Cover for underground structures

Abstract

To provide a lid for an underground structure which can convert an electromagnetic wave transmitted from a radio communication device stored inside an underground structure into an electromagnetic wave having desired frequency (wavelength), and can transmit the electromagnetic wave.SOLUTION: A lid body 5 of a lid 1A for an underground structure includes a lid body part 10 capable of closing an opening 3, a through hole part 20A transmitting through the lid body part 10 in a first direction D1, and a wavelength control part 30A for changing a wavelength of the electromagnetic wave, when electromagnetic waves transmitted from a radio communication device 6 stored inside an underground structure 2 transmit through the through hole part 20A. The wavelength control part 30A includes a first transmission part 70A having first electromagnetic wave transmission characteristics, and a second transmission part 80A which is adjacent to the first transmission part 70A in the first direction D1, and has second electromagnetic wave transmission characteristics different from the first electromagnetic wave transmission characteristics.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a lid for an underground structure provided with a lid that is supported so as to be openable and closable by a frame body that forms an opening connecting a road surface and an underground structure.

Background Art

[0002] In Patent Document 1, when an information storage medium capable of wirelessly reading and writing position information, maintenance information, etc. is installed in a lid body, electromagnetic waves for communicating with the information storage medium are less likely to be disturbed and stable communication can be performed. In order to provide a lid for an underground structure, the lid for an underground structure includes a lid body and a receiving frame that supports the lid body so as to be openable and closable. The lid body is formed of resin, and an information storage medium capable of wirelessly reading and writing information such as position information and maintenance information is disposed in a recess provided on the back surface of the lid body, and a fixing member is fitted into the bottom surface side of the recess.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the lid for an underground structure, conventionally, stable communication with an information storage medium installed in the lid body has been studied, but it is not easy to transmit electromagnetic waves transmitted from a wireless communication device housed inside the underground structure.

Means for Solving the Problems

[0005] One aspect of the present invention is a cover for an underground structure, comprising a cover supported by a frame that forms an opening connecting a road surface and an underground structure, the cover being openable and closable. The cover includes a cover body capable of closing the opening, a through-hole portion penetrating the cover body portion in a first direction, and a wavelength control unit that changes the wavelength of electromagnetic waves transmitted from wireless communication equipment housed inside the underground structure as the electromagnetic waves pass through the through-hole portion. The wavelength control unit includes a first transparent portion having first electromagnetic wave transmission characteristics, and a second transparent portion adjacent to the first transparent portion in a first direction or in a second direction intersecting the first direction, the second transparent portion having second electromagnetic wave transmission characteristics different from those of the first electromagnetic wave transmission characteristics.

[0006] In this cover for underground structures, the wavelength control unit includes transparent sections having different electromagnetic wave transmission characteristics adjacent to each other. Therefore, by changing the combination of transparent sections with different electromagnetic wave transmission characteristics, the wavelength of electromagnetic waves can be controlled as they pass through the through-hole. Thus, it is possible to provide a cover for underground structures that can convert electromagnetic waves transmitted from wireless communication equipment housed inside the underground structure into electromagnetic waves of a desired frequency (wavelength) and transmit them through the through-hole.

[0007] In this cover for underground structures, the wavelength control unit is located inside the through-hole, the first and second transmission sections are adjacent in the first direction, the first electromagnetic wave transmission characteristics may include a first dielectric constant, and the second electromagnetic wave transmission characteristics may include a second dielectric constant greater than the first dielectric constant. By having the electromagnetic wave input to the through-hole pass through both of the two transmission sections having different dielectric constants, a two-stage wavelength conversion can be applied to the electromagnetic wave as it passes through the through-hole.

[0008] In this case, the first electromagnetic wave transmission characteristic may include a first dielectric loss tangent, and the second electromagnetic wave transmission characteristic may include a second dielectric loss tangent that is larger than the first dielectric loss tangent, making it easier to linearly control the wavelength shortening effect and the electromagnetic wave attenuation effect.

[0009] In this case, it is preferable that the first transparent portion includes a first length in the first direction, and the second transparent portion includes a second length smaller than the first length in the first direction. By making the length of the second transparent portion, which has a high dielectric constant and high dielectric loss tangent, smaller than the length of the first transparent portion, which has a low dielectric constant and low dielectric loss tangent, the electromagnetic wave conversion effect by the second transparent portion is mitigated, and the wavelength control unit can be miniaturized.

