JP7266238B2 - Drainage device for burial box - Google Patents

Description

The present invention relates to a drainage device for underground boxes such as manholes and handholes.

2. Description of the Related Art For various cables such as electric wires laid through the ground, underground boxes called manholes and handholes are buried for connection work and inspection of the various cables.
The above-mentioned underground box has a cover attached to the top exposed to the ground, and various cables are inserted through the sides of the cover. Therefore, by removing the cover, it becomes possible to perform cable work, inspection, and the like.
Here, rainwater from the ground that leaks from the lid and groundwater that leaks from the sides may permeate the underground box, and a drainage port is formed on the bottom surface to discharge the drainage. there is In addition, a backflow preventive device is attached to the drain port so as to prevent backflow of underground water, etc. from the downstream side while discharging the drainage in the underground box.

Patent No. 3171331 JP 2017-210969

The above-described conventional backflow prevention device includes a float valve having a float with a lower specific gravity than water. The structure of the float valve is such that when groundwater flows backward from the downstream side, the floating float comes into contact with the valve seat to close the drainage channel and prevent the backflow of groundwater into the underground box.
Here, the backflow prevention device having the float valve requires a space for the float to move up and down, so there is a problem that the backflow prevention device becomes large in the vertical direction. In addition, the increased size of the backflow prevention device increases the thickness of the underground box, resulting in an increase in manufacturing cost.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a drainage device for an underground box that is compact and can be manufactured at low cost.

The present invention according to claim 1 for solving the above problems is an underground box buried in the ground,
A drainage device for an underground box, comprising a backflow prevention device attached to a drainage channel continuing from a drainage port formed in the underground box,
The backflow prevention device includes a valve body that opens and closes the drainage channel ;
a fixing member for fixing the valve body in the drainage channel ;
The valve body is an umbrella valve comprising a shaft portion fixed in the drainage channel and an umbrella-shaped opening/closing portion formed around the shaft portion, and opens and closes the drainage channel by elastic deformation ,
The drainage device for an underground box is characterized in that the fixed member has a valve seat with which the valve element abuts at the lower end thereof to block the drainage channel .

The present invention according to claim 2 provides an underground box buried in the ground,
A drainage device for an underground box, comprising a backflow prevention device attached to a drainage channel continuing from a drainage port formed in the underground box,
The backflow prevention device includes a valve body that opens and closes the drainage channel ;
a fixing member for fixing the valve body in the drainage channel ;
The valve body is a self-sealing valve including an opening/closing portion that closes the drainage channel by abutment of opposing side surfaces, and opens and closes the drainage channel by elastic deformation ,
The fixing member is inserted from the drain port with the valve body attached, and fixes the valve body in the drainage channel.

In the present invention according to claim 3, the backflow prevention device is
3. The drainage device for an underground box according to claim 1, wherein the fixing member is detachable in the drainage channel together with the valve body.

In the present invention according to claim 4, the backflow prevention device
Collecting members are provided on the upstream side and the downstream side of the valve body,
4. The drainage device for an underground box according to claim 3 , wherein at least the collecting member on the downstream side engages with the fixing member and is detachable together with the fixing member.

According to a fifth aspect of the present invention , the underground box is a manhole or a handhole . be.

According to the present invention, since the valve body opens and closes the drainage channel by elastic deformation, it does not require a space for the float to move up and down, unlike the conventional float valve that utilizes the buoyancy of the float. Miniaturization is possible.
In addition, since the fixing member for fixing the valve body in the drainage channel is detachable together with the valve body, cleaning and replacement of members can be easily performed.

