid. On the other hand, since a person walks while touching one leg at a time, the entire weight hangs on the iron lid. Be as in the following table and performing the calculations taking into account the above, the pressure per unit area is 1.09 kg / cm ² in diameter tires, it is 0.32 kg / cm ² in the sole. The bottom of shoes is about one-third that of small-diameter tires, but for small-diameter tires, you can think that the entire grounding part is always in contact with the ground, whereas the bottom of shoes is intentionally on one foot. There is no grounding on the entire surface except when standing, and the friction force is generated by the protrusion of the manhole iron cover biting into the grounding part of the shoe sole, so there is no difference as seen in the difference in surface pressure, If anti-slip for small-diameter tires is effective, it is considered effective as anti-slip for shoes.

  Since the present invention is configured and operates as described above, the underground structure having a necessary and sufficient anti-slip effect by a large number of independent small protrusions and a visually appealing aesthetic by the design protrusions. An object lid can be provided. Further, according to the present invention, when the design protrusion is provided on the surface of the lid body, the design protrusion placement method that does not substantially impair the anti-slip effect has been clarified. Even in cases where the problem is balanced and the anti-slip effect is prioritized, the design iron lid can be used.

  Hereinafter, the present invention will be described in more detail with reference to the illustrated embodiments. FIG. 1 shows an example 1 of an underground structure lid 10 according to the present invention, and the underground structure lid 10 in Example 1 is a circular lid of φ600 made of ductile cast iron. An uneven structure 14 is formed on the entire surface of the lid main body 11 except for the peripheral edge portion 13 of the lid body in order to increase frictional resistance with the grounding portion 12 of the passing tire and prevent slippage. (See FIGS. 2 and 3).

  The concavo-convex structure 14 is composed of a number of independent small protrusions 15 formed on the surface of the lid body 11 and a design protrusion 16 having a design that causes an aesthetic appearance through vision. The independent small protrusion 15 has a pyramidal truncated pyramid shape with a lower portion and a smaller upper portion, and a convex polygonal planar shape as a basic shape. If it becomes, it has a ditch | groove in the side surface which each protrusion inclined so that a different pattern from the beginning may appear on an upper surface. This is because the protrusions in the invention disclosed in Japanese Patent No. 3356694 of Patent Document 2 are applied to the independent small protrusions 15 in the present invention, and wear of small triangular or square portions appearing in FIG. As it grows, irregularities due to concave portions (concave grooves) and convex portions (protrusions) provided on the side surface appear, so that the original shapes of triangles and quadrangles change.

  In the example of FIG. 1, the design protrusion 16 has a pattern in which a motif that causes aesthetics to be visually observed is a so-called flower bird style moon, and a circular protrusion 17 having a diameter L1 of about 100 mm is included in the pattern. Is enclosed. The protruding rim 17 is formed with a drainage groove 18 through which the water passes through the rim so that the water is not blocked by the rim. Four such design protrusions 16 are arranged in the group of the independent small protrusions of the lid body 11, and each is arranged on the same circumference at equal intervals. As shown in FIGS. 1 to 3, the diameter of the design protrusion 16 is L1, the shortest distance between the plurality of design protrusions is L2, and the diameter of the design protrusion 16 is based on the length L3 of the tire ground contact portion 12. Are short (L1 <L3), and the shortest distance L2 between the design protrusions is larger than one half of the length of the tire ground contact portion (L2> 0.5L3). The distance L4 between the design protrusion 16 and the outer peripheral protruding edge 13 conforms to the condition of L4> 0.25L3, and the distance necessary for preventing slip is also maintained in this portion. In addition, w has shown the width | variety of the tire grounding part 12, and is smaller than the diameter L1 of the design projection part 16 (w <L1).

  The independent small protrusion 15 has a depth (height) D1 from the surface to the space between the independent small protrusions of about 6 mm, the surface of the design protrusion 16 is flush with the surface of the independent small protrusion 15, and The depth (height) D2 from the surface of the design protrusion to the base is set to about 3 mm (see FIG. 2). The numerical value of about 6 mm is due to the standard depth (height) of the uneven structure for preventing slippage provided on the surface of the so-called manhole iron lid being 6 mm. It is set to about 3mm from the years. However, if there is a need for a relationship with the design, etc., it can be selected in the range up to about 6 mm which is the same as the depth (height) D1 of the independent small protrusion 15.

  The configuration of Example 1 applies similarly to the examples shown in FIG. In Example 2 shown in FIG. 4, one design protrusion 26 having a diameter of φ100 is provided at the center of the circular lid body 21 having the same φ600 as in Example 1, and the diameter of the design protrusion 26 is as follows. L1, the shortest distance L2 between the plurality of design projections does not exist, but the necessary condition is satisfied, and the diameter L1 of the design projection 26 is shorter than the length L3 of the tire contact portion 12 (L1 <L3) Therefore, a sufficient slip prevention effect by the independent small protrusion 15 is obtained. Since the other configuration is the same as that of Example 1, reference numerals are used and detailed description thereof is omitted.