[0010] In this case, the first permeable portion is preferably positioned closer to the underground structure in the central axis direction of the opening than the second permeable portion, the first permeable portion includes a first outer peripheral portion formed in the circumferential direction of the first direction, the second permeable portion includes a second outer peripheral portion formed in the circumferential direction, the first outer peripheral portion includes a first outer wall surface that contacts the inner peripheral portion of the through-hole over its entire circumference, and a second outer wall surface that protrudes or recesses in a third direction intersecting the first direction with respect to the first outer wall surface, and the second outer peripheral portion preferably includes a third outer wall surface that contacts the inner peripheral portion over its entire circumference.

[0011] In this cover for underground structures, the first permeable portion is positioned on the side of the underground structure (e.g., the lower side) in the central axis direction of the opening, relative to the second permeable portion. Furthermore, the outer periphery of the first permeable portion includes not only a first outer wall surface that contacts the inner circumference of the through-hole portion all around, but also a second outer wall surface that protrudes or recesses in a third direction (e.g., laterally) intersecting the first direction relative to the first outer wall surface. Therefore, for example, by hooking the laterally protruding or recessed second outer wall surface of the first permeable portion, which is positioned below the through-hole portion, onto the inner circumference of the through-hole portion, the orientation of the wavelength control unit relative to the through-hole portion can be easily maintained. Thus, it is possible to provide a cover for underground structures that can stably convert electromagnetic waves of a desired frequency (wavelength) and transmit them through the through-hole portion.

[0012] In this cover for underground structures, the wavelength control unit is located inside the through-hole, and the first and second transparent sections are adjacent in the second direction. The first transparent section may include a conductive section, and the second transparent section may include an insulating section. By allowing electromagnetic waves input to the through-hole to pass only through the insulating section, the electromagnetic wave conversion effect of the conductive section to the electromagnetic waves passing through the through-hole can be eliminated.

[0013] In this cover for underground structures, the wavelength control unit is located outside the through-hole, the first and second transparent sections are adjacent in a second direction, the first transparent section includes a conductive section, the second transparent section includes an insulating section, the conductive section includes a first length in a second direction, and the insulating section includes a second length in a second direction, and the cover may include a length adjustment mechanism that increases the first length by a third length while simultaneously decreasing the second length by a third length. Since the electromagnetic wave conversion action by the insulating section can be controlled using the length adjustment mechanism, it is easy to convert electromagnetic waves passing through the through-hole to a desired frequency (wavelength) according to the installation environment of the cover for underground structures. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a cross-sectional view of a cover for an underground structure according to the first embodiment of the present invention. [Figure 2] Figure 2 is a cross-sectional view of the main part of the cover for the underground structure shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view of the main part of a cover for an underground structure according to a second embodiment of the present invention. [Figure 4] Figure 4 is a cross-sectional view of the main part of a cover for an underground structure according to a third embodiment of the present invention. [Modes for carrying out the invention]

[0015] <First Embodiment> Figure 1 is a cross-sectional view of a cover 1A for an underground structure according to a first embodiment of the present invention. The cover 1A for an underground structure comprises a frame 4 that forms an opening 3 connecting the road surface RS and the underground structure 2, and a cover 5 that is supported by the frame 4 so as to be openable and closable. The frame 4 has an inner circumferential surface 4a that defines the opening 3 and has a cylindrical shape. The opening 3 is circular in shape because it is formed by the inner circumferential surface 4a of the frame 4. In this example, the central axis C1 of the opening 3 extends along the vertical direction VD. The central axis C1 of the opening 3 is in a direction that intersects with respect to the road surface RS, and is typically in a direction perpendicular to the road surface RS. Although not shown in the figures, the cover 1A for an underground structure may be provided with a hinge mechanism on one end of the cover 5 that connects the cover 5 to the frame 4 so as to be openable and closable, and a locking mechanism on the other end of the lower surface of the cover 5. Examples of covers for underground structures 1A include manhole covers, large iron covers, and sewage manhole covers that close openings connecting underground buried objects or underground structural facilities in sewers to the surface; openable and closable iron covers for utility tunnels, power transmission iron covers, and power distribution iron covers that protect underground facilities or underground cables in electrical or communication equipment; and fire hydrant covers, water control valve covers, gate valve covers, air valve covers, gas piping covers, and water meter covers that function as opening and closing doors connecting buried conduits and their associated equipment below the road surface to the surface in water supply or gas piping.