It is sectional drawing which shows the construction state of this invention. It is a cross-sectional perspective view which shows a backflow prevention apparatus. It is a cross-sectional view showing a backflow prevention device. FIG. 4 is a cross-sectional view showing each member of the backflow prevention device; FIG. 4 is an exploded perspective view showing each member of the backflow prevention device; It is the (a) top view (b) front view which shows a fixing member. FIG. 4 is a cross-sectional view showing a state in which a drainage channel is opened; It is sectional drawing which shows the construction state of this invention which concerns on 2nd embodiment. It is a cross-sectional view showing a backflow prevention device. FIG. 4 is a cross-sectional view showing each member of the backflow prevention device; It is the (a) top view (b) front view which shows a fixing member. FIG. 4 is a cross-sectional view showing a state in which a drainage channel is opened; It is a sectional view showing a third embodiment. FIG. 11 is an exploded cross-sectional view showing each member of the fourth embodiment; FIG. 4 is a cross-sectional view showing a check valve; It is a sectional view showing a fifth embodiment.

Hereinafter, a drainage device for an underground box according to the present invention will be described with reference to the drawings. It should be noted that the invention described below is intended to facilitate understanding of the embodiments, and should not be construed as limiting the invention.

The underground box 1 is a manhole or handhole to be buried in the ground, and as shown in FIGS. , a substantially rectangular parallelepiped box having an open upper surface, and the open upper surface is closed by a lid portion 14 . The underground box 1 has through holes 17 formed in opposite sides 15 and 16, and protective tubes 18 through which various cables (not shown) are inserted. 2 is installed.

As described below, the backflow prevention device 2 according to this embodiment includes a flange member 3 , a fixing member 4 , a valve body 5 , a perforated plate 6 and a perforated plate 7 .

The flange member 3 is attached to the bottom surface 19 of the underground box 1, and is a hollow cylindrical member forming a drainage channel inside. to form In addition, the flange member 3 has a flange portion 32 extending outward on the entire circumference of the upper end, and on the inner surface thereof, a convex portion 33 that engages with the fixing member 4 and a stepped portion formed below the convex portion 33 . 34. A pipe body 8 made of PVC is arranged below the flange member 3 .

The fixing member 4 is made of hard synthetic resin, and as shown in FIGS. 47 and a valve seat 49 with which the valve element 5 abuts.
The annular portion 41 has a cutout 42 , a plate-like portion 43 , and an inclined portion 44 formed on its upper surface. Two of each are formed at symmetrical positions. Further, the annular portion 41 is formed with a concave portion 45 and a groove portion 46 on its outer surface.
The notch 42 is a recessed groove formed on the outer periphery of the upper surface of the annular portion 41, and its width is configured so that the convex portion 33 of the flange member 3 can pass therethrough.
The plate-like portion 43 extends upward from the upper surface of the annular portion 41 and has a rectangular opening 431 formed therein.
The inclined portion 44 gradually protrudes upward from the notch 42 toward the plate-like portion 43 in the counterclockwise direction, and the end portion is formed so as to be continuous with the plate-like portion 43 .
The concave portion 45 is formed along the entire circumference of the side surface of the annular portion 41, and is fitted with an annular packing P that contacts the inner surface of the flange member 3. As shown in FIG.
The groove portion 46 is formed over the entire outer circumference of the annular portion 41 below the recess portion 45, and the perforated plate 7 is engaged when the construction is completed.
The mounting portion 47 is arranged in the center of the fixed member 4 and has a mounting hole extending in the vertical direction, and the valve body 5 is inserted through the mounting hole. The inner diameter of the mounting hole is approximately the same as the outer diameter of the shaft portion 51 of the valve body 5 .
The grip portion 48 connects the inner surface of the annular portion 41 and the outer surface of the mounting portion 47 to support the mounting portion 47, and functions as a handle when the valve body 5 is attached or detached.
The valve seat 49 is the lower end of the annular portion 41, and is inclined in a direction in which the diameter increases as it proceeds downward. As shown in FIG. The opening/closing portion 52 of the valve body 5 abuts along the circumference to close the drainage channel.