  In Example 3 shown in FIG. 5, three design protrusions 36 having a diameter of φ100 are arranged in a row in the center of the circular lid body 31 having the same φ600 as in Example 1, and the design protrusion 36 The diameter L1 is L1, the shortest distance between the plurality of design protrusions is L2, the diameter L1 of the design protrusion 36 is shorter than the length L3 of the tire ground contact portion 12 (L1 <L3), and the design protrusion The shortest distance L2 between the two is greater than half the length of the tire ground contact portion (L2> 0.5L3). The concavo-convex structure 34 of Example 3 includes a large number of independent small protrusions 15 and three design protrusions 36. In addition, about the structure similar to Example 1, a code | symbol is used and detailed description is abbreviate | omitted.

In Example 4 shown in FIG. 6, four regular hexagonal design protrusions 46 having a diagonal length corresponding to φ100 are equally provided at the center of the circular lid body 41 having the same φ600 as in Example 1, respectively. The design protrusions 46 have a diameter L1, the shortest distance between the plurality of design protrusions L2, and the design protrusions 46 have a diameter L1 from the length L3 of the tire ground contact part 12. Are short (L1 <L3), and the shortest distance L2 between the design protrusions is larger than one half of the length of the tire ground contact portion (L2> 0.5L3). The concavo-convex structure 44 of Example 4 includes a large number of independent small protrusions 15 and four design protrusions 46.
In addition, about the structure similar to Example 1, a code | symbol is used and detailed description is abbreviate | omitted.

  In Example 5 shown in FIG. 7, four square design protrusions 56 having a diagonal length corresponding to φ100 are equally spaced from each other at the center of the circular lid body 51 having the same φ600 as in Example 1. The design projection 56 has a diameter L1, the shortest distance between the plurality of design projections L2, and the design projection 56 has a diameter L1 greater than the length L3 of the tire ground contact portion 12. It is short (L1 <L3), and the shortest distance L2 between the design protrusions is greater than one half of the length of the tire ground contact portion (L2> 0.5L3). The concavo-convex structure 54 of Example 5 includes a large number of independent small protrusions 15 and four design protrusions 56. In addition, about the structure similar to Example 1, a code | symbol is used and detailed description is abbreviate | omitted.

  Example 6 shown in FIG. 8 is an example of a so-called parent-child lid having a circular and small lid body 62 of φ600 at a portion shifted from the center of a large circular lid body 61 of φ900. Four circular design projections 66 having a diameter of φ100 are arranged in a circular arc shape at equal intervals at a position deviated from the position, and four design projections 67 having a diameter of φ100 are also provided on the small lid body 62. The design projection 66 has a diameter L1, the shortest distance between the plurality of design projections L2, and the design projection 66 has a diameter L1 shorter than the length L3 of the tire contact portion 12 (L1 < L3), and the shortest distance L2 between the design protrusions is larger than one half of the length of the tire ground contact part (L2> 0.5L3). Distance between Jo edging 68, 68 'L4 have a relationship of L4> 0.25L3. Reference numerals 68, 68 'and 13 denote borders, respectively. The concavo-convex structure 64 of Example 6 includes a large number of independent small protrusions 15 and eight design protrusions 66 and 67. Moreover, about the structure similar to Example 1, a code | symbol is used and detailed description is abbreviate | omitted.

  Example 7 shown in FIG. 9 includes four circular design projections 76 having a diameter of φ100 as in Example 1 and six outer design projections 77 surrounding the circular lid main body 71 of φ900 as in Example 1. The design projections 76 and 77 are arranged on concentric circles at equal intervals, the diameter of the design projections 76 and 77 is L1, the shortest distance between the plurality of design projections is L2, and the diameter L1 of the design projections 76 and 77 is the tire ground contact The length 12 is shorter than the length L3 of the portion 12 (L1 <L3), and the shortest distance L2 between the design protrusions is larger than half the length of the tire ground contact portion (L2> 0.5L3). It is in. The concavo-convex structure 74, 75 of Example 7 includes a large number of independent small protrusions 15 and ten design protrusions 76, 77. In addition, about the structure similar to Example 1, a code | symbol is used and detailed description is abbreviate | omitted.

  In Example 8 shown in FIG. 10, two design projections 86 having a diameter of φ100 are arranged in a horizontal row in the center of a rectangular lid body 81 of 500 mm × 650 mm in length and width as in Example 1. The diameter is L1, the shortest distance between the plurality of design protrusions is L2, and the diameter L1 of the design protrusion 86 is shorter than the length L3 of the tire ground contact part 12 (L1 <L3). The shortest distance L2 is greater than half the length of the tire ground contact portion (L2> 0.5L3). The concavo-convex structure 84 of Example 8 includes a large number of independent small protrusions 15 and two design protrusions 86. In addition, 83 shows the peripheral part of a lid | cover main body, but about the structure similar to Example 1, a code | symbol is used and detailed description is abbreviate | omitted.