[0016] The cover 5 includes a cover body portion 10 capable of closing the opening 3, a through hole portion 20A that penetrates the cover body portion 10 in a first direction D1 (vertical direction VD in this example), and a wavelength control portion 30A disposed inside the through hole portion 20A. The cover body portion 10 is substantially disc-shaped and includes an upper surface 11 that is exposed on the road surface RS when the cover 5 is closed to the frame 4 (hereinafter simply referred to as the "closed state"), a lower surface 12 that faces the opening 3 in the closed state, and a circular outer peripheral surface 13 that connects the upper surface 11 and the lower surface 12. In this example, the first direction D1 coincides with the direction in which the central axis C1 of the opening 3 extends (central axis direction). The through-hole portion 20A includes an upper opening 11a that penetrates the upper surface 11 of the lid body portion 10 in a first direction D1, a lower opening 12a that penetrates the lower surface 12 of the lid body portion 10 in the first direction D1, and a through-passage portion 14 that connects the upper opening 11a and the lower opening 12a. The through-hole portion 20A has, for example, an arc-shaped inner circumference portion 21 that follows the circular outer circumference 13 of the lid body portion 10 when viewed from above. Therefore, the wavelength control unit 30A, which is arranged inside the through-hole portion 20A, has an outer circumference portion that follows the shape of the inner circumference portion 21 of the through-hole portion 20A when viewed from above. The wavelength control unit 30A is detachably fixed to the through-hole portion 20A by bringing its outer circumference portion into close contact with the inner circumference portion 21 of the through-hole portion 20A. The wavelength control unit 30A changes the wavelength of electromagnetic waves transmitted from wireless communication equipment 6 housed inside the underground structure 2 as the electromagnetic waves pass through the through-hole 20A. In this specification, electromagnetic waves refer to energy waves such as radiation, light, and radio waves that propagate through space while their electric and magnetic fields influence each other.

[0017] The wireless communication device 6 has a transmitting function, and a water level sensor (not shown) is connected to it, for example, to measure the water level of sewage flowing inside the underground structure 2. The water level information measured by the water level sensor is transmitted as radio waves from the wireless communication device 6. The radio waves, including the water level information transmitted from the wireless communication device 6, are transmitted through the through-hole 20A and are received by wireless equipment (not shown) with a receiving function installed outside the underground structure 2. The information transmitted from the wireless communication device 6 is not limited to water level information, but may also include information about odors inside the underground structure 2 or information including the concentration of a specific gas, and multiple pieces of this information may be transmitted from the wireless communication device 6. The wireless communication device 6 is not limited to having a transmitting function, but may also have a receiving function, or may have both a transmitting and receiving function.

[0018] Figure 2 is a cross-sectional view of the main part of the underground structure cover 1A. As shown in Figure 2, the through passage portion 14 of the through hole portion 20A may include one or more passage portions that are inclined with respect to the first direction D1 in the process of connecting the upper opening 11a and the lower opening 12a. The through passage portion 14 in this example is formed in a crank shape as a whole and includes a first passage portion 40 extending from the upper opening 11a toward the side of the underground structure 2 in the first direction D1 (underground structure side D12, the downward side in this example), a second passage portion 60 that is connected to the first passage portion 40 and extends in a second direction D2 (horizontal direction HD in this example) that intersects the first direction D1, and a third passage portion 50 that is connected to the second passage portion 60 and extends toward the underground structure side D12 to reach the lower opening 12a. The second direction D2 in this example is a direction perpendicular to the first direction D1.

[0019] The first passage section 40 includes a pair of upper wall surfaces 41, 42 (the first upper wall surface 41 and the second upper wall surface 42) facing the second direction D2. The second passage section 60 includes a first intermediate wall surface 61 that is connected to the first upper wall surface 41 and extends in the second direction D2, a second intermediate wall surface 62 that is connected to the first intermediate wall surface 61 and extends toward the underground structure side D12, a third intermediate wall surface 63 that is connected to the second upper wall surface 42 and extends toward the underground structure side D12, and a fourth intermediate wall surface 64 that is connected to the third intermediate wall surface 63 and extends in the second direction D2. The third passage section 50 includes a first lower wall surface 51 that is connected to the second intermediate wall surface 62 and extends toward the underground structure side D12, and a second lower wall surface 52 that is connected to the fourth intermediate wall surface 64 and extends toward the underground structure side D12. The first lower wall surface 51 and the second lower wall surface 52 face each other in the second direction D2. These wall surfaces 41, 42, 61, 62, 63, 64, 51 and 52 constitute the inner circumference 21 of the through passage section 14. Therefore, the interior of the through hole section 20A is an internal space surrounded by the inner circumference 21 of the through passage section 14 between the upper opening 11a and the lower opening 12a.