The valve body 5 is made of an elastic soft material such as rubber or silicon and has a substantially T-shaped cross section, and has a shaft portion 51 fixed in the drainage channel and an umbrella shape formed around the shaft portion 51 . It is an umbrella valve consisting of an opening and closing part 52 of .
The shaft portion 51 is rod-shaped and formed at the center of the valve body 5, and a bulging portion 53 having a larger diameter than the mounting hole is formed in the middle of the shaft portion 51. As shown in FIG.
The opening/closing part 52 is a thin film having a thickness of 1 mm or less and extending outward from one end of the shaft part 51. As shown in FIG. It is rounded and sloping. The opening/closing portion 52 is in contact with the valve seat 49 when the valve body 5 is fixed to the mounting portion 47 . Here, as shown in FIG. 3 , the opening/closing portion 52 in contact with the valve seat 49 is deformed along the inclination of the valve seat 49 . At this time, the opening/closing portion 52 is deformed in a direction opposite to the direction of inclination of the opening/closing portion 52 at the point of contact with the valve seat 49 , so that the restoring force of the opening/closing portion 52 strongly brings the valve body 5 into surface contact with the valve seat 49 . , it is possible to reliably close the drainage channel.

The perforated plate 6 is a collecting member arranged on the upstream side of the valve body 5, and has a mortar shape in cross section, and is a collecting portion formed by opening a plurality of collecting holes in the vertical direction. have. An engaging portion 61 is provided on the side surface of the perforated plate 6 so as to protrude outward and is fixed to the fixing member 4 by engaging with the opening 431 of the fixing member 4 .

The perforated plate 7 is a collecting member disposed on the downstream side of the valve body 5, and has a concave cross-sectional shape, and has a collection portion formed by vertically opening a plurality of collection holes. have. The perforated plate 7 has an engaging portion 71 projecting inward and is fixed to the fixing member 4 by engaging with the groove portion 46 of the fixing member 4 .

As described above, the valve body 5 of the present invention has the perforations 6 and 7 above and below the fixing member 4, respectively. Here, the perforated plate 6 arranged above the fixing member 4 catches garbage and the like in the sewage discharged from the underground box 1, and the perforated plate 7 catches the garbage and the like in the underground water from the downstream side. .

The backflow prevention device 2 is constructed as follows.

First, the shaft portion 51 is inserted through the mounting portion 47 , and the shaft portion 51 is pulled from the opposite side to mount the valve body 5 to the fixing member 4 . At this time, the bulging portion 53 formed on the shaft portion 51 has a larger diameter than the mounting portion 47, but since the valve body 5 is made of a soft material, the bulging portion 53 is deformed by pulling strongly. can be installed. During the attachment, the opening/closing portion 52 of the valve body 5 abuts against the valve seat 49 and deforms along the inclined surface of the valve seat 49 as shown in FIG. surface contact over the entire circumference.
Next, the engaging portion 71 of the perforated plate 7 is engaged with the groove portion 46 of the fixing member 4 to attach the perforated plate 7 to the fixing member 4 .
Next, the fixing member 4 to which the valve body 5 and the perforated plate 7 are attached is inserted into the flange member 3 in a state in which the projections 33 and the cutouts 42 are aligned with each other. Then, after inserting the fixing member 4 into the flange member 3 until the upper surface of the annular portion 41 is positioned below the convex portion 33, the fixing member 4 is rotated clockwise so that the fixing member 4 is attached to the flange member 3. It is attached. During the rotation, the inclined portion 44 comes into contact with the convex portion 33, so that part of the stress associated with the clockwise rotation is converted into stress that pushes the fixing member 4 downward. As a result, the packing P is strongly pressed against the stepped portion 34 formed on the inner circumference of the fixing member 4, and the gap between the outer surface of the fixing member 4 and the inner surface of the flange member 3 is completely stopped.
Finally, the perforated plate 6 is placed on the fixing member 4 and the engaging portion 61 is engaged with the opening portion 431 to complete the construction.