  The lid for an underground structure according to the present invention is configured in this manner, and the independent small protrusions 15 that have already been established for the anti-slip effect are formed on almost the entire surface of the lid body 11. One or two or more design protrusions 16 that secure a basic anti-slip effect and cause aesthetics through vision are arranged at appropriate intervals. Although the prior arts that deal with anti-slip of manhole iron lids and the like so far have basically provided a difference in height with respect to the height of the protrusions such as independent small protrusions in the present invention, the present invention provides an anti-slip effect. Based on the anti-slip effect of the independent small protrusion 15, a method of arranging the design protrusions 16 at an allowable interval was discovered, and this was applied to a cover for an underground structure. I don't see.

  In the present invention, research has been conducted focusing on small-diameter tires such as moped bicycles, and the theory has been developed. The diameter of the design protrusion 16... The principle of 50 to 100 mm is based on the relationship with the contact surface shape of a small-diameter tire having a length of about 125 mm and a width of about 55 mm. However, the design projecting portion 16... Is designed with the diameter or diagonal length of L1, the shortest distance between the plurality of design projecting portions as L2, and the length of the ground contact portion of the tire passing through the surface of the lid body as L3. The diameter of the protrusion or the length of the diagonal line is shorter than the length of the tire contact portion (L1 <L3), and the shortest distance between the design protrusions is greater than one half of the length of the tire contact portion (L2 > 0.5L3) is universal, and may be considered to be applied to, for example, motorcycle tires other than small-diameter tires. The same applies to the relationship L4> 0.25L3 regarding the distance L4 between the design protrusions 16... And the outer peripheral protrusions 13.

It is a top view which shows Example 1 of the lid | cover for underground structures which concerns on this invention. It is sectional drawing which expands and shows the principal part same as the above. It is a top view which expands and shows the principal part similarly. It is a top view which shows Example 2 of the lid | cover for underground structures which concerns on this invention. FIG. 9 is a plan view showing Example 3 in the same manner. FIG. 10 is a plan view showing Example 4 in the same manner. FIG. 10 is a plan view showing Example 5 in the same manner. Similarly, Example 6 is shown, in which A is a plan view of only the parent lid, and B is a plan view as a parent-child lid. 9 is a plan view showing Example 7 in the same manner. FIG. 9 is a plan view showing Example 8 in the same manner. FIG.

DESCRIPTION OF SYMBOLS 10 Cover for underground structures 11, 21, 31, 41, 51, 61, 62, 71, 81 Cover body 12 Tire grounding part 13, 68, 68 ', 83 Perimeter of cover body 14, 24, 34, 44 , 54, 64, 74, 75, 84 Uneven structure 15 Independent small protrusion 16, 26, 36, 46, 56, 66, 67, 76, 77, 86 Design protrusion 17 Projection-shaped edge 18 Drain groove L1 Design protrusion Diameter or diagonal length L2 Shortest distance between multiple design protrusions L3 Length of tire contact area L4 Shortest distance between design protrusion and peripheral edge of lid body

Claims (4)

In order to increase the frictional resistance between the ground contact part of the tire passing through the surface of the lid body or the bottom of shoes and to prevent slipping, it is a lid for an underground structure in which an uneven structure is formed on the surface of the lid body. And
As the concavo-convex structure, a large number of independent small protrusions made of a geometric pattern are formed on the surface of the lid body, and the design protrusions having a pattern made of a non-geometric pattern that causes aesthetic appearance through vision are Place one or more in a group of small protrusions,
The above-mentioned design projection is based on the ground contact surface length of a small-diameter tire of about 125 mm × width of about 55 mm, and the diameter or diagonal length L1 is about 50 to 100 mm and the diameter of the design projection Alternatively, when the length of the diagonal line is L1, the shortest distance between the plurality of design protrusions is L2, and the length of the ground contact part of the small-diameter tire passing through the surface of the lid body is L3, the diameter of the design protrusion or the length of the diagonal line The length is shorter than the length of the tire ground contact portion (L1 <L3), and the shortest distance between the design protrusions is greater than half the length of the tire ground contact portion (L2> 0.5L3). A lid for an underground structure characterized by that. When the shortest distance between the design protrusion and the peripheral edge of the lid body is L4, the shortest distance between the design protrusion and the peripheral edge of the lid body is larger than a quarter of the length of the tire ground contact portion (L4>). 0.25L3) underground structures lid of claim 1, wherein in a relationship. The lid for an underground structure according to claim 1, wherein the design protrusion is surrounded by a protruding edging, and a drainage groove is formed on the protruding edging to pass through the inside and outside of the edging part. The depth from the surface of the independent small protrusion to the surface of the space between the independent small protrusions where the roots are located is about 6 mm, the surface of the design protrusion is flush with the surface of the independent small protrusion, and The lid for an underground structure according to claim 1, wherein the depth from the surface of the design protrusion to the base is about 3 mm or more and not more than the depth of the independent small protrusion.

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