[0020] The wavelength control unit 30A disposed inside the through-hole portion 20A includes a first transmission portion 70A having a first electromagnetic wave transmission characteristic, and a second transmission portion 80A that is adjacent to the first transmission portion 70A in a first direction D1 and has a second electromagnetic wave transmission characteristic different from the first electromagnetic wave transmission characteristic. The second transmission portion 80A is disposed on the side of the road surface RS in the first direction D1 (road surface side D11, in this example, the upper side) relative to the first transmission portion 70A. The first electromagnetic wave transmission characteristic includes a first dielectric constant, and the second electromagnetic wave transmission characteristic includes a second dielectric constant greater than the first dielectric constant. Also, the first electromagnetic wave transmission characteristic includes a first dielectric loss tangent, and the second electromagnetic wave transmission characteristic includes a second dielectric loss tangent greater than the first dielectric loss tangent. The first transmission portion 70A includes a first outer peripheral portion 71 formed in the circumferential direction CD of the first direction D1, a lower wall surface 72a that is continuous with an end portion of the first outer peripheral portion 71 on the underground structure side D12 and extends in a second direction D2, and an upper wall surface 72b that is continuous with an end portion of the first outer peripheral portion 71 on the road surface side D11 and extends in the second direction D2. The second transmission portion 80A includes a second outer peripheral portion 81 formed in the circumferential direction CD, a lower wall surface 82a that is continuous with an end portion of the second outer peripheral portion 81 on the underground structure side D12 and extends in the second direction D2, and an upper wall surface 82b that is continuous with an end portion of the second outer peripheral portion 81 on the road surface side D11 and extends in the second direction D2. The wavelength control unit 30A is formed by attaching the upper wall surface 72b and the lower wall surface 82a to each other so that the first transmission portion 70A and the second transmission portion 80A are integrated. The first transmission portion 70A preferably has a length L1 in the first direction D1, and the second transmission portion 80A preferably has a length L2 smaller than the length L1 in the first direction D1. The second transmission portion 80A is preferably more weather-resistant than the first transmission portion 70A. The first transmission portion 70A is made of, for example, natural rubber, and the second transmission portion 80A is made of, for example, chloroprene rubber. Chloroprene rubber is more weather-resistant than natural rubber and has a larger dielectric constant and dielectric loss tangent than natural rubber.

[0021] The first transmission portion 70A includes a first outer peripheral portion 71 formed in the circumferential direction CD of the first direction D1, a lower wall surface 72a that is continuous with an end portion of the first outer peripheral portion 71 on the underground structure side D12 and extends in a second direction D2, and an upper wall surface 72b that is continuous with an end portion of the first outer peripheral portion 71 on the road surface side D11 and extends in the second direction D2. The second transmission portion 80A includes a second outer peripheral portion 81 formed in the circumferential direction CD, a lower wall surface 82a that is continuous with an end portion of the second outer peripheral portion 81 on the underground structure side D12 and extends in the second direction D2, and an upper wall surface 82b that is continuous with an end portion of the second outer peripheral portion 81 on the road surface side D11 and extends in the second direction D2. The wavelength control unit 30A is formed by attaching the upper wall surface 72b and the lower wall surface 82a to each other so that the first transmission portion 70A and the second transmission portion 80A are integrated.

[0022] The first outer peripheral portion 71 of the first transmission portion 70A includes a first outer wall surface 73 that contacts the inner peripheral portion 21 of the through-hole portion 20A over the entire circumference, and a second outer wall surface 76 that protrudes or recesses in a third direction D3 that intersects the first direction D1 with respect to the first outer wall surface 73. In this example, the third direction D3 is a direction orthogonal to the first direction D1. Also, in this example, the third direction D3 is parallel to the second direction D2. The first outer wall surface 73 includes a pair of contact surfaces 74, 75 (the first contact surface 74 and the second contact surface 75) that contact the pair of upper wall surfaces 41, 42. The first contact surface 74 contacts the first upper wall surface 41, and the second contact surface 75 contacts the second upper wall surface 42. The second outer wall surface 76 is disposed in the second passage portion 60 with a space S interposed between the second intermediate wall surface 62. The second outer wall surface 76 includes a recess 77 that is continuous with the first contact surface 74 and recesses with respect to the first contact surface 74, and a protrusion 78 that protrudes from the bottom 77a of the recess 77. The protrusion 78 protrudes such that the tip 78a of the protrusion 78 approaches the first intermediate wall surface 61. The second outer peripheral portion 81 of the second transmission portion 80A includes a third outer wall surface 82 that contacts the inner peripheral portion 21 of the through-hole portion 20A over the entire circumference.