Although the flange member 3 is attached to the underground box 1, the attachment method is not limited at all. That is, a mounting hole may be formed in the bottom surface 19 of the underground box 1 and the flange member 3 may be adhered, or the flange member 3 may be inserted into the bottom surface 19 by placing concrete after placement.

When performing maintenance on the backflow prevention device 2, the fixing member 4 can be removed from the flange member 3 by rotating the fixing member 4 counterclockwise.

The operation of the drainage device for the underground box 1 equipped with the backflow prevention device 2 will be described below.

First, as shown in FIG. 3, in a state where there is no sewage or the like in the underground box 1 and there is no backflow of groundwater or the like from the downstream side, the opening/closing portion 52 of the valve body 5 is opened by its own elasticity. The drainage channel is blocked by surface contact with the seat 49 over the entire circumference. The center of the valve body 5 and the center of the flange member 3 are aligned, and the opening/closing portion 52 is evenly stressed toward the valve seat 49 by its own elasticity. Therefore, the opening/closing part 52 is in uniform surface contact with the valve seat 49 over the entire circumference using its own elasticity as a biasing means, and stably closes the drainage channel without concentration of stress at a specific point. ing.
Here, if dirty water or the like is generated in the underground box 1 by rainwater leaking from the lid portion 14 or groundwater seeping from the joint portion 13 between the upper portion 11 and the lower portion 12, the dirty water or the like is discharged to the drain port 31. influx. At this time, as shown in FIG. 7, sewage or the like that has flowed into the drain port 31 applies stress to the opening/closing portion 52 of the valve body 5, causing the opening/closing portion 52 to elastically deform downstream. As a result, the opening/closing part 52 is separated from the valve seat 49, and the sewage and the like are discharged to the outside of the underground box 1 by opening the drainage channel. When all the sewage and the like in the underground box 1 is discharged, the valve body 5 is restored by its own elasticity, and the opening/closing part 52 is again in surface contact with the valve seat 49 over the entire circumference, thereby opening the drain port 31. The drainage channel continuous from is blocked.
On the other hand, when backflow of groundwater or the like occurs from the downstream side, stress is applied to the valve body 5 in the direction in which the opening/closing part 52 is pressed against the valve seat 49, so that the drainage channel is maintained closed and the underground box is closed. Backflow of groundwater into 1 is prevented.
Rocks, earth and sand contained in sewage and underground water are collected by the perforated plate 6 or the perforated plate 7 so that the operation of the backflow prevention device 2 is not hindered.

A second embodiment of the present invention will be described below with reference to FIGS. 8 to 12. FIG. In the second embodiment, a self-sealing valve is used as the valve element of the backflow prevention device. In addition, in the second embodiment described below, since only the fixed member 4, the valve body 5, and the perforated plate 7 are different from the first embodiment, only the different members will be described, and the other members will be described. The same numbers as in the first embodiment are given and the description thereof is omitted.

The fixing member 4 is made of hard synthetic resin, and has a cylindrical annular portion 41 and a gripping portion 48 formed on the inner periphery of the annular portion 41 as shown in FIGS. 9 to 11 .
The annular portion 41 has a cutout 42 , a plate-like portion 43 , and an inclined portion 44 formed on its upper surface. Two of each are formed at symmetrical positions. Further, the annular portion 41 is formed with a recess 45, a groove portion 46, and a mounting portion 471 on the outer surface thereof.
The notch 42 is a recessed groove formed on the outer periphery of the upper surface of the annular portion 41, and its width is configured so that the convex portion 33 of the flange member 3 can pass therethrough.
The plate-like portion 43 extends upward from the upper surface of the annular portion 41 and has a rectangular opening 431 formed therein.
The inclined portion 44 gradually protrudes upward from the notch 42 toward the plate-like portion 43 in the counterclockwise direction, and the end portion is formed so as to be continuous with the plate-like portion 43 .
The concave portion 45 is formed along the entire circumference of the side surface of the annular portion 41, and is fitted with an annular packing P that contacts the inner surface of the flange member 3. As shown in FIG.
The groove portion 46 is formed over the entire outer circumference of the annular portion 41 below the recess portion 45, and the perforated plate 7 is engaged when the construction is completed.
The mounting portion 471 is an outer flange portion formed below the groove portion 46, and the upper end of the valve body 5 is fitted thereon.
A grasping portion 48 is formed on the inner side surface of the annular portion 41 and functions as a handle when attaching and detaching the valve body 5 .