[0023] In this lid 1A for the underground structure, the wavelength control portion 30A disposed inside the through-hole portion 20A of the lid main body portion 10 includes transmission portions 70A, 80A having different electromagnetic wave transmission characteristics adjacent to each other. Therefore, by changing the combination method of the transmission portions 70A, 80A having different electromagnetic wave transmission characteristics, the wavelength of the electromagnetic wave can be controlled when the electromagnetic wave passes through the through-hole portion 20A. Therefore, the electromagnetic wave transmitted from the wireless communication device 6 housed inside the underground structure 2 can be converted into an electromagnetic wave of a desired frequency (wavelength) and transmitted through the through-hole portion 20A.

[0024] Furthermore, in this underground structure cover 1A, the first permeable section 70A and the second permeable section 80A are adjacent in the first direction D1, the first electromagnetic wave transmission characteristics include a first dielectric constant, and the second electromagnetic wave transmission characteristics include a second dielectric constant that is greater than the first dielectric constant. Therefore, the electromagnetic waves input to the through-hole 20A pass through both the two permeable sections 70A and 80A, which have different dielectric constants, thereby providing a two-stage wavelength conversion to the electromagnetic waves passing through the through-hole 20A.

[0025] Furthermore, since the first electromagnetic wave transmission characteristic includes a first dielectric loss tangent, and the second electromagnetic wave transmission characteristic includes a second dielectric loss tangent that is larger than the first dielectric loss tangent, it is easier to linearly control the wavelength shortening effect and the electromagnetic wave attenuation effect.

[0026] Furthermore, by reducing the length of the second transparent section 80A (second length L2), which has a high dielectric constant and high dielectric loss tangent, compared to the length of the first transparent section 70A (first length L1), which has a low dielectric constant and low dielectric loss tangent, the electromagnetic wave conversion effect of the second transparent section 80A can be mitigated, and the wavelength control unit 30A can be miniaturized.

[0027] Furthermore, in this underground structure cover 1A, the first permeable portion 70A is positioned closer to the underground structure D12 than the second permeable portion 80A. In addition, the first outer peripheral portion 71 of the first permeable portion 70A includes not only a first outer wall surface 73 that contacts the inner peripheral portion 21 of the through-hole portion 20A over its entire circumference, but also a second outer wall surface 76 that protrudes or recesses in a third direction D3 (for example, sideways) relative to the first outer wall surface 73. Therefore, even if an external force such as an attempt to move the wavelength control unit 30A to the road surface D11 acts on it, the second outer wall surface 76 of the first permeable portion 70A that protrudes or recesses laterally can be hooked onto the inner peripheral portion 21 of the through-hole portion 20A, thereby maintaining the positional orientation of the wavelength control unit 30A relative to the through-hole portion 20A. Specifically, the projection 78 catches on the first intermediate wall surface 61, thereby maintaining the orientation of the wavelength control unit 30A relative to the through-hole 20A. Therefore, it is possible to stably convert the electromagnetic waves to the desired frequency (wavelength).

[0028] Furthermore, by making the length of the first transparent portion 70A (first length L1) greater than the length of the second transparent portion 80A (second length L2), a complex shape, rather than a simple shape that merely adheres to the through-hole portion 20A, can be formed from a single material (the material forming the first transparent portion 70A). An example of a complex shape is the case in this embodiment, where a second outer wall surface 76, i.e., a recess 77 and a protrusion 78, is formed, but even such a shape is easy to form. In this way, by making the length of the first transparent portion 70A on the underground structure side D12 greater than the length of the second transparent portion 80A on the road surface side D11 of the wavelength control unit 30A, and by arranging a second outer wall surface 76 having a complex shape such as a recess 77 and a protrusion 78 on the first transparent portion 70A on the underground structure side D12, it is possible to ensure that the adhesion surface between the upper wall surface 72b and the lower wall surface 82a is not included in the second outer wall surface 76. Therefore, it is possible to prevent the first permeable portion 70A and the second permeable portion 80A from separating at the adhesion surface due to stress that may occur when the protruding portion 78 catches on the first intermediate wall surface 61. In this example, the third direction D3 is parallel to the second direction D2, but it is also possible to design the third direction D3 in which the second outer wall surface 76 protrudes or recesses to be non-parallel to the second direction D2.

[0029] <Second Embodiment> Figure 3 is a cross-sectional view of the main part of the underground structure cover 1B according to the second embodiment of the present invention. In the second embodiment, components common to the first embodiment may be denoted by the same reference numerals and their description may be omitted. The main difference between the underground structure cover 1B according to the second embodiment and the underground structure cover 1A according to the first embodiment is that the first transparent section 70B and the second transparent section 80B of the wavelength control unit 30B are adjacent to the second direction D2 which intersects (orthogonal in this example) the first direction D1.

[0030] The through-passage portion 14 of the through-hole portion 20B of the underground structure cover 1B includes a passage connecting the upper opening 11a and the lower opening 12a in a first direction D1. The first permeable portion 70B includes a conductive portion 90, and the second permeable portion 80B includes an insulating portion 100. For example, both the conductive portion 90 and the insulating portion 100 are made of rubber, and the rubber used in the conductive portion 90 has higher conductivity than the rubber used in the insulating portion 100. The conductive portion 90 includes a first length L3 in the second direction D2, and the insulating portion 100 includes a second length L4 in the second direction D2.

[0031] In this underground structure cover 1B, the wavelength control unit 30B, located inside the through-hole 20B of the cover body 10, includes adjacent transparent sections 70B and 80B having different electromagnetic wave transmission characteristics. Therefore, by changing the combination of the transparent sections 70B and 80B having different electromagnetic wave transmission characteristics, the wavelength of electromagnetic waves can be controlled when they pass through the through-hole 20B. Consequently, electromagnetic waves transmitted from wireless communication equipment 6 housed inside the underground structure 2 can be converted into electromagnetic waves of a desired frequency (wavelength) and transmitted through the through-hole 20B.

[0032] Furthermore, in this underground structure cover 1B, the first permeable portion 70B and the second permeable portion 80B are adjacent in the second direction D2, the first permeable portion 70B includes a conductive portion 90, and the second permeable portion 80B includes an insulating portion 100. Therefore, electromagnetic waves input to the through-hole portion 20B pass only through the insulating portion 100, thereby eliminating the electromagnetic wave conversion effect of the conductive portion 90 on electromagnetic waves passing through the through-hole portion 20B.

[0033] Furthermore, in this underground structure cover 1B, the wavelength control unit 30B can be fixed to the through-hole 20B by making the length Lw of the wavelength control unit 30B in the second direction D2 equal to the length Lh of the through-hole 20B in the second direction D2. For example, by preparing a wavelength control unit 30B that is longer than the length Lh of the through-hole 20B in advance, and then cutting at least one of the conductive part 90 and the insulating part 100 at the construction site to make the length Lw of the wavelength control unit 30B in the second direction D2 equal to the length Lh of the through-hole 20B, the length of the conductive part 90 (first length L3) and the length of the insulating part 100 (second length L4), which are suitable for converting electromagnetic waves transmitted from the wireless communication device 6 into electromagnetic waves of a desired frequency, can be easily adjusted.

[0034] <Third Embodiment> Figure 4 is a cross-sectional view of the main part of the underground structure cover 1C according to the third embodiment of the present invention. In the third embodiment, components common to the second embodiment may be denoted by the same reference numerals and their description may be omitted. The main difference between the underground structure cover 1C according to the third embodiment and the underground structure cover 1B according to the second embodiment is that the wavelength control unit 30C is located outside the through-hole portion 20C rather than inside it, and the cover body 5 includes a length adjustment mechanism 110 that increases the first length L3 of the conductive portion 90 by a third length L5, while simultaneously decreasing the second length L4 of the insulating portion 100 by a third length L5. The wavelength control unit 30C includes a metal plate portion 120 as a conductive portion 90 that covers a part of the through-hole portion 20C from the underground structure side D12, and a space 121 as an insulating portion 100 adjacent to the metal plate portion 120 in a second direction D2.

[0035] The length adjustment mechanism 110 in this example is a lead screw mechanism that converts rotational motion into linear motion, and includes a lead screw member 111 attached to the metal plate portion 120 and moving the metal plate portion 120 in a second direction D2, a nut member 112 that moves the lead screw member 111 in the second direction D2 by applying rotational force to the lead screw member 111, and a nut bearing member 113 attached to the lid body portion 10 and rotatably supporting the nut member 112.