The valve body 5 has a substantially cylindrical shape and is made of an elastic soft material such as silicon rubber, and forms a drainage channel inside. In addition, on the upstream side of the valve body 5, an inflow port having a substantially U-shaped cross-section attached to the mounting portion 471 of the fixed member 4 and side surfaces facing each other below the inflow port are formed so as to gradually approach each other. It is composed of an inclined surface 54 and an opening/closing portion 52 which is formed at the tip of the inclined surface 54 and closes the drainage channel by abutting the opposed side surfaces.
The opening and closing portion 52 of the valve body 5 closes the drainage channel by maintaining the contact state between the opposing surfaces due to its own elasticity. It keeps the drainage channel closed as long as no gas or fluid passes through it.

The perforated plate 7 is a collecting member disposed on the downstream side of the valve body 5, and has a concave cross-sectional shape, and has a collection portion formed by vertically opening a plurality of collection holes. have. The perforated plate 7 has an engaging portion 71 projecting inward and is fixed to the fixing member 4 by engaging with the groove portion 46 of the fixing member 4 .

The backflow prevention device 2 is constructed as follows.

First, the inlet of the valve body 5 is fitted to the mounting portion 471 .
Next, the engaging portion 71 of the perforated plate 7 is engaged with the groove portion 46 of the fixing member 4 to attach the perforated plate 7 to the fixing member 4 .
Next, the fixing member 4 to which the valve body 5 and the perforated plate 7 are attached is inserted into the flange member 3 in a state in which the projections 33 and the cutouts 42 are aligned with each other. Then, after inserting the fixing member 4 into the flange member 3 until the upper surface of the annular portion 41 is positioned below the convex portion 33, the fixing member 4 is rotated clockwise so that the fixing member 4 is attached to the flange member 3. It is attached. During the rotation, the inclined portion 44 comes into contact with the convex portion 33, so that part of the stress associated with the clockwise rotation is converted into stress that pushes the fixing member 4 downward. As a result, the packing P is strongly pressed against the stepped portion 34 formed on the inner circumference of the fixing member 4, and the gap between the outer surface of the fixing member 4 and the inner surface of the flange member 3 is completely stopped.
Finally, the perforated plate 6 is placed on the fixing member 4 and the engaging portion 61 is engaged with the opening portion 431 to complete the construction.

Although the flange member 3 is attached to the underground box 1, the attachment method is not limited at all. That is, a mounting hole may be formed in the bottom surface 19 of the underground box 1 and the flange member 3 may be adhered, or the flange member 3 may be inserted into the bottom surface 19 by placing concrete after placement.

When performing maintenance on the backflow prevention device 2, the fixing member 4 can be removed from the flange member 3 by rotating the fixing member 4 counterclockwise.