[0036] In this underground structure cover 1C, the wavelength control unit 30C, located outside the through-hole 20C of the cover body 10, includes adjacent transparent sections 70C and 80C having different electromagnetic wave transmission characteristics. Therefore, by changing the combination of the transparent sections 70C and 80C having different electromagnetic wave transmission characteristics, the wavelength of electromagnetic waves transmitted through the through-hole 20C can be controlled. Consequently, electromagnetic waves transmitted from wireless communication equipment 6 housed inside the underground structure 2 can be converted into electromagnetic waves of a desired frequency (wavelength) and transmitted through the through-hole 20C.

[0037] Furthermore, in this underground structure cover 1C, the first permeable portion 70C and the second permeable portion 80C are adjacent in the second direction D2, the first permeable portion 70C includes a conductive portion 90 (metal plate portion 120), and the second permeable portion 80C includes an insulating portion 100. Therefore, electromagnetic waves input to the through-hole portion 20C pass only through the insulating portion 100 (space 121), thereby eliminating the electromagnetic wave conversion effect of the conductive portion 90 on electromagnetic waves passing through the through-hole portion 20C.

[0038] Furthermore, in this underground structure cover 1C, the length adjustment mechanism 110 allows for simultaneous adjustment of the first length L3 of the conductive part 90 (metal plate part 120) and the second length L4 of the insulating part 100 (space 121). Therefore, the electromagnetic wave conversion effect of the insulating part 100 can be easily controlled at the construction site. Thus, it is possible to provide an underground structure cover 1C that can easily convert electromagnetic waves passing through the through-hole part 20C to a desired frequency (wavelength) according to the installation environment of the underground structure cover 1C.

[0039] The present invention is not limited to the embodiments described above, but also includes those defined in the claims. The through-hole portion 20A includes an upper opening 11a that penetrates the upper surface 11 of the lid body portion 10 in the first direction D1, and a lower opening 12a that penetrates the lower surface 12 of the lid body portion 10 in the first direction D1. The intermediate passage connecting the upper opening 11a and the lower opening 12a may be inclined with respect to the first direction D1. "Penetrating the lid body portion in the first direction" means that the upper opening 11a and the lower opening 12a formed at both ends of the through-hole portion penetrate the lid body portion 10 in the first direction D1. Furthermore, in the above embodiment, a wavelength control unit with a two-layer structure in which a first transparent portion and a second transparent portion adjacent to the first transparent portion in the first or second direction are stacked has been described. However, the wavelength control unit may also have a three-layer structure in which the first, second, and third transparent portions are stacked adjacent to each other in the first or second direction, or it may have four or more layers. A two-layer structure is preferred to achieve electromagnetic wave conversion to a desired frequency (wavelength) using a low-cost and compact wavelength control unit. Furthermore, the stacking direction of the transparent portion may be one of the first and second directions, or both. In addition, although the above embodiment shows an example where the through-hole portion has an arc-shaped inner circumference when viewed from above, and the radial direction of this arc shape is taken as the second direction, the second direction can be any direction intersecting the first direction. Specifically, the circumferential direction (longitudinal direction) of the inner circumference of the through-hole portion can be taken as the second direction, and the first and second transparent portions can be arranged adjacent to each other in this second direction.

[0040] Furthermore, although expressions such as "horizontal," "vertical," "circular," "disk-shaped," "arc-shaped," and "cylindrical" were used in the above embodiments, it is not necessary for the object to be strictly in these states. In other words, each of these expressions allows for deviations in manufacturing accuracy, installation accuracy, etc. [Explanation of Symbols]

[0041] 1A, 1B, 1C Cover for underground structure, 2 Underground structure, 3 Opening, 4 Frame, 5 Cover, 6 Wireless communication equipment, 10 Cover body, 20A, 20B, 20C Through-hole, 30A, 30B, 30C Wavelength control section, 70A, 70B, 70C First transparent section, 71 First outer periphery, 73 First outer wall surface, 76 Second outer wall surface, 80A, 80B, 80C Second transparent section, 81 Second outer periphery, 82 Third outer wall surface, 90 Conductive section, 100 Insulating section, 110 Length adjustment mechanism, D1 First direction, D2 Second direction, RS Road surface, L1, L3 First length, L2, L4 Second length, L5 Third length

Claims

1. A cover for an underground structure, comprising a cover body supported by a frame that forms an opening connecting the road surface and the underground structure, which is openable and closable, The lid comprises a lid body portion capable of closing the opening, The lid body portion has a through hole portion that penetrates in the first direction, The underground structure includes a wavelength control unit that changes the wavelength of electromagnetic waves transmitted from wireless communication equipment housed inside the underground structure as the electromagnetic waves pass through the through-hole, The wavelength control unit includes a first transmission portion having a first electromagnetic wave transmission characteristic, and a second transmission portion adjacent to the first transmission portion in the first direction, which has a second electromagnetic wave transmission characteristic different from that of the first transmission portion. The wavelength control unit is located inside the through-hole. The first electromagnetic wave transmission characteristics include a first dielectric constant, The second electromagnetic wave transmission characteristic includes a second dielectric constant that is greater than the first dielectric constant. The first transparent portion includes a first length in the first direction, A cover for an underground structure, wherein the second permeable portion includes a second length smaller than the first length in the first direction.