The underground box 1 equipped with the backflow preventive device 2 having the valve element 5 can be operated in a state where there is no sewage inside the box 1 and no backflow of groundwater from the downstream side. As shown in 9, the valve body 5 closes the drainage channel by contacting the opening/closing portions 52 with each other due to the elasticity of the valve body 5 itself.
Here, if dirty water or the like is generated in the underground box 1 by rainwater leaking from the lid portion 14 or groundwater seeping from the joint portion 13 between the upper portion 11 and the lower portion 12, the dirty water or the like is discharged to the drain port 31. influx. At this time, as shown in FIG. 12, sewage or the like that has flowed into the drain port 31 applies a stress to expand the opening/closing portion 52 of the valve body 5 from the inside, thereby elastically deforming the opening/closing portion 52 . As a result, sewage and the like are discharged to the outside of the underground box 1 by opening the drainage channel. When all the sewage and the like in the underground box 1 is discharged, the valve body 5 is restored by its own elasticity, and the opening/closing parts 52 come into contact with each other, thereby closing the drainage channel continuing from the drainage port 31. be.
On the other hand, when backflow of groundwater or the like occurs from the downstream side, stress is applied to the valve body 5 in the direction in which the opening and closing portions 52 facing each other abut against each other. Backflow of groundwater into the interior is prevented.

According to the drainage device for the underground box of the present invention, by providing the backflow prevention device 2 using an umbrella valve or a self-sealing valve as the valve body 5, drainage equipped with a backflow prevention device using a conventional float valve It becomes possible to suppress the total height of the device rather than the device. In other words, umbrella valves and self-sealing valves do not require a space for the float to move up and down, unlike conventional backflow prevention devices using float valves, so the size of the device can be reduced. Further, according to the present invention, the wall thickness of the underground box 1 can be reduced, and the product can be manufactured at a low cost.
The backflow prevention device 2 includes a fixing member 4 for fixing the valve body 5 in the drainage channel, and the fixing member 4 can be attached to and detached from the drainage channel together with the valve body 5 and the perforated plate 7 . As a result, the operator can attach and detach the fixing member 4, the valve body 5, and the perforated plate 7, which is the collecting member, as a unit from the apparatus, so that cleaning and replacement of the members can be easily performed. In the present invention, the fixing member 4 is attached by a rotation lock structure with the convex portion 33 and the inclined portion 44. As shown in FIG. Therefore, it is possible to reduce the amount of rotation required when attaching and detaching the fixing member 4, as opposed to attachment using screw engagement by a male screw and a female screw.

Although the embodiment of the present invention has been described above, various design changes are possible for the drainage device for the underground box of the present invention without departing from the gist of the invention.
For example, the attachment/detachment method of the fixing member 4 is not limited at all. That is, in the above-described first and second embodiments, the method for attaching and detaching the fixing member 4 was the rotation lock structure using the convex portion 33 and the inclined portion 44, but other methods may be used. For example, as shown in FIG. 13, a mounting/dismounting method using engagement between the flange member 3 and the fixing member 4 may be used. In addition, in FIG. 13 , the fixing is achieved by engaging the projection 33 with the opening 431 .
Further, as shown in FIGS. 14 and 15, the fixing member 4 is not formed with the convex portion 33, and the attachment/detachment method utilizes the friction of the packing P generated when the fixing member 4 is pushed into the flange member 3. can be
In the attachment/detachment method shown in the third and fourth embodiments, it is possible to attach/detach the fixing member 4 only by pushing it downward/pulling it upward without rotating the fixing member 4 . In addition, after arranging the fixing member 4 at a predetermined position, the fixing member 4 may be fixed in the drainage channel by attaching another member.
Also, as shown in FIG. 16, a water shutoff valve 9 for closing the drain port 31 may be prepared. In this case, 1. 2. A specification in which the drain port 31 is always blocked by the water shutoff valve 9; 3. A specification in which the water stop valve 9 is not attached and the drain port 31 is always open; It is possible to selectively use three specifications such as a specification in which only the backflow from the downstream side is prevented by the backflow prevention device 2 . That is, in areas such as coastal areas where the groundwater level is high and flooding into the underground box 1 cannot be stopped, the above 1. 2. In an area where the drain port 31 is always blocked by the stopcock 9 and the groundwater level is lower than the underground box 1; 3. In areas where the groundwater level temporarily fluctuates due to torrential rains, etc., the specification is such that the drain port 31 is always open without the stopcock 9 attached. It is possible to change the specifications of the drainage device according to the place where the underground box 1 is installed and its application, such as a specification in which only the backflow from the downstream side is prevented by the backflow prevention device 2 . At this time, according to the present invention, since the valve body 5 and the collecting member can be easily attached and detached by the fixing member 4, it is possible to easily change the specifications.

Moreover, in the above embodiment, the perforated plate is provided as the collecting member, but a porous filter having a large number of fine holes may be arranged as the collecting member. Also, a perforated plate and a filter may be used together. By configuring in this way, the operation of the valve body 5 can be further stabilized.
Moreover, when it corresponds to the thick-walled underground box 1, the length may be extended by attaching a long tubular body 8. - 特許庁Alternatively, the perforated plate 7 may be protruded from the back surface of the underground box 1 without attaching the tubular body 8. - 特許庁
In each of the above-described embodiments, the backflow prevention device 2 is provided with collection members on the upstream and downstream sides of the valve body 5 . Further, the fixing member 4 is engaged with the collecting member on the downstream side, and the collecting member can be attached and detached together with the fixing member 4 . The collecting member on the upstream side of the valve body 5 may be detachable from the apparatus together with the fixing member 4.
Also, the use of the underground box 1 is not limited at all. Therefore, the various cables may be of any type, such as for telephone use or for power supply.

1 Underground box 11 Upper part 12 Lower part 13 Joint part 14 Lid part 15 Side surface 16 Side surface 17 Through hole 18 Protective tube 19 Bottom surface 2 Backflow prevention device 3 Flange member 31 Drain port 32 Flange 33 Protrusion 34 Step 4 Fixing member 41 Annular portion 42 Notch 43 Plate-like portion 431 Opening 44 Inclined portion 45 Recessed portion 46 Groove 47 Attachment portion 471 Attachment portion 48 Grip portion 49 Valve seat 5 Valve body 51 Shaft portion 52 Opening/closing portion 53 Swelling portion 54 Inclined surface 6 Perforated plate 61 Engaging portion 7 Perforated plate 71 Engaging portion 8 Tubular body 9 Stop cock P Packing

Claims (5)

an underground box buried in the ground;
A drainage device for an underground box, comprising a backflow prevention device attached to a drainage channel continuing from a drainage port formed in the underground box,
The backflow prevention device includes a valve body that opens and closes the drainage channel ;
a fixing member for fixing the valve body in the drainage channel ;
The valve body is an umbrella valve comprising a shaft portion fixed in the drainage channel and an umbrella-shaped opening/closing portion formed around the shaft portion, and opens and closes the drainage channel by elastic deformation ,
A drainage device for an underground box, wherein the fixed member has a valve seat with which the valve body abuts at the lower end thereof to block the drainage channel . an underground box buried in the ground;
A drainage device for an underground box, comprising a backflow prevention device attached to a drainage channel continuing from a drainage port formed in the underground box,
The backflow prevention device includes a valve body that opens and closes the drainage channel ;
a fixing member for fixing the valve body in the drainage channel ;
The valve body is a self-sealing valve including an opening/closing portion that closes the drainage channel by abutment of opposing side surfaces, and opens and closes the drainage channel by elastic deformation ,
A drainage device for an underground box, wherein the fixing member is inserted from the drain port with the valve body attached, and fixes the valve body in the drainage channel. The backflow prevention device is
3. The drainage device for an underground box according to claim 1 , wherein the fixing member is detachable in the drainage channel together with the valve body. The backflow prevention device is
Collecting members are provided on the upstream side and the downstream side of the valve body,
4. A drainage device for an underground box according to claim 3 , wherein at least the collecting member on the downstream side engages with the fixing member and is detachable together with the fixing member. 5. A drainage device for an underground box according to claim 1 , wherein said underground box is a manhole or a handhole.

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