2. A cover for an underground structure, comprising a cover body supported by a frame that forms an opening connecting the road surface and the underground structure, which can be opened and closed, The lid comprises a lid body portion capable of closing the opening, The lid body portion has a through hole portion that penetrates in the first direction, The underground structure includes a wavelength control unit that changes the wavelength of electromagnetic waves transmitted from wireless communication equipment housed inside the underground structure as the electromagnetic waves pass through the through-hole, The wavelength control unit includes a first transmission portion having a first electromagnetic wave transmission characteristic, and a second transmission portion adjacent to the first transmission portion in the first direction, which has a second electromagnetic wave transmission characteristic different from that of the first transmission portion. The wavelength control unit is located inside the through-hole. The first electromagnetic wave transmission characteristics include a first dielectric constant and a first dielectric loss tangent. The second electromagnetic wave transmission characteristic includes a second dielectric constant greater than the first dielectric constant, and a second dielectric loss tangent greater than the first dielectric loss tangent. The first transparent portion includes a first length in the first direction, A cover for an underground structure, wherein the second permeable portion includes a second length smaller than the first length in the first direction.

3. The first permeable portion is positioned closer to the underground structure in the central axis direction of the opening than the second permeable portion. The first transparent portion includes a first outer peripheral portion formed in the circumferential direction in the first direction, The second transparent portion includes a second outer peripheral portion formed in the circumferential direction, The first outer periphery includes a first outer wall surface that contacts the inner periphery of the through hole over its entire circumference, and a second outer wall surface that protrudes or recesses in a third direction intersecting the first direction relative to the first outer wall surface. The cover for an underground structure according to claim 1 or 2, wherein the second outer periphery includes a third outer wall surface that contacts the inner periphery over its entire circumference.

4. A cover for an underground structure, comprising a cover body supported by a frame that forms an opening connecting the road surface and the underground structure, which can be opened and closed, The lid comprises a lid body portion capable of closing the opening, The lid body portion has a through hole portion that penetrates in the first direction, The underground structure includes a wavelength control unit that changes the wavelength of electromagnetic waves transmitted from wireless communication equipment housed inside the underground structure as the electromagnetic waves pass through the through-hole, The wavelength control unit includes a first transmission portion having a first electromagnetic wave transmission characteristic, and a second transmission portion adjacent to the first transmission portion in a second direction intersecting the first direction, the second transmission portion having a second electromagnetic wave transmission characteristic different from that of the first transmission portion. The wavelength control unit is located inside the through-hole. The first transparent portion includes a conductive portion, The second permeable portion includes an insulating portion, The insulating portion has a surface on the road surface side and a surface on the underground structure side in the central axis direction of the opening, the entire area between the road surface side and the underground structure side is made of an insulating material, the entire road surface side is open to the road surface side, and the entire underground structure side is open to the underground structure side, a cover for an underground structure.

5. A cover for an underground structure, comprising a cover body supported by a frame that forms an opening connecting the road surface and the underground structure, which can be opened and closed, The lid comprises a lid body portion capable of closing the opening, The lid body portion has a through hole portion that penetrates in the first direction, The underground structure includes a wavelength control unit that changes the wavelength of electromagnetic waves transmitted from wireless communication equipment housed inside the underground structure as the electromagnetic waves pass through the through-hole, The wavelength control unit includes a first transmission portion having a first electromagnetic wave transmission characteristic, and a second transmission portion adjacent to the first transmission portion in a second direction intersecting the first direction, the second transmission portion having a second electromagnetic wave transmission characteristic different from that of the first transmission portion. The wavelength control unit is located outside the through-hole portion. The first transparent portion includes a conductive portion, The second permeable portion includes an insulating portion, The conductive portion includes a first length in the second direction, The insulating portion includes a second length in the second direction, The cover for an underground structure includes a length adjustment mechanism that increases the first length by the amount of the third length and simultaneously decreases the second length by the amount of the third length.

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